Body composition, insulin sensitivity, and cardiovascular disease profile in healthy Europeans

Objective: To assess whether insulin sensitivity can explain the associations of leg‐fat mass (LFM) and trunk‐fat mass (TFM) with the cardiovascular disease (CVD) risk profile in healthy European men and women. Methods and Procedures: We studied 142 healthy men and women of a multicenter European study on insulin sensitivity, aged 30–60 years, from the centres in Hoorn, the Netherlands and Rome, Italy. Whole‐body dual‐energy X‐ray absorptiometry (DXA) was used to determine fat and lean soft tissue mass in the trunk and legs. Fasting glucose, insulin, and lipid levels were measured. Insulin sensitivity (M/I‐ratio) was measured during a euglycemic‐hyperinsulinemic clamp. Associations between fat distribution and CVD risk factors were studied with linear regression analyses with adjustment for other body compartments, and subsequent adjustment for insulin sensitivity. Results: In men, larger LFM was significantly and independently associated with lower triglyceride levels (TGs) and higher high‐density lipoprotein (HDL) cholesterol (P < 0.10) and tended to be associated also with lower low‐density lipoprotein (LDL) cholesterol, and lower fasting insulin levels. In women, larger LFM was associated with favorable values of all CVD risk factors, although the associations were not statistically significant. In both sexes, larger TFM was independently and significantly associated with unfavorable values of most CVD risk factors, and most associations did not markedly change after adjustment for insulin sensitivity. Discussion: In a relatively young and healthy European population, larger LFM is associated with a lower and TFM with a higher cardiovascular and metabolic risk, which can not be explained by insulin sensitivity.     

Reproductive isolation among sympatric cryptic species in marine diatoms

Pseudo-nitzschia is a marine cosmopolitan genus of chain-forming planktonic diatoms. As for the vast majority of phytoplankton organisms, species identification within this genus mostly relies upon morphological features. Taxa were initially identified based on cell shape and gross morphology of their composite silica cell wall, called the frustule. Yet, observations of the frustule in electron microscopy showed many additional characters for species identification and results of molecular studies have demonstrated that genetically distinct groups might exist within morpho-species. However, these studies have not addressed the biological meaning of these genetic differences. Here, we bridge that gap by comparing ultrastructural features and sequence data (three ribosomal and one plastid marker) of 95 strains with results of mating experiments among these strains. Experiments were performed on two morphologically distinct entities: P. delicatissima and P. pseudodelicatissima. Each of the two entities consisted of multiple genetically distinct and reproductively isolated taxa, all occurring in sympatry: P. delicatissima was composed of three phylogenetic and reproductively distinct groups, whereas P. pseudodelicatissima consisted of up to five. Once these taxa had been defined both genetically and biologically, subtle ultrastructural differences could be detected as well. Our findings not only show that cryptic genetic variants abound in sympatry, but also that they are reproductively isolated and, therefore, biologically distinct units.     

Temporal Changes in Population Structure of a Marine Planktonic Diatom

A prevailing question in phytoplankton research addresses changes of genetic diversity in the face of huge population sizes and apparently unlimited dispersal capabilities. We investigated population genetic structure of the pennate planktonic marine diatom Pseudo-nitzschia multistriata at the LTER station MareChiara in the Gulf of Naples (Italy) over four consecutive years and explored possible changes over seasons and from year to year. A total of 525 strains were genotyped using seven microsatellite markers, for a genotypic diversity of 75.05%, comparable to that found in other Pseudo-nitzschia species. Evidence from Bayesian clustering analysis (BA) identified two genetically distinct clusters, here interpreted as populations, and several strains that could not be assigned with ≥90% probability to either population, here interpreted as putative hybrids. Principal Component Analysis (PCA) recovered these two clusters in distinct clouds with most of the putative hybrids located in-between. Relative proportions of the two populations and the putative hybrids remained similar within years, but changed radically between 2008 and 2009 and between 2010 and 2011, when the 2008-population apparently became the dominant one again. Strains from the two populations are inter-fertile, and so is their offspring. Inclusion of genotypes of parental strains and their offspring shows that the majority of the latter could not be assigned to any of the two parental populations. Therefore, field strains classified by BA as the putative hybrids could be biological hybrids. We hypothesize that P. multistriata population dynamics in the Gulf of Naples follows a meta-population-like model, including establishment of populations by cell inocula at the beginning of each growth season and remixing and dispersal governed by moving and mildly turbulent water masses.     

On the mechanism of action of lead in the testis: in vitro suppression of FSH receptors, cyclic AMP and steroidogenesis

Previous evidence has shown that prenatal and neonatal exposure to low levels of Pb result in decreased FSH binding and steroidogenesis in the testes at the onset of puberty. The purpose of the present study was to determine by in vitro methods, if Pb acts by interfering directly with hormone binding, cyclic AMP production and steroidogenic enzyme activity. Sertoli cells were isolated from testes of prepubertal rats and cultured in the presence of 2.64 x 10(-4)M of either NaAc (control) or PbAc for 1, 4, 24, 48, 96 or 144 hr. There was no reduction in FSH binding and in FSH-induced cyclic AMP after a 1-4 hr exposure to Pb. After a 24-hr exposure to Pb, the cells exhibited a 10-20% decrease in FSH binding and cyclic AMP production and after 96 hr there was a 75% decrease in these 2 parameters. The inhibition was greater in cells from 16 day old than from 20 day old rats, so that in the former, after a 144 hr exposure the FSH-induced cyclic AMP of the Pb exposed cells was only 3% of the amount produced by the NaAc exposed cells (i.e. a 97% inhibition). After in vitro exposure to Pb for 48 hr, the steroidogenic activity (progesterone conversion to steroid metabolites) of Sertoli cells was significantly reduced and their steroidogenesis was no longer stimulated by FSH. A crude testicular enzyme preparation containing 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) exhibited approximately 25% reduction in activity if the assay buffer contained PbCl2 instead of the equivalent in NaCl. Prolonged in vivo exposure to Pb resulted in approximately 50% reduction in 3 beta-HSD activity. This is the first indication that in the testis Pb may act directly (immediate effect) by suppressing enzyme activities, and indirectly (long term effect) by reducing gonadotropin-receptor binding and the resultant cyclic AMP production.     

Dilution rate as a determinant of mycelial morphology in continuous culture

The morphology of mycelial fungi in liquid culture effects culture rheology and this in turn may affect product yield. It is therefore important to understand how environmental factors influence mycelial morphology and this paper describes the effect of dilution rate on two strains of Fusarium graminearum, the relatively sparsely branched parental strain (A3/5) and a relatively highly branched "colonial" variant (C106). At any given dilution rate, the concentration of mycelial fragments present at steady state of both strains remained approximately constant with time, suggesting that mycelial fragmentation occurred in a regular manner. However, for both strains fragment concentration decreased with increasing dilution rate. The strains had a similar morphology at a dilution rate of 0.07 h(-1). The length of the hyphal growth unit of A3/5 increased with increase in dilution rate, while that of C106 decreased with increase in dilution rate. At all dilution rates, C106 produced up to ten times more macroconidia than A3/5.     

Metabolism of progesterone by avian granulosa cells in culture

Previous studies have demonstrated that progesterone is the primary product of steroidogenesis in avian granulosa cells during short-term incubation. However, during more prolonged culture, lasting several days, the progesterone content in the medium was found to decrease progressively, indicating in vitro metabolic conversion. In the present study we have isolated and identified a number of progesterone metabolites. Granulosa cells, isolated from mature ovarian follicles of laying hens, were cultured in medium 199 supplemented with fetal calf serum and containing [14C]progesterone. After 4 days in culture, cells + media were extracted and the radioactive metabolites separated and identified by TLC, HPLC and GC-MS. Several of the metabolites were further characterized by derivatization and crystallization to constant specific activity. A total of 24 radioactive substances was detected. Of these, 15 have been positively identified, 5 tentatively and the remaining 4 are unidentified. The principal metabolite, representing more than 45% of the total radioactivity, was identified as 3 alpha-hydroxy-5 beta-pregnan-20-one. In addition, significant amounts of 3 alpha-hydroxy-5 alpha-pregnan-20-one (5.76%), 5 beta-pregnane-3,20-dione (3.05%), and 5 alpha-pregnane-3,20-dione (2.95%) were detected and identified. The results indicate that avian granulosa cells possess 3 alpha-hydroxy-steroid dehydrogenase (3 alpha-HSD), 17 beta-HSD, 20 alpha-HSD, 20 beta-HSD, 17 alpha-hydroxylase, C17-20-lyase and 5 alpha- and 5 beta-reductase activities. These enzyme activities may convert progesterone to biologically inactive or less active metabolites. However, a functional role for some of these metabolites cannot be ruled out.     

Influence of hydrogen fluoride fumigation on the water economy of soybean plants

The influence of hydrogen fluoride fumigation on water economy was studied using soybean (Glycine max [L] Merr.). Fumigation caused partial stomatal closure in 1 hour and practically complete closure within 4 hours. The transpiration rate was greatly reduced by fumigation, while the leaf temperature was increased. Water potential increased after 1 day but fell drastically when necrosis occurred. Effects of interrupted fumigation during the day were somewhat less severe in all respects than those of continuous fumigation; nighttime fumigation caused only minor effects. Fluoride uptake was also much less from nighttime than from daytime fumigations.     

125I]iodohydroxynitrobenzylthioinosine: a new high-affinity nucleoside transporter probe

[125I]iodohydroxynitrobenzylthioinosine ([125I]IH-NBMPR), a new gamma-labeled nucleoside transport inhibitor, has been prepared at a theoretical specific activity of 2000 Ci/mmol (1 Ci = 37 GBq). IH-NBMPR was more acidic than hydroxynitrobenzylthioinosine (H-NBMPR), having a pKa of 4.6. Site-specific binding of [125I]IH-NBMPR to membrane-enriched fractions (MEF) from S49 mouse lymphoma cells was pH dependent, increasing with the fraction of undissociated molecules present; it was maximal at pH 4.5 and negligible at pH 7.0. Scatchard analysis of specific binding to MEF from S49 cells under equilibrium conditions at pH 5.0 yielded a Kd of 15 nM (equivalent to 4.0 nM for the undissociated fraction of inhibitor molecules) and maximum number of binding sites (Bmax) of 4.9 pmol/mg protein. Specific binding of IH-NBMPR could not be demonstrated in MEF from AE1 cells, a nucleoside transport-deficient mutant of S49 cells. Influx of uridine into mouse erythrocytes at pH 5.0 in the presence of 5 microM IH-NBMPR (1.4 microM undissociated IH-NBMPR) was reduced to about 7% of the control value, indicating that this compound is an effective nucleoside transport inhibitor. Photoactivation of site-bound [125I]IH-NBMPR, following equilibration of the ligand with MEF from S49 cells at pH 5.0, resulted in specific covalent labeling of a polypeptide with a relative molecular mass of 52,000-63,000, identified on sodium dodecyl sulfate-polyacrylamide gels. These results indicate that the new, iodinated ligand is an inhibitor of nucleoside transport and that it binds specifically and with high affinity to nucleoside transporter polypeptides in mammalian cells.     

Arylsulfatase Activity in Salt Marsh Soils

The presence of arylsulfatase(s) was confirmed in salt marsh soils. The temperatures of maximum activity and inactivation, the pH range over which the enzyme was active, and the K_m values were similar to those of soil enzymes. Unlike soil arylsulfatases, however, the salt marsh enzymes do not appear to be repressed by sulfate. It is postulated that these enzymes may be necessary for the initiation of arylsulfate ester metabolism.