Studies on the biology of Spirorbinae (Polychaeta)

Of four species studied, tolerance of extreme temperatures in greatest in Spirorbis pagenstecheri (which extends highest on the shore) and least in S. corallinae (which always occurs immersed in water). The latter species breeds between May and August, the other three from May to October. S. borealis liberates its larvae mainly at the moon's quarters, but this fortnightly rhythm is less obvious in S. corallinae and not found in the other two species. S. corallinae differs from S. borealis in being slower to re-emerge after disturbance and in having a lesser breeding size, maximum size and life span. Growth in the laboratory is slower in S. tridentatus than in the other species. Growth of S. borealis under natural conditions is much faster in summer than in winter.     

2,3,7,8, tetrachlorodibenzo-p-dioxin induces oxygen activation associated with cell respiration

We have investigated the influence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on bioenergetic functions of isolated heart-mitochondria. Electron transfer and energy conservation activities were found to be decreased in the presence of very low amounts of the polychlorinated biphenyl compound (1.5 nmol/mg mitochondrial protein). The effect was greatest when substrates for complex I were used. In this case coupling of oxidative phosphorylation to respiration was drastically diminished, essentially at the expense of state 3 respiration, and P/O values were found around 2 instead of 3. Succinate-related energy conservation remained practically unaffected in the presence of TCDD, suggesting an interference of the toxic compound at coupling site I. SOD plus catalase were found to protect energy-linked respiration from the effect of dioxin indicating the involvement of superoxide radicals and H2O2 in the development of the observed phenomena. The present contribution provides experimental evidence on the formation of these oxygen species in the presence of TCDD. Furthermore, the site of action of TCDD is demonstrated and discussed in relation to the oxygen radical formation observed.     

A rapid posttranslational myristylation of a 68-kD protein in D. discoideum

Cells incubated with [3H]myristate were shown to rapidly and specifically acylate a 68-kD protein, p68, in a developmentally-regulated manner. The fatty acid incorporated into p68 was identified as myristate, and is linked to the protein via an amide bond, apparently to an NH2-terminal glycine. The acylation of p68 in D. discoideum displays some unusual properties. Unexpectedly, myristylation of p68 is a posttranslational event and occurs in the presence of inhibitors of protein synthesis. Another unusual finding was that although p68 is a stable protein, the acyl moiety is removed with a half time of approximately 15 min.     

Role of extracellular signaling on endothelial cell proliferation and protein N-glycosylation

In vitro studies of angiogenic phenomenon have been limited due to nonavailability of a simple and biologically relevant model of the capillary wall. Recent development of a capillary endothelial cell line from the vascular bed of bovine adrenal medulla made us to study the effect of heparin, thrombin, thyroxine, glucagon, insulin, and phorbol myristate acetate (PMA) on the proliferative and metabolic activities such as glycosylation of asparagine-linked glycoproteins of these cells in culture. Out of six different agents studied here, only heparin, thrombin, and thyroxine reduced the doubling time of these cells by 24 hr with no observed morphological abnormality. Glucagon, showed marginal reduction in the cell doubling time. By contrast, insulin and PMA enhanced the doubling time. Insulin treatment though induced the S phase of cell cycle but it blocked the cells entry into the G2 + M phase. PMA arrested the cells in G0/G1 phase. The cellular response to protein N-glycosylation is increased in the presence of thyroxine, insulin, and thrombin and the effect is dose dependent. Further analysis on SDS-PAGE indicated that glycosylation of 80-120 kDa and 43 kDa glycoprotein species are enhanced when these cells are treated with insulin and thrombin. Glycopeptide generated from these glycoproteins suggested that they all carry "high mannose" and "complex" type oligosaccharide chains attached to their protein core.     

A novel functional cell surface dimer (Kp43) expressed by natural killer cells and T cell receptor-gamma/delta+ T lymphocytes. I. Inhibition of the IL-2-dependent proliferation by anti-Kp43 monoclonal antibody.

In the present study we describe a novel functional cell surface molecule, designated as Kp43, which is expressed among leukocytes by NK cells, TCR-gamma/delta + T lymphocytes, and some CD8+ CD56+TCR-alpha/beta + T cell clones. The Kp43 Ag is a 70-kDa disulfide-linked dimer, which migrates in SDS-PAGE under reducing conditions as a single 43-kDa band. Two-color immunofluorescence staining of fresh PBL revealed that only a fraction of CD16+, and of TCR-gamma/delta + T lymphocytes expressed the Ag. The analysis of TCR-alpha/beta + T cell clones showed that a small proportion (2 out of 20) weakly expressed Kp43 together with the CD8 and CD56 molecules. By immunoperoxidase staining of different tissues the anti-Kp43, reactivity was detected exclusively in lymphoid organs, where a minority of scattered cells was stained, and in some liver sinusoidal cells. Essentially all NK cells acquired Kp43 when stimulated with a B lymphoblastoid cell line. By contrast, the pattern of distribution of Kp43 remained stable upon in vitro culture of T-gamma/delta lymphocytes, thus delineating two subsets according to its expression. In lymphokine-activated killer populations, obtained by culturing either PBL or NK cells with high concentration of IL-2, most CD16+ and CD56+ cells became Kp43+. The Kp43-specific mAb inhibited the IL-2-dependent proliferative response of cultured NK and TCR-gamma/delta + T cells without affecting their non-MHC-restricted cytotoxicity. The partial inhibitory effect, which was mediated as well by pepsin digested F(ab')2 fragments, was lost upon reduction to Fab. The anti-Kp43 mAb did not interfere with the specific binding of IL-2 to its surface receptors. Altogether the data point out that the Kp43 dimer is involved in the regulation of the IL-2-dependent proliferative response of NK cells and a subset of TCR-gamma/delta + T lymphocytes.     

Chemotaxis,induced gene expression and competitiveness in the rhizosphere

Rhizobia are soil bacteria which symbiotically infect legume roots and generate nodules in which they fix atmospheric nitrogen for the plant in exchange for photosynthetically fixed carbon. A crucial aspect of signal exchange between these symbionts is the secretion of phenolic compounds by the host root which induce nodulation gene expression in the bacteria. Stimulation of nod gene expression by host phenolics is required for nodule formation, is biochemically specific at 10^-6 M, and is mediated by nodD. We and others have shown that rhizobia display chemotaxis to 10^-9 M of the same phenolic compounds. Chemotaxis to inducer phenolics is selectively reduced or abolished by mutations in certain nod genes governing nodulation efficiency or host specificity. Conversely, mutations in rhizobia that affect general motility or chemotaxis have substantial effects on nodulation efficiency and competitiveness. These findings suggest that microbes entering the rhizosphere environment may utilize minor, non-nutrient components in root exudates as signals to guide their movement towards the root surface and elicit changes in gene expression appropriate to this environment.     

Susceptibility of laboratory-reared female Lutzomyia longipalpis (Lutz & Neiva, 1912) to infection by different species and strains of Leishmania Ross, 1903

A study was undertaken to compare the susceptibility of laboratory-reared female Lutzomyia longipalpis to infection by different species or strains of New World Leishmania. The sand flies proved to be highly susceptible to infection by a strain of Le. guyanensis, with flagellates developing in all (18/18) of the specimens examined. A lower infection rate of 37% (10/27) was recorded in flies exposed to infection by a strain of Le. amazonensis. Flagellates developed in 13% (6/46) of the sand flies that blood fed on dogs in the early stage of experimental infection with an old laboratory strain of Le. chagasi. In contrast, promastigotes did not develop in sand flies that blood fed on dogs with naturally acquired Le. chagasi. The naturally infected dogs were in an advanced stage of disease. Flagellates developed in 9% (3/32) of the sand flies that blood fed on lesions of hamsters infected with a strain of Le. braziliensis and in 9% (3/34) of those that fed on hamsters with lesions due to a parasite of the mexicana complex (strain MHOM/BR/73/BH121). Sand flies did not develop flagellate infections after blood feeding on hamsters bearing lesions induced by strain MHOM/BR/71/BR49. Factors influencing the susceptibility of Lu. longipalpis to infection by New World species of Leishmania are discussed.     

Nef genes of SIV

Molecular clones of SIVmac were constructed that differed only in sequences within the nef gene. DEAE-transfection of viral DNA containing an open from of nef yielded virus that replicated with similar kinetics and to a similar extent in macaque peripheral blood lymphocyte (PBL) cultures as virus with a deletion or stop codon within nef. Rhesus monkeys that received each kind of molecularly cloned virus became infected. Our results additionally suggest that mutant forms of virus are selected in vitro while open, functional forms are selected in vivo. In animals infected with virus containing a stop codon within nef, reversion of the stop codon to a coding codon was demonstrated in five of five clones analyzed. These results indicate that nef is playing some role crucial to the virus life cycle in vivo.     

Effect of oestradiol delivered from a perioviducal device on ovum transport in mice

Silastic devices impregnated with oestradiol and blank devices were placed around both oviducts and around skeletal muscle bundles in the forelegs to attain local and systematic delivery, respectively. Another group of mice received an oestradiol-impregnated device around one oviduct and a blank device in the contralateral oviduct. Implantation of blank devices around the oviducts and in the forelegs did not alter ovum transport. Devices impregnated with oestradiol placed around both oviducts produced a dose-dependent delay of ovum transport, which was more pronounced than the effect of devices located in the forelegs. Oviducts receiving an oestradiol-loaded device had a larger retention of ova than did the contralateral oviducts receiving a blank device. These results demonstrate a direct action of oestradiol upon the oviduct to delay ovum transport in the mouse.