Genetic divergence in South African Wildebeest: comparative cytogenetics and analysis of mitochondrial DNA.

The blue and the black wildebeest, Connochaetes taurinus and C. gnou, are currently classified as congeneric, but previous reports have placed C. taurinus in its own genus, Gorgon. To further clarify the evolutionary relationship between these two species, we examined and compared their mitotic chromosomes and mitochondrial DNA (mtDNA). No species-specific G-banded or C-banded chromosomal markers were found, and we conclude that the karyotypes are invariant at the level of resolution obtained. An evolutionary divergence time of approximately 1 million years was calculated from mtDNA restriction fragment data, indicating a close phylogenetic relationship for the two wildebeest species. The low nucleotide diversity detected within the black wildebeest (0.09%) is thought to reflect the recent population bottleneck to which the species has been subjected. In contrast, the limited heterogeneity (0.02%) within the South African blue wildebeest herds sampled in this study was surprising, and we argue that for many populations, especially those on smaller reserves, this may reflect common descent from a small number of animals through management-controlled translocations.     

Anti-insulin antibody structure and conformation. I. Molecular modeling and mechanics of an insulin antibody.

A knowledge-based three-dimensional model of an anti-insulin antibody, 125, was constructed using the structures of conserved residues found in other known crystallographic immunoglobulins. Molecular modeling and mechanics were done with the 125 amino acid sequences using QUANTA and CHARMm on a Silicon Graphics 4D70GT workstation. A minimal model was made by scaffolding using crystallography coordinates of the antibody HyHEL-5, because it had the highest amino acid sequence homology with 125 (84% light chain, 65% heavy chain). The three hypervariable loop turns that are longer in 125 than in HyHEL-5 (L1, L3, and H3) were modeled separately and incorporated into the HyHEL-5 structure; then other amino acid substitutions were made and torsions optimized. The 125 model maintains all the structural attributes of an antibody and the structures conserved in known antibodies. Although there are many polar amino acids (especially serines) in this site, the overall van der Waals surface shape is determined by positions of aromatic side chains. Based on this model, it is suggested that hydrogen bonding may be key in the interaction between the human insulin A chain loop antigenic epitope and 125.     

Spectral properties of cobalt carboxypeptidase A. Interaction of the metal atom with anions

At pH greater than 7 the absorption and magnetic circular dichroic spectra of cobalt carboxypeptidase A are insensitive to anions [Latt, S. A., & Vallee, B. L. (1971) Biochemistry 10, 4263-4270], but at pH less than 6 chloride and other anions perturb them in a manner specific for each anion. Lowering of the pH apparently facilitates the entry of an anion into the metal coordination sphere, suggesting that an acidic group normally stabilizes a metal-coordinated water molecule against displacement. The lack of sensitivity to anions at pHs between 7 and 9--when the enzyme is maximally active--and its evident abolition upon protonation of an active-site group are consistent with this interpretation. Selective modification of cobalt carboxypeptidase at Glu-270 using a carbodiimide affinity reagent generates sensitivity to anions at pH 7 very similar to that of the unmodified enzyme at pH approximately 5. This suggests that the group stabilizing the metal-coordinated water is the catalytically essential carboxylate of Glu-270. These and related results provide evidence for a mechanistically important interaction of Glu-270 with a metal-bound water molecule.     

Genetic Variation and the Reproduction of Cordylanthus maritimus ssp. maritimus to Sweetwater Marsh, California

This study evaluated the genetic consequences of a reintroduction of the endangered annual plant Cordylanthus maritimus ssp. maritimus to Sweetwater Marsh (San Diego County, California). A survey of 21 enzyme loci in natural populations revealed that genetic diversity is very low and is primarily found as rare alleles at a few loci, making this species especially susceptible to the loss of alleles and heterozygosity through genetic drift. The reintroduction was performed in 1991 and 1992 by sowing seeds (collected from Tijuana Estuary) in numerous small patches of suitable habitat. For this study, leaf tissue was collected from all plants in all patches during flowering in 1995 and surveyed for genotype at the three enzyme loci that are polymorphic at Tijuana Estuary. Rare alleles were absent in 27 out of 30 patches for Pgm-1, in 17 out of 30 patches for Pgm-2, and in 10 out of 11 patches for Mdh-1. In all, half of the patches lacked any rare allele. Rare alleles tended to occur in patches with few individuals. Overall rare allele frequency was lower than in the colonies from which seeds were collected at two of the three loci, and heterozygosity was reduced. The Sweetwater Marsh population is at risk of losing most of its genetic variation at enzyme loci through the extinction of patches with few individuals. Future reintroduction attempts should attempt to create contiguous sets of patches or to periodically reseed existing patches to reduce the loss of genetic variation.     

New labdane resin acids from Pinus elliottii

Slash pine needles and cortex oleoresin have been found to contain a new major diterpene constituent, imbricataloic acid. The closely related imbricatoloic acid, previously reported only in Araucaria imbricata, was found to be present in small amounts in slash pine needle extract. Spectral data are given for an unidentified diterpene alcohol isolated from the cortex oleoresin.     

Status and reaction to anoxia of rat fetuses developing in conditions of placental insufficiency

Significant adverse correlation of the fetus mass and the degree of its hydration was noted at term in rats with placental insufficiency induced by ligation of about 40% of preplacental vessels on the 16th day of gestation. Disorders revealed in transplacental water-salt metabolism are apparently of some importance for the pathogenesis of fetal growth retardation. Even moderate retardation alters fetal respiratory activity in anoxia, which is associated with the changes in the function of respiratory centres and neuromuscular abnormalities.     

Correlation of titers of antibodies to the measles virus by an immunoenzyme method and in the hemagglutination inhibition reaction

The authors analyze the results of comparative studies on 15 paired sera from children with suspected measles, of 32 sera from children and adolescents aged 1.5 to 16 immunized against measles, and of 21 sera from adults aged 19 to 86 with a history of the disease. EIA proved to be more sensitive than HAIT: the detection rate of positive sera was higher, as were the titers of antibodies detected by it, in examinations of the sera from vaccinated children and the adults. Analysis of the distribution of sera with different titers of antibody to measles virus in EIA and HAIT has revealed a correlation between the titers in the sera with high antibody levels. In the cases with low antihemagglutinin titers, no correlation between the titers determined in the two tests has been observed.