On the renal inner medullary concentration of sodium

Summary The principle of central volume is applied to the sodium and water contents of the inner medulla of the mammalian kidney. The analysis raises questions about the possibility of concentrating sodium ions in the inner medulla by a mechanism that postulates, in the same tissue segment, water withdrawal from the descending thin limb of the loop of Henle and sodium entry from the ascending thin limb.     

The renal plumbing system: aquaporin water channels

Aquaporins are channels that facilitate movement of water across lipid bilayers. They are expressed in multiple tissues and are essential for regulation of body water homeostasis. The kidney is the main organ responsible for this regulation, and at least seven aquaporins are expressed at distinct sites in the kidney. Aquaporin expression correlates with observed water permeability of each nephron segment: proximal tubule and descending thin limb of Henle have constitutive high water permeability due to expression of AQP1, whereas collecting duct water permeability is tightly regulated by the antidiuretic hormone vasopressin via regulation of AQP2. This review aims at providing insight into renal aquaporins, with special focus on AQP2.Received 9 December 2004; received after revision 8 April 2005; accepted 11 April 2005     

Cell culture models and animal models for studying the patho-physiological role of renal aquaporins

Aquaporins (AQPs) are key players regulating urinary-concentrating ability. To date, eight aquaporins have been characterized and localized along the nephron, namely, AQP1 located in the proximal tubule, thin descending limb of Henle, and vasa recta; AQP2, AQP3 and AQP4 in collecting duct principal cells; AQP5 in intercalated cell type B; AQP6 in intercalated cells type A in the papilla; AQP7, AQP8 and AQP11 in the proximal tubule. AQP2, whose expression and cellular distribution is dependent on vasopressin stimulation, is involved in hereditary and acquired diseases affecting urine-concentrating mechanisms. Due to the lack of selective aquaporin inhibitors, the patho-physiological role of renal aquaporins has not yet been completely clarified, and despite extensive studies, several questions remain unanswered. Until the recent and large-scale development of genetic manipulation technology, which has led to the generation of transgenic mice models, our knowledge on renal aquaporin regulation was mainly based on in vitro studies with suitable renal cell models. Transgenic and knockout technology approaches are providing pivotal information on the role of aquaporins in health and disease. The main goal of this review is to update and summarize what we can learn from cell and animal models that will shed more light on our understanding of aquaporin-dependent renal water regulation.     

Peptide YY enhances NaCl and water absorption in the rat colon in vivo.

Peptide YY (PYY) is thought to possess paracrine and endocrine functions. The highest concentrations of this peptide are in the colonic mucosa. The effect of PYY on electrolyte and water transport in the rat colon was studied in vivo. Under urethane anesthesia, rat colonic loops were perfused at a constant rate with physiological buffer solution containing phenol red as a nonabsorbable volume marker, and net movements of water, sodium, chloride and potassium in the perfused colon were determined every 10 min. Intravenous administration of PYY produced a dose-dependent increase in the net absorption of sodium chloride and water, as well as a decrease in the net secretion of potassium. PYY inhibited the reduction in net absorption of sodium chloride and water evoked by vasoactive intestinal peptide (VIP), but did not affect the VIP-evoked increase in net potassium secretion. These findings suggest that PYY acts as an enhancer of sodium chloride and water absorption and as an antagonist to VIP-induced secretion in the colon.     

Peptide YY enhances NaCl and water absorption in the rat colon in vivo

Peptide YY (PYY) is thought to possess paracrine and endocrine functions. The highest concentrations of this peptide are in the colonic mucosa. The effect of PYY on electrolyte and water transport in the rat colon was studied in vivo. Under urethane anesthesia, rat colonic loops were perfused at a constant rate with physiological buffer solution containing phenol red as a nonabsorbable volume marker, and net movements of water, sodium, chloride and potassium in the perfused colon were determined every 10 min. Intravenous administration of PYY produced a dose-dependent increase in the net absorption of sodium chloride and water, as well as a decrease in the net secretion of potassium. PYY inhibited the reduction in net absorption of sodium chloride and water evoked by vasoactive intestinal peptide (VIP), but did not affect the VIP-evoked increase in net potassium secretion.These findings suggest that PYY acts as an enhancer of sodium chloride and water absorption and as an antagonist to VIP-induced secretion in the colon.     

Molecular biology of water and salt regulation in the kidney

The kidney plays a central role in the regulation of the salt and water balance, which depends upon an array of solute and water transporters in the renal tubules and upon vascular elements in the various regions of the kidney. Many recent studies have improved our understanding of this process. In this review, we summarize the current data on the molecules involved in sodium and water transport in the renal tubules, focusing in particular on aquaporins and renal sodium transporters and channels.     

Binding of D-alpha-tocopherol to rat liver nuclear components.

When D-alpha-tocopherol is administered i.v. to vitamin E deficient rats, significant amounts of this vitamin are bound to a nucleoprotein complex in hepatic nuclei, and this complex can be solubilized by high concentrations of sodium chloride (0.6 M). The bound vitamin in this complex, extractable by ethanol, was found to be identical with authentic alpha-tocopherol by thin layer chromatography.     

The effect of hexamethonium on the secretion induced by sodium deoxycholate in the rat jejunum

Summary The i.v. administration of hexamethonium reduces or abolishes net water secretion induced by sodium deoxycholate in the denervated rat jejunum. The findings suggest that a local nervous reflex may be involved in bile salt-induced intestinal secretion.This research was sponsored by grants from the Swedish Medical Research Council (14X-2855), from the Swedish Society for Medical Sciences, from Magnus Bergvalls Stiftelse and from the Medical Faculty, University of Göteborg.     

Die Wirkung von synthetischem Oxytocin (Syntocinon) und Acetazolamid auf die Ausscheidung von Wasser,Natrium und Kalium

Summary Changes in water, sodium, and potassium excretion following administration of synthetic oxytocin (Syntocinon)—alone or in combination with acetazolamide— resemble the changes that occur after an equivalent dose of neurohypophysial extract containing oxytocin. Since the action of Syntocinon on water and sodium excretion is manifest when carbonic anhydrase in kidney tissue is fully inhibited by acetazolamide, it may be assumed that the mechanism whereby Syntocinon increases sodium excretion is independent of carbonic anhydrase. Oxytocin does not affect ultrafiltration in the glomeruli (Krause ⁴) and would therefore appear to modify the reabsorption or excretion process in the tubuli.     

Sidedness of the inhibitory effects of diamide on Na and water transport in amphibian skin

Summary Diamide, a thiol-oxidizing agent, blocks cAMP-mediated stimulation of Na and water transport when added to the outer solution bathing frog skin. No inhibition was found with diamide in the inner solution. These effects may be due to a perturbation of the thiol-disulfide status of specific components of the outer membrane of the epithelium.This work was supported by grants No. 3.1300.73 and 3.043-0.76 from the Swiss National Science Foundation.     

Decreased cyclic GMP levels in rat cecum mucosa during adaptive stimulation of Na-K-ATPase.

In rat cecal mucosa, Na-K-ATPase specific activity and sodium and fluid absorption were increased by giving polyethylene glycol administration with the drinking water. Whereas cyclic AMP levels were unchanged, cyclic GMP was reduced by about 50%. This finding suggests a regulatory role of cyclic GMP in intestinal sodium and fluid absorption.     

Water and electrolyte movements across the duodenal mucosa in laying hens during in vivo perfusion]

The net water movements through the duodenum in laying hens are directly dependent on the applied osmotic gradient. The passive water permeability (Lp) of the mucosa is 6 times higher during absorption (mucosa to serosa: 70 microliter/h/mOsm) than in the opposite direction (secretion: 11.5 microliter/h/mOsm) and its semi permeability is 0.49 (reflexion coefficient sigma). Net sodium and potassium movements seem to be linked to net water flux. Duodenal water absorption should not be explained by a process of passive permeability.     

Potentiating effect of aldosterone on the diuretic action of atrial extract

The typical stimulatory effect of a rat heart atrial extract on urinary water, sodium, potassium and kallikrein excretion is significantly increased by a previous administration of aldosterone (0.5 microgram/100 g b. wt) in the rat.     

Cellular events in denervated limb stumps ofAmbystoma larvae during re-innervation and subsequent regeneration

Summary Amputated, denervatedAmbystoma forelimbs undergo cellular dedifferentiation and slight resorption through 12 days post-amputation. Subsequently, as limb stumps become re-innervated, there occur mitosis, blastema formation, and regeneration. The initial increase in the mitotic index in once-denervated limb stumps is closely correlated with the presence of ingrowing nerve fibres.This work was supported by grant PCM 76-11807 from the National Science Foundation.     

Löslichkeitserhöhung von Sulfonamiden durch Pektin

Summary The addition of pectin increases the water solubility of different sulfonamide compounds and salicylic acid. It should be emphasized that this effect is not only observed with the acid pectin but also with neutral sodium pectinate.     

场助纳米二氧化钛薄膜光催化降解甲紫的研究

纳米二氧化钛是一种重要的无机功能材料。本文采用溶胶-凝胶法制备了TiO_2薄膜,利用"场助"影响其光催化特性。光催化实验以可能具有致癌性并且难以生化降解的三苯甲烷类染料——甲紫作为降解物质,用2100型分光光度计来测量降解率,以确定电场、磁场强度对光催化特性的影响。光催化实验结果表明,外加电场(未参与水的电解)、磁场对于协助光催化降解甲紫有着明显的效果。随着外加电场、磁场强度的增加,甲紫溶液的降解率有大幅提高。反应符合一级动力学方程。     

东太平洋海盆多金属结核的物质组构及形成环境意义

运用反光显微镜、电子探针对东太平洋CC区多金属结核中壳层构造及鲕粒的韵律层进行了初步的研究。结果表明，多金属结核的构造及其形成是环境的反映。结核中鲕粒的微纹层构造是结核形成时的一个较短时间段内海洋环境的演化反映。鲕粒纹层的反射率与鲕粒中的δ-MnO2结晶程度有关，每层的元素含量与形成时环境的Eh、pH值有关，元素含量的变化与结晶程度有着相同的变化规律。     

Molecular and Cellular Basis of Regeneration and Tissue Repair

Upon amputation of the urodele limb, the epidermal cells surrounding the amputation plane migrate to heal the wound. The resulting wound epidermis (WE) induces the regeneration process, resulting in blastema formation, cell division, and ultimately repatterning into a new limb. Despite its central role in the initiation of limb regeneration, little is known about how the WE forms. Here we discuss various models of WE formation and the experimental data in support of each.     

Effect of sublethal concentrations of sumithion on limb regeneration of fresh water field crab Oziotelphusa senex senex

The initiation and progress of regeneration following the removal of the left 4th walking leg were altered in the crab (Oziotelphusa senex senex) by exposure to sumithion. Depending on the concentration used, sumithion caused a complete inhibition of regeneration, a delay of initiation of limb bud development or a reduction of limb bud growth rate. Crustacean limb regeneration can also be used as a sensitive bioassay for studying the effects of environmental pollutants.     

Human Genome and Diseases:¶Apaf1 in developmental apoptosis and cancer: how many ways to die?

Apaf1 has been described as the core of the apoptosome. Deficiency in murine Apaf1 leads to embryonic lethality with a phenotype affecting many aspects of developmental apoptosis. In the developing brain, Apaf1 is a death regulator of the neuronal founder cells. Combined intercrosses of mouse lines mutant for members of the mitochondrial death pathway are providing us with some clues about the relative regulation existing among neuronal cell populations. Apaf1-deficient embryos display an interesting phenotype in the inner ear and in limb development, which involves different caspase-dependent and -independent pathways. Moreover, APAF1 is mutated in human melanomas, and its depletion contributes to malignant transformation in a mouse model of cancer. This review has a double aim: the analysis of the alternatives taken by the embryo to bring into the suicidal program different cells at different stages, and the relevance of APAF1 in the onset and progression of cancer. Received 5 March 2001; received after revision 19 April 2001; accepted 4 May 2001