Differential requirement of protein tyrosine kinase and protein kinase C in the generation of IL-2-induced LAK cell and αCD3-induced CD3-AK cell responses

This study examined the role of protein tyrosine kinase (PTK) and protein kinase C (PKC) in the signal transduction pathways for lymphocyte activation through IL-2R to generate LAK cells and through TCR—CD3 to generate CD3-AK cells. Two PTK inhibitors [herbimycin A and genistein (PTK-I)] and two PKC inhibitors [calphositin C and staurosporine (PKC-I)] were used in the experiments. It was found that the primary activation pathway through IL-2R was PTK-dependent; that is, generation of both the IL-2-induced proliferative and the cytotoxic responses was completely abrogated by PTK-I and not by PKC-I. Quite different results were obtained with the αCD3-induced CD3-AK cell response. First, the αCD3-induced proliferation was only partially inhibited by PTK-I or PKC-I alone. Second, generation of CD3-AK cytotoxic response was primarily PKC-dependent; that is, only PKC-I induced significant inhibition. Genistein was found to reduce protein tyrosine phosphorylation in both LAK cells and CD3-AK cells, indicating that CD3-AK cells were also susceptible to PTK-I treatment. Further studies showed that PTK-I and not PKC-I suppressed perforin mRNA expression and N-2-benzyoxycarbonyl-l-lysine thiobeneylester esterase production in LAK cells, and the opposite was true for CD3-AK cells. These results indicate that different pathways were employed in lymphocyte activation through IL-2R and TCR—CD3. The former pathway is primarily PTK-dependent. Activation through TCR—CD3 is a more complex event. Induction of a proliferative response can employ either a PTK- or a PKC-dependent pathway, whereas induction of a cytotoxic response is primarily PKC-dependent. Furthermore, it appears that a PTK-independent pathway exists for the induction of a CD3-AK response and thus suggests that activation of the second messenger PKC may not necessarily be preceded by PTK activation.     

Synthesis and antiplatelet, antiinflammatory, and antiallergic activities of 2-substituted 3-chloro-1,4-naphthoquinone derivatives

A series of 2-substituted 3-chloro-1,4-naphthoquinones was synthesized, and the antiplatelet, antiinflammatory, and antiallergic activities of these compounds were evaluated. The structure-activity relationships in this series were also examined. Most of the 2-alkyl/arylcarboxamido derivatives of 3-chloro-1,4-naphthoquinone showed potent activities with similar trends in each of the activities evaluated.     

cAMP-stimulated termination of vitellogenesis in Hyalophora cecropia: formation of a diffusion barrier and the loss of patency

Activation of cAMP-dependent protein kinase (PKA) by cell-permeable analogs of cAMP causes early and mid-vitellogenic follicles of Hyalophora cecropia to terminate vitellogenin uptake [[Wang and Telfer, 1996], Insect Biochem. Mol. Biol. 26, 85-94 (1996)]. The response is shown here to entail the formation of an epithelial diffusion barrier. Follicle cells that have been loosely organized to provide intercellular pathways for the movement of vitellogenin to the oocyte surface transform into a tight epithelium within 1-2h of exposure to PKA activators. The follicle cells can now prevent the escape of Lucifer yellow CH that has been iontophoresed into the space surrounding the oocyte, and the entry of labeled vitellogenin from the medium. As they form this functional equivalent of a tight junction, the follicle cells further reduce the intercellular spaces by enlarging and pressing against each other, and by slowing the secretion of the sulfated glycosaminoglycan matrix that separates them during vitellogenesis. The activation of PKA in early and mid-vitellogenic follicles thus appears to trigger prematurely a set of changes that do not normally occur until the follicle has grown to a length of about 2.0mm.     

C to T and/or G to A transitions are responsible for loss of a MspI restriction site at the 5′-end of the human apolipoprotein AI gene

We detected the loss of a MspI restriction site by a C to T transition at +83 bp and a G to A transition at +84 bp of the 5-end non-coding region of the human apolipoprotein AI gene. This base change occurred at the hot spot (CCGG) for methylation, which may be important in the regulation of gene expression. The population frequency for the loss of the MspI site is 6.1%.     

鄂西南山地植被的基本特征

本文系湖北省区划办委托进行的湖北植被类型图、植被区划图过程中的一个阶段性小结。鄂西南山地位于中国亚热带东部(湿润)常绿阔叶林亚区域,为湖北植被区划中鄂西南山地植被区,所属范围包括整个鄂西自治州、宜昌地区的大部及神农架南坡。约当北纬29°05′—31°22′,东经108°30′—111°47′的地理位置。     

Functional groups at the catalytic site of F1 adenosine triphosphatase

The protection of F1 ATPase by inorganic phosphate, ADP, ATP, and magnesium ion against inactivation by 1-fluoro-2,4-dinitrobenzene, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, and 1-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline, respectively, has been investigated. Dissociation equilibrium constants and rate constants for the labeling reactions have been deduced from a quantitative treatment of the kinetic data. Comparison of these dissociation constants with each other and with the corresponding literature values indicates that the essential Tyr, Arg, Lys, and Glu or Asp residues are indeed located at the catalytic site of the enzyme. Examination of the rate constants for the labeling reactions in the presence of excess inorganic phosphate, ADP, ATP, or magnesium ion, respectively, suggests that the essential phenol and amino groups are located nearer to the bound inorganic phosphate or the gamma-phosphate group than to the alpha- or beta-phosphate group of the bound ATP, that the essential guanidinium group is located nearer to the alpha- or beta-phosphate group than to the gamma-phosphate group of the bound ATP or the bound inorganic phosphate, and that the essential carboxylate group is located slightly farther away but complexed with magnesium ion which it shares with the bound inorganic phosphate. A mechanism consistent with these topographical relationships is proposed for the catalytic hydrolysis and synthesis of ATP.