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Biomedical subjects

K G Johnson

Publications and source records attributed to K G Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1982

The effects of Mount St. Helens volcanic ash on the pulmonary function of 120 elementary school children.

The 1977 Montana legislature funded an extensive Montana Air Pollution Study (MAPS). One hundred and twenty children in the fourth and fifth grades in Missoula, Montana had their pulmonary functions tested on 6 days during the 1979-80 school year. On May 18, 1980, Mount St. Helens erupted, resulting in very high total suspended particulates (TSP) levels due to ash (peak day = 11,054 micrograms/m3 24-hour average) through May 22. When these children returned to school on May 23, they had their pulmonary functions tested a seventh time. There was no substantial decrease in pulmonary function after the ash exposure. By comparison, the childrens' pulmonary tests did show a significant decrease after 3 days of high urban air pollution (440 micrograms/m3 3-day average). Businesses and schools were closed for 4 days after the eruption and people were advised to remain indoors; hence, lack of measured pulmonary function test effects from the ash may be due to the protective precautions taken by the children.

Air Pollutants↗
PubMed1981

The association between body strike and dermatophilosis of sheep under controlled conditions.

The association of dermatophilosis with body strike of sheep caused by Lucilia cuprina was studied in a controlled environment. When sheep with areas of wet normal fleece and areas of wet fleece containing scabs induced by infection of the skin with Dermatophilus congolensis were exposed to gravid L. cuprina the files oviposited only on dermatophilosis-affected areas. In wet dermatophilosis-affected fleece, naturally oviposited L. Cuprina eggs hatched and the larvae developed to the second instar stage. Artificially implanted L cuprina eggs hatched in both wet dermatophilosis-affected fleece and wet normal fleece. In wet dermatophilosis-affected fleece the larvae from implanted eggs developed normally but in wet normal fleece they did not develop past the first instar stage. It was concluded that wet but otherwise uncomplicated dermatophilosis lesions are attractive to L. cuprina and provide sufficient protein to allow larval development to take place.

Actinomycetales Infections↗
PubMed1981

Ampicillin resistance in Neisseria denitrificans: studies on ampicillin-sensitive enzymes.

The beta-lactam sensitivities of enzymes involved in peptidoglycan synthesis were examined in two strains of Neisseria denitrificans having widely disparate degrees of ampicillin sensitivity. One strain of n. denitrificans was 400 times more resistant to ampicillin than the other; the former is known to have altered penicillin-binding proteins. No differences in the levels of sensitivities of total peptidoglycan synthesis as measured by the incorporation of glutamate into peptidoglycan, or of D-alanine carboxypeptidase, were observed between the two strains. However, the rate of glutamate incorporation into peptidoglycan by logarithmic growth phase cells was somewhat less for the ampicillin-resistant cells than for the parent cells.

Ampicillin↗
PubMed1980

Antibiotic resistance in Neisseria denitrificans.

An ampicillin-resistant strain of Neisseria denitrificans was produced by serial passage of the organisms in media containing increased concentrations of antibiotic. The 400-fold increase in resistance obtained was a relatively stable characteristic. Ampicillin resistance in this organism was apparently related to a loss or modification of the penicillin-binding proteins associated with the cytoplasmic membranes. Membranes isolated from the ampicillin-resistant strain bound significantly less radioactive penicillin than those isolated from the parent strain and revealed one major and three minor penicillin-binding proteins. All four penicillin-binding proteins were present in reduced amounts or had a decreased capacity for penicillin binding in the ampicillin-resistant cells. The increased resistance did not involve enzymic degradation of the antibiotic or a general reduction in the permeability of the outer layers of the cell. No difference in the amount of peptidoglycan present in the parent and ampicillin-resistant cells or in the gross chemical structure of the peptidoglycans of the two strains was observed.

Ampicillin↗
PubMed1978

Heat-stable enterotoxin from Escherichia coli: factors involved in growth and toxin production.

Six enterotoxigenic strains of Escherichia coli produced variable levels of heat-stable enterotoxin (ST) when grown under pH control at 8.5 in a simple synthetic medium containing neither amino acids nor vitamins. Bacterial growth and ST production were at levels as high as or higher than those observed in complex media. ST elaboration was detectable in the early logarithmic phase of growth and appeared to be related to disappearance of glucose in the growth medium. The results of this study did not suggest pH-dependent release of ST. Imposition of pH control in complex media resulted in increased growth rates, earlier detectable ST synthesis, and elevated levels of ST. In synthetic medium, attainment of the stationary growth phase was followed by a significant decrease in culture density and a concomitant increase in ST. Cellular autolysis experiments revealed that as much as 20% of the total ST activity was present in a cell-associated form.

Bacteriolysis↗
PubMed1978

Immunological relationships of some non-pathogenic Neisseria.

A collection of nine stock strains of non-pathogenic Neisseria species and one strain of Branhamella catarrhalis has been examined serologically by a simple immunodiffusion technique utilising cultures growing on solid medium.

Antibodies, Bacterial↗
PubMed1978

Glycogen metabolism in the genus Neisseria: synthesis from sucrose by amylosucrase.

Eight strains (seven species) of Neisseria were found to possess intracellular amylosucrases capable of synthesizing glycogen directly from sucrose. All eight systems were stimulated by primer glycogen, possessed similar kinetic parameters, and were competitively inhibited to similar degrees by fructose. The enzymes bound tightly to their polysaccharide products but these complexes could be readily dissociated by polyacrylamide gel electrophoresis. Some of the enzyme-product complexes appeared to be virutally free of contaminating proteins.

Binding, Competitive↗
PubMed1978

Structure of the D-glucans produced by Neisseria perflava.

A chemical and enzymic study of the cellular glucan of Neisseria perflava and of the glucan produced from sucrose by a cell-free extract of N. perflava showed from optical rotation, 13C nuclear magnetic resonance, methylation analysis, and alpha- and beta-amylase hydrolysis studies that the glucans had glycogen-like structures. These structures were composed of chains of 1-4-alpha-D-glucopyranosyl units with branch points of 4-O- and 6-O-disubstituted D-glucopyranose units. While the backbone structures of the two glucans were similar, the release of maltose by the action of beta-amylase indicated that the 1-4 linked nonreducing side chains of the cell-free enzymically synthesized glucan were longer (approximately seven units) than those present in the cellular glucan (approximately two to three units), a result in agreement with methylation analyses.

Cell-Free System↗
PubMed1977

In vitro interaction of Neisseria gonorrhoeae type 1 and type 4 with tissue culture cells.

As a basis for studies of gonococcal pathogenicity, tissue culture cells were infected with type 1 or type 4 Neisseria gonorrhoeae to determine intracellular viability. A simple and objective means of measurement was devised, based on the uptake of tritiated protein and deoxyribonucleic acid precursors by cycloheximide-inhibited cells infected with gonococci. Cycloheximide was found to inhibit protein synthesis by over 97% tissue culture cells at a concentration of 100 microng/ml. In contrast, N, gonorrhoeae was found to be highly resistant to this antibiotic, and protein synthesis was unaffected by concentrations up to 1,000 microng/ml. Extracellular gonococci were eliminated by treatment with high concentrations of penicillin during cycloheximide inhibition and prior to the addition of radioisotope. Levels of protein and deoxyribonucleic acid synthesis by N. gonorrhoeae in the cycloheximide-treated cells were significantly higher in T1-infected cells (RE2, HeLa, or HEp-2) than in the corresponding T4-infected cells. No differences were observed in tissue cell susceptibility to gonococcal infection. Intracytoplasmic localization of N. gonorrhoeae was confirmed by electron microscopy.

Bacterial Proteins↗
PubMed1977

Mitogenic activity of Neisseria gonorrhoeae surface antigens in mouse splenic lymphocyte culture.

The mitogenic effects of Neisseria gonorrhoeae endotoxin, fractionated envelope componenents, and intact cells were examined on unsensitized mouse splenic lymphocytes in vitro. The stimulatory effect of these substances was measured by increased [3H]thymidine incorporation in spleen cell cultures. Intact cells, purified lipopolysaccharide (LPS), and cell envelope preparations were highly stimulatory and the stimulation index was dose dependent. Fractionated components of the envelope demonstrated variable stimulation when tested at identical LPS concentrations, reflecting the mitogenic activity of the protein moieties. The stimulatory dose responses for purified N. gonorrhoeae and Escherichia coli LPS were compared and mitogenicity was higher with gonococcal LPS at all concentrations tested. Alkaline detoxification or succinylation of N. gonorrhoeae LPS results in loss of ability to induce blast transformation. The mitogenicity of cell-surface components of N. gonorrhoeae is discussed in terms of LPS and protein content.

Animals↗
PubMed1977

Glycogen synthesis by amylosucrase from Neisseria perflava.

Amylosucrase (sucrose:1,4-alpha-D-glucan 4-alpha-glucosyltransferase; EC 2.4.1.4) which mediates the transfer of the glucosyl moiety of sucrose to a growing alpha-1,4-glucan chain is a constitutive enzyme of Neisseria perflava. The products of enzymic action are insoluble glycogenlike polysaccharides and fructose, the latter being a competitive inhibitor of the enzyme (Ki=20 mM). The enzyme is extremely stable and appears to bind very tightly to its polymerized product. Properties of product-bound enzyme reflect those of the native complex.

Cell-Free System↗
PubMed1976

Improved techniques for the preparation of bacterial lipopolysaccharides.

Liopolysaccharides were prepared from six organisms by the use of two cell-disruption procedures before conventional phenol-water extraction. Disruption of cells by grinding with glass beads or by digestion with hen egg white lysozyme before phenol extraction facilitated rapid purification and greater yields of lipopolysaccharide. Pretreatment of cells with lysozyme in the presence of ethylenediaminetetraacetic acid was the most efficient method in terms of lipopolysaccharide yield and ease of preparation. Increase in lipopolysaccharide yield achieved by use of the lysozyme method, compared with the conventional phenol extraction, varied from 1.7- to 12.4-fold. Preparations were designated as pure according to several criteria and were judged not to have undergone changes as a result of prephenol extraction procedures.

Bacteria↗
PubMed1976

Studies of the cellular and free lipopolysaccharides form Neisseria canis and N. subflava.

Cellular and free lipopolysaccharides (LPS) obtained from Neisseria canis and N. subflava were essentially identical. Both cellular and free lipopolysaccharides contained O-polysaccharides of the following composition: L-rhamnose (46 mol), D-glucose (16 mol), L-glycero-D-manno-heptose (2 mol), ethanolamine (2 mol), 3-deoxy-D-manno-octulosonic acid (1 mol), and phosphate (1.5 mol). The core oligosaccharide, which was common to the cellular and free LPS of both organisms, contained L-rhamnose (4 mol), D-glucose (2 mol), L-glycero-D-manno-heptose (2 mol), 3-deoxy-D-manno-octulosonic acid (1 mol), ethanolamine (2 mol), and phosphate (1.5 mol). Accumulated results on LPS composition and structure indicated that Neisseria perflava, N. subflava, and N. flava could not be combined into a single species. On the basis of its nutritional requirements and LPS structure, N. canis could be considered a strain of N. subflava.

Ethanolamines↗
PubMed1976

Sucrose-mediated giant cell formation in the genus Neisseria.

Growth of Neisseria perflava, Neisseria cinerea, and Neisseria sicca strain Kirkland in media supplemented with sucrose (0.5 to 5.0% w/v) resulted in the formation of giant cells. Response to sucrose was specific in that a variety of other carbohydrates did not mediate giant cell formation. Giant cells appeared only under growth conditions and did not lyse upon transfer to medium lacking sucrose or upon resuspension in hypotonic media. Reversion of giant to normal cells occurred when giant cells were used as inocula and allowed to multiply in media lacking sucrose.

Carbohydrate Metabolism↗