Expression of CspA and GST by an Antarctic psychrophilic bacterium Colwellia sp. NJ341 at near-freezing temperature

Summary A psychrotrophic bacterium Colwellia sp. NJ341 from Antarctic sea ice could grow at −5 and 22 °C, and the extent of cellular protein content and growth were greater at low temperatures (0–10 °C) than at higher temperatures. SDS-PAGE analysis demonstrated the presence of a 7 kDa cold-shock protein. The further result of two-dimensional electrophoresis (2-DE) showed that two proteins a and c were newly synthesized at near-freezing temperatures. With matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) analysis, proteins a and c were identified as glutathione S-transferase (GST) and cold-shock protein A (CspA), respectively, which were involved in cold-adaptation at near-freezing temperature in an Antarctic psychrophilic bacterium Colwellia sp. NJ341.     

Effect of resistance exercise on dehydroepiandrosterone sulfate concentrations during a 72-h recovery: relation to glucose tolerance and insulin response

Serum dehydroepiandrosterone sulfate (DHEA-S) concentration is known to be associated with the whole-body insulin sensitivity. The main purpose of the study was to investigate the effect of resistance exercise on DHEA-S concentration during a 72 h post-exercise recovery, and its relation to glucose tolerance and insulin sensitivity. Morning fasted serum samples was obtained from 19 male volunteers (aged 21.1+/-0.4 years) 24 h before the onset of exercise and 24 h, 48 h, and 72 h following exercise for measurements of DHEA-S, cortisol, and TNF-alpha. Oral glucose tolerance test (OGTT) and insulin response were determined 24 h before and 48 h after exercise. We found that resistance exercise causes a delayed suppression in serum DHEA-S levels during recovery (48 h and 72 h). This exercise challenge did not affect glucose tolerance, but insulin response during OGTT was significantly elevated. The increased insulin level was not associated with serum levels of cortisol and TNF-alpha. In conclusion, the present study found that resistance exercise has a DHEA-S lowering effect that persisted for 72 h. This change could be related to the elevated insulin concentrations during OGTT.     

Blocking of N-acetylglucosaminyltransferase V induces cellular endoplasmic reticulum stress in human hepatocarcinoma 7,721 cells

N-acetylglucosaminyltransferase V （GnT-V） is an important tumorigenesis and metastasis-associated enzyme. To study its biofunction, the GnT-V stably suppressed cell line （GnT-V-AS/7721） was constructed from 7721 hepatocarcinoma cells in previous study. In this study, cDNA array gene expression profiles were compared between GnT-V-AS/7721 and parental 7721 cells. The data indicated that GnT-V-AS/7721 showed a characteristic expression pattern consistent with the ER stress. The molecular mechanism of the ER stress was explored in GnT-V-AS/7721 by the analysis on key molecules in both two unfolded protein response （UPR） pathways. For ATF6 and Irel/XBP-1 pathway, it was evidenced by the up-regulation of BIP at mRNA and protein level, and the appearance of the spliced form ofXBP-1. As for PERK/eIF2α pathway, the activation of ER eIF2α kinase PERK was observed. To confirm the results from GriT-V-AS/7721 cells, the key molecules in the UPR were examined again in 7721 cells interfered with the GnT-V by the specific RNAi treatment. The results were similar with those from GnT-V-AS/7721, indicating that blocking of GnT-V can specifically activate ER stress in 7721 cells. Rate of 3H-Man incorporation corrected with rate of 3H-Leu incorporation in GnT-V-AS/7721 was down-regulated greatly compared with the control, which demonstrated the deficient function of the enzyme synthesizing N-glycans after GnT-V blocking. Moreover, the faster migrating form of chaperone GRP94 associated with the underglycosylation, and the extensively changed N-glycans structures of intracellular glycoproteins were also detected in GnT-V-AS/7721. These results supported the mechanism that blocking of GnT-V expression impaired functions of chaperones and N-glycan-synthesizing enzymes, which caused UPR in vivo.     

MAPK-Activated Protein Kinase 2 Is Required for Mouse Meiotic Spindle Assembly and Kinetochore-Microtubule Attachment

MAPK-activated protein kinase 2 (MK2), a direct substrate of p38 MAPK, plays key roles in multiple physiological functions in mitosis. Here, we show for the first time the unique distribution pattern of MK2 in meiosis. Phospho-MK2 was localized on bipolar spindle minus ends and along the interstitial axes of homologous chromosomes extending over centromere regions and arm regions at metaphase of first meiosis (MI stage) in mouse oocytes. At metaphase of second meiosis (MII stage), p-MK2 was localized on the bipolar spindle minus ends and at the inner centromere region of sister chromatids as dots. Knockdown or inhibition of MK2 resulted in spindle defects. Spindles were surrounded by irregular nondisjunction chromosomes, which were arranged in an amphitelic or syntelic/monotelic manner, or chromosomes detached from the spindles. Kinetochore–microtubule attachments were impaired in MK2-deficient oocytes because spindle microtubules became unstable in response to cold treatment. In addition, homologous chromosome segregation and meiosis progression were inhibited in these oocytes. Our data suggest that MK2 may be essential for functional meiotic bipolar spindle formation, chromosome segregation and proper kinetochore–microtubule attachments.     

A new model of myofibroblast-cardiomyocyte interactions and their differences across species

Although coupling between cardiomyocytes and myofibroblasts is well known to affect the physiology and pathophysiology of cardiac tissues across species, relating these observations to humans is challenging because the effect of this coupling varies across species and because the sources of these effects are not known. To identify the sources of cross-species variation, we built upon previous mathematical models of myofibroblast electrophysiology and developed a mechanoelectrical model of cardiomyocyte-myofibroblast interactions as mediated by electrotonic coupling and transforming growth factor-β1. The model, as verified by experimental data from the literature, predicted that both electrotonic coupling and transforming growth factor-β1 interaction between myocytes and myofibroblast prolonged action potential in rat myocytes but shortened action potential in human myocytes. This variance could be explained by differences in the transient outward K⁺ current associated with differential Kv4.2 gene expression across species. Results are useful for efforts to extrapolate the results of animal models to the predicted effects in humans and point to potential therapeutic targets for fibrotic cardiomyopathy.     

MeCP2 prevents age‐associated cognitive decline via restoring synaptic plasticity in a senescence‐accelerated mouse model

Age‐related cognitive decline in neurodegenerative diseases, such as Alzheimer''s disease (AD), is associated with the deficits of synaptic plasticity. Therefore, exploring promising targets to enhance synaptic plasticity in neurodegenerative disorders is crucial. It has been demonstrated that methyl‐CpG binding protein 2 (MeCP2) plays a vital role in neuronal development and MeCP2 malfunction causes various neurodevelopmental disorders. However, the role of MeCP2 in neurodegenerative diseases has been less reported. In the study, we found that MeCP2 expression in the hippocampus was reduced in the hippocampus of senescence‐accelerated mice P8 (SAMP8) mice. Overexpression of hippocampal MeCP2 could elevate synaptic plasticity and cognitive function in SAMP8 mice, while knockdown of MeCP2 impaired synaptic plasticity and cognitive function in senescence accelerated‐resistant 1 (SAMR1) mice. MeCP2‐mediated regulation of synaptic plasticity may be associated with CREB1 pathway. These results suggest that MeCP2 plays a vital role in age‐related cognitive decline by regulating synaptic plasticity and indicate that MeCP2 may be promising targets for the treatment of age‐related cognitive decline in neurodegenerative diseases.     

Level of habitat fragmentation determines its non-linear relationships with plant speciesn richness,frequency and density at desertified grasslands in Inner Mongolia,China

Aims This study aimed to examine the changes in plant species richness, frequency and density along a habitat fragmentation gradient (with varied degrees of habitat fragmentation [DHFs]) in a desertified grassland of Horqin Sandy Land, northeastern Inner Mongolia, China.