ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90002-H

出版商:Wiley    

年代:2003

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90003-I

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractWe previously reported that the inositol phosphates (IPs) synthesis is induced by muscarinic agonists in the rat cochlea and that this stimulation is maximal at postnatal day 12. This peak response is concomitant with the onset of the efferent synaptogenesis at the outer hair cell level. Whether the correlation between this neuronal plasticity and the enhanced IPs formation is unique to the rat or a general feature of the developing vertebrate cochlea is not known. To examine this question, we measured, in the presence of LiCl, the accumulation of (3H)‐IPs induced by carbachol, in the developing chick cochlear duct during a period ranging from embryonic day (E) 8 to post‐hatching day (P) 20. Carbachol (1 mM) causes a significant increase of IPs formation relative to basal values at all ages. This IPs accumulation is maximal at E8 (1854% of the basal level), then, rapidly decreases until P13 when it reaches a steady‐state level of 294% of the basal level. Strikingly, this gradual decline in IPs formation is interrupted between E15 and E19, by a transient increase in IPs synthesis. This rise peaks at E16 with a stimulation value of 757% of the control level. This maximal stimulation is inhibited by atropine in a dose‐dependent manner, as is the case at E9, suggesting the involvement of muscarinic receptors. Interestingly, the occurrence of the peak response is concomitant with the plastic events associated with the maturation of the efferent innervation of the cochlear duct. Thus, these results suggest that there may be a correlation between cochlear plasticity and enhanced IPs synthesis, which is not species‐specific. The possible significance of the overall decrease in IPs formation, occurring during embryonic development, is discussed.

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90004-J

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractIt is well demonstrated that in intact animals the degradation rate of the junctional acetylcholine receptor (AChR) is significantly slower than that of the extrajunctional receptor. Such data, however, are not available for human AChRs because the required experimentation cannot be performed in humans. We have now studied the degradation rate of the junctional and extrajunctional AChRs, utilizing our tissue culture model, in which well‐differentiated neuromuscular junctions (NMJs) form on human muscle cultured in monolayer and innervated long‐term by fetal rat spinal cord neurons. Half‐life of AChRs was studied by a method utilizing the autoradiography of125I‐αbungarotoxin and computerized video image analysis. Extrajunctional AChRs degraded with a half‐life of 1.3 days whereas junctional AChRs degraded with a half‐life of 3.5 days. Our studies demonstrate for the first time that in innervated cultured human muscle: (a) the life span of human junctional AChR, is approximately 3 times longer than that of the extrajunctional AChR and (b) the stability of human AChR is neuronally regulated. This system can now be applied to evaluate the influence of pharmacologie agents on the stability of human junctional AChR, which is of potential importance in the treatment of myasthenia gravis and other diseases of the NMJ.

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90005-K

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractHyaluronic acid was localized in acetone‐fixed cryostat sections of brain and spinal cord obtained from adult, newborn and embryonal rat. The sections were incubated with glial hyaluronatebinding protein (GHAP) of human origin and the protein was visualized by indirect immunofluorescence with monoclonal antibodies raised to human GHAP andnotstaining rat brain by immunofluorescence. GHAP is a brain extracellular matrix (ECM) glycoprotein, approximately 60,000 molecular weight, which is structurally related to the HA‐binding region of cartilage ECM proteins. The distribution of hyaluronate in adult brain white matter and cerebellar cortex was similar to that previously reported for GHAP. In both cases, the reaction product formed a mesh surrounding myelinated axons and granule cells. Hyaluronate was also found in parts of the brain that did not contain GHAP. A finely reticulated mesh was observed in the neuropil between cell bodies in cerebral cortex and basal ganglia. Scattered cortical neurons were surrounded by a rim of reactive material. Perineural staining was the rule rather than the exception in spinal cord anterior horn motoneurons, inferior olivary nucleus, large bulbar reticular neurons and dentate nucleus of cerebellum. The only part of the brain which appeared relatively free of hyaluronate was the molecular layer of the cerebellum. In newborn and embryonal rat, the densely packed cell bodies in cerebral gray matter, periventricular germinal layer and external granular layer of cerebellum were surrounded by hyaluronate. Small droplets of hyaluronate were observed inbetween the cylindrical epithelial cells lining the neural tube in 11 day embryos. Non‐myelinated fiber tracts and the molecular layer of the developing cerebellum were relatively unstained. No hyaluronate was detected in the ependyma lining the cerebral ventricles and the central canal of the spinal cord.

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90006-L

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractPreviously reported serum‐free defined media for muscle cell culture require supplementation with hormones, purified growth factors or attachment factors. This report describes a culture system that enhances embryonic chick, skeletal muscle cell growth and differentiation in a serum‐free defined medium, without added specialized trophic factors. Myoblasts adhered more to and proliferated more rapidly on a reconstituted basement membrane substrate, Matrigel, than on rat‐tail collagen. Matrigel contains several basement membrane attachment molecules which apparently obviate the need for added purified attachment factors. Matrigel also appeared to play a trophic role in subsequent development by enabling the serum‐free growth of myotubes which suggests that Matrigel mediates the cellular interaction of growth or attachment factors. Collagen, on the other hand, did not support serum‐free myotube growth. Supplementation of defined medium with increasing levels of horse serum enhanced total protein in myotubes grown on both substrates; protein was higher in Matrigel cultures for each medium tested. The serum‐free defined medium supported complete morphological differentiation of myotubes grown on Matrigel and maintained myotube cultures up to 22 days. Fibroblast proliferation was higher in cultures on collagen in defined medium with high serum levels, but was virtually eliminated in cultures on Matrigel in serum‐free defined medium. The culture system described supports the differentiation of embryonic muscle cells in a simple, serum‐free defined medium, thus providing anin vitromodel of developing myotubes which should be particularly useful for studies of regulation mediated by extracellular factors.

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90007-M

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractAlthough the role of oxidant‐antioxidant metabolism in total ischemia and reperfusion in the central nervous system and cardiac myocardium have been well studied, less is known about the consequences of partial ischemic episodes. Here we show that reperfusion contributes to free radical formation as judged by conjugated diene formation. Also, antioxidants and Ca++antagonists were able to reduce free radical formation. These results would suggest that free radical generation following ischemia and reperfusion may result from more than one injury process in cerebral cortex.

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90008-N

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractThis is a report of the changes observed in the pattern of sensory innervation of muscle spindles in hindlimb muscles of kittens during the first four weeks of life. The structural analysis, made on teased, silver‐stained preparations, was complemented by a series of recordings of afferent responses of kitten spindles during ramp‐and‐hold stretches of the muscle. The primary endings of spindles from newborn animals showed a large degree of variability in their branching pattern and branches formed a network across the intrafusal fibres. In older animals there was less variability and lateral branches of stem axons began to encircle the intrafusal fibres. The process of maturation was characterized by a more uniform shape of the endings and more complete, evenly spaced, annulospiral terminals. Recordings of the responses of primary endings of spindles during muscle stretch showed that several features of the adult response were already present in the newborn, although the overall rate of discharge was very much lower. It was concluded that the changes observed in the structure of the sensory endings of kitten spindles did not have clearly identifiable physiological correlates. It appears that an annulospiral shape of the sensory terminals is not a necessary prerequisite for the generation of stretch responses. The predominant factor which appears to determine the responses of spindles to stretch is the maturity of the intrafusal fibres, in particular, the bag2fibre.

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90009-O

出版商:Wiley    

年代:2003

数据来源: WILEY

摘要:

AbstractIn this study we have examined structural and neurochemical aspects of retinal and optic nerve development in experimentally growth‐retarded fetal guinea pigs following maternal unilateral artery ligation. Eye weight (n= 4) and total retinal area (n= 6) at 62 days gestation (term ∼66 days) were both relatively spared when expressed as a percentage of body weight but in absolute terms were significantly reduced by 18% (P<0.001) and 13% (P<0.05) respectively when compared with age‐matched controls.The numerical density of neurons in the ganglion cell layer was significantly higher at both 52 days (n= 4) and 62 days (n= 4) in growth‐retarded fetuses compared with controls. However, there was no difference between the groups in the total number of neurons in this retinal layer at either age, since retinal areas are reduced in growth retardation. The area of neuronal somata in the ganglion and inner nuclear layers was significantly reduced in growth‐retarded fetuses compared with controls. There was a concomitant reduction in the width of the cellular layers in the retina and also in the plexiform (synaptic) and photoreceptor layers. The growth of the outer segments of the photoreceptor layer was particularly affected in peripheral retina. The higher packing density of cells and the reduced growth of the plexiform layers suggests a reduction in the growth of the neuropile in growth‐retarded fetuses compared with controls. The radial bundling of ganglion cell axons coursing across the retina to enter the optic nerve head was poorly defined in growth retardation. In addition myelination was delayed in the optic nerve with the numerical density of myelinated axons being significantly reduced (P<0.005) in growth‐retarded fetuses compared with controls.There was a significant reduction (P<0.01) in the number of amacrine cells in the inner plexiform layer expressing Substance P‐like immunoreactivity in growth‐retarded fetuses compared with controls. Glutamate‐like immunoreactivity was most intense in the five laminae of the inner plexiform layer and in the outer plexiform layer and less pronounced in photoreceptors, ganglion cells and their axons. There was no qualitative difference in glutamate immunoreactivity between control and growth‐retarded fetuses in any of these structures.Thus we have shown that intrauterine growth retardation has specific effects on the development of the fetal guinea pig retina, reducing the growth of several types of neurons and their processes and affecting the expression of the neuropeptide substance‐P in amacrine cells.

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90010-W

出版商:Wiley    

年代:2003

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/0736-5748(92)90011-N

出版商:Wiley    

年代:2003

数据来源: WILEY