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At least 55 records · Page 3Linked to original sources
PubMed1975

Biological characterization of Fusobacterium necrophorum. Cell fractions in preparation for toxin and immunization studies.

Fusobacterium necrophorum isolated from bovine liver abscesses was grown in bulk at 37 C for 24 h under a strict anaerobic atmosphere. Harvested washed cells were disrupted ultrasonically and fractionated by differential centrifugation into the intracellular (cytoplasm) and cell wall fractions. Both intact cells and cell fractions induced generalized cytopathic effect on primary pig kidney cultures and caused a variety of signs of illness and/or death of intraperitoneally injected mice. The intact cells, disrupted cells, and cell walls produced necrotic lesions and erythema on intradermally injected guinea pigs and rabbits, whereas the cytoplasm mainly erythema. By contrast, the used culture medium (culture filtrate) of F. necrophorum did not show any detectable toxicity. The toxic component of the cytoplasm appears to be associated with nondialyzable, hemolytic, high-molecular-weight proteins and its toxicity is reduced by trypsin and pronase. Heating at 60 C for 10 min decreased markedly its erythemal and cytotoxic ability, wheras the toxicity of the cell walls appeared to be only slightly affected even when heated at 100 C for 1 h. These results suggest that at leasttwo distinct cell-bound toxic factors are present in F. necrophorum cells.

Amino Acids↗
PubMed1975

Subpopulations of mouse spleen lymphocytes. II. Immunological reactivity of spleen cells fractionated on BSA density gradients.

We found in previous experiments that fractionation of non-immune mouse spleen cells on bovine serum albumin density gradients yields two subpopulations of T cells, one of high, the other of low density. Both subopopulations could be stimulated in corporate thymidine by the T cell-specific mitogen concanavalin A (con A). In the present investigation, spleen cells of mice immunized to sheep red cells (SRC) were similarly fractionated and the fractions recovered were assayed for: (a) reactivity to con A; (B) REACTIVITY TO SRC and (c) capacity to function as helper cells when stimulated with the homologous (SRC) or with a heterologous (donkey red cells) (DRC) antigen. Two subpopulations of cells reacting to con A were found in the spleens of the primed mice, corresponding to the subpopulations found in the non-immune mice. Both subpopulations contained cells responding to SRC (as measured by thymidine incorporation) and cells endowed with helper activity. The two subpopulations appeared to differ, however, in their specificity: while the denser cells could only exert their helper effect when stimulated by the specific antigen, the light cells could be effectively stimulated by both the specific (SRC) and the nonspecific (DRC) antigen.

Animals↗
PubMed1975

The ability of cell fractions of mouse spleen to repopulate the hemopoietic tissue and to mount graft-versus-host reaction.

Mouse spleen cells were separated into seven fractions on a discontinuous gradient of dextran. The lightest, uppermost fraction contained colony-forming units and was capable of repopulating the hemopoietic tissues damaged by irradiation. The fraction below it also contained the colony-forming units, but its repopulating ability was limited. Heavy fractions contained immunocompetent cells capable of mounting graft-versus-host reaction, but the performance of the cells depended on the type of assay, i.e. on whether the cells were assayed in irradiated or in non-irradiated recipients. It is concluded, firstly, that the technique used resolved the colony-forming units into two classes - those capable of self-renewal and those committed to differentiation - which were concentrated in different portions of the light part of the gradient; and secondly, that the cells implementing graft-versus-host reaction were probably also resolved into two classes - the inciting and the proliferating cells - which were concentrated in different portions of the heavy part of the gradient.

Animals↗
PubMed1979

[Sulfhydryl and amino groups in the cell fractions of white rat tissues: ontogenetic characteristics].

The author investigated total protein, percentage of protein sulfhydril and amino-groups of those in the cytoplasm and total sulfhydril groups in mitochondria, lysosomes and cytoplasm in liver, kidney and spleen of rats. There was a tendency to an increase of total protein in single tissue components with the advancement of age. The amount of sulfhydril groups was altered with advancement of age as well. Their maximal value was in animals, aged 5 days. In all examined cell fractions there was a statisticaly significant lowering in the subsequent age group, which tendency continued till the end of the examined period (5, 10, 15, 20, 25, and 30 -- day rats). The changes, observed in amino-groups were statisticaly significant and reflected the specificity in the metabolism of the three examined organs in accordance with their functions. Statistificaly significant lowering of the present sulfhydril groups, determined by DYNB, and nonsignificant changes of amino-groups showed that proteins in the examined tissues exposed various amount of sulfhydril groups probably due to the various water content of the tissues at different age periods. Perhaps there could be an effect of other factors as well, having connection with oxidation and reduction of sulfhydril groups.

Aging↗
PubMed1975

[Studies on bradykinin-binding cell fractions. 1. Characterization of kininase activity of the microsomal and membrane fraction from the rat uterus].

In the membrane fraction of rat uterus, kinin-destroying activity was found and characterized as kininase II by means of several kininase inhibitors. It could be shown that sudies of bradykinin-receptor interactions requires the use of kininase inhibitors like phenanthroline or the use of a stable bradykinin analogue like [8-erythro-alpha-amino-beta-phenylbutyric acid]-bradykinin.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1975

Epstein-Barr virus-induced transformation of human leukocytes after cell fractionation.

The efficiency of transformation of human lymphocytes after infection with Epstein-Barr virus (EBV) was determined in fractionated and non-fractionated preparations derived from 16 human cord blood samples and two blood samples from adult donors. The transformation efficiency of macrophage-depleted leukocytes was consistently lower as compared to non-fractionated leukocytes. Additional depletion of B-cells resulted in a further decrease. Reduction of T-cells, however, did not influence significantly the transformation rate. In non-fractionated leukocyte cultures, as well as in macrophage-depleted and B-cell enriched cultures, colonies of transformed cells were regularly observed within the first week of cultivation. All cell lines established after EBV-infection revealed membrane-bound immunoglobulin. Reconstruction of macrophages-depleted, B-cell enriched or B-cell depleted cultures with autologous macrophages resulted in an increase of the transfromation efficiency up to the values of non-fractionated leukocyte preparations. Addition of heterologous human embryonic lung fibroblasts resulted in a similar increase. The results support the interpretation that EBV transforms only those cells of the hematopoetic system which are derived from the bone-marrow entity. The transformation efficiency is considerably increased by co-cultivation of lymphocytes with macrophages and heterologous human fibroblasts which seem to excert a feeder-layer effect by enhancing survival of lymphocytes in vitro.

B-Lymphocytes↗
PubMed1979

Metabolism and binding in vitro of 5 alpha-androstane-3 beta, 17 beta-diol and of 5 alpha-androstane-3 alpha, 17 beta-diol in cell fractions of rat ventral prostate and liver.

Rat ventral prostate and liver were investigated for the binding in vitro to particulate fractions and for the metabolism of 5 alpha-androstane-3 beta, 17 beta-diol. Comparative investigations were carried out on the metabolism of 5 alpha-androstane-3 alpha, 17 beta-diol. Preparations of the liver were investigated in order to establish the organ specificity of the method. In the prostate, the bulk of the metabolites of 5 alpha-androstane-3 beta, 17 beta-diol was present as steroids of high polarity. Of the less polar metabolites, 17 beta-hydroxy-5 alpha-androstan-3-one, 3 beta-hydroxy-5 alpha-androstan, 17-one and 5 alpha-androstane-3 alpha, 17 beta-diol were detectable. The binding of a 5 alpha-androstane-3 beta, 17 beta-diol to mitochondria and microsomes was unspecific. In the liver, among the less polar metabolites, 3 beta-hydroxy-5 alpha-androstan-17-one was the main metabolite, and the binding was unspecific. The main metabolite in the prostate homogenate of 5 alpha-androstane-3 alpha, 17 beta-diol was 17 beta-hydroxy-5 alpha-androstan-3-one. The portion of highly polar steroids was very low. The portion of unmetabolized hormone was distributed almost equally among the different cell preparations except the nuclei, in which 17 beta-hydroxy-5 alpha-androstan-3-one was higher and 5 alpha-androstane-3 alpha, 17 beta-diol was lower than in the remaining cell fractions.

Androstane-3,17-diol↗
PubMed1977

[Immunologic properties of various cell fractions of a wild strain and a mutant strain of Saccharomyces cerevisiae Hansen].

Some fractions of the Saccharomyces cerevisiae cell wall have been prepared by the action of Helix pomatia juice on intact cells. Immunosera were obtained by injecting rabbits with these fractions. Immunofluorescence reactions, obtained with these sera, show that some fractions of mannopeptides when extracted from a "smooth-colony" mutant strain, have lost antigenic determinants.

Cell Wall↗
PubMed1979

Regulation of the cell cycle of 3T3 cells in culture by a surface membrane-enriched cell fraction.

Addition of a suspension of a surface membrane enriched fraction prepared from confluent 3T3 cells to sparse 3T3 cells in culture results in a concentration dependent and saturable decrease in the rate of DNA synthesis. The inhibition of cell growth by membranes resembles the inhibition of cell growth observed at confluent cell densities by a number of criteria: 1) In both cases the cells are arrested in the G1 portion of the cell cycle; 2) the inhibition by membranes or by high local cell density can to a large extent be compensated for by raising the serum concentration or by addition of fibroblast growth factor plus dexamethasone. Membranes prepared from sparse cultures inhibit less well than membranes from confluent cultures in a manner which suggests that binding of membranes to cells is not by itself sufficient to cause inhibition of cell growth. The inhibitory activity has a subcellular distribution similar to phosphodiesterase (a plasma membrane marker) and appears to reside in one or more intrinsic membrane components. Maximally, membranes can arrest about 40% of the cell population in each cell cycle. Plasma membranes obtained from sparse 3T3 cells are less inhibitory than membranes obtained from confluent cells. This suggests either that the inhibitory component(s) in the plasma membrane responsible for growth inhibition may be in part induced by high cell density, or that this component(s) may be lost from these membranes during purification.

Animals↗
PubMed1977

Detection of mitogen-activated T and non-T lymphocytes by virus plaque assay. Virus plaque assay on the cells fractionated by unit gravity sedimentation.

Virus plaque assay (VPA) was utilized for the quantitative evaluation of activated lymphocytes. We examined what types of cells, especially which of activated T and non-T lymphocytes, were detected as infective centres after infection with vesicular stomatitis virus. Marked increases in DNA synthesis and in virus-plaque forming cells (V-PFC) were observed not only during the activation of T lymphocytes with Con A, but also, though to a lesser extent, during the activation with lipopolysaccharide (LPS) of non-T lymphocyte preparations of nude spleen from which theta-positive lymphocytes and macrophages were completely depleted. The latter observation was further confirmed by the VPA on the populations enriched in LPS-activated non-T lymphocytes fractionated by the unit gravity sedimentation method. Fast sedimenting cells were found to be more active in DNA synthesis and contained more infective centres after infection than those sedimenting slowly and original unfractionated cells. Both the capacity for DNA synthesis and virus-replication were considered to be general properties accompanying lymphocyte activation.

Animals↗
PubMed1992

Rat bone marrow erythroid cell fractionation by counter current distribution in non-charge-sensitive two-phase systems.

Counter-current distribution in non charge-sensitive aqueous poly(ethylene glycol)-dextran two phase systems allows the fractionation of rat bone marrow cells into two broad cell subpopulations with different distribution coefficients in a relatively short time. Morphological identification and enzymatic studies suggest that erythroid cells are mainly present in the subpopulation with the higher distribution coefficient. The distribution coefficient and, therefore, surface hydrophobicity of these cells, apparently increase in parallel with an increase in their degree of differentiation and maturation.

Animals↗
PubMed1978

[Possibility of using enriched glial and neuronal cell fractions to study transport of neurotransmitter amino acids in old age].

Calculated on a protein basis the yield of neuronal and glial cell-enriched fractions obtained from the brain of aged and adult rats was found to be equal. In aged animals the high affinity uptake of 14C-GABA by neuronal fractions is reduced by 27.34% while that of glial fractions by 11.87%. At 0 degrees both age groups studied the uptake of 14C-GABA is greatly inhibited--by 66% in neurones and 92% in glia. The conclusion is drawn that glial cells are changed much less with age than neurones and thus their role as modulators of neuronal function increases with age.

Aging↗