Glial cells express N-CAM/D2-CAM-like polypeptides in vitro

The joining together of neurites to form fascicles and the growth of axons along glial surfaces during early development suggest that neurone-neurone and neurone-glial adhesion interactions are of considerable importance for defining nerve tracts. In vitro studies have indicated that adhesion between neurones involves a glycoprotein that has been independently studied under the names of N-CAM (for neural cell adhesion molecule), D2-CAM and BSP-2 (refs 10, 11). As N-CAM/D2-CAM appears to be a homophilic ligand that binds to N-CAM/D2-CAM polypeptide on adjacent cells, this glycoprotein is potentially important in adhesion interactions between any two N-CAM/D2-CAM-expressing cells. While it has been suggested that neurone-glial adhesion involves molecules other than N-CAM/D2-CAM, it is known that N-CAM/D2-CAM antigenic determinants are expressed by glial cells in vivo and that injection of anti-N-CAM antibodies into the eye-cup of chick embryos disrupts normal patterns of neuritic apposition to glial endfeet in the developing optic stalk. Do the molecules expressed by glia share restricted antigenic determinants, or binding domains, with N-CAM/D2-CAM, or are N-CAM/D2-CAM polypeptides expressed by glia? Here we present immunocytochemical evidence which suggests that all classes of macroglia express N-CAM/D2-CAM antigenic determinants on their surfaces and immunochemical analyses which indicate that the molecules expressed by purified astrocytes are closely similar, or identical, to at least some forms of N-CAM/D2-CAM obtained from whole brain or purified neurones. However, our results also suggest that different N-CAM/D2-CAM polypeptides may be separately expressed by neurones and astrocytes.     

5-(Hydroxyimino)-4-methoxy-2-(pivaloylimino)thiazolidine-3 -acetamide, a reduced nitroheterocyclic derivative with potent schistosomicidal properties

The synthesis and antischistosome properties of 5-(hydroxyimino)-4-methoxy-2-(pivaloylimino)thiazolidine-3- acetamide (1) are described. The compound was prepared by reduction of the nitrothiazoline (2) with stannous chloride in methanol, and represents the first example of a reduced nitroheterocyclic compound showing potent schistosomicidal properties. The possible relationship of compounds such as 1 to the as yet unidentified reduced active but toxic entities formed in vivo from nitroheterocyclics like metronidazole is discussed.     

Cortical magnification factor and the ganglion cell density of the primate retina

It has long been contentious whether the large representation of the fovea in the primate visual cortex (V1) indicates a selective magnification of this part of the retina, or whether it merely reflects the density of retinal ganglion cells. The measurement of the retinal ganglion-cell density is complicated by lateral displacements of cells around the fovea and the presence of displaced amacrine cells in the ganglion cell layer. We have now identified displaced amacrine cells by GABA immunohistochemistry and by retrograde degeneration of ganglion cells. By reconstructing the fovea from serial sections, we were able to compare the densities of cones, cone pedicles and ganglion cells; in this way we found that there are more than three ganglion cells per foveal cone. Between the central and the peripheral retina, the ganglion cell density changes by a factor of 1,000-2,000, which is within the range of estimates of the cortical magnification factor. There is therefore no need to postulate a selective magnification of the fovea in the geniculate and/or the visual cortex.     

Multiple endocrine neoplasia type 1 gene maps to chromosome 11 and is lost in insulinoma

Multiple endocrine neoplasia type 1 (MEN-1) is a predisposition to hyperplasia of the parathyroid glands, and to hyperplasia or tumours of the anterior pituitary and the endocrine pancreas, and is inherited as an autosomal dominant trait. Here we map the MEN-1 locus to chromosome 11 by family studies, and demonstrate tight linkage with the human muscle phosphorylase gene. By comparing constitutional and tumour tissue genotypes of insulinomas from a pair of brothers who had inherited MEN-1 from their mother, we have shown that oncogenesis in these cases involves unmasking of a recessive mutation at this locus.     

Circadian rhythm of apical Na-channels and Na-transport in rabbit distal colon

In vivo and in vitro studies showed that electrogenic sodium transport in rabbit distal colon is modulated by aldosterone. It varies in a circadian rhythm; the external synchronizer is the light-dark cycle. The site of regulation was found to be in the apical membrane of colonic epithelial cells, in which the number of conducting sodium-channels is increased by aldosterone.     

Phenol and HCl at 550 degrees C yield a large variety of chlorinated toxic compounds

During the past decade it has been shown conclusively that the incineration of municipal and industrial wastes gives rise to emissions of chlorinated dibenzodioxins and dibenzofurans. However, the mechanism by which these toxic compounds are formed has not yet been fully established. Some researchers believe that the presence of organically bound chlorine is necessary, but others consider that inorganic forms of chlorine may also participate in the process. We now report the synthesis of a large number of chlorinated environmental pollutants in a simple high-temperature experiment. The results show that phenol and HCl are the most likely precursors of the chlorinated dibenzodioxins and dibenzofurans formed in the combustion of wastes. The dependence of the reaction on the concentration of HCl indicates a way of controlling the formation of these toxic compounds during incineration.     

New lectins and other putative adhesins in Aeromonas hydrophila

The ability of strains of Aeromonas hydrophila to bind 125I-labelled collagen types I and IV, fibronectin, laminin, lactoferrin, and immobilized mucins and orosomucoid on latex beads was found to be a property common to all the isolated strains. The binding was specific, was inhibited by homologous unlabelled glycoproteins, and was protease sensitive. The nature of the binding is discussed.