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Biomedical subjects

A Wise

Publications and source records attributed to A Wise.

At least 91 records · Page 5Linked to original sources
PubMed1984

Dietary fat and cecal microbial activity in the rat.

Weanling rats were fed low-fat (1% w/w safflower oil) or high-fat (1% w/w safflower oil plus 35% w/w beef fat or cocoa butter) diets for 30 days, and the activities of five cecal microbial enzymes were determined. When compared with the low-fat diet, beef fat significantly increased total cecal beta-glucuronidase activity, but cocoa butter, with a similar fatty acid composition, did not. Both high-fat diets significantly decreased total cecal azoreductase, beta-glucosidase, and nitrate reductase activities, but neither significantly affected urease activity. When expressed as specific activities (per 10(11) bacteria), cocoa butter decreased azoreductase, and beef fat caused increases of beta-glucuronidase and urease. Beef fat, but not cocoa butter, significantly reduced cecal bacterial numbers when compared to the low-fat diet. Both high-fat diets led to equivalent reductions in the proportion of aerobic bacteria.

Anaerobiosis↗
PubMed1983

Transient neurologic disturbances, brain tumors, and normal computed tomography scans.

During a 4-year period, four patients presented with transient disturbances in neurologic function that were diagnosed as seizures in two and transient ischemic attacks in the other two. Computed tomography (CT scan), both with and without contrast, was normal in all four patients. Isotopic brain scans (3 patients), cerebral angiograms (4 patients), and lumbar punctures (4 patients) were normal. Electroencephalograms (EEG) were normal in two patients and abnormal in two patients (consisting of focal slowing). Within 4.5 months, all patients developed symptoms and signs of a brain tumor, and in all four, CT scan now revealed a large mass lesion which at surgery was shown to be a malignant astrocytoma. These four patients constituted 4% of the total number of patients with malignant astrocytomas that were seen at the NYU Medical Center during this same time period. It is stressed that the CT scan may be normal early in the course of patients with brain tumors, particularly if they present with a transient disturbance in neurologic function. The first evidence of the tumor in such patients may be a slow-wave abnormality on the EEG. Patients who are suspected of having a brain tumor should, if the initial CT scan is normal, have the scan repeated later.

Adult↗
PubMed1983

A comparison of the activity of five microbial enzymes in cecal content from rats, mice, and hamsters, and response to dietary pectin.

Rats, mice, and hamsters were fed a fiber-free purified diet for 30 days and the activity of a number of cecal microbial enzymes was determined. Expressed per gram cecal content, azoreductase activity was greatest in preparations from the hamster and least from the mouse, and beta-glucosidase and beta-glucuronidase activities were least active from the rat. Nitroreductase was less active and nitrate reductase more active from the hamster in comparison to the other species. When expressed per kilogram body weight, bacterial activities were always greatest from the hamster. When the basal diet was supplemented with pectin (50 g/kg diet), nitrate reductase activity was increased six- to sevenfold per gram cecal content for rats and mice (tenfold when expressed per kilogram body weight), but there was no effect on the nitrate reductase activity of hamster microflora. Pectin also significantly increased beta-glucuronidase activity in rats, but significantly reduced the activities of the other enzymes in at least one of the three species.

Animals↗
PubMed1983

Effect of dietary cellulose on the metabolic activity of the rat caecal microflora.

Alpha-cellulose, added to a purified diet at six levels [0%, 2.5%, 5%, 10%, 20%, and 40% (w/w)] and fed to weanling rats for 3 weeks, had no effect on body weight, but it increased the weight of caecal contents and decreased the numbers of bacteria per total caecal contents. Caecal microbial azoreductase, nitroreductase, beta-glucosidase and nitrate reductase activities per total caecal contents were also significantly decreased by 10% dietary cellulose and above, yet beta-glucuronidase activity was only affected significantly by 40% dietary cellulose. Azoreductase and nitroreductase activities were highly correlated with one another and showed a similar response to cellulose.

Animals↗
PubMed1983

Metabolic profile of caecal micro-organisms from rats fed indigestible plant cell-wall components.

A fibre-free diet, or the same diet supplemented with 100 g cabbage or carrot cell-wall preparation/kg, was fed to rats for 28 days and the activities of a number of caecal microbial enzymes (azoreductase, aryl nitroreductase, beta-glucosidase, beta-glucuronidase, imidazole nitroreductase and nitrite reductase) were determined in vitro. The plant cell-wall preparations diluted the gut contents and decreased the number of bacteria per gram of caecal contents. Enzyme activities per gram of caecal contents were also decreased, with the exception of beta-glucosidase activity which was significantly increased. These plant cell-wall preparations also increased caecal size, and thereby significantly increased total activity per caecum of microbial azoreductase, aryl nitroreductase, beta-glucosidase and beta-glucuronidase. When bacterial metabolism was expressed per 10(9) bacteria, all enzyme activities were significantly increased in caecal samples from rats fed the plant cell-wall preparations. There was an overall concordance of 0.91 between all the enzymes when expressed per 10(9) bacteria, but of only 0.38 when enzyme activities were expressed per gram of caecal contents.

Animals↗
PubMed1983

Dietary protein and cecal microbial metabolism in the rat.

Adult rats were fed diets containing 0, 25, 50, 100, 200, or 400 g lactalbumin/kg diet for 10 days, and the activities of six cecal microbial enzymes were determined. Total activity per cecum of azoreductase, beta-glucosidase, and urease increased significantly with increasing dietary protein, whereas the activities of beta-glucuronidase and nitroreductase were not significantly affected. Nitrate reductase activity decreased significantly. Total numbers of cecal bacteria were not significantly altered by the treatment.

Animals↗
PubMed1983

Interaction between pectin and rat hindgut microflora.

The contents of the lower alimentary tract from rats fed a semisynthetic, pectin-supplemented diet showed increased nitrate reductase activity and an increase in the amount of luminal contents in the intestine and cecum. Nitrate reductase activity was associated with the insoluble fraction of the gut contents which was sedimented by centrifugation (5,100 X g,20 min) and was abolished after treating the animals with streptomycin, neomycin, and bacitracin for 7 days. The pectin-dependent increase in cecal size and microbial nitrate reduction were reversed when animals were transferred from a pectin-supplemented onto a control semisynthetic diet. Polygalacturonic acid (pectic acid) was without effect on either cecal size or cecal microbial nitrate reductase activity. The studies demonstrate that pectin influences microbial metabolism in the alimentary tract.

Animals↗
PubMed1983

Effect of dietary carrageenan and pectin on the reduction of nitro-compounds by the rat caecal microflora.

Rats were fed either a basal purified diet, or that diet supplemented with 50 g/kg pectin or iota carrageenan for 50 days, and caecal microbial nitroreductase activity determined using p-nitrobenzoic acid, p-nitrophenol, 2,4-dinitrotoluene, nitrofurantoin and metronidazole as substrates. Both pectin and carrageenan increased the weight of caecal contents, and pectin also increased the number of bacteria per caecum. In contrast, carrageenan decreased the caecal bacterial population. Pectin significantly increased the rate of reduction of metronidazole and the rate of conversion of p-nitrobenzoic acid to p-aminobenzoic acid, while carrageenan significantly decreased the rate of reduction of every compound studied. The results demonstrate that microbial reduction of the nitro-group may be altered by diet, although the response found with one nitro-compound may differ from that seen with another substrate.

Animals↗
PubMed1983

Microbial metronidazole metabolism: rat diets for safety testing procedures.

High concentration of metronidazole decrease the nitroreductive activity of the rat's cecal microflora, and preincubation with the drug lowers metabolic activity in vitro. Therefore high doses of metronidazole may lead to a lower yield of potential carcinogenic intermediate(s) in vivo. Since diet influences cecal microbial nitroreductive activity, a combination of diet and dose control may be used to maximize the potential carcinogenicity of the drug in safety evaluation procedures.

Animals↗
PubMed1982

Interaction of diet and toxicity--the future role of purified diet in toxicological research.

There is a growing awareness of the importance of diet as a determinant of the toxicity of many compounds. This paper briefly reviews some of the ways in which diet affects toxicity, and draws some conclusions regarding the ideal diet for toxicological investigations. Then the two competing types of diet, stock and purified (including those frequently called semi-synthetic and semi-purified), are described and their characteristic strengths and weaknesses are discussed. Stock diets are very variable commodities, may be nutritionally poorly balanced, and also contain many non-nutritive components that influence toxicity. The formulation and preparation of purified diet are discussed. It is concluded that investigations of the mechanisms of toxicity, as well as studies of absorption, distribution and metabolism of toxic compounds, could benefit from the use of well-defined purified diets.

Animal Feed↗
PubMed1982

In vitro competition between calcium phytate and the soluble fraction of rat small intestine contents for cadmium, copper and zinc.

Calcium phytate precipitates were mixed with cadmium (Cd), copper (Cu), or zinc (Zn); in each case most of the trace metal was found to bind to the precipitate. In the presence of some amino acids, picolinic acid or soluble contents of rat intestine, binding was reduced. The solubility effects were low for Cd and Zn, but much higher for Cu. The extent to which Cd was solubilized by intestinal extract was correlated with calcium concentration, but for Cu and Zn it appeared that the concentration of amino groups was the most important factor.

Amino Acids↗
PubMed1982

Phytate hydrolysis by germfree and conventional rats.

Phytic acid is naturally occurring compound that reduces intestinal absorption of many metals. Early work suggests that some dietary phytate may be hydrolyzed in the large intestines by bacteria, but more recently nutritionists have suggested that a mucosal enzyme is responsible. This paper reports a study intended to resolve this controversy. The hydrolysis of dietary phytic acid was measured in germfree and conventional rats fed either of two diets that differed in their calcium content. Negligible phytate hydrolysis occurred in the germfree rats, whereas 22 and 56% of the phytic acid was hydrolyzed by conventional rats fed high- and low-calcium diets, respectively. We concluded that bacteria were responsible for the hydrolysis of phytate in these diets and that any activity of endogenous enzyme was negligible.

Animals↗
PubMed1982

Long term survival among patients with malignant brain tumors.

Eight of 57 patients (14%) with malignant astrocytomas lived at least 2 years. The mean survival time was 143 weeks (range, 104 to 250 weeks). All of the patients were treated with operation, radiation, and chemotherapy. Four of the 8 patients died because of tumor recurrence, 1 died from a second primary tumor, 2 died of cases unrelated to the tumor, and 1 is still alive. Diffuse cortical dysfunction associated with cortical atrophy that could not be related to tumor regrowth and was not explained by focal deficits, psychotic of depressive thought disorders, metabolic or endocrine abnormalities, or hydrocephalus developed in the 3 longest-surviving patients. The diffuse dysfunction was initially apparent only through psychometric testing, but eventually became so disabling as to result in 2 of the 3 patients retiring from work. Although small, but gratifying, gains have been made in the treatment of patients with malignant brain tumors, accompanying these gains have been problems of a magnitude that is only now beginning to be appreciated.

Adult↗
PubMed1982

Dietary fibre, bacterial metabolism and toxicity of nitrate in the rat.

1. A semi-synthetic diet, the semi-synthetic diet plus pectin, and a stock diet were fed to rats, and three metabolic functions of the caecal bacteria (reduction of amaranth, p-nitrobenzoic acid and nitrate) were measured in vitro. 2. No consistent differences were noted between diets for the reduction of amaranth and p-nitrobenzoic acid. 3. No consistent differences in nitrate reductase activity were noted for rats maintained on a stock diet or a fibre-free diet. However, the addition of 5% pectin to the latter diet resulted in a several-fold increase in nitrite production. 4. This increased nitrite production in vitro was associated with methaemoglobinaemia following the oral administration of nitrate to rats fed the diet containing pectin. Animals receiving the basal fibre-free diet were unaffected by nitrate.

Animals↗