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Biomedical subjects

H Wagner

Publications and source records attributed to H Wagner.

At least 523 records · Page 29Linked to original sources
PubMed1986

Vascular resistance, metabolism and EEG within cerebral grey and white matter during hypoxia in neonatal piglets.

To study unsolved problems of the causal chain of neonatal hypoxic brain damage in 31 hypoxic newborn non-anesthetized piglets cerebro-vascular, metabolic and EEG reactions were investigated (FiO2: 0.06-0.10, 1 h). Only in artificially ventilated newborn piglets this acute hypoxic hypoxia provoked a vital decompensation by critical depression of mean arterial blood pressure (less than or equal to 4.67 kPa [35 mmHg]) and/or a critical increase of vascular resistance (Rc) in the cerebral white matter (greater than 50%). Spontaneously breathing piglets survived always showing hyperventilation, higher pHa and an increase of cerebral O2-consumption in cerebral grey matter, partly also in white matter. This critical increase of Rc was related to a critical decrease of O2-consumption in the white matter and an insufficient decrease of Rc of the grey matter. The observed strong metabolic and hemodynamic differences between these two brain compartments can explain the evaluated special morphological vulnerability of cerebral white matter in ventilated animals.

Animals↗
PubMed1985

Characterization of beta-adrenoceptor subtypes in rat kidney with new highly selective beta 1 blockers and their role in renin release.

Highly selective beta-adrenoceptor blocking agents with a beta 1: beta 2-selectivity ratio of 0.015 to 3400 were used to characterize the beta-adrenoceptors present in rat kidney and to identify those mediating renin release. The results obtained with ICYP binding to kidney membranes revealed the presence of both beta 1- and beta 2-adrenoceptors in a ratio of 1:1. The pKD beta 1- and pKD beta 2-values of selective beta-antagonists obtained in rat kidney membranes correlated well with those found in guinea pig left ventricle (beta 1) and lung (beta 2), indicating that kidney receptor subtypes are pharmacologically identical with those in the ventricle and lung, respectively. In the isolated perfused rat kidney, the apparent pA2 values of beta 1-selective blockers for inhibition of isoprenaline-stimulated renin release correlated well with pKD beta 1, but not with pKD beta 2 values. These results clearly show that the beta 1-adrenoceptor subtype mediates renin release in the rat kidney.

Adrenergic beta-Antagonists↗
PubMed1985

Allorestricted cytotoxic T cells. Large numbers of allo-H-2Kb-restricted antihapten and antiviral cytotoxic T cell populations clonally develop in vitro from murine splenic precursor T cells.

Cytotoxic T lymphocyte (CTL) responses of splenic T cells from C57BL/6 B6) mice and mutant H-2Kbm1 (bm1) mice to haptenic (trinitrophenyl [TNP] ) and herpes simplex virus (HSV) determinants in the context of an allogenic (wild-type or mutant) H-2Kb molecule were analyzed in a modified limiting dilution system. In the B6-anti-bm1TNP mixed leukocyte reaction (MLR), estimated frequencies for precursors of CTL clones that lysed bm1TNP targets ranged from 1/120 to 1/400; in the bm1-anti-B6TNP MLR, estimated frequencies of precursors of CTL clones that lysed B6TNP targets ranged from 1/500 to 1/1,300. Estimated frequencies for precursors of CTL clones that lysed the respective unmodified and TNP-modified allogeneic targets were two- to three-fold lower. Lytic specificity patterns determined by split-well analysis showed that at least 20-30% of the generated CTL populations (selected for a high probability of clonality) in both MLR displayed allorestricted lysis of TNP-modified concanavalin A blast targets. In the B6-anti-bm1HSV MLR, estimated frequencies for precursors of CTL clones that lysed bm1HSV targets ranged from 1/70 to 1/300; in the bm1-anti-B6HSV MLR, estimated frequencies for precursors of CTL clones that lysed B6HSV targets ranged from 1/300 to 1/1,200. Again, estimated frequencies for precursors of CTL clones that lysed the respective noninfected and virus-infected allogeneic targets were two- to fourfold lower. Of the CTL populations selected for a high probability of clonality at least 30-60% displayed allorestricted lysis of virus-infected lipopolysaccharide blast targets in both MLR. It is concluded that a large fraction of clonally developing CTL populations stimulated with TNP-modified or HSV-infected allo-H-2Kb-bearing cells displayed an allorestricted pattern of recognition. It was further evident that the estimated frequencies of splenic precursors that generated allorestricted CTL clones was two- to threefold higher than the estimated frequencies of precursors that gave rise to the respective alloreactive CTL populations.

Animals↗
PubMed1985

A rapid colorimetric assay for the determination of IL-2-producing helper T cell frequencies.

Interleukin 2 (IL-2) activity is tested in conditioned media by assessing its ability to support proliferation of selected IL-2 dependent T cell lines, conventionally measured by [3H]thymidine incorporation. Here, we compare this [3H]thymidine uptake test for measuring IL-2 activity with a rapid and sensitive colorimetric method which is based on the ability of viable cells to cleave 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). The sensitivity of the colorimetric method was dependent on the indicator cell line used, being greatest with the cytotoxic T cell line 16 (CTLL-16). The colorimetric method is at least as sensitive as [3H]thymidine uptake tests, does not rely on radioactivity, and is ideally suited to screen large numbers of individual samples for IL-2 activity. The latter point was demonstrated by calculating IL-2-producing helper T cell frequencies in heterogeneous murine lymphocyte populations: in this assay, splenic T cells were clonally expanded under limiting dilution conditions and supernatants conditioned by these in vitro growing T cell clones were tested for IL-2 activity with the colorimetric method. This allowed us to obtain reliable estimates of the frequency of progenitor cells of IL-2-producing T cell clones in various populations.

Animals↗
PubMed1985

Analysis of immunological tolerance to major histocompatibility complex antigens. I. High frequencies of tolerogen-specific cytotoxic T lymphocyte precursors in mice neonatally tolerized to class I major histocompatibility complex antigens.

Injection of (CBA X A)F1 cells into neonatal CBA mice rendered them tolerant to skin grafts of (CBA X A)F1 origin. Limiting dilution analysis revealed a very low frequency of tolerogen-inducible cytotoxic T lymphocyte precursors (CTL-P) in spleens of tolerant mice. Two in vitro procedures allowed, however, the induction of tolerogen-specific CTL-P of high frequencies in tolerant mice: (a) the "by-pass" activation of spleen cells from tolerant mice by concanavalin A under short-term bulk culture conditions followed by culture of limiting numbers of activated responder cells, and (b) absorption of spleen cells from tolerant mice on monolayers of tolerogen-activated T cells from normal syngeneic mice. Furthermore, spleen cells from tolerant mice, recently challenged with a tolerogen-bearing skin graft, specifically suppressed the activation of tolerogen-reactive splenic CTL-P from normal CBA mice under limiting dilution conditions. These data confirm the presence of tolerogen-specific CTL-P of high frequency in tolerant mice and suggest their functional inactivation through a suppressive mechanism.

Animals↗
PubMed1985

Alloreactive cytotoxic T cells. I. Alloreactive and allorestricted cytotoxic T cells.

Nylon wool-nonadherent spleen cells from three inbred mouse strains of H-2k (CBA), H-2d (BALB/c) and H-2b (C57BL/6) haplotype were co-cultured with 2,4,6-trinitrophenyl (TNP)-modified or nonmodified allogeneic stimulator cells in a limiting dilution system. Using a recently described restimulation protocol, a surprisingly large number of splenic cytotoxic lymphocyte precursors (CLP) was clonally expanded in this primary in vitro response to allo-H-2 plus TNP determinants; measured CLP frequencies ranged from 1/30 to 1/300. The lytic specificity patterns of individual microcultures (selected for a high probability of clonality) were defined by split well analysis, and were furthermore followed up in time by sequentially reassaying microcultures at different time points of in vitro incubation. This analysis revealed the following: a large fraction of cytotoxic T lymphocyte clones lysed TNP-modified but not nonmodified allogeneic concanavalin A blast targets, i.e., were allorestricted; this was found in all 6 allogeneic strain combinations set up with b, k and d haplotype mice; allorestricted lytic patterns predominated in microcultures with low numbers of responder cells per well, and at late time points of in vitro culture; allorestricted lytic cultures were specific for the stimulating allogeneic H-2 plus TNP determinant(s); and allorestricted lytic patterns were also found in microcultures stimulated by nonmodified allogeneic cells. To our knowledge, these are the highest CLP frequencies yet reported in limiting dilution systems that used a specific (re)stimulation protocol and measured the lytic responses obtained in a specificity-controlled readout.

Animals↗
PubMed1985

Signal requirements for the in vitro differentiation of cytotoxic T lymphocytes (CTL): distinct soluble mediators promote preactivation of CTL-precursors, clonal growth and differentiation into cytotoxic effector cells.

We describe here that the requirement of accessory cells for the polyclonal activation of high-density (resting) murine T lymphocytes can be bypassed by soluble mediators present in culture supernatants of concanavalin A (Con A)-activated murine spleen cells. Induction of responsiveness is confined to Lyt-2+ T cells; GK 1.5+ T helper cells require signals provided by accessory cells. Using this system the lymphokine signal requirements for the polyclonal activation of Lyt-2+ cytotoxic T lymphocyte (CTL) precursors could be defined. We show that Con A fails to trigger in Lyt-2+ responder T cells the expression of interleukin 2 (IL 2) receptors and assume that this explains why recombinant (rec) DNA-derived IL 2 fails to induce proliferative responses. Complementation of rec IL 2 with an IL 2 receptor-inducing factor (RIF) induces proliferative responses. RIF alone triggers IL 2 receptor expression in 10-12% of Lyt-2+ T cells exposed to Con A. This lymphokine appears to be distinct from colony-stimulating factor 1, IFN-gamma and IL 1. Resting Lyt-2+ T cells cultured in limiting numbers in the presence of Con A, RIF plus rec IL 2 do proliferate, yet exhibit no cytolytic activity. Differentiation into CTL can be brought about by addition of cytotoxic T cell differentiation factor (CTDF). We conclude that the polyclonal activation pathway of CTL from resting CTL precursors can be subdivided into three stages: preactivation, clonal growth and CTL differentiation. Each of these stages appears to be controlled by a distinct lymphokine, RIF, IL 2 and CTDF, respectively.

Animals↗
PubMed1985

Activation of human T lymphocytes. III. Triggering of bystander cytotoxicity in cytotoxic T cell clones by antibodies against the T3 antigen or by a calcium ionophore.

The role of T cell differentiation antigens in antigen-specific and nonspecific cytotoxicity by human cytotoxic T lymphocyte (CTL) clones was investigated. In contrast to other reports, several monoclonal antibodies (mAb) against the T3 antigen only marginally blocked antigen-specific cytotoxicity at high concentrations but induced cytotoxicity against third party cells at concentrations from 10 to 0.001 micrograms/ml. Susceptibility to anti-T3-induced lysis was variable but was found with all target cells. Incubation of CTL with anti-T3 mAb even led to self-destruction of the CTL. The effect was independent of the presence of Fc receptors on the target cell and could be obtained with F(ab')2 fragments of the antibody as well. Only activated but not resting T cells could be induced to lyse by anti-T3. Furthermore, this type of bystander killing of target cells could also be induced by the Ca2+ ionophore A23187. Antibodies against the T8 differentiation antigen inhibited antigen-specific, oxidation-induced and anti-T3-induced cytotoxicity by T8+ CTL clones, whereas triggering by the ionophore A23187 was not inhibited. These results show that undirected killing can be triggered in CTL by activating a transducing molecule directly without involving the antigen receptor. Since this triggering of the lethal hit can still be inhibited by mAb against the T8 molecule, the T8 molecule probably has a regulatory role in a late phase of CTL triggering.

Antibodies, Monoclonal↗
PubMed1985

Preliminary electrophysiological data after the obliteration of cochlear blood vessels by the action of a magnetic field on circulating iron particles.

In order to develop an experimental model for studying local disturbances of the inner ear microcirculation we conducted a series of experiments using small iron particles. Suspensions of iron were infused into the carotid artery of a tracheotomized guinea pig, after which a magnetic force was applied to the basal part of the cochlea. The cochlear microphonics were measured every 10 min over a frequency range from 200 Hz to 10 000 Hz. The amplitude of the cochlear microphonic decreased with this decrease dependent on the time after the application of the magnet. We then found that this amplitude was up to 30 dB less after 110 min. We were able to demonstrate histologically that the thrombosis induced by the iron particles blocks the circulation of the inner ear and results in a loss of its function.

Acoustic Stimulation↗
PubMed1985

Recombinant interleukin 2 rapidly augments human natural killer cell activity.

Recombinant human interleukin 2 (r-IL-2) rapidly stimulated human natural killer cell activity in vitro. Augmentation of NK activity occurred within 1 hr of preincubation with r-IL-2. Responsive killer cells were typical NK cells as shown by cell fractionation procedures. These included Percoll density gradient separation and depletion of OKT3+ T cells by an indirect rosetting method. Analysis with a panel of polyclonal and monoclonal antibodies against alpha and gamma interferon revealed that this early enhancement of NK activity by r-IL-2 was independent of the production of both types of interferon.

Antibodies↗
PubMed1985

The action of anticlastogens in human lymphocyte cultures and their modification by rat-liver S9 mix. II. Studies with vitamins C and E.

The action of vitamins C (VC) and E (VE) on the clastogenic activity of trenimon (TR), cyclophosphamide (CP) and bleomycin (BM) was tested on cultures of human peripheral blood lymphocytes with and without addition of rat-liver S9 mix. In addition, the influence of both anticlastogens on the SCE-inducing activity of TR and CP was examined under the same conditions. A distinct dose-dependent anticlastogenic effect of VC was detected in the action of long-term treatment (24 h) with TR, if the vitamin was added to the cultures simultaneously with or before the clastogen. In the short-term tests (2 or 3 h clastogen treatment ending 23 h or 21 h before harvesting) simultaneous addition of both vitamins did reduce the chromosome-damaging action of TR whether S9 mix was present or absent. While VC also decreased the frequency of chromosome damage induced by S9-mix-activated CP, VE was inactive under the same conditions. Neither vitamin significantly affected the chromosome-breaking activity of BM if S9 mix was absent, but they increased the clastogenicity of BM metabolized by S9 mix. In contrast to their anticlastogenic efficacy neither of the vitamins displayed any significant anti-SCE effect, nor were they active in affecting the inhibition of cell proliferation caused by TR or CP.

Animals↗
PubMed1985

Human cytotoxic T lymphocytes. I. Limiting-dilution analysis of alloreactive cytotoxic T-lymphocyte precursor frequencies.

A limiting-dilution system was established to measure the frequency of alloreactive cytotoxic T-lymphocyte precursors (CTL-p) in human peripheral blood T cells. Culture medium supplemented with recombinant interleukin-2 enabled clonal expansion of all CTL-p stimulated by allogeneic peripheral blood or spleen cells. The range of CTL-p frequencies in fully HLA-mismatched responder-stimulator combinations was 1:240 to 1:1230. Split-well analysis of individual microwells showed that the cytotoxic T-cell clones generated under limiting-dilution conditions showed exquisite specificity for the stimulating alloantigens. Alloreactive CTL-p were enriched in the OKT4- T-cell subset. This limiting-dilution system was highly reproducible and can thus be applied to investigate human cytotoxic T-cell precursor frequencies in various clinically relevant situations.

Cells, Cultured↗
PubMed1985

Methylation pattern of fish lymphocystis disease virus DNA.

The content and distribution of 5-methylcytosine in DNA from fish lymphocystis disease virus was analyzed by high-pressure liquid chromatography, nearest-neighbor analysis, and with restriction endonucleases. We found that 22% of all C residues were methylated, including methylation of the following dinucleotide sequences: CpG to 75%, CpC to ca. 1%, and CpA to 2 to 5%. Comparison of relative digestion of viral DNA with MspI and HpaII indicated that CCGG sequences were almost completely methylated at the inner C. The degree of methylation of GCGC was much lower. The methylation pattern of fish lymphocystis disease virus DNA differed from that of the host cell DNA.

Animals↗