Nucleotide sequence of a spectinomycin adenyltransferase AAD(9) determinant from Staphylococcus aureus and its relationship to AAD(3") (9)

Summary The nucleotide sequence of the spc determinant of the Staphylococcus aureus transposon Tn554 has been determined. This gene encodes a spectinomycin adenyltransferase, AAD(9), that mediates resistance to spectinomycin but not to streptomycin. The sequence predicts a 260 amino acid protein of molecular weight 28,943. A spectinomycin-sensitive mutant (spc-1) contains a GA transition resulting in substitution of threonine (ACA) for alanine (GCA) at residue 165. The predicted amino acid sequence is 36% homologous to that of a widely distributed, gramnegative streptomycin/spectinomycin adenyltransferase, AAD(3) (9), specified by the aadA determinant (Holingshead and Vapnek 1985).     

Taxonomic studies of the genus Hypoxis in East Africa

East African material of the genus Hypoxis L. has preliminarily been divided into the heterogenous, probably apomictic H. obtusa Burch- complex (2n = 40–50, ca. 75, 76, ca. 85, >86, ca. 92, ca. 98, ca. 108, 130–135, 160–200) and 5 rather homogenous species: H. angustifolia Lam. (2n = 14, 28), H. goetzei Harms (2n = ca. 62), H. kilimanjarica Bak., H. malosana Bak. (2n = 14) and H. macrocarpa Holt & Staubo sp. nov. H. kilimanjarica is divided into ssp. kilimanjarica and ssp. prostrata Holt & Staubo ssp. nov.     

Characteristics of bacterium GB-2, a presumptiveCytophaga species with novel immunoregulatory properties

A Gram-negative, psychrophilic bacterium, designated GB-2, was isolated from fetal calf serum and analyzed for its morphological, physiological, and biochemical characteristics. Gliding motility, sensitivity to actinomycin D, the presence of the pigment flexirubin and cytochrome c, growth on a variety of carbohydrates, the production of acid fermentation products, and a 34.9 mol% guanine+cytosine (G+C) content of bacterial DNA indicate GB-2 to be a member either of the generaCytophaga orFlexibacter. Growth of GB-2 was optimized in a simple defined medium to facilitate isolation and characterization of bacterial products. Liquid growth of GB-2 resulted in the release of significant quantities of a macromolecule free of both endotoxin and protein into the growth supernatant, which activated the proliferation of murine lymphocytes. The relationship between this bacterium and its end-products to other species of theCytophaga/Flexibacter group is discussed.     

The interaction of cadmium with calcium and cisplatin with chloride

Changes in the locomotor rate of the ciliateTetrahymena pyriformis were used to quantitatively evaluate chemical interactions produced by: cadmium in combination with varying amounts of calcium, andcis-dichlorodiammineplatinum (II) (cisplatin) with varying amounts of sodium chloride. Cadmium (as CdCl₂) produces a measurable decline in the locomotor rate of the cells. Cadmium's detrimental effect can be reduced by the addition of calcium (as CaCl₂) in combination with cadmium. At a ratio of 30∶1 (calcium: cadmium), cadmium's negative effect upon motility is essentially nullified. It is suggested that the “protective” action afforded by calcium stems from the chemical similarity of the two cations and their involvement/competition for molecular sites responsible for the energy release and/or delivery of ciliary activity. Cisplatin will also effect a reduction in ciliary activity. However, the interaction between cisplatin, sodium chloride, and the cell appears more complex than that found with cadmium-calcium. At the lower range of chloride (as NaCl) used in this study, increased chloride concentration produces an increase in cisplatin's action against ciliary activity. At the higher levels, the chloride reduced cisplatin's negative effects. It is suggested that the increases in cisplatin's effects are caused by mass chemical action of increased chloride, which increases the concentration of the nonpolar cisplatin. The reduced effects found with the higher concentrations of sodium chloride may be because of the presence and action of elevated NaCl in/on the cell. This study clearly demonstrates differences in biologically relevant chemical interactions occurring with the two sets: cadmium-calcium and cisplatin-chloride.     

The met-enkephalin analog FK 33-824 and naloxone do not directly influence cortisol secretion by cultured human adrenocortical cells

Systemic administration of the enkephalin analog FK 33.824 was previously shown to inhibit ACTH secretion in man. In this study, the direct action of this analog on cortisol release was studied. The enkephalin analog (1 uM and 10 uM) did not influence basal or ACTH-stimulated cortisol production by cultured isolated adrenocortical cells prepared from the hyperplastic adrenal glands from three patients with Cushing's disease. Naloxone (10 uM) had also no direct effect on cortisol release. It is concluded that the met-enkephalin analog used in this study and naloxone do affect the hypothalamo-pituitary-adrenal axis via a central effect.     

Potentiation of antibody responses by specific IgM: specificity and thymus dependency

Modulation of antibody responses induced by IgM directed against the immunogen was investigated. When IgM directed against ox erythrocytes (ORBC) was given together with trinitrophenyl (TNP)-ORBC, the subsequent antibody response to the carrier, ORBC, as well as the response to the hapten, TNP, was potentiated. In contrast, IgG with carrier specificity inhibited both responses. The hapten-specific potentiation was found in both direct and indirect plaques, and was antigen-dose dependent, i.e., no potentiation was found with the lowest antigen doses. The response to 2,4-dinitrophenyl (DNP)-labeled proteins was potentiated by a monoclonal IgM with specificity for the hapten. The effects were observed both in primary and secondary responses. One strict requirement for IgM potentiation to occur was observed. The determinant against which potentiation was achieved had to be physically linked to the determinant against which the IgM was directed, be it hapten or carrier determinants. Thus, irrelevant IgM-antigen complexes were incapable of potentiating the responses. Similar specificity requirements were found for IgG induced suppression of antibody responses. Experiments with nude mice and their euthymic littermates showed that IgM potentiation of antibody production is T-cell dependent. Furthermore, passive transfer of carrier-primed spleen cells together with antigen challenge suggests that IgM potentiation of secondary antibody responses is dependent on specific carrier-primed immune T cells.     

Ultrastructure and distribution of microbodies in leaves of grasses with and without CO2-photorespiration

Summary A comparative study was made of the ultrastructure, distribution and abundance of leaf microbodies in four species of temperate grasses with high and four tropical grasses with low CO₂-photorespiration. The temperate grasses were all festucoid; the tropical grasses included two panicoid species and two chloridoid. Comparisons of relative abundance were made by computing the average numbers of microbody profiles per cell section.Although microbodies were present in the green parenchymatous leaf cells in all grasses examined, their average number per cell was in general severalfold greater in the grasses with high CO₂-photorespiration than in those with low. Furthermore, whereas in the grasses with high CO₂-photorespiration the microbodies were distributed through the mesophyll, in those with low CO₂-photorespiration they were concentrated in the vascular-bundle-sheath cells and were smaller and relatively scarce in the mesophyll cells. The leaf microbodies of the eight grass species resembled one another in general morphology, but differed to some extent in regard to size and type of inclusion. Microbodies of all four festucoid species contained numerous fibrils with a discernible substructure. Those of the two panicoid species contained clusters of round bodies with transparent cores. The equivalence of the microbodies to peroxisomes as biochemically defined was shown cytochemically by employing 3,3-diaminobenzidine for the localization of catalase, a marker enzyme for the peroxisome. This reaction was blocked by the catalase inhibitor, aminotriazole.The observations on the relative abundance and distribution of peroxisomes in leaves of grasses with high CO₂-photorespiration versus those with low are consistent with the published biochemical data on the levels and distribution of peroxisomal enzymes in representatives of plants with high and low CO₂-photorespiration, and may help explain the differences in apparent photorespiratory levels between these two groups of plants.