Alterations in tissue Mg++, Na+ and spinal cord edema following impact trauma in rats

Alterations in water content and total tissue Na+ and Mg++ of rat spinal cord tissue were followed over time after a 100 g-cm impact injury to the T-9 spinal cord segment. Rats subjected to laminectomy but not trauma served as controls. In the injured segment there was a progressive increase in water content with increased Na+ and decreased Mg++ at 1 hour and 24 hours after trauma. At seven days, water and Na+ content remained elevated, whereas Mg++ levels had returned to preinjury baseline values. Because of its important role in many metabolic and physiological regulatory processes the early decline in Mg++ concentration after trauma may contribute to the development of secondary tissue damage after spinal cord injury.     

Determination of the depth of bromine atoms in bilayers formed from bromolipid probes

X-ray diffraction analysis has been performed on a series of 1-palmitoyl-2-dibromostearoyl-phosphatidylcholines (BRPCs) with bromine atoms at the 6, 7-, the 11, 12-, or the 15, 16-positions on the sn-2 acyl chains. The diffraction patterns indicate that, when hydrated, each of these lipids forms liquid-crystalline bilayers at 20 degrees C. For each lipid, electron density profiles and continuous Fourier transforms were calculated by the use of swelling experiments. In the electron profiles, high-density peaks, due to the bromine atoms, are observed. The separation between these bromine peaks in the profile decreases as the bromine atoms are moved toward the terminal methyl of the acyl chain. For the 6, 7- and 11, 12-bromolipids, experimental Fourier transforms can be approximated by the sum of the transform of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and the transform of two symmetrically placed peaks of electron density (the bromines). For the case of the 15, 16-bromolipids, a better fit is obtained for the transforms of a model bilayer where the thickness of the methylene chain region of the bilayer is 3 A greater than that of POPC. Our analysis indicates the following: for each of these bromolipids, the bromines are well localized in the bilayer; the distance of the bromines from the head-group-hydrocarbon boundary are 3.5, 8.0, and 14 A, for 6, 7-, 11, 12-, and 15, 16-BRPC, respectively; the bilayer thickness and perturbation to bilayer hydrocarbon chain packing caused by the bromine atoms depend on the position of the bromines on the hydrocarbon chain.     

Neuronal calcium channel antagonists. Discrimination between calcium channel subtypes using omega-conotoxin from Conus magus venom

The omega-conotoxins from the venom of fish-hunting cone snails are probably the most useful of presently available ligands for neuronal Ca channels from vertebrates. Two of these peptide toxins, omega-conotoxins MVIIA and MVIIB from the venom of Conus magus, were purified. The amino acid sequences show significant differences from omega-conotoxins from Conus geographus. Total synthesis of omega-conotoxin MVIIA was achieved, and biologically active radiolabeled toxin was produced by iodination. Although omega-conotoxins from C. geographus (GVIA) and C. magus (MVIIA) appear to compete for the same sites in mammalian brain, in amphibian brain the high-affinity binding of omega-conotoxin MVIIA has narrower specificity. In this system, it is demonstrated that a combination of two omega-conotoxins can be used for biochemically defining receptor subtypes and suggested that these correspond to subtypes of neuronal Ca2+ channels.     

Differential expression in male and female mouse liver of very similar mRNAs specified by two group 1 major urinary protein genes.

The major urinary proteins of the mouse are encoded by a large multigene family composed of several distinct groups of genes distinguished by differences in sequence and expression characteristics. The genes in the largest group (group 1) show greater than 99% pairwise similarity in their exons. By hybridization between RNA and a specifically designed oligonucleotide, we confirmed that genes of this group are expressed mainly in the liver. By using additional gene-specific oligonucleotide probes, we have been able to distinguish between the species of mRNA corresponding to two of these genes and to measure their abundance in male and female liver. Both mRNAs are present in male liver at high but different levels. Both are also present in female liver, one at a much lower level than in the male and the second at a very low level indeed. Both are present at male levels in the livers of females induced with testosterone. These results show unequivocally that the expression of different group 1 Mup genes is differentially influenced by the hormonal status of the mouse.     

The haplotype distribution of the ΔF508 mutation in cystic fibrosis families in Scotland

Summary The gene defective in cystic fibrosis (CF) has recently been isolated and the major mutation identified. The haplotype distribution of this mutation (ΔF508) has been determined for 215 CF chromosomes in the Scottish population. ΔF508 represents 73% of all CF mutations in this group. There remains considerable linkage disequilibrium between XV2c and KM19 and other mutations in the CF gene.     

Crystals of an ATPase fragment of bovine clathrin uncoating ATPase

A 44,000 Mr amino-terminal, clathrin-independent ATPase fragment of the bovine clathrin uncoating ATPase has been crystallized in a form suitable for X-ray diffraction studies. The crystals are orthorhombic, space group P2(1)2(1)2(1), a = 145.3 A, b = 65.0 A, c = 46.9 A, with one protein molecule per asymmetric unit (1 A = 0.1 nm).