摘要:

AbstractThe presence and the neuroanatomical topography of sex hormone concentrating cells in the brain of the American chameleon,Anolis carolinensishave been demonstrated by these experiments. After3H‐estradiol administration large numbers of hormone concentrating cells were found in the amygdala, septum, medical preoptic area, anterior hypothalamic area, the ventromedial and periventricular nuclei of the hypothalamus, and anterior pituitary. In addition, labelled cells were found in the torus semicircularis, in and around the nucleus isthmus pars parvocellularis. A small number of labelled cells could also be found in the rostral pallium, motor nucleus of the fifth cranial nerve, the raphe nuclei, and the spinal cord. After3H‐testosterone or3H‐dihydrotestosterone administration the neuroanatomical pattern was very similar to that found after3H‐estradiol; however, fewer labelled cells were seen after the androgens were given. Two exceptions to the similarity of pattern were in a caudal part of the pallium and in the mesencephalic tegmental area. Hormone‐concentrating cells were found after3H‐testosterone or3H‐dihydrotestosterone administration, while labelled cells in these two areas after3H‐estradiol administration were extremely rare. The pattern of hormone‐concentrating cells was the same in male and female brains, for each of the hormones. The preoptic area, hypothalamus, and anterior pituitary have been demonstrated in reptiles to be involved in neuroendocrine regulation and in the control of sex behaviors.The presence and neuroanatomical pattern of sex steroid binding cells in the brains of a wide variety of vertebrates have been documented. Large numbers of hormone‐concentrating cells were found in all of these species in the medial preoptic area, tuberal hypothalamus, specific limbic structures, the mesencephalon deep to the tectum, and the anterior pituitary. Most hormone‐concentrating cells in the brain ofA carolinensiswere found in these same brain regions, thus indicating a vertebrate‐wide stable core of hormone‐concentrating cells in neuroana

ISSN:0092-7317    

DOI:10.1002/cne.901880202

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

年代:1979

数据来源: WILEY

摘要:

AbstractRetinal ganglion cells and retinotectal synapses of chick embryos can be activated by electrical stimulation at early stages of development (Rager, '76a,b), whereas light evoked responses occur only towards the end of the incubation period. Thus, photoreceptors seem to be the last cells to mature in the chain of elements necessary to enable transmission of visual information to tectal neurons. In the present study the development of light evoked activity in the retina was investigated and compared with the strutural maturation of retinal cells. This ontogenetic approach offers a solution to the problem of the cellular origin of the b‐wave called in question by recent records of the potassioretinogram (KRG).Lamellar structures in the developing outer segments of photoreceptors can first be observed on incubation day 17. Late on the same day a corneal electroretinogram (ERG) and a visual evoked response on the optic tectum (VER) can be recorded. The response properties of the developing b‐wave and VER were tested using various stimulus parameters. From the latencies of the b‐wave and of the VER it is concluded that the b‐wave is not generated directly by the activity of neurons involved in intraretinal signal transmission. Thus it is necessary to consider secondary processes triggered by neuronal activity such as depolarization of glial cells. In the chick retina, Müller cells are virtually the only glial cells. They fulfill all structural requirements necessary to explain the current which spreads through the retina during the b‐wave. Electronmicroscopic analysis reveals that Müller cells undergo drastic changes during the early phase of b‐wave development (incubation day 18). In particular, the number of microtubules per unit volume and the surface area of Müller cell processes in the outer plexiform layer increase considerably. It is, therefore, suggested that the b‐wave originates in the depolarization of Müller cells secondary to synaptic activity in the oute

ISSN:0092-7317    

DOI:10.1002/cne.901880203

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

年代:1979

数据来源: WILEY

摘要:

AbstractRods and cones of the C57BL/6J mouse retina have been examined by light and electron microscopy to distinguish the structural features of the two photoreceptor types. By light microscopy, cone nuclei are conspicuously different from rod nuclei in 1‐2 μm plastic sections. Cone nuclei have an irregularly shaped clump of heterochromatin that appears in single sections to be one to three clumps, whereas rod nuclei are more densely stained and have one large, central clump of heterochromatin. Cone nuclei make up approximately 3%; of the photoreceptor nuclei in both the central and peripheral retina at all ages examined up to 267 days. Cone nuclei are confined to the outer half of the outer nuclear layer, and more than 50%; of the cone nuclei lie adjacent to the outer limiting membrane. By electron microscopy, cones in the mouse retina meet virtually every morphological criterion of mammalian cones. The outer segments are conically shaped. Many, if not all of the outer segment discs are continuous with the outer plasma membrane, whereas almost all of the rod discs are not. Cone outer segments are only about half the length of the rod outer segments, and they are contacted by long, villous pigment epithelial cell processes. The cone inner segment diameter is greater than the outer segment diameter, and the accumulation of mitochondria present at the apical end of the inner segment forms a more conspicuous ellipsoid than in rods. The internal fiber or axon of the cone is larger in diameter than that of the rod, and it terminates in a large synaptic pedicle with multiple ribbon synapses, whereas the rod terminal is a smaller spherule with only a single ribbon synaptic compl

ISSN:0092-7317    

DOI:10.1002/cne.901880204

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe period of cell genesis of rod and cone photoreceptor cells has been determined in the retinas of C57BL/6J mice. Embryonic mice were exposed to a single dose of3H‐thymidine at embryonic day (E) 10‐18 by injecting pregnant mice intraperitoneally. Animals at postnatal ages were injected subcutaneously once between postnatal day (P) 0‐10. The eyes were removed at one to three months of age. After fixation, they were embedded in glyol methacrylate, sectioned at 1.5 μm and prepared for autoradiographic analysis. All of the cone cells are generated over a relatively short time interval during the fetal period. In the posterior retina, the peak of cone cell genesis occurs at E13‐E14, and no cones are generated after E16. The rods, by contrast, are generated later and over a longer time period. They first begin to be generated in the posterior retina on E13, but the peak of cell genesis in not reached until the day of birth, and some rods are generated as late as P5. For both rods and cones the peaks of cell genesis in the peripheral retina occur two to three days later than in the posterior retina. The findings demonstrate that rods and cones are developmentally distinct cell types in the mous

ISSN:0092-7317    

DOI:10.1002/cne.901880205

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

年代:1979

数据来源: WILEY

摘要:

AbstractAntisera to highly purified basic protein (BP)7from rat and chicken brain were prepared and their purity and specificity demonstrated by double immunodiffusion and cross‐immunoadsorption. These antisera were used for immunohistochemical localization of BP in the brains of adult and developing rat and chick.Myelin basic protein was exclusively localized to myelin or the myelin forming elements of the CNS. It was present in high concentrations in white matter and absent in areas free of myelin. Neuronal parikarya and dendrites were negative as were axons cut in cross section and at Nodes of Ranvier. The latter was best observed in cross sections of human spinal cord demonstrating also the immunoreactivity of the antibodies with human BP. The internodal distance in a fine (1.5 μm) rat cortical fiber was determined to be approximately 45 μm. Myelin basic protein was shown to extend into cranial roots, in contrast to myelin proteolipid protein which abruptly lost fluorescence as the nerves emerged from the brain.During development, BP was first observed on the fourteenth day of incubation in chick and at birth in the rat. The protein appeared in oligodendrocyted and in association with fibers near these cells. Fluorescent processes were frequently observed connecting the oligodendrocytes with the fibers. As myelination progressed, the intensity of the immunohistochemical reaction decreased in the oligodendrocytes while the brightness in fibers increase. Eventually, the oligodendrocytes became undetectable. Fibers with immature myelin exhibited a beaded or varicosed appearance with the highest concentration of immunofluorescence in the outer portion of the varicosities. The varicosities were postulated to represent dilations in the newly forming sheath between intervals of compaction along the axon undergoing myelination. These dilations might represent areas of increased cytoplasmic volume which could serve as channels for transport and/or storage sites for myelin proteins prior to incorporation into the membrane. The varicosities became less prominent with the thickening of the myelin sheath and mature myelinated fibers became smooth. The process of synthesis of BP, transport of the protein to the varicosed fibers, and maturation of the myelin sheath was seen to progress in a more or less caudal to rostral direction as myelination of the CNS takes place. In the rat, this was accomplished over approximately a 30‐day period starting near the time of birth. In the chick, most of the myelination was accomplished in the three or four days immediately before hatching. At this time, innumerable oligodendrocytes were observed producing BP simultaneously in the major white fiber tracts. It is postulated that in chick some degree of oligodendrocytic cell death occurs normally during myelin

ISSN:0092-7317    

DOI:10.1002/cne.901880206

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe visual fields of 16 cats raised with monocular eyelid suture were measured by means of a visual orienting test. We separately measured the fields of nondeprived and deprived eyes. Each cat was tested preoperatively, and 13 of the cats were tested following lesions of the visual cortex, superior colliculus, and/or optic chiasm.Preoperatively with the nondeprived eye, every cat had a normal monocular field extending roughly from 90μ ipsilateral to 45μ contralateral to the eye being tested. Fields for the deprived eye seemed to depend upon the nature of the deprivation. Fourteen of the cats had complete lid fusions, and 13 of these had virtually identical deprived eye fields which essentially included only the monocular segment (i.e., roughly 45v to 90μ ipsilateral). Only these 13 cats were tested postoperatively. The fourteenth cat with complete lid closure may have had a visual field for the deprived eye that included the entire ipsilateral hemifield, but its responses were extremely unreliable. Two of the cats had incomplete lid fusions which exposed the cornea and thus permitted some pattern vision during development. Their visual fields for the deprived eye included the entire hemifield. We conclude that rearing a cat with complete monocular lid occlusion produces for the deprived eye a field which is effectively limited to the monocular segment.Following postoperative testing, histological verification of neural lesions was obtained for every cat except one. An optic chiasm transection in one cat rendered its deprived eye totally blind on these tests, presumably because crossing nasal fibers which represent the monocular segment were cut. The chiasm transection also reduced the nondeprived eye's field to 0μ to 45μ contralateral. Cortical ablations in the other 12 cats were contralateral to the deprived eye or bilateral, and they ranged in size from lesions of areas 17 and 18 to total occipitotemporal ablations. (Cats with the latter ablations also had tectal lesions to counteract hemianopia due to large cortical lesions.) Each of these 12 cats showed a dramatic postoperative increase of the deprived eye's visual field to include most or all of the ipsilateral hemifield. The smallest lesion (involving areas 17 and 18 contralateral to the deprived eye) produced such an expansion of the deprived eye's field. Collicular ablations in another cat suggest that these expanded fields following cortical lesions depend upon retinotectal pathways. Postoperative fields for the nondeprived eyes were more variable. Generally, smaller lesions caused little change in these fields from preoperative measurements; larger lesions tended to reduce the fields to include only the ipsilateral hemifield. Two cats with bilateral occipitotemporal cortical ablations and transections of the commissure of the superior colliculus exhibited no obvious behavioral differences between use of the nondeprived and deprived eyes, and the monocular fields included the ipsilateral hemifield for each eye.One interpretation of these results is based upon prior suggestions that retinotectal pathways develop fairly normally in monocularly deprived cats, while geniculocortical pathways do not. The animals' preoperatively tested visual behavior and collicular reponse properties tend to reflect the status of cortical pathways, but following cortical lesions, the orienting functions of retinotectal pathways are more fully expressed. Since these retinotectal pathways are dominated by nasal retina, the entire nasal retina of the deprived eye after appropriate cortical lesions is functional for visual orien

ISSN:0092-7317    

DOI:10.1002/cne.901880207

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

年代:1979

数据来源: WILEY

摘要:

AbstractProjections from the subiculum to retrohippocampal areas were studied by reduced silver impregnation of anterograde degeneration and by autoradiographic tracing of transported proteins following injections of radioactive amino acids. The subiculum was found to project to the presubiculum and to the medial and lateral parts of the entorhinal area. The projections are exclusively ipsilateral, and arranged in a dorso‐ventral topographical order with the terminations confined to the deep cortical layers. The projections form part of multisynaptic chains within the hippocampal region and must also be implicated in output routes for hippocampal activity additional to the fimbria‐fornix sys

ISSN:0092-7317    

DOI:10.1002/cne.901880208

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

年代:1979

数据来源: WILEY

摘要:

AbstractRetinal projections were mapped in Tasmanian devils which had one eye injected with3H‐proline. The retinal fibers terminate in seven regions in the brain. These are (1) dorsal lateral geniculate nucleus (LGNd), (2) ventral lateral geniculate nucleus, (3) lateral posterior nucleus, (4) pretectum, (5) superior colliculus, (6) hypothalamus and (7) accessory optic system. The pattern of retinal input to six of these regions is similar to that seen in other marsupials.The pattern of retinal projections to the LGNd, while basically similar to that observed in other polyprotodont marsupials, is much simpler than that seen in the related native cat,Dasyurus viverrinus.The LGNd ofSarcophiluspresents the simplest cytoarchitectural organisation of any marsupial examined so far. Each LGNd receives overlapping projections from both eyes. Suggestions of an intermittent lamination are seen in the LGNd contralateral to an eye injection of3H‐proline. On the ipsilateral side there are two patches of label, a large lateral patch and a smaller medial patch, both of which occupy areas receiving contralateral input. The monocular segment, occupying the ventral 40%; of the nucleus, is more extensive than has been reported in any other polyprotodont marsup

ISSN:0092-7317    

DOI:10.1002/cne.901880209

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

年代:1979

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901880201

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

年代:1979

数据来源: WILEY