Immobilization of Saccharomyces cerevisiae on to modified carboxymethylcellulose for production of ethanol

In this work, modified carboxymethylcellulose (CMC) was used as a new support material for production of ethanol. Crosslinked graft copolymers of CMC with N-vinyl-2-pyrrolidone (N-VP) were prepared in different grafting yields. The beads material was characterized by means of fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and swelling experiment. Saccharomyces cerevisiae was immobilized using entrapment method in the graft copolymers of carboxymethylcellulose-g-poly(N-vinyl-2-pyrrolidone) (CMC-g-PVP) for ethanol fermentation. The effects of grafting yield, initial glucose concentration and crosslinker concentration on the yield of ethanol process were investigated. Reusability of the immobilized yeasts was investigated and found that the materials can be used four times without losing their activity. Ethanol production increased to 59.3 g/L from 46.4 g/L when percentage of N-VP in the graft copolymer was increased. The highest ethanol productivity was found to be 1.75–2.25 g/L h. Fermentation time decreased with the decreasing of crosslinker concentration. The results suggest that the proposed method for immobilization of Saccharomyces cerevisiae has potential in industrial applications for ethanol process.     

XPD and hOGG1 gene polymorphisms in reperfusion oxidative stress

Knee replacement surgery is an ischemia/reperfusion model, as it uses tourniquet applied to the knee area to stop the blood flow during the operation. Fifty patients that were undergoing elective arthroscopic knee surgery were included in our study. Human 8-oxoguanine glycosylase 1 (hOGG1) is an enzyme to repair specific DNA lesions and a good marker of hydroxyl radical damage to DNA. XPD is another DNA repair gene. We investigated the effect of hOGG1 (Ser326Cys) and XPD (Lys751Gln) polymorphisms on the oxidative stress level after reperfusion. To evaluate oxidative stress conditions, we measured 8-hydroxyguanosine and malondialdehyde (MDA) levels. Polymorphism analyses were done by PCR-RFLP; serum 8-hydroxyguanosine and MDA levels were determined by enzyme-linked immunoassay. There were no significant differences between serum MDA and 8-hydroxyguanosine levels in the samples taken before and after tourniquet application; none of these parameters were related with hOGG1 genotypes. However, we observed increased MDA levels after tourniquet application in M allele carriers for the XPD gene; this could mean that M allele carriers are more prone to DNA damage due to oxidative activity.     

Ultrastructure of islet ghrelin cells in the human fetus

Ghrelin is a peptide hormone predominantly produced in the stomach. Ghrelin expression has also been reported in other tissues including the pancreas. We have reported that ghrelin cells constitute a novel endocrine cell type in the human and the developing rat islets. The cells are most numerous pre- and neonatally and, in humans, constitute 10% of all islet cells from mid-gestation to birth. Since gastric ghrelin expression is low before birth, the islets may be the main source of circulating ghrelin during this time. In the present investigation, we have performed an ultrastructural analysis of pancreatic ghrelin cells in human fetuses by using transmission electron microscopy and immunogold labelling. In addition, morphometrical analysis of secretory granules size was performed. Our data provide evidence for the unique ultrastructural features of ghrelin cells versus other islet cells. Notably, the secretory granules of ghrelin cells were of small size with a mean dense-core diameter of 110 nm. We conclude that ghrelin cells constitute a novel islet cell type, distinct from the previously hormonally characterised islet cell types.This work was supported by grants from the Swedish Medical Research Council (Project No. 4499), the Royal Physiographic Society and the Novo Nordic, Påhlsson and Gyllenstiernska Krapperup Foundations     

Dose-dependent effects of carbendazim on rat thymus

In this study, the effects of carbendazim on the thymus in male rats were evaluated. Carbendazim was administered at 0, 150, 300 and 600 mg kg(-1) day(-1) doses by gavage to male rats for 15 weeks. Body weights of rats in all groups were recorded weekly during treatment. At the end of the experiment, the effects of carbendazim on the thymus were investigated histopathologically and morphologically. Also, based on these effects, change in immunolocalization of fibronectin (FN), which is a component of the extracellular matrix, was investigated immunohistochemically. Fibrosis and oedema were observed in the thymus of rats treated with 300 and 600 mg kg(-1) day(-1) doses of carbendazim. Also in this region, an increase in FN density was noted at the end of the immunohistochemical investigation. A decrease was observed in absolute and relative thymus weights of rats treated with carbendazim compared with the control group. While the decrease in absolute thymus weight was statistically significant in rats exposed to carbendazim at the highest dose, the decrease in relative thymus weights was statistically significant for all carbendazim doses.     

Antagonistic Coevolution Under Sexual Conflict

The theory of sexual conflict predicts that sexual coevolution will be very dynamic, with in principle perpetual evolutionary arms races and chases. These arms races are expected to stop once the costs of conflict adaptations become too high. We argue that this prediction is contingent on specific assumptions about the sexual interaction and the adaptations involved in the arms race. More generally, evolutionary arms races stop when the fitness benefit of further escalations is outweighed by the fitness costs. For this it is not necessary that the absolute costs of conflict must be high at the stable state, or that the population fitness must be decreased at equilibrium. We expect the outcome of sexual antagonistic coevolution to be determined by the possibility to reach compromises and by the relative ability of each sex to control the outcome of the interaction. We exemplify with a theoretical conflict model, which leads to population extinction when conflict is settled by armaments with expression-level determined costs. The model predicts a compromise with small conflict costs for the population, if costs are in addition determined by the extent of conflict between the sexes, which may be the case when the cost depends on behavioural antagonism.     

Effects of Nutrient Level on Maternal Choice and Siring Success in <Emphasis Type="Italic">Cucumis sativus</Emphasis> (Cucurbitaceae)

Plants have evolved many mechanisms to increase the chance of gene dispersal mainly through pollen and environmental factors play an important role. Understanding the mechanism behind gene dispersal is therefore crucial in the correct evaluation of the use of genetically modified crops for cultivation. In this paper we address the question of weather nutrient availability for the female affects the outcome of pollen competition between two pollen donor cultivars of Cucumis sativus. We do this by carrying out controlled crosses of female plants grown at three different nutrient levels. We separated the effect of a specific donor from the effect of pollen tube growth rate by using reversed crosses of fast and slow pollen. Our results show that female effects on siring ability vary with nutrient level. Pollen with a high pollen tube growth rate was more successful when nutrient availability for the female was high. This could be the result of selection on the female to adjust preference according to environmental circumstances. Pollen tube growth rate was measured under nutrient rich circumstances, thus high performers possessed traits adapted to a nutrient rich situation. Due to trade-off effects, these traits might not be advantageous in poor environments. Instead, individuals adapted to low nutrient circumstances will have a higher pollen tube growth rate. If siring ability varies with the environment of the recipient plant, this means that assessments of gene flow must account for this variation and include both pollen donors and recipient plants subjected to a range of environmental circumstances. In risk assessments of transgenic plants, plants are often kept under experimental, homogenous conditions. If our results also apply to other species, estimates of gene flow under constant conditions may be misleading. Selection on siring ability and female preference have fundamental effects on gene flow and need to be considered in risk assessments of transgenic plants.Co-ordinating editor: I. Olivieri