Cytokine-activated natural killer cells exert direct killing of hepatoma cells harboring hepatitis C virus replicons.

Hepatitis C virus (HCV)-specific impairments in host immunity have been described at multiple levels of the innate and adaptive response, which may lead to viral persistence in the majority of infections. Understanding of HCV-associated immune defects could lead to novel therapeutic advances. Natural killer (NK) cells, the major effector cells of the innate immune system, are functionally impaired in chronic HCV infection. It has been suggested that this phenotype is a result of virus-specific defects in antigen-presenting cells (APCs) that regulate NK cell activity, as normal NK function is restored when they are stimulated ex vivo. In this study, we used human NK cell cytotoxicity assays to evaluate the activation-induced effects of NK cells on the HCV replicon-containing hepatic cells. We found that cytokine-activated NK cells were capable of inducing an HCV-associated, perforin/granzyme-dependent lysis of human hepatoma cells and that this required direct cellular contact and was independent of MHC class I expression levels. In contrast, on removal of cytokine stimulation, NK cells failed to exert any direct cytolytic effect on replicon targets. These findings suggest an important underlying mechanism by which NK cells control HCV infection and, with appropriate understanding of HCV-associated immune defects, could lead to novel therapeutic advances.     

Non-invasive Assessment of Coronary Flow Velocity Reserve: A New Method Using Transthoracic Doppler Echocardiography

Coronary flow reserve (CFR) has been used toassess coronary microcirculation and epicardial coro-nary stenoses[1— 3 ] . CFR is defined as the ratio ofcoronary flow under maximal coronary vasodilatationto coronary flow under resting conditions[4 ] .Whenthe cross- sectional area of epicardial coronary arteriesis constant,coronary flow velocity (CFV) ratios areequal to volume flow ratios.The most common method used clinically formeasuring CFVR is intracoronary Doppler flow(ICD) analysis re…     

Evolution of the sperm aster after microinjection of isolated human sperm centrosomes into meiotically mature human oocytes

This study examined the feasibility of isolating and transferringthe centrosome-containing region of spermatozoa to mature humanoocytes. The findings demonstrate that individual sperm centrosomescan be transferred and are capable of nucleating maternal tubulinto form a well-developed sperm aster in the recipient oocyte.The results are discussed with respect to centrosome functionin early human development and applications in clinical in-vitrofertilization in the treatment of certain forms of male factorinfertility.     

Cortical circumferential profile of SPECT cerebral perfusion in Alzheimer''s disease

We developed a semiautomatic method termed “cortical circumferential profiling” for objective analysis of cerebral cortex function in emission tomographic neuroimaging studies. This method treats cortex as a continuous ring near the outer brain edge. A computer algorithm samples the cortex at 60 contiguous, equiangular locations, using 1-cm² samples. These values are plotted as a function of cortical angle to produce the cortical circumferential profile. This method was used in a study of regional cerebral perfusion in 15 patients with Alzheimer's disease and 8 elderly control subjects using N-isopropyl [I-123]-iodoamphetamine. Cortical circumferential profiling decreases variability, examines the entire cortex within slices at preselected levels above the orbital-meatal line, and facilitates intrasubject and intersubject comparisons.     

Sarcoplasmic reticulum calcium load regulates rat arterial smooth muscle calcium sparks and transient KCa currents

Voltage-gated Na⁺ current is reduced by acid solution. Protons reduce peak Na⁺ conductance by lowering single channel conductance and shift the voltage range of gating by neutralizing surface charges. Structure-function studies identify six carboxyls and a lysine in the channel's outer vestibule. We examined the roles of the superficial ring of carboxyls in acid block of Na_v1.4 (the rat skeletal muscle Na⁺ channel isoform) by measuring the effects of their neutralization or their substitution by lysine on sensitivity to acid solutions, using the two-micropipette voltage clamp in Xenopus oocytes. Alteration of the outer ring of carboxylates had little effect on the voltage for half-activation of Na⁺ current, as if they are distant from the channels' voltage sensors. The mutations did not abolish proton block; rather, they all shifted the p K _a (-log of the dissociation constant) in the acid direction. Effects of neutralization on p K _a were not identical for different mutations, with E758Q > D1241A > D1532N > E403Q. E758K showed double the effect of E758Q, and the other lysine mutations all produced larger effects than the neutralizing mutations. Calculation of the electrostatic potential produced by these carboxylates using a pore model showed that the p K _a values of carboxylates of Glu-403, Glu-758, and Asp-1532 are shifted to values similar to the experimentally measured p K _a. Calculations also predict the experimentally observed changes in p K _a that result from mutational neutralization or introduction of a positive charge. We propose that proton block results from partial protonation of these outer ring carboxylates and that all of the carboxylates contribute to a composite Na⁺ site.