Repetitive sequences of the sea urchin genome: Distribution of members of specific repetitive families

Three repetitive sequence families from the sea urchin genome were studied, each defined by homology with a specific cloned probe one to a few hundred nucleotides long. Recombinant λ-sea urchin DNA libraries were screened with these probes, and individual recombinants were selected that include genomic members of these families. Restriction mapping, gel blot, and kinetic analyses were carried out to determine the organization of each repeat family. Sequence elements belonging to the first of the three repeat families were found to be embedded in longer repeat sequences. These repeat sequences frequently occur in small clusters. Members of the second repeat family are also found in a long repetitive sequence environment, but these repeats usually occur singly in any given region of the DNA. The sequences of the third repeat are only 200 to 300 nucleotides long, and are generally terminated by single copy DNA, though a few examples were found associated with other repeats. These three repeat sequence families constitute sets of homologous sequence elements that relate distant regions of the DNA.     

Scanning electron microscopic study of uropathogen adherence to a plastic surface

We used a polyethylene surface to study the adherence of various urinary pathogens to a representative inert surface. The bacteria were suspended in filter-sterilized urine during this adhesion study, and differential adhesion was clearly demonstrated. Pseudomonas aeruginosa adhered most avidly and formed large microcolonies that were surrounded by an extensive amorphous matrix. Staphylococcus saprophyticus also formed microcolonies on the surface of the plastic droppers. In general, piliated strains of Escherichia coli adhered less avidly than the other organisms, but more avidly than nonpiliated strains; however, one piliated strain of E. coli adhered very poorly and behaved like a nonpiliated strain.     

Topochemistry of blood cells of the Gallus domesticus (Aves, Galliforme).

Blood smears of both male and female chicken Gallus domesticus were analysed by using the following topochemical methods: a) Periodic acid-Schiff (PAS) for glycogen. b) Mercury-bromophenol blue for protein. c) O-Toluidine for myeloperoxidase. d) Sudan black B for lipid. The PAS reaction revealed glycogen in the cytoplasm of all thrombocytes and in a few heterophils. The presence of proteins was evidenced in all types of cells. However variation in the intensity of staining of protein granules was observed in the fusiform structures of the heterophils. A negative reaction for myeloperoxidase was found in all cells. Although some evidence of myeloperoxidase activity was show in the polymorphonuclears it was not enough to ascertain a positive reaction. Lipids were detected in the cytoplasm of few heterophils, eosinophils and monocytes.     

Comparison of two techniques for quantifying environmental contaminants in human serum

Peak area matching and linear regression were used to quantify eight chlorinated pesticides and polychlorinated biphenyls (as Aroclor 1260) in human serum. There are no statistically significant differences in data obtained by these two quantifying techniques which were indicated by the paired t-test. For chlorinated pesticides, p = 0.053-0.62, and for polychlorinated biphenyls (as Aroclor 1260), p = 0.64. Analyte residues for the chlorinated pesticides ranged from 0.5 ppb for hexachlorobenzene (HCB) to 186 ppb for dichlorodiphenyldichloroethylene (DDE). Analyte residues for the polychlorinated biphenyls (as Aroclor 1260) ranged from 5-114 ppb. The absolute mean percent difference between the two quantifying techniques ranged from 0.06% for DDE to 8.06% for dieldrin (HEOD) among the chlorinated pesticides. The absolute mean percent difference between the two quantifying techniques for the polychlorinated biphenyls (as Aroclor 1260) was 3.4%. Peak area matching and linear regression were found to be comparable for quantifying these environmental residues in serum when the following conditions apply: 1) the concentration of the chlorinated pesticides is greater than or equal to 0.5 ppb (e.g., HCB, hexachlorocyclohexane (HCCH), oxychlordane (OC), heptachlor epoxide (HE), transnonachlor (TN), HEOD, and dichlorodiphenyltrichloroethane (DDT); 2) the concentration of the chlorinated pesticide is greater than or equal to 3 ppb (e.g., DDE); and 3) the total concentration of polychlorinated biphenyls (e.g., as Aroclor 1260) is greater than or equal to 5 ppb.     

Interferon inhibits DNA Synthesis induced in Mouse Lymphocyte Suspensions by Phytohaemagglutinin or by Allogeneic Cells

IN addition to its well known antiviral activity, interferon has recently been shown to inhibit the multiplication of tumour and mammalian cells in cell culture^1–6. We report here the inhibition by interferon of DNA synthesis induced in mouse spleen lymphocytes by the non-viral stimuli phytohaemagglutinin (PHA) and allogeneic lymphocytes. These findings are in accord with our contention that interferon affects cell function and, furthermore, they suggest that by acting on lymphocytes, interferon plays a role in the immunological response of the host.