摘要:

AbstractDutch‐belted rabbits were enucleated shortly after birth and allowed to survive 14–26 weeks. In some animals, the second eye was then removed and the distribution of retinal axons studied. It was found that while there was no evidence of axonal sprouting in the lateral geniculate body, uncrossed retinofugal axons had spread throughout the lateral half of the superior colliculus, in areas normally innervated only by the contralateral eye.Other animals were prepared for electrophysiological recording, to see if neurons in the area of new axonal growth could be activated by light or electric shock to the optic nerve. Only four of 70 neurons tested could be driven by light, and only two of 26 tested could be driven by shock. All responsive neurons were judged to be located within the limits of the normal ipsilateral projection. It is concluded that while anatomical evidence of spreading of the uncrossed retinal input has been shown, the functional significance of this new growth is yet to be demonstra

ISSN:0092-7317    

DOI:10.1002/cne.901510402

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe times at which the receptor types completed their final S phase was measured by injecting3H‐thymidine at a series of incubation times and then rearing the embryos to hatching. Incorporation of3H‐thymidine by the developing receptors was examined, subsequently, in EM autoradiographs of differentiated receptors whose type could be identified. The time at which each receptor type completed final S was estimated from the proportions unlabelled at each of the times at which3H‐thymidine was injected. The incubation time at which 50% of the receptor type had completed final S was 134.2 hours for principal cones, 139.5 hours for rods, 145.6 hours for single cones and 153.5 hours for accessory cones. It is unlikely, from these estimates, that a principal cone, rod, single cone and an accessory cone, which constitute the repeating group in the retinal mosaic pattern in the periphery, are formed from one stem cell. Each receptor type in a repeating group is probably formed, in the final cell cycle, from a different precursor

ISSN:0092-7317    

DOI:10.1002/cne.901510403

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

年代:1973

数据来源: WILEY

摘要:

AbstractAnatomical studies on the organization of the visual system ofEugeres plumierihave been initiated with an analysis of the distribution of retinal fibers in the brain. Twelve adult specimens were unilaterally enucleated. After postoperative survival periods ranging from six to 30 days, the fishes were perfused and the brains processed according to several modifications of the Nauta technique for the demonstration of degenerating axons and terminals (Ebbesson, '70). Although some terminal degeneration can be seen as early as six days, the degenerating fibers and terminals are best demonstrated in specimens with post‐operative survivals of 15 days or longer.The optic tract is entirely crossed and issues fascicles to the hypothalamus, nucleus geniculatus lateralis, nucleus opticus dorsolateralis thalami, nuclei pretectales, nucleus corticalis, and tectum opticum. The nucleus geniculatus lateralis is unusually large and well laminated, as is the optic tectum. The retinal input to the latter is distributed to, and terminates in, the stratum opticum and the highly differentiated stratum griseum et fibrosum superficiale. Debris of degeneration was also consistently seen in the stratum album central

ISSN:0092-7317    

DOI:10.1002/cne.901510404

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

年代:1973

数据来源: WILEY

摘要:

AbstractXenoplastic eye exchanges were made between domestic chick and Bobwhite quail embryos, using microsurgical techniques at early stage 11. Donor (quail) eyes were found to be incorporated in 78% of the operations, and it was suggested that an optimal period (late stage 10 ‐ early stage 11, approximately 10.3 somites) exists, during which transplantation of these organs may be maximally successful. The majority of the transplanted eyes appeared normal, and histological examination revealed normally decussating and ingrowing optic nerves which formed normal appearing optic tracts and found terminations within the contralateral tecta. Inspection of donor retinae and the isthmo‐optic nuclei contralateral to the transplant, both known to undergo cellular degeneration in the absence of their appropriate projection fields, showed normal cellular complements and organization in most cases. Functional capacities of the transplanted eyes were assessed by viewing the pupillary light reflex. This test indicated that functional connections were made, at least as far as mesencephalic centers, with the latencies of and threshold intensities for elicitation of the reflex virtually identical in normal and transplanted eyes. The latencies of the reflex virtually identical in normal and transplanted eyes. The latencies of the donor (quail) eyes were considerably shorter than those usually found in these embryos at the age viewed. Some form of host induction of precocial responsiveness is discussed in this connect

ISSN:0092-7317    

DOI:10.1002/cne.901510405

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

年代:1973

数据来源: WILEY

摘要:

AbstractDeaf white cats with congenitally determined lesions of the organ of Corti were found to have transneuronal degeneration in the form of reduced cell size in the ventral cochlear nucleus and the superior olivary complex. A young deaf white cat with a normal spiral ganglion cell population showed no evidence of acoustic nerve fiber or ending loss despite the presence of atrophied cells in the ventrical cochlear nucleus. Spiral ganglion cell depopulation as found in an adult deaf white cat was evident only in the lower cochlear turns. Graphic reconstructions of the cochleas showed that deaf white cats fell within the normal range of cochlear length and spiral development. A non‐deaf white cat with overdeveloped convolutions of the lateral superior olivary nucleus had the most extensively coiled cochlea of the cats examine

ISSN:0092-7317    

DOI:10.1002/cne.901510406

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

年代:1973

数据来源: WILEY

摘要:

AbstractMyoneural junctions are described in the body musculature of the leech. Although similar to cholinergic junctions elsewhere, these exhibit a distinctive postjunctional membrane specialization consisting of discrete, concave patches, occupying a small proportion of the total postjunctional area, at which both the inner and outer surfaces of the membrane appear to be coated. The outer coating consists of a hexagonal array of projections which arise from the outer dense lamina of the plasma membrane and extend into the junctional cleft. The projections are spaced at intervals of ∼ 150 Å and are thickened at their tips. The inner dense lamina of the membrane is coated by an amorphous cytoplasmic material. Details of this specialization show up well in specimens that have not been post‐osmicated but are stained (in sections) with permanganate and uranyl acetate. It is hypothesized that the morphologically specialized patches are composed of units containing the acetylcholine recep

ISSN:0092-7317    

DOI:10.1002/cne.901510407

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

年代:1973

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901510401

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

年代:1973

数据来源: WILEY