Comparison of diverse transport signals in synthetic peptide-induced nuclear transport

Several investigations have demonstrated the ability of synthetic peptides homologous to the nuclear transport signal of simian virus 40 large T antigen to induce the nuclear transport of nonnuclear carrier proteins. To determine the generality of peptide-induced transport, six peptides with sequences derived from four previously identified nuclear transport signals were synthesized and examined for their ability to induce the transport of mouse immunoglobulin G following microinjection into the cytoplasm of mammalian cells. Peptides containing transport signals from simian virus 40 T antigen, Xenopus nucleoplasmin, and adenovirus E1A proteins were highly efficient at peptide-induced transport, while a peptide homologous to yeast MAT alpha 2 protein was incapable of inducing transport. A short nucleoplasmin peptide that contained only the basic amino acid domain was capable of inducing transport but yielded a much slower rate of transport than a long nucleoplasmin peptide encompassing the previously identified minimal transport signal. The short nucleoplasmin signal exhibited a greater capacity for transport than a peptide homologous to the cytoplasmic mutant T antigen signal when conjugates with a low number of signals coupled per carrier protein were examined. However, the short nucleoplasmin peptide was only marginally more effective than the T antigen mutant peptide when conjugates with a high number of signals coupled per carrier protein were examined.     

Winter energetics of Virginia opossums Didelphis virginiana and implications for the species' northern distributional limit

While climatic limitations are widely recognized as primary factors determining the distributions of many species, the physiological link between climate and species' persistence is poorly understood. The Virginia opossum Didelphis virginiana is a species for which winter energetics have been evaluated and a northern geographical limit has been hypothesized. Expansion of opossum populations beyond this limit, however, suggests that a previous winter energetics model requires modification. I update this energetics model by incorporating random foraging success to estimate the probability of opossum survival under varying winter temperature regimes. Estimation of opossum "success" for winters in Amherst, Massachusetts, since 1926 showed that juvenile females, the key breeding component of the population, would survive at a rate high enough to maintain a stable population in only 4 of the 77 yr. The model correctly predicted the fate of 13 of 14 opossums monitored in the Amherst area during the winters of 2000–2003. The current energetics model does not correctly predict autumn weight gain, but it does accurately estimate opossum winter survival. However, the model predicts that opossums should be winter-limited in areas such as Amherst, Massachusetts, where in fact they are well established. This discrepancy may be explained in three ways: weather station data do not adequately reflect available microclimates, opossums show high levels of flexibility in cold-weather foraging behavior, and most likely, humans provide food and shelter that mitigate the effect of winter.     

The injurious effect of pisatin on the plasma membrane of pea

The main cause of wilting which occurs in pea leaves heavilyinfected with powdery mildew was suggested to be due to theinjurious effect of pisatin, a defensive antifungal substanceproduced by the host leaves, which affects the plasma membraneof the same host cells. (Received May 29, 1975; )     

Loss of aPKCλ in Differentiated Neurons Disrupts the Polarity Complex but Does Not Induce Obvious Neuronal Loss or Disorientation in Mouse Brains

Cell polarity plays a critical role in neuronal differentiation during development of the central nervous system (CNS). Recent studies have established the significance of atypical protein kinase C (aPKC) and its interacting partners, which include PAR-3, PAR-6 and Lgl, in regulating cell polarization during neuronal differentiation. However, their roles in neuronal maintenance after CNS development remain unclear. Here we performed conditional deletion of aPKCλ, a major aPKC isoform in the brain, in differentiated neurons of mice by camk2a-cre or synapsinI-cre mediated gene targeting. We found significant reduction of aPKCλ and total aPKCs in the adult mouse brains. The aPKCλ deletion also reduced PAR-6β, possibly by its destabilization, whereas expression of other related proteins such as PAR-3 and Lgl-1 was unaffected. Biochemical analyses suggested that a significant fraction of aPKCλ formed a protein complex with PAR-6β and Lgl-1 in the brain lysates, which was disrupted by the aPKCλ deletion. Notably, the aPKCλ deletion mice did not show apparent cell loss/degeneration in the brain. In addition, neuronal orientation/distribution seemed to be unaffected. Thus, despite the polarity complex disruption, neuronal deletion of aPKCλ does not induce obvious cell loss or disorientation in mouse brains after cell differentiation.     

Colonization of vegetation-rich moraines and inference of multiple sources of colonization in the High Arctic for Salix arctica

Vegetation-rich patches in the High Arctic may serve as a significant source for vegetation reconstruction in the climate changes. Diversity and colonization, however, of such potential source populations in the High Arctic has rarely been studied. We examined chloroplast sequence variation in Salix arctica, a key species in the Canadian High Arctic, from four adjacent glacial moraines of differing ages on Ellesmere Island, Canada, as well as two other populations located at the center and southern end of the species’ range. The estimated ages of the moraines varied from 35,000 to 250 years old. The older moraine populations showed higher within-population genetic variation compared with the other moraine populations, which is generally attributed to differences in establishment age associated with plant densities among moraines. The moraines with smaller plant density had lower genetic diversity and had no private haplotypes, indicating the local population size and genetic diversity may not be recovered within a few thousand years. This suggests seed dispersal at a local scale may be limited even in species with high velocity of seed dispersal, and that High Arctic vegetation-rich patches may serve as significant source populations for sustaining local genetic diversity. In addition, the three regions we observed comprised an evolutionarily distinct lineage and significant population differentiation. This implies multiple sources for the colonization during the most recent deglaciation, resulting in the current wide distribution. Local as well as range-wide processes of colonization would be essential to understand vegetation responses in High Arctic to the environmental changes.     

Physiological Characterization of an Anaerobic Ammonium-Oxidizing Bacterium Belonging to the “Candidatus Scalindua” Group

The phylogenetic affiliation and physiological characteristics (e.g., K_s and maximum specific growth rate [μ_max]) of an anaerobic ammonium oxidation (anammox) bacterium, “Candidatus Scalindua sp.,” enriched from the marine sediment of Hiroshima Bay, Japan, were investigated. “Candidatus Scalindua sp.” exhibits higher affinity for nitrite and a lower growth rate and yield than the known anammox species.     

Exploring the effects of immunity and life history on the dynamics of an endogenous retrovirus

Mammalian DNA is littered with the signatures of past retroviral infections. For example, at least 8% of the human genome can be attributed to endogenous retroviruses (ERVs). We take a single-locus approach to develop a simple susceptible–infected–recovered model to investigate the circumstances under which a disease-causing retrovirus can become incorporated into the host genome and spread through the host population if it were to confer an immunological advantage. In the absence of any fitness benefit provided by the long terminal repeat (LTR), we conclude that signatures of ERVs are likely to go to fixation within a population when the probability of evolving cellular/humoral immunity to a related exogenous version of the virus is extremely small. We extend this model to examine whether changing the speed of the host life history influences the likelihood that an exogenous retrovirus will incorporate and spread to fixation. Our results reveal the parameter space under which incorporation of exogenous retroviruses into a host genome may be beneficial to the host. In our final model, we find that the likelihood of an LTR reaching fixation in a host population is not strongly affected by host life history.     

Metabolic stability and inhibitory effect of O-methylated theaflavins on H2O2-induced oxidative damage in human HepG2 cells

Seven new O-methylated theaflavins (TFs) were synthesized by using O-methyltransferase from an edible mushroom. Using TFs and O-methylated TFs, metabolic stability in pooled human liver S9 fractions and inhibitory effect on H₂O₂-induced oxidative damage in human HepG2 cells were investigated. In O-methylation of theaflavin 3′-O-gallate (TF3′G), metabolic stability was potentiated by an increase in the number of introduced methyl groups. O-methylation of TF3,3′G did not affect metabolic stability, which was likely because of a remaining 3-O-galloyl group. The inhibitory effect on oxidative damage was assessed by measuring the viability of H₂O₂-damaged HepG2 cells treated with TFs and O-methylated TFs. TF3,3′G and O-methylated TFs increased cell viabilities significantly compared with DMSO, which was the compound vehicle (p?<?0.05), and improved to approximately 100%. Only TF3′G did not significantly increase cell viability. It was suggested that the inhibitory effect on H₂O₂-induced oxidative damage was potentiated by O-methylation or O-galloylation of TFs.