Bretylium-induced voltage-gated sodium current in human lymphocytes.

Using the whole-cell variation of the patch-clamp technique it has been determined that 0.25-3 mM bretylium tosylate (BT) exerts a repolarizing effect on partially depolarized human lymphocytes. The repolarizing effect was ouabain (40 microM)-sensitive, and was inhibited by the removal of external Na+ or by the Na(+)-channel-blocker amiloride (10-44 microM), but K(+)-channel-blockers 4-aminopyridine (0.1-5 mM) and quinine (100 microM) had no effect. The drug induced a sodium dependent, amiloride-sensitive transient inward current reaching its maximum value approx. 20-30 s after the administration of BT and lasting for 6-10 min. This current was activated by depolarization within 25 ms at around -42 mV, its inactivation took about 2 s and its reversal potential was +24 +/- 5 mV. An increase in the intracellular sodium concentration (1.8-3.2 mM) has been observed upon the addition of BT by monitoring the SBFI fluorescence of the dye-loaded cells. It has been shown that whole-cell K+ currents are significantly decreased by BT. The existence of voltage and ligand (BT)-gated sodium channels has been postulated in human lymphocytes. These channels are thought to participate in the initiation of membrane repolarization in human lymphocytes, and thereby influence mitogenic or antigen-induced cell-activation processes.     

Shock-induced triploidy and its effect on growth and gonad development of the European catfish, Silurus glanis L.

Triloidy was induced in European catfish, Silurus glanis L., by cold-shocking eggs at 4°C for 30 and 40 min respectively, starting 5 min after fertilization. The hatching success of cold-shocked eggs was 25–30%. Cold shocks longer than 1 h caused total mortality. The triploid character of the cold-shocked European catfish was proved by karyological and red blood cell size analyses. The gonads of the triploid fish were significantly smaller than those of the diploids, while the growth rate values of the triploids were significantly higher than those of the diploids.     

Membrane permeability changes induce hyperpolarization in transformed lymphoid cells under high-density culture conditions

BACKGROUND: Membrane potential changes in cells from the human lymphoid B cell line, JY, evoked by increasing cell density in culture were investigated, as data published on other cell types are controversial. An attempt was also made to clear the underlying mechanism. METHODS: Nonadherent JY cells were isolated from high-density plateau-phase cultures (type A cells), medium-density log-phase cultures (type B cells), and low-density lag-phase cultures (type C cells). They were analyzed for transmembrane potential, intracellular free concentration of potassium and sodium, membrane permeability for monovalent cations, cell cycle distribution by measuring DNA content, and glucose uptake. RESULTS: C type cells proved to be relatively depolarized (-41 +/- 3 mV) and cells obtained from the highest density cultures hyperpolarized (-60 +/- 3 mV). Intracellular concentrations ([K](i) = 92-97 mM and [Na](i) = 34-35 mM) were almost identical for each type of cell. The sodium/potassium permeability constant ratio in the A and C type of cells was 0.047 and 0.094, respectively. High-density culture conditions resulted in a pronounced G(1)-phase arrest. CONCLUSIONS: Differences in the membrane potential values induced by high-density culture conditions were maintained by changes in the membrane permeability for the monovalent cations.     

Detection of channel proximity by nanoparticle-assisted delaying of toxin binding; a combined patch-clamp and flow cytometric energy transfer study

Gold nanoparticles of 30 nm diameter bound to cell-surface receptor major histocompatibility complex glycoproteins (MHCI and MHCII), interleukin-2 receptor subunit (IL-2R), very late antigen-4 (VLA-4) integrin, transferrin receptor, and the receptor-type protein tyrosin phosphatase CD45 are shown by the patch-clamp technique to selectively modulate binding characteristics of Pi₂ toxin, an efficient blocker of K_v1.3 channels. After correlating the electrophysiological data with those on the underlying receptor clusters obtained by simultaneously conducted flow cytometric energy transfer measurements, the modulation was proved to be sensitive to the density and size of the receptor clusters, and to the locations of the receptors as well. Based on the observation that engagement of MHCII by a monoclonal antibody down-regulates channel current and based on the close nanometer-scale proximity of the MHCI and MHCII glycoproteins, an analogous experiment was carried out when gold nanoparticles bound to MHCI delayed down-regulation of the K_v1.3 current initiated by ligation of MHCII. Localization of K_v1.3 channels in the nanometer-scale vicinity of the MHC-containing lipid rafts is demonstrated for the first time. A method is proposed for detecting receptor–channel or receptor–receptor proximity by observing nanoparticle-induced increase in relaxation times following concentration jumps of ligands binding to channels or to receptors capable of regulating channel currents.     

EFFECTS OF DIETARY SUPPLEMENTAL L-CARNITINE AND ASCORBIC ACID ON PERFORMANCE,CARCASS COMPOSITION AND PLASMA L-CARNITINE CONCENTRATION OF BROILER CHICKS REARED UNDER DIFFERENT TEMPERATURE

The present study was initiated to determine whether dietary supplemental L-carnitine and ascorbic acid affect growth performance, carcass yield and composition, abdominal fat and plasma L-carnitine concentration of broiler chicks reared under normal and high temperature. During the experiment, two temperature regimes were employed in two experimental rooms, which were identical but different in environmental temperature. The regimes were thermoneutral (20-22°C for 24 h) or recycling hot (34-36°C for 8 h and 20-22°C for 16 h). One-day-old broiler chicks (ROSS) were used in the experiment. A 2 x 2 x 2 factorial arrangement was employed with two levels (0 and 50 mg/kg) of supplemental L-carnitine and two levels (0 or 500 mg/kg) of supplemental ascorbic acid in drinking water under thermoneutral or high temperature regimes. Body weight gain was affected by high temperature. However, body weight gain was significantly improved in animals receiving supplemental L-carnitine, ascorbic acid or L-carnitine + ascorbic acid compared to animals receiving unsupplemented diet under high temperature. On the other hand, supplemental L-carnitine or L-carnitine + ascorbic acid reduced body weight gain under thermoneutral condition. Supplemental ascorbic acid significantly improved feed conversion efficiency, the improvement was relatively greater under high temperature. The L-carnitine content in the plasma was higher in the groups receiving supplemental L-carnitine and ascorbic acid under high temperature, while broilers fed supplemental L-carnitine and ascorbic acid had a decreased level of plasma L-carnitine concentration under normal temperature. It is concluded that dietary supplemental L-carnitine or L-carnitine + ascorbic acid may have positive effects on body weight gain, carcass weight under high temperature conditions.     

Relationship between exchangeable body sodium and urinary 6-keto-prostaglandin F1 alpha excretion in normal man

The renal prostaglandins are involved in the regulation of sodium balance. In the present study exchangeable body sodium (NaE) and the urinary excretion of the stable metabolite of prostacyclin, 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha) were determined simultaneously in 10 hospitalized healthy individuals. NaE was 1461 +/- 107 mmol/m2 body surface area, or 98.5 +/- 6.9% when expressed as percent of the normal value assessed on the basis of measurements in 54 control subjects. The excretion of 6-k-PGF1 alpha amounted to 68.3 +/- 39.2 ng/4 hr. Statistical evaluation revealed significant correlation between NaE and PGF1 alpha excretion (r = 0.642; p less than 0.05) and between the serum Na concentration and the urinary excretion of 6-k-PGF1 alpha (r = 0.865; p less than 0.001). The obtained results indicate that urinary 6-k-PGF1 alpha excretion, hence the renal synthesis of prostacyclin, are regulated, among other factors, by body sodium stores. The increased production of prostacyclin with expanding sodium space might be regarded as a compensatory response contributing to the renal elimination of excess sodium from the body. The signal to this response could be the serum Na concentration.     

Effect of chronic ACTH treatment on the physical state of lipid droplets in rat adrenocortical cells

A histophysical method has been adapted to determine the thermotropic phase transitions of adrenocortical lipid droplets using a polarizing microscope equipped with a cold/hot stage. Cryosections of freshly-removed, unfixed adrenals, derived from control (untreated), and 14 days ACTH-treated rats were examined. The lipid droplets in the zona fasciculata and zona reticularis of the untreated rats were birefringent at room temperature (22°C). The birefringence of zona glomerulosa lipids selectively increased in the temperature range from −10 to −15°C. In cryosections prepared from ACTH-treated rats, thermotropic phase transitions of the lipid droplets appeared at a temperature range between −30 and −40°C in each cortical zone. The chemical analysis of the isolated lipids revealed that the relative amount of triglycerides in the zona fasciculata lipids increased, while that of free and esterified cholesterol decreased after chronic ACTH treatment. Present data suggest that the increased fluidity of lipid droplets promotes lipid mobilization in response to the enhanced demand of the chronically stimulated adrenocortical cells. Viscosity-dependent mobilization of free cholesterol from lipid droplets is not a rate-limiting process in adrenal steroidogenesis, but rather may represent an important control of the availability of precursor from lipid stores.