Effects of meal size, clutch, and metabolism on the energy efficiencies of juvenile Burmese pythons, Python molurus.

We explored meal size and clutch (i.e., genetic) effects on the relative proportion of ingested energy that is absorbed by the gut (apparent digestive efficiency), becomes available for metabolism and growth (apparent assimilation efficiency), and is used for growth (production efficiency) for juvenile Burmese pythons (Python molurus). Sibling pythons were fed rodent meals equaling 15%, 25%, and 35% of their body mass and individuals from five different clutches were fed rodent meals equaling 25% of their body mass. For each of 11-12 consecutive feeding trials, python body mass was recorded and feces and urate of each snake was collected, dried, and weighed. Energy contents of meals (mice and rats), feces, urate, and pythons were determined using bomb calorimetry. For siblings fed three different meal sizes, growth rate increased with larger meals, but there was no significant variation among the meal sizes for any of the calculated energy efficiencies. Among the three meal sizes, apparent digestive efficiency, apparent assimilation efficiency, and production efficiency averaged 91.0%, 84.7%, and 40.7%, respectively. In contrast, each of these energy efficiencies varied significantly among the five different clutches. Among these clutches production efficiency was negatively correlated with standard metabolic rate (SMR). Clutches containing individuals with low SMR were therefore able to allocate more of ingested energy into growth.     

Salinity-linked growth in anguillid eels and the paradox of temperate-zone catadromy

Temperate-zone anguillid eels use both saline (marine or brackish) and fresh waters during their continental phase, but use of fresh waters is paradoxical because on average these fishes grow more rapidly in saline than in fresh waters. Based on data from anguillid eels whose habitat-residency histories had been determined by Sr:Ca otolithometry, superiority of growth rates in saline water is much greater in American eels Anguilla rostrata in north-eastern North America (mean saline:fresh growth rate ratio 2·07) than in European Anguilla anguilla , Japanese Anguilla japonica and shortfinned Anguilla australis eels (range of mean ratios 1·12–1·14). Data from A. rostrata in the Hudson Estuary, U.S.A., and Prince Edward Island, Canada, were used to test adaptive explanations of catadromous migrations. The hypothesis that lower mortality in fresh water offsets faster growth in saline water was not supported because loss (mortality + emigration ) rates did not vary between saline and fresh zones of the Hudson Estuary. Hypotheses that anguillid eels move to fresh water to escape from larger anguillid eels in saline water or to evaluate habitat quality were not supported by size and age distributions. Catadromy in temperate-zone anguillid eels increases the diversity of occupied habitats and therefore lowers fitness variance caused by environmental fluctuations. Catadromy in temperate-zone anguillid eels could be due to natural selection for maximum geometric mean fitness which is sensitive to fitness variance. Temperate-zone catadromy might also be maladaptive, at least in local areas, due to shifts over time in selective pressures or to inability of panmictic genetic systems to adapt to local conditions.     

Is otolith science transformative? New views on fish migration

Publications focused on fish otolith applications grew exponentially from 1981–2000 but have subsequently stabilized, suggesting maturation of otolith applications. Over the past 30 years >3,500 primary journal publications were identified prompting the question, how have otoliths fundamentally changed our understanding of fishes and their environment? Has otolith science in this way been transformative? I use Harden Jones’ 1968 Fish Migration as a benchmark of fish migration concepts prior to Pannella’s 1971 breakthrough paper on otolith microstructure. For case study species I highlight how otolith science has informed migration concepts including, (1) parent stream theory (Atlantic bluefin tuna), (2) adoptive homing (Atlantic herring), and (3) partial migration (European eel). Harden Jones’ overall conclusion that life cycle closure leads to population structure (also known as the migration triangle) is a first principle in fisheries science, but in recent years has been challenged by otolith science. In particular, a transformative discovery attributable to otoliths is that life cycles vary substantially within populations. New avenues of otolith science are now exploring the causes and consequences of this life cycle diversity, and large advances are expected through integration of otolith approaches with electronic tagging, genetics, field manipulations, and modeling that will permit migration concepts to be tested at multiple ecological scales.     

Molecularly cloned SHIV-1157ipd3N4: a highly replication- competent, mucosally transmissible R5 simian-human immunodeficiency virus encoding HIV clade C Env

Human immunodeficiency virus type 1 (HIV-1) clade C causes >50% of all HIV infections worldwide, and an estimated 90% of all transmissions occur mucosally with R5 strains. A pathogenic R5 simian-human immunodeficiency virus (SHIV) encoding HIV clade C env is highly desirable to evaluate candidate AIDS vaccines in nonhuman primates. To this end, we generated SHIV-1157i, a molecular clone from a Zambian infant isolate that carries HIV clade C env. SHIV-1157i was adapted by serial passage in five monkeys, three of which developed peripheral CD4(+) T-cell depletion. After the first inoculated monkey developed AIDS at week 137 postinoculation, transfer of its infected blood to a na?ve animal induced memory T-cell depletion and thrombocytopenia within 3 months in the recipient. In parallel, genomic DNA from the blood donor was amplified to generate the late proviral clone SHIV-1157ipd3. To increase the replicative capacity of SHIV-1157ipd3, an extra NF-kappaB binding site was engineered into its 3' long terminal repeat, giving rise to SHIV-1157ipd3N4. This virus was exclusively R5 tropic and replicated more potently in rhesus peripheral blood mononuclear cells than SHIV-1157ipd3 in the presence of tumor necrosis factor alpha. Rhesus macaques of Indian and Chinese origin were next inoculated intrarectally with SHIV-1157ipd3N4; this virus replicated vigorously in both sets of monkeys. We conclude that SHIV-1157ipd3N4 is a highly replication-competent, mucosally transmissible R5 SHIV that represents a valuable tool to test candidate AIDS vaccines targeting HIV-1 clade C Env.     

Detection and identification of cyanogenic glucosides in six species of Acacia

The presence of prunasin in Acacia deanei ssp. paucijuga, sambunigrin in Acacia cunninghamii, and acacipetalin in Acacia giraffae has been established by both chromatographic and NMR spectral evidence. Mandelonitrile glucosides of unknown configuration in Acacia parramattensis and Acacia pulchella and (an) as yet unidentified glycoside(s) in Acacia farnesiana are also reported.     

The Effects of Natural Hybridization on the Regulation of Doubly Uniparental Mtdna Inheritance in Blue Mussels (Mytilus Spp.)

Blue mussels in the Mytilus edulis species complex have a doubly uniparental mode of mtDNA inheritance with separate maternal and paternal mtDNA lineages. Female mussels inherit their mtDNA solely from their mother, while males inherit mtDNA from both parents. In the male gonad the paternal mtDNA is preferentially replicated so that only paternal mtDNA is transmitted from fathers to sons. Hybridization is common among differentiated blue mussel taxa; whenever it involves M. trossulus, doubly uniparental mtDNA inheritance is disrupted. We have found high frequencies of males without and females with paternal mtDNA among hybrid mussels produced by interspecific matings between M. galloprovincialis and M. trossulus. In contrast, hybridization between M. galloprovincialis and M. edulis does not affect doubly uniparental inheritance, indicating a difference in the divergence of the mechanisms regulating mtDNA inheritance among the three blue mussel taxa. Our data indicate a high frequency of disrupted mtDNA transmission in F(1) hybrids and suggest that two separate mechanisms, one regulating the transmission of paternal mtDNA to males and another inhibiting the establishment of paternal mtDNA in females, act to regulate doubly uniparental inheritance. We propose a model for the regulation of doubly uniparental inheritance that is consistent with these observations.     

Inhibitory effects of some esters of 2- and 3-substituted alkoxyphenylcarbamic acids on photosynthetic characteristics

The inhibitory effect of 23N-alkyl-4-piperidylesters (alkyl = ethyl-butyl) (APEA) and 8N-ethyl-2-pyrrolidinylmethylesters (EPMEA) of 2- and 3-substituted alkoxyphenylcarbamic acids (alkoxy = butoxy-heptyloxy-) on photosynthetic Hill reaction activity of spinach chloroplasts and on chlorophyll (Chl) synthesis in green algaeChlorella vulgaris was investigated. Inhibitory activities of these compounds were strongly connected with the lipophilicity of the whole molecule. A lower inhibitory activity of 2-alkoxy-substituted derivatives in relation to the corresponding 3-substituted ones was confirmed. Electron spin resonance (ESR) spectra of spinach chloroplasts demonstrated that the studied compounds affected the structure of photosystem (PS) 2 with the release of Mn²⁺ ions into interior of thylakoid membranes.     

IL-4 preferentially activates a novel STAT6 isoform in mast cells

IL-4 is a pleiotropic cytokine that signals through STAT6 to direct the transactivation of multiple gene targets. In this study, we demonstrate that mast cells express a distinct STAT6 isoform. This "mast cell STAT" is a product of the STAT6 gene, but is only 65 kDa in size and appears to lack the defined C-terminal transactivation domain. Despite the presence of the conventional 94-kDa STAT6 molecule, it is the smaller isoform that associates with a consensus STAT6 binding site in extracts from IL-4-treated mast cells. This is the first evidence that STAT6 isoforms can be preferentially activated and bind to DNA in a cell-specific manner. These results imply that an additional level of specificity in the IL-4R signaling mechanism exists and may partially explain the diverse effects that IL-4 exerts on different cell types.