The ant Lasius niger shows no relationship between task efficiency and body size variation among workers

In ants, workers of different sizes may perform various tasks, even in so-called monomorphic species with relatively low body size variation. However, it is unclear if the body size diversity of monomorphic workers correlates with task efficiency, especially in stressful contingencies. Here we tested if the body size variation of workers corresponds with its efficiency in transferring pupae. Transferring brood is a pre-set behavioral response to stress, e.g. suboptimal temperature. Here we applied a laboratory experiment simulating nest damage. The study was performed on the common garden ant (Lasius niger (Linnaeus, 1758)) – a species with no distinct worker subcastes. The efficiency of workers was measured as the latency of transferring pupae from a lit part of the experimental colony to a darkened part, while the body size diversity was expressed as the within-colony coefficient of variation in head width. We did not find any significant correlation between efficiency and body size variation. Summarizing the existing studies and the present results, we propose the hypothesis that the body size diversity of L. niger may have implications for workers’ division of labor but not for their task efficiency in a stressful contingency.     

Inoculation with native soil improves seedling survival and reduces non-native reinvasion in a grassland restoration

Losses of grasslands have been largely attributed to widespread land-use changes, such as conversion to row-crop agriculture. The remaining tallgrass prairie faces further losses due to biological invasions by non-native plant species, often with resultant ecosystem degradation. Of critical concern for conservation, restoration of native grasslands has been met with little success following eradication of non-native plants. In addition to the direct and indirect effects of non-native invasive plants on beneficial soil microbes, management practices targeting invasive species may also negatively affect subsequent restoration efforts. To assess mechanisms limiting germination and survival of native species and to improve native species establishment, we established six replicate plots of each of the following four treatments: (1) inoculated with freshly collected prairie soil with native seeds; (2) inoculated with steam-pasteurized soil with native seeds; (3) noninoculated with native seeds; or (4) noninoculated/nonseeded control. Inoculation with whole soil did not improve seed germination; however, addition of whole soil significantly improved native species survival, compared to pasteurized soil or noninoculated treatments. Inoculation with whole soil significantly decreased reestablishment of non-native invasive Bothriochloa bladhii (Caucasian bluestem); at the end of the growing season, plots receiving whole soil consisted of approximately 30% B. bladhii cover, compared to approximately 80% in plots receiving no soil inoculum. Our results suggest invasion and eradication efforts negatively affect arbuscular mycorrhizal hyphal and spore abundances and soil aggregate stability, and inoculation with locally adapted soil microbial communities can improve metrics of restoration success, including plant species richness and diversity, while decreasing reinvasion by non-native species.     

The stimulatory effect of chronic lithium treatment on basal thyrotropin secretion in rats: In vivo antagonism by methylparaben

Chronic treatment of rats with lithium chloride was examined in order to determine its effect on hypothalamic monoamine and metabolite content, basal thyrotropin (TSH) secretion and thyroid function. The hypothalamic concentrations of noradrenaline (NA), dopamine (DA) and its metabolites, dihydroxyphenylacetic acid. (DOPAC) and homovanillic acid (HVA) in the lithium treated rats remained unaltered when compared to control levels. NA turnover and the NA metabolite, 3-methoxy-4-hydroxyphenylglycol (total MHPG), were significantly lower (p<0.01), whereas both serotonin (5-HT) and its metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA), were significantly higher (p<0.01 and p<0.02, respectively) in the lithium treated rat hypothalami than in controls. Chronic lithium treatment significantly elevated basal TSH levels (p<0.05). This effect was antagonized by methylp-hydroxybenzoate (methylparaben, p<0.01), which did not itself affect basal TSH levels. Free serum T₃ and T₄ levels were not significantly affected by chronic lithium treatment, although T₄ tended to be slightly lower than control levels. The monoamine changes observed in the hypothalamus of lithium treated rats did not appear to account for the elevated TSH levels observed in these rats since NA activity which is generally regarded as stimulatory was decreased and 5-HT which has an inhibitory effect on TSH secretion, was increased. The elevated TSH levels may have been due to a reduced negative feedback inhibition of TSH release by the mildly reduced circulating T₄ levels caused by chronic lithium treatment. A further possibility is that the pituitary cGMP (and hence TSH) response to TRH may have been enhanced by chronic lithium treatment and methylparaben may have antagonized this effect.     

Sulfation of hypertensive and hypotensive drugs by monkey brain phenol sulfotransferase

The substrate specificity and affinity of two forms of phenol sulfotransferase (PST) from Rhesus macaque brain cortex were studied. Catecholamines, their methylated metabolites (normetanephrine, metanephrine) and methylated precursor, -methylDOPA, were examined as substrates for both the cationic (PST I) and the anionic (PST II) forms of the enzyme. Sulfation of hypertensive drugs (phenylephrine, octopamine, metaraminol), hypotensive drugs (-methylDOPA, minoxidil), and related agents without a free hydroxy group on the benzene ring were also studied. Results indicated that both PST forms sulfated -methylDOPA and minoxidil, but only PST II transferred the sulfate group to catecholamines and most of the adrenergic agents examined.     

Anti-Candida activity of four antifungal benzothiazoles

Abstract Anti- Candida activity of 6-amino-2- n -pentylthiobenzothiazole (I), benzylester of (6-amino-2-benzothiazolylthio)acetic acid (II) and of 3-butylthio-(1,2,4-triazolo)-2,3-benzothiazole (III) was followed and compared to that of 2-mercaptobenzothiazole (IV). I and II exhibited good activity against the C. albicans yeast form, similar to IV. They were inhibitorily active against other Candida strains, IC₅₀ values being of the order of 10⁻⁵ M, which means better activity than IV. Compound I also exhibited inhibitory activity on germ-tube formation and mycelial growth in the C. albicans strains, while II, III and IV were not active in these tests. III was the least active form of the compounds tested, IC₅₀ values being of the order of 10⁻⁴ M. All the compounds tested were highly active on a nystatin-resistant C. albicans mutant, with IC₅₀s of the order of 10⁻⁶ M−10⁻⁵ M.     

Genetic variation in the Y chromosome and sex-biased DNA methylation in somatic cells in the mouse

Mammalian Genome - Several lines of evidence suggest that the presence of the Y chromosome influences DNA methylation of autosomal loci. To better understand the impact of the Y chromosome on...     

Influences of sea level changes and volcanic eruptions on Holocene vegetation in Tonga

Here, we investigate Mid- to Late-Holocene vegetation changes in low-lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh (‘Uta Vava’u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7-m-long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai’o’vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha’afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low-lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change.     

Time-Dependent Effects of Progressive Gamma -Linolenate Feeding on Hyperphagia,Weight Gain,and Erythrocyte Fatty Acid Composition During Growth of Zucker Obese Rats

Obese Zucker rats (fa/fa) have low levels of arachidonic acid (AA) in liver phospholipids (PL). We have previously shown that a 70% gamma-linolenate concentrate (GLA; an AA intermediate) fed at a fixed dose (0.07 g/day) normalized hepatic PL AA and reduced weight gain selectively in the obese animals. In a follow-up study, 16 obese (fa/fa) and 16 lean (Fa/Fa) 4-week-old male rats were randomized into 4 groups of 8 each and gavaged daily with soybean oil (SOY) containing 55% 18:2ω6 (an AA precursor) or GLA, using a progressive dose (≤ 5% of total calories) based on body weight. A defined diet with 11% of energy as SOY was fed ad libitum for 60 days. GLA obese had lower body weight (p<0.0001) and 60-day cumulative food intake (p<0.05) compared to SOY obese, but neither parameter differed between the lean groups. For the last twenty days cumulative food intake was identical for GLA obese and SOY lean, whereas SOY obese consumed 18% more (p<0.05). Thus the progressive dose of GLA selectively suppressed hyperphagia in obese Zucker rats. Erythrocytes collected at 15-day intervals showed parallel increases in AA in both genotypes over time, suggesting normal AA availability during rapid growth. Thus, the reduced PL AA in the livers from the obese rats probably reflects impaired distribution in selected tissues rather than reduced hepatic production. Due to the potential health risks of enriching tissue lipids with AA, great caution is advised in considering GLA as therapy for human obesity.     

Acyl Group Migrations in 2-Monoolein

Acyl migration in 2-monoolein dissolved in solvents under conditions common in lipid modification reactions has been studied. The effects on acyl migration of solvent, incubation temperature, water activity, polar additives and solid additives have been investigated. Extensive acyl migration occured in aliphatic hydrocarbons and water-miscible alcohols under dry conditions. The acyl migration rate could be decreased in several nonpolar solvents by adding a small amount of water or an alcohol. Increasing water activity had no effect in isooctane, but decreased the acyl migration rate dramatically in methyl tert-butyl ether and methyl isobutyl ketone. Several commonly used enzyme supports catalysed acyl migration, showing that supports with surface charges could catalyse acyl migration.