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Biomedical subjects

G R Davis

Publications and source records attributed to G R Davis.

At least 73 records · Page 4Linked to original sources
PubMed1982

Ox bile treatment of severe steatorrhea in an ileectomy-ileostomy patient.

Bile salt therapy is not used in patients with steatorrhea due to bile salt deficiency because of fear that severe diarrhea would be caused or exacerbated. We report a patient who previously had had colectomy, partial ileectomy, and ileostomy for Crohn's disease. She had severe steatorrhea due to bile salt deficiency and severe diarrhea (the latter apparently due to fatty acid inhibition of electrolyte and water absorption). The diarrhea was improved by loperamide, but severe steatorrhea and malnutrition persisted. The steatorrhea and malnutrition were corrected by ox bile, without an increase in diarrhea. Presumably, the deleterious effect of bile salts per se on small bowel absorption of water and electrolytes was mitigated by correction of fat malabsorption. At least in this patient, bile salt therapy was highly beneficial.

Bile Acids and Salts↗
PubMed1981

Effect of vasoactive intestinal polypeptide on active and passive transport in the human jejunum.

The effect of intravenous vasoactive intestinal polypeptide (VIP) on normal transport mechanisms in the human jejunum in vivo was examined with the triple-lumen, steady-state perfusion technique. By using special test solutions that revealed different aspects of jejunal transport, we were able to evaluate the effect of VIP on specific transport processes, such as active bicarbonate absorption, active chloride secretion, and passive absorption or secretion of sodium chloride. At an infusion rate of 200 pmol/kg per h, VIP inhibited active bicarbonate absorption by approximately 42%, stimulated active chloride secretion to a slight extent, and slightly reduced passive sodium chloride absorption. A larger dose of VIP, 400 pmol/kg per h, had essentially the same effect on active bicarbonate absorption and active chloride secretion, but it markedly depressed passive sodium chloride absorption and also inhibited passive secretion induced by mannitol. VIP reduced the lumen-to-plasma unidirectional sodium and chloride flux rates, while the plasma-to-lumen flux rates were decreased to a lesser extent or remained unchanged. The potential difference became more lumen-negative with VIP, but the sodium diffusion and glucose-stimulated potential were not affected. We conclude that the major effect of VIP in the human jejunum is to decrease the normal absorption of water and electrolytes--not only active bicarbonate-mediated absorption, but also the passive absorption in response to osmotic forces generated by active or facilitated absorptive processes. Although an increase in chloride secretion does occur, this does not appear to be of major importance.

Adult↗
PubMed1981

Effect of light and incubation temperature on production by species of Fusarium of metabolites toxic to larvae of Tenebrio molitor L.

Larvae of Tenebrio molitor L., Gembloux strain, race F, having an initial weight of 10 mg were reared for 4 weeks at 27 +/- 0.25 degrees C 65 +/- 5% relative humidity on rye seed incubated with single isolates of four strains of Fusarium. The fungi had been cultured in total darkness or in constant light at a temperature of 8, 14, 20 or 24 degrees C. Two isolates of Fusarium poae (Peck). Wollenw. (7450 and 7452) retarded growth more than the third isolate of this species or than the isolate of Fusarium accuminatum Ell. & Ev. Nutritional value of rye seed decreased with increasing temperature, but declined to a larger extent when Fusarium species were present than when they were absent. The results suggest that changes in weight and mortality of larvae are good criteria for determining toxicity of fungal metabolites in Insects.

Animals↗
PubMed1981

Effect of commercial processing of canola and rapeseed on growth of larvae of the yellow mealworm, Tenebrio molitor L.

Larvae of Tenebrio molitor L., Gembloux strain, race F, were used to determine the nutritional quality of commercial canola and rapeseed products. Application of heat in commercial processing increased considerably the nutritive values of Midas, Tower and Torch cultivars, and to a lesser extent that of Candle. This improvement was most noticeable for thigh-glucosinolate cultivars, presumably through the destruction of a mechanism for production of isothiocyanates that may be phagodeterrent or toxic to the larvae. For low-glucosinolate varieties, the improvement may be related to inhibition of nitrile production in heated material. The processing also reduced the concentration of available lysine in the products of all four cultivars; however, growth was unimpaired by this reduction. The latter results suggest that the feed products resulting from processing may exceed the optimal dietary requirement of lysine by larvae of Tenebrio molitor.

Animals↗
PubMed1980

DNA sequence of the promoter region for the alpha ribosomal protein operon in Escherichia coli.

Previous studies showed that the gene for RNA polymerase subunit alpha at 72 min on the Escherichia coli chromosome is co-transcribed with genes for ribosomal proteins (r-proteins) S11, S4, and L17, and probably S13. DNA sequence analysis of a deletion mutant has now established that the S13 gene is a part of the alpha operon and the gene order is promoter (P alpha), rpsM (S13), rpsK (S11), rpsD(S4), rpoA(alpha), and rplQ(L17). The DNA sequence extending 650 bases before S13 gene was determined. In vitro transcription experiments establish the probable location of the alpha promoter (P alpha) within this sequence. The start site is 94 nucleotides upstream from the initiation codon (GUG) of the S13 gene. This promoter has features previously noted as common to E. coli promoters. However, comparison with four other sequenced promoters of r-protein operons shows no unique common features that might account for the common regulation of synthesis of r-proteins. This lack of sequence similarity in promoters of r-protein operons may be because r-protein synthesis is regulated at least partially at a post-transcriptional level.

Amino Acid Sequence↗
PubMed1980

Active chloride secretion in the normal human jejunum.

To determine whether the small intestine normally secretes fluid, it would be necessary to reduce or inhibit the greater absorptive processes that would otherwise mask such secretion if present. To do this, we perfused bicarbonate-free solutions in the jejunum of normal subjects, because it has been shown that active absorption from this part of the human small intestine is dependent on luminal bicarbonate. We found that the jejunum did secrete sodium chloride and water when isotonic bicarbonate-free solutions were perfused. Further studies revealed that the sodium secretion was passive, but that chloride was secreted against an electrochemical gradient and that observed chloride flux ratios did not agree with the flux ratios calculated for passive chloride movement. We conclude, therefore, that the normal jejunum actively secretes chloride, but that this is masked by greater absorptive processes when balanced electrolyte solutions are perfused. The rate of this active chloride secretion may be one of the factors that regulate the rate of fluid absorption in the normal human intestine.

Bicarbonates↗
PubMed1980

Effect of somatostatin infusion on jejunal water and electrolyte transport in a patient with secretory diarrhea due to malignant carcinoid syndrome.

The effect of intravenous somatostatin infusion was investigated in a patient with severe secretory diarrhea due to malignant carcinoid syndrome. Continuous somatostatin infusion for 48 hr (4 microgram/kg/hr) reduced stool volume from 2.2 to 0.7 liters/day. Intestinal perfusion studies before intravenous somatostatin infusion revealed decreased water and sodium absorption and jejunal chloride secretion. Somatostatin infusion for 2 hr (8 microgram/kg/hr) reversed chloride secretion to absorption and markedly enhanced water and sodium absorption. These results suggest that somatostatin inhibited a secretory component of water and ion movement in the small bowel of the patient with malignant carcinoid syndrome.

Aged↗
PubMed1980

Development of a lavage solution associated with minimal water and electrolyte absorption or secretion.

Ingestion of large volumes of a balanced electrolyte solution has previously been shown to be an effective method of cleaning the colon for diagnostic studies. However, in this paper we have shown that total gut perfusion with such a solution results in absorption of 2400 ml water and 375 meq of sodium over 3 hr, which is the approximate time required to clean the colon by this technique. This might be hazardous to patients who are unable to readily excrete a salt and water load. We, therefore, designed a solution containing mainly sodium sulfate that was associated with only trivial amounts of water and sodium absorption or secretion during total gut perfusion. This new solution might be useful in colon cleansing before colonoscopy, barium enema, and surgery. In addition, such a solution may have some therapeutic indications, including bowel cleaning in patients with hepatic encephalopathy or as a rapid washout technique for ingested toxins.

Diarrhea↗
PubMed1980

Inhibition of water and electrolyte absorption by polyethylene glycol (PEG).

Polyethylene glycol (PEG) is commonly used as a nonabsorbable volume marker in intestinal perfusion and flow studies. It has been assumed that PEG does not affect water and electrolyte movement, but this has not been extensively investigated. Using triple-lumen tube perfusion technique, we examined the effect of various PEG concentrations (0, 2, 5, 10, and 20 g/liter) on water and electrolyte absorption by the jejunum and ileum in normal subjects. 14C-labeled PEG served as the nonabsorbable marker in the 0 PEG concentration solution. There was a progressive reduction in water, sodium, and chloride absorption as the concentrations of PEG was increased from 0 to 20 g/liter. Though further studies are necessary to establish the mechanism responsible for this PEG effect, the observed changes in luminal fluid osmolality and electrolyte concentrations suggest that the reduction in absorption most likely results from an osmotic effect rather than an inhibition of active absorption or stimulation of secretion.

Electrolytes↗
PubMed1979

Somatostatinoma syndrome. Biochemical, morphologic and clinical features.

Diabetes mellitus, steatorrhea, cholelithiasis and a tumor distorting the duodenum prompted a work-up for somatostatinoma in a 52-year-old man. The responses of pancreatic B-cells but not of A-cells to nutrient stimuli were inhibited, and growth-hormone release was suppressed, suggesting somatostatin resistance in some target tissues. Plasma somatostatin-like immunoreactivity ranged from 9000 to 13,000 pg per milliliter (normal: 88+/-8, mean +/- S.E.M.) and was distributed in four molecular forms, including free somatostatin. The primary tumor contained 5 microgram of somatostatin-like immunoreactivity per milligram of wet tissue, distributed in three of the molecular forms noted in plasma. Plasma calcitonin was also elevated (4650 pg per milliliter; normal: less than 120). Immunocytochemical studies showed that cells of the primary tumor contained somatostatin and calcitonin but no other peptide hormones. Only somatostatin was present in the metastases. Somatostatin was localized electron microscopically in all secretory granules, irrespective of size and shape, whereas calcitonin was present only within a single subpopulation of small granules in the same cells.

C-Peptide↗
PubMed1979

Protein nutrition of Tenebrio molitor L. XX. Growth response of larvae to graded levels of amino acids.

Larvae of Tenebrio molitor L;, Gembloux strain, race F, having an average initial weight of 10 mg were reared for 4 weeks at 27 +/- 0.25 degrees C and 65 +/- 5% relative humidity on diets containing an amino-acid mixture resembling the composition of larval tissues; Each of 14 amino acids was tested individually at levels of 0, 10, 20, 50, 100 and 200% of the amount found in larval tissues, while the concentration of other amino acids remained constant. Diets were maintained isonitrogenous at 1.6% nitrogen with supplementary glutamic acid, glycine, serine and tyrosine; Maximum fresh weight gains and dry weights were achieved by larvae fed reference levels of all essential amino acids except phenylalanine, threonine and tryptophan. Maximum growth was achieved by larvae fed 50% of the phenylalanine level found in larval tissues, Threonine and tryptophan were the limiting amino acids in this study and are probably required in the diet in excess of twice the concentration occuring in larval tissues, Probable ranges for quantitative amino-acid requirements of T. molitor were determined and suggestions were made for improving the nutritional adequacy of the amino-acid mixture.

Amino Acids↗
PubMed1979

Ileal chloride secretion as a cause of secretory diarrhea in a patient with primary intestinal tuberculosis.

Severe secretory diarrhea resulting in dehydration and hypokalemia was observed in a patient in whom primary cecal tuberculosis was diagnosed by colonoscopy. Although the ileum appeared normal at colonoscopy and by biopsy, intestinal perfusion studies showed that the ileum was secreting water and electrolytes. Chloride secretion against a high electrical gradient suggested active anion secretion. Absorption in the colon was unimpaired. The diarrhea resolved after 4 wk of antituberculous therapy. Repeat perfusion studies after 3 mo showed normal absorption in the ileum. This case report suggests that intestinal tuberculosis can cause secretory diarrhea. The mechanism by which secretion occurs is not clear, but probably involves active anion secretion.

Cecal Diseases↗
PubMed1979

Fecal incontinence in chronic diarrhea. Report of a case with improvement after training with rectally infused saline.

Patients with chronic diarrhea and fecal in continence are unable to retain as much rectally infused saline as patients without incontinence. We explored the effect of training such a patient to retain rectally infused saline. The patient was a 31-yr-old female with chronic diarrhea of obscure etiology who had daily episodes of fecal incontinence which markedly restricted her lifestyle. Training was accomplished by urging the patient to retain as much of a 25-min rectal infusion of 1500 ml saline as possible. After 10 training sessions, the patient increased her ability to hold rectally infused saline almost sevenfold. This increase was well maintained over 10 wk. In spite of continued diarrhea, the patient's incontinence did not recur after the first week of training, and she was able to resume a normal life. Anal sphincter pressure and a test of continence for a solid sphere did not change during or after training. This simple training technique has potential as a treatment for disabling fecal incontinence in patients with chronic diarrhea.

Adult↗
PubMed1977

Determination of useful barley selections in an improvement program for increased lysine content by larvae of Tenebrio molitor L.

Larvae of the yellow mealworm, Tenebrio molitor L., Gembloux strain, race F, were reared for 4 weeks at 27 +/- 0.25 degrees C and 65 +/- 5% relative humidity. They were fed on each of 22 cultivars of barley, at the protein level occurring in harvested seed and at a protein level of 10% of dietary protein. Growth and body composition of the larvae were correlated positively and significantly with the concentrations of basic amino acids in the barleys and negatively and significantly with the concentrations of leucine. The percentage of crude protein in larval tissues can be used as a measure of available lysine in barley cultivars, and gains in fresh weight of larvae as indices of arginine concentrations. Differences were evident between the biological and chemical estimations of these amino acids. Several of the Saskatoon barley selections, derived from crosses with Hiproly, were equal to Hiproly or Risø varieties in the amounts of lysine available to the larvae.

Amino Acids↗
PubMed1976

Nutritional evaluation of wheat and barley cultivars by growth rate and body composition of larvae of Tenebrio molitor.

Larvae of the yellow mealworm, Tenebrio molitor L., Gembloux strain, race F, were reared on diets of 17 cultivars of wheat and 29 cultivars of barley, prepared for determination of digestible energy with mice, for 4 weeks at 27 +/- 0.25 degrees C and 65 +/- 5% relative humidity. Values for percentage crude protein of tissues of larvae fed wheat cultivars were significantly and positively correlated with values for digestible energy as determined with mice. These values were not correlated for larvae fed barley cultivars; however, values for per cent dry matter content of larvae were significantly and positively correlated with values for digestible energy determined with mice. This apparent discrepancy is explained on the basis of the chemical constitution of barley and the availability of amino acids of barley to the larvae. Use of larvae of Tenebrio molitor to indicate the digestible energy of cereal grains is feasible, provided that the proper parameter is chosen. Nevertheless, use of this biological method seems more suitable for evaluation of protein quality and of amino acid availability than for a measure of digestible energy of feeds.

Animal Nutritional Physiological Phenomena↗