A chimeric tyrosine/tryptophan hydroxylase

The neurotransmitter biosynthetic enzymes, tyrosine hydroxylase (TH), and tryptophan hydroxylase (TPH) are each composed of an amino-terminal regulatory domain and a carboxylterminal catalytic domain. A chimeric hydroxylase was generated by coupling the regulatory domain of TH (TH-R) to the catalytic domain of TPH (TPH-C) and expressing the recombinant enzyme in bacteria. The chimeric junction was created at proline 165 in TH and proline 106 in TPH because this residue is within a conserved five amino-acid span (ValProTrpPhePro) that defines the beginning of the highly homologous catalytic domains of TH and TPH. Radioenzymatic activity assays demonstrated that the TH-R/TPH-C chimera hydroxylates tryptophan, but not tyrosine. Therefore, the regulatory domain does not confer substrate specificity. Although the TH-R/TPH-C enzyme did serve as a substrate for protein kinase (PKA), activation was not observed following phosphorylation. Phosphorylation studies in combination with kinetic data provided evidence that TH-R does not exert a dominant influence on TPH-C. Stability assays revealed that, whereas TH exhibited a t_1/2 of 84 min at 37°C, TPH was much less stable (t _1/2=28.3 min). The stability profile of TH-R/TPH-C, however, was superimposable on that of TH. Removal of the regulatory domain (a deletion of 165 amino acids from the N-terminus) of TH rendered the catalytic domain highly unstable, as demonstrated by at _1/2 of 14 min. The authors conclude that the regulatory domain of TH functions as a stabilizer of enzyme activity. As a corollary, the well-characterized instability of TPH may be attributed to the inability of its regulatory domain to stabilize the catalytic domain.     

A study of the relationship between ambient lead and blood lead among lead battery workers

 Objective: To examine the relationship between ambient lead levels and blood lead levels and to explore the modifiers of the relationship between ambient lead and blood lead. Method: A cross-sectional study was conducted in two lead battery factories. Blood lead level and ambient lead concentration were measured for each participant concurrently. A structured questionnaire was administered to collect sociodemographic characteristics and occupational history. Design: Biological and personal environmental measurements of 219 lead-exposed workers were analyzed by both simple and multiple linear regression. A regression model was selected for interpretation. Results: A high correlation (r=0.62) between ambient lead (PbA) and blood lead (PbB) was observed. In addition, numerous factors, including age, sex, alcohol consumption, personal hygiene practice and type of lead exposure, were also found to influence blood lead levels. Although PbB was highly correlated with PbA, blood lead level may not be effectively lowered by reducing ambient lead level. Based on the regression coefficients, improvement of hygienic practice was more effective at lowering PbB than reducing ambient lead level. Good hygienic practice may be the preferential way to reduce lead exposure in current conditions. Conclusion: Education of correct work practice may be more important than engineering control in the developing countries to lower blood lead levels in lead battery factories. Received: 28 May 1996/Accepted: 30 August 1996     

电脑控制连续式料位仪的研制

论述了电脑控制连续式料位仪的原理及性能，研制了一种先进可靠的物料料位测量工具。     

Evidence for nitric oxide participation in down-regulation of CYP2B1/2 gene expression at the pretranslational level

Septic or inflammatory stimuli suppress drug metabolism by cytochrome P-450 in the liver, presumably at the pretranslational level. We have shown previously that nitric oxide is responsible at least in part for the inhibition by bacterial lipopolysaccharide of phenobarbital-induced CYP2B1/2 activity in vivo. This was attributed to the interaction of nitric oxide with heme in the active-center of cytochrome P450, leading to enzyme inactivation. Here, we report of nitric oxide with heme in the active-center of cytochrome P450, leading to enzyme inactivation. Here, we report that endogeneous nitric oxide also contributes to LPS-induced suppression of CYP2B1/2 in vivo by down-regulating the expression of CYP2B1/2 protein and mRNA.     

大鼠肝细胞Ⅰ，Ⅲ型前胶原基因表达及PDGF的影响

目的观察大鼠肝细胞Ⅰ，Ⅲ型前胶原基因的表达及ＰＤＧＦ对其表达的影响．方法应用原位杂交技术检测分离培养的ＳＤ大鼠肝细胞（ｎ＝３０）内Ⅰ，Ⅲ型前胶原基因的表达．同时观察１０μｇ／Ｌ（ｎ＝３０）和３０μｇ／Ｌ（ｎ＝３０）ＰＤＧＦ促进前胶原基因表达的作用．测定基因表达颗粒总面积占细胞总面积的百分比，并作比较分析．结果无论正常肝细胞或是在两种浓度的ＰＤＧＦ存在时，肝细胞内均可见到Ⅰ，Ⅲ型前胶原基因的表达．正常肝细胞Ⅰ，Ⅲ型前胶原基因表达面积的百分比（％）为７７±１９和７５±２１；加１０μｇ／ＬＰＤＧＦ后为１１５±１９和１１２±１０，而加３０μｇ／Ｌ后为１５２±３４及１８１±２８，且在后者中表达明显增强（Ｐ＜００５及Ｐ＜００１）．结论ＰＤＧＦ在转录水平上促进肝细胞胶原的合成．     

Cellular distribution of the new growth factor Pleiotrophin (HB-GAM) mRNA in developing and adult rat tissues

Summary Pleiotrophin (PTN), also known as HBGAM, belongs to an emerging cytokine family unrelated to other growth factors. We report here the first comprehensive study using in situ hybridization on the cellular distribution of this new heparin-binding growth factor mRNA in rat tissues. PTN mRNA was developmentally expressed in many — but not all — neuroectodermal and mesodermal lineages, whilst no PTN mRNA was detected in endoderm, ectoderm and trophoblast. PTN mRNA was found in the nervous system throughout development, with a post-natal peak of expression. In the adult nervous system, significant expression persisted in hippocampal CA1 pyramidal neurons and in cortical neurons, but also in different non-neuronal cells types in various locations (olfactory nerve, cerebellar astrocytes, pituicytes, Schwann cells surrounding the neurons in sensory ganglia). PTN mRNA was also found during development in the mesenchyme of lung, gut, kidney and reproductive tract, in bone and cartilage progenitors, in dental pulp, in myoblasts, and in several other sites. Expression was differently regulated in each location, but usually faded around birth. In the adult, PTN mRNA was still present in the meninges, the iris, the Leydig cells of the testis and in the uterus. PTN mRNA was also strongly expressed in the basal layers of the tongue epithelium, which is the only epithelium and ectodermal derivative to express PTN mRNA, and this only after birth. PTN is known to be a growth factor for perinatal brain neurons and a mitogen for fibroblasts in vitro. Recently, trophic effects on epithelial cells and a role as a tumour growth factor have been reported. The mechanisms of regulation and the functions of PTN are however still uncertain. Its expression pattern during development suggests important roles in growth and differentiation. Moreover, the presence of PTN mRNA in several adult tissues and the up-regulation of PTN mRNA expression in the gravid uterus indicate that PTN also has physiological functions during adulthood.     

不同年龄,职业及文化程度人群心身健康特点的研究

探讨我国不同年龄、职业及文化程度的心身健康特点。方法根据我国人口学资料分层抽样，采用标准化的中国心身健康量表进行人群心身健康测查。结果（１）以５５～６４，２５～３４及４５～５４岁年龄组，离退休人员、干部及技术人员的心身健康量表分均较高，工人及军人次之，而农民心身健康各量表分最低；（２）初、高中者心身健康各量表分较高，大学次之，小学最低。结论我国不同年龄、职业及文化程度的心身健康状况不同。     

Interactions between peripheral blood CD8 T lymphocytes and intestinal epithelial cells (iEC)

Intestinal intraepithelial lymphocytes (iIEL) are primarily CD8 cells and most of them have a CD28^? phenotype, the phenotype of effector cytotoxic T cells. We asked whether the predominance of CD8⁺ CD28^? T cells in the gut may result from peripheral blood T cells preferentially migrating to the iIEL compartment and adhering to iEC. Compared with CD4 cells, adhesion of resting CD8⁺ T cells to iEC cell lines was significantly higher. Adhesion could be blocked with a MoAb to gp180, a molecule expressed on iEC which is known to interact with CD8/lck. No significant difference in the level of adhesion was observed between CD8⁺ CD28⁺ and CD8⁺ CD28^? T cells. Thus CD8 cells may preferentially migrate to the iIEL compartment, but loss of CD28 expression could occur in situ after migration. Consistent with this hypothesis, the CD8⁺ CD28^? cells became enriched after co-culturing T cells with iEC cell lines and primary iEC. Induction of the CD8⁺ CD28^? phenotype in cord blood and adult T cells was observed in co-cultures with iEC and also with mitogens and superantigens. In the latter case, CD28 down-modulation was seen specifically in the Vβ subset targeted by the superantigen, indicating that loss of CD28 expression is a direct result of T cell receptor (TCR)-mediated stimulation. The combined results suggest that CD8⁺ CD28^? T cells are antigen experienced T cells, and that they may have a survival advantage in the presence of gut epithelial cells in vitro. This may contribute to the predominance of CD8⁺ CD28^? T cells in the iIEL compartment.     

梅毒螺旋体外膜蛋白Gpd的基因型分析及其重组蛋白的免疫原性鉴定

目的　构建梅毒螺旋体 (Treponemapallidum ,Tp)外膜蛋白Gpd基因的原核表达载体 ,检测其表达产物的免疫原性 ,并比较梅毒螺旋体各菌株Gpd基因序列的同源度。方法　从TpNichols株基因组模板中PCR扩增Gpd基因 ,与GenBank登录的序列做blast比较 ,定向克隆构建原核表达重组体pET2 8b( + ) -Gpd ,转入大肠杆菌ril表达菌 ,SDS -PAGE分析重组蛋白的表达 ,Western -blot检测重组蛋白的免疫原性。结果　载体上所连目的基因片段序列与GenBank登录的Nichols株Gpd基因序列完全一致 ,同其他病原性密螺旋体菌株登陆序列比较同源度为 98%～ 1 0 0 %。SDS -PAGE检测诱导产物显示有一Mr约为 41kDa的特异蛋白带 ,免疫印迹技术检测其能与梅毒阳性标准血清反应。结论　Tp原核表达重组体pET2 8b( + ) -Gpd成功构建 ,且能够在ril表达菌中融合表达 ,为进一步研究该蛋白的生物学功能奠定了一定的实验基础。