Systematics within Gyps vultures: a clade at risk

Background  

Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis.     

Gene expression in Brassica campestris showing a hypersensitive response to the incompatible pathogen Xanthomonas campestris pv. vitians

Xanthomonas campestris pv. vitians, a pathogen of lettuce, elicits a hypersensitive response within 12 hours of inoculation into Brassica leaves, characterized by tissue collapse, loss of membrane integrity, vein blockage and melanin production. In contrast, the compatible pathogen, X. c. pv. campestris, has no visible effects on leaves for 48 hours, after which inoculated areas show chlorosis which eventually spreads, followed by rotting.mRNA was prepared from leaves inoculated with suspensions of both pathovars or with sterile medium up to 24 hours following inoculation. In vitro translation of total and poly A⁺ RNA in rabbit reticulocyte lysate in the presence of ³⁵S methionine followed by separation of the polypeptide products by 2D-PAGE, allowed comparison of the effects of these treatments on plant gene expression. Major changes in gene expression were observed as a consequence of the inoculation technique. In addition, after inoculation with X. c. vitians, up to fifteen additional major polypeptides appeared or greatly increased by four hours. Some of these had disappeared by nine hours and several more had appeared. No major polypeptides disappeared or decreased greatly in intensity following inoculation with X. c. vitians.     

Domains of neuronal heparan sulphate proteoglycans involved in neurite growth on laminin

Summary A single neuronal cell assay of neurite growth was utilized to determine types and domains of neuronal proteoglycans involved in neurite growth on laminin. Perturbations of biosynthesis and processing, enzymatic digestion with specific lyases, and competition with glycosaminoglycan side chains produced complementary data consistent with a molecular model implicating glycosaminoglycan (GAG) residues of heparan sulphate proteoglycans (HSPGs) in neurite growth. The observations suggest that HSPGs promote neurite growth on laminin by bridging between binding domains for HSPGs on laminin and on the neuronal cell surface, and that the bridge is tethered at both ends by noncovalent interactions between the binding domains and GAG side chains. Sulphation of the GAGs of HSPGs appears to be critical to the tethering and/or neurite growth-promoting activity of neuronal HSPGs.     

Adenine nucleotide synthesis de novo in mature rat cardiac myocytes

Inadequate oxygenation of cardiac muscle leads to rapid loss of high energy compounds essential for contractile function. ATP can be regenerated by synthesis de novo, a route operating at a relatively slow rate in the heart. Myocytes isolated from mature rat heart have been used to measure the rate of ATP synthesis de novo from both [14C]glycine and [14C]ribose. Incorporation of glycine into ATP is accelerated 10-fold in the presence of 1 mM ribose. Myocytes also accumulate both precursors into IMP and four other metabolites on the de novo synthesis pathway. These metabolites represent 80% of the glycine entering the pathway. The potential of de novo synthesis for restoration of adenine nucleotides appears to be limited by the rates of early reactions, adenylosuccinate synthetase being only one of the enzymes operating at a sufficiently slow rate to make this pathway an inherently weak route for the restoration of normal energy status in post-ischemic myocardium. Interventions are being sought to alleviate these apparent metabolic delays.     

Environmental versus social factors as determinants of growth in nestlings of a communally breeding bird

Summary Nestlings of the communally breeding Greycrowned Babbler (Pomatostomus temporalis) were studied to discover if supplemental feeding by auxiliary birds at nests enhanced their growth. Growth of wing, bill, tarsus and weight was measured. Growth curves were fitted by computer using a commercial program (MLAB). Our data provided little support for possible sibling competition. A significant component of the variance in asymptote and growth constant for some variables could be attributed to differences among nests. Environmental variables such as temperature and rainfall were much more strongly associated with nestling growth than were the numbers of auxiliary birds feeding broods.     

Synthesis of RNA by Rhodomicrobium vannielii swarmer cells

Abstract Protein synthesis in Rhodomicrobium vannielii swarmer cells, incubated anaerobically in the dark, is dependent upon a rifampicin-sensitive step, indicating a dependence upon de novo RNA synthesis. In addition, toluene treatment has shown that the motile, non-differentiating swarmer cells have the capacity to initiate and sustain RNA synthesis. The major form of the DNA-dependent RNA polymerase responsible for this RNA synthesis has been identified.     

Genetic Determinants of Circadian Rhythmicity in Neurospora

Timex, a strain of Neurospora crassa which exhibits a circadian rhythm of conidia formation in growth-tube cultures, has been found to differ from wild-type strains by two genes. One gene, inv, is responsible for an invertase deficiency, whereas the second gene, bd, is of unknown function. Both genes map independently from other genes known to induce Neurospora rhythmicity. The inv gene is not essential for the timex phenotype because bd strains express that phenotype on certain media. Although inv strains do exhibit some rhythmicity of their own, the rhythmicity apparently is not a direct result of the invertase deficiency, since there is no correlation between invertase level and rhymicity in 29 strains tested. Of the 29 strains tested, 20 exhibited some rhythmicity in growth-tube cultures, suggesting that morphological manifestations of rhythmicity in Neurospora may result from the function or the loss of function of numerous genes, or both. There was no correlation in these strains between rhythmicity and (i) genetic background; (ii) geographical origin; or (iii) nutritional requirements.     

Gene-Enzyme Relationships in Neurospora Invertase

A spontaneous, single-gene mutation responsible for a total lack of invertase activity in Neurospora crassa is described. The mutation is believed to lie in the structural gene for invertase, since an immunologically cross-reacting protein is made by the mutant strain. In addition, there was no evidence for a defect in regulation of invertase activity or synthesis by the following criteria. (i) The invertaseless condition was recessive in heterokaryons; (ii) no invertase inhibitor was found in mutant extracts by mixing experiments; and (iii) none of the several sugars able to induce activity in wild-type strains was able to induce activity in the mutant strain. It was also discovered that most of the wild-type enzyme (55 to 75%) cannot be washed free from the rapidly sedimenting cell debris. This finding provided additional support for the hypothesis that Neurospora invertase is located within or about the cell wall.