摘要:

AbstractElectron microscopic and Golgi studies on the inferior lobes of sunfish and goldfish are described. The inferior lobe consists primarily of a nucleus ventricularis of densely packed cells surrounding the lateral recess of the third ventricle, and a peripherally situated nucleus diffusus consisting mostly of scattered neurons. A cell‐sparse zone of dense neuropil is located between the two cellular areas. Neurons of both nuclei have spiny dendrites and axons which originate from basal dendrites. In some cases axons are found to send a collateral into the cell‐sparse zone. Neurons of the nucleus diffusus possess collaterals that extend a considerable distance within the nucleus itself. The ultrastructure of cells of both nuclei reveals cytoplasmic organelles typical of most neurons. Synapses containing dense‐cored and clear vesicles are present on the spines and shafts of the dendrites of both neuronal types. In only rare cases synapses were observed on the soma of neurons of the nucleus ventricularis. Possible anatomical substrates involved in the control of feeding and aggression in teleosts are considered in light of the present findings. Morphological similarities of the inferior lobes and related areas in various fishes and amphibians are discussed and their possible significance for the understanding of the evolution of hypothalamic mechanisms is consi

ISSN:0092-7317    

DOI:10.1002/cne.901610402

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

年代:1975

数据来源: WILEY

摘要:

AbstractRuthenium red and horseradish peroxidase were used to compare the uptake of exogenous molecules into crayfish motor axons and their sheaths in severed and intact peripheral nerves. Both tracers penetrated the axonal sheath and were subsequently seen lining small vesicles and tubules in the axoplasm. Tracer appeared to enter the axon via pinocytotic vesicles. There were no perceptible quantitative or qualitative differences in ruthenium red uptake between intact and severed axons. However, counts of tracer‐filled vesicles in axons exposed to peroxidase showed that at least three times as much tracer penetrated the severed as opposed to the intact axon

ISSN:0092-7317    

DOI:10.1002/cne.901610403

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

年代:1975

数据来源: WILEY

摘要:

AbstractYoung dogs were anesthetized by intrathoracic injection of sodium pentobarbital and perfused with buffered aldehydes. Lining tissue samples from the cranial subarachnoid space were prepared for scanning electron microscopy (SEM) by postfixing in buffered OsO4. Samples were then dehydrated, dried in a Critical Point Drying System, and coated with carbon and palladiumgold. Specimens were viewed in a Cambridge S4 scanning electron microscope. After thorough scanning, selected samples were routinely prepared for transmission electron microscopy (TEM) and viewed in a Philips EM‐200 transmission electron microscope.This study depicts the surface morphology of the meningeal linings of the cranial subarachnoid space. The cranial pia mater possesses natural gaps or fenestrations between cells. SEM reveals a more complex morphology of arachnoid trabeculae than previously interpreted from light and transmission electron microscopy. Many free cells are observed on the meningeal linings of the subarachnoid space. The present study establishes that these free cells are macrophages by means of definitive TEM correlates. Microvillous‐like processes extending between macrophages and the pial surface are present. The frequency and the nature of these thin processes suggest the possibility of a plasmalemmamediated system of communicat

ISSN:0092-7317    

DOI:10.1002/cne.901610404

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe embryonic development of reflex forelimb movements produced by cutaneous stimulation of the forepaw was examined in five inbred strains of the house mouse,Mus musculus. A quantitative electron microscopic study of synapse formation between the neurons that comprise the spinal cutaneous reflex arc was also carried out on specimens from three of the strains subjected to reflex testing. This investigation provides evidence that there is significant genetically‐associated variability in the developmental timing of synapse formation within this disynaptic pathway and in the reflex behavior which it mediates. Specifically, it was found that C57BL/6J embryos had greater numbers of synaptic junctions in the reflex pathway at embryonic days 14–16, and they also showed reflex movements earlier than LP/J embryos. C57BL/6J embryos also showed a more rapid increase in the number of boutons during this embryonic period. CBA/CaJ embryos displayed a temporal pattern of development that differed from both C57BL/6J and LP/J. At E15, CBA/CaJ embryos were more similar to LP/J with regard to both reflex activity and synapse number, but by E16, CBA/CaJ values for both of these measures were more similar to C57BL/6J. On the basis of the data detailed in the text, we suggest that the strains differ in the following manner: C57BL/6J embryos develop boutons rapidly but appear to be relatively inefficient in the actual formation of synaptic junctions; CBA/CaJ embryos develop boutons at a slower rate than C57BL/6J but form synaptic junctions more efficiently; LP/J embryos develop boutons slowly and are also relatively inefficient in forming synaptic junctions. The genetic implications of — and some developmental processes which might be responsible for — the observed strain differences in the timing of synaptic development are discussed in the text.There was no detectable genetic variability of the basic sequence in which the neurons of the cutaneous reflex arc develop their synaptic connections. For all three strains examined, the data indicated that synaptic closure occurred in a retrograde sequence with respect to the direction that neurotransmission normally flows between the neurons of this pathway. This finding agrees with results obtained by other investigators from a number of diverse vertebrate species, and such a widespread lack of variability implies that a retrograde sequencing of synapse formation is involved in the development of specific neuronal connect

ISSN:0092-7317    

DOI:10.1002/cne.901610405

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe ependymal surface of the hypothalamic third ventricle of the adult female and male mouse was examined with the scanning electron microscope. The material was dried with the critical point method. Supraependymal cells, exhibiting a variety of forms, lie among the cilia of the rostrodorsal two‐thirds of the ventricle. The cell bodies are usually between 8 and 10 μ in diameter and have dividing pseudopodial processes which may be broad or narrow, flat or stout, smooth or varicosed. The textured surfaces of the cells seen in this material appear to have no cilia, microvilli or membraneous folds though they may have small bleb‐like protrusions. Some cells and adjacent cilia bear clusters of friable‐looking material that may be secretory.In several female mice, mounds of debris, that could be degenerating cells or secretory material, were seen in intimate association with clusters of cells. The cells' processes extend over and through the surface of the mound.While some supraependymal cells may be neurons or glia, it is suggested that many of the cells seen may be morphological variants of one cell line, mononuclear phagocytes.Sausage‐shaped structures at the end of long cilia‐like stalks are described and their possible identity

ISSN:0092-7317    

DOI:10.1002/cne.901610406

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

年代:1975

数据来源: WILEY

摘要:

AbstractMicroelectrode recording techniques were used to investigate the projection of the visual field into the lateral geniculate nucleus (LGN) ofMacaca mulatta. The data were used to construct charts plotting visual direction, designated in terms of azimuth and elevation, onto sections of the nucleus cut in coronal, sagittal and horizontal Horsley‐Clarke planes. The projection of the horizontal meridian divides the LGN along its plane of symmetry into a medial‐superior half having negative elevations and a lateral‐inferior half having positive elevations. Elevations become more positive or negative with distance from this plane. Azimuths closest to the vertical meridian are located posteriorly, while the most peripheral azimuths are found at the anterior pole. Two families of surfaces representing visual directions of constant azimuth and elevation are described. Visual field zones of increasing eccentricity are represented serially along the posterior‐anterior axis of the LGN, with the foveal area restricted to the posterior pole and the monocular crescent projecting to the anterior pole. The mapping is completely continuous across the horizontal meridian. The edges of the stacked cell laminae exposed around the periphery of the LGN form an oval band which receives the projection of the perimeter of the contralateral hemifield. The vertical meridian is represented by the posterior two‐thirds of this band, while the periphery of the hemifield projects to the anterior third.The central visual field out to the optic disc is represented by six cell layers, while the rest of the binocular field projects to four layers only (2 parvocellular and 2 magnocellular). The monocular crescent is represented by one parvocellular and one magnocellular layer. Features associated with the projection column of the optic disc are integrated into the transition from six to four layers. Details of the receptive field topography in the vicinity of the optic disc discontinuities indicate that these gaps are produced by intralaminar mechanisms.The magnification factor (mm3/steradian) increases monotonically from peripheral visual fields to the foveal center, varying over a range of three decades. This range is intermediate between those derived from data reported in the literature for the retina and the striate cortex. The ratio of LGN magnifications at any two angular eccentricities is a power function, with an exponent of 1.34, of the corresponding ratio of retinal ganglion cell densities. Similarly, the ratio of cortical magnifications (mm2/steradian) at any two eccentricites is a power function, with an exponent of 1.35, of the corresponding ratio of LGN magni

ISSN:0092-7317    

DOI:10.1002/cne.901610407

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe ultrastructure of pulse labeled (3H‐thymidine) cells in rat optic nerve undergoing Wallerian degeneration is described. The study was limited to the first ten days after enucleation since cell proliferation during this interval is greater than in normal optic nerve (Skoff and Vaughn, '71). Approximately one‐third of the pulse labeled cells are astrocytes. The majority of the proliferating astrocytes are in a reactive state, having changed their normal fibrous appearance to one showing a paucity of filaments. Thirty percent of the pulsed cells can be classified as microglia. Only immature oligodendrocytes proliferate, and they account for less than 10% of the pulse labeled cells. About 30% of the labeled population are undifferentiated glial precursor cells. Electron microscopic autoradiographic data obtained from normal optic nerve and presented in this paper indicates that glial precursor cells which have divided shortly before enucleation continue to proliferate after it. The evidence suggests that recently formed glial precursor cells transform into phagocytes following enucleation. Less than 3% of the pulse labeled cells examined in this study are ultrastructurally similar to mononuclear leukocytes. The results of the present study together with previous studies of degenerating optic nerve indicate that most phagocytes in Wallerian degeneration are derived from proliferation of intrinsic glia rather than from an invasion of exogenous ce

ISSN:0092-7317    

DOI:10.1002/cne.901610408

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

年代:1975

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901610401

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

年代:1975

数据来源: WILEY