Characterization of singlet oxygen-accumulating mutants isolated in a screen for altered oxidative stress response in <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

Background  

When photosynthetic organisms are exposed to harsh environmental conditions such as high light intensities or cold stress, the production of reactive oxygen species like singlet oxygen is stimulated in the chloroplast. In Chlamydomonas reinhardtii singlet oxygen was shown to act as a specific signal inducing the expression of the nuclear glutathione peroxidase gene GPXH/GPX5 during high light stress, but little is known about the cellular mechanisms involved in this response. To investigate components affecting singlet oxygen signaling in C. reinhardtii, a mutant screen was performed.     

Can splenocytes enhance pancreatic β-cell function and mass in 90% pancreatectomized rats fed a high fat diet?

AimsRecent studies have shown that splenocytes may act as a possible neogenic source with regard to β-cells in rodent diabetic models. Accordingly, we sought to determine whether splenocytes played an important role in promoting β-cell function and mass among type 2 diabetic rats with and without spleen.Main methodsWe randomly divided female 90% pancreatectomized (Px) Sprague Dawley rats into three groups: splenectomy (SPX), splenectomy plus the injection of male splenocytes (SPI), and no splenectomy (NSP). They were administered with 40 energy percent fat diets over the course of five weeks. At the end of the experimental period, insulin secretion capacity was measured by hyperglycemic clamp. At 6 h after BrdU⁺ injection, the pancreas was prepared with 4% paraformaldehyde in order to perform immunohistochemistry.Key findingsSPX increased and sustained serum glucose levels more than NSP and SPI during oral glucose tolerance testing. During hyperglycemic clamp, first and second phase insulin secretion decreased in the SPX rats while splenocyte injections counteracted this. Beta-cell mass in the SPX group was reduced more than among NSP and SPI. This was the result of a decrease in the number of small β-cell clusters in SPX, which is indicative of a decrease in β-cell neogenesis.SignificanceSplenocytes play an important role with regard to the neogenesis of β-cells in insulin deficient type 2 diabetic rats, although they are not critical for β-cell regeneration.     

Genbank accession #: AJ131961

Plant Molecular Biology -     

Injection drug use and HIV/AIDS transmission in China

INTRODUCTION Although sexual transmission accounts for most of the AIDS epidemic globally, HIV/AIDS among injecting drug users (IDUs) is a growing problem worldwide. First de- tected in China in 1989 among drug abusers on the Yunnan border, HIV/AIDS subse…     

Protandrous migration and variation in morphological characters in Emberiza buntings at an East Asian stopover site

The effect of the timing of spring migration on reproductive success differs between the sexes. As a consequence, various sex‐specific tactics relating to the timing of migration have evolved in migratory avian groups. Various hypotheses have been proposed to explain differential migration to breeding or wintering grounds, and inter‐ and intrasexual size differences are often considered one of the proximate mechanisms. We investigated arrival patterns in the spring by individuals of each sex, sexual size dimorphism and related morphological variables, and the relationship between size variation and arrival date in five bunting species that passed through an East Asian migratory flyway stopover site in 2006–08. Males of all the study species arrived before females, and significant sexual dimorphism was observed. Several morphological characters, including total length, wing‐length and tail‐length, contributed to the size variation. Although larger males arrived earlier, there was no relationship between arrival date and size in females. Our study confirmed that East Asian buntings display a discriminated protandrous migration pattern at the stopover site as well as at the breeding grounds. This is consistent with the view that larger body size in males is favoured due to its association with early arrival to help ensure access to the best resources and hence enhanced mating success.     

Increased heterologous protein production by Saccharomyces cerevisiae growing on ethanol as sole carbon source

Saccharomyces cerevisiae is a widely used host organism for the production of heterologous proteins, often cultivated in glucose-based fed-batch processes. This production system however has many factors limiting the productivity, mainly towards the end of the fermentation. For the optimised production of a Camelid antibody fragment this process was evaluated. In shake flask cultivations, it was found that ethanol has a strong effect on productivity increase and therefore glucose and ethanol fed-batch fermentations were compared. It appeared that specific heterologous protein production was up to five times higher in the ethanol cultivation and could be further optimised. Then the key characteristics of ethanol fed-batch fermentations such as growth rate and specific production were determined under ethanol limitation and accumulation and growth limiting conditions in the final phase of the process. It appeared that an optimal production process should have an ethanol accumulation throughout the feed phase of approximately 1% v/v in the broth and that production remains very efficient even in the last phase of the process. This productivity increase on ethanol versus glucose was also proven for several other Camelid antibody fragments some of which were heavily impaired in secretion on glucose, but very well produced on ethanol. This leads to the suggestion that the ethanol effect on improved heterologous protein production is linked to a stress response and folding and secretion efficiency.