Cocarcinogenesis between cadmium and Aroclor 1254 in planarians is enhanced by inhibition of glutathione synthesis

Asexual Dugesia dorotocephala planaria continuously exposed to 50 micrograms/beaker of Aroclor 1254 (A1254) and cadmium (Cd) developed tumors after 11 days of continuous exposure to 0.65 or 1.3 mg/liter Cd and after 23 days to 0.13 mg/liter Cd. The tumor rate at 14 days averaged 53% for the survivors in both 0.65 and 1.3 mg/liter Cd + A1254 and 40% at 0.13 mg/liter Cd + A1254. Other groups were either preexposed or coexposed to L-buthionine-S,R-sulfoximine (BSO), a specific inhibitor of glutathione synthesis. In the presence of A1254 (50 micrograms/beaker), animals continuously exposed to BSO and 0.13 mg/liter Cd first developed tumors at 18 days, with a tumor yield equal to 41% of the survivors. Tumors developed by 6 days at 0.65 mg/liter Cd, with a yield equal to 75% of survivors. At 1.3 mg/liter Cd, BSO did not change the rate or frequency of planarian tumor production. Continuous BSO always produced high mortality over 20 days. In contrast, a 24-h preexposure to BSO caused little mortality. In these groups, tumor yields increased with cadmium concentration (0.13, 0.25, 0.65 mg/liter), and the large cocarcinogenic effect of A1254 was clearly evident. No tumors developed in animals exposed only to 50 micrograms/beaker of Aroclor 1254 or continuously only to 1 mM BSO.

Stimulation of proximal small intestinal mucosal growth by luminal polyamines

The purpose of this study was to determine whether luminal polyamines stimulate intestinal mucosal growth in vivo. Rats received 2% alpha-difluoromethylornithine (DFMO) added to their drinking water throughout the experiment. The polyamines spermidine and spermine (3 mg each/100 g body wt) were given intragastrically in combined doses once at 9:30 A.M. and again at 5:30 P.M. Duodenal and jejunal mucosal ornithine decarboxylase (ODC) activity in the DFMO-treated rats was inhibited significantly for the duration of the study. DFMO also markedly decreased the rate of [3H]thymidine incorporation into DNA of duodenal and jejunal mucosa. The decrease in [3H]thymidine incorporation was significant 4 days and maximal 6 and 8 days after beginning treatment with DFMO. Decreased ODC activity and DNA synthesis were paralleled by decreases in total mucosal DNA, RNA, and protein content. Administration of the polyamines significantly reversed the effects of DFMO except the inhibition of ODC. In fact, there were no significant differences in mucosal growth parameters between the controls (without DFMO) and those treated with DFMO plus polyamines. Oral administration of spermidine and spermine at a dose of 4.5 mg each/100 g body wt for 6 days to rats not treated with DFMO increased the normal rate of mucosal growth in the duodenum and jejunum as well. Polyamine accumulation in IEC-6 cells was measured to determine whether it was altered by DFMO. IEC-6 cells took up [3H]putrescine and [3H]spermidine from their surrounding environment and the uptake was stimulated by serum. DFMO (5 mM) totally inhibited the increase in ODC activity but had no effect on the cellular uptake of polyamines in the presence of putrescine.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary health risks among northwest loggers

Spirometry, respiratory symptom questionnaires, and chest radiographs were obtained from 688 loggers in Oregon and Washington. These were compared against previously published National Institute for Occupational Safety and Health studies of nonexposed blue-collar workers to determine if these predictions fit our population. The loggers forced expiratory volume in 1 second and forced vital capacity values were significantly greater than predicted, and their forced expiratory volume in 1 second/forced vital capacity values were less than predicted. The only consistent difference in symptoms between the sample and reference populations was for recent chest illnesses, which were more prevalent in the loggers than in the reference population. The chest radiographs showed a small excess of pleural thickening that we believe is most likely due to chest trauma. We conclude that the National Institute for Occupational Safety and Health studies spirometry prediction equations may not be generalized to other blue-collar populations.

Spirometry in the Lung Health Study. 1. Methods and quality control

The Lung Health Study is a randomized clinical trial designed to determine whether a smoking intervention program and prescription of an inhaled bronchodilator can reduce the annual rate of decline of FEV1 (FEV1 slope) in cigarette smokers with mild to moderate airflow limitation. During the recruitment period, spirometry measurements were obtained during three screening visits from 5,887 cigarette smokers 35 to 60 yr of age. To improve the statistical power of the study to detect significant differences in the FEV1 slopes among study groups, the spirometry testing protocol carefully controls for multiple factors that are known to increase intraindividual variability of FEV1 and FVC results. These factors include participant preparation, maneuver acceptability and reproducibility, technician training and performance monitoring, equipment design and calibration, and result processing. The objective of this report is to describe the success of the spirometry quality control program in minimizing the short-term intraindividual FEV1 variability. The mean difference between the FEV1 values obtained at the second and third screening visits (mean 25 days apart) was +5.7 ml in women and -14.7 ml in men, with a mean intraindividual variability of 119 ml in women and 162 ml in men, with a coefficient of variation of 5.8% for both. During only 2.1% of the test sessions were participants unable to produce three acceptable FVC maneuvers with the two best FEV1 values matching within 5% or 100 ml. Institution of site visits and technician performance monitoring was associated with improved test session quality grades and maintenance of high quality grades thereafter.

Role of polyamines in gastrointestinal mucosal growth

The polyamines have been under active investigation for nearly three decades. There is a great deal of evidence that they play an important role in gastrointestinal mucosal growth, but the mechanisms through which this role is carried out are still not fully explained. This review examines the role of the polyamines in the regulation of mucosal growth, the control of intracellular polyamine levels, the biosynthesis of the polyamines, and some known mechanisms of their action. Finally, we propose a model of polyamine action that reconciles the effects of various trophic agents and situations in which growth is stimulated along with concomitant changes in polyamine levels. It accounts for both humoral and gradient-oriented features of various adaptive responses of the gastrointestinal mucosa and is intended to provide a framework for the future investigation of the role of the polyamines in this tissue.

Retrogasserian rhizotomy causes expression of nerve growth factor receptor-immunoreactive protein in motoneurons within the adult feline trigeminal motor nucleus

The effect of lesions on nerve growth factor receptor (NGFr) immunoreactivity (IR) in motoneurons within the mature feline trigeminal motor nucleus was investigated. Ten days following complete unilateral retrogasserian trigeminal rhizotomy including transection of the trigeminal motor root, motoneurons within the ipsilateral trigeminal motor nucleus showed NGFr-IR. In contrast, motoneurons within the contralateral trigeminal motor nucleus and within both trigeminal motor nuclei in unoperated control subjects did not show NGFr-IR. It is suggested that the appearance of NGFr-IR in motoneurons within the ipsilateral trigeminal motor nucleus after rhizotomy represents an attempts towards recovery and may be associated with the regrowth of its cut axons.

Putrescine uptake and release by a normal rat small intestine crypt cell line, IEC-6

IEC-6 cells were cultured on permeable filter inserts with separate access to the apical and basolateral sides. [3H]Putrescine uptake favored the apical side and its release (in Earle's balanced salt solution containing 0.1% bovine serum albumin) was six times greater in the apical-to-basolateral than in the basolateral-to-apical direction. Release in DMEM did not show this preference. The uptake of [3H]putrescine was stimulated approximately 1.3 times the basal level by 10 mM asparagine (ASN) or 5% dialyzed fetal bovine serum whether the [3H]putrescine was added at a concentration of 1 or 100 nM. The increased uptake was maintained for up to 6 h. When [3H]putrescine was removed after 4 h of uptake, the cells continued to release it into the medium on both sides for up to 4 h. Stimulated cells released only 50% as much as unstimulated cells. Unlabeled putrescine reduced the uptake of [3H]putrescine with an IC50 of 1.81 x 10(-6) M (r = 0.9476) and 1.02 x 10(-6) M (r = 0.9967) for unstimulated and ASN-stimulated cells, respectively. When the intracellular putrescine was reduced by difluoromethylornithine, the uptake of [3H]-putrescine was not changed, but its release was inhibited. Sodium was not required for [3H]putrescine uptake or release. Although the stimulated cells attained intracellular levels of [3H]putrescine which, if expressed as concentration based on cell volume, were up to 500 times the original extracellular concentration, a true concentration gradient could not be proven because 85% of the [3H]putrescine was probably bound to polyanions as shown by butanol extraction.

Activation of thymocyte deoxyribonucleic acid degradation by endogenous glucocorticoids

Immature lymphocytes in the thymus gland are killed by treatment with exogenous glucocorticoids. This steroid-mediated lymphocytolysis is preceded by numerous alterations in lymphocyte metabolism, including a DNA-degrading process in which the genome is cleaved at internucleosomal intervals. To date, this process has only been characterized by treating lymphocytes in vitro with glucocorticoids or by exogenous treatment of whole animals with adrenal steroids. To determine whether thymocyte DNA degradation could be activated by endogenous glucocorticoids, 4-wk-old chicks were treated with porcine adrenocorticotropic hormone (ACTH). This procedure elevated serum corticosterone levels approximately 80-fold within 2 h of hormone treatment. Following ACTH administration, thymocyte DNA was isolated and analyzed by agarose gel electrophoresis. The ACTH activated a DNA-degrading process that generated internucleosomal fragments of DNA identical in size to those observed following exogenous treatment with synthetic or naturally occurring glucocorticoids. Furthermore, this response could be inhibited by the glucocorticoid antagonist RU486 (17 beta-hydroxy-11 beta, 4-dimethylaminophenyl-17 alpha-propynl-estra-4,9,diene-3-one), indicating that adrenal steroids activate this process via the glucocorticoid receptor. These results demonstrate that lymphocyte DNA degradation does not result solely from exogenous glucocorticoid treatment; moreover, endogenous glucocorticoids can mediate this process and may thereby play an important role in thymic gland function.

Polyamines and ornithine decarboxylase during repair of duodenal mucosa after stress in rats

This investigation shows whether polyamines and ornithine decarboxylase have a role in duodenal mucosal repair following stress-induced microscopic damage. Rats were fasted for 22 hours, placed in restraint cages, and immersed in water to the xiphoid process for 6 hours. Animals were killed either immediately after the period of stress or at 2-hour intervals up to 24 hours thereafter. Duodenal mucosa was examined histologically, and ornithine decarboxylase and polyamine levels were measured. Ornithine decarboxylase activity was increased significantly up to 6 hours following stress, peaking at 4 hours at a level 10 times the prestress control. By 8 hours, enzyme activity had returned to near normal. Increases in mucosal putrescine, spermidine, and spermine content paralleled the changes in ornithine decarboxylase activity and peaked 4 hours after stress. Stress resulted in microscopic damage evidenced by a nearly complete absence of villi. Significant macroscopic lesions were not present following stress. Mucosal repair was evident 12 hours after stress and almost complete by 24 hours, although the restituted villi were short and blunted. The decreases in mucosal DNA, RNA, and protein content caused by stress were restored and reached near-normal levels 12 hours after the period of stress. In animals given the specific inhibitor of ornithine decarboxylase, alpha-difluoromethylornithine, increases in duodenal mucosal ornithine decarboxylase activity and polyamine levels were inhibited and mucosal repair was almost completely prevented following stress. alpha-Difluoromethylornithine also prevented the recovery of DNA, RNA, and protein content of the duodenal mucosa. These results indicate that duodenal mucosal damage following stress is repaired rapidly; the repair process is accompanied by significant increases in ornithine decarboxylase activity and polyamine levels; and the increases in ornithine decarboxylase and polyamines are absolutely required for the normal repair of the mucosa.

Mucosal ornithine decarboxylase, polyamines, and hyperplasia in infected intestine

Ornithine decarboxylase (ODC), through the regulation of polyamine biosynthesis, influences normal mucosal growth and cell proliferation. The purpose of our study was to determine whether mucosal ODC activity and polyamines play a role in the dramatic increase in mucosal mass and crypt elongation associated with parasite-induced inflammation in the small intestine. Rats were inoculated orally with L1 larvae of the parasitic nematode Trichinella spiralis and killed at different times during the enteric phase of infection. Duodenal and jejunal mucosal ODC activities increased significantly from 2 to 14 days, peaking 7 days postinfection (PI). By 21 days PI, enzyme activity had returned to near normal values. In the ileal mucosa, ODC activity was increased only at 7 days PI. Increases in ODC activity were paralleled by increases in mucosal putrescine, spermidine, and spermine content. Infection with T. spiralis induced DNA synthesis and evoked a significant rise in DNA, RNA, and protein content in the mucosa. Increases in nucleic acid and protein levels were most prominent in the proximal half of the small intestine where the majority of worms reside. Treatment of rats with alpha-difluoromethylornithine (DFMO) prevented the infection-induced elevations in mucosal ODC activity, polyamine levels, DNA synthesis, and DNA, RNA, and protein content without influencing the development of inflammation or the parasite's life cycle. These results suggest that mucosal hyperplasia caused by infection may be regulated, in part, by the growth-promoting effects of ODC, presumably through the stimulation of crypt cell proliferation. Thus ODC may be an important determinant of the intestinal response to infection.

Reliability of crevicular fluid measurements taken in the presence of supragingival plaque

The measurement of gingival crevicular fluid (GCF) is commonly used in clinical studies to quantitate the severity of gingival inflammation. This study examined the influence of the presence of supragingival plaque on GCF readings. Bilateral pairs of maxillary premolars received replicate GCF measurements. One of the teeth was randomly selected to be the test tooth. Supragingival plaque was removed from the test tooth between the first and second GCF measurements. Plaque was not removed from the control tooth. The crevicular fluid was collected on filter paper strips which were placed just subgingivally. The quantity of crevicular fluid was determined with the aid of the Periotron 6000. The mean difference between the first and second GCF measurement for the control teeth was -1.5 +/- 5.7 (+/- SD). This change was not significant (P = 0.21). The mean difference between the first and second GCF measurements for the experimental teeth (-21.3 +/- 16.5) was significant (P less than or equal to .001). The mean difference between the control and the experimental GCF differences were found to be highly significant (P less than or equal to .001). The data indicate that the presence of supragingival plaque can significantly elevate the GCF measurements when determined with the Periotron 6000.

Luminal polyamines stimulate repair of gastric mucosal stress ulcers

The purpose of this study was to examine whether luminal polyamines can substitute for tissue polyamines in the healing process of gastric mucosal stress ulcers. Rats were fasted 22 h, placed in restraint cages, and immersed in water to the xiphoid process for 6 h. Animals were killed either immediately or at 4, 12, or 24 h after the period of stress. Stress significantly increased ornithine decarboxylase (ODC) activity and tissue polyamine content. Mucosal polyamine levels peaked 4 h after stress and remained significantly elevated for 12 h. The healing process, which was significant by 12 h, was inhibited by DL-alpha-difluoromethylornithine (DFMO), a specific inhibitor of ODC. DFMO totally prevented the marked increases in ODC and polyamine levels that usually followed stress. Oral administration of polyamines, putrescine, cadaverine, spermidine, or spermine, immediately after stress increased the normal rate of healing and prevented the inhibition of repair caused by DFMO. Spermidine or spermine accelerated healing better than putrescine or cadaverine. The delayed recovery of mucosal DNA, RNA, and protein content after stress in the DFMO-treated rats was also significantly prevented by exogenous polyamines. The reduced amounts of gastric mucosal spermidine and spermine in rats treated with DFMO returned toward control levels after administration of exogenous spermidine (100 mg/kg). These results show that 1) increased levels of polyamines provided by ODC are absolutely required for normal healing of gastric mucosal stress ulcers, 2) the polyamines are active from the luminal side, and 3) polyamines accelerate healing at least partly through a mechanism involving cell renewal.

Glucocorticoid activation of deoxyribonucleic acid degradation in bursal lymphocytes

Treatment of animals with exogenous adrenal steroids or elevation of endogenous glucocorticoids results in a profound involution of lymphoid tissue. In rodent species, this lymphoinvolution is accompanied by lymphocyte cell death and extensive degradation of the genome prior to lymphocytolysis. In the present study, this process was investigated in the bursa of Fabricius of domestic fowl. Four-wk-old chicks were treated with a single injection of dexamethasone, and bursal regression and cell viability were monitored over a 72-h period. Following hormone treatment, DNA was extracted from bursal lymphocytes and analyzed by agarose gel electrophoresis. Dexamethasone treatment resulted in a rapid regression of bursal tissue that could be detected as soon as 6 h posttreatment, but lymphocyte viability was not altered until 24 h afterward. The DNA isolated from bursal lymphocytes of glucocorticoid-treated birds appeared to be degraded at internucleosomal sites and generated a "ladder" of discrete DNA fragments when analyzed by agarose gel electrophoresis. This form of hormone-induced cell death, referred to as programmed cell death, may play a key role in glucocorticoid-mediated immunosuppression.

Long-term reproducibility of tests of small airways function. Comparisons with spirometry

We used a tracking index to measure the reproducibility of single breath nitrogen test variables (CV/VC, CC/TLC, delta N2/L) and spirometric variables (FEV1 and FEV1/FVC) and to compare the characteristics of individuals whose pulmonary function tracks well with those whose pulmonary function tracks poorly. Data were derived from two cohorts followed longitudinally over a 9-11 year period. All variables were adjusted for age, sex and height by expressing them as Z-scores. In all smoking groups and in both cohorts, the tracking index was highest for FEV1, indicating that this variable was the most reproducible over the period of follow-up; delta N2/L and FEV1/FVC had very similar but slightly lower tracking indices; CV/VC consistently had the lowest tracking indices. Tracking indices were generally higher in smokers than in nonsmokers. The reproducibility of CC/TLC increased over the period of follow-up whereas the FEV1 reproducibility remained constant. We found no significant difference between those with high tracking indices and those with low indices in terms of sex, smoking status, prevalence of respiratory symptoms, history of respiratory disease, and rate of decline of FEV1. We conclude that FEV1 is the most reproducible of the variables examined, both within and between individuals, and that poor tracking or reproducibility are not related to smoking or to the presence of respiratory symptoms or disease.

Regulation of ornithine decarboxylase activity in LoVo cells

The role of Na+ and Na(+)-H+ exchange in the stimulation of ornithine decarboxylase (ODC) activity has been investigated in a human colon adenocarcinoma cell line, LoVo. Asparagine (Asn; 10 mM) or 10% fetal bovine serum (FBS) increased ODC activity from undetectable levels to greater than 500 pmol CO2.mg protein-1.h-1 in 4 h. This increase could be reduced 50% by concentrations of Na(+)-H+ exchange inhibitors that did not reduce protein synthesis. (approximately 0.2 mM for amiloride and 0.05 mM for hexamethyleneamiloride). Asn was able to double the uptake of 22Na+, whether an ionic (choline chloride) or nonionic (D-mannitol) substance was substituted for Na+, and the substitution of these compounds as well as N-methyl-glucamine for Na+ largely prevented the stimulation of ODC by Asn. Another factor influencing ODC activity was extracellular pH (pHo). When pHo was lowered, intracellular pH (pHi) also fell, and ODC activity was reduced. When pHo was raised, pHi also rose, and ODC activity increased. The well-known correlation between increased pHi and Na+ uptake with the stimulation of growth may be due to their influence on ODC activity.

Gastric and duodenal mucosal ornithine decarboxylase and damage after corticosterone

We recently found that stress increases gastric and duodenal ornithine decarboxylase (ODC) activity and damages both tissues. The current study investigated whether corticosterone induces ODC activity in gastric and duodenal mucosa in rats and compared plasma corticosterone levels after stress and treatment with corticosterone to determine whether this hormone mediated the effects of stress on the mucosa. Rats were fasted 22 h, placed in a restraint cage, and immersed in water to the xiphoid process for 6 h. Stress markedly increased plasma corticosterone levels; the increase was 10.5 times control and lasted the duration of stress. The maximum increase was observed 1 h after a single injection of corticosterone (5 mg/kg sc) and represented 11.1 times control values. By 6 h, plasma corticosterone had returned to normal levels. A single injection of corticosterone had no effect on the gastric mucosa, but duodenal ODC was increased significantly from 4 to 8 h after injection, peaking at 6 h. Histological examination revealed no damage in either tissue. Administration of corticosterone three times daily for 3 days dramatically elevated ODC activity and produced significant microscopic damage. The surface epithelium of the stomach was disrupted, with many surface cells shed, and most villi were absent from the duodenal mucosa. Corticosterone also markedly decreased DNA and RNA content of both tissues. Inhibition of ODC with DL-alpha-difluoromethylornithine additionally decreased DNA, RNA, and protein content, exacerbating the damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of occupational exposure to inorganic arsenic based on urinary concentrations and speciation of arsenic

An analytical speciation method, capable of separating inorganic arsenic (As (V), As (III] and its methylated metabolites (MMAA, DMAA) from common, inert, dietary organoarsenicals, was applied to the determination of arsenic in urine from a variety of workers occupationally exposed to inorganic arsenic compounds. Mean urinary arsenic (As (V) + As (III) + MMAA + DMAA) concentrations ranged from 4.4 micrograms/g creatinine for controls to less than 10 micrograms/g for those in the electronics industry, 47.9 micrograms/g for timber treatment workers applying arsenical wood preservatives, 79.4 micrograms/g for a group of glassworkers using arsenic trioxide, and 245 micrograms/g for chemical workers engaged in manufacturing and handling inorganic arsenicals. The maximum recorded concentration was 956 micrograms/g. For the most exposed groups, the ranges in the average urinary arsenic speciation pattern were 1-6% As (V), 11-14% As (III), 14-18% MMAA, and 63-70% DMAA. The highly raised urinary arsenic concentrations for the chemical workers, in particular, and some glassworkers are shown to correspond to possible atmospheric concentrations in the workplace and intakes in excess of, or close to, recommended and statutory limits and those associated with inorganic arsenic related diseases.

Tricyclic antidepressant toxicosis

Accidental ingestions of TCAs by companion animals often occur. During the past 4 years, over 450 cases have been reported to the IAPIC. At least 7% of the animals that displayed clinical signs of toxicosis eventually died. Overdoses of TCAs adversely affect the cardiovascular, parasympathetic, and central nervous systems. The cardiovascular system is involved most seriously and ventricular arrhythmias with severe hypotension are believed to be the primary cause of death. Animals that ingest a potentially lethal dose (over 15 mg/kg) may die within 1 to 2 hours if appropriate treatment is not administered. Treatment involves the use of initial life-supportive measures (control of seizures, maintenance of an airway, ventilation, and so on), detoxification of the animal (enterogastric lavage, activated charcoal, etc.), and the intravenous use of sodium bicarbonate (2-3 mEq/kg) to control signs of acidosis, hypotension, tachycardia, bradycardia, and other cardiac conduction abnormalities. The animal must then be monitored closely for the return of the clinical signs and sodium bicarbonate therapy should be repeated as needed. In addition, to enhance removal of the TCAs from the gastrointestinal tract and, ultimately, from the body, activated charcoal should be repeated at 3-hour intervals until the animal is asymptomatic.

Intestinal ornithine decarboxylase: half-life and regulation by putrescine

Ornithine decarboxylase (ODC) is the primary rate-limiting enzyme for polyamine synthesis. ODC levels are increased in most tissues, including the intestinal mucosa, by growth-promoting agents. This enzyme has a brief half-life of from 5 to 30 min in mammalian tissues and is regulated by its product; putrescine. The current study examines the turnover and regulation of ODC in the mucosa of the small intestine. With the use of scraped intestinal mucosa from cycloheximide-treated rats, the time course of the decline in ODC activity yielded a half-life of approximately 22 min. Labeling enzyme protein with [3H]difluoromethylornithine (DFMO) resulted in a nearly identical estimation of half-life. ODC activity of mucosa from isolated gut segments stimulated by luminal glycine (0.1-0.4 M) was enhanced 60-100% by 10 mM putrescine administered luminally. Putrescine alone had no effect on ODC. In contrast, 10(-7) M putrescine prevented 80% of the ODC activity stimulated by asparagine in IEC-6 cells (a rat intestinal crypt cell line). The half-life of ODC in unstimulated IEC-6 cells was 20 min and increased to 35 min in cells exposed to 10 mM asparagine. These data demonstrate that ODC of nonproliferating villous cells is regulated differently from the identical enzyme in proliferating crypt cells. Therefore, conclusions regarding mucosal growth should not be based totally on ODC activity from whole mucosa, since it is essentially a measure of only the enzyme present in the villous cells.

Role of ornithine decarboxylase in repair of gastric mucosal stress ulcers

The purpose of this study was to determine whether ornithine decarboxylase (ODC) has a role in mucosal repair during the first 24 h after stress-induced damage. Rats were fasted 22 h, placed in a restraint cage, and immersed in water to the xiphoid process for 6 h. Animals were killed either immediately after the period of stress or at 2-h intervals up to 24 h thereafter. Gastric mucosal ODC increased significantly from 0 to 12 h and peaked 4 h after the 6-h stress period. By 24 h enzyme activity in the gastric mucosa was near normal. Macroscopic lesions were regularly produced after 6 h of stress. Histologically, stress caused extensive damage to the superficial epithelial cells, extending in some cases into the mucosa and beyond the basal lamina. However, after stress the mucosa recovered quickly, returning to near normal 24 h later. The decreases in mucosal content of DNA, RNA, and protein caused by stress also were restored and reached near-normal levels 24 h after stress. alpha-Difluoromethylornithine (DFMO), a specific inhibitor of ODC, not only inhibited the ODC activity but significantly delayed the recovery from injury as well. DFMO also prevented the restoration of DNA, RNA, and protein content of the gastric mucosa. In conclusion, stress-induced gastric mucosal lesions are accompanied by significant increases in ODC activity. The increased ODC is necessary for the normal repair of the mucosa.

Induction of gastric and duodenal mucosal ornithine decarboxylase during stress

The purpose of this study was to determine whether gastric and duodenal mucosal ornithine decarboxylase (ODC) activity increased during a period of ulcer-producing stress and whether changes in enzyme activity altered the severity of damage. Rats were fasted for 22 h, placed in a restraint cage, and immersed in water to the xiphoid process for different times lasting from 2 to 8 h. After 6 h, stress slightly increased gastric mucosal ODC and caused a sevenfold increase in duodenal mucosal ODC activity. Macroscopic ulcers developed in the oxyntic gland mucosa but not duodenal mucosa. Interestingly, however, after 6 h microscopic inspection showed an absence of most villi from the duodenum. DNA, RNA, and protein content of both tissues decreased over the time rats were exposed to stress. DL-alpha-Difluoromethylornithine (DFMO, a specific ODC inhibitor) prevented the increase in ODC in both tissues and increased the loss of DNA and RNA from duodenal mucosa. The degree of damage was not altered by DFMO in either tissue in response to 6 h of stress. These results show that 1) stress causes microscopic damage to the duodenum, 2) stress increases ODC in both gastric and duodenal mucosa, and 3) the inhibition of ODC during 6 h of stress does not alter the severity of damage.

Respiratory symptoms, lung function, and mortality in a screening center cohort

Numerous studies have documented the effects of smoking and reduced pulmonary function on all-cause mortality. The effects of respiratory symptoms are less well studied. This paper examines the joint effects of respiratory symptoms, lung function, and smoking using 11-year mortality data on 698 subjects aged 25 years and older. Copies of death certificates were obtained for all 120 confirmed deaths, and cause of death was coded by a nosologist using the rules of the International Classification of Diseases, Ninth Revision. Symptoms of cough/phlegm, wheeze, and dyspnea were significantly associated with all-cause mortality in separate univariate analyses. On a cause-specific basis, these associations appeared to hold for chronic obstructive pulmonary disease, lung cancer, and vascular disease. Further analysis indicated that, for both smokers and nonsmokers, the presence of chronic cough and/or sputum production was related to mortality only in the presence of wheezing. In addition, among smokers, the presence of both cough/phlegm and wheeze. In addition, among smokers, the presence of both cough/phlegm and wheeze was significantly associated with mortality only among subjects with low initial lung function. Although the limited number of deaths and the nonrandom nature of the cohort limit the generalizability of our findings, it seems clear, based on these results and other published studies, that symptoms of cough, phlegm, and/or wheeze have important adverse health implications even in the absence of smoking and reduced lung function. More studies using common methodological approaches are needed.

Urinary arsenic concentrations and speciation in Cornwall residents

Inorganic arsenic and its methylated metabolites were determined in urine from adults and children in Cornwall and from corresponding control groups in Glasgow. In the mineralised south-west of England, where it has been suggested that the highly enriched soil arsenic concentrations may at least be a cofactor in the increased incidence of skin cancer, urinary arsenic levels were, in general, only slightly elevated. The potential for increased intake of inorganic arsenic in Cornwall was, however, reflected in the more frequent occurrence of trivalent inorganic arsenic and monomethylarsonic acid in urine and, of especial significance, in two comparatively highly elevated sum of arsenic species concentrations of 48.7 and 20.8 μg g(-1) creatinine recorded for two pre-school children. These findings are discussed with reference to recommended limits and pathways of exposure to inorganic arsenic.