Investigation of the levels of free purine and pyrimidine bases and metabolites in mechanically recovered meats

Levels of free purine and pyrimidine bases and metabolites, in particular xanthine, have been investigated in poultry meat and MRM as potential qualitative or quantitative markers for the presence of MRM in meat products. Only xanthine was found to exhibit significantly different levels between the source meat and MRM product where, for example, it was found to be present at approximately 100 μg/g in turkey MRM but only 57, 33 and 14 μg/g in the neck, leg and breast meat respectively. The wide variation in levels within a cut, together with the overlap between figures for source meat and MRM, preclude the use of xanthine as a robust qualitative or quantitative marker. Processing of turkey meat by subjecting it to an increasing level of comminution does not appear to elevate the indigenous level of free xanthine.     

Fusion-competent vaccines: broad neutralization of primary isolates of HIV

Current recombinant human immunodeficiency virus (HIV) gp120 protein vaccine candidates are unable to elicit antibodies capable of neutralizing infectivity of primary isolates from patients. Here, "fusion-competent" HIV vaccine immunogens were generated that capture the transient envelope-CD4-coreceptor structures that arise during HIV binding and fusion. In a transgenic mouse immunization model, these formaldehyde-fixed whole-cell vaccines elicited antibodies capable of neutralizing infectivity of 23 of 24 primary HIV isolates from diverse geographic locations and genetic clades A to E. Development of these fusion-dependent immunogens may lead to a broadly effective HIV vaccine.     

Thrombin receptor (PAR-1) antagonists. Heterocycle-based peptidomimetics of the SFLLR agonist motif

Phorbol ester treatment of MCF-7 cells led to the tyrosine phosphorylation and activation of PKC delta. However, through Western blot analysis and in vitro immunecomplex kinase assays, we detected a differential localization of tyrosine-phosphorylated PKC delta and catalytically active PKC delta. Catalytically active PKC delta was concentrated in Triton X-100 solubilized-membrane fractions while tyrosine-phosphorylated PKC delta was localized to the cytosol fraction. Phorbol ester treatment of MCF-7 cells stimulated both the time-dependent in vivo association of Src with PKC delta, evidenced in Src immunoprecipitates by the co-immunoprecipitation of PKC delta, and activation of Src, evidenced in Src immunoprecipitates as an increase in reactivity with a Src antibody (clone 28) reactive only with active Src (dephosphorylated on residue 530) and in Src and PKC delta immunoprecipitates by an increase in Src kinase activity. While our data are consistent with reports in the literature showing the activator/stimulus-dependent tyrosine phosphorylation of PKC delta, our data show that the tyrosine phosphorylation of PKC delta is not essential for kinase activity. These results are the first to demonstrate an in vivo association between PKC delta and active Src in the absence of over-expression of either PKC delta or Src, and support the association of Src and PKC delta towards a physiological function.     

Functional expression of the cystic fibrosis transmembrane conductance regulator in yeast

Recombinant human cystic fibrosis transmembrane conductance regulator (CFTR) has been produced in a Saccharomyces cerevisiae expression system used previously to produce transport ATPases with high yields. The arrangement of the bases in the region immediately upstream from the ATG start codon of the CFTR is extremely important for high expression levels. The maximal CFTR expression level is about 5-10% of that in Sf9 insect cells as judged by comparison of immunoblots. Upon sucrose gradient centrifugation, the majority of the CFTR is found in a light vesicle fraction separated from the yeast plasma membrane in a heavier fraction. It thus appears that most of expressed CFTR is not directed to the plasma membrane in this system. CFTR expressed in yeast has the same mobility (ca. 140 kDa) as recombinant CFTR produced in Sf9 cells in a high resolution SDS-PAGE gel before and after N-glycosidase F treatment, suggesting that it is not glycosylated. The channel function of the expressed CFTR was measured by an isotope flux assay in isolated yeast membrane vesicles and single channel recording following reconstitution into planar lipid bilayers. In the isotope flux assay, protein kinase A (PKA) increased the rate of 125I- uptake by about 30% in membrane vesicles containing the CFTR, but not in control membranes. The single channel recordings showed that a PKA-activated small conductance anion channel (8 pS) with a linear I-V relationship was present in the CFTR membranes, but not in control membranes. These results show that the human CFTR has been expressed in functional form in yeast. With the reasonably high yield and the ability to grow massive quantities of yeast at low cost, this CFTR expression system may provide a valuable new source of starting material for purification of large quantities of the CFTR for biochemical studies.     

Parental exposure to pesticides and poor clutch viability in American alligators

In central Florida, alligators (Alligator mississippiensis) inhabiting lakes contaminated with organochlorine pesticides (OCPs) produce eggs that have high OCP concentrations and low clutch viability (proportion of eggs in a clutch that yield a live hatchling) compared to those from less contaminated lakes (reference lakes). However, a clear dose-response relationship has not been established between OCPs and poor clutch viability. In order to better elucidate a cause and effect relationship between OCP exposure and clutch viability, we conducted concurrent field and laboratory studies. Our field study reaffirmed that eggs of wild alligators from OCP-contaminated lakes and wetlands continue to have lower clutch viability and higher OCP burdens than eggs from reference lakes. Our field study also demonstrated that OCP egg burdens were strongly correlated with clutch viability for some of the OCP-contaminated sites, but not all. To better test causal relationships, a parental exposure study was conducted using captive adult alligators. Our laboratory study demonstrated that dietary exposure of captive alligators to an ecologically relevant OCP mixture caused alligators to produce eggs with higher OCP burdens and reduced clutch viability, as compared to the captive-control population. The experimentally induced egg burdens and clutch viability reductions were similar to those of wild alligators from OCP-contaminated sites. Our field and laboratory results suggest parental OCP exposure may be contributing to low clutch viability in wild alligators inhabiting OCP-contaminated habitats, raising some concern for endangered crocodilians living in OCP-contaminated habitats.     

Language-specific lexical access of homographs by bilinguals.

Spanish-English bilinguals were tested in a two-part lexical-decision experiment. Word stimuli were (a) noncognates (words with differently spelled translations, e.g., dog and perro), (b) cognates (words with identically spelled translations, e.g., actual), and (c) homographic noncognates (words spelled identically in both languages but with different meanings, e.g., red). The noncognate and cognate words had similar frequencies of usage in each language, but the homographic noncognates differed. In each part of the experiment, subjects looked for words in a single target language. In both parts, word latencies were primarily determined by frequency of usage of a word in the target language. In the unanticipated cross-language-transfer trials in Part 2, no cross-language facilitation of noncognate translations was found. However, there was equivalent cross-language facilitation of cognates and homographic noncognates (i.e, repetitions of the same spelling pattern). This cross-language transfer was independent of the target language and frequency of usage in the target languages. The results of this experiment are consistent with the hypothesis that lexical information is represented in language-specific lexicons and that word recognition requires searching the language-appropriate lexicon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Healing response to various forms of human demineralized bone matrix in athymic rat cranial defects

PURPOSE: This study compared the ability of a bone autograft and four distinct forms of human demineralized bone (DBM) to elicit bone repair in a critical size cranial defect in athymic rats. MATERIALS AND METHODS: Cranial defects were created in athymic rats and then grafted with either an autograft, rat DBM particles in glycerol (rGel), or one of four forms of human DBM: 1) hGel; 2) Putty (DBM fibers in glycerol); 3) Sheet (sheet of DBM fibers); or 4) Flex (DBM fiber sheet with glycerol). Histology, histomorphometry, and radiographic density of the graft sites were evaluated at 8 weeks. RESULTS: Of the grafted defects, 29% to 58% were found to be filled with new bone. The rGel and human forms of DBM stimulated similar amounts of new bone growth in comparison with the autograft-filled defects. The fiber-based grafts produced the largest amounts of new bone. CONCLUSIONS: Human DBM in gel, putty and sheet forms were found to perform as well as an autograft in a critical size cranial defect in the athymic rat.