bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytochrome oxidase staining marks dendritic zones of the rat olfactory bulb external plexiform layer
Authors: Mouradian Laurie E. , Scott John W.
Published: May 2005

Cytochrome oxidase staining of the rat olfactory bulb external plexiform layer (EPL) produces a darkly stained intermediate zone bordered by lightly stained superficial and deep zones. Similar zonal staining was seen in cats, rabbits, and hamsters. These zones vary in relative thickness around the circumference of the olfactory bulb; the deep zone is proportionally thicker in the most dorsal and ventral parts of the bulb. Tufted cell somata are unevenly distributed within the EPL; the outer part of the EPL has more somata. The distribution of the cytochrome oxidase reaction product shows that the darkly stained intermediate zone is not produced by staining of tufted cell somata.

Zones of cytochrome oxidase staining correspond to the sublaminar distribution of mitral and tufted cell basal dendrites. This was demonstrated by labeling mitral and tufted cells with small extracellular horseradish peroxidase injections and processing alternate sections for horseradish peroxidase and for cytochrome oxidase. Because there was cross‐reaction of the cytochrome oxidase procedure with horseradish peroxidase, it was possible to trace many neurons through both series of sections. Middle tufted cells of the superficial EPL have basal dendrites confined to the superficial zone of light cytochrome oxidase staining. Internal tufted cells and middle tufted cells of the intermediate zone send their basal dendrites into the intermediate zone. One group of mitral cells (type I) has basal dendrites confined to the deep zone of lighter cytochrome oxidase staining. A second group of mitral cells (type II) and tufted cells of the intermediate EPL has basal dendrites primarily confined to the intermediate zone of dark cytochrome oxidase staining. The correlation of the enzyme staining with the dendritic laminar patterns supports the existence of three relatively distinct sublaminae in the EPL and supports the designation of two types of mitral cells. The staining pattern also provides an independent method for evaluating the sublaminae of the EPL without the necessity of labeling individual groups of cells. Finally, the staining pattern suggests that the intermediate zone of the EPL may be subjected to more tonic synaptic input, causing it to have an increased level of metabolic activity.
Distribution of glucagonlike peptide I (GLP‐I), glucagon, and glicentin in the rat brain: An immunocytochemical study
Authors: Jin S.‐L. C. , Han V. K. M. , Simmons J. G. , Towle A. C. , Lauder J. M. , Lund P. K.
Published: May 2005

Although glucagonlike immunoreactants (GLIs) are present in the central nervous system of several mammalian species, their structural relationship with pancreatic proglucagon is not defined, and their precise anatomical distribution has not been studied extensively. To obtain further information about the structure and biological significance of brain GLIs, the anatomical distribution of three different antigenic determinants of pancreatic proglucagon‐‐glucagonlike peptide I (GLP‐I), glucagon, and glicentin‐‐was mapped in the brain of colchicine‐treated rats by immunocytochemistry using the avidin‐biotin‐peroxidase method.

Neuronal cell bodies immunoreactive with antisera specific for GLP‐I, glucagon, and glicentin were found only in the caudal medulla oblongata. Within the caudal medulla immunostained cell bodies were found at levels from approximately 0.55 mm rostral to the obex to 0.45 mm caudal to the obex, and were located within the nucleus of the solitary tract (NTS) and the dorsal (MdD) and ventral (MdV) parts of the medullary reticular nucleus. The NTS contained three times more immunoreactive cell bodies than the MdD and MdV, and these cell bodies were located in the midline, medial, and lateral subnuclei of the caudal third of the NTS. Immunostaining of the same cell bodies in paired adjacent sections incubated with GLP‐I and glucagon antisera or glucagon and glicentin antisera provided evidence for coexistence of the three antigens within the same neurons of the NTS. Nerve fibers and terminals immunoreactive with GLP‐I, glucagon, and glicentin antisera were widely distributed throughout the rat brain and there was no discernible difference in the distribution of fibers and terminals immunoreactive with each of the three antisera. The highest densities of immunostained fibers and terminals were observed in the hypothalamus, thalamus, and septal regions, and the lowest in the cortex and hindbrain. The localization of neuronal cell bodies containing GLP‐I, glucagon, and glicentin within the NTS and the MdD and MdV, and the extensive distribution of immunoreactive fibers and terminals throughout the rat brain suggest a role for these peptides in the integration of autonomic as well as central nervous system functions.
Auditory hair cell innervational patterns in lizards
Authors: Miller Malcolm R. , Beck Janet
Published: May 2005

The pattern of afferent and efferent innervation of two to four unidirectional (UHC) and two to nine bidirectional (BHC) hair cells of five different types of lizard auditory papillae was determined by reconstruction of serial TEM sections. The species studies were Crotaphytus wislizeni (iguanid), Podarcis (Lacerta) sicula and P. muralis (lacertids), Ameiva ameiva (teiid), Coleonyx variegatus (gekkonid), and Mabuya multifasciata (scincid). The main object was to determine in which species and in which hair cell types the nerve fibers were innervating only one (exclusive innervation), or two or more hair cells (nonexclusive innervation); how many nerve fibers were supplying each hair cell; how many synapses were made by the innervating fibers; and the total number of synapses on each hair cell.

In the species studies, efferent innervation was limited to the UHC, and except for the iguanid, C. wislizeni, it was nonexclusive, each fiber supplying two or more hair cells.

Afferent innervation varied both with the species and the hair cell types. In Crotaphytus, both the UHC and the BHC were exclusively innervated. In Podarcis and Ameiva, the UHC were innervated exclusively by some fibers but nonexclusively by others (mixed pattern). In Coleonyx, the UHC were exclusively innervated but the BHC were nonexclusively innervated. In Mabuya, both the UHC and BHC were nonexclusively innervated.

The number of afferent nerve fibers and the number of afferent synapses were always larger in the UHC than in the BHC.

In Ameiva, Podarcis, and Mabuya, groups of bidirectionally oriented hair cells occur in regions of cytologically distinct UHC, and in Ameiva, unidirectionally oriented hair cells occur in cytologically distinct BHC regions.
Disruption of microfilament organization and deregulation of disk membrane morphogenesis by cytochalasin D in rod and cone photoreceptors
Authors: Williams David S. , Linberg Kenneth A. , Vaughan Dana K. , Fariss Robert N. , Fisher Steven K.
Published: May 2005

Morphogenesis of photoreceptor outer segment disks appears to occur by an evagination of the ciliary plasma membrane (Steinberg et al., J Comp Neurol 190: 501–519, 80). We tested if polymerized actin (F‐actin) was necessary for the regulation of this postulated process by incubating Xenopus eyecups with 5 or 25 μM cytochalasin D for 6–28 hours. During the second hour, the incubation medium contained 3H‐leucine. Both concentrations of cytochalasin resulted in: (1) dissolution of the rhodamine‐phalloidin labeling pattern of photoreceptors, and (2) collapse of the calycal processes (which are normally filled with actin filaments) and disappearance of the inner segment microfilaments. In addition, the few most basal rod and cone outer segment disks appeared several times their normal diameter. These oversized disks had incorporated 3H‐leucine and extended along the margin of the outer or inner segment. The nature of the overgrown disks is consistent only with a morphogenetic process involving evaginations of the ciliary plasma membrane. Deregulation by cytochalasin D was manifest by excessive growth of a few nascent disks rather than normal growth of many. Therefore, the normal network of actin filaments is apparently not necessary for continued evagination of the membrane, but it does seem to be an essential part of the mechanism that initiates the evagination of the ciliary plasma membrane and\or the mechanism that controls how far nascent disks grow.
Development of intersecting CNS fiber tracts: The corpus callosum and its perforating fiber pathway
Authors: Hankin Mark H. , Silver Jerry
Published: May 2005

What are the mechanisms acting during development at points of intersection of central nervous system fiber tracts which influence the direction taken by a population of growing axons? In order to address this question, the ontogeny of the intersecting rostral corpus callosum and its perforating fiber pathway (PF), and the microenvironment through which these fiber systems grow, were examined in a series of mouse embryos and early postnates.

Our results show that the perforating fibers are identifiable in silverstained sections between embryonic days (E) 15 and 16, at least 1 day prior to the initial appearance of the callosal projection. Soon after the PF can be identified, a dense accumulation of subventricular cells surrounds the PF at a point just ventral to the location where the callosum and PF will intersect (i.e., at the corticoseptal boundary). Callosal axons, which are present at the point of intersection beginning on E17, do not join the perforating fibers, nor do they appear to penetrate the underlying population of subventricular cells. Instead, the callosal fibers turn across the PF and enter the contralateral cerebral hemisphere.

Thus, the intersection of the callosal and perforating fiber systems during development may be related both to the sequential development of each pathway and to the altered nonneuronal environment at the point of intersection.
Development of projections from auditory to visual areas in the cat
Authors: Innocenti Giorgio M. , Berbel Pere , Clarke Stephanie
Published: May 2005

In newborn kittens, cortical auditory areas (including AI and AII) send transitory projections to ipsi‐ and contralateral visual areas 17 and 18. These projections originate mainly from neurons in supragranular layers but also from a few in infragranular layers (Innocenti and Clarke: Dev. Brain Res. 14:143–148, 84; Clarke and Innocenti: J. Comp. Neurol. 251:1–22, 86). The postnatal development of these projections was studied with injections of anterograde tracers (wheat germ agglutinin‐horseradish peroxidase [WGA‐HRP]) in AI and AII and of retrograde tracers (WGA‐HRP, fast blue, diamidino yellow, rhodamine‐labeled latex beads) in areas 17 and 18. It was found that the projections are nearly completely eliminated in development, this, by the end of the first postnatal month. Unitl then, most of the transitory axons seem to remain confined to the white matter and the depth of layer VI; a few enter it further but do not appear to form terminal arbors. As for other transitory cortical projections the disappearance of the transitory axons seems not to involve death of their neurons of origin. In kittens older than 1 month and in normal adult cats, retrograde tracer injections restricted to, or including, areas 17 and 18 label only a few neurons in areas AI and AII. Unlike the situation in the kitten, nearly all of these are restricted to layers V and VI. A similar distribution of neurons projecting from auditory to visual areas is found in adult cats bilaterally enucleated at birth, which suggests that the postnatal elimination of the auditory‐to‐visual projection is independent of visual experience and more generally of information coming from the retina.
Distribution pattern of cell bodies and fibers with neurotensinlike immunoreactivity in the cat hypothalamus
Authors: Hu Haitao , Rao Jayashree K. , Prasad Chandan , Jayaraman A.
Published: May 2005

Neurotensin is widely distributed in the central and peripheral nervous systems. Extensive radioimmunoassay and immunohistochemical studies in rats show that the neurotensin immunoreactive perikarya and fibers are most prominent in the hypothalamus. Radioimmunoassay studies have suggested that the levels of neurotensin in the hypothalamus of cats may be six times higher than that of rats. We studied the distribution pattern of neurotensin immunoreactivity within the hypothalamus of the cat by avidinbiotin modification immunohistochemical methods: (1) to define its distribution pattern within the hypothalamus, and (2) to compare our findings with the patterns that have been described in rats. Results show that neurotensin immunoreactive cell bodies and fibers are most prominent in the rostral and intermediate regions of the cat hypothalamus. Cell bodies with neurotensinlike immunoreactivity are seen maximally in the medial preoptic region, the infundibular nucleus, and the lateral hypothalamus. The neurotensin positive fibers are dense in the periventricular regions of the entire rostrocaudal extent of the hypothalamus. This pattern of distribution of neurotensin immunoreactivity is similar to that described in rats. The suprachiasmatic nuclei of the cat hypothalamus, however, contained a significant number of neurotensin immunoreactive cell bodies, an observation not noted in the rat hypothalamus. The neurotensin immunoreactive neurons were more numerous in the lateral hypothalamus than has been reported in rats, but the paraventricular nucleus of the hypothalamus in cats contained fewer neurotensin immunoreactive perikarya. The presence of neurotensin immunoreactive perikarya in the suprachiasmatic nucleus and the apparent increase in the number of neurotensin immunoreactive neurons in the lateral hypothalamus may account for the increased levels of neurotensin reported in cats. Neurotensin has been speculated to play a role in nociception, thermoregulation, and control of arterial pressure by acting as a hormone or a neurotransmitter. Details of the pattern of colocalization of neurotensin with that of other neuropeptides and neurotransmitters will aid in our understanding of its role in these functions.
Quantitative comparisons of gamma‐aminobutyric acid neurons and receptors in the visual cortex of normal and dark‐reared cats
Authors: Mower George D. , Rustad Robin , White W. Frost
Published: May 2005

Physiological studies suggest that the function of the visual cortical gamma‐aminobutyric acid (GABA) system is abnormal in cats reared in total darkness. The present study asked whether visual input is necessary for the normal postnatal anatomical development of the GABA system by comparing GABA neurons and receptors in the visual cortex of normal and dark‐reared cats. Immunohistochemical techniques (anti‐GABA) were used to localize GABA neurons. In both rearing conditions, GABA neurons were stained rather uniformly in all cortical layers. Counts of GABA cells indicated a marked increase in density in dark‐reared compared to normal cats. Counts of total cellular density in cresyl‐stained sections, however, indicated a comparable increase in dark‐reared cats. When corrected for total cellular density, there were no differences between dark‐reared and normal cats in the density of GABA cells per layer, or the relative proportion of GABA cells across cortical layers.

In vitro receptor binding of 3H‐muscimol was used to compare GABAA receptors in the two rearing conditions. When corrected for total cellular density, saturation kinetics indicated no difference in the total number or affinity of receptors. Similarly, autoradiographic histology indicated no difference in the laminar distribution of receptors across cortical layers between dark‐reared and normal cats.

These results indicate that the postnatal development of GABA neurons and receptors occurs normally in the absence of visual input.
Central projections and trigeminal ganglion location of corneal afferent neurons in the monkey, Macaca fascicularis
Authors: Marfurt Carl F. , Echtenkamp Steven F.
Published: May 2005

The method of transganglionic transport of horseradish peroxidasewheat germ agglutinin conjugate (HRP‐WGA) was used to determine the location within the monkey trigeminal ganglion of the primary afferent neurons that innervate the cornea, and the brainstem and spinal cord termination sites of these cells. In each of four animals, Gelfoam pledgets were saturated with 2% HRP‐WGA in saline and applied to the scratched surface of the central cornea for 30 minutes. Postmortem examination of the corneal whole mounts revealed that the tracer solution remained confined to approximately the central one‐fourth of the cornea with no spread into the peripheral cornea or limbus. Seventy‐two to 96 hours after tracer application, 126–242 labeled cell bodies were observed in the medial region of the ipsilateral trigeminal ganglion. The majority of neurons were concentrated in an area of the ganglion that lay directly caudal to the entering fibers of the ophthalmic nerve, but smaller numbers of cells lay somewhat more laterally, near the region where the ophthalmic and maxillary nerves come together. A very small number of neurons in one animal innervated the cornea by sending their fibers into the maxillary nerve. HRP‐WGA‐labeled terminal fields were present to some extent in all four major rostrocaudal subdivisions of the ipsilateral trigeminal brainstem nuclear complex (TBNC), but the size of the terminal fields and the intensity of labeling differed markedly from one level of the TBNC to the next. Labeled fibers projected heavily to the transitional zone between caudal pars interpolaris and rostral pars caudalis (i.e., the “periobex” region of the TBNC) and moderately to the trigeminal main sensory nucleus, pars oralis, and caudal pars caudalis at the level of the pyramidal decussation. Remaining areas of the TBNC, including rostral pars interpolaris and the midlevel of pars caudalis, received few, if any, corneal afferent projections. Occasional labeled fibers were observed in the dorsal horn of C1 and in the rostral half of C2. It is hoped that data generated in the current investigation of nonhuman primates will contribute to a better understanding of the neural substrates that subserve corneal sensation and the blink reflex in humans.
Long‐spined polymorphic neurons of the medial cortex of lizards: A Golgi, timm, and electron‐microscopic study
Authors: Lopez‐Garcia C. , Martinez‐Guijarro F. J. , Berbel P. , Garcia‐Verdugo J. M.
Published: May 2005

The morphology, ultrastructure, and principal synaptic input of longspined neurons located in the inner plexiform layer of the medial cortex in three related species of lizards is described.

Golgi impregnations have been used to define the external morphology of these neurons and their axonal trajectories. Their most striking characteristic is the presence of very long spines or “microdendrites” especially abundant on the distal dendritic segments. Axons have ascendent trajectories, pass through the cell layer, and ramify in the outer plexiform layer. Combined Golgi‐electron microscopy as well as standard electron microscopy permitted the definition of the ultrastructure of these neurons. Timm and sulfide‐osmium methods permitted the detection and characterization of their principal synaptic input (i.e., zinc‐containing boutons).

Gamma aminobutyric acid (GABA)‐immunostained sections in one of the species studied allowed the identification of GABA‐immunoreactive somata which had the same morphology and ultrastructure as long‐spined neurons; these GABAwimmunoreactive somata and their processes were found in the same location as long‐spined neurons. This suggests that at least some long‐spined polymorphic neurons are GABA‐ergic and presumably inhibitory.

Finally, the neurobiological significance of these long‐spined neurons is discussed and briefly compared with that of similar neurons of the hilus of the fascia dentata of the rat.
Elimination of neurons from the rhesus monkey's lateral geniculate nucleus during development
Authors: Williams Robert W. , Rakic Pasko
Published: May 2005

The timing, magnitude, and spatial distribution of neuron elimination was studied in the dorsal lateral geniculate nucleus of 57 rhesus monkeys (Macaca mulatta) ranging in age from the 48th day of gestation to maturity. Normal and degenerating cells were counted in Nissl‐stained sections by using video‐enhanced differential interference contrast optics and videooverlay microscopy.

Before embryonic day 60 (E60), the geniculate nucleus contains 2,200,000 ± 100,000 neurons. Roughly 800,000 of these neurons are eliminated over a 40‐ to 50‐day period spanning the middle third of gestation. Neurons are lost at an average rate of 300 an hour between E48 and E60, and at an average rate of 800 an hour between E60 and E100. Very few neurons are lost after E100, and as early as E103 the population has fallen to the adult average of 1,400,000 ± 90,000. Degenerating neurons are far more common in the magnocellular part of the nucleus than in the parvicellular part. In 20 of 29 cases, the number of neurons is greater on the right than on the left side. The right‐left asymmetry averages about 8.5% and the difference is statistically significant (X2 = 38, p< .001).

The period of cell death occurs before the emergence of cell layers in the geniculate nucleus, before the establishment of geniculocortical connections, and before the formation of ocular dominance columns (Rakic, 76). Most important, the depletion of neurons in the geniculate nucleus begins long before the depletion of retinal axons. The number of geniculate neurons is probably a key factor controlling the number of the retinal cells that survive to maturity.
Highly active neuromuscular system in developing lobsters with programmed obsolescence
Authors: Govind C. K. , Kirk Mark D. , Pearce Joanne
Published: May 2005

The primary locomotory apparatus in the three larval stages of the lobster, Homarus americanus, are paddlelike structures on the thoracic appendages called exopodites, which beat almost continuously. Consequently their power and return‐stroke muscles are examples of highly active but short‐lived neuromuscular systems. The muscles, which are well vascularized, are of the fast type with 2‐3‐μm sarcomere lengths and 6 thin filaments surrounding a thick one. The most striking feature, however, is the large volume of mitochondria making up 40‐50% of the fiber. They appear as simple cylinders packed several layers deep along the periphery of the fiber and as large, multibranched forms distributed throughout the fiber and subdividing it into smaller units. The motor innervation to the return‐stroke muscle is via 3 excitatory axons, which generate large junctional potentials and twitch contractions. The muscle is densely populated with large neuromuscular synapses, most of which have a well‐defined active site or dense bar denoting the site of transmitter release. Altogether this motor system is specialized for prolonged activity. Atrophy of the neuromuscular system occurs by the late larval third stage. The muscle fibers lose their identity, fuse, and become vacuolated. The myofibrils condense and erode and the mitochondria are lost. Atrophy of motor innervation is gradual with individual axons dropping out. The largest axon providing most of the innervation is the first to degenerate. Early degenerative changes affect the axon and neuromuscular terminals but not the synaptic contacts, dense bars, and vesicles, which appear intact. Continued atrophy in the postlarval fourth stage reduces the exopodites to vestiges. Thus the returnstroke muscle of the larval exopodites in which muscle fiber and motoneurons are identifiable permits study of the interaction between a neuron and its target muscle undergoing programmed obsolescence.
Peripheral nerve transection induces innervation of embryonic neocortical transplants by specific thalamic fibers in adult mice
Authors: Erzurumlu Reha S. , Ebner Ford F.
Published: May 2005

Embryonic neocortical tissue survives and differentiates when grafted to injured adult neocortex. While these transplants are readily innervated by the host cholinergic fibers, specific thalamic fibers fail to innervate them. The present study was designed to test whether changing the activity levels of the thalamic ventrobasal projection neurons would promote sprouting of their axons into the embryonic cortical implants placed in the barrel field cortex. To achieve this the main input to the these thalamic neurons was eliminated two synapses away, by blocking the peripheral sensory input to the barrel field cortex. Adult hosts underwent unilateral transection of the infraorbital nerve and two days later the contralateral barrel field cortex was lesioned enough to insert an embryonic neocortical graft. Following a one month post‐transplantation period we examined the amount of specific thalamic axon ingrowth into the transplants by injecting the ventrobasal nucleus with horseradish peroxidase. The control cases without prior nerve damage confirmed previous observations that ventrobasal nucleus neurons fail to innervate the implanted neocortex. Transection of the infraorbital nerve prior to transplantation resulted in an unprecedented ingrowth of specific thalamic axons into the transplants. There was no significant difference in the amount of thalamic fiber ingrowth into the transplants when the peripheral nerve was (transection) or was not (cautery) allowed to regenerate. However, transection of the infraorbital nerve permits the nerve to regenerate and at least partially reconnect the sensory periphery, thus leading to the possibility of functional integration of the neocortical transplants into the host trigeminal system.

The morphology and distribution of host acetylcholinesterase‐positive fibers that grow into the transplants under both experimental and control conditions were distinctly different from those of thalamic axons. These results provide the first demonstration of peripheral sensory nerve induction of regenerative propensity in specific thalamocortical projection neurons. The thalamic fiber ingrowth should lead to enhanced functional innervation of the neocortical implants and better incorporation of the graft into the adult host brain circuitry.
Neurochemical organization of the hypothalamic projection to the spinal cord in the rat
Authors: Cechetto David F. , Saper Clifford B.
Published: May 2005

The hypothalamus provides a major projection to the spinal cord that innervates primarily lamina I of the dorsal horn and the sympathetic and parasympathetic preganglionic cell columns. We have examined the chemical organization of the neurons that contribute to this pathway by using combined retrograde transport of fluorescent dyes and immunohistochemistry for 15 different putative neurotransmitters or their synthetic enzymes. Our results demonstrate that 5 cytoarchitectonically distinct cell groups in the hypothalamus contribute to the spinal projection and that each has its own predominant chemical types. In the paraventricular nucleus, substantial numbers of hypothalamo‐spinal neurons stain with antisera against arginine vasopressin (25‐35%), oxytocin (20‐25%), and metenkephalin (10%). About 25% of the neurons with spinal projections in the retrochiasmatic area stain with an antiserum against α‐melanocyte‐stimulating hormone. Nearly 100% of the hypothalamo‐spinal neurons in the tuberal lateral hypothalamic area stain with this same antiserum, but these cells do not stain for other proopiomelanocortin‐derived peptides, and so probably contain a cross‐reacting peptide. This population must be distinguished from an adjacent cell group, in the perifornical region, where many spinal projection neurons stain with antisera against dynorphin (25%) or atrial natriuretic peptide (20%). Finally, in the dorsal hypothalamic area as many as 55‐75% of the neurons with spinal projections are dopaminergic, on the basis of their staining with an antiserum against tyrosine hydroxylase.

These 5 neurochemically distinct projections from the hypothalamus to the spinal cord are discussed in the context of their possible functional significance.
Visual cortex of the dolphin: An image analysis study
Authors: Morgane Peter J. , Glezer Ilya I. , Jacobs Myron S.
Published: May 2005

On cytoarchitectonic grounds we have identified two distinct types of cortical formations composing the lateral gyrus (visual cortex) of the dolphin and have termed these heterolaminar cortex and homolaminar cortex. The heterolaminar cortex occupies the medial and lateral banks of the entolateral sulcus whereas the homolaminar cortex occupies the remainder of the lateral gyrus both lateral and medial to the entolateral sulcus. Each of these cortices exhibits special cytoarchitectonic features, a major difference being that heterolaminar cortex contains an incipient layer IV whereas layer IV is clearly absent in homolaminar cortex. Quantitative imaging procedures reveal that there is greater laminar differentiation in heterolaminar than in homolaminar cortex. Golgi analysis of neuronal forms and dendritic architecture confirms this distinction between the two types of cortex composing the lateral gyrus. Computer‐assisted morphometric methods have been applied to both types of cortex and indicate by a variety of parameters several quantitative differences in the cellular numbers, types, and organization in each type of cortex. Both types of cortex, homolaminar and heterolaminar, exhibit a markedly higher cellular density in the posterior sector of the lateral gyrus than in the anterior sector. We have also for the first time been able to identify a columnar type of organization of the cetacean visual cortex and have described two types of cytoarchitectonic columns, major and minor, in each of these types of cortex. Comparisons in organization of these basic columnar units between the bat, representing a prototypic brain, and the dolphin reveal many similarities but also major quantitative differences in type of organization between the visual cortices in these species. Marked differences are also seen between the cytoarchitectonic columnar organization of the visual cortices in the dolphin and columnar organization of striate cortex in the human brain, the number of columns per unit of cortex in the human being almost twice that seen in the dolphin brain. Some phylogenetic implications of these findings are discussed in relation to the so‐called „initial”︁ type of cortical organization reconstructed largely by retrospective inference.
Association fiber pathways to the frontal cortex from the superior temporal region in the rhesus monkey
Authors: Petrides M. , Pandya D. N.
Published: May 2005

The projections to the frontal cortex that originate from the various areas of the superior temporal region of the rhesus monkey were investigated with the autoradiographic technique. The results demonstrated that the rostral part of the superior temporal gyrus (areas Pro, Ts1, and Ts2) projects to the proisocortical areas of the orbital and medial frontal cortex, as well as to the nearby orbital areas 13, 12, and 11, and to medial areas 9, 10, and 14. These fibers travel to the frontal lobe as part of the uncinate fascicle. The middle part of the superior temporal gyrus (areas Ts3 and paAlt) projects predominantly to the lateral frontal cortex (areas 12, upper 46, and 9) and to the dorsal aspect of the medial frontal lobe (areas 9 and 10). Only a small number of these fibers terminated within the orbitofrontal cortex. The temporofrontal fibers originating from the middle part of the superior temporal gyrus occupy the lower portion of the extreme capsule and lie just dorsal to the fibers of the uncinate fascicle. The posterior part of the superior temporal gyrus projects to the lateral frontal cortex (area 46, dorsal area 8, and the rostralmost part of dorsal area 6). Some of the fibers from the posterior superior temporal gyrus run initially through the extreme capsule and then cross the claustrum as they ascend to enter the external capsule before continuing their course to the frontal lobe. A larger group of fibers curves round the caudalmost Sylvian fissure and travels to the frontal cortex occupying a position just above and medial to the upper branch of the circular sulcus. This latter pathway constitutes a part of the classically described arcuate fasciculus.
Immunohistochemical localization of gonadotropin‐releasing‐hormone‐associated peptide in the brain of the frog
Authors: Andersen A. C. , Danger J. M. , Fasolo A. , Kah O. , Tonon M. C. , Vaudry H.
Published: May 2005

Gonadotropin‐releasing‐hormone (GnRH)‐associated peptide (GnRH‐AP) is a 56 amino acid neuropeptide derived from the GnRH prohormone. GnRH‐AP corresponds to the C‐terminal fragment flanking the GnRH peptide. Using an antiserum raised against human GnRH‐AP [1‐56], or against human GnRH, we have investigated the neuronal systems containing either peptide in the central nervous system of the frog Rana ridibunda by immunohistological techniques. A main group of GnRH‐AP‐containing perikarya was found in a dorsoventral orientation of the supra anterior preoptic area (SAPA) just in front of the preoptic recess. Fibers originating from these perikarya projected rostrally toward the medial septal nucleus and the diagonal band of Broca. A network of GnRH‐AP‐immunoreactive (ir) fibers runs caudally from the SAPA toward the ventral hypothalamus. A high density of GnRH‐AP‐ir terminals was found in the median eminence. A few positive fibers were detected in the neural lobe of the pituitary, particularly in the region bordering the pars intermedia. Labelling of consecutive sections by either GnRH‐AP or GnRH antibodies showed that GnRH and GnRH‐AP‐like irs were contained in the same cells of the SAPA. The double‐staining technique with electrophoretic elution confirmed the colocalization of GnRH and GnRH‐AP within the same neurons. Such a coexistence indicates that frog GnRH originates from a high molecular weight precursor which is closely related to rat pro‐GnRH. The relative preservation of the C‐terminal sequence of the pro‐GnRH during evolution suggests that GnRH‐AP may possess intrinsic biological activity. The high density of GnRH‐AP‐containing neurons projecting through the external zone of the median eminence would support the concept that GnRH‐AP is involved in the modulation of pituitary hormone secretion.
Organization of histaminergic fibers in the rat brain
Authors: Inagaki Naoyuki , Yamatodani Atsushi , Ando‐Yamamoto Maya , Tohyama Masaya , Watanabe Takehiko , Wada Hiroshi
Published: May 2005

Detailed information on innervation of the histaminergic system in the brain is essential to an understanding of the physiological roles of this system. In a previous immunocytochemical study with antihistidine decarboxylase (HDC) antibody, we detected extensive networks of histaminergic fibers in many areas of the rat brain (Watanabe et al., ′84).

In the present study, we improved the immunocytochemical procedure and examined the detailed distribution of histaminergic innervation in the rat brain with anti‐HDC antibody. As reported previously, the highest concentrations of fibers were found in the hypothalamic nuclei and medial forebrain bundle. With the modified procedure, we detected more dense networks of HDC‐immunoreactive (HDCI) fibers. Furthermore, we demonstrated for the first time the existence of HDCI fibers in other regions, namely, the thalamic nuclei, median eminence, fimbria of the hippocampus, habenular nuclei, superior colliculus, nucleus of the optic tract, parabrachial nuclei, mesencephalic trigeminal nucleus, superior, lateral, and spinal vestibular nuclei, posterior lobe of the hypophysis, and vascular organ of the lamina terminalis. We also found dense transverse fibers in the retrochiasmatic area and supraoptic decussation, which suggests bilateral innervation of the histaminergic system. These results indicate that innervation of the rat brain by the histaminergic system is more extensive than observed previously.
Identities, antigenic determinants, and topographic distributions of neurofilament proteins in the nervous systems of adult frogs and tadpoles of Xenopus laevis
Authors: Szaro Ben G. , Gainer Harold
Published: May 2005

Three proteins with nominal molecular weights of 73 kDa (XNF‐L), 175 kDa (XNF‐M), and 205 kDa (XNF‐H) were identified as putative neurofilament proteins in the nervous system of the frog, Xenopus laevis. These conclusions were based on four criteria: (1) these proteins were enriched in cytoskeletal preparations; (2) they reacted with a monoclonal antibody (anti‐IFA) that cross‐reacts with an epitope found in all intermediate filament proteins; (3) they cross‐reacted with monoclonal antibodies directed against specific mammalian neurofilaments; and (4) antibodies that reacted with these proteins on Western blots specifically stained neurons in immunohistochemical analyses. The neurofilament proteins in Xenopus were antigenically similar, but not identical to mammalian neurofilament proteins. The principal difference was that four antibodies that reacted on Western blots with rat NF‐H reacted with XNF‐M in Xenopus. However, similarly to mammals, antibodies against phosphorylated XNF‐M specifically labeled axons, whereas an antibody that reacted only with dephosphorylated epitopes on XNF‐M specifically labeled neuronal cell bodies in immunohistochemistry. Three other antibodies that reacted equally well with untreated or alkaline‐phosphatase‐treated XNF‐M or XNF‐H proteins also showed axonally restricted staining in the adult Xenopus nervous system. An XNFL (XC5D10) antibody was produced which stained axons and cell bodies equivalently throughout the adult Xenopus nervous system. By 3 days of development (stage 42; Xenopus tadpoles), antibodies to all three molecular weight forms of the frog neurofilament proteins detected specific neurons in the brainstem and spinal cord; and antibodies to phosphorylated and dephosphorylated epitopes on XNF‐M could discriminate between axons and cell bodies in the rhombencephalon. The immunoreactivities of four antibodies directed at XNF‐L, ‐M, or ‐H, which were unaffected by alkaline phosphatase treatment, differed significantly in their immunohistochemical staining patterns in adult vs. premetamorphic frogs.
The accessory optic system of the wallaby, Setonix brachyurus: Anatomy in normal animals and after early unilateral eye removal
Authors: Coleman L.‐A. , Beazley L. D.
Published: May 2005

We have traced primary visual projections to nuclei of the accessory optic system in the mature wallaby, Setonix brachyurus, the „quokka,”︁ following unilateral intraocular injections of horseradish peroxidase. The organization of pathways and nuclei is similar to that of other marsupials and to that of eutherian mammals. The dorsal, lateral and medial terminal nuclei receive bilateral input, though nuclei ipsilateral to the injected eye are weakly labelled in comparison with their contralateral counterparts.

We also report on the accessory optic system in animals which were unilaterally enucleated neonatally or at postnatal day 35. At maturity in enucleated animals, ipsilateral projections to all nuclei of the accessory optic system are more densely labelled than normal. This exuberance is more pronounced in neonatally enucleated animals than in those enucleated at the later stage.
Anuran accessory optic system: Evidence for a dual organization
Authors: Fite Katherine V. , Bengston Lynn C. , Montgomery Neil M.
Published: May 2005

The accessory optic system of Rana pipiens consists of lateral and medial fascicles of the basal optic root (BORl, BORm) and a single terminal nucleus, nBOR. The present study provides new evidence that these two fascicles differ not only in their trajectories but in fiber spectra and innervation patterns as well. BORl contains a substantially higher percentage of large, myelinated axons than does BORm, and the mean diameter of axons in BORl is greater than that of BORm. BORl innervates the entire terminal field of nBOR. The ventrolateral portion of nBOR is uniquely innervated by BORl and contains several types of neurons not found in the central and medial regions of nBOR which are innervated by both fascicles.

Cytoarchitectural analysis of nBOR with Golgi techniques has revealed a number of similarities between the anuran nBOR and the mammalian medial terminal nucleus (MTN) with regard to cellular morphology, dendritic geometry, and retinofugal arborization patterns. In frog, nBOR appears comparable to the ventral subdivision of the mammalian MTN, while the peri‐nBOR region, which contains neurons postsynaptic to nBOR, may represent a more primordial version of the mammalian dorsal MTN.
Development of parasagittal zonation in the rat cerebellar cortex: MabQ113 antigenic bands are created postnatally by the suppression of antigen expression in a subset of Purkinje cells
Authors: Leclerc Nicole , Gravel Claude , Hawkes Richard
Published: May 2005

Monoclonal antibody mabQ113 recognizes a polypeptide antigen that, in the adult cerebellum, is confined to a subset of Purkinje cells that are clustered together to form parasagittal bands interposed by similar nonimmunoreactive bands. The Purkinje cell compartments are congruent with bands of climbing fibers projecting from subregions of the inferior olivary complex (ICC). The array of mabQ113 parasagittal bands appears late in the development of the cortex. Weak mabQ113 immunoreactivity is first seen at postnatal day 6 (P6) in the Purkinje cells of the posterior lobe of the vermis. From the earliest stages there are signs of differential expression of the mabQ113 antigen in clusters of Purkinje cells: four mabQ113+ clusters are clearly present in the posterior lobe of the vermis at P6‐P7. Their relation to the adult band display remains uncertain. During the next few days immunoreactivity spreads rostrally throughout the rest of the vermis and laterally to include the Purkinje cells in the hemispheres, until by P12 all the Purkinje cells in the cerebellum are mabQ113+. Nevertheless, signs of the adult band display are seen already in the vermis where the cells destined to become the vermal mabQ113+ bands (P1+, P2+ and P3+) stain more intensely than their neighbours. Following the stage of global mabQ113 epitope expression, bands are created by the selective suppression of immunoreactivity by Purkinje cells in the P— regions. By P15 the mabQ113+ and mabQ113— bands are clearly differentiated in the vermis and selective staining has begun to appear in the hemispheres also. The band pattern matures gradually during the third and fourth postnatal weeks until the adult appearance is attained by P30. The cerebellar afferent projections were lesioned to explore the interplay of cerebellar input and mabQ113 expression. The olivocerebellar projection was lesioned bilaterally by using 3‐acetylpyridine in the adult and unilaterally in the newborn by electrolytic lesion and unilateral inferior cerebellar pedunculectomy. Mossy fibers from the dorsal and ventral spinocerebellar tracts were lesioned surgically both in adults and in newborns and trigeminal projections to the cerebellum were removed in the newborn by unilateral ablation of the spinal trigeminal nucleus. The consequences of total blockage of vibrissal and hindlimb inputs were also explored in both adults and neonates. None of these treatments led to a modification in the pattern of mabQ113 epitope expression. Therefore, although parasagittal zonation is present in the afferent projection before synaptic contact is made with the Purkinje cells, it appears that the mabQ113+/mabQ113– bands can develop independently of afferent synaptic input.
Generation patterns of four groups of cholinergic neurons in rat cervical spinal cord: A combined tritiated thymidine autoradiographic and choline acetyltransferase immunocytochemical study
Authors: Phelps Patricia E. , Barber Robert P. , Vaughn James E.
Published: May 2005

This report examines the generation of cholinergic neurons in the spinal cord in order to determine whether the transmitter phenotype of neurons is associated with specific patterns of neurogenesis. Previous immunocytochemical studies identified four groups of choline acetyltransferase (ChAT)‐positive neurons in the cervical enlargement of the rat spinal cord. These cell groups vary in both somatic size and location along the previously described ventrodorsal neurogenic gradient of the spinal cord. Thus, large (and small) motoneurons are located in the ventral horn, medium‐sized partition cells are found in the intermediate gray matter, small central canal cluster cells are situated within lamina X, and small dorsal horn neurons are scattered predominantly through laminae III‐V. The relationships among the birthdays of these four subsets of cholinergic neurons have been examined by combining 3H‐thymidine autoradiography and ChAT immunocytochemistry.

Embryonic day 11 was the earliest time that neurons were generated within the cervical enlargement. Large and small ChAT‐positive motoneurons were produced on E11 and 12, with 70% of both groups being born on E11. ChAT‐positive partition cells were produced between E11 and 13, with their peak generation occurring on E12. Approximately 70% of the cholinergic central canal cluster and dorsal horn cells were born on E13, and the remainder of each of these groups was generated on E14.

Other investigators have shown that all neurons within the rat cervical spinal cord are produced in a ventrodorsal sequence between E11 and E16. In contrast, ChAT‐positive neurons are born only from E11 to E14 and are among the earliest cells generated in the ventral, intermediate, and dorsal subdivisions of the spinal cord. However, all cholinergic neurons are not generated simultaneously; rather their birthdays are correlated with their positions along the ventrodorsal gradient of neurogenesis. The fact that large motoneurons and medium‐sized partition cells are born before small central canal cluster and dorsal horn cells would appear to support the generalization that large neurons are generated before small ones. However, the location of spinal cholinergic neurons within the neurogenic gradient seems to be more importantly associated with the time of cell generation than somal size. For example, when large and small motoneurons located at the same dorsoventral spinal level are compared, both sizes of cells are generated at the same time and in similar proportions. In summary, the present results suggest that information associated with a cell's position within the neurogenic gradient is a more potent determinant of neuronal birthdays than somal size or transmitter phenotype.
Monoclonal antibodies to the molluscan small cardioactive peptide SCPB: Immunolabeling of neurons in diverse invertebrates
Authors: Masinovsky Boris , Kempf Stephen C. , Callaway Joseph C. , Willows A. O. Dennis
Published: May 2005

We reported a development of murine monoclonal antibodies to a molluscan small cardioactive peptide (SCPB) and their application to immunolabeling of neurons in several molluscan and arthropod species. In vitro stimulations of mouse lymphocytes with SCPB conjugated to a carrier protein yielded exclusively IgM class antibodies; in vivo stimulation resulted in generation of both IgM and IgG classes of antibodies. Monoclonal antibodies of the IgM class labeled identified SCP‐containing neuron B11 in the frozen sections of the buccal ganglia of Tritonia diomedia. These antibodies failed to stain any neurons in whole mount preparations. A monoclonal antibody of IgG1 subclass selectively labeled neurons in both frozen sections and whole mount preparations of diverse invertebrate species. Thus, neurons B11, B12, and GE1 and several other neurons of the buccal and gastroesophageal ganglia of T. diomedia bound the antibody, and a similar pattern of immunolabeling was found in the closely related gastropod Tritonia festiva. We also observed SCPB‐like immunoreactivity in the central neurons of other nudibranch and pulmonate molluscs and in examples of insect (Acheta domesticus and Thermobia domestica) and crustacean (Semibalanus cariosus) classes of the Arthropoda. Our results suggest a specific pattern of distribution of SCPB‐like immunoreactivity in the gastropod nervous system and a broad occurrence of SCPB‐like antigenicity in the diverse invertebrates.