bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological and immunocytochemical observations on the visual callosal projections in the cat
Authors: Voigt Thomas , LeVay Simon , Stamnes Mark A.
Published: May 2005

The connections between the left and right 17‐18 border regions of the cat's visual cortex were labeled by axonal transport of peroxidase‐conjugated wheat‐germ agglutinin (WGA‐HRP) and examined by light and electron microscopy. The cells of origin of the pathway were further characterized by transport of fluorescent microspheres (“beads”) followed by in vitro injection of cells with Lucifer Yellow, and by beads transport followed by immunocytochemistry with antibodies to gamma‐aminobutyric acid (GABA).

The cells of origin of the callosal pathway were located in the lower part of layer 2/3, the upper part of layer 4, and layer 6. In layers 2/3 and 6, they were pyramidal cells; in layer 4 they were star pyramids or spiny stellate cells. None of them were spinefree or sparsely spinous cells, and none were GABA‐positive. The axon terminals of the callosal pathway formed type 1 (asymmetric) synapses, and most of them contacted dendritic spines. Both the cells of origin and the terminals were arranged in patches.

The findings suggest that the direct action of the callosal pathway is excitatory. The callosal system appears to represent only a subset of the cell types that have intrinsic horizontal projections within areas 17 or 18.
The nervous system of the male Dinophilus gyrociliatus (polychaeta, dinophilidae): II. Electron microscopical reconstruction of nervous anatomy and effector cells
Authors: Windoffer R. , Westheide W.
Published: May 2005

All neuronal cells in the dwarf male of the dimorphic polychaete species Dinophilus gyrociliatus were individually identified by means of serial ultrathin sections. Altogether 68 neural cells–including 40 sensory neurons and 2 glial cells–constitute a small but complex nervous system. Fifty‐three neural cells are located in three pairs of ganglia and connected by paired nerve cords. The prominent frontal ganglia, each consisting of a well‐developed neuropile and surrounded by 20 or 21 neural cells, represent the animal's brain. The ventral ganglia contain only 2 neurons each. The penis ganglia–four cells each–are associated with the copulatory organ. A conspicuous circumpenial fiber mass surrounds the basal part of the penis. The effector cells–22 multiciliated epidermal cells, 34 muscle cells, and different gland cells (?)–were also reconstructed and their innervation was partly elucidated. Sensory‐motor neurons were unambigously identified. They are discussed in regard to the small body size of the animal. The male's nervous organization resembles a very simple rope ladder and may represent a reduced derivative of a nervous system in normal‐sized males of monomorphic species. Similarities, however, also occur with the developing nervous system of a planktotrophic metatrochophore. The neuronal organization, with its two centers (frontal ganglia and ventral ganglia vs. penis ganglia and circumpenial fiber mass), accords well with the bipartite behavioral pattern, which is entirely devoted to locomotion and copulation, respectively.
GABAergic basal forebrain neurons project to the neocortex: The localization of glutamic acid decarboxylase and choline acetyltransferase in feline corticopetal neurons
Authors: Fisher R. S. , Buchwald N. A. , Hull C. D. , Levine M. S.
Published: May 2005

Our objective was to determine whether GABAergic and cholinergic basal forebrain neurons project to the neocortex. The retrograde connectivity marker wheat germ agglutinin lectin‐bound horseradish peroxidase was injected into the neocortex of adult cats. Histo‐ and immunohistochemical methods were combined to label sequentially connectivity and transmitter markers (glutamic acid decarboxylase; choline acetyltransferase) in forebrain neurons. The labels of each marker were identified by correlative light and electron microscopy.

Two principal types of doubly labeled neurons were demonstrated. The connectivity marker was colocalized with glutamic acid decarboxylase or choline acetyltransferase. The neurons were located in the basal forebrain. Their ultrastructural, cellular, and regional organization supported 2 conclusions. (1) GABAergic basal forebrain neurons project to the neocortex. This is important new morphological evidence for the origin of inhibitory neocortical afferents from a subcortical brain site. (2) The GABAergic and cholinergic basal forebrain neurons projecting to the neocortex exhibit remarkable structural similarities. The transmitter diversity of these intertwined neocortical afferents may be significant for the pathology and treatment of human neurological disorders such as Alzheimer's disease.
Auditory brainstem of the ferret: Effects of unilateral cochlear lesions on cochlear nucleus volume and projections to the inferior colliculus
Authors: Moore David R. , Kowalchuk Nancy E.
Published: May 2005

Unilateral lesions of the right cochlea were made in ferrets aged postnatal day (P)12 to P93. The extent of the lesions was assessed by counting remaining hair cells and ganglion cells in midmodiolar sections through the lesioned cochleas and by comparison with a sample of unlesioned cochleas. The neural effects of the lesions were assessed by measuring the volume of each cochlear nucleus (CN) and by counting the number of neurons in each CN that were retrogradely labeled following injections of WGA‐HRP in the left inferior colliculus (IC). Survival times between lesioning and injection of the tracer ranged from 11 to 98 days. CN volume and projections to the IC were also measured in a sample of normal adult ferrets and in normal infants aged P39 to P80.

Cochlear lesions resulted in a reduction of the volume of the CN on the lesioned side, relative to the other CN, in animals of all ages and survival times. The extent of the CN volume reduction was negatively correlated with the number of remaining cochlear ganglion cells. However, even where the number of ganglion cells was within the normal range, significant volume reductions occurred. The ventral CN was more severely affected by the lesions than the dorsal CN, but no difference was found between the anteroventral and posteroventral divisions of the nucleus. There was no significant difference in the extent of CN volume reductions between animals of different ages or survival times.

Lesions of the right cochlea in younger animals (P14 to P24) resulted, after 90 days survival, in an increase in the number of left CN neurons projecting to the left IC. No significant increase was seen following lesions in older (P90) ferrets or following short (11 or 30 days) survival times in young (P14 to P24) ferrets. The extent of the increase in the ipsilateral CN‐IC projection was not related to the number of remaining ganglion cells or to the division of the CN examined. Lesions did not affect the contralateral CN‐IC projection.

We conclude that cochlear lesions in infant ferrets can alter auditory brainstem morphology and connectivity. The dependence of these alterations on the age of the animal, survival time following lesion, and extent of the lesion varies markedly with the index examined.
Monoamine innervation of the organum vasculosum laminae terminalis (OVLT): A high resolution radioautographic study in the rat
Authors: Bosler Olivier , Descarries Laurent
Published: May 2005

The monoamine innervation of the organum vasculosum laminae terminalis (OVLT) was examined in the adult rat by light and electron microscope radioautography after intraventricular administration of tritiated serotonin ([3H]5‐HT) or dopamine ([3H]DA). Radioautographic and biochemical controls after 5,7‐dihydroxytryptamine or 6‐hydroxydopamine lesioning established the respective serotonin (5‐HT) and catecholamine (CA) identities of the axonal varicosities labeled under the conditions of the present experiments. For descriptive purposes, the OVLT was subdivided in three parts: two parenchymal zones, one juxtaventricular, the other juxtavascular, and the vascular core. Almost 10% of all axonal varicosities in the OVLT were found to be labeled with [3H]5‐HT. This 5‐HT innervation was most prominent in the rostrocaudal and ventrodorsal portions of the juxtaventricular zone and the dorsal aspect of the juxtavascular zone; there was none in the vascular core. [3H]DA‐labeled varicosities were much less abundant and yet more numerous than earlier histofluorescent and immunohistochemical studies would have predicted. They predominated in the juxtavascular zone, where a majority presumably had a dopamine (DA) rather than a noradrenaline identity. Some were also found in the vascular core, where they most likely corresponded to peripheral autonomic noradrenaline endings. In the juxtaventricular zone of the OVLT, a significant proportion of the [3H]5‐HT‐labeled varicosity profiles could be observed to form axodendritic synapses, but in the juxtavascular zone no 5‐HT or any [3H]DA‐labeled ones were ever seen in synaptic junction. In the juxtavascular zone, the 5‐HT and the presumed DA endings established close relationships with neurosecretory axons, and with astrocytic or tanycytic processes on which they occasionally formed “synaptoid contacts.” A few endings of either type were also seen to abut directly on the outer basement membrane of the perivascular space. It therefore appears probable that in OVLT monoamines influence neural and nonneural elements. At a proximal level of regulation (juxtaventricular zone), 5‐HT could act both synaptically and nonsynaptically as an interneuronal transmitter or modulator. In contrast, distally (juxtavascular zone), both DA and 5‐HT could be released as neurohormones in addition to modulating neurosecretion. 5‐HT and DA varicosities in the OVLT could also behave as sensors for circulating factors that do not cross the blood‐brain barrier.
Vasoactive intestinal peptide in the hypothalamohypophysial system of the mongolian gerbil
Authors: Mikkelsen Jens D. , Møller Morten
Published: May 2005

By use of the indirect peroxidase‐antiperoxidase immunohistochemical technique the location of perikarya and fibers exhibiting vasoactive intestinal peptide (VIP)‐like immunoreactivity was investigated in the hypothalamus and the posterior pituitary of the Mongolian gerbil (Meriones unguiculatus), because of the involvement of VIP in several neuroendocrine functions.

In the hypothalamus, a large number of VIP‐immunoreactive perikarya were seen in the ventromedial part of the suprachiasmatic nucleus. Few VIP‐positive perikarya were present in the periventricular, paraventricular, and supraoptic nuclei and in the medial preoptic area close to the third ventricle. The perikarya in the paraventricular nucleus projected fibers in the direction of the median eminence. In the median eminence VIP‐immunoreactive fibers were present especially in the external layer, concentrated in the perivascular spaces surrounding the portal vessels. Scattered VIP‐immunoreactive fibers were also located in the internal layer of the median eminence as well as in the posterior pituitary lobe. In the latter, large VIP‐positive Herring‐like bodies were observed.

With receptor autoradiography a large number of grains were demonstrated in the anterior pituitary lobe in contrast to the neural lobe.

Many VIP‐positive fibers and some perikarya were observed within the ependyma covering the rostroventral part of the third ventricle. Finally, fibers exhibiting VIP immunoreactivity were also seen in the organum vasculosum laminae terminalis (OVLT).

These results support the concept that VIP is released into the portal vascular system and plays a role in the regulation of the activity of the anterior pituitary. In addition, VIP might be secreted into the cerebrospinal fluid of the third ventricle.
Organization of spinocerebellar projection map in three types of agranular cerebellum: Purkinje cells vs. granule cells as organizer element
Authors: Nunes M. L. Arsénio , Sotelo C. , Wehrlé R.
Published: May 2005

The organization of the spinocerebellar projection was analysed by the anterograde axonal WGA‐HRP (horseradish peroxidase‐wheat germ agglutinin conjugate) tracing method in three different types of agranular cerebellar cortex either induced experimentally by X‐irradiation or occurring spontaneously in weaver (wv/wv) and staggerer (sg/sg) mutant mice.

The results of this study show that in the X‐irradiated rat and weaver mouse, in both of which the granule cells are directly affected and die early in development, the spinal axons reproduce, with few differences, the normal spinocerebellar pattern. Conversely, in staggerer mouse, in which the Purkinje cells are intrinsically affected and granule neurons do not seem to be primarily perturbed by the staggerer gene action, the spinocerebellar organization is severely modified. These findings appear somewhat paradoxical because if granule cells, the synaptic targets of mossy spinocerebellar fibers, were necessary for the organization of spinocerebellar projection, the staggerer cerebellum would exhibit a much more normal projectional map than the weaver and the X‐irradiated cerebella. It is, therefore, obvious that granule cells, and even specific synaptogenesis, are not essential for the establishment of the normal spinocerebellar topography. On the other hand, the fact that the Purkinje cells are primarily affected in the unique agranular cortex in which the spinocerebellar organization is severely modified suggests that these neurons could be the main element in the organization of the spinocerebellar projection map. This hypothesis is discussed in correlation with already‐reported findings on the zonation of the cerebellar cortex by biochemically different clusters of Purkinje cells.
Physiological and morphological characterization of OFF‐center amacrine cells in the turtle retina
Authors: Ammermüller Josef , Weiler Reto
Published: May 2005

OFF‐center amacrine cells were intracellularly recorded and stained with Lucifer yellow to investigate the cell correlations between photoresponses and morphological features.

All OFF‐amacrine cells were monostratified and branched within the outer half of the inner plexiform layer. In the flat‐mounted retina, however, three distinct morphological classes were distinguishable, which correlated with observed physiological differences.

Class 1 consisted of wide‐field, stellate amacrine cells with long, thin processes, which branched only close to the soma. The diameter of the circular dendritic field ranged from 0.8 mm to 2.0 mm. Their photoresponse to spot stimulation was a hyperpolarization during light‐ON and a small depolarization after light‐OFF. They showed strong antagonistic center‐surround organization of the receptive field. Its size was approximately equal to the dendritic field size.

Class 2 consisted of wide‐field, giant amacrine cells with a „central”︁ dendritic field formed by thick dendrites, and a „peripheral”︁ dendritic field formed by a few long and thin, „axonlike”︁ processes. The shape of the dendritic field was elongated, with the long axis parallel to the visual streak. Their receptive field size was considerably smaller than their dendritic field size, which was several millimeters of diameter along the long axis. Their photoresponse to spot stimulation was a fast depolarization after light‐OFF, and about 50% of these cells showed strong antagonistic center‐surround receptive field organization.

Class 3 consisted of small‐ or medium‐field, „starburstlike”︁ amacrine cells with circular dendritic fields of 0.1 mm to 0.6 mm diameter. Their fine, beaded dendrites branched predominantly in the distal parts of the dendritic field. Their photoresponses to light were similar to the of the giant amacrine cells; however, their receptive field size exceeded the dendritic field size.

Radial sections of the retinas with labeled cells were incubated in antisera to reveal the putative transmitters GABA, serotonin, neurotensin, met‐enkephalin and glucagon. No immunoreactivity with these antisera was detected within the stained OFF‐center amacrine cells.
The histaminergic system in the guinea pig central nervous system: An immunocytochemical mapping study using an antiserum against histamine
Authors: Airaksinen Matti S. , Panula Pertti
Published: May 2005

Using an antiserum against conjugated histamine we mapped the histaminergic somata and their fiber projection areas in carbodiimide‐fixed guinea pig central nervous system. The neurons were large and they were found exclusively in the posterior hypothalamus, as in the rat, but in the guinea pig they were more numerous and distributed more widely in a thin layer around the posterior mammillary nucleus, scattered between and within the medial mammillary nuclei, and in a dense cell cluster emerging from the caudal magnocellular nucleus and extending to the medial preoptic area.

The density of histamine‐immunopositive fibers was very high in the olfactory tubercle, diagonal band of Broca, nucleus accumbens, medial and cortical amygdaloid nuclei, periventricular and lateral basal hypothalamus, paraventricular thalamus, and in a region from the medial central gray to the locus coeruleus and the parabrachial nucleus. Dense fiber networks were found in the piriform and entorhinal cortex, septum, dentate gyrus, and subiculum, in most parts of amygdala, and in many areas of the hypothalamus, thalamus, substantia nigra, raphe nuclei, inferior olivary, solitary tract and medial vestibular nuclei, and neurohypophysis. Medium fiber density was observed in the internal layers of the olfactory bulb, anterior olfactory nuclei, neocortex, zone CA1 of hippocampus, and many midbrain and hindbrainregions. Low density was present in the outer layers of the olfactory bulb, other parts of hippocampus, the globus pallidus, most of the caudatus‐putamen, the cerebellar cortex, and the dorsal horn of the spinal cord. The retina and most of the myelinated white matter had single or no histaminergic fibers.

It may be concluded from the results that most fibers seem to follow a ventromedial route to the forebrain, reaching the amygdala ventral to the medial forebrain bundle, the hippocampus via subiculum, and the hindbrain structures via the medial central gray. As compared to the rat, the fiber projections in the guinea pig brain were denser, particularly in the hippocampus, thalamus, pons‐medulla, and neurohypophysis. The fiber densities in various regions of the guinea pig brain are compared to histamine receptor densities and the possible functions of histamine are discussed.
GABA‐immunoreactive synaptic boutons in the rat basal forebrain: Comparison of neurons that project to the neocortex with pallidosubthalamic neurons
Authors: Ingham C. A. , Bolam J. P. , Smith A. D.
Published: May 2005

Although the basal forebrain, including the globus pallidus, contains a high concentration of gamma‐aminobutyric acid (GABA), it is not known whether all types of neuron in the globus pallidus receive GABAergic synaptic input. We have studied two types of neuron: typical pallidal neurons that project to the subthalamic nucleus and magnocellular neurons which are found in the medial and ventral borders of the globus and project to the sensorimotor cortex.

The postembedding immunogold staining of endogenous GABA revealed many preterminal axons and synaptic boutons that contained GABA immunoreactivity. Neurons that projected to the neocortex were postsynaptic to some of the GABA‐immunoreactive boutons, the majority of which formed symmetrical membrane specializations. From a series of random electron micrographs through the perikarya and proximal dendrites of such retrogradely labelled neurons the density of GABA‐containing afferent synaptic boutons was estimated to be 0.58 GABA‐containing boutons per 100 μm of neuronal membrane. The GABA‐containing boutons accounted for 72% of the total afferent input in the proximal regions of the pallidocortical neurons examined. The pallidosubthalamic neurons received many more afferent boutons than did the cortically projecting neurons, a high proportion (80.4%) of which were immunoreactive for GABA. The density of GABA‐containing boutons in contact with pallidosubthalamic neurons was 8.9 boutons per 100 μm.

It is concluded that cortically projecting basal forebrain neurons, that are probably cholinergic, are innervated by GABA‐containing afferent boutons. However, pallidosubthalamic neurons in the same part of the basal forebrain are much more densely innervated by GABA‐containing boutons.
Ultrastructure and synaptic organization of luteinizing hormone‐releasing hormone (LHRH) neurons in the anestrous ewe
Authors: Lehman Michael N. , Karsch Fred J. , Robinson Jane E. , Silverman Ann‐Judith
Published: May 2005

Electron microscopic immunocytochemistry was employed to examine the ultrastructure of luteinizing hormone‐releasing hormone (LHRH) neurons and their projections to the median eminence in the sheep brain. LHRH perikarya in the preoptic area of anestrous ewes are less innervated than nonimmunoreactive cells in the same sections, but still receive numerous synaptic inputs, primarily onto distal dendrites and small somatic protuberances. Axon terminals synapsing upon LHRH cells contain a combination of clear spherical vesicles and larger dense‐core vesicles. Interestingly, LHRH cell bodies and dendrites are almost entirely surrounded by glial processes. These processes intervene between immunoreactive elements that at a light microscopic level appear to be in contact with each other. Thus no evidence was obtained at the ultrastructural level for contacts among adjacent LHRH cells or dendrites in the preoptic area. Synaptic inputs onto LHRH cell bodies and dendrites appear to penetrate this glial sheath. In contrast to the absence of contacts among LHRH cells in the preoptic area, individual LHRH terminals in the median eminence are often clustered in direct plasma membrane contact. Comparisons between animals of differing reproductive status are needed to determine whether alterations in synaptic inputs, glial ensheathment, or LHRH‐LHRH appositions, may underlie seasonal changes in the activity of LHRH neurons.
Localization of glycine‐containing neurons in the Macaca monkey retina
Authors: Hendrickson Anita E. , Koontz Margaret A. , Pourcho Roberta G. , Sarthy P. Vijay , Goebel Dennis J.
Published: May 2005

Autoradiography following 3H‐glycine (Gly) uptake and immunocytochemistry with a Gly‐specific antiserum were used to identify neurons in Macaca monkey retina that contain a high level of this neurotransmitter. High‐affinity uptake of Gly was shown to be sodium dependent whereas release of both endogenous and accumulated Gly was calcium dependent. Neurons labeling for Gly included 40‐46% of the amacrine cells and nearly 40% of the bipolars. Synaptic labeling was seen throughout the inner plexiform layer (IPL) but with a preferential distribution in the inner half. Bands of labeled puncta occurred in S2, S4, and S5.

Both light and postembedding electron microscopic (EM) immunocytochemistry identified different types of amacrine and bipolar cell bodies and their synaptic terminals. The most heavily labeled Gly+ cell bodies typically were amacrine cells having a single, thick, basal dendrite extending deep into the IPL and, at the EM level, electron‐dense cytoplasm and prominent nuclear infoldings. This cell type may be homologous with the Gly2 cell in human retina (Marc and Liu: J. Comp. Neurol. 232:241‐260, ′85) and the AII/ Gly2 of cat retina (Famiglietti and Kolb: Brain Res. 84:293‐300, ′75; Pourcho and Goebel: J. Comp. Neurol. 233:473‐480, ′85a). Gly+ amacrines synapse most frequently onto Gly− amacrines and both Gly− and Gly+ bipolars. Gly+ bipolar cells appeared to be cone bipolars because their labeled dendrites could be traced only to cone pedicles. The pattern of these labeled dendritic trees indicated that both diffuse and midget types of bipolars were Gly+. The EM distribution of labeled synapses showed Gly+ amacrine synapses throughout the IPL, but these composed only 11‐23% of the amacrine population. Most of the Gly+ bipolar terminals were in the inner IPL, where 70% of all bipolar terminals were labeled. These findings are consistent with previous data from cats and humans and suggest that both amacrine and bipolar cells contribute to glycine‐mediated neurotransmission in the monkey retina.
Origins of brainstem‐spinal projections in the duck and goose
Authors: Webster Deirdre M. S. , Steeves John D.
Published: May 2005

The purpose of this study was to determine the location of neuronal cell bodies with projections to the cervical or lumbar spinal cord in the adult duck and goose. Bilateral or unilateral injections (5‐10 μl) of the retrograde tracer dye True Blue (TB:5%) were made into the high cervical or high lumbar levels of the spinal cord. Similar results were obtained in both species. First, we found no evidence of retrogradely labelled cells in the telencephalon. In the brainstem, the distribution of TB cells was similar to those previously reported for the pigeon; however, the present study now demonstrates that some of these descending pathways project as far as the lumbar cord. We also discovered that there is a topographical representation of spinal projecting neurons within the avian medullary‐pontine reticular formation.
Control of tectal cell number during larval development in Rana pipiens
Authors: Kollros Jerry J. , Thiesse Mary L.
Published: May 2005

Cell production and cell deaths were determined in larval Rana pipiens both in control tecta and in tecta following unilateral eyeball removal in embryos and larvae. Such enucleations produce significantly reduced rates of cell division in the contralateral tecta for virtually the entire larval period (confirming studies with enucleation almost exclusively performed in embryos—Kollros: J. Exp. Zool. 123:153–187, '53, and J. Comp. Neurol. 205:171–178, '82). Significant numbers of cell deaths in all nonependymal tectal cell layers were also observed. Control cell division rates peak at stage X, while cell death peaks are reached in stages XIII–XX. Overall, about 106 nonependymal cells are produced in control tecta, and about 350,000 of them die by the end of metamorphosis. Control of cell numbers following enucleation is shown to depend mainly on reductions in cell division rates when the operation occurs early in development and mainly on increases in cell death rates are invariably present within 1 day of the operation whereas the reduced division rates ordinarily require several more days to be seen. The modified rates, both of cell divisions and cell death, are limited to tectal areas to which optic nerve fibers have already extended. Maps of the positions of tectal cell divisions in many larval stages provide the basis for modifying the current dogma that tectal formation occurs as a series of newly formed mediocaudal wedges pushing previously produced wedges rostrolaterad. All such “old” wedges receive substantial cell additions for many stages, with the rate of addition decreasing rostrad earlier than caudad.
Serotonin‐immunoreactive neurons in the cnidarian Renilla koellikeri
Authors: Umbriaco Denis , Anctil Michel , Descarries Laurent
Published: May 2005

The cellular localization of 5‐hydroxytryptamine (5‐HT) was investigated in the pennatulid anthozoan Renilla koellikeri by means of peroxidase‐antiperoxidase‐immunohistochemistry with an antiserum against 5‐HT‐formaldehyde‐protein conjugate. In many colonies, strong 5‐HT‐immunoreactivity was displayed by the cell bodies and beaded processes of relatively small neuronlike elements predominating in the outer ectoderm or scattered in the underlying mesoglea. The immunostained neurons of the mesoglea were generally bipolar and their relatively short processes extended toward myoepithelial cells. In the ectoderm, most immunostained neurons appeared pseudounipolar. These cell bodies were endowed with a small, superficially directed, conical appendage reaching the outer surface of the epithelium. Their neurites emerged from the inner pole of the perikarya and branched toward other immunopositive ectodermal and mesogleal nerve cells, or nematocytes in the tentacles. The networklike distribution of the presumed 5‐HT ectodermal neurons varied between the different regions of colonies and along the autozooid column. In the context of earlier observations in cnidarians, these cytological features suggest a sensory as well as a modulatory function for 5‐HT in Renilla koellikeri.
Angiotensin converting enzyme in the human basal forebrain and midbrain visualized by in vitro autoradiography
Authors: Chai Siew Yeen , McKenzie John S. , McKinley Michael J. , Mendelsohn Frederick A. O.
Published: May 2005

Angiotensin converting enzyme converts angiotensin I to angiotensin II, a peptide that plays an important role in the central regulation of blood pressure and fluid and electrolyte homeostasis. However, the distribution of this enzyme in the human brain has not been well described. In this study, angiotensin converting enzyme was mapped in the human basal forebrain and midbrain by using quantitative in vitro autoradiography employing a derivative of a potent converting enzyme inhibitor, 125I‐351A, as radioligand. This radioligand binds specifically and with high affinty to angiotensin converting enzyme and also exhibited these properties in binding to slide‐mounted sections of human basal ganglia.

In the basal ganglia, high levels of binding of 125I‐351A are found in the caudate nucleus, putamen, nucleus accumbens, both divisions of the globus pallidus, and substantia nigra pars reticulata. High densities of labelling also occur in the ventral pallidum. In the hypothalamus, a moderate level occurs in the paraventricular and supraoptic nuclei, and a diffuse, low level of binding is found throughout the periventricular region.

The organum vasculosum of the lamina terminalis, one of the circumventricular organs, displays the highest concentration of binding. The choroid plexus contains only moderate density of labelling in contrast to other mammalian species previously studied. Major fibre tracts are devoid of activity except for the posterior limb of the internal capsule, which contains fascicles of intense activity.

In the midbrain, a moderate density of binding is detected in the periaqueductal gray. The dorsal, central linear, and, more caudally, the centralis superior medialis raphe nuclei also contain moderate densities of labelling.

Angiotensin converting enzyme is heterogeneously distributed in the caudate nucleus and putamen, with distinct patches of high concentrations surrounded by a matrix of diffuse, lower levels. In the caudate nucleus, these patches of high binding corresponded to striosomes since they register with acetylcholinesterase‐poor zones.

The high concentration of angiotensin converting enzyme found in the basal ganglia suggests that the enzyme may be involved in processing neuropeptides that occur in high concentrations in these structures. Possible substance P and enkephalins, which are also concentrated in striosomes.
GABA‐ergic and glycinergic pathways in the inner plexiform layer of the goldfish retina
Authors: Muller Jay F. , Marc Robert E.
Published: May 2005

GABA‐ergic and glycinergic circuitry in the inner plexiform layer of the goldfish retina was evaluated by electron microscopic autoradiography of 3H‐GABA and 3H‐glycine uptake, combined with retrograde horseradish peroxidase (HRP) labeling of ganglion cells. GABA‐ergic and glycinergic synapses were found on labeled ganglion cells throughout the inner plexiform layer. This reinforces the idea that physiological evidence of GABA‐ergic and glycinergic influence on a variety of ganglion cells in goldfish and carp often reflects direct inputs. Double‐labeled synapses are presented as evidence of direct type Ab amacrine cell input to on‐center ganglion cells. At least one population of type Aa sustained‐off GABA‐ergic amacrine cell is proposed, on the basis of profuse GABA‐ergic inputs onto bipolar cells in sublamina a. Similar GABA‐labeled profiles are shown to synapse onto HRP‐labeled probable offcenter ganglion cells. Thus GABA‐ergic amacrine cells not only provide the predominant feedback to depolarizing (on‐center) and hyperpolarizing (offcenter) bipolar cells but also provide feed‐forward inputs to on‐ and off‐center ganglion cells. Large‐caliber GABA‐ergic dendrites present in both sublaminae a and b resemble those expected of a previously described bistratified, transient amacrine cell. These processes synapse onto HRP‐labeled ganglion cell profiles in both sublaminae. Two morphologies of glycinergic amacrine cell are proposed on the basis of light microscopic autoradiography, (1) the previously described small pyriform cell and (2) a multipolar cell. The differential connectivity of the glycinergic neurons described, however, remains indistinguishable. Whereas abundant glycinergic inputs to ganglion cells occur throughout the inner plexiform layer, contacts between glycinergic profiles and bipolar cells are extremely rare. Therefore, interpreting the meaning of glycinergic input to ganglion cells will require further study of amacrine cell circuitry.
Characterization and partial purification of different factors with contraction‐potentiating activities from neurohaemal organs of the locust
Authors: Schiebe Michael , Orchard Ian , Watts Robert , Lange Angela B. , Atwood Harold L.
Published: May 2005

Phe‐Met‐Arg‐Phe (FMRF‐NH2) and structurally related peptides enhance neuromuscular transmission and contraction of the M. extensor tibiae preparations of the locusts Locusta migratoria and Schistocerca gregaria (Walther et al.: Neurosci. Lett. 45:99‐104, '84). Similar effects could also be obtained with extracts of locust ganglia (Walther and Schiebe: Neurosci. Lett. 77:209‐214, '87). By using two HPLC systems, we have partially purified extracts of the unpaired median nerves (including their neurohaemal organs) of different locust ganglia. The biological activity of the extracts served as an estimate for the degree of purification. Six different bioactive fractions were identified migrating at and close to retention times of known ‐RFamide peptides with similar bioactivity. No fraction coeluted with authentic FMRF‐NH2 or FLRF‐NH2. We demonstrate that extensor tibiae muscle contractions were potentiated by HPLC fractions from raw material with ‐RF‐NH2 immunoreactivity, but also by HPLC fractions from raw material without such immunoreactivity.
Functional morphology of the telson‐uropod stretch receptor in the sand crab Emerita analoga
Authors: Wilson L. J. , Paul D. H.
Published: May 2005

The telson‐uropod stretch receptor in Emerita analoga belongs to a segmental array of axial‐coxal receptors having sensory neurons with central somata. It consists of an elastic strand innervated by four giant, nonspiking, mechanoreceptive neurons. We examined the elastic (sensory) strand by light and electron microscopy to discover whether (1) functional differences between the four sensory neurons could be surmised from their peripheral terminations and (2) the process of mechano‐electric transduction in this type of receptor might be revealed by the ultrastructure of the dendritic terminals.

The elastic strand is divided into nonoverlapping domains by the mechanoreceptive neurons. We discerned no differences other than their serial order along the strand‐ Each neuron has three morphological zones in the periphery. In the zone of dendrite entry, the dendrite bifurcates into 40–60μ primary branches that enter the strand at acute to right angles and turn rostrally and caudally along the strand's axis. The zone of branching consists of 4–35 μm diameter dendritic branches within the strand. Approximately 21,000 dendritic tips (diameters, 0.1–0.7 μm; lengths, 3–20μ) per sensory neuron arise via short stubs from all levels of the zone of branching and constitute the zone of dendrite termination.

The repeated bifurcations of dendrites within the zone of branching take place by radial intrusion of longitudinally oriented, partitions of extracellular matrix each of which extends the length of the pair of dendritic branches it divides. Tips project into these partitions. Since they change shape when the elastic strand is stretched, which compresses the extracellular matrix of the partitions, they are probably the site of mechanosensory transduction.

Cross‐sectional profiles of dendritic tips are significantly larger but less numerous in stretched than in relaxed receptors. We propose a model in which stretch compresses distal portions of tips until they are too small to be recognized. The large profiles are the proximal portions of tips that have been expanded by hydrostatic pressure.

The very large number of dendritic tips/nonspiking mechanoreceptor may be what endows each neuron with (1) high sensitivity to stretch of the elastic strand and (2) ability to respond to a broader range of tensions than is usual for single sensory cells (the entire range experienced by the stretch receptor).
Changes in astroglial scar formation in rat optic nerve as a function of development
Authors: Trimmer Patricia A. , Wunderlich Roshna E.
Published: May 2005

Although astroglial scar formation is a common response to almost any type of injury to the adult central nervous system, lesions in fetal and neonatal rats have been reported to induce little or no scar formation. To examine this developmental difference further, rats ranging in age from 1 to 65 days postnatal were unilaterally enucleated, a surgical procedure that causes the axons in the optic nerve to degenerate. The optic nerves were processed for light and electron microscopy at times ranging from 7 to 365 days postenucleation. Pronounced and permanent glial scars were formed in every age group examined, including the neonates. However, the time course for removal of the degenerating axonal debris and formation of a compact, debris‐free glial scar varied as a function of developmental age. In neonatal rats, a compact glial scar formed in 1–2 weeks whereas 3–5 months were required for compact glial scar formation in juveniles and adults. Changes in cross‐sectional area were also associated with optic nerve degeneration and glial scar formation. Whereas lesioned neonatal optic nerves underwent little change in area, there was a substantial decrease in area in the juvenile and adult. Morphometric analysis showed that irrespective of the age of the animal at the time of enucleation, the final area of the compact glial scar was 10–20% of the unlesioned adult control. These results suggest that conflict in the literature over the ability of neonatal astrocytes to form a glial scar may be due to the nature of the lesion or the method of detection since astrocytes in the neonatal rat optic nerve clearly have the capacity to become reactive and form a glial scar.
Mandibular motor neurons of the caterpillar of the hawk moth Manduca sexta
Authors: Griss Christian
Published: May 2005

As part of a planned study of the central neural basis of feeding behaviour in larval Manduca sexta, the morphology and physiology of the mandibular motor system is here described.

The gross neuroanatomy of the postoral head segments has been investigated, especially the course and structure of the mandibular nerves.

The electrophysiology of the mandibular opener and closer muscles has been investigated by extra‐ and intracellular recording during feeding behaviour and during electrical stimulation of the motor nerve. All the muscle fibres examined are of the “fast,” twitch type. Contraction is associated exclusively with locally or completely propagated overshooting action potentials, never with local functional potentials. Control of the muscles is by recruitment of more motor units and/or an increase of frequency of action potentials. No inhibitory synaptic potentials could be found.

The motor neurons of the mandibular muscles have been identified by cobalt backfills of the mandibular nerve, and characterized by intracellular recording and dye injection. There are 12 closer and 8 opener motor neurons. All motor neurons recorded so far evoke 1:1 twitches in the muscle, and none appear to be inhibitory. No GABA‐immunoreactive axons could be found in the mandibular nerve.
Postnatal development of striatal neurotensin immunoreactivity in relation to clusters of substance P immunoreactive neurons and the “dopamine islands” in the rat
Authors: Zahm D. S. , Eggerman K. W. , Sprung R. F. , Wesche D. E. , Payne E.
Published: May 2005

Conventional immunoperoxidase preparations of the coronally sectioned brains of rats killed at various times during the early postnatal period revealed the distributions of tyrosine hydroxylase, substance P, and neurotensin immunoreactivities. At birth, patches of dense tyrosine hydroxylase immunoreactivity were present across the breadth of the rostral striatum, whereas patches displaying substance P immunoreactivity were present only in its lateral half, appearing in its medial half by about postnatal day 3. Neuronal neurotensin immunoreactivity was absent in the rostral striatum at birth, although some neurotensin immunoreactive cells were present in the tail of the caudate‐putamen. Rostrally, neurotensin immunoreactive cells appeared first along the lateral margin of the caudate‐putamen on postnatal day 3, became numerous there about day 5, spread medially into the striatum by day 7, and achieved their medialmost distribution by about day 10. Their numbers and those of substance P immunoreactive neurons diminished thereafter.

Substance P immunoreactive patches, which contained numerous labeled neurons and “puncta,” shared coextensive distributions with patches of dense tyrosine hydroxylase immunoreactivity, but interdigitated with neurotensin immunoreactive cell clusters. The neurotensin immunoreactive cell clusters lacked puncta, the light microscopic representation of axon terminals, or swellings.

It is concluded that the patchy infrastructure of the striatum, which is established prior to birth, is substrate for the progression of separate “waves” of elevated neuronal peptide content, one reflecting substance P and a later one reflecting neurotensin. These proceed along rostromedialward trajectories to involve interdigitating neuronal domains.
Pathways for motion analysis: Cortical connections of the medial superior temporal and fundus of the superior temporal visual areas in the macaque
Authors: Boussaoud Driss , Ungerleider Leslie G. , Desimone Robert
Published: May 2005

To identify the cortical connections of the medial superior temporal (MST) and fundus of the superior temporal (FST) visual areas in the extrastriate cortex of the macaque, we injected multiple tracers, both anterograde and retrograde, in each of seven macaques under physiological control. We found that, in addition to connections with each other, both MST and FST have widespread connections with visual and polysensory areas in posterior prestriate, parietal, temporal, and frontal cortex. In prestriate cortex, both areas have connections with area V3A. MST alone has connections with the far peripheral field representations of V1 and V2, the parieto‐occipital (PO) visual area, and the dorsal prelunate area (DP), whereas FST alone has connections with area V4 and the dorsal portion of area V3. Within the caudal superior temporal sulcus, both areas have extensive connections with the middle temporal area (MT), MST alone has connections with area PP, and FST alone has connections with area V4t. In the rostral superior temporal sulcus, both areas have extensive connections with the superior temporal polysensory area (STP) in the upper bank of the sulcus and with area IPa in the sulcal floor. FST also has connections with the cortex in the lower bank of the sulcus, involving area TEa. In the parietal cortex, both the central field representation of MST and FST have connections with the ventral intraparietal (VIP) and lateral intraparietal (LIP) areas, whereas MST alone has connections with the inferior parietal gyrus. In the temporal cortex, the central field representation of MST as well as FST has connections with visual area TEO and cytoarchitectonic area TF. In the frontal cortex, both MST and FST have connections with the frontal eye field.

On the basis of the laminar pattern of anterograde and retrograde label, it was possible to classify connections as forward, backward, or intermediate and thereby place visual areas into a cortical hierarchy. In general, MST and FST receive forward inputs from prestriate visual areas, have intermediate connections with parietal areas, and project forward to the frontal eye field and areas in the rostral superior temporal sulcus. Because of the strong inputs to MST and FST from area MT, an area known to play a role in the analysis of visual motion, and because MST and FST themselves have high proportions of directionally selective cells, they appear to be important stations in a cortical motion processing system.
Quantitative, three‐dimensional analysis of granule cell dendrites in the rat dentate gyrus
Authors: Claiborne Brenda J. , Amaral David G. , Cowan W. Maxwell
Published: May 2005

The three‐dimensional organization of dentate granule cell dendritic trees has been quantitatively analyzed with the aid of a computerized microscope system. The dendrites were visualized by iontophoretic injection of horseradish peroxidase into individual granule cells in the in vitro hippocampal slice preparation. Selection criteria insured that the analyzed cells were completely stained and that only neurons with two or fewer cut dendrites in the distal portion of the molecular layer were analyzed. Twenty‐nine of the 48 sampled granule cells had no cut dendrites.

The granule cells had between one and four primary dendrites. Granule cell dendritic branches were covered with spines and most extended to the hippocampal fissure or pial surface. The mean total dendritic length was 3,221 μm with a range from 2,324 μm to 4,582 μm. The dendrites formed an elliptical plexus with the transverse spread averaging 325 μm and the spread in the septotemporal axis averaging 176 μm. On individual neurons, the maximum branch order ranged from four to eight and the number of dendritic segments ranged from 22 to 40. Approximately 63% of the dendritic branch points occurred in a zone that included the granule cell layer and the inner one‐third of the molecular layer. The dendritic tree was organized so that, on average, 30% of the length was in the granule cell layer and proximal third of the molecular layer, 30% was in the middle third, and 40% was in the distal third. Comparisons were made between the dendrites of granule cells in the suprapyramidal and infrapyramidal blades of the dentate gyrus. Suprapyramidal cells had a significantly greater total dendritic length than infrapyramidal cells, their transverse spread was higher, and they had a greater number of dendritic segments. When neurons in the suprapyramidal blade were further subdivided on the basis of somal position within the depth of the cell body layer, superficial neurons were found to have a greater number of primary dendrites, more elliptical trees, and larger transverse spreads of their dendrites. There were no significant differences in dendritic segment number or total dendritic length between superficial and deep cells.