ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90013-4

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractEmerging evidence indicates that trophic interactions that influence brain development are critical throughout life, mediating processes as diverse as learning, memory and regrowth after injury. This review summarizes recent work suggesting that impulse activity regulates trophic interactions in the brain, allowing the conversion of millisecond‐to‐millisecond signalling into long‐term changes in neural circuit function. For example, depolarizing stimuli regulate trophic factor gene expression, an effect mediated by excitatory transmitters. Responsiveness to trophic factors is also regulated by activity, since depolarization increases the expression of trophic receptor genes. Moreover, different excitatory transmitter receptor subtypes mediate trophic or regressive effects, allowing a neural system to precisely memorialize excitatory or inhibitory experiences. A number of open questions are articulated to define potential future directions.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90014-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe postnatal development of laminar pattern of AMPA receptor mRNA subtypes GluR‐A through to GluR‐D (flip variants) in the visual cortex of both normally raised and monocularly deprived rats (one eyelid sutured at the age of 11 days) was studied usingin situhybridization histochemistry and computer‐assisted image analysis. The AMPA receptors GluR‐A through to GluR‐D transcripts exhibit a differential laminar expression pattern in the developing rat visual cortex. At birth the levels of GluR‐A transcripts are lower by about 50% in each visual cortical layer as compared to the adult values. In contrast, GluR‐B to GluR‐D mRNAs are expressed in all cases at higher levels at birth than in the adult brain.Unilateral eyelid closure at postnatal day 11 for several periods of time resulted in both transient and permanent changes in the laminar development of GluR‐A through to GluR‐C transcripts but hardly affected the GluR‐D mRNA subtype. The distinct laminar developmental pattern of AMPA receptor mRNAs in rat visual cortex as well as the differential effects of visual deprivation suggest specific roles of AMPA receptor subtypes during the early postnatal maturation of visual function.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90015-6

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractGlutamate and its analogues play a central role in excitatory neurotransmission throughout the brain. Their signal in the postsynaptic cells can be transduced by several second messengers. Here we show that in primary cultures of embryonic rat striatum, excitatory amino acid receptor stimulation increases cyclic GMP intracellular concentration and the magnitude of this response depends upon the time in culture. Formation of cyclic GMP appears to be mediated by bothN‐methyl‐d‐aspartate (NMDA) and non‐NMDA type excitatory amino acid receptors, it is blocked by specific excitatory amino acid antagonists and requires extracellular Ca++. The effect mediated via the NMDA receptor is also regulated by extracellular Mg++.These results show that excitatory amino acids make use of cyclic GMP for signal transduction in striatal neuronsin vitro. We suggest that cyclic GMP may be an independent second messenger possibly important in the development of a defined population of striatal neurons.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90016-7

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractEarly in the development of the hypothalamic‐pituitary‐adrenal (HPA) axis, the rat undergoes a stress hyporesponsive period of blunted responses to several Stressors including cold exposure (CE) and maternal deprivation (MD). We examined the development of the axis by monitoring adrenocorticotropin hormone (ACTH) plasma levels in an animal model of depression and/or anxiety characterized by learned helpless (LH) behavior and a dysfunctional HPA axis in adult life. On postnatal day 7 there was no significant difference in basal plasma ACTH levels between congenital (cLH) and controls, but cLH animals showed a blunted response to CE (P<0.001). By postnatal day 14 there was a dramatic increase in ACTH response to CE (P<0.005). On postnatal day 21 baseline ACTH and response to CE were again significantly suppressed in cLH rats. Stress responsiveness to MD was present in all groups and was insignificantly different for all ages of development between groups. These findings suggest that rats with congenital learned helplessness undergo a differential response in the development of the HPA axis in that the axis was hypersensitive at postnatal day 14 and became hyporesponsive beyond day 14 and this may, in part, account for the dysfunctional stress response observed during adulthood.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90017-8

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe appearance and distribution of calcitonin gene‐related peptide immunoreactive (CGRP‐IR) nerve fibers was studied by indirect immunofluorescence microscopy in the developing salivary glands of the rat at daily age intervals from the 15th dayin utero(i.u.) until birth and subsequently on the 2nd, 5th, 7th, 16th, 30th postnatal (p.n.) days. The findings were compared to samples of adult rats. CGRP‐IR fibers appeared on day 20 i.u. both in parotid and submandibular glands. In submandibular glands, fibers were first seen surrounding the developing ductal branches, in the mesenchyme and also in association with developing ducts and blood vessels. In the parotid gland CGRP‐IR fibers first appeared around ductal branches and blood vessels on day 20 i.u. and on day 21 i.u. CGRP‐IR nerve fibers were found in the mesenchyme and around developing ducts. The density of CGRP‐IR fibers was highest between the 2nd and 16th postnatal days, after which the amount of CGRP immunoreactivity slowly decreased to the levels of adult glands. The increase in a number of CGRP‐IR nerve fibers especially around the ductal and vascular elements in the developing salivary glands indicates that they may play a role in the functional maturation of salivary glands.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90018-9

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractEarly cortical plate and subplate cells in the developing neocortex of many animal species and humans contain one specific plasma protein, fetuin. Fetuin is heavily glycosylated and it is possible that due to the large amount of sugars, this molecule may play a part in cellular recognition during brain development.Cellular and extracellular carbohydrates in the developing brain of the sheep were studied histochemically using a battery of fluorescein‐labelled lectins. Two neuraminic acid specific lectins, Sambucus nigra and Maackia amurensis, labelled consistently the fetuin‐positive cells as demonstrated by double labelling with lectins and antifetuin antibodies. Brain sections from other species, known to contain fetuin‐positive cells (fetal cow, postnatal tammar wallaby) showed a similar lectin staining pattern to that of the sheep fetus. Additionally, sections from species thought to contain fetuin in their developing brains that failed to cross‐react with available antifetuin antibodies (postnatal Monodelphis, fetal cat) also demonstrated lectin‐positive staining in the same neuronal cell population.Thus, neuraminic acid is a common and well conserved terminal carbohydrate in cortical plate and subplate neurons of the developing brain. Neuraminic‐specific lectins are useful markers for these neurons in addition to the more traditional use of immunocytochemical methods in studies of formation of the neocortex.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90019-A

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe aim of the present study was to test the capacity of spinal cord scar tissue to assist and sustain axon regrowth. In adult rats and cats the dorsal funiculus (DF) was cut at mid‐thoracic or lumbar level and a superficial incision in the DF rostral to the lesion was made in order to extend the penetrating lesion. Axonal tracing in rats 50–100 days postinjury with anterogradely transported wheatgerm agglutinin‐conjugated horseradish peroxidase or rhodamine‐conjugated dextran demonstrated that nerve fibers had entered the scar tissue. Axon ingrowth in the scar was further indicated by axonal immunoreactivity to the growth‐associated protein GAP‐43. The scar tissue showed low‐affinity neurotrophin receptor‐like immunoreactivity in association with blood vessels and in the interstitium. The integrity of the blood‐brain barrier in the extended dorsal funiculus lesion was disrupted for at least 11 months postinjury, assessed by i.v. injections of free HRP or Evans blue. The present study shows that penetrating injury in the dorsal funiculus produces a CNS environment permissive for axonal sprouting and that PNS influence is not necessary for spinal tract regrowth. A possible relationship between the absence of an intact BBB and injury‐induced axonal sprouting is discussed.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90020-E

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractIn sporadic Alzheimer's disease (AD), a number of metabolic alterations to the brain have been observed soon after the onset of the initial clinical symptoms. In particular, impairments of glucose utilization and related metabolic pathways are prominent and well‐established findings in incipient AD, resembling metabolic abnormalities such as have been found in noninsulin‐dependent diabetes mellitus. To mimic these abnormalities, we administered an intracerebroventricular (icv) injection of streptozotocin (STZ) to rats and studied the effects on glucose and glycogen metabolism in the cerebral cortex and hippocampus compared with controls. The enzymatic activities studied dropped significantly by 10–30% in brain cortex (cort.) and hippocampus (hc) 3 and 6 weeks after icv STZ injection: hexokinase (15% 3 weeks cort.; 14% 6 weeks cort.; 12% 3 weeks hc; 28% 6 weeks hc), phosphofructokinase (15%; 15%; 24%; 15%), glyceraldehyde‐3‐phosphate dehydrogenase (10%; 12%; 30%; 19%), pyruvate kinase (22%; 13%; 22%; 28%), glucose‐6‐phosphatase (10%; 23%; 14%; 19%) and phosphorylase a (22%; 11%; 30%; 15%).The content of glycogen was significantly higher in STZ‐treated rats than in control animals (7% 3 weeks and 15% 6 weeks in cortex).In contrast to the reduced enzymatic activities, we observed no changes in the concentrations of the glycolytic intermediates glucose, glucose‐6‐phosphate, fructose‐6‐phosphate, fructose‐1,6‐diphosphate, pyruvate, lactate and glucose‐1‐phosphate. These data clearly indicate reduced glycolytic enzyme activity after icv administration of STZ and suggest gluconeogenesis consequent on abnormalities in glucose breakdown. This model may thus be assumed to be a useful tool to investigate pathogenetic factors involved in sporadic dementia of Alzheimer type.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90021-5

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe expression of two astroglial differentiation markers, vimentin and glial fibrillary acidic protein, was investigated in a previously established human glioma cell line of clonal origin (GL15). Vimentin immunolabelling was homogeneously expressed in all cells. Glial fibrillary acidic protein and its encoding message, investigated by immunocytochemistry andin situhybridization, showed a mosaic‐like expression. Only 30% of the cell population expressed glial fibrillary acidic protein and its mRNA. Western and Northern blots performed for both markers confirmed the presence of both proteins and messages, and their level was correlated with the observed antigenic and molecular probe labelling. The overall antigenic pattern suggests that GL‐15 cells do not belong to the O‐2 A progenitor cell lineage and may arise from a clonal expansion of astrocyte precursors.

ISSN:0736-5748    

DOI:10.1016/0736-5748(93)90022-6

出版商:Wiley    

年代:2003

数据来源: WILEY