Search

The complexity and biologically challenging nature of arid landscapes can generate high inter‐ and intra‐species diversity, although these biomes remain poorly studied. We investigated whether prominent geomorphic features in an Australian arid landscape had similar influences on patterns of intra‐specific genetic diversity of three small mammals with different distribution and life history traits. Specifically, we tested (a) whether mountain ranges harbour high diversity and act as refugia, (b) the extent to which ephemeral river systems pose barriers to gene flow or (c) whether environmental differences explain genetic structure in these species.

The taxonomy of Australian Isoodon bandicoots has changed continuously over the last 20 years, with recent genetic studies indicating discordance of phylogeographic units with current taxonomic boundaries. Uncertainty over species relationships within southern and western Isoodon, encompassing I. obesulus, I. auratus, and I. fusciventer, has been ongoing and hampered by limited sampling in studies to date. Identification of taxonomic units remains a high priority, as all are threatened to varying extents by ongoing habitat loss and feral predation. To aid diagnosis of conservation units, we increased representative sampling of I. auratus and I. fusciventer from Western Australia (WA) and investigated genetic relationships of these with I. obesulus from South Australia (SA) and Victoria (Vic) using microsatellite markers and mitochondrial DNA. mtDNA analysis identified three major clades concordant with I. obesulus (Vic), I. auratus, and I. fusciventer, however, I. obesulus from SA was polyphyletic to WA taxa, complicating taxonomic inference. Microsatellite data aided identification of evolutionarily significant units consistent with existing taxonomy, with the exception of SA I. obesulus. Further, analyses indicated SA and Vic I. obesulus have low diversity, and these populations may require more conservation efforts than others to reduce further loss of genetic diversity.

Habitat fragmentation can have profound effects on the distribution of genetic variation within and between populations. Previously, we showed that in the ornate dragon lizard, Ctenophorus ornatus, lizards residing on outcrops that are separated by cleared agricultural land are significantly more isolated and hold less genetic variation than lizards residing on neighbouring outcrops connected by undisturbed native vegetation. Here, we extend the fine-scale study to examine the pattern of genetic variation and population structure across the species' range. Using a landscape genetics approach, we test whether land clearing for agricultural purposes has affected the population structure of the ornate dragon lizard. We found significant genetic differentiation between outcrop populations (FST = 0.12), as well as isolation by distance within each geographic region. In support of our previous study, land clearing was associated with higher genetic divergences between outcrops and lower genetic variation within outcrops, but only in the region that had been exposed to intense agriculture for the longest period of time. No other landscape features influenced population structure in any geographic region. These results show that the effects of landscape features can vary across species' ranges and suggest there may be a temporal lag in response to contemporary changes in land use. These findings therefore highlight the need for caution when assessing the impact of contemporary land use practices on genetic variation and population structure.

The influence of geographic range on species persistence has long been of interest and there is a need for a better understanding of the genetic consequences for species with restricted distributions, particularly with the increasing rate of global species extinctions. However, the genetic effects of restricted range are often confounded by the impacts of population distribution. We compared chloroplast and nuclear genetic diversity and differentiation in two acacias, the restricted, patchily distributed Acacia atkinsiana and the widespread, semi-continuously distributed A. ancistrocarpa. Lower intra-population diversity and higher differentiation between populations were seen in A. atkinsiana compared to its widespread congener, A. ancistrocarpa. There was little evidence of geographical influences on population genetic structure in A. ancistrocarpa whereas A. atkinsiana exhibited nuclear genetic structure with isolation by distance, differentiation of near-coastal populations from those in the ranges, and differentiation of peripheral populations from those in the centre of the distribution. These results are consistent with expectations of the effect of geographic range and population distribution on genetic diversity, but indicate that distribution of populations rather than geographic range has influenced the observed genetic structure. The contrasting patterns observed here demonstrate that conservation approaches for species management and ecological restoration need to consider the distribution of populations in geographically restricted species.

We isolated 11 new polymorphic microsatellite markers from Acacia atkinsiana, a plant species endemic to the Pilbara region in Western Australia. Next generation (454) sequencing was used to identify 28 microsatellite markers that were trialled in individuals across the species range. Characterisation of 11 of these loci in 24 individuals from a single population yielded between two and nine alleles per locus, and observed heterozygosity ranged from 0.042 to 0.958. Four loci that amplified in A. atkinsiana were also successfully amplified and polymorphic in Acacia ancistrocarpa. These loci will be valuable for assessing population genetic structure in A. atkinsiana and identifying seed sources for rehabilitation of disturbed sites.

An important question for the conservation of species dwelling in fragmented habitats is whether changes to the intervening landscape create a barrier to gene flow. Here, we make use of the spatial distribution of the granite outcrop-dwelling lizard, Ctenophorus ornatus, to compare inferred levels of gene flow between outcrops in a nature reserve with that between outcrops in the adjacent agricultural land. Genetic variation, relatedness and subdivision were compared within groups of individuals from different outcrops similar in size and distance apart at each site. In the agricultural land, we found significantly lower genetic variation within outcrops and greater genetic differentiation between outcrops than in the reserve. Further, the rate at which genetic divergence between outcrops increased over geographical distance was significantly greater in the agricultural land than in the reserve. We also found that individuals were more closely related within outcrops but more distantly related between outcrops in the cleared land. These effects occur over a small spatial scale with an average distance between outcrops of less than five kilometres. Thus, even though land clearing around the outcrops leaves outcrop size unchanged, it restricts gene flow, reducing genetic variation and increasing population structure, with potentially negative consequences for the long-term persistence of the lizards on these outcrops.

αMUPA transgenic mice spontaneously consume less food compared with their wild type (WT) ancestors due to endogenously increased levels of the satiety hormone leptin. αMUPA mice share many benefits with mice under caloric restriction (CR) including an extended life span. To understand mechanisms linked to cardiac aging, we explored the response of αMUPA hearts to ischemic conditions at the age of 6, 18, or 24 months. Mice were subjected to myocardial infarction (MI) in vivo and to ischemia/reperfusion ex vivo. Compared to WT mice, αMUPA showed functional and histological advantages under all experimental conditions. At 24 months, none of the WT mice survived the first ischemic day while αMUPA mice demonstrated 50% survival after 7 ischemic days. Leptin, an adipokine decreasing under CR, was consistently ~60% higher in αMUPA sera at baseline. Leptin levels gradually increased in both genotypes 24h post MI but were doubled in αMUPA. Pretreatment with leptin neutralizing antibodies or with inhibitors of leptin signaling (AG-490 and Wortmannin) abrogated the αMUPA benefits. The antibodies also reduced phosphorylation of the leptin signaling components STAT3 and AKT specifically in the αMUPA myocardium. αMUPA mice did not show elevation in adiponectin, an adipokine previously implicated in CR-induced cardioprotection. WT mice treated for short-term CR exhibited cardioprotection similar to that of αMUPA, however, along with increased adiponectin at baseline. Collectively, the results demonstrate a life-long increased ischemic tolerance in αMUPA mice, indicating the attenuation of cardiac aging. αMUPA cardioprotection is mediated through endogenous leptin, suggesting a protective pathway distinct from that elicited under CR.

Major histocompatibility complex (MHC) gene polymorphism is thought to be driven by host-parasite co-evolution, but the evidence for an association between the selective pressure from parasites and the number of MHC alleles segregating in a population is scarce and inconsistent. Here, we characterized MHC class I polymorphism in a lizard whose habitat preferences (rock outcrops) lead to the formation of well-defined and stable populations. We investigated the association between the load of ticks, which were used as a proxy for the load of pathogens they transmit, and MHC class I polymorphism across populations in two types of habitat: undisturbed reserves and agricultural land. We hypothesized that the association would be positive across undisturbed reserve populations, but across fragmented agricultural land populations, the relationship would be distorted by the loss of MHC variation due to drift. After controlling for habitat, MHC diversity was not associated with tick number, and the habitats did not differ in this respect. Neither did we detect a difference between habitats in the relationship between MHC and neutral diversity, which was positive across all populations. However, there was extensive variation in the number of MHC alleles per individual, and we found that tick number was positively associated with the average number of alleles carried by lizards across reserve populations, but not across populations from disturbed agricultural land. Our results thus indicate that local differences in selection from parasites may contribute to MHC copy number variation within species, but habitat degradation can distort this relationship.

We describe the isolation and development of 18 polymorphic microsatellite loci for the western rock lobster Panulirus cygnus (Decapoda: Palinuridae). The loci were tested in 37 individuals from a single population situated near the centre of the species’ distribution. No evidence of linkage disequilibrium was detected between any pair of loci. However, seven loci showed significant departures from Hardy–Weinberg expectations. The number of alleles per locus ranged from three to 31.

We describe the isolation and development of 20 polymorphic microsatellite loci for the ornate dragon lizard Ctenophorus ornatus. Characterization of these loci in 29 individuals from a single population yielded between five and twenty alleles per locus. Expected heterozygosities ranged from 0.32 to 1.00 and only one locus deviated from Hardy–Weinberg expectations. There was no evidence of linkage disequilibrium between any pair of loci.

Sperm competition theory predicts that males should increase their expenditure on the ejaculate with increasing risk of sperm competition, but decrease their expenditure with increasing intensity. There is accumulating evidence for sperm competition theory, based on examinations of testes size and/or the numbers of sperm ejaculated. However, recent studies suggest that ejaculate quality can also be subject to selection by sperm competition. We used experimental manipulations of the risk and intensity of sperm competition in the cricket, Teleogryllus oceanicus . We found that males produced ejaculates with a greater percentage of live sperm when they had encountered a rival male prior to mating. However, when mating with a female that presented a high intensity of sperm competition, males did not respond to risk, but produced ejaculates with a reduced percentage of live sperm. Our data suggest that males exhibit a fine-tuned hierarchy of responses to these cues of sperm competition.

Species inhabiting ancient, geologically stable landscapes that have been impacted by agriculture and urbanisation are expected to have complex patterns of genetic subdivision due to the influence of both historical and contemporary gene flow. Here, we investigate genetic differences among populations of the granite outcrop-dwelling lizard Ctenophorus ornatus, a phenotypically variable species with a wide geographical distribution across the south-west of Western Australia. Phylogenetic analysis of mitochondrial DNA sequence data revealed two distinct evolutionary lineages that have been isolated for more than four million years within the C. ornatus complex. This evolutionary split is associated with a change in dorsal colouration of the lizards from deep brown or black to reddish-pink. In addition, analysis of microsatellite data revealed high levels of genetic structuring within each lineage, as well as strong isolation by distance at multiple spatial scales. Among the 50 outcrop populations’ analysed, non-hierarchical Bayesian clustering analysis revealed the presence of 23 distinct genetic groups, with outcrop populations less than 4 km apart usually forming a single genetic group. When a hierarchical analysis was carried out, almost every outcrop was assigned to a different genetic group. Our results show there are multiple levels of genetic structuring in C. ornatus, reflecting the influence of both historical and contemporary evolutionary processes. They also highlight the need to recognise the presence of two evolutionarily distinct lineages when making conservation management decisions on this species.

The significance of serum IgG and IgA antibodies to cytomegalovirus (CMV) at various stages of human immune deficiency virus (HIV) infection was studied in 175 homosexual men. Sera were obtained from 123 HIV seropositives [41 asymptomatic, 29 with lymphadenopathy associated syndrome (LAS), 22 with AIDS related complex (ARC), and 31 AIDS patients], 17 HIV seroconverters, and 35 HIV asymptomatic seronegatives. The sera were tested blindly for CMV IgA and IgG antibodies using the immunoperoxidase assay (IPA) and CMV infected human embryo cells. Cross-sectional analysis of CMV IgG antibodies at a titer of greater than or equal to 20 showed 87% and 100% prevalence in the HIV seronegative groups and in the HIV seropositive groups, respectively (P less than 0.05). CMV IgG antibodies at a titer of greater than or equal to 80 were present in significantly higher proportions among the HIV seropositive subjects of the various groups as compared with the HIV seronegative homosexual men. However, in the HIV seronegatives who later seroconverted to HIV, a significantly higher prevalence of CMV antibodies (35%) was detected before HIV seroconversion, as compared with the persistently HIV seronegative subjects (14.3%) (P less than 0.05). The HIV seronegatives pre-HIV seroconversion also exhibited a significantly higher geometric mean titer (GMT) of CMV IgG antibodies (62.17 +/- 0.64) as compared with the persistently HIV seronegatives (34.0 +/- 0.6) (P = 0.03). Significantly higher GMTs of CMV IgG antibodies were detected in all the HIV seropositive groups as compared with the persistently HIV seronegative group. CMV IgG antibodies were not detected in the HIV seronegative subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

The design, synthesis and pharmacology of novel long-acting exenatide analogs for the treatment of metabolic diseases are described. These molecules display enhanced pharmacokinetic profile and potent glucoregulatory and weight lowering actions compared to native exenatide. [Leu(14)]exenatide-ABD is an 88 residue peptide amide incorporating an Albumin Binding Domain (ABD) scaffold. [Leu(14)]exenatide-ABP is a 53 residue peptide incorporating a short Albumin Binding Peptide (ABP). [Leu(14)]exenatide-ABD and [Leu(14)]exenatide-ABP exhibited nanomolar functional GLP-1 receptor potency and were metabolically stable in vitro in human plasma and in a pancreatic digestive enzyme mixture. Both molecules displayed picomolar and nanomolar binding association with albumin across multiple species and circulating half lives of 16 and 11 hours, respectively, post a single IV dose in rats. Unlike exenatide, both molecules elicited robust glucose lowering when injected 1 day prior to an oral glucose tolerance test, indicative of their extended duration of action. [Leu(14)]exenatide-ABD was compared to exenatide in a Lep (ob/ob) mouse model of diabetes. Twice-weekly subcutaneously dosed [Leu(14)]exenatide-ABD displayed superior glucose lowering and weight loss in diabetic mice when compared to continuously infused exenatide at the same total weekly dose. A single oral administration of each molecule via an enteric coated capsule to cynomolgus monkeys showed superior pharmacokinetics for [Leu(14)]exenatide-ABD as compared to [Leu(14)]exenatide-ABP with detectable exposure longer than 14 days. These studies support the potential use of these novel long acting exenatide analogs with different routes of administration for the treatment of type 2 diabetes.

The mechanism-based inactivation of human neutral endopeptidase 24.11 (NEP) was studied with N-[(R)-2-benzyl-5-cyano-4-oxopentanoyl]-L-phenylalanine (1) and its peptidic analogue, N(-)[N-(cyanoacetyl)-L-phenylalanyl]-L-phenylalanine (2). While both these active-site-directed molecules inactivate NEP, the related angiotensin-converting enzyme (ACE) is only inactivated by compound 2 [Ghosh et al. J. Med. Chem. 1992, 35, 4175-4179]. The selectivity in inactivation was addressed further by a comparative study of the interaction of compounds 1 and 2 with five other zinc proteases. The selective inactivation of NEP observed with the ketomethylene compound 1 suggests that the active site of NEP is less discriminating in its requirements for binding such substrate analogues as compared to ACE, a characteristic that may be exploited for designing specific mechanism-based inactivators for NEP. It is proposed that the inactivation is a result of NEP-catalyzed formation of ketenimine intermediates, which are subsequently trapped by an active-site nucleophile.

A sensitive solid-phase, enzyme-linked immunosorbent assay (ELISA) was developed for detection of serum IgA antibodies to varicella-zoster virus (VZV). The antigen consisted of a sonically disrupted extract of VZV-infected human embryo cells. Rabbit antihuman IgA peroxidase conjugate was used to detect human IgA bound to viral antigens. In parallel, IgM and IgG antibodies to VZV were studied by ELISA and by an immunoperoxidase antibody to membrane antigen technique, respectively. VZV IgA antibodies were detected in high titers in all 5 varicella and 8 zoster patients. Specific VZV IgM antibodies were detected in all 5 varicella patients, but only in 2 of 8 zoster patients. No VZV IgA antibodies (less than 40) were detected in 50 healthy control sera. Neither were they found in paired sera of 5 patients with herpes simplex infections, 2 patients with Epstein-Barr virus infections, and 5 patients with human cytomegalovirus infections. The potential application of ELISA IgA techniques in serodiagnosis of both primary and reactivated VZV infections is discussed.

A sensitive enzyme-linked immunosorbent assay (ELISA) is described for detection of IgA antibodies to human cytomegalovirus (CMV). The antigen consisted of a sonicated extract of CMV infected human embryo cells. The tested sera were absorbed with staphylococcus aureus (strain Cowan 1) before analysis. Rabbit antihuman IgA peroxidase conjugate was used to detect human IgA bound to viral antigen. In parallel, IgM and IgG antibodies to CMV were studied by ELISA and by the immunoperoxidase antibody to membrane antigen (IPAMA) technique, respectively. CMV IgA was detected in high titers by ELISA in eight out of nine CMV patients. The maximal IgA titers were generally lower than the IgM titers detected by ELISA. No CMV IgA antibodies (titer < 20) were detected by ELISA in 57 control sera (healthy adults, hospitalized patients with various other diseases), paired sera of five patients with acute herpes simplex infection, two patients with Epstein-Barr infections, one patient with varicella, and one with zoster infections. The potential application of the ELISA CMV IgA technique in serodiagnosis of CMV infections is discussed.