bluuebunny/crossref_metadata_2025_split huggingface dataset:
Symmetry in a receptor mosaic demonstrated in the chick from the frequencies, spacing and arrangement of the types of retinal receptor
Authors: Morris Valerie B. 
Published: December 2004

AbstractThe mean percentages of receptors in the central retina were 14% rods, 32% double cones and 54% single cones. The mean percentages in the periphery were 33% rods, 30% double cones and 37% single cones. Single cones were classified into type I, type II and type III and the ratio of these types was about 5:2:1, respectively, in both central and peripheral retina. A statistical analysis showed that each type of receptor was evenly spaced in the receptor mosaic, but single cone type I tended to occur in pairs. The types of receptor were arranged in a pattern which was in the form of a hexagonal lattice. The pattern in the mosaic is regarded as the outcome of an evenly spaced distribution of the types of receptor. Perhaps pattern in the receptor mosaics of other vertebrate retinae should be interpreted as evenly spaced distributions of the types of receptor present. A method for detecting pattern in receptor mosaics, in which pattern is obscure, is described. A scheme accounting for the formation of the pattern in the chick retina during development is proposed.
Fine structural localization of acetylcholinesterase in sensory and motor neurons of the muscle receptor organ in Homarus
Authors: Nadol Joseph B. , Brzin Miro , de Lorenzo A. J. Darin 
Published: December 2004

AbstractHistochemical techniques with the electron microscope for the localization of specific acetylcholinesterase and non‐specific cholinesterases have been applied to preparations of the abdominal muscle receptor organ, or stretch receptor, of the lobster. Reaction product specific for AChE was found to be localized in a discrete but interrupted fashion on the external surface of the cell membranes of both the fast and slow sensory neurons at the levels of axon, cell body, large and small dendritic processes, and fine dendritic terminations. Reaction product specific for AChE was also found on the external surface of the limiting membranes of motor axons, but not at neuromuscular endings. Non‐specific ChE was limited to cytoplasmic vacuoles and cisternae of the Schwann cells of the neural sheaths. These findings lend support to the hypothesis that in the lobster the ACh system may mediate membrane excitability of nerve fibers. Furthermore, at the level of dendritic terminations this system may mediate the transduction of mechanical into electrical energy via reversible permeability changes.
Fiber spectrum and functional properties of pyramidal tract neurons in the american opossum
Authors: Biedenbach M. A. , Towe A. L. 
Published: December 2004

AbstractThe number and size of pyramidal tract (PT) axons and the functional properties of cerebral PT neurons were examined in the American opossum. The pyramidal tract contains 30,000–40,000 axons, none greater than 5 μ in diameter and 99% of 3 μ or less in diameter. Cerebral neurons were isolated and classified as PT or non‐PT according to standard antidromic spike criteria in response to stimulation of the medullary pyramid. Response to natural stimulation and to electrical stimulation of the four paws was tested. PT neurons displayed a wider convergence than non‐PT neurons, but the more superficially isolated PT neurons showed only weak or nonexistent excitation from the skin. Response to stimulation of one paw could be blocked by prior stimulation of another paw, whether or not the conditioning stimulus evoked a discharge. At least some of the blocking may be due to intracortical inhibitory synapses, for weak conditioning shocks applied to the pyramidal tract could block the peripherally evoked response in half of the neurons tested, both PT and non‐PT. During high‐frequency stimulation of the pyramidal tract, antidromic spikes readily separated into distinct A and B components, the B spike frequently failing altogether. The slow antidromic conduction speeds, 4–14 m/sec, agreed well with the small axon diameters found by histological methods.
A quantitative ultrastructural study of the inner plexiform layer of the rat retina
Authors: Sosula Leo , Glow Peter H. 
Published: December 2004

AbstractThe inner plexiform layer (IPL) and adjacent regions of the rat retina were studied by electron microscopy. The IPL contains neural processes of amacrine, bipolar, and ganglion cells, and glial (Müller) processes. Type 1 amacrine processes (maximum diameter 3.1 μ) traced from their somata structurally resemble amacrine perikarya. These processes rarely form synapses. Type 2 amacrine processes (maximum diameter 0. 7 μ) are radially oriented, forming synaptic expansions en passant, giving origin to collaterals, also with expansions. The type 2 amacrine processes form conventional synapses onto bipolar, ganglionic and other amacrin processes, onto amacrine and ganglionic somata, and onto dendritic spines. Amacrine perikarya in rare cases contain synaptic vesicles and form somatic synapses onto surrounding processes.Bipolar processes traverse the IPL, forming terminal expansions up to 6 μ in diameter near the ganglion somata, which they contact without synaptic vesicle clustering. Bipolar processes form synapses onto dyads. In 73% of dyads, both processes are vesiculated. One process of the dyad pair could usually be identified as an amacrine by its reciprocal synapse back onto the presynaptic bipolar process. The other dyad process, when vesiculated, contains vesicles which are significantly larger and less concentrated than in the adjacent amacrine, and is presumably a ganglion cell dendrite.The ratio of the incidence of amacrine synapses: bipolar synapses is about 8:1. A subdivision of the IPL into thirds shows that the highest incidence of amacrine synapses is in the middle third. Amacrine somata are significantly larger than bipolar somata. Synaptic vesicles in receptor terminals of the outer plexiform layer are significantly larger and more concentrated than those in axonal processes of the IPL. The functional aspects of these findings are discussed in relation to physiological investigations and interspecies differences described in the literature.
Neuromuscular junctions on the muscle cells in the central nervous system of the leech, Hirudo medicinalis
Authors: Tulsi Ram S. , Coggeshall Richard E. 
Published: December 2004

AbstractThe central nervous system of the leech is surrounded by fibrous tissue in which are contained muscle cells whose presumed function is to accommodate the length of the nervous system to coincide with changes in the length of the animal. In this paper a three‐dimensional reconstruction of these muscles was described. Each neuromuscular junction consists of 5–50 neural terminals closely applied to the muscle. Furthermore, some morphologic evidence for synaptic interaction between terminals was obtained. We believe that this complex morphology of the terminals indicates that there is a relatively complex integrative mechanism for neuromuscular transmission at the periphery.
Somatotopic organization of spider monkey somatic sensory cerebral cortex
Authors: Pubols Benjamin H. , Pubols Lillian M. 
Published: December 2004

AbstractOrganization of the tactile receiving area of the postcentral gyrus of the spider‐monkey (Ateles) has been investigated using microelectrode recording procedures. The neocortical region in which single units or unit clusters respond to light mechanical region in skin (SmI) is smaller than the tactile receiving area as defined by earlier evoked potentials studies, failing to extend into sylvian sulcus or to the posterior margin of the postcentral gyrus. It forms a precise, detailed, and somatotopically organized pattern of representation of the complete contralateral body surface. The sensory sequence is orderly and continuous from tail to tongue with one exception, each body region in represented by a band of cortical tissue extending anteroposteriorly across SmI. The ratio, area of glabrous surface of the hand as it is for the glabrous tail pad, which correlates with the greater tactile acuity of the former.
The interpeduncular nuclear complex of selected rodents
Authors: Ives W. R. 
Published: December 2004

AbstractThe internal differentiation of the interpeduncular nuclear complex was determined by quantitative cytoarchitectonic analysis in specimens from each of the suborders of Rodentia: rat (Rattus) of the Myomorpha; guinea pig (Cavia), chinchilla (Chinchilla), and capybara (Hadrochoerus) of the Caviamorpha; and the mountain beaver (Aplodonia) from the Sciuromorpha. In each of these rodents the constituent cells of the complex ae grouped into four spatially distinct subnuclei: pars lateralis (PL), pars medialis (PM), pars dorsalis magnocellularis (PDM), and pars dorsalis parvocellularis (PDP). There is a fifth subnucleus, the paramedian, in Chinchilla. Sample distributions, and means, of cell sixes were measured in each of these subdivisions in each species; and cell densities of each subdivision were determined in Rrattus. In all these animals PD had the smallest cells. PDM had the largest cells, except that in Hydrochoerus cells of PL, and in Cavia cells of PM, were as large as those of PDM. In Rattus and Aplodontia PL and PM were not different in cell size, and in Rattus their cells were of the same density. These findings cast doubt upon criteria previously used to subdivide this nuclear complex, and provide a consistent and replicable classification of its components.
Hypothalamo‐hypophyseal neurosecretory and vascular systems in the catfish, Heteropneustes fossilis (Bloch)
Authors: Sundararaj Bangalore I. , Viswanathan N. 
Published: December 2004

AbstractThe hypothalamo‐neurohypophyseal system of the catfish, as revealed by in situ techniques, consists of the prominent nucleus preopticus, the axonal tracts, and the neurohypophysis. The preoptic nucleus, which is composed of the pars magnocellularis and the parvocellularis, is situated on either side of the optic recess slightly anterior to the optic decussation. Axons arising from the nucleus preopticus form two ventro‐lateral tracts; bundles of axons separate out from these tracts at 10 to 12 points and extend medially to form two ventro‐medial tracts lying on either side of the optic recess. The ventro‐lateral and ventro‐medial tracts eventually merge slightly anterior tc the hypophysis to form the infundibular stalk which penetrates the pituitary and ramifies. The nucleus lateralis tuberis is situated rostral and antero‐ventral to the third ventricle and their axons join the ventro‐medial tracts.The arterial supply to the hypophysis is through a median hyophyseal vessel whose branches penetrate the pituitary along with the infundibular stalk and follow the ramifications of the neurohypophysis. A portal circulation between the hypothalamus and the hypothalamus is discussed.
The cat coeliac and hypogastric ganglia following post‐ganglionic nerve ligation. A study by electron autoradiography and formol fluorescence techniques for noradrenaline distribution
Authors: McQuiston R. W. , Ivens Caroline , Lever J. D. , Spriggs T. L. B. , Graham J. D. P. 
Published: December 2004

AbstractNoradrenaline uptake is a property not only of sympathetic axons but also of their ganglion cells. This has been shown by electronautoradiography which indicates higher than background levels of 3H‐noradrenaline in ganglion cells (incubated in isotope solution) following post‐ganglionic nerve ligation. Under these circumstances noradrenaline concentrations have been found specifically related to the Golgi complex and granular endoplasmic reticulum in hypogastric ganglion cells.
Stellate cells of the rat parietal cortex
Authors: Peters Alan 
Published: December 2004

AbstractStellate cells have rounded or oval cell bodies which contain nuclei bounded by a ruffled, and frequently indented, nuclear envelope. Te cytoplasm of these neurons is usually darker than that of pyramidal neurons because it contains a greater concetration of ribosomes. Where the perikaryal cytoplasm is thick, the granular endoplasmic reticulum is often arranged in parallel arrays. On the surface of the perikarya are three types of synapses: (1) ones with a wide cleft and a prominent postsynaptic density, (2) ones with a wide and straight synaptic cleft that lack a prominent postsynaptic density, and (3) ones with a narrow synaptic cleft and short synaptic complexes. The dendrites of stellate cells lack spines and frequently bear many synapses. On the thinner dendritic branches the type of synapse with a side cleft and a prominent postsynaptic density is most common. The cytoplasm of the dendrites is characterized by closely arranged microtubules.
Neurogenesis in the optic tectum of larval Rana pipiens following unilateral enucleation
Authors: Eichler Victor B. 
Published: December 2004

AbstractDNA synthesis and interlayer migrations of cells in the optic tectum of larval Rana pipiens were investigated, using several series of larvae which had been subjected to unilateral enucleation at stage 25, the last embryonic stage. It has been found that DNA synthesis occurs in all cellular layers of the tectum with least activity in peripheral layers. The location of the most active DNA synthesis during the larval period is the same as the location of cell division in the larval tectum, namely, in the layers bordering the ventricle of the optic lobeUnilateral enucleation of stage 25 embryos results in a decrease in DNA synthesis in all cellular layers of the optic tectum contralateral to the operation when compared to the corresponding layers in the ipsilateral tectum. The differences in rate of incorporation of 3H‐thymidine between the control and affected lobes become greater during development. Fewer cells are found in each layer of the affected larval tectum than in the corresponding layer of the control tectum. The decrease is greatest in more peripheral layers, whose cells are more intimately associated with the visual circuit than are cells of the deeper layers. Peripheral to layers 1 and 2, the percentages of labeled cells found in each layer are very similar on the two sides, suggesting common factors which control migration. Differences in cell number, therefore, reflect differential cell production rather than differential cell migrations.The distribution of label resulting from 3H‐thymidine incorporation at stage III indicates that the distribution of mitotic activity is not uniform in the cephalocaudal axis of the tectum. Greater cell proliferation occurs in the posterior portion of the tectum than in the anterior region throughout larval development.The peripheral control of mitotic divisions in the frog optic tectum remains unknown. The data in the present study, however, support the hypothesis that influences from afferent fibers of the optic tract modify the rates or timing of DNA synthesis in the optic tectum. The data support the notion that the deepest tectal cells respond earliest to the stimulus and these may be ependymal cells which have processes extending to the outer surface of the tectum.
An experimental study of ascending connections from the posterior group of thalamic nuclei in the cat
Authors: Heath C. J. , Jones E. G. 
Published: December 2004

AbstractThe cortical projections of the posterior group of thalamic nuclei have been studied in the cat by means of the Nauta technique. Small stereotaxic lesions introduced in such a manner as to cause no direct damage to the main thalamic nuclei adjoining the posterior group or to the overlying cortex, indicate the following pattern of projections: Only that part of the posterior group consisting of the suprageniculate and magnocellular medial geniculate nuclei, and particularly the region of transitions between the two, projects to the cortex. The cortical region of fibers is a band comprising the third auditory area (AIII) of Tunturi, the insular cortex, the banks of the anterior ectosylvian sulcus, zones A and B of Carreras and Andersson ('63) in the upper part of the anterior ectosylvian gyrus, the vestibular projection area, the suprasylvian fringe of Woolsey ('61). It is possible that different parts of the suprageniculate‐magnocellular complex project to different parts of this cortical band. The suprageniculate‐magnocellular complex and certain parts of the band of cortex to which it projects are regions of multi‐sensory convergence. Although all parts of the posterior group as presently defined, have been damaged, no part seems to project to the first (SI) or second (SII) somatic sensory areas (other than AIII and zone B, which overlap SII). The main efferent connections of these parts of the poeterior group appear to be with the striatum. The results can be correlated to some extent with previous studies carried out with the method of retrograde cellular degeneration, but there are certain problems in relation to electrophysiological studies.
Median and caudal apertues in the roof of the fourth ventricle in rodents and primates
Authors: Cammermeyer Jan 
Published: December 2004

AbstractIn serial paraffin sections of brainstems fixed by perfusion, ventriculo‐cisternal communications in the caudal part of the fourth ventricle are demonstrable in seven species of a total of 27 species, representing Marsupialia, Edentata, Lagomorpha, Rodentia, Ungulata, Carnivora, and Primates, in all of which the lateral apertures of Luschka are well developed. Caudal apertures appear as irregular defects in the taenia of the fourth ventricle with flattening of the roof against the surrounding leptomeninges over the crebello‐medullary cistern in the guinea pig, the mulatta monkey, the squirrel monkey and the cynomolgus monkey. In addition, the one capuchin monkey and the one vervet monkey studied have a midline defect in the roof. In the capybara, a circular midline opening through the roof is closed off dorsally by the cerebellar vermis. These caudal and median defects are thought to be ruptures developed late in fetal life due to accumulation of cerebrospinal fluid before egress through lateral apertures of Luschka is established; although they seem to have served their purpose in the fetus and are no longer needed in the adult, they are kept open by continued flow. Study of fetuses from these selected species could prove useful to determine factors concerned with the development of cerebrospinal fluid circulation.
The red nucleus in the monkey (Macaca mulatta): A Golgi and an electron microscopic study
Authors: King James S. , Schwyn Robert C. , Fox Clement A. 
Published: December 2004

AbstractThis study of the ultrastructure of the red nucleus of the monkey (Macaca mulatta) also includes light microscopic observations made with Golgi, Nissl and one micron plastic section techniques.Sagittal Nissl sections reveal the abrupt transition between the magnocellular and parvicellular division of the nucleus; therefore, it is advantageous to study the red nucleus in this monkey because small tissue blocks from each of its subdivisions can be prepared for electron microscopy.The characteristic neurons of the magnocellular division have well formed, evenly distributed Nissl bodies. The multipolar cell bodies (50–70 μ) and elongated cell bodies (80–90 μ in length) are the large or giant neurons; those 30 to nearly 50 μ are the medium‐size neurons of some descriptions.The characteristic neurons (20–30 μ) of the parvicellular division, referred to here as medium‐size neurons, have no distinct Nissl granules and their Nissl substance usually occupies the peripheral rim of their cell bodies. In both subdivisions of the nucleus there are small (10–15 μ), achromatic, Golgi type II neurons.The cell bodies of the large neurons have prominent somatic spines and their dendrites and the dendrites of the medium‐size neurons have scattered spines. There are large (4–5 × 10–12 μ) and small (1–2 μ) synaptic endings on the dendrites. Some of the former are formed at nodes of Ranvier. It is suggested that the large endings are terminals of the superior cerebellar peduncle.
Changes in the hypothalamus associated with regeneration of the hypothalamo‐neurohypophysial tract after pituitary stalk section in the ferret
Authors: Adams James Hume , Daniel Peter Maxwell , Prichard Marjorie Mabel Lucy 
Published: December 2004

AbstractAnatomical features of the hypothalamus of the normal ferret are described. Transection of the pituitary stalk, with or without the insertion of a barrier to prevent reunion, caused consistent changes in the neural tissue of the median eminence. The rostral part of the median eminence was relatively unaffected but the caudal part, near the site of the lesion, showed marked changes. In the early post‐operative stage there was a large mass, containing few cells but much neurosecretory material (NSM), projecting up from the neural tissue of the median eminence into the infundibular recess of the third ventricle. After a few weeks this seemingly structureless mass had disappeared and the neural tissue had become reorganised and enlarged, and contained large numbers of newly grown nerve fibers and heavy concentrations of NSM. The appearances suggested that an ectopic infundibular process had formed at this level, even in animals in which the original infundibular process had also been re‐innervated. Changes in the supraoptic and paraventricular nuclei were surprisingly slight.In the ferret the hypothalamo‐neurohypophysial tract runs through an unusually long median eminence. Thus many of its nerve fibers (or their collaterals) may terminate well above the level of stalk section, and this may account for the minimal changes seen both in the rostral part of the median eminence and in the supraoptic and paraventricular nuclei.An explanation is suggested for the persistent but diminishing diabetes insipidus that occurred in the stalk‐sectioned animals.
Somatotopic organization and response properties of neurons of the ventrobasal complex in the opossum
Authors: Sousa Aglai P. B. , Oswaldo‐Cruz E. , Gattass R. 
Published: December 2004

AbstractThalamic responses to somatic stimulation were studied in 47 specimens of the South American opossum, D. marsupialis aurita. Topographic representation of the body surface in the ventrobasal complex was determined by recording unit cluster responses to natural stimulation in sodium pentobarbital anesthetised animals. The pattern of representation observed was similar to that reported in the North American subspecies and comparable to the findings in eutherian mammals.The analysis of single units recorded with extra‐cellular microelectrodes showed that the great majority of neurons are place and modality specific. A predominance of skin (vs. deep) sensibility was observed. Units activated by displacement of hairs and vibrissae displayed receptive fields similar to those reported in higher mammals. Of the units isolated within the anatomical boundaries of the ventrobasal complex only 1% showed wide receptive fields, or bilateral representation. None of the units could be activated by auditory stimulation. Neurons displaying wide, discontinuous or bilateral receptive fields showing auditory‐somatic convergence were isolated in nucleus parafascicularis, subparafascicularis and in the Posterior group.