Down-regulation of epidermal growth factor receptors by nerve growth factor in PC12 cells is p140(trk)-, Ras-, and Src-dependent.

Nerve growth factor (NGF) treatment causes a profound down-regulation of epidermal growth factor receptors during the differentiation of PC12 cells. This process is characterized by a progressive decrease in epidermal growth factor (EGF) receptor level measured by 125I-EGF binding, tyrosine phosphorylation, and Western blotting. Treatment of the cells with NGF for 5 days produces a 95% reduction in the amount of [35S]methionine-labeled EGF receptors. This down-regulation does not occur in PC12nnr5 cells, which lack the p140(trk) NGF receptor. However, in PC12nnr5 cells stably transfected with p140(trk), the NGF-induced heterologous down-regulation of EGF receptors is reconstituted in part. NGF-induced heterologous down-regulation, but not EGF-induced homologous down-regulation of EGF receptors, is blocked in Ras- and Src-dominant-negative PC12 cells. Treatment with either pituitary adenylate cyclase-activating peptide (PACAP) or staurosporine stimulates neurite outgrowth in PC12 cell variants, but neither induces down-regulation of EGF receptors. NGF treatment of PC12 cells in suspension induces down-regulation of EGF receptors in the absence of neurite outgrowth. These results strongly suggest a p140(trk)-, Ras- and Src-dependent mechanism of NGF-induced down-regulation of EGF receptors and separate this process from NGF-induced neurite outgrowth in PC12 cells.

Staurosporine induces neurite outgrowth in neuronal hybrids (PC12EN) lacking NGF receptors.

A novel neuronal model (PC12EN cells), obtained by somatic hybridization of rat adrenal medullary pheochromocytoma (PC12) and bovine adrenal medullary endothelial (BAME) cells, was developed. PC12EN cells maintained numerous neuronal characteristics: they expressed neuronal glycolipid conjugates, synthesized and secreted catecholamines, and responded to differentiative agents with neurite outgrowth. PC12EN lacked receptors for EGF and both the p75 and trk NGF receptors, while FGF receptor expression was maintained. Staurosporine (5-50 nM), but not other members of the K252a family of protein kinase inhibitors, rapidly induced neurite outgrowth in PC12EN, as also found in the parental PC12 cells, but not in BAME cells. Similarly, both acidic and basic FGF (1-100 ng/ml) were neurotropic in PC12EN. In contrast to the mechanism by which FGF promoted neurite outgrowth in PC12EN, the neurotropic effect of staurosporine did not involve activation of established signalling pathways, such as tyrosine phosphorylation of erk (ras pathway) or SNT (a specific target of neuronal differentiation). In addition, staurosporine induced the tyrosine phosphorylation of the focal adhesion kinase p125FAK. However, since the latter effect was also observed with other protein kinase inhibitors of the K252a family, which induced PC12EN cells flattening but no neurite extension, we propose that FAK tyrosine phosphorylation may be related to ubiquitous changes in cell shape. We anticipate that PC12EN neuronal hybrids will become useful models in neuroscience research for evaluating unique cellular signalling mechanisms of novel neurotropic compounds.

The differences among Jewish communities--maternal and paternal contributions.

The haplotypes of Y chromosome (paternally inherited) and mtDNA (maternally inherited) were analyzed in representatives of six Jewish communities (Ashkenazic, North African, Near Eastern, Yemenite, Minor Asian/Balkanian, and Ethiopian). For both elements, the Ethiopian community has a mixture of typically African and typically Caucasian haplotypes and is significantly different from all others. The other communities, whose haplotypes are mostly Caucasian, are more closely related; significant differences that were found among some of them possibly indicate the effects of admixture with neighboring communities of non-Jews. The different contribution of the Y chromosome and mtDNA haplotypes to the significant differences among the communities can be explained by unequal involvement of males and females in the different admixtures. In all communities, except the Ethiopians, the level of diversity (h) for Y chromosome haplotypes is higher than that for mtDNA haplotypes, suggesting that in each community the people who become parents include more males than females. An opposite proportion (more females than males) is found among the Ethiopians.

Complete foetal ECG morphology recording by synchronised adaptive filtration.

Present noninvasively measured indices of foetal stress are indirect and not sufficient. Foetal electrocardiography (FECG) is a potential noninvasive measurement of the foetus wellbeing which has been little utilised because of the difficulties of measuring it. The development of time-sequenced adaptive filters which are synchronised to the QRS complex by the use of Doppler echocardiography allowed the recording of relatively noise-free FECG. The paper describes the use of this technique for obtaining the complete complex of the FECG. Several sets of time-sequenced adaptive filters are combined to allow a multilead abdominal recording to produce a measurement system which rejects maternal ECG and enhances the FECG. Five subjects have been analysed, and their FECGs have been accurately reproduced with minimal changes of the filters' parameters.

Regulation of the Ig kappa-chain enhancer by the adenovirus E1A gene products. Repression in lymphoid cells, activation in fibroblasts.

Proteins encoded by early region 1A (E1A) regulate transcription of viral and cellular genes. The mechanism of this trans-activation is not understood, but is of considerable interest as an example of transcription regulation through a cellular intermediate. We have therefore studied the effect of E1A products on the activity of the kappa L chain gene promoter and enhancer. By using transient and stable transfections into lymphoid and nonlymphoid cells, we found that the E1A proteins have a pleiotropic effect on the regulation of the mouse kappa-chain gene enhancer. In lymphoid cells the E1A products repress kappa-chain enhancer, whereas in fibroblasts, the kappa-chain enhancer is activated by the E1A products whether the E1A gene is in an extrachromosomal location or stably integrated in the genome. Furthermore, a functional kappa-chain promoter, containing the octanucleotide and "TATA" sequences is needed in order to be transcribed in E1A-producing cells. This ability of E1A products to negatively and positively regulate kappa-chain transcription may reflect a more general phenomenon in which a given cellular protein could participate in a variety of different cellular controls.