Home range use and the exploitation of gum in the marmosetCallithrix jacchus jacchus

Three wild groups of common marmoset, Callithrix jacchus jacchus,in north-east Brazil, of approximately similar size, had home ranges between 2.5 and 6.5 ha. But their core areas were similar in size between 1.0 and 1.5 ha, with a monthly area of heavy use between 1.1 and 1.6 ha. The groups were selective in the use of their home ranges, even though they were small: they used some areas heavily and others lightly. The core areas had higher densities of trees that produced gum exudates than did other parts of the home ranges. Our data suggest that a group of marmosets in this habitat may require a minimum of about 50 gum trees in its home range at a minimum density of about 50 trees/ha. In addition, the animals require suitable trees in which to sleep. We suggest that patches of forest with these desirable properties remain relatively fixed in size and location over the years and that individual animals are constantly in flux between them.     

Liver connective tissue cells isolated from human schistosomal fibrosis or alcoholic cirrhosis represent a modified phenotype of smooth muscle cells

Hepatic connective tissue cells associated with schistosomal fibrosis and alcoholic cirrhosis were studied in vitro. Primary cell lines were isolated from all biopsies: they were identified as specific homogeneous cell populations, named liver connective tissue cells (LCTC). They were recognized as analogous to smooth muscle cells, different from true fibroblasts by morphological and physiological criteria. The proliferative capacity of LCTC is directly proportional to the degree of fibrosis in hepatic tissues. LCTC are able to secrete type I, III and IV collagen, fibronectin, laminin and amyloid P component. Their relationship with specific pathology of intrahepatic vascular tree in schistosomiasis is hypothesized.     

Complement-dependent induction of DNA synthesis and cell proliferation in human liver connective tissue cells in vitro

Summary Liver connective tissue cells (LCTC) isolated from patients with fibrotic livers have morphological and biochemical characteristics of myofibroblasts. We have examined the proliferation of LCTC derived from normal livers and from livers with fibrosis of different etiologies, as well as proliferation of skin fibroblasts. We have compared proliferation rates in the presence of fresh human serum and heat-inactivated serum. While skin fibroblast and LCTC from normal liver showed no difference, proliferation of LCTC from fibrotic livers was markedly decreased in the presence of heat-inactivated serum. We demonstrate that the native complement component C1 is a factor involved in the induction of DNA synthesis and proliferation of LCTC isolated from fibrotic livers. We propose that native C1, acting probably in cooperation with other growth factors, is involved in the expansion of connective tissue cells during the development of liver fibrosis.     

Inspection and evaluation of host plant by the butterfly Mechanitis lysimnia (Nymph., Ithomiinae) before laying eggs: a mechanism to reduce intraspecific competition

Parasites of all kinds affect the behaviour of their hosts, often making them more susceptible to predators. The associated loss in expected future reproductive success of infected hosts will vary among individuals, with younger ones having more lose than older ones. For this reason, young hosts would benefit more by opposing the effects of parasites than old ones. In a laboratory study, the effects of the trematode Telogaster opisthorchis on the anti-predator responses of the upland bully (Gobiomorphus breviceps) and of the common river galaxias (Galaxias vulgaris) were examined in relation to fish age. In a bully population where parasites were very abundant, the magnitude of the fish's anti-predator responses decreased as the number of parasites per fish increased, and this effect was significantly more pronounced in age 2 + and, to a lesser extent, age 3 + fish than in age 1 + fish. In another bully population where parasites were 10 times less abundant, similar effects were noticeable but not significant, whereas no effects of parasites on the responses of galaxiids to predators were apparent. Differences in the abundance of parasites and in their sites of infection in fish may explain the variability among host populations or species. However, in the bully population with high parasite abundance, parasitism has age-dependent effects on responses to predators, providing some support for the prediction that young fish with high expected future reproductive success invest more energy into opposing the effects of parasites than do older fish.     

Applications of DNA shuffling to pharmaceuticals and vaccines

DNA shuffling is a practical process for directed molecular evolution which uses recombination to dramatically accelerate the rate at which one can evolve genes. Single and multigene traits that require many mutations for improved phenotypes can be evolved rapidly. DNA shuffling technology has been significantly enhanced in the past year, extending its range of applications to small molecule pharmaceuticals, pharmaceutical proteins, gene therapy vehicles and transgenes, vaccines and evolved viruses for vaccines, and laboratory animal models.     

Inhibition of protein tyrosine phosphatase activity by diamide is reversed by epidermal growth factor in fibroblasts.

Diamide (azodicarboxylic acid bis(dimethylamide] inhibits protein tyrosine phosphatase activity in fibroblasts without altering protein tyrosine kinase activity associated with the epidermal growth factor receptor. The loss of protein tyrosine phosphatase activity caused by diamide is reversed by 2-mercaptoethanol or epidermal growth factor.     

Use of lactose to induce expression of soluble NifA protein domains of Herbaspirillum seropedicae in Escherichia coli

Overexpression and purification are procedures used to allow functional and structural characterization of proteins. Many overexpressed proteins are partially or completely insoluble, and can not be easily purified. The NifA protein is an enhancer-binding protein involved in activating the expression of nif and some fix genes. The NifA protein from many organisms is usually insoluble when over-expressed, and therefore difficult to work with in vitro. In this work we have overexpressed the central + C-terminal and the central domains of the Herbaspirrilum seropedicae NifA protein in an Escherichia coli background. Expression was induced with either IPTG or lactose. The data showed that induction with lactose promoted a significantly higher percentage of these proteins in the soluble fraction than with IPTG. This probably reflects a slower kinetics of induction by lactose.     

Allelic diversity and phylogeny of homB, a novel co-virulence marker of Helicobacter pylori

Background  

The homB gene is a Helicobacter pylori disease-marker candidate, strongly associated with peptic ulcer disease, while homA, its paralogue gene with 90% sequence identity, is correlated with non-ulcer dyspepsia. The HomB encoded outer membrane protein was shown to contribute to the proinflammatory properties of H. pylori and also to be involved in bacterial adherence.     

Characterization of the receptor for insulin-like growth factor on Leishmania promastigotes

Insulin-like growth factor (IGF)-I constitutively present in the skin is one of the first growth factors that Leishmania parasites encounter after transmission to the vertebrate host. We have previously shown that IGF-I is a potent growth-promoting factor for Leishmania parasites. IGF-I binds specifically to a single-site putative receptor at the parasite membrane, triggering a cascade of phosphorylation reactions. In the present article we characterize the receptor for IGF-I on Leishmania (Leishmania) mexicana promastigotes. The receptor is a monomeric glycoprotein with a molecular mass of 65 kDa and is antigenically related to the alpha chain of human type 1 IGF-I receptor. Upon IGF-I stimulation the receptor undergoes autophosphorylation on tyrosine residues with activation of its signaling pathway. Activation of the IGF-I receptor also leads to phosphorylation of an 185-kDa molecule that is homologous to the substrate of the insulin receptor present in human cells, the insulin receptor substrate 1 (IRS-1).     

Ubiquilin overexpression reduces GFP-polyalanine-induced protein aggregates and toxicity

Several human disorders are associated with an increase in a continuous stretch of alanine amino acids in proteins. These so-called polyalanine expansion diseases share many similarities with polyglutamine-related disorders, including a length-dependent reiteration of amino acid induction of protein aggregation and cytotoxicity. We previously reported that overexpression of ubiquilin reduces protein aggregates and toxicity of expanded polyglutamine proteins. Here, we demonstrate a similar role for ubiquilin toward expanded polyalanine proteins. Overexpression of ubiquilin-1 in HeLa cells reduced protein aggregates and the cytotoxicity associated with expression of a transfected nuclear-targeted GFP-fusion protein containing 37-alanine repeats (GFP-A37), in a dose dependent manner. Ubiquilin coimmunoprecipitated more with GFP proteins containing a 37-polyalanine tract compared to either 7 (GFP-A7), or no alanine tract (GFP). Moreover, overexpression of ubiquilin suppressed the increased vulnerability of HeLa cell lines stably expressing the GFP-A37 fusion protein to oxidative stress-induced cell death compared to cell lines expressing GFP or GFP-A7 proteins. By contrast, siRNA knockdown of ubiquilin expression in the GFP-A37 cell line was associated with decreased cellular proliferation, and increases in GFP protein aggregates, nuclear fragmentation, and cell death. Our results suggest that boosting ubiquilin levels in cells might provide a universal and attractive strategy to prevent toxicity of proteins containing reiterative expansions of amino acids involved in many human diseases.