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Biomedical subjects

T K Smith

Publications and source records attributed to T K Smith.

At least 145 records · Page 8Linked to original sources
PubMed1987

Effect of dietary methionine, arginine and ornithine on the metabolism and accumulation of polyamines, S-adenosylmethionine and macromolecules in rat liver and skeletal muscle.

The interrelationship and possible causality of polyamine synthesis and the transmethylation pathway in the growth-retarding effects of inadequate or excess dietary methionine was studied in young male rats. Feeding the rats for 2 weeks diets containing toxic concentrations of methionine had no effect on polyamine and S-adenosylmethionine metabolism in skeletal muscle, but resulted in markedly elevated concentrations of S-adenosylmethionine and S-adenosylhomocysteine and slightly decreased accumulation of spermine and RNA in the liver. These changes were accompanied by liver-specific stimulation of methionine adenosyltransferase and reduction of spermine synthase activities. Inadequate arginine feeding or supplementation of the diets with ornithine or excess arginine resulted in no apparent changes in tissue methionine or polyamine metabolism and did not alleviate the effects of varied dietary methionine supply. Inhibition of putrescine synthesis by supplementing the diets with 2-difluoromethylornithine did not modify the effects of toxic concentrations of dietary methionine. It is suggested that although hepatic spermine synthase is sensitive to excess methionine feeding, methionine toxicity is not mediated by defective polyamine metabolism.

Amino Acids↗
PubMed1987

Prevention of complications in orthopedic surgery secondary to nutritional depletion.

One of the major factors in the prevention of complications in orthopedic surgery patients is the maintenance of adequate nutrition. Trauma and elective surgery patients have nutritional requirements that are far greater than is generally realized. The use of nutritional assessment profiles will help to reveal patients who are malnourished or becoming malnourished, and will help to assess nutritional replacement. Protein and calorie malnutrition has a significant effect on wound healing, immunocompetence, and fracture healing. Surgeons should have the nutritional status of their patients in mind at all times and thereby avoid the complications associated with malnutrition.

Humans↗
PubMed1986

Enteric neural regulation of slow waves in circular muscle of the canine proximal colon.

The spontaneous electrical activities of circular muscle cells of the canine proximal colon were studied with intracellular micro-electrodes. All circular muscle cells exhibited slow waves at frequencies ranging between 2.8 and 7.0 cycles/min. The slow waves consisted of an upstroke phase followed by a plateau phase of variable duration (2-40 s). Many cells displayed a slow diastolic depolarization, or 'pre-potential' between slow waves. Slow waves spontaneously varied in duration and frequency in most preparations, creating distinctive slow wave patterns. Atropine, 2 X 10(-6) M, decreased the durations of slow waves in many preparations and often changed the pattern to a series of relatively uniform slow waves. A further reduction in mean slow wave duration was produced by additional treatment with tetrodotoxin, 10(-6) M. These results suggested that slow wave duration and pattern were affected by spontaneous discharge from both cholinergic and non-cholinergic excitatory nerves. Transmural nerve stimulation caused a short latency increase in slow wave duration (up to 38 s) that was abolished by atropine. In the presence of atropine, transmural stimulation evoked inhibitory junction potentials that reduced the amplitude and duration of the subsequent slow wave. The slow wave of reduced amplitude was followed by a slow wave of increased duration. The increase in duration of the slow wave did not appear to be related to the size of the preceding hyperpolarization, suggesting it was mediated by the release from non-cholinergic excitatory nerves. All responses to transmural stimulation were blocked by tetrodotoxin. Microejection of acetylcholine on to the muscle adjacent to the micro-electrode also produced an atropine-sensitive increase in slow wave duration. Tissues that had been stored in the cold overnight to reduce intrinsic neural activity exhibited regular slow waves of short duration. It is proposed that the basic myogenic pattern of spontaneous slow wave activity consists of regularly occurring slow waves of short duration (2-5 s). Intrinsic cholinergic and non-cholinergic excitatory nerves appear to modulate slow wave activity in vitro, producing distinctive slow wave patterns of variable instantaneous frequency and duration.

Acetylcholine↗
PubMed1986

Motoneurones of the submucous plexus regulate electrical activity of the circular muscle of canine proximal colon.

The hypothesis that the circular muscle of the canine proximal colon receives motor input from neurones in the submucous plexus was tested. Circular muscle cells were impaled with micro-electrodes and submucous plexus neurones were stimulated by electrical field stimulation and microejection of acetylcholine (ACh). In the presence of atropine to block the direct muscarinic effects, microejection of ACh onto the submucosa where intact submucous ganglia were suspended evoked: (i) an inhibitory junction potential (i.j.p.) that reduced the amplitude, duration and rate of rise of the subsequent slow wave; (ii) a slow wave of increased duration following the initial inhibitory response. These responses were enhanced by increasing the volume of ACh administered. Responses to ACh were blocked by hexamethonium, 10(-4) M; d-tubocurarine, 10(-4) M; or tetrodotoxin (TTX), 10(-6) M, suggesting they were neural in origin. Both inhibitory and excitatory responses were the result of non-cholinergic and non-adrenergic nerves. The transmitters mediating these effects are unknown. Removal of the longitudinal muscle, myenteric plexus, and the serosal portion of the circular muscle had no apparent effect on the responses to application of ACh to submucosal ganglia. In these preparations the responses to field stimulation were identical to those produced by ACh. The submucous plexus also provides cholinergic input to the circular muscle. When ACh was discretely applied to the submucosa cholinergic responses were elicited at the muscle cell which were significantly reduced by hexamethonium or TTX. These findings suggest that the cholinergic responses were the result of ACh release by neurones at the effector and not by overflow of the exogenous ACh. Cholinergic responses were also elicited in preparations in which the myenteric plexus had been removed. Slow waves in circular muscle of the proximal colon yield excitation-contraction coupling in the absence of Ca2+ action potentials. Therefore the influence of submucous neurones on electrical slow waves has direct consequences on motor activity. Reduction in the amplitude and duration of slow wave by i.j.p.s. results in reduction in the amplitude and duration of phasic contractions. Excitatory inputs enhance contractions. The data support a new concept: motoneurones emanating from submucous ganglia innervate the circular muscle and provide inhibitory and excitatory inputs to regulate slow wave activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1986

Tryptophan requirement of growing swine as determined by the oxidation of an indicator amino acid.

The tryptophan requirement of growing swine was determined using the oxidation of L-[1-14C]-phenylalanine as an indicator of the adequacy of the dietary tryptophan level. Forty crossbred boars (30 to 45 kg) were fed a basal diet containing 16% protein supplied by corn and gelatin. A series of experimental diets containing .05, .08, .10, .15, .20 and .25% L-tryptophan were prepared. The diets were supplemented with crystalline amino acids to provide 135% of the recommended levels. Release of 14CO2 was measured for 1 h following a meal of the experimental diet containing 20 microCi 14C phenylalanine. Increasing dietary tryptophan from .05 to .13% decreased release of 14CO2. Further increases in dietary tryptophan concentration did not significantly influence 14CO2 production. Regression analysis using a two-phase linear regression crossover model indicated that phenylalanine oxidation was minimized by a dietary tryptophan concentration of .13%. It was concluded that at a concentration of .13%, tryptophan was no longer limiting the retention of the other amino acids, thus this is the requirement for maximum protein retention by the young, growing boar.

Animal Nutritional Physiological Phenomena↗
PubMed1986

Influence of dietary lysine concentration on the oxidation of an indicator amino acid by growing boars.

The influence of dietary lysine concentration on the oxidation of 14C-phenylalanine by growing boars was determined. Forty-five crossbred boars (30 to 40 kg) were fed a ground corn diet fortified with crystalline L-lysine to provide .28, .50, .85, 1.00, 1.25 and 1.54% total lysine. All other essential amino acids were supplemented to provide 135% of NRC (1979) recommendations. Release of 14CO2 from L-[1-14C]-phenylalanine was measured for 1 h following a meal of the experimental diet, which contained 20 mu Ci 14C-phenylalanine. Increasing dietary lysine concentration from .28 to .85% decreased 14CO2 production. Regression analysis of the data using a two-phase linear regression crossover model indicated that phenylalanine oxidation was minimized at a dietary lysine concentration of .65%. It was concluded that a concentration of .65% lysine minimized the oxidation of amino acids and provided them as possible substrates for protein deposition. The oxidation of an indicator amino acid can, therefore, be used to determine the effect of dietary lysine concentration on the partition of amino acids between metabolic fuels and body protein.

Amino Acids, Essential↗
PubMed1985

Evaluation of Malthus 128H microbiological growth analyser for detecting significant bacteriuria.

In a pilot study a prototype Malthus 128H microbiological growth analyser was used to study the growth of six commonly encountered urinary pathogens in a range of five different laboratory media. No single medium had been able to show acceptable conductance changes for all bacteria within five hours. Subsequently, the Malthus system, with fastidious anaerobe broth as the culture medium, was used to screen 500 consecutive clinical specimens of urine for significant bacteriuria. After two and a half hours the Malthus system detected 32 out of the 40 true positives and eight of the 44 contaminated urines. Increasing the detection time to five hours permitted the recognition of 39 true positives and 37 contaminated urines.

Bacteriological Techniques↗
PubMed1985

Effect of leucine-rich dietary protein on in vitro protein synthesis in porcine muscle.

Experiments were conducted to determine the effect of feeding diets containing leucine-rich proteins on in vitro protein synthesis in porcine muscle. Swine (10 kg initial weight) were fed for 4 weeks diets composed mainly of corn gluten meal, corn and soybean meal, and containing a total of 2.00, 2.33, 2.92, 3.12, 3.53, and 4.01% leucine. At the end of the growing period, six swine fed each diet were killed and samples of biceps femoris, longissimus dorsi, and triceps brachii were excised. Incorporation of [14C]phenylalanine into newly synthesized protein was measured using a cell-free in vitro system following recombination of purified soluble protein and ribosomal fractions. The feeding of diets containing increasing amounts of leucine-rich protein increased the free leucine concentration in plasma and skeletal muscle. There was no significant effect of diet on incorporation of [14C]phenylalanine into muscle protein following simple recombination of soluble protein and ribosomal fractions from the same tissues. Combination of muscle soluble protein from animals fed 2.00% leucine with ribosomal fractions of animals fed increasing quantities of leucine-rich protein, however, indicated increased protein synthetic activity of the ribosomal fraction in all muscles tested. Protein synthetic activity of the soluble protein fraction was not affected by diet. It was concluded that the feeding of leucine-rich dietary proteins beyond requirements for maximal rate of growth can increase the protein synthetic potential of porcine muscle cells although whole body growth is depressed.

Animals↗
PubMed1985

Infection about the spine associated with low-velocity-missile injury to the abdomen.

We reviewed the cases of twenty patients who had a fracture or disruption of the disc space of a lower thoracic or lumbar vertebra that was associated with a low-velocity-missile wound to the abdomen. All of the patients underwent an exploratory laparotomy at the time of admission and all received broad-spectrum antibiotics for a minimum of two days. None of the patients had an immediate laminectomy or an immediate debridement of the paraspinal area. In eight patients the gastrointestinal tract was not perforated, and none of them had evidence of infection. In four patients the stomach and small bowel were perforated by the bullet before it struck the vertebral column, and none of them had meningitis, paraspinal infection, or osteomyelitis. In contrast, meningitis, paraspinal infection, or osteomyelitis did develop in seven of eight patients in whom the bullet perforated the colon before it hit the vertebra. Perforation of the colon by a low-velocity missile before the missile fractured the thoracic or lumbar vertebra was associated with a high incidence of infection. The appropriate management may require early operative intervention. This is in contrast to the non-operative approach that has been advocated for low-velocity gunshot wounds to the spine. We agree that a non-operative approach is indicated for gunshot wounds of the abdomen that do not involve the colon.

Abdominal Injuries↗
PubMed1985

Comparison of the supravital DNA dyes Hoechst 33342 and DAPI for flow cytometry and clonogenicity studies of human leukemic marrow cells.

Human leukemic bone marrow cells were studied by flow cytometry and a colony-forming assay. Two supravital DNA dyes, Hoechst 33342 (H33342) and 4',6-diamidino-2-phenyl indole dihydrochloride (DAPI), were compared in terms of DNA histograms by flow cytometry and toxicity to cells by colony-forming assay. Initially, Chinese hamster ovary (CHO) cells were used, and the optimal staining conditions for the two dyes were determined: 30 min exposure to 10 micrograms/ml at 37 degrees C for H33342 and at 23 degrees C for DAPI. DAPI demonstrated DNA profiles with better coefficients of variation for Go/G1 cells than did H33342. This difference was consistently shown in four additional mammalian cell lines and bone marrows freshly obtained from five patients, four of which were leukemic. Both dyes, in the optimal staining conditions, can suppress the growth of CHO cells with H33342 more toxic than DAPI. In experiments on three leukemic bone marrows, H33342 was shown to be more toxic than DAPI in terms of colony-forming capability. Although there is considerable variation in the degree of the toxicity between different cases, more than 50% of leukemic colony-forming cells can survive after DAPI staining. These data indicate that DAPI is preferable to H33342 for use with human leukemic cells because the staining technique required is less stringent; there is a more homogenous staining of the DNA, and there is less cytotoxicity induced. Supravital staining of DNA with DAPI and viable sorting by flow cytometry should be reasonably possible for functional studies such as colony formation after sorting.

Acute Disease↗
PubMed1984

Effect of diet on T-2 toxicosis.

T-2 toxin is an emetic trichothecene mycotoxin produced by Fusarium molds. This compound causes feed refusal, emesis and lesions in the gastrointestinal tract of livestock, poultry and man. Studies in our laboratory have indicated that the feeding of high fibre diets, non-nutritive mineral additives and high fat diets can largely overcome feed refusal caused when T-2 toxin is fed to rats. Subsequent experiments were designed to determine the mechanism by which such diets exert this effect. Rats were fed for two weeks diets containing varying levels of alfalfa meal, bentonite or corn oil in a casein-based semi-purified diet. Rats were then orally dosed with [3H] T-2 toxin and urine and feces were collected for 21 hours after which all animals were killed and tissues excised. Diet had no significant effect on the fraction dose of 3H excreted in the urine. Significant increases in fecal excretion of 3H were seen, however, with all test diets. Only high fat diets reduced hepatic residues of 3H while alfalfa had a similar effect in kidney and both alfalfa and bentonite lowered muscle residues. It was concluded that such dietary treatments overcome T-2 toxicosis mainly by promoting fecal excretion of toxin thereby reducing absorption and biological half-life.

Animals↗
PubMed1984

Effect of whole and fractionated dietary alfalfa meal on zearalenone toxicosis and metabolism in rats and swine.

Experiments were conducted to determine the mechanism by which dietary alfalfa can protect against zearalenone toxicosis. Female weanling rats were fed semipurified diets containing whole alfalfa meal, fractionated alfalfa meal (fiber, solvent extract, and water extract), and purified components of alfalfa (coumestrol, saponin, lignin, coumestrol + lignin, and saponin + lignin) with and without 250 mg zearalenone/kg of diet. All ingredients were provided for 2 weeks at levels corresponding to those found in diets containing 15 and 25% alfalfa. Yorkshire gilts were fed 15 and 25% alfalfa meal with and without 10 mg zearalenone/kg of diet for 4 weeks. The feeding of zearalenone to rats reduced growth and food consumption but this was overcome by 25% alfalfa. Zearalenone also increased the activity of hepatic 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD), the enzyme believed to metabolize zearalenone to alpha- and beta-zearalenols. Dietary alfalfa did not overcome this effect. Alfalfa fiber was the only fraction to partially overcome the growth-depressing effects of zearalenone while the other fractions had no beneficial effects and 3 alpha-HSD was not affected by diet. None of the purified components affected growth parameters or 3 alpha-HSD. The enzyme was also not affected by zearalenone or alfalfa in swine diets. Coumestrol, alpha-zearalenone, and beta-zearalenone were shown to be competitive inhibitors of 3 alpha-HSD in rat liver. It was concluded that the fiber fraction of alfalfa protects against zearalenone toxicity, and that this effect is not dependent on coumestrol or saponin and is not likely mediated through 3 alpha-HSD.

3-Hydroxysteroid Dehydrogenases↗
PubMed1983

Effect of feeding alfalfa and refined plant fibers on the toxicity and metabolism of T-2 toxin in rats.

Experiments were conducted to determine the effect of dietary fibers on T-2 toxicosis in rats. Weanling rats were fed varying levels of cellulose, hemicellulose, lignin and pectin with and without T-2 toxin (3 micrograms/g feed) for 2 weeks. Only lignin showed promise of overcoming feed refusal and growth depression in animals fed T-2 toxin. Further experiments feeding alfalfa meal (0, 5, 10, 15, 20 or 25%) with and without T-2 toxin indicated that this lignin-rich feedstuff could largely overcome feed refusal and growth depression caused by the toxin. There was no effect of diet, however, on the activity of hepatic esterase, the enzyme believed to catabolize T-2 toxin. Rats were fed diets containing 0, 5, 12.5 or 20% alfalfa for 2 weeks and then dosed orally with [3H]T-2 toxin. Dietary alfalfa increased fecal excretion of 3H, whereas urinary excretion was unaffected. Residual 3H in kidney and muscle was reduced with alfalfa feeding when [3H]T-2 toxin was administered orally. Residual 3H in the digesta in the intestinal lumen increased. Alfalfa feeding was found to reduce intestinal transit time. It was concluded that the feeding of alfalfa reduced T-2 toxicosis in rats by binding the toxin in the intestinal lumen thereby promoting fecal excretion.

Animals↗
PubMed1983

Role of bentonite in prevention of T-2 toxicosis in rats.

Experiments were conducted to determine the effect of bentonite and nonnutritive dietary polymers on toxicity and metabolism of T-2 toxin in rats. Male weanling rats were fed diets containing 5% bentonite, anion exchange resin, cation exchange resin or vermiculite-hydrobiotite. Each diet was fed with and without 3 micrograms T-2 toxin/g of feed for 2 wk. Bentonite and anion exchange resin were the treatments most successful at overcoming growth depression and feed refusal caused by T-2 toxin. Subsequent experiments tested bentonite and anion exchange resin at 0, 2.5, 5.0, 7.5 and 10% of the diet. Bentonite fed at 10% was the most effective treatment at overcoming feed refusal and growth depression. Rats were fed 0, 5, 7.5 or 10% bentonite for 2 wk and then dosed with [3H] T-2 toxin. Urine and feces were collected for 21 h after dosing and tissues were excised for determination of residual 3H. Feeding bentonite had little effect on the fraction of the dose excreted in the urine. Significant increases in fecal excretion of 3H were shown, when the feeding of 5, 7.5 or 10% bentonite was compared with the casein-based, semi-purified control diet. Dietary bentonite had no effect on residual 3H in liver or kidney, but all concentrations of bentonite tested reduced residual 3H in muscle. More 3H was found in the digesta in the small intestine and in the wall of the intestinal tissue when rats fed 5% bentonite were compared with the controls. Intestinal transit time for rats fed bentonite diets was reduced compared with that of the controls as indicated by chromic oxide marker studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

The tracer method of curriculum analysis: identifying changes in oncology subject matter in medicine.

Changes occurring in oncology subject matter in an undergraduate medical curriculum over a 5-year period were documented using the tracer method of curriculum analysis. The tracer method is an empirical approach somewhat analogous to tracing one thread through a tapestry, as a way of following a subject matter interwoven throughout a curriculum. Advantages of the method can be to bring particular material to the attention of teaching staff and students, to facilitate more efficient instruction, and to introduce peer review of educational material.

Curriculum↗