摘要:

AbstractWe have used diaphorase histochemistry to study the morphology of cells expressing nitric oxide synthase in the superficial layers of the superior colliculus of developing and adult rats. The nitric oxide synthase‐positive cells showed a Golgi‐like morphology and were classified according to the cell types identified by several authors using the Golgi method. The first nitric oxide synthase‐positive cells appeared at postnatal day 7 and the number of stained cells increased progressively reaching a maximum at postnatal day 15. The poor staining of the dendritic tree and cell bodies in animals younger than postnatal day 15 allowed no unambiguous identification of the different cell types before that age. At postnatal day 15, based on cell soma and dendritic morphology, we have found that the following cell types express nitric oxide synthase: marginal, horizontal, narrow and wide‐field vertical and stellate. In the adult, the same cell types were found to express nitric oxide synthase but the staining intensity and frequency of each cell type was different from the developing animal. Our results show that cells expressing nitric oxide synthase constitute a subpopulation of neurons in which all cell types are represented. Furthermore, our observations of nitric oxide synthase expression by collicular cells starting by the end of the first postnatal week and reaching a maximum by postnatal day 15 parallels the functional development of the retino‐colliculur and cortico‐tectal projections and suggest that nitric oxide synthase‐positive cells might be involved in this process.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00085-2

出版商:Wiley    

年代:1999

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)90003-9

出版商:Wiley    

年代:2004

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(96)80195-X

出版商:Wiley    

年代:2006

数据来源: WILEY

摘要:

AbstractWe had found that 5‐azacytidine (5Az), a cytidine analogue, could produce apoptosis of fetal developing neuronal cells on the day after injection of the agent into dams by the i.p. route at 11 days of gestation. To make a further understanding of the phenomenon by comparing the results between thein‐vivoandin‐vitrosystem, this study was carried out. Entire cephalic parts of the fetuses were collected aseptically at days 11 of gestation and a mixed culture, consisting of neuronal and mesenchymal cells, was established after one week of incubation. The silver‐staining revealed pyknotic nuclei and loss of dendrites of neuronal cells in the lower (5 μg/ml) dose of the 5 Az‐added group. SEM showed shrinkage of the cell body and blebbing formation on the cell surface. TEM evoked margination, segmentation and complete condensation of the nuclear chromatin. Scattered positive signals identical to the apoptotic cells and aggregated fragmented DNA were detected by the TUNEL method. Treatment of higher doses of 5Az (50 and 500 μg/ml), however, induced necrosis of both neuronal and mesenchymal cells, light‐ and electron‐microscopically. On the contrary, the control group (0 μg/ml) showed normal development of neuronal cells and very few positive signals of physiological apoptosis. It was concluded that 5Az could induce apoptosis of developing neuronal cells at lower doses, but necrosis of a wider cell population at higher doses. Involvement of hypomethylation, an important biochemical function of 5Az, in apoptosis was also speculated.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00084-4

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractSix per cent of rat pheochromocytoma (PC12) cells extended neurites (processes greater than one cell diameter in length) in the presence of 300 μM extracellular GTP or 300 μM guanosine for 48 hr, compared to only 2.5% of cells in control cultures. In the presence of 40 ng/ml of 2.5S NGF, about 20–35% of PC12 cells had neurites after 48 hr, and the addition of 300 μM guanosine or GTP together with NGF synergistically increased the proportion of cells with neurites to 40–65%. GTP and guanosine also increased the average number of branches per neurite, from 0.6 in NGF‐treated cultures to 1.2 (guanosine) or 1.5 (GTP). Neurites formed after exposure to NGF alone had axonal characteristics as determined by immunocytochemistry with antibody, SMI‐31, against axonal‐specific polyphosphorylated neurofilament epitopes. Neurites generated with the addition of both guanosine or GTP had the same characteristics.GTP probably did not exert its effects via the P2Xor P2Ypurinoceptors because the adenine nucleotides ATP, ATPγS, ADPβS, and ADP, which are all agonists of these receptors, inhibited rather than enhanced, NGF‐induced neurite outgrowth. UTP also enhanced the proportion of cells with neurites, although not to the same degree as did GTP. This may indicate activity through a P2U‐like nucleotide receptor. However, the response profile obtained, GTP>UTP ≫ ATP, does not fit the profile of any known P2Y, P2Xor P2Ureceptor. The poorly hydrolyzable GTP analogues, GTPγS and GDPβs were also unable to enhance the proportion of cells with neurites. This implied that GTP may produce its effects through a GTP‐specific ectoenzyme or kinase. This idea was supported by results showing that another poorly hydrolyzable analogue, GMP‐PCP, competitively inhibited the effects of GTP on neurite outgrowth. GTP did not exert its effects after hydrolysis to guanosine since the metabolic intermediates GDP and GMP were also ineffective in enhancing the proportion of cells with neurites. Moreover, the effects of GTP and guanosine were mutually additive, implying that these two purines utilized different signal transduction mechanisms.The effects of guanosine were not affected by the nucleoside uptake inhibitors nitrobenzylthioinosine (NBTI) and dipyridamole, indicating that a transport mechanism was not involved. Guanosine also did not activate the purinergic P1receptors, because the A2 receptor antagonists, 1, 3‐dipropyl‐7‐methylxanthine (DPMX) or CGS15943, and the At receptor antagonist, 1, 3‐dipropyl‐8‐(2‐amino‐4‐chloro)xanthine (PACPX) did not inhibit its reaction. Therefore guanosine enhanced neurite outgrowth by a signal transduction mechanism that does not include the activation of the Pt purinoceptors.The enhancement of the neuritogenic effects of NGF by GTP and guanosine may have physiological implications in sprouting and functional recovery after neuronal injury in the CNS, due to the high levels of nucleosides and nucleotides released from dead or injured cells.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00083-6

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractThe distribution of GM1 and GM3 gangliosides in human brain development between gestational week (g.w.) 6 and 15 was demonstrated by an immunocytochemical approach using polyclonal anti‐GM1 and anti‐GM3 antibodies. The first appearance of GM1‐ and GM3‐positive cells was recorded as early as in g.w. 6. Both antibodies labeled the cells in the ventricular zone of the telencephalic wall, with radially oriented fibers toward the pial surface, which represent radial glia cells with glia fibers. The intensive GM3 immunoreactivity was also exhibited in proliferating cells in the ventricular zone between g.w. 6 and 12. During the period from g.w. 12 to 15, characterized by a rapid multiplication of neurons and glia cells, an increased number of GM1‐ and GM3‐positive cells was observed. Prominent GM1 ganglioside staining was observed at the surface of the cell bodies in the ventricular zone. Besides surface labeling in migrating cells, GM1 immunoreactivity was identified inside the soma in the regions of cortical plate and subplate. GM1 immunoreactivity was more pronounced on the membrane of neuronal cells migrating along radial glia fibers, especially at the contact site between neuronal and glial cells. The GM3 ganglioside was localized mostly inside the soma, showing a granular immunoreactivity pattern.Our observations confirm the presence of GM1 and GM3 gangliosides in neuronal and glial cells in early human brain development. The involvement, especially of GM1 ganglioside in glia‐neuronal contacts during migration of neuroblasts to their final destination, as well as the presence of GM3 ganglioside in proliferative cells in the ventricular zone of the telencephalic wall was also recorded.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00078-X

出版商:Wiley    

年代:1999

数据来源: WILEY

摘要:

AbstractOrganotypic cerebellar cultures derived from neonatal mice were exposed to the DNA synthesis inhibitor, cytosine arabinoside, or to cytosine arabinoside plus picrotoxin, an anti‐GABA agent that increased neuronal activity, for the first five daysin vitro. The group treated with cytosine arabinoside alone was subsequently maintained in standard nutrient medium, while the group exposed to both cytosine arabinoside and picrotoxin was continuously maintained in medium with incorporated picrotoxin. Granule cells were destroyed and astrocytes were functionally compromised in both culture groups, and both groups exhibited Purkinje cell axon collateral sprouting, with projection of sprouted inhibitory terminals to unensheathed Purkinje cell somata and to Purkinje cell dendritic spines in equal numbers. Spontaneous cortical discharge rates were the same in both groups, and antidromic stimulation of Purkinje cell axons induced inhibition of cortical activity. These results differed from those of a previous study in which chronic exposure of otherwise untreated cerebellar cultures to anti‐GABA agents increased the complement of inhibitory terminals on glially ensheathed Purkinje cell somata and resulted in a reduction of spontaneous cortical discharge rates. These differences were attributed to the failure of picrotoxin (1) to alter the plastic changes consequent to exposure to cytosine arabinoside, in which Purkinje cells had excess inhibitory projections, and (2) to extend inhibitory synaptogenesis in a system in which inhibitory synapse development was already enhanced.

ISSN:0736-5748    

DOI:10.1016/0736-5748(95)00082-8

出版商:Wiley    

年代:1999

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(96)80198-5

出版商:Wiley    

年代:2006

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(96)80201-2

出版商:Wiley    

年代:2006

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(96)80207-3

出版商:Wiley    

年代:2006

数据来源: WILEY