In vitro effects of thyroxine on the mechanical properties of erythrocytes

In vitro effects of thyroxine on erythrocyte deformability and mechanical fragility were observed. Deformability of erythrocytes was improved in a dose dependent manner by thyroxine. Mechanical hemolysis was found to be lower if thyroxine was included in erythrocyte suspensions at concentrations close to the physiological levels (10(-9)M). These changes might be related to the alterations of intracellular calcium concentration, as in the erythrocyte suspensions containing 10(-9)M thyroxine, intracellular calcium concentration was found to be 30 times lower than the control suspensions which did not contain thyroxine. Thyroxine also reduced the mechanical hemolysis ratio in calcium loaded cells. These observations suggest that thyroxine might play some role in the regulation of the mechanical properties of erythrocytes which might be mediated via the effects on calcium metabolism.     

Enhanced Expression of an Endothelin ETA Receptor in Capillaries from Human Glioblastoma: A Quantitative Receptor Autoradiographic Analysis Using a Radioluminographic Imaging Plate System

Abstract: We identified and characterized ¹²⁵I-endothelin-1 (¹²⁵I-ET-1) binding sites in tumor capillaries isolated from human glioblastomas, using the quantitative receptor autoradiographic technique with pellet sections. Quantification was done using the computerized radioluminographic imaging plate system. High-affinity ET receptors were localized in capillaries from glioblastomas and the surrounding brain tissues (K_D = 4.7 ± 1.0 × 10^?10 and 1.6 ± 0.3 × 10^?10M, respectively; B_max = 161 ± 38 and 140 ± 37 fmol/mg, respectively; mean ± SEM, n = 5). BQ-123, a selective antagonist for the ET_A receptor, potently competed for ¹²⁵I-ET-1 binding to sections of the microvessels with IC₅₀ values of 5.1 ± 0.3 and 5.1 ± 1.5 nM, and 10^?6M BQ-123 displaced 84 and 58% of ET binding to capillaries from tumors and brains, respectively. In addition, competition curves obtained in the presence of increasing concentrations of ET-3 showed two components (IC₅₀ = 5.7 ± 2.5 × 10^?10 and 1.4 ± 0.2 × 10^?6M for tumor microvessels, 1.8 ± 0.6 × 10^?10 and 1.1 ± 0.3 × 10^?6M for brain microvessels, respectively). Our results indicate that (a) the method we used is simple and highly sensitive for detecting and characterizing various receptors in tumor capillaries, especially in the case of a sparse specimen, and (b) capillaries in glioblastomas express specific high-affinity ET binding sites, candidates for biologically active ET receptors, which predominantly belong to the ET_A subtype.     

Expression of the T antigen on a T-lymphoid cell line, SupT1

We have measured glycosyltransferase activities of SupT1 cells, a T-lymphoid cell line shown to react with autoantibodies in the sera of many HIV patients. Since considerable -N-acetylgalactosaminyl-transferase and 1, 3 galactosyl-transferase activities were found in SupT1 cells, at least the O-glycan core 1 structure can probably be synthesized. FACS analysis using an anti-T monoclonal antibody showed expression of the T antigen (Gal 1-3 GalNAc). Glycoproteins with the T antigen were isolated by immunoprecipitation with the anti-T antibody from a SupT1 cell lysate labelled metabolically with³H-glucosamine and then analysed by SDS-PAGE. It was revealed that the precipitate contained a glycoprotein with a molecular weight corresponding to that of leukosialin. O-glycans were prepared from the immunoprecipitate by alkaline-borohydride treatment and then fractionated on Bio-Gel P-2, GalNAcOH and Gal-GalNAcOH being identifiedinter alia. These results suggest that an anti-T antibody may be included in the autoantibodies found in HIV-1 infected individuals.     

The role of estrogens in the regulation of lactate dehydrogenase activity and its submolecular organization in rat anterior pituitary

Estrogens increase LDH activity and decrease H/M subunit ratio in rat anterior pituitary in both the experimental circumstances and the physiological conditions. The cellular messengers mediating estrogenic effect are structure- and stereospecific. The activity increasing and subunit ratio decreasing potency of the three tested estrogens was of following decreasing order: 17 beta-estradiol, estrone, and estriol. 17 alpha-estradiol did not affect activity parameters and submolecular organisation of the enzyme. The estrogen induced activity increase is consequence of the enhanced de novo enzyme protein synthesis which could be inhibited by Actinomycin-D. The lack of adrenocorticoids did not involve the alteration of LDH activity and H/M ratio in female rat anterior pituitary. Accordingly, these steroids do not mediate estrogenic action. 17 beta-estradiol had a substantial increasing effect on LDH activity in the subrenal implanted pituitary homografts and decreased H/M subunit ratio. Pituitary LDH activity in androgenized female rats decreased only after the removal of the polycystic ovaries. The two latter observations suggest that hypothalamic hormones are not involved in the regulation of pituitary LDH activity and its submolecular organization. De novo synthesis of LDH enzyme protein and the regulation its submolecular organization is induced by the direct action on anterior pituitary cells of the estrogens.     

DNA damage causes TP53-dependent coupling of self-renewal and senescence pathways in embryonal carcinoma cells

Comment on: Wu R, et al. Clin Cancer Res 2011; 17:7359–72     

Parasporin 1Ac2, a Novel Cytotoxic Crystal Protein Isolated from Bacillus thuringiensis B0462 Strain

Two novel parasporin (PS) genes were cloned from Bacillus thuringiensis B0462 strain. One was 100 % identical even in nucleotide sequence level with that of parasporin-1Aa (PS1Aa1) from B. thuringiensis A1190 strain. The other (PS1Ac2) showed significant homology (99 % identity) to that of PS1Ac1 from B. thuringiensis 87-29 strain. The 15 kDa (S¹¹³–R²⁵⁰) and 60 kDa (I²⁵¹–S⁷⁷⁷) fragments consisting of an active form of PS1Ac2 were expressed as His-tag fusion. Upon purification under denaturing condition and refolding, the recombinant polypeptides were applied to cancer cells to analyze their cytotoxicities. 3-(4,5-Dimethyl-2-thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide assay revealed that either of 15 or 60 kDa polypeptide exhibited no cytotoxicity to HeLa cells, but they became cytotoxic upon mixed together. Our results suggested that PS1Ac2 was responsible for the cytotoxicity of B. thuringiensis B0462 strain, and that the formation of hetero-dimer of 15 and 60 kDa polypeptide was required for their cytotoxicity.     

Diversity of extremophilic bacteria in the sediment of high-altitude lakes located in the mountain desert of Ojos del Salado volcano,Dry-Andes

Ojos del Salado, the highest volcano on Earth is surrounded by a special mountain desert with extreme aridity, great daily temperature range, intense solar radiation, and permafrost from 5000 meters above sea level. Several saline lakes and permafrost derived high-altitude lakes can be found in this area, often surrounded by fumaroles and hot springs. The aim of this study was to gain information about the bacterial communities inhabiting the sediment of high-altitude lakes of the Ojos del Salado region located between 3770 and 6500 m. Altogether 11 sediment samples from 4 different altitudes were examined with 16S rRNA gene based denaturing gradient gel electrophoresis and clone libraries. Members of 17 phyla or candidate divisions were detected with the dominance of Proteobacteria, Acidobacteria, Actinobacteria and Bacteroidetes. The bacterial community composition was determined mainly by the altitude of the sampling sites; nevertheless, the extreme aridity and the active volcanism had a strong influence on it. Most of the sequences showed the highest relation to bacterial species or uncultured clones from similar extreme environments.     

Facilitatory role of NO in neural norepinephrine release in the rat kidney

We examined modulation by nitric oxide (NO) of sympathetic neurotransmitter release and vasoconstriction in the isolated pump-perfused rat kidney. Electrical renal nerve stimulation (RNS; 1 and 2 Hz) increased renal perfusion pressure and renal norepinephrine (NE) efflux. Nonselective NO synthase (NOS) inhibitors [N(omega)-nitro-L-arginine methyl ester (L-NAME) or N(omega)-nitro-L-arginine], but not a selective neuronal NO synthase inhibitor (7-nitroindazole sodium salt), suppressed the NE efflux response and enhanced the perfusion pressure response. Pretreatment with L-arginine prevented the effects of L-NAME on the RNS-induced responses. 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), which eliminates NO by oxidizing it to NO(2), suppressed the NE efflux response, whereas the perfusion pressure response was less susceptible to carboxy-PTIO. 8-Bromoguanosine cGMP suppressed and a guanylate cyclase inhibitor [4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one] enhanced the RNS-induced perfusion pressure response, but neither of these drugs affected the NE efflux response. These results suggest that endogenous NO facilitates the NE release through cGMP-independent mechanisms, NO metabolites formed after NO(2) rather than NO itself counteract the vasoconstriction, and neuronal NOS does not contribute to these modulatory mechanisms in the sympathetic nervous system of the rat kidney.