A quantitative scuba-diving survey of the sublittoral macrobenthos at subantarctic Marion Island

Summary A SCUBA-diving survey of the macrobenthos of hard substrata in the sublittoral zone at subantarctic Marion Island was conducted during March and April 1988. Dense beds (12 kg m^–2) of the kelp Macrocystis laevis occur in depths > 5 m. Durvillaea antarctica is found along the infralittoral fringe and Desmarestia rossi and Durvillaea sp. occur in a narrow zone from 3 m–6 m. Under-storey algae (chiefly rhodophytes) tend to decrease in biomass with depth, with mean values of 1.57 kg m^–2 at 5m, 0.75 kg m^–2 at 10m and 0.49 kg m^–2 at 15 m. Encrusting coralline algae are particularly abundant in shallow areas (¯x = 0.92 kg m^–2) but are insignificant in deeper areas. Total biomass of macrozoobenthos increased with depth with mean values of 0.12 kg m^–2 at 5 m, 0.34 kg m^–2 at 10 m and 0.46 kg m^–2 at 15 m. Polychaetes, crustaceans, echinoderms, molluscs, sponges and bryozoans dominated the macrozoobenthos in terms of biomass. Approximately 200 species of macrobenthic animals were recorded and numerically, polychaetes, crustaceans, molluscs, nematodes and echinoderms dominated. The sublittoral benthos at Marion Island is compared with that occurring at other subantarctic and Antarctic islands, in particular, the Kerguelen Island group. Zoogeographic trends and the possible effects of nutrient input from seabird guano are briefly discussed.     

RFLP variability in peanut (Arachis hypogaea L.) cultivars and wild species

Summary RFLP variability was studied in eight U.S. peanut cultivars, representing the four market types, and in 14 wild Arachis species accessions, using random genomic clones from a PstI library. Very low levels of RFLP variability were found among the allotetraploids, which included the U.S. cultivars and Arachis monticola, a wild species. The diploid wild species were very diverse, however. RFLP patterns of the allotetraploids were more complex than the diploids, and the two constituent genomes could usually be distinguished. On the basis of RFLP band sharing, A. ipaensis, A. duranensis, and A. spegazzinii appeared most closely related to the diploid progenitor species of the allotetraploids. A dendrogram of relationships among the diploid wild species was constructed based on band sharing.     

Unusual properties of two branched RNA''s with circular and linear components.

Irradiation with ultraviolet light was used to create two nonlinear RNA molecules. Circular potato spindle tuber viroid (PSTV) RNA was crosslinked at a single site to generate a figure eight-shaped molecule; 5S rRNA from HeLa cells was transformed into an alpha-shaped molecule with a small circular element and two arms (1). Crosslinked RNA's could be separated from their untreated counterparts by electrophoresis in polyacrylamide gels containing urea. The gel mobility of crosslinked PSTV was not altered by boiling, treatment with E. coli RNase III or glyoxalation. However, mild nuclease digestion ("nicking") produced derivatives which migrated more slowly than the starting material in gels of certain polyacrylamide concentrations, but not in others. Limited nuclease digestion of crosslinked 5S rRNA did not generate any detectable products with reduced mobility in the gels tested. Thus, the ability of the "nicking assay" to reveal circular elements within nonlinear RNA's can vary depending upon the composition of the gel chosen for analysis and on the size of the circular element relative to the rest of the molecule.     

Uptake and dissimilation of glycerol by wild type and glycerol nonutilizing strains of Neurospora crassa

Summary Seven mutant strains defective for utilization of glycerol, glyceraldehyde or dihydroxyacetone were isolated. One strain was deficient for NAD-linked glycerol-3-phosphate dehydrogenase, two for glycerol kinase, and four had no detected enzymatic deficiency, although one of the latter strains was deficient in glycerol uptake. Glycerol uptake was increased by incubation in glycerol, glycerol-3-phosphate, erythritol, and propanediol, and was protein-mediated below 0.14 mM glycerol, but at higher concentrations free diffusion predominated. Glycerol uptake was decreased by cycloheximide and was more sensitive to sodium azide than to iodoacetate.     

Effect of carbon source on enzymes involved in glycerol metabolism inNeurospora crassa

Specific activities of eight enzymes involved in glycerol metabolism were determined in crude extracts of three strains ofNeurospora crassa after growth on six different carbon sources. One of the strains was wild type, which grew poorly on glycerol as sole carbon source; the other two were mutant strains which were efficient glycerol utilizers. A possible basis for this greater effeciency of glycerol utilization was catabolite repression of glyceraldehyde kinase by glycerol in wild type, and two-fold higher glycerate kinase activity in the mutant strains after growth on glycerol, thus apparently allowing two routes for glyceraldehyde to enter the glycolytic pathway in the mutant strains but only one in wild type. The preferential entry of glyceraldehyde to the glycolytic pathway through glycerate was suggested by the lack of glyceraldehyde kinase in all three strains after growth on one or more of the carbon sources and the generally higher levels of aldehyde dehydrogenase and of glycerate kinase than of glyceraldehyde kinase.     

The effect of PGI2 on canine renal function and hemodynamics

The effect of prostaglandin I₂ (prostacyclin) on renal and intrarenal hemodynamics and function was studied in mongrel dogs to elucidate the role of this novel prostaglandin in renal physiology. Starting at a dose of 10^?8 g/kg/min, PGI₂ decreased renal vascular resistance and redistributed the blood flow away from the outer cortex (zone 1) and towards the juxtamedullary cortex (zone 4). At 3 × 10^?8 g/kg/min, the renal vascular resistance decreased even further, but at this dose the mean arterial blood pressure also declined 13% indicating recirculation of this prostaglandin. PGI₂ infusion at a vasodilatory dose resulted in natriuresis and kaliuresis. With a decline in filtration fraction, these changes were most likely secondary to the hemodynamic effects of this prostaglandin. Unlike PGE₂, PGI₂ had no direct effect on free water clearance indicating lack of activity at the collecting duct. PGI₂ may be the important renal prostaglandin involved in modulating renal vascular resistance and intrarenal hemodynamics as well as influencing systemic blood pressure.     

Characterization of glycerol nonutilizing and protoperithecial mutants ofNeurospora

Summary Mutants defective in polyol metabolism and/or in protoperithecial development were selected inNeurospora tetrasperma, a species in which protoperithecial development occurs at nonpermissively high temperature if certain polyols are used in lieu of sucrose as carbon source. Mutants selected for nonutilization of one of the four polyols tested, glycerol, mannitol, sorbitol, or xylitol, were usually found to be nonutilizers of the other three polyols as well. Mutants blocked at various stages of protoperithecial development complemented pairwise to produce more advanced developmental stages, usually mature protoperithecia and, when of opposite mating type, mature perithecia. About one-third of the mutants manifested both polyol auxotrophy and defective protoperithecial development upon initial isolation, but protoperithecial defectiveness in such mutants usually showed erratic segregation in crosses and/or instability to repeated vegetative transfer, whereas polyol auxotrophy usually did not and was, therefore, studied further. Two glycerol nonutilizing strains were introgressed intoN. crassa to facilitate genetic analysis. One,glp-4, lacked both inducible and constitutive glycerol kinase and mapped to linkage group VI, betweenad-1 andrib-1; the other,glp-5, lacked glyceraldehyde kinase and mapped to linkage group I, proximal toad-9. Another mutant,gly-u(234), has been reported by other investigators to lack inducible glycerol kinase but to map to linkage group I, distal toad-9.     

The lack of an effect of furosemide on uterine prostaglandin metabolism in vivo

We determined the effect of 2 mg/kg intravenous furosemide on the production and metabolism of prostaglandin E2 in the utero-placental unit of pregnant dogs. Uterine venous prostaglandins E2 and 15-keto-13,14-dihydro E2 were measured by gas chromatography-mass spectrometry. Even though the dose of furosemide was adequate to effect a good diuresis, neither the production nor the metabolism of prostaglandin E2 by the uterus was altered by that dose of the drug. Using radioactive microspheres to measure hemodynamic parameters, we observed no change in uterine vascular resistance while renal vascular resistance decreased. Although the renal concentration of furosemide may be higher than the uteroplacental concentration, there is so far no evidence in vivo that usual doses of furosemide enhance the production or inhibit the metabolism of prostaglandin E2.