Nisin stimulates oxygen consumption by Staphylococcus aureus and Escherichia coli.

Nisin stimulated oxygen consumption by nongrowing, glucose-metabolizing Staphylococcus aureus and Escherichia coli cells, indicating a protonophore mode of action. A similar stimulation in E. coli cells osmotically stressed to disrupt the outer cell membrane confirmed the cytoplasmic membrane as the site of nisin action and showed that nisin uptake was not prevented by the outer membrane.     

High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans

We compared male-reproductive-tract polypeptides of Drosophila melanogaster and D. simulans by using two-dimensional gel electrophoresis. Approximately 64% of male-reproductive-tract polypeptides were identical between two randomly chosen isofemale lines from these two species, compared with 83% identity for third-instar imaginal wing-disc polypeptides. Qualitatively similar differences were found between reproductive tracts and imaginal discs when D. sechellia was compared with D. melanogaster and with D. simulans. When genic polymorphism was taken into account, approximately 10% of male- reproductive-tract polypeptides were apparently fixed for different alleles between D. melanogaster and D. simulans; this proportion is the same as that found for soluble enzymes by one-dimensional gel electrophoresis. Strikingly, approximately 20% of male-reproductive- tract polypeptides of either D. melanogaster or D. simulans had no detectable homologue in the other species. We propose that proteins of the Drosophila male reproductive tract may have diverged more extensively between species than have other types of proteins and that much of this divergence may involve large changes in levels of polypeptide expression.      

Induction of an immune response through the idiotypic network with monoclonal anti-idiotype antibodies in the carcinoembryonic antigen system.

Anti-idiotype antibodies can mimic the conformational epitopes of the original antigen and act as antigen substitutes for vaccination and/or serological purposes. To investigate this possibility concerning the tumor marker carcinoembryonic antigen (CEA), BALB/c mice were immunized with the previously described anti-CEA monoclonal antibody (MAb) 5.D11 (AB1). After cell fusion, 15 stable cloned cell lines secreting anti-Ids (AB2) were obtained. Selected MAbs gave various degrees of inhibition (up to 100%) of the binding of 125I-labeled CEA to MAb 5.D11. Absence of reactivity of anti-Id MAbs with normal mouse IgG was first demonstrated by the fact that anti-Id MAbs were not absorbed by passage through a mouse IgG column, and second because they bound specifically to non-reduced MAb 5.D11 on Western blots. Anti-5.D11 MAbs did not inhibit binding to CEA of MAb 10.B9, another anti-CEA antibody obtained in the same fusion as 5.D11, or that of several anti-CEA MAbs reported in an international workshop, with the exception of two other anti-CEA MAbs, both directed against the GOLD IV epitope. When applied to an Id-anti-Id competitive radioimmunoassay, a sensitivity of 2 ng/ml of CEA was obtained, which is sufficient for monitoring circulating CEA in carcinoma patients. To verify that the anti-Id MAbs have the potential to be used as CEA vaccines, syngeneic BALB/c mice were immunized with these MAbs (AB2). Sera from immunized mice were demonstrated to contain AB3 antibodies recognizing the original antigen, CEA, both in enzyme immunoassay and by immunoperoxidase staining of human colon carcinoma. These results open the perspective of vaccination against colorectal carcinoma through the use of anti-idiotype antibodies as antigen substitutes.     

The proteolysis of immunoglobulin G with long-acting thyroid-stimulating activity

1. Proteolysis of immunoglobulin G with long-acting thyroid-stimulating activity with papain and pepsin shortened the duration of thyroid stimulation in mice prepared for the McKenzie (1958) bioassay. The time-course appeared to be related to molecular size. 2. The activity after proteolysis was recovered solely in the electrophoretically slow F(ab)-fragment. 3. There was no immunological cross-reaction between pituitary thyroid-stimulating hormone and the active fragments of the long-acting thyroid stimulator despite their similar behaviour in the bioassay. 4. The implications of these findings are discussed.     

Spatial and temporal gene expression patterns occur during corm development.

We investigated gene expression patterns that occur during taro corm development. Two-dimensional gel electrophoresis identified several different prevalent proteins that accumulate during corm development. Microsequencing studies indicated that some of these proteins are related to taste-modifying proteins, such as curculin and miraculin, and proteins found in other storage organs, such as sporamin and the Kunitz trypsin inhibitor. A curculin-encoding cDNA clone, designated as TC1, was identified that corresponds to a highly prevalent 1-kb corm mRNA. The TC1 mRNA accumulates during corm development, is more prevalent in corm apical than basal regions, and is either absent, or present at low concentrations, in other vegetative organs such as the leaf and root. In situ hybridization experiments showed that the TC1 mRNA is highly concentrated in corm storage parenchyma cells and is absent, or present in reduced concentrations, in other corm cells and tissues. Our results show that corm development is associated with the differentiation of specialized cells and tissues, and that these differentiation events are coupled with the temporal and spatial expression of corm-specific genes.     

Effects of pair migratory behavior on breeding phenology and success in a partially migratory shorebird population

In migratory systems, variation in individual phenology can arise through differences in individual migratory behaviors, and this may be particularly apparent in partial migrant systems, where migrant and resident individuals are present within the same population. Links between breeding phenology and migratory behavior or success are generally investigated at the individual level. However, for breeding phenology in particular, the migratory behaviors of each member of the pair may need to be considered simultaneously, as breeding phenology will likely be constrained by timing of the pair member that arrives last, and carryover effects on breeding success may vary depending on whether pair members share the same migratory behavior or not. We used tracking of marked individuals and monitoring of breeding success from a partially migrant population of Eurasian oystercatchers (Haematopus ostralegus) breeding in Iceland to test whether (a) breeding phenology varied with pair migratory behavior; (b) within‐pair consistency in timing of laying differed among pair migratory behaviors; and (c) reproductive performance varied with pair migratory behavior, timing of laying, and year. We found that annual variation in timing of laying differed among pair migratory behaviors, with resident pairs being more consistent than migrant and mixed pairs, and migrant/mixed pairs breeding earlier than residents in most years but later in one (unusually cold) year. Pairs that laid early were more likely to replace their clutch after nest loss, had higher productivity and higher fledging success, independent of pair migratory behavior. Our study suggests that the links between individual migratory behavior and reproductive success can vary over time and, to a much lesser extent, with mate migratory behavior and can be mediated by differences in laying dates. Understanding these cascading effects of pair phenology on breeding success is likely to be key to predicting the impact of changing environmental conditions on migratory species.     

The Expression of Connexins and SOX2 Reflects the Plasticity of Glioma Stem-Like Cells

Glioblastoma (GBM) is the most malignant primary brain tumor, with an average survival rate of 15 months. GBM is highly refractory to therapy, and such unresponsiveness is due, primarily, but not exclusively, to the glioma stem-like cells (GSCs). This subpopulation express stem-like cell markers and is responsible for the heterogeneity of GBM, generating multiple differentiated cell phenotypes. However, how GBMs maintain the balance between stem and non-stem populations is still poorly understood. We investigated the GBM ability to interconvert between stem and non-stem states through the evaluation of the expression of specific stem cell markers as well as cell communication proteins. We evaluated the molecular and phenotypic characteristics of GSCs derived from differentiated GBM cell lines by comparing their stem-like cell properties and expression of connexins. We showed that non-GSCs as well as GSCs can undergo successive cycles of gain and loss of stem properties, demonstrating a bidirectional cellular plasticity model that is accompanied by changes on connexins expression. Our findings indicate that the interconversion between non-GSCs and GSCs can be modulated by extracellular factors culminating on differential expression of stem-like cell markers and cell-cell communication proteins. Ultimately, we observed that stem markers are mostly expressed on GBMs rather than on low-grade astrocytomas, suggesting that the presence of GSCs is a feature of high-grade gliomas. Together, our data demonstrate the utmost importance of the understanding of stem cell plasticity properties in a way to a step closer to new strategic approaches to potentially eliminate GSCs and, hopefully, prevent tumor recurrence.     

Hepatitis B and C in the hemodialysis unit of Tocantins,Brazil: serological and molecular profiles

A survey was conducted in the hemodialysis population of the state of Tocantins, Brazil, aiming to assess the prevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections, to analyze associated risk factors, and also to investigate these viruses genotypes distribution. During January and March 2001, all patients (n = 100) were interviewed at the unique dialysis unit in Tocantins. Blood samples were collected and serum samples were screened for HBV serological markers. Hepatitis B surface antigen positive samples were tested for HBV DNA. All samples were also tested for anti-HCV antibodies and HCV RNA. An overall prevalence of 45% was found for HBV infection (4% were HBsAg/anti-HBc positive, 2% were anti-HBc only and 39% had anti-HBc/anti-HBs markers). Concerning HCV infection, anti-HCV and HCV RNA were detected in 13% and 14% of the subjects, respectively. Three patients were HCV RNA positive and anti-HCV negative, resulting in an overall HCV prevalence of 16%. Univariate analysis of risk factors showed that only shift and length of tile on hemodialysis were associated with HBV and HCV positivity respectively. Among the four HBsAg-positive samples, HBV DNA was detected in three of them, which were identified as genotype A by restriction fragment length polymorphism (RFLP) analysis. All 14HCV RNA-positive samples were genotyped by INNO-LiPA. Genotypes la and 3a were found in 85% and 15%, respectively. The present data show low HBsAg and HCV prevalence rates. The risk factors associated with HBV and HCV positivity suggest that nosocomial transmission may influence in spreading these viruses in the dialysis unit studied.