抗黄体酮联合Aromatase抑制剂或iNOS终止恒河猴妊娠

[目的]评价抗黄体酮(mifepristone)联合Aromatase抑制剂(letrozole或aminoglutethimide)或iNOS抑制剂(aminoguandine)是否能有效终止恒河猴早期妊娠。[方法]将30只猴子随机分为5组(治疗组每组6只,对照组6只),并在妊娠30,31和32天进行如下处理:对照组,每只动物1ml安慰剂;A组,Mifepristone(1mg/kg,sc.);B组,Mifepristone(sc.)+Letrozole(2.5mg/只sc.);C组,Mifepristone(1mg/kg,sc.)+aminoglute-chimide(50mg/kgsc.,bid);D组,Mifepristone(1mg/kg,sc.)+aminoguanidine(150mg/kg,sc.,bid)。所有妊娠猴在妊娠29天通过超声波确认。[结果]在B、C、D组,所有的动物的妊娠都在妊娠早期被终止(6/6)。A组和对照组的妊娠终止率分别为3/6和2/6。同时,联合用药能够有效排空子宫腔和减少出血。[结论]该处理能有效地终止恒河猴早期妊娠。联合用药比用于女人的妊娠治疗更有效,并减少了流血时间,或许可以代替目前的终止妊娠的医疗方法。     

Alkaline proteinase inhibitor of Pseudomonas aeruginosa: a mutational and molecular dynamics study of the role of N-terminal residues in the inhibition of Pseudomonas alkaline proteinase

Alkaline proteinase inhibitor of Pseudomonas aeruginosa is a 11.5-kDa, high affinity inhibitor of the serralysin class of zinc-dependent proteinases secreted by several Gram-negative bacteria. X-ray crystallography of the proteinase-inhibitor complex reveals that five N-terminal inhibitor residues occupy the extended substrate binding site of the enzyme and that the catalytic zinc is chelated by the alpha-amino and carbonyl groups of the N-terminal residue of the inhibitor. In this study, we assessed the effect of alteration of inhibitor residues 2-5 on its affinity for Pseudomonas alkaline proteinase (APR) as derived from the ratio of the dissociation and associate rate constants for formation of the enzyme-inhibitor complex. The largest effect was observed at position Ser-2, which occupies the S1' pocket of the enzyme and donates a hydrogen bond to the carboxyl group of the catalytic Glu-177 of the proteinase. Substitution of Asp, Arg, or Trp at this position increased the dissociation constant KD by 35-, 180-, and 13-fold, respectively. Mutation at positions 3-5 of the trunk also resulted in a reduction in enzyme-inhibitor affinity, with the exception of an I4W mutant, which exhibited a 3-fold increase in affinity. Molecular dynamics simulation of the complex formation between the catalytic domain of APR and the S2D mutant showed that the carboxyl of Asp-2 interacts with the catalytic zinc, thereby partially neutralizing the negative charge that otherwise would clash with the carboxyl group of Glu-177 of APR. Simulation of the interaction between the alkaline proteinase and the I4W mutant revealed a major shift in the loop comprised of residues 189-200 of the enzyme that allowed formation of a stacking interaction between the aromatic rings of Ile-4 of the inhibitor and Tyr-158 of the proteinase. This new interaction could account for the observed increase in enzyme-inhibitor affinity.     

The age of major monocot groups inferred from 800+ rbcL sequences

Phylogenetic research on monocots has been extraordinarily active over the past years. With the familial interrelationships being sufficiently understood, the question of divergence times and crown node ages of major lineages comes into focus. In this study we present the first attempt to estimate crown and stem node ages for most orders and families of monocots, based on rbcL sequence data and comprehensive taxon sampling. From our analysis it is obvious that considerable monocot diversification took place during the Early Cretaceous, with most families already present at the Cretaceous–Tertiary boundary. Araceae, Arecaceae and Orchidaceae are among the oldest families with crown node ages reaching back into the Early Cretaceous. We comment on possible error sources and the necessity for methodological improvement in molecular dating.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 385–398.     

The estimation of crop evacuation rates in Chaoborus larvae (Diptera: Chaoboridae) using natural prey

SUMMARY. 1. Crop evacuation rates were estimated for the first time in Chaoborus larvae, using natural prey.
2. Fourth instar C. americanus Matheson digested copepods (Diaptomus leptopus S.A. Forbes) 48.7% faster than daphnids (Daphnia rosea Leydig) of similar size; meal size did not significantly affect the instantaneous rate of digestion (IRD) within each prey type. Prey specific IRD has not been reported before for zooplankton.
3. Prey specific differences in IRD require the use of natural prey when digestion experiments are to be used to estimate natural rates of food consumption of animals.     

THE EFFECT OF ADDED NITROGEN ON THE RATE OF DECOMPOSITION OF ORGANIC MATTER

(1) N added to decomposing organic matter often has no effect or a negative effect on microbial activity, at least in the long term. More than 60 papers are cited in support of this statement.
(2) The negative effect of N is mainly found with recalcitrant organic matter with a high C/N ratio (straw, wood, etc.), whereas a positive effect of N is common for easily degradable organic material with low C/N ratio.
(3) The negative effect of N could be explained by: (i) N disturbs the outcome of competition between potent and less potent decomposers; (ii) through 'ammonia metabolite repression', N blocks production of certain enzymes, at least in basidiomycetes, and enhances breakdown of the most available cellulose, whereby recalcitrant lignocellulose accumulates; (iii) amino compounds condense with polyphenols and other decomposition products, forming 'browning precursors' which are toxic or inhibitory.
(4) The effect of adding N may depend on the microflora present.
(5) There are indications that some microorganisms have a 'luxury uptake' of N when it is present in sufficient amounts, thereby delaying N mineralization.
(6) The addition of N seems to increase the formation of water-soluble , brown, recalcitrant compounds, but to decrease the amount of humus formed.     

Electrophysiological and biochemical responses of mouse vomeronasal receptor cells to urine-derived compounds: possible mechanism of action

Receptor cells of the vomeronasal organ (VNO) are thought to detect pheromone-like molecules important for reproductive physiology. Several compounds derived from male mouse urine have been demonstrated to affect endocrine events in female mice. In the present study, the ability of these compounds to affect VNO activity was tested. In dissociated VNO cells held under voltage clamp conditions, application of dehydro-exo-brevicomin (DHB) evoked an outward current at negative holding potentials and an inward current at positive holding potentials. Under current clamp, DHB reduced action potential firing. Since DHB application caused a decrease in membrane conductance, this compound appeared to act by reducing inward current through closing an ion channel. Biochemical experiments tested the effects of DHB and 2- (sec-butyl)-4,5-dihydrothiazole (SBT) on cAMP levels in the VNO. A mixture of DHB and SBT decreased cAMP levels in VNO sensory tissue and had no effect on VNO non-sensory tissue. The results suggest that pheromones have an inhibitory influence on action potential generation and on cAMP levels in receptor cells of the VNO.      

CELL DEATH,SURVIVAL AND PROLIFERATION IN TETRAHYMENA THERMOPHILA. EFFECTS OF INSULIN,SODIUM NITROPRUSSIDE, 8-BROMO CYCLIC GMP,NG-METHYL-L-ARGININE AND METHYLENE BLUE

Cells of the ciliate Tetrahymena thermophila produce compounds that act as autocrine (paracrine) survival and/or growth factors. 8-Bromo cyclic GMP, sodium nitroprusside, hemin, protoporphyrin IX, human recombinant and bovine insulin were tested for their ability to substitute for the cell-produced factors and stimulate cell survival and proliferation. The cells were inoculated into conical flasks in a nutritionally complete, chemically defined medium at known cell densities from 5 to 5000cells/ml. In unsupplemented medium cells at 5 to 500cells/ml (‘low initial cell density cultures’) died within 8h, whereas cells at 1000 and 5000cells/ml (‘high initial cell density cultures’) proliferated with lag phases lasting for up to 4h. In the presence of insulin compounds, hemin, protoporphyrin IX, or 8-bromo cyclic GMP, cells also proliferated at all low initial cell densities. Sodium nitroprusside was effective over two separate concentration ranges: at the nanomolar levels as well at low pico- to femtomolar levels. At initial population densities of up to 50cells/ml the cells at both concentrations of sodium nitroprusside survived about 4-fold longer than the controls. At 500 initial cells/ml, cells at thehigh concentrations of sodium nitroprusside survived about 4-fold longer than those of the control cultures; they proliferated in the low concentrations of sodium nitroprusside. Concentrations of hemin, too low to have any effects on their own, had synergistic effects with sodium nitroprusside. N^G-methyl-L-arginine inhibited proliferation at high initial cell densities. This inhibitory action was reduced by high concentrations of L-arginine, protoporphyrin IX, sodium nitroprusside, or 8-bromo cGMP, but not by insulin. Methylene blue inhibited cell proliferation at high initial cell densities. This inhibition was circumvented by addition of 8-bromo cGMP. The findings that insulin-related material may be released from Tetrahymena and that insulin and sodium nitroprusside increase intracellular cGMP in these cells are discussed in relation to the presented results. Together these observations suggest that cGMP is responsible for supporting cell survival in Tetrahymena and switching the cells into their proliferative mode, and that cell-produced signal molecules and insulin stimulate an NO-dependent guanylate cyclase into producing cGMP.