Biomedical subjects

Natascha Sommer

Publications and source records attributed to Natascha Sommer.

3 recordsLinked to original sources

PubMed2006

Oxygen sensors in hypoxic pulmonary vasoconstriction.

Hypoxic pulmonary vasoconstriction (HPV) is an essential mechanism adapting lung perfusion to regional ventilation. Perturbations to HPV, such as those occurring in pneumonia, acute respiratory distress syndrome and liver failure, can result in arterial hypoxemia. Under conditions of general hypoxia, HPV increases pulmonary vascular resistance and thus causes acute pulmonary hypertension. Despite intensive research, the underlying mechanisms of HPV have not been fully elucidated. Deciphering signalling pathways that result in HPV could suggest novel approaches to address a failure of HPV, as well as for the treatment of pulmonary hypertension associated with HPV. Within this context, this review focuses on current concepts in the oxygen sensing mechanisms that underlie HPV.

Adenosine Triphosphate↗

PubMed2005

Endothelial inducible costimulator ligand expression is increased during human cardiac allograft rejection and regulates endothelial cell-dependent allo-activation of CD8+ T cells in vitro.

The role of costimulatory molecules other than CD80/CD86 in endothelial cell (EC)-dependent CD8(+) T cell activation including the generation of a distinct subset of endothelium-specific CTL (EC-CTL) remains unclear. Inducible costimulator (ICOS) and its ligand (ICOSL) are new members of the CD28 family mediating effector T cell differentiation and graft rejection in animal models. In this study endothelial ICOSL expression/regulation and effects on CD8(+) T cell allo-activation were analyzed. Constitutive expression of ICOSL was found on human EC. IL-1alpha and TNF-alpha induced ICOSL in an NF-kappaB-dependent manner on human umbilical vein endothelial cells (HUVEC). ICOS receptor was not detected on resting CD8(+) T cells but was induced in co-cultures with HUVEC. ICOSL blockade reduced CD8(+) T cell proliferation by 70% along with a marked decrease of IL-2 and IFN-gamma production in co-cultures with HUVEC. IL-2 supplementation of co-cultures could overcome the effect of ICOSL blockade; similarly the generation of EC-CTL was not impaired by ICOSL blockade in an IL-2-containing system. In vivo, weak constitutive ICOSL expression was found on coronary microvessels, which was significantly up-regulated during acute cardiac allograft rejection (p=0.04). Our data indicate a distinct role for ICOSL in EC-mediated CD8(+) T cell costimulation with implications for human cardiac allograft rejection.

Acute Disease↗

PubMed2005

Chronic exposure to nitrous oxide increases [3H]MK801 binding in the cerebral cortex, but not in the hippocampus of adult mice.

Chronic exposure of adult mice to inhalational anesthetic nitrous oxide (N2O) results in anesthetic tolerance. N2O is an NMDA (N-methyl-D-aspartate) antagonist. It has been demonstrated that chronic administration of members of the NMDA antagonist class of drugs (e.g., MK801) causes upregulation of NMDA receptors in certain brain regions that could, at least in part, explain the development of tolerance. We sought to determine whether the anesthetic tolerance resulting from chronic exposure to N2O reflects changes in the number and/or distribution of NMDA receptors. We exposed mice to either a 50- or 75-vol% N2O atmosphere continuously for 1 or 2 weeks and performed binding studies with [3H]MK801 and NR1 antibodies. Binding studies revealed a significant (P < 0.05) increase in [3H]MK801 binding in the cerebral cortex after 2 weeks of N2O (50- and 75-vol%) exposure. Immunocytochemical binding of NR1 antibodies in selected brain regions showed no changes in distribution pattern. The timing of this increase in [3H]MK801 binding correlates with the time period required for development of tolerance.

Anesthetics, Inhalation↗