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R H Davis

Publications and source records attributed to R H Davis.

At least 163 records · Page 9Linked to original sources
PubMed1979

The effect of selected amino acids on gelatin-induced inflammation in adult male mice.

Several studies have indicated to us that certain amino acids may exhibit antiinflammatory activity. In the present study we attempted to evaluate the inhibitory effect of various amino acids on gelatin-induced abdominal inflammation in mice using peritoneal fluid cytology as the diagnostic tool. The L-amino acids tested were tryptophan, phenylalanine, alanine, cystine, hydroxyproline, tyrosine, citrulline, leucine, and valine. Hydrocortisone was used as an antiphlogistic steroid control. Tryptophan, phenylalanine, alanine, cystine, hydroxyproline, and tyrosine all significantly decreased the inflammation. Citrulline and valine, however, both exhibited strong antiiflammatory responses. Based on these results, three related dipeptides were also screened: L-valy-L-alanine, L-valyl-L-tryptophan, and L-tyrosl-L-valine. Valyl alanine was found to produce a strong antiinflammatory effect. In a final test, the combination of the steroid, hydrocortisone, and the amino acid, cystine, was screened for a synergistic effect. The combined treatment inhibited the gelatin-induced inflammation more than either the amino acid or the steroid administered alone.

Amino Acids↗
PubMed1979

Purification and characterization of the myoglobins of Paramecium tetraurelia.

1. The molecular variants of the myoglobins of Paramecium tetraurelia have been purified as five separate components and designated Mb 1 to Mb 5. 2. The five molecular forms are homogeneous on polyacrylamide gel electrophoresis (PAGE) and isoelectric focusing (IF). 3. The myoglobin species appear to have identical molecular weights and amino acid compositions and differ only in their isoelectric points and relative concentrations in vivo. 4. The myoglobin species have an apparent molecular weight of 15,000 +/- 500 and possess a single heme group per mole which appears to be protoporphyrin IX. 5. The amino acid composition of the five species is: lys12, his3, arg4, asp17, thr9, ser6, glu16, pro4, gly11, ala15, cys0, val8, met2, ile7, leu10, tyr5, phe7. 6. The spectra of several ferrous and ferric derivatives of the mixture Mb 1-Mb 5 are presented.

Animals↗
PubMed1979

Genetics of arginine biosynthesis in Neurospora crassa.

A large number of arginine-requiring mutants of Neurospora was isolated, using a strain already partially impaired in an enzyme of the pathway. Among the mutants, all previously described loci, except one, were represented, and several new loci were defined and mapped. Four groups of mutants were of particular interest. First, the large group of arg-6 mutants, when tested for intragenic complementation, suggested a bifunctional gene, possibly controlling two steps in ornithine synthesis. This is consistent with the limited enzymic information about this locus. Second, the arg-13 locus was represented by 14 new mutants. All five tested were quite leaky, suggesting that the function controlled by this gene can be carried out to a limited extent spontaneously or by another gene product. Third, a new locus, arg-14, was defined. It controls a step in ornithine syntheses. It lies in a 1 to 2 map-unit interval between arg-2 and pyr-3 on LG IVR, as shown by mapping in relation to translocation breakpoints. Fourth, a second new locus whose mutants render the partial mutation in starting material auxotrophic was defined and mapped near the centromere of LG VIL. These new mutants are unable to derepress enzymes of the pathway and may qualify as regulatory mutants.

Arginine↗
PubMed1979

Screening for amino acid pool mutants of Neurospora and yeasts: replica-printing technique.

A replica-printing technique has been developed for permeabilized colonies of Neurospora and yeast by which endogenous amino acid pools are visualized. By the use of cation-exchange paper, the method has detected Neurospora mutants unable to store the large pools of basic amino acids characteristic of wild type. Mutants of this sort were sought to study the function of the fungal vacuole.

Amino Acids↗
PubMed1979

Chronic occlusion of the rabbit Fallopian tube with silicone polymer.

Investigators have previously reported good retention, antifertility efficacy, and good retrievability with no adverse tissue reactions in rabbit oviducts occluded with silicone rubber for 55 days. The present study attempts to determine the long-term effects of this silicone polymer system installed into the oviducts of 12 New Zealand White rabbits for 7 months. 9 rabbits had both oviducts occluded while 3 had only one oviduct treated. All animals were visualized by X-rays and were mated an average of six times over the experimental period. Oviduct tissue was examined with light and scanning electron microscopy. There was no evidence of inflammation, distortion, or tissue irritation. Good retention and antifertility efficacy were exhibited.

Animals↗
PubMed1979

Chronic occlusion of the monkey fallopian tube with silicone polymer.

Investigators have previously reported good retention, antifertility efficacy, and oviduct polymer compatibility in rabbit oviducts in studies of both short-term and chronic occlusion with high viscosity silicone polymer. The present study attempts to determine the chronic effects of the silicone polymer installed into the oviducts of 10 rhesus monkeys. Unlike former studies with rabbits, the polymer was installed into the fimbrial end of the monkey's oviducts because of the complexity of the uterotubal junction's musculature. Studies with light and scanning electron microscopy were conducted to examine tissue reaction to plug retention. Despite our major modification of the installation technique, we obtained a retention rate of 50%. In addition, there was no evidence of inflammation or tissue distortion, and the polymer plugs were not affected by menstrual bleeding.

Animals↗
PubMed1979

The exceptional potential in each primary care consultation.

A four-point framework is described which has been found to be helpful for general practitioners who try to achieve greater breadth in each consultation. The framework has also provided a useful stimulus in undergraduate and postgraduate teaching, because it provides a nomenclature to identify four major components of clinical practice which are particularly relevant to primary care.

Methods↗
PubMed1978

Intracellular compartmentation and transport of metabolites.

The intracellular locations of enzymes and metabolites were determined for ornithine metabolism in Neurospora. Pulse label experiments were used to measure the rates of intracellular translocations and the sizes of compartmented pools of metabolites in the mitochondrial, cytosolic and vesicular compartments. The results indicate that rapid equilibration occurs between these pools during growth in minimal medium, although the vast majority of the ornithine is confined to the vesicular compartment. Arginine, the biosynthetic end-product of ornithine metabolism, regulates ornithine utilization through a combination of feedback inhibition, repression, and control of intracellular translocations. The last phenomenon plays a decisive role indicating that the regulation of intercompartmental translocations may be a common mechanism in rapid adaptation responses in eukaryotic cells.

Arginine↗
PubMed1978

Solubilization and characterization of the partially purified penicillin sensitive D-alanine carboxypeptidase of Neisseria gonorrhoeae.

Treatment of crude gonococcal cell envelopes with a solution of 2 M KCl + 1% Brij 36T resulted in the solubilization of a portion of the D-alanine carboxypeptidase activity of Neisseria gonorrhoeae envelopes. This soluble enzyme preparation was partially resolved by chromatography on a column of DEAE-cellulose. The partially purified enzyme eluted from the column with a gradient of NaCl (0-1 M), catalysed the release of D-alanine from a radioactively labelled UDP-N-acetylmuramyl-pentapeptide with a pH optimum of 8.6. The Km for the soluble enzyme acting on this substrate was 0.18 mM. The enzyme activity was sensitive to inhibition by low concentrations of the beta-lactam antibiotics, penicillin G, ampicillin, oxacillin and mecillinam.

Carboxypeptidases↗