Breeding program for the lesser kudu (Tragelaphus imberbis) in North America

The lesser kudu (Tragelaphus imberbis) has been kept in North American zoological parks since 1930 but has never been a common species in collections. In 1987 this population totaled 28 animals: 15 males and 13 females. A pedigree evaluation in 1987 of the existing population indicated that eight effective founders and one potential founder were represented in the North American herd. Three new potential founders from European captive populations were added to the population in 1987 to increase the number of existing founder lines to 12 animals. As this species is not endangered or threatened in its native habitat, it is not a high priority to qualify for designation as an SSP species. Because of this, the institutions holding lesser kudu in North America decided to join informally and draft a breeding program to better manage this small captive population. This program was designed to minimize inbreeding and equalize genetic representation of founder animals to maximize genetic diversity. It requires a shift in management philosophy to establish stable groups of breeding females at participating institutions while rotating appropriate breeder males through these herds in a controlled manner to ensure minimization of inbreeding and maximization of genetic diversity. It is hoped that this program can serve as a model for the management of other small captive populations of non-SSP species.     

Erythema infectiosum and pregnancy-related complications.

Erythema infectiosum, an acute, communicable viral disease with a highly distinctive exanthem, follows the usual course of a self-limiting benign disease. In pregnant women, however, it may be associated with fetal death and nonimmune hydrops fetalis. Because of the association of human parvovirus (HPV) B19 infection with fetal damage we reviewed the current knowledge of the clinical aspects of erythema infectiosum, focusing on pregnancy and fetal outcome, to determine the magnitude of fetal risk and offer recommendations for management. Among 180 infected pregnant women 44 fetal deaths (24%) occurred, 1 to 12 weeks after the infection was noted. Pregnant women should be advised that (a) because of the high prevalence (up to 65%) of anti-HPV B19 IgG antibody among adults most of them are not at risk and (b) if maternal infection does occur therapeutic abortion is not indicated since intrauterine infection causes fetal death more often than abnormal development. Infection should be suspected in pregnant women who exhibit the symptoms of erythema infectiosum with or without arthropathy. They should be monitored for an elevated serum alpha-fetoprotein level (indicating fetal aplastic crisis) and undergo serial ultrasonography for the detection of hydrops fetalis. Although the incidence of congenital malformation is no higher than the expected rate in the general population (3% to 5%), the precise incidence of fetal adverse outcomes remains unknown and requires investigation in larger, prospective studies.     

Sexual dimorphism in leg length among orb-weaving spiders: a possible role for sexual cannibalism

The degree and direction of sexual dimorphism across different species is commonly attributed to differences in the selection pressures acting on males and females. The extent of these differences is especially apparent in species that practise sexual cannibalism, where the female attempts to capture and eat a courting male. Here, we investigate the relationship between sexual dimorphism in size and leg length, sexual cannibalism and courtship behaviour in three taxonomic groups of orb-weaving spiders, using morphological data from 249 species in 36 genera. Females are larger than males in all three taxonomic groups, and males have relatively longer legs than females in both the Araneinae and Tetragnathidae. Across genera within each taxonomic group, male body size is positively correlated with both female body size and male leg length, and female body size is positively correlated with female leg length. Sexual size dimorphism is negatively correlated with relative male leg length within the Araneinae, but not within either the Tetragnathidae or the Gasteracanthinae. There was no negative correlation between sexual size dimorphism and relative female leg length in any taxonomic group. We argue that the relationship between sexual size dimorphism and relative male leg length within the Araneinae may be the result of selection imposed by sexual cannibalism by females.     

Refined crystal structure of Streptomyces griseus trypsin at 1.7 A resolution

Streptomyces griseus trypsin (SGT) is a bacterial serine proteinase that is more homologous to mammalian than to other bacterial enzymes. The structure of SGT has been solved primarily by molecular replacement, though some low-resolution phase information was supplied by heavy-atom derivatives. The mammalian pancreatic serine proteinases bovine trypsin (BT) and alpha-chymotrypsin (CHT) were used as molecular replacement models. Because these proteins have low homology with SGT compared to the majority of other successful replacement models, new strategies were required for molecular replacement to succeed. The model of SGT has been refined at 1.7 A resolution to a final R-factor of 0.161 (1 A = 0.1 nm); the correlation coefficient between all observed and calculated structure factor amplitudes is 0.908. Solvent molecules located in the crystal structure play an important role in stabilizing buried charged and polar groups. An additional contribution to stability can be seen in the fact that the majority of the charged side-chains are involved in ionic interactions, sometimes linking the two domains of SGT. A comparison of SGT with BT shows that the greatest similarities are in the active-site and substrate-binding regions, consistent with their similar substrate specificities. The modeling of complexes of SGT with two inhibitors of BT, pancreatic trypsin inhibitor (PTI) and the third domain of Japanese quail ovomucoid (OMJPQ3), helps to explain why PTI inhibits SGT but OMJPQ3 does not. Like BT, but unlike other bacterial serine proteinases of known structure, SGT has a buried N terminus. SGT has also a well-defined Ca2+-binding site, but this site differs in location from that of BT.     

Inhibition of human immunodeficiency virus type 1 multiplication by antisense and sense RNA expression.

Human immunodeficiency virus type 1 (HIV-1) primarily infects CD4+ lymphocytes and macrophages and causes AIDS in humans. Retroviral vectors allowing neomycin phosphotransferase (npt) gene expression were engineered to express 5' sequences of HIV-1 RNA in the antisense or sense orientation and used to transform the human CD4+ lymphocyte-derived MT4 cell line. Cells expressing antisense or sense RNA to the HIV-1 tat mRNA leader sequence, as part of the 3' untranslated region of the npt mRNA, remained sensitive to HIV-1 infection. In contrast, resistance to HIV-1 infection was observed in cells expressing antisense RNA to the HIV-1 primer-binding site or to the region 5' to the primer-binding site as part of the 3' region of the npt mRNA. Cells expressing the tat mRNA leader sequence in the sense orientation as a precise replacement of the 5' untranslated region of npt mRNA were also resistant to HIV-1. These results indicate that sense and antisense approaches can be used to interfere with HIV-1 multiplication.     

Characterization of the DNA-binding properties of the receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin

The DNA-binding properties of the receptor for 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) were investigated using chromatography on DNA-cellulose columns. A maximal binding of about 40% of the total receptor complex to DNA-cellulose was observed. In order to interact with DNA, the receptor must first bind TCDD. A heat-activation step followed by gel permeation chromatography using Sephadex G-25 increased the binding of the cytosolic receptor to DNA. The DNA-binding ability of the receptor was almost lost following mild proteolysis using trypsin or alpha-chymotrypsin, although these treatments did not reduce its ligand binding capacity and had no apparent effect on its size. Furthermore, pre-treatment of the DNA-cellulose column with an intercalating drug, ethidium bromide, resulted in inhibition of the binding of the TCDD-receptor complex to DNA, indicating that not only electrostatic interactions but also the configuration of DNA are of importance in receptor-DNA interactions.     

Sugar utilization by developing wild type and shrunken-2 maize kernels

To characterize the movement of sugars during kernel development in maize, a newly devised in vitro kernel development scheme was utilized. Viable seeds of wild type maize (Zea mays L.) as well as the mutant shrunken-2 (sh2) were found to mature when grown in culture with reducing sugars or sucrose as the carbon source. However, wild type and sh2 kernels had greater germination, starch content, and seed weight when sucrose, rather than reducing sugars, was the carbon source. By the use of labeled sucrose it was shown that sucrose can move into endosperm tissue without intervening degradation and resynthesis. These results show that when grown in vitro the maize seed can utilize reducing sugars for development, but it prefers sucrose.