Military history of patients with inflammatory bowel disease: an epidemiological study among U.S. veterans

OBJECTIVES

The military history of patients with inflammatory bowel disease (IBD) contains types of exposure that are not available through other sources and may provide clues about the as-yet unknown etiology of IBD. We therefore sought to describe the epidemiology of IBD among veterans, with particular emphasis on their military history.

METHODS

A case-control study compared 10,544 IBD patients and 42,026 controls with respect to age, gender, ethnicity, time period of military service, military duty in Vietnam, status as prisoner of war, and exposure to Agent Orange.

RESULTS

Subjects with Crohn's disease were younger than those with ulcerative colitis or without IBD (odds ratio: 0.85; 95% confidence interval [CI]: 0.83-0.87). Both types of IBD affected female veterans significantly more often than male veterans, the relative female predominance being more pronounced in Crohn's disease than ulcerative colitis (0.70; 0.61-0.81 vs 0.83; 0.71-0.96). Whites were more prone to develop both types of IBD than nonwhites (2.46; 2.27-2.68 vs 2.11; 1.95-2.27). Military duty in Vietnam and a status as prisoner of war both exerted a protective influence against Crohn's disease (0.84; 0.75-0.96 and 0.60; 0.41-0.87, respectively), but not ulcerative colitis.

CONCLUSIONS

The results are consistent with the hypothesis that exposure to poor sanitation decreases the future risk of developing Crohn's disease.

The impact of peptic ulcer disease and infection with Helicobacter pylori on life expectancy

OBJECTIVE

Knowledge about the influence of H. pylori-related disease on life expectancy might affect physician behavior in dealing with such disease. The aim of this study was to assess how life expectancy is influenced by H. pylori infection and peptic ulcer disease.

METHODS

The declining exponential approximation of life expectancy was used to model the effects of H. pylori and various peptic ulcer disease conditions on life expectancy. Deaths from peptic ulcer and gastric cancer were determined from the Vital Statistics of the United States. H. pylori prevalence rates were derived from the existing literature.

RESULTS

Cure of active peptic ulcer increases life expectancy by 2.3 yr in persons aged 40-44 yr and 121 days in persons aged 70-74 yr. More substantial impact occurs in complicated ulcer, with increases in life expectancy ranging between 26.1 and 6.3 yr. Primary prevention of H. pylori could increase life expectancy by 190 days in those aged 40-44 yr and 26 days in 70-74-yr-old subjects.

CONCLUSION

The benefit of ulcer cure or H. pylori prevention diminishes as age advances. Cure of ulcers in young patients or in those who have sustained complications results in an appreciable increase in life expectancy. Successful primary prevention of H. pylori in selected populations could substantially increase life expectancy.

Genomic organization of the human alpha 3 integrin subunit gene

The alpha 3 beta 1 integrin is a receptor for various laminin isoforms and plays an important role in the maintenance of tissue integrity. We have characterized the genomic structure of the complete gene for the human alpha 3 integrin subunit. The gene contains 26 exons spanning a region of 36.3 kb of genomic DNA. Its structure closely resembles that of alpha 6, another of the three integrin alpha-subunits that are part of laminin receptors, except that it lacks the corresponding exon 5A, which encodes an X1 region in the extracellular domain of alpha 6. However, the alpha 3 gene contains the equivalent of an exon 5B for an X2-like region, which in alpha 6 and alpha 7 is present only in certain tissue-specific alternative transcripts. The two A and B cytoplasmic variants of alpha 3, which are common to the three laminin receptor integrin alpha-subunits, are encoded by separate exons.

Hemidesmosome formation is initiated by the beta4 integrin subunit, requires complex formation of beta4 and HD1/plectin, and involves a direct interaction between beta4 and the bullous pemphigoid antigen 180

Hemidesmosomes (HDs) are stable anchoring structures that mediate the link between the intermediate filament cytoskeleton and the cell substratum. We investigated the contribution of various segments of the beta4 integrin cytoplasmic domain in the formation of HDs in transient transfection studies using immortalized keratinocytes derived from an epidermolysis bullosa patient deficient in beta4 expression. We found that the expression of wild-type beta4 restored the ability of the beta4-deficient cells to form HDs and that distinct domains in the NH2- and COOH-terminal regions of the beta4 cytoplasmic domain are required for the localization of HD1/plectin and the bullous pemphigoid antigens 180 (BP180) and 230 (BP230) in these HDs. The tyrosine activation motif located in the connecting segment (CS) of the beta4 cytoplasmic domain was dispensable for HD formation, although it may be involved in the efficient localization of BP180. Using the yeast two-hybrid system, we could demonstrate a direct interaction between beta4 and BP180 which involves sequences within the COOH-terminal part of the CS and the third fibronectin type III (FNIII) repeat. Immunoprecipitation studies using COS-7 cells transfected with cDNAs for alpha6 and beta4 and a mutant BP180 which lacks the collagenous extracellular domain confirmed the interaction of beta4 with BP180. Nevertheless, beta4 mutants which contained the BP180-binding region, but lacked sequences required for the localization of HD1/plectin, failed to localize BP180 in HDs. Additional yeast two- hybrid assays indicated that the 85 COOH-terminal residues of beta4 can interact with the first NH2-terminal pair of FNIII repeats and the CS, suggesting that the cytoplasmic domain of beta4 is folded back upon itself. Unfolding of the cytoplasmic domain may be part of a mechanism by which the interaction of beta4 with other hemidesmosomal components, e.g., BP180, is regulated.

Ligand-independent role of the beta 4 integrin subunit in the formation of hemidesmosomes

Recently, we have shown that a region within the beta4 cytoplasmic domain, encompassing the second fibronectin type III (FNIII) repeat and the first 27 amino acids of the connecting segment, is critical for the localization of alpha6 beta4 in hemidesmosomes. In addition, this region was shown to regulate the distribution of HD1/plectin in transfected cells. In order to investigate the function of the beta4 extracellular and cytoplasmic domains in the assembly and integrity of hemidesmosomes, we have constructed chimeric receptors consisting of the extracellular and transmembrane domains of the interleukin 2 receptor (IL2R), fused to different parts of the beta4 cytoplasmic domain. These chimeras are expressed as single subunits at the plasma membrane. The results show that the first and the second FNIII repeat, together with the first part of the connecting segment (in total a stretch of 241 amino acids spanning amino acids 1,115 to 1,356) are both essential and sufficient for the localization of beta4 in pre-existing hemidesmosomes. Moreover, expression of the IL2R/beta4 chimeric constructs in COS-7 and CHO cells, which do not express alpha6 beta4 or the bullous pemphigoid (BP) antigens but do express HD1/plectin, revealed that the stretch of 241 amino acids is sufficient for inducing the formation of type II hemidesmosomes. Expression of the IL2R/beta4 chimeras in a keratinocyte cell line derived from a patient lacking beta4 expression, showed that amino acids 1,115 to 1,356 can also induce the formation of type I hemidesmosomes. We further demonstrate that type I and II hemidesmosomes can also be formed upon adhesion of alpha6 beta4-expressing cells to fibronectin. These findings establish that the beta4 extracellular domain is not essential for the induction of hemidesmosome assembly. Moreover, they demonstrate that binding of alpha6 beta4 to ligand, and heterodimerization of alpha6 with beta4, are not required for hemidesmosome formation. This indicates that the assembly of hemidesmosomes can be regulated from within the cell.

Empirical therapy versus diagnostic tests in gastroesophageal reflux disease: a medical decision analysis

Our objective was to describe the conditions that determine the costs of empirical therapy in gastroesophageal reflux disease (GERD). Our design was a threshold analysis using a decision tree. The costs of medications were estimated from the average wholesale prices. The costs of diagnostic procedures were expressed as the sum of physician and facility costs. A decision tree was modeled to calculate the threshold probability of GERD, for which empirical therapy became the preferred management strategy. Bayes' formula was used to transform the sensitivity and specificity of various symptoms and the joint occurrence of multiple symptoms into disease probabilities. The decision in favor of empirical therapy is influenced by four factors: the probability of GERD, the duration or costs of GERD therapy, the costs of erroneous empirical therapy in patients with diagnosis other than GERD, and the costs of diagnostic procedures. In general, the expected benefit of saving the costs of a diagnostic procedure outweighs the costs of occasional erroneous empirical therapy. However, if surgical therapy is considered or antisecretory therapy is administered for a time period of 10 or more years, diagnostic confirmation of GERD should be sought. In the long run, the failure to differentiate between peptic ulcer and GERD results in the highest cost associated with erroneous empirical therapy. In patients with multiple characteristic symptoms of GERD, the diagnosis can be ascertained with sufficient confidence to warrant empirical therapy.

Cost savings in duodenal ulcer therapy through Helicobacter pylori eradication compared with conventional therapies: results of a randomized, double-blind, multicenter trial. Gastrointestinal Utilization Trial Study Group

BACKGROUND

We hypothesized that treatment of duodenal ulcer disease with antibiotic therapy directed toward Helicobacter pylori infection is more cost-effective than therapy with antisecretory agents.

METHODS

A randomized, double-blind, multicenter clinical trial of adult patients with active duodenal ulcer and H. pylori infection was conducted. Patients were randomized to receive 500 mg of clarithromycin 3 times a day plus 40 mg of omeprazole daily for 14 days followed by 20 mg of omeprazole daily for an additional 14 days (group 1), 20 mg of omeprazole daily for 28 days (group 2), or 150 mg of ranitidine hydrochloride twice a day for 28 days (group 3). The use of ulcer-related health care resources was documented during monthly interviews for 1 year after the initial therapy. Clinical success was evaluated 4 to 6 weeks and 1 year after the end of therapy.

RESULTS

Of the 819 patients enrolled, 727 completed the study. Group 1 included 243 patients; group 2, 248 patients; and group 3, 236 patients. Patients in group 1 used fewer ulcer-related health care resources during the 1 year after therapy compared with groups 2 and 3 (comparisons are given as group 1 vs group 2 and group 1 vs group 3, respectively): the number of endoscopies performed, 28 vs 76 (P<.001) and vs 71 (P<.001); patients receiving drugs to treat an ulcer, 118 vs 180 (P<.001) and vs 168 (P<.001); clinic visits, 83 vs 135 (P=.05) and vs 161 (P<.001); hospitalizations, 0 vs 5 (P=.045) and vs 6 (P=.02); and length of hospital stay, 0 vs 24 days (P=.04) and vs 37 (P=.04). When ulcer-related costs were defined as the outcome variable in a multivariate linear regression analysis, therapy was determined to have a significant influence on costs (group 1 vs group 2, P<.001; group 1 vs group 3, P=.008). Clinical success rates at the end of the study and cure of H. pylori infection were significantly greater in group 1 compared with groups 2 and 3 (P<.001). Therapy with clarithromycin plus omeprazole provided savings of $1.94 and $2.96 (compared with therapy with omeprazole and with ranitidine hydrochloride, respectively) per dollar spent within the first year after therapy. This incremental cost-benefit translates to savings of $547 or $835 per patient in group 1 (compared with patients in group 2 or group 3, respectively) during the first year after therapy.

CONCLUSIONS

Combination therapy with clarithromycin and omeprazole resulted in significantly fewer uses of ulcer-related health care resources than conventional antisecretory therapy during a 1-year follow-up and significant savings in associated costs during the same period. Patients who received clarithromycin plus omeprazole also showed a significantly improved clinical outcome compared with patients who received only omeprazole or ranitidine.

Knockout and knockin of the beta1 exon D define distinct roles for integrin splice variants in heart function and embryonic development

The beta1D integrin is a recently characterized isoform of the beta1 subunit that is specifically expressed in heart and skeletal muscle. In this study we have assessed the function of the beta1D integrin splice variant in mice by generating, for the first time, Cre-mediated exon-specific knockout and knockin strains for this splice variant. We show that removal of the exon for beta1D leads to a mildly disturbed heart phenotype, whereas replacement of beta1A by beta1D results in embryonic lethality with a plethora of developmental defects, in part caused by the abnormal migration of neuroepithelial cells. Our data demonstrate that the splice variants A and D are not functionally equivalent. We propose that beta1D is less efficient than beta1A in mediating the signaling that regulates cell motility and responses of the cells to mechanical stress.

An endo-1,4-beta-xylanase-encoding gene from Agaricus bisporus is regulated by compost-specific factors

Compost is the preferred substrate for growth of the edible fungus Agaricus bisporus. Utilization of compost requires the production of enzymes involved in degradation of lignocellulolytic components. For molecular characterization of these processes we are isolating the encoding genes. By applying heterologous screening techniques, we have cloned such a gene, which is specifically induced on compost encoding an endo-1,4-beta-xylanase (xlnA) belonging to glycosyl hydrolase family 10. The gene encodes a pre-protein of 333 amino acid residues with a predicted molecular mass of 34,946 for the mature protein. The open reading frame is interrupted by ten introns of which introns 5 and 6 are separated by an exon of only two base-pairs. High expression of the xlnA gene was observed in vegetative mycelium grown on sterilized compost while xlnA messengers were not detected in fruit bodies. Addition of glucose or xylose to compost repressed xlnA expression. When glucose-grown colonies were transferred to a medium containing cellulose, xylan or xylose as sole carbon source, the organism responded by expressing xlnA at a high level for a short period. Transfer from glucose to compost yielded a much stronger and constant xlnA induction. A similar pattern of expression was found for the cel3 gene encoding a cellulase, suggesting that these genes are induced by compost-specific factors rather than by the substrates they act upon. Antiserum raised against XLNA protein, which was heterologously expressed in Escherichia coli, detected, when the fungus was grown on compost, an extracellular protein of 33 kDa with endo-xylanase activity.

Incidence and risk factors for self-reported peptic ulcer disease in the United States

Incidence and risk factors for peptic ulcer disease in the United States have not been well defined. During the 1989 National Health Interview Survey, a population-based sample of 42,392 individuals responded to questions regarding doctor-diagnosed ulcers with confirmation by either an upper gastrointestinal series or endoscopy. Ulcers present during the previous 12 months were considered either incident ulcers if diagnosed during this period or chronic active ulcers if diagnosed more than 12 months before the interview. The incidence of ulcers over the year prior to the interview was 5.27 per 1,000 adults. Whereas incident duodenal ulcer cases represented only 2.4 percent of all persons with a history of duodenal ulcer, the corresponding value for gastric ulcer was 8.7 percent. Risk factors for incident ulcers included increasing age, lower income and educational attainment, and musculoskeletal pain or headache. These were similar to risk factors for chronic active ulcers, except smoking was an additional important risk factor for chronic active ulcers. Thus, incident peptic ulcers are common in the United States but represent a small proportion of persons with a history of ulcer disease. Smoking may be a stronger risk factor for chronic ulcers than for new ulcers.

Role of the bullous pemphigoid antigen 180 (BP180) in the assembly of hemidesmosomes and cell adhesion--reexpression of BP180 in generalized atrophic benign epidermolysis bullosa keratinocytes

Bullous pemphigoid antigen 180 (BP180) is a transmembrane component of hemidesmosomes (HD), cell-substrate attachment complexes in stratified and complex epithelia. To determine the role of BP180 in the assembly of HD and cell adhesion, using SV40 virions we have immortalized BP180-deficient keratinocytes derived from a patient with the inherited skin blistering disorder generalized atrophic benign epidermolysis bullosa (GABEB). The GABEB keratinocytes form HD-like structures, which contain alpha 6 beta 4 integrin and HD1/plectin, but not the bullous pemphigoid antigen 230 (BP230). The expression of integrin subunits by GABEB keratinocytes was comparable to that of an immortalized normal human keratinocyte cell line (NHK), except for alpha 6 and beta 4, which were less strongly expressed in GABEB cells. In short-term adhesion assays, both GABEB keratinocytes and NHK bound strongly and to a similar extent to laminin-1, laminin-5, fibronectin, and type IV and V collagens, which suggests that BP180 is not involved in promoting the initial adhesion to these ligands. Transfection of GABEB keratinocytes with cDNAs for wild-type or a mutant of BP180 lacking the collagenous extracellular domain resulted in the expression of recombinant BP180 proteins that were correctly polarized at the basal cell surface together with alpha 6 beta 4. In addition, restored synthesis of BP180 affected the subcellular localization of BP230, which was no longer diffusely distributed in the cytoplasm, but was found in HD-like structures. In contrast, a BP180 mutant with a 36-amino-acid deletion from the amino terminus of the cytoplasmic domain failed to localize to HD-like structures. These results demonstrate that a region within the cytoplasmic domain of BP180 is essential for its localization into HD and that BP180 may play a critical role in coordinating the subcellular distribution of BP230.

Glomerular extracellular matrix components and integrins

It has become apparent that extracellular matrix components and their cellular receptors, the integrins, are important regulators of glomerular development and function. In this rapidly evolving field we studied the production of extracellular matrix components and integrins by rat glomerular visceral epithelial and mesangial cells, using molecular probes and antibodies that have recently become available. Special attention was paid to laminin isoforms and to splice variants of the integrin subunits alpha 3 and alpha 6. Results were compared to the in vivo expression in human fetal, newborn and adult kidneys. The mesangial cells were found to produce laminin-1, nidogen and two as yet unidentified laminin isoforms with putative alpha chains of about 395 (alpha x) and of 375 kDa (alpha y), tentatively described before as bovine kidney laminin. Furthermore, they expressed the integrins alpha 1 beta 1, alpha 2 beta 1, alpha 3A beta 1, alpha 5 beta 1, alpha v beta 3, alpha v beta 5, and small amounts of alpha 6A beta 1 and alpha 6B beta 1. The glomerular visceral epithelial cells produced the two new laminin isoforms mentioned above, laminin-5, but no laminin-1 or nidogen. The integrins alpha 2 beta 1, alpha 3A beta 1, alpha 6A beta 4, alpha 6B beta 4 and the integrin subunit alpha v were found to be expressed. We show that during nephrogenesis, the laminin alpha 1 chain disappears and is replaced by another alpha chain, possibly one of the two as yet unidentified alpha chains mentioned above. The laminin beta 1 chain is replaced by the beta 2 chain somewhat later in glomerular development. In general, the integrins found to be expressed in glomeruli of adult kidney were consistent with those found in cultured glomerular visceral epithelial and mesangial cells. No splice variant switch of the integrin alpha 3 or alpha 6 subunits could be demonstrated during nephrogenesis. Our results suggest an important role for the mesangial cell in providing nidogen as a crucial component of the supramolecular structure of the glomerular basement membrane. Furthermore our results indicate that laminin alpha x beta 2 gamma 1 and alpha y beta 2 gamma 1 isoforms are important in the glomerulus of adult kidney and that the integrin alpha 3A beta 1 is the main integrin receptor for laminin isoforms on glomerular visceral epithelial and mesangial cells, both in vitro and in vivo.

Review article: Medical decision models of Helicobacter pylori therapy to prevent gastric cancer

The aim of the present article is to study the utility of Helicobacter pylori eradication programmes in decreasing the incidence of gastric cancer. Three types of decision models are employed to pursue this aim, i.e. decision tree, present value, and declining exponential approximation of life expectancy (DEALE). 1) A decision tree allows one to model the interaction of multiple variables in great detail and to calculate the marginal cost, as well as the marginal cost-benefit ratio, of a preventive strategy. The cost of gastric cancer, the efficacy of H. pylori therapy in preventing cancer, and the cumulative probability of developing gastric cancer exert the largest influence on the marginal cost of cancer prevention. The high cost of future gastric cancer and a high efficacy of therapy make screening for H. pylori and its eradication the preferred strategy. 2) The present value is an economic method to adjust future costs or benefits to their current value using a discount rate and the length of time between now and a given time point in the future. It accounts for the depreciation of money and all material values over time. During childhood, the present value of future gastric cancer is very low. Vaccination of children to prevent gastric cancer would need to be very inexpensive to be practicable. Cancer prevention becomes a feasible option, only if the time period between the preventive measures and the occurrence of gastric cancer can be made relatively short. 3) The DEALE provides a means to calculate the increase in life expectancy that would occur, if death from a particular disease became preventable. Life expectancy of the general population is hardly affected by gastric cancer. For life expectancy to increase appreciably by vaccination or antibiotic therapy directed against H. pylori infection, these interventions would need to be focused towards a sub-population with an a priori high risk for gastric cancer.

Spatial and temporal expression of the beta1D integrin during mouse development

The beta1D protein is a recently characterized isoform of the integrin beta1 subunit that is present in cardiac and skeletal muscles. In this study, we have examined the expression of beta1D in different types of skeletal muscle and in cardiac muscle and studied its distribution during mouse development, using new monoclonal antibodies specific for beta1D. Immunoprecipitation studies revealed that, while beta1A is strongly expressed in proliferating C2C12 myoblasts, beta1D is only expressed after their differentiation to myotubes. In these myotubes, beta1D is associated with different alpha subunits, namely alpha3A, alpha5, alpha7A, or alpha7B. Initially, during embryogenesis, the alpha1A subunit is the only beta1 variant expressed in skeletal and cardiac muscle. The beta1D subunit is first detected in skeletal muscle at E17.5, whereas in cardiac muscle its expression begins around the time of birth. Later the expression of beta1A in skeletal and cardiac muscle becomes restricted to capillary cells, whereas beta1D eventually becomes the only variant expressed in adult cardiac and skeletal muscle cells. The switch from the beta1A to the beta1D subunit in cardiac muscle cells coincides with the expression of alpha7. In adults there is a distinct concentration of beta1D at the myotendinous junctions of muscle fibers and at costameres in both cardiac and skeletal muscle. In addition, beta1D is present at intercalated discs in cardiac muscle and at neuromuscular junctions in skeletal muscle cells. The amount of beta1D in different types of skeletal muscle (fast, slow, and mixed-type) was similar, but cardiac muscle expressed almost five times as much of this protein. We suggest that beta1D plays a role in the maintenance of the cytoarchitecture of mature muscle and in the functional integrity of the muscle cells.

The two phenylalanines in the GFFKR motif of the integrin alpha6A subunit are essential for heterodimerization

The membrane-proximal domain of the integrin alpha subunit contains a conserved motif of five amino acid residues, GFFKR. We deleted this motif from the human alpha6A subunit and found that in COS-7 cells this mutant cannot associate with the beta1 subunit and is retained in the endoplasmic reticulum. Point mutations in the GFFKR motif of the glycine residue or the two highly charged amino acids, or deletion of the lysine and arginine residues, had no effect on the ability of alpha6 to interact with beta1 and to be expressed at the cell surface. In contrast, by replacing either of the two phenylalanines with alanine, or by deletion of both of these residues, alpha6 was incapable of associating with beta1. The alpha6 point mutants that associated with beta1 were expressed in K562 cells and their responsiveness to integrin-activating factors was determined. None of these transfectants bound spontaneously to laminin-1, but binding could be induced by either PMA or the stimulating anti-beta1 antibody TS2/16 to the same extent as that of the wild-type transfectant. The ability of these mutants to initiate focal-contact formation in CHO cells plated on laminin-1 substrates also appeared to be unaltered. Thus the behaviour of alpha6 mutants involving the glycine, lysine or arginine residues was indistinguishable from that of wild-type alpha6 both in inside-out and outside-in signalling. In contrast, deletion of the cytoplasmic domain of alpha6 C-terminal of the GFFKR motif resulted in a loss of responsiveness of alpha6beta1 to PMA stimulation and formation of focal contacts on laminin-1. However, this mutant was targeted to focal contacts formed by other integrins, even when they had not bound ligand. Together, these results suggest that the two phenylalanine residues of the GFFKR motif provide a site for interaction of the alpha6A subunit with beta1, whereas the cytoplasmic domain C-terminal of this motif is involved in the regulation of bidirectional signalling via alpha6Abeta1.

Associations between different forms of gastro-oesophageal reflux disease

AIMS

To study the epidemiology and natural history of gastro-oesophageal reflux disease (GORD).

METHODS

Retrospective cohort study involving all 172 hospitals of the Department of Veterans Affairs. A total of 194,527 patients with GORD were followed between 1981 and 1994. Distribution of oesophagitis, oesophageal ulcer, oesophageal stricture, strictured hiatus hernia, hiatus hernia, and pyrosis by age, sex, and ethnicity were determined. The comorbid occurrence of various forms of GORD in identical patients was analysed by an age and race standardised morbidity ratio. The population of all hospitalised veterans was used for comparison.

RESULTS

Severe forms of GORD associated with oesophageal erosions, ulcers, or strictures, affected elderly, white, male patients more often than their corresponding opposite demographic group. All forms of GORD clustered in the same patient population; on average, any form of GORD was 10 times more likely to occur in a patient with another form of GORD than without. The highest morbidity ratio (22) was found in oesophageal ulcer and stricture. About one third of all patients with oesophageal erosions, ulcers, or strictures also had hiatus hernia; 46% of patients with hiatus hernia were diagnosed as having other forms of GORD. While one third of all oesophageal strictures appeared in patients without other forms of GORD diagnosed at any time, oesophageal ulcers were always associated with some other form of GORD. No clear cut progression in different forms of GORD was found.

CONCLUSIONS

Older age, male sex, and white ethnicity are risk factors in the development of severe forms of GORD. The most severe grade of GORD is reached at the onset of the disease.

Cost-analysis of prophylactic antibiotics in spontaneous bacterial peritonitis

BACKGROUND & AIMS

Antibiotic prophylaxis has been shown to decrease the incidence of spontaneous bacterial peritonitis (SBP) in patients with cirrhosis and ascites. The aim of this study was to test whether antibiotic prophylaxis for SBP is cost-effective and to compare the costs associated with different patient groups and treatment strategies.

METHODS

A cost-effectiveness analysis was performed using a Markov chain model. The costs incurred during 1-year treatment with prophylactic antibiotics vs. no prophylaxis in patients with cirrhosis and ascites were calculated. The incidence rates of primary and recurrent SBP and the mortality rate of SBP were obtained from the literature. Total direct costs of SBP treatment were determined from the wholesale price of drugs and from disbursements by the Health Care Financing Administration.

RESULTS

Norfloxacin prophylaxis resulted in savings between $2216 and $8545 per patient per year, depending on the patient group studied. Trimethoprim-sulfamethoxazole prophylaxis resulted in savings between $2934 and $9251 per patient per year. The groups that benefited most from prophylaxis were patients with an ascitic fluid total protein concentration of < or = 1 g/dL and those with a previous history of SBP.

CONCLUSIONS

The use of prophylactic antibiotics to decrease the incidence of SBP is a cost-saving strategy in patients with cirrhosis and ascites.

Comorbid occurrence of laryngeal or pulmonary disease with esophagitis in United States military veterans

BACKGROUND & AIMS

It has been speculated that gastroesophageal reflux disease (GERD) represents a risk factor for the occurrence of extraesophageal complications. The aim of this study was to compare the comorbid occurrence of sinus, laryngeal, and pulmonary diseases in case subjects with and control subjects without reflux esophagitis.

METHODS

The case population consisted of all patients with erosive esophagitis (International Classification of Diseases code 530.1) or esophageal stricture (ICD code 530.3) who were discharged from hospitals of the Department of Veteran Affairs between 1981 and 1994. In multivariate logistic regressions, the occurrence of sinus, pharyngeal, laryngeal, or pulmonary disease was compared between cases with and an equal number of controls without esophagitis or stricture.

RESULTS

A total of 101,366 case subjects was analyzed. Erosive esophagitis and esophageal stricture were associated with sinusitis (odds ratio, 1.60; 95% confidence interval, 1.51-1.70), pharyngitis (1.48; 1.15-1.89), aphonia (1.81; 1.18-2.80), laryngitis (2.01; 1.53-2.63), laryngeal stenosis (2.02; 1.12-3.65), chronic bronchitis (1.28; 1.22-1.34), asthma (1.51; 1.43-1.59), chronic obstructive pulmonary disease (1.22; 1.16-1.27), pulmonary fibrosis (1.36; 1.25-1.48), bronchiectasis (1.26; 1.09-1.47), pulmonary collapse (1.31; 1.23-1.40), and pneumonia (1.15; 1.12-1.18).

CONCLUSIONS

Patients with reflux esophagitis are at an increased risk of harboring a large variety of sinus, pharyngeal, laryngeal, and pulmonary diseases.

A minimal region on the integrin beta4 subunit that is critical to its localization in hemidesmosomes regulates the distribution of HD1/plectin in COS-7 cells

The integrin alpha6 beta4 is a major component of hemidesmosomes, in which it mediates firm adhesion to laminin 5. Previous studies have shown that the incorporation of alpha6 beta4 into hemidesmosomes requires a 303 amino acid stretch of the cytoplasmic domain of beta4, comprising part of the first fibronectin type III (FNIII) repeat, the second FNIII repeat and the segment that connects the second to the third FNIII repeat (connecting segment). Now, we have further defined sequences within beta4 that are critical for its localization in hemidesmosomes and we demonstrate that these sequences also induce the redistribution of HD1/plectin into junctional complexes containing the integrin alpha6 beta4 in COS-7 cells, transfected with cDNAs encoding alpha6A and beta4. Truncation of the cytoplasmic domain of beta4 after amino acids 1,382 or 1,355 in the connecting segment, by which a potential tyrosine activation motif (TAM) is removed, does not prevent the localization of alpha6 beta4 in hemidesmosomes in the rat bladder carcinoma cell line 804G and neither did it eliminate the ability of alpha6 beta4 to change the subcellular distribution of HD1/plectin in COS-7 cells. In contrast, beta4 subunits in which the entire connecting segment had been deleted or which were truncated after amino acid 1,328, which removes almost the complete segment, had lost both of these functions. Furthermore, when beta4 subunits with either a deletion of the second FNIII repeat or a small deletion in this repeat were co-expressed with alpha6, the integrins were not localized in hemidesmosomes and did not induce the redistribution of HD1/plectin in COS-7 cells. Finally, the fourth FNIII repeat of beta4 could not replace the second in either of these activities. These findings establish that a region in beta4, which encompasses the second FNIII repeat and a stretch of 27 amino acids (1,329-1,355) of the connecting segment, is critical for the localization of alpha6beta4 in hemidesmosomes and that it regulates the distribution of HD1/plectin.

Implications of intragenic marker homozygosity and haplotype sharing in a rare autosomal recessive disorder: the example of the collagen type XVII (COL17A1) locus in generalised atrophic benign epidermolysis bullosa

Generalised atrophic benign epidermolysis bullosa (GABEB) is a form of junctional epidermolysis bullosa with a recessive mode of inheritance. The gene considered likely to be involved in this disease is COL17A1, since in the majority of GABEB patients the product of that gene, the 180-kD bullous pemphigoid antigen (BP180), is undetectable in skin. We have identified an intragenic COL17A1 microsatellite marker for which 83% of randomly selected control individuals are heterozygous. We observed homozygosity for different alleles of this marker in five out of six collagen type XVII-negative GABEB patients of different European descent. Five of the six COL17A1 alleles of three patients originating from the eastern part of the Netherlands were identical, as were the haplotypes including flanking markers. The 2342delG mutation was identified in all these five alleles. This confirms the expectation that due to genetic drift and hidden inbreeding for an autosomal recessive disorder with low gene frequency, such as collagen type XVII-negative GABEB, most disease alleles from a restricted geographical area will be "identical by descent". Our results demonstrate that involvement of a candidate gene can be confirmed by looking for identity by descent of highly informative intragenic markers.

Time trends of physician visits and treatment patterns of peptic ulcer disease in the United States

BACKGROUND

In the last 4 decades, the prevalence rates of peptic ulcer disease and our understanding of its pathophysiological features underwent major changes.

OBJECTIVE

To analyze how these trends affected physician visits and treatment of ulcer disease.

METHODS

The National Diseases and Therapeutic Index of IMS America Ltd, Plymouth Meeting, Pa, was used as the data source. Survey data were obtained from a representative sample of US physicians 4 times per year during a 48-hour period and extrapolated to a national level. Physician visits for gastric, duodenal, and all peptic ulcers were expressed as rates per 100,000 living US population.

RESULTS

Between 1958 and 1995, physician visits for duodenal ulcer showed a marked decline, while those for gastric ulcer remained largely unchanged. In 1995, 4 million patients visited a physician because of peptic ulcer, corresponding to a rate of 1500 per 100,000 US population. The predominant therapy changed from anticholinergics, tranquilizers, and antacids between 1958 and 1977 to histamine2 receptor antagonist from 1978 until 1988, which subsequently became replaced in part by sucralfate and proton pump inhibitors. In 1995, about 75% of ulcers were still treated primarily with antisecretory medications, and only 5% received antibiotic therapy.

CONCLUSIONS

Peptic ulcer is still common, although duodenal ulcer rates continue to decrease. The historical trends of treatment regimens show a steady change between various medications. No therapeutic class dominated ulcer therapy for more than 20 years. This trend is likely to continue, particularly, in light of the small fraction currently treated by antibiotics to eradicate Helicobacter pylori.

The unique cytoplasmic domain of the human integrin variant beta4E is produced by partial retention of intronic sequences

A novel cytoplasmic splice variant of the human beta4 integrin subunit has been identified by reverse transcription polymerase chain reaction using mRNA from cultured keratinocytes as the template. This fifth beta4 variant, called beta4E, is expressed in a wide variety of tissues including the epidermis, lung, duodenum, heart, spleen and stomach and in several human epithelial cell lines. The beta4E cDNA contains an insert of 37 base pairs which produces a frame shift in the sequence encoding the beta4 cytoplasmic domain and generates a new stop codon after a stretch of cDNA encoding a unique 114-amino acid peptide. Analysis of the genomic organization at the site of this insertion in the human beta4 gene reveals that beta4E is produced by partial retention of an intron in the final transcript.

Identification of the cleavage sites in the alpha6A integrin subunit: structural requirements for cleavage and functional analysis of the uncleaved alpha6Abeta1 integrin

The alpha6A and alpha6B integrin subunits are proteolytically cleaved during biosynthesis into a heavy chain (120 kDa) that is disulphide-linked to one of two light chains (31 or 30 kDa). Analysis of the structure of the alpha6A subunit on the carcinoma cell line T24 and human platelets demonstrated that the two light chains of alpha6 are not differentially glycosylated products of one polypeptide. Rather they possess different polypeptide backbones, which presumably result from proteolytic cleavage at distinct sites in the alpha6 precursor. Mutations were introduced in the codons for the R876KKR879, E883K884, R890K891 and R898K899 sequences, the potential proteolytic cleavage sites, and wild-type and mutant alpha6A cDNAs were transfected into K562 cells. The mutant alpha6A integrin subunits were expressed in association with endogenous beta1 at levels comparable to that of wild-type alpha6Abeta1. A single alpha6 polypeptide chain (150 kDa) was precipitated from transfectants expressing alpha6A with mutations or deletions in the RKKR sequence. Mutations in the EK sequence yielded alpha6A subunits that were cleaved once into a heavy and a light chain, whereas alpha6A subunits with mutations in one of the two RK sequences were, like wild-type alpha6A, cleaved into one heavy and two light chains. Thus a change in the RKKR sequence prevents the cleavage of alpha6. The EK site is the secondary cleavage site, which is used only when the primary site (RKKR) is intact. Microsequencing of the N-termini of the two alpha6A light chains from platelets demonstrated that cleavage occurs after Arg879 and Lys884. Because alpha6(RKKG), alpha6(GKKR) and alpha6(RGGR) subunits were not cleaved it seems that both the arginine residues and the lysine residues are essential for cleavage of RKKR. alpha6A mutants with the RKKR sequence shifted to the EK site, in such a way that the position of the arginine residue after which cleavage occurs corresponds exactly to Lys884, were partly cleaved, whereas alpha6A mutants with the RKKR sequence shifted to other positions in the alpha6A subunit, including one in which it was shifted two residues farther than the EK cleavage site, were not cleaved. In addition, alpha6A mutants with an alpha5-like cleavage site, i.e. arginine, lysine and histidine residues at positions -1, -2 and -6, were not cleaved. Thus both an intact RKKR sequence and its proper position are essential. After activation by the anti-beta1 stimulatory monoclonal antibody TS2/16, both cleaved and uncleaved alpha6Abeta1 integrins bound to laminin-1. The phorbol ester PMA, which activates cleaved wild-type and mutant alpha6Abeta1, did not activate uncleaved alpha6Abeta1. Thus uncleaved alpha6Abeta1 is capable of ligand binding, but not of inside-out signalling. Our results suggest that cleavage of alpha6 is required to generate a proper conformation that enables the affinity modulation of the alpha6Abeta1 receptor by PMA.

Health impact of peptic ulcer in the United States

OBJECTIVES

To assess the general outcome and impact of current and previous peptic ulcer disease on health status in the United States.

METHODS

During the National Health Interview Survey of 1989, a special questionnaire on digestive diseases was administered to 41,457 randomly selected individuals. Various measures of impaired health in ulcer patients were expressed by their age- and sex-standardized prevalence rates.

RESULTS

Ten to 15% of all subjects with a recent ulcer reported that they had been in poor health, incapable of major activity, or unable to work for some time during the 12 months preceding the interview. Twenty to 25% of the subjects with recent ulcers complained about restricted activity and had spent 7 or more days per year in bed. About 40% of all ulcer subjects had seen a physician five or more times within 12 months before the interview. These percentages were significantly lower in patients with previous ulcer histories but no active ulcer within 12 months, but they were still significantly higher than in subjects with no ulcer history at all. In the United States, expenditures attributed to recent ulcers amounted to $5.65 billion per year.

CONCLUSIONS

In the United States, peptic ulcer disease is associated with major morbidity. Ulcer cure would result in large economic and medical savings.

The A and B variants of the alpha 3 integrin subunit: tissue distribution and functional characterization

The alpha subunits of the laminin-binding integrins alpha 3 beta 1, alpha 6 beta 1, and alpha 7 beta 1 have homologous sequences and are similar in structure. Two cytoplasmic variants, A and B, have been identified for each of these alpha subunits, although the alpha 3B splice variant has been detected only at the mRNA level. We prepared a panel of mouse monoclonal antibodies specific for the A and B variants of the alpha 3 subunit to study their tissue distribution. Four monoclonal antibodies react with alpha 3A, one of which recognizes only the nonphosphorylated form; of the three anti-alpha 3B antibodies, one cross-reacts with alpha 6B. Reverse transcriptase-PCR analysis of various human tissues revealed the presence of alpha 3B mRNA in brain, heart, and skeletal muscle. Moreover, the alpha 3B protein was detected by immunoblotting in brain and heart tissue but not in skeletal muscle. In contrast, alpha 3A mRNA and protein were present in all tissues studied. Thus, the expression of alpha 3B in adult tissues is more restricted than that of alpha 3A. Immunohistochemical studies showed that in brain tissue, both variants are exclusively expressed on small blood-vessel endothelium, whereas in heart tissue their distribution patterns differ markedly. Although alpha 3A is strongly expressed on vascular smooth muscle cells, alpha 3B is detected only on endothelial cells of veins. Expression of the two variant forms of alpha 3 in K562 cells revealed that the ligand-binding specificities of alpha 3A beta 1 and alpha 3B beta 1 are identical: both bind human laminin-2 and -4, laminin-5, and laminins isolated from bovine kidney, but not bovine laminin-2 and -4, mouse laminin-1, or human fibronectin. In addition, adhesion mediated by both integrins is induced to the same extent by phorbol 12-myristate 13-acetate. The alpha 3A, but not the alpha 3B subunit, is phosphorylated; and phosphorylation of alpha 3A increases after phorbol 12-myristate 13-acetate stimulation. Thus, we found no differences between the adhesion functions of the A and B variants of alpha 3.

Integrin alpha 6 beta 4 forms a complex with the cytoskeletal protein HD1 and induces its redistribution in transfected COS-7 cells

The integrin alpha 6 beta 4 is a major component of hemidesmosomes, in which it is linked to intermediate filaments. Its presence in these structures is dependent on the beta 4 cytoplasmic domain but it is not known whether beta 4 interacts directly with keratin filaments or by interaction with other proteins. In this study, we have investigated the interaction of GST-cyto beta 4A fusion proteins with cellular proteins and demonstrate that a fragment of beta 4A, consisting of the two pairs of fibronectin type III repeats, separated by the connecting segment, forms a specific complex containing a 500-kDa protein that comigrates with HD1, a hemidesmosomal plaque protein. A similar protein was also bound by a glutathione S-transferase fusion protein containing the cytoplasmic domain of a variant beta 4 subunit (beta 4B), in which a stretch of 53 amino acids is inserted in the connecting segment. Subsequent immunoblot analysis revealed that the 500-kDa protein is in fact HD1. In COS-7 cells, which do not express alpha 6 beta 4 or the hemidesmosomal components BP230 and BP180, HD1 is associated with the cytoskeleton, but after transfecting the cells with cDNAs for human alpha 6 and beta 4, it was, instead, colocalized with alpha 6 beta 4 at the basal side of the cells. The organization of the vimentin, keratin, actin, and tubulin cytoskeletal networks was not affected by the expression of alpha 6 beta 4 in COS-7 cells. The localization of HD1 at the basal side of the cells depends on the same region of beta 4 that forms a complex containing HD1 in vitro, since the expression of alpha 6 with a mutant beta 4 subunit that lacks the four fibronectin type III repeats and the connecting segment did not alter the distribution of HD1. The results indicate that for association of alpha 6 beta 4 with HD1, the cytoplasmic domain of beta 4 is essential. We suggest that this association may be crucial for hemidesmosome assembly.

Economic analysis of dyspepsia

A variety of organic and non-organic diseases can present with symptoms of dyspepsia or upper abdominal pain, and a large diagnostic and therapeutic armamentarium is available to manage symptoms of dyspepsia. How extensively should a diagnostic search be conducted; and where does the best path run through the maze of potential combinations of tests and therapies? Physicians have hoped that economic and medical decision analyses would help them to find the most cost-effective and most efficacious means to deal with dyspepsia. Because of the large variety of potential diagnoses, diagnostic procedures and therapeutic means, however, it is very doubtful that a single most effective or least expensive strategy can ever be developed to apply to every patient with dyspepsia. Following the lines of common medical sense is probably more cost-effective than observing a rigid regimen derived from an economical analysis.

The localization of bullous pemphigoid antigen 180 (BP180) in hemidesmosomes is mediated by its cytoplasmic domain and seems to be regulated by the beta4 integrin subunit

Bullous pemphigoid antigen 180 (BP180) is a component of hemidesmosomes, i.e., cell-substrate adhesion complexes. To determine the function of specific sequences of BP180 to its incorporation in hemidesmosomes, we have transfected 804G cells with cDNA-constructs encoding wild-type and deletion mutant forms of human BP180. The results show that the cytoplasmic domain of BP180 contains sufficient information for the recruitment of the protein into hemidesmosomes because removal of the extracellular and transmembrane domains does not abolish targeting. Expression of chimeric proteins, which consist of the membrane targeting sequence of K-Ras fused to the cytoplasmic domain of BP180 with increasing internal deletions or lacking the NH2 terminus, indicates that the localization of BP180 in hemidesmosomes is mediated by a segment that spans 265 amino acids. This segment comprises two important regions located within the central part and at the NH2 terminus of the cytoplasmic domain of BP180. To investigate the effect of the alpha6beta4 integrin on the subcellular distribution of BP180, we have transfected COS-7 cells, which lack alpha6beta4 and BP180, with cDNAs for BP180 as well as for human alpha6A and beta4. We provide evidence that a mutant form of BP180 lacking the collagenous extracellular domain as well as a chimeric protein, which contains the entire cytoplasmic domain of BP180, are colocalized with alpha6beta4. In contrast, when cells were transfected with cDNAs for alpha6A and mutant forms of beta4, either lacking the cytoplasmic COOH-terminal half or carrying phenylalanine substitutions in the tyrosine activation motif of the cytoplasmic domain, the recombinant BP180 molecules were mostly not colocalized with alpha6beta4, but remained diffusely distributed at the cell surface. Moreover, in cells transfected with cDNAs for alpha6A and a beta4/beta1 chimera, in which the cytoplasmic domain of beta4 was replaced by that of the beta1 integrin subunit, BP180 was not colocalized with the alpha6beta4/beta1 chimera in focal adhesions, but remained again diffusely distributed. These results indicate that sequences within the cytoplasmic domain of beta4 determine the subcellular distribution of BP180.

Relation between gastric cancer and previous peptic ulcer disease

BACKGROUND

It is presently not well understood to what extent peptic ulcer and gastric cancer represent related diseases.

AIMS

The objective of this study was to assess past occurrence of gastric and duodenal ulcers in patients with cancer of the gastric cardia or other parts of the stomach.

METHODS

The association between peptic ulcer and gastric cancer was studied among patients followed up at hospitals of the US Department of Veterans Affairs. Two populations of 1069 subjects with cancer of the cardia and 3078 subjects with cancer of other parts of the stomach were compared with a control population of 89082 subjects without gastric cancer. In multivariate logistic regressions, presence or absence of cancer served as the outcome variable, while age, sex, race, previous histories of gastric ulcer, duodenal ulcer, peptic ulcer site unspecified, gastric resection, or vagotomy served as modifier variables.

RESULTS

Old age, non-white ethnicity, and male sex proved strong and independent risk factors for non-cardiac gastric cancer. A previous history of gastric, but not duodenal ulcer was associated with a significantly raised odd ratio of 1.53 (95% confidence interval: 1.24 to 1.87). Cancer of the cardia affected predominantly whites, and was relatively more common in men than non-cardiac gastric cancer. Past gastric ulcers exerted no significant influence (1.02, 0.67 to 1.56), while duodenal ulcers and peptic ulcer site unspecified were protective (duodenal ulcer: 0.68, 0.47 to 0.95; peptic ulcer disease: 0.66, 0.47 to 1.00). Partial gastrectomy was a risk factor for non-cardiac gastric cancer (1.86, 1.32 to 2.63), but not for cancer of the cardia (1.09, 0.54 to 2.20).

CONCLUSION

These epidemiological patterns might stem from underlying differences in the influences of gastritis and acid secretion on the development of the two cancer types.

The subcellular distribution of the high molecular mass protein, HD1, is determined by the cytoplasmic domain of the integrin beta 4 subunit

The high molecular mass protein, HD1, is a structural protein present in hemidesmosomes as well as in distinct adhesion structures termed type II hemidesmosomes. We have studied the distribution and expression of HD1 in the GD25 cells, derived from murine embryonal stem cells deficient for the beta 1 integrin subunit. We report here that these cells possess HD1 but not BP230 or BP180; two other hemidesmosomal constituents, and express only traces of the alpha 6 beta 4 integrin. By immunofluorescence and interference reflection microscopy HD1 was found together with vinculin at the end of actin filaments in focal contacts. In OVCAR-4 cells, derived from a human ovarian carcinoma which, like GD25 cells, only weakly express alpha 6 beta 4, HD1 was also localized in focal contacts. Upon transfection of both GD25 and OVCAR-4 cells with cDNA for the human beta 4 subunit the subcellular distribution of HD1 changed significantly. HD1 is then no longer present in focal contacts but in other structures at cell-substrate contacts, colocalized with alpha 6 beta 4. These junctional complexes are probably the equivalent of the type II hemidesmosomes. Transfection of GD25 cells with beta 1 cDNA did not affect the distribution of HD1, which indicates that the localization of HD1 in focal contacts was not due to the absence of beta 1. Moreover, in GD25 cells transfected with cDNA encoding a beta 4/beta 1 chimera, in which the cytoplasmic domain of beta 4 was replaced by that of beta 1, the distribution of HD1 was unaffected. Our findings indicate that the cytoplasmic domain of beta 4 determines the subcellular distribution of HD1 and emphasize the important role of alpha 6 beta 4 in the assembly of hemidesmosomes and other junctional adhesive complexes containing HD1.

Economic aspects of endoscopic screening for intestinal precancerous conditions

The relationship of costs to effectiveness in endoscopic screening depends on the incidence rate of cancers arising from precancerous lesions, the sensitivity and specificity rates of endoscopic screening, and the effectiveness of timely diagnosis and surgery in preventing death. Because all these parameters, which enter a medical decision analysis, have a relatively large margin of error, it is not possible to resolve the issue whether a screening should be performed based on economic analyses alone. A crude "back of the envelope" comparison of different screening programs suggests that colonoscopy in ulcerative colitis would result in the highest yield and gastroscopy of the gastric stump in the lowest yield.

Association of esophagitis and esophageal strictures with diseases treated with nonsteroidal anti-inflammatory drugs

BACKGROUND

It has been speculated that intake of nonsteroidal anti-inflammatory drugs (NSAIDs) represents a risk factor for the occurrence of esophagitis and esophageal strictures.

METHODS

A case-control study was conducted to compare the occurrence of comorbid diseases treated with NSAIDs in case and control subjects with and without esophageal disease, respectively. The case population was comprised of all patients with esophagitis (International Classification of Diseases code 530.1) or esophageal stricture (code 530.3) who were discharged from hospitals of the Department of Veteran Affairs between 1981 and 1994. In separate multivariate logistic regressions, the occurrence of esophagitis or esophageal stricture served as the outcome variable, and age, gender, ethnicity, and comorbid occurrence of an NSAID-related diagnosis served as modifier variables.

RESULTS

A total of 101,366 individual case subjects were included, of whom 92,860 presented with esophagitis and 14,201 with stricture. The occurrence of erosive esophagitis was associated with osteoarthritis (odds ratio = 1.42, 95% confidence interval = 1.36-1.48), osteoporosis (1.38, 1.25-1.52), back pain (1.49, 1.42-1.56), femur bone fracture (1.46, 0.92-2.32), fibrositis (1.57, 1.41-1.75), tension headache (1.34, 1.27-1.40), ankylosing spondylitis (1.33, 1.24-1.42), rheumatoid arthritis (1.13, 1.05-1.21), sicca syndrome (1.15, 1.05-1.26), and systemic sclerosis (6.16, 4.65-8.14). NSAID-related diagnoses represented similar risk factors for both esophagitis and esophageal stricture.

CONCLUSIONS

A large variety of diseases treated by NSAIDs are associated with a significantly increased risk of esophageal erosion or stricture; the risk appears similar for both of these. In some comorbid conditions, the underlying disease process may contribute to the occurrence of esophageal pathology.

Colorectal cancer after gastric surgery: a meta-analysis

BACKGROUND

Until now, the question of whether previous gastric surgery results in an increased risk of colorectal cancer has remained controversial. A meta-analysis was performed to resolve this issue.

METHODS

The numbers of colorectal tumors in the two populations with and without gastric surgery were retrieved from all relevant articles found through a MEDLINE search. If available, the most detailed breakdown of the data by patient gender, type of peptic ulcer, type of surgery, time since gastric surgery, and by tumor location was chosen. The Mantel-Haenszel procedure was used to calculate a weighted odds ratio from the individual studies. The method of DerSimonian and Laird was used to calculate a weighted average of the difference between tumor rates in patients with and without gastric surgery.

RESULTS

The summary odds ratio was 1.09 with a 95% confidence interval of 0.96-1.24. The length of time after surgery, gender, tumor location, initial ulcer type, and different types of surgery were not associated with any significant influence. The summary rate difference was not significantly different from zero. The test for heterogeneity yielded a chi 2 = 26.87, df = 13, p = 0.013. After ignoring one obvious outlier study, the chi 2 test dropped to a nonsignificant level. A L'Abbé plot failed to show any prevailing influence of rate size on the overall heterogeneity among the various studies.

CONCLUSIONS

Surgery for peptic ulcer does not result in an increased risk for colorectal tumors. This lack of influence was shown consistently by all tests of the present meta-analysis.

Distribution of laminin variants and their integrin receptors in human secondary lymphoid tissue. Colocalization suggests that the alpha 6 beta 4-integrin is a receptor for laminin-5 in lymphoid follicles

Laminins are a family of multifunctional basement membrane glycoproteins. Over the last years, many laminin isoforms have been characterized, which were shown to be composed of distinct combinations of variant alpha, beta and gamma chains. Some of these isoforms show remarkable tissue specificity, which suggests functional involvement in local processes. In this study the previously described mAb 4C7, which recognize epithelial basement membranes as well as endothelial basement membranes in lymphoid follicles, was identified as an anti-laminin-5 antibody. Using a set of mAbs against various variant laminin chains we established that specifically the gamma 2 chain of laminin-5 was confined to the endothelial basement membranes of vessels in lymphoid follicles, whereas other variant laminin chains were also expressed elsewhere in the lymphoid follicles, whereas other variant laminin chains were also expressed elsewhere in the lymphoid tissue. Additionally, the expression of the known integrin receptors of laminin-5 was also examined. The alpha 6 beta 4 integrin-receptor for laminin was found to be colocalized with the laminin-5 gamma 2 chain on the abluminal surface of endothelial cells, whereas the alpha 3 integrin chain could not be detected in lymphoid follicles. This finding suggests that the alpha 6 beta 4 integrin (and not the alpha 3 beta 1 integrin) serves as a laminin-5 receptor on endothelial cells in the follicular compartment of lymphoid tissue. Furthermore, alpha 6 beta 4 was also found in the same punctuated pattern on FDCs as laminin-5. The function of the laminin-alpha 6 beta 4 complex in this particular localisation is still obscure, but a role in the maintainance of the follicular compartment via hemidesmosome-like attachment sites is postulated.

The role of the cytoplasmic domain of alpha 6 integrin in the assembly and function of alpha 6 beta 1 and alpha 6 beta 4

We have studied the role of the cytoplasmic domain of alpha 6 in the assembly and function of the alpha 6 beta 4 integrin, and compared it with the role of alpha 6 in the assembly and function of alpha 6 beta 1, by transfection of cDNAs encoding cytoplasmic mutants of alpha 6 into K562 cells with or without full-length beta 4 cDNA. Des-(1022-1050)-alpha 6, which contains a deletion C-terminal to the GFFKR motif, was expressed in association with beta 1, but associated preferentially with beta 4, whereas the wild-type alpha 6 subunit associated efficiently with beta 1 and beta 4. Des-(1016-1050)-alpha 6, which lacked also the GFFKR sequence, was only expressed at the cell surface when beta 4 was available. Transient expression in COS-7 cells showed that des-(1016-1050)-alpha 6 was retained in the endoplasmic reticulum as a monomer, which suggests that truncation of the cytoplasmic domain reduces the affinity of alpha 6 for beta 1, particularly when the GFFKR sequence is absent. Although the GFFKR motif is not essential for association of alpha 6 with beta 4, it increases the stability of the alpha 6 beta 4 integrin. The cytoplasmic domain of alpha 6 is essential for inside-out and outside-in signaling via the alpha 6 beta 1 receptor, but not for adhesion via alpha 6 beta 4. We show that alpha 6 beta 4 is a constitutively active receptor. Thus, unlike adhesion by most other integrins, adhesion by alpha 6 beta 4 does not seem to depend on any active cellular process. Binding of alpha 6 beta 4 to ligand was only slightly affected by truncation of the alpha 6 cytoplasmic domain N-terminal to the GFFKR sequence and became partially dependent on metabolic energy. These data indicate that truncations of the cytoplasmic domain of the alpha 6 subunit affect the assembly and function of alpha 6 beta 1 more strongly than those of alpha 6 beta 4. This difference may be due to the greater affinity of alpha 6 for beta 4 than for beta 1, which makes alpha 6 beta 4 less susceptible to the effect of truncations.

Comorbid occurrence of cholelithiasis and gastrointestinal cancer

OBJECTIVE

To test whether gallstone disease represents a general risk factor for gastrointestinal cancer.

METHODS

The comorbid occurrences of cholelithiasis or choledocholithiasis with cancers of the biliary tract, pancreas, small and large intestine were analysed in a population of 3.41 million military veterans who were discharged from VA hospitals distributed throughout the USA between 1981 and 1993. Comorbidity was calculated as the ratio between the observed and expected number of hospitalized veterans with cholelithiasis plus cancer. A 95% confidence interval was calculated based on the Poisson distribution of the observed number of patients with comorbidity.

RESULTS

In cholelithiasis, the ratio of comorbid occurrence with biliary cancer was 4.59 (4.06-5.31). In choledocholithiasis, the ratio of comorbid occurrence with biliary cancer was 9.31 (7.20-11.84) and with pancreatic cancer 4.34 (3.80-4.94). These ratios remained significant when the analyses were confined to cholelithiasis or choledocholithiasis documented before the first diagnosis of cancer. The ratios of the comorbid occurrences between cholelithiasis and cancers of the small or large intestine were only significant when total comorbid occurrences were analysed, but vanished in the analysis restricted to cholelithiasis or choledocholithiasis documented before the first diagnosis of cancer.

CONCLUSION

The occurrence of gallstones represents a risk factor for pancreaticobiliary cancer, but not cancers involving other parts of the gastrointestinal tract. This association appears particularly strong in patients with choledocholithiasis.

Hemidesmosomes: roles in adhesion, signaling and human diseases

Our understanding of the role of hemidesmosomes in cell-substratum adhesion has greatly improved both as a result of targeted gene mutation experiments and by means of observations of several blistering disorders of the skin in which the absence or defects of hemidesmosomal proteins have been demonstrated. Functionally important domains within the proteins that constitute hemidesmosomes have recently been identified by transfection and mutagenesis studies. These multiprotein complexes appear not only to mediate cell adhesion, but also to transduce signals from the extracellular matrix to the cell interior that may profoundly modulate cell behavior.

Cost-benefit analysis of testing for Helicobacter pylori in dyspeptic subjects

OBJECTIVES

It has remained controversial how to manage patients who present with symptoms of dyspepsia. Should all dyspeptic patients undergo a radiological or endoscopic procedure to diagnose peptic ulcer, or would a serological test for Helicobacter pylori provide sufficient evidence to start all H. pylori-positive patients on empirical antibiotic therapy?

METHODS

The outcome of serological testing for H. pylori in dyspepsia is analyzed using a decision tree. Successful eradication is associated with the potential benefits of healing dyspepsia and preventing peptic ulcer or gastric cancer. In a sensitivity analysis, all of the transition rates and benefits are varied over a wide range to test the robustness of the calculated decision outcomes.

RESULTS

The cost-benefit relationship of serological screening for H. pylori in dyspeptic patients is influenced primarily by the response rate of nonulcer dyspepsia to H. pylori eradication and secondly by the monetary benefit of ulcer prevention and the prevalence rate of peptic ulcer in H. pylori-positive patients. A response to H. pylori eradication in 5-10% of all patients with nonulcer dyspepsia would make screening and treatment for H. pylori a beneficial option, irrespective of any other potential benefits. If ulcer prevention were associated with long term benefit of $4000 or more and if the ulcer prevalence rate exceeded 10% of all dyspeptic patients, serological screening for H. pylori would also pay off.

CONCLUSIONS

As long as no unequivocal evidence exists that nonulcer dyspepsia responds to eradication of H. pylori, treating all dyspeptic patients who test positive for H. pylori cannot be recommended. At the present time, antibiotic therapy should be reserved to patients with proven ulcer or to patients with nonulcer dyspepsia for whom other measures have failed.

Epithelial detachment due to absence of hemidesmosomes in integrin beta 4 null mice

Integrins are heterodimeric transmembrane glycoproteins which are engaged in a variety of cellular functions, such as adhesion, migration and differentiation1. The integrin alpha 6 beta 4 is expressed on squamous epithelia, on subsets of endothelial cells, immature thymocytes and on Schwann cells and fibroblasts in the peripheral nervous system. In stratified epithelia, alpha 6 beta 4 is concentrated in specialised adhesion structures, called hemidesmosomes, which are implicated in the stable attachment of the basal cells to the underlying basement membrane by connecting the intermediate filaments with the extracellular matrix. The nature of the interactions between the various hemidesmosomal proteins, that lead to the formation of hemidesmosome is poorly understood. To study the contribution of the integrin alpha 6 beta 4 in hemidesmosome formation and their anchoring properties, we inactivated the beta 4 gene in mice by targeted gene disruption. Homozygous beta 4 null mice died shortly after birth and displayed extensive detachment of the epidermis and other squamous epithelia. The dramatically reduced adhesive properties of the skin was accompanied by the absence of hemidesmosomes at the basal surface of keratinocytes. No evidence was found for impaired T-cell development, nor for defects in myelination in the peripheral nervous system.

Deficiency of the integrin beta 4 subunit in junctional epidermolysis bullosa with pyloric atresia: consequences for hemidesmosome formation and adhesion properties

Junctional epidermolysis bullosa (JEB) comprises a group of inherited autosomal recessive blistering disorders characterized by dermo-epidermal separation through the lamina lucida of the basement membrane. We identified a patient with JEB associated with pyloric atresia (PA), in whom the integrin beta 4 subunit was completely absent. At the ultrastructural level, the hemidesmosomes were reduced in number, appeared rudimentary and lacked a subbasal dense plate and frequently an inner attachment plaque. However, keratin filaments were still anchored to the cytoplasmic plaque of the hemidesmosome. Immunofluorescence analysis showed that the beta 4 subunit was absent in the skin of the PA-JEB patient, whereas the alpha 6 subunit appeared to be normally distributed along the basement membrane zone, as were the other hemidesmosomal components BP230, BP180 and HD1. Furthermore, the alpha 3 and beta 1 subunits were not only detected at the lateral membranes of basal cells in PA-JEB skin, as in normal skin, but also along the basement membrane zone. The few hemidesmosome-like structures found in cultured keratinocytes from the PA-JEB patient contained the hemidesmosomal components BP230, BP180 and HD1, but not the integrin alpha 6 subunit. Like alpha 3, this subunit was colocalized with vinculin in focal contacts at the ends of actin stress fibers. Immunoprecipitation analysis revealed that alpha 6 was associated with beta 1 on PA-JEB keratinocytes, whereas normal human keratinocytes (NHKs) exclusively express alpha 6 beta 4 on their cell surface. The initial adhesion of PA-JEB and normal keratinocytes to laminin-1 and laminin-5, both ligands for alpha 6 beta 1 and alpha 6 beta 4, was similar. In migration assays, the PA-JEB keratinocytes were more motile on laminin-5 than normal keratinocytes. Our observations indicate that the integrin alpha 6 beta 4 plays a crucial role in the proper assembly of hemidesmosomes and in the stabilization of the dermal-epidermal junction. The fragility of the skin and the blistering in this patient appear to have been due to the deficiency of the integrin beta 4 subunit, which results in the formation of too few and structurally abnormal hemidesmosomes.

Genomic organization of the mouse beta 1 gene: conservation of the beta 1D but not of the beta 1B and beta 1C integrin splice variants

We have determined the genomic organization of the 3'-region of the murine beta 1 gene and cloned the murine beta 1D integrin splice variant. Overlapping genomic clones encompassing the region of the beta 1D-specific exons were isolated from a phage lambda FIXII library, mapped and partially sequenced. All of the exon-intron junctions identified in the murine beta 1 gene fit with the consensus splice donor and acceptor sequences and occur at the same positions as in their human counterparts. cDNA clones for the beta 1D integrin were isolated from a murine skeletal muscle library. The human and murine beta 1D sequences are conserved at the nucleotide (93%) and amino acid (100%) level, suggesting an important role of this muscle-specific variant throughout mammalian phylogenesis. In contrast, murine sequences for beta 1B are very different from human beta 1B at both the nucleotide as well as amino acid level. Moreover, no specific polyadenylation signal for the beta 1B variant could be identified in genomic clones, suggesting that this variant is not present in the mouse. Finally, we were not able to identify a murine beta 1C splice variant by sequencing analysis, Southern hybridization techniques or polymerase chain reaction of mRNA from platelets. These findings indicate that the beta 1B and beta 1C variants emerged relatively late in the phylogenesis of the beta 1 integrin family.

Cleavage of the alpha6A subunit is essential for activation of the alpha6Abeta1 integrin by phorbol 12-myristate 13-acetate

The alpha6 integrin subunit is proteolytically cleaved during biosynthesis in a covalently associated heavy and light chain. To examine the importance of cleavage for the function of the alpha6 subunit, we introduced mutations in the cDNA encoding the RKKR (876-879) sequence, the presumed cleavage site, in which either one or two basic residues were replaced by glycine. Wild-type and mutant alpha6A cDNAs (alpha6GKKR, alpha6RKKG and alpha6RGGR) were transfected into K562 cells. The mutant alpha6A integrin subunits were expressed in association with endogenous beta1, at levels comparable to that of the wild-type alpha6Abeta1. A single alpha6A polypeptide chain (150 kDa) was precipitated from surface-labeled alpha6GKKR, alpha6RKKG, and alpha6-RGGR transfectants, while the separate heavy (120 kDa) and light chains (31 or 30 kDa) were precipitated from the wild-type alpha6RKKR transfectant. Thus, a change in the RKKR sequence prevents cleavage of alpha6. After activation by the anti-beta1 stimulatory mAb TS2/16 both cleaved and uncleaved alpha6Abeta1 integrins bound and spread on laminin-1. Remarkably, the phorbol ester phorbol 12-myristate 13-acetate, which activates wild-type alpha6Abeta1 to bind to laminin-1, did not activate uncleaved alpha6Abeta1. We conclude that uncleaved alpha6Abeta1 is capable of ligand binding and transducing outside/in signals, like wild-type alpha6A-beta1. However, inside/out signaling is affected. It appears that cleavage of alpha6 is required to generate the proper conformation in alpha6 that enables affinity modulation of the alpha6A-beta1 receptor by phorbol 12-myristate 13-acetate.

Generalized atrophic benign epidermolysis bullosa. Either 180-kd bullous pemphigoid antigen or laminin-5 deficiency

BACKGROUND

Generalized atrophic benign epidermolysis bullosa (GABEB) is a form of nonlethal junctional epidermolysis bullosa, clinically characterized by generalized blistering after birth, atrophic healing, and incomplete universal atrophic alopecia with onset in childhood. Recently, we discovered a deficiency of the 180-kd bullous pemphigoid antigen (BP180) and a reduced amount of BP180 messenger RNA in three patients with GABEB. It is not yet clear, however, whether GABEB is invariably caused by BP180 deficiency.

RESULTS

We examined 18 patients with nonlethal junctional epidermolysis bullosa from unrelated families; nine of these individuals presented with the clinical characteristics of GABEB. Specimens of clinically normal skin obtained from the patients were stained by immunofluorescence with monoclonal antibodies to BP180 and laminin-5. The BP180 epitopes were not expressed in eight patients, all of whom were sharing the typical clinical features of GABEB. In one of the nine patients with GABEB, the BP180 level was sufficient, but the laminin-5 level was reduced. Among the nine patients with junctional epidermolysis bullosa without atrophic alopecia, laminin-5 level was not expressed in one patient, while in the other patients both antigens were normally expressed.

CONCLUSIONS

Not all patients with GABEB are deficient in BP180, since some individuals with GABEB only exhibit reduction of the laminin-5 expression. The BP180 deficiency in the skin invariably seems to result in GABEB. Immunofluorescence analysis using monoclonal antibodies against BP180 (and laminin-5) may allow early subtyping, which is of prognostic significance, in children born with junctional epidermolysis bullosa.

The prevalence of self-reported peptic ulcer in the United States

OBJECTIVES

The purpose of this study was to draw a current picture of the sociodemographic characteristics of peptic ulcer in the United States.

METHODS

During the National Health Interview Survey of 1989, a special questionnaire on digestive diseases was administered to 41,457 randomly selected individuals. Data were retrieved from public use tapes provided by the National Center for Health Statistics. Odds ratios were calculated by logistic regression after adjustment for sample weights in the survey.

RESULTS

Of adult US residents, 10% reported having physician-diagnosed ulcer disease, and one third of these individuals reported having an ulcer in the past year. Old age, short education, low family income, being a veteran, and smoking acted as significant and independent risk factors. Gastric and duodenal ulcer occurred in both sexes equally often. Duodenal ulcer was more common in Whites than non-Whites, while gastric ulcer was more common in non-Whites.

CONCLUSIONS

The age-related rise and socioeconomic gradients of peptic ulcer represent the historic scars of previous infection rates with Helicobacter pylori. The racial variations reflect different ages at the time of first infection; younger and older age at the acquisition of H. pylori appear to be associated with gastric and duodenal ulcer, respectively.

Risk factors of colorectal cancer in inflammatory bowel disease

BACKGROUND

It is unknown whether colorectal cancer (CRC) in patients with inflammatory bowel disease (IBD) behaves differently from regular CRC in patients without IBD. A case-control study was conducted to compare CRC in patients with and without underlying IBD.

METHODS

The Department of Veterans Affairs (VA) maintains a computerized file of all hospital discharges among U.S. military veterans since 1970. This file accrues the data of 1 million hospital discharges per year. All patients with IBD and all patients with CRC who had been discharged from a VA hospital between 1981 and 1993 were selected. The influence of various risk factors on the occurrence of CRC in IBD and its mortality in patients with and without IBD was tested by logistical regression analyses.

RESULTS

Of the 11,446 subjects with IBD, 371 had colon cancer. CRC was diagnosed in 52,243 subjects without IBD. CRC patients with IBD were 7 yr younger than those without IBD, but in patients with Crohn's disease, more cancers were located in the proximal colon (chi 2 = 18.10, df = 5, p = 0.003). The occurrence of CRC in IBD was influenced by the following risk factors: age [odds ratio (OR) = 1.45, 95% confidence interval (CI) = 1.35-1.57], sclerosing cholangitis (OR) = 3.41, CI = 2.03-5.73), and history of a disease associated with consumption of nonsteroidal anti-inflammatory drugs (NSAID) (OR = 0.84, CI = 0.65-1.09). Sex, race, and type of IBD did not exert a significant influence on the development of cancer. Cancer-related mortality was influenced by the following risk factors: age (OR = 1.16, CI = 1.14-1.18), male gender (OR = 1.23, CI = 1.06-1.44), white race (OR) = 0.97, CI = 0.96-0.99), and history of NSAID consumption (OR = 0.68, CI = 0.65-0.72). Presence of IBD was not associated with a significant influence on CRC mortality (OR = 1.00, CI = 0.70-1.43).

CONCLUSIONS

CRC affects IBD patients at a younger age and is characterized by a more proximal localization when compared with CRC of non-IBD patients. NSAID exert a protective influence against CRC in patients with IBD similarly as in patients without IBD. Sclerosing cholangitis is associated with a strong risk of developing colon cancer in patients with IBD.

Prevention of colorectal cancer by flexible endoscopy and polypectomy. A case-control study of 32,702 veterans

OBJECTIVE

To determine whether patients with colorectal cancer are less likely than unaffected controls to have had one or more endoscopic procedures (flexible sigmoidoscopy, colonoscopy, or polypectomy) before being diagnosed with cancer.

DESIGN

Case-control study.

SETTING

Hospitals of the Department of Veterans Affairs.

PATIENTS

8722 and 7629 case-patients with colon and rectal cancer, respectively, and age-, sex-, race-matched controls who were discharged at the same time as the corresponding case-patients.

MEASUREMENTS

Number and type of endoscopic procedures of the large bowel done from 1981 until the development of colorectal cancer in each case-patient. The influence of endoscopic procedures on the development of colorectal cancer was tested by conditional multiple logistic regression analysis.

RESULTS

Compared with controls, patients with colorectal cancer were less likely to have had an endoscopic procedure of the large bowel before being diagnosed with cancer (odds ratio for colon cancer, 0.51 [95% CI, 0.44 to 0.58]; odds ratio for rectal cancer, 0.55 [CI, 0.47 to 0.64]). In patients who had flexible sigmoidoscopy, colonoscopy, and polypectomy, the odds ratios were even smaller. When analyzed by separate 1-year intervals, patients with cancer had significantly fewer procedures during periods of up to 6 years before their onset of their cancer. Similarly, fewer inpatient and outpatient procedures were done in patients than in controls.

CONCLUSIONS

Endoscopic procedures of the large bowel reduce the risk for developing colon and rectal cancer by 50%, their protective influence lasting 6 years.

Expression patterns of laminin receptor splice variants alpha 6A beta 1 and alpha 6B beta 1 suggest different roles in mouse development

The alpha 6 beta 1 integrin is a receptor for laminins and is present from early stages of mouse embryogenesis. In the present study we determined the temporal and spatial expression of the two cytoplasmic splice variants of the alpha 6 integrin subunit, alpha 6A and alpha 6B, in the early- and mid-gestation mouse postimplantation embryo using RT-PCR, in situ hybridization, and immunofluorescence. Our results show that alpha 6B is present in the embryo at all stages studied and is expressed before alpha 6A. alpha 6A expression begins in 8.5 day p.c. embryos and is initially exclusively localized to the developing heart. In 8.5 (and 9.5) day p.c. embryos alpha 6A mRNA and protein are present in a gradient in the myocardium of the heart tube from strongest expression in the sinus venosus and in the common atrial chamber to a weakening expression along the ventricle and bulbus cordis. In 10.5 day p.c. embryos this gradient is less evident and in 12.5 day p.c. embryos alpha 6A mRNA and protein are present in comparable amounts between atria and ventricles. Neither alpha 6A nor alpha 6B is present in endocardial cushion tissue. By day 12.5 p.c. alpha 6A expression is also present in the developing epidermis, dental primordia, lens, gonads, and in a few epithelia such as those of the digestive tract. alpha 6B expression is always much more widespread than alpha 6A expression. For example, only alpha 6B is present in the myotome of the somites of 9.5 day p.c. embryos, in the developing central and peripheral nervous systems, and in the nephrogenic system at all stages studied, except after the differentiation of the gonads when alpha 6A is also present. Furthermore, alpha 6B is the only splice variant present on endothelial cells. We also examined the distribution of the beta 4 integrin subunit to determine whether the alpha 6 beta 4 integrin was present during these stages of development. Beta 4 protein was absent in early postimplantation stages but was present in the epidermis and digestive tract of 12.5 day p.c. embryos. These results show a differential distribution of alpha 6A and alpha 6B during mouse development and thus strongly suggest a different function of these splice variants during embryogenesis. Our results point to a possible role for the alpha 6A beta 1 integrin in the development of the myocardium of the developing heart, but not in the migration of endocardial cushion cells, while alpha 6B beta 1 could be important in the developing nephrogenic and nervous systems.

Distribution of extracellular and cytoplasmic domains of the alpha 3 and alpha 6 integrin subunits in solid tumors

Integrins play an important role in malignant transformation and the invasion of tumors. They mediate cell-cell and cell-matrix interactions and participate in transduction of signals across the plasma membrane, processes dependent on the extracellular and cytoplasmic domains of integrins. We studied a selection of solid tumors by immunohistochemistry using monoclonal antibodies (MAbs) against the extracellular domain and the cytoplasmic variants (A and B) of the alpha 3 and alpha 6 integrin subunits. The tissue-specific expression of ecto- and cyto-domains of alpha 3 and alpha 6 is maintained in a subset of breast, colon, kidney and parotid tumors. In a few breast tumors, there was a switch in variant expression in that alpha 6B was detected instead of alpha 6A in normal breast tissue. In many colon and parotid tumors, one of the variants of alpha 6 was missing, while both were detectable in the corresponding normal tissues. In contrast, coexpression of the alpha 6 variants was found in some kidney tumors, whereas only one of the variants was detected in the normal tissue. In a minority of colon and kidney tumors, the cyto-domains of alpha 3 and alpha 6 were undetectable and total absence of alpha 3 and alpha 6 was noted in a subset of breast, colon, kidney and parotid tumors. These observations show that expression of the integrin variants in tumors varies considerably and support the concept that changes in expression may contribute to malignant behavior.

Protection by endoscopy against death from colorectal cancer. A case-control study among veterans

BACKGROUND

Although several clinical and epidemiologic studies suggest that timely diagnostic procedures of the large bowel may reduce mortality from colorectal cancer, the evidence for this relationship is primarily circumstantial.

METHODS

A case-control study was conducted among hospitalized US military veterans to investigate whether diagnostic procedures of the large bowel were performed in the period preceding the diagnosis of colorectal cancer less frequently in patients dying of colorectal cancer than in control patients. Data files of a total of 4411 veterans dying of colorectal cancer between 1988 and 1992 were extracted from the records of the US Department of Veterans Affairs, Washington, DC. Data of four living control patients and four dead control patients without colorectal cancer were matched by age, sex, and race to each case patient. The case and the two control populations were compared by conditional logistic regression, calculating odds ratios, and their 95% confidence interval.

RESULTS

Diagnostic procedures of the large bowel reduced mortality from colorectal cancer, the odds ratio being 0.41 (range, 0.33 to 0.50) for the comparison with living control patients. The protective effects of proctosigmoidoscopy, colonoscopy, and polypectomy lasted for 5 years. The procedures were protective against death from cancer of the colon, as well as cancer of the rectum. The most protective influence was associated with removal of tissue through biopsy, fulguration, and polypectomy. Similar influences were found comparing case patients with dead control patients.

CONCLUSION

Removal of tissue represents the most effective means to reduce mortality from cancers of the large bowel. It retains its efficacy over a time period of 5 years.