Endothelin-induced vasoconstriction and release of atrial natriuretic peptides in the rat

Endothelin-1 (ET-1) was given to male Sprague-Dawley rats in i.v. bolus injections to evaluate its effects on blood pressure and the release of atrial natriuretic peptides (ANP). In awake rats ET-1 (0.3, 1 and 3 nmol kg-1 body wt) transiently reduced mean arterial pressure (MAP) and increased heart rate (HR), followed by a prolonged increase in MAP. The magnitude of these changes and the duration of the increase in MAP were dose-related. The increase in MAP was completely blocked by verapamil, reversed by sodium nitroprusside, slightly reduced by rat atrial natriuretic factor (103-126) and unaffected by saralasin. The initial fall in MAP was also unaltered by these agents. In all groups HR changes were mirror-images of MAP. In anaesthetized rats ET-1 (1 nmol kg-1 body wt) induced a sustained release of ANP. Right atrial pressure increased transiently and then fell below baseline. When the increase in MAP was blocked with sodium nitroprusside, ET-1 still produced an increase in ANP. In conclusion we find that repeated i.v. administration of ET-1 induces immediate vasodilatation, without signs of tachyphylaxis, followed by long-lasting severe vasoconstriction. Baroreceptor function seems to be unchanged. ET-1 appears to induce ANP release by a direct action on atrial myocytes, independent of right atrial and systemic arterial pressure. We hypothesize that endothelin may be a mediator of stretch-induced release of ANP.     

Y chromosome microdeletions, in azoospermic or near-azoospermic subjects, are located in the AZFc (DAZ) subregion

Submicroscopic deletions of the Y chromosome and polymorphisms of the androgen receptor (AR) gene in the X chromosome have been observed in men with defective spermatogenesis. To further define the subregions/genes in the Y chromosome causing male infertility and its relationship to polymorphisms of the AR polyglutamine tract, we screened the genomic DNA of 202 subfertile males and 101 healthy fertile controls of predominantly Chinese ethnic origin. Y microdeletions were examined with 16 sequence-tagged site (STS) probes, including the RBM and DAZ genes, spanning the AZFb and AZFc subregions of Yq11, and related to the size of trinucleotide repeat encoding the AR polyglutamine tract. Y microdeletions were detected and confirmed in three out of 44 (6.8%) of azoospermic and three out of 86 (3.5%) severely oligozoospermic patients. No deletions were detected in any of the patients with sperm counts of >0.5 x 10(6)/ml, nor in any of the 101 fertile controls. All six affected patients had almost contiguous Y microdeletions spanning the entire AZFc region including the DAZ gene. The AZFb region, containing the RBM1 gene, was intact in five of the six subjects. Y deletions were not found in those with long AR polyglutamine tracts. Our study, the first in a Chinese population, suggest a cause and effect relationship between Y microdeletions in the AZFc region (possibly DAZ), and azoospermia or near-azoospermia. Y microdeletions and long AR polyglutamine tracts appear to be independent contributors to male infertility.      

Changes in immunoregulatory lymphocyte populations in patients with histoplasmosis

Circulating T-lymphocyte subpopulations were enumerated in 65 patients with histoplasmosis and correlated with the different clinical manifestations of the disease. Acute pulmonary histoplasmosis, rheumatologic, disseminated, and chronic inflammatory manifestations of histoplasmosis were all associated with a significant elevation above normal of OKT₈+ (suppressor-cytotoxic) lymphocytes and a significantly lower than normal OKT₄+ (helper-inducer)-lymphocyte to OKT₈+-lymphocyte ratio. In contrast, cavitary disease was associated with an increase in OKT₄+ lymphocytes, a decrease in OKT₈+ lymphocytes, and a higher than normal OKT₄/OKT₈ ratio. Clinical recovery was associated with normalization of these values. Functional activity determined by coculture techniques correlated closely with T-lymphocyte subset measurements. These distinct subset abnormalities may help monitor immunological aspects of disease activity.     

Absence of demonstrable phospholipid turnover in B cells stimulated by low mitogenic concentrations of dextran-anti-immunoglobulin conjugates.

Previously we have demonstrated that when anti-immunoglobulin (Ig) is conjugated to high molecular weight dextran (Dex) it stimulates B cell activation at pg/ml concentrations in the absence of detectable phosphoinositide hydrolysis or increases in intracellular ionized calcium. To study carefully whether anti-Ig-Dex recruited a phosphoinositide-dependent pathway of activation, we stimulated B cells that were labeled with 32P and [3H]glycerol with anti-Ig-Dex conjugates at concentrations ranging from 1-1 x 10(-4) micrograms/ml. Thirty seconds to thirty minutes after stimulation lipids were extracted and analyzed by thin layer chromatography and spots correlating with known lipid standards were isolated and counted. There was a four- and tenfold increase in the ratio of 32P/3H incorporated into phosphatidic acid (a metabolite of diacylglycerol) and phosphatidylinositol, respectively, when cells were stimulated with 0.1-1.0 microgram/ml of anti-Ig-Dex for 30 min. Below 1 ng/ml there was no detectable increase in the turnover of these metabolites despite the fact that in parallel cultures B cells were stimulated to proliferate by this concentration of anti-Ig-Dex. To determine whether a cAMP-dependent pathway was recruited by low concentrations of conjugates, we evaluated cAMP levels from B cells that were stimulated with anti-Ig-Dex for 5-60 min using a radioimmunoassay. While cholera toxin stimulated a 50-100-fold increase in the levels of cAMP, we observed no alteration in cAMP in anti-Ig-stimulated cells. These results support and extend our previous findings by demonstrating that B cell activation that is induced by cross-linking of surface Ig may not stimulate phosphoinositide-dependent or cAMP-dependent pathways of activation. Possible alternative mechanisms of activation will be discussed.     

Detection of brain-reactive autoantibodies in the sera of autoimmune mice using ELISA.

There are considerable problems with developing an assay to detect the often small quantities of autoantibodies which react against antigens in a heterogeneous and complex mixture from a source such as brain. An indirect enzyme-linked immunosorbent assay (ELISA) has been developed which can detect naturally occurring autoantibodies in serum that are reactive with integral brain membrane antigens. Sera were collected from autoimmune BXSB and NZB mice and non-autoimmune C57BL/6 mice at various ages and were assayed for the presence of brain-reactive autoantibodies (BRAAs). It is shown that this technique provides a highly sensitive, specific, and rapid assay for detecting BRAAs in serum. It shows that integral membrane antigens from whole brain can be isolated and used to detect and quantitate antibodies in the sera of autoimmune and non-autoimmune mice. The data also confirm studies, using different techniques, showing higher levels of autoantibodies to brain in autoimmune as compared to non-autoimmune mice. There are numerous potential applications for this ELISA, such as in rapidly screening large numbers of samples of biological fluids, tracking autoimmune disease progression over time, detecting small quantities of antibody against brain antigens, and as an assay system for investigating the role of BRAAs in the pathogenesis of immune mediated CNS disease.     

Is ATP-sensitive K+ channel (K+ATP) recruitment a common mechanism for ECG-ST segment depression and elevation?

ATP sensitive (K(+)(ATP)) potassium cardiac channels are recruited when ATP levels are low as in ischemic injury and acute trauma. Such activation results in ECG-ST elevation and cardiac arrhythmias. K(+)(ATP) channel recruitment may be blocked by the sulfonylurea glibenclamide, permitting a wide variety of animal experimentation designed to test the genesis of ECG-ST segment elevations and depressions in diverse conditions including digitalis effect, acute arterial occlusion, tachycardias, and acute pericarditis. A specific series of animal experiments designed to test this hypothesis is proposed. Clinical implications are discussed.