Isolation of two saxitoxin-sensitive sodium channel subtypes from rat brain with distinct biochemical and functional properties

Summary Two different³H-saxitoxin-binding proteins, with distinct biochemical and functional properties, were isolated from rat brain using a combination of anion exchange and lectin affinity chromatography as well as high resolution size exclusion and anion exchange HPLC. The alpha subunits of the binding proteins had different apparent molecular weights on SDS-PAGE (Type A: 235,000; Type B: 260,000). When reconstituted into planar lipid bilayers, the two saxitoxin-binding proteins formed sodium channels with different apparent single-channel conductances in the presence of batrachotoxin (Type A: 22 pS; Type B: 12 pS) and veratridine (Type A: 9 pS; Type B: 5 pS). The subtypes were further distinguished by scorpion (Leiurus quinquestriatus) venom which had different effects on single-channel conductance and gating of veratridine-activated Type A and Type B channels. Scorpion venom caused a 19% increase in single-channel conductance of Type A channels and a 35-mV hyperpolarizing shift in activation. Scropion venom double the single-channel conductance of Type B channels and shifted activation by at least 85 mV.     

Different long-term effects of bilateral and unilateral nucleus basalis lesions on rat cerebral cortical neurotransmitter content

Young adult rats received either unilateral or bilateral ibotenic acid infusions in their nucleus basalis, destroying most of the cholinesterase-staining neurons in that region. Cerebral cortex levels of choline acetyltransferase, somatostatin, neuropeptide Y, and monoamines were then assayed 2.5 and 10 months after bilateral lesions, or, 2.5, 10, and 14 months after unilateral lesions. Entorhinal and cerebral cortex levels of several amino acid transmitters were also measured. As expected, choline acetyltransferase activity was decreased in the frontal cortex ipsilateral to the ibotenic acid infusion in unilaterally or bilaterally lesioned animals. Parietal cortex concentrations of somatostatin and neuropeptide Y were altered by lesioning in a complicated, time-dependent manner. Thus, while unilateral lesions transiently decreased or had no effect on these neuropeptide levels, bilateral lesions elevated the level of each neuropeptide by over 100% at 10 months. Other cortical transmitter systems investigated appeared to be less affected by nucleus basalis-lesions. Unilateral lesions had no effect on prefrontal cortex norepinephrine, serotonin, or dopamine content at 14 months post-lesioning. These different neurochemical effects of unilateral and bilateral nucleus basalis lesions may be important for developing a model for the trans-synaptic effects of cortical cholinergic deafferentation.     

Re-evalution of “Typothorax”meadei,a Late Triassic aetosaur from the United States

Aetosaur specimens from Howard County, Texas, USA, namedTypothorax meadei by Sawin (1947) represent a new genus here namedLongosuchus (type and only species -L. meadei). Longosu-chus is characterised by the possession of seven dentary teeth, a dentary excluded from the ventral margin of the lateral mandibular fenestra and by the angular, spinose lateral scutes throughout the dorsal region with lateral horns which have faceted sides.Longosuchus is found in mid-late Carnian strata in Texas, New Mexico and North Carolina, USA. Aetosaurs can be used to distinguish three successive biochrons in Late Triassic strata of the American Southwest, which are, in ascending order of age, theLongosuchus biochron, theStagonolepis biochron and theTypothorax biochron.     

Extracellular lipase from Pseudomonas aeruginosa is an amphiphilic protein.

Lipase (triacylglycerol acylhydrolase, EC 3.1.1.3) secreted by Pseudomonas aeruginosa PAC1R was purified from cell-free growth medium by preparative isoelectric focusing. After blotting the N-terminal amino acid sequence and the amino acid composition were determined and compared to P. fragi and P. cepacia lipases yielding significant homology between all three species. Additionally, a consensus sequence K-Y-P-i-v-l-V-H-G was identified residing at the N-terminus of Pseudomonas lipases and in the central part of Staphylococcus lipases. Treatment of lipase with the serine-specific inhibitor diethyl p-nitrophenyl phosphate caused a rapid and complete inhibition of enzyme activity indicating the presence of a serine at the catalytic site as expected from lipase consensus sequences. Upon charge-shift electrophoresis the electrophoretic mobility of purified lipase was shifted either anodally or cathodally in the presence of sodium deoxycholate and cetyltrimethylammoniumbromide, respectively. This result demonstrates that extracellular lipase of P. aeruginosa exhibits an amphiphilic character like intrinsic membrane proteins.     

A framework for the analysis of gender,intra-household dynamics,and livestock disease control with examples from Uasin Gishu district,Kenya

As livestock disease control programs in Africa begin to rely more upon para-professionals and livestock producers as deliverers of animal health care services, understanding the role different household members play in providing animal health care becomes increasingly important. This paper presents a framework for the analysis of gender aspects of livestock disease control based on a similar framework developed by Feldstein and Poats (1989). The utility of this framework is illustrated using household-level data collected from a district in central Kenya. Adult women and elderly men in the sample have primary responsibility for livestock care, and are therefore well placed to diagnose illness. Dipping and spraying of animals to prevent tick-borne and other diseases is the primary responsibility of adult males. Decisions regarding use of milk from the morning milking are more likely to be made by adult men. It is morning milk that is most often sold. Adult women, however, make decisions about use of evening milk, which is most often kept for household consumption. Knowledge of livestock diseases did not appear to vary significantly by gender, although some elderly men did possess extensive knowledge of indigenous disease categories and traditional remedies. The importance of recognizing gender issues in planning and implementing livestock disease control programs is discussed.     

Glutathione synthesis in maize genotypes with different sensitivities to chilling

The effect of chilling on enzymes, substrates and products of sulfate reduction, gultathione synthesis and metabolism was studied in shoots and roots of maize (Zea mays L.) genotypes with different chilling sensitivity. At full expansion of the second leaf, chilling at 12 °C inhibited dry weight increase in shoots and roots compared to controls at 25 °C and induced an increase in adenosine 5-phosphosulfate sulfotransferase and -glutamylcysteine synthetase (EC 6.3.2.2) activity in the second leaf of all genotypes tested. Glutathione synthetase (EC 6.3.2.3) activity was about one order of magnitude higher than -glutamylcysteine synthetase activity, but remained unchanged during chilling except for one genotype. During chilling, cysteine and glutathione content of second leaves increased to significantly higher levels in the two most chilling-tolerant genotypes. Comparing the most tolerant and most sensitive genotype showed that chilling induced a greater incorporation of³⁵S from [³⁵S]sulfate into cysteine and glutathione in the chilling-tolerant than in the sensitive genotype. Chilling decreased the amount of³⁵S-label incorporated into proteins in shoots of both genotypes, but had no effect on this incorporation in the roots. Glutathione reductase (EC 1.6.4.2) and nitrate reductase (EC 1.6.6.1) activity were constitutively higher in the chilling-tolerant genotypes, but showed no changes in most examined genotypes during 3 d at 12 °C. Our results indicate that in maize glutathione is involved in protection against chilling damage.Abbreviations APSSTase adenosine 5-phosphosulfate sulfotransferase - EC -glutamylcysteine - GR glutathione reductase - OSH glutathione - NR nitrate reductase We thank M. Suter for preparing [³⁵S]adenosine 5-phosphosulfate, Dr. A. Fleming (both our Institute) for correcting the English and M. Soldati (Eschlikon, Switzerland) for his help with the plant material. This work was supported by COST 814 Crop development for the wet and cool regions of Europe.     

Reproductive and neonatal outcomes in captive bred baboons (Papio hamadryas)

Abstract: Baboons are widely used in biomedical research. Although it is widely held that Papio hamadryas breed well in captivity, each established colony has a different reproductive success often hypothesised to be due to husbandry practices. The National Baboon Colony in Australia is a unique colony that houses Papio hamadryas to mimic that structure seen in the wild. In this article; we have analysed their reproductive parameters and neonatal outcomes. The success of the colony husbandry practices was demonstrated by lack of maternal mortality, low foetal morbidity, and known maternal and paternal linage.     

Listeria monocytogenes phosphatidylinositol (PI)-specific phospholipase C has low activity on glycosyl-PI-anchored proteins.

The ability of the phosphatidylinositol-specific phospholipase C (PI-PLC) from Listeria monocytogenes to hydrolyze glycosyl phosphatidylinositol (GPI)-anchored membrane proteins was compared with the ability of the PI-PLC from Bacillus thuringiensis to hydrolyze such proteins. The L. monocytogenes enzyme produced no detectable release of acetylcholinesterase from bovine, sheep, and human erythrocytes. The cleavage of the GPI anchors of alkaline phosphatase from rat and rabbit kidney slices was less than 10% of the cleavage seen with the PI-PLC from B. thuringiensis. Activity for release of Fc gamma receptor IIIB (CD16) on human granulocytes was also low. Variations in pH and salt concentration had little effect on the release of GPI-anchored proteins. Our data show that L. monocytogenes PI-PLC has low activity on GPI-anchored proteins.     

Dissolution of sulphur particles by Thiobacillus ferrooxidans: substrate for unattached cells

The growth of Thiobacillus ferrooxidans on sulphur is known to proceed through the attachment of cells to the sulphur particles. Experiments, However, show that the cells in the liquid phase, which are not attached to the sulphur particles, also grow. It has been shown through the use of a two-compartment membrane reactor that this increase is partially due to the release of ions, corresponding to partially oxidized of sulphur, into the solution by the attached cells. The main soluble ion has been found to the thiosulphate, but traces of sulphite have also been detected. (c) 1993 John Wiley & Sons, Inc.