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The analgesia produced by 24 hr of food deprivation was examined in 4-mo, 14-mo, and 24-mo old rats. To assess opioid and hormonal involvement in food deprivation induced analgesia, different groups of rats from each age group were injected with naltrexone (7 mg/kg), dexamethasone (0.4 mg/kg), or equivolume saline. Results revealed that food deprivation produced an equivalent analgesic response in each saline-treated age group. Also, naltrexone and dexamethasone were equally potent in blocking food deprivation induced analgesia in each age group. These results demonstrated that food deprivation activates an endogenous opioid-mediated analgesic system that involves hormonal factors and that this system does not change in function with increasing age. 相似文献
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Knisely JM Li Y Griffith JM Geuze HJ Schwartz AL Bu G 《Experimental cell research》2007,313(15):3298-3307
The LDL receptor-related protein 1B (LRP1B) is a putative tumor suppressor homologous to LRP1. Both LRP1 and LRP1B contain cytoplasmic tails with several potential endocytosis motifs. Although the positions of these endocytic motifs are similar in both receptors, LRP1B is internalized at a 15-fold slower rate than LRP1. To determine whether the slow endocytosis of LRP1B is due to the utilization of an endocytosis motif other than the YATL motif used by LRP1, we tested minireceptors with mutations in each of the five potential motifs in the LRP1B tail. Only mutation of both NPXY motifs together abolished LRP1B endocytosis, suggesting that LRP1B can use either of these motifs for internalization. LRP1B contains a unique insertion of 33 amino acids not present in LRP1 that could lead to altered recognition of trafficking motifs. Surprisingly, deletion of this insertion had no effect on the endocytosis rate of LRP1B. However, replacing either half of the LRP1B tail with the corresponding LRP1 sequence markedly accelerated LRP1B endocytosis. From these data, we propose that both halves of the LRP1B cytoplasmic tail contribute to a unique global conformation, which results in less efficient recognition by endocytic adaptors and a slow endocytosis rate. 相似文献
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van Dijken JP Bauer J Brambilla L Duboc P Francois JM Gancedo C Giuseppin ML Heijnen JJ Hoare M Lange HC Madden EA Niederberger P Nielsen J Parrou JL Petit T Porro D Reuss M van Riel N Rizzi M Steensma HY Verrips CT Vindeløv J Pronk JT 《Enzyme and microbial technology》2000,26(9-10):706-714
To select a Saccharomyces cerevisiae reference strain amenable to experimental techniques used in (molecular) genetic, physiological and biochemical engineering research, a variety of properties were studied in four diploid, prototrophic laboratory strains. The following parameters were investigated: 1) maximum specific growth rate in shake-flask cultures; 2) biomass yields on glucose during growth on defined media in batch cultures and steady-state chemostat cultures under controlled conditions with respect to pH and dissolved oxygen concentration; 3) the critical specific growth rate above which aerobic fermentation becomes apparent in glucose-limited accelerostat cultures; 4) sporulation and mating efficiency; and 5) transformation efficiency via the lithium-acetate, bicine, and electroporation methods. On the basis of physiological as well as genetic properties, strains from the CEN.PK family were selected as a platform for cell-factory research on the stoichiometry and kinetics of growth and product formation. 相似文献
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Luaine Bandounas Nick JP Wierckx Johannes H de Winde Harald J Ruijssenaars 《BMC biotechnology》2011,11(1):1-11
Background
The number of biotransformations that use nicotinamide recycling systems is exponentially growing. For this reason one of the current challenges in biocatalysis is to develop and optimize more simple and efficient cofactor recycling systems. One promising approach to regenerate NAD+ pools is the use of NADH-oxidases that reduce oxygen to hydrogen peroxide while oxidizing NADH to NAD+. This class of enzymes may be applied to asymmetric reduction of prochiral substrates in order to obtain enantiopure compounds.Results
The NADH-oxidase (NOX) presented here is a flavoenzyme which needs exogenous FAD or FMN to reach its maximum velocity. Interestingly, this enzyme is 6-fold hyperactivated by incubation at high temperatures (80°C) under limiting concentrations of flavin cofactor, a change that remains stable even at low temperatures (37°C). The hyperactivated form presented a high specific activity (37.5 U/mg) at low temperatures despite isolation from a thermophile source. Immobilization of NOX onto agarose activated with glyoxyl groups yielded the most stable enzyme preparation (6-fold more stable than the hyperactivated soluble enzyme). The immobilized derivative was able to be reactivated under physiological conditions after inactivation by high solvent concentrations. The inactivation/reactivation cycle could be repeated at least three times, recovering full NOX activity in all cases after the reactivation step. This immobilized catalyst is presented as a recycling partner for a thermophile alcohol dehydrogenase in order to perform the kinetic resolution secondary alcohols.Conclusion
We have designed, developed and characterized a heterogeneous and robust biocatalyst which has been used as recycling partner in the kinetic resolution of rac-1-phenylethanol. The high stability along with its capability to be reactivated makes this biocatalyst highly re-useable for cofactor recycling in redox biotransformations. 相似文献9.
Lindström Irene Bontell Neil Hall Kevin E Ashelford JP Dubey Jon P Boyle Johan Lindh Judith E Smith 《Genome biology》2009,10(5):R53-17
Background
Toxoplasma gondii is a zoonotic parasite of global importance. In common with many protozoan parasites it has the capacity for sexual recombination, but current evidence suggests this is rarely employed. The global population structure is dominated by a small number of clonal genotypes, which exhibit biallelic variation and limited intralineage divergence. Little is known of the genotypes present in Africa despite the importance of AIDS-associated toxoplasmosis. 相似文献10.
Margaret?O?Nwagwu Helen?Baines Jeffrey?B?Kerr Francis?JP?EblingEmail author 《Reproductive biology and endocrinology : RB&E》2005,3(1):48