Response of the Italian agile frog (Rana latastei) to a Ranavirus, frog virus 3: a model for viral emergence in naïve populations

Ranavirus (family Iridoviridae) is a genus of pathogens of poikilotherms, and some ranaviruses may play a role in widespread mortality of amphibians. Ecology of viral transmission in amphibians is poorly known but can be addressed through experimentation in the laboratory. In this study, we use the Ranavirus frog virus 3 (FV3) as an experimental model for pathogen emergence in naive populations of tadpoles. We simulated emerging disease by exposing tadpoles of the Italian agile frog (Rana latastei), to the North American Ranavirus FV3. We demonstrated that mortality occurred due to viral exposure, exposure of tadpoles to decreasing concentrations of FV3 in the laboratory produced dose-dependent survival rates, and cannibalism of virus-carrying carcasses increased mortality due to FV3. These experiments suggest the potential for ecological mechanisms to affect the level of exposure of tadpoles to Ranavirus and to impact transmission of viral pathogens in aquatic systems.     

Estrogen receptor ligands. Part 6: Synthesis and binding affinity of dihydrobenzodithiins

Dihydrobenzodithiin compounds (1-6) were prepared to explore the expansion of the dihydrobenzoxathiin lead compounds I-III as SERAMs (Selective Estrogen Receptor Alpha Modulators). The dihydrobenzodithiin compounds generally maintained a high degree of selectivity for ERalpha over ERbeta, however, they lacked the in vivo antagonism/agonism activity exhibited by the lead class in an immature rat uterine growth model.     

Genetic diversity across a vertebrate species' range: a test of the central-peripheral hypothesis

Although it has been long presumed that population genetic variability should decrease as a species' range margin is approached, results of empirical investigations remain ambiguous. Sampling strategies employed by many of these studies have not adequately sampled the entire range. Here we present the results of an investigation of population genetic diversity in a vertebrate species, the Italian agile frog, Rana latastei, sampled comprehensively across its entire range. Our results show that genetic variability is not correlated with population location with respect to the range periphery. Instead, the model that best explains the genetic variation detectable across the range is based on an east-to-west gradient of declining diversity. Although we cannot state definitively what has led to this distribution, the most likely explanation is that the range of Rana latastei expanded postglacially from a Balkan refugium.     

Relatedness,body size and paternity in the alpine newt,Triturus alpestris

Sexual selection has traditionally been investigated assuming that male quality is as skewed as patterns of male reproductive success can sometimes be. Recently, female choice has been investigated under the model of genetic compatibility, which assumes that each individual female has her own 'best' mate and there is no overall optimal choice for all females. We investigated female mate choice in the newt species Triturus alpestris, a member of a genus where female choice has been investigated only within the context of the optimal male (female choice for condition-dependent traits). We provided females with two males that differed in one condition-dependent trait (body size) and overall genetic composition. Both male body size and female body size did not influence paternity, but the degree of genetic relatedness between females and potential mates did. Two components of fitness (fecundity and hatching success) did not differ between singly and multiply sired clutches, indicating that females do not employ polyandry as a means of increasing offspring fitness through genetic bet-hedging. Instead, we hypothesize that females may mate initially for fertility assurance, but prefer less-related males as the most genetically compatible mates.     

Alzheimer's disease-related overexpression of the cation-dependent mannose 6-phosphate receptor increases Abeta secretion: role for altered lysosomal hydrolase distribution in beta-amyloidogenesis

Prominent endosomal and lysosomal changes are an invariant feature of neurons in sporadic Alzheimer's disease (AD). These changes include increased levels of lysosomal hydrolases in early endosomes and increased expression of the cation-dependent mannose 6-phosphate receptor (CD-MPR), which is partially localized to early endosomes. To determine whether AD-associated redistribution of lysosomal hydrolases resulting from changes in CD-MPR expression affects amyloid precursor protein (APP) processing, we stably transfected APP-overexpressing murine L cells with human CD-MPR. As controls for these cells, we also expressed CD-MPR trafficking mutants that either localize to the plasma membrane (CD-MPRpm) or to early endosomes (CD-MPRendo). Expression of CD-MPR resulted in a partial redistribution of a representative lysosomal hydrolase, cathepsin D, to early endosomal compartments. Turnover of APP and secretion of sAPPalpha and sAPPbeta were not altered by overexpression of any of the CD-MPR constructs. However, secretion of both human Abeta40 and Abeta42 into the growth media nearly tripled in CD-MPR- and CD-MPRendo-expressing cells when compared with parental or CD-MPRpm-expressing cells. Comparable increases were confirmed for endogenous mouse Abeta40 in L cells expressing these CD-MPR constructs but not overexpressing human APP. These data suggest that redistribution of lysosomal hydrolases to early endocytic compartments mediated by increased expression of the CD-MPR may represent a potentially pathogenic mechanism for accelerating Abeta generation in sporadic AD, where the mechanism of amyloidogenesis is unknown.     

The developmental expression of vasoactive intestinal peptide (VIP) in cholinergic sympathetic neurons depends on cytokines signaling through LIFRbeta-containing receptors

Sympathetic ganglia are composed of noradrenergic and cholinergic neurons. Cholinergic sympathetic neurons are characterized by the expression of choline acetyl transferase (ChAT), vesicular acetylcholine transporter (VAChT) and the vasoactive intestinal peptide (VIP). To investigate the role of cytokine growth factor family members in the development of cholinergic sympathetic neurons, we interfered in vivo with the function of the subclass of cytokine receptors that contains LIFRbeta as essential receptor subunit. Expression of LIFRbeta antisense RNA interfered with LIFRbeta expression and strongly reduced the developmental induction of VIP expression. By contrast, ganglion size and the number of ChAT-positive cells were not reduced. These results demonstrate a physiological role of cytokines acting through LIFRbeta-containing receptors in the control of VIP expression in sympathetic neurons.     

Characterization and chromosome assignment of the porcine AHCY gene for S-adenosylhomocysteine hydrolase

The gene for S-adenosylhomocysteine hydrolase (AHCY) is involved in the regulation of cellular methylation reactions. Here we report the cloning, sequencing, and chromosomal assignment of the porcine AHCY gene. The gene consists of 10 exons spanning approximately 19 kb of genomic DNA. It encodes a protein of 432 amino acids that shows about 96% identity to the orthologous S-adenosylhomocysteine hydrolases from human, rat, and mouse. The porcine AHCY gene is located very close to the agouti signaling protein gene (ASIP) on SSC17q21. The chromosomal localization was subsequently confirmed by RH mapping and the genetic mapping of an intragenic microsatellite that maps to 57 cM on the linkage map of SSC17.     

ARF1.GTP,tyrosine-based signals,and phosphatidylinositol 4,5-bisphosphate constitute a minimal machinery to recruit the AP-1 clathrin adaptor to membranes

At the trans-Golgi network, clathrin coats containing AP-1 adaptor complexes are formed in an ARF1-dependent manner, generating vesicles transporting cargo proteins to endosomes. The mechanism of site-specific targeting of AP-1 and the role of cargo are poorly understood. We have developed an in vitro assay to study the recruitment of purified AP-1 adaptors to chemically defined liposomes presenting peptides corresponding to tyrosine-based sorting motifs. AP-1 recruitment was found to be dependent on myristoylated ARF1, GTP or nonhydrolyzable GTP-analogs, tyrosine signals, and small amounts of phosphoinositides, most prominently phosphatidylinositol 4,5-bisphosphate, in the absence of any additional cytosolic or membrane bound proteins. AP-1 from cytosol could be recruited to a tyrosine signal independently of the lipid composition, but the rate of recruitment was increased by phosphatidylinositol 4,5-bisphosphate. The results thus indicate that cargo proteins are involved in coat recruitment and that the local lipid composition contributes to specifying the site of vesicle formation.