610 Medizin und Gesundheit
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Characterization of the env gene and of two novel coding regions of the human spumaretrovirus
(1988)
Recombinant clones harboring retroviral DNA were established. The nucleotide sequence of the central and 3' region of the genome of the human spumaretrovirus was determined. The 5' end of the deduced protein sequence was homologaus to the endonuclease domain of retroviral reverse transcriptases. A small intergenic region is followed by a lang open reading frame of 985 aminoacid residues that according to its genomic location and structural features is a typical retroviral env gene. Surprisingly, the postenv region contains two open reading frames that encodes two novel retroviral genes, termed bel-l and bel-2. The 3' LTR is 963 nucleotides lang and contains the signal sequences characteristic for transcriptional regulation of retrovirus genomes.
Adenosine modulates a variety of physiological functions via membrane-bound receptors. These receptors couple via G proteins to adenylate cyclase and K+channels. The A1 subtype mediates an inhibition of adenylate cyclase and an opening of K+-channels, and the A2 subtype a Stimulation of adenylate cyclase. Both subtypes have been characterized by radioligand binding. This has facilitated the development of agonists and antagonists with more than 1000-fold A1 selectivity. A1-selective photoaffinity labels have been used for the biochemical characterization of A1 receptors and the study of their coupling to adenylate cyclase. Such selective ligands allow the analysis of the involvement of adenosine receptors in physiological functions. Selective interference with adenosine receptors provides new pharmacological tools and eventually new therapeutic approaches to a number of pathophysiological states.
Human heterophile antibodies (HHA) that are present in normal human sera (NHS)play an important role in hyperacute xenograft rejection. The aim of this study was to analyze the occurrence, mode of action and molecular specificity of HHA in NHS that are directed against xenogeneic Iymphocytes (isolated from mouse, rat, guinea pig, rabbit, cattle and pig) and isolated rat pancreatic islets. All sera contained variable amounts of HHA that killed the target cells via the classical complement pathway. The cytotoxic activity of these HHA was specifically inhibited by certain carbohydrates (a-D-melibiose, ß-Iactose, ß-gentiobiose, ß-cellobiose, D-mannose, N-acetyl-ß-D-mannosamine and a-D-rhamnose) and by rat IgM. By means of affinity chromatography with immobilized inhibitors we obtained an antibody preparation of mainly IgG type from NHS (up to 3.5 mg/IO ml serum) that reacted strongly with rat lymphocytes and isolated rat pancreatic islets. Though thus far residual xenospecific antibody activity has remained in the sera even after multiple affinity chromatography, these data suggest that specific elimination of HHA is feasible and that it may be thus possible to overcome a major obstacle to xenotransplantation.
The endogenous opioid system includes three major families of peptides [22): dynorphins (derived from pre-proenkephalin B); endorphins (derived from pre-proopiomelanocortin) and enkephalins (derived from pre-proenkephalin A). Multiple species of opioid peptides are derived from these major precursors and many of them possess potent cardiovascular properties. Multiple forms of opioid receptors have been defined in the central nervous system. Although the relationship of these receptors to the multiple actions of the opioid systems is not weil understood, some predications can be made: in vitro the dynorphin-related peptidesbind preferentially to kappa-opioid receptors; the enkephalins bind preferentially to delta and JL-opioid receptors and while beta-endorphin binds to mu- and delta-, but not to kappa-opioid receptors. While littleis known on the roJe ofthe opioid system in normal cardiovascular regulation, it has become clear that cardiovascular stress situations substantially modify the activity ofthe endogenous opioid system. This review focuses on the mu-opioid system in the hypothalamus with special emphasis on its potential roJe in cardiovascular control of both normal and pathophysiologic states.