摘要:

AbstractIt is known that manipulation of the visual environment results in changes in the developmental pattern of several neurotransmitter receptors and that the GABA receptor shows a high degree of plasticity in differential illumination experiments. In the present paper we investigated whether exposure to a visual pattern has a developmental effect on GABA receptor expression during early postnatal life. Two groups of newly hatched chicks were used: one was exposed to a simple and specific visual pattern and the other was deprived of any visual pattern. GABA receptors at each developmental stage were determined by binding experiments performed in a crude membrane fraction. Saturation studies were carried out in a fraction enriched in synaptic membranes. The developmental pattern of both high and low affinity GABA binding sites was affected by the visual pattern. This effect displays its maximal expression by the end of the first postnatal week. The modification in receptor expression was due to a change in the receptor density while the affinity was not affected.The change in receptor density induced by the presence of a visual pattern was highest at the end of the first postnatal week suggesting that at that time there is a brief period of higher plasticity for GABA receptor expression in the visual system than at other times. Our results also suggest that variations in GABA receptor density could be instrumental in adaptative changes in the visual system in response to variations in the environmental stimulation.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90040-S

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe interaction between growth factors and ethanol on cholinergic neuronal expression was studied in the chick embryo during early neuroembryogenesis using choline acetyltransferase activity as a cholinergic marker. As we have previously reported (Brodie&Vernadakis,Dev. Brain Res.56:223–228, 1990; Kentroti and Vernadakis,Dev. Brain Res.56:205–210, 1990), ethanol administrationin ovoat embryonic days 1–3 produced a 30% decrease in choline acetyltransferase activity. Nerve growth factor and epidermal growth factor administration alone, at embryonic days 1–3, produced a slight increase in choline acetyltransferase activity of both brain and spinal cord when examined at embryonic day 8. Concomitant administration of either nerve growth factor or epidermal growth factor with ethanol eliminated the decrease in choline acetyltransferase activity produced by ethanol. Moreover, administration of either nerve growth factor or epidermal growth factor at embryonic days 4–7 to embryos pretreated with ethanol at days 1–3 raised choline acetyltransferase activity to a level similar to that observed in controls. Thus the growth factors reversed the ethanol‐induced cholinergic insult and restored the cholinergic population to normal.These findings provide evidence of a possible role of NGF and EGF in interfering with the neurotoxic effects of ethanol during embryogenesis.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90041-J

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractChanges in neurite outgrowth parameters and in the immunolocalization of the neuronal growth‐associated protein B‐50 (GAP‐43) were studied in cultured neocortex as a function of development. In addition, we studied the effects of chronic blockade of bioelectric activity (BEA) with tetrodotoxin (TTX) on these parameters.Axonal outgrowth rate in control cultures reached a maximum at 8 daysin vitro(DIV) and declined to a low level at 21 DIV. B‐50 staining shifted from the perikaryon to the axons and growth cones during the first 3 DIV. In axons the intensity of B‐50 staining increased towards the growth cone. Within growth cones, the central/basal region and filopodia were intensely stained, whereas lamellipodia showed only marginal staining. Growth cone size gradually decreased after 3 DIV, due to the successive loss of lamellipodia and filopodia, and became club‐shaped during the second week, until by 21 DIV growth cones were completely lost, and axons started retracting and degenerated. In the central area of the cultures, growth cones also decreased in size with time, but became stabilized as presynaptic elements onto other neurons.Acute addition of TTX did not affect the outgrowth rate at 6 DIV. Chronic TTX treatment led to an earlier retraction and degeneration of axons than in control cultures and to a loss of B‐50‐stained cells and varicosities during the third week, but did not affect growth cone morphology or B‐50 staining. The regressive phenomena are probably due to an increased neuronal cell death shown to occur after chronic TTX treatment. The developmental changes in axonal elongation rate and growth cone morphology may be related to developmental changes in the content and/or phosphorylation of B‐50 (GAP‐43, which are studied in the same cultures in the following paper [Ramakerset al.(1991)Int. J. Devl Neurosci.9, 231–241].

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90042-K

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe content and phosphorylation of the neuronal growth‐associated protein B‐50 (GAP‐43) were studied in cultured neocortex as a function of normal development and development in the presence of tetrodotoxin (TTX), a blocker of bioelectric activity (BEA). The observations were correlated with previous morphological findings on neurite outgrowth and B‐50 immunolocalization in the same cultures.In control cultures, the concentration of B‐50 reached a maximum at 7 daysin vitro(DIV) and decreased thereafter, whereas the concentration of neuron specific enolase (NSE), which was used as a neuronal reference marker, rose till 28 DIV and leveled off towards 42 DIV. The degree of basal phosphorylation of B‐50 (relative to that of total protein) decreased after the first weekin vitro. Stimulation of B‐50 phosphorylation by phorbol ester also decreased with agein vitro, indicating that changes in B‐50 phosphorylation were mainly due to changes in protein kinase C (PKC) activity.The chronic presence of TTX led to a reduced content of B‐50 and NSE after 14 DIV. The basal phosphorylation of B‐50 was neither affected by acute nor chronic TTX treatment. However, upon stimulation of PKC with phorbol esters, some alterations of B‐50 phosphorylation were revealed in cultures grown in TTX. These biochemical observations are in line with the absence of effects of TTX on neurite outgrowth during the first 2 weeks in culture, and later effects of TTX on neuronal survival.The developmental changes in B‐50 concentration and phosphorylation largely correlate with previous morphological observations on axonal outgrowth and growth cone shape in the same cultures. We suggest that B‐50 phosphorylation plays an important role in transducing extracellular signals into directed neurite outgrowth.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90043-L

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractIn view of the likelihood that the heparin‐binding growth factors of fibroblast growth factors are neurotrophic for the neurones of the chick ciliary ganglion a study has been made of the retrograde axonal transport of the acidic and basic fibroblast growth factors by these neurones. No high capacity retrograde axonal transport of these molecules was seen. The amount of transport was equivalent to the low level seen with many proteins such as horse radish peroxidase or bovine serum albumin rather than the convincing transport seen for nerve growth factor in the sympathetic system. The iodinated proteins retained their ability to bind to neuronal receptors. Thus, if the fibroblast growth factors are neurotrophic in the ciliary ganglion, they may exert their action by mechanisms other than the retrograde axonal transport of the factor itself.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90044-M

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractSpecific and localized lesions of the 5‐HT fibers in the hippocampus induce homotypic collateral sprouting and enhance serotonergic fiber outgrowth from adult neurons and transplanted fetal tissue. In this study, hippocampal extracts were prepared and applied to primary cultures of fetal serotonergic neurons. The effects of plating density and serum additives were examined. The growth of the serotonergic neurons in the rostral brainstem dissociated cultures were estimated by measuring the specific uptake of [3H]5‐HT. The results indicate the presence of a trypsin‐sensitive factor which is active when prepared fresh at dilutions up to 1/10,000. The factor is higher in hippocampus than cerebellum. Young male tissue contained more activity than either female or aged hippocampus. Although both positive and negative effects are described, higher dilutions of factor (1/1,000) were generally stimulatory in high density cultures while lower dilutions (1/10) were inhibitory in low density cultures. Specific removal of 5‐HT hippocampal afferents with fornix‐fimbria microinjections of 5,7‐dihydroxytryptamine resulted in an initial loss of activity (2 days and 2 weeks) followed by an enhanced activity (2 months) compared to normal hippocampal extract. Several possibilities are discussed as to the identity of the serotonergic growth factor from hippocampal supernatant.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90045-N

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractProteoglycan synthesis by two clonal murine skeletal muscle cell lines, G8‐1 and C2, was examined. Cultures of skeletal muscle cells at both the myoblast and myotube stages were radiolabeled using [35S]sulfate as a precursor. The proteoglycans of the cell layer and medium were separately extracted and isolated by ion exchange chromatography on DEAE‐Sephacel followed by gel filtration chromatography on Sepharose CL‐2B. The cell layer proteoglycans eluted from Sepharose CL‐20 as a single peak with aKavof 0.66 and contained glycosaminoglycan chains with an average molecular weight of 20,000. The glycosaminoglycan chains were composed of nearly equal mixtures of chondroitin sulfate and heparan sulfate with the exception that C2 myoblast cultures contained larger amounts of heparan sulfate. Of interest, this line differentiates more rapidly in our laboratory than G8‐1. The medium proteoglycans also eluted from Sepharose CL‐2B as a single peak with aKavof 0.66 but contained glycosaminoglycan chains with an average molecular weight of 32,000. Based upon enzymatic and chemical analysis, the medium glycosaminoglycan chains were composed of a mixture of chondroitin sulfate (71–80%) and heparin sulfate (19–22%). Following chondroitinase ABC digestion, the predominant disaccharide released from all glycosaminoglycan fractions was chondroitin‐4‐sulfate. When the extracted cell layer proteoglycans were chromatographed on Sepharose CL‐28 in the absence of detergent, a small but consistent proportion (14–18%) eluted in the void volume, suggesting the association of at least a portion of this proteoglycan with cellular lipid. These differences distinguish proteoglycan metabolism in fusing clonal lines from primary muscle cell cultures suggesting their utility in evaluating the contribution of these macromolecules in myogenesis.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90046-O

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractBrain cells from embryonic chick (stage 28–29) were cultivated for 16 days under serum‐free conditions. Nerve cells were found to mature during the first 7 days in culture, as indicated by the presence and developmental pattern of the relative amount of dendritic‐specific microtubule‐associated protein type 2 (MAP2). Maximal amounts of MAP2 antigen were found to be directly correlated with the number of cells plated out. Astroglia cell proliferation and differentiation, as measured by the amounts of glial fibrillary acidic protein (GFAP), were found to stabilize after a certain astrocyte cell density was reached. Variation in culture plate coating procedure, oxygen tension and addition of serum or of the cytostatic drug Ara‐C were found to differently affect viability and maturation processes of astroglia and of nerve cells. Moreover, optimal culture conditions for long‐term brain cell cultures are described.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90047-P

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThese studies were designed to examine the differential effects of prenatal or postnatal administration of ACTH 1‐39 and nicotine, on 5‐HT high affinity uptake in brainstem and hippocampal synaptosomes. ACTH was administered prenatally (to pregnant dams) and postnatally to the neonates. Postnatal administration of ACTH significantly increased high‐affinity 5‐HT uptake in the hippocampus and especially the brainstem at both 7 and 21 days after birth. Prenatal ACTH, on the other hand, transiently increased 5‐HT uptake in only the brainstem at 7 days, a change that was reversed at 21 days. While the effects of postnatal nicotine administration were essentially the same as those of postnatal ACTH treatment, prenatal nicotine, unlike ACTH, did not alter 5‐HT uptake in 7‐day‐old rats but did reduce uptake in both tissues at 21 days. The observation that postnatal nicotine mimics the effects of postnatal ACTH and that nicotine stimulates ACTH release, suggests that the postnatal effects of nicotine may be exerted through ACTH.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90048-Q

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractBinding of [3H]glutamate, [3H]AMPA (RS‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolo‐propionate) and [3H]kainate was investigated in membranes prepared from cerebral cortex of 4‐day‐old and adult mice and from cerebral cortex neurons cultured for different periods of time (2, 4, 8 and 14 days). For all ligands, the number of binding sites increased as a function of development bothin vivoand in culture. A significant number of binding sites for the ligands could be demonstrated on the cultured neurons already after 2 days in culture. Scatchard analysis of the binding data showed a single population of binding sites for glutamate (KD≈200 nM) and kainate (≈6 nM) regardless of the developmental stagein vivoor in culture. In case of [3H] AMPA binding two binding sites withKDvalues of ≈6 nM and 100–200 nM could be demonstrated bothin vivoand in culture. Binding of [3H]glutamate to cultured neurons could be displaced byN‐methyl‐d‐aspartate (100 μM) and quisqualate (3 μM) in an additive manner butd,l‐4‐aminophosphonobutyrate (100 μM) had no effect. AMPA binding to cultured neurons was much more (40‐fold) sensitive than kainate binding to the newly developed AMPA selective antagonist NBQX (2,3‐dihydroxy‐6‐nitro‐7‐sulphamoyl‐benzo(F)quinoxaline) indicating that kainate and AMPA bind to independent binding sites. Monitoring membrane potentials in the cultured neurons using the lipophilic cation TPP+(tetraphenylphosphonium) it was demonstrated that potassium (55 mM) as well as glutamate, AMPA and kainate (100 μM) could depolarize the neurons both at early (2 days) and late (9 days) developmental stages in culture. The demonstration of functionally active receptors for the 3 excitatory amino acids in both immature (2 days in culture) and mature (8–9 days in culture) neurons is discussed in the light of previous studies of the development as a function of the culture period of effects of excitatory amino acids in neurons. It is concluded that no simple correlation exists between expression of binding sites for the excitatory amino acids and their ability to induce cytotoxicity and neurotransmitter release.

ISSN:0736-5748    

DOI:10.1016/0736-5748(91)90049-R

出版商:Wiley    

年代:2003

数据来源: WILEY