The influence of gamma radiation on arachidonic acid release and prostacyclin synthesis

Cultured pulmonary artery endothelial cells produce PGI₂ as their primary prostaglandin. Conditions which inhibit cell division have been shown to accelerate the synthesis of this compound. Exposure of endothelial cells to γ raidation results in an irreversible cessation of growth and enhanced production of PGI₂. The level of PGI₂ measured after radiation exposure exceeds that observed in cultures rendered quiescent by serum reduction. This indicates a role for γ radiation in the elevation of PGI₂ levels which is distinct from its effect on cell division. Result presented indicate that exposure to γ radiation does not, in and of itself, elevate PG levels but capacitates cells for enhanced production when presented with appropriate stimuli. Increased PGI₂ synthesis appears to be a result of an observed increase in arachidonic acid release and an activation of cyclooxygenase.     

Morphine and Cocaine Exert Common Chronic Actions on Tyrosine Hydroxylase in Dopaminergic Brain Reward Regions

We studied levels of tyrosine hydroxylase immunoreactivity and phosphorylation state in the ventral tegmental area (VTA) and nucleus accumbens (NAc) in an effort to understand better the mechanisms by which these brain reward regions are influenced by opiates and cocaine. In the VTA, chronic, but not acute, administration of either morphine or cocaine increased levels of tyrosine hydroxylase immunoreactivity by 30-40%, with no change observed in the relative phosphorylation state of the enzyme. In the NAc, chronic, but not acute, morphine and cocaine treatments decreased the phosphorylation state of tyrosine hydroxylase, without a change in its total amount. In contrast, morphine and cocaine did not regulate tyrosine hydroxylase in the substantia nigra or caudate/putamen, brain regions generally not implicated in drug reward. Morphine and cocaine regulation of tyrosine hydroxylase could represent part of a common biochemical basis of morphine and cocaine addiction and craving.     

Arboriculture in the Mussau Islands,Bismarck Archipelago

The Mussau Islanders of the Bismarck Archipelago in northeastern Papua New Guinea cultivate 26 indigenous tree species both for food and non-food uses in tree gardens surrounding the villages. Several trees which volunteer in these arboriculture zones are also tended and encouraged. I present ethnobotanical information on methods of cultivation, how and when the trees are harvested, preparation and use. The tree crop zone has a random spatial distribution overall, but some species within the zone are aggregated spatially. This clumping is related to the restricted habitat requirements of certain species, as well as individual species ’ reproductive traits. Coconut is the most frequent species in the arboriculture zone and is randomly distributed. Vertical stratification is attributable to the presence of a distinct herb layer and a subcanopy stratum of maturePandanus spp. The stratification of some species pairs results from the deliberate planting of subcanopy trees next to canopy trees. The introduction of exotic garden species and the increasing availability of western packaged foods is changing the composition of traditional Mussau Islands tree gardens.     

Specific gangliosides increase rapidly in rat liver following partial hepatectomy

Rat liver gangliosides (sialic acid containing glycosphingolipids) were analyzed by HPTLC and HPLC following either partial hepatectomy or sham operation. Analysis of whole liver gangliosides by HPTLC demonstrated that within 6 h after partial (68%) hepatectomy, there was a significant increase in GM1 compared to both sham and control animals. By 48 h, GM1 was further increased and the polysialylgangliosides GD1a, GD1b and GT1b had also risen significantly, whereas changes in GM3 were negligible. Gangliosides associated with the plasma membrane were increased up to 3.5-fold in regenerating liver compared to sham-hepatectomized controls as assessed by HPLC. Although elevations in membrane gangliosides were associated with hepatocyte proliferation, they did not closely follow the growth curve. The time course of changes in ganglioside biosynthesis suggests differential upregulation of GM3 synthase and GD3 synthase in regenerating livers.     

Artemia monica cyst production and recruitment in Mono Lake,California, USA

Annual egg production was determined for Artemia monica in Mono Lake, California, from 1983 to 1987. Annual oviparous (overwintering cyst) production was 3 and 7 million cysts m^–2 yr^–1 in 1986 and 1987, respectively, as measured by in situ sediment traps. Cyst production for the entire five year period was calculated using Artemia census data and inter-brood duration derived from mixolimnetic temperature. These estimates ranged from 2 to 5 million cysts m^–2 yr^–1. This method underestimated annual production by 30%, when compared to estimates using sediment traps. Cyst production was similar during 1983–1986 and showed a significant increase in 1987, which was due primarily to a larger reproductive population later in the year. Recruitment into the adult populations of the following spring ranged between 1.4 to 3.2%. Overall abundance of this generation reflected the patterns in annual cyst production. Compensatory effects must operate on the second generation of each year, since summer populations were similar in all years despite differences in cyst production.     

Vascular atrial natriuretic factor receptor subtypes are not independently regulated by atrial peptides

The regulation of the atrial natriuretic factor (ANF) receptor system in cultured rat vascular smooth muscle cells (RVSMC) was examined following long term pretreatment of these cells with rANF99-126 or with any one of a series of truncated and ring-deleted analogs. The latter analogs are reported to bind selectively the ANF-C or clearance receptor. Initial competition binding studies revealed that all analogs examined showed comparable apparent receptor binding affinities (Ki values did not differ by more than 10-fold). In contrast, the extent of interaction of the ANF analogs with the receptor pool coupled to particulate guanylate cyclase (the ANF-B receptor) was much more variable, with some ligands failing to stimulate cGMP production or particulate guanylate cyclase over the concentrations tested. Pretreatment of cells for 24 h with rANF99-126 or any of the truncated analogs that interact with the ANF-B receptor caused a dose- and time-dependent decrease in the number of ANF binding sites (99% of which are uncoupled in RVSMC) without any change in affinity. Examination of the binding activity following pretreatment of the cells with ANF suggested that the observed reduction in 125I-rANF99-126 binding capacity was not because of the retention of the peptide on its receptor. Furthermore, this down-regulation was associated with desensitization of particulate guanylate cyclase resulting in a decreased responsiveness of intracellular cGMP accumulation to ANF. In contrast, however, analogs selective for the ANF-C receptor pool failed to cause down-regulation or desensitization. These findings suggest that ANF-C receptors in RVSMC are not independently down-regulated by selective ligands but that nonselective analogs that down-regulate and desensitize the ANF-B receptor system can by some cooperative mechanism reduce the size of the predominant ANF-C receptor pool in these cells.     

Structure of tendon organs in fishes of the genus Polymixia

Summary Modified branchiostegal rays 1 through 3 support the proximal end of the paired hyoid barbels in the beardfish (Beryciformes: Polymixiidae). The polymixiid barbel is unusual in that it has an unique intrinsic muscular system. Using silver impregnation and electron microscopic techniques, unencapsulated, free nerve endings were located within the tendon of the third modified branchiostegal ray. Branchiostegal rays 1 and 2 do not have any free nerve endings associated with their tendons, however. It is suggested that the free nerve endings are proprioceptors acting as stretch-sensitive mechanoreceptors, and that branchiostegal ray 3 acts as part of a sensory apparatus for monitoring the positional state of the barbel. Branchiostegal rays 1 and 2 merely provide support for the barbel.Abbreviations used in Figures BA barbel - br r 3 branchiostegal ray 3 - IM intermandibularis - IOP interoperculum - LIM interoperculomandibular ligament - MD mandible - MX maxilla - OP operculum - PM premaxilla - POP preoperculum - SOP suboperculum     

Transposition of the kanamycin-resistance transposon Tn903

Summary The insertion of the kanamycin-resistance transposon, Tn903, into the Escherichia coli chromosome was studied. Tn903 is similar in structure to the well known transposons Tn5 and Tn10 in that it has a unique central sequence flanked by inverted repeat sequences extending more than a thousand base pairs. However, the central region of Tn903 has enough single-frame coding capacity only for the drug modifying enzyme, whereas Tn5 and Tn10 carry multigenic unique sequences. In this paper we demonstrate that two different classes of insertion event occur: (1) the first class is a complex event in which all or part of the genome of the bacteriophage lambda vector is co-inserted near the purE locus on the E. coli chromosome (11.7 min); (2) the second class appears to be a simple transposition event in which the transposon alone is inserted at relatively nonspecific sites in the chromosome, as has been described for Tn5 and Tn10. Furthermore both classes show dependency on homology-requiring recombination systems. We suggest that Tn903 transposes infrequently because it must utilize a recA-controlled host function, whereas Tn5 and Tn10 are recA-independent and encode similar but more active functions on the transposon DNA.     

Biochemical studies of mammalian oogenesis: Metabolic cooperativity between granulosa cells and growing mouse oocytes

Freeze fracture and lanthanum tracer experiments have shown that gap junctions exist throughout folliculogenesis between granulosa cells and growing mouse oocytes (Anderson and Albertini, J. Cell Biol.71, 680–686, 1976). The following lines of experimentation in the present study suggest that metabolic cooperativity exists between granulosa cells and their enclosed oocytes, i.e., gap junctions are functional, and that in most cases examined, greater than 85% of the metabolites present in follicle-enclosed oocytes were originally taken up by the granulosa cells and transferred to the oocyte via gap junctions: (1) When incubated with various radiolabeled compounds, follicle-enclosed oocytes contained more intracellular radioactivity than did oocytes with no attached granulosa cells (denuded oocytes); (2) for two radiolabeled ribonucleosides examined, the distribution of phosphorylated metabolites in follicle-enclosed oocytes resembled that of granulosa cells and differed significantly from that in denuded oocytes; (3) pulse-chase experiments with radiolabeled ribonucleosides revealed that during the chase period more radioactivity became associated with the follicle-enclosed oocyte; (4) treatments known to disrupt gap junctions in other cell types were effective in reversibly uncoupling metabolic cooperativity between granulosa cells and oocytes; and (5) a series of control experiments using (a) medium conditioned by granulosa cells and (b) cocultures of denuded oocytes and granulosa cells in which physical contact between the two cell types was not permitted demonstrated that contact between follicle cells and oocytes was necessary for observing metabolic cooperativity. Metabolic cooperativity was also found between follicle cells and oocytes in the two culture systems which support growth of mouse oocytes in vitro. The fact that oocytes do not grow well, if at all, in the absence of follicle cells and the large contribution of nutrients apparently furnished to the oocyte by the granulosa cells is consistent with the concept that gap junction mediated metabolic cooperativity between follicle cells and their enclosed oocytes is vital for mammalian oocyte growth.     

Lectin induction of lymphokines in cultured murine leukocytes

Antigens induce sensitized lymphocytes to undergo mitosis and to secrete soluble products, termed lymphokines, which modulate the immune response. Plant lectins are known to act as polyclonal lymphocyte mitogens and, in some cases, stimulate lymphocytes to produce lymphokines. In an effort to explore the relationship of specific cell surface glycoconjugates to the induction of mitosis and the production of lymphokine activities we have examined the ability of the mitogenic lectins, concanavalin A and Wistaria floribunda mitogen, and the nonmitogenic hemagglutinin from Wistaria floribunda seeds to stimulate the production of macrophage migration inhibition factor (MIF), macrophage chemotactic factor (CF), and lymphotoxin (LT). Concanavalin A causes lymphocytes to produce MIF and LT but no detectable CF activities. W. floribunda mitogen induces lymphocytes to produce soluble substances which exhibit all three lymphokine activities. The nonmitogenic W. floribunda agglutinin causes lymphocytes to produce MIF and CF but no observable LT activity. Within the sensitivity of the assays employed, the results indicate that mitogenesis is not a corequisite of the expression of either macrophage migration inhibition factor or lymphocyte-derived chemotactic factor but it may be associated with the induction of lymphotoxin. It is also apparent that the expression of each lymphokine activity is independent of the expression of the other lymphokines studied.