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Biomedical subjects

D J Walker

Publications and source records attributed to D J Walker.

At least 127 records · Page 7Linked to original sources
PubMed1977

A prospective study of respiratory infection in asthmatic patients treated with beclomethasone dipropionate and sodium cromoglycate.

A prospective study of forty adult asthmatic patients attending two chest clinics in the City of Liverpool was undertaken. All patients had reversible airways obstruction and were under treatment with either beclomethasone dipropionate or sodium cromoglycate. Satisfactory symptomatic control was achieved in both groups of patients on a subjective basis, but there was a statistically significant (P less than 0-001) reduction in the number of admissions to hospital in the treatment year compared to the preceding 12 months in the beclomethasone aerosol group. No increased incidence of lower respiratory tract infections or non-specific sore throats was found in either group studied. No cases of clinical oral Candida infection occurred in the beclomethasone aerosol treated patients. It is concluded that beclomethasone dipropionate in aerosol form is not only a safe and effective method for symptomatic control of adult bronchial asthma but is also economically worthwhile as a means of reducing hospital admissions in this vulnerable group of patients.

Adult↗
PubMed1975

Serological relationship between a pathogenic strain of Marek's disease virus, its attenuated derivative and herpes virus of turkeys.

Precipitating antigens present in extracts of chick embryo cells infected with the HPRS-16 attenuated strain of Marek's disease virus (att-MDV) were separated by gel filtration on Sephadex G200 and some of their properties determined. The two main antigens detected with convalescent MD serum, referred to as 'B' and 'C' antigens, had mobilities of 0-55 and 0-25 respectively relative to phenol red on electrophoresis in 7-5% acrylamide gel. The B antigen was relatively stable and of low mol. wt. in comparison with the C antigen. B and C antigens were in some instances also detected in culture medium of infected cells, but were distinguishable from the A antigen, a major glycoprotein antigen released into the culture medium of cells infected with HPRS-16. The results of immunodiffusion studies suggest that B antigen is common to MDV and strains of herpes virus of turkeys(HVT) and that at least 2 antigens (including C) are MDV specific. The A antigen was also common to MDV and HVT strains. It was noted however that the capacity of HPRS-16/att to synthesize A antigen was considerably reduced in comparison with HPRS-16 and HVT strains, and in some preparations the A antigen could not be detected. Evidence was also obtained for the presence of HVT-specific antigens associated mainly with the cell fraction.

Animals↗
PubMed1971

Fate of carbon passing through the glucose pool of rumen digesta.

The metabolism of the free glucose pool in rumen digesta from sheep fed roughage rations was studied by adding an insignificant quantity of glucose as uniformly labeled (14)C-glucose of high specific activity to in vitro incubation systems. In all experiments wherein only trace quantities of glucose were added to digesta, most of the (14)C-glucose entered acetate. This was true whether label was presented either as a single dose or by continuous addition over a period of 2 hr. Digesta collected at all times after feeding either once daily or at hourly intervals gave similar glucose dissimilation patterns. If, however, a relatively large quantity of carrier glucose was added together with the tracer, the (14)C-acetate: (14)C-propionate ratio was reduced by a factor of about 10. Physical removal of most of the protozoa from digesta generally had little effect on the dissimilation of (14)C-glucose added in tracer amounts, but in one experiment there was a decreased turnover of the free glucose pool and a marked reduction in (14)C entering butyrate. The paucity of (14)C entering propionate when only trace amounts of glucose were added to digesta suggests that this acid was largely formed from substrates whose carbon did not equilibrate with that in free glucose or with that in intermediates of free glucose metabolism.

Acetates↗
PubMed1970

Metabolic fate of cysteine and methionine in rumen digesta.

Estimates were obtained of the extent to which cysteine and methionine were incorporated into the protein of the microbes of rumen digesta without prior degradation and resynthesis. By using the amino acids labeled with both (35)S and (14)C, it was observed that a large proportion of the (35)S appeared in the sulfide pool and of the (14)C appeared in volatile fatty acids. By isolating the appropriate amino acid, obtaining the (14)C to (35)S ratio, and comparing this with the ratio in the added amino acid, the degree of direct incorporation was calculated. For cysteine it was estimated that at most 1% and for methionine, at most 11% of the amino acid in the free pool was incorporated unchanged into microbial protein. As a consequence of these findings, it is considered that the method for measuring microbial protein synthesis in rumen digesta based upon incorporation of (35)S from the free sulfide pool is not seriously affected by direct utilization of sulfur amino acids arising from dietary sources.

Animals↗
PubMed1968

Energy utilization for polysaccharide synthesis by mixed rumen organisms fermenting soluble carbohydrates.

Synthesis of reserve polysaccharide by mixed rumen organisms fermenting glucose, maltose, cellobiose, and xylose has been studied in relation to the adenosine triphosphate energy calculated to be available from substrate fermentation. About 80% of the energy available from glucose and xylose was used for polysaccharide synthesis, whereas, assuming hydrolytic cleavage of the disaccharides, more than 100% was used when cellobiose and maltose were the substrates. If, however, phosphorolytic cleavage of the disaccharides, for which there is evidence, was involved, the energy from both maltose and cellobiose fermentation was used with about the same efficiency as that from glucose and xylose fermentation. The rumen fluid used was collected 24 hr after feeding, and growth of microorganisms in such samples was sufficient to account for utilization of less than 10% of the total energy becoming available during the 40-min incubation period.

Journal Article↗
PubMed1968

Method for measuring microbial growth in rumen content.

Radioactive sodium sulfide was used to label the sulfide pool of rumen contents in vitro. Microbial protein synthesis was calculated from the size and rate of dilution of label in the sulfide pool, and from the radioactivity incorporated into protein together with a conversion factor specifying the nitrogen-sulfur ratio determined for microbial protein. The microbial cell yield, calculated on the basis of the adenosine triphosphate (ATP) available from fermentation, was 13 to 14 g (dry weight) per mole of ATP, which is in good agreement with the values obtained for pure cultures of bacteria. Calculation of microbial protein yield per kilogram of ration agreed fairly well with previous estimates for similar rations.

Animals↗