Influence of changes in glutathione concentration on body temperature and tolerance to cerebral ischemia

Two compounds that deplete glutathione (buthionine sulfoximine and diethyl maleate) with different mechanisms of action decrease body temperature and increase tolerance to complete global cerebral ischemia, both correlating closely with the glutathione concentration decrease. Glutathione apparently participates in the regulations of these functional parameters. GSH diethyl ester does not influence the latter, though it increases moderately the GSH concentration. Injection of GSH ester into the cerebral ventricles or subcutaneously selectively increases the GSH level in the brain and liver. An influence of the brain on the glutathione system in the liver was revealed. Diethyl maleate and GSH ester increase the activity of glutathione metabolizing enzymes under certain conditions.     

Kir1.1 expression in embryonic kidney epithelia

K(+) channels may regulate cell cycling, cell volume, and cell proliferation. We have recently shown a role for an inwardly rectifying K(+) channel, Kir6.1/SUR2(B), in the regulation of cell proliferation during early kidney development. Here, we show that the protein of a further K(+) channel, Kir1.1 (ROMK), is also developmentally expressed in prenatal rat kidney epithelia. In the embryonic stage, Kir1.1 protein was localized to the plasma membrane of ureteric buds and collecting ducts, and of nephron stages up to the comma-shaped body. Experimental increase in cAMP upregulated Kir1.1b (ROMK2) mRNA abundance in ureteric buds. Kir1.1 protein was restricted to the distal nephron during later postnatal development and adulthood, as has been reported. In conclusion, we demonstrate redundancy of Kir channel expression in early embryonic kidney which could suggest that Kir1.1 acts in a similar way as Kir6.1/SUR2(B) to promote cell proliferation or other developmental functions.     

Hydration, structure, and molecular interactions in the headgroup region of dioleoylphosphatidylcholine bilayers: an electron spin resonance study

The relationship between bilayer hydration and the dynamic structure of headgroups and interbilayer water in multilamellar vesicles is investigated by electron spin resonance methods. Temperature variations of the order parameter of a headgroup spin label DPP-Tempo in DOPC in excess water and partially dehydrated (10 wt % water) show a cusp-like pattern around the main phase transition, Tc. This pattern is similar to those of temperature variations of the quadrupolar splitting of interbilayer D2O in PC and PE bilayers previously measured by 2H NMR, indicating that the ordering of the headgroup and the interbilayer water are correlated. The cusp-like pattern of these and other physical properties around Tc are suggestive of quasicritical fluctuations. Also, an increase (a decrease) in ordering of DPP-Tempo is correlated with water moving out of (into) interbilayer region into (from) the bulk water phase near the freezing point, Tf. Addition of cholesterol lowers Tf, which remains the point of increasing headgroup ordering. Using the small water-soluble spin probe 4-PT, it is shown that the ordering of interbilayer water increases with bilayer dehydration. It is suggested that increased ordering in the interbilayer region, implying a lowering of entropy, will itself lead to further dehydration of the interbilayer region until its lowered pressure resists further flow, i.e., an osmotic phenomenon.     

Structure-activity relationships in the hydrophobic interactions of polyphenols with cellulose and collagen

Polyphenol interactions with both cellulose and collagen in the solid state have been studied by using chromatography on cellulose and by evaluating the hydrothermal stability of the polyphenol treated sheepskin collagen. Twenty-four polyphenolic compounds were studied, including seven glucose-based gallotannins, five polyalcohol-based gallotannins, and twelve ellagitannins. In the cellulose-polyphenols systems, the polyphenol's affinity to cellulose is positively correlated with their molecular masses, the number of galloyl groups, and their hydrophobicity (logP). The polyphenol treatment increased the hydrothermal stability of collagen samples, and such effects are also positively correlated with the molecular masses, total number of galloyl groups and the hydrophobicity of polyphenols. Ellagitannins showed much weaker interactions with both biopolymers than gallotannins having similar molecular mass, the same number of galloyl groups, and the same number of phenolic hydroxyl groups. It is concluded that, for the polyphenol interactions with both cellulose and collagen, (1) the galloyl group of polyphenols is the functional group; (2) the strength of interactions are positively correlated with molecular size, the number of galloyl groups and the hydrophobicity of polyphenols; (3) the hydrophobic interactions are of great significance; and (4) the interactions are strongly dependent on the flexibility of galloyl groups.     

Oil/water and pre-emulsified oil/water (PIT) dispersions in a stirred vessel: Implications for fermentations

This study examines dispersions of rapeseed oil (RSO) in water by mechanical agitation under conditions mimicking those found in certain antibiotic fermentations; for example, in the presence of air, antifoam, and finely divided CaCO(3) particles. A problem with residual oil has been reported for such fermentations, and it has been suggested that the use of pre-emulsified oil can reduce this problem. Hence, the dispersion of a pre-emulsified oil produced by the "phase inversion temperature (PIT) method" has been evaluated. In both cases, the volume fraction of oil was 2%. For the RSO systems, a relatively high agitation speed was required to disperse the oil, especially in the presence of the particles and, when the agitation was stopped, separation occurred rapidly. The Sauter mean drop diameters depended on the system, being at an average energy dissipation rate of approximately 0.9 W kg(-1), 180 microm for RSO/water, 130 microm for RSO/water(antifoam)/air, 580 microm for RSO/water/CaCO(3), and 850 microm for RSO/water(antifoam)/air/CaCO(3). For the same four systems, the PIT emulsion, once dispersed, was very stable and the drop size was essentially independent of the operating conditions, with a Sauter mean diameter of approximately 0.3 microm. The implications of these findings for fermentations in which oil is used as a carbon source are assessed.     

Allometric and nonallometric components of Drosophila wing shape respond differently to developmental temperature

Phenotypic plasticity of wing size and shape of Drosophila simulans was analyzed across the entire range of viable developmental temperatures with Procrustes geometric morphometric method. In agreement with previous studies, size clearly decreases when temperature increases. Wing shape variation was decomposed into its allometric (24%) and nonallometric (76%) components, and both were shown to involve landmarks located throughout the entire wing blade. The allometric component basically revealed a progressive, monotonous variation along the temperature. Surprisingly, nonallometric shape changes were highly similar at both extremes of the thermal range, suggesting that stress, rather than temperature per se, is the key developmental factor affecting wing shape.     

Effects of salinity and temperature on reproductive and life span characteristics of clonal Artemia. (International Study on Artemia. LXVI)

An apomictic clone of the tetraploid parthenogenetic Artemia population from M. Embolon (Thessaloniki, Greece) was assayed for 10 reproductive and life span characteristics under laboratory conditions (in various salinity and temperature regimes). Salinity was proved to have significant impact on the majority of the characters used in this study. Discriminant function analysis gave an overall prediction of 97.32% over the three salinities (50, 80 and 120 ppt). The temperature of 30°C seemed to be an extreme one affecting significantly nearly all of the studied variables. The overall prediction according to the discriminant analysis was 94.69% among the three temperatures (22, 26 and 30°C). The clone performed best at 80 ppt and 22°C. The data presented in this study may generate useful suggestions to investigate the potentiality of using a single genetic lineage in order to visualize the effects of different environmental cues on a specific clone.     

Nest relocation in the golden spiny ant, <Emphasis Type="Italic">Polyrhachis ammon:</Emphasis> environmental cues and temporal castes

Summary Despite its apparent costs, nest relocation is a common phenomenon among ants. Polyrhachis ammon, a common ant in open habitats of eastern Australia, exhibits a high rate of colony emigration to new nest sites. We conducted a field survey and shading experiments in different seasons and years to determine which factors affect colony emigration in this species. We also compared morphological features characterising workers involved in adult transport to determine if workers performing different tasks belong-ed to discernible temporal castes. Nests that were abandon-ed after four weeks were smaller, although distance from a food source and low-level disturbance did not alter re-location rates. The effects of shading and nest temperature on nest survival varied between seasons, as did rates of nest relocation. Transporter workers could not be distinguished from foragers, but had greater mandibular wear and smaller dry mass than transportees. Our results suggest that cues promoting nest relocation in P. ammon may be the result of a combination of factors with varying temporal importance.     

Effect of pre-cooling, with and without thigh cooling, on strain and endurance exercise performance in the heat

Body cooling before exercise (i.e. pre-cooling) reduces physiological strain in humans during endurance exercise in temperate and warm environments, usually improving performance. This study examined the effectiveness of pre-cooling humans by ice-vest and cold (3 degrees C) air, with (LC) and without (LW) leg cooling, in reducing heat strain and improving endurance performance in the heat (35 degrees C, 60% RH). Nine habitually-active males completed three trials, involving pre-cooling (LC and LW) or no pre-cooling (CON: 34 degrees C air) before 35-min cycle exercise: 20 min at approximately 65% VO2peak then a 15-min work-performance trial. At exercise onset, mean core (Tc, from oesophagus and rectum) and skin temperatures, forearm blood flow (FBF), heart rate (HR), and ratings of exertion, body temperature and thermal discomfort were lower in LW and LC than CON (P<0.05). They remained lower at 20 min [e.g. Tc: CON 38.4+/-0.2 (+/-S.E.), LW 37.9+/-0.1, and LC 37.8+/-0.1 degrees C; HR: 177+/-3, 163+/-3 and 167+/-3 b.p.m.), except that FBF was equivalent (P=0.10) between CON (15.5+/-1.6) and LW (13.6+/-1.0 ml.100 ml tissue(-1) x min(-1)). Subsequent power output was higher in LW (2.95+/-0.24) and LC (2.91+/-0.25) than in CON (2.52+/-0.28 W kg(-1), P=0.00, N=8), yet final Tc remained lower. Pre-cooling by ice-vest and cold air effectively reduced physiological and psychophysical strain and improved endurance performance in the heat, irrespective of whether thighs were warmed or cooled.