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Biomedical subjects

G R Davis

Publications and source records attributed to G R Davis.

At least 55 records · Page 3Linked to original sources
PubMed1985

Feeding responses by adult males of Melanoplus sanguinipes (Fabricius) to carbohydrates and amino acids.

Adult males of Melanoplus sanguinipes (Fabricius), the migratory grasshopper, were starved for 18 h and were placed, one per arena, into arenas containing treated glass-fibre discs. The discs had been dipped into aqueous solutions of carbohydrates or amino acids of 0.0001, 0.001, 0.01, or 0.1 M concentration and allowed to dry at air temperature. They were placed vertically on pins and distributed at random among five equidistant stations around the periphery of the bottom of the arena. Each arena was provided with a glass-fibre disc that had been dipped in distilled water, as a control. The grasshoppers were allowed to feed at room temperature at 16:8 (L:D) for 24 h. Determinations of the effects of nutrient chemicals on feeding were determined by dry-weight differences between the weights of the treated discs before and after testing. Ribose, glucose, mannose and trehalose had no influence on feeding; 0.01 M fructose of 0.1 M arabinose, galactose, melibiose or sucrose increased feeding over that obtained with the control discs (P = 0.05); and 0.01 M xylose or sorbose depressed feeding. Each of the 11 amino acids investigated was phagodeterrent to adult males of M. sanguinipes. The present results confirm the variability of responses to carbohydrates among acridids; however, the reversal of phagodeterrency of sorbose or xylose at 0.1 M concentration is believed to be the first reported instance of such behaviour. In contrast to other reports of phagostimulation of acridids by individual amino acids or amino-acid mixtures, all protein amino acids tested in the present study were phagodeterrent to adult males of M. sanguinipes, even at low concentrations.

Amino Acids↗
PubMed1985

Effects of amino-acid mixtures on food utilization and growth in Tenebrio molitor L.

Ten holidic diets, varying in amino-acid concentration or composition, were fed to larvae of Tenebrio molitor for four weeks at 27 +/- 0.25 degrees C and 65 +/- 5% r.h. Effects of diet on growth, food utilization and energy utilization were recorded for individual larvae. Differences in gains in fresh weight or in dry matter among larvae fed diets containing 0% to 5% of the amino-acid mixture were not demonstrated. However, larvae fed 10% or 20% of this mixture gained more than the former, but less than larvae fed a diet of ground whole wheat and brewer's yeast (9:1, w/w). When the amino-acid mixture was supplemented with alanine, aspartic acid, and serine, or with these three and asparagine, and was fed to larvae at the 10% level, growth was slower than with the unsupplemented mixture. Supplementation of the amino-acid mixture with the first three amino acids did not reduce larval growth when fed at the 20% level. Amounts of food and of energy utilized were positively correlated with larval fresh-weight and dry-matter gains. Energy utilization was negatively correlated with dietary amino-acid level. Food and energy utilization and larval growth were influenced by dietary amino acids, either metabolically or through phagostimulation.

Amino Acids↗
PubMed1984

Cognitive-behavioral treatment of depressed affect among epileptics: preliminary findings.

Controlled study showed skills training for the management of depression in an epilepsy population to be effective. Cognitive-behavioral methods were utilized in a structured learning format with 13 clinically depressed epileptic "students." Significantly greater reductions in dysphoria/depression as measured by the Depression Adjective Checklist and the Generalized Contentment Scale occurred among Ss in the treatment group than among control group Ss. Significant decreases in anger and anxiety/stress and increases in social activities were noted on the Community Adjustment Questionnaire (CAQ). Similar trends were evident on the Beck Depression Inventory and the CAQ depression scale.

Adult↗
PubMed1984

Stress as a risk factor for seizures among adults with epilepsy.

This study examines the effects of major life events, daily hassles and uplifts, and daily stress levels as they increase or decrease the risks of having seizures and estimates risk ratios for specific stressors and perceived stress levels. Utilizing a prospective design, 12 adults with severe epilepsy monitored the occurrence of seizures, stressors, and stress levels over a 3-month period. In within-individual analyses, high stress levels and stressful events were associated with more frequent seizures for most participants. The association between higher stress levels and increased seizures was confirmed in group analyses. This study provides empirical evidence of the association between stress and seizures and describes the use of a statistical model that is useful for investigating risk factors as they influence physical and mental illness.

Activities of Daily Living↗
PubMed1984

Cancer-associated myasthenic (Eaton-Lambert) syndrome: distribution of abnormality and effect of treatment.

Treatment with plasma exchange, steroids, immunosuppressant drugs and cytotoxic chemotherapy was effective in two cases of cancer-associated Eaton-Lambert myasthenic syndrome. The clinical improvement noted during treatment was accompanied by improvement in the electrophysiological abnormality; this was much more marked in abductor digiti minimi and trapezius than in extensor digitorum brevis.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1984

An evaluation of the importance of gastric acid secretion in the absorption of dietary calcium.

Since calcium solubility is a prerequisite to calcium absorption, and since solubility of calcium is highly pH-dependent, it has been generally assumed that gastric acid secretion and gastric acidity play an important role in the intestinal absorption of calcium from ingested food or calcium salts such as CaCO3. To evaluate this hypothesis, we developed a method wherein net gastrointestinal absorption of calcium can be measured after ingestion of a single meal. A large dose of cimetidine, which markedly reduced gastric acid secretion, had no effect on calcium absorption in normal subjects, and an achlorhydric patient with pernicious anemia absorbed calcium normally. This was true regardless of the major source of dietary calcium (i.e., milk, insoluble calcium carbonate, or soluble calcium citrate). Moreover, calcium absorption after CaCO3 ingestion was the same when intragastric contents were maintained at pH 7.4 (by in vivo titration) as when intragastric pH was 3.0. On the basis of these results, we conclude that gastric acid secretion and gastric acidity do not normally play a role in the absorption of dietary calcium. Other possible mechanisms by which the gastrointestinal tract might solubilize ingested calcium complexes and salts are discussed.

Achlorhydria↗
PubMed1983

The spc ribosomal protein operon of Escherichia coli: sequence and cotranscription of the ribosomal protein genes and a protein export gene.

The genes encoding the 52 ribosomal proteins (r-proteins) of Escherichia coli are organized into approximately 19 operons scattered throughout the chromosome. One of these, the spc operon, contains the genes for ten ribosomal proteins: L14, L24, L5, S14, S8, L6, L18, S5, L30 and L15 (rp1N, rp1X, rp1E, rpsN, rpsH, rp1F, rp1R, rpsE, rpmD, and rp1O). We now report the entire 5.9 kb nucleotide sequence of the spc operon. DNA sequence analysis has confirmed the genetic organization and refined the amino acid sequence of the ten r-proteins in this operon. It has also revealed the presence of two open reading frames past the last known gene (L15) of the spc operon. One of these corresponds to a gene (pr1A or secY) which recently has been shown by others to be involved in protein export. In addition, S1 mapping experiments indicate that a significant proportion of transcription initiated from the spc operon continues not only into the two putative genes, but also without termination into the downstream alpha r-protein operon.

Bacterial Proteins↗
PubMed1983

A dedicated microcomputer-based instrument for interval analysis of multicomponent wave forms in single fibre EMG.

We have developed a self-contained microprocessor-based instrument compatible with conventional EMG equipment for the analysis of multicomponent SFEMG wave forms suitable for single operator use. Intervals between 4 components of a MUAP can be analysed using 3 types of threshold or window triggers. The amplitude, duration and polarity of each of these triggers can be varied independently. The instrument is portable and useful in the clinical setting.

Computers↗
PubMed1983

Evaluation of chloride/bicarbonate. Exchange in the human colon in vivo.

During perfusion of a plasma-like solution, colonic absorption rate of chloride was much higher than the secretion rate of bicarbonate (34 vs. 3.5 meq/h, respectively). This might suggest that anion exchange (Cl/HCO3) accounts for only a small fraction of total chloride absorption. However, if the colon absorbs as well as secretes bicarbonate, this reasoning would underestimate the magnitude of the anion exchange. To see if the colon absorbs bicarbonate, we perfused a chloride-free solution (which would eliminate bicarbonate secretion via (Cl/HCO3 exchange) and found that the colon absorbed bicarbonate at a rate of 5.1 meq/h. Calculation of electrochemical gradients and measurement of luminal fluid PCO2 indicated that this bicarbonate absorption was mediated passively in response to electrical gradients, rather than via reversed Cl/HCO3 exchange or acid secretion. The combined results of the plasma-like and chloride-free perfusion experiments suggest Cl/HCO3 exchange at a rate of 8.6 meq/h (the sum of bicarbonate movements, 3.5 and 5.1 meq/h, observed in the two experiments). To obtain a second estimate under different experimental conditions, a choline chloride-choline bicarbonate (sodium-free) solution was perfused; with this solution, chloride and bicarbonate absorption dependent on active sodium transport should be eliminated or markedly reduced, and the magnitude of Cl/HCO3 exchange should be revealed. This experiment suggested a Cl/HCO3 exchange rate of 9.3 meq/h, similar to the first estimate. As chloride was absorbed at a rate of 34 meq/h during perfusion of the plasma-like solution, the Cl/HCO3 exchange provides for approximately one-fourth of total chloride absorption.

Absorption↗
PubMed1983

Influence of canola hulls on gain in weight of larvae of the yellow mealworm, Tenebrio molitor L.

Larvae of the yellow mealworm, Tenebrio molitor L., Gembloux strain, race F, were reared on diets in which the protein component was supplied by defatted ground seed, defatted ground dehulled fraction, or defatted ground hulls of Brassica napus L. cv. Tower or Brassica campestris L. cv. Candle, obtained from autoclaved seed. They were also fed casein diets to which defatted ground hulls of Tower or Candle seed were added. Gain in weight was equally good for all diets containing Candle seed fractions and for diets containing Tower ground seed. However, it was lower for diets containing the ground dehulled fraction or the ground hulls of Tower. Addition of Candle hulls or of a mixture of equal proportions (w/w) of Candle and Tower hulls to diets containing dehulled Tower did not improve the gain in weight of larvae, compared with that of larvae fed diets containing the dehulled fraction, alone. Similar additions of Tower hulls or of the mixture to diets containing the dehulled fraction of Candle had no adverse effect on larval gain in weight, compared to that registered by larvae fed the dehulled fraction of Candle. Significant improvement in weight gain in comparison with that recorded for larvae fed the unsupplemented casein diet could not be demonstrated when ground hulls of Tower or Candle were added to this diet. Considered collectively, weight gains of larvae of T. molitor were consistently greater when Candle products were fed than when Tower products provided the protein fraction of the diet.

Animals↗
PubMed1983

Absorption of phosphate in the jejunum of patients with chronic renal failure before and after correction of vitamin D deficiency.

To examine the role of vitamin D in human phosphate absorption, we studied patients with chronic renal disease on hemodialysis, before and after correction of vitamin D deficiency. Thirty-centimeter segments of jejunum were perfused with test solutions containing varying concentrations of phosphate; phosphate absorption rate and electrical potential difference were measured. The data reveal that dialysis patients have depressed phosphate absorption, but the degree of this depression is modest, compared to the extent of their depressed calcium absorption. Therapy with 1,25-(OH)2D3 for 1 wk restored phosphate absorption rate to near normal. With or without 1,25-(OH)2D3 therapy, phosphate absorption was not influenced by calcium in the perfused test solutions. Examination of kinetic data suggests that the vitamin D deficiency of chronic renal failure causes a reduction by half in the rate of active phosphate absorption. By contrast, our data suggest that vitamin D deficiency does not alter passive phosphate absorption. By aspirating jejunal contents after ingestion of different foods, with and without aluminum hydroxide, the physiologic luminal phosphate concentration was found to vary between 0.7 and 12.2 mM. At the lower end of this range, phosphate absorption would be mediated entirely by active transport; at the higher phosphate concentrations, phosphate absorption would be mainly mediated by passive transport.

Adult↗
PubMed1982

Toxigenic isolates of Fusarium sporotrichioides obtained from hay in Saskatchewan.

An isolate of Fusarium sporotrichioides Sherbakoff obtained from hay from Kindersley, Saskatchewan, and producing metabolites toxic to insect larvae, rats, and mice was cultured on sterile rye grain and extracted with ethyl acetate. The most toxic fraction derived from column chromatography on silica gel was purified by thin-layer chromatography of silica gel and elution of the main band. This compound was identified as T-2 toxin by comparison with the pure chemical by thin-layer chromatography and, after crystallization, by determination of melting point, infrared spectrum, and nuclear magnetic resonance spectrum. This work demonstrates that strains of F. sporotichioides capable of producing T-2 toxin may be present on hay in western Canada.

Animal Feed↗
PubMed1982

Studies of the mechanism of the antidiarrheal effect of codeine.

To determine whether the antidiarrheal action of opiate drugs in humans is due to enhanced intestinal absorption rates, as suggested by recent experiments in animals, or is due to altered intestinal motility, as traditionally thought, we studied the effect of therapeutic doses of codeine on experimental diarrhea and on the rate of intestinal absorption of water and electrolytes in normal human subjects. Our results show that codeine (30-60 mg i.m.) markedly reduced stool volume during experimental diarrhea induced by rapid intragastric infusion of a balanced electrolyte solution. There was, however, no evidence that codeine stimulated the rate of intestinal absorption in the gut as a whole or in any segment of the gastrointestinal tract, either in the basal state or when absorption rates were reduced by intravenous infusion of vasoactive intestinal polypeptide. We also measured segmental transit times to determine whether and where codeine delayed the passage of fluid through the intestine. Codeine caused a marked slowing of fluid movement through the jejunum, but had no effect on the movement of fluid through the ileum or colon. In other studies, we found that the opiate antagonist naloxone did not significantly affect water or electrolyte absorption rates in the jejunum or ileum. We conclude (a) that therapeutic doses of codeine increase net intestinal absorption (and thereby reduce stool volume) by increasing the contact time of luminal fluid with mucosal cells, not by increasing the rate of absorption by the mucosal cells; and (b) that endogenous opiates do not regulate intestinal absorption in humans.

Adult↗
PubMed1982

Permeability characteristics of human jejunum, ileum, proximal colon and distal colon: results of potential difference measurements and unidirectional fluxes.

In order to assess the passive permeability characteristics of the human intestine in vivo, we measured potential difference in the jejunum, ileum, proximal colon, and distal colon during perfusion of various test solutions that were designed to establish chemical gradients for sodium or chloride, or both or neither. In addition, unidirectional fluxes of sodium and chloride were measured in 30-cm segments of the jejunum and ileum and entire colon during perfusion of balanced electrolyte solution. These studies indicate that there are marked differences in the pathways for passive ion movement in the areas of the intestine studied. In the jejunum, this pathway appears to be highly permeable to both sodium and chloride with modest cation selectivity. In the ileum this pathway is much more cation selective, predominantly because of a relative impermeability to chloride. In the colon, on the other hand, these passive pathways appear to be more anion than cation selective. The implication of these results for normal transport physiology are discussed.

Action Potentials↗