摘要:

AbstractWe have applied thin sectioning and freeze‐fracture techniques to investigate the terminal loop structure of photoreceptive disks in frog retinal rod outer segments. Our studies of this region demonstrate a highly curved terminal loop bilayer that is continuous with both lamellar bilayers of the disk, and equivalent to them in dimensions and staining properties. Rhodopsin, however, appears to be excluded from this region of high curvatur

ISSN:0092-7317    

DOI:10.1002/cne.902570102

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn addition to a lipid bilayer component (Corless, Fetter, and Costello:J. Comp. Neurol. 257:1–8, '87), the terminal loop region of frog rod outer segment (ROS) disks displays a clustering of discrete elements referred to as theterminal loop complex.It consists of (1) semicircular or crescentic densities within the terminal loop, (2) linear interdisk densities spanning the cytoplasm near terminal loops, and (3) distinctive freeze‐fracture particles associated with the terminal loop, located between 1 and 2.The linear interdisk densities are organized on a two‐dimensional lattice that appears to ensheath completely the lamellar domains of all ROS disks. Indirect evidence is presented for a net axial alignment of intraloop densities. We interpret the large freeze‐fracture particles of the terminal loop region to reflect transmembrane components that connect the interdisk and intraloop densities. Thus, we propose that the entire terminal loop (TL) complex is organized on a two‐dimensional net. We further infer that each TL complex is organized as a dimeric unit and that such dimers interact axially and laterally to generate the observed lattice structure. It is suggested that one component of the terminal loop complex is the high molecular weight protein localized along the disk perimeter by Papermaster, Schneider, Zorn, and Kraehenbuhl (J. Cell Biol 78:415

ISSN:0092-7317    

DOI:10.1002/cne.902570103

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe perimeter of rod outer segment (ROS) disks displays a two‐dimensional lattice of components referred to as the terminal loop complex (Corless, Fetter, Zampighi, Costello, and Wall‐Buford:J. Comp. Neurol 257: 9–23, '87b). We take the view that this pattern of structural organization reflects the mechanism(s) whereby the disk perimeter is defined and constructed. Herein we develop and partially evaluate a generalized template mechanism of disk perimeter development, to account for the structure and the axial alignment of both marginal and incisural domains. Components of the terminal loop complex are conceived as the morphogens that determine the location and guide the differentiation of the disk perimeter. Briefly, we postulate that transmembranous components of the terminal loop complex are present within the reflection of plasmalemma that forms the base of the rod outer segment. These components interact with thecytoplasmictemplate provided by the perimeter lattice present along the lower surface of the most basal disk, thereby propagating the lattice and creating an extracellular template. The latter is then available to interact with corresponding elements distributed, within the apical surface of the adjacent disk precursor evagination. The progressive interaction and alignment of these extracellular domains form the scaffolding that guides the restructuring of the plasmalemma, to form the mature disk margin topology. Successive repetitions of this process are seen to produce an axial stacking of disks whose perimeters are aligned and ensheathed by a two‐dimensional net.Several predictions of the model are developed and ev

ISSN:0092-7317    

DOI:10.1002/cne.902570104

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

年代:1987

数据来源: WILEY

摘要:

AbstractCortical projections arising from areas 4 and 6 and terminating in midbrain cell groups known to project to the inferior olive (IO) have been studied in the cat. Injections of the bidirectional tracers horseradish peroxidase (HRP) and wheat germ agglutinin (WGA) conjugated to HRP were made into the midbrain. All cases of lateralized midbrain injections resulted in virtually ipsilateral labelling of lamina V cortical neurons. Retrogradely labelled neurons in cortical areas 4 and 6 were found after injections located in the interstitial nucleus of Cajal (INC), nucleus of Darkschewitsch (ND), and in the caudal parafascicular (Pf) and subparafascicular (sPf) nuclei (perifascicular region, PF). Injections that were more caudal and within the parvi‐ and magnocellular red nucleus (RNp and RNm) labelled cells not only in areas 4 and 6 but also in portions of adjacent areas 3a, 3b, 5a, and 7. These midbrain injections also resulted in the anterograde labelling of projections observed to terminate in the ipsilateral IO.The distribution in the midbrain of projections arising from cortical areas 4 and 6, and portions of areas 3a and 3b, was studied with autoradiographic methods. After injections of tritium‐labelled amino acids in those cortical areas, a pattern of largely ipsilateral terminations was revealed. Whereas all cortical areas studied labelled the PF, differential grain distributions in central mesencephalic nuclei were apparent after injections in various portions of the motor and adjacent somatosensory cortex. Injections involving the frontal eye fields (FEF) labelled the INC bilaterally, but ipsilateral terminations were densest. These cases also labelled the region of the fields of Forel. When the neck region of the cortex was involved in the injections, the more caudal aspects of the INC (INCc) and the RN were labelled. The cortical areas related to the upper limb gave rise to terminations in the ND and the RNp. Contributions to both ND and RNp inputs from injections in the FEF and neck regions were also occasionally but not consistently noted. A relatively discrete injection in the vibrissae field weakly labelled ND. Additional components of the motor cortical projections to the superior colliculus (SC) and pretectal nuclei were also analysed since those regions also project to the IO. Cortical regions involving the representation of the neck musculature were shown to project principally ipsilaterally to lamina IV of the SC as well as to the anterior pretectal nucleus. The densest SC terminations were found in cases involving the presylvian FEF, and only those cases had additional labelling in the posterior pretectal nucleus.These topographic relations indicate that certain collicular, pretectal, and mesodiencephalic neuronal groups relay somatotopically, and perhaps functionally, specific information from the cortex to the IO. In comparison with the direct corticoolivary projection, which involves primarily neck, axial, proximal forebody, and FEF cortical areas, the motor cortical projection to the midbrain arises from the entire somatic representation in the motor cortex and adjacent portions of the somatosensory cor

ISSN:0092-7317    

DOI:10.1002/cne.902570105

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

年代:1987

数据来源: WILEY

摘要:

AbstractA study has been made, using Golgi preparations, of the organization of neurons with smooth or sparsely spined dendrites, here called local circuit neurons, of the macaque monkey primary visual cortex. Since these neurons include those responsible for inhibitory circuitry of the cortex, a better understanding of their anatomical organization is essential to concepts of functional organization of the region. This account describes those neurons found with cell body and major dendritic spread within the thalamic recipient zone of lamina 4C and its border zone with lamina 5A. The neurons are grouped firstly in terms of in which laminar division the soma occurred– 4CβbT, 4CβaL or the border zone of 5A‐4CβbT–and secondly, into varieties on the basis of the interlaminar projection patterns of their axons. Most, if not all, of the local circuit neurons of these divisions have interlaminar axon projections as well as an arbor local to their cell body and dendritic field. These interlaminar projections are highly specific, targeting from one to five laminar divisions depending on the variety of neuron; on this basis 17 varieties of local circuit neuron are described. While the number of varieties appears dauntingly large in terms of understanding the functional circuitry of the region, the clear‐cut organization of the interlaminar links may provide clues as to the information processing that concerns each neuron. The local circuit neuron axon projections can be related to a wealth of information already available concerning the laminar organization of afferent axons and efferent cell groups, the organization of spiny neuron intrinsic relays (presumed to be excitatory), and physiological properties of different laminar divisions. It is hoped that the information derived from this study can serve as a guide for correlated physiological‐anatomical studies on single cells o

ISSN:0092-7317    

DOI:10.1002/cne.902570106

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution of neuropeptide Y (NPY)‐like immunoreactivity within the hypothalamus of the adult golden hamster was investigated with conventional immunohistochemical techniques. Neuropeptide Y immunoreactive cell bodies were found in greatest numbers in the arcuate nucleus while a few stained perikarya were seen in the internal and subependymal zones of the median eminence. Isolated perikarya were observed in the anterior commissure and supracommissural portion of the interstitial nucleus of the stria terminalis. Immunoreactive axons were located throughout the hypothalamus with the highest concentrations in the subependymal and internal zones of the median eminence, the interstitial nucleus of the stria terminalis, the medial preoptic area, and in the following nuclei: periventricular, suprachiasmatic, paraventricular, perifornical, median preoptic, and arcuate. Moderate to dense plexuses of immunoreactive fibers were observed in the anterior, lateral, and posterior hypothalamic areas and in the infundibular stalk. The supraoptic nucleus and lateral preoptic area displayed a small number of labeled axons whereas the ventromedial nucleus contained only a few fibers. NPY immunoreactive fibers were present in the optic tract and in the dorsomedial aspect of the optic chiasm. Labeled fibers penetrated the ependymal lining of the third ventricle throughout the ventral aspect of the periventricular zone. Additional fibers were observed in the pia lining the ventral aspect of the hypothalamus. This systematic analysis of hypothalamic NPY immunoreactivity in the adult golden hamster suggests that a portion of the labeled fibers display a distribution that is similar to previously described noradrenergic fibers in the hypothalamu

ISSN:0092-7317    

DOI:10.1002/cne.902570107

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution of thalamocortical neurons projecting to layer I of the cat auditory cortical fields was examined by the horseradish peroxidase (HRP) method. After HRP injection into layer I of the primary auditory cortex (AI), HRP‐labeled neuronal cell bodies were distributed mainly in the medial, dorsal, and ventrolateral divisions of the medial geniculate nucleus CMGN and suprageniculate nucleus (Sg), and additionally in the lateral and medial divisions of the posterior group of the thalamus (Pol and Pom), lateroposterior thalamic nucleus (Lp), and nucleus of the brachium of the inferior colliculus (BIN). After HRP injection into layer I of the second auditory cortex (AII), labeled neurons were seen mainly in the medial, dorsal, and ventrolateral divisions of the MGN and Sg and additionally in the Pom, Lp, and BIN. After HRP injection into layer I of the anterior auditory field (AAF), labeled neurons were located mainly in the medial and dorsal divisions of the MGN, Sg, Pol, and BIN, and additionally in the ventrolateral divisions of the MGN, Pom, and Lp. After HRP injection into layer I of the dorsal part of the posterior ectosylvian gyrus (Epv), labeled neurons were observed chiefly in the medial and dorsal divisions of the MGN, Sg, and Lp and additionally in the ventrolateral division of the MGN, Pom, and BIN. After HRP injection into layer I of the ventral part of the posterior ectosylvian gyrus (Epv), labeled neurons were distributed chiefly in the medial and dorsal divisions of the MGN and Pol and additionally in the ventrolateral division of the MGN, Sg, and BIN. Thus no labeled neurons were found in the ventral division of the MGN after HRP injection into layer I of all auditory cortical fields examined in the present study. The average soma diameters of neurons that were labeled after HRP injection into layer I were statistically smaller than those of neurons that were labeled after HRP injection into layer I

ISSN:0092-7317    

DOI:10.1002/cne.902570108

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

年代:1987

数据来源: WILEY

摘要:

AbstractCertain neurons of dorsal root ganglia (DRG) and some fibers of the sciatic nerve contain histochemically demonstrable carbonic anhydrase activity. Since the distribution of this enzyme throughout the nervous system has not yet been evaluated systematically, we conducted a comprehensive histochemical survey focusing particularly on structures derived from the neural crest and nonneural crest ectoderm. In the peripheral nervous system, we observed carbonic anhydrase activity in some, but not all, neurons of dorsal root, trigeminal, celiac, and myenteric ganglia as well as in glial cells throughout the CNS. Some neurons of the nodose ganglion also showed carbonic anhydrase activity. In all first order sensory ganglia that were studied, the enzyme was found only in large (50 μm or above) and medium (20–50 μm) size neurons; in the case of spinal ganglia, the reactive neurons constituted approximately 30% of the total neuronal population. Of these reactive neurons, 56% were heavily stained and 44% were moderately stained. Several possible roles for neuronal carbonic anhydrase are conside

ISSN:0092-7317    

DOI:10.1002/cne.902570109

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

年代:1987

数据来源: WILEY

摘要:

AbstractA well‐defined, gonadotropin‐releasing hormone (GnRH)‐containing fiber pathway, the ventral hypothalamic tract (VHT), is described by immunostaining in fetal rhesus macaques (109–156 days gestation). The VHT arises above the lateral aspects of the optic chiasm near the supraoptic nucleus, and courses ventromedially close to the ventral hypothalamic surface to terminate in the infundibulum and zona externa of the median eminence. It is formed by the confluence of GnRH‐immunopositive (GnRH +) axons from local neurons, from a few GnRH+ cells in the inferior thalamic peduncle, and probably from more anterior neurons in the septum and preoptic area. Bipolar GnRH 4‐ neurons contributing directly to the VHT are grouped at its origin dorsolateral to the optic chiasm, dorsal and medial to the optic tracts, at the infundibular lip, and within the pathway between. At the infundibular lip, GnRH+ perikarya are generally lateral or ventral to the infundibular (arcuate) nucleus, and are rarely within the nucleus itself. Cell bodies here are sometimes tripolar, but GnRH+ intercellular contacts are seldom seen. A few VHT fibers extend to the ventral surface of the brain just beneath the pia mater. Abundant capillaries in the subarachnoid space suggest a possible route for delivery of GnRH to the adenohypophysis in early gestation, before maturation of the hypophysial portal system occurs. Posterior to the infundibulum, a few VHT fibers are joined by descending periventricular fibers forming a dense fiber band beneath the premammillary recess of the third ventricle.Totals of GnRH+ cell bodies in the prosencephalon of the fetal rhesus macaque are estimated to be 5,600 in females (n=2) and 2,600 in males (n=3). More than 60% of VHT neurons are located in the medial basal hypothalamus, and the majority of basal hypothalamic GnRH+ neurons (86%) are associated with the VHT. Furthermore, reports of the autonomy of the medial basal hypothalamic‐hypophysial unit in control of gonadotropin secretion suggest that the VHT may be the most important GnRH system involved in primate reproduction. It is clear that fetal material may offer the best model to study the GnRH neuronal syste

ISSN:0092-7317    

DOI:10.1002/cne.902570110

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe objective of this paper is to report the presence and localization of serotonin and dopamine in the retina of the lizardUta stansburiana.High performance liquid chromatography and electrochemical detection were used to identify and quantitate the two amines. Both compounds are present as endogenous molecules in this retina and are found in concentrations similar to those reported in other non‐mammalian retinas. The same methods were employed to confirm, in the isolated retina, the synthesis of serotonin from precursor, tryptophan.Immunocytochemical methods were used to localize, in the neural retina, serotonin and the rate‐limiting enzyme of dopamine synthesis, tyrosine hydroxylase. Serotonin immunoreactivity was observed in bistratified amacrine cells (ca.7 μU dia.) with processes ramifying in sublayers 1,4, and 5 of the inner plexiform layer. Immunoreactivity to tyrosine hydroxylase was observed in a different population of bistratified amacrine cells (ca. 11 μ dia.) that had processes ramifying in sublayers 1 and 5 (and perhaps 3) of the inner plexiform layer. The enzymes for further metabolism of dopamine were not found in the retina of this lizard by immunocytochemical methods.The results of this research suggest that only single classes of serotoninergic and dopaminergic neurons are present in the retina ofU. stansburiana.This retina might, therefore be an appropriate place in which to investigate the functioning of these amines in visual information proce

ISSN:0092-7317    

DOI:10.1002/cne.902570111

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

年代:1987

数据来源: WILEY