Artificial insertion of a dominant gene for resistance to avian leukosis virus into the germ line of the chicken

Summary This report describes the unique biological properties of a transgenic chicken line that contains a defective avian leukosis virus (ALV) proviral insert that we call alv6. Chick embryo fibroblasts (CEF) containing this insert express subgroup A envelope glycoprotein since they yield focus-forming pseudotype virus when co-cultivated with transformed quail cells expressing envelope-defective Bryan high-liter Rous sarcoma virus (RSV). In addition, these cells display high interference to subgroup A RSV but not to subgroup B RSV infection. Chickens containing this insert are highly resistant to pathogenic subgroup A ALV infection, but show little immunological tolerance to subgroup B ALV infection. Thus we have artificially inserted a dominant gene for resistance to avian leukosis infection into the chicken germ line.     

Chromosomal localization of three endogenous retrovirus loci associated with virus production in White Leghorn chickens.

Proposed mechanisms for the generation of endogenous retrovirus loci have been examined by determining the chromosomal distribution of these loci by means of in situ hybridization. Unlike the clustering on chromosome 1 of five endogenous retrovirus loci associated with the gs- chf- phenotype A. Tereba and S. M. Astrin, submitted for publication), three loci associated with endogenous retrovirus production (V+ phenotype) were located on three separate chromosomes. ev2, which codes for the prototype endogenous RAV-0 genome in line 7(2) chickens, was localized near the middle of the long arm of chromosome 2, ev7, coding for a noninfectious, inducible genome present in line 15B chickens, was located near the end of the long arm of the Z chromosome. A third V+ locus, designated ev14, was detected near the middle of chromosome 3. This arrangement of V+ loci is consistent with an integration mechanism employing randomly distributed integration sites in the chicken genome. In addition, these data provide evidence suggesting that the gs- chf- -associated loci may have been generated by a different mechanism.     

Biological activity of leukotriene B4 analogs: inhibition of guinea pig eosinophil migration in vitro by the 2,6-disubstituted pyridine analogs U-75,302 and U-75,485.

A "late phase" antigen-induced bronchoalveolar eosinophilia has been demonstrated in ovalbumin sensitized guinea pigs (1,2). This in vivo response to antigen inhalation can be inhibited by a 2,6-disubstituted pyridine analog of LTB4, U-75,302(2) (3). In the present study, the mechanism of the drug action was studied by assessing the activity of U-75,302 and a second analog, U-75,485 to displace [3H]-leukotriene B4 binding at the guinea pig eosinophil membrane, as well as their action as chemoattractants or inhibitors of the directional migration of guinea pig eosinophils in vitro. Radioligand competition experiments demonstrated that both analogs interacted strongly with the high affinity LTB4 binding sites on guinea pig eosinophil membrane. Both analogs are powerful chemoattractants for guinea pig eosinophils since they induced directional migration of guinea pig eosinophils when administered alone. In addition, when the cells were treated with either analog and their chemotaxis response was measured in response to a natural chemoattractant, both U-75,302 and U-75,485 at concentrations of 0.1 to 100 microM dose dependently inhibited the LTB4 induced chemotaxis response. The EC50s obtained for U-75,302 and U-75,485 as inhibitors of LTB4 induced guinea pig eosinophil chemotaxis were estimated to be 11.5 +/- 5.5 microM and 5.4 +/- 2.5 microM respectively. Under the same conditions, they had no significant effect upon eosinophil migration induced by zymosan activated plasma at concentrations below 100 microM. We suggest that the inhibition of antigen-induced eosinophil infiltration in guinea pig airway in vivo by U-75,302 or U-75,485 may be a result of partial antagonism or desensitization at the LTB4 receptor level of guinea pig eosinophils.     

Synbiotic Microcapsules That Enhance Microbial Viability during Nonrefrigerated Storage and Gastrointestinal Transit

A Bifidobacterium infantis strain was microencapsulated within a film-forming protein-carbohydrate-oil emulsion. This novel encapsulant incorporated prebiotics and substantially protected the bacterium during nonrefrigerated storage and gastrointestinal transit. The dried microcapsules were small (15 to 20 μm), had low water activity (0.2 to 0.3), and rapidly released the bacteria in simulated intestinal fluid.     

Developmental and evolutionary assumptions in a study about the impact of premature birth and low income on mother–infant interaction

In order to study the impact of premature birth and low income on mother–infant interaction, four Portuguese samples were gathered: full-term, middle-class (n = 99); premature, middle-class (n = 63); full-term, low income (n = 22); and premature, low income (n = 21). Infants were filmed in a free play situation with their mothers, and the results were scored using the CARE Index. By means of multinomial regression analysis, social economic status (SES) was found to be the best predictor of maternal sensitivity and infant cooperative behavior within a set of medical and social factors. Contrary to the expectations of the cumulative risk perspective, two factors of risk (premature birth together with low SES) were as negative for mother–infant interaction as low SES solely. In this study, as previous studies have shown, maternal sensitivity and infant cooperative behavior were highly correlated, as was maternal control with infant compliance. Our results further indicate that, when maternal lack of responsiveness is high, the infant displays passive behavior, whereas when the maternal lack of responsiveness is medium, the infant displays difficult behavior. Indeed, our findings suggest that, in these cases, the link between types of maternal and infant interactive behavior is more dependent on the degree of maternal lack of responsiveness than it is on birth status or SES. The results will be discussed under a developmental and evolutionary reasoning.     

FBF and Its Dual Control of gld-1 Expression in the Caenorhabditis elegans Germline

FBF, a PUF RNA-binding protein, is a key regulator of the mitosis/meiosis decision in the Caenorhabditis elegans germline. Genetically, FBF has a dual role in this decision: it maintains germ cells in mitosis, but it also facilitates entry into meiosis. In this article, we explore the molecular basis of that dual role. Previous work showed that FBF downregulates gld-1 expression to promote mitosis and that the GLD-2 poly(A) polymerase upregulates gld-1 expression to reinforce the decision to enter meiosis. Here we ask whether FBF can act as both a negative regulator and a positive regulator of gld-1 expression and also investigate its molecular mechanisms of control. We first show that FBF co-immunoprecipitates with gld-1 mRNA, a result that complements previous evidence that FBF directly controls gld-1 mRNA. Then we show that FBF represses gld-1 expression, that FBF physically interacts with the CCF-1/Pop2p deadenylase and can stimulate deadenylation in vitro, and that CCF-1 is partially responsible for maintaining low GLD-1 in the mitotic region. Finally, we show that FBF can elevate gld-1 expression, that FBF physically interacts with the GLD-2 poly(A) polymerase, and that FBF can enhance GLD-2 poly(A) polymerase activity in vitro. We propose that FBF can affect polyadenylation either negatively by its CCF-1 interaction or positively by its GLD-2 interaction.     

Toxicity and cellular responses of intestinal cells exposed to titanium dioxide

The increasing use of nanomaterials in healthcare and industrial products heightens the possibility of their ingestion by humans, other mammals, and fish. While toxicity of many nanomaterials has recently been studied, reports of non-lethal effects of nanomaterials remain ill-defined. This study investigates possible pathways by which nanoparticles, titanium dioxide (TiO₂), could cross the epithelium layer by employing both toxicity and mechanistic studies. This study provides evidence that at 10 μg/mL and above, TiO₂ nanoparticles cross the epithelial lining of the intestinal model by transcytosis, albeit at low levels. TiO₂ was able to penetrate into and through the cells without disrupting junctional complexes, as measured by γ-catenin. To monitor the epithelial integrity, transepithelial electrical resistance (TEER) was employed and determined low concentrations (10 or 100 μg/mL) of TiO₂ do not disrupt epithelial integrity. Live/dead analysis results did not show cell death after exposure to TiO₂. In addition, at 10 μg/mL (and above) TiO₂ nanoparticles begin alteration of both microvillar organization on the apical surface of the epithelium as well as induce a rise in intracellular-free calcium. The latter is a mechanism cells use to respond to extracellular stimuli and may be linked to the alteration of the apical microvilli. Although TiO₂ does not show cell death, the implication of other, non-lethal, effects could lead to undesired outcomes (i.e., disease, malnutrition, shortened life span, etc.).     

Cellular analyses of the mitotic region in the Caenorhabditis elegans adult germ line

The Caenorhabditis elegans germ line provides a model for understanding how signaling from a stem cell niche promotes continued mitotic divisions at the expense of differentiation. Here we report cellular analyses designed to identify germline stem cells within the germline mitotic region of adult hermaphrodites. Our results support several conclusions. First, all germ cells within the mitotic region are actively cycling, as visualized by bromodeoxyuridine (BrdU) labeling. No quiescent cells were found. Second, germ cells in the mitotic region lose BrdU label uniformly, either by movement of labeled cells into the meiotic region or by dilution, probably due to replication. No label-retaining cells were found in the mitotic region. Third, the distal tip cell niche extends processes that nearly encircle adjacent germ cells, a phenomenon that is likely to anchor the distal-most germ cells within the niche. Fourth, germline mitoses are not oriented reproducibly, even within the immediate confines of the niche. We propose that germ cells in the distal-most rows of the mitotic region serve as stem cells and more proximal germ cells embark on the path to differentiation. We also propose that C. elegans adult germline stem cells are maintained by proximity to the niche rather than by programmed asymmetric divisions.