摘要:

AbstractWe have measured the spatial density of cones and rods in eight wholemounted human retinas, obtained from seven individuals between 27 and 44 years of age, and constructed maps of photoreceptor density and between‐individual variability. The average human retina contains 4.6 million cones (4.08–5.29 million). Peak foveal cone density averages 199,000 cones/mm2and is highly variable between individuals (100,000–324,000 cones/mm2). The point of highest density may be found in an area as large as 0.032 deg2. Cone density falls steeply with increasing eccentricity and is an order of magnitude lower 1 mm away from the foveal center. Superimposed on this gradient is a streak of high cone density along the horizontal meridian. At equivalent eccentricities, cone density is 40–45% higher in nasal compared to temporal retina and slightly higher in midperipheral inferior compared to superior retina. Cone density also increases slightly in far nasal retina. The average human retina contains 92 million rods (77.9–107.3 million). In the fovea, the average horizontal diameter of the rod‐free zone is 0.350 mm (1.25°). Foveal rod density increases most rapidly superiorly and least rapidly nasally. The highest rod densities are located along an elliptical ring at the eccentricity of the optic disk and extending into nasal retina with the point of highest density typically in superior retina (5/6 eyes). Rod densities decrease by 15–25% where the ring crosses the horizontal meridian. Rod density declines slowly from the rod ring to the far periphery and is highest in nasal and superior retina. Individual variability in photoreceptor density differs with retinal region and is similar for both cones and rods. Variability is highest near the fovea, reaches a minimum in the midperiphery, and then increases with eccentricity to the ora serrata. The total number of foveal cones is similar for eyes with widely varying peak cone density, consistent with the idea that the variability reflects differences in the lateral migration of photoreceptors during development. Two fellow eyes had cone and rod numbers within 8% and similar but not identical photorecep

ISSN:0092-7317    

DOI:10.1002/cne.902920402

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of CNS and PNS axotomy of the IVth nerve on cell death, soma size, axon size, and axon number were investigated. In adult cats, the IVth nerve was axotomised by using four surgical paradigms: (1) peripheral IVth nerve crush, (2) peripheral IVth nerve cut, (3) peripheral IVth nerve resection, and (4) a CNS IVth nerve cut in the velum. The extent of cell death resulting from each surgical paradigm was determined. Following axotomy distal to the decussation of the IVth nerves, cell death was least after nerve crush, intermediate after nerve cut, and maximal after resection of 5–7 mm of the nerve. Following axotomy at the decussation—a CNS lesion—most cells died but some successful regeneration was observed.Soma size measurements following a short‐term survival (3 days to 4 weeks) before the regenerating axons reached their target muscle revealed that somas of axotomised cells underwent hypotrophy within 1 week of axotomy and then gradually increased in size. They re‐attained normal size by 4 weeks postoperative when regenerating axons first reach their target. Following a long‐term survival (>2 months), somas were significantly hypertrophied, and the degree of hypertrophy was inversely related to the extent of cell survival up to a limit of 40% soma size increase.Counts and measurements of axons revealed that mean axon diameter of regenerated axons was much smaller than normal 3 months after axotomy, increased during the third to sixth postoperative months, but then showed no subsequent increase and remained below normal. In animals with cell death varying from 10% to 70%, the number of axons in the nerve was maintained constant at approximately 1,000. These data indicate that there is a mechanism for the production and maintenance of the appropriate number of regenerative axonal branches following axotomy. In animals in which cell death exceeded 70%, the number of axons was controlled by a maximum ratio of 3 to 4 axon branches per surviving cell.The results suggest that axon number is strongly influenced by the target muscle and that hypertrophy of regenerated cells is related to the number of axonal sprouts each cell has to produce and support in order to re‐establish the preoperative number of axons in the regenerated tr

ISSN:0092-7317    

DOI:10.1002/cne.902920403

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn the chicken, serotonin‐immunoreactive cells were widely distributed not only in the carotid body but also in the wall of the common carotid artery and around each artery arising from the common carotid artery. Almost all of the serotonin cells in the wall of the common carotid artery were intensely immunoreactive to the neuropeptide Y, met‐ and leu‐enkephalin antisera, whereas in the carotid body only a few cells were immunoreactive to these antisera. Innervation of the serotonin cells in and around arteries of chickens was investigated by immunohistochemistry and electron microscopy, in comparison with that of the carotid body. The serotonin cell groups in and around arteries, as well as the carotid body, received numerous peptidergic nerve fibers. Calcitonin gene‐related peptide (CGRP)‐and substance P‐immunoreactive varicose nerve fibers were densely distributed, and somatostatin‐immunoreactive fibers were moderately distributed in the serotonin cell groups. Galanin‐and vasoactive intestinal peptide (VIP)‐immunoreactive fibers were sparsely distributed in the cell groups. By electron microscopy, the serotonin cells in and around arteries were characterized by the presence of numerous dense‐cored vesicles, 70–220 nm in diameter. The granule‐containing cells were in close association with numerous axons. Naked axons regarded axon terminals were frequently apposed on the granular cells. The axon terminals were usually long and often partly invested the granular cells. Numerous synaptic junctions were detected along the contact between the granular cells and axon terminals. Most of the synaptic junctions showed afferent morphology; the secretory granules were accumulated near and attached to the asymmetrical membrane thickenings. Thus, the serotonin cells in and around arteries, like the carotid body, constitut

ISSN:0092-7317    

DOI:10.1002/cne.902920404

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

年代:1990

数据来源: WILEY

摘要:

AbstractCell proliferation was studied in the retina of rabbits at various postnatal stages. Autoradiography was performed with animals that received a single injection of3H‐thymidine and were sacrificed 1 hour later. This short survival time allowed the determination of the position of a cell undergoing DNA synthesis at that moment.Between birth and day 6, cells engaged in DNA synthesis were seen in the inner nuclear layer (INL) of the entire retina. Cytogenesis ceases in this layer after the first postnatal week. Few labeled cells were detectable in the INL at day 9; these were found close to the ora serrata. Thus neurogenesis, which is known to occur in this layer of the retina, ceases by that time.In the nerve fiber layer (NFL), labeled cells were found at all ages between birth and day 27, which was the oldest stage examined in this study. By using horizontal sections through the NFL of entire retinae, it was observed that almost all labeled cells were confined to the medullary ray region, which is the neuroglia (astrocyte and oligodendrocyte)‐ bearing part of the NFL. Microglial cells, the only cellular elements present in the NFL outside the medullary ray region, were rarely labeled, and thus do not play a major role in gliogenesis occurring in the NFL. In addition to neuroglia, some endothelial cells were labeled after day 9. It is concluded that gliogenesis taking place in the NFL persists after the cessation of neurogenesis, suggesting that both processes occur independen

ISSN:0092-7317    

DOI:10.1002/cne.902920405

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe objective of this study was to determine the sources of cholecystokinin within the neostriatum of the cat. Cholecystokinin‐immunoreactive cells and fibers were detected by means of the peroxidase antiperoxidase immunohistochemical technique. This method was combined with intrastriatal injections of the retrograde marker horseradish peroxidase conjugated with wheatgerm agglutinin to survey the possible afferent sources of cholecystokinin to the feline neostriatum. Intrinsic, apparently aspiny cholecystokinin‐immunoreactive neurons organized in a pericapsular pattern were found within both the caudate and putamen of the cat. In addition, both thalamostriatal and mesostriatal projections containing cholecystokinin were observed. These results indicate that cholecystokinin within the neostriatum of the cat arises from both intrinsic and extrinsic si

ISSN:0092-7317    

DOI:10.1002/cne.902920406

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

年代:1990

数据来源: WILEY

摘要:

AbstractPrimary gustatory neurons and their peripheral and central processes were evaluated histochemically in the geniculate and petrosal cranial nerve ganglia, lingual fungiform taste buds, and the nucleus of the solitary tract (NST) using (1) the plant lectinGriffonia simplicifoliaI‐B4, which binds specifically to D‐galactose residues and selectively labels primarily nonpeptidecontaining peripheral somatosensory neurons, and (2) calcitonin gene‐related peptide immunoreactivity (CGRP‐IR), which labels most peptidergic somatosensory neurons.Lectin reactivity was expressed by the vast majority of geniculate and petrosal ganglion cells, while CGRP‐IR labeled very few cells. Peripherally, gustatory intragemmal axons penetrating fungiform taste buds were labeled only by the lectin and were depleted following chorda tympani transection. However, both lectin‐labeled and CGRP‐IR subpopulations of somatosensory perigemmal axons surrounding the taste buds were observed and were eliminated by section of the lingual nerve. The differing brainstem projection patterns of lectin‐reactive vs. CGRP‐IR central axons reflected their distinct ganglionic origins and the differential distributions of lectin reactivity and CGRP‐IR among taste buds. Central lectin‐reactive terminals were found throughout the entire rostrocaudal extent of the NST, including its rostral lateral “gustatory” zone; the extensive lectin‐reactive visceral afferent projection can be presumed to have originated mainly from the large proportion of lectinlabeled neurons in the nodose ganglion. The lectin also prominently and selectively labeled the area postrema. CGRP‐IR central terminals, however, was relatively sparse and restricted primarily to the caudal and medial “visceral” divisions of the NST.The results are discussed with respect to the possible functional implications of cell surface glycoconjugate expression by gustatory axons innervating taste

ISSN:0092-7317    

DOI:10.1002/cne.902920407

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

年代:1990

数据来源: WILEY

摘要:

AbstractDespite extensive study of corticospinal connections in a variety of species, little is known about the detailed morphology of corticospinal axon arbors. Results in previous studies of primates based on intra‐axonal filling with horseradish peroxidase (HRP) staining of a limited sample of fibers suggest that corticospinal arbors branch widely to multiple motoneuronal pools. To determine whether this pattern of corticospinal connectivity is present in nonprimate species as well, we studied the branching patterns of corticospinal axon arbors in a rodent species, the golden hamster. The axons were labeled by iontophoretic ijection ofPhaseolus vulgaris‐leucoagglutinin (PHA‐L) into small regions of the forelimb and hindlimb sensorimotor cortex, and immunohistochemistry with the peroxidase‐antiperoxidase (PAP) method was used to reveal fine details of terminal arbors within the cervical and lumbar enlargements of the spinal cord. As in higher mammals, corticospinal connections are topographically organized. Moreover, corticospinal axons arising from somatosensory cortx project primarily to the dorsal horn, whereas those from motor cortex terminate most heavily in the ventral horn. This differential projection pattern, not previously demonstrated in rodents, implies functional differences between somatosensory and motor components of the corticospinal pathway. Reconstruction of corticospinal arbors in the ventral horn showed that in both cervical and lumbar spinal cord segments, axons branch widely into interneuronal regions. A surprising number appear to extend into motoneuron cell groups, and some of these axons branch into multiple motoneuronal pools. Widely divergent corticospinal axons that branch to multiple motoneuron pools have been shown to mediate activity in functionally related muscle groups of the primate forearm. The present results suggest that in other species, such as the rodent, a similar divergence of corticospinal arbors may also function to facilitate activity in subsets of

ISSN:0092-7317    

DOI:10.1002/cne.902920408

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

年代:1990

数据来源: WILEY

摘要:

AbstractSynaptic contacts of photoreceptors in the turtle retina were studied by intracellular injection of horseradish peroxidase (HRP) and electron microscopy. Both cone and rod photoreceptors radiated basal processes (telodendria) from their terminal endings. These telodendria ran laterally in the outer plexifrom layer. The telodendria of cones gave rise to many fine branches that penetrated synaptic cavities of several neighboring cones. Tips of these branches terminated near the walls of synaptic cavities. Some of the telodendrial contact formed two types of basal junction: symmetrical and punctate. The distribution of cones that made telodendrial contacts with the HRP‐filled cone were quantitatively investigated. Green‐sensitive cones (n = 3) made telodendrial contacts with neighboring red‐and blue‐sensitive cones, blue‐sensitive cones (n = 4) with red‐ and green‐sensitive cones, and red‐sensitive cones (n = 9) with red‐ and green‐sensitive cones. In contrast to these cone connections, rod telodendria did not penetrate neighboring photoreceptors. Direct synaptic contacts were not found between rods and cones. Our results clarify the variety of cone couplings in turtle retina: the three chromatic classes of cones areselectivelycoupled by the basal junctions at the ends of tel

ISSN:0092-7317    

DOI:10.1002/cne.902920409

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe distribution of primary olfactory and vomeronasal (VMN) glomeruli is demonstrated in the forebrain of the larval (stage III tadpole) and adult bullfrog. Olfactory glomeruli are massed at the anterior end of the olfactory bulb; farther posterior, they are located at the periphery and then become distributed in a superficial layer all along the ventral surface of the bulb. Glomeruli of the accessory olfactory bulb (AOB) of the tadpole are less compact and show larger dendritic profiles and fewer synaptic junctions per unit area than those of the adult AOB. Axons of both tadpole and adult VMN nerve are ultrastructurally indistinguishable from those of the primary olfactory nerve; in comparing VMN axons of tadpole and adult, however, differences were observed in the number of neurofilament profiles in axons at the proximal and distal ends of the VMN nerve. Counts of neurofilament profiles in the two ends of the nerve suggest that neurofilament segments accumulate near terminations of their axons. The VMN nerve of tadpole and adult frog are roughly the same size, and calculations indicate that they contain comparable numbers of axons. The primary olfactory nerve of the tadpole is estimated to contain about 660,000 axons; the adherent VMN nerve of the tadpole contains about 270,000 axons (a ratio of about 2.5:1). In the adult, the ratio of primary to VMN axons is about 64:1, reflecting the quantitative growth of the primary olfactory nerve with development from an aquatic tadpole to an air‐breathing adul

ISSN:0092-7317    

DOI:10.1002/cne.902920410

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe ultrastructure of the accessory olfactory bulb (AOB) of the bullfrog tadpole and adult was examined, and the main difference between tadpole and adult is that the latter is more compact and shows more synapses. Except for vomeronasal (VMN) glomeruli, the AOB is not highly organized, with mitral cell neurons scattered throughout the neuropil. VMN axon terminals from asymmetric synapses with mitral cell dendrites in glomeruli; in VMN axon terminals, dense‐cored vesicles are seen along with the more abundant lucent vesicles 40–50 nm in diameter. Counts indicated that more than 90% of the dendro‐dendritic synapses between mitral cells and presumed granule cells are of the asymmetrical type, and reciprocal asymmetrical‐symmetrical synapses are not common. Lucent vesicles with round or slightly ellipsoidal profiles and less abundant dense‐cored vesicles 60–90 nm in diameter are found in pre‐ and postsynaptic dendrites; sometimes the dense‐cored vesicles lie against or near the presynaptic membrane. Microtubules were often seen to be closely associated with pre‐ and postsynaptic elements of dendro‐dendritic synapses. The most characteristic feature of mitral cell bodies, apart from their large size, is an extensive Golgi system that may extend well into their major dendritic extensions. Dense‐cored vesicles are associated with Golgi membranes, from which they probably originate. Centrioles are associated with the Golgi system, and some become basal bodies and give rise to cilia

ISSN:0092-7317    

DOI:10.1002/cne.902920411

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

年代:1990

数据来源: WILEY