Effects of continued pentaerythritol tetranitrate administration on myocardial circulation and metabolism

Zusammenfassung Die Untersuchungsergebnisse stützen die Vorstellung, dass die gute Wirkung der prophylaktischen Anwendung von Pentaerythritol-tetranitrat bei Patienten mit Coronarinsuffizienz auf Abnahme der Herztätigkeit und Zunahme der Herzmuskelleistung, nicht aber auf eine Zunahme des Coronarkreislaufes zurückzuführen ist.     

Cyanophages infecting the oceanic cyanobacterium Prochlorococcus

Prochlorococcus is the numerically dominant phototroph in the tropical and subtropical oceans, accounting for half of the photosynthetic biomass in some areas. Here we report the isolation of cyanophages that infect Prochlorococcus, and show that although some are host-strain-specific, others cross-infect with closely related marine Synechococcus as well as between high-light- and low-light-adapted Prochlorococcus isolates, suggesting a mechanism for horizontal gene transfer. High-light-adapted Prochlorococcus hosts yielded Podoviridae exclusively, which were extremely host-specific, whereas low-light-adapted Prochlorococcus and all strains of Synechococcus yielded primarily Myoviridae, which has a broad host range. Finally, both Prochlorococcus and Synechococcus strain-specific cyanophage titres were low (< 10(3) ml(-1)) in stratified oligotrophic waters even where total cyanobacterial abundances were high (> 10(5) cells x ml(-1)). These low titres in areas of high total host cell abundance seem to be a feature of open ocean ecosystems. We hypothesize that gradients in cyanobacterial population diversity, growth rates, and/or the incidence of lysogeny underlie these trends.     

Dominant and recessive deafness caused by mutations of a novel gene, TMC1, required for cochlear hair-cell function

Positional cloning of hereditary deafness genes is a direct approach to identify molecules and mechanisms underlying auditory function. Here we report a locus for dominant deafness, DFNA36, which maps to human chromosome 9q13-21 in a region overlapping the DFNB7/B11 locus for recessive deafness. We identified eight mutations in a new gene, transmembrane cochlear-expressed gene 1 (TMC1), in a DFNA36 family and eleven DFNB7/B11 families. We detected a 1.6-kb genomic deletion encompassing exon 14 of Tmc1 in the recessive deafness (dn) mouse mutant, which lacks auditory responses and has hair-cell degeneration. TMC1 and TMC2 on chromosome 20p13 are members of a gene family predicted to encode transmembrane proteins. Tmc1 mRNA is expressed in hair cells of the postnatal mouse cochlea and vestibular end organs and is required for normal function of cochlear hair cells.     

A protein kinase homologue controls phosphorylation of ganciclovir in human cytomegalovirus-infected cells.

Human cytomegalovirus (HCMV) is a major pathogen in immunosuppressed individuals, including patients with acquired immune deficiency syndrome. The nucleoside analogue ganciclovir (9-(1,3-dihydroxy-2-propoxymethyl)-guanine) is one of the few drugs available to treat HCMV infections, but resistant virus is a growing problem in the clinic and there is a critical need for new drugs. The study of ganciclovir-resistant mutants has indicated that the selective action of ganciclovir depends largely on virus-controlled phosphorylation in HCMV-infected cells. The enzyme(s) responsible have not been identified. Here we report that the HCMV gene UL97, whose predicted product shares regions of homology with protein kinases, guanylyl cyclase and bacterial phosphotransferases, controls phosphorylation of ganciclovir in HCMV-infected cells. A four-amino-acid deletion of UL97 in a conserved region, which in cyclic AMP-dependent protein kinase participates in substrate recognition, causes impaired ganciclovir phosphorylation. The implications of these results for antiviral drug development and drug resistance are discussed.     

Aetiology of AIDS--antibodies to human T-cell leukaemia virus (type III) in haemophiliacs

Human T-cell leukaemia virus type III (HTLV-III) is suspected of having a key role in the pathogenesis of acquired immune deficiency syndrome (AIDS). Epidemiological data suggest that AIDS is transmitted by an infectious agent through intimate contact with body secretions, blood or blood products. To maintain haemostasis, many haemophiliac patients depend on commercially prepared clotting concentrates made from large multi-donor plasma pools and are thus at increased risk of developing the disease. We report here that, using indirect membrane immunofluorescence and radioimmunoprecipitation with SDS-polyacrylamide gel electrophoresis, we have detected antibodies to HTLV-III in 30 of 47 (64%) asymptomatic haemophiliacs and in all of three haemophiliacs who either had or soon developed AIDS. Of 34 samples drawn before 1984, 18 (53%) were antibody-positive, whereas of 16 samples drawn during 1984, 15 (94%) were positive (P less than or equal to 0.002). These data suggest that exposure to HTLV-III antigens is widespread among asymptomatic haemophiliacs.     

A mutation that prevents GTP-dependent activation of the alpha chain of Gs

Membrane-bound G proteins carry information from receptors on the outside of cells to effector proteins inside cells. The alpha subunits of these heterotrimeric proteins bind and hydrolyse GTP and control the specificity of interactions with receptor and effector elements. Signalling by G proteins involves a cycle in which the inactive alpha beta gamma-GDP complex dissociates to produce alpha*-GTP, which is capable of activating the effector enzyme or ion channel; the alpha*-GTP complex hydrolyses bound GTP and reassociates with beta gamma to form the inactive complex. We have characterized a mutation that interrupts this GTP-driven cycle in alpha s, the alpha-chain of Gs, the G protein that stimulates adenylyl cyclase. The mutation converts a glycine to an alanine residue in the presumed GDP-binding domain of alpha s. The location and biochemical consequences of this mutation suggest a common mechanism by which binding of GTP or ATP may induce changes in the conformation of a number of nucleoside triphosphate binding proteins.