Interaction of vanadate with membrane-bound ATPase from Mycobacterium phlei

Vanadate inhibited the formation of proton gradient and membrane potential as well as Ca2+ transport by everted membrane vesicles from Mycobacterium phlei, with half-maximal inhibition occurring at 5 to 14 microM. That this is due to the inhibition of the proton-translocating ATPase was suggested by the observation that the inhibition described above occurred only when the processes were driven by the hydrolysis of ATP but not when energized by the oxidation of succinate and NADH. Furthermore, vanadate did indeed inhibit ATP hydrolysis by these membrane vesicles. Although the inhibition of ATP hydrolysis could be demonstrated only in the presence of high concentrations (e.g. 11 mM) of Mg2+, this was presumably due to the fact that we were measuring the sum of ATP hydrolysis by both coupled and partially uncoupled enzymes. This is the first reported effect of vanadate on bacterial proton-translocating ATPase.     

Predator detection and avoidance by starlings under differing scenarios of predation risk

Practically all animals must find food while avoiding predators.An individual's perception of predation risk may depend on manyfactors, such as distance to refuge and group size, but it isunclear whether individuals respond to different factors ina similar manner. We tested whether flocks of foraging starlingsresponded in the same way to an increased perception of predationrisk by assessing three factors: (1) neighbor distances, (2)habitat obstruction, and (3) recent exposure to a predator.We found that in all three scenarios of increased risk, starlingsreduced their interscan intervals (food-searching bouts), whichincreased the frequency of their vigilance periods. We thenexamined how one of these factors, habitat obstruction, affectedescape speed by simulating an attack with a model predator.Starlings were slower to respond in visually obstructed habitats(long grass swards) and slower when they had their head downin obstructed habitats than when they had their head down inopen habitats. In addition, reaction times were quicker whenstarlings could employ their peripheral fields of vision. Ourresults demonstrate that different sources of increased riskcan generate similar behavioral responses within a species.The degree of visibility in the physical and social environmentaffects both the actual and perceived risk of predation.     

Selective 19-hydroxylase inhibition by an aromatase inhibitor, 4-hydroxyandrostenedione

19-Nor-deoxycorticosterone is a newly recognized mineralocorticoid which has been associated with some forms of genetic, experimental, and human hypertension. To further examine this relationship, specific inhibitors of 19-nor-deoxycorticosterone biosynthesis must be developed. Since 19-hydroxylation is the pivotal step in both 19-nor-deoxycorticosterone biosynthesis and aromatization of androgens to estrogens, we evaluated an aromatase inhibitor, 4-hydroxyandrost-4-ene-3,17-dione on the inhibition of 19-hydroxylation in both rat and human adrenal mitochondria in vitro and 19-nor-deoxycorticosterone production and blood pressure in spontaneously hypertensive rats in vivo. Adrenal mitochondria from 48 male Sprague-Dawley rats and 1 patient with an aldosterone-producing adenoma were incubated in the presence of deoxycorticosterone substrate both with and without 4-hydroxyandrost-4-ene-3,17-dione. 4-Hydroxyandrost-4-ene-3,17-dione produced significant inhibition of 19-hydroxy-deoxycorticosterone production in both rat and human adrenal mitochondria, with a smaller and not significant inhibition of corticosterone and 18-hydroxy-corticosterone. 4-Hydroxyandrost-4-ene-3,17-dione given subcutaneously to spontaneously hypertensive rats lowered 19-nor-deoxycorticosterone by 69% and completely abolished hypertension compared to Wistar-Kyoto controls. These data demonstrate that 4-hydroxyandrost-4-ene-3,17-dione is a specific inhibitor of 19-hydroxylase, that it lowers 19-nor-deoxycorticosterone production and prevents hypertension in the spontaneously hypertensive rat. These studies reinforce the possible pathogenic significance of 19-nor-deoxycorticosterone in hypertension in spontaneously hypertensive rats.     

Spectroscopic studies on copper (II) complexes of human lactoferrin

The interaction of Cu(II) with human lactoferrin has been studied as a function of pH, using electronic and electron spin resonance spectroscopy. Specific Cu(II) binding, with bicarbonate as the co-anion, occurs over the pH range 6 to 9. In the presence of a fiftyfold molar excess of oxalate, a monocopper(II) lactoferrin oxalate complex forms when the Cu(II) to protein is 1:1. If this ratio is increased to 2:1, a hybrid complex forms, in which the second copper utilizes bicarbonate as the co-anion, thus demonstrating, as for serum transferrin, a difference in the anion binding sites. The quenching of the intrinsic fluorescence of apolactoferrin is significantly less in the presence of oxalate than bicarbonate. The interaction of Cu(II) with apolactoferrin in the presence of the malonate, glycolate, thioglycolate, glycinate, and ethylenediaminetetraacetate ions has been examined.     

Inactivation of cephalothin and cephaloridine by Staphylococcus aureus

Benner, Ernest J. (University of Washington School of Medicine, Seattle), John V. Bennett, Jean L. Brodie, and William M. M. Kirby. Inactivation of cephalothin and cephaloridine by Staphylococcus aureus. J. Bacteriol. 90:1599-1604. 1965.-Marked differences were observed in the susceptibility of penicillinase-producing staphylococci to cephalothin and cephaloridine. All of 100 strains of penicillin G-resistant Staphylococcus aureus, with the use of a large inoculum, were found to be susceptible to 2 mug/ml of cephalothin, whereas only 50% were susceptible to this concentration of cephaloridine, and 15% required 15 mug/ml or more for inhibition. In contrast, penicillin G-sensitive strains were more susceptible to cephaloridine and did not show the marked inoculum effect observed with the cephaloridine-resistant strains. These differences were due to a much greater destruction of cephaloridine than of cephalothin by staphylococcal penicillinase. Cephaloridine-resistant staphyloccoci were stronger penicillinase producers than were susceptible strains, and the resistant strains were found to inactivate cephaloridine by hydrolysis of the beta-lactam ring. In population studies, cephaloridine-resistant cells differed from methicillin-resistant cells in that they decreased in numbers as the drug concentration was increased, and the survivors in higher drug concentrations were no more resistant than was the parent strain. Treatment with acriflavine eliminated resistance of the cells to both penicillin G and cephaloridine. It was concluded that cephaloridine resistance was due to hydrolysis by penicillinase, and that this was related to the pyridine ring substitution in the cephalosporanic acid nucleus.     

Anion binding by human lactoferrin: results from crystallographic and physicochemical studies.

The anion-binding properties of lactoferrin (Lf), with Fe3+ or Cu2+ as the associated metal ion, have been investigated by physicochemical and crystallographic techniques. These highlight differences between the two sites and in the anion-binding behavior when different metals are bound. Carbonate, oxalate, and hybrid carbonate-oxalate complexes have been prepared and their characteristic electronic and EPR spectra recorded. Oxalate can displace carbonate from either one or both anion sites of Cu2(CO3)2Lf, depending on the oxalate concentration, but no such displacement occurs for Fe2(CO3)2Lf. Addition of oxalate and the appropriate metal ion to apoLf under carbonate-free conditions gives dioxalate complexes with both Fe3+ and Cu2+, except when traces of EDTA remain associated with the protein, when hybrid complexes M2(CO3)(C2O4)Lf can result. The anion sites in the crystal structures of Fe2(CO3)2Lf, Cu2-(CO3)2Lf, and Cu2(CO3)(C2O4)Lf, refined at 2.2, 2.1, and 2.2 A, respectively, have been compared. In every case, the anion is hydrogen bonded to the N-terminus of helix 5, an associated arginine side chain, and a nearby threonine side chain. The carbonate ion binds in bidentate fashion to the metal, except in the N-lobe site of dicupric lactoferrin, where it is monodentate; the difference arises from slight movement of the metal ion. The hybrid complex shows that the oxalate ion binds preferentially in the C-lobe site, in 1,2-bidentate mode, but with the displacement of several nearby side chains. These observations lead to a generalized model for synergistic anion binding by transferrins.     

中国蝾螈科动物的反捕行为(正文)

中国的蝾螈科(Family Salamandridae)动物演化出了卓越的,多种多样的特征,而这些特征往往伴随着强烈的皮肤毒腺存在来保护自己免受捕食者的侵害。这些反捕食行为机制分布列入表1,并以照片解释其反捕行为,来用于已创建的定义和术语是非常重要的。这些定义和术语与不同反捕行为是密切相关的。该科中大多数蝾螈都有鲜艳的腹部色型,有皮肤分泌物毒素存在以警告捕食者。有的蝾螈,象兰尾蝾螈Cynops cyanura和中国瘰螈Paramesotriton chinensis甚至向上翻转显示腹部颜色。