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Biomedical subjects

E Weiss

Publications and source records attributed to E Weiss.

At least 253 records · Page 14Linked to original sources
PubMed1976

Enzymatic activities of cell-free extracts of Rickettsia typhi.

Cell-free extracts of Rickettsia typhi were tested for activities of enzymes of the tricarboxylic acid cycle, of glutamate catabolism, and of glycolysis. The organisms were grown in the yolk sacs of chicken embryos, harvested shortly before the time of embryo death, purified by Renografin density gradient centrifugation, and ruptured in a French pressure cell. The following enzymatic activities were demonstrated: high levels of malate dehydrogenase (MDH), moderate levels of glutamate-oxaloacetate transaminase, glutamate, succinate, and isocitrate dehydrogenases, and citrate synthase, and low levels of glutamate-pyruvate transaminase. The specific activities of some of these enzymes were higher when the rickettsiae were harvested at a time of active proliferation, 3 to 4 days prior to embryo death. Rickettsial MDH was differentiated from host MDH by its migration pattern on polyacrylamide gel electrophoresis. The activities of MDH and two other dehydrogenases, demonstrable after the cells had been disrupted, were absent from purified, intact rickettsial preparations. No activity was detected for glucose-6-phosphate, 6-phosphogluconate, glyceraldehyde-3-phosphate, lactate dehydrogenases, phosphoglucose isomerase, fructoaldolase, or pyruvate kinase. Our results suggest that extracts of R. typhi that contain demonstrable enzymes involved in the catabolism of glutamate and tricarboxylic acid cycle intermediates, unlike Coxiella burnetti, lack detectable glycolytic activity.

Alanine Transaminase↗
PubMed1975

Electron microscopical study of initial and final stages of fowl plague virus-replication in chick embryo cells.

Cellular uptake of fowl plague virus occurs 10-30 minutes after inoculation of chick embryo cells. The penetration of the virions is by pinocytosis (viropexis); fusion with the cellular membrane has not been observed. After pinocytosis the virions become gradually disintegrated. Budding of newly formed virions from the cellular membrane starts 3 hours post inoculation (p.i.) and reaches its maximum 8 hours p.i. At the same time budding takes place into electron microscopically empty and autophagic vacuoles. Eight hours p.i. about 3 per cent of the infected cells show budding of virions from the surface and into cytoplasmic vacuoles. Labelling of the cellular membrane with ruthenium red demonstrated that these cytoplasmic vacuoles are not simple cross-sections of invaginations of the cellular membrane. Cluster-like structures were found at 6 hours p.i. in the nuclei of infected cells; however, the suggestion that the clusters develop from nucleoli could not be confirmed.

Animals↗
PubMed1975

Separation of viable Rickettsia typhi from yolk sac and L cell host components by renografin density gradient centrifugation.

Rickettsia typhi cultivated in the yolk sac of chicken embryos or in L cells irradiated 7 days previously was separated from host cell components by two cycles of Renografin density gradient centrifugation. Preliminary steps involved differential centrifugation and centrifugation over a layer of 10% bovine plasma albumin of infected yolk sac suspensions, or trypsinization and passage through filters of wide porosity of infected L cell suspensions. Rickettsial preparations obtained by these methods appeared to be free from host cell components while retaining high levels of hemolytic activity, egg infectivity, and capacity to catabolize glutamate. Average yields were 3.3 mg of rickettsial protein per yolk sac or 0.44 mg per 16-oz (ca. 475-ml) L cell culture. Extracts from these two preparations displayed malate dehydrogenase activity of electrophoretic mobility identical to each other but quite different in migration patterns from the corresponding host cell enzymes. This method of separation of rickettsiae from host cell constituents appears to be particularly well suited for the study of rickettsial enzymatic activity.

Animals↗
PubMed1975

[Effect of the vagus nerve on isolated rabbit atria in ganglionic blockade due to hexamethonium].

By quantitative stimulation of the vagus nerves of isolated rabbit atria frequency-response relations were obtained for both the electrotropic effect (reduction of the area of the monophasic action potential) and the inotropic response. An addition of hexamethonium in a final concentration of 10(-5) g/ml resulted in a diminution of vagal effectivity in the range of lower and medium frequencies of stimulation, and was connected with a shift of the frequency-response characteristic to the right. At higher frequencies vagal effectivity was increased. In contrast to the inhibitory effect of hexamethonium the facilitating action is irreversible. By raising the concentration up to 4-10(-5) g/ml the vagal effects were reduced to a large extent, and the frequency dependence of the response was abolished at medium frequencies. In the range of 20 sec(-1) to 100 sec(-1) this dependence was re-established and may be considered as a part of a normal frequency-response relation extremely shifted to the right. The time courses of both types of effect are characterized by a steep rise and a decay of the response during the stimulation period. A mathematical handling of the frequency-response characteristics provides quantitative evidence for the extent of the hexamethonium blockade of vagal ganglion cells in the atria; furthermore it leads to the conception of these cells to act as a distributing system for a homogeneous innervation by a widespread divergency of postganglionic fibres.

Action Potentials↗
PubMed1974

Protein fraction with immunogenic potential and low toxicity isolated from the cell wall of Neisseria meningitidis group B.

Several fractions were extracted from the cell envelope (CE) of Neisseria meningitidis group B and characterized with regard to their morphology, antigenicity, protein composition, and toxicity. Whole bacterial cells were suspended in a medium of low ionic strength and disrupted in a French pressure cell. The crude CE thus obtained were separated into cell membrane (CM) enriched and cell wall (CW) enriched fractions on sucrose density gradients. In addition, CM and CW fractions were separated from CE on the basis of differential solubility in the nonionic detergent, Triton X-100. The Triton-insoluble fraction, containing primarily CW components, was further treated with a mixture of Triton and ethylenediaminetetraacetic acid, which was shown to remove additional protein and most of the lipopolysaccharide. Electron microscope examination of the various fractions revealed typical unit membrane structures in the case of CM, or large, open segments in the case of CW. The Triton-insoluble and especially the Triton-ethylenediaminetetraacetic acid-insoluble fractions consisted of small vesicular structures. All fractions, except the Triton-soluble fraction, when assayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were shown to contain one major protein component accounting for more than 50% of the total. Sera from rabbits immunized with the various fractions formed precipitin lines in immunodiffusion tests against the homologous and some of the heterologous fractions. High-titer bactericidal antibodies were also demonstrated in these sera when tested against the homologous strains. Toxicity studies in rats sensitized with lead acetate indicate that the level of contamination of Triton-insoluble/Triton-ethylenediaminetetraacetic acid-insoluble fractions with lipopolysaccharide was significantly smaller than that of the other fractions.

Animals↗
PubMed1974

Phase transition of gonococci in mammalian cell cultures.

Neisseria gonorrhoeae was cultivated in mammalian cell cultures in an effort to determine if this environment will elicit a T4 --> T1 transition. Of four avirulent (T4) isolates tested, only one, H4, yielded T1 colonies. This change was consistently obtained in HeLa, WI-38, and MK2 cells, even when the multiplicity of the gonococcal infection was less than 1 per culture. Growth of the gonococci took place primarily on the surface of the cells, as demonstrated by light and electron microscopy, but occasional bacteria were undoubtedly intracellular. T1 colonies were seen at 24 h and were the major population at 48 h. This shift was favored by the presence of viable cells, since smaller yields of T1 were obtained when the cells were irradiated or heat inactivated. It was also favored by low pH, since T1 recovery was reduced when the buffering capacity of the medium was increased. Although the results suggest that T1 gonococci derived from H4 have a selective advantage over T4 in cell cultures, this is not true of all T1 and T4 colony types. F62 T4, which does not undergo a T4 --> T1 shift, propagated as well as T1 in HeLa cell cultures. The change in colony type of strain H4 to T1 was accompanied by formation of pili and by gain in capacity for deoxyribonucleic acid-mediated transformation. It is concluded that gonococci can undergo T4 --> T1 phase transition in mammalian cell cultures, but this property is not retained by all strains.

Animals↗
PubMed1974

Tumours of the soft (mesenchymal) tissues.

This is a classification of tumours of fibrous tissue, fat, muscle, blood and lymph vessels, and mast cells, irrespective of the region of the body in which they arise. Tumours of fibrous tissue are divided into fibroma, fibrosarcoma (including "canine haemangiopericytoma"), other sarcomas, equine sarcoid, and various tumour-like lesions. The histological appearance of the tumours is described and illustrated with photographs.

Animals↗
PubMed1974

Tumours of the skin.

Tumours occur more frequently in the skin than in any other part of the body. Epithelial tumours are described under the following headings: basal cell tumour, squamous cell carcinoma, papilloma, sebaceous gland tumour, tumour of hepatoid glands, sweat gland tumour, mixed tumour of apocrine sweat glands, carcinoma of apocrine sweat glands, tumour of hair follicle, and intracutaneous cornifying epithelioma. Tumours of the melanogenic system are divided into benign melanoma and malignant melanoma, the latter being subdivided into the following types: epithelioid, spindle cell, epithelioid and spindle cell, dendritic, and whorled.

Adenoma↗
PubMed1973

DNA base composition of rickettsiae.

There is a small but distinct difference in DNA base composition between the typhus and spotted fever groups of rickettsiae. The molar percentages of guanine plus cytosine for Rickettsia prowazeki, R. typhi, and R. canada are approximately 30, for R. rickettsi, R. conori, and R. akari they are about 32.5. The percentage for trench fever rickettsia, Rochalimaea quintana, is 38.6.

Animals↗