bluuebunny/crossref_metadata_2025 huggingface dataset:
Intracellular labeling of neurons in the medial accessory olive of the cat: II Ultrastructure of dendritic spines and their gabaergic innervation
Authors: De Zeeuw C. L. , Ruigrok T. J. H. , Holstege J. C. , Jansen H. G. , Voogd J.
Published: January 2005

In order to describe the morphology of dendritic spines of identified neurons in the cat inferior olive together with their gamma‐aminobutyric acid (GABA) synaptic input, a technique was used combining intracellular labeling of horseradish peroxidase with postembedding gold‐immunocytochemistry. With this technique physiologically identified olivary cells were reconstructed with the light microscope, and the horseradish peroxidase reaction product and immunogold labeling were subsequently examined in serial sections at the ultrastructural level. In addition, a degenerating neuron was observed, resulting in a triple labeling in single ultrathin sections.

Quantitative and three‐dimensional analysis showed that the dendritic spines were composed of long, thin stalks ending in one or more spine heads. The spines of cells located in the caudal half of the medial accessory olive (type I cells, characterized by dendrites which run away from the soma) were found to be less complex than those, of cells located rostrally in this olivary subnucleus (type II cells, characterized by dendrites which tend to turn back towards the soma). Most, if not all, of the spines of both cell types were located within glomeruli. On average, the spines within individual glomeruli originated from 6 different dendrites (with a maximum of 8). Different spines within the same glomerulus were never derived from different dendrites of the same olivary neuron, but single spines frequently gave rise to several spine heads, which could be located either within different glomeruli or inside a single glomerulus, The glomerular spine heads originating from the same spine were rarely located near one another. All spines and most of the spine heads were contacted by both GABAergic and non‐GABAergic terminals. Most of the GABAergic terminals contained pleomorphical vesicles and displayed symmetric, synapses whereas the non‐GABAergic terminals showed usually round to oval vesicles and asymmetric synapses.
Gonadotropin‐releasing hormone (GnRH) immunoreactive system in the brain of the dwarf gourami (Colisa lalia) as revealed by light microscopic immunocytochemistry using a monoclonal antibody to common amino acid sequence of GnRH
Authors: Oka Yoshitaka , Ichikawa Masumi
Published: January 2005

The present paper aims to give a morphological basis for the study of the terminal nerve system and its relation to the whole gonadotropin‐releasing hormone (GnRH) immunoreactive (ir) neuronal system. We examined the GnRH‐ir neuronal system of a tropical fish, the dwarf gourami, by using a recently developed monoclonal antibody against GnRH (LRH13) which recognizes the amino acid sequence common to all known variants of GnRH (Park and Wakabayashi, Endocrinol. Jpn. 33:257–272, '86). The ganglion cells of the terminal nerve (TN‐ggl cells) in the transitional area between the olfactory bulb and the telencephalon reacted strongly with the LRH13. A distinct bundle of axons emanating from the TN‐ggl cells ran caudally through the ventral telencephalon and the preoptic area. Some of these axons entered the optic nerve and innervated the retina. The remaining axons continued caudally to enter the hypothalamus and the midbrain. A second group of GnRH‐ir cell bodies was found in the preoptic area. A distinct bundle of GnRH‐ir fibers originating from these cell bodies innervated the pituitary. This pathway is equivalent to the preoptico‐infundibular pathway of other vertebrates, and the GnRH in this pathway is presumed to function as hypophysiotrophic hormone to facilitate the release of gonadotropins from the pituitary. The distribution of GnRH‐ir fibers in the brain was extensive. Most fibers apparently originated from the TN‐ggl cells and covered various brain regions from the olfactory bulb to the spinal cord. They were especially abundant in the olfactory bulb, ventral telencephalon, preoptic area, optic tectum, and some hypothalamic areas. Thus, GnRH might function as a neuromodulator and/or neurotransmitter in these areas. The abundant GnRH‐ir fibers in the ventral telencephalon and the preoptic area might affect some aspects of sexual behavior, since these areas have been suggested to be involved in the control of sexual behavior in teleosts.
Development of compartmentalized innervation of the rat gluteus maximus muscle
Authors: English Arthur W. M.
Published: January 2005

The innervation territories of the nerves to the gluteus maximus muscle were investigated in neonatal rats by using evoked electromyographic mapping techniques. Similar methods were employed to determine the terminal fields of individual motoneurons. Both at birth and after the period of neuromuscular synapse elimination, rat gluteus maximus is partitioned by its two muscle nerves. Each of these partitions is further divided into neuromuscular compartments by the primary branches of the muscle nerves. The terminal fields of individual motoneurons are about as well localized in early neonates as in 26 day‐old animals. Intracellular records from gluteal muscle cells reveal that some myotubes in a narrow region near the center of the muscle receive inputs from both of the muscle nerves during the period of polyneauronal innervation. Such cross‐compartmental innervation could be demonstrated only until the eighth postnatal day, even though polyneuronally innervated muscle cells were found as late as postnatal day 18. Analysis of the trajectories of individual axons filled with horseradish peroxidase indicates that they branch into only one primary branch of the nerves to gluteus maximus, both in newborn and 14 day‐old pups. The innervation of gluteus maximus at birth is essentially restricted to neuromuscular compartments. Synapse elimination probably plays a minor role in establishing neuromuscular compartments.
Selective labeling of sensory hair cells and neurons in auditory, vestibular, and lateral line systems by a monoclonal antibody
Authors: Kornblum Harley I. , Corwin Jeffrey T. , Trevarrow Bill
Published: January 2005

This study reports that zn‐1, a monoclonal antibody, labels hair cells but not supporting cells in the inner ear and the lateral line of the axolotl salamander, Ambystoma mexicanum. Zn‐1 immunocytochemically labels the cytoplasm and stereocilia of mature hair cells in the sacculus, in the utriculus, and in the mechanoreceptive neuromast organs of the lateral line. Lower levels of labeling mark newly formed hair cells in the periphery of the sacculus and in regenerating neuromasts. Zn‐1 also selectively labels neuronal processes and perikarya in the lateral line nerves and ganglia and the VIIIth cranial nerve and ganglion. Processes and perikarya are labeled by zn‐1 in the dorsolateral medulla oblongata, at sites of termination of the afferent octaval and lateral line neurons. Western blot analysis revealed that zn‐1 labels one or more proteins with molecular weights of 80 and 160 kDa. The identity of these protein bands remains to be determined. The presence of a specific epitope expressed in both hair cells and neurons, but not in supporting cells, in the vestibular and auditory epithelia of the ear and in the mechanoreceptive neuromasts of the lateral line suggests shared cytogenetic heritages. These findings are consistent with a close evolutionary relationship between otic and lateral line senses, such as that inherent to the theoretical evolutionary scheme outlined in van Bergeijk's “acousticolateralis hypothesis.” The protein recognized by zn‐1 is as yet unidentified, but its conservative evolution suggests that it may serve an important function in the statoacoustic and lateral line systems.
Rod bipolar cells in the mammalian retina show protein kinase C‐like immunoreactivity
Authors: Greferath Ursula , Grünert Ulrike , Wässle Heinz
Published: January 2005

An antibody directed against protein kinase C (PKC) was applied to various mammalian retinae. In the cat, rat, rabbit, and macaque monkey we found PKC‐like immunoreactivity in bipolar cells which had the morphology of rod bipolar cells; in the rat some amacrine cells were also immunoreactive. In the outer plexiform layer, labeled dendrites were always the central elements of the rod spherule invagination, and in the inner plexiform layer only rod bipolar axons and their axon terminals were immunoreactive. The antibody against PKC thus can be used to distinguish rod bipolar cells from cone bipolar cells.

The antibody against PKC was used to determine the densities of rods and rod bipolar cells in the cat retina. In the central retina we found a rod to rod bipolar ratio of 16 to 1, in the periphery the ratio increases to 25 to 1.

In freshly dissociated retina, cells with rod bipolar morphology could be identified; these cells were also labeled with the anti‐PKC antibody. Hence, PKC‐like immunoreactivity can be used to recognize rod bipolar cells in vitro.
Organization of serotonin 1A and 1B receptors in the nucleus of the solitary tract
Authors: Manaker Scott , Verderame Holly M.
Published: January 2005

We utilized 3H‐8‐hydroxy‐N,N‐dipropyl‐2‐aminotetralin (3H‐DPAT) and 125I‐iodocyanopindolol (125I‐CYP) to label serotonin (5HT) 1A and 5HT1B receptors, respectively, in sections of the rat brain after characterizing the pharmacologic specificity of these agents. We then used quantitative autoradiography to measure the concentrations of 5HT1A and 5HT1B receptors in individual subnuclei of the nucleus of the solitary tract (NTS) and adjacent structures of the dorsal vagal complex. The highest 5HT1A receptor concentrations were observed within the central and intermediate subnuclei of the NTS, with low quantities of 3H‐DPAT binding sites observed in the hypoglossal nucleus and dorsal motor nucleus of the vagus. In contrast, the density of 5HT1B receptors was relatively homogeneous through all NTS subnuclei, with the highest concentrations localized within the ventrolateral subnucleus. The hypoglossal and dorsal motor nuclei had slightly higher 5HT1B receptor densities than the NTS subnuclei, whereas the area postrema had a very low density. These data suggest that 5HT1A receptors are organized in a manner consistent with the cytoarchitectural and hodological parcellation of the NTS into individual subnuclei. The high concentrations of 5HT1A receptors in the central and intermediate subnuclei suggest a role for these receptors in medullary reflex pathways subserving deglutition. The relatively high density of 5HT1B receptors in the ventrolateral subnucleus suggests that these receptors modulate respiratory neurons, whereas the diffuse organization of 5HT1B receptors in the remaining subnuclei suggests that they are associated with central 5HT afferent pathways to the NTS. Further studies will be required to understand the physiologic role of 5HT1 receptors within the NTS.
Effects of cochlea removal on GABAergic terminals in nucleus magnocellularis of the chicken
Authors: Code Rebecca A. , Durham Dianne , Rubel Edwin W.
Published: January 2005

The effects of unilateral cochlea removal on GABA‐immunoreactive (GABA‐I) terminals in nucleus magnocellularis (NM) of the chick were assessed by immunocytochemical (ICC) techniques. Posthatch chicks (5–8 days old) survived from 1–37 days following unilateral cochlea removal. In the ipsilateral NM, the density of GABA‐I terminals appeared to increase relative to normal controls. 10–37 days after cochlea removal. However, most of that increase could be attributed to a decrease in cell size, cell number, and volume of the nucleus as a result of deafferentation. In the contralateral NM, the density of GABA‐I terminals decreased relative to the ipsilateral NM and to normal animals 1–21 days after cochlea removal. The number of GABA‐I terminals per NM neuron also decreased in the contralateral NM while that in the ipsilateral NM was comparable to normal controls. To ascertain whether these changes represented changes in the number of terminals or in the amount of GABA contained within the terminals, we also examined these terminals using an antibody to glutamic acid decarboxylase (GAD), the biosynthetic enzyme for GABA. Following unilateral cochlea removal, there was no difference in the density of GAD‐I terminals in NM between the two sides of the brain for any of the survival times. Similarly, bilateral cochlea removal had no discernible effect on the density of GABA‐I terminals in NM. These data suggest that unilateral deafferentation may temporarily downregulate the biosynthesis of GABA in the contralateral NM.
Immunohistochemical distribution of calcium‐activated neutral proteinases and endogenous CANP inhibitor in the rabbit hippocampus
Authors: Fukuda Takaichi , Adachi Eijiro , Kawashima Seiichi , Yoshiya Ikuto , Hashimoto Paulo H.
Published: January 2005

Intracellular accumulation of Ca2+ after brain ischemia is regarded as one of the principal causes of neuronal death, but details of the intracellular events occurring after Ca2+ accumulation have not yet been described. We propose that a calcium‐activated neutral proteinase which can degrade neuronal cytoskeletal proteins might link Ca2+ accumulation and irreversible injury of the neuronal intracellular structure. First, therefore, we examined the distribution of calcium‐activated neutral proteinase in normal brains.

Immunohistochemical distribution of calcium‐activated neutral proteinases (CANP) with high and low sensitivity to Ca2+ (m̈CANP and mCANP) and of endogenous CANP inhibitor was investigated in the dorsal hippocampus of the rabbit. μCANP‐immunoreactivity was detected in almost all of the pyramidal cells and granule cells and in some other neurons. A full‐length staining from perikarya to dendrites was shown in μCANP ‐positive neurons.

mCANP‐immunoreactivity was found mainly in four kinds of hippocampal interneurons: (1) basket cells in the stratum oriens of Ammon's horn, (2) pyramidal basket cells at the boundary of pyramidal cell layer and stratum oriens, (3) polymorphic cells in the hilar region of dentate gyrus, and (4) pyramidal or fusiform basket cells at the inner boundary of the granule cell layer and the hilar region. The distribution of these four kinds of neurons was similar to that of parvalbumin‐containing GABAergic neurons.

CANP inhibitor immunoreactivity was confined to pyramidal cells in the CA3–CA3c region and some hilar neurons. Neuropil areas corresponding to commissural and association fiber terminals from CA3 pyramidal cells and hilar neurons, i.e., stratum radiatum and stratum oriens of CA1 to CA3c, and the inner part of dentate molecular layer, also exhibited the CANP inhibitor immunoreactivity.

The above‐mentioned CANP and inhibitor distribution is discussed in relation to the selective vulnerability of hippocampal neurons to ischemia.
Spatial and morphological differentiation of trigger zones in afferent fibers to the teleost utricle
Authors: Saidel William M. , Popper Arthur N. , Chang Janet S.
Published: January 2005

A morphological correlate of the trigger site (the locus of action potential initiation) was identified in afferent axons of the utricle in the ear of two species of teleost fish. These sites were identified by the ferric‐ferrocyanide (Prussian blue) cytochemical procedure and they were correlated with the geometries of afferent intraepithelial arbors as visualized by means of a silver stain.

The intraepithelial arbors of afferent fibers show regional distributions that correlate with axon diameter and Prussian blue staining. Afferent axons with diameters greater than 4–5 μm only innervate the striola regions of the epithelium and terminate as one of two distinct types of intraepithelial arbors. Afferent axons with diameters smaller than 4 μm are ubiquitously distributed throughout the epithelium.

Arbors that stained by Prussian blue within the utricular epithelium are restricted to the striolar regions. These arbors possess nodal‐like membrane in different branches as postsynaptic membrane. Afferents that innervate hair cells in the extrastriolar epithelial regions stained with Prussian blue only at the extraepithelial terminal heminode. The postsynaptic membrane of these afferents is passive or dendritic‐like.
Dendritic morphologies of retinal ganglion cells projecting to the lateral geniculate nucleus in the rabbit
Authors: Pu Mingliang , Amthor Franklin R.
Published: January 2005

Small injections of fluorescent Rhodamine‐latex microspheres and Fast Blue were made into the dorsal lateral geniculate nucleus (dLGN) of fifteen rabbits. After 8–15 day survival times, the somas of projecting ganglion cells were found to be labelled in the contralateral retinas by retrograde transport. The dendritic morphologies of the labelled ganglion cells were revealed by intracellular injection of Lucifer Yellow or horseradish peroxidase while superfusing the retinas. At least ten distinct dendritic morphologies were observed among 161 injected ganglion cells. The three most commonly recovered dendritic morphologies were those of: (1) alpha‐like cells; (2) large, complex dendritic field cells; and (3) cells with small, dense dendritic fields that resemble intracellularly identified brisk sustained cells (Amthor et al., J. Comp. Neurol. 1989; 280:72–96). Smaller percentages of cells whose dendritic morphologies resembled those of several physiologically identified sluggish and complex receptive field ganglion cell classes (Amthor et al, J. Comp. Neurol. 1989; 280:72–96, 97–21) were also recovered. Several morphological types were also found that were previously unknown or could not be confidently related to those of previously known classes. Most dLGN injections labelled many different types of ganglion cells, but restricted injections in some dLGN loci labelled only a limited number of ganglion cell classes.
Restoration of thalamostriatal projections in rat neostriatal grafts: An electron microscopic analysis
Authors: Xu Z. C. , Wilson C. J. , Emson P. C.
Published: January 2005

The thalamostriatal projections to rat neostriatal grafts were studied by using the Phaseolus vulgaris‐leucoagglutinin (PHA‐L) axonal tracing technique. Two to 6 months after implantation of striatal primordia into adult neostriata, PHA‐L was injected into two different portions of the intralaminar nuclear complex of the thalamus.

In the host neostriatum, labeled fibers from the parafascicular nucleus (PF) arborized in a large region in the neostriatum, but avoided small patchlike areas. Most of the fibers from PF had irregular curved trajectories with short side branches that formed boutons. Labeled fibers from the centromedial and paracentral nuclei (CeM‐PC) projected to a similarly large area within the neostriatum but did not show any nonuniformity. CeM‐PC axons had relatively straight trajectories and formed boutons en passant.

Both sets of thalamostriatal projection fibers were found in the grafts. Some of the labeled fibers in the grafts formed dense, focal arborizations. Compared to the host neostriatum, the distribution of postsynaptic elements in the grafts was altered dramatically. In the host neostriatum, 89% of the terminals from PF terminated onto dendritic shafts; 93% of the CeM‐PC terminals contacted dendritic spines. However, only 47% of the PF terminals in the grafts contacted dendritic shafts; 53% of them terminated on dendritic spines. In grafts, 81% of the terminals from CeM‐PC region contacted dendritic spines; 19% of them made synapses on dendritic shafts.

The shift of postsynaptic elements in the grafts suggests a loss of pathway specificity in the induction of dendritic spines on neostriatal neurons in grafts.
Estradiol increases the number of nuclear pores in the arcuate neurons of the rat hypothalamus
Authors: Perez Julio , Hernandez Pedro , Garcia‐Segura Luis M.
Published: January 2005

Freeze‐fracture replicas of hypothalamic arcuate neurons and of Purkinje and granule cells of the cerebellar cortex from adult female rats were assessed in order to test the possible influence of estradiol on nuclear pores. Rats were ovariectomized and injected either with estradiol or with vehicle. An additional group of rats in proestrus was also studied. Pore diameter was not affected by ovariectomy or estrogen treatment. In arcuate neurons, the number of nuclear pores per nuclear membrane area, the total number of pores per nucleus, and the percentage of nuclear pores arranged in clusters were decreased by ovariectomy and increased within 30 minutes after estradiol administration to ovariectomized rats. The effect of estradiol on nuclear pores was sustained for several days; the number of pores and the percentage of pores in clusters reverted to control values by 1 month after the hormonal treatment. None of the above mentioned changes was observed in Purkinje and granule cells of the cerebellar cortex. These results indicate that estradiol may modulate the number and distribution of nuclear pores in arcuate neurons and suggest that the modification of the ultrastructure of the nuclear envelope may be one of the first effects of gonadal steroids on target cells.
Neuroarchitecture of the central complex in the brain of the locust Schistocerca gregaria and S. americana as revealed by serotonin immunocytochemistry
Authors: Homberg Uwe
Published: January 2005

The central complex is a prominent structure in the insect brain, yet its anatomical organization and functional role is still poorly understood. To facilitate investigations on the physiology of the central complex, this study describes its anatomical organization in the brain of locusts (Schistocerca gregaria and Schistocerca americana) based on an investigation of serotonin immunocytochemistry. Most subdivisions of the central complex including the protocerebral bridge, several layers in the upper division of the central body, and the noduli of the central body are innervated by serotonin‐immunoreactive neurons, while the lower division of the central body does not exhibit serotonin‐like immunoreactivity. Several types of serotonin‐immunoreactive neurons can be distinguished. A system of about 60 columnar neurons innervates the protocerebral bridge, layer III of the upper division of the central body, and the noduli. A group of 15–20 bilateral pairs of serotonin‐immunoreactive neurons connects the posterior optic tubercles with the protocerebral bridge. About ten pairs of neurons with somata in the inferior protocerebrum innervate layer la of the upper division of the central body. In addition, large‐field neurons arborize in layers Ia and Ib of the upper division of the central body and in the lateral accessory lobes. The detailed mapping of serotonin immunoreactivity provides further insight into the anatomical organization of the central complex and suggests that serotonin is a major neuroactive substance within this brain structure.
Morphological relationships among extensor digitorum longus, tibialis anterior, and semitendinosus motor nuclei of the cat: An investigation employing the retrograde transport of multiple fluorescent tracers
Authors: Hoover J. E. , Durkovic R. G.
Published: January 2005

To determine the morphological relationships among extensor digitorum longus (EDL), tibialis anterior (TA), and semitendinosus (St) motor nuclei in the spinal cord of the cat, these nuclei were retrogradely labeled with three different fluorescent tracers. The fluorochromes‐bisbenzimide, nuclear yellow, and propidium iodide‐were applied by intramuscular injection or soaking the muscle nerve. The positions of the labeled motor nuclei were bilaterally symmetrical The EDL and TA motoneurons were located in close proximity to one another, in the lateral regions of lamina IX in spinal segments L6 and L7. Although the boundaries of each nucleus were tightly opposed, the EDL and TA motor nuclei overlapped minimally, with the somata of EDL motoneurons positioned dorsal to those of TA. The St motor nucleus was located ventromedial to that of EDL and extended from the caudal portion of L6 through S1. Supplemental studies of the reflex effects evoked in EDL, TA, and St muscles by cutaneous nerve stimulation provided physiological observations that maybe related to these anatomical results.
Trigeminal primary afferent projections to “non‐trigeminal” areas of the rat central nervous system
Authors: Marfurt Carl F. , Rajchert Donna M.
Published: January 2005

The central projections of rat trigeminal primary afferent neurons to various “non‐trigeminal” areas of the central nervous system were examined by labeling the fibers with wheat germ agglutinin‐horseradish peroxidase (WGA‐HRP) transported anterogradely from the trigeminal ganglion. This technique produced a clear and comprehensive picture of trigeminal primary afferent connectivity that was in many ways superior to that which may be obtained by using degeneration, autoradiography. cobalt labeling, or HRP transganglionic transport techniques. Strong terminal labeling was observed in all four rostrocaudal subdivisions of the trigeminal brainstem nuclear complex, as well as in the dorsal horn of the cervical spinal cord bilaterally, numerous brainstem nuclei, and in. the cerebellum. Labeling in the ipsilateral dorsal horn of the cervical spinal cord was very dense at C1, moderately dense at C2 and C3, and sparse at C4‐C7. Numerous fibers crossed the midline in the medulla and upper cervical spinal cord and terminated in the contralateral pars caudalis and dorsal horn of the spinal cord from C1‐C5. The latter axons terminated most heavily in the mandibular and ophthalmic regions of the contralateral side. Extremely dense terminal labeling was observed in the ipsilateral paratrigeminal nucleus and the nucleus of the solitary tract, moderate labeling was seen in the supratrigeminal nucleus and in the dorsal reticular formation, and small numbers of fibers were observed in the cuneate, trigeminal motor, lateral and superior vestibular nuclei, and in the cerebellum. The tatter fibers entered the cerebellum in the superior cerebellar peduncle and projected to the posterior and anterior lobes as well as to the interposed and lateral deep cerebellar nuclei. Most projections in this study originated from fibers in the dorsal part of the spinal tract of V, suggesting a predominantly mandibular origin for these fibers. Projections from the ophthalmic and maxillary divisions, in contrast, were directed mainly to the cervical spinal cord bilaterally, to contralateral pars caudalis, and to certain areas of the reticular formation. In conclusion, this study has demonstrated that somatosensory information from the head and face may be transmitted directly to widespread and functionally heterogeneous areas of the rat central nervous system, including the spinal cord dorsal horn, numerous brainstem nuclei, and the cerebellum. These projections may play important roles in trigeminospinal reflexes (dorsal horn of spinal cord C1‐C7), fusion of the sensory maps of the right and left sides of the head (contralateral projections), trigeminovisceral integration (paratrigeminal and solitary), control and integration of oral motor behavior (supratrigeminal and motor V), orofacial reflexes (reticular formation), and the coordination and stabilization of head posture and gaze (cuneate, vestibular, and cerebellum).
Midget ganglion cells of the parafovea of the human retina: A Study by electron microscopy and serial section reconstructions
Authors: Kolb Helga , Dekorver Laura
Published: January 2005

In this study we used serial section electron microscopy and three‐dimensional reconstructions to examine four midget ganglion cells of the human retina. The four cells were located in the parafoveal retina 2.5 mm or 8° from the foveal center. Both type a (with dendritic trees in distal inner plexiform layer) and type b (with dendritic trees in proximal inner plexiform layer) midget ganglion cells have been studied. These culls have dendritic trees of 7–9 μm diameter, and their complete dendritic trees in the neuropil of the inner plexiform layer can be analyzed, as well as the bipolar cell axon terminals having synaptic input, by a study of 100–150 serial ultrathin sections. Type a midget ganglion cells appear to be in a one‐to‐one relationship with fiat midget bipolar cell axon terminals ending in distal inner plexiform layer. Type b midget ganglion cells are in a one‐to‐one synaptic relationship with invaginating midget bipolar cell axon terminals in proximal inner plexiform layer. The midget bipolar cells primarily involved with the midget ganglion cells do not contact other ganglion cell dendrites. In other words, midget bipolar cells appear to be in exclusive contact with single midget ganglion cells in the human retina.

The midget ganglion cells receive most of their input from their associated midget bipolar cells in the form of ribbon synapses at dyads or monads (55–81 ribbons total), although ribbonless synapses are seen occasionally. In all four midget ganglion cells reconstructed, one or two other bipolar cell axon terminals, presumed to be from wide‐field bipolar types, provide 1–3 ribbon synapses each. The number of amacrine synapses upon a midget ganglion cell's dendritic tree is approximately equal to the number of bipolar ribbon inputs (43%–56% bipolar ribbons: 44%–57% amacrine synapses).

We assume from our knowledge of response characteristics of ganglion cells in other mammalian retinas (Nelson et al., '78: J. Neurophysiol. 41:427–483), that the type a midget ganglion cell and its exclusive connectivity with a flat midget bipolar cell forms a single cone connected OFF‐center pathway, whereas the type b midget ganglion cell with its exclusive connectivity to an invaginating midget bipolar cell forms a single cone connected ON‐center pathway, through the retina to the brain.
Subgroup of alpha ganglion cells in the adult cat retina is immunoreactive for somatostatin
Authors: White C. A. , Chalupa L. M.
Published: January 2005

We have previously shown that two types of cells in the ganglion cell layer of the adult cat retina are immunoreactive for somatostatin (White et al., '90). One of the types was identified by morphological criteria as a wide‐field amacrine cell. The other cell type had a large, angular soma that resembled the alpha ganglion cell, but evidence was not available to identify it definitively as a ganglion cell. Both cell types were distributed preferentially in the inferior retina. In this report, we demonstrate that the two types of cell are, indeed, displaced amacrine cells and alpha ganglion cells. First, when retrograde tracers were injected into central visual targets, the immunoreactive large cells but not the displaced amacrine cells were found to be labeled. Second, after unilateral section of the optic nerve, the immunoreactive large cells disappeared from the retina on the lesioned side, but the displaced amacrine cells occurred in the same numbers in both retinae. In the periphery, the large cells ranged in diameter from 33 to 47 μm, comparable only to alpha ganglion cells (Boycott and Wässle, '74). An antiserum to parvalbumin was used to visualize the dendrites (Röhrenbeck and Wässle, '88) of somatostatin‐immunoreactive large cells. Based on dendritic stratification within the inner plexiform layer (Famiglietti and Kolb, '76), the somatostatin‐immunoreactive large cells were found to include both on‐center cells and off‐center cells, but were predominantly of the off‐center type. Within a local region, they were found to be arrayed with greater regularity than the overall population of alpha ganglion cells. These results indicate that alpha ganglion cells of the cat retina can be subdivided on the basis of their immunoreactive staining for somatostatin and suggest that the diversity of ganglion cells in the cat retina may be greater than has been recognized on the basis of morphological criteria alone.
Variation in terminal morphology and presynaptic inhibition at crustacean neuromuscular junctions
Authors: Tse F. W. , Marin L. , Jahromi S. S. , Atwood H. L.
Published: January 2005

Synaptic terminals of excitatory and inhibitory neurons supplying muscle fibers in leg muscles of crabs (Pachygrapsus crassipes and Hyas areneus) were investigated with light and electron microscopy. Terminals responsible for large excitatory postsynaptic potentials (EP‐SPs) at low frequencies of activation had a compact configuration with clusters of terminal boutons radiating from the main axon branch. Terminals responsible for small EPSPs had a more diffuse organization, with boutons often arranged in series along thin axon branches. Inhibitory neurons, when activated, produced both presynaptic and postsynaptic inhibitory effects, with the former being more potent at low frequencies of activation. Presynaptic inhibition was variable in magnitude but was generally strong in fibers with large EPSPs. Representative terminals from regions of strong and weak presynaptic inhibition were identified by activity‐dependent uptake of horseradish peroxidase, serially sectioned, and reconstructed from electron micrographs. Both regions were found to contain axo‐axonal synapses from inhibitory to excitatory terminals, with a larger number in the region of strong presynaptic inhibition. In addition, axo‐axonal synapses were more uniformly distributed in the latter region. The number of inhibitory presynaptic dense bars (active zones) was somewhat higher in the region of weak inhibition, but larger individual dense bars occurred in the region of strong inhibition. Possible factors contributing to the differences in strength of inhibition include: (1) morphology and electrical properties of terminals; and (2) high probability of transmission at a relatively small number of inhibitory synapses during low frequency activation in the region of strong inhibition.
Myelin‐axon relationships established by rat vagal Schwann cells deep to the brainstem surface
Authors: Fraher John P. , Rossiter John P.
Published: January 2005

The central‐peripheral transitional zones of rat dorsolateral vagal rootlets are highly complex. Peripheral nervous tissue extends centrally for up to several hundred micrometers deep to the brainstem surface along these rootlets. In some instances this peripheral nervous tissue lacks continuity with the peripheral nervous, system (PNS) and so forms an island within the central nervous system (CNS). In conformity with the resulting complexity of the CNS‐PNS interface, segments of vagal axons lying deep to the brainstem surface are myelinated by one or more intercalated Schwann cells, contained in peripheral tissue insertions or islands, at either end of which they traverse an astroglial barrier. Intercalated Schwann cells are thus isolated from contact or contiguity with the Schwann cells of the PNS generally. They are short, having a mean internodal length of around 60% of that of the most proximal Schwann cells of the PNS proper, which lie immediately distal to the CNS‐PNS interface and which are termed transitional Schwann cells. The thickness of the myelin sheaths produced by intercalated Schwann cells is intermediate between that of transitional Schwann cells and that of oligodendrocytes myelinating vagal axons of the same calibre distribution. This is not due to limited blood supply or to insufficient numbers of intercalated Schwann cells, the density of which is greater than that of transitional Schwann cells. These factors are unlikely to restrict expression of their myelinogenic potential. Nevertheless, the regression data show that the setting of the myelin‐axon relationship differs significantly between the two categories of Schwann cell. Thus, the myelinogenic response of Schwann cells to stimuli emanating from the same axons may differ between levels along one and the same nerve bundle. Mean myelin periodicity was found to differ between sheaths produced by intercalated and by transitional Schwann cells.
Naturally occurring cell death in the developing dentate gyrus of the rat
Authors: Gould Elizabeth , Woolley Catherine S. , McEwen Bruce S.
Published: January 2005

The rat dentate gyrus is a unique brain structure in that most of its neurons are born postnatally. Cell death is known to be an important phenomenon in brain development and yet it is at present unknown whether the dentate gyrus undergoes a period of naturally occurring cell death. In order to determine whether or not cell death plays a role in the development of the dentate gyrus, we examined the density of degenerating cells and healthy cells in the suprapyramidal and infrapyramidal granule cell blades and the hilus during the postnatal period. Light microscopic examination of Nissl‐stained brain tissue revealed substantial numbers of pyknotic cells throughout the dentate gyrus during the first postnatal week. Quantitative analysis of the suprapyramidal blade showed a peak in the density of pyknotic cells at the end of the first postnatal week. This peak in the density of degenerating cells coincided with a significant decrease in the density of healthy cells in this region. No rostrocaudal gradient in cell death was observed for the suprapyramidal blade. However, cell death in the suprapyramidal blade proceeded along superficial to deep as well as lateral to medial gradients.

Within the infrapyramidal blade/hilus, cell death occurred at different times depending on the rostrocaudal level of the dentate gyrus. Peak density of pyknotic cells was observed the day after birth in the rostral part of the infrapyramidal blade/hilus while pyknosis did not reach a peak in the middle and temporal thirds of this region until the end of the first postnatal week. Cell death in the infrapyramidal blade proceeded in a superficial to deep and lateral to medial direction. These results indicate that the dentate gyrus undergoes a significant period of naturally occurring cell death during the early postnatal period.
Labeling and distribution of AII amacrine cells in the rabbit retina
Authors: Mills Stephen L. , Massey Stephen C.
Published: January 2005

The fluorescent dye 4,6‐diamino‐2‐phenylindole (DAPI) has previously been used to label starburst amacrine cells selectively in the rabbit retina and AII amacrine cells in the cat retina. Using the rabbit retina, we show that intraocular injection of DAPI labels starburst amacrine cells as seen 1–2 days later. In contrast, after a brief in vitro incubation with DAPI, AII amacrine cells are selectively labeled. Amacrine cells were identified by intracellular staining with Lucifer Yellow. AII amacrine cells are arranged in a regular mosaic with a density of 2,800 cells/mm2 near the visual streak declining to about 500 cells/mm2 in the far periphery. The coverage of the lobular dendritic field in sublamina α is approximately 1.5 across the retina, but the coverage of the fine dendritic field in sublamina b increases from 3 centrally to 4 in the inferior periphery, and to above 8 in the superior periphery.
Distribution and developmental expression of the nerve terminal protein NT75 in the rat cerebellum
Authors: Wright David J. , Ritchie Teresa C. , Coulter Joe D.
Published: January 2005

Previous studies of the nerve terminal protein NT75 in the developing spinal cord have suggested an association between the appearance of NT75 immunoreactivity and the process of synaptogenesis. To examine the time course of NT75 expression further, the current study. Compared the localization of NT75 and the synaptic vesicle protein synaptophysin in the adult and developing rat cerebellum and in cerebellar tissue cultures. In the adult cerebellum, dense NT75 staining is confined to the molecular layer, where it is associated with parallel fiber endings of cerebellar granule cells. During development, NT75 immunoreactivity is first detectable in the cerebellar cortex as a dense band of staining in the deepest portion of the molecular layer at postnatal day 10. The stained zone expands to occupy a progressively greater portion of the molecular layer until about postnatal day 20. Synaptophysin staining occurs in granule cell processes earlier than NT75 and is found throughout the molecular layer by postnatal day 7. Quantitatively, rapid increases in both NT75 and synaptophysin occur in the first three postnatal weeks, with NT75 activity reaching levels exceeding the adult value by 50% over postnatal days 20 through 30, whereas synaptophysin plateaus at near adult levels by postnatal day 20. In cerebellar cultures, NT75 staining in neurites develops over several days, increasing coincidentally with development of synaptic contacts, whereas synaptophysin staining is already present in most neurites after only 1 day in vitro. The results indicate that NT75 expression in developing cerebellar granule cell nerve terminals is closely associated with the appearance of mature nerve terminals, suggesting that the protein may have a role in the formation/stabilization of the synaptic ending or in the mechanisms of synaptic transmission.
In situ hybridization analysis of the FMRFamide neuropeptide gene in Drosophila. II. Constancy in the cellular pattern of expression during metamorphosis
Authors: O'Brien Martha A. , Schneider Lynne E. , Taghert Paul H.
Published: January 2005

We have studied changes in the pattern of specific neuropeptide gene expression during the metamorphosis of the Drosophila nervous system. Prior to metamorphosis, the Drosophila FMRFamide gene is expressed exclusively within the central nervous system in a stereotyped pattern that comprises roughly 60 neurons (Schneider et al., '91). Using in situ hybridization, we found that the FMRFamide gene was continuously expressed throughout all stages examined: at each of 15 stages of adult development and through at least the first 10 days of adult life. There were no differences between the results observed with 2 exon‐specific hybridization probes, thus indicating little if any alternative splicing during postembryonic development. Despite many changes in the positions of individual hybridization signals due to the large‐scale reorganization of the nervous system, the continuous pattern of gene expression through adult development permitted many adult signals to be identified as larval signals. We concluded that the adult pattern of FMRFamide gene expression was largely derived from persistent larval neurons. Adult‐specific hybridization signals in the brain and ventral ganglion were also detected and these corresponded to many of the ∼ 40 adult‐specific FMRFamide‐immunoreactive neurons. One specific larval signal was lost during adult development and the intensities of other signals fluctuated in reproducible manners. These stereotyped differences in hybridization signal intensity resemble similar observations made in larval stages (Schneider et al., '91) and support the hypothesis that the steady‐state levels of FMRFamide transcripts are differentially regulated among the diverse neurons that express the gene.
Sexually dimorphic distribution of a galanin‐like peptide in the central nervous system of the teleost fish Poecilia latipinna
Authors: Cornbrooks Ellen B. , Parsons Rodney L.
Published: January 2005

Immunohistochemical techniques were used to visualize areas of the brain and spinal cord containing a galaninlike peptide in the teleost fish, the sailfin molly. Galaninlike immunoreactivity (GAL‐LI) in both males and females was identified in neurons in the nucleus preopticus periventricularis, nucleus lateralis tuberis, and nucleus commissuralis. GAL‐LI fibers had a comparable distribution in the forebrain, preoptic, hypothalamic, and visceral sensory areas of both sexes. In striking contrast to these areas, the optic tectum, torus semicircular is, brainstem tegmentum, and spinal cord of the male contained much higher levels of GAL‐LI than the female. GAL‐LI in these dimorphic areas in the female was limited to single fiber bundles in the ventromedial tegmentum and in the trigeminal system. Additionally, a population of neurons in the preoptic nucleus was found to contain GAL‐LI in the male only.

Sexual dimorphism was especially prominent in the spinal cord, where extensive GAL‐LI fibers were found in the male only. These fibers were oriented in the longitudinal plane and confined largely to the gray matter. Comparative studies were performed on the goldfish spinal cord, in which GAL‐LI was localized solely in the dorsal horn and exhibited no sexual dimorphism. Further, examination of spinal cord material from neonatal mollies revealed a lack of spinal GAL‐LI at this developmental stage. As the extent of GAL‐LI in the male molly spinal cord differs from both the goldfish and from that reported for the mammalian spinal cord, and a prominent sexual dimorphism in GAL‐LI extends from the diencephalon to the caudal spinal cord, it is suggested that a galaninlike peptide may play a unique, sex‐specific role in this species.
Cytoskeletal specializations at the rod photoreceptor distal tip
Authors: Roof Dorothy , Adamian Michael , Jacobs Deborah , Hayes Annmarie
Published: January 2005

We have examined microtubules and microtubule‐like elements within the toad rod photoreceptor outer segment in order to define regional specializations of the photoreceptor cytoskeleton. “Ciliary” microtubules were localized within the rod outer segment (ROS) by using thin section electron microscopy, immunofluorescence, and rapid‐freeze deep‐etch microscopy. All three methods showed that ciliary microtubules stop short of the extreme ROS distal tip, although abundant microtubule‐like structures distinct from the ciliary microtubules were found within the distal 10–15 μm of the ROS tip. These heretofore undescribed “distal ROS tubules” are clustered at the clefts or incisures of the disk membrane stack and resemble microtubules in overall size and shape, although they are not closely related antigenically to tubulin. The distal ROS tubules are more abundant in green rods than red rods and vary in number during the daily light/dark cycle. Quantitation of these tubules at two time points during the light/dark cycle suggests that there are three‐ to fourfold more tubules in the ROS tip one hour after light onset than one hour before light onset. Retinas prevented from normal disk membrane shedding by separation of the retina from the adjacent pigment epithelium, failed to develop increased numbers of tubules after light onset. This suggests that the newly described distal ROS tubules may modulate or be modulated by light‐induced interactions between the photoreceptors and pigment epithelium, such as those that occur during the disk shedding phase of membrane turnover.