bluuebunny/crossref_metadata_2025 huggingface dataset:
Vomeronasal and olfactory nerves of adult and larval bullfrogs: I. Axons and the distribution of their glomeruli
Authors: Burton Paul R. , Coogan Mary M. , Borror Cheryl A.
Published: January 2005

The distribution of primary olfactory and vomeronasal (VMN) glomeruli is demonstrated in the forebrain of the larval (stage III tadpole) and adult bullfrog. Olfactory glomeruli are massed at the anterior end of the olfactory bulb; farther posterior, they are located at the periphery and then become distributed in a superficial layer all along the ventral surface of the bulb. Glomeruli of the accessory olfactory bulb (AOB) of the tadpole are less compact and show larger dendritic profiles and fewer synaptic junctions per unit area than those of the adult AOB. Axons of both tadpole and adult VMN nerve are ultrastructurally indistinguishable from those of the primary olfactory nerve; in comparing VMN axons of tadpole and adult, however, differences were observed in the number of neurofilament profiles in axons at the proximal and distal ends of the VMN nerve. Counts of neurofilament profiles in the two ends of the nerve suggest that neurofilament segments accumulate near terminations of their axons. The VMN nerve of tadpole and adult frog are roughly the same size, and calculations indicate that they contain comparable numbers of axons. The primary olfactory nerve of the tadpole is estimated to contain about 660,000 axons; the adherent VMN nerve of the tadpole contains about 270,000 axons (a ratio of about 2.5:1). In the adult, the ratio of primary to VMN axons is about 64:1, reflecting the quantitative growth of the primary olfactory nerve with development from an aquatic tadpole to an air‐breathing adult.
Met5‐enkephalin‐Arg6‐Gly7‐Leu8‐like immunoreactivity in the pelvic ganglion of the male rat: A light and electron microscopic study
Authors: Wang Bai‐Ren , Senba Emiko , Tohyama Masaya
Published: January 2005

By using both light and electron microscopic immunocytochemical methods, Met5‐Enkephalin‐Arg6‐Gly7‐Leu8 (MEAGL)‐like immunoreactive structures were detected in the pelvic ganglion of male rats. Denervation studies were carried out to determine the origin of these immunoreactive fibers and the projection of immunoreactive neurons within the pelvic ganglion. MEAGL‐like immunoreactivity was found in numerous axon boutons, some small, intensely fluorescent (SIF) cells, and a few principal ganglion neurons. Most of the immunoreactive nerve fibers formed pericellular plexuses surrounding the ganglion cells. In addition, there were a few scattered varicose fibers. These fiber plexuses could be classified into two types: type I (∼90% of fibers), which consisted of 80‐120 small boutons that synapsed on either the dendrites (80% of cases) or somata (20% of cases) of principal neurons; and type II (∼10% of fibers), which consisted of 20‐40 larger boutons that formed axodendritic synapses exclusively. After transection of the hypogastric and pelvic nerves, virtually all of the pericellular fiber remained. According to their ultrastructure, these remaining fibers were considered to arise from SIF cells. Following the injection of Fast Blue into the bladder wall, some of the MEAGL‐like immunoreactive principal neurons were retrogradely labeled. The results of this study indicate that there are two origins for the MEAGL‐like immunoreactive fibers detected in the pelvic ganglion: most arise from preganglionic neurons in the spinal cord, and a small proportion may originate from intraganglionic MEAGL‐like immunoreactive SIF cells or principal neurons. Some MEAGL‐like immunoreactive principal neurons may project to the urinary bladder.
Region‐specific consequences of PCD gene expression in the olfactory system
Authors: Baker Harriet , Greer Charles A.
Published: January 2005

These studies investigated the response of olfactory bulb juxtaglomerular dopamine neurons to the loss of mitral cells in 6–7–month‐old Purkinje cell degeneration (PCD) mice. Previous studies in normal mice, with tyrosine hydroxylase (TH) enzyme as a marker, demonstrated that following peripheral olfactory afferent denervation in TH activity and immunoreactivity. These intrinsic dopamine neurons also receive afferent input via dendrodendritic contacts with mitral cells. In contrast to the deficits produced by peripheral denervation, following mitral cell degeneration in homozygous recessive PCD mice, TH activity and immunoreactivity were unaltered as compared to normal heterozygous littermates. Moreover, TH activity in the substantia nigra also was unchanged, thus suggesting that the dopamine phenotype is resistant to the influences of the pcd gene. Despite the absence of a well‐defined effect of the pcd gene on neurons earing the TH phenotype, the expression of this mutation within the olfactory system is not limited to mitral cell degeneration. The current studies also demonstrate the absence of the anterior commissure, especially pars anterior, in homozygous recessive PCD mice at 6–7 months postnatal. Whether or not the loss of the anterior commissure is a primary effect or one that is secondary to mitral cell degeneration, this structural alteration provides evidence that the pcd gene exerts more widespread effects within the olfactory system than previously appreciated. The neuronal specificity of those effects remains apparent as indicated by the lack of change in TH expression.
Heterogeneity of chandelier neurons in monkey neocortex: Corticotropin‐releasing factor‐and parvalbumin‐immunoreactive populations
Authors: Lewis David A. , Lund Jennifer S.
Published: January 2005

Chandelier neurons are a unique subclass of cortical nonpyramidal neurons. The axons of these neurons terminate in distinctive vertically arrayed cartidges that synapse on the axon initial segment of pyramidal neurons. In this study, the rapid Golgi method and immunohistochemical techniques were used to characterize the morphology, regional distribution, laminar location, and biochemical content of chandelier neurons in the prefrontal and occipital cortices of three monkey species. As in our previous studies of visual areas V1 and V2 (Lund:Journal of Comparative Neurology 257:60‐92, 1987; Lund et al.:Journal of Comparative Neurology 202:19‐45, 1981, 276:1‐29, 1988), Golgi impregnations of areas 46 and 9 of macaque prefrontal cortex show chandelier neurons to be present in layers 2 through superficial 5. The vertical arrays of terminal boutons (axon cartridges) typical of this neuron class are also present in layers 2‐6 of the prefrontal cortex, but are not found in layer 1 or the subcortical white matter. In immunohistochemical studies, a calcium‐binding protein, parvalbumin, and a neuropeptide, corticotropin‐releasing factor (CRF), identify rod‐like structures that are morphologically similar to the axon cartridges of chandelier neurons seen in the Golgi material. In addition, both parvalbumin‐and CRF‐immunoreactive cartridges are located below the somata of unlabeled pyramidal neurons and appear to outline the axon initial segment of these neurons. However, we find that parvalbumin and CRF are present in only subpopulations of chandelier axon cartridges. For example, in adult primary visual cortex, parvalbumin‐labeled cartridges are present in very low numbers only in layers 2‐3, whereas in prefrontal and occipital association cortices these cartridges are a very prominent component of layers 2‐superficial 3 and are present in much lower density in the deeper cortical layers. In contrast to these findings in adult macaque monkeys, prefrontal and occipital association cortices of infant macaque monkeys contain a very high density of parvalbumin‐labeled cartridges in layer 4 and relatively few in the superficial cortical layers. Furthermore, in adult squirrel monkey prefrontal cortex, CRF‐labeled cartridges are predominately present in layer 4, but these CRF‐immunoreactive structures have not been observed in the homologous regions of infant or adult macaque monkeys. These findings indicate that even for neurons of such distinctive morphology and presumably constant functional role as chandelier neurons, factors such as regional and laminar location, age, and primate species are associated with differences in the biochemical content of subpopulations of these neurons.
Development of the electrosensory nervous system of Eigenmannia (gymnotiformes): II. The electrosensory lateral line lobe, midbrain, and cerebellum
Authors: Lannoo Michael J. , Maler Leonard , Vischer Heinrich A.
Published: January 2005

The somatotopically and functionally organized electrosensory system of gymnotiform teleosts provides a model for the study of the formation of ordered nerve connections. This paper describes the development of the major electrosensory nuclei within the hind‐ and midbrain. All three main electrosensory nuclei‐the electrosensory lateral line lobe (ELL), dorsal torus semicircularis (torus), and tectum‐grow by adding cells at their caudolateral borders. Toral and tectal germinal zones arise from lateral ventricular outpocketings that either completely or partially close by maturity. In the ELL before day 5 postspawning, germinal cells form from an initial periventricular germinal zone, then migrate to the caudolateral border of the hindbrain and begin dividing. The ELL grows from two main germinal zones, one for the medial segment, and one for the three lateral tuberous segments. Within each ELL germinal zone, newly formed cells arise from two areas: granular cells arise from a ventral subzone, pyramidal cells are generated more dorsally. Granular cells remain in situ, whereas pyramidal cells may migrate rostromedially. Cells begin differentiating as soon as they are formed. Spherical and pyramidal cells send ascending axons into the internal plexiform layer by day 14–18 and the ELL gradually begins to assume its mature laminar appearance.

The ELL grows caudally, preceding the caudal lobe of the cerebellum, which will eventually lie over and fuse with it. Primary electrosensory afferents enter the ELL by day 6: incoming afferents form four fascicles within the ELL, suggesting the formation of separate ELL segments. Unlabelled projections between labelled fields from a single nerve branch filled with HRP on day 7 suggest that somatotopic order is already present at this early age.

In the periphery, receptor addition is unordered, occurring along nerve branch pathways. Meanwhile the ELL adds cells in an orderly fashion at its caudolateral border. This suggests that primary afferents shift position caudally with growth to maintain their somatotopic relationships. Because all three central nuclei are in topographic register and grow by adding cells caudally, during growth ELL efferents to the torus and toral efferents to the tectum may utilize pessive mechanisms, such as fiber‐fiber interactions, to guide axons.
Subnuclear organization of the lateral tegmental field of the rat. I: Nucleus ambiguus and ventral respiratory group
Authors: Ellenberger H. H. , Feldman J. L.
Published: January 2005

Three classes of neurons within the lateral tegmental field of the rat medulla having different target projections were identified by retrograde labelling with three different fluorescent tracers. Labelled bulbospinal premotor and propriobulbar interneurons of the ventral respiratory group and vagal motoneurona of nucleus ambiguus formed partially intermingled longitudinal columns encompassed within a common region of the lateral tegmental field. Labelled neurons of each class were organized in a nonuniform distribution within these columns forming subdivisions distinguished by neuron morphology, orientation, and target projection. The three major rostrocaudal divisions of the ventral respiratory group (VRG) previously identified in the cat and rabbit were identified here in the rat, suggesting a common pattern of VRG organization among these species.
Efferent projections of the subthalamic nucleus in the squirrel monkey as studied by the PHA‐L anterograde tracing method
Authors: Smith Y. , Hazrati L.‐N. , Parent A.
Published: January 2005

The organization of the efferent connections of the subthalamic nucleus was studied in the squirrel monkey (Saimiri sciureus) by using the lectin Phaseolus vulgaris‐leucoagglutinin (PHA‐L) as an anterograde tracer. At the level of the basal forebrain, anterogradely labeled fibers and axon terminals were mostly found in the striatopallidal complex and the substantia innominata. In cases in which the PHA‐L injection sites were placed in the central or the lateral third of the subthalamic nuclus, numerous anterogradely labeled fibers were seen to arise from the injection loci and innervate massively the globus pallidus. At pallidal levels the fibers formed bands lying parallel and adjacent to the medullary laminae. The number and the complexity of the topographical organization of these bands varied with the size and the location of the PHA‐L injection site. When examined at a higher magnification, the bands of subthalamopallidal fibers appeared as rich plexuses of short axon collaterals with small bulbous enlargements that closely surrounded the cell bodies and primary dendrites of pallidal cells. In contrast, PHA‐L injection involving the medial tip of the subthalamic nucleus did not produce bandlike fiber patterns in the globus pallidus. Instead, the labeled fibers formed a diffuse plexus occupying the ventral part of the rostral pole of the globus pallidus as well as the subcommissural pallidal region. The substantia innominata contained a moderate number of labeled fibers and axon terminals following injection of PHA‐L in the medial tip of the subthalamic nucleus. A small to moderate number of anterogradely labeled fibers were seen in the putamen after all PHA‐L injections. These subthalamostriatal fibers were long, linear, and branched infrequently. At midbrain level the substantia nigra contained a significant number of anterogradely labeled fibers and axon terminals following PHA‐L injection in the subthalamic nucleus. The subthalamonigral fibers descended along the ventromedial part of the cerebral peduncle and swept laterally to reach their target. Most of these fibers formed small plexuses along the base of the pars reticulata, whereas a few others ascended along the cell columns of the pars compacta that impinged deeply within the pars reticulata. More caudally in the brainstem, a small number of fibers occurred in the area of the pedunculopontine nucleus and in the periaqueductal gray. These findings indicate that besides its well‐known connection with the pallidum, the subthalamic nucleus gives rise to widespread projections to other components of the basal ganglia in primates.
VIP‐and PHI‐immunoreactivity in olfactory centers of the adult cat
Authors: Sanides‐kohlrausch Claudia , Wahle Petra
Published: January 2005

The purpose of the study was to determine the morphology and distribution of vasoactive intestinal polypeptide‐ and peptide histidine isoleucineimmunoreactive (VIP‐ and PHI‐ir) neurons and innervation patterns in the main and accessory olfactory bulb, anterior olfactory nucleus, and piriform cortex of the adult cat. In these centers, VIP‐ and PHI‐immunoreactive material are present in the same neuronal types, respectively, therefore summarized as VIP/PHI‐ir neurons. In the main olfactory bulb, the majority of VIP/PHI‐ir neurons are localized in the external plexiform layer. These neurons give rise to two or more locally branching axons. They form boutons on mitral and external tufted cell bodies. According to the morphology and location, we have classified these neurons as Van Gehuchtencells. Some VIP/PHI‐ir neurons are present in the glomerular layer. They have small somata and give rise to dendrites branching exclusively into glomeruli. We have classified these neurons as periglomerular cells. In the granule cell layer, neurons with long apical dendrites and one locally projecting axon are present. In the accessory olfactory bulb, VIP/PHI‐ir neurons are localized in the mixed external/mitral/internal plexiform layer. They represent Van Gehuchten cells.

In the anterior olfactory nucleus and piriform cortex, VIP/PHI‐ir bipolar basket neurons are present. They are localized mainly in layers II/III. These neurons are characterized by a bipolar dendritic pattern and by locally projecting axons forming basket terminals on large immunonegative cell somata. Because of their common morphological features, we summarize them as the retrobulbar VIP/PHI‐ir interneuron population.

The PHI‐ir neurons display the same morphology as the VIP‐ir cells. However, they are significantly lower in number with a ratio of VIP‐ir to PHI‐ir cells about 2:1 in the main and accessory olfactory bulb and in the anterior olfactory nucleus. By contrast, in the piriform cortex the ratio is about 1:1.
Development of catecholaminergic projections to the spinal cord in the North American opossum, Didelphis virginiana
Authors: Pindzola Ronda R. , Ho Raymond H. , Martin George F.
Published: January 2005

The intent of our study was to determine when catecholaminergic axons grow into each of their adult targets in the spinal cord of the North American opossum (Didelphis virginiana) and to identify the origin of catecholaminergic axons in the lumbosacral cord at different stages of development. Tyrosine hydroxylase‐like immunoreactive axons, presumed to be catecholaminergic, were demonstrated at different stages of development by the indirect antibody peroxidase‐antiperoxidase technique of Sternberger. The neurons giving rise to such axons in the lumbosacral cord were identified by using the retrograde transport of Fast Blue and immunofluorescence for tyrosine hydroxylase‐like immunoreactive neurons.

At birth, 12‐13 days after conception, tyrosine hydroxylase‐like immunoreactive axons are present in the marginal zone throughout the length of the spinal cord. Such axons are particularly numerous in the dorsolateral marginal zone, the region containing most of them in adult animals. By postnatal day 3, a few immunoreactive axons are present in the intermediate (mantle) zone of the spinal cord; and by postnatal day 8, they are most concentrated in the presumptive intermediolateral cell column. Laminae I and II of the dorsal horn are not innervated by such axons until approximately postnatal day 15. By postnatal day 44, the distribution of tyrosine hydroxylase‐like immunoreactive axons in the spinal cord resembles that in adult animals, although some areas may be hyperinnervated.

At birth, tyrosine hydroxylase‐like immunoreactive cell bodies are present in all of the brainstem areas providing catecholaminergic projections to the spinal cord in adult animals (Pindzola et al.: Brain Behav. Evol. 32:281‐292,'88); and by at least postnatal day 5, lumbosacral injections of Fast Blue retrogradely label tyrosine hydroxylase‐like immunoreactive neurons in all such areas. Retrogradely labeled immunoreactive neurons were also found in areas that do not contain them in adult animals. Such areas include the dorsal part of the nucleus coeruleus and certain areas of the reticular formation. During development, spinally projecting tyrosine hydroxylase‐like immunoreactive neurons are numerous medial to the nucleus ventralis lemnisci lateralis (the paralemniscal region), whereas only a few are present in the same location in adult animals. Our results suggest that catecholaminergic axons grow into the spinal cord prenatally, that they innervate their adult targets postnatally and over an extended time period, and that during some stages of development they originate from areas that do not supply them in the adult animal.
Control of neuronal survival by anomalous targets in the developing brain
Authors: Linden Rafael
Published: January 2005

Described here is an aberrant parabigeminothalamic projection that follows neonatal lesions of the superior colliculus in rats, with evidence that this anomalous projection may sustain a normal number of neurons in the parabigeminal nucleus after early removal of the latter's tectal target. The aberrant projection was traced radioautographically to the tectorecipient zone of the lateral posterior nucleus after an injection of tritiated amino acid in the parabigeminal nucleus. Histochemical staining for cholinesterase revealed an anomalous patch of high enzyme activity in register with both the aberrant parabigeminothalamic projection and an abnormal retinal projection that also follows tectal lesions. Histochemical staining after either binocular enucleation or a tegemental lesion made simultaneous with the tectal ablation showed that the anomalous enzyme patch is a reliable marker of the aberrant parabiogeminothalamic projection. It was also shown that the retinal projection is not needed for the formation of the anomalous parabigeminothalamic pathway. Ablation of the superior colliculus at birth failed to produce a net cell loss in the contralateral middle division of the parabigeminal nucleus after the period of natural neuronal death. Lesions extending toward the anomalous terminal field in the lateral posterior nucleus, however, prevented the survival of a normal number of neurons in the parabigeminal nucleus. When the unilateral tectal ablation was made together with a lesion of the ipsilateral posterior neocortex that produced cell loss in the thalamus, the number of neurons remaining in the middle division of the contralateral parabigeminal were linearly related to the cell content of the lateral posterior nucleus. We conclude that the anomalous target in the tectorecipient zone of the lateral posterior nucleus effectively replaces the normal projection field in the superior colliculus, with regard to the trophic requirements for neuronal survival during development of the parabigeminal nucleus.
Serotoninergic innervation of the locust mandiblar closer muscle modulates contractions through the elevation of cyclic adenosine monophosphate
Authors: Baines Richard A. , Tyrer N. Mark , Downer Roger G. H.
Published: January 2005

The mandibular closer muscles of the locust receive innervation that is immunoreactive for the putative transmitter 5‐hydroxytrptamine (5‐HT). Cobalt‐labelling suggests that the origin of this innervation is a group of cells located anteriorly in the suboesophageal ganglion. Bath application of 5‐HT while the muscles are active produces marked changes in the contractions, increasing their amplitude, rate of contraction, and rate of relaxation. Incubation of isolated muscles with 5‐HT shows that this amine elevates the levels of the cyclic nucleotide cyclic adenosine monophosphate (cAMP). In addition compounds that artificially elevate the levels of cAMP in the muscle‐3‐isobutyl‐1‐methylxanthine (IBMX), forskolin, and the cAMP analogue 8‐(4‐chlorophenylthio) cAMP‐mimic the actions of 5‐HT, whereas a potent inhibitor of insect adenylate cyclase, adenosine, considerably delays the onset of the effects produced by 5‐HT.

The effects observed with 5‐HT in the mandibular muscle are similar to those of octopamine in the locust extensor tibiae muscle, and it is possible that this is an analogous modulatory system.
Serotoninergic and noradrenergic projections to the ventral posterolateral nucleus of the monkey thalamus
Authors: Westlund Karin N. , Sorkin Linda S. , Ferrington Dale G. , Carlton Susan M. , Willcockson Helen H. , Willis W. D.
Published: January 2005

In the present study, serotoninergic and noradrenergic varicosities were identified in the ventral posterolateral nucleus of the macaque monkey. Monoaminergic neurons projecting to the ventral posterolateral nucleus of the thalamus were identified by using retrograde labeling with horseradish peroxidase combined with immunocytochemical staining for serotonin or dopamine‐β‐hydroxylase. The midbrain nucleus raphe dorsalis was the major site of origin for neurons providing a serotoninergic projection to the ventral posterolateral nucleus. A few retrogradely labeled serotonin‐containing neurons were also observed in the central superior and the raphe pontis nuclei. Noradrenergic cells with projections to the thalamus were primarily located in the nucleus locus coeruleus with some projection neurons in the nucleus subcoeruleus, and the A5 catecholamine cell group of the pons.
Innervation and geometry of rabbit ciliary ganglion cells after preganglionic nerve regeneration
Authors: Hadley Robert D.
Published: January 2005

Previous studies have shown a consistent relationship between the dendritic complexity of autonomic neurons and the number of preganglionic axons that innervate them. This relationship is established postnatally, probably through mitigation of preganglionic competition on neurons with increasing dendritic complexity. The present study examines whether a similar relationship between neuronal geometry and the number of axons that innervate rabbit ciliary ganglion neurons is established when the preganglionic nerve is interrupted and then allowed to regenerate. Such a pattern would indicate that the mechanisms responsible for establishing the relationship between innervation and postsynaptic geometry in neonates persist in the adult animal.

Ganglion cells were fully reinnervated by about 8 weeks after preganglionic nerve crush. On average, the number of inputs to reinnervated neurons was similar to normal (range = 1 to 4 inputs/cell, mean = 2.1).

The number of inputs that cells received was related to their dendritic complexity. Neurons that received a single input had very simple dendritic arbors, or lacked dendrites altogether, whereas neurons that received 2 or more inputs had considerably more complex arbors.

The correlation between dendritic complexity and innervation suggests that the geometry of postsynaptic neurons continues to influence the number of inputs each ganglion cell receives in maturity. As a corollary, changes in the dendritic arbors of adult neurons would presumably influence the arrangement of their synaptic inputs.
Regenerative organization of the trigeminal ganglion following mental nerve section and repair in the adult rat
Authors: Zuniga John R. , Pate Jenifer D. , Hegtvedt Arden K.
Published: January 2005

Sequential double‐fluorescence labeling techniques were employed to determine the regenerative somatotopic organization of first‐order mandibular neurons following mental nerve transection and surgical repair in the adult rat. Twenty‐four ganglia from 12 adult rats were examined microscopically in the following double‐labeling paradigm: (i) Fast Blue was injected directly into the mental nerves bilaterally; (ii) 7 days later the nerves were transected and immediately rejoined by microscopic suture techniques; (iii) Diamidino Yellow was then injected directly into the regenerated nerve, distal to the point of repair, 30, 60, and 90 days postrepair; and (iv) the animals were sacrificed 3 days later and the ganglia removed for fluorescent microscopic examination. Results were compared with 12 ganglia each of unrepaired/resected controls and sham surgery controls made in parallel.

The organization of fluorescence‐labeled mandibular cells followed an orderly somatotopic distribution along the lateral dorsoventral axis of the trigeminal ganglion in all groups. The difference in mean total number of fluorescence‐labeled cells within and between groups was insignificant or minimal. There was no evidence of heteronymous (nonmandibular) or homonymous (mandibular) sprouting following neuronal regeneration. Regeneration, as determined by the presence of double‐labeled cells, was negligible if the transection injury was not repaired but significant 30 days following repair. Additionally, mandibular regeneration gradually improved, as shown by the significant increase of double‐labeling at 60 and 90 days postrepair. However, 90 days later, the percentage of regenerated cells had not reached sham control conditions.

The results of these studies suggest that following nerve transection and immediate repair in the adult rat: (i) mental sensory neuronal perikarya regenerate from and maintain an organized somatotopic area within the mandibular division of the trigeminal ganglion; (ii) reorganization by collateral sprouts from nonmental sensory mandibular and/or nonmandibular trigeminal ganglion cells is not evident or is negligible in the adult rat; and (iii) regeneration of resected trigeminal sensory neurons is a gradual process which is enhanced by immediate surgical intevention.
Distribution of calcium‐activated protease calpain in the rat brain
Authors: Perlmutter Lynn S. , Gall Christine , Baudry Michel , Lynch Gary
Published: January 2005

Calpain is a calcium‐activated neutral protease that degrades a number of cytoskeletal proteins. It may participate in the maintenance of the cytoskeleton and in the rapid turnover of structural proteins associated with synaptic plasticity. Calpain may also be involved in the neurodegeneration that accompanies aging and age‐related diseases. To aid in the interpretation of disease‐related alterations in staining patterns, the present study examined calpain's normal distribution in the mammalian brain and spinal cord. A monoclonal antibody was employed with the avidin‐biotin‐peroxidase immunocytochemical technique on samples of rat tissue. Glia (astrocytes, microglia) and virtually all neurons were immunopositive, although neuronal processes exhibited varying staining patterns. The axonal staining pattern depended upon either the origin or destination of the process: those axons remaining within the brain (e.g., corpus callosum) were only lightly immunoreactive, whereas spinal cord and peripheral axons (trigeminal nerve) were more darkly labeled. The architecture of the dendritic tree determined the dendritic staining pattern: neurons with prominent apical and basal dendritic trees (e.g., pyramidal cells) were immunolabeled along their entire extent; labeling of multipolar cells (e.g., hilar cells of dentate gyrus) was limited to the proximal dendrites. The ubiquitous distribution of calpain argues against a primary role for the enzyme in the regional pattern of neuronal death seen in Alzheimer's disease. An alteration in the concentration, localization, or inhibition of the enzyme could, however, lead to the abnormal accumulations of cytoskeletal elements seen with the disease.
Effects of monocular deprivation on the morphology of retinogeniculate axon arbors in a primate
Authors: Lachica E. A. , Crooks M. W. , Casagrande V. A.
Published: January 2005

Previous studies of the monocularly deprived (lid‐sutured) primate (Galago crassicaudatus) have shown that magnocellular (M) and parvocellular (P) lateral geniculate nucleus (LGN) cells that receive input from the deprived eye are smaller than counterparts that receive input from the nondeprived eye; deprived koniocellular (K) cells show wide variability in size, but they do not differ from their nondeprived counterparts (Casagrande and Joseph, '80)‐ Although deprivation results in cell‐size changes, the physiological properties of deprived LGN cells do not change from normal (that is, P cells have normal X‐like properties, M cells have normal Y‐like properties, and K cells have normal W‐like properties)

Because of these findings, we were interested in determining how the morphology of retinogeniculate axon arbors is affected by deprivation. To this end, 104 horseradish‐peroxidase‐filled retinogeniculate arbors from galagos deprived from birth to maturity were completely reconstructed within the binocular segment of the LGN. These arbors were qualitatively and quantitatively compared with 56 arbors reconstructed from normal galagos as part of another study (Lachica and Casagrande, '88)

Our main findings are as follows. Deprived M and P arbors are affected by deprivation in the same general manner: compared with normal arbors, they are altered in shape (rather than being round or columnar, respectively, both groups have terminals that are elongated parallel to laminar borders); they are smaller in area, and they have fewer boutons but innervate the LGN with a greater density of boutons. K arbors are affected by deprivation in the same manner, but less severely. Finally, our results show that nondeprived arbors are also affected by eyelid suture. Specifically, all nondeprived arbor groups are smaller in area than normal and possess more boutons/mm3. We interpret these changes in the morphology of deprived retinogeniculate axons to suggest that abnormal competitive interactions begin by affecting primarily immature LGN cells and their axons and that the retinogeniculate axons presynaptic to these cells experience secondary degenerative effects. Our results also show that similar manipulations of visual experience can result in changes that are not necessarily comparable across species such as cats and primates.
Origins and distribution of cerebrovascular nerve fibers showing calcitonin gene‐related peptide‐like immunoreactivity in the major cerebral artery of the dog
Authors: Nozaki Kazuhiko , Uemura Yoshihiko , Okamoto Shinichiro , Kikuchi Haruhiko , Mizuno Noboru
Published: January 2005

The origins and overall distribution of perivascular nerve fibers showing calcitonin gene‐related peptide‐like immunoreactivity (CGRP‐LI) in the major cerebral arteries were investigated immunohistochemically in the dog by using whole‐mount preparations of the arterial trees around the circle of Willis. Perivascular nerve fibers with CGRP‐LI were seen most abundantly in the basilar artery, vertebral artery, common anterior cerebral artery, proximal part of the anterior cerebral artery, and terminal part of the internal carotid artery. They were far less numerous in the middle cerebral artery, posterior cerebral artery, superior cerebellar artery, and distal part of the anterior cerebral artery. Neuronal cell bodies with CGRP‐LI were observed in the trigeminal, nodose, superior cervical, and dorsal root ganglia.

CGRP‐LI fibers in the large pial arteries in the circle of Willis were eliminated ipsilaterally after unilateral transection of the ophthalmic division of the trigeminal nerve, and slightly reduced in number ipsilaterally after unilateral transection of the maxillary division of the trigeminal nerve. They did not show any noticeable changes after unilateral transection of the mandibular division of the trigeminal nerve. On the other hand, CGRP‐LI fibers in the basilar and vertebral arteries did not show any appreciable changes after unilateral transection of the trigeminal nerve, but they were eliminated after bilateral ganglionectomy of the dorsal root ganglia of the first, second, and third cervical nerves. After ganglionectomy of the ciliary, pterygopalatine, otic, nodose, or superior cervical ganglion, no changes were observed in perivascular nerve fibers with CGRP‐LI in the major cerebral arteries.

The data indicate that perivascular nerve fibers with CGRP‐LI in the large pial arteries forming the circle of Willis originate mainly from the ophthalmic division of the trigeminal nerve, and partly from the maxillary division of the trigeminal nerve, and that CGRP‐LI fibers in the basilar artery and distal part of the vertebral artery originate mainly from the dorsal root ganglia of the upper cervical nerves.
Distribution of phosphate‐activated glutaminase in the human cerebral cortex
Authors: Akiyama Haruhiko , Kaneko Takeshi , Mizuno Noboru , McGeer Patrick L.
Published: January 2005

Phosphate‐activated glutaminase (PAG), which catalyses conversion of glutamine to glutamate, is a potential marker for glutamatergic, and possibly GABA, neurons in the central nervous system. A polyclonal antibody, raised in rabbits against rat brain PAG, was applied to postmortem human brain tissue to reveal the distribution of PAG in the cerebral cortex. PAG immunoreactivity was observed in pyramidal and non‐pyramidal neurons but not in glial cells. In the neocortex, large to medium‐sized pyramidal neurons in layers III and V were stained most intensely, while the majority of smaller pyramidal cells were labeled either lightly or moderately. Such modified pyramids as the giant Betz cells, the large pyramidal cells of Meynert, and the solitary cells of Ramón y Cajal were also stained intensely. Fusiform cells in layer VI showed moderate to intense labeling. A number of cortical non‐pyramidal neurons of various sizes stained moderately to intensely. These included large basket cells which were identified by their characteristic morphology and size in primary cortical areas. Pyramidal cells in the hippocampal formation as well as basket cells of the stratum oriens stained moderately to intensely. Since pyramidal cells are believed to be glutamatergic and large basket cells GABAergic, these results suggest that PAG plays a role in generating not only transmitter glutamate, but also GABA precursor glutamate.
Topographic intermingling of striatonigral and striatopallidal neurons in the rhesus monkey
Authors: Selemon L. D. , Goldman‐Rakic P. S.
Published: January 2005

The topography and interrelationship of striatofugal neurons have been examined using a double retrograde tracing paradigm to label striatopallidal and striatonigral neurons in the same neostriatum. The rostral globus pallidus and the rostral substantia nigra in the same hemisphere were injected simultaneously with fluorescent tracers in three monkeys. In addition, the caudal globus pallidus and the caudal substantia nigra were injected separately in a fourth and fifth monkey with a fluorescent dye and wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP), respectively. Digitized plots of fluorescent dye‐labeled neurons revealed that large numbers of striatonigral projection neurons lie within both neostriatal nuclei, i.e., the caudate and putamen. Similarly, neurons innervating the globus pallidus were found in both caudate and putamen. The distribution of retrogradely labeled neurons observed was consistent with the topography of striatofugal projections that has been described previously, i.e., the rostrocaudal and mediolateral axes of the neostriatum are preserved in the striatopallidal and striatonigral projections (e.g., Szabo, '62, '67, 70, '72) and the dorsoventral axis is inverted in the projection of the neostriatum onto the nigra but not in the striatopallidal projection (Nauta and Domesick, '79; Gerfen, '85). Analysis of cases in which striatonigral and striatopallidal neurons were present in large numbers within the same region of the neostriatum disclosed that the two populations are intermingled such that small clusters of striatopallidal neurons are surrounded by striatonigral neurons and vice versa. The clustered arrangement of striatofugal neurons observed in the fluorescent cases was unambiguous in a case in which HRP was injected into the caudal substantia nigra. In this case, both anterogradely labeled terminals and retrogradely labeled neurons exhibited a striking, compartmental‐like distribution in the posterior putamen.

Our observations indicate that the matrix compartment of the neostriatum is comprised of a patchwork of interposed clusters of nigral and pallidal efferent neurons. We hypothesize that these clusters of efferent neurons may direct interdigitated cortical inputs into distinct nigro‐and pallido‐thalamic pathways. In view of the parallel nature of processing throughout the basal ganglia, it appears that convergence of these segregated nigral and pallidal loops must occur at the cortical level where prefrontal and premotor targets of the basal ganglia are interconnected via corticocortical projections (Selemon and Goldman‐Rakic, '88).
Photoreceptor mosaic: Number and distribution of rods and cones in the rhesus monkey retina
Authors: Wikler Kenneth C. , Williams Robert W. , Rakic Pasko
Published: January 2005

Video‐enhanced differential interference contrast optics was used to determine the number and distribution of photoreceptors across the entire retinal surface of 9 eyes obtained from 7 adult rhesus monkeys. We found that the retina of this primate contains an average of 3,100,000 cones (±130,000) and 61,000,000 rods (±7,500,000). Variation among animals in the number of rods and cones cannot be accounted for by differences in sex, age, or retinal surface area, nor is there a correlation between the number of rods and cones (a retina with a high number of rods does not typically have a high number of cones).

Cone density peaks at 141,000 cones/mm2 in the foveola and decreases about 100‐fold toward the periphery. Rod density in a central annulus around the fovea is 130,000/mm2 and decreases 6–8‐fold toward the periphery. In all 9 retinae, we found that an area 4–5 mm dorsal to the fovea had the highest rod density at 184,000 rods/mm2. The functional significance of this area, which we term the dorsal rod peak DRP), may be related to high sensitivity vision under scotopic conditions. Outside of the DRP, rod density is symmetrical around the major axes of the retina, whereas cone density is elevated in nasal retina. Among animals, both rods and cones display a 2‐fold individual difference in receptor density at any given eccentricity.

Although rods and cones differ in absolute number, the location and magnitude of their peak densities, and their central to peripheral density gradients, the ratio of the density of rods to cones (15–30:1) is remarkably stable from 3 mm to 15 mm eccentricity. The relative consistency in the proportion of rods and cones in extrafoveal retina may be related to mechanisms of retinal development and functional interactions between scotopic and photopic systems.
Visual and electrosensory circuits of the diencephalon in mormyrids: An evolutionary perspective
Authors: Wullimann Mario F. , Glenn Northcutt R.
Published: January 2005

Mormyrids are one of two groups of teleost fishes known to have evolved electroreception, and the concomitant neuroanatomical changes have confounded the interpretation of many of their brain areas in a comparative context, e.g., the diencephalon, where different sensory systems are processed and relayed. Recently, cerebellar and retinal connections of the diencephalon in mormyrids were reported. The present study reports on the telencephalic and tectal connections, specifically in Gnathonemus petersii, as these data are critical for an accurate interpretation of diencephalic nuclei in teleosts. Injections of horseradish peroxidase into the telencephalon retrogradely labeled neurons ipsilaterally in various thalamic, preglomerular, and tuberal nuclei, the nucleus of the locus coeruleus (also contralaterally), the superior raphe, and portions of the nucleus lateralis valvulae. Telencephalic injections anterogradely labeled the dorsal preglomerular and the dorsal tegmental nuclei bilaterally.

Injections into the optic tectum retrogradely labeled neurons bilaterally in the central zone of area dorsalis telencephali and ipsilaterally in the torus longitudinalis, various thalamic, pretectal, and tegmental nuclei, some nuclei in the torus semicircularis, the nucleus of the locus coeruleus, the nucleus isthmi and the superior reticular formation, basal cells in the ipsilateral valvula cerebelli, and eurydendroid cells in the contralateral lobe C4 of the corpus cerebelli. Weaker contralateral projections were also observed to arise from the ventromedial thalamus and various pretectal and tegmental nuclei, and from the locus coeruleus and superior reticular formation. Tectal injections anterogradely labeled various pretectal nuclei bilaterally, as well as ipsilaterally the dorsal preglomerular and dorsal posterior thalamic nuclei, some nuclei in the torus semicircularis, the dorsal tegmental nucleus, nucleus isthmi, and, again bilaterally, the superior reticular formation.

A comparison of retinal, cerebellar, tectal, and telencephalic connections in Gnathonemus with those in nonelectrosensory teleosts reveals several points: (1 the visual area of the diencephalon is highly reduced in Gnathonemus, (2) the interconnections between the preglomerular area and telencephalon in Gnathonemus are unusually well developed compared to those in other teleosts, and (3) two of the three corpopetal diencephalic nuclei are homologues of the central and dorsal periventricular pretectum in other teleosts. The third is a subdivision of the preglomerular area, rather than an accessory optic or pretectal nucleus, and is related to electroreception. The preglomerulo‐cerebellar connections in Gnathonemus are therefore interpreted as uniquely derived characters for mormyrids.
Development of the lateral geniculate nucleus: Interactions between retinal afferent, cytoarchitectonic, and glial cell process lamination in ferrets and tree shrews
Authors: Hutchins James B. , Casagrande Vivien A.
Published: January 2005

We have studied the relationship of retinal afferents, glial cell processes, and neuronal cytoarchitectonics in the lateral geniculate nucleus (LGN) of two species: tree shrews (Tupaia belangeri) and ferrets (Mustela putoris). Both species are relatively immature at birth, allowing the development of these features to be studied in the perinatal period.

Retinal afferents, visualized by intraocular injection of a wheat germ agglutinin/horseradish peroxidase conjugate (WGA‐HRP), are apparently the first elements of the developing LGN to exhibit a characteristic layered pattern in tree shrews and ferrets. Some radial glia still remain in the LGN of both species as the retinal afferents are in the process of segregating.

Glial cell processes were visualized immunohistochemically with antibodies to glial fibrillary acidic protein (GFAP) or vimentin. In both the ferret and tree shrew, layering of glial cell processes is first seen as the overlap of retinal terminal fields diminishes. In the tree shrew LGN, these bands of dense glial cell staining are seen in apparent future cellular layers, whereas in the ferret, glial cell banding appears in interlaminar zones. If one or both eyes are removed at birth in tree shrews (before LGN cell layers are formed), the glial cell pattern seen 1 week later is in accord with the distribution of surviving nerve cells. The glial processes do not appear to invade regions left by degenerating retinal terminals or dying LGN cells.

Several days after the appearance of layered glial cell processes (in the tree shrew) or at about the same time as glial layering (in the ferret), the first interlaminar spaces develop between neuronal cells, marking the beginning of cytoarchitectonic lamination, with its distinctive alternating cell‐rich and cell‐poor zones. Over the next several weeks, LGN neurons in both species continue to segregate into characteristic layers until the final, adult pattern of neuronal lamination is evident; as this process is completed, glial cell lamination disappears.

These observations suggest that glial cells may be involved in establishing the neuronal layers that characterize the mature LGN of many species.