bluuebunny/crossref_metadata_2025_split huggingface dataset:
A re‐examination of anatomical plasticity in the rat retina
Authors: Chernenko Garry A. , West Roger W. 
Published: January 2005

AbstractPrevious investigators have reported an increase in numbers of amacrine synapses in the inner plexiform layer (IPL) of the rat retina following light deprivation, and an increase in amacrine along with a decrease in bipolar synapses following light damage. Since there are several points of disagreement between the published reports on this subject we undertook a more detailed study of the effects of light deprivation and light damage on the retina.Four groups of eight male albino rat pups (14 days old) were raised for eight weeks under different conditions: (1) unsutured, bright light reared (UB); (2) bilaterally lid‐sutured, bright light reared (SB); (3) unsutured, low light reared (UL); and (4) bilaterally lid‐sutured, dark reared (SD). The intensity of the light given the UL group was equated with that striking the corneas of the SB group.Light microscopy showed that the retinas of the SB as well as the UB groups had almost complete degeneration of the outer retinal layers, indicating that even low intensity light, when continuous, causes severe retinal damage. The SD group was thicker in many of the retinal layers compared to the UL (control) group.Electron microscopy revealed that there were no significant changes in the incidences of any type of synapse in the IPL following light deprivation or light damage when averaged over total depth. This is in contradiction to the reports of other investigators. However, when the IPL was analyzed by levels, the incidence of amacrine‐ganglion synapses was significantly greater (p < 0.05) in groups UB and SD, but only in the outer third of the IPL. Thus, extensive postnatal plasticity of IPL synapses in the rat retina did not occur under our experimental conditions. We found, at best, only limited effects which were confined to the amacrine‐ganglion synapses.
Categories of axons in mammalin rami communicantes
Authors: Coggeshall R. E. , Hancock M. B. , Applebaum M. L. 
Published: January 2005

AbstractThe present study is an electron microscope analysis of the rami communicantes and its purpose is to determine the functional categories of unmyelinated axons in these nerves. Our findings indicate that the grey rami of segments T7, T8, or T9 in the cat consist of approximately 5,000 unmyelinated axons and 20 myelinated axons, and that these axons are post‐ganglionic sympathetics. Although the numbers are new data, this conclusion confirms classic work. The white rami from the same segments contain approximately 3,200 unmyelinated axons and 1,600 myelinated axons. 80–90% of the myelinated axons are preganglionic sympathetics and the remainder are presumably sensory. This conclusion is also in confirmation of classic work. The new conclusions are that approximately 30% of the unmyelinated axons are preganglionic sympathetics, approximately 60% seem to be post‐ganglionic sympathetics and the surprisingly small remainder may be sensory.
Scanning electron microscopy of the subarachnoid space in the dog. IV. Subarachnoid macrophages
Authors: Malloy John J. , Low Frank N. 
Published: January 2005

AbstractYoung dogs of both sexes were used in this study. Transmission and scanning electron microscopy were utilized for the examination of the spinal cord and choroid plexus with emphasis on the study of free cells. These procedures were modified so that, in certain cases, the same cells observed in scanning electron microscopy could be analysed internally by transmission electron microscopy. One half of the animals were injected under anesthesia with horseradish peroxidase for observation of phagocytosis.This study confirms that the free cells observed in the subarachnoid space with the scanning and transmission electron microscopes are identical. The internal morphology of these cells corresponds to that of macrophages. This is further subtantiated by the ability of these cells to localize horseradish peroxidase in discrete vacuoles within their cytoplasms. Both pial macrophages and epiplexus cells localize peroxidase in an identical manner in the same animal after one injection. In addition macrophages on the surface of the pia mater respond to extravasated red blood cells in a characteristic manner including phagocytosis. The plentiful population of macrophages on the surface of the pia mater supports the concept that these cells are of major importance in maintaining asepsis in the subarachnoid space.
Synaptogenesis in the ventromedial hypothalamus of the prenatal mouse
Authors: Beals Jacquelyn K. 
Published: January 2005

AbstractMouse embryos from day 13 to day 19 of gestation (E13 through E19) were removed by Caesarean section and their brains were prepared for electron microscopy. Coronal sections were examined in three planes through the ventromedial hypothalamus: anterior, the level at which the optic tracts pass posterolaterally to become partially enclosed in the major brain mass; middle, the level at which the floor of the third ventricle begins to widen and flatten; posterior, the level at which the most anterior infundibulum appears.Three types of junctional complexes were examined.Close junctions are identified as straight, parallel areas of two apposed membranes which appear more electron‐dense than immediately adjacent regions. The membranes are separated by a clearly visible cleft. Unlike synapses, no clear synaptic vesicles are found in either of the adjacent profiles unless randomly distributed and accompanied by ribosomes or glycogen. Close junctions are seen most frequently on day E15, then decrease in number through E19. Their participation in synaptogenesis is discussed from temporal, morphological, distributional and quantitative perspectives and is provisionally rejected.Immature synapses show only the minimal membrane specialization found in close junctions, but vesicles are present, ribosomes absent in at least one of the adjacent cytoplasms. Their appearance peaks on E17–E18, paralleling and slightly preceding that of the mature synapses. Their evolution from close junctions has only weak temporal support.Mature synapses display the cytoplasmic densities which immature synapses lack. They attain their greatest prenatal numbers on E18, then decrease in number on E19.The conclusion is advanced that synaptogenesis does—or at least can—occur without the prior appearance of avesicular regions of increased membrane density.
The organization and postnatal development of the commissural projection of the rat somatic sensory cortex
Authors: Wise S. P. , Jones E. G. 
Published: January 2005

AbstractAnterograde and retrograde tracing experiments have been used to demonstrate the origin and terminal distribution of commissural fibers in the first somatosensory cortex (SI) of the rat. The commissural fibers originate from pyramidal cells of all layers, but predominantly from layers III and V. The fibers terminate in a series of approximately vertical bands. In each of these there are concentrations of terminals extending from the inner portion of the molecular layer to the deep portion of layer III as well as in the superficial part of layer V, and in layer VI. Discrete vertical bands of cortex are reciprocally connected across the midline to give both the origin and terminal regions of the projection a patchy or “columnar” appearance. The commissural fibers arise from and terminate in areas of the cortex that lie between and alongside the aggregations of granule cells that distinguish SI of the rat. No commissural fibers terminate within the aggregations of layer IV cells themselves but the more superficial terminal ramifications may come to overlie these aggregations. A heterotopic projection to the contralateral second somatosensory cortex has been observed and is similar in form to the homotopic projection to SI.Many commissural fibers have crossed the midline in the corpus callosum by the day of birth but lie in the underlying white matter and do not enter the cortical plate until at least the third postnatal day. During the first postnatal week these fibers grow somewhat diffusely into the maturing cortex and their topographic and laminar pattern of distribution attains its adult characteristics by the end of the first week. Commissural axons, thus, arise from immature cells but the maturation of cell form seems to precede the ingrowth of these axons and the acquisition of commissural synapses.
Histochemical mapping of dopamine neurons and fiber pathways in dog mesencephalon
Authors: Shimada Shozo , Ishikawa Masatsune , Tanaka Chikako 
Published: January 2005

AbstractA topographic mapping of dopamine (DA)‐containing neurons and fibers was done mainly in the mesencephalon of the dog using the fluorescent histochemical technique of Falck and Hillarp. The extensive DA neuron system was found to be located in the ventral and medial regions of the mesencephalon; the pars compacta of the substantia nigra, the area almost corresponding to the ventral tegmental area of Tsai (hich consists of three groups, a caudal, the nucleus parabrachialis pigmentosus, a ventral, the nucleus paranigralis and a rostral, the caudal part of the nucleus tegmentalis gventralis of Tsai), the nucleus linearis of the raphe, and the mesencephalic reticular formation.The nigro‐neostriatal projection can be traced in the non‐treated or nialamide plus L‐dopa treated puppies without the lesion‐degeneration technique. Most fibers arising from these DA cell groups assemble at the prerubral area and ascend just dorsal to the medial forebrain bundle. Most fibers turn laterally at the lateral hypothalamus and enter the neostriatum via the dorsal part of the subthalamic nucleus, the zona incerta and the capsula interna. These findings show that the distribution of DA neurons and the nigro‐neostriatal pathway are fundamentally similar to those in other mammals. In this study, the processes of the nigral and paranigral DA neurons have been demonstrated to project into the pars reticulata in the dog.
Electron microscopic autoradiographic studies of gliogenesis in rat optic nerve. II. Time of origin
Authors: Skoff Robert P. , Price Donald L. , Stocks Adelaine 
Published: January 2005

AbstractThe time of origin for astrocytes and oligodendrocytes in rat optic nerve was studied by 3H‐thymidine autoradiographic techniques similar to those used in dating the time of origin for neurons. This study shows that astrocytes are formed throughout late embryonic and all of postnatal development, while oligodendrocytes are generated only during the postnatal period.A few astroglia undergo their final cell division as early as 15.5 days of gestation, but most astrocytes are not generated until the first week of postnatal development. Although the final cell division for more than half of the astrocytes takes place before the end of the first postnatal week, fully mature, fibrous astrocytes are not observed in electron micrographs until after 14 days of age. This time lag implies that the differentiation of these early generated cells takes place gradually over a 2‐to 3‐week interval.Oligodendroglia begin their final division a day or two before the onset of myelination (6–7 days postnatal), but the vast majority are produced during the period of myelinogenesis. After almost all of the axons have been myelinated, oligodendrocytes are still being generated in small numbers. These late forming cells are generally less differentiated in appearance than those formed earlier; this suggests that the degree of differentiation of oligodendrocytes may be dependent upon the number of axons available for myelination. As with astrocytes, oligodendrocytes show a lag of about two weeks from the time of final cell division until they transform into morphologically differentiated cells.In transverse sections of the optic nerve heavily labeled neuroglia are randomly distributed, indicating there are no temporal‐radial gradients for the individual cell types. This observation taken together with the other information obtained from the present and the previous study (Skoff et al., '76) strongly suggest that the factors controlling gliogenesis are different from those governing neuronogenesis.
Recovery from deafferentation by cricket interneurons after reinnervation by their peripheral field
Authors: Murphey R. K. , Matsumoto S. G. , Mendenhall B. 
Published: January 2005

AbstractThe physiological and morphological recovery of cricket (Acheta domesticus) abdominal giant interneurons following varying periods of deafferentation and subsequent regeneration was examined. The principal afferent input to two identified interneurons was removed by surgically ablating an abdominal sensory appendage, the cercus. Deafferentation restricts the growth of the dendrites of the medial giant interneuron. Reinnervation by the peripheral sensory field leads to recovery of the dendrite length which is dependent on the time allowed for recovery. The response properties of the reinnervated neurons never completely recovers irregardless of how short the period of deafferentation. Reinnervated neurons respond more weakly to standard tones than do control neurons. This is due in part to faciliation of an inhibitory synaptic input which is activated by the control cercus. The results suggest that the balance between the excitatory and the inhibitory synaptic inputs to these interneurons is irrevocably altered by brief periods of deafferentation early in life.
The efferent connections of the ventromedial nucleus of the hypothalamus of the rat,
Authors: Saper C. B. , Swanson L. W. , Cowan W. M. 
Published: January 2005

AbstractThe efferent connections of the ventromedial nucleus of the hypothalamus (VMH) of the rat have been examined using the autoradiographic method. Following injections of small amounts (0.4–2.0 μCi) of tritium labeled amino acids, fibers from the VMH can be traced forward through the periventricular region, the medial hypothalamus and the medial forebrain bundle to the preeoptic and thalamic periventricular nuclei, to the medial and lateral preoptic areas, to the bed nucleus of the stria terminalis and to the ventral part of the lateral septum. Some labeled axons continue through the bed nucleus of the stria terminalis into the stria itself, and hence to the amygdala, where they join other fibers which follow a ventral amygdalopetal route from the lateral hypothalamic area and ventral supraoptic commissure. These fibers terminate in the dorsal part of the medial amygdaloid nucleus and in the capsule of the central nucleus. A lesser number of rostrally directed fibers from the VMH crosses the midline in the ventral supraoptic commissure and contributes a sparse projection to the contralateral amygdala.Descending fibers from the VMH take three routes: (i) through the medial hypothalamus and medial forebrain bundle; (ii) through the periventricular region; and (iii) bilaterally through the ventral supraoptic commissure. These three pathways are interconnected by labeled fibers so that it is not possible to precisely identify their respective terminations. However, the periventricular fibers seem to project primarily to the posterior hypothalamic area and central gray, as far caudally as the anterior pole of the locus coeruleus, while the medial hypothalamic and medial forebrain bundle fibers apparently terminate mainly in the capsule of the mammillary complex, in the supramammillary nucleus and in the ventral tegmental area. The ventral supraoptic commissure fibers leave the hypothalamus closely applied to the medial edges of the two optic tracts. After giving off their contributions to the amygdala, they continue caudally until they cross the dorsal edge of the cerebral peduncle to enter the zona incerta. Some fibers probably terminate here, but others continue caudally to end in the central tegmental fields, and particularly in the peripeduncular nucleus.Within the hypothalamus, the VMH appears to project extensively to the surrounding nuclei. However, we have not been able to find evidence for a projection from the VMH to the median eminence. Isotope injections which differentially label the dorsomedial or the ventrolateral parts of the VMH have shown that most of the long connections (to the septum, amygdala, central tegmental fields and locus coeruleus) originate in the ventrolateral VMH, and there is also some evidence for a topographic organization within the projections of this subdivision of the nucleus.
Cerebellar corticonuclear and corticovestibular fibers of the anterior lobe vermis in a prosimian primate (Galago senegalensis)
Authors: Haines Duane E. 
Published: January 2005

AbstractEfferent projections of the anterior vermis were studied in a prosimian primate (Galago senegalensis). Cerebellar corticonuclear and corticovestibular fibers of the anterior lobe vermis are, in toto, ipsilateral. Two additional main points emerge. First, evidence is given which suggests that the cortical area defined as vermis converges, in a rostral direction (from lobules V to I + II), as the hemispheres of these lobules become latero‐medially foreshortened. The anterior vermis is a cortical region reflected by its efferent projections and not an arbitrary median strip of cortex which is either constant in width or morphologically separated from adjacent paravermal areas. Secondly, two patterns of organization emerge concerning cortical efferents, one suggestive of longitudinal zones and a second which shows that individual lobules project mainly to specific areas of the ipsilateral NM and into portions of the vestibular complex. Three zones are recognized. A very narrow midline area which appears to project bilaterally to the NM, a wider intermediate area (homologous to zone A) related to the ipsilateral NM, and a lateral area (homologous to zone B) related mainly to the ipsilateral vestibular complex, primarily its lateral nucleus. Within this overall zonal organization individual lobules project to specific areas of the NM and vestibular complex. Lobules V and IV project to rostrodorsal and rostrocentral NM respectively and into the dorsal LVN. Lobules III and II + I project to rostroventral‐medial and rostroventral‐lateral NM respectively, throughout the LVN and minimally into the SVN and SpVN. The specificity of corticonuclear terminations in the NM from the anterior vermis, heretofore not described for any primate, are similar, in terms of a general pattern, to that recently reported for the cat (Courville and Diakiw, '76).
Single unit studies on the dorsal and intermediate acoustic striae
Authors: Adams Joe C. 
Published: January 2005

AbstractStudies were made of the fiber composition and of single unit discharge characteristics in the dorsal and intermediate acoustic striae. Counts of fibers and cells revealed more than twice as many fibers as cochlear nucleus cells of the types known to contribute axons to these tracts. Recordings were made in the striae to confirm the classes of discharge patterns which are transmitted from the posterior cochlear nucleus to more central structures and to seek evidence for descending activity entering the cochlear nucleus through the striae. Discharge patterns of the majority of units resembled those seen in previous studies when recordings were made from regions of the cochlear nucleus which are known to contribute fibers to the striae. Some patterns, however, were unlike any which have been reported in the cochlear nucleus on the same side as the recording site, but resembled activity of other auditory structures, suggesting that these were descending inputs. To confirm the presence of descending activity, recordings were made in the dorsal acoustic stria at a point medial to where the stria had been completely severed. Recordings made under these conditions demonstrated the presence of descending activity. The physiological findings help explain the disparity between the counts of fibers and cells, and point out a need for more detailed descriptions of the origins of descending inputs through the striae.
Some quantitative results on golgi impregnated axons in rat visual cortex using a computer assisted video digitizer
Authors: Paldino A. M. , Harth E. 
Published: January 2005

AbstractAxonal fiber distributions of pyramidal cells in the visual cortex of the albino rat have been investigated using the rapid Golgi method and modern data collecting techniques. Three dimensional coordninate information was extracted from Golgi‐impregnated axonal networks using a computer‐assisted video digitizer. Computer programs used this data to generate various statistical distributions. In particular, angular distributions of the initial collateral segments and their endpoints were examined and found to reveal anisotropies. Inspection of the spatial distributions of the endpoints indicated a clustering at two distinct levels with respect to the pyramidal cell from which they orignate. Dynamic graphic displays of the three dimensional data have been obtained and presented in the form of computer tracings of various orthogonal projections.
The pigmented‐rat optic nerve: Fibre count and fibre diameter spectrum
Authors: Hughes A. 
Published: January 2005

AbstractA well distributed electron microscopic sample of 52,000 fibres from the pigmented rat optic nerve cross section indicates a total count of 120,000±1,600 (S. E. M.) fibres ranging from 0.437μ to 5.2μ in diameter. The fibre diameter spectrum is essentially unimodal with a peak at 1.0μ with a well developed “tail”. These results are identical to those available in the literature for the albino rat.
Morphometric analysis of the effects of exenteration and enucleation on the development of third and sixth cranial nerves in the rat
Authors: Bronson Roderick T. , Hedley‐Whyte E. Tessa 
Published: January 2005

AbstractThe effects on rat cranial nerve growth of removing various amounts of extraocular muscle was studied using morphometric techniques. Growth in the third cranial nerves was found to be severely retarded when most of the muscle tissue was removed. By contrast, removal of the eye alone, leaving extraocular muscles relatively intact, was found to have little or no effect on the subsequent growth of third and sixth cranial nerve fibers and of extraocular muscle fibers. This conclusion could be drawn only through the application of statistical methods which take into account several generally unrecognized facts: frequency distributions of axon circumference and myelin sheath thickness are highly variable from nerve to nerve even in normal rats, which often have more large fibers in left than in right nerves. The bimodal nature of peripheral nerve fiber distributions precludes the use of such parametric tests as the commonly and inappropriately used t‐test, but a non‐parametric test such as the Kolmogorov‐Smirnov test, extensively used in these studies, is inadequate for data comprising several sets of distributions to be compared. The application of the analysis of variance to some of the data and the merits of the procedure are discussed.