Regulation of the abundance of renal sodium transporters and channels by vasopressin

Vasopressin plays a role in both salt and water balance in the kidney. Classic studies, utilizing isolated perfused tubules, have revealed that vasopressin increases sodium reabsorption in the kidney thick ascending limb and the collecting duct. Furthermore, the activity of several sodium transport proteins expressed in these segments, such as the bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2) and the epithelial sodium channel (ENaC), have been shown to be directly increased by vasopressin. Increased protein abundance might be one means through which sodium transporter and channel activity is enhanced. We have used immunoblotting and immunohistochemistry in order to investigate the regulation of abundance of the major sodium transporters and channels expressed along the renal tubule in response to vasopressin. Chronic (7-day) studies were performed in which vasopressin levels were elevated either endogenously by water restriction of Sprague-Dawley rats or exogenously through infusion of the vasopressin V2-receptor-selective agonist, dDAVP (1-deamino-8d-arginine-vasopressin), to Brattleboro rats. We found a significant increase in protein abundance for NKCC2 and the beta- and gamma-subunits of ENaC with either water restriction or dDAVP infusion. The alpha-subunit of Na-K-ATPase was increased by water restriction, but not by dDAVP infusion, and alpha-ENaC and the thiazide-sensitive cotransporter (NCC) were increased by dDAVP infusion but not by water restriction. Acute (60-min) in vivo exposure to dDAVP led to an increase in both beta- and gamma-ENaC abundance in kidney cortex homogenates, displaying the rapid nature of some of these changes. Overall these increases in sodium transporter and channel abundances likely contribute to both the antidiuretic and antinatriuretic actions of vasopressin.     

Impact of macrophage and dendritic cell subset elimination on antiviral immunity, viral clearance and production of type 1 interferon

We report herein that vesicular stomatitis virus (VSV) induced a concurrent primary Th1 (T helper 1) and Th2 cytokine response detectable ex vivo. Liposome-encapsulated clodronate-mediated elimination of CD8- marginal dendritic cells (DCs) and splenic macrophages (m Phi), but not CD8+ interdigitating DCs, prior to infection resulted in a markedly diminished chemokine and Th1 (IL-2, interferon-gamma) cytokine response, although the Th2 response (IL-4) remained relatively intact. Repopulation with marginal DCs and marginal metallophilic macrophages (MMM) restored Th1 cytokine profiles but did not restore chemokine responsiveness or reduce VSV-induced morbidity/mortality. Chemokine competency returned approximately 4 weeks post-depletion, which correlated temporally with repopulation of the spleen with marginal zone macrophages (MZM) and red pulp macrophages (RPM). Unexpectedly, virus-induced morbidity persisted for over 1 month post-depletion and was associated with virus dissemination and distinctive histological lesions in the liver. Depletion of interferon-producing plasmacytoid dendritic cells did not account for virus-induced morbidity because serum levels of type I interferon were not diminished in Cl2MBP-liposome-treated mice. Thus, distinct m Phi subsets are critical for chemokine production and viral clearance, and, in their absence, VSV disseminates even in the presence of high titers of interferon.     

Effects of long-term propranolol and octreotide on postprandial hemodynamics in cirrhosis: a randomized, controlled trial

BACKGROUND & AIMS: Postprandial increases in portal pressure may influence esophageal variceal rupture. The effects of chronic propranolol and octreotide (100 and 200 microg subcutaneously in a single dose) on postprandial hemodynamics were evaluated. METHODS: FIRST STUDY: 36 cirrhotic patients were studied at baseline and 30 and 60 minutes after a standard meal and then treated with propranolol (139 +/- 9 mg/d during 39 +/- 2 days). SECOND STUDY: After baseline measurements, patients were randomized into 3 groups: (1) placebo, (2) octreotide (100 microg), or (3) octreotide (200 microg) (n = 12 for each group). Thirty minutes postinjection a new baseline was established and measurements were repeated 30 and 60 minutes after the meal. RESULTS: First study: Baseline portal pressure was 18.1 +/- 1.2 mm Hg, 30 and 60 minutes after the meal it was 21.5 +/- 0.8 mm Hg and 20.5 +/- 0.8 mm Hg, respectively (both P < 0.01 vs. baseline). Cardiac index (CI) was 4.5 +/- 0.2, 4.8 +/- 0.2, and 4.9 +/- 0.2 L x min(-1) x m(-2), respectively (both P < 0.05 vs. baseline). Peripheral vascular resistance was 1012 +/- 56, 902 +/- 51 (P = NS), and 884 +/- 49 dynes x sec x cm(-5) (P< 0.05 vs. baseline), respectively. Second study: Propranolol and placebo did not blunt postprandial increase in portal pressure. Octreotide (100 microg) partially ameliorated postprandial increase in portal pressure. Octreotide (200 microg) significantly enhanced the portal hypotensive effect of propranolol and blunted the postprandial increase in portal pressure. CONCLUSIONS: Octreotide blunts postprandial increase in portal pressure not prevented by long-term propranolol administration.     

Retinal pigment epithelial function: a role for CFTR?

In the vertebrate eye, the photoreceptor outer segments and the apical membrane of the retinal pigment epithelium (RPE) are separated by a small extracellular (subretinal) space whose volume and chemical composition varies in the light and dark. Light onset triggers relatively fast (ms) retinal responses and much slower voltage and resistance changes (s to min) at the apical and basolateral membranes of the RPE. Two of these slow RPE responses, the fast oscillation (FO) and the light peak, are measured clinically as part of the electrooculogram (EOG). Both EOG responses are mediated in part by apical and basolateral membranes proteins that form a pathway for the movement of salt and osmotically obliged fluid across the RPE, from retina to choroid. This transport pathway serves to control the volume and chemical composition of the subretinal and choroidal extracellular spaces. In human fetal RPE, we have identified one of these proteins, the cystic fibrosis transmembrane conductance regulator (CFTR) by RT-PCR, immunolocalization, and electrophysiological techniques. Evidence is presented to suggest that the FO component of the EOG is mediated directly or indirectly by CFTR.     

Recovery from lactacidosis-induced glial cell swelling with the aid of exogenous anion channels

Hypotonic challenge induces transient swelling in glial cells, which is typically followed by a regulatory volume decrease (RVD). In contrast, lactic acidosis (lactacidosis) induces persistent cell swelling in astrocytes without an accompanying RVD. In the present study, we studied the mechanisms by which lactacidosis interferes with normal volume regulation in rat astrocytic glioma C6 cells. Following exposure of C6 cells to a hypotonic challenge, a current was detected that exhibited properties consistent with those of volume-sensitive outwardly rectifying (VSOR) anion channels. When exposed to in vitro conditions designed to simulate lactacidosis, C6 cells failed to respond to hypotonic stress with an RVD, and VSOR anion currents were not activated. When added to C6 cells, an anion channel-forming protein purified from Helicobacter pylori, VacA, was found to form anion-selective channels in the plasma membrane, and the activity of the VacA channel was not affected by lactacidosis (pH 6.2). Cells preincubated with VacA and then exposed to lactacidotic conditions underwent transient swelling followed by RVD. In contrast, application of a cation ionophore, gramicidin, failed to inhibit lactacidosis-induced persistent cell swelling. From these results, we conclude that inhibition of a volume-sensitive anion channel contributes to persistent swelling induced by lactacidosis in glial cells. Introduction of anion channel activity into glial cells might provide a novel approach for treating cerebral edema, which is associated with lactacidosis in cerebral ischemia or head injury.     

辛夷二氯甲烷提取物抗炎，抗过敏作用研究

目的：研究中药辛夷二氯甲烷提取物的药理作用。方法：采用体外,体内多种动物模型对辛夷二氯甲烷提取物进行了抗炎,抗过敏方面的研究。结果：辛夷二氯甲烷提取物对组胺（HA）、乙酰胆碱（Ach)引起的豚鼠离体回肠收缩具有显著的抑制作用,并能抑制卵白蛋白（OA）所致的豚鼠离体回肠过敏性收缩,对HAc引起的小鼠腹腔毛细血管通透性增高具有抑制作用,能显著抑制角叉菜胶引起的小鼠足肿胀,并减少前列腺素E2（PGE2）在炎症组织中产生。结论：辛夷二氯甲烷提取物具有明显的抗炎,抗过敏作用。     

8-Cl-cAMP induces cell cycle-specific apoptosis in human cancer cells

8-Cl-cyclic adenosine monophosphate (8-Cl-cAMP) has been known to induce growth inhibition and differentiation in a variety of cancer cells by differential modulation of protein kinase A isozymes. To understand the anticancer activity of 8-Cl-cAMP further, we investigated the effect of 8-Cl-cAMP on apoptosis in human cancer cells. Most of the tested human cancer cells exhibited apoptosis upon treatment with 8-Cl-cAMP, albeit with different sensitivity. Among them, SH-SY5Y neuroblastoma cells and HL60 leukemic cells showed the most extensive apoptosis. The effect of 8-Cl-cAMP was not reproduced by other cAMP analogues or cAMP-elevating agents, showing that the effect of 8-Cl-cAMP was not caused by simple activation of protein kinase A (PKA). However, competition experiments showed that the binding of 8-Cl-cAMP to the cAMP receptor was essential for the induction of apoptosis. After the treatment of 8-Cl-cAMP, cells initially accumulated at the S and G2/M phases of the cell cycle and then apoptosis began to occur among the population of cells at the S/G2/M cell cycle phases, indicating that the 8-Cl-cAMP-induced apoptosis is closely related to cell cycle control. In support of this assumption, 8-Cl-cAMP-induced apoptosis was blocked by concomitant treatment with mimosine, which blocks the cell cycle at early S phase. Interestingly, 8-Cl-cAMP did not induce apoptosis in primary cultured normal cells and non-transformed cell lines, showing that 8-Cl-cAMP-induced apoptosis is specific to transformed cells. Taken together, our results show that the induction of apoptosis is one of the mechanisms through which 8-Cl-cAMP exerts anticancer activity.     

从三元混合溶剂中回收二氯甲烷的试验

采用0．15g/ml醋酸钾乙二醇溶液作为分离剂，用加盐萃取精馏法对某抗生素原药合成所产生的二氯甲烷－甲醇－水三元体系的母液进行分离，找到了合适的试验条件，并得到纯度为99．6％的二氯甲烷。结果表明醋酸钾乙二醇溶液是一种来源方便、价格便宜、易于回收、分离效果较理想的加盐萃取剂。     

应用加压毛细管电色谱技术检测鸡蛋中四环素类农兽药残留的研究

目的 建立了鸡蛋样品中四环素类农药多残留同时检测的加压毛细管电色谱分析方法。方法 以二氯甲烷为沉淀剂处理鸡蛋样品,运用加压毛细管电色谱法进行快速检测。以甲醇-乙腈-20 mmol/L草酸溶液(pH=4.25)(10：20：70,v/v/v)作流动相,等度洗脱,外加电压为-4kV,检测波长为270 nm。结果 经方法学考察,4种四环素类药品土霉素、4-差向金霉素、盐酸金霉素、强力霉素在各自标准曲线浓度范围内线性良好,R2均在0.993以上。回收率为80.46％～100.49％,日内和日间精密度的相对标准偏差(RSD)均低于5％。结论 该方法简单方便,重现性好,准确可靠,回收率较高,适用于鸡蛋样品中抗生素多残留的测定。     

(1)H-MRS can detect aberrant glycosylation in tumour cells: a study of the HeLa cell line

Glycosylation is the most abundant and diverse form of post-translational modification of proteins. Two types of glycans exist in glycoproteins: N-glycans and O-glycans often coexisting in the same protein. O-glycosylation is frequently found on secreted or membrane-bound mucins whose overexpression and structure alterations are associated with many types of cancer. Mucins have several cancer-associated structures, including high levels of Lewis antigens characterized by the presence of terminal fucose. The present study deals with the identification of MR signals from N-acetylgalactosamine and from fucose in HeLa cells by detecting a low-field signal in one-dimensional (1D) spectra assigned to the NH of N-acetylgalactosamine and some cross peaks assigned to fucose in two-dimensional (2D) spectra. The increase of Golgi pH by treatment with ammonium chloride allowed the N-acetylgalactosamine signal assignment to be confirmed. Behaviour of MR peak during cell growth and comparison with studies from literature taken together made it possible to have more insight into the relationship between aberrantly processed mucin and the presence of non-processed N-acetylgalactosamine residues in HeLa cells. Fucose signals, tentatively ascribed to residues bound to galactose and to N-acetylglucosamine, are visible in both intact cell and perchloric acid spectra. Signals assigned to fucose bound to galactose are more evident in ammonium chloride-treated cells where structural changes of mucin-related Lewis antigens are expected as a result of the higher Golgi pH. A common origin for the N-acetylgalactosamine and fucose resonances attributing them to aberrantly processed mucin can be inferred from the present results.