摘要:

AbstractDuring metamorphosis of the moth,Manduca sexta, an identified leg motor neuron, the femoral extensor motor neuron (FeExt MN) undergoes dramatic reorganization. Larval dendrites occupy two distinct regions of neuropil, one in the lateral leg neuropil and a second in dorsomedial neuropil. Adult dendrites occupy a greater volume of lateral leg neuropil but do not extend to the dorsomedial region of the ganglion. The adult dendritic morphology is acquired by extreme dendritic regression followed by extensive dendritic growth. Towards the end of larval life, MN dendrites begin to regress, but the most dramatic loss of dendrites occurs in the 3 days following pupation, such that only a few sparse dendrites are retained in the lateral region of leg neuropil. Extensive dendritic growth occurs over the subsequent days such that the MN acquires an adult‐like morphology between 12 and 14 days after pupation. This basic process of dendritic remodeling is not dependent upon the presence of the adult leg, suggesting that neither contact with the new target muscle nor inputs from new leg sensory neurons are necessary for triggering dendritic changes. The final distribution of MN dendrites in the adult, however, is altered when the adult leg is absent, suggesting that cues from the adult leg are involved in directing or shaping the growth of MN dendrites to specific regions of neuropil. © 1993 John Wiley&Sons, I

ISSN:0022-3034    

DOI:10.1002/neu.480240102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractTo investigate the short‐and long‐term effects of axotomy on the survival of central nervous system (CNS) neurons in adult rats, retinal ganglion cells (RGCs) were labelled retrogradely with the persistent market diI and their axons interrupted in the optic nerve (ON) by intracranial crush 8 or 10 mm from the eye or in intraorbital cut 0.5 or 3 mm from the eye. Labelled RGCs were counted in flat‐mounted retinas at intervals from 2 weeks to 20 months after axotomy. Two major patterns of RGC loss were observed: (1) an inital abrupt loss that was confined to the first 2 weeks after injury and was more severe when the ON was cut close to the eye; (2) a slower, persistent decline in RGC densities with one‐half survival times that ranged from approximately 1 month after intraorbital ON cut to 6 months after intracranial ON crush. A small population of RGCs (approximately 5%) survived for as long as 20 months after intraorbital axotomy. The initial loss of axotomized RGCs presumably results from time‐limited perturbations related to the position of the ON injury. A. persistent lack of terminal connectivity between RGCs and their targets in the brain may contribute to the subsequent, more protracted RGC loss, but the differences between intraorbital cut and intracranial crush suggest that additional mechanisms are involved. It is unclear whether the various injury‐related processes set in motion in both the ON and the retina exert random effects on all RGCs or act preferentially on subpopulations of these neurons. © 1993 John Wil

ISSN:0022-3034    

DOI:10.1002/neu.480240103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn a cross speciesin vitroassay, growth cones from fish temporal retina elongating on laminin lanes were observed with time‐lapse videomicroscopy as they encountered lanes and territories that carried membrane fragments from the chick caudal tectum. Caudal tectal membranes of adult fish and embryonic chick are known to possess a repellent guiding component for temporal retinal axons. The caudal membranes of chick exert a particularly strong influence on fish temporal axons. Contacts with chick caudal membranes by just a few filopodia and parts of the lamellipodia evoked a turning response away from the membrane lane of the entire growth cone. Contacts by filo‐ and lamellipodia over the entire circumference of the growth cone, however, caused invariably growth cone collapse and retraction. During growth cone turning and collapse and retraction, filopodia remained in contact with the tectal membrane fragments, suggesting strong membrane–filopodia adhesion simultaneous to growth cone repulsion by the repellent guiding component. © 1993 John Wiley&Son

ISSN:0022-3034    

DOI:10.1002/neu.480240104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA system of brain nuclei controls song learning and behavior in zebra finches (Poephila guttata). The size of song‐control nuclei are much larger in males, which sing, than in females, which do not sing. This study examined the distribution of fibers, terminals, and cell bodies that are immunoreactive for tyrosine hydroxylase (TH) (the rate‐limiting enzyme in the synthesis of catecholamines) in song‐control nuclei of adult males and females and juvenile males. In addition, the broad pattern of TH staining throughout the brain was described. There was a sex difference in TH immunoreactivity within song‐control nuclei: males had light to moderate staining in all three cortical nuclei examined, whereas females had little or no label in corresponding areas [lateral magnocellular nucleus of the anterior neostriatum (IMAN), higher vocal center (HVC), and robust nucleus of the archistriatum (RA)]. The song‐control nucleus area X (X), located in the striatum of avian basal ganglia, was more darkly stained than the surrounding striatum only in males; X was not defined by more intense immunoreactivity in females and hence could not be visualized. There were no apparent differences in TH staining in males ranging in age from 50 days to adulthood (>90 days). Outside of the song‐control system there were no substantive differences as a function of sex or age in the pattern or intensity of TH labeling. Major areas of telencephalic staining included the striatal region of basal ganglia, which was covered with dense, fine‐grained label, and the septum, where cell bodies were encircled by extremely well‐labeled thick processes. In the diencephalon, the preoptic area and hypothalamus included a complex pattern of darkly stained somata and fiber and terminal labeling. Darkly stained somata surrounded the pretectal nucleus, and labeled processes ramified throughout the superficial layers of the optic tectum. The midbrain and hindbrain contained a dense plexus of extremely dark cell bodies corresponding to mammalian substantia nigra, adjacent tegmental areas, and locus ceruleus. Labeled hindbrain cells were also seen in the pontine region, around nucleus solitarius, and in the ventrolateral medulla. © 1993 John

ISSN:0022-3034    

DOI:10.1002/neu.480240105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe development and regeneration of the ipsilateral retinopetal projection of the nucleus olfactoretinalis (NOR) in the cichlid fishHaplochromis burtoniwas studied with 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethyl indocarbocyanine perchlorate (DiI) in fixed tissue. Through out development most NOR cells projected to the contralateral retina. Only an insignificant, transient elevation of a projection to the ipsilateral retinawas found in a few animals; however, after severing the contralateral processes of NOR cells by either enucleation or nerve crush, many animals had significantly more NOR cells with a regenerated process to the ipsilateral retina. Nevertheless, within a few weeks of surgery, the number of animals with ipsilaterally projecting cells were reduced to control values. The transiently enhanced ipsilateral projections to the retina imply changes in the guiding mechanism after these operations and the existence of control mechanisms against unusual connections to the retina in this bony fish. © 1993 John Wil

ISSN:0022-3034    

DOI:10.1002/neu.480240106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the rat, the central part of the medial preoptic nucleus (MPNc) of the male is larger in volume and has a greater number of neurons than that of the female. The nucleus of the female, however, can be “sex reversed” by exposing the rat to gonadal steroids perinatally. The purpose of the present study was to examine the development of the MPNc to determine when the sex difference first appears and whether this difference occurs due to the relative accumulation of neurons into the compact part of the MPNc of the male and sex‐reversed female rat or to the loss of MPNc neurons in the control female. Pregnant, female Sprague‐Dawley rats were given an injection of [3H]methyl thymidine on embryonic day 18 (E18). Rats were exposed to testosterone propionate (TP) or vehicle from E20 to postnatal day 10 (PN10) or until the time of sacrifice. Pups from three groups [males (oil), females (oil), and sex‐reversed females (TP)]were sacrificed on PN2, PN4, PN7, PN10, or PN30. The volume of the compact part of the MPNc increased in males and sex‐reversed females after PN4 but the volume in the nucleus of females remained relatively constant. The number of neurons and [3H]thymidine‐labeled cells remained elevated from PN2–PN30 in males or sex‐reversed females but decreased dramatically in oiltreated females between PN4 and PN7, reaching a minimal number by PN10. Cell cross‐sectional area increased with age while cell density decreased. These observations are consistent with the hypothesis that the lack of growth of the compact part of the MPNc of the female is due to a loss of neurons while the increase in volume of the male's nucleus is due at least in part to growth of its constituent neurons. © 1993

ISSN:0022-3034    

DOI:10.1002/neu.480240107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA wide variety of cell types respond to electric fields in culture. Despite evidence for electric fields existing in the mammalian embryo, there are few studies testing the effects electric fields exert on neurons from the mammalian central nervous system (CNS). The present study demonstrates orientation responses to focally applied electric fields of embryonic rat hippocampal neurons isolated in culture. The most striking result from this study is that different growth cones of the same neuron can show differential responsiveness to focally applied electric fields: growth cones on the short straight processes that are destined to become dendrites, oriented toward the cathode, whereas growth cones on the longest process, the presumptive axon, did not orient. The present experiments bring a significant increase in resolution to the study of neuronal growth cone orientation by applied electric fields: a novel examination of the early events leading to orientation. Growth cones on dendrites displayed a spectrum of orientation responses: directed lamellipodial extension, directed filopodial extension and/or reorientation, cytoplasmic swelling of existing filopodia, consolidation of filopodia, and rapid elongation of the entire process. Individual growth cones displayed only one or two of these responses. Additionally, not all growth cones on these short processes sustained their initial orientation response: 35% adapted within 6 min. © 1993 John Wiley&Sons, Inc

ISSN:0022-3034    

DOI:10.1002/neu.480240108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe appearance of Substance P (SP) and Neuropeptide Y (NPY) has been studied using light microscopic immunocytochemical labeling throughout the complete developmental span ofMacaca nemestrinamonkey striate cortex. In the adult, 80% of the NPY + neurons occur in the white matter (WM) and most of the remainder are medium to large multipolar neurons in layer 2. Fibers occur in all layers except 4C and are very numerous, given the relatively small number of NPY+ cell bodies. NPY+ neurons first were seen at embryonic day (E) 75. Most neurons were in the intermediate zone (IZ), but a few were in the immature cortical plate (CP). An adultlike distribution was present by E125 for neurons and by birth for fibers, but fiber staining intensity and number increased to postnatal year 1 (P1yr). In adult cortex, numerous SP+ nonpyramidal neurons were present in layers 2–6 and WM, but SP+ fibers were surprisingly infrequent. During development, significant numbers of SP+ neurons were not seen in the CP until E113–125. Later prenatal ages had a prominent plexus of SP+ cell bodies and fibers at the layer 5/6 border. This plexus disappeared by P12wk due to either down‐regulation of SP or cell death. SP+ neurons in IZ/WM were very sparse until birth after which they increased in number and staining intensity up to P1yr, suggesting a postnatal up‐regulation of SP in a preexisting WM subpopulation. Cell densities were determined for SP, NPY, and the neuron‐specific marker microtubule‐associated protein 2 (MAP2) to clarify the developmental dynamics of IZ/WM neurons. MAP2+ cell densities in WM peaked around birth and then declined 20% in the outer half and 77% in the inner half of WM. SP+ cell density rose 57% from birth to P20wk and then declined 20% into adult hood. NPY+ cell density was fairly constant prenatally and then rose 300% by adulthood. Neuropeptide cell density changes took place predominatly in the outer WM. These data indicate that cell death does occur in the general population of monkey striate cortical WM neurons. In contrast, both SP+ and NPY+ cells are characterized by minimal cell death and a late expression of neuropeptides which causes an increase in neuropeptide+ cell density in postnatal WM. © 1993 John Wil

ISSN:0022-3034    

DOI:10.1002/neu.480240109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe larval–pupal transformation ofManduca sextais accompanied by the loss of the abdominal prolegs. The proleg muscles degenerate, the dendritic arbors of proleg motoneurons regress, and a subset of the proleg motoneurons dies. The regression and death of proleg motoneurons are triggered by the prepupal peak of ecdysteroids in the hemolymph. To investigate the possible involvement of protein synthesis in these events, we gave insects repeated injections of the protein synthesis inhibitor, cycloheximide (CHX), during the prepupal peak. Examination of insects 3–5 days following CHX treatment showed that CHX inhibited the death of proleg motoneurons and the production of pupal cuticle in a dose‐dependent fashion. When insects were allowed to survive for 10 days after the final CHX injection, motoneuron death and pupal cuticle production sometimes occurred belatedly, apparently in response to the ecdysteroid rise that normally triggers adult development. CHX treatments that inhibited motoneuron death were less effective in inhibiting dendritic regression in the same neurons. In another set of experiments, abdomens were isolated from the ecdysteroid‐secreting glands prior to the prepupal peak, and infused with 20‐hydroxyecdysone (20‐HE). Single injections of CHX delivered just prior to the start of the 20‐HE infusion inhibited motoneuron death and pupal cuticle production, but in the range of doses tested, did not prevent dendritic regression. Our findings suggest that protein synthesis is a required step in the steroid‐mediated death of proleg motoneurons, and that dendritic regression is less susceptible to inhibition by CHX than is motoneuron death. © 1993 John

ISSN:0022-3034    

DOI:10.1002/neu.480240110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0022-3034    

DOI:10.1002/neu.480240101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY