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.     

Functional torque-velocity and power-velocity characteristics of elite athletes

Technical limitations of some isokinetic dynamometers have called into question the validity of some data on human muscle mechanics. The Biodex dynamometer has been shown to minimize the impact artefact while permitting automatic gravity correction. This dynamometer was used to study quadriceps muscle torque and power generation in elite power (n = 6) and elite endurance (n = 7) athletes over 12 randomly assigned isokinetic velocities from 30 degrees.s-1 to 300 degrees.s-1. The angle at peak torque varied as a negative, linear function of angular velocity, with the average angle across test velocities being 59.5 degrees (SD 10.2 degrees). Power athletes developed greater peak torque at each angular velocity (P less than 0.05) and experienced a 39.7% decrement in torque over the velocity range tested. Endurance athletes encountered a 38.8% decline in peak torque. Torques measured at 60 degrees of knee flexion followed a similar trend in both groups; however the greatest torques were recorded at 60 degrees.s-1 rather than at 30 degrees.s-1. Leg extensor muscle power increased monotonically with angular velocity in both power (r2 = 0.728) and endurance athletes (r2 = 0.839); however these curves diverged significantly so that the power athletes produced progressively more power with each velocity increment. These inter group differences probably reflected a combination of natural selection and training adaptation.     

DNA sequence has an effect on the extent and kinds of alkylation of DNA by a potent carcinogen

A system has been developed to study the effects of base sequence (neighboring bases) upon the alkylation of guanine (G) and adenine (A) bases in DNA. The study was performed on the synthetic polydeoxyribonucleotides, poly(dG).poly(dC), poly(dG-dC).poly(dG-dC), poly(dA).poly(dT), poly(dA-dT).poly(dA-dT), poly(dA-dC).poly(dG-dT), poly(dA-dG).poly(dC-dT), as well as calf thymus DNA. Each polynucleotide was treated with N-[3H]methyl-N-nitrosourea (MNU), depurinated, and the freed alkylpurines separated by HPLC and quantitated by liquid scintillation counting. The amounts of 3-methylguanine (3-MG), 7-MG, and O6-MG relative to guanine, and 3-methyladenine (3-MA) and 1-MA plus 7-MA relative to adenine, and also the O6-MG/7-MG ratios were highly reproducible for a given polynucleotide. Significant differences were found in the amounts of each of the methylpurines formed when compared among the six synthetic polynucleotides and DNA. This evidence is interpreted as an effect upon alkylation which is ultimately dependent upon the base sequence. These findings may have significance in defining the specificity of chemical carcinogens in terms of the susceptability to modification of nucleotide sequences such as those found in certain oncogenes.     

Ultrastructural Changes During Germination of Dictyostelium discoideum Spores

Spores of Dictyostelium discoideum undergo significant changes in fine structure during germination. The mitochondria progressively become less dense and lose their peripherally attached ribosomes, and the tubuli become more pronounced as germination proceeds. During this period, the three-layered spore wall breaks down in two stages: first, the outer and middle layers are ruptured as a unit, and, second, the inner wall is breached. Crystals and dark (lipid) bodies disappear shortly before or during emergence of the myxamoebae. Autophagic vacuoles are found in dormant spores and throughout the entire germination process. The addition of cycloheximide to germinating spores inhibited the loss of the crystals and dark (lipid) bodies. In addition, the drug inhibited the breakdown of the inner wall layer. Cycloheximide did not prevent the formation of the water expulsion vesicle or the apparent function of the autophagic vacuoles.     

Patterns of divergence during evolution of alpha 1-proteinase inhibitors in mammals

alpha 1-Proteinase inhibitor (alpha 1-PI), a member of the serine proteinase inhibitor superfamily, has a primary role in controlling neutrophil elastase activity within the mammalian circulation. Several studies have indicated that the reactive center region of alpha 1-PI, the amino acid sequence of which is critical to recognition of and binding to target proteinases, is highly divergent within and among species. This appears to be a consequence of accelerated rates of evolution that may have been driven by positive Darwinian selection. In order to examine this and other features of alpha 1-PI evolution in more detail, we have isolated and sequenced cDNAs representing alpha 1- PI mRNAs of the mouse species Mus saxicola and Mus minutoides and have compared these with a number of other mammalian alpha 1-PI mRNAs. Relative to other mammalian mRNAs, the extent of nonsynonymous substitution is generally high throughout the alpha 1-PI mRNA molecule, indicating greater overall rates of amino acid substitution. Within and among mouse species, the 5'-half of the mRNA, but not the 3'-half, has been homogenized by concerted evolution. Finally, the reactive center is under diversifying or positive Darwinian selection in murid rodents (rats, mice) and guinea pigs yet is under purifying selection in primates and artiodactyls. The significance of these findings to alpha 1-PI function and the possible selective forces driving evolution of serpins in general are discussed.