bluuebunny/crossref_metadata_2025 huggingface dataset:
Spinal terminal fields of dorsal root fibers in the pigeon (Columba livia)
Authors: Leonard Robert B. , Cohen David H.
Published: May 2005

This paper describes the spinal pattern of brachial and lumbosacral dorsal root terminations in the pigeon. These are presented within the framework of the cytoarchitectonic analysis of the preceding report (Leonard and Cohen, '75).

At the level of dorsal root section and immediately adjacent sections dense terminal fields were evident throughout the ipsilateral dorsal horn (Layers I–V), including the substantia gelatinosa. However, degeneration in the substantia gelatinosa was prominent only with short survival times. There were mediolateral differences in the density of degenerating material in the dorsal horn, as well as variations between the patterns at the cervical and lumbosacral enlargements. The general pattern of degeneration in the dorsal horn extended approximately three segments rostral and two segments caudal to the level of root section, becoming progressively less dense with distance from the level of rhizotomy. An exception to this was degeneration in the dorsal magnocellular (Clarke's) column where, following section of either brachial or lumbosacral roots, degeneration could be traced into the thoracic spinal cord. However, these ascending and descending projections upon the column at thoracic levels overlap minimally if at all.

Degeneration was sparse in the intermediate zone and ventral horn (Layers VI–IX). It tended to concentrate centrally in Layer VI at the enlargements, and much of the degeneration ventral to this was interpreted as fibers en passage to the motoneuronal cell groups, Layer IX. Terminal fields in Layer IX were evident at both cervical and lumbosacral enlargements. They were largely restricted to the lateral motoneuronal cell group and were more prominent at cervical levels where degeneration was commonly observed around cell bodies and their proximal dendrites.

As with the cytoarchitectonic organization of the spinal gray in the pigeon, the terminal fields of brachial and lumbosacral dorsal root fibers appear to have a pattern similar to that reported in the mammalian literature.
The pattern of projection of cortical areas 17, 18, and 19 onto the laminae of the dorsal lateral geniculate nucleus in the cat
Authors: Updyke B. V.
Published: May 2005

The projection of cortical areas 17, 18, and 19 onto the laminar part of the dorsal lateral geniculate nucleus was investigated with degeneration methods and with the autoradiographic axon tracing method. In agreement with previous accounts, degenerating cortical axons stained by the Nauta method were restricted to laminae A, A1, C and to the interlaminar zones. In contrast, adjacent sections stained with the Fink‐Heimer method showed fine dust like degeneration throughout all of the laminae of the nucleus. Comparisons of Fink‐Heimer degeneration resulting from lesions of area 17 with that resulting from lesions of areas 18 and 19 further suggested that the area 17 projection is heavier and more uniform than the projections from areas 18 and 19.

Autoradiographic tracing of axons after intracortical injections of 3H‐proline provided detailed demonstrations of the cortical projection patterns that confirmed the Fink‐Heimer results. Following restricted injections of areas 17 or 18 the termination zones in the dorsal lateral geniculate nucleus consisted of columns of labeled tissue oriented perpendicular to the laminae of the nucleus. Area 17 was found to project heavily and uniformly throughout all of the laminae of the nucleus. The projection from area 18 also extended throughout all of the laminae of the nucleus, but was sparser and less uniformly distributed than that from area 17. Projections from area 18 distributed more heavily to the interlaminar zones and to lamina C than to laminae A, A1, C1, C2, or C3. A projection from area 19 to laminae C1, C2, and C3 was also demonstrated autoradiographically.
The organisation of the spinotectal projection. An experimental study in the rat
Authors: Antonetty C. M. , Webster K. E.
Published: May 2005

The spinal grey projects upon the contralateral superior colliculus via two overlapping pathways in the lateral funiculus. One, more ventrally placed, is the classical spinotectal tract, which crosses immediately in the spinal cord and remains crossed. The other, lying more dorsally, ascends homolaterally but is subject to delayed crossing in the brainstem (especially the intertectal) commissures to reach the contralateral colliculus. Both sets of fibers end only in the caudal half of the colliculus, predominantly in the stratum album intermedium. The projections from individual cord segments distribute in an ordered fashion as a series of transverse, overlapping bands, the cervical cord projecting most rostrally, the sacro‐coccygeal most caudally. Additional fibers, which distribute with less marked topography, end in the lateral extreme of the stratum griseum profundum and stratum album profundum.
Non‐randomness in the sequential formation of principal cones in small areas of the developing chick retina
Authors: Morris Valerie B.
Published: May 2005

Systematic variation in the stage of development within small retinal areas could account for the overlap between the times of formation of the receptor types in the chick retina. The distributions of unlabelled and labelled principal cones in maps of the receptor mosaic, constructed from retinae exposed to tritiated thymidine during incubation, were analysed by grid analysis (Greig‐Smith, '64) and by two computer programmes. The computer programmes were generally more successful than grid analysis in detecting contagion in the distribution of unlabelled and labelled principal cones in the receptor maps. The contagion has been interpreted as evidence that the stage of development varies systematically in small retinal areas and that the overlap between the times of formation of the receptor types may be absent amongst small groups of cells.
Histochemical characterization of a neocortical projection of the nucleus locus coeruleus in the squirrel monkey
Authors: Freedman Robert , Foote Stephen L. , Bloom Floyd E.
Published: May 2005

Histochemical evidence is presented for a catecholamine‐containing projection from the nucleus locus coeruleus to the neocortex in the squirrel monkey. The innervation of superior temporal gyrus has been examined in particular. Glyoxylic acid‐induced fluorescence shows an extensive arborization of fine, catecholamine‐containing fibers with prominent varicosities in all layers of the neocortex. The nucleus locus coeruleus is identified as a source of these fibers by both ortho‐ and retrograde axonal tracing techniques. After injection of horseradish peroxidase into the neocortex, labelled cell bodies are localized throughout the major portions of the locus coeruleus. Conversely, after microinjection into the nucleus locus coeruleus, tritiated proline is transported into the neocortex where it appears within fibers similar in distribution to those revealed by fluorescence histochemistry. Both transport techniques indicate that cortical projections of the locus coeruleus originate from both ipsilateral and contralateral nuclei.
The origin of efferent pathways from the primary visual cortex, area 17, of the macaque monkey as shown by retrograde transport of horseradish peroxidase
Authors: Lund Jennifer S. , Lund Raymond D. , Hendrickson Anita E. , Bunt Ann H. , Fuchs Albert F.
Published: May 2005

The retrograde transport of horseradish peroxidase has been used to identify efferent cells in area 17 of the macaque. Cells projecting to the lateral geniculate nucleus are small to medium sized pyramidal neurons with somata in lamina 6 and the adjacent white matter. The projection to the parvocellular division arises preferentially from the upper half of lamina 6, while that to the magnocellular division arises preferentially from the lower part of the lamina. The projection to both superior colliculus and inferior pulvinar arises from all sizes of pyramidal neurons lying in lamina 5B (Lund and Boothe, '75); at least the largest pyramidal neurons of lamina 5B send collateral axon branches to both destinations. Injections with extensive spread of horseradish peroxidase show that many cells of lamina 4B and the large pyramidal neurons of upper lamina 6 also project extrinsically but their terminal sites have not been identified.

Other studies have indicated that cells of laminae 2 and 3 project to areas 18 and 19. Therefore every lamina of the visual cortex, with the exception of those receiving a direct thalamic input, contains cells projecting extrinsically. Further, each lamina projects to a different destination and from Golgi studies can be shown to contain cells with specific patterns of dendritic branching which relate to the distribution of thalamic afferents and to the patterns of intracortical connections. These findings emphasise the significance of the horizontal organisation of the cortex with relation to the flow of information through it and contrast with the current concept of columnar organisation shown in physiological studies.
Organization and development of brain stem auditory nuclei of the chicken: Tonotopic organization of N. magnocellularis and N. laminaris
Authors: Rubel Edwin W. , Parks Thomas N.
Published: May 2005

Extracellular recordings of responses to tone‐burst stimulation were used to determine the tonotopic organization of n. magnocellularis (NM) and n. laminaris (NL) in hatchling chickens. NM cells show “primary‐like” response patterns to ipsilateral stimulation, and are arranged in dorso‐ventral isofrequency columns. Units responding to the highest frequency tones (about 4,100 Hz) are situated at the rostromedial pole of the medial division. Units with lower characteristic frequencies (CF's) are found at successively caudal and lateral sites, until extremely low CF's (<500 Hz) are represented dorsoventrally in the caudolateral tail of the lateral division. No evidence was found of auditory input to the region which receives projections from the macula lagena. NL receives polarized, binaural, excitatory input. Units have similar CF's and thresholds to tones presented to either ear. The tonotopic organization in NL matches that found in NM — high CF's rostromedially and low CF's caudal and lateral. Quantitative procedures were developed for relating CF to the position of a unit within either nucleus. These analyses account for 79% and 89% of the frequency variance found within NM and NL, respectively, and predict the CF of a neuron by its position within each nucleus.
The olivocerebellar projection in the cat studied with the method of retrograde axonal transport of horseradish peroxidase
Authors: Brodal Alf , Walberg Fred , Hoddevik Grethe H.
Published: May 2005

The distribution of labeled cells in the inferior olive of the cat has been mapped following injections of small amounts of horseradish peroxidase in the paramedian lobule of the cerebellum.

The distribution of labeled cells was plotted in drawings of approximately serial transverse sections. The findings in each case were transferred to a standard diagram of the olive to facilitate comparison of cases.

Previous studies of the distribution of retrograde cell loss in the inferior olive following cerebellar lesions (Brodal, '40b) showed that fibers ending in the paramedian lobule come from the caudal part of the ventral lamella of the principal olive. This was confirmed with the peroxidase method, but in addition three other separate and well circumscribed areas of the olive showed labeling: one in the dorsal accessory olive, another in the rostral part of the medial accessory olive, a third in the caudal part of the dorsal lamella of the principal olive (fig. 7). There is some degree of topical arrangement within the projection of each of these olivary areas to the paramedian lobule. It is particularly striking that the projection areas of the caudal one‐third of the lobule are different from and overlap only little with those of the rostral two‐thirds. On account of diffusion of the injected peroxidase solution in the folia it could not be decided whether the different olivary areas project to particular longitudinal zones in the paramedian lobule.

The main findings can be correlated with the physiological observations of Armstrong et al. ('74). Some of the “paramedian” olivary areas are labeled also following peroxidase injections in other cerebellar parts, among them the nuclei interpositus anterior and posterior. The findings are compatible with the notion that olivocerebellar fibers branch to supply more than one cerebellar region.

It is confirmed that the olivocerebellar projection, including that of the nuclei, is almost completely crossed. In the DISCUSSION it is emphasized that afferents from several sources converge on all four olivary regions projecting onto the paramedian lobule. The olivocerebellar projection obviously allows for divergence as well as convergence of impulses from the olive to the cerebellum.

For further insight into the anatomical organization of the inferior olive, the entire olivocerebellar projection has to be mapped with the peroxidase method, and further studies of the afferents to the olive are needed. In such studies, as well as in physiological ones, it is essential that findings are described with meticulous reference to the topography of the olivary subdivisions.
An electron microscopic study of the neuromuscular junction in the myotomes of larval lamprey, Lampetra japonica
Authors: Nakao Taisuke
Published: May 2005

The neuromuscular junction in the myotomes of larval and adult lampreys, Lampetra japonica, was studied with the electron microscope. In larval lampreys of 26 days after artificial insemination, the myotome consists of triangular lamellae of muscle cell with their bases laterally and apexes medially oriented and placed one on the other. The lateral aspect of the myotome is covered by a layer of flattened cell, and the other aspect is covered by an external lamina which does not extend into the intercellular space between adjacent cells within a myotome. A bundle of thin axons was found in a depression at the middle of medial edge (apex) of each muscle lamella of the myotome and neuromuscular junction was formed here. No nerve endings were found at the myoseptal ends or at the lateral borders of the muscle lamellae. Enlarged axon terminals contained numerous clear vesicles with a few cored vesicles, mitochondria and neurofilaments. The presynaptic axolemma was separated from the postsynaptic sarcolemma by an interspace (50–55 mμ wide) with an interposed external lamina.

In the trunk musculature of adult lampreys, nerve endings were found on the surface of the parietal fibers whereas they were seen on both the myoseptal ends near the myotendinous junction along the medial border of each central fiber. Thickening and enhancement in the electron density and accumulation of filamentous material on the sarcoplasmic surface of the postsynaptic sarcolemma were noted in both the larval and adult lampreys. Any other specific alterations were not found on both the pre‐ and postsynaptic membrane in the neuromuscular junctions of larval and adult lampreys.

A brief comment was made on the relationship in development of the characteristic muscle units and patterns of the motor innervation in the larval and adult lampreys. The significance of the neuromuscular junction in the very young larvae reported here was also discussed in respect to the evolution of the neuromuscular junction, particularly in lower chordates, and it was presumed to be the most primitive pattern of innervation in the vertebrate skeletal muscle.
Formation of cockroach interganglionic connectives: An in vitro analysis
Authors: Provine Robert R. , Seshan K. R. , Aloe Luigi
Published: May 2005

Individual ganglia of the cockroach embryo (Periplaneta americana) were explanted on clean glass coverslips immersed in a chemically defined liquid medium and incubated for periods up to eight weeks. Substantial, straight interganglionic connections were formed between: (1) rows of ganglia arranged in the normal in vivo configuration; (2) rows of ganglia placed in abnormal orders; (3) rows of ganglia which never form connections in vivo because they occur singly in the embryo; and (4) rows of ganglia in natural sequences but which have had their rostro‐caudal axes rotated 90° in relation to the line of the row. Therefore fascicles and interganglionic connectives were formed without regard to normal in vivo relationships.

Daily observations with a Nomarski microscope indicated that several processes are involved in connective formation. (1) Initial outgrowth is in a random, radial pattern. (2) Intersecting fibers from adjacent ganglia are deflected toward each others' perikarya. (3) Initially bowed fiber connectives are straightened, perhaps by increases in fiber tension or by fiber shortening which may be brought about by neuronal or extraneuronal (glial) processes. (4) Outgrowing fibers follow already established fiber pathways.

The present results indicate that fiber‐fiber and fiber‐target interactions play a significant role in the formation of interganglionic connectives. In this system, the spatial relationships between ganglia determine the patterns and varieties of permissible neuronal connections. Thus, major, straight nerve trunks may be formed between adjacent ganglia which are growing out fibers on a glass surface submerged in a liquid medium which offers minimal orientation cues and provides a growth substrate vastly different and simpler than that encountered by outgrowing fibers in vivo.
Experimental reorganization of the cerebellar cortex. V. Effects of X‐irradiation schedules that allow or prevent cell acquisition after basket cells are formed
Authors: Altman Joseph
Published: May 2005

In Long‐Evans rats the area of the cerebellum was X‐irradiated with two schedules beginning on day 8 by which time the bulk of basket cells were formed. The shorter schedule of four successive daily doses of 200 r between 8–11 days was designed to allow some cell recovery, the longer schedule between 8–15 days was expected to prevent it. Neither of the schedules interfered with the differentiation of basket cells. Purkinje cells remained aligned in a monocellular layer and formed singularly long, upright stem dendrites which were surrounded by the descending collaterals of basket cell axons. This supported the hypothesis that the directed growth of Purkinje cell stem dendrite is promoted by morphogenic interaction with basket cells. The upright stem dendrites had few or no smooth branches where cell recovery was prevented or had few such branches where recovery occurred. It was postulated that the outgrowth of smooth branches is dependent on interaction with stellate cells which form after the acquisition of basket cells. The absence or scarcity of smooth branches did not prevent the formation of spiny branchlets which grew downward to establish synaptic contacts with the spared parallel fibers of granule cells formed before the start of irradiation. In the group with some granule cell recovery, spiny branchlets grew to a limited extent upward into the pile of parallel fibers formed after the irradiation.
Development of myelination in optic tract of the cat
Authors: Moore Claire L. , Kalil Ronald , Richards Whitman
Published: May 2005

The postnatal development of myelin in the optic nerve and tract of normal and dark reared cats has been studied quantitatively with light and electron microscopy. In the newborn cat few myelinated fibers (3% of the population) are seen in the optic tract. Until the end of the second postnatal week, the total number of myelinated axons in the tract remains low (23%). At this time, however, there is an explosive increase in the rate of myelination and by the end of the fourth postnatal week 80% of the optic tract axons have acquired a myelin sheath. Thereafter, the number of myelinated axons increases gradually, reaching adult levels (100%) at 12 weeks. During the initial period of myelination, the average axon diameter is 0.6 μ for unmyelinated fibers and 1.2 μ for myelinated fibers. Both of these means remain substantially unchanged until myelination is completed, suggesting that initial myelination of an axon is not a continuous process but rather proceeds in a step‐wise manner. Dark rearing appears to have no effect on the initiation of myelination.
Telencephalic projections in two teleost species
Authors: Vanegas Horacio , Ebbesson Sven O. E.
Published: May 2005

The efferent pathways of the telencephalon were investigated in the percomorph Eugerres and the berycomorph Holocentrus. One telencephalic hemisphere was resected by suction and the animals were perfused 7–35 days thereafter. The brains were processed according to a modification (Method 7 in Ebbesson, '70) of the Fink‐Heimer ('67) technique for selective silver impregnation of degenerating axons and terminals.

Some fibers emerging from the lesioned telencephalic hemisphere terminate upon the contralateral hemisphere. The large bulk of efferent fibers, however, descends into the ipsilateral diencephalon and gives off the so‐called strio‐tectal bundle (STB) as well as the medial forebrain bundle (MFB). The remaining contingent eventually splits into the so‐called strio‐lobar bundle (SLB) and the lateral forebrain bundle (LFB), but, previous to splitting, it contributes most of the telencephalic projection to the optic tectum in Eugerres, and gives abundant terminals to the ipsilateral nucleus rotundus or prethalamicus in both Eugerres and Holocentrus. The STB conveys all telencephalo‐tectal fibers in Holocentrus, and some of them in Eugerres. Telencephalic efferents terminate ipsilaterally in the middle level of the tectum's stratum griseum centrale; in Holocentrus there is also a small projection to the stratum opticum.

The MFB terminates at the caudal hypothalamus and gives terminals all along its course. The LFB also gives terminals all along its course and terminates upon a nucleus located between the midline and the corpus glomerulosum. The SLB spreads out and terminates in the inferior lobe of the hypothalamus.
Prenatal development of central optic pathways in albino rats
Authors: Lund R. D. , Bunt Ann H.
Published: May 2005

The development of the central optic projections in albino rat fetuses has been studied using light and electron microscopic degeneration techniques and the horseradish peroxidase method for demonstrating axonal projections of neurons. The first optic axons to reach the region of the optic chiasm arrive at day 15. By day 16, a substantial optic chiasm is seen and the optic tract can be traced into the epithalamus, having first passed through the ventral lateral geniculate nucleus and a thin lamina of cells which is thought to correspond to part of the future dorsal lateral geniculate nucleus. A growth rate of 80–100 μm per hour is estimated for the fastest growing axons. By day 16‐1/3 the first axons have entered the anterior border of the superior colliculus and in the next day have grown across the entire rostrocaudal extent with the exception of the medial and lateral edges. The optic axons are recognized at day 17 as bundles lying just below the surface, but in older animals they come to lie deeper, as the whole layer of optic innervation broadens. The first synapses to be formed in the superior colliculus (some of them of optic origin) appear on day 17. Subsequently, there is a gradual increase in the number of contacts, the great majority being formed by optic axons.

Compared with previous studies on Xenopus and chick, one of the most striking features of the development of the central visual connections in the rat is the relatively long time before the first optic axons reach the brain and the speed with which they innervate the central structures once they have arrived.
Hormone concentrating cells in vocal control and other areas of the brain of the zebra finch (Poephila guttata)
Authors: Arnold Arthur P. , Nottebohm Fernando , Pfaff Donald W.
Published: May 2005

Using the autoradiographic method in the zebra finch (Poephila guttata), areas of the brain were identified which contain cells which accumulate testosterone or its metabolites after intramuscular injection of tritiated testosterone. Among these areas are the caudal nucleus of the hyperstriatum ventrale, nucleus intercollicularis of the midbrain, and the tracheosyringeal portion of the hypoglossal nucleus of the medulla (nXIIts). These three are known to control or influence androgen dependent song and other vocalizations of passeriform birds, and nXIIts is composed of the motoneurons innervating the vocal (syringeal) muscles. Other areas containing hormone‐concentrating cells are the medial preoptic area, nucleus periventricularis magnocellularis of the hypothalamus, dorsal infundibular layers, dorsomedial thalamus, lateral septum, magnocellular nucleus of the anterior neostriatum, periventricular medial neostriatum, nucleus taeniae of the archistriatum, and ventral paleostriatum augmentatum. Accumulation by cells in the preoptic area, hypothalamus, and limbic forebrain is consistent with a general vertebrate pattern of distribution of brain cells which accumulate sex steroids. Some of these same areas may be involved in the control of androgen dependent events such as courtship, copulation, aggression, and feedback regulation of the hypophysis.
Observations on the projections and intrinsic organization of the pigeon optic tectum: An autoradiographic study based on anterograde and retrograde, axonal and dendritic flow
Authors: Hunt S. P. , Künzle H.
Published: May 2005

Three aspects of the labelling pattern seen after the injection of 13 different radioactive amino acids into the pigeon optic tectum have been described: The efferent projections of the optic tectum; the specific labelling of two pathways; and the dendritic organisation of tectal layer III neurons based on the retrograde and anterograde movement of label within these dendrites.

Discrete injections of tritiated amino acid that involved all or only the superficial tectal layers suggested that layer III gave rise to the massive non‐topographically organised and bilateral projections (fibers crossing within the decussatio supraoptica ventralis) upon the nuclei rotundus, subpraetectalis and interstitio‐praetecto‐subpraetectalis and to the ipsilaterally directed pathways terminating within the nuclei praetectalis, triangularis, subrotundus, dorsolateralis anterior thalami, posteroventralis and ventrolateralis thalami. Layer III neurons may also be the source of efferents to the posterior dorsolateral thalamus (the layer III pathway), the pontine grey and, bilaterally to the reticular formation and of the layer IV or tectal commissural pathway terminating within the contralateral tectal cortex. In contrast projections originating from layer II were generally topographically organised and terminated either within certain of the isthmic nuclei (n. isthmi pars parvocellularis, n. isthmo‐opticus and n. semilunaris) or ran within layer I (layer I pathway) to end in the pretectum (griseum tectale) and ventral thalamus (n. ventrolateralis thalami, n. geniculatus, pars ventralis). A small projection from layer II upon the ipsilateral nucleus rotundus may also be present.

Tritiated serine and tyrosine were found to be particularly effective in labelling perikarya as well as axons and terminals. The layer I pathway could be selectively labelled after tectal injections of 3H‐GABA while the cell bodies of Ipc neurons were labelled in a retrograde fashion after tectal injections of 3H‐glycine, serine or alanine.

Intrinsic tectal labelling was found by correlation with Golgi material to reflect both anterograde and retrograde transport of label within dendrites of layer III cells. Anterograde movement of label indicated that the terminal portions of layer III cell dendrites ended in an orderly radial arrangement within sublayers IIb and IId, while the retrograde movement of label resulted in the labelling of layer III perikarya outside the injection field.
Organization and morphologies of acetylcholinesterase‐containing neurons in the thalamus and hypothalamus of the rat
Authors: Parent André , Butcher Larry L.
Published: May 2005

The distribution and morphologies of neurons containing acetylcholinesterase (AChE, EC 3.1.1.7) in the thalamus and hypothalamus of the rat were studied by means of a pharmaco‐histochemical technique involving staining for AChE (Karnovsky‐Roots' procedure) at various times after administration of bis‐(l‐methylethyl)phosphorofluoridate. This method enables visualization of individual AChE‐containing neuronal somata and their processes to a degree not possible with other protocols for the enzyme.

The strongest AChE activity occurring at the level of the thalamus is found within the small, round to oval, somata of nucleus anterior dorsalis. Most of the intralaminar nuclei, as well as nucleus reticularis, are composed of mediumsized multipolar neurons displaying moderate to strong AChE activity. Moderately stained AChE neurons are also found in pars ventralis of nucleus geniculatus lateralis and in pars lateralis of nucleus habenularis. Most of the neurons of the lateral and posterior thalamic territories, however, are nearly devoid of AChE.

At the level of the hypothalamus, the neurons of nuclei supraopticus and paraventricularis show strong AChE activity. The AChE neurons of nucleus supraopticus are surrounded by numerous AChE‐containing processes of some large lateral preoptic area neurons that stain intensely for the enzyme. Numerous intensely stained AChE perikarya occur in the lateral, dorsal, and supramammillary hypothalamic areas. These neurons often possess several AChE‐containing processes. Nuclei arcuatus and ventromedialis consist mainly of neurons displaying a weak to moderate intensity of AChE staining. At the level of the mammillary bodies most neurons show moderate AChE activity except the neuronal somata of nucleus mammillaris lateralis which stain very strongly for the enzyme.
The cerebellofugal projections in the brachium conjunctivum of the rat. II. The ipsilateral and contralateral descending pathways
Authors: Faull R. L. M.
Published: May 2005

The cerebellofugal projections in the ipsilateral and contralateral descending pathways of the brachium conjunctivum (B.C.) in the rat have been investigated in 22 animals using the Fink‐Heimer technique to demonstrate the axonal degeneration resulting from complete B.C. lesions (6), partial B.C. lesions (14) and control lesions dorsal to the B.C. (2). The incidental degeneration resulting from the concomitant involvement of the structures surrounding the B.C. is accounted for in terms of known fiber pathways and from the results in the control experiments.

This study confirms Ramón y Cajal's ('03) original observation that cerebellofugal fibers in the B.C. project caudally throughout the length of the hindbrain via both ipsilateral and contralateral descending pathways. The fibers forming the ipsilateral descending pathway proceed ventrally from the B.C. at the level of the trigeminal motor nucleus, turn caudally and terminate within nucleus reticularis parvocellularis (Rpa). In particular, fibers within this pathway terminate densely in two cytoarchitecturally distinct Rpa subnuclei – nucleus “k” (Meessen and Olszewski, '49) and a caudal linear subnucleus – which project to the cerebellum (Faull, '77). The contralateral descending pathway (B.C.de) proceeds caudally from the decussation of the B.C. within the ventromedial region of the magnocellular nuclei of the reticular formation of the pons and medulla. Cerebellofugal fibers of the B.C.de terminate in a distinctive pattern within precerebellar brainstem nuclei: densely throughout the middle third of nucleus reticularis tegmenti pontis; in a longitudinal zone of each of the three pontine gray subnuclei; in the principal and dorsal accessory nuclei of the inferior olive; and sparsely within nucleus reticularis paramedianus. Fibers in the B.C.de also terminate within the magnocellular nuclei of the reticular formation, principally the nuclei reticularis pontis oralis and caudalis.
A morphological study of the axons and recurrent axon collaterals of cat sciatic α‐motoneurons after intracellular staining with horseradish peroxidase
Authors: Cullheim S. , Kellerth J.‐O.
Published: May 2005

Utilizing the centrifugal neuronal transport of intracellularly injected horseradish peroxidase (HRP), we have performed a light microscopic (LM) investigation of the intramedullary parts of the axons and axon collaterals of sciatic α‐motoneurons in the adult cat.

The intramedullary parts of the α‐motor axons had comparatively short internodes (down to 75 μm) and were thinner than reported in earlier studies on the ventral root. Positive correlations were obtained when relating nodal diameters (2.8–7.8 μm) or the mean diameters of the motor axons in the white matter (4.4–9.0 μm) to the diameters of the initial axonal segments (2.3–4.9 μm).

Eighty percent of the motor axons gave off one to five collaterals. There was no correlation between the numbers of collaterals and the lengths of the parent motor axons in the gray matter. The branching patterns of the axon collaterals showed considerable variation and the number of end branches from a single collateral ranged between 1 and 39. The rostro‐caudal distribution of the collateral end branches was arranged symmetrically within a narrow space (± 300 μm) around the origins of the first order collaterals.

Outbulgings of the motor axon collaterals, interpreted as synaptic terminals, were found along (59%) or at the ends (41%) of the collateral branches, and were located 200–700 μm away from the origin of the first order collateral. No characteristic LM feature of the outbulgings was distinguished.
Projections of the superior cerebellar peduncle in rats and the development of new connections in response to neonatal hemicerebellectomy
Authors: Castro Anthony J.
Published: May 2005

The normal distribution pattern of cerebellar efferents was determined using the Fink‐Heimer technique in adult rats that sustained stereotaxic transection of the superior cerebellar peduncle. This pattern was found to be essentially similar to earlier studies and corroborated more recent reports of projections to the pontine gray and inferior olivary nuclei.

Comparisons were made to a second group of animals that underwent neonatal hemicerebellectomy in addition to adult transection of the contralateral superior cerebellar peduncle. Abnormal projections to the ipsilateral red nucleus and ventral thalamus were observed in addition to evidence suggestive of axonal sprouting within the oculomotor complex. These animals also demonstrated an absence of cells in the pontine gray and inferior olive on the side contralateral to the hemicerebellectomy and in the lateral reticular and lateral cuneate nuclei on the ipsilateral side.
The cochlear nerve in the cat: Topography, cochleotopy, and fiber spectrum
Authors: Arnesen Atle Rønning , Osen Kirsten Kjelsberg
Published: May 2005

The topographical and cytological features of the cochlear nerve in normal adult cats were studied by microdissection, light microscopy, transmission and scanning electron microscopy. The 2‐mm long cochlear nerve trunk is situated within the internal acoustic meatus. The nerve is wrapped like a roll with the more basal fibers situated peripheral to the more apical ones. The fibers are fasciculated according to their target in the cochlea and follow a helical course with the sharpest spiralling in the distal portion of the fiber. Apical and basal coil fibers are of approximately the same length measured from the spiral lamina to the rostral border of the anteroventral cochlear nucleus. The nerve contains about 90% thick, myelinated fibers, about 10% unmyelinated axons, and a few thin, but heavily myelinated axons. The first group shows a unimodal distribution of axonal diameters, with a gradual increase in average diameter from basal to apical coil fibers. The number of axonal microtubules and neurofilaments have a high linear correlation to axonal circumference without principal cochleotopic differences. The myelin sheaths are thicker and the internodal segments shorter than expected from similarly sized peripheral fibers in rodents. The possible nature and origin of the three fiber categories are discussed.
Association and commissural fiber systems of the olfactory cortex of the rat. I. Systems originating in the piriform cortex and adjacent areas
Authors: Haberly Lewis B. , Price Joseph L.
Published: May 2005

The association and commissural fiber systems arising in the olfactory cortical areas caudal to the olfactory peduncle (the piriform cortex, nucleus of the lateral olfactory tract, anterior cortical nucleus of the amygdala, periamygdaloid cortex and entorhinal cortex) have been studied utilizing horseradish peroxidase as both an anterograde and a retrograde axonal tracer.

In the piriform cortex two sublaminae within layer II (IIa and IIb) and layer III have been found to give rise to distinctly different projections. Retrograde cell labeling experiments indicate that the association fiber projection from layer IIb is predominantly caudally directed, while the projection from layer III is predominantly rostrally directed. Cells in layer IIa project heavily to areas both caudal and rostral to the piriform cortex. The commissural fibers from the piriform cortex are largely restricted in their origin to layer IIb of the anterior part of the piriform cortex and in their termination on the contralateral side to the posterior part of the piriform cortex and adjacent olfactory cortical areas. A projection to the olfactory bulb has also been found to arise from cells in layers IIb and III of the ipsilateral piriform cortex, but not in layer IIa.

In addition to those from the piriform cortex, association projections have also been found from other olfactory cortical areas. The nucleus of the lateral olfactory tract has a heavy bilateral projection to the medial part of the anterior piriform cortex and the lateral part of the olfactory tubercle (as well as a lighter projection to the olfactory bulb); both the anterior cortical nucleus of the amygdala and the periamygdaloid cortex project ipsilaterally to several olfactory cortical areas. The entorhinal cortex has been found to project to the medial parts of the olfactory tubercle and the olfactory peduncle. The olfactory tubercle is the only olfactory cortical area from which no association fiber systems (instrinsic or extrinsic) have been found to originate.

A broad topographic organization exists in the distribution of the fibers from several of the olfactory areas. This is most obvious in the anterior part of the olfactory cortex, in which fibers from the more rostral areas (the anterior olfactory nucleus and the anterior piriform cortex) terminate in regions near the lateral olfactory tract, while those from more caudal areas (the posterior piriform cortex and the entorhinal cortex) terminate in areas further removed, both laterally and medially, from the tract.

Projections to olfactory areas from the hypothalamus, thalamus, diagonal band, and biogenic amine cell groups have been briefly described.
Quantitative analysis of the opossum's optic nerve: An electron microscope study
Authors: Hokoç J. N. , Oswaldo‐Cruz Ė.
Published: May 2005

An electron microscope examination of the optic nerve of the opossum, Didelphis marsupialis aurita, indicates a total count of 74,700 fibers of which approximately 20% are unmyelinated. The diameters of myelinated fibers ranged from 0.5–7.0 μm (mode at 1.25 μm) and those of the unmyelinated fibers ranged from 0.25–2.25 μm (mode at 0.75 μm). Myelinated and unmyelinated fibers are uniformly distributed throughout the nerve. Myelin sheath structure is similar to that described in other species and are formed by 2 to 17 myelin rings (mode at 6). There is a good correlation (r = 0.92) between axon and myelin areas. The relation between myelin thickness and axons diameter shows a wide distribution with a peak at 0.77.
Prenatal development of the cerebellar system in the rat. II. Cytogenesis and histogenesis of the inferior olive, pontine gray, and the precerebellar reticular nuclei
Authors: Altman Joseph , Bayer Shirley A.
Published: May 2005

Aspects of the prenatal development of the inferior olive, lateral reticular nucleus, nucleus reticularis tegmenti pontis, and of the pontine gray were investigated in the rat. The material used was the same as in the preceding study of cerebellar development, including histological preparations from normal and x‐irradiated embryos at daily intervals (days E13 to E22), and autoradiograms from adult rats injected with two successive doses of 3H‐thymidine on overlapping days from days E13 + 14 on.

Neurons of the inferior olive form on days E13 and 14: those settling rostrally in the principal nucleus somewhat ahead of those settling in the medial accessory nucleus caudally. The olivary neurons are generated in the neuroepithelium of the lateral recess of the fourth ventricle, migrate ventrally by way of the olivary migratory stream, split into two branches and provide cells to the olivary complex from its lateral and medial aspect. The migrating cells are differentiated, radioresistant elements. It was postulated that since the olivary migratory path and the course of olivary fibers (the inferior cerebellar peduncle) are on the same trajectory, climbing fibers could reach the surface of the cerebellum before the arrival of the radially migrating Purkinje cells.

Neurons of the lateral reticular nucleus form predominantly on days E13 and 14, of the nucleus reticularis tegmenti pontis on days E15–17, and of the pontine gray on days E17–19. The pontine neurons originate several days after but at the same site as the olivary neurons. The cells migrating in the pontine migratory stream are undifferentiated elements and follow a course different to that of their prospective axons in the middle cerebellar peduncle. The earliest forming pontine neurons settle near the pyramidal tract, the later arriving cells form cap‐like shells around this core. Axonogenesis of pontine cells begins after the settling of the perikarya on day E19. The middle cerebellar peduncle appeared to approach the cerebellum on day E22, suggesting that pontine mossy fibers do not establish contact with cerebellar elements before the perinatal period, by which time the external germinal layer and the Purkinje cells have formed a cortical mantle over the entire cerebellum.

In an attempt to correlate the chronology of cytogenesis in some of the precerebellar nuclei with cell production and maturation in the cerebellum, it was hypothesized that mossy fibers of reticular origin exert influence on Purkinje cell dendrites in the lower parts of the molecular layer, whereas mossy fibers of pontine origin influence the upper parts of Purkinje cell dendrites. Reference is made to behavioral results indicating the mediation of dissociable functions by elements of the lower and upper molecular layer.
The corticopontine projection from the visual cortex of the cat: An autoradiographic investigation
Authors: Fries W. , Albus K.
Published: May 2005

The cortico‐pontine projections from striate (kV), parastriate (paV) and peristriate (peV) areas of the neocortex of the cat have been investigated using an anterograde axoplasmic tracing method. Injections of tritiated amino‐acids have been made at cortical locations whose visual field positions were determined in some experiments electrophysiologically. It has been found that the density of the projection varies depending on the location of the injections within each area. In addition differences in the density of the pontine projection have been found between the three visual areas. Both in kV and paV no pontine projection was detected from cortex representing the area centralis. An increase of the projection from cortex with paracentral to peripheral visual field representations was found in kV for the lower hemifield (the upper hemifield has not been investigated) and in paV for the entire hemifield. In addition it has been found that a denser projection arises from the representation of the lower visual field in paV and peV than from the representation of the lower visual field in paV and peV than from the representation of the upper visual field.

The cortico‐pontine projection has been found to increase from kV (V1) through paV (V2) to peV. Since the injections in peV were not restricted to the region of the third visual representation (V3), they do not allow a definite conclusion to what extent the increased projection from peV can be attributed to V3.

The terminations from the three visual areas are largely restricted to the rostral third of the pontine basilar gray. The labelled terminals were not restricted to any one of the nuclei of this region which have been delimited by Brodal and Jansen ('46). The terminals formed patches of variable size near the ventral aspect of the cerebral peduncles. A clear retinotopic distribution of these patches could not be demonstrated.
Monoamine fluorescence and electron microscopic studies on small intensely fluorescent (granule‐containing) cells in human sympathetic ganglia
Authors: Chiba Tanemichi
Published: May 2005

In the present study, surgically removed adult human sympathetic ganglia were explored for the presence of small intensely fluorescent (SIF) cells using a combined monoamine fluorescence and electron microscopic method (Chiba et al., '76b). It was confirmed that SIF or granule‐containing (GC) cells exist as a persisting constituent of the ganglia. The population of SIF cells in human sympathetic ganglia was found to be much smaller than that of the rat and the guinea pig. Most SIF cells were found as small clusters in the connective tissue stroma in close relationship with blood vessels. GC cells were characterized by large polymorphic granular vesicles (100–300 nm in diameter) in their cytoplasm. Most GC cells were innervated by cholinergic axons which most probably originated from preganglionic sympathetic neurons. No efferent synapses were found from GC cells as far as they were examined.

Axon varicosities containing small dense granular vesicles (50 nm in diameter) may correspond to varicose fluorescent network of axons among principal ganglionic neurons. The functional significance of SIF or GC cells in human sympathetic ganglia was discussed in the light of the present observations.