Morphology of rabbit collecting duct.

Recently the assumed structural and functional homogeneity of the collecting duct (CD) has been questioned. The objective of this study was to determine if heterogeneity occurs in luminal surface membrane structure or in cytoplasmic configuration of cells in the collecting duct or both. Straight segments of cortical and medullary CD were examined in perfusion-fixed rabbit kidneys with scanning electron microscopy (SEM), light (LM) and transmission electron microscopy (TEM). Principal cells were the most abundant cells in all CD regions; intercalated cells comprised 37% of the cell population on the cortex, 18% in the outer medulla, and less than 1% in the inner medulla. SEM revealed two surface patterns among the ciliated principal cells: 1, located in the cortex and outer medulla, with few surface microvilli, and 2, located in the inner medulla, with abundant microvilli. Intercalated cells exhibited four distinctive luminal surface configurations: I, numerous short microvilli; II, both short and elongate microvilli; III, microplicae alone; and IV, both microvilli and microplicae. Intercalated cells with patterns I and II were predominant in the cortex, while cells with patterns III and IV were most common at the corticomedullary junction. TEM confirmed that marked variation existed in cytoplasmic structures of both principal and intercalated cells. These findings may either indicate the presence of several specific types of principal and intercalated cells or reflect different functional states of the principal and intercalated cells. Regardless of their significance, their presence must be considered in studies seeking to establish precise structural-functional relationships in this region of the rabbit renal tubule.     

Methods for collecting follicular oocytes from mares

A series of experiments was conducted to develop a procedure for consistent, repeatable collection of oocytes from the preovulatory follicle of the mare. In one experiment, in situ follicular aspiration with a needle and syringe was performed on 19 mares. From 37 aspirations, four oocytes were recovered (10% recovery rate). In a second experiment, ovaries were visualized via standing flank laparotomy during which two different aspiration techniques were used. Use of a needle and syringe as in the first experiment resulted in successful oocyte recovery in one of seven (14%) attempts. Aspiration via a continuous irrigation vacuum system (CIV), developed for use during laparotomy, resulted in collection of oocytes from six of 10 (60%) attempts. In the third experiment, oocytes were recovered from seven of 18 (38%) attempts at in situ follicular aspiration using a double-lumen needle attached to the CIV. In each experiment, some mares were subjected to stimulation of follicular maturation by exogenous hormones. Oocyte recovery was significantly increased in treated mares as compared with nontreated mares. Results indicate that collection of equine follicular oocytes by in situ aspiration is possible with moderate success. Oocytes apparently are not physically damaged by the procedure, as most retained either the corona radiata or the entire cumulus cell mass.     

昆虫血淋巴的收集技术与方法

血淋巴是昆虫生理生化研究的重要材料之一。文章分析归纳各类昆虫血淋巴的不同收集方法、收集前的昆虫准备以及收集后血淋巴的预处理,并结合该试验室研究阐述在收集昆虫血淋巴过程中的一些问题和经验,为能有效提取血淋巴提供一定的方法支持。     

Potassium secretion by the cortical collecting tubule

The isolated perfused rabbit cortical collecting tubule has been shown to actively transport K from bath to lumen. The first step in this process is active uptake of K across the basolateral membrane via and Na:K exchange pump as evidenced by: 1) basolateral localization and Na:K exchange properties of the ouabain-sensitive Na,K-ATPase, 2) ouabain sensitivity of the Na and K fluxes, 3) interdependence of the Na and K fluxes, and 4) ouabain-sensitivity of 42K uptake into the cell across the basolateral membrane. At the luminal border, a significant K permeability of the apical cell membrane has been identified using electrophysiological techniques. This K permeability is insensitive to the diuretic amiloride, and, thus, differs from the pathway for Na entry, which is highly amiloride sensitive. A significant K permeability of the paracellular pathway is not apparent. It is concluded that K secretion by the rabbit cortical collecting tubule occurs via a two-step process: active uptake of K across the basolateral membrane via the Na:K exchange pump, followed by passive efflux of K across the apical membrane via an amiloride-insensitive K conductive pathway.     

Copal and rattan collecting in the Philippines

Minor forest products such as rattan and Manila copal have long been an important source of cash income for indigenous forest collectors in Southeast Asia. Focusing on the Tagbanua of Palawan Island in the Philippines, the history and economic significance of forest collecting in the region are described. The paper also documents the growing scarcity of forest products in Palawan and discusses several policy options intended to help preserve rattan and copal resources.

     

CytReD: A database collecting human cytokinome information

The cytokines/related receptors system represents a complex regulatory network that is involved in those chronic inflammatory processes which lead to many diseases as cancers. We developed a Cytokine Receptor Database (CytReD) to collect information on cytokine receptors related to their biological activity, gene data, protein structures and diseases in which these and their ligands are implicated. This large set of information may be used by researchers as well as by physicians or clinicians to identify which cytokines, reported in the literature, are important in a given disease and, therefore, useful for purposes of diagnosis or prognostic. AVAILABILITY: The database is available for free at http://www.cro-m.eu/CytReD/     

Na-K pump current in the Amphiuma collecting tubule

There is strong evidence supporting the hypothesis of an electrogenic Na-K pump in the basolateral membrane of several epithelia. Thermodynamic considerations and results in nonepithelial cells indicate that the current carried by the pump could be voltage dependent. In order to measure the pump current and to determine its voltage dependence in a tight epithelium, we have used the isolated perfused collecting tubule of Amphiuma and developed a technique for clamping the basolateral membrane potential (Vbl) through transepithelial current injection. The transcellular current was calculated by subtracting the paracellular current (calculated from the transepithelial conductance measured in the presence of luminal amiloride) from the total transepithelial current. Basolateral membrane current-voltage (I-V) curves were obtained in conditions where the ratio of the pump current to the total basolateral membrane current had been maximized by loading the cells with Na+ (exposure to low-K+ bath), and by blocking the basolateral K+ conductance with barium. The pump current was defined as the difference of the current across the basolateral membrane measured before and 10-15 s after the addition of strophanthidin (20 microM) to the bath solution. With a bath solution containing 3 mM K+, the pump current was nearly constant in the Vbl range of -20 to -80 mV (52 +/- 5 microA.cm-2 at -60 mV) but showed a marked voltage dependence at higher negative Vbl (pump current decreased to 5 +/- 9 microA.cm-2 at -180 mV). In a 1.0 mM K bath, the shape of the pump I-V curve was similar but the amplitude of the current was decreased (24 +/- 4 microA.cm-2 at -60 mV). In a 0.1 mM K bath, the pump current was not significantly different from 0. Our results indicate that the basolateral Na-K pump generates a current which depends on the extracellular potassium concentration. With physiological peritubular concentration of K+ and in the physiological range of potential, the pump activity, measured as the pump-generated current, was independent of the membrane potential.