bluuebunny/crossref_metadata_2025 huggingface dataset:
Anatomical consequences of long‐term monocular eyelid closure on lateral geniculate nucleus and atriate cortex in squirrel monkey
Authors: Tigges Margarete , Henrickson Anita E. , Tigges Johannes
Published: January 2005

The effects of long‐term monocular deprivation on the geniculostriate system in squirrel monkeys were studied with neuroanatomical methods. Four neonates were visually deprived by monocular eyelid suture during their first 10 days of life and survived form 9 to 40 months. In the lateral geniculate nucleus (LGN), deprivation resulted in severe cell size changes. Neurons in the deprived laminae were smaller compared to those in the undeprived laminae. Deprivation left the reciprocal connections between LGN and striate cortex intact: After horseradish peroxidase (HRP) injections into striate cortex, retrogradely transported enzyme labeled a wedge of neurons in deprived and undeprived LGN laminae; anterogradely transported HRP filled preterminal and terminal axons in this wedge.

Following 3H‐proline injections into the deprived eye for transneuronal transport, autoradiography showed in the ipsilateral striate cortex a silver grain distribution over most of layer IVc similar to that in normal squirrel monkeys, except for a small strip in the anterior calcarine fissure. Here, a few, irregularly spaced “patches” of higher grain density occurred deep in layer IVc Layer IVc of contralateral area 17 was also uniformly labeled over most of its extent, except for a very few and inconspicuous accumulations of slightly increased silver grains. After visual stimulation of the deprived eye, the 14C‐2‐deoxyglucose method showed in the contralateral striate cortex some alternating “patches” of higher uptake superimposed on the heavy labeling in layer IVc. Layer IVc in the ipsilateral cortex was more uniformly labeled. Regularly spaced arrays of labeled “puffs” in layers II/III were present in both hemispheres. Cytochrome oxidase staining showed on change in the distribution pattern of the enzyme in the deprived monkeys from the basic pattern of normal adults. No changes in cell sizes were found in layer IVc in cresyl‐violet‐acetate‐stained sections. These results lead to the conclusion that in area 17 of squirrel monkeys there is no distinct segregation of inputs from the two eyes into anatomically discrete ocular dominance columns and they support the view of a predominantly binocular organization of area 17.
The distribution and origin of a novel brain peptide, neuropeptide Y, in the spinal cord of several mammals
Authors: Gibson S. J. , Polak J. M. , Allen J. M. , Adrian T. E. , Kelly J. S. , Bloom S. R.
Published: January 2005

The distribution of neuropeptide Y [NPY]‐immunoreactive material was examined in the spinal cord and dorsal root ganglia of rat, guinea‐pig, cat, marmoset, and horse. Considerable concentrations of NPY and similar distribution patterns of immunoreactive nerve fibres were found in the spinal cord of all species investigated. The dorsal root ganglia of the cat and the horse contained numerous immunoreactive nerve fibres, but in these species, as in the other three studied [rat, guinea‐pig, marmoset], no positively stained cell bodies were found. Neuropeptide Y‐immunoreactive nerves were observed at all levels of the spinal cord, being most concentrated in the dorsal horn. In the rat, guinea‐pig, and marmoset, there was a marked increase of NPY‐immunoreactive fibres in the lumbosacral regions of the spinal cord, and this was reflected by a considerable increase of extractrable NPY. Estimations of NPY‐immunoreactive material in the various regions of the rat spinal cord were as follows: cervical, 13.8 ±1.0; thoracic, 21.1 ±2.5; lumbar, 16.3 ±2.9; sacral, 92.4 ±8.5 pmol/gm wet weight of tissue ±SEM. In the ventral portion of the guinea‐pig spinal cord they were as follows: cervical, 7.1 ±1.2; thoracic, 8.2 ±3.6; lumbar, 22.6 ±7.0; sacral, 36.7 ±9.5 pmol/gm wet weight of tissue ±SEM. Analysis of spinal cord extracts by reverse phase high performance liquid chromatography [HPLC] demonstrated that NPY‐immunoreactive material elutes in the position of pure NPY standard.

No changes in the concentration and distribution of the NPY‐like material in the rat spinal cord were observed following a variety of surgical and pharmacological manipulations, including cervical rhizotomy, sciatic nerve section and ligation, and local application of capsaicin [50 mM] to one sciatic nerve. It is therefore suggested that most of the NPY‐immunoreactive material in the spinal cord is derived either from intrinsic nerve cell bodies or from supraspinal tracts.
The accessory optic system of rodents: A whole‐mount HRP study
Authors: Terubayashi Hirofumi , Fujisawa Hajime
Published: January 2005

The three‐dimensional fiber pathways of the accessory optic system in three species of rodents (rat, golden hamster, guinea pig) were examined on whole‐mounted preparations of the diencephalon and the midbrain, without sectioning, by anterograde labeling of retinal axons with horseradish peroxidase (HRP). HRP histochemical studies on the serial coronal sections were also done. In this study, only the accessory optic system on the side contralateral to the eye injection of HRP was clearly detected. The rat accessory optic system consisted of the inferior fasciculus, the superior fasciculus, the medial terminal nucleus, the lateral terminal nucleus, and the dorsal terminal nucleus. After the inferior fasciculus arrived at the ventromedial border of the cerebral peduncle, some fibers from the inferior fasciculus ran caudally to the medial terminal nucleus. The remaining fibers from the inferior fasciculus further proceeded dorsocaudally on the surface of the cerebral peduncle and left the inferior fasciculus at various levels of the cerebral peduncle to be mixed up with the fibers from the superior faciculus. The golden hamster accessory optic system also consisted of the inferior fasciculus, the superior fasciculus, the medial terminal nucleus, the lateral terminal nucleus, and the dorsal terminal nucleus. However, all fibers of the inferior fasciculus ran caudaily on the lateral surface of the hypothalamus or along the ventromedial border of the cerebral peduncle to terminate at the medial terminal nucleus. The guinea pig accessory optic system and rat accessory optic system were similar, but the posterior fibers of the superior fasciculus decreased in number, and the dorsal terminal nucleus and the posterior portion of the lateral terminal nucleus were not observed in the guinea pig accessory optic system.
Fine structural studies of cholecystokinin‐8‐like immunoreactive neurons and axon terminals in the nucleus of tractus solitarius of the rat
Authors: Takagi Hiroshi , Kubota Yoshiyuki , Mori Shiro , Tateishi Kayoko , Hamaoka Toshiyuki , Tohyama Masaya
Published: January 2005

Cholecystokinin (CCK)‐8‐like immunoreactive structures in the nucleus of tractus solitarius (NTS) were studied by using the peroxidase‐antiperoxidase (PAP) immunohistochemical method. Immunoreactivity was localized in cell bodies and nerve fibers. The perikarya were oval or fusiform (average length 13 μm) and were mostly located in the dorsal half of the medial subnucleus of the NTS at the level of the area postrema (AP). One to three straight immunoreactive dendritelike processes emerged from the perikarya. Neurons that had first been identified under light microscopy were also studied by electron microscopy. Each neuron had a moderate amount of cytoplasm and an oval or elongated nucleus that was eccentrically located in the soma. A few synaptic inputs were found on the CCK immunoreactive perikarya, while a moderate number were seen on both proximal and distal dendrites. These neurons received both asymmetrical and symmetrical synaptic inputs. The immunoreactive dendrites were most frequently in asymmetrical synaptic contact with nonreactive boutons (max. 2.7 μm in diameter) containing fairly densely packed, small round vesicles.

CCK immunoreactive boutons located in the NTS at the level of the AP were analyzed using electron microscopy; these boutons formed asymmetrical synaptic contact with other neuronal elements. Their postsynaptic targets were immunoreactive and nonreactive perikarya and dendrites.

These data suggest that CCK‐containing afferents might affect the neurotransmission of heterogenous types of solitary neurons.
Time course of mossy fiber degeneration following pontine ablation in the rat
Authors: Anderson W. A. , Flumerfelt B. A.
Published: January 2005

The normal ultrastructure of mossy fiber terminals within the ansiform lobule of the rat was investigated in parasagittal sections of the cerebellar cortex. Four types of mossy fiber varicosities (simple and complex dispersed, simple and complex clustered) were distinguished on the basis of the presence or absence of clublike excrescences and the concentration of synaptic vesicles within the cortical zone of the terminal.

Removal of the pontocerebellar input to the contralateral cerebellar hemisphere was performed electrolytically. Such lesions, when placed in the basilar pontine gray using a dorsal approach, resulted in the degeneration of nearly the entire population of mossy fiber varicosities within the contralateral ansiform lobule. As early as 3 days following pontine ablation, degenerative changes were observed within the synaptic portions of the mossy fibers. Two distinct axonal reactions were apparent within this population of degenerating varicosities. A small population of mossy fiber varicosities (12%) of the simple clustered variety underwent a rapid course of electron‐dense degeneration, which was complete by the fifth day. These mossy fiber varicosities were very susceptible to phagocytosis by reactive glial elements. The second group which consisted of simple (60%) and complex (26%) varieties of dispersed terminals, underwent a very slow course of electron‐dense degeneration. Reactive glial cells were rarely found in association with this second group of degenerating varicosities. As a result, most glomeruli were found to contain debris from degenerating mossy fiber varicosities throughout the first 57 days following pontine lesions. The majority of the cerebellar glomeruli, however, were denervated by 80 days.
The architecture and some of the interconnections of the rat's amygdala and lateral periallocortex
Authors: Turner Blair H. , Zimmer Jens
Published: January 2005

The connections between the cerebral cortex and amygdala were studied in the rat by means of silver degeneration techniques. To help define the sites of origin and termination of cortico‐amygdaloid connections, the architecture of the cortex and the amygdala was studied in sections from normal brains stained for cells, fibers, acetylcholinesterase activity, and heavy metals (Timm staining).

The amygdalopetal cortex on the dorsal and lateral surfaces of the rat brain is limited to a narrow strip of periallocortex that forms the dorsal wall and lip of the rhinal sulcus. Histochemical stains indicate that this cortex comprises several stages of cortical differentiation that are intermediate between the ventrally adjacent allocortices and the dorsally adjacent neocortices. The lateral periallocortex consists of two major divisions, the agranular insula (area 13) anteriorly, and a temporal agranular cortex (areas 35 and 36) posteriorly. The principal amygdaloid target for this cortex is the lateral nucleus. Anterior area 13 and posterior area 35 project to the anterior and posterior halves, respectively, of the medial division of this nucleus, while posterior area 13 and anterior area 35 projects to the lateral division of this nucleus. All divisions of periallocortex also send projections to a part of the putamen that surrounds the lateral half of the central nucleus. All of area 13 also sends efferents to the anterior part of the basal nucleus, while the anterior half of area 13 sends an additional projection to the central nucleus.

Comparison of these data with those obtained in the cat and monkey suggests that a constant feature of eutherian brains is the existence of a subset of efferents from each of the four neocortical sensory systems that is routed so as to provide subcortical limbic structures with modality‐specific information. The initial sequence in this sensorilimbic system consists of one or more modality‐specific corticocortical relays that originate in the primary sensory cortices and terminate in one of four topographically adjacent, modality‐specific areas of the insular and temporal cortices. These insular and temporal areas then each establish modality‐specific connections within the amygdaloid complex. The final set of relays presumably comprises the connection that each of these amygdaloid areas makes with the autonomic and endocrine nuclei of the brain.
The distribution of glutamic acid decarboxylase immunoreactivity in the diencephalon of the opossum and rabbit
Authors: Penny G. R. , Conley M. , Schmechel D. E. , Diamond I. T.
Published: January 2005

We have examined the distribution of neurons and terminals immunoreactive for glutamic acid decarboxylase (GAD) in the thalamus and adjacent structures of the opossum (Didelphis virginiana) and the rabbit and have compared this distribution with the distributions we described previously for the cat and bushbaby (Galago senegalensis). The significance of these experiments depends, first, on the fact that GAD is the synthetic enzyme for GABA, and therefore that GAD immunoreactivity is a marker for GABAergic inhibitory neurons, and second, on previous findings that suggest that GABAergic neurons in the dorsal thalamus are local circuit neurons.

In both cat and Galago, GAD‐immunoreactive neurons are distributed essentially throughout the entire thalamus. In the opossum, GAD neurons are chiefly confined to the dorsal lateral geniculate nucleus and the lateral extremity of the lateral posterior nucleus. The distribution of GAD neurons in the rabbit is intermediate between that found in the opossum on the one hand and cat and Galago on the other. Like opossum, about 25% of the neurons in the lateral geniculate nucleus of rabbit are GAD immunoreactive. Unlike opossum, however, as many as 18% of the cells in the ventral posterior nucleus of the rabbit are GAD immunoreactive, and scattered cells are also labeled in other thalamic areas, such as the medial geniculate and the lateral group.

Aside from the findings in the dorsal thalamus, the chief observation is that GAD‐immunoreactive neurons and/or terminals densely fill all principal targets of the optic tract, including the ventral lateral geniculate nucleus; the superficial gray layer of the superior colliculus; the anterior, posterior, and olivary pretectal nuclei; the nucleus of the optic tract; and the medial and lateral terminal nuclei of the accessory optic tract.

These results support the idea first put forward by Cajal that local circuit neurons increase in number during the course of the evolution of complex mammalian brains. If we can assume that the conservative opossum retains characteristics reflecting an early stage of mammalian evolution, the results suggest that thalamic local circuit neurons arose first in the visual system and only later in evolution spread throughout the thalamus.
Comparative localization of neurons containing ovine corticotropin releasing factor (CRF)‐like and neurophysin‐like immunoreactivity in the diencephalon of the pigeon (Columba livia domestica)
Authors: Péczely Péter , Antoni Ferenc A.
Published: January 2005

Neural elements immunoreactive for ovine corticotropin releasing factor‐like immunoreactivity(oCRF‐LI) were shown to be present in the diencephalon of the pigeon by using peroxidase‐antiperoxidase immunocytochemistry. The external zone of the anterior median eminence contains a rich network of varicose oCRF‐LI fibers in close proximity to the pituitary portal capillaries. Perikarya reactive for oCRF‐LI were found in several regions known to innervate the median eminence and gave rise to axons which joined the hypothalamo‐hypophyseal tract. A close topographical relationship between neurophysin‐containing and oCRF‐LI‐containing neurons was found in anterior periventricular regions. These observations suggest that oCRF‐LI material might be involved in the hypothalmic control of anterior pituitary hormone secretion in birds, and that neurophysin‐ and oCRF‐LI‐producing nerve cells might be functionally coupled.
Developing descending neurons of the early Xenopus tail spinal cord in the caudal spinal cord of early Xenopus
Authors: Nordlander Ruth H.
Published: January 2005

The enzyme horseradish peroxidase (HRP) was used to describe and identify neurons, axons of which initiate the earliest descending pathways of the tail spinal cord of Xenopus embryos and larvae. Spinal cords were pierced at different rostrocaudal levels with fine insect pins coated with HRP. The resulting pattern of cellular labeling indicated that primitive sensory (Rohon‐Beard) axons were at the lead of developing descending tracts followed by axons of primary motor neurons. Axons of these two neuron types travel in widely separated fascicles located dorso‐ and ventrolaterally, respectively. Subsequently, axons of several morphologically distinct intersegmental interneurons establish several additional fascicles positioned dorsal to the descending motor axons. Descending supraspinal axons appear only later. The distinctive morphological characteristics of each of the early descending cell types are illustrated along with some stages in their early differentiation. These observations establish the temporal pattern by which new axons are added to descending pathways beginning with the simplest level of the amphibian spinal cord and determine the identity of neurons to which axons at early stages in this sequence belong.
Genesis of neurons in the dorsal lateral geniculate nucleus of the cat
Authors: Hickey T. L. , Hitchcock Peter F.
Published: January 2005

Neurons that will ultimately form the dorsal and ventral lateral geniculate nuclei, the medial interlaminar nucleus, the perigeniculate nucleus, and the nucleus reticularis of the cat undergo their final cell division beginning on, or slightly before, embryonic day 22 (E22) and ending on, or before, E32. Early in this period, neurogenesis proceeds for all of these geniculate nuclei, whereas only in the dorsal lateral geniculate nucleus does cell birth continue until E32. Distinct spatiotemporal gradients of cell birth are not obvious within any of the individual geniculate nuclei. For the dorsal lateral geniculate nucleus in particular, and for the other geniculate nuclei in general, neurons born early in this period exhibit a full range of adult soma sizes, including large and small neurons. Neurons born late in this period exhibit only small adult somas.

The location and size of a neuron within the dorsal lateral geniculate nucleus provide clues to that cell's functional properties. On the basis of presently available information regarding the relationship between structure and function of neurons in the cat's dorsal lateral geniculate nucleus, the findings described here suggest that all functional classes of neurons in the dorsal lateral geniculate nucleus are born at the same time throughout most of this period.
Genesis of morphologically identified neurons in the dorsal lateral geniculate nucleus of the cat
Authors: Hitchcock Peter F. , Hickey T. L. , Dunkel Carol G.
Published: January 2005

Neurons in the dorsal lateral geniculate nucleus of the cat can be grouped into five morphological classes based on a variety of structural characteristics. These same structural characteristics can serve as morphological signatures for the three physiological classes (X, Y, W) of neurons found in this nucleus. The purpose of this study was to determine if a relationship exists between the birthdate of neurons within the dorsal lateral geniculate nucleus and the adult morphology of those neurons. Seven cats, each of which had received a single injection of 3H‐thymidine, were studied. A total of 2,138 Golgi‐impregnated neurons were identified in the dorsal lateral geniculate nuclei of these seven cats; 1,517 of these neurons were successfully resectioned and recovered, of which 385 (25%) were found to contain the 3H label. Neurons from each of the five morphological classes were labeled in each of the six animals that received a 3H‐thymidine injection between embryonic day 24 (E24) and E28. Class 3 and class 5 neurons were labeled in a cat injected with 3H‐thymidine on E30. These findings demonstrate that the development of the morphological class of a neuron in the dorsal lateral geniculate nucleus is independent of the time of its final cell division. Further, given the relationship that exists in the cat's dorsal lateral geniculate nucleus between neuronal structure and function, the present findings suggest that the different physiological classes of cells found in this nucleus undergo their final cell divisions throughout most of the period of neurogenesis except that the functional role of neurons born late in this period may be more restricted.
Catecholamine‐ and indoleamine‐ containing neurons in the turtle retina
Authors: Witkovsky P. , Eldred W. , Karten H. J.
Published: January 2005

We identified a population of presumed dopaminergic amacrine cells and populations of presumed serotonergic bipolar and amacrine cells in the retina of the turtle Pseudemys scripta elegans by a combination of autoradiographic, fluorescence, and immunocytochemical techniques. Antisera directed against the dopamine‐synthesizing enzyme, tyrosine hydroxylase (TOH), stained perikarya located at the border of inner nuclear (INL) and inner plexiform (IPL) layers. Processes emitted by these cells arborized in sublaminae 1, 3, and 5 of the IPL. Incubation of retinas in 10−6 M 3H‐dopamine yielded a labeling pattern identical to the staining pattern achieved with TOH antisera, but when the concentration of 3H‐dopamine was increased 25‐fold, both amacrine and bipolar cells are labeled. Following intraocular injection of dopamine, fluorescence micrography revealed both stained amacrine and bipolar cells. The bipolar cells had Landolt's clubs, pyriform perikarya located in the distal portion of the INL, and axons that coursed horizontally in the INL, then entered the IPL, and ramified in both its superficial and deeper layers. Although no fluorescent neuronal profiles were revealed following injection of serotonin (5HT), bipolar cells identical to those described were visualized with 5HT antisera. The intensity of bipolar cell staining with 5HT antisera was improved by preinjection of the eye with exogenous 5HT. We suggest that the bipolar cell is serotonergic, but that it also can actively accumulate dopamine. The 5HT antisera also stained a population of large amacrine cells whose processes ramified in IPL sublaminae 1, 4, and 5. The same populations of presumed serotonergic bipolar and amacrine cells were labeled following incubation of the eyecup in 10−6 M 3H‐5HT.
Postembryonic changes in the peripheral electrosensory system of a weakly electric fish: Addition of receptor organs with age
Authors: Zakon Harold H.
Published: January 2005

The organization of the peripheral electrosensory system of the cheek was studied in an age‐graded series of Sternopygus dariensis in Nissl‐stained sections and silver‐stained whole mounts of skin. As in other gymnotoids, both ampullary and tuberous electroreceptors are present. Small fish have only one ampullary organ or tuberous organ per axon, and the number of receptor organs per axon increases with age in both ampullary and tuberous systems. Large fish may have up to ten tuberous organs per axon, although the distribution of tuberous organs per axon is bimodal with one peak occurring at a single receptor organ per axon and the other peak shifting upward in relation to the age of the fish. The ampullary system adds receptor organs at a faster rate and a large fish may have 20 ampullary organs per axon. With increasing size, the number of sensory receptor cells in each organ remains constant for both types of electroreceptors. Evidence is presented for addition of new electroreceptor units by de novo production in small fish and increases in the number of organs in existing electroreceptor units by division of previously formed organs in medium‐sized and large fish. As the surface area of the skin increases with growth, the density of electroreceptor units decreases and, although new receptor organs are still being added to existing receptor units, no generation of new receptor units occurs in medium‐sized to large fish.
Thalamic projections to the somatosensory cortex of the echidna, Tachyglossus aculeatus
Authors: Ulinski Philip S.
Published: January 2005

Evoked potential studies (Lende, '64) suggest that echidnas have a single, topographically organized somatosensory area (SMI) that spans a mediolaterally oriented sulcus called sulcus alpha. A motor area (MI) is situated on the prealpha gyrus. This study examines the cytoarchitecture and thalamic afferents of SMI in the echidna, Tachyglossus aculeatus.

SMI contains two cytoarchitectonic fields. A caudal field extends across the postalpha gyrus and onto the floor of sulcus alpha. It has a well‐developed layer 4 and a relatively small number of medium‐sized pyramidal cells in layer 5. The rostral field extends from the floor of sulcus alpha onto its rostral bank. It also has a well‐developed layer 4 but has a large number of large pyramidal cells in layer 5. Layer 4 thins as it is followed onto the crown of the prealpha gyrus. The remainder of this gyrus contains a single cytoarchitectonic field with a thin layer 4 and a layer 5 heavily populated with larger pyramidal cells. This field corresponds to the physiologically defined motor area MI.

Thalamic afferents to SMI were examined by placing pressure injections of horseradish peroxidase into the two cytoarchitectonic fields. An injection that involved both fields retrogradely labeled neurons throughout the ventral posterior nucleus of the thalamus. An injection restricted to the caudal field labeled a band of neurons that extends rostrocaudally throughout the ventral part of the ventral posterior nucleus. An injection restricted to the rostral field labeled a band of neurons situated dorsally in the ventral posterior nucleus. No other thalamic groups contained labeled neurons comparable to the labeling seen in the intralaminar or posterior nuclei following a horseradish peroxidase injection into SI of marsupial or placental mammals.

These results indicate that SMI in Tachyglossus contains two cytoarchitectonic fields that resemble areas 3a and 3b in some placental mammals, suggesting that the constellation of cytoarchitectonic fields corresponding to areas 4, 3a, and 3b is a basic mammalian character which has been modified in marsupial and many placental mammals.
Rules for retinotectal terminal arborizations in the goldfish optic tectum: A whole‐mount study
Authors: Stuermer Claudia A. O.
Published: January 2005

Retinal axons were labeled in the retina and optic nerve with horseradish peroxidase and traced in tectal whole‐mounts. The typical network formed by retinal fibers in the five retinorecipient layers of tectum is illustrated in camera lucida drawings. Three size classes of terminal arbors were identified in the Stratum fibrosum et griseum superficiale (SFGS)–ca. 34 × 52, ca. 103 × 150, and ca. 158 × 274 μm. Terminal arbors are flattened and occupy three sublayers of SFGS.

Passing an HRP‐coated needle through the optic nerve labeled ganglion cells in retina and axons and terminal arbors in tectum. Terminal arbors of axons that originated in retinal annuli lay in distinct annular regions in SFGS, with old generations from central retina lying central to younger generations from peripheral retina. The tectal annuli were concentric with one another and agreed with the retinotopic map as it had been described before.

The youngest terminal arbors from peripheral retina were next to the path of their fascicle along the tectal periphery, connected to their fascicle by short, centrally directed extrafascicular axons. The oldest terminal arbors from central retina were caudally displaced from their rostral fascicle of entrance, at the end of long, caudally directed extrafascicular axons. Terminal arbors from intermediate retina occupied intermediate positions in the tectum. Rostrally, they arose from centrocaudally directed extrafascicular axons but caudally from axons of various orientations. Terminal arbors arising from those extrafascicular axons exhibited different orientations and shapes depending on their tectal position.

The spatial order of intratectal paths and terminal arbor sites, and the variability of terminal arbor orientation and shape, are consistent with an earlier model on shifting retinotectal terminals (Easter and Stuermer, '84).
Cortical and thalamic afferent connections of the insular and adjacent cortex of the cat
Authors: Guldin W. O. , Markowitsch H. J.
Published: January 2005

The thalamo‐cortical and cortico‐cortical afferents of the cat's insular cortex were investigated with the retrograde horseradish peroxidase technique. The most prominent loci of thalamic labeling were the suprageniculate nucleus and parts of the posterolateral nucleus. Injections into the anterior part of the insular cortex also resulted in labeled cells in the ventromedial posterior nucleus and in the intralaminar nuclei, while injections into posterior parts revealed projections from the medial and dorsal parts of the medial geniculate nucleus. Only the anterior and most ventral parts of the insular cortex overlying the anterior rhinal sulcus were connected with the mediodorsal nucleus of the thalamus. All injections into the gyrus sylvius anterior showed a specific pattern of cortical afferents: With the exception of the labeling in the prefrontal cortex and the inferotemporal region, the labeled cells were very narrowly restricted to the presylvian, the suprasylvian, and the splenial sulcus.

The thalamic neurons projecting to the cortex were generally organized in a bandlike pattern which crossed nuclear borders. The majority of the cortico‐cortical connections originated from sulcal areas next to the prefrontal, parietal, and cingulate cortex, that is, next to so‐called association cortices.

In the light of the present results the role of the insular cortex as a multifunctional association area is discussed, as well as its relation to other cortical centers.
Nonintralaminar thalamostriatal projections in the gray squirrel (Sciurus carolinensis) and tree shrew (Tupaia glis)
Authors: Lin Chia‐Sheng , May Paul J. , Hall William C.
Published: January 2005

In mammals, the corpus striatum receives prominent projections from the neocortex and from the intralaminar nuclei of the dorsal thalamus. The present study provides evidence based on anterograde degeneration and axonal transport that the corpus striatum also receives input from two nonintralaminar thalamic nuclei, the pulvinar and the medial geniculate body. Each of these nuclei projects to a separate region of the corpus striatum. Moreover, the same regions of the corpus striatum that receive projections from the pulvinar and medial geniculate body also receive projections from the cortical targets of these nuclei.
The serotonin and norepinephrine innervation of primary visual cortex in the cynomolgus monkey (Macaca fascicularis)
Authors: Kosofsky Barry E. , Molliver Mark E. , Morrison John H. , Foote Stephen L.
Published: January 2005

The morphology and laminar distribution of norepinephrine (NE) and serotonin (5‐hydroxytryptamine, 5‐HT) axons in the primary visual cortex of cynomolgus monkeys (Macaca fascicularis) have been analyzed by immunocytochemistry with antibodies directed against dopamine‐beta‐hydroxylase (DBH) and against 5‐HT. The NE and 5‐HT innervation of primary visual cortex (area 17) in the monkey exhibit highly differentiated laminar patterns. Both of these monoamine axonal systems form tangentially continuous laminar bands that differ in density, morphology, and predominant orientation of constituent fibers. Serotonin axons, present in all cortical layers, form two especially prominent, dense bands of arborizing fibers; one extending from midlayer III through IVC‐alpha and the other from VA through VI. NE axons within cynomolgus visual cortex are markedly less dense than 5‐HT axons, and laminar differences in NE density are less prominent. NE axons form two broad bands of moderate density extending through deep and superficial cortical layers, separated by layer IVC, which is conspicuously poor in NE fibers. The laminar complementarity of 5‐HT and NE innervation that is a notable feature of the squirrel monkey visual cortex is not present in cynomolgus monkey; in this Old World monkey NE and 5‐HT axons show considerable overlap such that the same cortical layers appear to be innervated by both neurotransmitters. By virtue of their laminar distribution, 5‐HT and NE axons may each have a selective influence on the intrinsic circuitry of primate cerebral cortex, and, for 5‐HT in particular, the specific cellular targets of this influence are likely to differ in New and Old World monkeys.
Ultrastructure of transganglionic degeneration in brain stem trigeminal nuclei during normal primary tooth exfoliation and permanent tooth eruption in the cat
Authors: Westrum L. E. , Johnson L. R. , Canfield R. C.
Published: January 2005

Electron microscopy is used to study changes in the axons and terminals in the cat brain stem trigeminal nuclei, main sensory, and partes interpolaris and caudalis, during the process of natural tooth shedding. Areas previously showing light optical argyrophilic degeneration products and adjacent areas lacking this degeneration are included. Various types of alteration occur early during tooth loss, including increased presumed glycogen, increased cytoplasmic density, flocculence, lucency, and neurofilamentous hyperplasia. By the stage of maximum exfoliation, terminals and axons of marked density become prominent in areas showing argyrophilia, whereas nondense forms occur elsewhere. By late eruption ages, all forms of degenerated terminals and axons are rare, but phagocytes are heavily laden with similar forms of debris. The sequence of ultrastructural events is discussed in light of recent studies of transganglionic degeneration, their correlation with light microscopic findings, and the potential implications for central plasticity in this system.
Hearing loss in dogs after lesions of the brachium of the inferior colliculus and medial geniculate
Authors: Heffner Rickye S. , Heffner Henry E.
Published: January 2005

Seven dogs were tested for their sensitivity to pure tones following lesions of the brachium of the inferior colliculus and medial geniculate body. Bilateral section of the brachium of the inferior colliculus consistently resulted in an average hearing loss of as much as 37 dB in the midrange of the animals' audiograms. Lesions of the medial geniculate appear to produce a similar hearing loss if the ventral division of the medial geniculate is completely destroyed.
Cerebellar efferents in the lizard Varanus exanthematicus. II. Projections of the cerebellar nuclei
Authors: Bangma G. C. , Donkelaar H. J. Ten , Dederen P. J. W. , de Boer‐Van Huizen R.
Published: January 2005

The projections of the cerebellar nuclei have been studied in the lizard Varanus exanthematicus with various experimental anatomical techniques. In anterograde degeneration experiments (lesions of the cerebellar peduncle) both ascending and decending contralateral projections were found. Ascending fibers which could be traced from the cerebellar commissure ventralward decussated at the level of the trochlear and oculomotor nuclei. These fibers coursed rostralward to the mesodiencephalic junction. With anterograde tracing techniques (3H‐leucine and HRP) this tract was found to terminate in the nucleus ruber and the interstitial nucleus of the fasciculus longitudinalis medialis. Moreover, retrograde tracer studies (HRP, “Fast Blue”) showed that this tract appeared to arise mainly in the lateral cerebellar nucleus. With both anterograde degeneration and tracing techniques (3H‐leucine and HRP) a bundle of fibers could be followed, which decussates in the basal part of the cerebellum and passes dorsally around the contralateral medial cerebellar nucleus to the lateral side of the brainstem. This contralaterally descending projection system was found, lateral to the vestibular nuclear complex, and as far caudally as the descending vestibular nucleus, to terminate on various vestibullar nuclei. Horseradish peroxidase studies showed that this contralaterally descending projection system originates mainly in the medial cerebellar nucleus, but ipsilaterally descending projections were also found. With the fluorescent double labeling technique (“Fast Blue” and “Nuclear Yellow”) the projections of the cerebellar nuclei described above were confirmed. Furthermore, double labeling revealed neurons in both cerebellar nuclei (especially the medial nucleus) that project to both the mesencephalon and the cervical spinal cord. The present results indicate that the efferent connections of the cerebellar nuclei in the lizard Varanus exanthematicus are organized as two main projections, an ascending projection comparable to the mammalian brachium conjunctivum arising in the lateral cerebellar nucleus, and a descending projection comparable to the mammalian hook bundle (fasciculus uncinatus), originating mainly in the medial cerebellar nucleus. Such projections are common for terrestrial vertebrates.
Electron microscopic analysis of the mesencephalic ventromedial tegmentum in the cat
Authors: Halliday Glenda M. , Törk Istvan
Published: January 2005

We have studied the normal ultrastructure of the ventral mesencephalic tegmentum (VMT) in the cat, particularly the morphology and distribution of presynaptic terminals and the types of synaptic junctions. The following subnuclei of the region were examined: n. linearis rostralis (LR), n. paranigralis (PN), and n. interfascicularis (IF). The qualitative and quantitative data revealed significant ultrastructural differences between these subnuclei. Each subnucleus had a characteristic dendritic structure. In LR the dendrites were nonspinous and cylindrical and had presynaptic terminals randomly distributed over their surface. In PN we observed varicose dendrites with spines; the presynaptic terminals formed clusters on the narrow segments of the dendrites and around the spines. Dendrodendritic synapses were also observed in this nucleus. In IF, there was an internal division regarding dendritic structure: in the rostral part of the nucleus there were cylindrical dendrites while in the caudal part irregularly shaped dendrites bearing long spines were found. In IF and LR some of the cylindrical dendrites were seen to be in direct contact with the basal lamina of blood vessels.

Four types of presynaptic terminals were distinguished by the morphology of their vesicles, and the proportion of each type in the total terminal population was determined. On this basis the compositions of the presynaptic terminal population in the three subnuclei were found to be very similar. Most terminals contained clear, round vesicles (62.6%), or both clear and dense‐cored vesicles (35.1%). Few terminals were seen with dense‐cored vesicles only (1.4%) or with pleomorphic vesicles (0.9%). The majority of synapses in the VMT were found to have symmetrical densities. LR had twice as many asymmetrical synapses as the other two subnuclei. Eighty percent of the terminals formed synapses with dendrites, although axosomatic and axoaxonic synapses were also seen. The density of the terminals was significantly different for each subnucleus: 191/1,000 μm2 in IF, 120/1,000 μm2 in PN, and 81/1,000 μm2 in LR. These data indicate that while the subnuclei of the VMT receive morphologically similar afferents, each has a unique way of processing the information provided by them, through a different internal circuitry.
The morphology of growth cones of regenerating optic nerve axons
Authors: Scalia Frank , Matsumoto Dan E.
Published: January 2005

The morphology of growth cones of regenerating optic nerve axons was examined by light and electron microscopy in adult frogs (Rana pipiens), using a horseradish peroxidase (HRP) fiber‐filling method, during early and later phases of regeneration. Optic nerve regeneration was initiated unilaterally by crushing the optic nerve in mid‐orbit. Fiber filling was accomplished by severing the affected nerve closer to the eye 24–48 hrs. prior to sacrifice and applying HRP to the central stump. Regenerating axons and their growth cones were observed in the optic nerves, chiasma, tract, pretectal neuropil, and optic tectum. Growth cones of normal‐appearing axons varied in shape and size. Flattened, foliate growth cones similar to those commonly described in vitro were observed in the pretectal neuropil and optic tectum. Other growth cones having vermiform, lanceolate, spatulate, and bulbous forms were observed throughout the optic pathway at all stages examined, although the longer (up to 70 μm) wormlike structures appeared only in the optic tract during the early period of outgrowth. Nearly complete serial‐section reconstructions were obtained for two growth cones in the contralateral optic tectum at 8 wks. regeneration time. One was thinly flattened (to 30–50 nm in places) and extended broadly (8 μm in diameter) in contact with a nouronal perikaryon. The other formed a hood over the blind end of a severed, nonregenerating myelinated axon, which was normal‐appearing except at its end within the confines of the growth cone. Morphological variation among the growth cones is discussed in relation to other descriptive in vivo studies and views concerning growth cone motility.
Torpedo electromotor system development: Developmentally regulated neuronotrophic activities of electric organ tissue
Authors: Richardson Guy P. , Rinschen Bernadette , Fox Geoffrey Q.
Published: January 2005

Explant cultures of electric lobe from 45–60 mm stage Torpedo embryos and both ganglionic and dissociated cell cultures prepared from 8‐day chick ciliary ganglia have been used to determine whether the electric organs of Torpedo marmorata contain developmentally regulated neuronotrophic activity. Electric lobe explants were evaluated by measuring their neurone density choline acetyltransferase (CAT), and low salt, Triton X‐100‐soluble protein contents. Addition of soluble extracts prepared from the electric organs of late stage embryos (8–105 mm) to standard medium results in the maintenance of nearly theoretical neurone densities in electric lobe explants during a 7‐day culture period. Soluble electric organ extracts from early embryonic stages (42–59 mm) do not increase neurone density relative to control cultures but cause an elevation in the CAT content of the explants over control values. On the basis of this analysis it is concluded (1) that late embryonic stage and adult electric organs contain neuronotrophic activity that allows electromotor neurones to survive in vitro and (2) that activity increases rapidly in the electric organs between the 59 and 72 mm stages of development at a time when rapid increases in postsynaptic membrane markers in the electric organs occur and when peripheral synaptogenesis begins. The activity of late stage embryonic electric organs is heat stable and lost on dialysis.

Using ciliary ganglion explants and evaluating both the initial fibre outgrowth and the CAT content after 4 days in vitro, trophic activity is found to be maximal at early embryonic stages (45–55 mm) and to decline thereafter. It is shown that the decline in activity is not due to an increase in toxicity. Using established dissociated ganglionic cell survival assays the specific activity of neuronotrophic factors allowing survival is constant between the 45 and 73 mm stages in the electric organs and then rapidly declines, but activity per electric organ increases rapidly between the 45 and 73 mm stages and then remains at a constant level. The use of poly‐dl‐ornithine substrates coated with heart‐conditioned medium for the cell survival assay results in up to tenfold increases in the trophic titre of the electric organ extracts. The neuronotrophic activity supporting survival of ciliary motorneurones present in embryonic electric organs is heat labile and retained on dialysis. It is concluded that developing electric organs contain at least two neuronotrophic factors that have different properties and are differently regulated. Both factors may contribute during development to bringing naturally occurring electromotor neurone cell death to an end.
Distribution and morphology of callosal commissural neurons within the motor cortex of normal and reeler mice
Authors: Terashima Toshio , Inoue Kaoru , Inoue Yoshiro , Mikoshiba Katsuhiko , Tsukada Yasuzo
Published: January 2005

Retrograde transport of horseradish peroxidase was used to examine the cells of origin, of the callosal commissural fibers (CC neurons) in the primary motor cortex of normal and reeler mice. Quantitative analysis of the intracortical, laminar distribution, and dendritic orientation of CC neurons was performed in conjunction with qualitative observation of their morphology. For comparison, similar quantitative data were obtained for the cells of origin of the corticospinal tract (CST) of normal and reeler mice from materials described previously by Terashima et al. ('83).

In the normal mouse, CC neurons are distributed in a bilaminar pattern such that the largest number of cells are located in supragranular layers II and III and in infragranular layer V. The majority of CC neurons are normal (upright) pyramids, although a few in the upper zone of layer VI are inverted pyramidal cells. In the reeler mutant, CC neurons are found in all cortical layers, but two‐thirds are situated in the lower half of the cortex. On the basis of the cell shape and orientation of the apical dendrite, CC neurons of the reeler were classified into six morphological types: (1) typical pyramidal, (2) inverted pyramidal, (3) tumbled, (4) hook‐shaped, (5) polymorphic, and (6) simple. The apical dendrites of the CC neurons in all layers of the cortex of the reeler mouse are randomly oriented; no direct relationship between the intracortical position of the soma and orientation of the apical dendrite was found. In contrast, CST neurons in the reeler mutant are concentrated in the outer third of the cortex, and there is a relationship between the laminar distribution of these cells and the alignment of their dendrites with respect to the pial surface: the apical dendrites of CST neurons lie in superficial layers tend to be oriented obliquely, whereas those of CST neurons in the deeper of cortex most often are oriented vertically, i.e, toward the pial surface. Quantitative analysis revealed that the relative intracortical positions of CC and CST neurons are reversed in the reeler mutant although both populations exhibited greater laminar disposition, and as a consequence, there is more intermingling of the two cell groups in the reeler than in the normal mouse. Thus, the present study suggests that the normal cytoarchitectonics of the primary motor cortex are inverted in the reeler mutant mouse.