Relative contribution of promoter and intragenic sequences in the hormonal regulation of rat beta-casein transgenes

In order to identify DNA sequences responsible for the regulation beta-casein gene expression, lines of transgenic mice bearing the entire rat beta-casein gene and two rat beta-casein promoter chloramphenicol acetyltransferase (CAT) fusion genes have been established. All three transgenes have been shown previously to be regulated in a tissue- and stage specific manner. To investigate the relative contribution of promoter and intragenic sequences in the hormonal regulation of the beta-casein gene, mammary explant cultures derived from these lines of mice have now been performed, and the effects of PRL and glucocorticoids on transgene as compared with endogenous beta-casein gene expression have been quantified. After the addition of PRL to cultures performed in the presence of insulin and glucocorticoids, a 25- to 40-fold induction of endogenous mouse beta-casein mRNA was observed after 48 hr. A comparable greater than 25-fold induction of transgene expression after PRL addition was observed in explant cultures derived from a line of mice expressing the entire rat beta-casein gene. In contrast, PRL addition elicited only a 1- to 4.5-fold increase in CAT activity in cultures derived from two lines of mice bearing casein-CAT fusion genes with either 524 or 2300 base pairs of 5'-flanking DNA. In the presence of insulin, glucocorticoid or PRL addition alone increased endogenous beta-casein gene expression 2- to 2.5-fold and 5- to 10-fold, respectively, but only a 1.2- to 2.5-fold induction of CAT activity was observed for each hormone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Function of the human immunodeficiency virus types 1 and 2 Rev proteins is dependent on their ability to interact with a structured region present in env gene mRNA.

The interaction of the human immunodeficiency virus type 1 (HIV-1) Rev protein with a structured region in env mRNA (the Rev-responsive element [RRE]) mediates the export of structural mRNAs from the nucleus to the cytoplasm. We demonstrated that unlike HIV-1 Rev, which functions with both the HIV-1 and HIV-2 RREs, HIV-2 Rev functions only with the HIV-2 RRE. Rev-RRE binding studies suggested that the lack of nonreciprocal complementation stems from the inability of HIV-2 Rev to interact with HIV-1 RRE RNA. Maintenance of RNA secondary structure, rather than the primary nucleotide sequence, appeared to be the major determinant for interaction of both HIV-1 and HIV-2 Rev with the HIV-2 RRE. Moreover, the binding domain of the HIV-2 RRE recognized by HIV-1 Rev was dissimilar to the binding domain of the HIV-1 RRE, in terms of both secondary structure and primary nucleotide sequence. Our results support the hypothesis that function of HIV Rev proteins and possibly the functionally similar Rex proteins encoded by the human T-cell leukemia viruses (HTLVs) HTLV-I and HTLV-II is controlled by the presence of RNA secondary structure generated within the RRE RNA.     

A chimeric mouse-human antibody that retains specificity for HIV gp120 and mediates the lysis of HIV-infected cells

Murine mAb BAT123, which was made against the envelope glycoprotein gp120 of HTLV-IIIB strain of HIV type 1 (HIV-1), is capable of neutralizing HTLV-IIIB in vitro. It also inhibits the fusion between uninfected CD4+ cells and HIV-1-infected cells to form syncytia. As a step to explore the potential utility of the anti-HIV antibody in vivo, we have constructed a mouse-human chimeric antibody by rDNA techniques. The chimeric antibody, which bears the variable domains of mouse antibody BAT123 and constant domains Cr1 and C kappa of human Ig retains the Ag specificity of BAT123 as determined by its reactivity with HIV-1-infected H9 cells, gp120 in Western blot analysis, and the oligopeptide recognized by BAT123. The antiviral activities of the chimeric antibody in neutralizing HIV-1 infection as well as inhibiting the syncytia formation are also found identical to those of the parent murine antibody. Moreover, in the presence of human blood mononuclear cells, the chimeric antibody but not BAT123 (mouse IgG1) induces antibody-dependent cellular cytotoxicity. The findings point to the potential usefulness of the chimeric antibody in treating patients infected with HIV-1.     

Intravenously injected sialidase inactivates attachment sites for lymphocytes on high endothelial venules

Blood-borne lymphocytes initiate entry into secondary lymphoid organs, such as peripheral lymph nodes (PN) and gut-associated Peyer's patches (PP), by a highly specific adhesive interaction between the lymphocytes and the endothelium of specialized blood vessels known as a high endothelial venules (HEV). The selectivity with which functional subpopulations of lymphocytes migrate into particular lymphoid organs is believed to be regulated by the expression of cell adhesion receptors and complementary ligands on lymphocytes and HEV, respectively. The entry of lymphocytes into PN and PP has clearly been shown to involve distinct receptor-ligand pairs. Employing the Stamper-Woodruff in vitro adhesion assay, which measures lymphocyte attachment to HEV in cryostat-cut sections of lymphoid organs, we have previously shown that treatment of PN sections with two different sialidases inactivates HEV-adhesive ligands, whereas treatment of PP tissue sections has no effect on HEV-adhesive function. We now report that in vivo exposure of HEV to sialidase (after i.v. injection of the enzyme) also selectively prevents subsequent in vitro attachment of lymphocytes to PN HEV but not to PP HEV. Consistent with this organ-selective impairment of HEV-adhesive function by sialidase, i.v. injection of the enzyme is shown to prevent short term lymphocyte accumulation within peripheral lymph nodes while having no significant effect on accumulation in PP, blood, or nonlymphoid organs. Histologic examination with the sialic acid-specific lectin from Limax flavus verified that i.v. injected sialidase effectively removes stainable sialic acid moieties from HEV in both PN and PP. This study confirms that sialic acid is required for the adhesive function of PN HEV-ligands. A role for sialic acid as either a recognition determinant or as a regulatory molecule can be envisioned. In view of the fact that many pathogens release sialidase and cause substantially elevated serum levels of this enzyme, the present observations may have pathophysiologic significance. One mechanism by which such pathogens may avoid destruction is to inactivate susceptible HEV-ligands and disrupt the entry of lymphocytes into lymphoid organs where immune responses against the pathogens would normally be initiated.     

The seasonal occurrence of ticks (Acari: Ixodidae) on sheep and in the field in the Judean area of Israel

A 2 year survey of ixodid ticks in the Judean area of Israel between 1983 and 1985 showed that sheep were parasitized by the following species:Rhipicephalus sanguineus group (30.6%),Rhipicephalus bursa (25.3%),Haemaphysalis cretica (20.5%),Haemaphysalis otophila (20.1%) andHyalomma anatolicum excavatum (3.1%). Three other species,Hyalomma marginatum rufipes, Boophilus annulatus andAmblyomma lepidum were also present but in very low numbers. A total of 50 816 specimens (78.1% adult ticks) were collected from the sheep. In the field, a total of 4780 ticks (8.7% adults) were collected and 64.3% consisted ofR. bursa. Other species found wereH. cretica (14.5%),H. a. excavatum (13.7%),H. otophila (3.4%),R. sanguineus group (1.9%) and 1.7% wasIxodes eldaricus. The number of ticks collected varied from year to year and seasonal activity was observed in all species except forH. a. excavatum. In all species, males outnumbered females, with the exception ofH. cretica. The seasonal occurrence, tick ecology and disease relationship is discussed for each species.     

Recent coral facies of the Indian Ocean Coast of Somalia with an interim check list of corals

Summary From a study of two areas, Jesira and the Bajuni Archipelago, about 400 km apart, a general pattern can be established for the Recent facies, together with the morphological and taxonomic features of the corals. Present day coral development is characterized by true fringing reefs in the Bajuni Archipelago and by scattered patches and knolls in the Jesira area. The coral fauna, consisting of 27 genera and 63 species so far (including all uncertainties, but not sight records), is rather poor, though coral communities are locally well developed. These figures probably reflect incomplete study and sampling. Although comparison with other areas may therefore be premature, a preliminary biogeographical analysis suggests that this fauna is more closely related to that of the Red Sea than to East Africa and the Seychelles. This differs from other published biogeographical work on Indian Ocean coral faunas, but further study of the corals in this and neighbouring areas of the Indian Ocean is needed in order to resolve this apparent anomaly.