摘要:

AbstractThe inhibitory effect of capsaicin on axoplasmic transport in cultured dorsal root ganglion cells was analyzed by video‐enhanced contrast microscopy. Capsaicin inhibited particle transports in a dose‐dependent manner, irrespective of the diameter of axons. The effect of capsaicin was reversible at low concentrations. Capsaicin affected both the anterograde and retrograde transport. Large organelles were more sensitive to capsaicin than small ones in the retrograde transport. An experiment using calcium‐sensitive dye, Fura 2, indicated that capsaicin raised the intraneuronal free calcium concentration preceding the inhibition of the transport. Electron microscopy revealed that microtubules and neurofilaments are disorganized and disoriented by capsaicin. We reached a conclusion that capsaicin inhibits fast axoplasmic transport of both anterograde and retrograde directions in all types of somatosensory neurons in culture by disorganizing intraaxonal cytoskeletal structures, through the elevated intracellular Ca2+concentration. © 1993 John Wiley&Son

ISSN:0022-3034    

DOI:10.1002/neu.480240502

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe marine gastropodAplysiahas a circadian clock in each eye that generates a circadian rhythm of optic nerve activity. The axons of pacemaker neurons carry the rhythmic activity to the brain where it can be recorded from various ganglionic connectives as it is distributed throughout the CNS. We had previously identified an eye‐specific 48‐kD protein using an antiserum, anti‐S, that recognizes theperiodgene product ofDrosophila. We have now obtained two partial amino acid sequences of the 48‐kD protein and raised a polyclonal antiserum using a synthetic peptide with the amino acid sequence of one of them. The antiserum recognizes a family of spots of Mr47–48 kD and Pi5.9–6.0 on 2D immunoblots of eye proteins. The immunoblot staining intensity does not exhibit a circadian rhythm. Used in immunocytochemistry, the antiserum recognizes fibers in the optic nerve and retinal neuropil, pacemaker neurons, certain photoreceptors, and the photoreceptor rhabdom layer. It stains the optic nerve fibers and optic fiber terminals in the cerebral optic ganglion and recognizes the cerebral optic tracts, putative synaptic exchange areas, and optic tract projections from the cerebral ganglion into various head nerves and interganglionic connectives. The function of the 48‐kD protein is not known but it could be involved in the maintenance or regulation of the retinal afferent pathways, including the pacemaker neuron axons, known from previous axonal transport and electrical recording studies to be the circadian output pathway. © 1993 John W

ISSN:0022-3034    

DOI:10.1002/neu.480240503

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe regulation of the expression of substance P (SP) in the rat superior cervical ganglion was compared to that of vasoactive intestinal peptide (VIP)in vivoafter axotomy andin vitroafter explantation. Previous studies have demonstrated that both neuropeptides increase after explantation, depolarization, and decentralization; however, whereas VIP expression increases after postganglionic axotomy, SP expression reportedly does not. To compare the effect of axotomy on these two peptides directly, the content of both was determined in individual ganglia at various times after surgery. The level of VIP‐like immunoreactivity (IR) is increased at 2 days, reaches a peak at 6 days, and then declines by 14 days to approximately half its peak value. The level of SP‐IR also increases 2 days after axotomy, but returns to control values by day 6. The increase in SP‐IR is accompanied by an increase in β‐preprotachykinin mRNA, suggesting that the elevation in SP content is due, at least in part, toenhanced peptide synthesis. Immunocytochemical localization of SP‐IR revealed the presence of immunoreactive principal neurons in axotomized, but not in sham‐operated ganglia. Similarities in the regulation of these two neuropeptides were also investigated in organ culture by examining the effects of dexamethasone and interleukin‐1β on VIP content, since the former has been shown to prevent the increase in SP in culture, while the latter has been found to enhance this increase (Kessler, Adler, Bell, et al., 1983,Neuroscience9:309–321; Freidin and Kessler, 1991,Proc. Natl. Acad. Sci. USA88:3200–3203; Hart, Shadiack, and Jonakait, 1991,J. Neurosci. Res.29:282–291). As with SP expression, dexamethasone reduces the increases in VIP expression, while interleukin‐1β increases it. Thus, bothin vivoandin vitro, similar changes in VIP and SP expression are observed following a number of experimental manipulations, suggesting that expression of the two peptides is regulated by qualitatively similar mechanisms in sympathetic neurons. ©

ISSN:0022-3034    

DOI:10.1002/neu.480240504

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

年代:1993

数据来源: WILEY

摘要:

AbstractDuring adult metamorphosis, the moth olfactory neurons and their glia‐like support cells pass through a coordinated and synchronous development. By 60% of development, the olfactory system is anatomically complete, but functional maturation does not occur until about 90% of development. Maturation is characterized by the onset of odorant sensitivity in the sensory neurons and the expression of certain antennal‐specific proteins including odorant binding proteins (OBPs) and odorant degrading enzymes (ODEs). The OBPs have been cloned and sequenced, and are thus useful models for investigating the molecular mechanisms coordinating final maturation of the developing olfactory system. The ecdysteroid hormones have been observed to regulate many cellular level neuronal changes during adult metamorphosis. In particular, the late pupal decline in ecdysteroids is known to influence programmed death of nerves and muscles at the end of metamorphoses. Experiments are presented here which indicate that this decline in ecdysteroids also induces the expression of the OBPs. Normal OBP expression occurs 35–40 h before adult emergence. In culture, OBP expression could be induced at least 90 h before adult emergence by the premature removal of ecdysteroid. This premature expression was blocked by culturing tissue in the presence of the biologically active ecdysteroid 20‐hydroxyecdysone. These findings suggest that maturation of the olfactory system is regulated by the decline in ecdysteroids, and support the view that olfactory development, in general, may be coordinated by chaging levels of pupal ecdysteroids. © 1993 John Wiley&S

ISSN:0022-3034    

DOI:10.1002/neu.480240505

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe modulatory actions of the biogenic amine octopamine on the femur tibia (FT) control loop in the stick insectCarausius morosuswere examined. The response properties of the FT control loop were determined under open loop conditions. Mechanical stimulation of the femoral chordotonal organ (fCO) was the input and tibial movement and motoneuronal activity were measured as the output of the system. Following octopamine injection into the hemolymph of intact, inactive animals, two consecutive phases occurred at the behavioral level. Octopamine caused initially an activation of the animal. During this first phase (3.5–12 min duration) the response properties of the FT control loop were similar to those found in animals that were activated by tactile stimuli under normal conditions. Afterward, animals became inactive. During this second phase (15–20 min duration), the gain of the control loop was zero and no resistance reflex in the FT joint was generated in response to fCO stimulation. However, active movements of the tibia could still be elicited. As we could show in restrained animals, where dl‐octopamine was applied topically onto the undesheated mesothoracic ganglion, the complete suppression of the resistance reflex on the motoneuronal level was dose dependent starting at concentrations of 5 ± 10−3Moctopamine. We could show that octopamine specifically suppressed the pathways involved in the resistance reflex, while feedback loop responses to fCO stimuli typical for active animals could still be elicited. Our results indicate that an increase in the octopamine concentration mimicks activation of the animal: Properties being characteristic for the control of the FT joint in the inactive animal are inhibited by octopamine, while properties of the FT control loop typical for the active animal appear to be facilitated following octopamine injection. The results clearly demonstrate that different pathways in the neuronal network underlying the FT control loop are involved in the responses of the control loop to fCO stimuli in the inactive and active behavioral states of the stick insect. © 1993 John Wiley&

ISSN:0022-3034    

DOI:10.1002/neu.480240506

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe longitudinal glia (LG), progeny of a single glioblast, form a scaffold that presages the formation of longitudinal tracts in the ventral nerve cord (VNC) of theDrosophilaembryo. The LG are used as a substrate during the extension of the first axons of the longitudinal tract. I have examined the differentiation of the LG in six mutations in which the longitudinal tracts were absent, displaced, or interrupted to determine whether the axon tract malformations may be attributable to disruptions in the LG scaffold. Embryos mutant for the geneprosperohad no longitudinal tracts, and glial differentiation remained arrested at a preaxonogenic state. Two mutants of the Polycomb group also lacked longitudinal tracts; here the glia failed to form an oriented scaffold, but cytological differentiation of the LG was unperturbed. The longitudinal tracts in embryos mutant forslitfused at the VNC midline and scaffold formation was normal, except that it was medially displaced. Longitudinaltracts had intersegmental interruptions in embryos mutant forhindsightandmidline. Inhindsight, there were intersegmental gaps in the glial scaffold. Inmidline, the glial scaffold retracted after initial extension. LG morphogenesis during axonogenesis was abnormal inmidline. Commitment to glial identity and glial differentiation also occurred before scaffold formation. In all mutants examined, the early distribution of the glycoprotein neuroglian was perturbed. This was indicative of early alterations in VNC pattern present before LG scaffold formation began. Therefore, some changes in scaffold formation may have reflected changes in the placement and differentiation of other cells of the VNC. In all mutants, alterations in scaffold formation preceded longitudinal axon tract formation. © 1993 John Wiley&Sons, Inc

ISSN:0022-3034    

DOI:10.1002/neu.480240507

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

年代:1993

数据来源: WILEY

摘要:

AbstractBrain nuclei that control song are larger in male canaries, which sing, than in females, which sing rarely or not at all. Treatment of adult female canaries with testosterone (T) induces song production and causes song‐control nuclei to grow, approaching the volumes observed in males. For example, the higher vocal center (HVC) of adult females approximately doubles in size by 1 month following the onset of T treatment. Male HVC projects to a second telencephalic nucleus, RA (the robust nucleus of the archistriatum), which projects in turn to the vocal motor neurons. Whether HVC makes a similar connection in female canaries is not known, although HVC and RA are not functionally connected in female zebra finches, a species in which testosterone does not induce neural or behavioral changes in the adult song system. This experiment investigated whether HVC makes an efferent projection to RA in normal adult female canaries, or if T is necessary to induce the growth of this connection. In addition, we examined whether T‐induced changes in adult female canary brain are reversible. Adult female canaries received systemic T implants that were removed after 4 weeks; these birds were killed 4 weeks after T removal (Testosterone‐Removal, T‐R). Separate groups of control birds received either (a) T implants for 4 weeks which were not removed (Testosterone‐Control, T‐C) or (b) empty implants (Untreated Control, øO‐C). Crystals of the fluorescent tracer DiI were placed in the song‐control nucleus HVC in order to anterogradely label both efferent targets of HVC, RA and Area X. Projections from HVC to RA and Area X were present in all treatment groups including untreated controls, and did not appear to differ either qualitatively or quantitatively. Thus, formation of efferent connections from HVC may be prerequisite to hormone‐induced expression of song behavior in adult songbirds. The volumes of RA and Area X were measured using the distribution of anterograde label as well as their appearance in Nissl‐stained tissue. RA was larger in T‐treated control birds than in untreated controls. Experimental birds in which T was given and then removed (T‐R) had RA volumes closer in size to untreated controls (ø‐C). Because the volume of RA in T‐treated controls (T‐C) was larger than that of birds that did not receive T (ø‐C), we conclude that the volume of RA increased in both T‐C and T‐R birds but regressed upon removal of T in T‐R birds. Surprisingly, the volume of Area X did not increase in T‐treated birds. Birds in this study were maintained on short days, suggesting that T‐induced growth of Area X reported previously may have resulted from an interaction between T and another seasonal or photoperiodic factor induced by exposure to

ISSN:0022-3034    

DOI:10.1002/neu.480240508

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe differentiation of vagal motor neurons and their emerging central relationship with vagal sensory afferents was examined in fetal rats. To identify peripherally projecting sensory and motor neurons, 1,1′‐dioctadecyl 3,3,3′,3′‐tetramethylindocarbocyanine perchloarate (DiI) was inserted into the proximal gut or cervical vagus nerve in fixed preparations. At embryonic day (E) 12, labeled vagal sensory neurons are present in the nodose ganglia and a few sensory axons project into the dorsolateral medulla. Central sensory processes become increasingly prevalent between E13 and E14 but remain restricted to the solitary tract. Vagal motor neurons are first labeled at E13, clustered within a region corresponding to the nucleus ambiguus (NA). Additional motor neurons appear to be migrating toward the NA from the germinal zone of the fourth ventricle. Motor neurons in the dorsal motor nucleus of the vagus (DMV) first project to the gut at E14 and have processes that remain in physical contact with the ventricular zone through E16. Sensory axons emerge from the solitary tract at E15 and project medially through the region of the nucleus of the solitary tract (NST) to end in the ventricular zone. A possible substrate for direct vagovagal, sensorimotor interaction appears at E16, when vagal sensory fibers arborize within the DMV and DMV dendrites extend into the NST. By E18, the vagal nuclei appear remarkably mature. These data suggest specific and discrete targeting of vagal sensory afferents and motor neuron dendrites in fetal rats and define an orderly sequence of developmental events that precedes the establishment of vagal sensorimotor circuits. © 1993 John Wiley

ISSN:0022-3034    

DOI:10.1002/neu.480240509

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

年代:1993

数据来源: WILEY

摘要:

AbstractWhen the electric organ (EO) of weakly electric fish is amputated, a blastema forms from which new EO and muscle cells arise. However, the progenitor cells that contribute to the blastema are unknown. We studied regeneration of the electric organ inSternopygusto answer this question. The EO of this species is composed of electrocyte cells surrounded by peripheral bundles of muscle fibers. Fish were injected with 5′‐bromodeoxyuridine (BrdU) 24 h after amputating the terminal portion of the EO. At this time, a population of small cells were labeled in the extracellular matrix between electrocytes and muscle fibers. These cells did not label in control fish injected with saline or in nonamputated BrdU‐injected fish. For the first 6 days postamputation, increasing numbers of BrdU‐labeled cells appeared at the wound margin. A blastema formed 6 days after amputation and contained numerous BrdU‐labeled cells. At 10 days postamputation, clusters of BrdU‐positive cells were seen throughout the wound margin and proximal blastema. At 14 days, BrdU‐labeled nuclei were present within developing electrocytes. Labeling alternate sections with MF20 antimyosin and AE1 anticytokeratin antibodies confirmed that BrdU‐positive multinucleate cells coexpress myosin and cytokeratin epitopes, diagnostic of newly regenerated electrocytes. Electron micrographs reveal that the small cells surrounding muscles and electrocytes are similar; they contain an elongate nucleus, are largely devoid of cytoplasm, and possess few organelles. This morphology and evidence of myogenic potential suggests that these cells are satellite cells. © 1993 John

ISSN:0022-3034    

DOI:10.1002/neu.480240510

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

年代:1993

数据来源: WILEY

摘要:

AbstractTo determine how voltage‐gated ion channels segregate between sibling cells at cytokinesis, we used a whole‐cell patch clamp to measure the electrophysiological phenotypes of siblings within 45 min of division. Recently born siblings in an immortalized line of embryonic retinal cells were identified as pairs of spherical cells adhering to one another. All siblings were electrically coupled when cells were simultaneously voltage clamped, whereas nonsiblings were not coupled. Twelve paris of siblings were electrically isolated by mechanical separation so that their phenotypes could be measured independently. Cells expressed two principal membrane conductances, delayed rectifier‐like (IK) and inward rectifier (IK(IR)) potassium currents. Despite qualitative and quantitative variability inIKandIK(IR)expression within the population, each cell of a given pair expressed similar steady‐state current densities between –110 and +50 mV. We estimatedIK(IR)slope conductance by blocking the current specifically with 5 mM Cs and calculatedIK(IR)ratios in siblings and nonsiblings. Three pairs of siblings expressedIK(IR)ratios of approximately 1.2, while ratios in three pairs of adhered nonsiblings varied between 1.6 and 5.4. When currents were sampled continuously through cytokinesis by using the perforated‐patch recording mode, current amplitude showed no net change within 30 min of division. Because channel number did not appear to change in siblings during this interval, parental channels were inherited by each daughter in proportion to the area of membrane received. Heterogeneity therefore arises after siblings reenter interphase and is not due to the asymmetrical segregation of channels at cytokinesis. © 1993 John Wil

ISSN:0022-3034    

DOI:10.1002/neu.480240511

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

年代:1993

数据来源: WILEY