bluuebunny/crossref_metadata_2025 huggingface dataset:
Normal and abnormal retinal projections following the crush of one optic nerve in goldfish (Carrassius auratus)
Authors: Springer Alan D.
Published: January 2005

Optic nerve regeneration was examined with [3H]proline radioautography in fish that had one nerve crushed. Fibers had not yet grown beyond the crush site at 2 days post‐crush (PC) and were at the optic chiasm by 4–5 days PC. By 6 days PC the fibers had reinnervated the rostral pole of the contralateral tectum, the lateral geniculate nucleus and area pretectalis dorsalis and ventralis. Area preopticus, nucleus opticus dorsolateralis and nucleus opticus commissurae posterior were partially reinnervated by 8 days PC. At this time numerous abnormal targets were labeled, including nucleus rotundus, nucleus isthmi, cerebellum, pituitary gland and ipsilateral optic tectum. Optic fibers also entered the posterior, intertectal and horizontal commissures, as well as tractus rotundus, the tectocerebellar, tectobulbar and mesencephalocerebellar tracts. In addition, fibers within the contralateral optic tectum were not restricted to their usual laminae. They were distributed from the superficial edge of the tectum to the ventricle. At 32 days PC only the normal retinal projections were evident, and all of the anomalous projections had disappeared. The anomalous projections may have either retracted or degenerated or become undetectable with radioautography.
Neurogenesis in the trigeminal ganglion of the albino rat: A quantitative autoradiographic study
Authors: Forbes Donna J. , Welt Carol
Published: January 2005

The time of neuron origin in the trigeminal ganglion was examined in autoradiograms of 60‐day‐old rats that were exposed to a single pulse of 3H‐thymidine on day 11, 12, 13, 14, or 15 of gestation. Heavily labeled neurons, representing cells in or near their last mitotic division at the time of the pulse label, were present in animals injected between embryonic days 11 and 13 with a peak on day 12. Within this time period, larger neurons were generated prior to smaller neurons with a peak for larger cells on day 12 and for smaller cells on day 13. Thus, the majority of trigeminal ganglion neurons are generated over a three‐day period just after the midpoint of gestation.

Neuron number, size, type, and cytoarchitectural organization were also examined in the ganglion. The mean neuron count per ganglion was 52,372. The size distribution of these cells ranged continuously from 7–61 μm (mean diameter) with no evidence for clearly defined subpopulations. The staining intensity and distribution patterns of the Nissl substance varied greatly from cell to cell precluding the classification of cells as light or dark. Little correspondence between these Nissl features and cell size was found. Among the clusters and rows of neurons in the ganglion, we did not see consistent cytoarchitectonic patterns which might reflect specific sensory receptive fields.
A golgi‐electron microscopic study of goldfish optic tectum. I. description of afferents, cell types, and synapses
Authors: Meek J.
Published: January 2005

A study of goldfish optic tectum was performed with conventional electron microscopy and with the Golgi‐EM technique described by Fairén et al. (1977). Five types of tectal afferents, three types of interneurons and three types of efferent neurons were investigated.

Afferents from the torus longitudinalis, which terminate in the marginal layer, contain round synaptic vesicles with a mean diameter of 43 nm. Optic afferents, which terminate in the superficial gray and plexiform layer, are characterized by pale mitochondria with dilated cristae and round vesicles with a mean diameter of 49 nm. Afferents of unknown origin, terminating in several tectal layers, can be subdivided in three types; one containing round vesicles and two containing pleomorphic vesicles with different degrees of ellipticity.

The three types of interneurons studied (type I, III and XIV, of Meek and Schellart, 1978) were selected on basis of their high frequency of occurrence. The apical dendrites of type I neurons make many synaptic contacts with the marginal axons. All three types have dendrites in the superficial gray and plexiform layer making contacts with optic nerve terminals. In addition, their dendrites and cell bodies make synaptic contacts with several types of unidentified presynaptic elements. The axon terminals of type I and of type XIV contain round vesicles with a mean diameter of 45 and 46 nm respectively.

Three of the four types of efferent neurons present in the goldfish tectum were studied (type VI, XII and XIII). Two of them make contact with optic terminals (type VI and XII) and two make contact with tectal afferents of unknown origin in the central white layer or in the lower part of the central gray layer (type XII and XIII). The axons of all three types become myelinated at some distance from their origin. Their intial unmyelinated parts are covered with a so‐called “outer surface coating”, have no collaterals and are occasionally (type VI and XII) or frequently (type XIII1) postsynaptic to other elements. The archiform axons of type XIII1, and to a lesser extent also the shepherds‐crook shaped axons of type XII, have a close apposition to looping and narrowing dendrites in the inner plexiform layer.

The present results concerning neuronal circuitry of the goldfish optic tectum are summarized in a tentative scheme.
Intracortical arborizations and receptive fields of identified ventrobasal thalamocortical afferents to the primary somatic sensory cortex in the cat
Authors: Landry Pierre , Deschênes Martin
Published: January 2005

The intracortical arborizations of neurons from the ventroposterolateral thalamic nucleus (VPL) in the cat were studied by intraaxonal injections of horseradish peroxidase (HRP) following identification of their receptive fields. In the primary somatic sensory cortex (SI) VPL cells terminated in different cytoarchitectonic areas according to their receptive field modality. Fibers excited by deep tissues or joint rotation arborized preferentially in area 3a. Those responding tonically to cutaneous stimuli were located in the anterior part of area 3b; hairdriven cells terminated in area 3b and in the rostral pole of area 1. All fibers had a similar laminar distribution within SI. Axons terminated mostly in layers VI, IV, and the lower part of layer III. None terminated in layers I and II. Most terminal arbors were oriented along the mediolateral axis of the brain. The main arborization of a single VPL cell formed a bush of about 500 μm in diameter. Some fibers generated two such bushes with an uninvaded region of about 300 μm between them. It is proposed that this patchy organization underlies in part the columnar organization of area SI. Many VPL cells had secondary projection sites in SI. These were issued from smaller‐sized collaterals and were located in a different cytoarchitectonic area than that of the main terminal plexuses. A significant number of these collaterals projected to area 4. Insufficient filling of the collaterals by HRP prevented a more complete characterization of the secondary arbors.
Metabolic response of optic centers to visual stimuli in the albino rat: Anatomical and physiological considerations
Authors: Toga Arthur W. , Collins Robert C.
Published: January 2005

The functional organization of the visual system was studied in the albino rat. Metabolic differences were measured using the 14‐C‐2‐deoxyglucose (DG) autoradiographic technique during visual stimulation of one entire retina in unrestrained animals. All optic centers responded to changes in light intensity but to different degrees. The greatest change occurred in the superior colliculus, less in the lateral geniculate, and considerably less in second‐order sites such as layer IV of visual cortex. These optic centers responded in particular to on/off stimuli, but showed no incremental change during pattern reversal or movement of orientation stimuli. Both the superior colliculus and lateral geniculate increased their metabolic rate as the frequency of stimulation increased, but the magnitude was twice as great in the colliculus. The histological pattern of metabolic change in the visual system was not homogenous. In the superior colliculus glucose utilization increased only in stratum griseum superficiale and was greatest in visuotopic regions representing the peripheral portions of the visual field. Similarly, in the lateral geniculate, only the dorsal nucleus showed an increased response to greater stimulus frequencies. Second‐order regions of the visual system showed changes in metabolism in response to visual stimulation, but no incremental response specific for type or frequency of stimuli.

To label proteins of axoplasmic transport to study the terminal fields of retinal projections 14C‐amino acids were used. This was done to study how the differences in the magnitude of the metabolic response among optic centers were related to the relative quantity of retinofugal projections to these centers. Fast and slow axoplasmic transport were studied using three separate amino acids. In each case over 64% of the radioactivity projecting contralateral from the eye was found in superior colliculus. Considerably less isotope was found in dorsal lateral geniculate (11–17%), ventral lateral geniculate (3.7–6.2%), pretectal nuclei (5–12%), and the accessory optic system (3–7%). The greatest concentration of radioactivity within each optic center was found in the visuotopic aspect subserving the superior visual field; particularly the medial aspects of the superior colliculus, olivary pretectal nucleus, and posterior pretectal nucleus, and the anterior portion of the nucleus of the optic tract. The representation of central vision in the colliculus was relatively pale, as was a zone within the middle of the contralateral dorsal lateral geniculate.

The anatomical and physiological results of this study suggest that differences in deoxyglucose metabolism among optic centers are primarily related to the number of retinofugal endings and the kind of visual stimulation. Changes within any one center primarily reflect the density of retinal endings subserving the visual field.
Distribution of methionine‐enkephalin immunoreactivity in the chick brain: An immunohistochemical study
Authors: De Lanerolle N. C. , Elde R. P. , Sparber S. B. , Frick M.
Published: January 2005

The distribution of Met‐enkephalin‐like immunoreactivity in the brains of 2‐week‐old domestic chicks was studied with immunohistofluorescence and the unlabeled antibody peroxidase‐antiperoxidase technique, using antibodies to Met‐enkephalin generated in rabbits. Immunoreactive cell bodies were found in the telencephalon, diencephalon, and mesencephalon in areas as yet uncharacterized as discrete nuclei in birds (E‐1, E‐2, E‐3, E‐4, E‐5); further cells were located in the diencephalic nucleus spiriformis lateralis, the midbrain medial intercollicular nucleus (E‐6), the nucleus mesencephalicus lateralis, pars dorsalis, the Edinger‐Westphal nucleus and dorsal occulomotor nucleus; and in the nucleus of cranial nerve X and an uncharacterized area in the dorsolateral medulla (E‐7). Immunoreactive fibers and/or terminals were located around the immunoreactive cell bodies and, in addition in the lateral septal area of the telencephalon; in the preoptic and hypothalamic areas of the diencephalon; in the anterior intercollicular area, periaqueductal central gray, area C, and the midventral tegmentum of the mesencephalon; in the nucleus solitarius, nucleus IX‐X, nucleus intercalatus, nucleus intermedius, and ventrolateral areas of the rhombencephalon. The pattern of distribution of met‐enkephalin in the chick is compared with that in the rat. A possible functional role for Met‐enkephalin in neural mechanisms mediating some behaviors of the chick is suggested.
Thin‐section and freeze‐fracture studies of crayfish stretch receptor synapses including the reciprocal inhibitory synapse
Authors: Hirosawa Kazushige , Tao‐Cheng Jung‐Hwa , Nakajima Yasuko , Tisdale Ann D.
Published: January 2005

The crayfish slow‐adapting abdominal stretch receptor organ is innervated by three inhibitory and several excitatory axons. A previous study by Tisdale and Nakajima ('76) showed that under certain fixation conditions inhibitory and excitatory synapses can be distinguished on the basis of synaptic vesicle structure. Using this morphological criterion we describe six types of synapses in the receptor: (1) the inhibitory axo‐dendritic synapse, (2) the excitatory neuromuscular synapse, (3) the inhibitory neuromuscular synapse, (4) the axo‐axonic synapse which suggests presynaptic inhibition on the excitatory synapse, (5) the axo‐axonic synapse which suggests presynaptic inhibition on the inhibitory synapse, (6) the reciprocal inhibitory axo‐axonic synapse, which is a new type of synapse. The presence of these six types of synapse suggests that inhibitory and excitatory axons interact synaptically in a complicated manner, resulting in a delicate control of receptor function. In freeze fracture we have observed the presynaptic membrane structures of inhibitory and excitatory synapses. The active zone of the inhibitory synapse has ridges with loosely aggregated particles on the tops of the ridges and indentations (vesicle attachment sites) along their sides. The active zone of the excitatory neuromuscular synapse consists of bands of particle aggregates which are situated on slightly elevated membrane regions and surrounded by wide, relatively particle‐free, flat membrane areas.
Generation of the ocular motor nuclei and their cell types in the rabbit
Authors: Shaw Marjorie D. , Alley Keith E.
Published: January 2005

Autoradiography of 3H‐thymidine incorporation was combined with horseradish peroxidase (HRP) transport to distinguish the birthdates of motoneurons and internuclear neurons of the abducens nucleus, and of specific motor pools within the oculomotor nucleus. Motoneurons were identified by their retrograde transport of HRP from the extraocular muscles. In other experiments, internucleur neuron types may be controlled by the local environment. The motor pools ofthe oculomotor nucleus are generated sequentially. This may reflect the mechanism whereby nuclei are constructed.
GABAergic synapses in the goldfish retina: An autoradiographic study of 3H‐muscimol and 3H‐GABA binding
Authors: Yazulla Stephen
Published: January 2005

The localization of synaptic receptor sites for γ‐amino butyric acid (GABA) in the goldfish retina was studied by light microscopic (LM) and electron microscopic autoradiography (EM‐ARG) of 3H‐muscimol and 3H‐GABA binding. Sodium‐independent binding of both 3H‐muscimol and 3H‐GABA was localized to a uniform band throughout the inner plexiform layer (IPL) by LM‐ARG of cryostat sections incubated in these compounds. No binding was observed over the outer plexiform layer. This binding pattern differs from the uptake pattern of 3H‐GABA in the IPL, which shows very heavy labeling in the most proximal IPL and little labeling throughout the rest of the IPL. Statistical analysis of EM‐ARGs of 3H‐muscimol (i.e., make GABAergic synapses). Labeled amacrine‐to‐amacrine synapses are mostly concentrated in the 20–80% levels of the IPL, whereas amacrine‐to‐bipolar synapses are concentrated at about the 70–90% depth. Maximal 3H‐GABA uptake, however, occurs at the 90–100% depth. This difference in the location of GABAergic synaptic binding and GABAergic uptake leads to the conclusion that the density of uptake label provides little information about the density of synaptic contacts. Thus, in order to localize GABAergic interactions, synaptic binding rather than neuronal uptake appears to provide the more appropriate description.
Organization of thalamic afferents to anterior dorsal ventricular ridge in turtles. I. Projections of thalamic nuclei
Authors: Balaban Carey D. , Ulinski Philip S.
Published: January 2005

Dorsal ventricular ridge (DVR) is a thalamorecipient, subcortical telencephalic structure in reptiles and birds. Although there is a fair amount of information about sources of afferents to DVR, little is known about the relationship of projections from individual thalamic nuclei to the organization of the structure. This study examines the relationship between thalamic projections and both areal and zonal divisions of anterior DVR (ADVR; Balaban,'78a) of emydid turtles with orthograde degeneration, and horseradish peroxidase techniques.

Individual thalamic nuclei contribute either a diffuse or a restricted projection to ADVR. Diffuse projections arise primarily from the dorsomedial anterior nucleus. These fine‐caliber axons distribute bilaterally over a wide region of the telencephalon via both medial and lateral thalamotelencephalic pathways. The terminal regions include septum, striatum and the medial bank of cortex caudal to the lamina terminalis. In ADVR, the fibers are distributed sparsely in zones 2–4 of dorsal, medial and ventral areas. Restricted projections to ADVR originate in nucleus rotundus, nucleus reuniens and nucleus caudalis. They ascend ipsilaterally in the lateral thalamotelencephalic pathway (lateral forebrain bundle), and enter ADVR rostral to the anterior commissure. Nucleus rotundus projects to zone 4 of dorsal area, nucleus caudalis projects to zones 2–4 of the dorsal division of medial area, and nucleus reuniens projects to zones 2–4 of both the ventral division of medial area and the ventral area.

Comparison of these results with thalamotelencephalic projections in mammals suggests that diffuse and restricted thalamic projection systems are a common feature of both groups. Restricted thalamic projections in reptiles, birds and mammals, terminating in anatomically distinct regions, also appear to be associated with different sensory modalities. The significance of diffuse systems is not clear.
Secondary vestibulocerebellar projections to flocculonodular lobe in a prosimian primate, Galago senegalensis
Authors: Rubertone J. A. , Haines D. E.
Published: January 2005

The organization of vestibulocerebellar projections to the flocculonodular and adjacent cortices were studied in Galago using horseradish peroxidase (HRP). Implants of HRP pellets or injections (0.14–0.95μI) were placed in floccular, parafloccular, nodular, and uvular cortices. Following survival times of 18–25 hours animals were killed via transcardiac perfusion of heparinized saline followed by a buffered solution of paraformaldehyde and glutaraldehyde. Tissues were processed using DAB as the chromogen.

Consequent to floccular implants HRP‐positive cells are found bilaterally in medial (MVN), spinal (SpVN), and superior (SVN) vestibular nuclei. Labeled neurons are present in the ipsilateral subgroup y and interstitial nucleus of the eighth nerve. The prepositus hypoglossal nuclei also contained HRP‐positive somata. A column of labeled cells is present exclusively in dorsomedial MVN subsequent to injection of the paraflocculus. Injections of nodular cortex reveal a distinct bilateral projection to this cortical area. Many labeled cells are located in SpVN, MVN, SVN, subgroups x and y, the interstitial nucleus, and the ganglion of the eighth nerve. Labeled somata are concentrated in dorsal and dorsolateral SpVN and in a bandlike configuration in subgroup x. HRP‐reactive cells appear to have a differential rostrocaudal distribution in MVN, while the majority of positive cells in SVN are found in central portions of the nucleus. After HRP injection into the transition area between nodular and uvular cortices, labeled neurons are present in MVN, SpVN, and the prepositus hypoglossal nucleus. A similar distribution of HRP‐positive cells is seen following injections of ventral uvula; however, cells are markedly fewer in number. In no case, subsequent to injection of the flocculonodular lobe and adjacent cortices, are HRP‐labeled neurons found in the lateral vestibular nucleus.
Regeneration of taste buds after reinnervation of a denervated tongue papilla by a normally nongustatory nerve
Authors: Zalewski Andrew A.
Published: January 2005

Taste buds degenerate and disappear after transection of their sensory nerve supply, and they differentiate anew from epithelial cells (e.g., lingual) following regeneration of sensory but not motor or autonomic axons. A controversy exists as to whether only gustatory sensory nerves can cause buds to reform or whether any sensory nerve can perform this function. This issue arose because the results of cross‐innervation studies revealed a specificity whereas grafting data demonstrated a nonspecificity. A retest of specificity in the cross‐reinnervation situation was performed by reinnervating the denervated vallate papilla of adult rat tongue with a sensory branch of the vagus nerve that is not normally gustatory. It was found that taste buds disappeared and remained lost from acutely and chronically denervated papilla. However, some buds were found 90–100 days after reinnervation by the normally nongustatory vagus nerve branch. Transection of the regenerated vagus nerve resulted in the loss of innervation and the degeneration of taste buds from reinnervated papilla indicating that this nerve had supported buds. These results show that a normally nongustatory nerve can induce the formation of taste buds after its axons grow into appropriate tissue. It appears that the ability to support taste buds is a nonspecific, rather than a specific, property of sensory nerve.
Organization of afferent input to subdivisions of area 8 in the rhesus monkey
Authors: Barbas H. , Mesulam M‐M.
Published: January 2005

The sources of ipsilateral afferents to subdivisions of one frontal eye field (Walker, '40a area 8 ) were studied with horseradish peroxidase (HRP) in macaque monkeys. There were major differences in the distribution of cells pro‐ jecting to the caudal and rostral parts of area 8. The majority (53%) of labeled cortical cells projecting to caudal regions were in visual association areas, and an additional 23% were in the ventral bank of the intraparietal sulcus, where neurons may have predominantly visual and visuomotor properties. In contrast, rostral area 8 had a much lower percentage of its cortical input originating in visual association areas (5%) or in the ventral bank ofthe intraparietal sulcus (8%). After HRP injection in this rostral part, 21% of labeled cells were in auditory association areas and 13% in paralimbic regions, whereas labeling in these two types of cortex was negligible after HRP administration to caudal parts of area 8. The percentage of cells in other association regions (portions of the banks of the superior temporal sulcus, dorsolateral parietal, medial parietal, and prefrontal cortices) was higher in the rostral (53%) than in the caudal case (21%). The results suggest that caudal area 8 may be involved in head and eye movements in response to visual stimuli, while its anterior subdivisions may be involved in directing the head and eyes in response to auditory stimuli. Furthermore, limbic input may also be relevant to the neural processing occurring in rostral frontal eye fields, perhaps by directing attention toward motivationally relevant stimuli.
Anatomical demonstration of multiple representation in the forelimb region of the cat motor cortex
Authors: Pappas C. L. , Strick P. L.
Published: January 2005

Retrograde transport of HRP was employed to examine the pattern of callosal connections in the forelimb region of area 4$ in the cat. According to the conventional view, areas of the motor cortex which contain the representation of distal body parts neither send nor receive callosal fibers. If this is true, then an absence of callosal connections would define the sites of distal forelimb representation. Following multiple injections of HRP into the contralateral motor cortex, many labeled neurons were found in the forelimb region of area 4$. However, within this region, two spatially separate areas were found where labeled neurons were either absent or present in very low density (“callosal holes”). The anatomically defined callosal holes corresponded in size, shape, and location to the physiologically defined digit zones. To provide direct evidence for this correspondence, retrograde HRP transport was combined with intracortical stimulation in the same animal. Small lesions placed in physiologically identified digit zones were located within the anatomically defined callosal holes. Thus, a double representation of the distal forelimb can be defined in area 4γ of the cat motor cortex using both anatomical and physiological methods.
A collateral pathway to the neostriatum from corticofugal neurons of the rat sensory‐motor cortex: An intracellular HRP study
Authors: Donoghue John P. , Kitai S. T.
Published: January 2005

A projection from large pyramidal cells in layer V of the rat somatic sensory‐motor (SSM) cortex both to the neostriatum and the brainstem was demonstrated by intracellular recording and injection of horseradish peroxidase (HRP). Layer V neurons that project to the brainstem were identified either by antidromic activation from the cerebral peduncle or by tracing the HRP‐labeled axon into the internal capsule in histochemically processed sections. Intracellular responses to stimulation of the hindlimb, forelimb or mystacial pad were also examined.

Five of 20 HRP‐injected neurons that project to the brainstem had a fine collateral branch within the striatum. These branched corticostriatal cells respond at short latency (7–12 msec) to somatic sensory stimulation. All of the injected corticofugal neurons that had a striatal collateral were large pyramidal neurons located in layer Vb of the forelimb and head areas of SSM cortex.

Branched corticofugal neurons have a rich basal dendritic field and a prominent apical dendrite that arborizes in the superficial cortical layers. Intracortical axon collaterals from the branched cells ramify in layers V and VI, and also project to the upper layers of cortex, near the apical dendrite. Beyond the cortex, the main axon has no collateral branches, except for a single laterally directed branch in the neostriatum. The diameter of the striatal collateral is small (about 0.5 μm), compared to that of the main axon (2.0–2.5 μm). It is concluded that these branched cells provide a parallel input to the neostriatum and to brainstem or spinal motor centers.
The organization of somatosensory area II in tree shrews
Authors: Sur Mriganka , Weller Rosalyn E. , Kaas Jon H.
Published: January 2005

Microelectrode multiunit recording methods were used to determine the somatotopic organization of the second somatosensory area, S‐II, in tree shrews. Neurons were activated by light tactile stimuli, and receptive fields were located on the contralateral body surface only. The orientation of S‐II was such that the top of the head adjoined S‐I and the distal limbs pointed away from S‐I so that the representation could be characterized as “erect.” In general, the distortions of the body surface in S‐II were similar to those found in S‐I of the tree shrew (Sur et al., '80), with the exception that proportionately less cortex was devoted to the glabrous nose. The representation in S‐II was more continuous than that in S‐I. Finally, cortex bordering S‐II caudally was found to be responsive to generally more intense somatosensory stimuli such as taps to the body surface.
Lesion‐induced synaptogenesis in the dentate gyrus of aged rats: I. Loss and reacquisition of normal synaptic density
Authors: Hoff Steven F. , Scheff Stephen W. , Benardo Larry S. , Cotman Carl W.
Published: January 2005

Quantitative electron microscopy was used to examine the ability of aged (2‐year‐old) and young adult (90‐day‐old) rats to replace those synapses lost (85–90%) in the outer two‐thirds of the molecular layer of the dentate gyrus after a complete unilateral lesion of the entorhinal cortex. In aged rats the synaptic density is significantly lower than that of young adults at 10 days postlesion. Synaptic replacement begins between 2 and 4 days postlesion in young adults, whereas there is a delay until after 10 days postlesion in aged rats. Once synapse replacement begins in aged rats, the rate of synapse reappearance is about equal that of young adults. Thus the initial 10 days postlesion appears critical to growth of responding afferents and reformation of synaptic contacts.

Analysis of synapses in terms of noncomplex and complex synaptic types shows that the noncomplex type accounts for the significant synaptic density difference between the two age groups. Replacement of complex synapses is nearly indistinguishable between age groups and is complete by 60 days postlesion. In contrast the initial replacement rate of noncomplex synapses in aged rats is much slower than young adults, though the control synaptic density is achieved by the end of the time course.
Immunohistochemical identification of neurons in the paraventricular nucleus of the hypothalamus that project to the medulla or to the spinal cord in the rat
Authors: Sawchenko P. E. , Swanson L. W.
Published: January 2005

A method that allows the concurrent localization of an antigen and a retrogradely transported fluorescent dye (true blue) was used to identify, immunohistochemically, cells in the paraventricular nucleus of the hypothalamus (PVH) that project to autonomic centers in the brainstem or in the spinal cord of the adult albino rat. After placing injections of true blue in the dorsal vagal complex or in upper thoracic segments of the spinal cord, series of evenly spaced sections through the PVH were stained with antisera directed against oxytocin, vasopressin, somatostatin, methionine‐enkephalin, or leucine‐encephalin. The results indicate that both oxytocin‐ and vasopressin‐stained cells in the PVH project to the spinal cord and (or) to the dorsal vagal complex, although about three times as many oxytocinstained cells were doubly labeled after injections centered in either terminal field. The oxytocin‐ and vasopressin‐stained cells that give rise to these long descending projections were found primarily in caudal parts of the parvo cellular division of the PVH, where immunoreactive cells were shown to be significantly smaller than oxytocin‐ and vasopressin‐stained cells in parts of the nucleus that project to the posterior pituitary. Small populations of cells in the PVH that cross‐react with antisera against somatostatin, leucine‐enkephalin, or methionine‐enkephalin were also shown to project directly to the region of the dorsal vagal complex and to the spinal cord, and to have a unique distribution within the PVH. Collectively, the total number of doubly labeled cells that were identified in these experiments accounts for only about one‐fourth of the total number of PVH neurons with long descending projections, thus suggesting that additional neuroactive substances are contained within these pathways.
Retinal ganglion cell projections to individual layers of the lateral geniculate body in Galago crassicaudatus
Authors: Itoh Kazuo , Conley Michael , Diamond Irving T.
Published: January 2005

The genus Galago provides an unique opportunity to study the relation between layers of the lateral geniculate body and classes of retinal ganglion cells. In the present experiments HRP was restricted to individual layers of the lateral geniculate body with the following results: After injections of the magnocellular layers, layers 1 and 2, labeled retinal ganglion cells ranged in size from 8 to 20 μm. After injections of the parvocellular layers, layers 3 and 6, labeled retinal ganglion cells ranged in size from 6 to 12 μm. After injections involving layers 4 and 5, which layers contain only very small, pale cells, labeled retinal ganglion cells ranged in size from 5 to 14 μm. Thus, the very largest ganglion cells were labeled only after injections of magnocellular layers 1 and 2, while small and medium retinal ganglion cells were labeled after HRP injections in every layer of the lateral geniculate body. Because the magnocellular layers actually contain a mixture of large, medium, and small‐sized cells, we suggest that retinal ganglion cells of different size‐classes project to geniculate relay cells of the corresponding size‐class.
Fiber connections of the corpus glomerulosum in a teleost, Navodon modestus
Authors: Sakamoto Noboru , Ito Hironobu
Published: January 2005

Fiber connections of the corpus glomerulosum (CG) in a teleost, Navodon modestus, were studied by means of horseradish peroxidase (HRP) and a pars rotunda (GR). Both the GR and the GA have the same cell components and glomeruli. The GR is composed of four layers arranged concentrically around a central fiber net in the following order (Ito and Kishida, 1975): a glomerular layer, a fibrous layer, a small‐cell layer, and a peripheral fibrous capsule including large cells. The GA consists of a central glomerular layer and a peripheral small‐cell which contains some large cells. Following HRP injections into the GR, HRP‐positive cells were found bilaterally in the nucleus corticalis and ipsilaterally in the nucleus intermedius of Brickner (1929). Lesions of the nucleus coryicalis produced degenerating terminals bilaterally in glomeruli in the CG. The course of the fiber connections was coincident with that of the commissura horizontalis. Lesions of the nucleus intermedius resulted in degenerating terminala in the fibrous layer of the GR and the small‐cell layer of the GA. Following the destruction of the GR degenerating terminals occurres in the ipsilateral lobus inferior. Both small and large cells in the ipsilateral CG were labeled after HRP injections into the lobus inferior.
Cytoarchitectonic heterogeneity of the primate neostriatum: Subdivision into island and matrix cellular compartments
Authors: Goldman‐Rakic Patricia S.
Published: January 2005

The cytoarchitecture of the caudate nucleus was examined in Nisslstained sections from rhesus monkeys, in some of which the corticostriatal terminals had also been labeled by anterograde transport of tritiated amino acids injected into prefrontal cortex. The cytoarchitectonic analysis revealed the existence of two cellular compartments that could be distinguished on the basis of cell size, density, orientation, and tinctorial properties: (1) cell islands consisting of approximately 1,500 to 15,000 densely packed neurons that form aggregates of variable shapes and sizes embedded in (2) a matrix compartment of slightly larger and more loosely packed neurons that comprise the remaining and greater part of the caudate nucleus. In coronal sections, cellular islands appear mostly as round or elliptically shaped areas, 300–600 μm in diameter, but can assume more elongated and complex forms particularly in the sagittal and horizontal planes. They are encircled by fibers arranged in a thin, cell‐sparse capsule that sets them apart from the matrix compartment. Analysis of cellular organization and corticostriatal connections in counterstained autoradiograms indicates that the prefrontal cortex projects only to the matrix zone and not to the territory occupied by island cells. Therefore, according to present observations the neostriatum in primates should be viewed as a cytoarchitectonically heterogeneous structure composed of at least two distinct cellular compartments with specific connectivity. These compartments may be related to the histochemical and functional diversity of the neostriatum.
Analysis of temporal and spatial patterns of rat vestibular hair cell differentiation by tritiated thymidine radioautography
Authors: Sans Alain , Chat Mireille
Published: January 2005

The location in time and space of the terminal mitoses of type I and type II sensory hair cells (HCI and HCII) of the developing crista ampullaris in rat lateral semicircular canal and macula utriculi was determined by radioautographs of specimens exposed to tritiated thymidine from the 13th to the 20th day of gestation. Qualitative analysis and statistical treatment of the percentages of labeled HCI and HCII show that the terminal mitoses occur first in the macula utriculi with a maximum percentage of the 14th day of gestation, for the HCI, and on the 15th day of gestation, for the HCII. In the lateral crista, the maximum percentage of labeled HCI occurs on the 17th and 18th day of gestation and on the 19th day of gestation for the HCII. A spatial distribution of this labeling activity is also described: the older cells are located at the top of the crista and at the level of the striola of the macula utriculi while the younger cells are found at the bottom of the crista and on the sides of the utricle. A study of the vestibular receptors in the fetuses shows that synaptic contacts already exist on the 18th day of gestation in the macula utriculi at the level of the striola and on the 19th day at the top of the crista; the cells situated on the periphery are still immature. The first hair cells to undergo their terminal mitoses are, therefore, connected first. These results also suggest that the two types of cells are genetically programmed and that the HCI start functioning first during the development of the labyrinth.
The thalamo‐cortical projection of the nucleus submedius in the cat
Authors: Craig A. D. , Wiegand S. J. , Price J. L.
Published: January 2005

The cortical projection of the nucleus submedius (Sm) was studied in the cat with the autoradiographic and horseradish peroxidase (HRP) methods. The results indicate that Sm projects topographically on to layer 3 of a distinct agranular cortical field that occupies the posterolateral gyrus proreus, the adjacent fundus of the rhinal sulcus, and the postero‐ventral portion of the medial wall of the presylvian sulcus. This cortical field is denoted the ventrolateral orbital cortex (VLO), consonant with previous nomenclature in the rat (Krettek and Price, '77a). The more ventral part (VLOβ) is cytoarchitectonically distinct from the dorsal part (VLOα); the former receives input from the anterior part of Sm (Sma), while the latter receives superficial layer 1 of VLO probably also arises from Sm, and there may be an input to layers 5 and 6. The corticothalamic projection from VLO to Sm reciprocates the ipsilateral thalamocortical projection and also has a moderate contralateral component. A dense, subpial layer 1 input to VLO arises from cells of the ventromedial nucleus (VM) subjacent to Sm. The present experiments also indicate that clusters of cells in VM probably provide input to layer 3 of the cortex in the fundus of the presylvian sulcus, as well as area 6aβ in the lateral wall of the presylvian sulcus and the ventral bank of the cruciate sulcus. Results from the HRP experiments additionally indicate that VLOβ and the anteroventral (Smv) portion of VLOα are reciprocally connected with the ventral agranular insular cortex and the cingulate cortex, ipsilaterally, while the posterodorsal (Smd) portion of VLOα is instead connected with specific portions of the somatosensory cortical areas bilaterally. All portions of VLOα appear to project to the ventrolateral periaqueductal gray.

In light of the recent suggestion that (Smd) is involved with nociception (Craig and Burton, '81), the present results suggest that the related portion of VLOα may serve as a cortical representation for noxious stimuli.
Origin and organization of pigment epithelial apical projections to cones in cat retina
Authors: Fisher Steven K. , Steinberg Roy H.
Published: January 2005

The apical surface of the retinal pigment epithelial cells (RPE) in the cat extend long sheetlike membranes that wrap concentrically above and around cone outer segments forming the cone sheath. The origin and organization of these sheetlike projections were studied in serial sections by electron microscopy. The apical surface of the RPE cells was found to consist of a thin zone of anastomosing ridges, or microplicae, from which longer projections extend. The lamellar projections forming the cone sheath originate from the microplicae as small cytoplasmic tabs that rapidly expand into broader sheets. Growth of individual sheets to their final size and shape continues by lateral and longitudinal expansion, fusion, and subdivision of the membrane. The small area of connection to the cell body allows the lamellae to overlap and interdigitate in forming the complex organization of the sheath. Microfilaments but not microtubules extend into the apical processes. RPE cilia (9 + 0 microtubules) with associated basal bodies, striated rootlets, and microtubules mark the location of retinal cones. These structures may be part of a microtubule organizing center that participates in morphogenesis of the cone sheath. They also may be involved in anchoring the apical projections forming the sheath, or in the movement of apical projections during the phagocytosis of outer segment discs shed from cone tips.
Forebrain projections to the periaqueductral gray in the monkey, with observations in the cat and rat
Authors: Mantyh Patrick W.
Published: January 2005

There is considerable evidence that the midbrain periaqueductal gray (PAG) is involved in visceral, emotive, and sexual responses and in endogenous analgesic effects. To see which of the forebrain areas directly influence the PAG, small injections of horseradish peroxidase were made into the various regions of monkey, cat, and rat PAG.

Despite the fact that different regions of the PAG were injected in separate animals the majority of the forebrain areas labeled remained constant. Retrogradely filled pyramidal neurons in layer V were found in the frontal lobe in areas 6, 8, 9, 10, 13, and 24. Labeled neurons also appeared in the amygdala, preoptic area, and the anterior, dorsal, periventricular, ventromedial, periarcuate, lateral, and posterior hypothalamic nuclei. The main route for the hypothalamic → PAG projection appeared to be via the periaqueductal bundle which immediately borders on the cerebral aqueduct. Labeled neurons were also observed in the zona incerta, mesencephalic reticular formation, deep layers of the superior colliculus, and the nucleus cuneiformis. Most labeling was ipsilateral to the injection site although a small but consistent contralateral labeling was present. Therefore a strict subdivision of the PAG based on each subnucleus having its own unique set of connections seems inappropriate. There were few striking differences found in the forebrain areas that project to the PAG in the three species examined.

These results are discussed in terms of the possible contribution these forebrain areas have in regulating the PAG with regard to its functions as a visceral, nociceptive, and cognitive integrator.
Retinal projections in the African cichlid fish, Haplochromis burtoni
Authors: Fernald Russell D.
Published: January 2005

The retinal projections of the African cichlid fish, Haplochromis burtoni, have been traced by two different methods. Following unilateral enucleation, a modified Nauta technique was used to demonstrate degenerating axons and terminals. Some degeneration was found after 5 days but optimal survival time was 20–25 days. Orthograde transport of horseradish peroxidase (HRP) into the cut optic nerve also was used to examine retinal fiber distribution in the brain. The optic nerve is completely crossed and gives rise to two major tracts, the tractus opticus dorsomedialis and the tractus opticus ventrolateralis, as well as minor fascicles. Projections were found in the suprachiasmatic nucleus, ventral thalamus, dorsal thalamus, the pretectal complex, and the tectum opticum. The optic tectum is large and laminated and the great majority of the optic fibers terminate there. Degeneration methods revealed projections in the tectum to the stratum opticum, stratum griseum et fibrosum superficiale, and stratum album centrale. HRP staining confirmed these projections and revealed another projection to the stratum griseum centrale.
Ventral lateral geniculate nucleus efferents to the rat suprachiasmatic nucleus exhibit avian pancreatic polypeptide‐like immunoreactivity
Authors: Card J. Patrick , Moore Robert Y.
Published: January 2005

The distribution of avian pancreatic polypeptide‐like (APP) immunoreactivity was investigated in the suprachiasmatic nucleus (SCN) of the rat hypothalamus with immunohistochemical methods. Specificity of the antisera was established by the absence of all immunoreactive staining in tissue incubated in antisera which had been preabsorbed with the pure APP antigen. In addition, the antisera exhibited no significant cross reactivity with vasoactive intestinal polypeptide, vasopressin, somatostatin, or secretin. Within the rat SCN, APP immunoreactivity is restricted to varicose axons in the ventral and lateral aspects of the nucleus; the dorsomedial component of the nucleus is totally devoid of immunoreactivity and immunoreactive perikarya are not present in any portion of the SCN. The immunoreactive axons in the ventrolateral portion of the nucleus form an extensive plexus which is distributed in a pattern closely corresponding to the distribution of retinal and ventral lateral geniculate (vLGN) efferents to the SCN. No immunoreactive perikarya are observed in the retina following immunoperoxidase staining for APP and neither unilateral nor bilateral enucleation causes an observable alteration in the pattern of APP axon distribution within the SCN, thus indicating that the fiber plexus is not of retinal origin. In contrast, APP immunoreactive neurons are present in the same area of the vLGN in which retrogradely filled neurons have been demonstrated following iontophoretic injection of HRP into the SCN. Bilateral electrolytic lesions of the vLGN result in a total loss of immunoreactive axons in both SCN. Unilateral vLGN lesions cause a loss of approximately 60 to 75% of the immunoreactive fibers in the ipsilateral SCN with a lesser contralateral loss. These observations provide further information on the organization of afferents to the rat SCN and demonstrate that the vLGN projection is chemically distinct from other SCN afferents.
Cytoarchitecture of auditory system in lower brainstem of the mustache bat, Pteronotus parnellii
Authors: Zook J. M. , Casseday J. H.
Published: January 2005

To begin an investigation of the auditory pathways in the brainstem of the mustache bat, we examined the cytoarchitecture of the cochlear nuclei, superior olivary complex, nuclei of the lateral lemniscus, and inferior colliculus. Although all of these auditory centers are hypertrophied in this echolocating bat, only some areas have unusual cytoarchitectural features: (1) In the anterior part of the anteroventral cochlear nucleus we do not find the large spherical cells seen in other mammals; instead, very small spherical cells are found in this area. (2) In the posterior part of the anteroventral cochlear nucleus there is a region containing a homogeneous population of very large multipolar cells. (3) The medial superior olive is unusually large for an animal with a small head. (4) The most striking observations are seen in the lateral lemniscus. The ventral nucleus of the lateral lemniscus has a distinct columnar organization. The intermediate area of the lateral lemniscus contains a large and very distinct nucleus. Each of these cytoarchitectural features distinguishes the auditory system of this bat from that of other mammals. The results raise questions about whether or not there are unique subdivisions in the auditory pathways of echolocating bats. The results also identify these unusual nuclei as candidates to play a role in the special auditory functions related to echolocation.