NOPR Collection:

An improved method for Isolation of photosystem II from marine alga Porphyra yezoensis Udea

2005-02-01T00:00:00Z

Title: An improved method for Isolation of photosystem II from marine alga Porphyra yezoensis Udea Authors: Gao, Z Q; Wang, G C; Tseng, C K Abstract: An improved method for isolation and characterization of photosystem (PS)II particles from thylakoid membranes of gametophytes of a marine alga Porphyra yezoensis Udea is reported. Thylakoid membranes were isolated using ultracentrifugation and differential speeds centrifugation and were further purified by the first sucrose density gradient centrifugation (SOGC). PSII particles with high 2, 6- dichloroindophenol (OCIP) photo-reduction activity were isolated by the second SOGC from the thylakoid membranes. Absorption and fluorescence spectra of the thylakoid membranes and PSII particles were recorded and their polypeptides composition was studied. Thylakoid membranes obtained by the above two methods showed similar spectral properties and polypeptides composition. PSII particles, in addition to common extrinsic proteins found in PSII of other plants, contained cyt c-550, a 20 kDa protein, along with two newproteins (14 kDa and 16 kDa). Page(s): 41-47

Effect of iron concentration on the expression and activity of catalase-peroxidases in mycobacteria

2005-02-01T00:00:00Z

Title: Effect of iron concentration on the expression and activity of catalase-peroxidases in mycobacteria Authors: Yeruva, Veena C; Sundaram, CAS Sivagami; Sritharan, Manjula Abstract: Mycobacterial catalases are known to exist in different isoforms. We studied the influence of iron concentration on the expression and activity of the different isoforms in Mycobacterium bovis BCG, M. smegmatis, M. fortuitum, M. kansasii and M. vaccae by growing them under iron-sufficient (4 µg Fe/mL) and iron-deficient (0.02 µg Fe/ml) conditions. Upon iron deprivation, significant differences were observed in the catalase/peroxidase activities in both quantitative spectrophotometric assays and in the activity staining in native gels. Notable feature was that the peroxidase activity showed a significant decrease upon iron deprivation in all the mycobacteria, except M. vaccae. Peroxidase activity in all the mycobacteria, irrespective of the iron status was susceptible to heat inactivation. However, the isoforms of catalase showed differences in their heat stability, indicating possible structural differences in these proteins. For example, M. bovis BCG expressed a heat labile catalase under iron-sufficient conditions, while a heat stable catalase band of similar mobility was expressed under iron-deprivation conditions. The study clearly indicates that iron plays an important role in the regulation of expression of the different isoforms of the catalase-peroxidases, Page(s): 28-33

Amino acids differentially regulate insulin receptor tyrosine kinase and phosphatidyl inositol-3-OH-kinase activities in human monocytes exposed to high glucose concentration

2005-02-01T00:00:00Z

Title: Amino acids differentially regulate insulin receptor tyrosine kinase and phosphatidyl inositol-3-OH-kinase activities in human monocytes exposed to high glucose concentration Authors: Srinivasan, V; Rajesh, M; Sulochana, K N; Indra, C; Ramakrishnan, S Abstract: Chronic hyperglycemia and insulin resistance are the common factors involved in the development of vascular complications in diabetes mellitus (DM) patients. Since insulin signaling pathway has been shown to be regulated by nutritional supplements, in the present study, we investigated the possible effects of free amino acids, such as lysine, arginine and alanine and their mixture in modulating the insulin receptor tyrosine kinase (IRTK) and phosphatidyl inositol-3-OH-kinase (PI3K) activities and on the changes in actin dynamics in monocytes (MC), exposed to high glucose concentration (25 mM). IRTK and PI3K activities were markedly decreased in MC, incubated with 25 mM glucose. However, on treatment with amino acids, only lysine was effective in augmenting IRTK and PI3K activities in a dose-dependent manner. Arginine had marginal effect in promoting these activities. Equimolar mixture of amino acids showed marginal effect of augmenting only IRTK activity. Alanine had no effect. The F-actin filaments showed grossly diminished organization in the cells treated with 25 mM glucose alone, as assessed by specific binding to phalloidin-FITC, when compared with cells treated with 5 mM glucose. On the other hand, a significant improvement in the F-actin organization was observed in the cells co-incubated with 25 mM glucose and lysine. A possible molecular mechanism is the antiglycating effect of amino acids. The signal transduction starts with binding of ATP to lysine at position 1030 in the β sub unit of the receptor. This lysine (1030) may be protected by the added lysine or to some extent arginine from glycation and loss of function. In summary, our findings suggest that the amino acids apart from their antiglycating property can also modulate/influence the activities of pivotal enzymes that are upstream in the insulin-mediated signal transduction pathway and bring down glucose. Page(s): 13-18

A simplified fluorimetric method for corticosterone estimation in rat serum, tissues and mitochondria

2005-02-01T00:00:00Z

Title: A simplified fluorimetric method for corticosterone estimation in rat serum, tissues and mitochondria Authors: Katyare, Surendra S; Pandya, Jignesh D Abstract: A simplified procedure has been developed for the extraction and estimation of corticosterone from rat serum, tissues and mitochondria. The suitably diluted samples were treated with freshly prepared chloroform: methanol mixture (2:1, v/v) and then extracted directly with the chloroform. Almost quantitative recoveries (90% and above) were obtained with the present method, compared to poor recoveries (65-81%) and variable results obtained by earlier procedure. Quantification of corticosterone content in tissues, such as liver, brain and heart, and in the mitochondria indicated significant concentration of corticosterone in tissues and mitochondria, as compared to the serum. The presence of corticosterone in the mitochondria suggests that the hormone may play a role in regulation of mitochondrial gene expression and/or their turnover Page(s): 48-53