Formation of domoic acid and fatty acids inPseudonitzschia pungens f.multiseries with scale of culture

Pseudonitzschia pungens f.multiseries was cultured in 20-L polycarbonate carboys, 350-L fibreglass columns and 500-L plastic bags to determine the effects of medium enrichment and scale of culture on cell yield, production of cellular domoic acid and formation of fatty acids, particularly the potential tracer acid 16:4n-1. Cell concentrations were highest in seawater enriched with stock levels of nitrate and phosphate, but with double the stock level of silicate, at all scales of culture. Cellular toxin in 20, 350 and 500-L cultures averaged 0.32, 0.04 and 2.56 pg cell^-1 and was independent of medium used. The order of magnitude difference in levels of cellular toxin was considered to reflect the varying levels of irradiance within the culture vessels. Support was given to this by the significant difference in content of total cellular fatty acids, due principally to the algal storage acid 16: 1n-7, which is known to be influenced by irradiance. Levels of cellular domoic acid correlated significantly with total fatty acids in 350 and 500-L cultures. Bag cultures producing significantly higher levels of cellular domoic acid provided lower relative proportions of 16:4n-1, which limited its use as a tracer for food-web studies.     

Seasonal ectomycorrhizal fungal biomass development on loblolly pine (Pinus taeda L.) seedlings

Ergosterol, a membrane sterol found in fungi but not in plants, was used to estimate live mycelial biomass in ectomycorrhizae. Loblolly pine (Pinus taeda L.) seeds were sown in April 1993 and grown with standard nursery culture practices. Correlations between total seedling ergosterol and visual assessment of mycorrhizal colonization were high during July and August but low as ectomycorrhizal development continued into the growing season. Percentages of mycelial dry weight over lateral roots decreased from 9% in July to 2.5% in November because seedling lateral root dry weight accumulated faster than mycelial dry weight. Total ergosterol per seedling increased from July through February. As lateral root dry weight ceased to increase during winter months, ectomycorrhizal mycelia became the major carbohydrate sink of pine seedlings. No distinctive seasonal pattern of soil ergosterol content was observed. The impact of ectomycorrhizal fungi on plant carbohydrate source-sink dynamics can be quantitatively estimated with ergosterol analysis but not with conventional visual determination.     

Differences Between Right and Left Arm Blood Pressures in the Elderly

Recommendations vary on whether blood pressures should be measured in the right or in the left arm because no frequency distributions for a pressure difference between the arms exist. We took a total of 12 blood pressure determinations in both arms of 174 elderly persons and analyzed the data by a least-squares components of variance method. The mean difference between the arms (right minus left) was 0.93 mm of mercury for systole and 0.70 mm of mercury for diastole. For systole the proportion of persons having arm pressure differences exceeding 10 mm of mercury is 1.4% and that exceeding 7.5 mm of mercury is 6.5%. For most people, the pressure difference between the arms is small.     

Physicians' Own Health—Some Advice for the Advisors

Information about physicians'' health and health practices is sparse and scattered. With a few exceptions, however—notably suicide and substance abuse—it appears that physicians'' health and health-promotion activities are at least similar to those of the general public. In some areas, such as smoking cessation, physicians have far outstripped the general public. As physicians gain more insight into their own health and health habits, advice to patients can be realistic and effective. Indeed, several personal health activities, including immunization, have direct, salutary impacts on patient care. Physicians should analyze and change their own health practices as indicated and pay special attention to “high yield” health habits, such as seat-belt use.     

Effect of prolonged prostaglandin exposure on prostaglandin synthesis by human lung fibroblasts

Pretreatment of human lung fibroblasts with PGE₂ but not PGF_2α enhanced synthesis of prostaglandins (PGs). The effect of the pretreatment on PG synthesis was related to the concentration of PGE₂ that was added to the culture medium. Pretreatment with PGE₂ at 5 × 10⁻¹²M did not enhance PG synthesis whereas pretreatment with PGE₂ at 5 × 10⁻⁶M induced a maximal effect. Production of PGs was increased following 1 day of pretreatment with PGE₂ and was increased further following 3 days of pretreatment. The PGE₂ treated cells showed only a slight increase in the bradykinin-induced release of radioactivity from cells prelabeled with [³H]arachidonic acid but showed a dramatic increase in the bradykinin-induced synthesis of radio-labeled PGs. The conversion of free arachidonate to PGs in both intact cells and in a cell-free preparation was increased by PGE₂ pretreatment. The presence of cyclohexamide during the pretreatment did not inhibit the PGE₂-induced activation of PG synthesis. Taken together, the results indicate that pretreatment of cells with PGE₂ increased PG synthesis by augmenting the conversion of arachidonate to PGs.     

Glycerolipid biosynthesis in rat adipose tissue 12. Properties of Mg2+-dependent and -independent phosphatidate phosphohydrolase

The properties of Mg²⁺-dependent and Mg²⁺-independent phosphatidate phosphohydrolase activities were investigated in different subcellular fractions in rat adipose tissue. Phosphatidate phosphohydrolase activity was measured in the presence of aqueous dispersed phosphatidate as substrate, and the release of inorganic phosphate was taken as a measure of phosphatidate phosphohydrolase activity. The Mg²⁺-dependent phosphatidate phosphohydrolase was inhibited in the presence of N-methyl- or N-ethylmaleimide, whereas the Mg²⁺-independent activity was unaffected by these agents. The Mg²⁺-dependent phosphatidate phosphohydrolase was more sensitive to proteolysis and to high temperature (55 °C) compared to the Mg²⁺-independent enzyme. The Mg²⁺-dependent phosphatidate phosphohydrolase activity was reduced significantly during aging without any appreciable effects on the Mg²⁺-independent phosphatidate phosphohydrolase activity. These studies demonstrate that, in addition to Mg²⁺-dependency, these two forms of phosphatidate phosphohydrolases differ in several respects irrespective of their location in the adipose cell.     

Albumin extinction followed by de novo methylation of its gene in somatic hybrids of a rat hepatoma

We have previously identified an Msp I site at the 5′ end of the rat albumin gene whose undermethylation is necessary but not sufficient for stable albumin expression in rat hepatoma cells [1]. We have also shown that the extinction of albumin expression in somatic hybrids is not the result of methylation at this site, since for two different crosses, rapid extinction was found to occur in the absence of any de novo methylation of the previously active gene[2]. In the present study, we examine albumin expression and albumin gene methylation for independent hybrid clones isolated from crosses between albumin expressing rat hepatoma cells and cells of two different non-expressing lines. The cells from hybrid clones of both crosses are characterized by stable extinction of albumin expression. Moreover, we find that de novo methylation of the “extinguished” albumin gene can occur in somatic hybrids, but only some weeks after the gene has ceased to be expressed.     

Description ofOceanospirillum kriegii sp. nov. andO. jannaschii sp. nov. and assignment of two species ofAlteromonas to this genus asO. commune comb. nov. andO. vagum comb. nov

Immunological studies of Fe-containing superoxide dismutase (FeSOD) and glutamine synthetase (GS) have established a close relationship betweenOceanospirillum linum (the type species of the genus),O. beijerinckii, Alteromonas communis, A. vaga, and two unnamed species of marine bacteria (groups H-1 and I-1). The four latter species have, consequently, been assigned to the genusOceanospirillum asO. commune comb. nov.,O. vagum comb. nov.,O. kriegii sp. nov. (group H-1; type strain 197, ATCC 27133), andO. jannaschii sp. nov. (group I-1; type strain 207, ATCC 27135). The phenotypic properties of these species are presented together with their distinguishing traits.     

Effects of estradiol-17β in the male xenopus laevis: Isolation and translation of cytoplasmic messenger rna populations

Summary Total Xenopus liver cytoplasmic RNA isolated following long-term estrogen administration (14 days) was fractioned using Sepharose 4B chromatography. One of the Sepharose 4B peaks was shown to contain RNA with a molecular weight reported for vitellogenin mRNA (34S). The presence of estrogeninduced vitellogenin mRNA in the peak 5 RNA was determined by translation of the RNA in the oocyte and analysis of the oocyte translational products by immunoprecipitation with anti-vitellogenin.Sepharose 4B peaks 2 and 3 were also observed to contain estrogen induced mRNA populations sedimenting between 9-18S. These findings suggest that Sepharose 4B chromatography might prove useful in separating different mRNA populations following estrogen-induced gene activation.     

Hoechst 33258 banding of Drosophila nasutoides metaphase chromosomes

Hoechst 33258 banding of D. nasutoides metaphase chromosomes is described and compared with Q and C bands. The C band positive regions of the euchromatic autosomes, the X and the Y fluoresce brightly, as is typical of Drosophila and other species. The fluorescence pattern of the large heterochromatic chromosome is atypical, however. Contrary to the observations on other species, the C negative bands of the large heterochromatic chromosome are brightly fluorescent with both Hoechst 33258 and quinacrine. Based on differences in the various banding patterns, four classes of heterochromatin are described in the large heterochromatic chromosome and it is suggested that each class may correspond to an AT-rich DNA satellite.