Estrogenic effects of zearalenone on the expression of progestin receptors and sexual behavior in female rats

Zearalenone is a resorcylic acid lactone compound that is produced by fungal infection of edible grains and is believed to influence reproduction by binding to estrogen receptors. In order to study the potential estrogenic effects of this compound in the brain, we examined the effects of zearalenone on the expression of neuronal progestin receptors and feminine sexual behavior in female rats. Ovariectomized rats were treated with zearalenone (0.2, 1.0, or 2.0 mg), estradiol benzoate, or vehicle daily for 3 days. They were then either perfused, and progestin receptors visualized by immunocytochemistry, or injected with progesterone and tested for sexual receptivity with male rats. Progestin receptor-containing cells were counted in the medial preoptic area and ventromedial hypothalamus. The two highest doses of zearalenone increased the concentration of neuronal progestin receptors, as did 10 microg of estradiol. The highest dose of zearalenone (2 mg) also induced progestin receptor staining density comparable to that of 10 microg of estradiol benzoate. In behavioral tests, ovariectomized animals treated with 2 mg of zearalenone followed by progesterone showed levels of sexual receptivity comparable to females treated daily with estradiol benzoate (2 microg) followed by progesterone. These studies suggest that, although structurally distinct and less potent than estradiol, zearalenone can act as an estrogen agonist in the rat brain.     

Estimates of the diffusion resistance of some large sunflower leaves in the field

Studies were made of resistance to gaseous exchange between large sunflower leaves and the bulk air in a crop canopy. Two components of the diffusive pathway for mass and sensible heat were evaluated; A) the resistance from the interior of the leaf to the leaf surface, and B) the resistance from the surface of the leaf through the leaf boundary air layer to the bulk air.     

Dietary zinc reduces osteoclast resorption activities and increases markers of osteoblast differentiation,matrix maturation,and mineralization in the long bones of growing rats

The nutritional influence of zinc on markers of bone extracellular matrix resorption and mineralization was investigated in growing rats. Thirty male weanling rats were randomly assigned to consume AIN-93G based diets containing 2.5, 5, 7.5, 15 or 30 μg Zn/g diet for 24 days. Femur zinc increased substantially as zinc increased from 5 to 15 μg/g diet and modestly between 15 and 30 μg/g (P<.05). By morphological assessment, trabecular bone increased steadily as dietary zinc increased to 30 μg/g. Increasing dietary zinc tended to decrease Zip2 expression nonsignificantly and elevated the relative expression of metallothionen-I at 15 but not 30 μg Zn/g diet. Femur osteoclastic resorption potential, indicated by matrix metalloproteinases (MMP-2 and MMP-9) and carbonic anhydrase-2 activities decreased with increasing dietary zinc. In contrast to indicators of extracellular matrix resorption, femur tartrate-resistant acid and alkaline phosphatase activities increased fourfold as dietary zinc increased from 2.5 to 30 μg Zn/g. Likewise, 15 or 30 μg Zn/g diet resulted in maximum relative expression of osteocalcin, without influencing expression of core-binding factor α-1, collagen Type 1 alpha-1, or nuclear factor of activated T cells c1. In conclusion, increased trabecular bone with additional zinc suggests that previous requirement estimates of 15 μg Zn/g diet may not meet nutritional needs for optimal bone development. Overall, the up-regulation of extracellular matrix modeling indexes and concomitant decrease in resorption activities as dietary zinc increased from 2.5 to 30 μg/g provide evidence of one or more physiological roles for zinc in modulating the balance between bone formation and resorption.     

Sex differences in the effects of juvenile and adult diet on age‐dependent reproductive effort

Sexual selection should cause sex differences in patterns of resource allocation. When current and future reproductive effort trade off, variation in resource acquisition might further cause sex differences in age‐dependent investment, or in sensitivity to changes in resource availability over time. However, the nature and prevalence of sex differences in age‐dependent investment remain unclear. We manipulated resource acquisition at juvenile and adult stages in decorated crickets, Gryllodes sigillatus, and assessed effects on sex‐specific allocation to age‐dependent reproductive effort (calling in males, fecundity in females) and longevity. We predicted that the resource and time demands of egg production would result in relatively consistent female strategies across treatments, whereas male investment should depend sharply on diet. Contrary to expectations, female age‐dependent reproductive effort diverged substantially across treatments, with resource‐limited females showing much lower and later investment in reproduction; the highest fecundity was associated with intermediate lifespans. In contrast, long‐lived males always signalled more than short‐lived males, and male age‐dependent reproductive effort did not depend on diet. We found consistently positive covariance between male reproductive effort and lifespan, whereas diet altered this covariance in females, revealing sex differences in the benefits of allocation to longevity. Our results support sex‐specific selection on allocation patterns, but also suggest a simpler alternative: males may use social feedback to make allocation decisions and preferentially store resources as energetic reserves in its absence. Increased calling effort with age therefore could be caused by gradual resource accumulation, heightened mortality risk over time, and a lack of feedback from available mates.     

Identification of proctolin in the central nervous system of the horseshoe crab, Limulus polyphemus

A proctolin-like peptide was isolated from the prosomal CNS of the chelicerate arthropod, Limulus, and purified using size exclusion, ion exchange and high performance liquid chromatography. Coincident bioassay (cockroach hindgut) and radioimmunoassay were employed to identify fractions which contained proctolin-like material. Proctolin-like activity coeluted with synthetic proctolin with all three chromatographic techniques employed. When applied to either the Limulus heart or hindgut preparations, purified Limulus proctolin produced excitatory responses which were indistinguishable from those produced by the synthetic peptide. Purified samples of the Limulus proctolin-like peptide were subjected to Edman degradation and tandem mass spectrometry and the amino acid sequence of the Limulus peptide was determined to be identical to that of cockroach proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH). The presence of proctolin in the Limulus CNS and its biological action on the isolated heart and hindgut suggest a physiological role for this peptide in the regulation of cardiac output and hindgut motility.     

Effects of bovine urine, plants and temperature on N2O and CO2 emissions from a sub-tropical soil

Grazing ruminants urinate and deposit N onto pastoral soils at rates up to 1,000 kg ha^?1, with most of this deposited N present as urea. In urine patches, nitrous oxide (N₂O) emissions can increase markedly. Soil derived CO₂ fluxes can also increase due to priming effects.While N₂O fluxes are affected by temperature, no studies have examined the interaction of pasture plants, urine and temperature on N₂O fluxes and the associated CO₂ fluxes. We postulated the response of N₂O emissions to bovine urine application would be affected by plants and temperature. Dairy cattle urine was collected, labelled with ¹⁵N, and applied at 590 kg N ha^?1 to a sub-tropical soil,with and without pasture plants at 11°, 19°, and 23°C. Over the experimental period (28 days), 0.2% (11°C with plants) to 2.2% (23°C with plants) of the applied N was emitted as N₂O. At 11°C, plants had no effect on cumulative N₂O-N fluxes, whereas at 23°C, the presence of plants significantly increased the flux, suggesting plant-derived C supply affected the N₂O producing microbes. In contrast, a significant urine application effect on the cumulative CO₂ flux was not affected by varying temperature from 11?C23°C or by growing plants in the soil. This study has shown that plants and their responses to temperature affect N₂O emissions from ruminant urine deposition. The results have significant implications for forecasting and understanding the effect of elevated soil temperatures on N₂O emissions and CO₂ fluxes from grazed pasture systems.     

Pathways mediating the nuclear import of histones H3 and H4 in yeast.

The correct assembly of chromatin is necessary for the maintenance of genomic stability in eukaryotic cells. A critical step in the assembly of new chromatin is the cell cycle-regulated synthesis and nuclear import of core histones. Here we demonstrate that the nuclear import pathway of histones H3 and H4 is mediated by at least two karyopherins/importins, Kap123p and Kap121p. Cytosolic H4 is found associated with Kap123p and H3. Kap121p is also present in the H4-PrA-associated fractions, albeit in lesser amounts than Kap123p, suggesting that this Kap serves as an additional import receptor. We further demonstrate that cytosolic Kap123p is associated with acetylated H3 and H4. H3 and H4 each contain a nuclear localization signal (NLS) in their amino-terminal domains. These amino-terminal domains were found to be essential for the nuclear accumulation of H3 and H4-green fluorescent protein reporters. Each NLS mediated direct binding to Kap123p and Kap121p, and decreased nuclear accumulation of H3 and H4 NLS-green fluorescent protein reporters was observed in specific kap mutant strains. H3 and H4 are the first histones to be assembled onto DNA, and these results show that their import is mediated by at least two import pathways.     

Phytochrome radioimmunoassay

A phytochrome radioimmunoassay with a detection limit of about 2 nanograms has been developed. The radioimmunoassay does not suffer from the potential drawbacks of the commonly used spectral assay and requires less than 1 microliter of crude extract from dark-grown plants for quantitation of phytochrome. Measurement of phytochrome in crude extracts by radioimmunoassay gives values about 25% greater than those obtained by spectral assay. The amount of phytochrome detected in crude extracts of light-grown oats by radioimmunoassay is approximately 1% of that detected in comparable extracts from dark-grown oats. General interference by crude plant extracts with radioimmunoassays was also observed and corrected for.     

Controlled comparison of cimetidine and carbenoxolone sodium in gastric ulcer.

Fifty-four outpatients with endoscopically diagnosed benign gastric ulcer were allocated at random to treatment with either cimetidine 800 mg daily for six weeks or carbenoxolone sodium 300 mg daily for one week then 150 mg daily for five weeks. Ulcers were reassessed by endoscopy at the end of the trial. The endoscopist was unaware of the treatment and did not take part in the clinical care of the patients. Twenty-one of the 27 patients (78%) given cimetidine and 14 of the 27 (52%) given carbenoxolone had healed ulcers. Symptomatic response occurred earlier with cimetidine but was not significantly better. Unwanted effects were more common in the carbenoxolone group: 12 patients developed hypokalaemia, four of whom needed oral potassium supplements. The results suggest that histamine H2-receptor blockade is at least as effective as carbenoxolone sodium for benign gastric ulcer and produces fewer side effects.     

Protein chaperones Q8ZP25_SALTY from Salmonella typhimurium and HYAE_ECOLI from Escherichia coli exhibit thioredoxin-like structures despite lack of canonical thioredoxin active site sequence motif

The structure of the 142-residue protein Q8ZP25_SALTY encoded in the genome of Salmonella typhimurium LT2 was determined independently by NMR and X-ray crystallography, and the structure of the 140-residue protein HYAE_ECOLI encoded in the genome of Escherichia coli was determined by NMR. The two proteins belong to Pfam (Finn et al. 34:D247–D251, 2006) PF07449, which currently comprises 50 members, and belongs itself to the ‘thioredoxin-like clan’. However, protein HYAE_ECOLI and the other proteins of Pfam PF07449 do not contain the canonical Cys-X-X-Cys active site sequence motif of thioredoxin. Protein HYAE_ECOLI was previously classified as a [NiFe] hydrogenase-1 specific chaperone interacting with the twin-arginine translocation (Tat) signal peptide. The structures presented here exhibit the expected thioredoxin-like fold and support the view that members of Pfam family PF07449 specifically interact with Tat signal peptides.