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Biomedical subjects

E Weiss

Publications and source records attributed to E Weiss.

At least 271 records · Page 15Linked to original sources
PubMed1973

Metabolism of Richettsia tsutsugamushi and Rickettsia rickettsi in irradiated host cells.

The metabolism of Rickettsia tsutsugamushi (Gilliam strain) multiplying in irradiated L cells was investigated by methods involving the use of (14)C-labeled substrates and cycloheximide, an inhibitor of eukaryotic metabolism. Cycloheximide-resistant amino acid and adenine incorporations were appreciably higher in infected than in uninfected cultures during the period from 3 to 5 or 6 days postinoculation. The metabolism of R. rickettsi was similarly studied in primary duck embryo cells, which are more susceptible to infection with this rickettsia than are L cells. A difference in cycloheximide-resistant activity between infected and uninfected cultures was also noted, but was small. This finding is attributed to the more limited growth of R. rickettsi.

Amino Acids↗
PubMed1972

Characterization of spheroplast membranes of Neisseria meningitidis group B.

Spheroplast membranes (spheroplast envelopes) of strain 2091 of group B Neisseria meningitidis were prepared by a procedure that included lysozyme treatment of the cells and osmotic lysis of the resulting spheroplasts. Electron microscopy revealed that the membranes consisted of two unit layers, generally parallel to each other. The membrane preparation migrated as a single component in a 40 to 70% sucrose gradient and consisted of 62% protein, 28% lipid, 9% ribonucleic acid, small amounts of carbohydrate, hexosamine, and deoxyribonucleic acid. When 1 or 10 mug (dry weight) was injected intravenously into rabbits, a mild pyrogenic reaction was elicited. In immunodiffusion tests, immune rabbit serum prepared against spheroplast membranes produced three major precipitin lines, with the homologous antigen solubilized with sodium dodecyl sulfate, and a single line with untreated antigen. The immune serum also reacted with a cell wall antigen, and to a lesser extent with some of the cytoplasmic antigens. Succinate dehydrogenase and reduced nicotinamide adenine dinucleotide (NADH) oxidase activities were found to be associated with the spheroplast membranes. NADH dehydrogenase also was associated with the membranes but was gradually released and recovered in other fractions. Glutamate-oxaloacetate transaminase, glutamate, glucose-6-phosphate, and isocitrate dehydrogenase activities were not found in the membrane preparation. About one-third of these enzymatic activities were recovered in the supernatant fluid after the sedimentation of the spheroplasts and two-thirds were recovered in the cytoplasmic fraction. N-acetylneuraminic acid (NAN)-condensing enzyme and cytidine monophosphate-NAN synthesizing enzyme also were identified in this organism. These enzymes were not associated with the membranes and were recovered from extracts from whole cells, spheroplasts, or cells exposed to osmotic shock, as well as from spheroplast supernatant and shock fluids. It is concluded that the spheroplast membranes of the strain of meningococci used in these studies are typical of those recovered from gram-negative bacteria.

Animals↗
PubMed1972

Metabolism of Rickettsia typhi and Rickettsia akari in irradiated L cells.

L cells that had been exposed to 3,000 r of (60)Co the previous day were used to study the growth and metabolism of Rickettsia typhi and R. akari. Viable (unirradiated) L cells were used to study the effect of rickettsial infection on host-cell metabolism. Monolayers were infected with a rickettsial multiplicity of 1.2 and given Eagle's minimal essential medium containing 25 mmN-2-hydroxyethylpiperazine-N'-2'-ethanesulfonic acid buffer and 10% calf serum. At various intervals, cycloheximide (2 mug/ml) was added to one set of cultures, to inhibit eukaryotic protein and deoxyribonucleic acid (DNA) metabolism; phosphate-buffered saline (PBS) was added to another set. After 1 hr, the cultures received a mixture of 15 (14)C-labeled amino acids or adenine-8-(14)C. The cultures were harvested 16 hr later and were tested for incorporation of labeled carbon into the fraction precipitated by cold trichloroacetic acid. Viable cells were exposed to thymidine-2-(14)C for 2-hr periods. Infectivity of R. typhi increased to a peak of 150 to 400 hemolytic units/culture on day 4; the titer remained approximately the same on days 5 and 6, and declined rapidly on day 7. Total amino acid incorporation was about the same in infected and uninfected cultures up to day 6, but metabolic activity was reduced to a negligible level on day 7 in infected cells. Cycloheximide-resistant activity was higher in the infected cultures, with a peak equivalent to one-half the total activity at day 4 to 5. Total as well as cycloheximide-resistant adenine incorporation was higher in the infected cells between days 3 and 5 after infection, with a peak at day 3 to 4. Somewhat similar results were obtained with R. akari, except that the cycle of infection and of cycloheximide-resistant activity proceeded and was completed more rapidly. (14)C-DNA of both rickettsiae was isolated from infected cultures that had received labeled adenine. With labeled thymidine, which was not incorporated by the rickettsiae, it was shown that R. typhi and R. akari differ considerably in their effects on the host cell. R. typhi elicited moderate inhibition, whereas R. akari infection led to a complete inhibition of thymidine incorporation by the third day, at the time of highest rickettsial activity. It is concluded that rickettsiae have the necessary enzymes for protein and nucleic acid synthesis, but, thus far, these enzymes have been activated or induced only in an intracellular environment.

Adenine↗
PubMed1972

Response of mice to injection of ribosomal fraction from group B Neisseria meningitidis.

Ribosomes of strain NOR-7 of group B Neisseria meningitidis were isolated by a procedure that included treatment of the cells with sodium dodecyl sulfate, disruption in a French pressure cell, and differential centrifugation. These preparations consisted of 66% ribonucleic acid and 24% protein and sedimented as a single component with a constant of approximately 66S. When used in immunodiffusion tests with homologous rabbit antiserum, untreated ribosomes formed two precipitin lines, when treated with ribonuclease three lines, and when Pronase-digested only one distinct line. Qualitatively indistinguishable reactions were obtained with the same antiserum and ribosomes from group A meningococci, but no precipitation occurred with those of Escherichia coli. When injected into mice, group B ribosomes elicited an increase in the number of antibody-producing spleen cells demonstrable by the hemolytic plaque technique using unsensitized sheep erythrocytes. Sensitization of the erythrocytes with increasing amounts of supernatant fluid of meningococcal cultures progressively reduced the number of demonstrable plaque-forming cells. Neuraminidase treatment of the erythrocytes increased immune hemolysis, whereas Pronase digestion reduced it. Injected mice were protected against homologous and heterologous meningococcal challenge. Both hemolysis and protection-inducing activities of the ribosomes were unimpaired by ribonuclease, but were reduced by Pronase. It is concluded that the immunological response elicited by the meningococcal ribosomes does not involve the group-specific carbohydrate antigen. The immunological mechanism by which the mice are protected against meningococcal challenge remains unknown.

Animals↗
PubMed1971

Partial Reassociation Between the Deoxyribonucleic Acids of Neisseria lactamicus and Neisseria meningitidis.

The similarity in polynucleotide sequence of seven strains of Neisseria lactamicus to N. meningitidis and to each other was investigated. The per cent reassociation between single-stranded N. lactamicus deoxyribonucleic acid (DNA), immobilized on membrane filters, with labeled single-stranded DNA fragments derived from strain SD-6 (group C) of N. meningitidis varied from 75 to 56. With strain ATCC 23972 of N. lactamicus furnishing the labeled DNA fragments, reassociation was 72% with N. meningitidis, 31% with N. subflava, and 98 to 72% with the other strains of N. lactamicus. It is concluded that on the basis of DNA reassociation N. lactamicus can be distinguished from N. meningitidis and N. subflava, but constitutes a relatively heterogeneous species.

Journal Article↗