A novel Delta9 acyl-lipid desaturase, DesC2, from cyanobacteria acts on fatty acids esterified to the sn-2 position of glycerolipids

Acyl-lipid desaturases are enzymes that convert a C-C single bond into a C=C double bond in fatty acids that are esterified to membrane-bound glycerolipids. Four types of acyl-lipid desaturase, namely DesA, DesB, DesC, and DesD, acting at the Delta12, Delta15, Delta9, and Delta6 positions of fatty acids respectively, have been characterized in cyanobacteria. These enzymes are specific for fatty acids bound to the sn-1 position of glycerolipids. In the present study, we have cloned two putative genes for a Delta9 desaturase, designated desC1 and desC2, from Nostoc species. The desC1 gene is highly similar to the desC gene that encodes a Delta9 desaturase that acts on C18 fatty acids at the sn-1 position. Homologues of desC2 are found in genomes of cyanobacterial species in which Delta9-desaturated fatty acids are esterified to the sn-2 position. Heterologous expression of the desC2 gene in Synechocystis sp. PCC 6803, in which a saturated fatty acid is found at the sn-2 position, revealed that DesC2 could desaturate this fatty acid at the sn-2 position. These results suggest that the desC2 gene is a novel gene for a Delta9 acyl-lipid desaturase that acts on fatty acids esterified to the sn-2 position of glycerolipids.     

Mammalian Rad9 plays a role in telomere stability, S- and G2-phase-specific cell survival, and homologous recombinational repair

The protein products of several rad checkpoint genes of Schizosaccharomyces pombe (rad1+, rad3+, rad9+, rad17+, rad26+, and hus1+) play crucial roles in sensing changes in DNA structure, and several function in the maintenance of telomeres. When the mammalian homologue of S. pombe Rad9 was inactivated, increases in chromosome end-to-end associations and frequency of telomere loss were observed. This telomere instability correlated with enhanced S- and G2-phase-specific cell killing, delayed kinetics of gamma-H2AX focus appearance and disappearance, and reduced chromosomal repair after ionizing radiation (IR) exposure, suggesting that Rad9 plays a role in cell cycle phase-specific DNA damage repair. Furthermore, mammalian Rad9 interacted with Rad51, and inactivation of mammalian Rad9 also resulted in decreased homologous recombinational (HR) repair, which occurs predominantly in the S and G2 phases of the cell cycle. Together, these findings provide evidence of roles for mammalian Rad9 in telomere stability and HR repair as a mechanism for promoting cell survival after IR exposure.     

Cardioprotective effect of lycopene in the experimental model of myocardial ischemia-reperfusion injury

The continuous advancements in cancer research have contributed to the overwhelming evidence of the presence of telomerase in primary and secondary tumours together with hsp90 and c-Myc. This review will discuss the important role of telomerase together with hsp90 and c-Myc within the initiation and progression of gliomas. Also it will review the differential expression of these genes in the different grades of gliomas and the possibility of new treatments targeting these specific genes.     

Development of pharmacophoric model of condensed pyridine and pyrimidine analogs as hydroxymethyl glutaryl coenzyme A reductase inhibitors

Quantitative structure-activity relationship (QSAR) has been established on a series of thirty-eight compounds of four different sets of condensed pyridine and pyrimidine analogs, for their hydroxymethyl glutaryl coenzyme (HMG-CoA) reductase inhibitor activity, in order to understand the essential structural requirement for binding with receptor, in terms of common biophoric and secondary sites employing APEX-3D software. Among several 3D pharmacophoric models with different sizes and arrangements, one model was selected based on r2 = 0.8, chance<0.001, match equivalent to 0.38 and all the 38 compounds were considered. The results suggest that hydrophobicity, hydrogen acceptor and optimum steric refractivity play a dominant role in the inhibition of HMG-CoA reductase. The information obtained from the present study can be used to design and predict more potent molecules as HMG-CoA reductase inhibitors, prior to their synthesis.     

Bioaffinity Based Oriented Immobilization of Stem Bromelain

Bromelain is a basic, 23.8 kDa thiol proteinase obtained from stem of the pineapple plant (Ananas comosus) and is unique in containing a single oligosaccharide chain attached to the polypeptide. This property allowed its affinity binding and favorable orientation on a Sepharose support pre-coupled with the lectin, concanavalin A (Con A). For comparison, bromelain was also immobilized by covalently coupling to the CNBr-activated Sepharose. The preparation obtained was more resistant to thermal inactivation as evident from the retention of over 50% activity after incubation at 60 for 100 min (as compared to 20% retained by the native enzyme and 30% retained by the covalently immobilized enzyme), exhibited a broader pH-activity profile with the enzyme retaining over 60% activity at pH 11 (as compared to over 25% retained by native and the enzyme immobilized covalently). The native, covalently-coupled and affinity-bound bromelains had apparent K _m values of 1.1, 2 and 0.54 mg/ml, respectively using casein as the substrate. The V _max values remained unaffected on immobilization.     

Swelling and de-swelling kinetics of gelatin hydrogels in ethanol-water marginal solvent

Controlled osmotic swelling and de-swelling measurements have been performed on gelatin, a polyampholyte, hydrogels suspended in water-ethanol marginal solvent at room temperature (20 degrees C) where the alcohol concentration was changed from 0 to 100% (v/v). The change in gel mass was monitored as function of time until osmotic equilibrium was established with the surrounding solvent. It was observed that osmotic pressure of polymer-solvent mixing, pi(m)相似文献   

Effect of salinity and different nitrogen sources on the activity of antioxidant enzymes and indole alkaloid content in Catharanthus roseus seedlings

The activities of antioxidant enzymes viz. glutathione reductase, GR; superoxide dismutase, SOD; peroxidase, POD; catalase, CAT and glutathione-S-transferase, GST and alkaloid accumulation were investigated in leaf pairs (apical, middle, basal) and in roots of Catharanthus roseus seedlings under the conditions of different nitrogen sources (20 mM KNO(3) and 2 mM NH(4)Cl) and salinity, in the absence (non-saline control) and in the presence of 100 mM NaCl in the nutrient solution. Salinity caused a reduction in plant biomass. The biomass production of ammonium-fed plants was lower than that of nitrate-fed plants. The antioxidant enzymes exhibited higher activity in saline-treated plants. Changes in antioxidant enzyme activity caused by different nitrogen sources differed in all leaf pairs, as well as in roots of C. roseus. Ammonium-fed plants showed higher CAT, GR and GST activity in leaf pairs as well as in roots, while POD and SOD activity were higher in nitrate-fed plants. Higher peroxidase activity concomitant with the increased accumulation of alkaloid was found in all leaf pairs, as well as in roots of C. roseus of NO(3)(-) fed plants as compared to NH(4)(+) fed plants.     

Glial cell-line derived neurotrophic factor-mediated RET signaling regulates spermatogonial stem cell fate

Normal spermatogenesis is essential for reproduction and depends on proper spermatogonial stem cell (SSC) function. Genes and signaling pathways that regulate SSC function have not been well defined. We report that glial cell-line-derived neurotrophic factor (GDNF) signaling through the RET tyrosine kinase/GFRA1 receptor complex is required for spermatogonial self-renewal in mice. GFRA1 and RET expression was identified in a subset of gonocytes at birth, was restricted to SSCs during normal spermatogenesis, and RET expressing cells were abundant in a cryptorchid model of SSC self-renewal. We used the whole-testis transplantation technique to overcome the limitation of neonatal lethality of Gdnf-, Gfra1-, and Ret-deficient mice and found that each of these genes is required for postnatal spermatogenesis and not for embryological testes development. Each mutant testis shows severe SSC depletion by Postnatal Day 7 during the first wave of spermatogenesis. These defects were due to lack of SSC proliferation and an inability of SSCs to maintain an undifferentiated state. Our results demonstrate that GDNF-mediated RET signaling is critical for the fate of undifferentiated spermatogonia and that abnormalities in this pathway may contribute to male infertility and testicular germ cell tumors.     

Fibronectin and laminin enhance engraftibility of cultured hematopoietic stem cells

To test the hypothesis that extracellular matrix (ECM) components maintain stem cell property, murine bone marrow (BM) cells were expanded in fibronectin and laminin coated plate in the presence of cytokines. We observed significant phenotypic and functional improvement of expanded cells. In 10 days, 800-fold expansion of colony-forming unit-granulocyte erythrocyte monocyte megakaryocyte (CFU-GEMM) was observed in the cultured cells. No apparent activation of cell cycle was observed, but CD29 and very late antigen-4 (VLA-4) expression was increased, as compared to the normal BM cells. A fraction of the expanded cells became verapamil sensitive, suggesting upregulation of multi-drug resistant gene(s), as found in the primitive hematopoietic stem cells (HSCs). Competitive repopulation assay confirmed that HSCs compartment was amplified during culture. Overall, our study clearly demonstrated that ex vivo culture of murine HSCs in the presence of fibronectin and laminin resulted in expansion of primitive stem cells and improvement in the marrow engraftibility.