Benefit of Combination Ezetimibe/Simvastatin Among High-Risk Populations: Lessons from the IMPROVE-IT Trial

PURPOSE OF REVIEW

The Improved Reduction of Outcomes: Vytorin Efficacy International Trial (IMPROVE-IT) demonstrated the clinical benefit of the combination of ezetimibe-simvastatin compared to placebo-simvastatin following acute coronary syndrome (ACS). This review highlights key findings from this study with particular attention to the practice-changing impact on guidelines for low-density lipoprotein cholesterol (LDL-C) reduction after ACS, especially among high-risk populations.

RECENT FINDINGS

Consistent reductions in LDL-C have been reported with newer lipid-lowering therapies (proprotein convertase subtilisin/kexin type 9 inhibitors, cholesterol ester transfer proteins, bempedoic acid) in combination with statin in high-risk subgroups. Since high-risk subgroups remain a focus of guidelines, exploration of high-risk subgroups can help define the optimal use of new therapies. Ezetimibe reduced the LDL-C by 16.7 mg/dL compared to placebo at 1 year, resulting in a significant reduction in the primary composite endpoint (absolute risk difference 2.0%; relative risk difference 6.4%, hazard ratio, 0.936; 95% confidence interval, 0.89 to 0.99; P = 0.016). The benefits achieved with ezetimibe in both LDL-C reduction and the primary clinical composite across 10 pre-specified high-risk subgroups, including the elderly; women; patients with diabetes, prior coronary artery bypass graft, history of stroke, polyvascular disease, low baseline LDL-C, renal dysfunction, prior heart failure, and an elevated TIMI risk score for secondary prevention, were similar or greater than in the corresponding non-high-risk subgroups. Safety events were similar between ezetimibe and placebo across the high-risk subgroups. These data support the addition of ezetimibe to statin therapy in high-risk patients who require additional therapy to lower the LDL-C post-ACS.

Factors Associated With Left Atrial Remodeling in the General Population

BACKGROUND

Although contributors to remodeling of the left ventricle (LV) have been well studied in general population cohorts, few data are available describing factors influencing changes in left atrial (LA) structure.

METHODS AND RESULTS

Maximum LA volume was determined by cardiac magnetic resonance imaging among 748 participants in the Dallas Heart Study at 2 visits a mean of 8 years apart. Associations of changes in LA volume (ΔLAV) with traditional risk factors, biomarkers, LV geometry, and remodeling by cardiac magnetic resonance imaging and detailed measurements of global and regional adiposity (by magnetic resonance imaging and dual-energy x ray absorptiometry) were assessed using multivariable linear regression. Greater ΔLAV was independently associated with black and Hispanic race/ethnicity, change in systolic blood pressure, LV mass and ΔLV mass, N-terminal probrain natriuretic peptide and change in N-terminal probrain natriuretic peptide, and body mass index (P<0.05 for each). In subanalyses, the associations of ΔLAV with LV mass parameters were driven by associations with baseline and ΔLV end diastolic volume (P<0.0001 for each) and not wall thickness (P=0.21). Associations of ΔLAV with body mass index were explained exclusively by associations with visceral fat mass (P=0.002), with no association seen between ΔLAV and subcutaneous abdominal fat (P=0.47) or lower body fat (P=0.30).

CONCLUSIONS

Left atrial dilatation in the population is more common in black and Hispanic than in white individuals and is associated with parallel changes in the LV. LA dilatation may be mediated by blood pressure control and the development of visceral adiposity.

Chemoprevention of precancerous gastric lesions with antioxidant vitamin supplementation: a randomized trial in a high-risk population

BACKGROUND

Gastric cancer is one of the most common malignancies worldwide. Histopathologic studies have identified a sequence of changes in the gastric mucosa that mark the slow progression from normal tissue to carcinoma. Epidemiologic evidence suggests that a diet rich in fresh fruit and vegetables could be a protective factor against this disease. This effect may be mediated through antioxidant vitamins.

METHODS

A randomized, double-blind chemoprevention trial was conducted among 1980 subjects in Tachira State, Venezuela (whose population is at high risk for gastric cancer), to determine the effect of dietary supplementation with vitamin C, vitamin E, and beta-carotene on the progression and regression of precancerous gastric lesions. Subjects were randomly assigned to receive either a combination of vitamin C (750 mg/day), vitamin E (600 mg/day), and beta-carotene (18 mg/day) or placebo for 3 years. Changes in the gastric mucosa were determined by histologic diagnosis based on five biopsies taken from prespecified areas of the stomach at baseline and annually for 3 years. All biopsies were reviewed by a single expert pathologist. Progression rates (and regression rates) were calculated by comparing the first and last available gastroscopies for each subject and dividing the number of subjects whose diagnoses increased (decreased) in severity by the total follow-up time. Overall rate ratios were calculated by Poisson regression, controlling for baseline diagnosis. All statistical tests were two-sided.

RESULTS

Median plasma vitamin levels were increased in the treatment group between baseline and 1 year after randomization from 0.43 micromol/L (interquartile range [IQR] = 0.26-0.69) to 2.89 micromol/L (IQR = 1.76-4.22) for beta-carotene, from 26.7 micromol/L (IQR = 23.1-31.2) to 54.9 micromol/L (IQR = 42.8-67.6) for alpha-tocopherol, and from 47.70 micromol/L (IQR = 36.9-58.5) to 61.9 micromol/L (IQR = 52.2-72.7) for vitamin C. Overall progression rates per 100 person-years were 74.3 in the placebo group and 67.8 in the group randomly assigned to vitamins. Overall regression rates were 109.4 in the placebo group and 116.5 in the group randomly assigned to vitamins. There was no statistically significant difference in progression rate (rate ratio = 0.92, 95% confidence interval [CI] = 0.74 to 1.15) or regression rate (rate ratio = 1.09, 95% CI = 0.90 to 1.33) between vitamin and placebo groups.

CONCLUSION

Supplementation with antioxidant micronutrients is not an effective tool for gastric cancer control in this high-risk population. The results of this trial are consistent with previous findings on the lack of effect of nutritional supplementation on precancerous gastric lesions.

Is ‘virtual histology’ the next step after the ‘virtual autopsy’? Magnetic resonance microscopy in forensic medicine

AIM

The study aimed to validate magnetic resonance microscopy (MRM) studies of forensic tissue specimens (skin samples with electric injury patterns) against the results from routine histology.

METHODS AND RESULTS

Computed tomography and magnetic resonance imaging are fast becoming important tools in clinical and forensic pathology. This study is the first forensic application of MRM to the analysis of electric injury patterns in human skin. Three-dimensional high-resolution MRM images of fixed skin specimens provided a complete 3D view of the damaged tissues at the site of an electric injury as well as in neighboring tissues, consistent with histologic findings. The image intensity of the dermal layer in T2-weighted MRM images was reduced in the central zone due to carbonization or coagulation necrosis and increased in the intermediate zone because of dermal edema. A subjacent blood vessel with an intravascular occlusion supports the hypothesis that current traveled through the vascular system before arcing to ground.

CONCLUSION

High-resolution imaging offers a noninvasive alternative to conventional histology in forensic wound analysis and can be used to perform 3D virtual histology.

Environmental factors in Helicobacter pylori-related gastric precancerous lesions in Venezuela

Although Helicobacter pylori (HP) infection has been acknowledged to play an etiological role in gastric carcinogenesis, its relatively weak association particularly in developing countries suggests critical roles of cofactors. Among a population with an extremely high prevalence of HP infection ( approximately 95%) in Venezuela, we examined the relationship of household characteristics, smoking, alcohol drinking, dietary consumption, and plasma nutrient levels with the prevalence of three different stages of gastric precancerous lesions, chronic atrophic gastritis (AG; n = 337), intestinal metaplasia (IM; n = 551), and dysplasia (n = 157), in comparison with those without any of these lesions (n = 1154). Length of refrigerator use was marginally inversely associated with the prevalence of the precursor lesions studied. The association was most pronounced for AG followed by dysplasia. On the other hand, smoking status was a significant predictor for IM and dysplasia. Those smoking >/=>10 cigarettes/day had 1.8-fold risk of IM and 3.6-fold risk of dysplasia compared with never smokers. There were no associations with alcohol consumption. When six food groups known to be associated with stomach cancer risk in Venezuela were tested, the prevalence of these lesions progressively increased with increasing starchy vegetable consumption and decreasing fresh fruit/fruit juice consumption. The association with fruits was more evident for dysplasia and AG and that with starchy vegetables for IM and AG. However, there were no inverse associations with plasma antioxidant vitamins. These findings offer important public health implications in preventing progression of HP-associated gastric precancerous lesions in high-risk populations.

Identification of a series of PPAR gamma/delta dual agonists via solid-phase parallel synthesis

We have developed a general solid-phase synthesis for identification of PPAR ligands. Synthesis of a 480-member library led to the identification of a potent PPAR gamma/delta dual agonist 23. Compound 23 showed good plasma exposure in rats and demonstrated antihyperglycemic and antihyperlipidemic efficacy in diabetic fatty Zucker rats.

A case-control study of gastric cancer in Venezuela

A case-control study to evaluate risk factors for gastric cancer was carried out among 292 cases of gastric cancer and 485 controls in a high-risk area of Venezuela. Subjects were interviewed using a structured questionnaire, which elicited information on residential history, socio-economic status, family history of gastric diseases, smoking, drinking and dietary habits. Habitual diet was estimated from a meal-structured food frequency questionnaire on 75 food items. There was a strong inverse association with social class, as measured by education and by indicators of poverty. The results of the dietary analysis suggest that a diet high in starch and low in meat, fish and fresh vegetables increases risk of gastric cancer. A protective effect was observed for frequent consumption of allium vegetables. Inverse associations were found with height, which may reflect nutritional status in childhood, and with refrigerator use in the first two decades of life. Alcohol and tobacco consumption was investigated among males only, since the prevalence of alcohol and tobacco use was very low in females. Alcohol drinkers were at higher risk than non-drinkers and there was a small excess risk for current smokers compared with never smokers. There was some evidence of familial aggregation of gastric cancer. These findings will have important implications in planning preventive strategies for gastric cancer in Venezuela.

Helicobacter pylori and stomach cancer: a case-control study in Venezuela

The role of Helicobacter pylori infection in gastric cancer was evaluated in a high-risk population in Venezuela using serological assays in a study of 302 cases and 483 neighborhood controls. To investigate the claim that assays for H. pylori should use antigens derived from local strains, four different assays derived from Venezuelan and European strains were used. Prevalence of IgG H. pylori antibodies in controls was very high, with estimates between 72 and 92%. Prevalence was similar in cases and controls. However, cases had lower antibody titers. This effect was observed only in subjects with low pepsinogen (PG) levels PGI/PGII <3.0), which suggested that extensive atrophy in cases causes a loss of H. pylori infection, with a consequent reduction in antibody titer. In addition, advanced cases (stage II or higher) had lower antibody titers than less advanced cases, which indicated that the lower antibody titers in cases may be attributable partially to a diminished immune response. All of the four assays for anti-H. pylori antibodies gave similar results. No evidence was found for the superiority of the assay based on Venezuelan strains. These results are consistent with other case-control studies in high-risk populations and highlight the difficulties of investigating H. pylori infection in retrospective studies.

Lewis antigen alterations in a population at high risk of stomach cancer

Anomalous Lewis(a) antigen and sulfomucin expression are considered as markers of progression in precursor lesions of gastric cancer. Additionally, Lewis antigen and secretor phenotype have been related to Helicobacter pylori infection and gastric epithelial damage. The two objectives of this study were to correlate Lewis antigen alterations with histochemical changes and to explore the relationship between Lewis and secretor phenotypes and gastric epithelial damage related to H. pylori infection. The study subjects were selected from a chemoprevention trial in Tachira State, Venezuela, an area with a high risk of gastric cancer. Anomalous Lewis(a) antigen expression in Lewis (a-b+) phenotype individuals was closely related to the severity of the histological lesions, especially to dysplasia and type III intestinal metaplasia lesions. A weak relationship was observed between nonsecretor individuals and more advanced lesions of IM, but this association was not statistically significant. There was no relationship between secretor phenotype and H. pylori status, atrophy, regenerative activity, erosion, or ulcer.

N-(2-Benzoylphenyl)-L-tyrosine PPARgamma agonists. 1. Discovery of a novel series of potent antihyperglycemic and antihyperlipidemic agents

We have identified a novel series of antidiabetic N-(2-benzoylphenyl)-L-tyrosine derivatives which are potent, selective PPARgamma agonists. Through the use of in vitro PPARgamma binding and functional assays (2S)-3-(4-(benzyloxy)phenyl)-2-((1-methyl-3-oxo-3-phenylpropenyl)+ ++amin o)propionic acid (2) was identified as a structurally novel PPARgamma agonist. Structure-activity relationships identified the 2-aminobenzophenone moiety as a suitable isostere for the chemically labile enaminone moiety in compound 2, affording 2-((2-benzoylphenyl)amino)-3-(4-(benzyloxy)phenyl)propionic acid (9). Replacement of the benzyl group in 9 with substituents known to confer in vivo potency in the thiazolidinedione (TZD) class of antidiabetic agents provided a dramatic increase in the in vitro functional potency and affinity at PPARgamma, affording a series of potent and selective PPARgamma agonists exemplified by (2S)-((2-benzoylphenyl)amino)-3-¿4-[2-(methylpyridin-2-ylamino+ ++)ethoxy ]phenyl¿propionic acid (18), 3-¿4-[2-(benzoxazol-2-ylmethylamino)ethoxy]phenyl¿-(2S)-((2- benzoylph enyl)amino)propanoic acid (19), and (2S)-((2-benzoylphenyl)amino)-3-¿4-[2-(5-methyl-2-phenyloxazol-4-y l)e thoxy]phenyl¿propanoic acid (20). Compounds 18 and 20 show potent antihyperglycemic and antihyperlipidemic activity when given orally in two rodent models of type 2 diabetes. In addition, these analogues are readily prepared in chiral nonracemic fashion from L-tyrosine and do not show a propensity to undergo racemization in vitro. The increased potency of these PPARgamma agonists relative to troglitazone may translate into superior clinical efficacy for the treatment of type 2 diabetes.

N-(2-Benzoylphenyl)-L-tyrosine PPARgamma agonists. 3. Structure-activity relationship and optimization of the N-aryl substituent

3-¿4-[2-(Benzoxazol-2-ylmethylamino)ethoxy]phenyl¿-(2S)-((2- benzoylph enyl)amino)propionic acid (1) and (2S)-((2-benzoylphenyl)amino)-3-¿4-[2-(5-methyl-2-phenyloxazol-4-y l)e thoxy]phenyl¿propionic acid (2) are peroxisome proliferator-activated receptor gamma (PPARgamma) agonists and have antidiabetic activity in rodent models of type 2 diabetes. As part of an effort to develop the SAR of the N-2-benzoylphenyl moiety of 1 and 2, a series of novel carboxylic acid analogues, 23-66, modified only in the N-2-benzoylphenyl moiety were synthesized from L-tyrosine and evaluated as PPARgamma agonists. In general, only modest changes in the N-2-benzoylphenyl moiety of 1 and 2 are tolerated. More specifically, the best changes involve bioisosteric replacement of one of the two phenyl rings of this moiety. Addition of substituents to this moiety generally produced compounds that are less active in the cell-based functional assays of PPARgamma activity although binding affinity to PPARgamma may be maintained. A particularly promising set of analogues is the anthranilic acid esters 63-66 in which the phenyl ring in the 2-benzoyl group of 1 and 2 has been replaced by an alkoxy group. In particular, (S)-2-(1-carboxy-2-¿4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phen yl¿ ethylamino)benzoic acid methyl ester (63) has a pKi of 8.43 in the binding assay using human PPARgamma ligand binding domain and a pEC50 of 9.21 in the in vitro murine lipogenesis functional assay of PPARgamma activity. Finally, 63 was found to normalize glycemia when dosed at 3 mg/kg bid po in the Zucker diabetic fatty rat model of type 2 diabetes.

Histological diagnosis of precancerous lesions of the stomach: a reliability study

BACKGROUND

Within the framework of a chemoprevention trial on stomach cancer, two substudies based on repeat measurement were undertaken to evaluate reliability of histological diagnoses of gastric precancerous lesions.

METHODS

A subgroup of 45 subjects received two endoscopies separated by a period of one month. The two biopsies were reviewed by a single pathologist. A second subsample of 50 subjects had a single endoscopy and the biopsy results were reviewed by two pathologists. Agreement between the two diagnoses was assessed by Cohen's Kappa and by repeat frequency.

RESULTS

When the same samples were reviewed by the pathologists involved in the trial, agreement was very high for advanced lesions (repeat frequency = 0.96 for intestinal metaplasia and 1.00 for dysplasia) but lower for less advanced lesions (repeat frequency = 0.73 for superficial gastritis and chronic gastritis, 0.65 for atrophic gastritis). When the same pathologist reviewed two sets of biopsies taken less than 2 months apart, the combination of random observer error and biopsy sampling error gave rise to quite low agreement, especially for early lesions, mainly attributable to biopsy sampling error. Comparison of diagnoses made at routine reading and at review by the same pathologist and by different pathologists showed substantial overall agreement with the exception of one pathologist for whom agreement was moderate.

CONCLUSIONS

These results confirm that misclassification of histological diagnosis may be a relevant problem in chemoprevention trials of stomach cancer, more so when baseline diagnosis is taken into account in the analysis to estimate progression and regression rates of precancerous lesions. Further, the results suggest that misclassification is limited to early lesions, while diagnostic reliability of severe lesions is quite high.

Antioxidants, Helicobacter pylori and stomach cancer in Venezuela

A randomized chemoprevention trial on precancerous lesions of the stomach is being conducted in Tachira State, Venezuela. The aims of the study are to evaluate the efficacy of vitamin supplementation in preventing the progression rate of precancerous lesions. Here we report on the pilot phase of the study in which two antioxidant preparations were evaluated on their ability to raise antioxidant levels in plasma and in gastric juice. The study aimed also to determine the antibiotic sensitivity profiles of Helicobacter pylori isolates prevalent in the area. Forty-three subjects with precancerous lesions (chronic gastritis, chronic atrophic gastritis, intestinal metaplasia and dysplasia) of the stomach were randomized to one of two antioxidant treatments. Treatment 1 (250 mg of standard vitamin C, 200 mg of vitamin E and 6 mg of beta-carotene three times a day) or treatment 2 (150 mg of standard vitamin C, 500 mg of slow release vitamin C, 75 mg of vitamin E and 15 mg of beta-carotene once a day) for 7 days. Blood levels of total vitamin C, beta-carotene and alpha-tocopherol and gastric juice levels of ascorbic acid and total vitamin C were measured before and after treatment on day 8. Both treatments increased the plasma levels of total vitamin C, beta-carotene and alpha-tocopherol/cholesterol but not those of ascorbic acid or total vitamin C in gastric juice. Treatment 1 was the best choice and resulted in a greater increase in the plasma levels of beta-carotene and alpha-tocopherol. H. pylori was cultured from 90% of the gastric biopsies; 35 isolates were identified which were highly resistant to metronidazole, a front-line antibiotic recommended against H. pylori in other settings.

Determinants of plasma anti-oxidant vitamin levels in a population at high risk for stomach cancer

Our objective was to identify the determinants of plasma levels of anti-oxidant vitamins which have been linked with decreased risk of cancer and other chronic diseases. Correlation analyses were performed between baseline plasma levels of ascorbic acid, alpha- and beta-carotenes, cryptoxanthin, lycopene and alpha- and gamma-tocopherols and baseline information on dietary and other demographic and life-style factors among 1,364 subjects 35-69 years of age, who are participants in a chemoprevention trial on pre-cancerous lesions of the stomach in Venezuela. Males had lower levels of ascorbic acid, alpha- and beta-carotene and cryptoxanthin and higher levels of alpha-tocopherol than females. This finding was confirmed in non-smokers and non-drinkers. In females, but not in males, age was positively associated with levels of ascorbic acid, cryptoxanthin, alpha- and beta-carotene and gamma-tocopherol. Male tobacco users had lower plasma levels of ascorbic acid, alpha- and beta-carotene and cryptoxanthin than nonusers, and regular alcohol drinkers had a decreased plasma levels of beta-carotene compared with non-drinkers. Female tobacco users had lower levels of ascorbic acid and cryptoxanthin than non-users, and regular alcohol drinkers had lower levels of ascorbic acid and lycopene than non-drinkers. Frequencies of consumption of fresh fruits, fruit juice, raw vegetables and plantains showed weak positive associations with plasma levels of several vitamins studied in both sexes. Sex, age in females, tobacco and alcohol use and dietary consumption affected plasma anti-oxidant vitamin levels in this population significantly. These factors may influence the effect of anti-oxidant treatment in intervention trials.

Prevalence of precancerous lesions of the stomach in Venezuela

Gastric biopsies from 1477 participants in a chemoprevention trial for precancerous lesions of the stomach in Venezuela were evaluated for the prevalence of precancerous lesions and Helicobacter pylori infection. These study subjects were selected from participants in an early detection program for gastric cancer using double-contrast X-ray. Overall, 94% had some type of chronic gastritis (CG) and were positive for H. pylori using Giemsa stain, 49% had atrophic gastritis, 34% had intestinal metaplasia (IM), and 6.5% had dysplasia. There were only three subjects (0.2%) with normal gastric mucosa, and 4% had only superficial gastritis. The prevalence of all of these precancerous lesions increased with age, but there was no clear difference by gender. The prevalence of the various lesions was higher in the antral mucosa than in the fundic mucosa. H. pylori infection was strikingly frequent in our study population, with prevalence rates ranging from 73% in subjects with superficial gastritis to 95% in those with atrophic gastritis and IM and 98% in those with CG. The prevalence of H. pylori was equally high in males and females, and it was significantly positively associated with the degree of infiltration of poly- and mononuclear cells and with that of active regeneration; it was inversely correlated with the degree of atrophy, IM, and dysplasia. Our findings support the precancerous nature of the various gastric lesions and the etiological role of H. pylori infection in CG.

[Inflammatory response associated with Helicobacter pylori infection in gastric mucosa with intestinal metaplasia in a population in high risk for gastric cancer]

Intestinal Metaplasia (IM) and Helicobacter Pylori (HP) infection had been related to gastric carcinogenesis. With the intention to know the relationship among HP infection, IM and inflammatory response of the mucosa in an area of high prevalence of gastric cancer, we studied 800 persons that attended the Gastric Cancer Mass Survey, ongoing in the State Tachira, Venezuela, since 1981. Out of these subjects, 259 had histology diagnosis of IM (32.4%) 52.1% were IM type Y, 19.3% type II and 22.8% type III (sulfomucin secretory). Histology demonstrated with Giemsa stain HP in 94.6% of the cases. Association between HP and inflammation response in gastric mucosa with IM, was statistically significant (p = 0.001). The are heavier bacteria overload in IM type I than in type III although it is not statistically significant. We ponder if gastric mucosa inflammation due to HP, conditions development of IM as a hostile way of the gastric environment to restrain bacterial growth. This phenomenon ally with other oncogeneous factors could induce to premalignant lesions and eventually gastric cancer.

[Macroscopic and histopathological aspects of atypical gastric epithelium]

Atypical Epithelium is a localized lesion, which has histological and macroscopic findings similar to gastric cancer. In this paper we evaluated 44 cases of atypical epithelium studied and treated in our institute. We found 3 cases of atypical epithelium associated with early gastric cancer. That is 2.66% of the total of all cases. We established the relationship of these lesions and following variables: age, size, localization, macroscopic shape and intestinal metaplasia. We found atypical epithelium in patients older than 50 years old, most of then smaller than 2 cm., localized in antrum and body gastric, and macroscopically were slight elevated lesions. Histologically all of them had intestinal metaplasia.

[Early gastric cancer: main objective in a mass screening program for gastric cancer]

In Táchira's State, Venezuela, there is a high incidence of Gastric Cancer. Screening for early gastric cancer (EGC) detection began in 1981. It observes the Japanese model, with Indirect Radiological (IR) as the move to the various Municipalities, offering the screening test. Subjects with IR abnormalities receive an invitation for an endoscopic examination. If lesions at endoscopy, biopsies were taken. Treatable patients went to surgery; the diagnosis on the surgical specimen was fulfilled by trained Pathologists. CGs cases are actively followed up. From 1981 to 1992 we did 150.023 radiological studies 52.562 gastric endoscopies and 18,480 endoscopic biopsies. We diagnosed 612 CGs:450 were advanced: 102 patients with 113 EGCs with confirmation after surgery; 60 cases were suspected by radiology and endoscopy as EGCs but were nor confirmed because the patients were not operated. 89 patients underwent gastroectomies, and 13 endoscopy resections. The EGCs were depressed (Types IIc, III) in 49% elevated (Types I, IIa) 26%, flat (Type IIb) 6% and intermediate (Types IIa + IIc) 19%. The invasion was confined to the mucosa in 60% and to the submucosa in 40%. By histopathology 60% were differentiated and 40% undifferentiated. In 9% we found metastasis in lymph nodes, only in 2% of the mucosal ones. Survival of patients with EGC after 5 year was 93%. We think a secondary prevention can be done in high risk regions through an appropriate screening for EGC.

[Gastric leiomyoblastoma. Histomorphologic and immunologic analysis of 3 cases]

We present three cases of Leiomioblastomas of stomach, diagnosed at the unit of Pathology of the Gastrointestinal Cancer Center "Dr Luis E. Anderson" -San Cristóbal-Táchira State Venezuela. The lesions are analyzed from the clinical, morphological and immunohistological points of view, utilizing Queratine and Vimentin techniques. This neoplasm is not frequent but it is interesting because its biologic behavior not always correspond to its histology-pattern.

[Endoscopic sphincterotomy experience at the Cancer Control Center]

Endoscopy Sphincterotomy is an important therapeutic procedure in the treatment of some biliary and pancreatic disorders. In this paper, we report our experience over this subject. In our patients the main indication to perform this procedure was common bile duct stones; they were 83% of the total cases. In those cases, 67% were residual stones after cholecystectomy by laparotomy and laparoscopy. We performed sphincterotomy in 33% of patients with gallbladders in situ. In five patients (7.57%), we made the diagnosis of Oddi's sphincter dysfunction taken in account clinical, biochemical an radiological findings. No manometric measurements were done. We found some unusual cases, such as: choledococele and Sump syndrome. In five patients we had complications, 3 of them bled and the other two developed edematous pancreatitis. All these complications were solved with medical treatment.

[The use of urea carbon 14 in breath tests as diagnostic method for Helicobacter pylori infections]

The Helicobacter Pylori has been indicated as a pathologic agent in the pathogenesis of antral gastritis, gastric and duodenal ulcers and probably in gastric cancer. Due to the high incidence of this infection in our place, we decided to look for a diagnostic method quick to perform, sensitive, reliable and no invasive. The breath test of 14C urea, based in the production of urea by the H. Pylori, represents this alternative. We have found, using does of 1 microCi, a high correlation with the diagnosis of H. Pylori by biopsies. We determined as negative less than 100 DPM, doubtful between 100 and 200 DPM and positive more than 200 DPM. The high pick of the curve keeps tight relation with the degree of infection. We checked this when we suppressed the H. Pylori with bismuth subsalicylate. The breath 14C Urea test showed high sensitivity (100%) and specificity (85.71%). We conclude that this breath test is an alternative way of diagnosing and follow up for H. Pylori infections. It is highly sensitive, reproducible and no invasive.

[Macroscopic aspect and depth in early gastric cancer]

Depth of invasion in Early Gastric Cancer (E.G.C.) is very important to be evaluated. We reviewed 78 cases of E.G.C., in patients of our program that were operated on. We established the relationship among three macroscopic variables (localization, size and macroscopic shape) and depth of invasion. We realized that the lesions located in the fundus, though diagnosed less frequently, has more tendency to invade the submucosa (50%), in relation to other localizations. We did not find a significant statistic relation chi 2 = 3.76 P: .58 df:5 between size and invasion. The macroscopic types IIa + IIc and the E.G.C. type III have tendency to further invasion (58.8 and 66.67%). The polypoid lesions Type I and IIa are mostly intramucosal, so they could be treated endoscopically in high risk and old patients.

[Endoscopic resection in early gastric cancer]

Development of therapeutic endoscopy has permitted the treatment of early gastric cancer (EGC) in its different macroscopic forms. In this paper we present 9 cases of EGC treated endoscopically in our Institution. We describe the criteria we follow to perform this procedure. The patients selected were of advanced age and high surgical risk. Seven cases were macroscopically Type I and two were Type IIa. According to localization six were proximal tumors (body and fundus) and three were located in the antrum. Six of the nine patients are alive after resection, one more than 6 years and 3 more than 3 years. Three patients died of ailments no related to cancer.

Amiodarone pulmonary toxicity--three unusual manifestations

Amiodarone is very useful treatment for refractory arrhythmias. However, it has a wide profile of adverse effects involving a number of organ systems. Pulmonary toxicity is the most serious of these side effects and often limits its clinical use. Three patients with unusual forms of amiodarone pulmonary toxicity are described. One had extensive unilateral alveolar disease, another pleural effusion, and in a third the pulmonary infiltrate improved with oral corticosteroids despite continuation of amiodarone therapy. Extensive unilateral alveolar disease and resolution of the pulmonary toxicity with corticosteroids despite continuing with amiodarone have not been previously reported. Pleural effusion has been noted only rarely. With the increasing use of amiodarone, pulmonary toxicity is likely to occur more frequently and it is important to be aware of its less common manifestations.

[Metastasis to lymph nodes in early gastric cancer]

The presence of metastasis in lymph nodes is one of the most important aspects to be evaluated in Early Gastric Cancer (EGC). In this paper we analyze the presence of that kind of metastasis in 70 EGC, in 66 patients studied in our Institute and surgically treated at the Central Hospital of San Cristobal. We found 3 cases with metastasis to perigastric (regional) lymph nodes (N1) and one case with extra perigastric lymph nodes metastasis (N3), that signify 5.7% of the total of all cases. We established the relationship of these metastasis and the following variables: macroscopic type, localization, size, depth of invasion within the gastric wall and the histological variety of the lesions. We found that the type IIa + IIc, the lesions located in the fundus, bigger that 3 cm, with invasion reaching the submucosa and histological differentiated (intestinal type), were the most important characteristics related with the presence of metastasis to the lymph nodes in our EGC.

[Gastric cancer in hyperplasia polyps]

We present 3 cases of Early Gastric Cancer in 82 Hyperplastic Polyps (HP) resected endoscopically (3.6%) during the years 1985 to 1989, at the GI Cancer Center "Dr. Luis E. Anderson", San Cristobal, Venezuela. The diagnosis criteria followed were those of Nakamura, T and Nagayo T. This paper shows the possibility of malignant changes of these lesions, advising endoscopic resection of HP as a mean of treatment and in order to make a complete study of the polyps. We compare our data with existing bibliography, finding similitude in results.

Rugose coral distribution as a test of Devonian palaeogeographic models

A data bank, based on stage by stage distributions of 420 rugose coral genera in 25 regions of the world is analysed, mostly by means of Otsuka coefficients, to test an Emsian reconstruction of the world proposed by Scotese. Devonian rugose corals inhabited a narrower range of facies than some other benthic groups, and even without regard to facies, provide a tool for testing geographic reconstructions. Basin dwelling coral genera typically have longer temporal and broader geographic ranges than corals living in shallower environments, and are less suitable for palaeogeographic studies. They are treated separately in this work.

For the most part, conclusions drawn from the analysis are either consistent with, or positively supportive of, the Scotese reconstruction. However, large but poorly known rugose coral faunas from Mongolia and the Amur Basin are at about 60° N in the reconstruction, and other well known coral faunas, from Altai-Sayan, are at 45°-50°N. In the light of known distributions of both modern corals and Devonian southern hemisphere corals, in all recently proposed palaeogeographic reconstructions, it is questionable that the original latitude of any large northern hemisphere Devonian coral fauna would have exceeded 45°.

[Asymptomatic stomach ulcer]

The purpose of this paper is to evaluate the frequency and some of the clinical and epidemiological characteristics of asymptomatic gastric ulcer, found in persons who attend the Center for Control of Gastrointestinal Cancer of San Cristóbal, Venezuela, as part of a gastric cancer mass screening program. 350 patients with active peptic ulcer were found, 176 duodenal and 174 gastric, diagnosed by means of endoscopy. Of the patients with gastric ulcers, 67 (38.5%) had no symptoms. This group of asymptomatic patients were analyzed regarding age, sex, place of residence, type of work and also the location of the ulcer and the histology. We conclude that this entity is frequent in our region that it is associated with agricultural workers and house wives. It is necessary to continue a prospective periodical evaluation of these patients in order to understand the natural history of the entity.

Modification of hypoxic pulmonary vasoconstriction by aerosolized cromolyn sodium

We have previously demonstrated the role of mast cell degranulation in the mediation of hypoxic pulmonary vasoconstriction, and its prevention by intravenous cromolyn sodium. In the present investigation, we studied the modification of the hypoxic pulmonary vascular response by aerosolized cromolyn sodium. In seven conscious sheep on two separate days, pulmonary arterial pressure, pulmonary arterial wedge pressure and cardiac output were measured for the calculation of pulmonary vascular resistance (Rpv) along with arterial oxygen tension (Pao2) during room air breathing and breathing a hypoxic gas mixture (13% O2-87% N2), without and with cromolyn sodium administration. Cromolyn sodium (20 mg X kg-1) was administered as an aerosol before and during 13% O2 breathing. The sheep had comparable degrees of hypoxia during low oxygen breathing on both days (mean PaO2: 43 and 46 mmHg). Breathing hypoxic gas mixture caused pulmonary vasoconstriction, with increases in mean Rpv of 89% (p less than 0.05). Aerosolized cromolyn sodium blunted the hypoxic pulmonary vascular response; mean Rpv increased by 27% (p less than 0.05), which was significantly different from the increase during hypoxia without cromolyn sodium treatment (p less than 0.05). We conclude that aerosolized cromolyn sodium (a mast cell membrane stabilizing agent) modifies hypoxic pulmonary vasoconstriction; however, unlike the intravenous form, aerosolized cromolyn sodium (at the dosage used) offers a partial protection.

The relative bioavailability of paracetamol and codeine after oral administration of a combination of buclizine, paracetamol and codeine, with or without docusate, and of paracetamol alone in healthy volunteers

A randomized, double-blind, crossover study was carried out in 10 healthy volunteers to investigate whether the inclusion of the wetting agent docusate sodium (10 mg) in a combined oral formulation ('Migraleve') with buclizine hydrochloride (6.25 mg), codeine phosphate (8 mg) and paracetamol (500 mg) had any effect on the bioavailability of the analgesics. On 3 occasions at weekly intervals, the subjects were given 2 tablets of the standard formulation, the combination without docusate or 500 mg paracetamol alone. Blood samples were taken before and at fixed times during the 4 hours after administration of each preparation for estimation of plasma concentrations of paracetamol, by gas-liquid chromatography, and of codeine, by radioimmunoassay. The results showed that there were no significant differences between the mean paracetamol concentrations achieved after administration of each of the 3 preparations at any of the time points. Peak paracetamol plasma concentrations were 11.25 +/- 1.74 micrograms/ml at 0.5 hours, 9.6 +/- 1.04 micrograms/ml at 0.75 hours, and 9.53 +/- 1.66 micrograms/ml at 0.5 hours, respectively, after the standard formulation, the combination without docusate, and paracetamol alone. Mean elimination half-lives for paracetamol were 2.83 +/- 0.51, 1.92 +/- 0.20 and 2.49 +/- 0.46 hours, respectively, and the differences were not significant. The difference between mean plasma concentrations of codeine after the two preparations including this analgesic bordered on significance at 3 hours and was significant at 4 hours, but the areas under the curve were not significantly different. Peak codeine plasma concentrations after the standard formulation were 42.1 +/- 9.4 ng/ml at 0.75 hours compared with 36.9 +/- 3.4 ng/ml at 1.5 hours after the combination without docusate.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in airway permeability and responsiveness after exposure to ozone

The purpose of this investigation was to examine the relationship between airway responsiveness and the permeability of histamine through the airways in conscious sheep after exposure to ozone (O3). Airway responsiveness was assessed by measuring the change from baseline in mean pulmonary flow resistance following a controlled 2-min inhalation challenge with 1% histamine, containing 200 microCi/ml of [3H]histamine. The rate of appearance of the [3H]histamine in the plasma during inhalation challenge was used to estimate airway permeability. To perturb the airways, conscious sheep were exposed to either 0.5 or 1.0 ppm O3 for 2 hr via an endotracheal tube. Airway responsiveness and airway permeability were measured prior to and 1 day after exposure. In six sheep exposed to 0.5 ppm O3, increased airway responsiveness and airway permeability were observed 1 day after exposure. Four of seven sheep exposed to 1.0 ppm O3 had enhanced airway responsiveness and airway permeability, while the remaining three sheep showed corresponding decreases in airway responsiveness and airway permeability. Since the O3-induced directional changes in airway responsiveness paralleled the directional changes in airway permeability in both the positive and negative directions, it was concluded that changes in airway responsiveness to inhaled histamine following exposure to O3 may be related to concomitant changes in airway permeability to this agent.

Does slow-reacting substance of anaphylaxis mediate hypoxic pulmonary vasoconstriction?

We have previously established a relationship between mast cell degranulation and hypoxic pulmonary vasoconstriction (HPV). In the present study, we investigated the possible role of slow-reacting substance of anaphylaxis (SRS-A) in the mediation of HPV. In 18 conscious sheep, pulmonary artery pressure, pulmonary arterial wedge pressure, and cardiac output were measured for the calculation of pulmonary vascular resistance (PVR) along with arterial oxygen tension (PaO2) while breathing room air and while breathing 13% O2 (balance, N2). Before and during 13% O2 breathing (pretreatment), Group 1 received an intravenous infusion of cromolyn sodium (3 mg/kg-1/min-1) and Group 2 was infused with FPL-57231, a SRS-A antagonist (2 mg/kg-1/min-1); Groups 3 and 4 received infusions of cromolyn sodium or FPL-57231 after induction of HPV. During 13% O2 breathing (mean PaO2, 47 mmHg), mean PVR increased to 190% of baseline. Pretreatment with cromolyn sodium prevented HPV, whereas infusion of cromolyn sodium after induction of HPV failed to reverse it; FPL-57231 both prevented HPV (pretreatment) and reversed it when infused after induction of HPV. Pretreatment with the prostaglandin synthetase inhibitor indomethacin (2 mg/kg) 1 h before the experiment failed to modify the FPL-57231-induced reversal of hypoxic vasoconstriction, thus excluding the release of inhibitory prostaglandins by this compound. We conclude that cromolyn sodium prevented HPV, presumably by inhibiting the release of SRS-A, which mediates pulmonary vasoconstriction directly or indirectly through other mechanisms.

Histamine receptor blocking effects of cimetidine in the airways

We investigated the modification of histamine-induced bronchoconstriction by the H2-antagonist cimetidine in conscious sheep. One hundred breaths of 5% histamine aerosol increased mean (SD) pulmonary resistance (RL) by 5.6 (1.4) cmH2O/l/sec. This increase in RL was completely blocked by intravenous clemastine (0.5 mg), a specific H1-antagonist, indicating that the histamine-induced bronchoconstriction was mediated by H1-receptors. Intravenous cimetidine caused a dose-dependent enhancement of the histamine response between 1 and 1000 mg with a mean peak delta RL of 15.3 (5) cmH2O/l/sec (p less than 0.05) at the 1000 mg dose, while it blocked the histamine response at a dose of 2400 mg [delta RL = 1.9 (2) cmH2O/l/sec, p = NS]. This paradoxic effect was not related to an anticholinergic mechanism as intravenous cimetidine (2400 mg) failed to block carbachol-induced (25 breaths of 1% solution) bronchoconstriction. We conclude that in the ovine airway, cimetidine is a selective H2-histamine receptor blocker at lower tissue concentrations, and a combined H2- and H1-histamine receptor blocker at high tissue concentrations.

Variability of hypoxic pulmonary vasoconstriction in sheep. Role of prostaglandins

In a minority of conscious sheep, the hypoxic pulmonary vasoconstrictor response is blunted ("nonresponders"). The purpose of this investigation was to determine if this blunted response is related to an increased activity of H2-histamine receptors, beta-adrenergic receptors, or the generation of inhibitory prostaglandins. We measured pulmonary arterial pressure, pulmonary arterial wedge pressure, and pulmonary blood flow for the calculation of pulmonary vascular resistance (PVR) in 5 "nonresponders" and 5 sheep with a typical hypoxic pulmonary vasoconstrictor response ("responders") while breathing room air and 13% O2 (balance, N2). Arterial oxygen tension (PaO2) was also determined as a measure of the severity of hypoxia. During hypoxia, mean PVR increased by 6% (p = NS) in the "nonresponders" (PaO2, 49 +/- 4 mmHg), and by 70% (p less than 0.01) in the "responders" (mean PaO2, 46 +/- 4 mmHg). Metiamide (H2-blocker) and propranolol (beta-adrenergic blocker) pretreatments did not restore the hypoxic pulmonary vascular response in the "nonresponders," whereas pretreatment with indomethacin (prostaglandin synthetase inhibitor) caused mean PVR to increase by 48% (p less than 0.01) during hypoxia, indicating a partial restoration of hypoxic pulmonary vasoconstriction. In the "responders," the hypoxic pulmonary vascular response was not potentiated by indomethacin pretreatment (68% increase in mean PVR). We conclude that some sheep exhibit a blunted hypoxic pulmonary vasoconstrictor response caused by enhanced production of inhibitory prostaglandins.

Hypoxic pulmonary vasoconstriction in conscious sheep: role of mast cell degranulation

We used pharmacologic and histologic techniques to investigate the role of mast cells in the mediation of hypoxic pulmonary vasoconstriction in conscious sheep. Breathing a hypoxic gas mixture (13%, 02, 87% nitrogen) caused hypoxic pulmonary vasoconstriction (HPV) with increases in mean pulmonary artery pressure and pulmonary vascular resistance by 97 and 90%, respectively. Intravenous pretreatment with the mast cell membrane stabilizing agent cromolyn sodium (3 mg/kg/min) completely blocked HPV, whereas the H1-histamine receptor antagonist chlorpheniramine, alone or in combination with the H2-receptor antagonist metiamide and the prostaglandin synthetase inhibitor indomethacin, failed to prevent HPV. Cromolyn sodium failed to modify the pulmonary pressor response to infusions of norepinephrine (alpha-agonist), tyramine (catecholamine-releasing agent), and histamine, indicating the specificity of cromolyn sodium action on the mast cells. Electromicroscopic studies of pulmonary perivascular mast cells showed that a 90-min exposure to the hypoxic gas mixture reduced the total number of granules per mast cell to 75% of control. This was blocked by cromolyn sodium pretreatment. We conclude that in conscious sheep], HP[V is initiated by the liberation of a mast cell product (other than histamine) that either directly or indirectly causes pulmonary vasoconstriction.

Characterization of H1- and H2-receptor function in pulmonary and systemic circulations of sheep

We investigated the histamine H1- and H2-receptor function in the pulmonary and systemic circulations of sheep by in vivo and in vitro techniques. Combined H1 and H2 stimulation (by intravenous histamine) in vivo increased pulmonary vascular resistance (PVR) to 435% of base line and decreased systemic vascular resistance (SVR) to 49% of base line. Selective H2 stimulation (histamine after chlorpheniramine pretreatment) decreased PVR and SVR to 86 and 82% at base line, respectively, while selective H1 stimulation (histamine after metiamide pretreatment) increased PVR to 424% of base line and decreased SVR to 64% of base line. Combined H1- and H2-antagonist pretreatment completely blocked the effects of histamine on SVR, while PVR still decreased to 85% of base line, suggesting a mild "atypical" H2-receptor response in the pulmonary circulation under conditions of resting vascular tone. With increased pulmonary vascular tone (hypoxia), histamine decreased PVR to 55% (H1-antagonist pretreatment) and to 58% (combined H1- and H2-antagonist pretreatment) of posthypoxia values, respectively, demonstrating a marked atypical H2-receptor response. In vitro, both pulmonary arterial and venous strips showed a contractile dose-response to histamine, which was blocked by the H1-antagonist pyrilamine (mepyramine). In precontracted strips, both histamine and the H2-agonists (dimaprit and impromidine) elicited a relaxant response, which was neither blocked by H1-antagonist alone nor by combined H1- and H2-antagonists. We conclude that in sheep the histamine-induced pulmonary vasoconstrictor response is mediated by H1-receptors, while the pulmonary vasodepressor response is mediated by atypical H2-receptors. The systemic vasodepressor response is mediated by both H1- and typical H2-receptors.

Role of ciliary motility in acute allergic mucociliary dysfunction

The purpose of this investigation was to determine if abnormal ciliary function contributes to allergic mucociliary dysfunction. In conscious sheep with Ascaris suum hypersensitivity, ciliated cells were obtained with a cytology brush and tracheal mucous velocity (TMV) was determined before and serially for 2 h following antigen inhalation. The recovered cells (also containing mast cells) were suspended in a chamber, and ciliary activity was viewed microscopically and recorded on videotape for subsequent slow-motion analysis of ciliary beat frequency (CBF). One hour after A. suum challenge mean CBF (+/- SE) showed a slight increase from a base-line value of 630 +/- 16 to 716 +/- 30 beats/min (P less than 0.05) when mean TMV was decreased to 57% of base line (P less than 0.05). After 2 h, both mean CBF and TMV returned toward base line. Since possible in vivo actions of chemical mediators liberated by antigen challenge may have been lost after suspension of the brushed cells, we also assessed the effects of antigen on CBF in vitro. A. suum caused a dose-dependent increase in CBF that was blocked by cromolyn sodium. We conclude that 1) allergic mucociliary dysfunction is not caused by a decrease in CBF and 2) antigen-induced release of chemical mediators increases CBF.

Effects of nitric acid on carbachol reactivity of the airways in normal and allergic sheep

The airway effect of a 4-hr exposure (via a Plexiglas hood) to 1.6 ppm nitric acid vapor were evaluated in seven normal and seven allergic sheep, i.e., animals that have a history of reacting with bronchospasm to inhalation challenge with Ascaris suum antigen. The nitric acid vapor was generated by ultrasonic nebulization of a 2% nitric acid solution. Airway effects were assessed by measuring the change in specific pulmonary flow resistance before and after a standard inhalation challenge with 2.5% carbachol aerosol. Nitric acid exposure did not produce bronchoconstriction in either group. Pre-exposure increases in specific pulmonary flow resistance after carbachol inhalation were 68% (SD +/- 13%) and 82% (SD +/- 35%) for the normal and allergic sheep, respectively. Within 24 hr, the largest post exposure increased in specific pulmonary flow resistance for the normal and allergic sheep were 108% [SD +/- 51% (P less than .06)] and 175% [SD +/- 87% (P less than .02)], respectively. We conclude that a short-term exposure to nitric acid vapor at levels below the industrial threshold limit (2 ppm), produces airway hyperreactivity to aerosolized carbachol in allergic sheep.

Differences in airway reactivity in normal and allergic sheep after exposure to sulfur dioxide

The effect of breathing 5 ppm sulfur dioxide (SO2) on airway reactivity was studied in both normal and allergic conscious sheep. Allergic sheep were defined as animals in which inhalation of Ascaris suum extract resulted in bronchospasm as evidenced by an increase in mean pulmonary flow resistance (RL), hyperinflation, and a fall in dynamic compliance. Airway reactivity was assessed by measuring the increase of RL after 18 breaths of 0.25% carbachol (c), from an initial RL value obtained after 18 breaths of buffered saline (s) [RL(c-s)]. RL and RL(c-s) were determined prior to, immediately after, and 24 h after exposure to 5 ppm SO4 for 4 h. In both groups RL remained unchanged after SO2 exposure. Prior to exposure, RL(c-s) was not significantly different in seven normal (0.3 +/- 0.1) and seven allergic sheep [0.4 +/- 0.2 (SD) cmH2O X l-1 X s], and there was no significant change in RL (c-s) immediately after SO2 exposure in either group. Twenty-four h later, RL(c-s) RL(c-s) increased to 0.7 +/- 0.8 (P less than 0.2) in normal and to 1.8 +/- 0.9 cmH2O X l-1 X s (P less than 0.01) in allergic sheep. Because the increase in RL(c-s) after 24 h was greater (P less than 0.01) in allergic than in normal sheep, we conclude that SO2 exposure increased airway reactivity more in the former than in the latter.

Effect of pharmacologic agents on antigen-induced decreases in specific lung conductance in sheep

The purpose of this investigation was to determine the primary mediators responsible for the decrease in specific lung conductance (SGL) after airway challenge with Ascaris suum antigen in allergic sheep. On different occasions, separated by 10 to 14 days, pulmonary resistance and thoracic gas volume were measured in 5 sheep with Ascaris suum hypersensitivity before and for 2 h after a standard inhalation challenge with this antigen. Initially and at the end of the study, inhalation challenge decreased mean SGL to 38 and 44% of baseline, respectively. Pretreatment by intravenous injection of the H1 receptor antagonist chlorpheniramine (2 mg/kg) completely prevented the antigen-induced decrease in SGL. Similar results were obtained with inhalation of the mediator release blocking agent, disodium cromoglycate (1 mg/kg), prior to antigen challenge. The decrease in SGL after inhalation challenge was not modified by pretreatment with the H2 receptor antagonist, metiamide (3 mg/kg), the anticholinergic agent, atropine (0.2 mg/kg), the prostaglandin synthetase inhibitor, indomethacin (2 mg/kg) by intravenous injection, or with inhalation of FPL-55712 (1% solution), an antagonist of slow-reacting substance of anaphylaxis (SRS-A). We concluded that during allergic bronchoconstriction in sheep (1) the decrease in SGL is mediated by histamine via H1 receptors, (2) other liberated or activated mediators including SRS-A do not decrease SGL, and (3) cholinergic reflex mechanisms are not involved in this response.

Impaired tracheal mucus transport in allergic bronchoconstriction: effect of terbutaline pretreatment

The transport velocity of mucus within the trachea, pulmonary resistance, and arterial blood gas composition were measured in intubated conscious sheep with Ascaris suum sensitivity before and during allergic bronchoconstriction. Inhalation of A. suum extract for 15 min increased mean pulmonary resistance significantly from 1.9 cm H2O . L-1 sec-1 to 5.1 cm H2O . L-1 sec-1 after 60 min and to 4.5 cm H2O . L-1 sec-1 after 120 min, while it decreased mean arterial PO2 from 85 to 59 and 53 mm Hg, respectively, without altering arterial PCO2 or pH. This was associated with a decrease in mean mucus velocity from 11.2 to 6.0 and 5.7 mm min-1, respectively. The decrease in mucus velocity was accompanied by endoscopically visible increases in the quantity of tracheal mucus. No alterations in mucus velocity or pulmonary resistance were observed in animals who inhaled a control antigen (ragweed) or breathed a mixture of 10% oxygen 90% nitrogen, which produced a mean arterial PO2 of 51 mm Hg. The administration of 0.25 mg terbutaline sulfate by subcutaneous injection prior to A. suum challenge prevented the changes in mucus velocity, pulmonary resistance, and arterial PO2. We conclude that the decreased mucus velocity in the trachea during antigen-induced bronchoconstriction in conscious sheep is related to the allergic response, and can be prevented by the subcutaneous administration of terbutaline sulfate, a beta adrenergic agonists. This suggests that the protective effect of terbutaline sulfate in antigen-induced bronchoconstriction includes the effect on the associated impairment of mucociliary function.