bluuebunny/crossref_metadata_2025 huggingface dataset:
Nomenclature and location of avian hypothalamic nuclei and associated circumventricular organs
Authors: Kuenzel Wayne J. , van Tienhoven Ari
Published: January 2005

Nineteen nuclei and two areas within the avian hypothalamus were identified and located on specific cross‐sectional planes of a stereotaxic atlas of the fowl. Latin terms applied to the nuclei and associated fiber tracts were compared among several authors and a suggested standardized nomenclature presented for hypothalamic structures. Nine circumventricular organs (CVOs) were also located throughout the prosencephalon, mesencephalon, and rhombencephalon of the chicken. A majority of the CVOs were found near nuclei.
Regulation in the number of fly photoreceptor synapses: The effects of alterations in the number of presynaptic cells
Authors: Nicol D. , Meinertzhagen I. A.
Published: January 2005

At the equator of the fly's eye, between dorsal and ventral eye halves, a systematic, natural addition of photoreceptor terminal input occurs at each of the fixed populations of uniquely identifiable postsynaptic interneurons in each cartridge of the first optic neuropile, or lamina. The equatorial cartridges are identical in composition except in having seven and eight receptor terminals (7R and 8R, respectively), compared with six elsewhere (6R cartridges). The effects of this augmented presynaptic input upon the frequency of the chief afferent class of photoreceptor tetrad synapse were studied compared with control data for 6R cartridges (Nicol and Meinertzhagen, ′82). The synapse population size and distribution within five depth levels of the lamina is, on average, approximately constant for all receptor terminals whether from 6R, 7R, or 8R cartridges. The overall determinant ofsynapse frequency is therefore presynaptic. Small (5–6%) average decreases in synapse frequency per receptor in 7R and 8R cartridges compared with 6R co‐vary with similar decreases in membrane area, each synapse occupying a patch of membrane of similar area in all cases. The tetradic postsynaptic composition of synapses was also similar in all cases. Because of the augmented synaptic input to the postsynaptic neurons, a morphometric analysis was undertaken of two (L1 and L2) which receive input as a pair from every synapse. There is the same dendrite number (about 180) in 8R L1/L2 as in 6R L1/L2 but they have different branching patterns, conforming to the different number and configuration of receptor terminals. Thus in an 8R cartridge each terminal is serviced by a comb of fewer dendrites, but each dendrite is longer, fatter, and services more synapses. The area of L1/L2 dendritic membrane exposed is increased, compared with 6R cartridges, in proportion with the number of synapses it participates at postsynaptically, so that all dendrites (6R and 8R) allocate the same mean area (about 0.55 μm2) of postsynaptic membrane per synapse.
On the distribution and origins of substance P in the papillae of the rat tongue: An experimental and immunohistochemical study
Authors: Nishimoto Tatsuya , Akai Michio , Inagaki Shinobu , Shiosaka Sadao , Shimizu Yoshiki , Yamamoto Kazumi , Senba Emiko , Sakanaka Masahiro , Takatsuki Kenichi , Hara Yoshinobu , Takagi Hiroshi , Matsuzaki Takashi , Kawai Yuriko , Tohyama Masaya
Published: January 2005

The distribution and the orgins of substance P (SP)‐positive fibers in the papillae of the rat tongue were investigated by means of the indirect immunofluorescent method.

Three types of papilla contain SP‐positive fibers, though the number ofthese fibers varies from papilla to papilla. The circumvallate papilla contains the greatest number of SP‐positive fibers, followed by the foliate papillae and the fungiform papillae; the filiform papillae lack SP‐positive fibers. The papillar SP‐positive fibers form dense bands in the lamina propria just beneath the epithelium. Some of the fibers enter the epithelium and the taste buds. It should be stressed that not every taste bud is provided with SP‐positive fibers: Only 95% of the taste buds in the foliate papillae, 70% of the taste buds in the fungiform papillae, and 40% of the taste buds in the circumvallate papillae contain detectable SP‐positive fibers. Unilateral section of the glossopharyngeal nerve resulted in a complete disappearance of SP‐positive fibers in the foliate papillae on the operated side, and a slight decrease in the circumvallate papillae on both sides. Bilateral section of the glossopharyngeal nerve resulted in a complete disappearance of SP‐positive fibers in the foliate and circumvallate papillae. Following unilateral section of the chorda tympani, SP‐positive fibers in the tastebuds of the fungiform papillae disappeared completely. In addition, unilateral neurotomy of the mandibular nerve resulted in a complete disappearance of SP‐positive fibers in the epithelium of the fungiform papillae. These facts strongly indicate that SP in the foliate and circumvallate papillae is supplied by the glossopharyngeal nerve, SP in the taste buds of the fungiform papillae by the chorda tympani, and SP in the epithelium of the fungiform papillae by the third division of the trigeminal nerve.
Androgen‐Concentrating cells in the periventricular brain of the female rhesus monkey
Authors: Sheridan Peter J. , Hagino Nobuyoshi , Weaker Frank J.
Published: January 2005

Although androgens act on the primate central nervous system to modulate both endocrine functions and a number of limbic‐related behaviors, little is known about the anatomical location of the neurons which sequester these steroids in primates. To determine the prime location of these androgen‐concentrating neurons in the forebrain of the primate, we injected three castrated female rhesus monkeys in the femoral vein with 1 μg of 5α‐dihydro (1, 2, 4, 5, 6, 7‐3H) testosterone (3H‐DHT, 107 Ci/mmole) per kg of body weight. One of these animals also received an IV injection of 100 μg/kg body weight of unlabeled dihydrotestosterone (DHT) to serve as a control. One hour after the injection of 3H‐DHT we rapidly exsanguinated each animal. The forebrain was sliced and blocks containing the amygdala, diencephalon, frontal pole, and hippocampus were frozen and stored in liquid nitrogen until processing. The tissue was then processed for autoradiography. A specific topographic pattern of nuclear concentration of DHT or one of its metabolites was obtained in neurons of the basal hypothalamus, preoptic region, amygdala, and hippocampus. This pattern was similar to that found in rodent species.
The motor nuclei and primary projections of the facial nerve in the monitor lizard Varanus exanthematicus
Authors: Barbas‐Henry Heleen A.
Published: January 2005

The location of the motor nuclei and the projection of the primary afferent fibers of the facial nerve of the reptile Varanus exanthematicus were studied by means of the HRP method and the anterograde degeneration technique. The motor nuclei are located ventrolaterally in the rhombencephalon and are constituted by a medial cell group consisting of large, polygonal cells and a lateral cell group consisting of medium‐sized, spindleshaped, and multipolar cells. From HRP applications to the various branches of the facial nerve it could be concluded that the medial cell group represents the branchiomotor nucleus and the lateral cell group the superior salivatory nucleus. The efferent axons from the motor nuclei course dorsomedially toward the fourth ventricle, where they form a genu, and exit from the brainstem in the ventral fiber bundle of the facial nerve.

The primary afferent fibers enter the brainstem in the dorsal bundle ofthe facial nerve. This bundle courses medially, enters the solitary tract, and diverges into rostrally and caudally running fibers. Part of the caudally directed fibers leave the solitary tract and course laterally toward the descending trigeminal tract. Some fibers enter the nucleus of this tract. There was no noticeable terminal degeneration in the solitary tract or in the descending trigeminal tract or its nucleus.
Synaptic complexes formed by functionally defined primary afferent units with fine myelinated fibers
Authors: Light A. R. , Perl E. R. , Réthelyi M.
Published: January 2005

The individual fine myelinated fibers of cutaneous mechanical nociceptors and “D‐hair” receptors were identified by electrophysiological recording with micropipette electrodes in cats and monkeys. Their intraspinal terminations were labeled by iontophoresing horseradish peroxidase intracellularly and subsequent diaminobenzidine histochemistry. These terminations were examined with light and electron microscopy to determine the nature and organization of their synaptic contacts.

Myelinated fibers of the mechanical nociceptors became unmyelinated before exhibiting many enlargements that made multiple synaptic contacts in the marginal zone (lamina I) and lamina V. Pre‐or postsynaptic contacts were found only on enlargements. In the marginal zone of the cat, enlargements made simple axodendritic contacts or were scalloped, central terminals in glomeruli. In glomeruli, myelinated mechanical nociceptor enlargements were presynaptic to several dendritic appendages and postsynaptic to two different types of profiles. One type was interpreted as a presynaptic axon terminal, the other as a presynaptic, vesicle‐containing, dendritic appendage. In lamina V of the cat the nociceptor synaptic complexes were similar, but simpler, and only axonal profiles were found to be presynaptic to them. In the monkey marginal zone and deep nucleus proprius, myelinated nociceptor terminations formed the central element of glomeruli, which consisted of postsynaptic dendritic appendages and presynaptic axon terminals.

D‐hair axons terminated in large numbers of enlargements in the nucleusproprius (laminae III and IV) and inner substantia gelatinosa (lamina III). Their large rounded enlargements formed the central terminals in glomeruli and were presynaptic to both ordinary and vesicle‐containing dendritic appendages; the presynaptic dendritic profiles also often contacted each other. Profiles interpreted as axonal in origin were the only terminals presynaptic to the primary ending within the D‐hair glomeruli.

The results suggest that transfer of primary afferent information occurs only at enlargements of the primary fiber and that each primary fiber enters into more than one kind of synaptic arrangement. They also point out that synaptic glomeruli are common to functionally different types of primary afferent fibers and that the internal organization of glomeruli varies with the kind of primary fiber and the locus of the complex.
The effects of environmental diversity on well‐fed and previously undernourished rats: I. Body and brain measurements
Authors: Bhide P. G. , Bedi K. S.
Published: January 2005

Rats were undernourished from the 16th day of gestation to 25 postnatal days of age and then weaned on to an ad libitum diet. Around 35 days of age, 12 previously undernourished (PU) male pups were assigned to an “enriched environmental condition” (EC) and 12 to an “isolated environmental condition” (IC). Well‐fed controls were similarly assigned. After 30 days in these conditions all rats were killed by perfusion with fixative.

Body and “forebrain” weights, and forebrain lengths and widths, were determined for each animal. The forebrains were subsequently embedded in paraffin wax and serially sectioned. Ten sections, identified by subcortical landmarks, were taken from each brain and used for cortical depth measurements. The whole experiment was carried out on two separate occasions.

In both the well‐fed and PU groups the EC rats were between 3% and 9% lighter in body weight and between 4% and 9% heavier in “forebrain” weight than IC animals. A two‐way analysis of variance (two‐way ANOVA) indicated significant effects of nutrition and environment on body and forebrain weights but no significant interaction. Nutrition, but not environment, also had significant effects on “forebrain” width and length measurements.

For the well‐fed groups, only one section out of all those measured from the two experimental series showed a significant effect of environment onthe cortical depth measurements.

For the PU groups, in experiment one the cortical thickness of the EC rats was significantly greater than their IC counterparts in four out of theten sections analyzed. In the second experiment only two sections exhibitedsignificant results. In contrast to experiment one, these showed that the IC rats had a slightly but significantly thicker cortex than the EC rats. A two‐way ANOVA of the data on cortical depths showed no significant effects of, or interaction between, nutrition and environment.

These observations are discussed in the context of previously publishedresults on the effects of a differential environment on body and brain measurements.
Fine structural localization of a new Purkinje cell‐specific glycoprotein subunit: Immunoelectron microscopical study
Authors: Langley O. K. , Reeber A. , Vincendon G. , Zanetta J. P.
Published: January 2005

The localization of a new low molecular weight glycoprotein subunit in cerebellum was studied with the aid of the indirect immunohistochemical method at the electron microscope level. The specificity of this molecule for Purkinje cells in the rat cerebellum suggested by earlier light microscope studies was confirmed. Immunoperoxidase reaction product indicative of the presence of this glycoprotein was exclusively limited to Purkinje cells, attached to the plasma membrane, membranes of the rough endoplasmic reticulum, the cytoplasmic surface of the nuclear membrane, and on polyribosomes. The antigen was found throughout the whole cell, except for the nucleus, and enabled Purkinje cell processes to be traced in the molecular layer, in the granule cell layer (including the nerve terminals in this layer), and to their axon terminals in the deep nuclei. The fine structural localization is discussed with reference to the known properties of this antigen.
Comparison of the morphology of physiologically identified abducens motor and internuclear neurons in the cat: A light microscopic study employing the intracellular injection of horseradish peroxidase
Authors: Highstein S. M. , Karabelas A. , Baker R. , McCrea R. A.
Published: January 2005

Abducens motoneurons and internuclear neurons were identified electrophysiologically in anesthesized, paralyzed cats and stained by intracellular injection of horseradish peroxidase. Neurons were reconstructed and surface area of selected cells measured by light microscopy. Surface area of motoneurons and internuclear neurons with similar soma size and shape were roughly comparable. Dendrites of motoneurons were highly tapered and highly branched. By contrast, dendrites of internuclear neurons were less tapered and less branched. Axons of motoneurons had no collaterals within the brainstem. Internucler axons crossed the midline at the level of their parent somata and ascended in the medial longitudinal fasciculus toward the oculomotor nucleus. Approximately 30% of the internuclear axons branched in the contralateral medial longitudinal fasciculus sending a fine collateral caudal toward the prepositus hypoglossi nucleus. The results suggest that, on the average, structural correlates of injected neurons (i.e., soma‐dendritic morphology) can account at least in part for the earlier firing and higher intraburst frequencies of internuclear neurons versus motoneurons during on‐direction rapid eye movements in alert cats.
Anatomical banding of intrinsic connections in striate cortex of tree shrews (Tupaia glis)
Authors: Rockland K. S. , Lund J. S. , Humphrey A. L.
Published: January 2005

The intrinsic connectivity of striate cortex was investigated by injecting horseradish peroxidase (HRP) into this area in tree shrews. Such HRP injections demonstrated periodically organized, stripelike connections within area 17. These stripes occur in layers I–IIIA and consist of a small number of retrogradely filled neurons, some clearly pyramidal, together with HRP‐labeled axon terminals. HRP‐filled axon trunks run between labeled stripes, interconnecting adjacent and distant regions of the stripe pattern. Correlation with Golgi‐stained tissue suggests that these stripes are horizontally interconnected by pyramidal neurons with long intracortical axon collaterals (followed for distances over 1 mm form the soma). The HRP‐labeled stripes measure about 230 μm in width, with a center‐to‐center repeat distance of 450–500 μm. They have been mapped over an 8 mm2 area of striate cortex and would thus seem capable of effecting lateral interactions over considerable portions of the retinotopic map. In their dimensions and overall pattern, these anatomical stripes resemble the 2‐deoxyglucose (2‐DG) bands resulting from visual stimulation of tree shrews with stripes of a single orientation. While the functional role of the HRP‐labeled stripes is unclear, their similarities with the 2‐DG pattern raise the intriguing possibility that they may be related to orientation selectivity. The striking regularity of these extensive lateral interconnections emphasizes the importance of horizontal intralaminar connections within the cortex.
Two types of synaptic glomeruli and their distribution in laminae I–III of the rat spinal cord
Authors: Ribeiro‐Da‐Silva A. , Coimbra Antonio
Published: January 2005

Systematic examination of photomontages revealed two types of synaptic glomeruli in laminae II‐III. Type I glomeruli have a dark small central (C) terminal of indented contour with closely packed spherical vesicles of variable diameter and few mitochondria. Among the peripheral terminals there are dendritic spines and a few presynaptic dendritic spines (V1 terminals) and axon endings rich in discoid vesicles (V2). These glomeruli occur in groups which are particularly evident in parasagittal sections in which successive C terminals are connected by narrower portions or dark unmyelinated profiles. Type II glomeruli have an electron‐lucent and large C terminal of regular contour with less packed synaptic vesicles of more uniform diameter, more mitochondria, and sometimes neurofilaments. Presynaptic dendrites are fewer and axon endings more numerous. C terminals in type II glomeruli are fusiform in longitudinal section, rarely occurring in groups.

Lamina I is virtually devoid of glomeruli. Within lamina II, glomeruli are rare in a dorsalmost 20‐μm band and abundant in the immediately ventral 20‐μm band in which type I glomeruu are prevalent (ñ 79%). In ventral lamina II, type II glomeruli predominate (66%), being pratically exclusive in lamina III where most contain neurofilaments. Considering the distribution of terminations of primary afferents, it is suggested that type I C terminals originate from unmyelinated primary afferents, type II C terminals without neurofilaments from direct myelinated fibers, and those with neurofilaments from recurrent large fibers. The distinct numbers of presynaptic dendritic and axonal endings suggest different modulatory mechanisms functioning in the two types and in ventral vs. dorsal areas of this region.
Axonal guidance during development of the great cerebral commissures: Descriptive and experimental studies, in vivo, on the role of preformed glial pathways
Authors: Silver Jerry , Lorenz Suzanne E. , Wahlsten Douglas , Coughlin Jack
Published: January 2005

Do structres exist within the embryonic central nervous system that guide axons across the midline during development of the great cerebral commissures (corpus callosum, anterior commissure)? With the use of serial section and reconstructive computer graphic techniques we have found that during normal ontogeny of the mouse forebrain and before the arrival of the pioneer fibers of the corpus callosum at the midline, a population of primitive glial cells migrates medially (through the fused walls of the dorsal septum) from the ependymal zones of each hemisphere. At the midline, and well rostral to the lamina terminalis, these cells unite to form a bridgelike structure of “sling” suspended below the longitudinal cerebral fissure. The first callosal axons grow along the surface of this cellular bridge as they travel toward the contralateral side of the brain. The “sling” disappears neonatally. The fibers of the anterior commissure grow within the lamina terminalis along a different type of preformed glial structure. Movement of these axons occurs through an aligned system of glial processes separated by wide extracellular spaces.

Do these transient glial tissues actually provide guidance cues to the commissural axons? Analyses of three situations in which the glial “sling” is genetically or surgically impaired or nonexistent indicate that this structure does, indeed, play an essential role in the development of the corpus callosum. We have analyzed (1) the embryonic stages of a congenitally acallosal mouse mutant (strain BALB/cCF), (2) several pouch stages of a primitive acallosal marsupial, Didelphys virginiana (opossum), and (3) animals in which the “sling” had been lesioned surgically through the uterine wall in the normal embryo (strain C57BL/6J).

In the acallosal mouse mutant fusion of the septal midline is delayed by about 72 hours and the “sling” does not form. Although the would‐be callosal axons approach the midline on schedule, they do not cross. Instead, the callosal fibers whirl into a pair of large neuromas adjacent to the longitudinal fissure. Similarly, in the opossum, fusion of the medial septal walls and formation of the glial “sling” are also lacking. However, in this species, instead of traveling dorsally, the “callosal” axons turn ventrally and pass contralaterally by way of the anterior commissure pathway. Surgical disunion of the glial “sling” also resulted in acallosal individuals. The callosal pathology in these affected animals mimicked exactly that of the genetically lesioned mutant. Our observations suggest that many different types of oriented glial tissues exist within the embryonic neural anlage. We propose that such tissues have the ability to influence the directionality of axonal movements and, thereby, play a crucial role in establishing orderly fiber projections within the developing central nervous system.
Segmental distribution and central projectionsof renal afferent fibers in the cat studied by transganglionic transport of horseradish peroxidase
Authors: Kuo David C. , Nadelhaft Irving , Hisamitsu Tadashi , de Groat William C.
Published: January 2005

The segmental and central distributions of renal nerve afferents in adult cats and kittens were studied by using retrograde and transganglionic transport of horseradish peroxidase (HRP). Transport of HRP from the central cut ends of the left renal nerves labeled afferent axons in the ipsilateral minor splanchnic nerves and sensory perikarya in the dorsal root ganglia from T12 to L4. The majority of labeled cells (85%) were located between L1 and L3. A few neurons in the contralateral dorsal root ganglia were also labeled. Labeled cells were not confined to any particular region within a dorsal root ganglion. Some examples of bifurcation of the peripheral and central processes within the ganglion were noted. A small number of preganglionic neurons, concentrated in the intermediolateral nucleus, were also identified in some experiments. In addition, many sympathetic postganglionic neurons were labeled in the renal nerve ganglia, the superior mesenteric ganglion, and the ipsilateral paravertebral ganglia from T12 to L3

Transganglionic transport of HRP labeled renal afferent projections to the spinal cord of kittens from T1 1 to L6, with the greatest concentrations between Ll and L3. These afferents extended rostrocaudally in Lissauer's tract and sent collaterals into lamina I. In the transverse plane, a major lateral projection and a minor medial projection were observed along the outer and inner margins of the dorsal horn, respectively. From the lateral projection many fibers extended medially in laminae V and VI forming dorsal and ventral bundles around Clarke's nucleus. The dorsal bundle was joined by collaterals from the medial afferent projection and crossed to the contralateral side. The ventral bundle extended into lamina VII along the lateroventral border of Clarke's nucleus. Some afferents in the lateral projection could be followed ventrally into the dorsolateral portion of lamina VII in the vicinity of the intermediolateral nucleus. In the contralateral spinal cord, labeled afferent fibers were mainly seen in laminae V and VI

These results provide the first anatomical evidence for sites of central termination of renal afferent axons. Renal inputs to regions (laminae I, V, and VI) containing spinoreticular and spinothajamic tract neurons may be important in the mediation of supraspinal cardiovascular reflexes as well as in the transmission of activity from nociceptors in the kidney. In addition, the identification of a bilateral renal afferent projection in close proximity to the thoracolumbar autonomic nuclei is consistent with the demonstration in physiological experiments of a spinal pathway for the renorenal sympathetic reflexes.
Patterns of extraocular innervation by the oculomotor complex in the chick
Authors: Heaton Marieta B. , Wayne Demise B.
Published: January 2005

The horseradish peroxidase retrograde tracer technique was used to map tne projection pattern of the oculomotor nuclear complex to the extra‐ocular muscles in the chick embryo. The following projection pattern was found: The dorsolateral oculomotor subnucleus innervates the ipsilateral in‐ferior rectus muscle, the dorsomedial subnucleus innervates the ipsilateral medial rectus muscle, a lateral division of the ventromedial subnucleus innervates the ipsilateral inferior oblique muscle, and a medial division of the ventromedial subnucleus innervates the contralateral superior rectus muscle. The so‐called central nucleus also innervates the contralateral superior rectus muscle. This pattern was extremely discrete, with virtually no overlapping representations. These results provide the first evidence for a functional medial‐lateral subdivision of the ventromedial subnucleus. This pattern relates to the unusual development of this subnucleus and suggests that only part of the primordium for this cell group migrates across the mid‐line during its ontogeny, rather than all of it, as was previously believed. The subnuclear organization of the avian oculomotor complex is also considered in comparison to such functional organization in other species.
Visuotopic organization of projections from striate cortex to inferior and lateral pulvinar in rhesus monkey
Authors: Ungerleider Leslie G. , Galkin Thelma W. , Mishkin Mortimer
Published: January 2005

Anatomical material from two series of monkeys (Macaca mulatta)was used to determine the full extent and visuotopic organization of striate projections to the pulvinar. One series was processed for degeneration by the Fink‐Heimer procedure following unilateral lesions of lateral, posterior, or medial striate cortex (representing the central, peripheral, and far peripheral visual field, respectively); collectively, the lesions included all of area 17. The second series was processed for autoradiography following tritiated amino‐acid injections into striate sites representing the center of gaze and eccentricities ranging from 0.5° to greater than 30° from fixation in both the upper and lower fields.

The results indicate the existence of two separate striate projection zones within the pulvinar. One, the PI/PL zone, is located primarily within the inferiorpulvinar (PI) but extends into the adjacentlateral pulvinar (PL). The other, the PL zone, is located entirely within the lateral pulvinar and partially surrounds the first zone along its dorsal, lateral, and ventral aspects.

Within the PI/PL zone, striate projections are topographically organized and represent the entire contralateral visual field. Central vision is represented laterally and posteriorly, with the fovea represented at the caudal pole of the nucleus; conversely, far peripheral vision is found medially and anteriorly, adjacent to the medial geniculate nucleus. The representation of the horizontal meridian runs obliquely across PI/PL, such that the upper visual field is located ventrolaterally and the lower visual field dorsomedially. The representation of the vertical meridian is located along the lateral margin of PI in anterior sections of the pulvinar, but within PL in posterior sections. Thus, the vertical meridian appears to form the border between the lateral margin of the PI/PL zone and the medial margin of the PL zone. At the lateral margin of the PL zone is the representation of its horizontal meridian. Striate projections to the PL zone, unlike those to the PI/PL zone, are limited to the representation of central vision. These results suggest that striate inputs contribute to the visual properties of neurons (Bender, 1981 a) throughout the PI/PL zone, but are insufficient to explain the visual properties of neurons outside of the central visual field representation in the PL zone.
Innervation of monkey extraocular muscles: Localization of sensory and motor neurons by retrograde transport of horseradish peroxidase
Authors: Porter John D. , Guthrie Barton L. , Sparks David L.
Published: January 2005

Neurons that provide sensory and motor innervation of extraocular muscles in the monkey have been identified and localized by retrograde transport of horseradish peroxidase (HRP). Injections of HRP into individual extraocular muscles of rhesus or pig‐tail monkeys labeled pseudounipolar neurons that were localized within the ipsilateral semilunar ganglion. The distribution of labeled neurons within the ganglion was consistent with its somatotopic organization as the majority were found within the ophthalmic subdivision. Absence of labeled neurons within either the trigeminal mesencephalic or spinal nucleus was in agreement with previous findings in the cat (Porter and Spencer, '82). Intracranial transection of the ophthalmic nerve prior to muscle injection eliminated all labeling within the ganglion. These data indicate that the extraocular muscles can be selectively deafferented in order to examine the potential role(s) of proprioception in the neural control of eye movements.

Injections of HRP into the extraocular muscles also resulted in the la beling of individual motoneuron populations. Each extraocular muscle was found to receive solely unilateral innervation, with contralateral representation of only the superior rectus and superior oblique. Within the oculomotor nucleus there was a moderate topographic segregation of individual motoneuron populations. Primate medial rectus and inferior rectus representations, while at variance with the classical descriptions (Warwick, '53), were consistent with those obtained in contemporary tracer studies (Büttner Ennever and Akert, '81; Spencer and Porter, '81). Superior rectus motoneurons were distributed along the medial aspect of the contralateral nucleus, with the predominant representation at caudal to midnuclear levels. Inferior oblique motoneurons filled the gap lateral to those of the superior rectus and ventral to medial rectus (dorsal subgroup) and inferior rectus representations at their respective levels. Following injections of the lateral rectus and superior oblique labeled motoneurons were found within the ipsilateral abducens nucleus and contralateral trochlear nucleus, respectively. Superior oblique motoneurons were strictly confined to the well‐defined neuronal borders of the trochlear nucleus. Those innervating the lateral rectus, in addition to lying within the abducens proper, extended ventrolaterally from the nucleus to form a discrete ventral abducens nucleus. Our data provide a complete description of the innervation pattern of primate extraocular muscles which is based upon contemporary tracer techniques. These findings include the first demonstration of the localization of monkey first‐order afferent neurons which subserve extraocular muscle proprioception.
Luteinizing hormone‐releasing hormone (LHRH) in rat olfactory systems
Authors: Witkin Joan W. , Silverman Ann‐Judith
Published: January 2005

The luteinizing hormone‐releasing hormone (LHRH) systems of rat olfactory bulbs and nasal areas were studied in neonatal and adult rats. Animals were perfused with Zamboni's fixative and olfactory bulbs with nasal olfactory areas intact were removed, postfixed, and decalcified. LHRH was immunohistochemically demonstrated in unembedded frozen or vibratome sections.

Luteinizinghormone‐releasinghormoneimmunoreactive elements were found along the course of the nervus terminalis (NT) and within both the main and accessory olfactory bulbs (MOB and AOB, respectively). Both LHRH neurons and fibers were present in the AOB, but only fibers were detected in the MOB. The fibers of the AOB were not confined to any particular lamina while fibers in the MOB were found mainly in the external plexi‐form layer. LHRH fibers were found in the mucosa of the olfactory epithelium of the vomeronasal organ in both neonatal and adult rats.

The NT probably serves as a source of LHRH fibers for both the AOB and the MOB and for fibers observed in the olfactory epithelium of the vomeronasal organ. Other likely sources of LHRH fibers in the olfactory bulb are discussed.
Bar synapses and gap junctions in the inner plexiform layer: Synaptic relationships of the interstitial amacrine cell of the retina of the cichlid fish, Astronotus ocellatus
Authors: Zimmerman Roger P.
Published: January 2005

The retina of the cichlid fish, Astronotus ocellatus, contains an unusual class of amacrine cell, the interstitial amacrine cell, which has its soma and processes restricted to a sublamina of the proximal inner plexiform layer. The interstitial amacrine cell is unique in making synapses which contain a presynaptic dense bar specialization. The interstitial amacrine cell makes reciprocal synapses with bipolar cell terminals and is presynaptic to other amacrine cells and to ganglion cell dendrites. Processes of interstitial amacrine cells are connected to each other by large gap junctions.
Postnatal development of corticotectal neurons in the kitten striate cortex: A quantitative study with the horseradish peroxidase technique
Authors: Tsumoto Tadaharu , Suda Kouhei , Sato Hiromichi
Published: January 2005

Postnatal development of striate cortical neurons projecting to the superior colliculus (SC) was studied in cats, ranging in age from newborn to adult, by injection of horseradish peroxidase (HRP) into the SC. At birth, HRP‐labelled cells were widely distributed throughout the cortex between the splenial and suprasylvian sulci, although a very rough topographic correspondence seemed to exist between the striate cortex and SC. The labelled cells were confined to layer V of the cortex, as in the adult. They were very densely packed and their somas were already pyramidal in shape although very slender.

During the third to eighth days, apical dendrites of a substantial number of cells, mostly locatcd in the upper bank of the splenial sulcus, were filled with HRP up to layer I and their somas were larger than those of cells located near the crown of the lateral and postlateral gyri. At the eighth day and thereafter, the distribution of the labelled cells across the visual cortex was not so widespread as that seen in the newborn kittens. The dendritic arborization pattern of labelled cells became nearly adultlike at the fourth week, and its full maturation was seen at the eighth week.

A quantitative analysis of the cross‐sectional areas of the cells and their packing density in layer V of the cortex revealed that (1) the size of cells increased very rapidly during the second week and became almost adultlike at the fifth week; (2) the density of cells reduced dramatically during the second week and thereafter at a low rate until the eighth week; and (3) the ratio of the labelled to unlabelled cells in layer V decreased remarkably also during the second week.

These results suggest that an elimination of axon collaterals of corticotectal cells or their death may take place mostly during the second week of age, when eye‐opening occurs in kittens. By comparison with previous data on functional development of the SC, it is also suggested that the maturation of visual response properties of SC neurons may depend on postnatal development of corticotectal cells.
The effects of undernutrition during early life on the rat optic nerve fibre number and size‐frequency distribution
Authors: Bedi K. S. , Warren M. A.
Published: January 2005

Male rats undernourished from the 18th day of gestation till 100days of age were nutritionally rehabilitated until 200 days of age. Six control and six experimental rats at each of 25, 50, 100, and 200 days of age were killed by perfusion with buffered 2.5% glutaraldehyde. Pieces of optic nerve from just behind the left eye of each rat were postfixed in osmium tetroxide and embedded in resin. Estimates of the total number of fibres and their mean diameter and size‐frequency distributions were made for each nerve.

Rats undernourished until 25 days of age had a mean ± of 57,464 ± 6,778 fibres per optic nerve. This represented a 36% deficit (P < 0.01) compared with the 25‐day‐old control value of 89,778 ± 6,625. In addition, these undernourished rats had proportionately more small fibres than the agematched controls. This resulted in a significant deficit in mean fibre diameter at this age. These deficits and distortions disappeared in all the older rats studied, despite the continued undernourishment of some animals up to 100 days of age.

It appears that even the lengthy period of undernutrition imposed in the present experiments could not produce a permanent deficit in optic nerve fibre number, size, and size distribution. It is suggested that the deficits seen initially at 25 days of age may have been due to a temporary delay in the growth and development of these nerve fibres.
An immunohistochemical study on the location of GABAergic neurons in rat septum
Authors: Panula P. , Revuelta A. V. , Cheney D. L. , Wu J.‐Y. , Costa E.
Published: January 2005

Antisera against L‐glutamate decarboxylase (GAD), the synthesizing enzyme of γ‐aminobutyric acid (GABA) were used to locate GABAergic neurons and nerve terminals in the septal complex of the rat by using the peroxidase‐antiperoxidase method. Varying densities of immunoreactive terminals were observed in saline‐treated rats but nerve cell bodies were only demonstrated after intraventricular or intraseptal injections of colchicine. Small and medium‐sized GAD‐positive neurons were found in lateral septal nuclei, the largest number of these cells being in the pars dorsalis, and in the bed nucleus of the stria terminalis. Several GAD‐immunoreactive neurons were located in the medial septal nucleus and the nucleus of the diagonal band of Broca (DB), where the cells were larger in the ventral than dorsal parts of the region. In the medial septal nucleus and in DB the GAD‐positive cell bodies were distributed similarly to cholinergic neurons. Large GAD‐positive neurons were also found in the septofimbrial nucleus. Intense immunoreactivity in nerve terminals was observed in the lateral septal nucleus, around the island of Calleja magna, between the DB and nucleus accumbens, and in the septofimbrial and triangular septal nuclei. In contrast, the medial septal nucleus, the DB, and the bed nucleus of the stria terminalis only showed weak to moderate immunoreactivity.

These results provide direct morphological evidence for the presence of neurons capable of synthesizing GABA in septal nuclei. We suggest that there are two different GABAergic neuronal systems operating in the septum: a population of small cells in the lateral septal nucleus and a group of large cells in the medial septum and DB.
The development of the cervical spinal cord of the mouse embryo. II. A Golgi analysis of sensory, commissural, and association cell differentiation
Authors: Wentworth Lee E.
Published: January 2005

The present report describes for the first time the early differentiation of dorsal root ganglion cells and internuncial cells in the spinal cord of mammals using the rapid Golgi technique; embryos of 9–11 days gestation (E9–E11, where E0 = day vaginal plug observed) were used. On E9 dorsal root ganglion cells are relatively undifferentiated and are just beginning to take on a bipolar appearance. A few commissural neurons are differentiating in the alar and basal plates, but their axons have not yet crossed the ventral commissure. Occasionally an ipsilateral funicular or association cell is seen in the alar plate. By E10 bipolar dorsal root ganglion cells send processes both centrally into the spinal cord and peripherally to join the ventral root as the spinal nerve. The relatively few association neurons are intermingled among commissural cells except that they are not found in the region of the ventral horn. The axon of many commissural neurons crosses the ventral commissure. On E11 a thin lateral funiculus is seen as well as the oval bundle of His (presumptive dorsal funiculus). An occasional dorsal root ganglion cell has attained the unipolar stage of differentiation. The commissural and association neurons are still intermingled along the outer regions of the mantle layer, especially in the alar plate region. Both commissural and association cells start to differentiate within the ventricular layer as radially oriented, bipolar neuroblasts. As the cell somas reach the outer region of the ventricular layer the cells become unipolar. The cells reorient more dorsoventrally and a primary dendrite grows first from the pole opposite the axon. This sequence of cell differentiation is in general agreement with what is seen in the differentiation of ventral root motoneurons.
The subnuclear organization of the rat interpeduncular nucleus: A light and electron microscopic study
Authors: Hamill Geoffrey S. , Lenn Nicholas J.
Published: January 2005

The subnuclear organization of rat interpeduncular nucleus (IPN) has been examined by light microscopy following staining with Nissl and Holmes methods, 3H‐leucine autoradiography, acetylcholinesterase (AChE), and cytochrome oxidase histochemistry, on plastic sections stained with toluidine blue, and by electron microscopy. Three unpaired and four paired subnuclei are recognized.

The rostral subnucleus is heavily stained for AChE, which clearly delineates its borders. It is distinguished ultrastructurally by two types of synapses on dendrites, and two on perikarya. Of the former, one type is formed by presynaptic processes which contain spherical and dense‐cored vesicles and make asymmetrical contacts. Dense‐cored vesicles are observed in many of the postsynaptic dendrites. A second type has presynaptic processes containing small, pleomorphic vesicles which make symmetrical contacts. Synapses on perikarya are found in the rostral, central, intermediate, lateral, and interstitial subnuclei. The dorsal subnucleus is continuous with the serotonin‐containing B8 cells. The central subnucleus is distinguished by longitudinally oriented medial habenular axons separating palisades of cell bodies. These axons, which also traverse the intermediate subnuclei, form en passant S synapses with small dendrites of the central subnucleus. The intermediate subnuclei react faintly for AChE and intensely for cytochrome oxidase. They contain crest synapses formed by two habenular afferents, one from each medial habenula, which contact a narrow dendritic process en passant. The lateral subnuclei react intensely for AChE and have ultrastructural features similar to the rostral subnuclei. The interstitial subnuclei lie within each fasciculus retroflexus as it enters IPN. The small dorsal lateral subnuclei are evident by light microscopy.
Relationship between preferred orientation and receptive field position of neurons in extrastriate cortex (area 19) in the cat
Authors: Leventhal Audie G. , Schall Jeffrey D. , Wallace Wendy
Published: January 2005

Orientation sensitivity is a characteristic of most retinal ganglion cells (Levick and Thibos, '82), most relay cells in the dorsal lateral geniculate nucleus (Vidyasagar and Urbas, '82), and most neurons in the visual cortex (Hubel and Wiesel, '62) in the cat. In the retina there is a systematic relationship between receptive field position (polar angle) and preferred orientation. Outside of the area centralis most retinal ganglion cells respond best to stimuli oriented radially, i.e., oriented parallel to the line connecting their receptive fields to the area centralis (Levick and Thibos, '82). This relationship is strongest along the horizontal meridian (the visual streak) and appears to reflect the innate, radial orientation of retinal ganglion cell dendritic fields (Leventhal and Schall, '83).

A relationship between preferred orientation and polar angle also exists in cat striate cortex; outside of the area centralis representation most cells respond best to lines oriented radially. This relationship is strongest for S type cells, the most orientation‐selective cells, and cells in regions representing the horizontal meridian (Leventhal, '83). To determine if similar relationships exist in cat extrastriate cortex, the preferred orientations and receptive field positions of 226 neurons in area 19 were studied. We find that, as in area 17, most area 19 cells outside of the representation of the area centralis respond best to lines oriented radially; this relationship is strongest for the cells having the narrowest receptive fields and in regions subserving the horizontal meridian. Unlike in striate cortex, in area 19 the relationship between preferred orientation and polar angle is not dependent upon cell type (S or C) or to the degree of orientation sensitivity exhibited. Also, in area 19, but not in area 17, the relationship between preferred orientation and polar angle fails for the cells having the widest receptive fields.

The results of this study show that the systematic relationship between preferred orientation and receptive field position which begins in the retina is largely preserved through extrastriate cortex. The functional architecture of orientation sensitive cells throughout the visual pathways may depend ultimately upon the innate, radial orientation of the dendritic fields of retinal ganglion cells.