Evidence of Pre-mating Reproductive Isolation in Two Allopatric Populations of the Vlei Rat,Otomys irroratus

Laboratory experiments were undertaken to ascertain whether or not individuals of two allopatric Otomys irroratus populations (Kamberg and Karkloof) distinguish between mates from the same (homotype) and the other (heterotype) population. The study aimed to establish the existence of pre-mating reproductive isolation mechanisms between the two populations. In both ‘whole-animal choice’ trials and olfactory discrimination tests, all females significantly preferred homotype stimulus males or odour. Although males of both populations preferred homotype females, males were less discriminating at the start of experiments, possibly because of increased exploratory drive at this time. Furthermore, Kamberg males demonstrated equal preference for both stimulus females during the dark phase of the light cycle; no explanation is given for this phenomenon. Overall, the results indicate the existence of population-specific courtship behaviour, with olfactory cues apparently playing an important role in mate recognition. It is therefore possible that, should representatives of the two populations meet in nature, they may be reproductively isolated through behavioural means.     

The molluscan genus Cominella (Gastropoda: Buccinidae) at the Three Kings Islands

Abstract

Three endemic taxa of Cominella Gray are recorded from the Three Kings Islands, New Zealand. Cominella (Josepha) regalis n.sp. and C. (Josepha) quoyana griseicalx n.ssp. occur sympatrically in relatively shallow water (to c.50m), whereas C. (Eucominia) mirabilis mirabilis Powell is known only from c.180m. The history of colonisation by these taxa is hypothesised and discussed.     

A gene-driven ENU-based approach to generating an allelic series in any gene

N-ethyl-N-nitrosourea (ENU) introduces mutations throughout the mouse genome at relatively high efficiency. Successful high-throughput phenotype screens have been reported and alternative screens using sequence-based approaches have been proposed. For the purpose of generating an allelic series in selected genes by a sequence-based approach, we have constructed an archive of over 4000 DNA samples from individual F₁ ENU-mutagenized mice paralleled by frozen sperm samples. Together with our previously reported archive, the total size now exceeds 6000 individuals. A gene-based screen of 27.4 Mbp of DNA, carried out using denaturing high-performance liquid chromatography (DHPLC), found a mutation rate of 1 in 1.01 Mbp of which 1 in 1.82 Mbp were potentially functional. Screening of whole or selected regions of genes on subsets of the archive has allowed us to identify 15 new alleles from 9 genes out of 15 tested. This is a powerful adjunct to conventional mutagenesis strategies and has the advantage of generating a variety of alleles with potentially different phenotypic outcomes that facilitate the investigation of gene function. It is now available to academic collaborators as a community resource.     

The interaction of protein A and Fc fragment of rabbit immunoglobulin G as probed by complement-fixation and nuclear-magnetic-resonance studies.

Protein-A-Fc-fragment complexes were observed in sedimentation-velocity experiments by ultracentrifugation. The interaction was studied by protein-fluorescence-quenching titrations of the Fc fragment with protein A, allowing the dissociation constant to be determined under a variety of conditions. The first component of the complement pathway, C1, is activated by complexes of protein A with rabbit IgG (immunoglobulin G), and the structural basis for this interaction was studied by using n.m.r. (nuclear magnetic resonance). The four Fc-fragment binding sites on protein A were shown to contain aromatic amino acids, and to be connected by mobile hydrophilic regions. Neither n.m.r. nor proton-relaxation-enhancement studies show evidence of a large conformational change of the Fc fragment on binding protein A, and this suggests that the cross-linking of the Fc fragments may be primarily responsible for the activation of component C1. This is supported by the inability of a univalent tryptic fragment of protein A to activate complement fixation by rabbit IgG.     

Androgen Regulated Genes in Human Prostate Xenografts in Mice: Relation to BPH and Prostate Cancer

Benign prostatic hyperplasia (BPH) and prostate carcinoma (CaP) are linked to aging and the presence of androgens, suggesting that androgen regulated genes play a major role in these common diseases. Androgen regulation of prostate growth and development depends on the presence of intact epithelial-stromal interactions. Further, the prostatic stroma is implicated in BPH. This suggests that epithelial cell lines are inadequate to identify androgen regulated genes that could contribute to BPH and CaP and which could serve as potential clinical biomarkers. In this study, we used a human prostate xenograft model to define a profile of genes regulated in vivo by androgens, with an emphasis on identifying candidate biomarkers. Benign transition zone (TZ) human prostate tissue from radical prostatectomies was grafted to the sub-renal capsule site of intact or castrated male immunodeficient mice, followed by the removal or addition of androgens, respectively. Microarray analysis of RNA from these tissues was used to identify genes that were; 1) highly expressed in prostate, 2) had significant expression changes in response to androgens, and, 3) encode extracellular proteins. A total of 95 genes meeting these criteria were selected for analysis and validation of expression in patient prostate tissues using quantitative real-time PCR. Expression levels of these genes were measured in pooled RNAs from human prostate tissues with varying severity of BPH pathologic changes and CaP of varying Gleason score. A number of androgen regulated genes were identified. Additionally, a subset of these genes were over-expressed in RNA from clinical BPH tissues, and the levels of many were found to correlate with disease status. Our results demonstrate the feasibility, and some of the problems, of using a mouse xenograft model to characterize the androgen regulated expression profiles of intact human prostate tissues.     

Is Port Stephens,eastern Australia,a global hotspot for biodiversity of Aplysiidae (Gastropoda: Heterobranchia)?

Port Stephens, a large natural harbour on the central New South Wales (NSW) coast, provides ideal oceanographic and benthic conditions for the growth of marine algae and seagrasses, and this promotes a suite of herbivorous heterobranch sea slugs such as sea hares and sap-sucking sea slugs. In this article we document both historic and recent observations of sea hares (family Aplysiidae) from Port Stephens with the intention of recording species diversity. The western South Pacific region has the richest aplysiid fauna in the world, with 16 species now recorded in Port Stephens. This location is the most taxonomically diverse for this family in Australia. Despite this hotspot of aplysiid diversity, the taxonomy and nomenclature of 12 species is uncertain, a fact highlighted by a series of nomenclatural notes included in this article. We herein report the first observation of Petalifera sp. in Australian waters. Dolabrifera jacksoniensis Pilsbry, 1896 Pilsbry, H. (1896) Genus III. Dolabrifera Gray, 1847. Manual of Conchology series 1, volume 16, part 63, 113–160, pls 32–43. [Google Scholar] is newly synonymised with D. brazieri G.B. Sowerby II, 1870. Recent reports of southern range extensions for other heterobranch sea slugs, both in Port Stephens and elsewhere in NSW, highlight the importance of recording the existing aplysiid diversity in the port. Thus, any future alteration to species composition and range shifts driven by climate change may be detected.