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Biomedical subjects

M G Johnson

Publications and source records attributed to M G Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1980

Quantitative, radial diffusion slide assay for staphylocoagulase.

A simple, quantitative radial diffusion assay for staphylocoagulase in culture fluids, using microscope slides coated with a thin layer of agar containing plasma and fibrinogen, was developed. No prior purification of the enzyme was needed, and only small quantities, 7 microliter, were required for each test. This method is particularly suitable for objectively comparing the relative amounts of coagulase produced by different cultures of Staphylococcus aureus.

Animals↗
PubMed1979

Cardiobacterium hominis endocarditis.

This report describes the isolation of Cardiobacterium hominis from a patient with a history of rheumatic heart disease. Seven blood cultures yielded the organism. This investigation includes the case history, significant details of the hospital course, and the bacteriological, biochemical, and antimicrobial characteristics of Cardiobacterium hominis, integrated with a brief review of the literature.

Aged↗
PubMed1978

Regional pancreatic concentration and in-vitro secretion of canine pancreatic polypeptide, insulin, and glucagon.

The regional concentrations and in-vitro secretions of canine pancreatic polypeptide (cPP), insulin, and glucagon were studied. CPP is found predominantly in the uncinate process of the dog pancreas, whereas insulin and, more markedly, glucagon predominate in the body and tail of the pancreas. In-vitro secretion studies of pancreatic pieces indicate that dibutyryl cyclic AMP (dcAMP) alone can stimulate cPP release whereas glucose and arginine alone have no effect. Arginine, but not glucose, potentiates this stimulant effect of dcAMP. These studies suggest that the cAMP generating system may play a role in regulation of cPP secretion.

Animals↗
PubMed1977

Increased numbers of heat-resistnat spores produced by two strains of Clostridium perfringens bearing temperate phage s9.

Sporulation kinetics and spore heat resistance data were compared for a lysogenic strain of Clostridium perfringens, s9, before and after curing with ultraviolet irradiation. The cured strain showed the same growth rate in broth media as the lysogenic strain but took 6 h longer to form refractile spores. For lysogenized and cured strains the percentages of refractile spores produced that were heat-resistant (80 degrees C for 15 min) were 50 and 0.2, respectively. When reinfected with the temperature phage, the cured strain produced spores in 2 to 3 h, like the original lysogenic culture, and 10% of the spores produced were heat-resistnat.

Bacteriophages↗
PubMed1976

Characteristics of bacteria isolated by the anaerobic roll-tube method from cheeses and ground beef.

In this study the methods of Hungate were used to quantitate the anaerobic bacteria present in commercially available ground beef, cheddar cheese, and German hand cheese. Of 235 anaerobic roll-tube isolates from ground beef and German hand cheese, all were facultative anaerobes. Of 213 anaerobic roll-tube isolates from cheddar cheese, 91% were facultative anaerobes and 9% were obligate anaerobes. Using results of biochemical tests, 14 or the 17 obligately anaerobic isolates from cheddar cheese were Propionibacterium acnes, two were strains of Propionibacterium that could not be speciated, and one was tentatively identified as a strain of Streptococcus evolutus. Obligate anaerobes were estimated to be present in the cheddar cheese at a level of about 10(6)/g. The possible significance of these levels of P. acnes in nonsterile foods is discussed.

Anaerobiosis↗
PubMed1969

Death of Salmonella typhimurium and Escherichia coli in the presence of freshly reconstituted dehydrated garlic and onion.

The kinetics of the decline of populations of Salmonella typhimurium inoculated into freshly reconstituted dehydrated onion and garlic powders was studied. Measurable bactericidal activity was observed for onion and garlic concentrations of 1 and 5% (w/v), respectively, with maximal death rates occurring for concentrations of 5 and 10%. At these concentrations, the decimal reduction times were 1.1 and 1.2 hr, respectively, for resting cell cultures and 1.8 and 2.1 hr, respectively, for growing cultures. Of the major volatile aliphatic disulfide compounds of onions, n-propyl allyl and di-n-propyl, at concentrations of 0.1%, showed a comparable activity against resting cells but only a bacteriostatic effect toward actively growing cultures, which overcame this effect in 2 to 6 hr. At comparable concentrations, growing cultures of Escherichia coli were as susceptible to garlic, but apparently more resistant to onion, than were those of S. typhimurium.

Escherichia coli↗