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Biomedical subjects

C Reinhardt

Publications and source records attributed to C Reinhardt.

At least 19 recordsLinked to original sources
PubMed2004

Changes in function and morphology of normal human skin: evaluation using optical coherence tomography.

BACKGROUND: Optical coherence tomography (OCT) is a noninvasive morphological method for investigating human skin. It allows high-resolution in vivo imaging of inflammatory skin diseases and tumours. Because it is a newly developed method, systematic studies on standardization and on evaluation of factors influencing the representation of the skin have not yet been performed. OBJECTIVES: In this study, normal human skin was treated with various external stimuli which induce changes of function and morphology. Changes in stratum corneum thickness as well as changes induced by pigmentation, oedema and erythema were investigated using OCT. METHODS: Healthy skin of human volunteers was treated with tape stripping, ultraviolet A irradiation, water, histamine, nicotinic acid and various ointments. RESULTS: In the tape stripping experiment, the thickness of the horny layer was quantified and monitored. Pigmentation increased the light attenuation of the tissue, whereas hydration and erythema led to a slight decrease of scattering. Topical treatment of the skin gave a nonspecific increase of penetration depth of the light due to the lower reflectivity of the surface. CONCLUSIONS: There are various physiological conditions which influence optical properties of the skin. These parameters should be considered when performing standardized OCT studies.

Adult↗
PubMed2001

Minimal flow sevoflurane and isoflurane anaesthesia and impact on renal function.

BACKGROUND AND AIM: Compound A generation and accumulation in sevoflurane anaesthesia is dependent on fresh gas flow. We investigated the extent of generation of compound A. METHODS: After Institutional Review Board approval and informed consent, patients with normal renal function were randomized to receive either sevoflurane (n = 33) or isoflurane (n = 43) minimal flow anaesthesia (0.5 L min-1) for at least 2 h under standardized conditions. Compound A concentrations were quantified and blood and urine samples were taken to assess renal involvement. Both groups were comparable. RESULTS: No significant differences concerning blood chemistry and urine measurements were found. The maximum mean compound A concentration was observed 90 min after flow reduction being 40 +/- 9 p.p.m. at a corresponding mean sevoflurane concentration of 2.1 +/- 0.5 vol%. Mean inspiratory compound A exposure was 102 +/- 33 p.p.m h-1. CONCLUSION: Compound A concentrations using 0.5 L min-1 fresh gas flow and a heated absorber were higher than previously published values using an inflow of 1 L min-1. Compound A exposure was similar to other clinical studies which did not show changes in renal and hepatic function.

Adult↗
PubMed2000

Normalization of elevated CD4-/CD8- (double-negative) T cells after thymectomy parallels clinical remission in myasthenia gravis associated with thymic hyperplasia but not thymoma.

T-cell-dependent B-cell help is likely to be of major importance in the pathogenesis of myasthenia gravis, but mechanisms provoking a pathological anti-acetylcholine receptor (AChR) response are poorly understood. We report on the dysregulation of recently identified CD4-/CD8- (double-negative) T cells (DN T cells), which have been shown to participate in immunoregulation and antibody augmentation. Compared with healthy controls, significantly increased frequencies of DN T cells were found in the blood of myasthenia gravis patients with lymphofollicular hyperplasia. After thymectomy, however, normalization in the number of these cells was seen in parallel with clinical improvement and reduction in anti-AChR antibody titers. The effect of thymectomy was observed irrespective of adjuvant treatment and held true for up to 4 years of follow-up. In marked contrast, frequencies similar to control values were found in myasthenia gravis patients with thymoma, with thymectomy having no further reducing effect. These data indicate that CD4-/CD8- T cells not only participate in the pathogenesis of myasthenia gravis but also correlate with disease activity and histological findings.

Adult↗
PubMed1999

Elevated frequencies of natural killer T lymphocytes in myasthenia gravis.

T lymphocytes are considered to exert a regulatory function in the development of antiacetylcholine receptor antibodies, but no clear T-cell alterations in patients with myasthenia gravis (MG) have yet been found. The authors report a significant increase of recently identified natural killer T lymphocytes expressing T-cell receptor Valpha24. A possible role in disease initiation or maintenance is suggested by the observed strong synthesis of interferon-gamma as well as of interleukin 4.

Adult↗
PubMed1998

Skewed TCRV beta repertoire in human thymus persists after thymic emigration: influence of genomic imposition, thymic maturation and environmental challenge on human TCRV beta usage in vivo.

In order to investigate the mechanisms involved in originating a diverse TCR repertoire in human peripheral blood we analyzed TCRV beta surface expression in different T cell subsets of unrelated individuals. The relative frequencies of 11 distinct V beta chains were determined for immature double positive (DP) as well as for mature CD4 single positive (4SP) and CD8 single positive (8SP) thymocytes, respectively. By comparing these data with expression in peripheral blood T lymphocytes of the same donors we were able to show that usage of TCRV beta in peripheral T cells is significantly (p < 0.001) depending on the pattern in mature SP thymocytes whereas the frequency of TCRV beta families in immature DP thymocytes has no impact (p > 0.2). No association with distinct HLA-haplotypes was observed. Preferential usage of V beta-families in either CD4- or CD8-positive peripheral T cells also correlates with the status in mature thymic precursors (p < 0.001). Altogether, this first combined study of TCR frequencies within different stages of human T cell ontogeny indicates that TCRV beta repertoire is determined mainly through selectional processes within the thymus. Since neither genomically imposed expression nor modulating events in the periphery seem to have strong influence on the relative expression of TCRV beta chains these findings have to be considered in future studies of human diseases.

Adolescent↗
PubMed1997

Different activation energies in glucose uptake in Saccharomyces cerevisiae DFY1 suggest two transport systems.

The analysis of initial glucose uptake in Saccharomyces cerevisiae at 25 degrees, 20 degrees, 15 degrees and 10 degrees C by computer-assisted nonlinear regression analysis predicts two transport systems. The first demonstrates Michaelis-Menten kinetics and the second shows first order behaviour. The activation energies of these two systems were calculated by the Arrhenius equation at four different growth phases, namely early exponential (EE), middle exponential (ME2), late exponential (LE) and early stationary (ES) with 2% glucose in the batch medium. The activation energies calculated from the V(m) values in EE, ME, LE and ES growth phases were 15.8 +/- 1.7, 13.5 +/- 1.0, 15.1 +/- 0.8 and 13.5 +/- 0.7 kcal/mol. These values are in agreement with activation energies calculated for the first mechanism, facilitated diffusion, which is the mechanism deduced from countertransport experiments. The activation energies derived for the second transport system from the first order rate constants in cells grown to EE, ME2, LE and ES were 8.0 +/- 2.1, 8.1 +/- 1.3, 9.6 +/- 3.0 and 7.5 +/- 2.6 kcal/mol. These values are still significantly higher than for free diffusion of glucose in water and lower as predicted for passage of glucose through the lipid phase. Therefore, we assume in addition to carrier-mediated facilitated diffusion the entrance of glucose into the cell through a pore.

Biological Transport↗
PubMed1996

Effects of diadenosine polyphosphates on renal function and blood pressure in anesthetized Wistar rats.

In this study, the effects of diadenosine polyphosphates on kidney function were examined. Intravenous application of diadenosine hexaphosphate (AP6A) led to a significant threefold increase in both urine flow (from 2.45 +/- 0.2 to 13.8 +/- 0.74 microL/min per 100 g body wt (P < 0.05)) and Na+ excretion (from 0.41 +/- 0.12 to 1.52 +/- 0.28 mumol/min per 100 g body wt at a dose of 1.0 mg/kg body wt). In contrast, diadenosine triphosphate dose-dependently reduced urine flow (from 3.74 +/- 0.3 to 2.57 +/- 0.1 microL/min per 100 g body wt (P < 0.05)) and Na+ excretion (from 0.45 +/- 0.1 to 0.13 +/- 0.1 mumol/min per 100 g body wt at a dose of 1.0 mg/kg body wt). ATP and the P2y purinoceptor agonist gamma-S-ATP did not significantly modulate urine flow and Na+ excretion. alpha, beta-methylene-ATP, a P2x purinoceptor agonist, significantly increased urine flow from 1.74 +/- 0.5 to 4.07 +/- 1.51 microL/min per 100 g body wt, whereas Na+ excretion was unaffected. The effects were independent of alterations in GFR. Pretreatment with indomethacin (2.0 mg/kg body wt iv) completely abolished the effects of AP6A on urine flow and Na+ excretion. Similarly, pretreatment with the endothelin antagonist bosentan abolished the effects of AP6A on both urine flow and Na+ excretion, whereas suramin had no effects on the AP6A-induced increase in urine flow. In conclusion, diadenosine polyphosphates exert specific actions on urine flow and Na+ excretion that are different from the effects of ATP. AP6A may partially influence renal function by stimulating prostaglandin and endothelin release.

Anesthesia↗
PubMed1995

In vivo expansion of HLA-B35 alloreactive T cells sharing homologous T cell receptors: evidence for maintenance of an oligoclonally dominated allospecificity by persistent stimulation with an autologous MHC/peptide complex.

The nature of alloantigens seen by T lymphocytes, in particular the role of peptides in allorecognition, has been studied intensively whereas knowledge about the in vivo emergence, diversity, and the structural basis of specificity of alloreactive T cells is very limited. Here we describe human T cell clones that recognize HLA-B35 alloantigens in a peptide-dependent manner. TCR sequence analysis revealed that several of these allospecific clones utilize homologous TCR: they all express TCRAV2S3J36C1 and TCRBV4S1J2S7C2 chains with highly related CDR3 sequences. Thus peptide-specific alloreactivity is reflected in homologous CDR3 sequences in a manner similar to that described for T cells that recognize nominal peptide/self-MHC complexes. The in vivo frequency of this TCR specificity was studied in unstimulated PBL of the responding cell donor who was not sensitized against HLA-B35. The vast majority (approximately 75%) of the VA2S3J36 junctional regions obtained from two samples of PBL, isolated at a 9-yr interval, encode CDR3 identical or homologous to those of the functionally characterized HLA-B35 allospecific T cells. These data are most easily explained by a model of alloreactivity in which persistent or recurrent exposure to a foreign peptide/self-MHC complex led to the in vivo expansion and long-term maintenance of specific T cells that show fortuitous crossrecognition of an HLA-B35/peptide complex and dominate the alloresponse against HLA-B35.

Amino Acid Sequence↗
PubMed1994

MHC class I allorecognition: the likes and dislikes of CTL and NK cells.

An allogeneic culture was established using cells of two HLA disparate individuals. No pattern of specificity could be discerned when the 6 day culture that contained a mixture of CD4+, CD8+ and CD56+ lymphocytes was tested for cytotoxicity against a panel of target cells. Three approaches were utilized to dissect this alloresponse. A CD8+ population was selected and expanded as a line. This CTL population had predominant specificity for HLA-B35 and showed differential recognition of molecularly defined B35 subtypes. A set of CD8+ T cell clones was selected that recognized B35 transfectant cells. These clones were shown to discriminate among B35 molecular subtypes and to be peptide dependent, presumably recognizing a variety of endogenous peptides expressed in human cells. A second component of the response seemed to be mediated by activated CD56+ lymphocytes. Here strong cytotoxicity was found to be directed against MHC class I mutant cell lines, such as 721.221 and C1R, as well as against some allogeneic target cells. Transfection of Cw7 DNA into the mutant cell lines led to resistance to lysis. A hierarchy in susceptibility was found to correlate with HLA-C type in the unrelated panel: cells expressing HLA-Cw7 were found to be most resistant to lysis by this effector cell population.

Animals↗
PubMed1993

Microheterogeneity in HLA-B35 alleles influences peptide-dependent allorecognition by cytotoxic T cells but not binding of a peptide-restricted monoclonal antibody.

Strong peptide dependency of HLA-B*3501-specific alloreactive T-cell clones was observed in the recognition of cells bearing closely related B35 variants. The single amino acid exchange in the beta-pleated sheet of B*3503 completely abolished the responses of all clones, whereas an amino acid exchange in the alpha 2 helix of the newest B35 member (B*3508) only altered allorecognition of one T-cell clone, demonstrating the differential impact of these positions on peptide binding to B35 molecules. In contrast to T cells, a mAb (TU165) recognizing the B35 specificity in a peptide-dependent manner bound to the B35 variants irrespective of their sequence heterogeneity. However, quantitative binding differences were detected with cells bearing the same B35 alleles. This is most likely due to variations in the amount of peptide(s) that associates with B35 and forms the ligand seen by this mAb. These results reveal how naturally occurring single amino acid substitutions have led to generation of functionally distinct molecules of another multimember HLA class I cluster.

Amino Acid Sequence↗
PubMed1993

Control of cell pH in immature primitive red cells from chick embryo.

1. The intracellular pH in primitive red cells from 4 day chick embryos was measured with the digitonin null-point method and the fluorescent indicator SNARF-1. At physiological pHe of 8.0 red cell pH is 7.39 at day 4. 2. The calculated proton equilibrium potential of -38 mV is in good agreement with previous measurements of Em (Engelke et al., 1988) and supports the conclusion that the Em is dominated by a proton conductance. 3. The sodium-proton exchanger is present in primitive red cells but quiescent under physiological conditions. 4. The results indicate that the bicarbonate-chloride exchange via Band 3 protein is impaired.

Animals↗
PubMed1992

Cytotoxic T lymphocytes show HLA-C-restricted recognition of EBV-bearing cells and allorecognition of HLA class I molecules presenting self-peptides.

Human CTL have been isolated that show self-restricted recognition of autologous lymphoblastoid cell lines and allorecognition. The lymphoblastoid cell line ligand most likely used a peptide that is expressed in EBV-bearing cells when the virus enters the lytic cycle. This peptide is presented to CD8+ CTL by HLA-Cw7 molecules. The allogeneic ligand recognized on non-EBV-infected cells is composed of a class I glycoprotein and a naturally selected self-peptide. In previous studies we demonstrated that this ligand is determined by two MHC-linked genes: one gene encodes the allogeneic class I molecule whereas the other controls the self-peptide. Despite the use of different peptides and different class I molecules, seemingly equivalent structures are formed that enable these two ligands to function as antigenic mimics of each other. CTL with the same patterns of dual specificity could be isolated from four unrelated donors, indicating that HLA-Cw7 is frequently involved in self-restricted recognition of EBV-harboring cells. Such CTL could help not only to contain lytic virus during a primary infection but also may be maintained life-long to eliminate cells in which reactivated virus appears.

Burkitt Lymphoma↗