Recognition of cyclooxygenase-2 (COX-2) active site by NSAIDs: a computer modelling study

The energetics and models of COX-2 complexed with nonsteroidal anti-inflammatory drugs (NSAIDs) having different degrees of selectivity for two isoforms of COX (COX-2 and COX-1) have been studied using computer modelling approach. The models are obtained for complexes of NS398 (NS), a selective COX-2 inhibitor; indoprofen (Ind), a non-selective inhibitor; di-tert-butylbenzofurans (DHDMBFs) with substituents at the 5th position: CONH(CH2)2OMe (BF1), CONH-c-Pr (BF2), 3-methylene-gamma-butyrolactonyl (BF3) and oxicams namely, meloxicam (Mel), piroxicam (Pir) and tenoxicam (Ten). These were optimized using molecular mechanics (MM) and molecular dynamics (MD) techniques. The binding energies and structures were compared with pharmacological parameters and available results with COX-1. In case of NS a larger difference in the binding energies between COX-2 and COX-1 was noticed as compared to that of Ind. It also had stronger interaction with His90 and Tyr355 which is considered important for COX-2 selectivity. There was a difference in the compactness at the channel entrance between COX-2 selective and non-selective ligands. Models with DHDMBFs and oxicams showed a similar correlation. The results were used to design a peptide inhibitor, Tyr-Arg-Cys-Ala-delta Phe-Cys (Pept) which could fit better in the COX-2 cavity. As per our MD simulation results this peptide inhibitor showed both higher activity and COX-2 selectivity.     

Growth of Streptomyces hygroscopicus in rotating-wall bioreactor under simulated microgravity inhibits rapamycin production

Growth of Streptomyces hygroscopicus under conditions of simulated microgravity in a rotating-wall bioreactor resulted in a pellet form of growth, lowered dry cell weight, and inhibition of rapamycin production. With the addition of Teflon beads to the bioreactor, growth became much less pelleted, dry cell weight increased but rapamycin production was still markedly inhibited. Growth under simulated microgravity favored extracellular production of rapamycin, in contrast to a greater percentage of cell-bound rapamycin observed under normal gravity conditions. Received: 20 September 1999 / Received revision: 18 November 1999 / Accepted: 19 November 1999     

Photoperiodic induction of ovarian growth and plasma estradiol secretion in a migratory finch, Emberiza melanocephala: involvement of circadian rhythm

To demonstrate the involvement of circadian rhythm in photoperiodic time measurement, photosensitive female blackheaded buntings were kept under different photoperiodic schedules consisting of 6 h of main photophase coupled with scotophases of various durations. Ovarian mass and circulating plasma estradiol concentration were found to be elevated in cycles of 6L:6D, 6L:36D, 6L:54D and in control 15L:9D groups. But cycles of 6L:18D, 6L:42D and 6L:66D did not stimulate ovarian growth or elevate circulating plasma estradiol concentration. These results are consistent with the Bünning hypothesis according to which a photoperiodic response is elicited as a result of the coincidence of light with the photoinducible phase of an endogenous circadian rhythm. The results thus indicate the involvement of a circadian rhythm of photoinducibility in ovarian growth and estradiol secretion.     

Analysis of guanine nucleotide binding and exchange kinetics of the Escherichia coli GTPase Era

Era is an essential Escherichia coli guanine nucleotide binding protein that appears to play a number of cellular roles. Although the kinetics of Era guanine nucleotide binding and hydrolysis have been described, guanine nucleotide exchange rates have never been reported. Here we describe a kinetic analysis of guanine nucleotide binding, exchange, and hydrolysis by Era using the fluorescent mant (N-methyl-3'-O-anthraniloyl) guanine nucleotide analogs. The equilibrium binding constants (K(D)) for mGDP and mGTP (0.61 +/- 0. 12 microgM and 3.6 +/- 0.80 microM, respectively) are similar to those of the unmodified nucleotides. The single turnover rates for mGTP hydrolysis by Era were 3.1 +/- 0.2 mmol of mGTP hydrolyzed/min/mol in the presence of 5 mM MgCl(2) and 5.6 +/- 0.3 mmol of mGTP hydrolyzed/min/mol in the presence of 0.2 mM MgCl(2). Moreover, Era associates with and exchanges guanine nucleotide rapidly (on the order of seconds) in both the presence and absence of Mg(2+). We suggest that models of Era function should reflect the rapid exchange of nucleotides in addition to the GTPase activity inherent to Era.     

Decomposition patterns of unprocessed and processed lignocellulosics in a freshwater fish pond

In an attempt to recycle the lignocellulosic wastes like Eichhornia crassipes, Salvinia cucullata and rice (Oryza sativa) straw as manurial inputs in freshwater fish pond ecosystem, a decomposition experiment was carried out in litter bags in an oligotrophic freshwater fish pond environment, with the above mentioned three substrates in unprocessed and microbially processed forms. The loss rates, associated microbial groups, oxygen consumption patterns and other related parameters like carbon, nitrogen, phosphorus, cellulose, hemicellulose and lignin were analysed. The mean daily dry matter loss rates (unprocessed: 10.44>6.97>1.97 and processed: 11.03>8.21>3.67) and oxygen uptake rate (unprocessed: 0.675>0.571>0.568 mg O₂ g^–1 h^–1 and processed: 0.592>0.424>0.407 mg O₂ g^–1 h^–1) in raw and processed substrates were in the sequence Eichhornia > rice straw > Salvinia. The oxygen consumption pattern almost covariated with variations in temperature of pond water, daily dry matter loss rates and fungal counts on substrates. During the decay, the percentage of N and P increased whereas that of C decreased, resulting in lowering of C/N and C/P ratios of the substrates. The structural polymeric fractions like cellulose and hemicellulose decreased along with dry matter whereas the lignin content increased after an initial decrease due to loss of other structural carbohydrates resulting in apparent per cent gain of lignin. A higher number of different heterotrophic bacterial groups was observed in the processed substrates as compared to their raw counterparts. However, cellulolytic bacterial numbers were found to fluctuate through the study period. The fungal load was found to be decreasing gradually as the decay progressed. In this study, bacteria were found to be the prominent microbial group responsible for the decay. The nitrogen-fixing, phosphatase-producing and phosphorus-solubilising bacterial groups were observed to play an important role in lowering the C/N and C/P ratios of the decomposing substrates during decay.     

Influence of Etherel and Gibberellic Acid on Carbon Metabolism,Growth, and Essential Oil Accumulation in Spearmint (Mentha Spicata)

Controlled environment chamber and glasshouse studies were conducted on six herbaceous annual species grown at 350 (AC) and 700 (EC) mol(CO₂) mol^-1 to determine whether growth at EC resulted in acclimation of the apparent quantum yield of photosynthesis (QY) measured at limiting photosynthetic photon flux density (PPFD), or in acclimation of net photosynthetic rate (P _N) measured at saturating PPFD. It was also determined whether acclimation in P _N at limiting PPFD was correlated with acclimation of carboxylation efficiency or ribulose-1,5-bisphosphate (RuBP) regeneration rate measured at saturating PPFD. Growth at EC reduced both the QY and P _N at limiting PPFD in three of the six species. The occurrence of photosynthetic acclimation measured at a rate limiting PPFD was independent of whether photosynthetic acclimation was apparent at saturating measurement PPFD. At saturating measurement PPFD, acclimation to EC in the apparent carboxylation efficiency and RuBP regeneration capacity also occurred independently. Thus at least three components of the photosynthetic system may adjust independently when leaves are grown at EC. Estimates of photosynthetic acclimation at both high and low PPFD are necessary to accurately predict photosynthesis at the whole plant or canopy level as [CO₂] increases.     

Acardiac anomaly spectrum

BACKGROUND: Acardiac anomaly spectrum is a rare congenital malformation found in monozygotic twin pregnancy. Besides the absence of heart, the condition is associated with variable grades of developmental disruption. Thus, no two cases are similar. METHODS: This case report is based on physical examination and autopsy findings. RESULTS: The twin had acardia and partial development of head and face. There was complete absence of upper extremities. CONCLUSIONS: The twin reversed arterial perfusion (TRAP) theory is the most accepted etiology of the disorder. Normally, the cephalic pole is the most severely affected, being most distal to the retrograde perfusion. In acardia, partial development of head, face, and brain is usually associated with the development of the upper extremities. However, in the present case, there was extensive cephalic development in the absence of upper extremity development.     

Amelioration of lead and mercury effects on germination and rice seedling growth by antioxidants

Germination of two rice (Oryza sativa L.) cultivars (Ratna and IR 36) in the presence of 10 μM PbCl2 and 10 μM HgCl2 decreased germination percentage, germination index, shoot/root length, tolerance index and dry mass of shoots and roots. Mercury was more toxic than lead. Reduced glutathione (GSH), cysteine (Cys), ascorbic acid, and α-tocopherol alleviated the adverse effects of these metals on plants in the order GSH > Cys > ascorbic acid > α-tocopherol. The effects were more pronounced in tolerant cultivar IR 36 than in the relatively susceptible cultivar Ratna. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fibril formation from cellulose by a novel protein from Trichoderma reesei: A non-hydrolytic cellulolytic component?

A low molecular weight protein, named fibril-forming protein (FFP), was isolated from the culture supernatant of Avicel-grown Trichoderma reesei. The protein was purified to homogeneity and it exhibited a molecular weight of 11,400Da. Low amounts of this protein caused apparently non-hydrolytic disruption of filter paper, releasing fibrils without any detectable release of reducing sugars. It displayed no hydrolytic activity on carboxymethylcellulose (CMC), p-nitrophenyl--d-glucoside (pNPG) or 4-methylumbelliferyl cellobioside. The pH optimum of the protein was between 4 and 5. The temperature optimum was 40°C and the computed activation energy (E_a) for the filter paper disruption process was 4.18kcal/mol, suggesting disruption of non-covalent bonds. It had no immunological cross reactivity with reported cellulase components of T. reesei.