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Biomedical subjects

R Eckert

Publications and source records attributed to R Eckert.

At least 55 records · Page 3Linked to original sources
PubMed1992

High-resolution measurements of gap-junctional conductance during perfusion with anti-connexin antibodies in pairs of cultured mammalian cells.

Antibodies against the main proteins in hepatic gap junctions--connexin-26 and connexin-32--have been used in conjunction with high-resolution patch-clamp techniques to investigate whether a relation exists between connexin type and conductance of single gap-junctional channels. Two different cell lines, BRL cells, derived from rat liver, and FL cells a human amniotic cell line exhibited the same single-channel conductances in double whole-cell recordings, but reacted differently upon dialysis with antibodies. Preliminary results indicate that both cell lines express mainly connexin-43. Thus, in spite of the inhibitory action of anti-cx26 and anti-cx32 antibodies observed, the data question the reliability of these antibodies for the functional characterization of gap-junction proteins in electrophysiological experiments.

Animals↗
PubMed1992

Immunogenicity of recombinant core particles of hepatitis B virus containing epitopes of human immunodeficiency virus 1 core antigen.

A Gag protein segment of human immunodeficiency virus 1 (HIV-1) has been fused to a C terminally truncated core antigen of hepatitis B virus (HBcAg) using an E. coli expression system. Fusion of 90 amino acids of HIV-1 Gag protein to HBcAg still allowed the formation of capsids presenting on their surface epitopes of HIV-1 core protein, whereas fusion of 317, 189, or 100 amino acids of Gag prevented self-assembly of chimeric particles. Mice immunized with recombinant particles emulsified with Freund's complete adjuvant (CFA) or aluminium hydroxide developed high anti-HBcAg titers. However, anti-HIVp24 antibodies were detected only in mice inoculated with immunogen emulsified with CFA.

AIDS Vaccines↗
PubMed1992

Cis-urocanic acid as a mediator of ultraviolet-light-induced immunosuppression.

Treatment of an organism with UVB light or PUVA (8-methoxypsoralen + UVA light) not only leads to alterations in the irradiated skin but also to systemic immunomodulation, due to the release of several chemical mediators of immunosuppression like prostaglandins, acute-phase proteins, IL-1 inhibitor, alpha-melanocyte-stimulating hormone, propiomelanocorticotropin or other cytokines. A recently described mediator is urocanic acid, which is transformed by UV light in the skin from the trans- to the cis-isomer and that exerts a systemic immunomodulatory effect. In our experiments, treatment with PUVA or with cis-urocanic acid prevents the rejection of rat heart allografts in 50% and 40% of cases, respectively. Control grafts are rejected in fewer than 10 days. PUVA treatment of donor leukocytes before transfusion into the prospective recipient inhibits only their sensitizing, not their graft-protecting, effect on subsequent skin grafts in mice. PUVA treatment also prevents acute lethal GVH disease in mice after irradiation with a sublethal dose of x-rays and transfusion of semiallogeneic spleen cells. Treatment of recipient mice with cis-urocanic acid has the same effect. The humoral immune response to sheep erythrocytes is not influenced by cis-urocanic acid. These results demonstrate that PUVA treatment or its chemical mediator, cis-urocanic acid, may be used in transplantation and hematology as naturally occurring immunosuppressive agents, especially for the control and manipulation of GVH leukemia reaction.

Animals↗
PubMed1991

Inhibitory modulation of fast and slow Ca(2+)-currents in neuroblastoma x glioma cells during differentiation.

Mouse neuroblastoma x rat glioma hybrid cells (N x G, 108CC15) were used to study the inhibitory effects of the synthetic opioid D-Ala2-D-Leu5-enkephalin (DADLE), somatostatin, adrenaline-alpha 2 and angiotensin II on voltage-dependent Ca(2+)-currents (ICa) using the patch-clamp technique in the whole-cell configuration mode. The inhibitory effects could be abolished by pretreatment of N x G cells with pertussis toxin or intracellular infusion of GDP beta S indicating an involvement of a pertussis toxin sensitive GTP-binding protein (G-protein), presumably Go. The effect of DADLE, the strongest inhibitor of ICa, was studied during dibutyryl cyclic AMP (dBcAMP) induced differentiation. Using omega-conotoxin GVIA (omega-CTX) and methoxyverapamil (D600) as specific Ca(2+)-channel blockers of the N- and L-type Ca(2+)-channels, it was found that in N x G cells DADLE predominantly induces inhibition of T- and N-type Ca(2+)-channels.

Animals↗
PubMed1991

Inhibition of Langerhans cell ATPase and contact sensitization by lanthanides--role of T-suppressor cells.

Lanthanides are rare earths, elements 55-71 in the periodic table, that are of interest in biologic systems as isomorphic competitors for calcium binding sites. Lanthanides were tested for their inhibitory influence on the Ca++/Mg(++)-dependent ATPase of epidermal langerhans cells in vitro, and on the immunologic function of Langerhans cells in vivo. The trivalent ions of lanthanides, lanthanum, and cerium completely inhibited the ATPase staining of Langerhans cells in vitro. When mice were sensitized with dinitrofluorobenzene on skin sites pretreated with topical lanthanum chloride, and challenged on untreated ear skin, a markedly reduced contact hypersensitivity response was observed. This hyporesponsiveness was found to be antigen specific, and could be passively transferred to naive syngeneic animals recipients by CD4-CD8+ spleen cells. These results suggest that inhibition of the epidermal Langerhans cell surface ATPase by application of topical lanthanum and the induction of antigen-specific immunologic tolerance may be related events.

Adenosine Triphosphatases↗
PubMed1991

Isolation, detection, and amplification of intact mRNA from dermatome strips, epidermal sheets, and sorted epidermal cells.

Three different strategies for isolating RNA from epidermal cells were compared. Starting with dermatome sections frozen or disaggregated epidermal cells purified by fluorescence activated cell sorting (FACS), RNA was isolated with a guanidinium thiocyanate technique. Specific mRNA were detected by Northern blot analysis (involucrin, keratin 5, actin), or by reverse transcription and amplification with the polymerase chain reaction (PCR), using primers specific for keratinocyte products (keratins 1 and 14) and Langerhans cells (CD1a). Messenger RNA's characteristic of Langerhans cells and of keratinocytes at different stages of differentiation were detected in dermatome and epidermal sheet preparations as well as in FACS-separated cells. The use of snap-frozen dermatome sections allows the isolation of RNA from epidermis that has undergone minimal trauma and is very close to its in vivo state, but that includes RNA from some dermal cells. Extraction of RNA from Dispase-separated sheets involves slightly more manipulation of the epidermis but provides a sample free from dermal contaminants. PCR analysis of sorted epidermal cells is both sensitive and specific, but involves still greater manipulation. This final technique, however, allows the investigation of mRNA produced by small groups of epidermal cells that are still much closer to their in vivo state than if they had been cultured. By combining these techniques it is possible to determine the baseline production of specific mRNA in the skin in vivo and to assign their production to specific groups of cells with a sensitivity and specificity greater than any approach previously described.

Base Sequence↗
PubMed1991

[Immunorestitutive action of hydrolysates and ultrafiltrates of bovine spleen].

Investigations with different spleen extracts of varied composition and purity have shown immunomodulatory effects. In the present study the in vivo effect of a bovine spleen hydrolysate (Prosplen) on a radiation-induced immunodeficiency model is demonstrated. Intraperitoneal application of 1 mg/g bw hydrolysate 3/times a week caused a highly significant acceleration of the restitution of the humoral and cell-mediated immunoreactivity towards sheep erythrocytes in sublethally (600 cGy) radiated mice: plaque-forming cells in the spleen, hemagglutination, hemolysistiter of the serum, delayed type of hypersensitivity = DTH reaction. The immunoreactivity of the treated groups reached normal levels within 6-8 weeks, whereas in the groups receiving placebo this was observed after 10 weeks at the earliest. Cytofluorometric investigations revealed an accelerated restitution of the B-lymphocyte fraction in the spleen. Mice that was not irradiated showed no effect after treatment with the hydrolysate. Similar results were obtained using an ultrafiltrate of the hydrolysate.

Adjuvants, Immunologic↗
PubMed1991

Inhibition of cellular immune reactions by zymosan.

Mice treated intraperitoneally with zymosan showed a strong inhibition of the DTHR (delayed-type hypersensitivity reaction) against sheep erythrocytes (SE), ovalbumin (OA), and alloantigen. Furthermore, the rejection time of skin transplants was nearly doubled while antibody formation against SE was significantly enhanced. When a DTHR against OA and an antibody formation against SE were induced at the same time in the same animals, than the suppressive and stimulating effects cancelled each other. These results are discussed with regard to the sensitivity of lymphocyte subpopulations, which may be different if exposed to phagocytosis-induced oxygen radicals.

Animals↗
PubMed1990

Calcium currents of neuroblastoma x glioma hybrid cells after cultivation with dibutyryl cyclic AMP and nickel.

The long-term modulation of calcium (Ca2+) currents (ICa) was studied in 108CC15 neuroblastoma x glioma hybrid (NxG) cells grown under various culture conditions. The following results were obtained: 1. Addition of 1 mM dibutyryl cyclic adenosine monophosphate (db-cAMP) or 0.1 microM forskolin to the culture medium increased a transient component of ICa two-fold within 3 days, from 21.0 +/- 1.6 pA/pF (n = 22) to a maximum of 40.0 +/- 2.6 pA/pF (n = 28). Under these conditions, cells also expressed a slowly inactivating ICa component (maximum after 3 days, 20.5 +/- 1.6 pA/pF, n = 28). 2. The fast inactivating ICa as well as the db-cAMP-induced slowly inactivating ICa were completely down-regulated during incubation of NxG cells with the inorganic Ca2+ channel blocker, nickel (Ni2+, 100 microM). The suppressing effect was reversed within 3 days of incubation in db-cAMP-containing medium lacking Ni2+. 3. Binding studies on membrane preparations of control and Ni2(+)-pretreated NxG cells revealed a marked difference in the maximal (+)3H-PN200-110 binding. The difference was seen in undifferentiated as well as in db-cAMP-incubated cells. 4. The protein synthesis blocker, cycloheximide, suppressed both the db-cAMP-induced increase and the reappearance of ICa following Ni2+ pretreatment. It is suggested that chronic application of db-cAMP or Ni2+ to NxG cells increases and decreases the number of Ca2+ channel proteins, respectively.

Animals↗
PubMed1990

Splenopentin (DAc-SP-5) accelerates the restoration of myelopoietic and immune systems after sublethal radiation in mice.

In 1981 a new splenic hormone was described by Audhya et al. (Biochemistry, 20, 6195-6200, 1981). At first designated as thymopoietin III, the complete amino acid sequence had been described as splenin in 1984. For the pentapeptide corresponding to amino acids 32-36 of splenin was shown to be active in immunological systems. The synthetic pentapeptide splenopentin (DAc-SP-5) and the sequence 32-36 of splenin are identical. In this study the recovery of immunocompetence in mice following sublethal irradiation is shown to be enhanced by DAc-SP-5. The treatment effects of DAc-SP-5 were verified by splenic plaque-forming response to a T-cell dependent antigen and in the hematopoietic colony-forming assay. These effects were associated with an accelerated recovery of leukocyte counts in peripheral blood and spleen without significant changes in the relation between leukocyte and lymphocyte subpopulations. Furthermore, in comparison to control animals DAc-SP-5 treated mice showed in the first weeks postexposure a significantly higher number of bone marrow derived cells as well as granulocyte-macrophage and macrophage colony-forming cells (GM-CFC and M-CFC). Therefore, DAc-SP-5 may be a useful substance for treating secondary forms of bone marrow depression.

Animals↗
PubMed1990

Splenopentin (DAc-SP5)--influence on engraftment and graft-vs-host reaction after non-H-2 bone marrow transplantation in mice.

The influence of DAc-SP5 on engraftment and graft-vs-host reaction (GVHR) was studied in different non-H-2 strain combinations. The engraftment was more or less enhanced in every case, whereas the situation in the GVHR was completely different. In one case splenopentin did not influence the course of the GVHR so much, in a second case the symptoms of the GVHR were completely abolished, and in a third case the GVHR was dramatically enhanced up to a great mortality. Therefore, before application of DAc-SP5 to the bone marrow transplantation in humans in order to improve the engraftment, parameters have to be found which allow an exact prediction about the influence of splenopentin on the GVHR in each single case.

Animals↗
PubMed1990

[Prolonging transplant survival time by PUVA treatment of the transplant recipient. Significance of cis-urocanic acid].

A PUVA treatment of the recipients of murine tail skin grafts led to a significant prolongation of transplant survival. A possible mechanism of the systemic immunomodulatory effects of ultraviolet light in the organism is the transformation of urocanic acid in the skin from its trans- to the cis-isomer, which acts as a mediator on the immune system. A treatment of graft recipients with cis-, but not trans-urocanic acid also prolonged graft survival. The rejection of secondary grafts and the humoral immune response of mice to sheep erythrocytes were not influenced by cis-urocanic acid. These results implicate that cis-urocanic acid may be get use in clinical organ transplantation and dermatology.

Animals↗
PubMed1990

[Change in the central relationship conflict by short-term therapy].

Luborskys method of the Core Conflictual Relationship Theme is introduced as a reliable tool for studying structural aspects of transference. The change of the components of the CCRT induced by a short term psychotherapy is described and discussed in terms of its clinical significance.

Adult↗
PubMed1989

Studies on the immunomodulatory effects of anthracycline antibiotics in mice: effects on immune responses and graft immunogenicity.

The immunomodulatory effects of adriamycin, a clinically used tumor antibiotic, were studied. A 5-day course of adriamycin therapy in mice led to a suppression of the primary but not of the secondary humoral response to sheep erythrocytes without significant alterations in peripheral blood leukocyte subsets or lymphocyte subpopulations in the spleen. The delayed type hypersensitivity (DTH) response to ovalbumin or alloantigens was not inhibited. Adriamycin-treated spleen cells were unable to stimulate an allogeneic mixed leukocyte reaction, which shows that antigen presentation is inhibited by this drug. Adriamycin-treated murine skin grafts show a prolonged survival after allotransplantation despite their unimpaired ability to induce DTH. The possible cellular mechanisms of these effects and clinical relevance of adriamycin are discussed.

Adjuvants, Immunologic↗
PubMed1989

Splenopentin (DAc SP-5)-accelerated reconstitution of antibody formation after syngeneic bone marrow transplantation.

Sublethally irradiated AB/Bln, mice (800 c Gy) and supplemented with syngeneic bone marrow cells were treated with or without a splenopentin derivative (DAc SP-5) and compared for their capacity to produce antibodies. In bone marrow cell plus DAc SP-5 treated animals antibody forming cells were found earlier and in a higher frequency than in mice treated with bone marrow cells only. These findings demonstrate that DAc SP-5 is able to induce bone marrow cell maturation.

Animals↗
PubMed1989

Splenopentin-induced reconstitution of the immune response after total body irradiation: optimization of treatment regime.

In former investigations our group obtained an immuno-reconstituting effect in mice treated by immunosuppression after a continuous treatment with splenopentin (SP5). The goal of the present study was to test whether a small number of injections right after immunosuppression possibly produces the same result in the sense of an initial effect. Although a short-term therapy induced an increase of antibody formation which was measurable after 4 weeks, the study clearly showed that only a continuous treatment by SP5 led to an optimum, i.e. complete reconstitution of antibody formation.

Adjuvants, Immunologic↗
PubMed1989

Prevention of graft-vs-host reaction induced immunodeficiency by treatment with splenopentin (DAc-SP5).

Early experiments had shown that splenopentin, the active part of the splenic hormone splenin, stimulates the differentiation of virgin B- and T-lymphocytes and significantly enhanced the reconstitution of immune reactions after immune suppression. The present study investigates the influence of splenopentin on the course of the graft-vs-host reaction (GVHR). The experimental model used were adult hybrid mice which received intravenously parental spleen cells. During the GVHR which has an chronical course in the strain combinations used a short stimulatory phase is followed by a long-lasting immunosuppression detected by antibody formation against sheep erythrocytes. Furthermore, the splenomegaly in the first weeks after spleen cell injection changed to a drastic decrease of the spleen weight up to strongly beyond normal values. Continuous treatment with splenopentin significantly prevented both symptoms of the GVHR: The suppression of the antibody formation was diminished widely, and no loss of spleen weight occurred. Furthermore, during the stimulatory phase anti-DNA-autoantibodies were produced in the untreated animals, while the splenopentin therapy prevented this reaction. During the further course of the experiment no increase of autoantibody production was detected later on.

Animals↗