bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional organization of crayfish abdominal ganglia: I. The flexor systems
Authors: Leise Esther M. , Hall Wendy M. , Mulloney Brian
Published: January 2005

For insect ganglia, Altman (A dvances in Physiological Science, Vol. 23. Neurobiology of Invertebrates. New York: Pergamon Press, pp. 537–555, '81) proposed that individual neuropils control different motor activities. A corollary of this hypothesis is that motor neurons involved in many behavioral functions should branch in more neuropils than those active in fewer behaviors. In crayfish, the abdominal fast‐flexor muscles are active only during the generation of the powerstroke for tailflips, whereas the slow‐flexor muscles are involved in the maintenance of body posture. The slow flexors are thus active in many of the crayfish's behavioral activities. To test the generality of Altman's idea, we filled groups of crayfish fast‐flexor and slow‐flexors were motor neurons with cobalt chloride and described their shapes with respect to the ganglionic structures through which they pass. Individual fast flexors were also filled intracellularly with HRP. Ganglia containing well‐filled neurons were osmicated, embedded in plastec, and sectioned. Unstained sections were examined by light microscopy and pertinent sections were photographed. We found that the paths of the larger neurites were invariant, that the dendritic domains of fast and slow motor neurons occupied distinctive sets of neuropils, and that dendrites of slow motor neurons branched in more ganglionic structures than did those of fast motor neurons. These results are consistent with Altman's hypothesis.
Immunohistochemical study on the development of serotoninergic neurons in the chick: I. Distribution of cell bodies and fibers in the brain
Authors: Sako Hiroko , Kojima Tokuzo , Okado Nobuo
Published: January 2005

The ontogenetic development of the serotoninergic system in the embryonic as well as in posthatching chick brain was studied with an indirect immunohistochemical technique with the aid of a specific antibody to serotonin (5‐hydroxytryptamine).

By embryonic day 4, rostral and caudal groups of serotonin‐immunoreactive cell populations appeared in the mesencephalon and rostral and caudal rhombencephalon. At this stage, the rostral group had a considerable number of labelled cells that sent axons toward more rostral parts of brain, whereas the caudal group consisted of a small number of scattered serotonin‐immunoreactive cells. The number of serotonin‐positive cells increased with development, such that by embryonic day 8 almost all the serotoninergic cell groups found in the adult chick were already present. Serotoninergic‐positive cells appeared in the paraventricular organ of the diencephalon as early as embryonic day 10. Judging from the cytoarchitectural organization of serotonin‐immunoreactive cells, all of the serotoninergic cell groups in the chick brain seemed to be fully developed by embryonic day 16.

On embryonic day 4, serotonin‐immunoreactive fibers were found to enter into the marginal layer of the mesencephalon. Subsequently, serotonin‐positive fibers ascended in the marginal layer of the brainstem up to the levels of the diencephalon and to the telencephalon on embryonic day 6 and 8, respectively. Serotonin‐positive fibers, which first began to penetrate into the mantle layer on embryonic day 8, reached to the rostral pole of the telencephalon by embryonic day 10. In general, serotonin fibers were found in almost all brain regions by embryonic day 16. However, “terminal formation” in some nuclei did not seem to begin until the late embryonic or posthatching period.

These observations indicate that the initial development of serotoninergic cell groups occurs during the first half of the 20th day of the incubation period of the chick. However, a longer time, ranging from early embryonic to posthatching stages, is necessary for the complete development of the serotoninergic projections.
Immunohistochemical study on the development of serotoninergic neurons in the chick: II. Distribution of cell bodies and fibers in the spinal cord
Authors: Sako Hiroko , Kojima Tokuzo , Okado Nobuo
Published: January 2005

Developmental changes of serotonin (5‐hydroxytryptamine) neurons and fibers in the spinal cord of the embryo and posthatching chick were studied with immunohistochemical techniques with the aid of an antibody against serotonin.

The first serotonin‐immunoreactive fibers were found in the marginal layer of the cervical and lumbar spinal cord on embryonic days 6 and 8, respectively. There was a time lag of a few days between the first appearance of serotonin fibers in the marginal layer (embryonic days 6–8) and the time of penetration of serotonin fibers into the mantle layer (embryonic day 8 or older). The developments of serotonin innervation in the rostral parts of the spinal cord precedes that of caudal regions.

Serotonin fibers penetrating into the mantle layer of the lumbar spinal cord were first found in lamina VII on embryonic day 8, whereas there were no serotonin‐immunoreactive fibers in lamina IX by embryonic day 10.

Large differences were found between embryonic day 16 and posthatching day 5 with regard to the density of serotonin varicosities and fibers in lamina IX, where profiles of soma and large‐sized dendrites were heavily covered with varicosities. Laminae I and II first received serotonin fibers on embryonic day 16 and had a much denser innervation by posthatching day 5. There were no traces of serotonin fibers in lamina III in the stages examined up to posthatching day 5.

Serotonin fibers were located in the lateral and ventral marginal layers in all specimens examined; only a few fibers were found in the dorsal marginal layer.

Although few, serotonin‐immunoreactive cell bodies were found in an area around the central canal of all animals from embryonic day 8 to adult. Some of these were located in the ependymal layer and sent processes toward the central canal; there were a small number of cells with long, fine processes. Serotonin‐immunoreactive fibers in the spinal cord were not altered in regions rostral to the spinal transection, whereas all the serotoninergic fibers of the supraspinal origin were eliminated in the spinal cord caudal to the gap.
Morphological features of spiking and nonspiking cells in the paratracheal ganglion of the ferret
Authors: Coburn Ronald F. , Kalia Madhu P.
Published: January 2005

The present series of experiments was designed to study details of the morphology and connectivity of functionally identified cells located in the paratracheal ganglia of the ferret. The morphology of 11 spiking (AH cells) and seven nonspiking (type B cells) ganglion cells was examined. Intraaxonally injected horseradish peroxidase (HRP) was used as the label. Each spiking and nonspiking cell was identified by intracellular recording prior to the HRP injection. “Whole mount preparations” were processed for HRP histochemistry with diaminobenzidine as the chromogen. HRP‐labeled cell bodies of both the spiking AH and nonspiking type B neurons demonstrated similar morphological features. Both types of ganglion cells showed (1) axons arising from a small, ill‐defined axon hillock which exited from the cell as single or multiple branches of equal diameter and coursed unidirectionally through the interganglionic nerve trunk to an adjacent ganglion; (2) short, fine, tapering processes (presumptive dendrites) in the immediate vicinity of the injected cell; and (3) processes extending out of the ganglion cell perpendicular to the interganglionic nerve trunk which could be followed into the smooth muscle. Extraperikaryal injections of HRP into a ganglion retrogradely labeled perikarya in the adjacent ganglia. These results demonstrate that in airway ganglia the morphology of spiking and nonspiking neurons is remarkably similar despite electrophysiological differences. In addition it appears that ganglion cells project to adjacent ganglia and to smooth muscle by means of independent axonal processes. These morphological features of the ganglion cells in airways and the trajectories of their axons correspond to known features of their physiology: i.e., (1) the axon of a ganglion cell travels unidirectionally toward the adjacent ganglion and arborizes there, providing anatomical evidence of communication between ganglia via the interganglionic nerve trunk; and (2) the spiking and nonspiking neurons possess similar morphological features that are typical of ganglion cells described in other systems, such as in the myenteric plexus.
Distribution of cholecystokinin‐immunoreactive cell bodies in the male and female rat: I. Hypothalamus
Authors: Micevych Paul E. , Park Sow Shim , Akesson Thomas R. , Elde Robert
Published: January 2005

The hypothalamic distribution of cholecystokinin‐immunoreactive (CCKI) cell bodies in colchicine‐treated male and female rats was studied. Immunoreactive neurons were visualized along the anterior two‐thirds of the third ventricle but were especially numerous in the preoptic periventricular nucleus. Dense aggregations of CCKI cells were found in the anterior magnocellular, posterior magnocellular, medial parvicellular, and posterior parvicellular divisions of the paraventricular nucleus. Both the supraoptic nucleus and the central, cell‐dense part of the dorsomedial nucleus contained large numbers of CCKI cells.

CCKI cells in the preoptic periventricular nucleus were more numerous in the female, as was a population of labeled cells in the dorsal medial preoptic area. However, CCKI cell bodies in this part of the medial preoptic area were larger in males than in females. Males had more CCKI cells in the central part, of the medial preoptic nucleus and in the posterior magnocellular subdivision of the paraventricular nucleus. Both males and females had similar numbers of immunoreactive cells in the anterior magnocellular and the parvicellular divisions of the paraventricular nucleus as well as in the anterior hypothalamus, dorsal areas, dorsomedial nucleus, and supramammillary region. These data provide morphological evidence for a sexually differentiated hypothalamic CCKI system.
Synaptic organization of cholinergic neurons in the monkey neostriatum
Authors: Difiglia Marian
Published: January 2005

Cholinergic neurons in the monkey neostriatum were examined at the light and electron microscopic level by immunohistochemical methods in order to localize choline acetyltransferase (ChAT), the synthesizing enzyme for acetylcholine. At the light microscopic level a sparse distribution of cholinergic neurons was identified throughout the caudate nucleus. Neurons had large (25–30 μm) somata, eccentric invaginated nuclei, primary dendrites of unequal diameters, and varicosities on distal dendritic branches. Ultrastructural study showed that the cholinergic cells had a cytoplasm abundant in organelles. Within dendritic branches, mitochondria and cisternae were localized primarily to varicosities, Synaptic inputs were distributed mostly to the dendrites and at least four types that formed symmetric or asymmetric synapses were observed.

Immunoreactive fibers were relatively numerous within the neuropil and exhibited small diameters (0.1–0.15 μm) and swellings at frequent intervals. Cholinergic boutons that formed synapses were compared to unlabeled terminals making asymmetric synapses with dendritic spines. Results showed that ChAT‐positive axons had significantly smaller cross‐sectional areas, shorter synaptic junctions, and a higher density and surface area of mitochondria than the unlabeled boutons. Cholinergic axons formed symmetric synapses mostly with dendritic spines (53%) and the shafts of unlabeled primary and distal dendrites (37%). A relatively small proportion of the boutons contacted axon initial segments (1%) and cell bodies (9%) that included medium‐sized neurons with unindented (spiny) and indented (aspiny) nuclei. The majority of dendritic spines contacted by cholinergic axons were also postsynaptic to unlabeled boutons forming asymmetric synapses.

The results suggest that cholinergic neurons in the primate neostriatum belong to a single morphological class corresponding to the large aspiny (type II) interneuron identified in previous Golgi studies. Present results along with earlier Golgi‐electron microscopic observations from this laboratory suggest that neostriatal cholinergic cells integrate many sources of intrinsic and extrinsic inputs. The observed convergence of ChAT‐immunoreactive boutons and unlabeled axons onto the same dendritic spines suggests that intrinsic cholinergic axons modulate extrinsic inputs onto neostriatal spiny neurons at postsynaptic sites close to the site of afferent input.
Immunocytochemical and autoradiographic localization of GABAergic neurons in the goldfish retina
Authors: Ball Alexander K.
Published: January 2005

The putative neurotransmitter gamma‐aminobutyric acid (GABA) was localized in goldfish retina by using an antiserum directed against GABA itself. The same types of cells were stained with this antibody as were labelled with an antiserum directed against the synthesizing enzyme for GABA, glutamic acid decarboxylase. Stained neurites of these cells were located throughout the inner plexiform layer (IPL) but staining was more intense in the proximal IPL. The GABA‐immunoreactive staining could be reduced or completely abolished by preabsorbing the primary antibody with GABA. Uptake of [3H]‐GABA or the GABA agonist [3H]‐muscimol was localized in GABA‐stained retinas using light microscope autoradiography. These experiments demonstrated that all types of GABA‐immunoreactive amacrine cells had high‐affinity uptake mechanisms for both [3H]‐GABA and ‐muscimol. Thirty percent of proximal inner nuclear layer (INL) and some cells in the ganglion cell layer (GCL) were labelled by all three GABAergic markers. Most GABA‐immunoreactive amacrine cells were lightly labelled due to [3H] ‐ GABA uptake but a few amacrines (Ab) were heavily labelled. These findings demonstrate that the autoradiographic localization of [3H]‐GABA or [3H]‐muscimol uptake and the immunocytochemical localization of GAD or GABA are appropriate methods for localizing GABAergic neurons in the retina. Few GABA‐immunoreactive amacrine cells accumulated the putative amino acid transmitter [3H]‐glycine, verifying that the goldfish retina contains distinct subpopulations of glycinergic and GABAergic amacrine cells.
Tests of the regenerative capacity of tectal efferent axons in the frog, Rana pipiens
Authors: Lyon Michael J. , Stelzner Dennis J.
Published: January 2005

Experiments were designed to determine if neurons of the ranid optic tectum, a major target of the optic nerve, possess the same regenerative potential as optic axons. Normal tectal efferent (TE) projections were reexamined by using the anterograde transport of 3H‐proline and autoradiography (n = 18), bulk‐filling damaged TE axons with horseradish peroxidase (HRP; n = 18) and anterogradely transporting wheat germ agglutinin‐HRP (n = 8) to label TE axons. Results were similar to reports that used degeneration methods (Rubinson: Brain Behav. Evol. 1:529–561, '68; Lazar: Acta. Biol. Hung. 20:171–183, '69). Following a brainstem hemisection just caudal to the nucleus isthmi (1–20 weeks), the ipsilateral descending TE pathway was autoradiographically examined (n = 20). While all other TE projections appeared normal, there was no detectable ipsilateral descending projection beyond the lesion site. Ascending TE axons were cut at the anterior tectal border by hemisecting the left diencephalon (LDH)–a lesion that also cuts optic axons projecting to the left tectum. There was no indication of TE axonal regeneration with the aid of autoradiography or HRP histochemistry 1–30 weeks postlesion (n = 48) even when the medial diencephalon was intentionally left intact (n = 4). However, in all four cases examined, optic axons regenerated following the same LDH where TE axonal regeneration failed (also see Stelzner, Lyon, and Strauss: Anat. Rec. 205:191A–192A, '83). Local effects of LDH should be similar for both the cut optic and cut TE axons. Other factors were tested that may contribute to the lack of TE axonal regeneration. Our results indicate that optic regeneration itself (n = 8), postaxotomy retrograde cell death of TE neurons (n = 6), deafferentation of the tectum of optic axons, and potential sprouting within tectal targets by intact contralateral TE axons (n = 10) are not critical factors aborting TE axonal regeneration. TE axons filled with HRP at chronic periods after LDH (n = 4) terminate anomalously near the LDH border. Many of these endings are similar to reactive endings or terminal clubs seen after axonal injury in the mammalian CNS. Our results suggest that this disparity in regenerative ability of optic and TE axons may be related to a difference in the responsive ability of these cell types to initiate or maintain axonal elongation after axotomy within the amphibian CNS environment.
Interhemispheric connections in the visual cortex of the squirrel monkey (Saimiri sciureus)
Authors: Gould Harry J. , Weber Joseph T. , Rieck Richard W.
Published: January 2005

The callosal connections within the posterior parietal and occipital cortices were studied in the squirrel monkey with horseradish peroxidase tracing techniques. The data were evaluated with particular emphasis on the relationship of major callosal connections along the 17–18 border. The overall pattern of callosal connections in the squirrel monkey also was compared with callosal patterns in other New World simians. Our results show that the dense band of callosal connections along the 17–18 border in the squirrel monkey differs from the connections observed in other New World monkeys in that it is virtually confined to area 18 and avoids area 17. In addition to a continuous band of callosal connections in area 18 that parallels the 17–18 border, rostral extensions of the band are oriented perpendicular to the 17–18 border and present an obvious periodicity. The remaining parieto‐occipital cortex contains a complex pattern of callosal connections that is strikingly similar to patterns reported for other New World monkeys. Thus, it is likely that the dorsolateral extrastriate visual cortex in the squirrel monkey is organized in a manner similar to that found within other New World monkeys.
Area postrema of the goldfish, Carassius auratus: Ultrastructure, fiber connections, and immunocytochemistry
Authors: Morita Yasuhiro , Finger Thomas E.
Published: January 2005

The area postrema in goldfish is a dorsal midline structure in the caudal medulla spanning the level of the obex. As in other vertebrates, the sinus capillaries of the area postrema in goldfish are fenestrated. In goldfish, however, the area postrema is organized in a unique laminar fashion; from superficial to deep: meninx, vasculature, palisade layer, cell body layer, and ventral neuropil layer.

Virtually all of the neurons of the area postrema exhibit tyrosine hydroxylase‐like immunoreactivity. Each immunoreactive neuron is essentially bipolar, with a short apical dendrite extending dorsally to reach the external basal lamina of the capillaries and a basal dendrite reaching into the subjacent layer of neuropil. The apical dendrites have no synaptic specializations and probably function as interoceptors detecting blood‐borne chemicals that leak out of the fenestrated capillaries. The basal dendrites receive synaptic input both within the neuropil of the area postrema and in the commissural nucleus of Cajal into which they extend. Primary afferent fibers of the subdiaphragmatic branches of the vagus nerve terminate within the area postrema and commissural nucleus. Thus the neurons of the area postrema may serve not only as direct chemoreceptive interoceptors but may also receive input from other visceral afferent systems.
The combined effects of unilateral enucleation and rearing in a “dim” red light on synapse‐to‐neuron ratios in the rat superior colliculus
Authors: Mackay D. , Bedi K. S.
Published: January 2005

Rats whose right eyes were enucleated on day 1 after birth and nonenucleated rats were raised in either “light” or “dark” (red light) conditions from birth until 39 days of age. This resulted in 4 groups of animals: light‐reared nonenucleated, light‐reared enucleated, dark‐reared nonenucleated, and dark‐reared enucleated. At 39 days of age, the animals were killed by perfusion with 2.5% sodium cacodylate buffered glutaraldehyde. The superior colliculi were dissected out and processed for embedding in resin. Stereological procedures at the light and electron microscopical levels were used to estimate the synapse‐to‐neuron ratios in the superficial layers of these colliculi.

Light‐reared, nonenucleated rats had about 1,850 synapses‐per‐neuron in both the right and left superior colliculi. Rearing nonenucleated rats in the dark reduced this value to about 1,200.

Enucleated rats reared in the light showed a differential response in the 2 colliculi. Thus, the contralateral (to the enucleated eye) colliculi showed a decrease, whereas the ipsilateral colliculi showed an increase in the synapse‐to‐neuron ratio compared with light‐reared, nonenucleated rats.

When enucleated rats were reared in the red light, there was a decrease in the ratio in both colliculi, although the extent of this decrease was more marked in the contralateral than the ipsilateral colliculi. However, the decrease in the contralateral colliculi was not significantly greater than that observed in the corresponding colliculi from dark‐reared, nonenucleated rats.

These results provide useful information on the combined and separate effects of unilateral enucleation at around birth and dark (red light) rearing during early life on the interneuronal connectivity of both the ipsi‐ and contralateral superior colliculi of rats. They also show the vast importance of visual stimulation for the normal development of the subcortical visual centers.
Structural features of the terminal loop region of frog retinal rod outer segment disk membranes: III. Implications of the terminal loop complex for disk morphogenesis, membrane fusion, and cell surface interactions
Authors: Corless Joseph M. , Fetter Richard D.
Published: January 2005

The perimeter of rod outer segment (ROS) disks displays a two‐dimensional lattice of components referred to as the terminal loop complex (Corless, Fetter, Zampighi, Costello, and Wall‐Buford: J. Comp. Neurol 257: 9–23, '87b). We take the view that this pattern of structural organization reflects the mechanism(s) whereby the disk perimeter is defined and constructed. Herein we develop and partially evaluate a generalized template mechanism of disk perimeter development, to account for the structure and the axial alignment of both marginal and incisural domains. Components of the terminal loop complex are conceived as the morphogens that determine the location and guide the differentiation of the disk perimeter. Briefly, we postulate that transmembranous components of the terminal loop complex are present within the reflection of plasmalemma that forms the base of the rod outer segment. These components interact with the cytoplasmic template provided by the perimeter lattice present along the lower surface of the most basal disk, thereby propagating the lattice and creating an extracellular template. The latter is then available to interact with corresponding elements distributed, within the apical surface of the adjacent disk precursor evagination. The progressive interaction and alignment of these extracellular domains form the scaffolding that guides the restructuring of the plasmalemma, to form the mature disk margin topology. Successive repetitions of this process are seen to produce an axial stacking of disks whose perimeters are aligned and ensheathed by a two‐dimensional net.

Several predictions of the model are developed and evaluated.
Distribution of neuropetide Y‐like immunoreactivity in the hypothalamus of the adult golden hamster
Authors: Sabatino Frank D. , Murnane Joan M. , Hoffman Roger A. , McDonald John K.
Published: January 2005

The distribution of neuropeptide Y (NPY)‐like immunoreactivity within the hypothalamus of the adult golden hamster was investigated with conventional immunohistochemical techniques. Neuropeptide Y immunoreactive cell bodies were found in greatest numbers in the arcuate nucleus while a few stained perikarya were seen in the internal and subependymal zones of the median eminence. Isolated perikarya were observed in the anterior commissure and supracommissural portion of the interstitial nucleus of the stria terminalis. Immunoreactive axons were located throughout the hypothalamus with the highest concentrations in the subependymal and internal zones of the median eminence, the interstitial nucleus of the stria terminalis, the medial preoptic area, and in the following nuclei: periventricular, suprachiasmatic, paraventricular, perifornical, median preoptic, and arcuate. Moderate to dense plexuses of immunoreactive fibers were observed in the anterior, lateral, and posterior hypothalamic areas and in the infundibular stalk. The supraoptic nucleus and lateral preoptic area displayed a small number of labeled axons whereas the ventromedial nucleus contained only a few fibers. NPY immunoreactive fibers were present in the optic tract and in the dorsomedial aspect of the optic chiasm. Labeled fibers penetrated the ependymal lining of the third ventricle throughout the ventral aspect of the periventricular zone. Additional fibers were observed in the pia lining the ventral aspect of the hypothalamus. This systematic analysis of hypothalamic NPY immunoreactivity in the adult golden hamster suggests that a portion of the labeled fibers display a distribution that is similar to previously described noradrenergic fibers in the hypothalamus.
Distrubution and size of thalamic neurons projecting to layer I of the auditory cortical fields of the cat compared to those projecting to layer IV
Authors: Mitani Akira , Itoh Kazuo , Mizuno Noboru
Published: January 2005

The distribution of thalamocortical neurons projecting to layer I of the cat auditory cortical fields was examined by the horseradish peroxidase (HRP) method. After HRP injection into layer I of the primary auditory cortex (AI), HRP‐labeled neuronal cell bodies were distributed mainly in the medial, dorsal, and ventrolateral divisions of the medial geniculate nucleus CMGN and suprageniculate nucleus (Sg), and additionally in the lateral and medial divisions of the posterior group of the thalamus (Pol and Pom), lateroposterior thalamic nucleus (Lp), and nucleus of the brachium of the inferior colliculus (BIN). After HRP injection into layer I of the second auditory cortex (AII), labeled neurons were seen mainly in the medial, dorsal, and ventrolateral divisions of the MGN and Sg and additionally in the Pom, Lp, and BIN. After HRP injection into layer I of the anterior auditory field (AAF), labeled neurons were located mainly in the medial and dorsal divisions of the MGN, Sg, Pol, and BIN, and additionally in the ventrolateral divisions of the MGN, Pom, and Lp. After HRP injection into layer I of the dorsal part of the posterior ectosylvian gyrus (Epv), labeled neurons were observed chiefly in the medial and dorsal divisions of the MGN, Sg, and Lp and additionally in the ventrolateral division of the MGN, Pom, and BIN. After HRP injection into layer I of the ventral part of the posterior ectosylvian gyrus (Epv), labeled neurons were distributed chiefly in the medial and dorsal divisions of the MGN and Pol and additionally in the ventrolateral division of the MGN, Sg, and BIN. Thus no labeled neurons were found in the ventral division of the MGN after HRP injection into layer I of all auditory cortical fields examined in the present study. The average soma diameters of neurons that were labeled after HRP injection into layer I were statistically smaller than those of neurons that were labeled after HRP injection into layer IV.
Visual system of the channel catfish (Ictalurus punctatus): II. The morphology associated with the multiple optic papillae and retinal ganglion cell distribution
Authors: Dunn‐meynell A. A. , Sharma S. C.
Published: January 2005

The retinal organization associated with the multiple optic papillae of the catfish Ictalurus punctatus was examined. In each retina from ten to 17 papillae form an oval ring (which is wider dorsoventrally than mediolaterally). The dorsalmost papilla in this ring lies at the center of the retina. In addition, up to seven small papillae lie within the ring. Bundles of fibers leave the neural retina via the papillae. These bundles remain separate as they pass through the distal portions of the neural retina and then merge before passing through the choroid. Bundles running through dorsal papillae receive fibers from a roughly wedge‐shaped retinal area; bundles running through ventral papillae receive fibers from a small area of central retina and a disproportionately large area of peripheral retina. A band of high ganglion cell density was observed extending between the nasal and temporal poles of the retina. No correlation was found between the retinal areas contributing fibers to the bundles of axons emerging from individual papillae and the areas of high cell density. Furthermore, no correlation was found between the average area of the retinal ganglion cells and the ganglion cell density. From HRP preparations and axon counts we estimate that each retina of 95‐mm catfish contains about 50,000 ganglion cells.
Choline acetyltransferase immunoreactivity in the rat thalamus
Authors: Levey Allan I. , Hallanger Ann E. , Wainer Bruce H.
Published: January 2005

The distribution of choline acetyltransferase immunoreactivity in the rat thalamus was investigated by using a specific monoclonal antibody and was compared with the pattern of acetylcholinesterase staining. The only choline acetyltransferase‐immunoreactive cell bodies in the thalamus were in the medial habenula. A wide range of densities of immunoreactive fibers and varicosities was found. The highest densities of stained varicosities were in the anteroventral, reticular, lateral mediodorsal, and intralaminar nuclei. At the other extreme, the anterodorsal, ventroposteromedial, and paraventricular nuclei were almost devoid of immunoreactive varicosities. A light density of fibers was observed in several medial nuclei, including parataenial, reuniens, and gelatinosus. Most other nuclei contained moderately dense regions of varicose fibers that were often heterogeneous or patchy. The pattern of choline acetyltransferase immunoreactivity in the thalamus was in general similar to that of acetylcholinesterase. A marked discrepancy, however, was found in the anterodorsal nucleus, which was intensely stained for acetylcholinesterase but contained no apparent choline acetyltransferase immunoreactivity. Numerous physiologic studies have demonstrated striking effects of acetylcholine on thalamic activity. The present study provides a description of choline acetyltransferase‐immunoreactive structures in the thalamic nuclei, providing a first step toward elucidating the anatomical basis for the physiologic and functional importance of cholinergic transmission in the thalamus.
Quantitative analysis of the choline acetyltransferase‐immunoreactive axonal network in the cat primary visual cortex: I. Adult cats
Authors: Stichel C. C. , Singer W.
Published: January 2005

The laminar distribution of cholinergic axons was analyzed quantitatively in the visual cortex of adult cats by using immunocytochemistry with a monoclonal antibody against choline acetyltransferase (ChAT). ChAT (+) fibers and varicosities were counted at different locations within area 17 and the distribution patterns in various animals were compared. Choline acetyl‐transferase‐immunoreactivity was localized in fine, varicose fibers, which were present in all layers of the visual cortex. The density of labeled fibers was highest in layer I, which contained 14% of all fibers and 19.5% of all varicosities, and decreased toward deeper layers. The number of varicosities decreased more markedly toward deeper layers than the frequency of fibers. These distribution patterns were very consistent, showing only slight intra‐ and interindividual variability.
Quantitative analysis of the choline acetyltransferase‐immunoreactive axonal network in the cat primary visual cortex: II. Pre‐ and postnatal development
Authors: Stichel C. C. , Singer W.
Published: January 2005

The pre‐ and postnatal development of cholinergic projections was investigated in the cat striate cortex by applying immunohistochemical methods based on a monoclonal antibody against choline acetyltransferase (ChAT).

The earliest age investigated was gestational day 54. At this stage a sparse network of ChAT(+) fibers was distributed throughout the striate cortex. Subsequent postnatal maturation of ChAT(+) fibers was characterized by an increase in fiber density that started in layer VI and gradually progressed toward more superficial layers. By 4 weeks of age the density of ChAT(+) fibers and varicosities had reached adult levels in layers V and VI but was still subnormal in layers I–IV. The mature pattern of cholinergic innervation was established by 13 weeks of age. There was no evidence for developmental gradients in the anteroposterior and mediolateral directions within area 17. These results indicate that the cholinergic projection to striate cortex develops continuously in an inside‐out sequence as is characteristic for most cortical maturation processes. There was no indication that striate cortex receives an especially dense cholinergic input during the critical period.
Interhemispheric connections of the somatosensory cortex in the rabbit
Authors: Ledoux M. S. , Whitworth R. H. , Gould H. J.
Published: January 2005

Corpus callosal connections of somatosensory cortex were studied in rabbits by combining anatomical tracing and electrophysiological mapping in the same animals. The results show that callosal connections are unevenly distributed in SI and SII. In SI, the representations of all body surfaces caudal to the neck and midline structures of the head have dense callosal connections. Conversely, connections are sparse to absent within representations of laterally positioned surfaces of the head, such as the sinus hairs, vibrissae, and nonmidline portions of the lips. Almost all of SII has dense callosal connections; only the representations of the vibrissae and sinus hairs have moderate callosal connections.

The laminar distribution of callosal connections in rabbit SI and SII is similar to that observed in other mammals. Callosal terminations extend from the inner portion of layer I to the outer portion of layer VI, are moderately denser in the supragranular layers, and are sparse in layer IV. Callosally projecting cells are found predominantly in layers II, III, and V and are sparse in layers IV and VI.

These data further emphasize the direct correspondence between the pattern of callosal connections in SI and the functional importance of particular body surfaces. Hence, representations of body surfaces important in the exploration of the environment are relatively free of callosal connections, whereas representations of midline and more lateral surfaces, less significant in tactile exploration, receive dense callosal connections.

Callosal connections in rabbits are distributed extensively throughout responsive koniocortical regions rather than being relegated to distinct, specialized regions of “unresponsive” dysgranular cortex as in rodents.
Effect of tetraploidy on dendritic branching in neurons and glial cells of the frog, Xenopus laevis
Authors: Szaro Ben G. , Tompkins Robert , Szaro Ben G.
Published: January 2005

Morphological aspects of four different groups of Golgi impregnated brain cells from a tetraploid strain of Xenopus laevis frogs were compared to analogous cells in comparably sized diploid frogs. The cells examined included neurons from the telencephalon, caudal hypothalamus, and optic tectum, and radial glial cells from the optic tectum. The brains of tetraploid frogs appeared grossly normal and were the same size and contained similar cell types as diploid brains. As observed in previous studies on polyploid amphibia, somal diameters increased significantly in tetraploid cells for each of the four groups of cells examined. Also, the total length of the dendritic arbors in tetraploid brain cells increased significantly by factors ranging from 1.4 to 2.4 times the total length of the analogous processes in diploid cells. Tetraploid neurons in the telencephalon and hypothalamus increased their arbor lengths predominantly by increasing the number of dendritic branches, while maintaining the average distance between branch points in the dendritic segments. In contrast, the tetraploid large pear‐shaped neurons in the optic tectum had significantly longer terminal dendritic segments than the analogous diploid neurons, although these tetraploid neurons maintained their average number of dendritic segments per cell. Tetraploid tectal radial glial cells appeared to increase both their number of branches and the lengths of their terminal segments. Thus, the mode by which tetraploid brain cells achieved longer dendritic arbors varied from cell type to cell type. These results suggest a hypothetical basis for possible effects of genomic size on vertebrate brain structure and evolution at the cellular level.
Patterns of angiogenesis in neural transplant models: I. Autonomic tissue transplants
Authors: Krum Janette M. , Rosenstein Jeffrey M.
Published: January 2005

Functional vascular connections must form rapidly to prevent ischemic damage to grafted neural tissues. The temporal sequence by which transplant circulation is re‐established provides information about the angiogenic capacity of either intact or damaged CNS blood vessels. This study compares the time course and mechanism of vascular reperfusion in allografts of superior cervical ganglia or adrenal medulla inserted either into the fourth ventricle or directly into the parietal cortex of perinatal rats. Tritiated thymidine was administered lo recipients to determine angiogenic patterns at various postoperative time periods. After processing for light microscopic autoradiography, host and graft endothelial labelling indices were determined in order to establish the temporal sequence and location of vascular proliferation, Correlative electron microscopy depicted the morphological changes in transplant vasculature. Some recipients were prelabelled with 3H thymidine prior to transplantation to determine if host vessels invaded the grafts.

Intraventricular graft vessels initially collapsed but sustained minimal ischemic damage and were completely reperfused by 24 hours postoperative. Adjacent intact host vessels attained peak 3H thymidine incorporation at 20 hours. Intrinsic graft vessels were radioactively labelled only after 48 hours. Intraparenchymal transplants surrounded by minimal trauma exhibited a similar temporal sequence of reperfusion and host endothelial proliferation. Intrinsic graft vessels in intraparenchymal grafts sustained more severe damage. With increased trauma, a concomitant delay in graft reperfusion time was observed. Grafts within prelabelled hosts rarely contained any labelled endothelium, indicating that anastomotic connections were made between original, intrinsic graft vessels and nearby host vascular sprouts.

This study demonstrates that mature autonomic tissue stimulates the growth of adjacent host vessels when transplanted to undamaged brain surfaces. The anastomosis of nascent host vessels with pre‐existing graft vessels is responsible for the rapid re‐establishment of circulation within the transplants. A similar mechanism occurs within intraparenchymal grafts, although the rapidity of reperfusion appears to be predicated on the amount of trauma present at the graft site.
Neuronal maturation in the normal and hypothyroid rat cerebellar cortex studied with monoclonal antibody MIT‐23
Authors: Gravel Claude , Hawkes Richard
Published: January 2005

By immunocytochemistry we have studied the expression of the mitochondria‐associated polypeptide MIT‐23 during the postnatal development of the normal and hypothyroid rat cerebellar cortex, in afferent fibers, and also in neurons of the cerebellar nuclei. The glial cells are never immunoreactive. In all neurons of the cerebellar cortex, MIT‐23 expression always occurs after the final mitosis and migration are complete, and persists throughout adult life. Almost all MIT‐23 expression begins postnatally. A few Purkinje cells are already immunoreactive at birth and the rest begin expression during the following two days. Immunoreactive Golgi and granule cells are found from postnatal day 4 (P4), basket cells from P10, and stellate cells from P16. Purkinje cells from different anteroposterior regions of the vermis express different levels of MIT‐23 with higher staining intensities in lobules I to IV. These differences appear early in development and are retained in the adult. MIT‐23 expression in the hypothyroid cerebellar cortex differs from that in control animals only in minor ways. However, sections immunoperoxidase‐stained with anti‐MIT‐23 antibody reveal that, in addition to previously reported alterations in cerebellar development due to a shortage of thyroid hormones, Purkinje cell axonal development is slowed down in the hypothyroid condition, and occasional Purkinje cells in normal and especially in hypothyroid animals have their somata and or dendrites in ectopic locations. Analysis of these cells reveals a preferential direction of dendritic trunk growth in the direction of the molecular layer. Furthermore, secondary branching of ectopic dendrites is confined exclusively to the developing molecular layer, as in normal Purkinje cells, thus suggesting that neither the mature nor immature granule cell environment is sufficient to sustain normal dendritic development.
Functional morphology of frog retinal ganglion cells and their central projections: The dimming detectors
Authors: Stirling R. V. , Merrill E. G.
Published: January 2005

Intracellular recordings were made from frog retinal ganglion cell axons in the optic nerve. Following electrophysiological characterisation of receptive field properties, HRP was injected into the axon, and the brain and retina were subsequently stained. The morphologies of retinal ganglion cells, their dendritic domains, and their central projections were determined with light microscopy, and the optic nerve portion of the ganglion cell axon was examined with electron microscopy. This paper describes the structural and functional features of one ganglion cell class, the off units (class IV or dimming detectors) whose characteristic response is a preferential sensitivity to decreasing light intensity within the receptive field. Typical receptive field diameter of these units was about 16° with a range of 3° to more than 30°. Examination of the spatial characteristics of their receptive field centers and surrounds showed that the class IV cells could be divided into two broad categories. Linear class IV cells did not respond to phase‐reversal of a fine grating pattern. These linear cells also tended to have clear surround suppression: illumination of the surround diminished their response to light off at the center. The second group responded briskly to each reversal of the fine grating pattern, whatever its position within the receptor field center. These nonlinear class IV cells did not show surround suppression, but rather they had surround antagonism and they responded to light on in the surround. Nonlinear units were much more frequently recorded in frogs maintained in summer conditions (12‐hour days, constant 20°C temperature).

In spite of this functional heterogeneity, all cells had similar morphology consisting of (1) a large ganglion cell with a large dendritic arbor (400–1,000 μm) confined to a single stratum in the outer third of the inner plexiform layer, (2) a medium‐sized axon (2.4‐μm diameter), (3) a smallish pretectal arbor, and (4) a large tectal arbor (300–700 μm) at layer 8.
Ultrastructural study of remodeled rubral afferents following neonatal lesions in the rat
Authors: Naus C. G. , Flumerfelt B. A. , Hrycyshyn A. W.
Published: January 2005

Following neonatal hemicerebellectomy, an aberrant ipsilateral cerebellorubral projection develops that maintains the topographic specificity of the normal contralateral projection. Similarly, neonatal lesions of the sensorimotor cortex lead to the appearance of an aberrant contralateral corticorubral projection that mirrors the topographic specificity of the normal ipsilateral input. The specificity of synaptic localization in these aberrant projections was studied by use of ultrastructural visualization of anterogradely transported HRP‐WGA. Following neonatal ablations, adults received HRP‐WGA injections in the unablated deep cerebellar nuclei or sensorimotor cortex. After 48 hours, animals were sacrificed and processed for ultrastructural localization of anterogradely transported HRP‐WGA. In hemicerebellectomized animals, both the contralateral and ipsilateral interpositorubral projections terminated on the somatic and proximal dendritic membrane of magnocellular neurons. Some of these labeled synaptic terminals were located on somatic and dendritic spines. Following HRP‐WGA injection in the unablated nucleus lateralis, anterogradely labeled synaptic terminals were located bilaterally on small‐ to medium‐sized dendrites of parvicellular neurons. Injection of HRP‐WGA in the remaining sensorimotor cortex of animals that had undergone neonatal unilateral ablation of the sensorimotor cortex resulted in labeled corticorubral synaptic terminals that contacted distal dendrites of ipsilateral and contralateral parvicellular neurons. These results demonstrate that, following neonatal deafferentation of the rat red nucleus, the topographic specificity of the aberrant rubral afferents is accompanied by a specificity of synaptic localization on discrete membrane areas of rubral neurons.
Serotonin‐containing structures in the nucleus raphe dorsalis of the cat: An ultrastructural analysis of dendrites, presynaptic dendrites, and axon terminals
Authors: Chazal G. , Ralston H. J.
Published: January 2005

In the nucleus raphe dorsalis of the cat, an electron microscopic immunocytochemistry method was used to identify the fine structure of serotoninergic dendritic profiles and axon terminals analyzed in serial sections. Two classes of serotoninergic dendrites were distinguished in the nucleus. The first class was constituted by conventional serotonin (5‐HT) dendrites that were contacted by unlabeled axon terminals containing differing populations of synaptic vesicles. The second class consisted of serotoninergic dendrites that contained vesicles in their dendritic shafts. Such 5‐HT dendrites were further subdivided into two groups according to their synaptic contacts. In some 5‐HT vesicle‐containing dendrites, the vesicles were densely packed in small clusters and were associated with a well‐defined synaptic specialization. These dendrites were classified as serotoninergic presynaptic dendrites and established synaptic contacts with unlabeled and labeled dendrites and were contacted by unlabeled axon terminals. In other 5‐HT vesicle‐containing dendrites, extensive serial section examination showed that the vesicles could be observed near the membrane but were never found to be associated with any synaptic membrane specialization. Serotoninergic axon terminals that were presumed to be recurrent collaterals of 5‐HT neurons were present in the nucleus. Some of them were observed in synaptic contact with dendrites or dendritic protrusions whereas others did not exhibit synaptic specializations. The existence of serotoninergic dendrodendritic synaptic contacts and axon terminals suggests direct local interactions between serotoninergic neurons within the nucleus raphe dorsalis.