Comparison of content with synthesis,uptake and breakdown of GABA in substantia nigra of unoperated,hemitransected and kainate-treated rats

The synthesis, high affinity uptake and degradation of GABA were compared with GABA content measured simultaneously in the nigras of unoperated, hemitransected and kainate-treated rats. In intact animals nigral GABA concentration was linearly related to glutamate decarboxylase activity, but not to GABA aminotransferase (GABA-T) or GABA uptake. One week after hemitransection all three parameters showed a linear reduction with GABA content, suggesting striatonigral GABA neurones may account for as much as 90% of the GABA and GAD, 31% of the GABA-T and 58% of GABA uptake sites in whole nigra. Nigral kainate treatment unexpectedly reduced all four parameters in parallel by as much as 50%, consistent with the formation of an unselective lesion.     

Unmasking effect of alamethicin on the (Na+,K+)-ATPase, beta-adrenergic receptor-coupled adenylate cyclase, and cAMP-dependent protein kinase activities of cardiac sarcolemmal vesicles

A mechanism for the activating effect of alamethicin on membrane enzymes was investigated, using a purified preparation of cardiac sarcolemmal vesicles. (Na+,K+)-ATPase, beta-adrenergic receptor-coupled adenylate cyclase, and cAMP-dependent protein kinase activities were measured. alamethicin increased ouabain-sensitive (Na+,K+)-ATPase activity of sarcolemmal vesicles 5- to 7-fold and adenylate cyclase activity 2.5- to 4-fold. Adenylate cyclase retained its sensitivity to the beta-adrenergic agonist isoproterenol after membranes were treated with alamethicin. Alamethicin caused a 4- to 6-fold increase in the number of detectable (Na+,K+)-ATPase enzymic sites, but no increase ws noted for the number of muscarinic-cholinergic receptor-binding sites. Phosphorylation of endogenous proteins of sarcolemmal vesicles by an intrinsic cAMP-dependent protein kinase activity was stimulated 5- to 7-fold by alamethicin. The regulatory subunit of the membrane-bound cAMP-dependent protein kinase was labeled with the photoaffinity probe 8-azido-adenosine 3':5'[32P]monophosphate (8-N3-[32P]cAMP), and it migrated with an apparent molecular weight of 55,000 in sodium dodecyl sulfate polyacrylamide gels. Alamethicin stimulated autophosphorylation of the regulatory subunit by [gamma-32P]ATP 6-fold and incorporation of of 8-N3-[32P]cAMP into the subunit 2.6-fold. The results suggest that alamethicin disrupts membrane barriers of sarcolemmal vesicles, which are mostly right side out, giving substrates and activators access to enzymic sites in the interior of the vesicles, while preserving functional coupling of enzymes to their effectors.     

Presence of two forms of fumarase (fumarate hydratase E.C. 4.2.1.2) in mammalian cells: Immunological characterization and genetic analysis in somatic cell hybrids. Confirmation of the assignment of a gene necessary for the enzyme expression to human chromosome 1

Two major forms of fumarate hydratase have been resolved in extracts prepared from a wide variety of mammalian cells by electrophoresis. Fractionation experiments with human and mouse cells suggest that one form (the slower migrating) is localized in the mitochondria, whereas the other form is predominant in the cytoplasm. Analysis of the segregation of the enzyme forms in human-mouse somatic cell hybrids indicates that a gene(s) necessary for the expression of both forms can be assigned to human chromosome 1 (confirmation of a previous assignment by van Someren et al., 1974). Electrophoretic analysis suggests that the two forms may be interrelated. Furthermore, they both exhibit identical reactivity toward anti-fumarate hydratase antiserum. It is suggested that a modification of one form may occur in vivo and that the modification may be important in determining the intracellular localization of the enzyme.     

Incorporation of methionine-[methyl-2H3] and mevalonic acid-[2-14C,(4R)-4-3H1] into Phycomyces blakesleeanus sterols

Ergosterol, episterol, 4α-methyl-5α-ergosta-8,24(28)-dien-3β-ol and 24-methylene-24,25-dihydrolanosterol, isolated from Phycomyces blakesleeanus grown in the presence of methionine-[methyl-²H₃], each contained two deuterium atoms; lanosterol, however, was unlabelled. The ¹⁴C:³H atomic ratio of the following sterols isolated from P. blakesleeanus grown in the presence of mevalonic acid-[2-¹⁴C,(4R)-4-³H₁], was: ergosterol, 5:3; episterol, 5:4; ergosta-5,7,24(28)-trien-3β-ol, 5:3; 4α-methyl-5α-ergosta-8,24(28)-dien-3β-ol, 5:4; 24-methylene-24,25-dihydrolanosterol, 6:5; lanosterol, 6:5. The significance of these results in terms of ergosterol biosynthesis is discussed.     

Global biogeography of warning coloration in the butterfly Danaus chrysippus

Warning coloration provides a textbook example of natural selection, but the frequent observation of polymorphism in aposematic species presents an evolutionary puzzle. We investigated biogeography and polymorphism of warning patterns in the widespread butterfly Danaus chrysippus using records from citizen science (n = 5467), museums (n = 8864) and fieldwork (n = 2586). We find that polymorphism in three traits controlled by known mendelian loci is extensive. Broad allele frequency clines, hundreds of kilometres wide, suggest a balance between long-range dispersal and predation of unfamiliar morphs. Mismatched clines for the white hindwing and forewing tip in East Africa are consistent with a previous finding that the black wingtip allele has spread recently in the region through hitchhiking with a heritable endosymbiont. Light/dark background coloration shows more extensive polymorphism. The darker genotype is more common in cooler regions, possibly reflecting a trade-off between thermoregulation and predator warning. Overall, our findings show how studying local adaptation at the global scale provides a more complete picture of the evolutionary forces involved.     

High affinity inhibitors of the dopamine transporter (DAT): novel biotinylated ligands for conjugation to quantum dots

Compounds capable of inhibiting the dopamine transporter protein (DAT) that can be conjugated to cadmium selenide/zinc sulfide/core shell nanocrystals may be used to image the location and distribution of the DAT in neuronal cell membranes. This letter describes the synthesis of biotinylated analogs of the DAT antagonists GBR 12909 and GBR 12935 that can be attached to streptavidin coated cadmium selenide/zinc sulfide/core shell nanocrystals.