摘要:

AbstractThe survival of neural tissues depends in part on the balance between the formation of free radicals due to oxidative metabolism and the transformation of the free radicals to non‐toxic compounds. Serial subculture of rat glial cells as described here resulted in a decrease of the specific activities of several antioxidant enzymes and a glial specific marker for astrocytes. Thus, there was an increased susceptibility to oxidative stress in cultures by the third passage. These subcultured glial cell cultures may represent a useful model for the study of free radical induced neural damage that may be relevant to CNS trauma and aging.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90028-2

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractLight microscopic numerical and morphometric studies were conducted on the olfactory epithelium of postnatal normal and hypothyroid rats. The normal rat olfactory epithelium undergoes marked growth and development during the suckling period (days 1–25): thickness, 50%; area, × 8, total number of olfactory neurons, basal and supporting cells, × 10, × 11 and × 8, respectively. The effects of thyroid hormonal deprivation on these proliferative postnatal growth changes were studied by adding PTU (n‐propylthiouracil, a reversible antithyroid goitrogen) to the litter's drinking water from birth to weaning (day 25).The general architecture of naso‐olfactory cavities as well as the histology and thickness of the olfactory epithelium were unaffected in the hypothyroid pups. However, the surface area of the olfactory receptor sheet was reduced by 40%, the reduction occurring throughout the cavity, though not uniformly. The total number of olfactory neurons, supporting and basal cells were reduced by 33, 45 and 47%, respectively. These results indicate that the postnatal vertical accretion of olfactory neurons occurring across the epithelial thickness is unaffected in the hypothyroid pups, while the horizontal proliferation of neurons accompanying the expansion of the sheet's surface area is markedly reduced. The results suggest differential effects of thyroid hormones on these modes of proliferative growth and imply further that in addition to possible direct effects, the influence of thyroid hormones on developmental growth of the olfactory epithelial sheets may be secondary to effects on the underlying submucosal connective tissue.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90029-4

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe evolution of excitatory amino acids‐(EAA) stimulated inositol phosphates (IPs) turnover during postnatal development was investigated in synaptoneurosomes prepared from rat forebrains. The two main EAA agonists which induce the IPs synthesis were quisqualate (QA) andN‐methyl‐d‐aspartate (NMDA). The QA and NMDA stimulations of IPs formation present a particular developmental pattern, characterized by an active phase during rat synaptogenesis. The QA‐evoked IPs accumulation peaked in synaptoneurosomes prepared from 8‐day‐old rat forebrains while that evoked by NMDA peaked in synaptoneurosomes from 12‐day‐old rats. These two developmental patterns are specific of the EAA agonists since the other various neuroactive substances tested (carbachol (Carb), noradrenaline, and high concentrations of potassium) induced an IPs accumulation, which increases during development and reaches a maximum in synaptoneurosomes of adult animals. Aging leads to a decrease in the capability of EAAs and muscarinic agonists to stimulate IPs formation in synaptoneurosomes, whereas the stimulation of IPs turnover by noradrenaline remains constant.Taken together, these results suggest that EAAs play a key role during brain development by sequentially activating two receptor subtypes, a new QA receptor, and a NMDA receptor, linked to the phosphoinositide metabolism. They may also indicate that these EAA‐induced IPs responses are related to neuronal plastic events, the amplitude of which decreases with aging.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90030-0

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractAcetylcholinesterase is expressed in chick dorsal root ganglia neurons very early in development. Since the physiological role of the enzyme in these cells is still obscure, it appeared of interest to investigate its modifications in the course of development.The specific activity of acetylcholinesterase in chick dorsal root ganglia increases, duringin ovodevelopment, from day E5 to day E13; after day E13 there is a decrease. Conversely, when acetylcholinesterase activity was expressed on a per ganglion basis, a continuous increase in the level of the enzyme until day E20 was observed.Acetylcholinesterase is a polymorphic enzyme and its molecular forms have different cellular localizations. Two globular forms, a tetramer (G4) and a dimer (G2), are present in the ganglia, as in chick brain. G4is the major form at day E5, where it represents about 85% of the activity. This form shows a progressive decrease since day E8, and at day E20 exhibits activity levels similar to those of G2.It is known that acetylcholinesterase‐producing cells are also able to release the enzyme in the extracellular space. We determined the release of acetylcholinesterase by cultured dorsal root ganglia neurons at various developmental stages: acetylcholinesterase release is significantly increased at day E20, as compared to younger stages, and 90% of the enzyme released is G4.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90031-2

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThe present immunohistochemical study investigates the presence and distribution of S‐100‐containing glial cells in the early stages of development in human spinal ganglia. From the earliest ages investigated immunoreactive cells could be detected in a continuous layer at the periphery as well as inside ganglionic rudiments in close relationship with neural elements, both at the light and ultrastructural levels. The possibility that these glial cells, exhibiting such a distinctive distribution, play a modulatory role on microenvironmental influences during maturation could be taken into account. Neither glial fibrillary acidic protein nor myelin basic protein could be detected at the ages investigated.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90032-4

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractBasal lamina components, such as heparan sulfate proteoglycan (HSPG) and laminin play an important role in neuritic outgrowth for CNS and PNS neurons in culture. The mutant mouse ‘Trembler’ is characterized by hypomyelinization and production of an excess of basal lamina layers around Schwann cells in peripheral nerves.In order to analyse whether or not the serum of the mutant animals contains neurite outgrowthpromoting factors, we cultured rat spinal cord neurons in the presence of Trembler serum. Under these conditions, the outgrowth of neurites was increased approx, 2 times as compared to control serum. Trembler serum induces neuritic outgrowth characterized both by an increase in number of primary neurites emerging from the nerve cell body as well as by an increase in peripheral branching of neurites.To characterize the factors implicated in this increase we added antibodies directed against HSPG or laminin to the mutant serum. As a result, the increase in neuritic outgrowth was reduced or abolished in both cases.Trembler effect on neurite growth disappeared when the number of the non‐neuronal cells was reduced, suggesting that the mutant serum did not act directly on neurons but by the intermediary action of non‐neuronal cells.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90033-6

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractTeleost and amphibian retina grows throughout life at the circumferential margin distal to the center. Retinas of two teleosts, goldfish andEugerres plumieri; and two mammals, rat and rabbit were dissected into concentric regions; center and periphery, or center, intermediate and periphery. The concentration of glutamic acid, taurine, and gamma‐aminobutyric acid was determined in these areas. A non‐significant difference was found between the center and periphery of retinas dissected into two regions. By dissecting the teleost retina in three concentric regions a progressive increase of gammaaminobutyric acid and taurine for center to periphery was observed, which was statistically significant for taurine. Rat and rabbit retina did not present this difference. The concentration of these amino acids was also determined in two concentric regions of goldfish retina 24 hr after crush of the optic nerve. Taurine content significantly increased in the center of the regenerating retina, but not in the periphery. Outgrowth was measured in expiants prepared from central and peripheral retina in the presence of exogenous taurine. The amino acid produced an increase of the nerve growth index of central expiants, but inhibited the growth from peripheral expiants. This report presents a correlation between taurine concentration in a region of the retina that could be considered as embryonic tissue, suggesting that this amino acid plays a role in the formation of new cells. Moreover, the results from post‐crush and cultured retina, with respect to taurine concentration or regenerating effect, suggest a saturation of the taurineenriched zone.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90034-8

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractDevelopment of cholinergic innervation in the hippocampal formation of normal and hypothyroid rats was studied by a combined biochemical and histochemical analysis of acetylcholinesterase (AChE) activity in normal and hypothyroid rats. The normal developmental pattern of cholinergic activity suggests an entrance of septal cholinergic fibers from the fimbria to different zones of the hippocampal formation mainly during the first postnatal week. By 10 days of age, the regional distribution of staining was similar to that in the adult. Thereafter, the intensity of staining increased without major changes in the laminar organization. As shown by closely related histochemical and biochemical findings, hypothyroidism led to a delay in the arrival of cholinergic afferences and a possible subsequent cholinergic hyperinnervation of the hippocampal formation in adulthood. These results are discussed taking into account the time course of structural development in the two synaptic compartments, namely the extrinsic septal neurons and intrinsic pyramidal and granule cells, in comparison with the development of thyroid function.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90035-X

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractWe have found that cholinergic neurons in spinal cord‐dorsal root ganglion cultures derived from E12–E13 mouse embryos are sensitive, as measured by changes in choline acetyltransferase activity, to factors secreted by non‐neuronal cells derived from the same tissue at an identical developmental stage. Conditioned medium was produced by incubating non‐neuronal cultures for 4 days in defined medium. The cholinotrophic activity present in the conditioned medium had a molecular weight of greater than 50,000 as determined by ultrafiltration and bound wheat germ lectin and heparin sepharose. Total RNA isolated from the non‐neuronal cells, used to produce the conditioned medium, was translated in frog oocytes. Conditioned medium from the injected oocytes was also found to contain cholinotrophic activity. In contrast, the conditioned medium from water‐injected oocytes was inactive.The interaction between the cholinotrophic activity in conditioned medium from frog oocytes and known second messengers was also examined. Dibutyryl cyclic AMP produced a concentrationdependent increase in choline acetyltransferase activity. If a maximal effective dose of dibutyryl cyclic AMP was added in conjunction with a maximal effective dose of conditioned medium from oocytes injected with total RNA a nearly additive response was noted. In contrast, the phorbol ester, phorbol 12‐myristate 13‐acetate, produced a biphasic change in the level of choline acetyltransferase activity; with lower doses stimulating and higher doses inhibiting the enzyme activity. When conditioned medium from oocytes injected with non‐neuronal cell RNA was added in conjunction with the phorbol ester a decrease in the physiological response was noted.

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90036-1

出版商:Wiley    

年代:2003

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(89)90037-3

出版商:Wiley    

年代:2003

数据来源: WILEY