bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellular and chemical changes during myelination: Histologic, autoradiographic, histochemical and biochemical data on myelination in the pyramidal tract and corpus callosum of rat
Authors: Schonbach J. , Hu K. H. , Friede R. L.
Published: January 2005

A quantitative study of myelination in the pyramidal tract and in the corpus callosum of rat was undertaken to establish the order and the possible correlation of various cellular and chemical changes in the tissue.

Myelination was initiated by a period of thymidine‐H3 labeling of nuclei and g±al proliferation, resulting in a rapid increase in the cell density or “myelination gliosis.” Slightly later, there was an increase in NAD‐diaphorase activity and in leucine‐H3 uptake in both the glia cells and throughout the tissue. The formation of myelin sheaths began when myelination gliosis was established; it overlapped the periods of high enzyme activity and high leucine‐H3 uptake. Cell proliferation continued during myelin formation after the onset of myelination gliosis; the cell density in the pyramidal tract decreased during this period, probably because the spacing of the cells increased due to the growth of the myelin sheaths. Staining of myelin sheaths was estimated with a semi‐quantitative method and paralleled an increase in biochemical assays of total cholestrol. The significance and possible interrelations between the morphological and chemical changes during myelination are discussed.
Distribution of dorsal root fibers in the medulla oblongata of the cat
Authors: Rustioni A. , Macchi G.
Published: January 2005

Afferent fibers to the medulla oblongata of the cat were studied in 25 animals following section of one or more dorsal roots.

Using the Nauta‐Laidlaw stain a map was constructed of the distribution of the fibers to the dorsal column nuclei and a survey made of the afferents to other bulbar nuclei: nucleus cuneatus lateralis, lateral reticular nucleus, descending root of the fifth cranial nerve and the nucleus tractus solitarii.

In the intermediate segment of the nucleus gracilis and the caudal two thirds of the nucleus cuneatus, there is a somatotopical arrangement with a dorso‐ventral and medio‐lateral shifting of the fibers from the dorsal roots as one goes from caudal segments to more cranial ones.

A bilateral projection is demonstrated in the nucleus gracilis after section of nearly all the coccygeal‐sacro‐lumbar‐thoracic roots; the contralateral degeneration is confined to the rostral pole of the nucleus gracilis. No bilateral degeneration is found in the nucleus cuneatus after section of the roots projecting to it. Degenerated axons in the nucleus cuneatus lateralis and in the lateral reticular nucleus are always present beginning from T6–T7 while in the descending root of the fifth cranial nerve they are recognizable in only one case with a section of the third sacral root.
The facial outflow and the superior salivatory nucleus: An histochemical study in the rat
Authors: Brown J. Clevedon , Howlett B.
Published: January 2005

Shute and Lewis ('60) presented the first definite evidence for the localization of the superior salivatory nucleus by means of the thiocholine method for demonstrating cholinestrase. The outflow from this nucleus postulated by these workers is questionable in the light of other observations (Brown, '64). A re‐investigation of the salivatory nuclei in the rat by the thiocholine method in conjunction with three‐dimensional reconstructions shows that two topographically related cholinesterasepositive pathways are present at facial levels. These are the visceral motor (salivatory) rootlets and the olivo‐cochlear tract. The reconstructions decisively indicate a typical visceral motor outflow to the nervus intermedius from the superior salivatory nucleus and endorse Rasmussen's description of the olivo‐cochlear tract.
Autoradiographic study of histogenesis in the mouse olfactory bulb. II. Cell proliferation and migration
Authors: Hinds James W.
Published: January 2005

Cell proliferation and migration in the developing mouse olfactory bulb was studied by autoradiography. Animals were injected with thymidine‐H3 at various developmental stages and killed one to 96 hours later. All neurons arise in the germinal zone surrounding the ventricle. Until the fourteenth day of gestation (E14) this zone consists only of a matrix (primitive ependymal) layer. From E14 to E17 both matrix and subependymal layers are found, and from E18 to maturity only the subependymal layer is present. The matrix layer produces the mitral cells and some tufted and granule cells; the subependymal layer gives origin to some tufted cells and most of the granule cells. Mitral cell neuroblasts migrate peripherally to reach the primitive mitral cell layer three days after final DNA synthesis. Tufted cell neuroblasts migrate through the developing mitral cell layer to reach their definitive locations; external granule cell neuroblasts migrate past both developing mitral and tufted cells. Neuroglia arise from scattered proliferating glioblasts, originally derived from the periventricular germinal zone. Time of origin and rate of migration of olfactory bulb neurons was checked against the histological development of the bulb. A good agreement corroborated the autoradiographic method used in this study and in previous studies on time of origin of neurons in the central nervous system.
Correlation of glial proliferation with age in the mouse brain
Authors: Dalton Mary Margaret , Hommes O. R. , Leblond C. P.
Published: January 2005

Radioautographs of brain sections were prepared after injection of 3H‐thymidine into mice aged 23, 100, 200 or 400 days.

The presence of a small number of labeled cells in all animals indicates that neuroglia do proliferate even at an advanced age. Proliferation is most active in the corpus callosum and least so in the corpus striatum.

Comparison of the counts of labeled and unlabeled nuclei suggests that glial cells are produced in numbers exceeding growth requirements and, accordingly, that they turn over, although slowly.
Some intrinsic connections of the hippocampus in the rat: An experimental analysis
Authors: Hjorth‐Simonsen A.
Published: January 2005

Some internal pathways of the hippocampus were mapped in adult rats using Fink‐Heimer silver impregnation methods for the demonstration of anterograde axon degeneration.

Cases with lesions of regio superior of the Ammon's horn showed that regio superior projects onto the subiculum by way of fibers in the alveus. The termination is most dense in the portion of the subiculum near the presubiculum. The fibers exhibit an orderly arrangement, in that the dorso‐ventral level of the subicular degeneration depends on the level of the regio‐superior lesion.

No evidence of connections from regio superior to regio inferior and area dentata appeared in this study.

The terminal fields of ipsilateral fibers from regio inferior to regio inferior and superior are pervaded by commissural fibers. This precludes selective destruction of the ipsilateral fibers in normal rats. In order to investigate these latter ipsilateral fibers, special animals were used in which the commissures had been transsected at the age of eight days. Secondary lesions were made in the hippocampus of the adults when no stainable commissural degeneration was demonstrable. The results obtained from these animals were the following.

Lesions of regio inferior cause degeneration both in this subfield and in regio superior. The fibers terminate in the stratum oriens and radiatum, and not in the stratum lacunosum‐moleculare or on pyramidal cell bodies. The total spread of fibers along the longitudinal axis of the hippocampus is 4–5 mm, being slightly less in the regio inferior than in the regio superior. When the lesion involves only the dentate area and the adjacent part of the regio inferior, the degeneration in the regio superior is most pronounced superficially in the stratum radiatum and is absent from the stratum oriens. The fibers remaining within the regio inferior have a special mode of termination: dorsal to the lesion, degeneration is present in the deeper half of the stratum radiatum and in the stratum oriens; ventral to the lesion, degeneration is found predominantly in the superficial one half of the stratum radiatum.
An ultrastructural study of the effects of hypophysectomy on the supraoptic nucleus of the rat
Authors: Raisman G.
Published: January 2005

The axons of the supraoptic neurons of the rat were sectioned by means of a hypophysectomy. A minority of the neurons survive this operation apparently indefinitely. These cells show an initial stage of accumulation of neurosecretory material. After the first few weeks, the remaining neurohypophysial tissue becomes reorganised into a “miniature” neural lobe so that the neurosecretory cells acquire a new channel for the release of their material into the blood stream. The transient diabetes insipids subsides, and the surviving neurons undergo considerable hypertrophy. The majority of the supraoptic neurons disappear over the first few months after operation. During the first two weeks postoperatively degenerating neurons are found. They are shrunken cells with electron dense cytoplasm and show various stages of degradation of intracellular organelles. They are ultimately removed by the phagocytic activity of glial and possibly other cells.
Synaptic reorganization in the degenerating lateral geniculate nucleus of the rabbit
Authors: Ralston Henry J. , Chow Kao Liang
Published: January 2005

An investigation of synaptic plasticity in the lateral geniculate nucleus has been carried out in rabbits surviving one day to one year following ipsilateral visual cortex removal. There is extensive retrograde degeneration of LGN neurons, and the altered nucleus thus provides a model for examining reorganization of optic tract axons which have been deprived of their normal postsynaptic membrane.

The distribution of synaptic contacts in normal LGN was quantitatively determined. In the animals surviving 1–14 days after cortex ablation, there was extensive cell death and loss of the axodendritic synapses of cortical origin, which constitute the most numerous synaptic type in normal LGN.

In animals surviving 4–12 months, there were few remaining neurons and dendrites. The fine structure of the nucleus was characterized by a shift from axodendritic synaptic contacts, as in the normal, to a ten–fold increase in axoaxonal synapses, which became the dominant population. The contribution of optic axons to this synaptic population was determined by contralateral retinal removal. It was found that the synaptic axoaxonal organization in the altered LGN follows the rules of normal organization, in that optic afferents are invariably the presynaptic component in round to flat vesicle axoaxonal synapses.

The LGN's undergoing chronic retrograde degeneration shrank to about twothirds the size of the normal nucleus. There was no evidence of reduction in the length of optic tract axons within the nucleus.

The evidence indicates that there are new synaptic contacts formed between surviving axons in the degenerating LGN, as a consequence of the loss of postsynaptic dendritic membrane. The new synapse formation is guided by the normal rules of axoaxonal organization, indicating a maintenance of recognition of appropriate membrane for synaptic contact in the reordered LGN. It cannot be stated whether sprouting of axons accompanies the formation of new synapses or whether the new synaptic contacts are exclusively between preexisting synaptic knobs in LGN.
An ultrastructural analysis of the photoreceptors of the squid and their synaptic connections. I. Photoreceptive and non‐synaptic regions of the retina
Authors: Cohen Adolph I.
Published: January 2005

As part of a larger ultrastructural study on the photoreceptors of the squid,Loligo pealei, this paper reports findings on non‐synaptic regions. The cross‐sectional profiles of individual distal segments coincided in horizontal sections as far as 75 μ apart, but progressively less with greater separations. Areas of cross‐section showed a unimodal distribution skewed towards 6 μ2, the smallest areas. The distribution of ratios of villous to smooth border was unimodal and skewed with 1.0 being the most numerous and minimal ratio. This ratio tended to increase linearly with area. Cells of small cross‐section were completely surrounded by villous border of other cells and about 60° of the perimeter of any cell had microvilli on both sides of the border. Cells participated in odd or even numbers of rhabdomes, up to eight. Pentalaminar membrane junctions between microvilli of the same or neighboring cells were observed. Cytoplasmic microtubules were concentrated near villous borders. In light adaptation some ommin granules entered the photoreceptor tips, and the rhabdomes which formerly began near the surface, now began somewhat below this level. A terminal bar zone existed proximal to the rhabdomes. Here glial cytoplasm separated photoreceptors and both cells contained ommin granules. Photoreceptor somas lacked glial separation and were highly interplicated. Mitochondria were longitudinally arranged along the somal membrane. The planes of the lamellate membrane bodies, seen in the somal cytoplasm of the cells, did not exhibit a rectilinear pattern such as that displayed by the basically rectangular distal segment cross‐sections and microvillar orientations.
Projections from the parietal cortex to the brain stem nuclei in the cat, with special reference to the parietal cerebro‐cerebellar system
Authors: Mizuno Noboru , Mochizuki Kaori , Matsushima Chihiro Akimoto Ryotaro , Sasaki Kazuo
Published: January 2005

Direct projections from the anterior portions of the parietal cortex of the cat to the brain stem nuclei, especially those sending fibers to the cerebellum, were investigated by the Nauta‐Gygax and Fink‐Heimer methods.

Following unilateral lesions of the anterior portions of the middle suprasylvian and/or lateral gyri, a significant amount of pericellular degeneration was found almost entirely ipsilaterally in the rostral levels of the red nucleus and its vicinities, and in the pontine nuclei. Projection fibers to the pontine nuclei appeared to extend over several longitudinal, columnar zones in the pontine gray. Fibers from the anterior portion of the lateral gyrus were observed mainly in the paramedian and lateral nuclei, and those from the middle suprasylvian gyrus in the ventral, paramedian and lateral nuclei. Degeneration in the nucleus reticularis tegmenti pontis of Bechterew was slight, and found bilaterally with ipsilateral predominance.

The significance of the anterior portion of the parietal cortex of the cat as a link of cerebro‐cerebellar loops was discussed.
Age changes in conduction velocity of unmyelinated fibers
Authors: Hopkins A. P. , Lambert E. H.
Published: January 2005

Increase of conduction velocity of unmyelinated fibers has been measured in the cervical sympathetic trunk of growing rats. Fibers in this nerve are almost all unmyelinated.

Conduction velocity is about half adult values at ten days after birth. The velocity in some nerves reaches the adult range by 50–80 days. There is evidence that the velocity of many fibers other than the fastest also reaches the adult range by this age.

During the period of growth from 10–112 days of age, velocity increases in direct proportion to the increase in length of the nerve.
Comparison of the cortical degeneration in the visual regions of the temporal lobe of the monkey following section of the anterior commissure and the splenium
Authors: Zeki S. M.
Published: January 2005

The patterns of degeneration in the visual centers of the temporal lobe of the rhesus monkey following section of the anterior commissure and the splenium of the corpus callosum have been compared. Both commissural systems distribute interhemispheric fibres to the anterior part of the inferior temporal neocortex whereas the posterior part receives commissural fibres predominantly from the splenium.

There were hints that the temporal visual neocortex may be further subdivided into discrete areas since the degeneration that follows section of either commissure does not fall within one continuous region but in patches, these patches being separated from one another either by cortex showing no degeneration or by cortex in which the density of degeneration is much reduced.
Contribution to the quantitative analysis of neuronal parameters: The effects of biased sampling procedures on estimates of neuronal volume, surface area and packing density
Authors: Mayhew T. M. , Momoh C. K.
Published: January 2005

Photomicrographs of motoneuron perikarya from the anterior horn of the rat cervical enlargement were analysed by various histometric and stereological procedures to compare the volumetric, volume‐to‐surface ratio, and packing density estimates obtained by several distinct sampling regimes. Information derived from unbiased motoneuron samples was compared with quantitative data derived from samples biased towards the nucleolus and from others containing cells above a minimal size (dimension‐biased samples). Nucleolarbiasing and dimension‐biasing techniques were found to produce only gross estimates of neuronal parameters. They produced substantial overestimates of cellular volume and perikaryal volume‐to‐surface ratio, together with significant underestimates of neuronal population density, perikaryal volume proportion and cytoplasmic volume/nuclear volume ratio. Unbiased sampling increased the amount of available material which could be analysed. It is concluded that meaningful estimates of these neuronal parameters are best obtained by the unbiased stereological approach, thereby giving a more accurate picture of the structural composition of nervous tissue.
Anterograde degeneration study of the superior colliculus in Tupaia glis: Evidence for a subdivision between superficial and deep layers
Authors: Harting J. K. , Hall W. C. , Diamond I. T. , Martin G. F.
Published: January 2005

The large, well developed superior colliculus of the tree shrew with its highly differentiated layers is ideal for analyzing the connections of individual layers. Our most significant finding concerns the differences between the projections of the superficial and deep layers. Lesions limited to those strata which receive projections from the retina and striate cortex (superficial 3 layers) result in terminal degeneration almost exclusively within the pulvinar, the pretectal area, and the dorsal and ventral lateral geniculate nuclei. In each case, the greatest amount of degeneration was present in the pulvinar, supporting previous suggestions that the tecto‐pulvinar pathway conveys visual information. In sharp contrast, lesions limited to the deep layers which receive multimodal input from nonstriate areas of the neocortex and from a variety of subcortical centers, produce terminal degeneration in entirely different thalamic nuclei — certain intralaminar nuclei, the subthalamic region, and a region homologous to the posterior nuclear group of Rose and Woolsey ('49). The deep lesions also result in terminal degeneration within the inferior colliculus, the parabigeminal nucleus, the reticulo‐tegmental nucleus, and the inferior olivary nucleus, as well as in the brainstem reticular formation. Finally, deep lesions produced scattered degenerating fibers in the motor facial nucleus. Our results favor a division of the tree shrew superior colliculus into superficial and deep portions based on strikingly different projection patterns and may be useful in resolving certain problems of thalamic homology.
An electron microscopic study of synaptic organization in the medial superior olive of normal and experimental chinchillas
Authors: Perkins Randolph E.
Published: January 2005

The medial superior olive (MSO) was studied in normal animals to determine the types of synaptic endings and their distribution over the surface of MSO neurons. Unilateral lesions were made in the anteroventral cochlear nucleus (AVCN) of experimental animals to determine the source of at least one synaptic type in the MSO.

The surfaces of MSO neurons in normal animals were studded with three distinct types of synaptic endings distinguished mainly by the size of their synaptic vesicles. There were endings with large vesicles, 510 Å in mean diameter; endings with small vesicles, 380 Å; and endings with vesicles intermediate in size. 435 Å. The large vesicle ending typically was greater than 2 μm in maximum diameter. It appeared as the termination of a myelinated axon or as a swollen portion of a node and made multiple asymmetrical synapses. Large vesicle endings occurred exclusively on dendrites where they formed 85% of the synaptic endings. Small vesicle endings typically were less than 2 μm in diameter. They appeared as the termination of a fine unmyelinated axon and made only one symmetrical synapse. Small vesicle boutons occurred infrequently over the entire neuronal surface. Intermediate vesicle synaptic endings were similar to large vesicle endings except that they were present only on the cell body, axon hillock, and proximal portions of the dendrites where they formed most of the synapses.

In AVCN lesioned animals degenerating myelinated axons and large vesicle synaptic endings were distributed to the lateral dendrites of the ipsilateral MSO and medial dendrites of the contralateral one. In addition, a few degenerating axons and large vesicle endings were found among the ipsilateral medial dendrites. The changes in the degenerating endings were characterized by an early proliferation of neurofilaments and swelling of the endings followed by collapse of the endings and increase in electron density, disappearance of filaments and synaptic vesicles, and phagocytosis of the degenerated endings by reactive glial cells. No degenerative changes were observed in the small and intermediate vesicle endings.

The results of this study indicate that the more numerous large vesicle endings presynaptic to the MSO dendrites are the axon terminals of neurons in the AVCN. The persistence after lesions of the small and intermediate vesicle endings suggests that they arise from as yet unidentified sources.
Reciprocal point‐to‐point connections between parastriate and striate cortex in the squirrel monkey (Saimiri)
Authors: Tigges J. , Spatz W. B. , Tigges Margarete
Published: January 2005

Experimental‐anatomical evidence is presented that in Saimiri two fiber systems project from area 18 upon area 17. Both systems terminate exclusively in layer I of area 17; in some other respects they exhibit characteristic differences.

The fibers of the Horizontal System ascend from their origin in area 18 directly into layer I where they travel horizontally and parallel to each other to their termination site in area 17. This system is locally restricted since it connects only posterior area 18 with anterior area 17, i.e., it connects portions of both areas located near the representation line of the zero vertical meridian of the visual field.

The fibers of the U‐fiber System arise from the supragranular layers of area 18. They reach their termination site in area 17 via the white matter from which they ascend perpendicularly into layer I. The U‐fiber system establishes a mirrorimage point‐to‐point connection between area 18 and area 17. This finding combined with the results of previous reports describing the similarly ordered association of area 17 with area 18 demonstrates a precisely organized reciprocal point‐to‐point connection between areas 17 and 18.
Investigation of glial cells in semithin sections. I. Identification of glial cells in the brain of young rats
Authors: Ling E. A. , Paterson Jean A. , Privat A. , Mori S. , Leblond C. P.
Published: January 2005

The staining of half‐micron thick Epon sections with toluidine blue provides a reliable method for the identification of glial cells. The diagnostic features of these cells observed in the corpus callosum of one‐month‐old rats are as follows: (1) Astrocytes have a very pale nucleus and cytoplasm; the nuclear envelope is sharply outlined by a thin chromatin lining with occasional chromatin beads; (2) Microglia have a small nucleus in which large, dark chromatin masses contrast with the nucleoplasm; the nucleus is round or elongated, and may be somewhat angular. The pericytes, which have a similar but usually crescentic nucleus, may be related to microglia. (3) Oligodendrocytes vary from pale to very dense and may be arbitrarily classified into three subgroups: The light oligodendrocytes are large pale cells with round to ovoid nucleus containing a prominent nucleolus and little or no condensed chromatin; the cytoplasm is extensive and appears pale, although less so than the nucleus. The medium shade oligodendrocytes are smaller cells that have an ovoid nucleus carrying small chromatin clumps and appearing moderately basophilic throughout; the cytoplasm is less extensive and somewhat darker than in the “light” subgroup. The dark oligodendrocytes are usually smaller than medium shade cells and often have an indented or angular nucleus with large chromatin masses; both nucleoplasm and cytoplasm are densely stained; the cytoplasm is often scanty and accumulated on one side of the nucleus.

Semithin sections of the cerebral cortex show glia with similar features, with the exception of the astrocytes, which have a smaller but more basophilic cytoplasm than in corpus callosum.

The cells of the subependymal layer of the lateral ventricle, when examined in semithin sections in the neighborhood of the corpus callosum, display a patchy, irregular nucleus and a scanty cytoplasm. Similar cells with a more regular nucleus are found outside the layer and in the corpus callosum; they are designated free subependymal cells.
Neuromuscular responses of sloths
Authors: Toole James F. , Bullock Theodore H.
Published: January 2005

Because sloths are among the slowest moving of mammals, it is of interest to determine whether the rate limiting factor is in their motivation, central nervous system, or their muscles.

Muscle characteristics of ten sloths (Choloepus hoffmanni and Bradypus tridactylus) were studied by neuromuscular examination, electrophysiological, biochemical, and histological methods. Muscle twitch contraction averages 120 msec and one‐half relaxation time was 108 msec. Muscle contraction and relaxation are extremely sensitive to cold but were unaltered by calcium, quinine or procaine amide.

Biochemical studies showed ATPase activity to be extremely low.

Ultrastructure conformed closely to that of mammalian twitch fibers.

Our data suggest that although muscle mechanics undoubtedly contribute to the slow movements of the sloth, they are not the only rate limiting factor.
The tectopontine projection in the cat: An experimental anatomical study with comments on pathways for teleceptive impulses to the cerebellum
Authors: Kawamura Koki , Brodal Alf
Published: January 2005

Following lesions of different sizes and locations of the superior colliculus the distribution of degenerating fibers in the pontine nuclei was determined in the cat in Nauta and Fink and Heimer impregnated sections. The superior colliculus projects exclusively to most of the dorsolateral nucleus in the ipsilateral pontine nuclei. There appears to be some degree of topical arrangement in the projection.

Three cases with lesions of the superior colliculus on one side and of the inferior colliculus, the cerebral auditory or cerebral visual areas, respectively, on the other side, permit comparisons between the projections of the superior colliculus with those from the other structures mentioned. The inferior colliculus projects onto the dorsolateral nucleus of the pons in an area which overlaps to some extent with that of the superior colliculus. Confirming more systematic studies of P. Brodal it is found that the pontine projection area of the auditory cortex to a large extent coincides with that of the superior colliculus, while the pontine projection area of the visual cortex is entirely different.

These findings, together with other data from the literature, strongly suggest that the pathway for optic impulses to the vermal visual area of the cerebellum passes via the superior colliculus and the dorsolateral pontine nucleus. Direct tectocerebellar fibers or pathways via the reticular formation are scarcely involved in this process. Anatomically there is evidence for another route for visual impulses to the cerebellum: via the visual cerebral cortex and the pons to regions in the cerebellar hemisphere. This is in agreement with physiological findings and suggests that there may be at least two visual areas in the cerebellum.

The anatomical data show that there are ample possibilities for an integration of optic, acoustic and other impulses in the superior colliculus as well as in its projection area in the pons.
A comparative study of spinal projections to the brain (except cerebellum) in three classes of poikilothermic vertebrates
Authors: Hayle T. H.
Published: January 2005

Lesions were made at varying levels in the spinal cords of a number of dogfish, rudd, and frogs. After a suitable survival period the resulting fibre degeneration was demonstrated by means of a silver impregnation technique. The findings have provided experimental confirmation of a profuse spinal projection to the reticular formation of the hindbrain in all three classes examined. These fibres were found to project to a constant sector of the reticular formation which closely corresponded not only between individual specimens of the same species, but between the three species, and which was situated ventrolaterally in the medulla oblongata. The density of this dengeneration was always greatest in the caudal brainstem and became progressively less at more rostral levels. All spinal projections to the reticular formation exhibited some degree of bilaterality, including those in specimens with lesions of hemisections or less. A spinotectal pathway was also demonstrated in certain specimens of dogfish. No involvement of cranial nerve nuclei was seen. These findings are discussed.
The effects of monocular lid suture upon the development of the lateral geniculate nucleus in squirrels (Sciureus carolinensis)
Authors: Guillery R. W. , Kaas J. H.
Published: January 2005

Three infant squirrels had the lids of one eye sutured prior to eye opening. The animals were killed when they were adults and the cells in the lateral geniculate nucleus were studied after Nissl staining.

The nerve cells within the deprived geniculate layers are smaller than the normally innervated cells. However, this asymmetry is seen only in the segment of the lateral geniculate nucleus that receives its inputs from the binocular portion of the visual field. Areas receiving from the monocular portion show no significant changes in cell size or cell packing. Thus, visual deprivation by itself does not affect perikaryal growth in the lateral geniculate nucleus. Growth is affected only in those parts of the geniculo‐cortical system in which the deprived cells have to compete with cells that are normally innervated.
The effects of age upon the main nucleus of the inferior olive in the human
Authors: Monagle Renee Dambiermont , Brody Harold
Published: January 2005

The neuronal population of the main inferior olivary nucleus was determined by complete cell counts of this structure in 18 human subjects of various ages. The age groups represent a progression from an immature infant of 23 weeks gestation to an 89 year old. The cell population was found to be lowest in the most immature infant (233,360), increasing in number up to the time of birth, the neo‐natal values being 327,330 for the three day old and 380,460 for the three month old. While minor cell fluctuations were noted in the specimens selected from the first to ninth decades, all values were relatively close to a post‐natal mean value of 363,784. A low value of 317,600 was found in an 82 year old and a high value of 405,580 in a 73 year old. Within comparable age groups the cell populations showed a similar pattern of distribution throughout the length of the nucleus.

The structural evolution of the inferior olive during the lifespan is characterized by a period of growth from a calculated length of 7.1 mm before nine years of age to the 14.5 mm calculated average length for all the specimens in the series beyond the nine year stage.
The development of bergmann glia in mutant mice with cerebellar malformations: Reeler, staggerer and weaver. Immunofluorescence study with antibodies to the glial fibrillary acidic protein
Authors: Bignami A. , Dahl D.
Published: January 2005

The development of Bergmann glia has been studied by immunofluorescence with glial fibrillary acidic (GFA) protein antiserum in three mouse mutants with cerebellar malformations: reeler, staggerer and weaver. In none of these mutants was astrocytic differentiation delayed. The appearance of Bergmann glia in four‐day‐old reeler, staggerer and weaver mice was normal. Abnormalities of the neuroglial framework in the cerebellar cortex were observed later in development. In reeler mice immunofluorescent astrocytic fibers formed a mesh throughout the cerebellum. Radially oriented fibers were not observed. In staggerer mice Bergmann fibers shorter and more irregular than in littermate controls were still observed on the 14th day. Bergmann fibers were no more demonstrated by immunofluorescence in staggerer mice sacrificed later in development and little immunofluorescence was observed anywhere in the cerebellum of these animals. Heterozygous weaver and normal littermates were easily recognized in cryostat sections stained with toluidine blue, but the immunofluorescent pattern of Bergmann fibers was identical throughout development. Bergmann fibers were present and apparently not decreased in number in homozygous weaver mice but they had an immature appearance, i.e., they were shorter, less straight and less evenly spaced than in normal littermates of comparable age. In one‐month‐old homozygous weaver mice a dense mesh of immunofluorescent fibers with the general orientation of Bergmann fibers was present within the molecular layer of the cerebellum.
Origin of cerebellar climbing fibers in the rhesus monkey
Authors: Rivera‐Dominguez Manual , Mettler Fred A. , Noback Charles R.
Published: January 2005

The inferior olivary nuclear complex is generally considered to be the major source of climbing fibers to the cerebellum (Bell and Dow, '67). To test the validity of this statement, experiments using monkeys were designed in which the olivocerebellar fibers were transected in their course through the medulla to the contralateral hemicerebellum. After allowing for anterograde degeneration of these transected fibers, the cerebellum of each monkey was stained and examined for the presence and condition of climbing fibers. In each monkey olivocerebellar fibers were transected at one of three sites: (1) within the right inferior olivary nucleus in one rhesus monkey, (2) at the decussation of the olivocerebellar fibers, within the region of the raphe, in five monkeys and (3) in the left parasagittal plane, just lateral to the inferior olivary nucleus, in one monkey. No noticeable reduction was found in the number of silver stained climbing fibers associated with the Purkinje cells of each hemicerebellum after these lesions. None of the monkeys exhibited durable, specific cerebellar signs. On the basis of the histological evidence obtained from the above experiments, it is concluded that the inferior olivary complex is not the major source of climbing fibers to the cerebellum.

Climbing fibers were readily identified in each of the sections examined. However, silver‐stained climbing fibers were not associated with many Purkinje cells in every one of these sections. There were 1.7 times more Purkinje cells without climbing fibers than those with climbing fibers. This ratio of 1.7 to 1 characterized normal cerebella as well as both hemispheres of the cerebella of the cerebella of the experimental monkeys.
Sequence of changes in neurofibrils (neurofilaments) induced in synaptic regions of bullfrogs by environmental temperature changes
Authors: Potter H. D. , Hafner G. S.
Published: January 2005

Prolonged exposure of bullfrogs (R. catesbeiana) to a cold (6°C) environment causes a progressive increase in numbers of neurofibrillar boutons in synaptic regions of the midbrain and induces thickening of perikaryal neurofibrils. Quantitative estimates of the numbers of boutons in lamina 5 of the optic tectum with controlled conditions for reduced silver staining, show the effects are graded with respect to both temperature and duration of exposure. Initial acclimation to 18°C results in few neurofibrillar rings but upon changing to 6°C the counts increase linearly with time to reach a 20 fold increase at three weeks. Rewarming to 18°C causes a return to the original numbers in less than one day.

In electron micrographs ring‐shaped bundles of 100 Å diameter neurofilaments are coextensive with the cold induced neurofibrillar boutons of light microscopy; both are absent following acclimation to a warm environment. The cold exposure also causes large accumulations of β glycogen particles to appear in axons, dendrites, and synaptic knobs.
Synaptic organization of the nucleus gracilis of the cat. Experimental identification of dorsal root fibers and cortical afferents
Authors: Rustioni Aldo , Sotelo Constantino
Published: January 2005

The synaptic organization throughout the nucleus gracilis has been investigated in unoperated cats. Axon terminals of variable size can establish synaptic contacts with neuronal somata, dendritic processes, initial segment of axons or with other axon terminals at “complex synaptic arrangements.” Large boutons with rounded vesicles are regularly associated with smaller boutons containing flattened vesicles; the latter type of bouton forms frequently a double synapse being presynaptic to the large bouton and to the element postsynaptic to this (“complex synaptic arrangements”). Medium‐sized to small axon terminals of the “isolated” type contain primarily either rounded or flattened vesicles. These boutons are surrounded by a thin glial process which also wraps the postsynaptic element, mostly represented by a small dendritic profile. The “isolated” type of bouton seems to be more abundant in the rostral than in the caudal part of the nucleus. In all unoperated control animals altered axons and axon terminals are present. They are enlarged and display hyperplasia and dilatation of tubular profiles of smooth endoplasmic reticulum as well as proliferation of microtubules and various aspects of mitochondrial degeneration.

In cats sacrificed 48 hours after section of lumbo‐sacral dorsal roots a high number of “dark” boutons are observed in various stages of degeneration. These terminals are identifiable with the large boutons containing rounded vesicles and postsynaptic to the smaller boutons with flattened vesicles. The morphology of dorsal root terminals in the nucleus gracilis is discussed in relation to that of primary afferent terminals in other central structures and to the functional aspects of axo‐axonic contacts.

The sensori‐motor cortex was removed in another series of animals which were sacrificed after one to four days. As a consequence of such lesions cortical fiber terminals in the nucleus gracilis may undergo either the “dark” or the “light” type of degeneration. These terminals are of smaller size than those of primary afferents, they usually synapse on dendritic profiles of small diameter, are not involved in axo‐axonic contacts and seem to contain rounded vesicles. Therefore they can be identified with at least some of the small and medium‐sized boutons of the “isolated” type.
An electron microscopic study of the newt (Triturus viridescens) Optic Nerve
Authors: Turner James E. , Singer Marcus
Published: January 2005

The newt (Triturus viridescens) optic nerve appears to be more primitive than that of higher vertebrates. Only one type of glial cell is present and their stellate cell bodies are located in the core of the nerve. They send radiating processes to the surface to form a glial limitans beneath the meninges. The processes and their branches enwrap fascicles of naked axons and scattered myelinated fibers. The position and cytological character of these cells and their processes suggest that they are primitive ependyma. They subserve the functions of astrocytes and oligodendrocytes, in the latter case forming myelin wrappings. The position of their cell bodies is reminiscent of that of embryonic ependymal cells which surround the lumen of the optic stalk of vertebrates during eye development. Their cytoplasm is of medium to high cytoplasmic density, contains numerous cytoplasmic organelles and exhibit both microtubules and microfilaments.
Ablation study of the superior colliculus in the tree shrew (Tupaia glis)
Authors: Casagrande V. A. , Diamond I. T.
Published: January 2005

The main conclusions rest on the results obtained by ablating the superior colliculus in eight tree shrews. Additional animals either normal or with lesions of the superior collculus or striate cortex were studied to support or extend the basic findings. All eight tree shrews showed a profound loss of pattern discrimination which could not be attributed to some general factor such as inattention or an incapacity to learn. Thus, all succeeded in discriminating differences in the orientation of stripes but all failed to learn a habit based on discriminating the orientation of triangles. Two of the eight appeared normal in their capacity to orient toward, follow and track objects on the basis of vision. Six of the eight showed a remarkable unresponsiveness to visual stimuli manifested by a failure to follow, track, orient or even avoid what normal animals would regard as a threatening stimulus. This difference was clearly related to the extent of the lesion. In the two cases with normal visually guided behavior only the superficial three layers of the superior colliculus were removed. In the six cases with visual neglect the lesions included the deeper layers of the superior colliculus and invaded adjacent structures, notably the pretectum. It was concluded on the basis of differences between superficial and deep layers in their connections and in the behavioral effects of their ablation that the superior colliculus consists of at least two subdivisions.
Prenatal development of the human chief sensory trigeminal nucleus
Authors: Brown Jerry William
Published: January 2005

The development of the chief (main or principal) sensory nucleus of V was studied in 27 human embryos and fetuses, 7 to 30 weeks of menstrual age (19 to 261 mm CR length). Nissl and protargol silver preparations were used.

The chief sensory nucleus develops by the migration of neuroblasts from the neuroepithelium lateral to the sulcus limitans. Migrations occur cAUdally at levels of the entering sensory root fibers and posterior trigeminal nucleus in the 18 mm, 7‐week embryo and later (24 mm, 8 weeks) at levels rostral to the motor nucleus of V. Cell differentiation within the nucleus progresses in a similar cAUdorostral sequence (cAUdally at 8.5 weeks, 27.4 mm and rostrally at 12.5 weeks, 65.5 mm) as well as in a dorsoventral sequence. Correlations between neuronal differentiation and functional activity indicate that the dorsal part of the chief sensory nucleus serves the maxillo‐mandibular divisions and the ventral part serves the ophthalamic division of V. In general, the ontogenetic development of the human chief sensory nucleus and the phylogenetic development of this nucleus are comparable.

At 7.5 weeks (20.7 mm) a group of better differentiated cells appears cAUdally in the dorsomedial region of the primitive chief sensory nucleus (level of the posterior trigeminal nucleus). In 8.5‐week fetuses the cells of this group exhibit characteristics of functional neurons and form a distinct island. Neurons in this position remain the largest and best differentiated of those in the chief sensory nucleus throughout the fetal period studied. These large, dorsomedially located cells appear at progressively more rostral levels so that at 12.5 weeks they extend nearly to the rostral pole of the nucleus. It is suggested that these neurons constitute at least part of the supratrigeminal nucleus and that they serve as an integral part of the reflex arc concerned with mouth opening which occurs as a part of the total pattern response of the human fetus to perioral stimulation at 8.5 weeks and later with other reflex jaw muscle activity.
The telencephalon, diencephalon, and mesencephalon of the canary, Serinus canaria, in stereotaxic coordinates
Authors: Stokes Tegner M. , Leonard Christiana M. , Nottebohm Fernando
Published: January 2005

A stereotaxic atlas of the telencephalon, diencephalon and mesencephalon of the canary, Serinus canaria, was prepared for use in anatomical and behavioral experiments. Canaries have a complex vocal and behavioral repertoire many of whose components are under hormonal control in the male, and are therefore useful for many physiological and anatomical experiments. They are available commercially, breed easily in captivity, are quite hardy and respond well to anesthetic and surgical procedures.

The atlas consists of 30 frontal plates from the frontal pole to the level of the motor nucleus of the trigeminus. One sagittal plate is included for reference purposes. Six birds (three males and three females) with marking lesions were used to make the atlas. Their brains were embedded in albumin‐gelatin media, cut at 50 and 25μ and stained with cresyl violet for cell bodies, Weil stain for myelinated fibers and the Fink‐Schneider method for unmyelinated fibers. Plates were drawn from the cresyl violet series and labeled using all three stains.

The completed atlas was tested for accuracy by making 12 small lesions in a number of predetermined discrete loci in several birds and evaluating their placement. Eleven of these lesions were found to be within the targeted structure. The results of this test, combined with the results of experiments in over 50 birds, have shown the atlas to be accurate in 80% of all cases.
Scanning electron microscopy of the subarachnoid space in the dog. II. Spinal nerve exits
Authors: Malloy John J. , Low Frank N.
Published: January 2005

Young dogs were perfused with buffered aldehydes. For scanning electron microscopy MICROFIL was injected to help prevent vascular collapse. The dura‐arachnoid was exposed leaving the nerve exits and rootlets intact. These were identified according to level and dissected free. Selected specimens were photographed at low magnification. Others were embedded in Epon 812 and sectioned for light and transmission electron microscopy. Similar specimens were prepared by critical point drying and palladium‐gold coating for scanning electron microscopy.

Nerve roots pierce the dura through single exits (upper cervical, lower lumbar, sacral), or by exits separate for dorsal and ventral roots (lower cervical, thoracic, lumbar), or by multiple exits (cervical). Scanning electron microscopy reveals complicated tissue relationships chiefly involving arachnoid trabeculae. At the point of nerve root exits the arachnoid gives rise to numerous arachnoid trabeculae which form highly fenestrated sheets. These attach to blood vessels and nerve roots. A lateral recess occurs between dorsal and ventral roots (cervical, lumbar). Numerous macrophages are present on the various surfaces studied.