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Biomedical subjects

M Kern

Publications and source records attributed to M Kern.

At least 181 records · Page 10Linked to original sources
PubMed1980

The lipid A moiety of lipopolysaccharide is specifically bound to B cell subpopulations of responder and nonresponder animals.

Employing autoradiography to detect [125I]-lipid A binding splenocytes and immunofluorescence to identify splenic B cells, it was observed that only a subpopulation of B cells bound lipid A. In contrast, non-B cells, including T cells and macrophage cells, exhibited either relatively little or no lipid A binding. LPS-responder and LPS-nonresponder substrains of mice exhibited essentially the same distribution of bound [125I]-lipid A among B cell subpopulations. Approximately 25% of the B splenocytes obtained from the LPS-responsive C3H/HeN substrain or from the LPS-nonresponsive C3H/HeJ, C57BL/10ScCR and C57BL/10ScN substrains bound [125I]-lipid A. On the other hand, 60% of the B splenocytes from both high- and low-responder mice derived from the CBA strain exhibited [125I]-lipid A binding. Taken in conjunction with the findings of other workers, these results are consistent with the possibility that the genetic defect in nonresponder mice is related to a lipid A triggering event rather than to lipid A binding.

Animals↗
PubMed1978

Differentiation of lymphoid cells: evidence for a B-cell specific serum suppressor.

The induction of immunoglobulin production by rabbit spleen cells is markedly inhibited by the presence of normal rabbit serum during cell culture. A similar inhibition is observed when spleen cell populations in which T cells have been inactivated are temporarily incubated with normal rabbit serum before being reconstituted with T cells by adding thymocytes. In contrast, no inhibition was observed upon temporary incubation of thymocytes with normal serum prior to addition of T cell-inactivated spleen cell populations. Removal of adherent cells did not affect the induction of immunoglobulin production or its inhibition by normal serum. Lipopolysaccharide-enhanced immunoglobin production was also inhibited by normal serum, thereby providing additional confidence that bone-marrow derived (B) cells are the target of the normal serum inhibitor.

Animals↗
PubMed1977

A prepaid medical plan. Cost, use, and effects in a retirement home.

A model experience of a prepaid medical plan for a group of people is analyzed. No-barrier cost and physician access lead to altered use characteristics. Among these are increased physician, nurse, and nursing home use, and decreased hospital use. The overall cost is increased. Any comprehensive health-care plan that would propose comprehensive first-dollar coverage would likely encounter similar use characteristics.

Aged↗
PubMed1977

Differentiation of lymphoid cells: the preferential binding of the lipid A moiety of lipopolysaccharide to B lymphocyte populations.

Lipid A, prepared from lipopolysaccharide, was labeled with 125 I. Such iodinated lipid A possesses the full mitogenic activity of untreated lipid A. Comparison of the 125 I-lipid A-binding activity of splenocytes and thymocytes from the same rabbit revealed that the extent of labeling of splenocytes was 10 to 20 times greater than that observed with an equivalent number of thymocytes. A similar preferential binding was detected in comparing cells in mouse and rat. Spleen populations depleted of adherent cells were essentially unaltered with regard to binding when compared to the original population. In addition, spleen cell populations enriched for thymus-derived cells (T cells) exhibited a marked loss of specific binding activity. On the other hand, spleen cell populations enriched for bone marrow-derived cells (B cells) exhibited the expected binding. The difference in binding behavior of B and T cell-enriched populations was confirmed by using three independent techniques to separate B and T cells. These findings are consistent with the mitogenic specificity of lipid A toward B cells rather than T cells and suggest that the observed cellular specificity resides in an early event in mitogenesis, i.e., binding of the mitogen.

Animals↗
PubMed1977

[Medium chain triglycerides in the feeding of praemature infants. Fat balance studies (author's transl)].

18 72-H Fat balance studies were performed in 9 premature infants with birthweights between 1650 and 2400 gm. At the age of two and three weeks, they received alternatively, one of two formulas identical in composition except for the type of fat: 30% of the vegetable fat in the first formula had been substituted by medium chain triglycerides (MCT) in the second formula. On the MCT-containing formula, the fat absorption significantly improved in the same infants as compared to their fat absorption capacity on the vegetable fat formula. The absorption of individual fatty acids, calculated by gaschromatographic analysis of pooled stool samples, also improved for most of the fatty acids with the MCT-formula. There were no adverse changes in blood glucose concentrations or in acidbase status of the infants when being fed the MCT-containing formula.

Acid-Base Equilibrium↗
PubMed1976

Differentiation of lymphoid cells. A selective anti-mitogenic component of normal serum which inhibits the induction of immunoglobulin production.

Rabbit lymph node cell populations cultured in vitro in the presence of fetal calf serum are induced to produce immunoglobulin M-secreting cells. The induction of such immunoglobulin production, measured by the capacity of the cell population to secrete immunoglobulins, was inhibited when cells were cultured with sera from a variety of species despite the presence of fetal calf serum. The addition of such inhibitory serum 36 hours after initiation of the cell culture or thereafter was without effect on the extent of induction of immunoglobulin production. On the other hand, the presence of inhibitory serum in culture during only the first 24 hours yielded the same inhibition as when serum was present throughout the 72-hour culture period. Inhibitory sera also suppressed the incorporation of thymidine into DNA. The induction of immunoglobulin production and the incorporation of thymidine into DNA were essentially equally inhibited by the same range of serum concentrations. Unlike conventional inhibitors of DNA synthesis, the inhibitory sera exhibited selective specificity with regard to the kind of cells that could be affected. Thus, such sera inhibited the DNA synthesis of lymph node cells cultured in the presence of fetal calf serum but did not inhibit concanavalin A-stimulated DNA synthesis of such cultured cells and, similarly, serum did not inhibit DNA synthesis of thymus cells cultured in the presence of fetal calf serum. The sera of all species examined were inhibitory except for fetal sera. As judged from a quantitative assay, bovine and porcine serum contained the highest titer of inhibitor, whereas sera from human, rat, mouse, and rabbit were clustered in a group exhibiting less inhibitor. Ascites fluid and lymph node extracellular fluids contained less inhibitor than found in the serum of the same animal and lysates of washed lymph node cells were devoid of inhibitor. Although fetal bovine serum and newborn bovine serum did not contain the inhibitor, it was detectable within 24 hours of parturition. The inhibitor is of relatively large apparent molecular weight (about 300,000) and has been purified about 70-fold.

Aging↗
PubMed1976

Differentiation of lymphoid cells: B cell as a direct target and T cell as a regulator in lipopolysaccharide-enhanced induction of immunoglobulin production.

The cells involved in the stimulatory effect of bacterial lipopolysaccharide (LPS) on the induction of immunoglobulin (Ig) production by rabbit spleen cells cultured in the absence of antigen has been analyzed. Addition of LPS caused a several-fold enhancement of both DNA synthesis and Ig production. These enhanced activities were not significantly affected by depletion of adherent cells in the spleen cell population. Although inactivation of splenic T cells by anti-thymocyte serum (ATS) treatment did not affect the enhancement of DNA synthesis due to LPS, such treatment did adversely affect the enhancement of Ig production by LPS. Furthermore, the enhancement of Ig production of ATS-treated spleen cells by LPS was found to be dependent on the number of thymocytes added. In addition, the prior incubation of ATS-treated spleen cells with LPS resulted in effective enhancement of Ig production when such ATS-treated spleen cells and thymocytes were combined after removal of LPS. An identical experiment, except that thymocytes instead of ATS-treated spleen cells received the prior incubation with LPS, did not result in enhancement of Ig production. Finally, the enhanced Ig production due to LPS was inhibited by hydroxyurea, a known inhibitor of cellular DNA synthesis. The relationship between the mitogenic activity of LPS on B cells, the regulatory function of T cells, and the enhancement of Ig production by LPS is discussed in relation to the contrasting reports concerning the cellular target of LPS.

Animals↗
PubMed1976

Differentiation of lymphoid cells: the non-mitogenic induction of immunoglobulin production by thymus cell extract and thymus cell culture filtrate.

The cell-free medium in which thymocytes have been cultured (filtrate) as well as sonic lysates of thymocytes (extract) enhance immunoglobulin production when added to spleen cells during tissue culture. In spite of the requirement for foetal calf serum in the culture medium, production of the enhancing factor in thymocyte culture filtrates occurred even in the presence of a variety of metabolic inhibitors including NaN3, puromycin and hydroxyurea. Although DNA synthesis is required as a prelude to the induction of immunoglobulin production, two lines of evidence indicate that the enhancement produced in response to filtrate and extract occurs via a non-mitogenic process. First, neither cell-free agent was mitogenic toward spleen cells. Secondly, the enhancement of immunoglobulin production due to filtrate or extract was observed even in the presence of inhibitors of DNA synthesis. Multiple functions for thymocytes in the induction of immunoglobulin production are indicated by the findings that thymocytes restore immunoglobulin production of anti-thymocyte serum-treated spleen cells, whereas filtrate and extract, alone or in combination, do not have this capability. Furthermore, filtrate and extract failed to enhance the induction of DNP-group-specific antibody production by cells incubated with DNP-protein, but filtrate and extract could partially restore anti-DNP antibody production of such anti-thymocyte serum-treated cells. The role of thymocytes, filtrate and extract in the antigen-independent and the antigen-dependent induction of immunoglobulin production is discussed.

Animals↗
PubMed1975

The absolute requirement for T-cells in the induction of IgM-secreting cells, in vitro.

Anti-rabbit thymocyte antibody can totally inhibit the induction of IgM production that ordinarily is observed whem lymphoid cells are incubated, in virto, in the absence of added antigen. Univalent as well as bivalent antithymocyte antibody preparations were inhibitory when added to cells before the induction of immunoglobulin production had occurred but not afterwards. Spleen cells that had been treated with antithymocyte antibody and then cultured with thymocytes for 72 hours exhibited an enhanced inducttion of immunoglobulin production. Untreated spleen cells also showed this property, although both untreated lymph node cells and lymph node cells treated with antithymocyte antiboyd did not respond to thymocytes. The enhancement of the induction of immunoglobulin production by lipopolysaccharide was found to be T-cell dependent as judged from studies using antithymocyte antibody.

Absorption↗