Genetic imprinting suggested by maternal heterodisomy in nondeletion Prader-Willi syndrome

Prader-Willi syndrome (PWS) is the most common form of dysmorphic genetic obesity associated with mental retardation. About 60% of cases have a cytological deletion of chromosome 15q11q13 (refs 2, 3). These deletions occur de novo exclusively on the paternal chromosome. By contrast, Angelman syndrome (AS) is a very different clinical disorder and is also associated with deletions of region 15q11q13 (refs 6-8), indistinguishable from those in PWS except that they occur de novo on the maternal chromosome. The parental origin of the affected chromosomes 15 in these disorders could, therefore, be a contributory factor in determining their clinical phenotypes. We have now used cloned DNA markers specific for the 15q11q13 subregion to determine the parental origin of chromosome 15 in PWS individuals not having cytogenetic deletions; these individuals account for almost all of the remaining 40% of PWS cases. Probands in two families displayed maternal uniparental disomy for chromosome 15q11q13. This is the first demonstration that maternal heterodisomy--the presence of two different chromosome 15s derived from the mother--can be associated with a human genetic disease. The absence of a paternal contribution of genes in region 15q11q13, as found in PWS deletion cases, rather than a mutation in a specific gene(s) in this region may result in expression of the clinical phenotype. Thus, we conclude that a gene or genes in region 15q11q13 must be inherited from each parent for normal human development.     

Substitution at residue 227 of H-2 class I molecules abrogates recognition by CD8-dependent, but not CD8-independent, cytotoxic T lymphocytes

The CD8 (Lyt 2) molecule is a phenotypic marker for T lymphocytes that recognize and react with major histocompatibility complex (MHC) class I molecules. Antibody blocking experiments and gene transfection studies indicate that CD8 binds to a determinant on MHC class I molecules on the target cells, facilitating interaction between effector T lymphocytes and the target cell. The CD8 molecule may also be involved in transmembrane signalling during T-cell activation. The existence of CD8- cytotoxic T lymphocytes (CTL) and class I-reactive CTL that are not inhibited by antibody to CD8 suggests that at least some CTL do not require the CD8 molecule to interact with and lyse target cells. We have recently demonstrated that cells transfected with an H-2Dd gene that carries a mutation at residue 227 are not killed by primary CTL8. Here we show that although this mutation abrogates recognition by primary CTL, it does not affect recognition by CD8-independent CTL, suggesting that residue 227 of class I molecules might contribute to a determinant that is the ligand of the CD8 molecule.     

电刺激肌力控制的新技术

利用宽范围内变化的运动单位动作电位发放率和募集控制模式来调节骨骼肌的收缩力,克服了神经肌肉电刺激技术中一个长期存在的障碍。对于猫的腓肠肌,控制模式中运动单位的募集可以控制初始肌力的50%直至100%。对应于线性增加的募集,肌力响应也是线性的,而对应于发放率,肌力出现非线性饱和段。     

Regulation of the retinal interphotoreceptor matrix Na by the retinal pigment epithelium during the light response

We examined the rabbit retinal pigment epithelium (RPE) for Na transport properties which would allow it to buffer undesirable changes in Na concentrations in the interphotoreceptor matrix (IPM) during light and dark cycles. The RPE is selectivity permeable to sodium. Open and short circuit transport studies with RPE indicate a circulating (choroid to retina and back) Na current which does not compromise the electrical integrity of the blood brain barrier but together with the Na permeselectivity is of sufficient magnitude to buffer both upwards and downwards movements of IPM [Na] during light or dark responses.     

Dissociated cell suspensions ofCarcinus maenas Y-organs as a tool to study ecdysteroid production and its regulation

In vitro ecdysteroid production by dissociated Y-organ cells of the shore crabCarcinus maenas was characterized during short-term incubations. Under optimized conditions (M199 adjusted to crab osmolality and with the addition of 10% foetal calf serum), ecdysteroid production by dispersed cells increased linearly during 4-hour incubations, with little intra-assay variation. 25-deoxyecdysone was mainly produced. PurifiedCarcinus molt inhbiting hormone (CamMIH) produced a dose-dependent inhibition of ecdysteroid production by dispersed cells. The cells were about 50 times more sensitive than whole glands to MIH. Other structurally-related peptides were tested.     

Protective effect of Shigyaku-to,a traditional Chinese herbal medicine,on the infection of herpes simplex virus type 1 (HSV-1) in mice

The antiviral activity of Shigyaku-to (TJS-109), a traditional Chinese herbal medicine, was investigated in mice infected with herpes simplex virus type 1 (HSV-1). TJS-109 is a combination of the medicinal plant extracts fromZingiberis siccatum rhizoma,Aconiti tuber andGlycyrrhizae radix in a specific proportion. Mice infected with a 10 LD₅₀ dose of HSV-1 were treated with TJS-109 orally at doses of 1.25 to 20 mg/kg 2 days before, and 1 and 4 days after the infection. The treated groups had 80% (1.25 mg/kg), 40% (5 mg/kg) and 23% (20 mg/kg) mortality rates 25 days after the infection as compared with a 100% mortality rate in control mice treated with saline. When HSV-1 infected mice (recipients) received CD8⁺T cell fractions derived from spleens of mice treated with TJS-109 (donors), 70% of recipients survived, as compared with 0% survivors in the groups of mice treated with saline, B cell fractions, CD4⁺ T cell fractions or macrophage-enriched fractions prepared from the same donors. TJS-109 did not show any virucidal activities against HSV-1 or any virostatic activities on the growth of HSV-1 in Vero cells. These results suggest that TJS-109 protected mice exposed to lethal amounts of HSV-1 through the activation of CD8⁺ T cells.     

Inhibition of glucose transport in human erythrocytes by 2,3-dioxoindole (Isatin)

10 mM isatin (2,3-dioxoindole) inhibited glucose influx into human erythrocytes by over 30%. The inhibition is of the competitive type, where the affinity constant (K_t) was increased from 5.71 (control) to 11.11 mM in the presence of isatin with no change in V_max (130 nmol/min/ml packed cells). The observed inhibition of sugar transport by isatin was not mediated through membrane–SH groups accessible to iodoacetate, iodoacetamide, DTNB, DNP or sodium arsenite. Isatin inhibited sugar transport in the presence of 2 mM harmaline, an alkaloid inhibitor of Na⁺, K⁺–ATP_ase activity. The inhibition was non additive which suggests that these two compounds interact with the same or a similar site on the erythrocyte membrane.     

模型校正在电子设备结构中的应用

为预测构件动态行为，用动力学有限元校正法建立某一航天用印刷电路板的动力学模型，用物理参数局部校正法导出物理意义明确的校正模型，用分步实验校正法提高模型的可靠度。结果表明，校正模型具有更大的适应性和可靠性。     

五峰垃圾填埋场渗滤液污染特征及处理系统

系统分析了五峰垃圾填埋场渗滤液中ＣＯＤ，ＢＯＤ＿５的季节变化特征，并对该填埋场的污水处理系统进行了研究和评价。