一氧化氮通过巯基亚硝化途径抑制海马神经元的延迟整流型钾电流

应用膜片钳全细胞记录模式研究了内源性一氧化氮(NO)对培养海马神经元延迟整流型钾电流的调控作用及其机制.给予NO合成酶的底物L-精氨酸(L-Arg,2mmol/L)可显著抑制海马神经元上的延迟整流型钾电流,但其同分异构体D-精氨酸(2mmol/L)对钾电流则无明显影响.并且,经一氧化氮合成酶抑制剂L-NAME(nomega-nitro-L-argininemethylester,0.5mmol/L)预处理后,L-Arg对钾电流的抑制作用消失,表明L-Arg抑制钾电流是通过产生NO而不是精氨酸本身.特异性鸟苷酸环化酶抑制剂ODQ(1H-[1,2,4]oxadiazolo[4,3-a]-quinoxalin-1-one,10!mol/L)预处理不影响L-Arg对钾电流的抑制作用,但巯基烷化剂NEM(N-ethylmaleimide,1mmol/L)预处理可完全阻断L-Arg的抑制效应.以上结果表明,内源性NO主要通过巯基亚硝化途径抑制海马神经元的延迟整流型钾电流.     

缓释型促性腺激素释放激素与生长激素治疗儿童中枢性性早熟的疗效观察

目的用生长激素与促性腺激素释放激素类似物(Gonadotropin-releasing hormone analogues,GHA)联合治疗中枢性性早熟女性患儿对其最终成人身高的影响.方法生长激素(GH)与促性腺激素释放激素类似物(GHA)联合治疗4例中枢性性早熟女性患儿半年,对比治疗前后患儿的第二性征,骨龄发育,性激素及最终成人身高的变化.结果第二性征的发育停止,骨龄发育被控制,实际生活年龄与骨年龄的比值提高(平均0.79→0.84);血LH对促性腺激素释放激素的反应及血浆雌激素水平平均已降至青春期前,分别为(平均25.79±10.60mlu/ml→1.13±0.21mlu/ml)及(平均64.87±27.51pg/ml→3.03±1.87pg/ml);预测最终成人身高增加(平均149.60±4.31cm→156.75±3.84cm)差异具有显著性(P＜0.05).结论生长激素与GHA联合治疗中枢性性早熟患儿,不仅能抑制第二性征发育,而且能有效改善最终成人身高,无任何毒付作用.     

USE OF UNIVERSAL PREENRICHMENT MEDIUM SUPPLEMENTED WITH OXYRASETM FOR THE SIMULTANEOUS RECOVERY OF ESCHERICHIA COLI O157:H7 AND YERSINIA ENTEROCOLITICA

Universal Preenrichment (UP) medium was used successfully for the simultaneous recovery of two strains each of Escherichia coli O157:H7 and Yersinia enterocolitica in the presence of Listeria monocytogenes and Salmonella typhimurium. E. coli O157:H7 and Y. enterocolitica populations reached ca. 10⁸ CFU/ml in UP medium in 18 h from an initial level ofca. 10² CFU/ml. Addition of Oxyrase_TM enhanced the growth of both E. coli O157:H7 strains and one strain of Y. enterocolitica. These three strains were able to recover from heat injury by 6 h when 24-h cultures were tested, but not when 18-h cultures were used. Injured and noninjured E. coli O157:H7 could be recovered from artificially inoculated food samples (shredded cheddar cheese, turkey ham, hot dogs, mayonnaise, and ground beef) in UP medium supplemented with Oxyrase^TM (UPO) by 18 h using immunoblotting. Y. enterocolitica could be recovered from turkey ham, hog dogs, and mayonnaise by direct plating on CIN agar from UPO medium. However, recovery of Y. enterocolitica from shredded cheddar cheese and ground beef required subsequent selective enrichment in sorbitol bile broth and isolation on Cefsulodin Irgasan Novobiocin agar (CIN). UPO medium can be used for simultaneous detection of E. coli O157:H7 and Y. enterocolitica from foods. However, subsequent selective enrichment and isolation on selective plating media are required for isolation of Y. enterocolitca from raw foods containing high population levels of background microflora.     

Detection of parent-of-origin effects for quantitative traits using general pedigree data

Genomic imprinting is a genetic phenomenon in which certain alleles are differentially expressed in a parent-of-origin-specific manner, and plays an important role in the study of complex traits. For a diallelic marker locus in human, the parental-asymmetry tests Q-PAT(c) with any constant c were developed to detect parent-of-origin effects for quantitative traits. However, these methods can only be applied to deal with nuclear families and thus are not suitable for extended pedigrees. In this study, by making no assumption about the distribution of the quantitative trait, we first propose the pedigree parental-asymmetry tests Q-PPAT(c) with any constant c for quantitative traits to test for parent-of-origin effects based on nuclear families with complete information from general pedigree data, in the presence of association between marker alleles under study and quantitative traits. When there are any genotypes missing in pedigrees, we utilize Monte Carlo (MC) sampling and estimation and develop the Q-MCPPAT(c) statistics to test for parent-of-origin effects. Various simulation studies are conducted to assess the performance of the proposed methods, for different sample sizes, genotype missing rates, degrees of imprinting effects and population models. Simulation results show that the proposed methods control the size well under the null hypothesis of no parent-of-origin effects and Q-PPAT(c) are robust to population stratification. In addition, the power comparison demonstrates that Q-PPAT(c) and Q-MCPPAT(c) for pedigree data are much more powerful than Q-PAT(c) only using two-generation nuclear families selected from extended pedigrees.