Polychlorinated biphenyls: penetration into the deep ocean by zooplankton fecal pellet transport.

High concentrations of polychlorinated biphenyls (PCB's) were found in fecal pellets from natural populations of euphausiids collected in the Ligurian Sea. Since biogenic particulate products, especially fecal pellets, are known to sink rapidly and intact to the ocean bottom, the transport of PCB's by such sinking particles could be an important mechanism which contributes to the penetration of PCB's into the deep sea.

Cholestyramine: use as a new therapeutic approach for chlordecone (kepone) poisoning.

In rats, as reported in humans, chlordecone (Kepone) is excreted predominantly in the feces. Cholestyramine, an anion exchange resin, binds chlordecone in rat intestine, increases its excretion into the feces, and decreases its content in the tissues. The resin appears to offer a practical method for treating chronic poisoning with this and possibly with other lipophilic toxins.

Nitrite and nitrate are formed by endogenous synthesis in the human intestine.

Studies of nitrate balance in humans and analyses of fecal and ileostomy samples indicate that nitrite and nitrate are formed de novo in the intestine, possibly by heterotrophic nitrification. These findings significantly alter our previous conceptions of human exposure to nitrite and suggest an even wider role for nitrite in the etiology of human cancer.

Bovine protoporphyria: the first nonhuman model of this hereditary photosensitizing disease.

Protoporphyria, a photosensitizing disease documented only in humans, was transmitted as a recessive trait to seven female calves. Cutaneous lesions were extensive, and erythrocyte and fecal protoporphyrin concentrations exceeded by far those of human protoporphyria. Average ferrochelatase activity was decreased to one-half of normal in the liver of carriers, and to about one-tenth of normal in liver, kidney, heart, spleen, lung, and marrow of protoporphyrics.

Influence of diets high and low in animal fat on bowel habit, gastrointestinal transit time, fecal microflora, bile acid, and fat excretion.

Epidemiological observations and animal experiments suggest that large bowel cancer is related to serveral factors. Among them, high dietary intakes of animal fat, the presence in the colon of relatively high levels of bile acids, specific patterns of intestinal microflora, slow transit through the gut, and low stool weights. Under metabolic conditions we have observed the effect on these variables of dietes containing 62 or 152 g/day of fat mainly of animal origin in six healthy young men over 4-wk periods. No change attributable to the diet was observed in the subjects' bowel habit, fecal weight, mean transit time through the gut, or in the excretion of dry matter. Total fecal bile acid excretion was significantly higher on the high fat diet (320 +/- 120 mg/day) than on the low fat diet (139.7) +/- 63 mg/day) t test = 7.78 P less than 0.001 as also was the total fecal fatty acid excretion, 3.1+/-0.71 and 1.14+/-0.35 g/day, respectively t test = 11.4 P less than 0.001). The fecal microflora including the nuclear dehydrogenating clostridia were unaltered by the dietary changes as was fecal beta-glucuronidase activity. Dietary changes which increase animal fat intake clearly influence fecal bile acid excretion in a way that would favor the development of large bowel cancer if current theories prove to be true. Dietary fat however has no effect on overall colonic function so other components of the diet must be responsible for the observed associations of bowel cancer with slow transit and reduced fecal bulk.

Role of pH in production of hydrogen from carbohydrates by colonic bacterial flora. Studies in vivo and in vitro.

Hydrogen produced by colonic bacteria and excreted in breath is a useful index of carbohydrate malabsorption. Since colonic contents are often acidic in individuals with carbohydrate malabsorption and in normal newborns, we determined the effect of colonic acidification on H2 production. Acidification of colonic contents by dietary means significantly reduced excess breath H2 excretion from 55.4 +/- 11.1 (SEM) to 12.2 +/- 3.1 ml/4 h (P less than 0.05) after administration of 0.3 g/kg of the nonabsorbable sugar lactulose to five normal adult subjects. Similarly, the breath H2 response to lactose was reduced or eliminated in two proven lactose malabsorbers after acidification. The correlation between pH and H2 production from carbohydrate was further investigated in adults and neonates, using an in vitro fecal incubation system. Glucose disappearance and H2 production were pH dependent and highly correlated (r = 0.94) in the pH range 5.5-7.6. Maximal production of H2 from glucose by fecal incubates occurred at pH 7.0-7.45. Inhibition of H2 production from carbohydrate occurred at acid pH. H2 per hour from glucose at pH 6.2 and 5.5 averaged 60.2% and 24.2%, respectively, of that produced at neutral pH. Rapid reversal of pH-induced inhibition by neutralization indicated a metabolic, rather than a bactericidal process. The observations indicate that the breath H2 response to malabsorbed carbohydrate is affected by colonic pH. It appears that the efficiency of bacterial carbohydrate metabolism in the colon is pH dependent.

The different effects on the serum lipids and fecal steroids of high carbohydrate diets given orally or intravenously.

The hypothesis that diets high in carbohydrate produce hyperlipidemia in man was tested in new experiments which provided all calories either by the intravenous route or orally. After a base-line general diet, eight healthy men were fed fat-free diets consisting of 80% of the calories from glucose and 20% from an amino acid hydrolysate. The calories were adequate to maintain body weight. The solutions (1 cal/ml) were infused by constant drip over a 24 h period through either a superior vena cava catheter or a nasogastric tube. Each feeding was for 12 days in sequence but assigned in random order. The high CHO diet given orally, as expected, increased the mean base-line serum triglyceride level from 176+/-29 (SE) to 274+/-47. The identical diet given intravenously (i.v.) failed to produce hypertriglyceridemia; triglyceride levels were not significantly changed, 154+/-37, nor were blood glucose levels. Serum insulin levels were higher during the intravenous feeding. In contrast, both i.v. and oral feedings greatly lowered mean serum cholesterol concentration from the base-line value of 220+/-13 mg/100 ml to 135+/-11 and 151+/-13, respectively. However, the serum cholesterol level was significantly lower (P < 0.01) with the intravenous feeding than with the oral feeding. In addition, the fecal excretion of both neutral sterols and bile acids diminished greatly during the period of intravenous feeding. The fecal mass was likewise decreased. The bacterial conversion of cholesterol to conprostanol did not occur with either intravenous or oral feeding, but with both regimens secondary bile acids predominated, as usual, in the bile acid fraction of the stool. These results emphasize the key role of the intestinal mucosa in the etiology of carbohydrate-induced hypertriglyceridemia and as a direct or indirect contributor to plasma triglyceride and cholesterol levels in the absence of dietary lipids. When the gut mucosa was bypassed, carbohydrate-induced hypertriglyceridemia did not occur and both serum triglyceride and serum cholesterol levels decreased greatly at a time when the excretion of steroids in the stool was also reduced.

Tryptophanase of fecal flora as a possible factor in the etiology of colon cancer.

Twenty-three strains of intestinal anaerobes obtained from two laboratories were examined for indole production from tryptophan. Among the 23 isolates tested, three of Bacteroides fragilis thetaiotaomicron and one Citrobacter sp. were indole positive. The tryptophanase of the indole-positive strains of intestinal anaerobes was inducible by tryptophan and was susceptible to glucose repression. The products of tryptophanase activity were formed in stoichiometric amounts by dialyzed, freshly prepared extracts. The tryptophan concentration and tryptophanase activity in feces from rats on an all-meat diet were significantly higher than those in feces from rats on a normal diet. The results indicated that the higher tryptophanase activity in the feces of rats fed an all-meat diet is due to the inducibility of this enzyme by tryptophan and is not due to any inhibitor in the feces of rats on a normal diet. The results also suggested that a population with a diet rich in meat has a greater chance for exposure to possible carcinogens such as indole and other tryptophan metabolites. This agrees with the hypothesis, based on epidemiologic data, that a high intake of meat may be related to the development of colon cancer in man.

Benzo(a)pyrene disposition and metabolism in rats following intratracheal instillation.

[3H]Benzo(a)pyrene [B(a)P] disposition and metabolism were investigated in male Sprague-Dawley rats. [3H]B(a)P, in a vehicle of triethylene glycol, was administered by intratracheal instillation (1 microgram/kg body weight), and the amount of radioactivity in various organs was determined at timed intervals between 5 and 360 min. Elimination of radioactivity from lungs was biphasic with half-lives of 5 and 116 min. Radioactivity in liver increased rapidly, reaching a maximum of 21% of the dose within 10 min after instillation and decreasing thereafter until less than 5% of the dose was detected at 360 min after instillation. The carcass accounted for 15-30% of the dose within the time intervals investigated. Toxicokinetic parameters to describe elimination of unmetabolized B(a)P from blood following intratracheal administration were found to be very similar to those calculated following i.v. administration. B(a)P metabolites in lung, liver, and intestinal contents were identified. Notably, quinones were at highest concentrations in both lung and liver 5 min after instillation, accounting for 12 and 7% of organic extractable material, respectively. B(a)P disposition was also investigated in animals with and without biliary cannulas. Distribution patterns among organs were similar though the amount excreted in bile and intestinal contents was 74 and 40% of the dose, respectively. Types of metabolites in bile and intestinal contents were identified and compared. Lower fractions of the administered dose were detected as thioether and glucuronic acid conjugates in intestinal contents than in bile, indicating that enterohepatic circulation of B(a)P metabolites was occurring.

Metabolic epidemiology of colon cancer: effect of dietary fiber on fecal mutagens and bile acids in healthy subjects.

Because of potential significance of fecal mutagens and secondary bile acids in the pathogenesis of colonic cancer and of inverse association between dietary fiber and colonic cancer risk, the effect of dietary wheat and rye fiber on fecal mutagenic activity and bile acid levels was studied in 15 healthy men and women who were consuming high fat/moderately low fiber diets and excreting high levels of fecal mutagens and bile acids. Each participant provided two 24-h stool specimens and a 3-day diet record while consuming their normal diet (control). All subjects were then asked to consume their normal diet plus 11 g of supplemental fiber per day in the form of whole grain bread for 4 weeks. During the last week of diet intervention, each subject provided two 24-h stool specimens and a 3-day dietary record. Fecal samples collected from both periods were analyzed for bile acids and for mutagens using Salmonella typhimurium strains TA98 and TA100 with and without microsomal activation. The concentration of fecal secondary bile acids was significantly lower during the fiber supplemental period in all subjects. Fiber supplementation also inhibited the fecal mutagenic activity in TA100 and TA98 with and without microsomal activation. Thus, the increased fiber intake in the form of whole wheat and rye bread may reduce the production and/or excretion of fecal mutagens and decrease the concentration of fecal secondary bile acids in humans.

Effects of dietary saturated and unsaturated fatty acids on fecal bile acids and colon carcinogenesis induced by azoxymethane in rats.

To determine whether the kind of dietary fat affects colon carcinogenesis, male Donryu rats were fed a 5% fat diet containing linoleate, an unsaturated fat, or stearate, a saturated fat, in semipurified fat-free chow. The rats were given azoxymethane (7.4 mg/kg body weight) s.c. once a week for 11 weeks and killed 15 weeks after the last injection of the carcinogen. The rats on the unsaturated fat diet had a significantly higher incidence of colon tumors. Fatty acid analysis of cholesterol esters in the liver and examination of the amount of fecal bile acids showed that the unsaturated fat diet increased the level of cholesterol linoleate and arachidonate in the liver and also increased the fecal excretion of bile acids, especially that of lithocholic acid. The colon tumors in rats on the unsaturated fat diet, compared with those in rats on the saturated fat diet, contained a higher level of lysophosphatidylcholine. These results suggest that increased fecal excretion of bile acids due to increased polyunsaturated cholesterol esters in the liver stimulates phospholipase A2 activity of colon initiated cells and enhances colon carcinogenesis in rats on the unsaturated fat diet.

Cholesterol homeotasis in rats fed a purified diet.

The rate of whole bodyb cholesterol synthesis was measured in male Sprague-Dawley rats fed either a standard chow, cereal-based diet or a semi-synthetic purified diet consisting of casein, sucrose and lard. The purified diet significantly decreased daily fecal excretion of neutral and acidic sterols, the specific acitvity of hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase, the bile acid pool size, and total daily cholesterol synthesis in the rat, while increasing plasma cholesterol concentrations and the total body content of cholesterol. The increased body content of cholesterol occurred primarily in muscle and connective tissue and not in the liver. The data demonstrate the importance of quantitating the net tissue accumulatin of cholesterol for accurate measurement of daily sterol synthesis in growing animals when sterol balance measurements are used. Tissue accumulation accounted for 7% of total daily cholesterol synthesis in rats fed the cereal diet, and 20% of daily synthesis in animals fed the purified diet.

Penetrability of proteins through the digestive system of Sarcophaga falculata blowfly.

On the background of the previous findings concerning the passage of a low molecular basic protein from cobra snake venom through the gut of a blowfly (Primor, N., Teitelbaum, Z. and Zlotkin, E. (1980) Biochim, Biophys, Acta 627, 71--81) several additional proteins were tested in the present study. With the aid of toxicity tests, radioiodinated proteins, gel filtration chromatography, and the usage of Sarcophaga falculata flies as test animals, the following information was obtained: 1. Out of the five species (representing four orders) of insects tested, only flies demonstrated the lethality by oral application of cobra snake venom. 2. The absence of oral toxicity of flies to phospholipase A2 (highly lethan by injection of cobra venom with molecular weight of about 13,000) was due to its impermeability through the digestive system. 3. About 2.2% of the orally applied low molecular weight basic neurotoxin (Mr 7000) from cobra venom crossed the gut and was found in the insects' hemolymph. 4. Bovine serum albumin (Mr 68,000) and an immunoglobulin (Mr 180,000), under the present experimental conditions, were found to be gut impermeable.

A new method for the assessment of thyroxine metabolism in the rat.

A new method for assessing thyroxine (T4) metabolism in the rat has been devised and the results that it yields have been compared to those obtained by other methods for assessing peripheral T4 metabolism. The new method uses a simple analysis of the kinetics of exogenous T4 metabolism in rats chronically treated with daily injections of exogenous labeled T4 to determine T4 clearance rates via both fecal and deiodinative pathways. Fecal clearance rates of endogenously labeled hormone measured in rats brought into approximate 125I/127I specific activity equilibrium by administration of iodide of know specific activity in the drinking water were nearly the same as those determined with this new method. Furthermore, total T4 clearance rate determined with the new method agreed well with that measured by the standard single injected technique utilizing radioactive T4. These results indicate that quantitation of the clearance rate of endogenous T4 via not only the fecal, but also the deiodinative, pathway for T4 disposal can be achieved with this new method. In rats made hyperthyroid with exogenous T4, clearance rates of T4 via both deiodinative and fecal pathways were markedly increased. This result supports the concept that hyperthyroidism increases the activity of the tissue mechanisms for metabolizing T4.

Effects of diflunisal on platelet function and fecal blood loss.

The effects of diflunisal, a nonacetylated difluorinated salicylate, on platelet function were compared with those of aspirin and placebo. In a randomized, double-blind trial, normal subjects were given diflunisal, 250, 500, or 1,000 mg twice daily; aspirin, 650 or 1,300 mg twice daily; or placebo for 8-day periods. Difunisal, 250 mg, had no effect on platelet function, whereas 500 mg induced minimal inhibition of colagen-induced release of platelet serotonin, and 1,000 mg inhibited platelet malondialdehyde production, moderately prolonged template bleeding times (P = NS), and increased fecal blood loss (P less than 0.05). In contrast, aspirin, 650 mg, markedly inhibited collagen-induced platelet aggregation and serotonin release, and 1,300 mg prolonged bleeding time (P less than 0.01) and increased fecal blood loss (P less than 0.01). The effects of aspirin lasted for up to 5 days, whereas changes induced by diflunisal had returned to baseline 24 hr after the drug was discontinued. We conclude that in doses in the same range as those of aspirin diflunisal inhibits platelet function less.

Metabolism of biliary steroids by human fecal flora.

Biliary excreted steroid hormones are metabolized by the intestinal flora. The metabolic pathways of deoxycorticosterone and progesterone, including the bacterial species involved, have been established. The pathways for other biliary steroids are unknown. Information on the biological activities of the metabolites is lacking, but methods for their investigation are now available. Evidence suggests that the formation of the metabolites is influenced by dietary habits, and that, in some cases, it may be controlled by suppression of the responsible bacteria.

Modification of stool content by increased bran intake.

Six healthy subjects, four males and two females, were studied for 8 weeks with daily dietary history, 72-hr weekly stool collections, and analysis of stool specimens for fecal weight, water, pH, and total aerobic and anaerobic qualitative and quantitative bacteria. Subjects were studied first for a 3-week control period, followed by 3 weeks of 5.4 g of crude fiber supplementation daily (Kellogg's "All Bran"), and then by a 2-week control period. Analysis of diets revealed that the mean intake of crude fiber rose to at least 10 g/day, and stool volume increased significantly during the high-fiber intake. The stools remained at the same pH, and the same percentages of water and solids were present durin- control and high-fiber-intake periods. Bacteriological analysis revealed no significant differences in qualitative or quantitative counts; however, the ratio of anaerobic to aerobic organisms appeared to increase.

Effect of citrus pectin on blood lipids and fecal steroid excretion in man.

Citrus pectin (15 g/day) was added for 3 weeks to metabolically controlled diets in nine subjects. Pectin was consumed with fruit and sugar as a gel in divided doses with meals. Plasma cholesterol concentrations were reduced by a mean of 13% (P less than 0.001). Fecal fat excretion increased by 44% (P less than 0.001); neutral steroids by 17% (P less than 0.001) and fecal bile acids by 33% (P less than 0.02). Plasma triglyceride levels did not change.

Effect of psyllium gum and wheat bran on spontaneous energy intake.

Energy intake, fecal energy output, and gastrointestinal symptoms were measured in 12 females who consumed either approximately 23 g/d supplementary fiber or a 4 g/d fiber control. Fiber supplements were crackers containing psyllium gum, wheat bran, or a combination of the two fiber sources. After 1 wk on the control cracker, subjects consumed the three high-fiber crackers and the control cracker for 2-wk periods in a balanced design. Gum and combination supplements gave increased bloating and flatulence. Increase in abdominal pain was reported with gum supplement. Mean daily fecal energy was 96 kcal/d with control crackers and was increased by 63 kcal with high-fiber crackers. Gum and combination supplements significantly decreased intake of digestible energy by 153 and 115 kcal/d, respectively. This suppression was not dependent upon fiber intolerance. Wheat bran supplement had no effect on energy intake.

Hypolipidemic effects in dogs of ML-236B, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase.

ML-236B, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, significantly reduced both serum cholesterol and phospholipid levels in dogs, when used at a dosage higher than 10 mg/kg per day. Triglyceride levels were not consistently changed, but beta- and pre-beta-lipoproteins were preferentially reduced. Serum cholesterol levels were reduced by 44--45% at the higher dosage of 100--400 mg/kg per day (for 5 weeks) but ML-236B caused no significant changes in the cholesterol content of the liver and aorta and in the activities of serum GOT, GPT, CPK and lecithin : cholesterol acyltransferase. Fecal excretion of neutral sterols was unaffected but that of bile acids was markedly elevated by the drug. Under these conditions, hepatic cholesterol 7alpha-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis, showed no detectable changes.