Inbreeding effects on fertility in humans: evidence for reproductive compensation.

The effects of inbreeding on prereproductive mortality have been demonstrated in many natural populations, including humans. However, little is known about the effects in inbred individuals who survive to adulthood. We have investigated the effects of inbreeding on fertility among inbred adult Hutterites and demonstrate significantly reduced fecundity among the most inbred Hutterite women, as evidenced by longer interbirth intervals (P=.024) and longer intervals to a recognized pregnancy (P=.010) but not by increased rates of fetal loss (P>.50). These data suggest the presence of recessive alleles that adversely affect fecundity among the population. In contrast, completed family sizes do not differ among the more and the less-inbred Hutterite women who were born after 1920, suggesting that reproductive compensation is occurring among the more-inbred and less-fecund women. This recent reproductive strategy would facilitate the maintenance of recessive alleles and contribute to an overall decline in fertility in the population.     

克拉玛依市2008年麻疹监测与控制情况分析

分析克拉玛依市麻疹流行状况及预防控制措施,为消除麻疹提供依据。采用描述流行病学分析方法,对2008年克拉玛依市麻疹资料进行分析。结果显示,克拉玛依市2008年麻疹发病率为38.83/10万(138/355381),呈高度散发,较2007年有所上升。发病高峰在3～5月,发病数占全年的83.33%。年龄分布大年龄组高于小年龄组,>20岁年龄组病例占50.00%,<1岁病例占18.84%;流动人口发病占51.11%。应切实提高麻疹常规免疫接种率和做好入托、入学儿童查验预防接种证工作,加强麻疹监测,提高实验室确诊病例的比例。     

A quantitative fluorimetric assay for the determination of oxidant production by polymorphonuclear leukocytes: its use in the simultaneous fluorimetric assay of cellular activation processes

A fluorimetric assay for the indirect determination of superoxide production during the respiratory burst of stimulated polymorphonuclear leukocytes was described. The method allowed the determination of submicromolar concentrations of superoxide, and was sufficiently sensitive that first-derivative kinetic analysis of the respiratory burst could be quickly analyzed. Conditions for the simultaneous fluorimetric analysis of superoxide production and intracellular calcium fluxes were described.     

Substrate specificities of recombinant murine Golgi alpha1, 2- mannosidases IA and IB and comparison with endoplasmic reticulum and Golgi processing alpha1,2-mannosidases

The catalytic domains of murine Golgi alpha1,2-mannosidases IA and IB that are involved in N-glycan processing were expressed as secreted proteins in P.pastoris . Recombinant mannosidases IA and IB both required divalent cations for activity, were inhibited by deoxymannojirimycin and kifunensine, and exhibited similar catalytic constants using Manalpha1,2Manalpha-O-CH3as substrate. Mannosidase IA was purified as a 50 kDa catalytically active soluble fragment and shown to be an inverting glycosidase. Recombinant mannosidases IA and IB were used to cleave Man9GlcNAc and the isomers produced were identified by high performance liquid chromatography and proton-nuclear magnetic resonance spectroscopy. Man9GlcNAc was rapidly cleaved by both enzymes to Man6GlcNAc, followed by a much slower conversion to Man5GlcNAc. The same isomers of Man7GlcNAc and Man6GlcNAc were produced by both enzymes but different isomers of Man8GlcNAc were formed. When Man8GlcNAc (Man8B isomer) was used as substrate, rapid conversion to Man5GlcNAc was observed, and the same oligosaccharide isomer intermediates were formed by both enzymes. These results combined with proton-nuclear magnetic resonance spectroscopy data demonstrate that it is the terminal alpha1, 2-mannose residue missing in the Man8B isomer that is cleaved from Man9GlcNAc at a much slower rate. When rat liver endoplasmic reticulum membrane extracts were incubated with Man9GlcNAc2, Man8GlcNAc2was the major product and Man8B was the major isomer. In contrast, rat liver Golgi membranes rapidly cleaved Man9GlcNAc2to Man6GlcNAc2and more slowly to Man5GlcNAc2. In this case all three isomers of Man8GlcNAc2were formed as intermediates, but a distinctive isomer, Man8A, was predominant. Antiserum to recombinant mannosidase IA immunoprecipitated an enzyme from Golgi extracts with the same specificity as recombinant mannosidase IA. These immunodepleted membranes were enriched in a Man9GlcNAc2to Man8GlcNAc2- cleaving activity forming predominantly the Man8B isomer. These results suggest that mannosidases IA and IB in Golgi membranes prefer the Man8B isomer generated by a complementary mannosidase that removes a single mannose from Man9GlcNAc2.      

Unique modulation of central 5-HT2 receptor binding sites and 5-HT2 receptor-mediated behavior by continuous gepirone treatment.

The effect of continuous treatment with the selective 5-HT1A agonist gepirone upon 5-HT2-mediated behavior and cortical 5-HT2 receptor binding sites was examined in naive rats or rats receiving noradrenergic (DSP4) or serotonergic (5,7-DHT) lesions. Continuous administration of gepirone in non-lesioned rats for 3, 7, or 14 days enhanced the head shake response to the 5-HT agonist quipazine. This enhancement of 5-HT2-mediated behavior occurred despite concomitant down-regulation of cortical 5-HT2 binding sites. However, 28 days of gepirone administration significantly reduced behavioral responsiveness to quipazine. The gepirone-induced facilitation of 5-HT2-mediated behavior observed after 7 days of continuous treatment was blocked in both DSP4 and 5,7-DHT-lesioned rats. However, both noradrenergic and serotonergic denervation failed to modify the down-regulation of 5-HT2 receptor binding sites produced by continuous gepirone administration. These results suggest that the curious dissociation of behavioral and biochemical indices of 5-HT2 receptor function produced by continuous gepirone treatment may be the result of a dual yet separate action of the drug on central presynaptic noradrenergic and serotonergic mechanisms and postsynaptic 5-HT receptors. Furthermore, the postsynaptic action of gepirone which reduces the maximal number of cortical 5-HT2 receptor binding sites may be the result of gepirone's agonist action at postsynaptic 5-HT1A receptors.     

S-Oxygenation of N-substituted thioureas catalyzed by the pig liver microsomal FAD-containing monooxygenase

The microsomal FAD-containing monooxygenase (EC 1.14.13.8, dimethylaniline monooxygenase) purified to homogeneity from hog liver catalyzes NADPH- and oxygen-dependent S-oxygenation of phenylthiourea, ethylenethiourea, thiocarbanilide, N-methylthiourea, and thiourea to their corresponding formamidine sulfinic acids. The sulfinic acids are formed by sequential enzymic oxidation of the thioureas through intermediate sulfenic acids. The reaction sequence was established by separating intermediate and final oxygenated metabolites of phenylthiourea and ethylenethiourea. The sulfenic and sulfinic acids of these two thioureas, produced enzymically, were chromatographically and spectrally identical with chemically synthesized reference compounds. Phenylformamidine and ethyleneformamidine sulfinic acids are slowly converted to their sulfonic acids upon prolonged incubation. While N-substituted formamidine sulfinic acids oxidize spontaneously to formamidine sulfonic acids at 37 °C, the further oxidation of ethyleneformamidine sulfinic acid may be, at least in part, enzyme catalyzed. The purified monooxygenase also catalyzes rapid oxygenation of mercaptoimidazoles to the corresponding imidazole sulfinic acids. The instability of S-oxygenated mercaptoimidazoles prevented their isolation and positive identification, but analysis of kinetic data obtained with sulfenic acid trapping agents suggests that these compounds are oxygenated by the same reaction sequence established for N-substituted thioureas. The NADPH- and oxygen-dependent oxidation of thiocarbamates and of 2-mercaptoimidazoles catalyzed by hog or hamster liver microsomes correlates with dimethylaniline N-oxidase activity and appears completely independent from cytochrome P-450. The S-oxidation of thiourea and its derivatives is not inhibited by n-octylamine, a known inhibitor of cytochrome P-450 dependent oxygenations. Furthermore, differential thermal inactivation of the flavin-containing monooxygenase totally abolishes phenylthiourea S-oxidase activity of hamster liver microsomes.     

Kinetics of pepsin-initiated coagulation of kappa-casein.

The kinetics of pepsin initiated coagulation of kappa-casein have been studied at pH 5.8. The primary and secondary phases of coagulation are shown to proceed simultaneously. The theory of enzymatically initiated clotting reactions proposed by Payens (Payens, T.A.J. (1976) Neth. Milk Dairy J. 30, 55--59) has been applied to this clotting system and has been used to obtain rate constants for the secondary phase of coagulation. As expected, clotting rate constants for kappa-casein increase with pepsin concentration. An activation energy of 30.6 kcal/mol has been obtained for the secondary phase of coagulation. Turbidity measurements are a convenient means for studying the secondary phase of coagulation but do not provide an unambiguous means for studying the primary phase of the reaction.     

Human embryonic stem cells: biology and clinical implications

Embryonic stem cells (ESCs) are derived from the inner cell mass of the preimplantation stage embryo and are capable of prolonged symmetrical self-renewal (both daughter cells remain escs) as well as differentiation into derivatives of all three embryonic germ layers. ESCs therefore have the potential to provide an unlimited supply of transplantable cells to replace or regenerate damaged or diseased tissues. However, several barriers must be overcome before successful clinical trials are possible: for example, pure populations of the desired cell type need to be selected and expanded in clinically relevant numbers, and a method for preventing immunological rejection of the transplanted cells without long-term immunosuppressive therapy is also required. In this review, we highlight recent developments in human ESC derivation and expansion, outline current understanding of the signalling pathways underlying stem cell renewal, and discuss challenging problems related to the selective differentiation and immune properties of human ESCs.