Neurotransmitter-Mediated Regulation of Brain Aromatase: Protein Kinase C- and G-Dependent Induction

Abstract: Aromatase in the diencephalic neurons, the level of which increases transiently during the prenatal to neonatal period, has been suggested to be involved in control of sexual behavior and differentiation of the CNS. Effects of neurotransmitters on levels of aromatase mRNA in cultured neurons were investigated to determine factors regulating the developmental increase that occurs in level of fetal brain aromatase. The expression of aromatase in diencephalic neurons of fetal mice at embryonic day 13, cultured in vitro, was significantly affected by α₁-adrenergic receptor ligands. Aromatase mRNA levels were higher in neurons treated with the α₁-agonist phenylephrine than in control neurons, whereas prazosin, an α₁-antagonist, suppressed this increase, and ligands for α₂- or β-adrenergic receptors did not exert any influence. The profile of α₁-adrenergic receptor subtypes during actual development in vivo suggested that the α_1B subtype is in fact responsible for the signal transduction. Substance P, cholecystokinin, neurotensin, and brain natriuretic peptide also increased the level of expression along with phorbol 12-myristate 13-acetate and dibutyryl-cyclic GMP, whereas forskolin and dibutyryl-cyclic AMP caused a decrease. These data indicate that stimulation via α₁ (possibly α_1B)-adrenergic receptors, as well as receptors of specific neuropeptides, controls the expression of aromatase in embryonic day 13 diencephalic neurons through activation of protein kinase C or G. β-Adrenergic receptors would not appear to participate in the regulation, judging from their developmental profile, although cyclic AMP might be a suppressive second messenger.     

Augmentation of Interferon Production after Cell-Differentiation of U937 Cells by TPA

Persistent infections with mumps virus were established in several human lymphoid cells of T-cell origin (Molt-4, TALL-1, and CCRF-CEM) and human monocyte cells (U937 and THP-1). 2′,5′-Oligoadenylate synthetase (2–5AS) activity was demonstrated to be only slightly induced by interferon (IFN) or TPA (12-O-tetradecanoyl-phorbol-13-acetate) treatment in these cells. Treatment of the persistently infected cells with IFN or TPA did not stimulate an increase in the amount of synthetase mRNA. Induction of cell differentiation and augmentation of IFN production by TPA were demonstrated in U937 cells persistently infected with mumps virus (U937-MP). Similar results for IFN production were obtained from differentiated U937 cells. It is suggested that cell differentiation of U937 cells might be associated with the development of IFN inducibility.     

The role of sulphur in detoxication of cadmium in young sugar beet plants

In young sugar beet plants cadmium suppressed the activity of nitrate reductase, glutamine synthetase and glutamate dehydrogenase, whereas sulphur exhibited a protective role towards activity of these enzymes, except of glutamine synthetase. Protein synthesis was suppressed in the absence of S in nutrient medium; the lowest level was at 10^-3 M Cd²⁺. Chloroplast pigment contents were increased by S while Cd²⁺, even in the lowest concentration, (10⁻⁵ M) showed a repressive effect. The highest concentrations of Cd²⁺ (10−3 M) caused a decrease in dry mass, whereas S induced its increase. Nitrate content was increased in the presence of Cd²⁺ and decreased by increased concentration of S. Acknowledgement: The authors acknowledge financial support of the Ministry for Science and Technology of Serbia. The paper was presented at 9th Congress of the Federation of European Societies of Plant Physiology, Brno, Czech Republic, 3–8 July 1994.     

大肠杆菌精氨酰－tRNA合成酶的Lys306为酶活力所必需

将大肠杆菌精氨酰ｔＲＮＡ合成酶（ＡｒｇＲＳ）上Ｌｙｓ３０６用基因点突变的方法分别变为Ａｌａ和Ａｒｇ的密码子;得到变种基因ａｒｇｓ３０６ＫＡ和ａｒｇｓ３０６ＫＲ。变种基因重组在ｐＵＣ１８上,转化到大肠杆菌ＴＧ１中,转化子中ＡｒｇＲＳ及其变种ＡｒｇＲＳ３０６ＫＡ和ＡｒｇＲＳ３０６ＫＲ所表达的蛋白量至少为ＴＧ１表达ＡｒｇＲＳ蛋白量的１００倍。细胞粗抽提液中ＡｒｇＲＳ的比活ＴＧ１、转化子ｐＵＣ１８－ａｒｇｓ、ｐＵＣ１８－ａｒｇｓ３０６ＫＡ和ｐＵＣ１８－ａｒｇｓ３０６ＫＲ分别为１．６５、２１０、１．８和３８单位／毫克。结果表明ＡｒｓＲＳ的Ｌｙｓ３０６为Ａｌａ取代使活力完全丧失;若被Ａｒｇ取代,则活力丧失８０％以上。Ｌｙｓ３０６为ＡｒｇＲＳ活力所必需。