bluuebunny/crossref_metadata_2025 huggingface dataset:
Organometallic materials for nonlinear optics
Authors: Nalwa Hari Singh
Published: December 2004

Almost three decades ago, the field of nonlinear optics evolved with the discovery of lasers. In the beginning, nonlinear optical (NLO) phenomena were investigated in inorganic materials, leading to the development of traditional NLO materials such as lithium niobate, potassium titanyl phosphate, quartz and gallium arsenide. In the 1970s, the importance of organic materials was realized because of the promise of large NLO responses, high laser damage thresholds, fast optical responses, architectural flexibility and ease of fabrication. Following work with organic materials, the scrutiny of organometallics also began recently. In organometallics, the metal‐ligand bonding is expected to display large molecular hyperpolarizability because of the transfer of electron density between the metal atom and the conjugated ligand system. In organometallics, the diversity of central metals, oxidation states and ligands fosters in optimization of the charge‐transfer interactions. Keeping this in view, second‐ and third‐order NLO properties of organometallics have been reviewed here, highlighting new materials that are emerging. Organometallics may have a wide range of applications in opto‐electronics including integrated optics, optical switching, telecommunications, bistability and modulation.
A mechanism of photo‐oxidative destruction for polythylene polymers in the presence of ferrocene derivative additives
Authors: Kalennikov E A , Kuzina S I , Yuran V S , Mikhailov A I , Popova L V
Published: December 2004

The effect of ferrocene additive concentrations on the stability of polythylene polymers under atmospheric ageing and ultraviolet irradiation is reported. At concentrations under ca 5 × 10−3 mol kg−1 polymer the ferrocene compound is shown to diminish polymer resistance to light, whereas above this concentration such a compound stabilizes the polymeric matrix. Another purpose of the work is to look into the photo‐oxidative destruction of polyethylene doped with ferrocene compound by using an EPR technique. A mechanism of photo‐oxidative destruction of polyethylene polymers in the presence of ferrocene compounds is proposed.
Fluorescent humic substances–arsenic complex in well water in areas where blackfoot disease is endemic in Taiwan
Authors: Lu Fung‐Jou , Hsieh Hung‐Pin , Yamauchi Hiroshi , Yamamura Yukio
Published: December 2004

The relationship between the four components, (1) fluorescence intensity, (2) arsenic concentration, (3) pH and (4) total dissolved solids, (TDS) measured in well waters from areas in Taiwan where blackfoot disease (BFD) is endemic was studied, as well as the relationships between the four degrees of BFD and each of the above four symptomatic components, in order to evaluate the etiological factors of BFD more progressively. The following 95% confidence intervals were obtained in well water samples (n = 1189): fluorescence intensity, 26.837–32.570; arsenic concentration, 0.103–0.127 mg dm−3; pH, 7.466–7.519; and TDS 733.063–801.647 mg dm−3. Fluorescence intensities of the four degrees of BFD were not all the same (F = 64.54, P < 0.001), and nor were arsenic concentrations (F = 72.03, P < 0.001), pH values (F = 7.30, P < 0.001), nor TDS values (F = 10.76, P < 0.001). In addition, multiple comparisons indicate that the higher the epidemical degree, the higher the fluorescence intensities, arsenic concentrations and pH values become; however, such a relationship is not found for TDS values. Moreover, the fluorescence intensities have positive linear correlations with arsenic concentrations (r = 0.49, P < 0.001), pH (r = 0.25, P < 0.001), and TDS (r = 0.18, P < 0.001), as do the arsenic concentrations with pH (r = 0.22, P < 0.001). Of the four epidemical degree groups, pairs are not significantly different from one another in correlation coefficients between fluorescence intensity and arsenic concentration, which implies a steady relationship between fluorescent compounds and arsenic. We conclude that fluorescent compounds in well water, as possible etiological factors of BFD, are closely related to arsenic along with pH and TDS values in the areas where BFD is endemic. In addition, we infer that a complex is formed by fluorescent compounds, arsenic and other metals.
Tin in pharmacy and nutrition
Authors: Tsangaris John M , Williams David R
Published: December 2004

The occurrence of tin in plants, animals and humans is discussed in relation to its abundance in the lithosphere and hydrosphere and the range of different tin(II) and tin(IV) complexes formed. A reasoned consideration of the essentiality or otherwise of tin for living species is given and it is concluded that tin is beneficial even if not yet proved to be an essential element.

After reference to the chemistry of tin compounds, there is a detailed discussion of their toxicity in animals and humans. Feasible routes for tin intake and uptake into humans are described.

The use of tin pharmaceuticals in previous and current times is reviewed and areas for which they are currently permitted for use in man as dentifrices and mouth washes, as radiopharmaceuticals and for the treatment of jaundiced newborns are described. A detailed review of tin‐coating antitumour agents as representative tin pharmaceuticals is given.

Finally, a range of tin compounds having other specific pharmaceutical applications and which are currently being investigated are listed.
Biotransformation of [3H]methylarsonic acid in a static seawater system containing Mytilus californianus
Authors: Cullen William R , Pergantis Spiros A
Published: December 2004

Mytius californianus exposed for 9 days to a seawater system containing [3H]methylarsonic acid, was found to contain [3H]methylarsonic acid along with [3H]arsenobetaine and two unknown 3H‐labeled compounds in the tissue parts of the mussel. A linear increase with time in the specific activity present in the flesh of Mytilus californianus was also observed. The highest specific activity was found in the visceral mass and the gills of the mussel.
The extrapyramidal systems of the spinal cord. II. Results of combined pyramidal and extrapyramidal lesions in the macaque
Authors: Goldberger Michael E.
Published: December 2004

Unilateral spinal lesions were made in six Macaques; in two, the bulbar pyramid was sectioned contralaterally. In four Macaques with chronic pyramidal section, contralateral spinal lesions were made. The effect of each lesion separately and of the combined lesions upon the locomotor status of the animals was evaluated behaviorally, by electromyography and the lesions studied histologically after two years' survival.

Spinal lesions provoked changes in resistance to passive stretch and tendon reflexes primarily, and changes in movement secondarily: when hypertonus appeared, movements in opposing muscles were restricted, whereas movements opposing muscles were restricted, whereas movements opposed by muscles with decreased tone were hypermetric. Spinal lesions greatly altered the paresis provoked by pyramidotomy: small ventrolateral lesions restored “contact” placing, improved stepping and hopping and made the hypotonic (“pyramidal”) limb hypertonic. Execution of movements was poor, however, poorest in an animal with combined pyramidal and ventral funiculus lesion. The importance of extrapyramidal tracts in return of function following pyramidotomy was demonstrated in relation (a) to the size of the spinal lesion and (b) to its cross‐sectional location.

Gross sequential movement of muscles normally fixating the limb appears when the pyramid is cut. These movements are greatly impaired when spinal lesions are added, and the usual grouping of synergists is disrupted. Fixation of the limb represents the integration of extrapyramidally activated, pyramidally inhibited synergistic contractions upon which discrete usage of distal muscle depends.
The foetal sheep: Morphogenesis of the nervous system and histochemical aspects of myelination
Authors: Barlow R. M.
Published: December 2004

The development of the central nervous system of the sheep foetus with particular reference to myelin forming cells and myelination has been studied by morphological and histochemical methods. The development of the spinal cord resembles that described for other species and broadly similar patterns of development have been found for the other major regions. Differentiation of definitive cell types is marked by the appearance of cytochrome oxidase activity in their cytoplasm. In gray matter strong cytochrome oxidase activity persists into post‐natal life whereas in white matter activity declines following commencement of myelination.

Lipids having the histochemical reactions of myelin first appear in a particular region as the capillary circulation of that region develops. It is suggested that phospholipid elements of perivascular lipid may be rapidly incorporated into the developing myelin sheath whilst galactolipids from the same location are more slowly utilized. The implications of the findings are discussed.
Developmental aspects of intracranial arterial supply in the alligator brain
Authors: Burda Doris J.
Published: December 2004

Intracranial arterial patterns were studied in injected Alligator adults and in serially sectioned Alligator embryos ranging in body length from 4.0 mm to 180 mm. The embryos show extensive developmental modifications involving in particular the posterior cerebral artery anterior cerebral artery, ophthalmic artery, and mesencephalic artery. The posterior cerebral arteries of both sides fuse to form the common ethmoidal artery, which forms a connection with the anterior cerebral artery. A portion of the latter then degenerates posterior to the common ethmoidal artery; the posterior cerebral arteries thus become the sole intracranial source of supply for the naso‐olfactory regions. The ophthalmic artery functions only during early embryonic stages and is later replaced by the orbital artery. The formation of flexures in the brain influences the development of the embryonic mesencephalic artery and causes the posterior ramus of this vessel to become the stem of the definitive mesencephalic artery.
Projections from the cerebral cortex to intralaminar nuclei in monkey
Authors: Devito June L.
Published: December 2004

The distribution of degenerating fibers within the intralaminar nuclei was studied following lesions of the cerebral neocortex in Macaca mulatta, M. nemestrima, M. irus, Cercopithecus aethiops sabaeus and Saimiri sciureus. Degenerating fibers were revealed by the Nauta silver method.

The cortex rostral to the central sulcus appeared to be the principal source of cortical fibers projecting to intralaminar nuclei. Very few degenerating fibers were observed in intralaminar nuclei following parietal, temporal or occipital lobe lesions. Efferent fibers of the prefrontal lobe terminated predominantly in paracentral and parafascicular nuclei. Premotor cortex projected mainly to central lateral and parafascicular nuclei. Motor cortex projected to central lateral and centromedian nuclei. The projection from motor cortex to the ventrolateral centromedian nucleus was topographically distributed, with fibers from leg area terminating lateral to those from arm area.
The accessory optic system in Erinaceus (Insectivora) and Galago (primates)
Authors: Tigges Johannes , Tigges Margarete
Published: December 2004

After unilateral eye removal in Erinaceus and Galago, Nauta‐gygax and Fink‐Heimer silver impregnation methods were used to study the accessory optic system. In Erinaceus the accessory optic fibers terminate contralaterally in the dorsal lateral and medial terminal nuclei of the accessory optic system; in Galago only the dorsal and lateral terminal nuclei are seen.

Hayhow's nomenclature of the accessory optic fibers in modified in such a way that they are now classified according to their terminations. The D‐fibers terminate in the dorsal terminal nucleus, the L‐fibers in the lateral terminal nucleus, and the M‐fibers in the medial terminal nucleus. Accordingly, D‐, L‐ and M‐fibers are found in Erinaceus, while only D‐ and L‐fibers are present in Galago.

As in the two monkey species recently studied, but contrasting sharply with the findings in all non‐primate mammals, the M‐fibers and the medial terminal nucleus are absent in Galago. It is hypothetized that the accessory optic system is similarly reduced in all other primates.

No retinal fibers terminate in the preoptic region, lamina terminalis, hypothalamus, subthalamic nucleus or substantia nigra.
Descending nerve tracts in the spinal cord of the rat. I. Fibers from the midbrain
Authors: Waldron H. A. , Gwyn D. G.
Published: December 2004

Unilateral stereotaxic lesions were made in the superior colliculus, the inferior colliculus, the red nucleus or the reticular formation of the midbrain of rats. The descending fibers from these sites were studied using the method of Nauta ('57).

One crossed and two uncrossed tracts descend from the superior colliculus. These tracts terminate mainly in the reticular formation of the medulla oblongata. Only a small number of tecto‐spinal fibers were found. These were confined to the upper contralateral cervical segments of the cord. The tecto‐spinal fibers terminate on cells in the ventral gray matter of the cord, corresponding in position to those in Rexed's lamina VIII in the cat.

One uncrossed descending tract passes from the inferior colliculus and terminates in the reticular formation of the medulla oblongata. No fibers were contributed to the tecto‐spinal tract by the inferior colliculus.

Rubro‐spinal fibers decussate completely in the ventral tegmental decussation and descend in the lateral funiculus of the cord into lumbar segments and on interneurons which correspond in position to those in Rexed's laminae V and VI in the cat.

From the reticular formation of the midbrain, ipsilateral fibers course in the ventral funiculus of the cord, descending to the ninth or tenth thoracic segments. These fibers terminate on cells corresponding in position to those in Rexed's lamina VIII in the cat. Considerable preterminal degeneration, mainly ipsilateral, was found in the brain stem of the animals with lesions in the midbrain reticular formation.

The findings are discussed in relation to what has been reported previously in the rat, and in other animals.
A light and electron microscopic study of the normal and the degenerating corticospinal tract in the rat
Authors: Dunkerley Gary B. , Duncan Donald
Published: December 2004

Motor and adjacent cortex of the right hemisphere was removed from 30 adult male rats and the animals were sacrificed at intervals between 1 and 360 days thereafter. Primary fixation was by perfusion with buffered 4% paraformaldehyde followed by preparation of blocks from the medulla and the mid‐cervical region for light and electron microscopy by conventional methods. The normal pyramidal tract contained approximately 100,000 myelinated fibers at the level of the medulla, with 89–99% of these fibers under 3.7 μ in diameter and 29–43% less than 1.0 μ. Shrinkage in the degenerating tract occurred gradually and progressively from the third day on and amounted to 70% in the medulla and 72% in the mid‐cervical region by 260 days. In the degenerating tract, throughout the entire period of degeneration, no mitotic figures or positively phagocytic cells were noted and there was no numerical increase or decrease in neuroglia or blood vessels. The rows of interfascicular oligodendrocytes were not altered in any manner except that adjacent rows became close together due to shrinkage. The degenerating fibers were replaced by astrocytic processes oriented in a longitudinal direction. The neuroglia displayed no observable role in the breakdown or removal of the degenerating fibers. Numerous alterations in the fine structure of axoplasm and myelin previously reported by others were confirmed.
Distribution and termination of spinoreticular afferents in the brain stem of sheep
Authors: Rao Gadde S. , Breazile James E. , Kitchell Ralph L.
Published: December 2004

A total of 13 adult sheep where utilized in this study. The spinoreticular afferents were traced to the following nuclei of the brain stem and thalamus employing Guillery et al modification of the Nauta‐Gygax silver impregnation technique: Nuclei supraspinalis, retroambigualis, medullae oblongatae centralis, lateralis reticularis, interfascicularis hypoglossi, raphe pallidus, Roller, parvocellularis, paramedium reticularis, tractus solitarii, gigantocellularis, pontis centralis caudalis and rostralis, subcoeruleus, central mesencephalic gray substance, reticularis thalami, centralis medialis, paracentralis, centralis lateralis and parafacicularis.

The ascending spino‐reticular afferents were observed to form a large medial fiberbundle terminating in the midline nuclei of bulbar recticular formation and a smaller lateral bundle terminating in the lateral ret cular nucleus.
Innervation ratios for large and small limb muscles in the baboon
Authors: Wray Shirley H.
Published: December 2004

The innervation ratio has been calculated for the abductor pollicis brevis muscle in the hand, and for the medial head of the gastrocnemius muscle in the leg of the baboon.

The data presented includes results of the total myelinated nerve fibre counts in the intact, de‐afferented and de‐efferented muscle nerves. The innervation ratio for each muscle has been calculated from the number of large efferent nerve fibres in the muscle nerve, and the total number of muscle fibres present in the muscle. It was calculated that there were 43 motor units in the abductor pollicis brevis muscle and 292 in the medial head of the gastroenemius muscle. The mean number of muscle fibres per motor unit was approximately 220 in the former muscle and 790 in the latter.

The calculation was complicated by the inability to section the muscle nerve above the level of axon branching, and by the difficulties encountered in attempting to produce complete de‐afferentation of the muscle.
The effects of environmental complexity on the histology of the rat hippocampus
Authors: Walsh R. N. , Budtz‐Olsen O. E. , Penny J. E. , Cummins R. A.
Published: December 2004

One group of rats was reared under conditions of environmental complexity, while their littermates served as isolation controls. The occipital cortex was 4.9% (p < 0.01) and the hippocampus 5.7% (P < 0.05) thicker in the environmental complexity rats than in the isolation control animals. Differntial cell counts demonstrated significant differences in neuroglia in the hippocampus.
The olfactory bulb and medial hemisphere wall of the rat‐fish, Chimaera
Authors: Faucette John R.
Published: December 2004

The Chimaerae are phylogenetically old cartilagenous fish which are included in the class Chondrichthyes with the sharks and rays. The telencephalon of these fish is connected to the diencephalon by a unique fibrous stalk. The telencephalic hemispheres are united only ventrally at midhemisphere levels in the region of the hippocampal and anterior commissures. The lateral ventricles join the midline ventricle through the interventricular foramen at this level.

Each olfactory bulb is divided into a dorsal and ventral part and each has a dorsal and a ventral accessory olfactory bulb. A dorsal and a ventral olfactory nerve unite the respective parts of the bulb with a nasal sac. The cup‐shaped mitral cell laminae share a common granular cell layer where they are in apposition. The granular lamina is replaced caudally by the anterior olfactory nucleus.

The medially situated primordial hippocampal formation consists of the anterior continuation, the primordial subiculum, the cornu ammonis and the dentate gyrus. Septal nucleu recognizable in this form include: a medial and a lateral septal nucleus, a septohippocampal nucleus, a nucleus triangularis, an accumbens nucleus, and a nucleus of the diagonal band. The medial zone of the olfactory tubercle occupies the ventromedial hemisphere wall. Major fiber connections of the medial limbic lobe include: the medial olfactory tract, the fornix, the medial forebrain bundle and the medial corticohabenular tract.
The accessory olfactory bulbs and the lateral telencephalic wall of the rat‐fish, Chimaera
Authors: Faucette John R.
Published: December 2004

The lateral telencephalon of Chimaera possesses several unique features but also has nuclei and fiber systems homologous with those of other sub‐mammalian vertebrates. Ventricular ridges, similar to those of reptiles, are quite evident. Accessory olfactory bulbs are associated with the dorsal and ventral parts of each olfactory bulb. These contribute to the lateral olfactory tract.

The internal granular layer caudal to the olfactory and the accessory bulbs blends with the anterior olfactory nucleus. Caudal to this nuclear area, the nuclei of the rostral telencephalon are well differentiated.

Nuclear areas distinguishable in the lateral hemisphere include: the primordial dorsal pallium, the primordial piriform cortex, the primordial striatal and amygdaloid nuclei, and the lateral zone of the olfactory tubercle. These areas replace dorsal, dorsolateral, ventrolateral and ventral parts of the anterior olfactory nucleus, respectively. The primordial striatum is subdivided into hyperstriatum, neostriatum, paleostriatum augmentatum and paleostriatum primitivum. The amygdaloid area has anterior, corticomedial and basolateral nuclear groups. The basolateral area is best differentiated. The hyperstriatum forms a rostral ventricular eminence; the basolateral amygdaloid nucleus is present in a larger caudal ventricular ridge.

Fiber tracts of the lateral wall include the lateral olfactory tract, the lateral corticohabenular tract, the lateral forebrain bundle and the stria terminalis. Nuclei of medial and lateral walls are interrelated through the hippocampal and the anterior commissures.
Microanatomy of the ganglionic roots of the abdominal cord of the crayfish, Orconectes virilis (hagen)
Authors: Somers Michael E. , Nunnemacher Rudolph F.
Published: December 2004

Low magnification electron micrographs were used to construct montage maps of cross sections of the three roots of the second abdominal ganglion of the crayfish Orconectes virilis. Arbitrary fiber diameter size ranges were established within the total size range of 0.2 μ to 55 μ. Fibers within each of the ranges were counted and their positions noted. The first root contains 2,451 fibers and is divided internally into distinct anterior and posterior halves. The posterior half contains 98.2% of the roots total number of fibers below 1 μ in diameter and these are contained primarily in 13 bundles. The second root is divided internally into five subregions and contains a total of 2,741 fibers. The size distribution of the fibers within each of the subregions is noted and compared with the fiber size distribution of the peripheral branches. The subregions are assigned functions based on their similarity to root branches of known activity. The third root contains two distinct elements, a phasic branch containing 13 fibers ranging from 6 μ to 55 μ and a tonic branch containing six fibers ranging from 3.5 μ to 21 μ.
The laminar distribution of retinal fibers in the dorsal lateral geniculate nucleus of the cat: A new interpretation
Authors: Guillery R. W.
Published: December 2004

The cell laminae of the lateral geniculate nucleus have been studied in relation to the retinogeniculate degeneration shown by the Nauta method. In agreement with previous accounts laminae A and A1 have been shown to receive contralateral and homolateral inputs respectively. However, ventral to lamina A1 three laminae have been defined. Lamina “C” contains large cells and receives coarse contralateral fibers, lamina “C1” contains smaller cells and receives fine homolateral fibers, while lamina “C2,” which consists of small cells next to the optic tract contains many fibers passing through to other laminae but shows no particular concentration of pericellular degeneration.

The precise relationship between fiber degeneration and cytoarchitectonic borders can be seen only in Nauta sections that have been counterstained by a Nissl method. Such material provides no evidence of any zone where homolateral and contralateral fibers overlap. Between laminae A and A1, and A1 and C there are narrow, relatively cell free zones, which, in many parts of the nucleus, receive no significant retinogeniculate input.

The fiber degeneration appears earliest in the peripheral parts of laminea A and A1, the homolateral degeneration slightly preceding the contralateral degeneration on the third day. The degeneration in the central parts of these laminae appears about 24 hours later and is never as dense. The fine fibers in lamina C1 do not show degeneration clearly until the sixth day.
Morphology and cytoarchitecture of the red nucleus of the domestic pig (sus scrofa)
Authors: Otabe Jack S. , Horowitz Aaron
Published: December 2004

The morphology and cytoarchitecture of the red nucleus was studied in 17 pigs of different ages and breeding. Transverse, sagittal and horizontal sections were stained by cresyl violet, Weil's method and the Klüver and Barrera method. The length of the red nucleus of the pig was about 6.09 mm and the width was 2.66 mm on horizontal section, while the height of the nucleus was approximately 2.87 mm on both transverse and sagittal sections.

Parvocellular and magnocellular parts were readily identified on horizontal section. The former occupied the three‐fifths rostral portion of the nucleus, and the latter occupied the two‐fifths caudal portion. There was a clear division between the two parts.

Five subdivisions within the nucleus were identified: N. ventrolateralis parvocellularis, N. dorsomedialis parvocellularis, N. ventromedialis magnocellularis, N. dorsolateralis magnocellularis and N. cornualis lateralis. Large, medium, and small neurons were identified. The large neurons were over 50 μ in diameter; the medium had a range between 26 μ and 49 μ and the small ones were under 25 μ. No nucleus minimus was identified. The red nucleus of the pig did not lie parallel to the midline. The longitudinal axes of right and left nuclei met caudad at 60°. The magnocellular part consisted of about 65% large, 28% medium and 7% small neurons. The ratio of the large, medium and small neurons of the whole nucleus was 4:5:2.
An experimental analysis of the determination of cell patterns in the spinal cord of the chick embryo
Authors: Narayanan C. H.
Published: December 2004

The effects of rotation of the brachial region of the spinal cord about its longitudinal axis between stages 12 to 15 were studied in a series of 30 chick embryos by transplanting that portion of the neural tube opposite somite levels 16 to 20 from a donor embryo to a host embryo at the same stage of development. Despite the altered topographical relationship between the transplanted neural tube and the adjacent mesodermal somites, the cytological characteristics of the cells and the organization of the major cell groups derived from the alar and basal halves of the cord remained unaffected. In the more successful experiments, well‐developed lateral motor columns and ventral roots and dorsal roots and spinal ganglia could be identified in the usual morphological relationships even though the graft piece of spinal cord was clearly inverted compared to the remaining part of the spinal cord of the host embryo. A limited number of cell counts of the lateral motor column in some of these cases showed no significant difference in cell number, nor was there an appreciable change in the general morphology of the cell groups in the transplanted cord compared to the lateral motor columns of control embryos at similar developmental stages.
Rubrobulbar projections of the opossum (didelphis virginiana)
Authors: Martin George F. , Dom Richard
Published: December 2004

The course and distribution of rubral pathways to the pons and medulla were determined for the opossum by employing the Nauta‐Gygax and Fink‐Heimer techniques on the brain stems of animals with lesions either within the red nucleus or involving the fibers emanating from it. Control material was provided by previous studies on corticomesencephalic and tectal efferent pathways and by the brains of specimens subjected to deep midbrain lesion which did not involve the red nucleus.

A predominantly crossed rubrobulbar pathway coursed through the brain stem as described by Voris and Hoerr ('32) and distributed to the nucleus “K” of Meessen and Olszewski ('49), to neurons interspersed between the fiber bundles of the motor root of the trigeminal nerve, to the parabrachial nucleus of the brachium conjunctivum, the parvocellular reticular formation, the ventral and medial portions of the spinal trigeminal nucleus (nucleus oralis and interpolaris), the lateral and intermediate portions of the motor nucleus of the facial nerve, the lateral reticular nucleus, the ventral external arcuate nucleus and the subnucleus reticularis dorsalis medullae oblongatae. The possible significance of these connections in the opossum is discussed.
Trigeminal proprioceptive projections to the hypoglossal nucleus and the cervical ventral gray column
Authors: Mizuno Noboru , Sauerland Eberhardt K.
Published: December 2004

Trigeminal proprioceptive projections to the hypoglossal nucleus and the cervical ventral gray column in the cat were investigated by means of neuroanatomical and neurophysiological methods. Degeneration studies (Nauta and Fink‐Heimer methods) involved circumscribed electrolytic lesions of the trigeminal mesencephalic nucleus and/or the supratrigeminal nucleus. Degenerated fibers in Probst's tract, which is composed of the central processes of trigeminal mesencephalic neurons, terminated in the ventrolateral portion of the ipsilateral hypoglossal nucleus and in the medial part of the ventral gray column of C1–C4. The descending juxtatrigeminal fascicle, a separate bundle of degenerated fibers, originated from the supratrigeminal region, which is known to receive processes from trigeminal mesencephalic neurons. This descending fascicle contributed fibers to the spinal trigeminal nucleus and the juxtatrigeminal reticular formation, from which region interneurons connect to the hypoglossal nucleus. Probst's tract, as well as the descending juxtatrigeminal fascicle, could be considered as parts of two separate polysynaptic pathways from trigeminal proprioceptors to those motoneurons responsible for the innervation of the tongue and infrahyoid musculature. Electrophysiological experiments revealed that proprioceptive muscle afferents from the masseter muscle project directly to the ipsilateral hypoglossal nucleus and to the ipsilateral upper cervical ventral column.
Cell proliferation, migration and differentiation in the cerebral cortex of the golden hamster
Authors: Shimada Morimi , Langman Jan
Published: December 2004

This work was undertaken: (1) to determine the sites of cell proliferation in the cerebral cortex of the hamster during prenatal life and shortly after birth; (2) to study the migration pattern of neuroblasts before and shortly after birth; and (3) to examine the differentiation of the neuroblasts during migration and after arrival at their final location.

Tritiated thymidine was injected in pregnant hamsters at various days of gestation and in newborn animals. When one hour after treatment the parietal cortex of the embryos was examined for DNA synthesis, labeled cells were found in the neuroepithelial layer but not in the cortical layers. In the newborn radioactive cells were found both in the neuroepithelial layer and in the subependymal layer, a layer consisting of polymorph cells and developing at the end of prenatal life. Hence during embryonic life cell proliferation in the parietal cortex is restricted to the neuroepithelial layer, but in the newborn the subependymal layer is also ctive in cell production.

When the generation time of the neuroepithelium was determined, the DNA synthetic phase was found to be six hours, the pre‐duplication and prophase about one and one‐half hours and the post‐duplication stage about four and one‐half hours. Hence the duration of the generation time of the neuroepithelial cells during embryonic life is about 12 hours.

To examine the migration pattern of the neurons formed during embryonic and postnatal life, pregnant hamsters were injected at successive days of gestation and the embryos sacrificed at the twentieth postnatal day. A similar procedure was followed for newborn animals. It was thus found that neuroblasts formed during the early stages of development occupy the deep layers of the cortex, while those formed during the later stages of intrauterine life and during the first postnatal days occupy the more superficial layers. Hence, neuroblasts produced during the final stages of development migrate through the cell layers formed at previous days to reach the surface of the cortex. The time required for this migration varied in the newborn hamster from three to five days.

When newborn hamsters were injected with tritiated thymidine and the labeled cells traced during the following ten days, it was noted that the cells released by the neuroepithelial layer arrived in the deeper layer of the cortex about 48 hours after labeling. The cells were characterized by a spindle‐shaped nucleus while the cytoplasm was seen to extend in peripheral direction. Shortly after arrival at the surface of the cortex the cells lost their spindle shape and the nucleus became oval‐shaped with a pale nucleoplasm. Subsequently the cells were characterized by a small round pale nucleus with two or three nucleoli close to the nuclear membrane. Approximately nine days after treatment the labeled cells were clearly recognizable as advanced neuroblasts with a large, pale nucleus and one or two nucleoli.
Cervicothalamic tract in the dog
Authors: Hagg Sigrid , Ha Hongchien
Published: December 2004

The spino‐cervico‐thalamic pathway in the dog was studied by means of the Marchi method. The pathway which takes its origin from the nucleus cervicalis lateralis (NCL) at the first two cervical segments of the spinal cord was demonstrated following restricted lesion in the dorsal quadrant involving the nucleus. The axon of neurons of NCL form a prominent bundle which crosses exclusively to the contralateral ventral funiculus via ventral white commissure. At first, the fiber bundle occupies a medial position and gradually shifts laterally as ascending. In the lower portion of the medulla oblongata the fiber bundle is closely attached to the lateral pole of the inferior olivary nucleus and gives collaterals to it. The pathway maintains its lateral position to the medial lemniscus throughout the brain stem and terminates in the nucleus ventralis posterolateralis of the thalamus occupying mainly its ventrolateral border.

The topographic relation between cervicothalamic and classical spinothalamic pathways are discussed.
Relationships between glial and neuronal elements in the development of long term cultures of the spinal cord of the fetal mouse
Authors: Guillery R. W. , Sobkowicz Hanna M. , Scott G. L.
Published: December 2004

The development of glial and synaptic relations has been studied in long term cultures of spinal cord by light and electron microscopy.

During the first three days in vitro there is extensive cell death in the superficial parts of the explants, where one sees many phagocytes and much cellular debris. The ependyma of the explants early forms a closed sac in the deep parts of the culture next to the collagen substrate. Cells migrate from this sac to form a continuous basal layer upon the substrate. Some of these cells turn around the edges of the explant and migrate onto its surface, where they contribute to an ependyma‐like epithelial covering. As the explants mature most of the cellular debris is cleared; the epithelial covering separates the neuronal elements from the feeding solution and from phagocytes, most of which migrate to lie freely on the surface of the epithelium.

Two types of outgrowth are formed. The first consists of bundles of nerve fibers which are accompanied by individual undifferentiated glial cells. The second forms as a broad sheet of undifferentiated glial cells and astrocytes and this is continuous, at the edge of the explant, with the glia of the basal layer. Nerve fibers that grow into this sheet appear to survive better than nerve fibers that grow out in bundles. Oligodendroglial cells become recognizable by electron microscopical criteria when the axons start to myelinate.

Dendrites can be identified in the sheet‐like outgrowth but not in the bundles. Synapses are seen only where dendrites are identifiable. Serial axo‐axonal junctions have not been found and axosomatic synapses are relatively rare.
Visual intensity and pattern discrimination deficits after lesions of ectostriatum in pigeons
Authors: Hodos William , Karten Harvey J.
Published: December 2004

Eighteen pigeons were trained to discriminate between visual stimuli that differed in either intensity or pattern. Bilateral, electrolytic lesions were made in ectostriatum or the lateral neostriatum. Pigeons with ectostriatum lesions had severe post‐operative performance deficits. The magnitude of the deficit and the amount of post‐operative retraining necessary to restore the birds to pre‐operative performance levels varied directly with the amount of bilateral destruction of ectostriatum. Pigeons with little or no involvement of ectostriatum showed little or no change in discrimination performance post‐operatively. Similarities between morphological and functional organization of the reptilian, avian and mammalian visual systems are discussed.
On the inferior olive of the albino rat
Authors: Schild Renée F.
Published: December 2004

The average of neuron counts made in five rat inferior olives was 24,400 neurons per olive, i.e., 48,800 per rat, — 6.8 times fewer than the number of rat cerebellar Purkinje cells. The medial accessory olive was larger, both in terms of volume and cell numbers, than either the dorsal accessory or principal olives. The overall packing density, determined in one olive, was 43,900 neurons/mm3, but there were local fluctuations within the olive. In particular, packing density was somewhat higher at the rostral end of the medial accessory olive.
Medullary cells of origin of vagal cardioinhibitory fibers in the pigeon. II. Electrical stimulation of the dorsal motor nucleus
Authors: Cohen David H. , Schnall Adrian M.
Published: December 2004

Stimulation of the peripheral end of the cervical vagus results in marked bradycardia, a secondary fall in blood pressure, and little change in respiration. Stimulation of the central end results in immediate apnea, a moderate fall in blood pressure, and little change in heart rate.

Electrical stimulation of the dorsal medulla produces short‐latency bradycardia at points clustering in: (a) lateral dorsal motor nucleus, 0.5–1.0 mm rostral to the obex; (b) solitary tract; and (c) commissural nucleus of Cajal. Apnea frequently accompanies bradycardia except when elicited by stimulation of the dorsal motor nucleus. Hypotension always follows bradycardia, while hypertension accompanies tachycardia. These bradycardia responses are abolished by bilateral vagotomy and severly diminished when the ipsilateral vagus is cut or pharmacologically blocked. Beta‐sympathetic blockade has no effect on the occurrence of bradycardia responses.

It is concluded that an efferent cardioinhibitory region in the pigeon is localized in the lateral dorsal motor nucleus 0.5–1.0 mm rostral to the obex and that bradycardia elicited from the solitary tract and commissural nucleus result from stimulating afferents. These results correlate nicely with the localization of the cells of origin of vagal cardioinhibitory fibers based on retrograde degeneration experiments, and together the anatomical and physiological findings indicate a concentration of these neurons in the ventrolateral aspect of the dorsal motor nucleus approximately three‐quarters of a millimeter rostral to the obex.
Increase in number of synapses in the inner plexiform layer of light deprived rat retinae: Quantitative electron microscopy
Authors: Sosula Leo , Glow Peter H.
Published: December 2004

One eye in each of five adult Wistar hooded rats was covered with opaque contact occluders for three or nine months. The rat retinae were studied with light and electron microscopy. No changes in retinal thickness or in gross structure were seen. However, quantitative differences in synaptic organisation were found.

(1) First comparison. A montage of a normal retina was compared with a similar montage of a three month lighted‐deprived retina. Taking equal areas of inner plexiform layer, the number of amacrine (conventional) synapses in the light‐deprived montage was larger by a factor of about 2.4 relative to the normal one. No significant difference in the number of bipolar (ribbon) synapses was found.

(2) Second comparison. Samples were compared from five normal and five light‐deprived retinae. The light‐deprived retinae showed a significantly larger number of amacrine synapses compared with the normal mean (p<0.02).

It was not possible to determine if the changes in synaptic number are related to changes in vesicle dimensions reported herein.

The increased number of conventional synapses seems evidence that central nervous tissue is capable of forming new synapses without changing the organisation of neural processes.
Reticulospinal fibers of the opsossum, Didelphis virginiana. II. Course, caudal extent and distribution
Authors: Martin George F. , Dom Richard
Published: December 2004

Lesions were placed in the deep midbrain tegmentum and within areas of the pontine and medullary reticular formation which were determined by the retrograde degeneration method to give rise to reticulospinal fibers. The location of each lesion was verified histologically and the spinal cords processed by either the Nauta or Fink‐Heimer method. Control material for the origin of degenerated fibers was provided by previous studies on corticospinal, tectospinal and rubrospinal fibers in the same form.

Fibers degenerating as a result of mesencephalic tegmental lesions followed the ipsilateral ventral funiculus and could be traced as far caudal as midthoracic levels. They ended in Rexed's laminae VII and VIII.

Lesions of the pontine reticular formation resulted in the degeneration of fibers within the ventral funiculus of the spinal cord. The great majority of these fibers followed an ipsilateral course. Such pontospinal fibers were present throughout the length of the spinal cord; their terminal distribution appears to take place mainly within laminae VII and VIII. At certain levels, however, such fibers could be traced into lamina IX.

Lesions in the medial medullary reticular formation resulted in fiber degeneration chiefly within the ipsilateral ventral and lateral funiculi. However, a few fibers were present on the side opposite the ablation. This fiber system extends throughout the length of the spinal cord and distributes itself in laminae VII and VIII and, at certain levels, also in lamina IX. Lesions isolated to the lateral, parvocellular portion of the medullary reticular formation resulted in fiber degeneration located within the propriospinal bundles of the lateral funiculus which could be traced to rostral cervical levels. Such lesions also interrupted the rubrospinal tract in the its medullary trajectory.
A quantitative study of morphological changes accompanying the initiation and progress of myelin production in the dorsal funiculus of the rat spinal cord
Authors: Matthews Murray A. , Duncan Donald
Published: December 2004

The dorsal funiculus in cervical spinal cords of rats from 3 to 120 days postnatal was studied in order to document and quantitate glial cell development and axonal growth as related to the initiation and progress of central myelination. Within the dorsal funiculus are three major and distinct tracts, each having distinct developmental trends and adult characteristics in terms of fiber sizes and amount of myelin. These tracts are the cuneate and gracile fasciculi and the cortico‐spinal tracts.

Glial cell counts and cross‐sectional surface area determinations of each tract at increasing ages show that the initial rate of glial population increase is similar. However, each tract is unique in terms of the age at which a maximum population density is reached and the rate at which the expected population dilution takes place. An electron‐microscopic examination indicates that oligodendrocytes constitute over 85% of the total glial population throughout the development period surveyed. As such, these cells are primarily responsible for the population density changes.

The diameters of unmyelixgnated fibers, promyelin fibers and some myelinated fibers in these tracts were measured at 5, 10, 15, 20 and 120 days postnatal. This was done both for the purpose of relating glial population density changes with the initiation and decline of active myelination, and for determining whether or not a critical diameter for myelination exists in the CNS as was found in peripheral nerves (Matthews, '68). For each tract there is a characteristic sequence of events involving not only myelination, but also changes in diameter distribution just prior to the appearance of myelin and during the period of active myelin formation. These events coincide with the concentration and dilution of the glial population, but it is also evident that there is no critical and constant diameter in the CNS above which all axons are myelinated and below which all are unmyelinated. Myelin appears first on larger axons, but as the animal matures, it is found on progressively smaller axons until between 20 and 120 days, axons 0.2–0.4 μ in diameter acquire myelin. Thus, myelination begins with axons destined to be large and then extends down to those which enlarge very little prior to acquiring myelin and remain very small even in adult animals.

Finally, from the determination, in adult rats, of the number of axons and oligodendrocytes in a defined volume of each tract and an estimation of internode length, the ratio of internodes to oligodendrocytes was calculated. The specific values obtained could vary by as much as ±50% and are only meant to serve as indicators of a trend. However, it is suggested that the number of internodes per oligodendrocyte may be inversely proportional to the length of the internode.
Histogenesis of the substantia nigra, ventral tegmental area of Tsai and interpeduncular nucleus: An autoradiographic study of the mesencephalon in the rat
Authors: Hanaway Joseph , McConnell Jo Ann , Netsky Martin G.
Published: December 2004

The origin of large neurons of the substantia nigra, ventral tegmental area of Tsai and interpeduncular nucleus was determined in three‐week‐old rats receiving a single injection of thymidine‐H3 during gestation. These neurons underwent final mitotic division on embryonic days 11 through 15 with maximal production on days 14 and 15. Glia and the smallest type of granular neurons were produced from day 11 through 22. Cells in the ventral angle of the neuroepithelium were not labeled one hour after injection of thymidine‐H3 in any of the series.

Study of animals receiving a single injection of thymidine‐H3 during gestation and killed at serial intervals thereafter showed that neurons forming the substantia nigra migrated from the middle third of the basal neuroepithelium and moved between existing cells in radial patterns. Production of neurons specifically for each division of the substantia nigra was not observed either in cross‐section or rostrocaudally, nor was the destination of neurons related to their time of origin. The ventral tegmental area of Tsai and interpeduncular nucleus formed from neurons originating in the medial third of the basal plate and migrating almost to the ventral surface of the mesencephalon. The neurons then divided into two streams to create a pattern of an inverted fountain comparable to the distribution of neurons containing catecholamines. Some of these neurons may have contributed to the substantia nigra. The primordia in all three nuclear areas were first seen on embryonic day 18.