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Biomedical subjects

M Kern

Publications and source records attributed to M Kern.

At least 163 records · Page 9Linked to original sources
PubMed1985

[Principles of polarization-optical analysis in the study of connective tissue].

Possibilities of polarization-optic methods for studying macromolecular organization of the intercellular matrix of the connective tissue are demonstrated. Topo-optic reactions, being histochemical, make it possible to reveal not only presence of the molecules studied, but also quantitatively determine degree of their orientational regularity in the structural organization of the intercellular matrix. Determination of changes in the orientational regularity of single molecules contributes to revealing morphogenetic peculiarities of the intercellular matrix of the connective tissue, normal and under development of the destructive-distrophic process. Methodological principles of reactions to collagen, glycosaminoglycanes, glycoproteins, elastin and non-collagenous proteins are presented. Their advantages comparing certain known histochemical reactions, as well as their limitations are demonstrated. Certain illustrative material is presented.

Aniline Compounds↗
PubMed1985

Splenic B cells from CBA/N mice acquire responsiveness to anti-immunoglobulin after a brief treatment with pronase.

Although splenic B cells of CBA/N mice do not synthesize DNA in response to anti-mouse IgM (mu-chain specific), the cells respond readily to Sepharose linked anti-mu. Subsequent to a brief treatment with pronase, CBA/N splenocytes exhibited anti-mu-mediated DNA synthesis at 40 to 100% of the DNA synthetic capacity detected with Sepharose linked anti-mu. Furthermore, spleen cell populations treated with anti-Thy-1.2 and complement or populations purified on anti-immunoglobulin-coated Petri plates (greater than 90% surface immunoglobulin positive) acquired responsiveness to anti-mu after pronase treatment.

Animals↗
PubMed1985

Pronase treatment of lymphocytes reduces the time required for onset of S phase in response to anti-immunoglobulin.

Murine B lymphocytes in the presence of antibody specific for surface membrane immunoglobulin begin to synthesize DNA at about the 36th hr of culture, although the onset of synthesis in response to other B cell-reactive mitogens occurs at approximately 18 hr. In contrast, the onset of DNA synthesis by Pronase-treated cells in response to anti-immunoglobulin required only 18 hr. This earlier onset of S phase was not observed when Pronase treatment was performed in the presence of ovalbumin or the protease inhibitors phenylmethylsulfonyl fluoride or aprotinin. It is unlikely that simple carryover of Pronase from the treatment procedure to the cell culture process was involved, because Pronase treatment for 1 hr at 3 degrees C rather than at 37 degrees C did not result in early onset of DNA synthesis. Cells treated with Pronase and then with mitomycin C to irreversibly inhibit their capacity to synthesize DNA were incapable of inducing early onset of S phase on co-culture with untreated cells, suggesting that Pronase may act directly on B cells rather than indirectly via other cells in the splenocyte population.

Animals↗
PubMed1984

Enhanced phosphorylation of endogenous membrane proteins during induction of B lymphocyte proliferation.

Phosphorylation of endogenous proteins was assessed employing membrane preparations derived from splenocytes induced to proliferate in response to Sepharose linked anti-immunoglobulins. Time course studies revealed that enhanced protein phosphorylation was preceded by cell enlargement and was either followed by or closely related in time to the onset of DNA synthesis. Thus maximal enhancement of phosphorylation was initially observed at 24 h whereas cell enlargement was optimal at 16 h at a time when there was no enhancement in protein phosphorylation. Furthermore thymidine incorporation was maximal at 32 h and low at 24 h when phosphoprotein synthesis was maximally enhanced. Taken together, these results suggest that phosphorylation of endogenous membrane proteins may be involved in signalling entry of cells into S phase of the cell cycle.

Animals↗
PubMed1984

Nonresponsiveness of immature B lymphocytes to anti-immunoglobulin is reversed by pronase.

Splenic B cells are induced to proliferate upon culture with antibody having specificity for surface membrane immunoglobulins. Cells treated with pronase, washed and then cultured with antibody, exhibited a greater than 5-fold enhancement of DNA synthesis whereas pronase treatment, per se, was not mitogenic. The pronase effect exhibited specificity in that the induction of proliferation with either lipopolysaccharide or dextran sulfate was not enhanced by prior enzyme treatment. Cells from mice at two weeks of age which essentially do not show a proliferative response to antibody become responsive subsequent to pronase treatment. These results are interpreted to suggest a possible growth regulatory role for the pronase sensitive surface membrane component.

Aging↗
PubMed1984

Fate of surface immunoglobulin during induction of lymphocyte proliferation.

The modulation of immunoglobulin on the surface of rabbit B lymphocytes by goat antibodies with specificity for rabbit surface membrane immunoglobulin or by such goat antibodies covalently linked to Sepharose was studied in relation to the proliferative response to these agents. Although the induction of DNA synthesis was greater in the presence of Sepharose-linked antibody than in the presence of free antibody, modulation of surface membrane immunoglobulin was induced with free but not with Sepharose-linked antibody. Thus, in the presence of free antibody the surface membrane immunoglobulin content of cells was rapidly decreased and remained at a low level throughout the culture period, whereas the surface immunoglobulin content of cells incubated with Sepharose antibody was essentially unaltered. The surface immunoglobulin lost from cells incubated with free goat antibodies reappeared slowly upon further incubation in culture medium devoid of antibody, and such reappearance of rabbit surface membrane immunoglobulin was inhibited by puromycin. Upon culture with Sepharose-linked antibody the surface membrane immunoglobulin content of B cells was unaffected by puromycin. This result was interpreted as indicating that surface membrane immunoglobulin loss followed by reappearance does not occur. Lastly, the linkage of surface membrane immunoglobulin to cytoskeletal elements induced by free antibody was not induced by Sepharose-linked antibody as judged from differences in detergent solubilization characteristics. Possible mechanisms to account for these differences in surface membrane immunoglobulin modulation as they relate to the proliferative response are considered.

Animals↗
PubMed1984

Age affects the metabolic rate of insect brain.

Brains of adult insects can be isolated and studied in vitro. In female blowflies the oxygen uptake of the brain is age dependent. A steady increase is followed by a precipitous decrease around the middle of the little span. These changes are accompanied by alterations of mitochondrial structure and deposits of lipofuscin-like material.

Aging↗
PubMed1983

Anti-immunoglobulin-induced proliferation of B cells. Parallelism in the inhibition by chloroquine, monensin and immunoglobulin.

Proliferation of rabbit lymphocytes was induced with goat anti-rabbit immunoglobulin. Chloroquine and monensin, known to inhibit internalization-related events, yielded inhibition of proliferation that paralleled the inhibition by a specific competitive ligand, rabbit immunoglobulin (IgG), whereas inhibition by puromycin did not. Moreover, virtually all of the cells that can be activated in freshly isolated populations adhered to anti-immunoglobulin-coated Petri plates, whereas all of the activatable population was recovered in the non-adherent fraction after a brief incubation of the cells with anti-immunoglobulin to induce internalization of surface membrane immunoglobulin. Using immunofluorescence it was further observed that monensin and chloroquine inhibit the reappearance of surface immunoglobulins on the cell surface to some extent subsequent to their removal induced by anti-immunoglobulin.

Animals↗
PubMed1983

Differential effect of vanadate on DNA synthesis induced by mitogens in T and B lymphocytes.

The effect of sodium orthovanadate on enhancement of DNA synthesis by T and B cell mitogenic agents was studied using murine thymocytes and splenocytes. Addition of vanadate to thymocyte cultures inhibited the mitogenic response induced by concanavalin A in a dose dependent manner (50% inhibition at 10 microM). On the other hand, DNA synthesis induced in thymocytes by pokeweed lectin and periodate treatment essentially was not inhibited at the lower vanadate concentrations that were markedly effective for concanavalin A induced synthesis. In addition, no significant inhibition of mitogenesis of splenic B cells in response to lipopolysaccharide and dextran was detectable at lower vanadate concentrations. In the absence of added mitogens, vanadate was found to be mitogenic for a subpopulation of thymus cells but not for splenocytes or T cell enriched splenocyte populations. These results suggest that vanadate affects the mitogenic responses in lymphocytes and that the interaction of vanadate with T and B cells is different.

Animals↗
PubMed1983

Novel differences in the characteristics of spleen and peripheral blood lymphocytes activated by anti-immunoglobulin.

A comparison of splenocytes and peripheral blood lymphocytes with regard to activation by anti-immunoglobulin revealed distinctions in the behavior of the populations. Thus, a three- to fourfold greater concentration of anti-immunoglobulin was required to achieve one-half maximal activation of splenocytes than that required for peripheral blood lymphocytes. This difference cannot be accounted for on the basis of binding data. That is, although the binding of 125I-labeled anti-immunoglobulin was found to be slightly greater for peripheral blood lymphocytes than for spleen cells, the concentration required for one-half maximal binding was essentially the same for the two populations. Other differences between the populations were also observed. For example, splenocytes but not peripheral blood lymphocytes were substantially inhibited in terms of activation by anti-immunoglobulin subsequent to the absorption and elution of cells from anti-immunoglobulin-coated petri plates at 4 degrees C, despite the fact that the recovery of cells in general and B cells in particular following absorption and elution from anti-immunoglobulin coated plates at 4 degrees C was essentially the same for both populations.

Animals↗
PubMed1982

Mechanism for signaling initiation and termination of B lymphocyte proliferation induced by anti-immunoglobulin.

Several lines of evidence were explored which taken together indicate that both the initiation and the termination signal for activation of rabbit lymphocytes to synthesize DNA in response to anti-rabbit immunoglobulin occurs at an immunoglobulin receptor on the surface membrane of B cells. Thus, the premature removal of anti-rabbit immunoglobulin by simply washing the cells at the 31st hour of a 48-h incubation period caused a 60% decrease in the induction of DNA synthesis. The addition of rabbit immunoglobulin to compete with B cell surface immunoglobulin for the combining sites on anti-rabbit immunoglobulin yielded a markedly diminished activation. Addition of rabbit immunoglobulin even during the latter part of a pulse label period with [3H]-thymidine was sufficient to result in reduced activation. Finally, insoluble anti-rabbit immunoglobulin at the same nominal concentration as soluble anti-rabbit immunoglobulin also was effective in inducing cells to DNA synthesis. However, it is noteworthy that under the incubation conditions used it was not possible to derive a soluble component from insoluble anti-rabbit immunoglobulin which stimulated DNA synthesis. These data have been interpreted to indicate a need for a continuous surface presence of anti-rabbit immunoglobulin to stimulate activation in a process that is not dependent upon internalization of anti-rabbit immunoglobulin.

Animals↗
PubMed1982

A novel mitogen released by lipid A-stimulated bone marrow cells.

Lipid A induced bone marrow cells derived from lipopolysaccharide responder strain C3H/HeN to release a component to the extracellular fluid that enhanced DNA synthesis of splenocytes derived from the lipopolysaccharide nonresponder strain C3H/HeJ. The mitogenic component was not selected when C3H/HeN splenocytes were used instead of bone marrow. The target cell in splenocyte populations responding to the mitogenic component released by lipid A-stimulated bone marrow cells is a B cell, as judged by the corresponding of individual cells undergoing DNA synthesis determined by autoradiograph and the presence of surface immunoglobulin detected by immunofluorescence. The mitogenic factor is heat-labile, sensitive to trypsin, and intensive to RNase.

Animals↗
PubMed1981

Mitogenic response of T-cell subclasses to agarose-linked and to free ribonucleotides.

Thymocytes incubated with either ATP or GTP exhibit a brief period of enhanced DNA synthesis in contrast to the prolonged period of enhanced synthesis observed when thymocytes were incubated with concanavalin A. The cells responding to nucleotides represent a sub-population of theta antigen-bearing T cells comprising approximately 2% of the total thymocyte population as judged by a combined immunofluorescent/autoradiographic analysis. Thymocytes responsive to ATP and GTP are sensitive to cortisone suggesting that they are relatively immature T cells. ATP-responsive cells also preferentially aggregate with immature T cells when incubated with peanut agglutinin. GTP-responsive cells, on the other hand, do not. Nucleotides rendered insoluble by linkage to agarose via the ribose moiety are more active mitogenically at lower concentrations than either soluble nucleotides or even nucleotides linked to agarose via the nucleic acid base. The results are consistent with the view that the mitogenic response of thymocytes to nucleotides may be limited to as little as a single round of DNA synthesis and that such mitogenesis is stimulated at a site located on the plasma membrane.

Adenosine Triphosphate↗
PubMed1980

Lipid A induces cells, uniquely present in bone marrow, to secrete proteins other than immunoglobulins.

The lipid-A moiety of lipopolysaccharide induced freshly isolated bone marrow cells incubated with radioactive leucine to exhibit enhanced release of proteins other than immuoglobulins. Such stimulation by lipopolysaccharide was essentially not observed with cell suspensions from spleen, thymus, appendix, peritoneal exudate, whole blood, lymph node, liver, testis, buffy coat of blood and reticulocyte-enriched blood. The extracellular appearance of proteins was shown to be due to secretion by excluding other alternatives. Thus, the rate of cell death and/or leakage of cellular contents, as well as the rate of shedding of surface membrane protein, was unaffected measurably by lipopolysaccharide. Secretion of non-immunoglobulin proteins was selective as judged by the finding that the rate of immunoglobulin released by bone marrow cells during the usual four-hour pulse-label period was not stimulated by lipopolysaccharide. Enhancement of mitogenesis and enhancement of secretion of non-immunoglobulin protein by lipoplysaccharide appeared to occur at independent sites or even in different cells because of splenocytes which readily exhibited mitogenic response to lipopolysaccharide essentially did not exhibit stimulatin of secretion of non-immunoglobulin protein.

Animals↗
PubMed1980

New phenotypic marker for lipopolysaccharide responsiveness.

Lipopolysaccharide-enhanced secretion of non-immunoglobulin proteins by bone marrow cells derived from responder, nonresponder, and low-responder mouse strains did not precisely correlate with the lipopolysaccharide responsiveness assessment based on the mitogenic reactivity of splenocytes. These findings suggest that enhancement of secretion of non-immunoglobulin protein may be useful for further characterization of lipopolysaccharide responsiveness.

Animals↗
PubMed1980

Teratogenic effect of 2'-thiourea in the rat.

The compound 2'-thiourea was studied for teratogenic effect in fetal rats. A 0.2% aqueous solution of 2'-thiourea (Merck) was administered ad libitum to pregnant rats from the first to the 14th day of pregnancy. The pregnancy was counted from the day when sperm was found in the vaginal smear. In the treated rat fetuses hypoplasia of the brain and spinal cord, internal hydrocephalus, hypoplasia of the spinal ganglia, kypholordosis, micromelia, micrognathia, cleft palate, retarded tooth development, exophthalmus, coloboma, and cataract were observed. In addition, generalized haemorrhages were found all over the body. The changes were similar to those produced by ethylene thiourea treatment in rat fetuses.

Animals↗