Compensatory Thrombopoietin Production from the Liver and Bone Marrow Stimulates Thrombopoiesis of Living Rat Megakaryocytes in Chronic Renal Failure

Background/Aims: Decreased thrombopoiesis has been ascribed a role in the pathogenesis of uremic bleeding in chronic renal failure (CRF). However, serum thrombopoietin (TPO) levels are usually elevated in CRF patients, suggesting increased thrombopoiesis. The aim of this study was to determine the thrombopoietic activity in CRF. Methods: Male Sprague-Dawley rats that underwent 5/6 nephrectomy were used as the model of CRF. Age-matched sham-operated rats were used as controls. Single megakaryocytes were isolated from the rat bone marrow, and their size distribution was examined. Megakaryocyte membrane invaginations were monitored by confocal imaging of di-8-ANEPPS staining, and patch clamp whole-cell recordings of membrane capacitance. TPO gene expression was assessed in various tissues. Results: Circulating platelet counts and the number of large megakaryocytes were increased in the bone marrow of CRF rats. Massive di-8-ANEPPS staining and increased membrane capacitance in large megakaryocytes demonstrated increased membrane invaginations. Unaffected Kv1.3-channel currents per cell surface area demonstrated unaltered channel densities. TPO transcription was decreased in the renal cortex but increased in the liver and bone marrow of CRF rats. Conclusion: Increased thrombopoiesis in CRF was thought to be a reactive mechanism to platelet dysfunction. Increased TPO production from the liver and bone marrow compensated for decreased production from damaged kidneys

0n climatogy in Misasa spa (twentieth report)

我々は1956年以降,三朝温泉地の気候について観察を行っている｡今回は1997年1月1日から1997年12月末日までの1年間の気象観察資料を報告する｡機器の故障により,記録の一部に欠落部分のあることをお断りしておく｡Climatological data of the last 12monnths (1997.1.1-1997.12.31) obtained by the climate autorecording system at the Misasa Medical Branch in Misasa SPa, Tottori-ken, Japan are presented

Vasopressin-independent renal urinary concentration: Increased rBSC1 and enhanced countercurrent multiplication

Vasopressin-independent renal urinary concentration: Increased rBSC1 and enhanced countercurrent multiplication.BackgroundA close association between the expression of the sodium transporter, rat bumetanide sensitive cotransporter (rBSC), in thick ascending limb of Henle and urinary concentration has been reported. However, direct evidence for this association and the mechanism of rBSC1 expression are still to be elucidated.MethodsBrattleboro (BB) rats weighing approximately 200g were dehydrated by water restriction for 4 hours, which induced around a 5% body weight reduction. Although plasma arginine vasopressin (AVP) was undetectable even after the water restriction, BB rats concentrated urine from 182 ± 23 (mean ± SD) at baseline to 404 ± 65 mOsm/kg · H2O.ResultsUrinary volume was reduced from 5.8 ± 1.8 to 1.4 ± 0.6mL/h. This treatment significantly increased sodium and urea accumulation in the renal medulla and reduced urinary sodium excretion. rBSC1 signals for both mRNA and protein were increased in dehydrated rats, although aquaporin type 2 (AQP2) expression was not enhanced in dehydrated BB rats. Subcutaneous infusion of desmopressin acetate (DDAVP) intensified rBSC1 signals of BB rats more than those in dehydrated condition.ConclusionDehydration increased rBSC1 expression and enhanced countercurrent multiplication even in AVP deficiency. These results supply strong evidence for the association between rBSC1 expression and urinary concentration, and indicate the presence of an AVP-independent mechanism for urine concentration

Reverse pharmacological effect of loop diuretics and altered rBSC1 expression in rats with lithium nephropathy

Reverse pharmacological effect of loop diuretics and altered rBSC1 expression in rats with lithium nephropathy.BackgroundRenal urinary concentration is associated with enhanced expression of rBSC1, a rat sodium cotransporter, in the thick ascending limb of Henle. Increased expression of rBSC1 was reported recently in nephrogenic diabetes insipidus induced by lithium chloride (Li nephropathy). However, the pathophysiological implication of altered rBSC1 expression has not yet been investigated.MethodsLi nephropathy was induced in rats by an oral administration of 40 mmol lithium/kg dry food. In rats with reduced urinary osmolality to less than 300 mOsm/kg H2O, we examined the expression of rBSC1 mRNA and protein, plasma arginine vasopressin (AVP) and RNA expression of kidney-specific water channel, aquaporin-2 (AQP2), of collecting ducts. Rats with Li nephropathy were treated with furosemide (3 mg/kg body weight), which blocks the activity of rBSC1, and changes in urine concentration, plasma AVP, medullary accumulation of Li ions, and apical AQP2 expression were determined.ResultsRats with Li nephropathy showed increased rBSC1 RNA and protein expression and reduced AQP2 RNA. In these rats, furosemide, which induces dilution of urine and polyuria in normal rats, resulted in a progressive and significant rise in urine osmolality from 167 ± 11 (mean ± SD) at baseline to 450 ± 45 mOsm/kg H2O at three hours after administration, and significant oliguria. In the same rats, plasma AVP decreased significantly from 5.7 to 3.0 pg/mL. In addition, recovery of apical AQP2 expression was noted in a proportion of epithelial cells of the collecting ducts. Although Li+ in the renal medulla was slightly lower in rats with Li nephropathy treated with furosemide, statistical significance was not achieved.ConclusionsOur results suggest that dehydration or high plasma AVP results in an enhanced rBSC1 expression in Li nephropathy, and that rBSC1 expression is closely associated with the adverse effects of Li ions on collecting duct function

Cobalt-Impregnated Magnetite as General Heterogeneous Catalyst for the Hydroacylation Reaction of Azodicarboxylates

Catalysts consisting of cobalt and nickel impregnated on magnetite have been prepared, characterized and used for the hydroacylation reaction of different azodicarboxylate compounds with aldehydes, using nearly stoichiometric amounts of both reagents in only 3 h. Furthermore, this reaction has been conducted with the smallest amount of catalyst. The cobalt catalyst is stable enough to be removed by magnetic decantation and recycled ten-fold without any detrimental effect on the results.This work was supported by the Spanish Ministerio de Economía y Competitividad (MICINN; CTQ2011-24151) and University of Alicante. J. M.P. thanks the MICINN (FPI program) for her fellowship

Salicylate Inhibits Thrombopoiesis in Rat Megakaryocytes by Changing the Membrane Micro-Architecture

Background/Aims: Salicylate causes drug-induced immune thrombocytopenia. However, some clinical studies indicate the presence of additional mechanisms in the drug-induced thrombocytopenia, by which the platelet production from megakaryocytes may directly be affected. Since salicylate is amphiphilic and preferentially partitioned into the lipid bilayers of the plasma membrane, it can induce some structural changes in the megakaryocyte membrane surface and thus affect the process of thrombopoiesis. Methods: Employing the standard patch-clamp whole-cell recording technique, we examined the effects of salicylate on the membrane capacitance in rat megakaryocytes. Taking electron microscopic imaging of the cellular surface, we also examined the effects of salicylate on the membrane micro-architecture of megakaryocytes. Results: Salicylate significantly decreased the membrane capacitance of megakaryocytes, indicating the decreased number of invaginated plasma membranes, which was not detected by the fluorescent imaging technique. As shown by electron microscopy, salicylate actually halted the process of pro-platelet formation in megakaryocytes. Conclusion: This study demonstrated for the first time that salicylate inhibits the process of thrombopoiesis in megakaryocytes, as detected by the decrease in the membrane capacitance. Salicylate-induced changes in the membrane micro-architecture are thought to be responsible for its effects