Plastid differentiation on 6-azauracil media

Résumé Les mutants au locusm de l'Arabidopsis ne réussissent pas à former de chloroplastes normaux dans certaines conditions et montrent des activités plus hautes en synthèse de pyrimidines que le témoin. La nutrition aseptique par 6-azauracile, inhibiteur spécifique de cette voie métabolique, restaure la différenciatin de structure lamellaire dans la plupart de ces organites, mais aux concentrations élevées, apparaissent des chloroplastes morphologiquement déviants, quoique de fonction efficace.     

Effect of erythropoietin on red cell differentiation binding of erythropoietin to DNA

Zusammenfassung Die Fähigkeit der DNS verschiedener Rattengewebe, Erythropoietin zu binden, wurde durch Differentialzentrifugation im Sucrosegradient untersucht. Es ergab sich, dass DNS von Knochenmark, Leber, Milz und Thymus Erythropoietin binden, DNS von Hirn und Nieren Erythropoitein hingegen nicht zu binden vermögen.     

A comparative study on the effects of brain extracts and mesodermal membrane extracts on nerve cell differentiation.

Extracts prepared from the mesodermal tissue surrounding the brain stimulate the differentiation of morphologically undifferentiated neuroblasts, while the differentiation of more mature neuroblasts is influenced by brain extracts.     

Effect of brocresine on conditioned avoidance behavior in mice

Summary Brocresine, an inhibitor of brain histamine biosynthesis, has been found to impair the ability of mice to avoid shock in a shuttle box CAR test; escape performance was unaffected in these studies.Supported in part by USPHS Grants Nos. MH-22570 and NS-10203. Brocresine dihydrogen phosphate was kindly provided by Lederle Laboratories.     

Neurotrophic effects of conditioned media of astrocytes isolated from different brain regions on hippocampal and cortical neurons

The present study was designed to reveal whether astroglial cells from different brain regions produce diffusible factors that differentially support the survival of neurons and the establishment of neuronal morphology. For this purpose, astrocyte conditioned media (ACM) were prepared by conditioning chemically-defined medium with type I astrocyte culture dissociated from cerebral cortex, hippocampus and hypothalamus. Hippocampal and cortical neurons were cultured in ACM or in non-conditioned medium. ACM derived from three brain regions all supported the survival of hippocampal and cortical neurons better than non-conditioned control medium. Of these, hypothalamic ACM was the most effective in supporting the survival of cortical neurons. The ACM also potentiated the elongation of the longest neurite of hippocampal and cortical neurons. However, there were no significant differences in the promoting effects on neurite elongation among ACM from three brain regions.     

Effect of cholinesterase inhibitors on differentiation of cultured sympathicoblasts

Summary The 2 cholinesterase inhibitors, eserine and BW 284 C 51, inhibited the nerve fibre growth and differentiation of immature sympathicoblasts at low concentrations. The effect was nerve cell-specific and appeared in the course of the in vitro development, indicating that cholinesterases might play an important role in the early differentiation of sympathicoblasts.     

Effect of cholinesterase inhibitors on differentiation of cultured sympathicoblasts

The 2 cholinesterase inhibitors, eserine and BW 284C 51, inhibited the nerve fibre growth and differentiation of immature sympatheticoblasts at low concentrations. The effect was nerve cell-specific and appeared in the course of the in vitro development, indicating that cholinesterases might play an important role in the early differentiation of sympathicoblasts.     

Ras proteins in the control of the cell cycle and cell differentiation

The Ras family of small GTPases includes three closely related proteins: H-, K-, and N-Ras. Ras proteins are involved in the transduction of signals elicited by activated surface receptors, acting as key components by relaying signals downstream through diverse pathways. Mutant, constitutively activated forms of Ras proteins are frequently found in cancer. While constitutive Ras activation induces oncogenic-like transformation in immortalized fibroblasts, it causes growth arrest in primary vertebrate cells. Induction of p53 and cyclin-dependent kinase inhibitors such as p15^INK4b, p16^INK4a, p19^ARF, and p21^WAF1 accounts for this response. Interestingly, while ras has usually been regarded as a transforming oncogene, the analysis of Ras function in most of the cellular systems studied so far indicates that the promotion of differentiation is the most prominent effect of Ras. While in some cell types, particularly muscle, Ras inhibits differentiation, in others such as neuronal, adipocytic, or myeloid cells, Ras induces differentiation, in some cases accompanied by growth arrest. Several possible mechanisms for the pleiotropic effects of Ras in animal cells are discussed. Received 8 March 2000; received after revision 24 May 2000; accepted 24 May 2000     

A comparative study of the differentiation of dissociated nerve cells under different culture conditions

Summary In vitro differentiation of chick embryo brain cells was compared under several culture conditions. Morphological observations and acetylcholinesterase histochemical staining revealed that the development was similar in all conditions tested if cells have been derived from 7 days embryos. Considering the cultures from 11 days embryos, the cell dissociation by trypsin and the plastic surface proved to be the most favourable conditions in contrast to mechanical dissection and collagen surface.M. Sensenbrenner is Maitre de Recherche au CNRS.     

Trichomes as models for studying plant cell differentiation

Trichomes, originating from epidermal cells, are present on nearly all terrestrial plants. They exist in diverse forms, are readily accessible, and serve as an excellent model system for analyzing the molecular mechanisms in plant cell differentiation, including cell fate choices, cell cycle control, and cell morphogenesis. In Arabidopsis, two regulatory models have been identified that function in parallel in trichome formation; the activator–inhibitor model and the activator–depletion model. Cotton fiber, a similar unicellular structure, is controlled by some functional homologues of Arabidopsis trichome-patterning genes. Multicellular trichomes, as in tobacco and tomato, may form through a distinct pathway from unicellular trichomes. Recent research has shown that cell cycle control participates in trichome formation. In this review, we summarize the molecular mechanisms involved in the formation of unicellular and multicellular trichomes, and discuss the integration of the cell cycle in its initiation and morphogenesis.     

Effect of nerve stimulation,denervation, and duct ligation,on kallikrein content and duct cell granules of the cat's submandibular gland

Summary Various procedures which reduce or deplete the kallikrein content of the cat's submandibular gland correspondingly reduce the number of apical granules in the striated duct cells. The kallikrein content is greatly reduced after chronic parasympathetic but not after sympathetic nerve section which suggests that the parasympathetic innervation is required for synthesis or storage of this enzyme.We wish to acknowledge the valuable assistance of Dr T. Nihei and Mr. J. Wimal in some of the enzyme measurements.This work was supported by grants from the Medical Research Council of Canada and the Alberta Heart Foundation.     

A comparative study of the differentiation of dissociated nerve cells under different culture conditions.

In vitro differentiation of chick embryo brain cells was compared under several culture conditions. Morphological observations and acetylcholinesterase histochemical staining revealed that the development was similar in all conditions tested if cells have been derived from 7 days embryos. Considering the cultures from 11 days embryos, the cell dissociation by trypsin and the plastic surface proved to be the most favourable conditions in contrast to mechanical dissection and collagen surface.