Patterns of vegetation surrounding springs in Goshen Bay,Utah County,Utah U.S.A.

Saline meadows in Goshen Bay, Utah County, Utah, USA, occur interspersed among large areas of salt playa. Springs irrigate these meadows which show concentric vegetational zones surrounding each spring. Each vegetational zone demonstrates its own unique dominant vascular plant species. The central zone is dominated primarily by Scirpus americanus, the middle zone by Eleocharis palustris and the outer zone by Juncus balticus, Distichlis spicata and Muhlenbergia asperifolia. As distance increases from the springs, pH and soluble salt concentration increase, while percent organic matter, percent moisture and phosphorus decrease. With the increase in salt levels and decrease in water levels, halophytic plant species generally increase with distance from the springs.     

Controls on calcium ion fluxes in injured or shocked corn root cells: Importance of proton pumping and cell membrane potential

Passive influx of ⁴⁵Ca²⁺ into non-growing corn root tissue ( Zea mays L.) was increased as a result of actions (cutting, rubbing, chilling, heating, acidifying) or agents (cyanide, uncouplers) known to depolarize the cell membrane, and was decreased by actions (washing) or agents (fusicoccin) known to hyperpolarize it. These responses indicate the presence of Ca²⁺ channels which are voltage controlled. If the injuries were extensive, however, voltage control was lost and hyperpolarization with fusicoccin was expressed by increased ⁴⁵Ca²⁺ influx. Control could be regained by tissue washing, and millimolar levels of external Ca²⁺ would protect against loss of control. Influx of Ca²⁺ was strongly inhibited by La³⁺, but only weakly by verapamil. Intact roots showed greater cold shock sensitivity in maturing cells than in growing cells. We conclude that corn roots normally restrict Ca²⁺ influx by a mechanism linked to hyper-polarization of the plasmalemma.
Calcium ions which enter cold-shocked tissue are partially extruded during the early phase of recovery by a process stimulated by fusicoccin and subject to uncoupling.     

Purification of human plasma retinol-binding protein by hydrophobic interaction chromatography

Human plasma retinol-binding protein has been purified to homogeneity by a simple method that requires an ammonium sulfate fractionation, a hydrophobic interaction chromatography on phenyl-Sepharose, which dissociates the complex between retinol-binding protein and its carrier, transthyretin, and a gel filtration on Sephadex G-50. The yield of pure protein is comparable or higher than that obtained with the more complex procedures previously reported.     

Na+/Ca2+ countertransport in plasma membrane of rat pancreatic acinar cells

Summary The presence of a coupled Na⁺/Ca²⁺ exchange system has been demonstrated in plasma membrane vesicles from rat pancreatic acinar cells. Na⁺/Ca²⁺ exchange was investigated by measuring⁴⁵Ca²⁺ uptake and⁴⁵Ca²⁺ efflux in the presence of sodium gradients and at different electrical potential differences across the membrane (=) in the presence of sodium. Plasma membranes were prepared by a MgCl₂ precipitation method and characterized by marker enzyme distribution. When compared to the total homogenate, the typical marker for the plasma membrane, (Na⁺+K⁺)-ATPase was enriched by 23-fold. Markers for the endoplasmic reticulum, such as RNA and NADPH cytochromec reductase, as well as for mitochondria, the cytochromec oxidase, were reduced by twofold, threefold and 10-fold, respectively. For the Na⁺/Ca²⁺ countertransport system, the Ca²⁺ uptake after 1 min of incubation was half-maximal at 0.62 mol/liter Ca²⁺ and at 20 mmol/liter Na⁺ concentration and maximal at 10 mol/liter Ca²⁺ and 150 mmol/liter Na⁺ concentration, respecitively. When Na⁺ was replaced by Li⁺, maximal Ca²⁺ uptake was 75% as compared to that in the presence of Na⁺. Amiloride (10^–3 mol/liter) at 200 mmol/liter Na⁺ did not inhibit Na⁺/Ca²⁺ countertransport, whereas at low Na⁺ concentration (25 mmol/liter) amiloride exhibited dose-dependent inhibition to be 62% at 10^–2 mol/liter. CFCCP (10^–5 mol/liter) did not influence Na⁺/Ca²⁺ countertransport. Monensin inhibited dose dependently; at a concentration of 5×10^–6 mol/liter inhibition was 80%. A SCN^– or K⁺ diffusion potential (=), being positive at the vesicle inside, stimulated calcium uptake in the presence of sodium suggesting that Na⁺/Ca²⁺ countertransport operates electrogenically, i.e. with a stoichiometry higher than 2 Na⁺ for 1 Ca²⁺. In the absence of Na⁺, did not promote Ca²⁺ uptake. We conclude that in addition to ATP-dependent Ca²⁺ outward transport as characterized previously (E. Bayerdörffer, L. Eckhardt, W. Haase & 1. Schulz, 1985,J. Membrane Biol. 84:45–60) the Na⁺/Ca²⁺ countertransport system, as characterized in this study, represents a second transport system for the extrusion of calcium from the cell. Furthermore, the high affinity for calcium suggests that this system might participate in the regulation of the cytosolic free Ca²⁺ level.     

Ca-pumps in smooth muscle: one in plasma membrane and another in endoplasmic reticulum

For several years it has been debated whether the Ca-pump in smooth muscle is located in the plasma membrane or in the endoplasmic reticulum (alias sarcoplasmic reticulum). Experimental evidence using skinned smooth muscle cells and subcellular membrane fractions isolated from a number of smooth muscles is reviewed here to hopefully resolve this issue. The inescapable conclusion is that there are two modes of nonmitochondrial ATP-dependent Ca-transport. The first one, unaffected by oxalate, is localized in the plasma membranes and the second, potentiated by oxalate, is localized in the endoplasmic reticulum. Clear experiments to delineate the roles of the two pumps in the excitation-contraction cycle of the smooth muscle remain to be conducted.     

Effect of atropine on plasma gastrin and somatostatin concentrations during sham feeding in man

The purpose of these studies was to measure circulating gastrin and somatostatin concentrations during sham feeding in humans and to evaluate the effect of two doses of intravenous atropine on circulating concentrations of these peptides. Gastric acid and bicarbonate secretion and pulse rate were also measured. Sham feeding increased plasma gastrin concentrations by approximately 15 pg/ml but had no effect on plasma somatostatin-like immunoreactivity (SLI). A small dose of atropine (5 micrograms/kg) augmented plasma gastrin concentrations during sham feeding significantly (P less than 0.01), but did not affect plasma SLI. Atropine also significantly inhibited gastric acid secretion and gastric bicarbonate secretion (by 62% and 52%, respectively), but pulse rate was not affected. A larger dose of atropine (15 micrograms/kg intravenously) suppressed plasma gastrin concentrations significantly compared to the smaller 5 micrograms/kg atropine dose (P less than 0.02), so that plasma gastrin concentrations when 15 micrograms/kg atropine was given were not significantly different from those during the control study. 15 micrograms/kg atropine reduced gastric acid and bicarbonate secretion by 81% and 66%, respectively, and also increased pulse rate by 15 min-1. These studies indicate that small doses of atropine enhance vagally mediated gastrin release in humans, probably by blocking a cholinergic inhibitory pathway for gastrin release. Although the nature of this cholinergic inhibitory mechanism is unclear, we found no evidence to incriminate somatostatin. Our finding that the larger dose of atropine reduced serum gastrin concentrations compared with the smaller dose suggests that certain vagal-cholinergic pathways may facilitate gastrin release.     

Isolation and characterization of plasma membrane fromAcanthamoeba culbertsoni

A rapid method for preparation of plasma membrane fromAcanthamoeba culbertsoni involving toluene treatment followed by lithium bromide extraction is described. In the plasma membrane preparation, 5′-nucleotidase, Na⁺ + K⁺ -ATPase, Mg²⁺ -ATPase and glucose-6-phosphatase activities were enriched. The membrane preparation was free from nucleic acid, cytochrome P-450 and cytochrome b5. Amino acid (¹⁴C-Ieucine) was not incorporated in the plasma membrane in 2 min. Succinic dehydrogenase was not detectable in the plasma membrane preparation. The molar ratio of cholesterol and phospholipids was 0.95 which is characteristics for plasma membranes. Under electronmicroscopy the preparation was homogenous without any other component of the cell. Plasma membrane proteins and glycoproteins were separated on acrylamide gel electrophoresis     

NaCl effects on 4-desmethylsterol composition of plasma-membrane-enriched preparations from citrus roots

Abstract The free 4-desmethylsterol composition of plasma-membrane-enriched preparations from white fibrous roots of Rangpur lime (Citrus reticulata var. austera hybrid?), Kharna khatta (C. kharna Raf.) and Etrog citron (C. medica L.) seedlings grown in the presence of 0, 50, or 100 mol m^?3 NaCl for 28 d was quantitated by gas chromatography (GC) on analytical capillary (SE-54 fused silica) columns and the sterols were identified by combined gas chromatography-mass spectrometry (GC-MS). Only three 4-desmethylsterols were positively identified by GC-MS, viz. campesterol, stigmasterol and sitosterol. Cholesterol could not be positively identified in any of the membrane preparations. Campesterol levels were generally similar for all treatments and for all three genotypes, approximating 30% of the total free 4-desmethylsterol content of the plasma membranes. At all levels of salinity (0, 50 or 100 mol m^?3 NaCl) sitosterol levels decreased in the order Rangpur lime > Kharna khatta > Etrog citron and stigmasterol levels decreased in the reverse order. The ratio of sitosterol to stigmasterol was highest in Rangpur lime and lowest in Etrog citron at each level of salinity and was reduced by salt treatment in all three genotypes. Salt-induced reductions in the ratio of ‘more planar’ to ‘less planar’ sterols correlated inversely with the accumulation of Cl^? in the leaves of the three genotypes suggesting a role for plasma membrane sterols in the Cl^? exclusion mechanism. A model relating sterol structure, membrane sterol composition and membrane permeability to Cl^? exclusion ability in citrus is presented.     

Zinc is a constituent of bovine heart cytochrome c oxidase preparations

Cytochrome c oxidase preparations from bovine heart muscle contain 1 zinc per 2 irons. Metal contents of nine preparations determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) show that Cu, Fe and Zn are the only metals present in significant amounts with average Cu/Fe, Fe/Zn, and Cu/Zn atom ratios of 1.3, 2.1 and 2.8, respectively. Removal of adventitious copper results in a Cu:Fe:Zn stoichiometry of 2:2:1. The zinc is tightly bound. Dialysis against a solution of 1,10-phenanthroline at pH 7.4 or an acidic buffer (pH 4.4) does not remove Zn. Dialysis against 0.8 M KCN at pH 10 causes partial loss of both Cu and Zn. This is the first evidence for the presence of Zn in a cytochrome c oxidase.