Rapid, simple and sensitive high-performance liquid chromatographic method for detection and determination of acyclovir in human plasma and its use in bioavailability studies

A rapid, simple and sensitive reversed-phase high-performance liquid chromatographic (HPLC) method has been developed for the measurement of acyclovir concentrations in human plasma and its use in bioavailability studies is evaluated. Unchanged acyclovir has been quantified without the introduction of an internal standard using the present method. Human plasma proteins were selectively precipitated by the addition of 7% perchloric acid to spiked plasma samples or to the plasma samples obtained after acyclovir administration to human volunteers and the mixture was spun at 1000 g for 10 min. The supernatant was directly injected into a Novaflex C₁₈ column and detected at 254 nm. The mobile phase consisted of octane sulfonic acid buffer (pH 2.5) and methanol (92:08). The limit of quantitation for acyclovir in plasma was 20 ng/ml, which enabled the determination of the area under the curve (AUC) more precisely, that is, it is much closer to its extrapolated value. The present method has been successfully applied to samples from bioavailability studies.     

Ontogeny of the hyobranchial apparatus in the salamanders Ambystoma talpoideum (Ambystomatidae) and Notophthalmus viridescens (Salamandridae): The ecological morphology of two neotenic strategies

Comparison of metamorphosis of skull and hyobranchial system in two species of neotenic salamanders reveals two different types of neoteny. Ambystoma talpoideum is completely neotenic owing to delayed metamorphosis. Notophthalmus viridescens exhibits limited neoteny as a result of incomplete metamorphosis. Morphological details of neoteny are compared to life history in both species in order to discuss the ecological morphology of the two neotenic strategies. Comparisons to Taricha granulosa, Triturus vulgaris, and Ambystoma gracile indicate that these two strategies are widely employed and may represent familial patterns.     

Molecular genetics of peripheral populations of Nova Scotian Unionidae (Mollusca: Bivalvia)

Peripheral populations of eight species of freshwater bivalves (Unionidae.) extending their geographic ranges into Nova Scotia, Canada, were examined electrophoretically to determine both the extent of genetic variability within such populations, and whether the hypothesized pathway of colonization across the Isthmus of Chignecto is reflected in patterns of genetic resemblance among these populations. The Nova Scotian species examined could be separated into two groups based on levels of observed heterozygosity and levels of variability in allele frequencies. The first group is characterized by low levels of heterozygosity and polymorphism compared with north-eastern American populations, and in the case of one species, Elliptio complanala, considerable variability in allele frequencies among populations occurring in similar habitats in different drainages. Populations of E. complanata from Nova Scotia can be differentiated from conspecific populations on the southern Atlantic Slope by possession of fast alleles at two loci. Multivariate analyses define subgroups within populations of E. complanata consistent with hypothesis that the species invaded Nova Scotia by way of the Isthmus of Chignecto, and then split into two groups, one of which colonized Cape Breton to the north and the other of which colonized southern areas of the Province. The second group of Nova Scotian species is characterized by little reduction in heterozygosity and polymorphism compared with values observed among north-eastern American conspecifics or congeners, little variability in allele frequencies from population to population, and little evidence to suggest that these species were dependent on the land bridge to invade the Province. The type of dispersal is hypothesized to be responsible, in part, for these differences: larvae of species in the first group rely on a parasitic attachment to fish with territorial habits limited to fresh water, and are thus likely to invade new drainages separated by salt water by chance, in small numbers, and in stepping-stone fashion. Species in the second group parasitize anadromous or saltwater tolerant hosts, are likely to be introduced into new habitats in greater numbers and/or receive greater amounts of gene flow subsequent to colonization, and seem less dependent on land-bridges to colonize new habitats.     

Predicted class-I aminoacyl tRNA synthetase-like proteins in non-ribosomal peptide synthesis

Background  

Recent studies point to a great diversity of non-ribosomal peptide synthesis systems with major roles in amino acid and co-factor biosynthesis, secondary metabolism, and post-translational modifications of proteins by peptide tags. The least studied of these systems are those utilizing tRNAs or aminoacyl-tRNA synthetases (AAtRS) in non-ribosomal peptide ligation.     

Typification of Linnaean taxa of annual Poaceae: Poeae related to Vulpia and Desmazeria

STACE, C. A. & JARVIS, C. E., 1985. TypiHcation of Linnaean taxa of annual Poaceae: Poeae related to Vulpia and Desmazeria. The status and typification of 15 Linnaean species of annual grasses related to Vulpia and Desmazeria are discussed. Of these 15, eight are represented by holotypes or lectotypes in LINN, two by lectotypes in Herb. A. van Royen (L), and one by a neotype in LINN. One (Festuca marina) is based on a pre-Linnaean polynomial and is represented by a lectotype in Herb. Sloane (BM); one (Cynosurus durus) has no known type specimens and we have chosen a Barrelier (1714) illustration as lectotype; one (Nardus aristatus) is an illegitimate name change for Nardus incurvus Gouan, for which we have selected a Scheuchzer (1719) illustration as lectotype; and finally Festuca incrassala appeared on a cancelled page of Species Plantarum and has no nomenclatural standing.     

High Altitude Frogs (Rana kukonoris) Adopt a Diversified Bethedging Strategy in the Face of Environmental Unpredictability

Environmental unpredictability can influence strategies of maternal investment among eggs within a clutch. Models predict that breeding females should adopt a diversified bet-hedging strategy in unpredictable environments, but empirical field evidence from Asia is scarce. Here we tested this hypothesis by exploring spatial patterns in egg size along an altitudinal gradient in a frog species(Rana kukunoris) inhabiting the Tibetan Plateau. Within-clutch variability in egg size increased as the environment became variable(e.g., lower mean monthly temperature and mean monthly rainfall at higher altitudes), and populations in environments with more unpredictable rainfall produced eggs that were smaller and more variable in size. We provide support for a diversified bet-hedging strategy in high-altitude environments, which experience dynamic weather patterns and therefore are of unpredictable environmental quality. This strategy may be an adaptive response to lower environmental quality and higher unpredictable environmental variance. Such a strategy should increase the likelihood of breeding success and maximize maternal lifetime fitness by producing offspring that are adapted to current environmental conditions. We speculate that in high-altitude environments prone to physical disturbance, breeding females are unable to consistently produce the optimal egg size due to physiological constraints imposed by environmental conditions(e.g., duration of the active season, food availability). Species and populations whose breeding strategies are adapted to cope with uncertain environmental conditions by adjusting offspring size and therefore quality show a remarkable degree of ability to cope with future climatic changes.