Histamine deficiency induces tissue-specific down-regulation of histamine H2 receptor expression in histidine decarboxylase knockout mice

AbstractHistidine decarboxylase (HDC) is the single enzyme responsible for histamine synthesis. HDC-deficient mice (HDC−/−) have no histamine in their tissues when kept on a histamine-free diet. Therefore, the HDC−/− mice provide a suitable model to investigate the involvement of histamine in the regulation of histamine receptor expression. Gene expression of H1 and H2 histamine receptors was studied in several organs of HDC−/− mice and compared to standard (HDC+/+) mice. In many tissues, prolonged absence of histamine induced down-regulation of the H2 receptor subtype. The expression of the H1 receptor was less sensitive to histamine deficiency. Exogenous histamine present in the diet abolished the differences observed in H2 receptor expression. These results suggest that the expression of mouse H2 receptor is under the control of histamine in a tissue-specific manner

A Monoclonal Antibody to Histoplasma capsulatum Alters the Intracellular Fate of the Fungus in Murine Macrophages▿ †

Monoclonal antibodies (MAbs) to a cell surface histone on Histoplasma capsulatum modify murine infection and decrease the growth of H. capsulatum within macrophages. Without the MAbs, H. capsulatum survives within macrophages by modifying the intraphagosomal environment. In the present study, we aimed to analyze the affects of a MAb on macrophage phagosomes. Using transmission electron and fluorescence microscopy, we showed that phagosome activation and maturation are significantly greater when H. capsulatum yeast are opsonized with MAb. The MAb reduced the ability of the organism to regulate the phagosomal pH. Additionally, increased antigen processing and reduced negative costimulation occur in macrophages that phagocytose yeast cells opsonized with MAb, resulting in more-efficient T-cell activation. The MAb alters the intracellular fate of H. capsulatum by affecting the ability of the fungus to regulate the milieu of the phagosome

Sleep Apnea Is Associated with Cardiovascular Risk Factors among Kidney Transplant Patients

Background and objectives: We assessed the prevalence of obstructive sleep apnea (OSA) and its clinical correlates in a large sample of patients who received a kidney transplant (Tx). We also compared the prevalence of the disorder between dialysis patients who were on the waiting list for a Tx (WL) and Tx patients