bluuebunny/crossref_metadata_2025_split huggingface dataset:
The superior colliculus control of pinna movements in the cat: Possible anatomical connections
Authors: Henkel Craig K. , Edwards Stephen B. 
Published: December 2004

AbstractPossible anatomical pathways mediating superior colliculus control of pinna movements were determined in the cat using the orthograde autoradiographic tracing method and the retrograde horseradish peroxidase technique. This was done in the following manner. First, the division of the the pinna muscles with HRP and surveying the facial nucleus for retrogradely filled cells. Second, the brainstem regions that project to the facial neucleus were identified using the horseradish peroxidase method. Third, the superior colliculus projections to these areas were studied using the autoradiographic tracing method.The results suggest that superior colliculus control of pinna movements is mediated entirely by indirect connections with the facial nucleus and that these connections occur mainly in a paralemniscal zone in the lateral midbrain. Of all the brainstem regions shown by the horseradish peroxidase experiments to project to the facial nucleus only this midbrain paralemniscal zone received a projection from the superior colliculus that was dense and overlapped precisely the region containing facial projecting neurons. Further autoradiographic tracing revealed that the facial nucleus was the primary brainstem target of this paralemniscal fibers projecting to the facial nucleus ended in the subdivision that innervates the pinna muscles. Other paralemniscal efferent terminate in the opposite paralemniscal zone. The data suggest that other connections between the superior colliculus and the facial nucleus may occur in the cuneiform nucleus of the midbrain, the region around the oculomotor complex, and the reticular formation dorsal to the superior olive.
Ultrastructural specificity of synaptic sites in nerve terminals mediating both presynaptic and postsynaptic inhibition
Authors: Smith Dean O. 
Published: December 2004

AbstractThe ultrastructural basis of presynaptic inhibition of the excitatory efferent axon innervating the opener muscle of the crayfish walking leg was studied using the electron microscope. The inhibitory efferent axon terminals form axoaxonal synapses onto excitor terminals in very close proximity to sites of excitatory transmitter release. There is no evidence that these synapses are located at regions of low safety factor of action potential conduction in the excitor. In the area of axoaxonal synaptic connections, the inhibitory axon also forms inhibitory neuromuscular junctions on the opener muscle. Synaptic vesicles are clustered in active zones bordered postsynaptically by extensive invaginations, or junctional folds, in the sarcolemma. These results are consistent with the hypothesis that the primary effect of presynaptic inhibition is to shunt depolarization‐secretion coupling at specific sites of transmitter release in the target cell, rather than to block impulse propagation into a more generalized population of nerve terminals distal to the axoaxonal synapse. Further physiological implications of this structural arrangement are considered.
The axonal arborizations of lateral geniculate neurons in the striate cortex of the cat
Authors: Ferster David , Levy Simon 
Published: December 2004

AbstractHorseradish peroxidase (HRP) was injected into the optic radiations of adult cats. With placements close to the lateral geniculate nucleus (LGN), the enzyme diffused retrogradely along the axons of geniculocortical relay neurons, entered their cell bodies, and, after reaction with diaminobenzidine, produced a Golgi‐like staining of entire neurons. When the injections were made close to the visual cortex, the enzyme diffused anterogradely and filled complete axonal arborizations in area 17.In the LGN, examples of type 1 and type 2 relay neurons (Guillery, '66) were reconstructed, and their axon diameters measured. The type 1 neurons (thought to correspond to Y‐cells – LeVay and Ferster, '77) possessed large diameter axons (2–3.3 μm), while the type 2 neurons (thought to be X‐cells) had medium‐sized axons (1–1.7 μm). Both types of neurons gave off axon collaterals to the perigeniculate nucleus.In the cortex, two types of afferent supplied layer IV. One distributed to the upper part of the layer (layer IVab), extending a short distance into layer III. The parent trunks of these axons, measured in the white matter, had diameters matching those of type 1 LGN relay cells. The other type distributed to layer IVc. The diameters of these axons matched those of type 2 LGN relay cells. Most afferents of both types gave off collaterals to layer VI — there were no axons which exclusively innervated this layer.The axons supplying layer IVab had a wide lateral spread in the cortex (up to 2 mm), and the boutons were grouped into two to five clumps, whose size and arrangement were similar to ocular dominance columns. The axons supplying layer IVc had a much more restricted arborization, usually consisting of a single clump of boutons.LGN neurons with very fine axons (less than 1 μm) were found in laminae C1–C3. They probably corresponded to Guillery's type 4 neurons. In the cortex, fine‐diameter axons arborized in the upper half of layer I. These axons sometimes had collaterals in the lower part of layer III and in layer V.Taken together, the arborizations of the cortical afferents observed in the present study account fully for the autoradiographic labelling pattern seen after 3H‐proline injections into the LGN (LeVay and Gilbert, '76).The identification of type 1 and type 2 neurons as Y‐ and X‐cells is strengthened by the observed difference in their axon diameters, in agreement with the different axonal conduction velocities reported for Y‐ and X‐cells. The presence of cells with very fine axons in the deeper C laminae is consistent with the reported presence of W‐cells (which have slowly conducting axons) in these layers. We conclude that the different classes of geniculate relay neuron have different laminar projections in area 17.
Development of the diencephalon in the rat. III. Ontogeny of the specialized ventricular linings of the hypothalamic third ventricle
Authors: Altman Joseph , Bayer Shirley A. 
Published: December 2004

AbstractThe development of the specialized linings of the hypothalamic third ventricle was examined autoradiographically in mature rats that were labelled with 3H‐thymidine during the developmental period, and in a closely spaced series of embryonic and infant rats. We distinguished in mature rats, apart from the typical ependymal wall, three specialized linings: the convoluted ependyma, the laminated epithelium, and the tanycytic epithelium. The ventricular wall of most of the anterior hypothalamus, and of the dorsal portion of the posterior hypothalamus, is composed of ciliated ependymal cells and most of them are generated several days before birth, soon after the cessation of neurogenesis in the adjacent hypothalamic nuclei. The cells of the rostral convoluted ependyma adjacent to the paraventricular nucleus are produced at about the same time as the neighboring cells of the smooth ependyma. Its cells come from the same germinal region that we have assumed to generate the neurons of the magnocellular neurohypophysial secretory system. The structural differentiation of the convoluted ependyma starts after birth and is completed by the beginning of the second week. Many of the ependymal cells of the laminated epithelium are produced postnatally, and the production of the specialized cells that form a parallel subependymal row extends into the third week. These cells appear to arise from the same matrix that generates earlier the neurons of the dorsomedial and ventromedial hypothalamic nuclei; their structural differentiation begins during the second week. Also the cells of the tanycytic epithelium are produced mostly postnatally, predominantly during the first week. They appear to arise from the same matrix that generated earlier the neurons of the hypophysiotropic tuberomammillary and arcuate nuclei. It is postulated that these three specialized ventricular linings are specifically related to the three components of the endocrine hypothalamus with which they have shared neuroepithelial sites of origin.
Opening of tight junctions in cerebral endothelium. I. Effect of hyperosmolar mannitol infused through the internal carotid artery
Authors: Nagy Zoltan , Pappius Hanna M. , Mathieson Gordon , Hüttner Istvan 
Published: December 2004

AbstractInfusion of 1.8 M mannitol solution into the internal corotid artery of Wistar rats allows horseradish peroxidase (HRP) to cross cerebral vascular endothelium via intercellular pathways. This was made evident by density gradients of HRP observed in consecutive tight junctional compartments following in vivo administration, and by the passage of colloidal lanthanum through junctional membrane appositions of glutaradehyde fixed cerebral endothelium. Three hours after mannitol infusion, small no‐capillary vascular segments were still focally permeable to HRP. Twenty‐four hours after the osmotic insult, the tracer was absent in the affected hemisphere. Water and electrolyte essays indicated absence of brain edema during the period of observation of blood‐brain barrier opening.
3H‐Estradiol, 3H‐Testosterone and 3H‐Dihydrotestosterone localization in the brain of the lizard Anolis carolinensis: An autoradiographic study
Authors: Morrell J. I. , Crews D. , Ballin A. , Morgentaler A. , Pfaff D. W. 
Published: December 2004

AbstractThe presence and the neuroanatomical topography of sex hormone concentrating cells in the brain of the American chameleon, Anolis carolinensis have been demonstrated by these experiments. After 3H‐estradiol administration large numbers of hormone concentrating cells were found in the amygdala, septum, medical preoptic area, anterior hypothalamic area, the ventromedial and periventricular nuclei of the hypothalamus, and anterior pituitary. In addition, labelled cells were found in the torus semicircularis, in and around the nucleus isthmus pars parvocellularis. A small number of labelled cells could also be found in the rostral pallium, motor nucleus of the fifth cranial nerve, the raphe nuclei, and the spinal cord. After 3H‐testosterone or 3H‐dihydrotestosterone administration the neuroanatomical pattern was very similar to that found after 3H‐estradiol; however, fewer labelled cells were seen after the androgens were given. Two exceptions to the similarity of pattern were in a caudal part of the pallium and in the mesencephalic tegmental area. Hormone‐concentrating cells were found after 3H‐testosterone or 3H‐dihydrotestosterone administration, while labelled cells in these two areas after 3H‐estradiol administration were extremely rare. The pattern of hormone‐concentrating cells was the same in male and female brains, for each of the hormones. The preoptic area, hypothalamus, and anterior pituitary have been demonstrated in reptiles to be involved in neuroendocrine regulation and in the control of sex behaviors.The presence and neuroanatomical pattern of sex steroid binding cells in the brains of a wide variety of vertebrates have been documented. Large numbers of hormone‐concentrating cells were found in all of these species in the medial preoptic area, tuberal hypothalamus, specific limbic structures, the mesencephalon deep to the tectum, and the anterior pituitary. Most hormone‐concentrating cells in the brain of A carolinensis were found in these same brain regions, thus indicating a vertebrate‐wide stable core of hormone‐concentrating cells in neuroanatomically defined regions.
The cellular origin of the b‐wave in the electroretinogram— a developmental approach
Authors: Rager Günter 
Published: December 2004

AbstractRetinal ganglion cells and retinotectal synapses of chick embryos can be activated by electrical stimulation at early stages of development (Rager, '76a,b), whereas light evoked responses occur only towards the end of the incubation period. Thus, photoreceptors seem to be the last cells to mature in the chain of elements necessary to enable transmission of visual information to tectal neurons. In the present study the development of light evoked activity in the retina was investigated and compared with the strutural maturation of retinal cells. This ontogenetic approach offers a solution to the problem of the cellular origin of the b‐wave called in question by recent records of the potassioretinogram (KRG).Lamellar structures in the developing outer segments of photoreceptors can first be observed on incubation day 17. Late on the same day a corneal electroretinogram (ERG) and a visual evoked response on the optic tectum (VER) can be recorded. The response properties of the developing b‐wave and VER were tested using various stimulus parameters. From the latencies of the b‐wave and of the VER it is concluded that the b‐wave is not generated directly by the activity of neurons involved in intraretinal signal transmission. Thus it is necessary to consider secondary processes triggered by neuronal activity such as depolarization of glial cells. In the chick retina, Müller cells are virtually the only glial cells. They fulfill all structural requirements necessary to explain the current which spreads through the retina during the b‐wave. Electronmicroscopic analysis reveals that Müller cells undergo drastic changes during the early phase of b‐wave development (incubation day 18). In particular, the number of microtubules per unit volume and the surface area of Müller cell processes in the outer plexiform layer increase considerably. It is, therefore, suggested that the b‐wave originates in the depolarization of Müller cells secondary to synaptic activity in the outer plexiform layer.
Rods and cones in the mouse retina. I. Structural analysis using light and electron microscopy
Authors: Carter‐Dawson Louvenia D. , Lavail Matthew M. 
Published: December 2004

AbstractRods and cones of the C57BL/6J mouse retina have been examined by light and electron microscopy to distinguish the structural features of the two photoreceptor types. By light microscopy, cone nuclei are conspicuously different from rod nuclei in 1‐2 μm plastic sections. Cone nuclei have an irregularly shaped clump of heterochromatin that appears in single sections to be one to three clumps, whereas rod nuclei are more densely stained and have one large, central clump of heterochromatin. Cone nuclei make up approximately 3%; of the photoreceptor nuclei in both the central and peripheral retina at all ages examined up to 267 days. Cone nuclei are confined to the outer half of the outer nuclear layer, and more than 50%; of the cone nuclei lie adjacent to the outer limiting membrane. By electron microscopy, cones in the mouse retina meet virtually every morphological criterion of mammalian cones. The outer segments are conically shaped. Many, if not all of the outer segment discs are continuous with the outer plasma membrane, whereas almost all of the rod discs are not. Cone outer segments are only about half the length of the rod outer segments, and they are contacted by long, villous pigment epithelial cell processes. The cone inner segment diameter is greater than the outer segment diameter, and the accumulation of mitochondria present at the apical end of the inner segment forms a more conspicuous ellipsoid than in rods. The internal fiber or axon of the cone is larger in diameter than that of the rod, and it terminates in a large synaptic pedicle with multiple ribbon synapses, whereas the rod terminal is a smaller spherule with only a single ribbon synaptic complex.
Development of chick paravertebral sympathetic ganglia. I. Fine structure and correlative histofluorescence of catecholaminergic cells
Authors: Luckenbill‐Edds L. , van Horn C. 
Published: December 2004

AbstractParavertebral sympathetic ganglia from the lumbosacral region of a series of chick embryos have been studied with electron microscopic methods, including aldehyde‐osmium and permanganate fixatives, and correlative histofluorescence (Grillo et al., '74). Our purpose was to assess the differentiation of catecholaminergic (CA) cells during histogenesis in ovo. Examination of comparable adult ganglia as a baseline for differentiating stages confirmed that the principal sympathetic neuron (PN) is similar to those of other species in that it contains predominately small dense‐cored vesicles (SDCV) preserved only by permanganate, and does not histofluoresce following the method of Grillo et al. ('74). At embryonic day (E) 7–8, when ganglia have just formed, areas fluorescing bright yellow‐green are correlated with two types of cells: (1) Neuroblasts with vesicular nuclei and large dense‐cored vesicles (LDCV) are common. As the neuroblasts grow and differentiate, LDCV move away from perikaryal cytoplasm into developing processes. Around E13–15, SDCV appear in the neuroblasts which continue to develop until they resemble miniature adult PN in late embryos and hatchlings. (2) Granule (GR) cells with clumped chromatin and sparse cytoplasm are clustered in the ganglionic periphery at E7–8, but are rare. The GR cells increase somewhat in size and numbers by E11, but retain essentially the same characteristics as at earlier stages. Neither bright fluorescence nor GR cells appear later than stages E13–15. These results are interpreted to mean that when chick sympathetic stem cells have migrated from the primary ganglia into the paravertebral ganglia, they give rise to two separate lines of CA cells, one of which is not maintained and subsequently disappears. The results are significant as a basis for understanding how a mixed population of CA cells might arise within sympathetic ganglia in situ.
Neuronal increase in various areas of the nervous system of the guppy, Lebistes
Authors: Birse Stewart C. , Leonard Robert B. , Coggeshall Richard E. 
Published: December 2004

AbstractThe numbers of 1) dorsal root ganglion cells in the 2nd spinal segment, 2) ventral horn cells in the 2nd spinal segment, 3) Purkinje cells of the cerebellum, and 4) neurons in the nucleus glomerulosus were counted and correlated with age and size in the guppy, Lebistes. The findings were that the neuronal numbers in all these areas increased throughout much of the life of the animal. These data, combined with the previously demonstrated increases in retinal neurons in goldfish and sensory and spinal neurons in stingrays, suggest that neurons are added to many areas of the nervous system of fish as the animal ages and grows. In this respect, the nervous systems of fish differ from the nervous systems of other vertebrates. We offer the suggestion that the comparatively greater ability of fish to regenerate their nervous system after injury may be related in part to their ability to add neurons to various parts of the nervous system throughout life.
Regions of the brain influencing the projection of developing optic tracts in the salamander
Authors: Harris William A. 
Published: December 2004

AbstractEye primordia from the Mexican axolotl or the California newt were transplanted into hosts of either species. These “third” eyes often developed an optic nerve that penetrated the host brain and made one of three central projections: bilateral to the dorsal thalami, tecta, and basal optic nuclei; ipsilateral to the same areas; or ipsilateral into the cord. The type of projection made by a transplanted eye seemed to depend on where its nerve first entered the brain. The optic fibers that reached the visual centers of the midbrain were organized retinotopically in the optic tectum and mediated visually‐guided behavior.
Immunocytochemical localization of tyrosine hydroxylase in the human fetal nervous system
Authors: Pickel Virginia M. , Specht Linda A. , Sumal Khushdev K. , Joh Tong H. , Reis Donald J. , Hervonen Antti 
Published: December 2004

AbstractThe peroxidase‐antiperoxidase (PAP) technique is used to determine the cellular localization of tyrosine hydroxylase in the human fetal nervous system. Antiserum to trypsin‐treated tyrosine hydroxylase from the bovine adrenal medulla can be detected immunocytochemically in peripheral sympathetic neurons in the 8‐mm (5‐week) fetus, but can not be detected in the central nervous system until later stages of development. The cytological features and distribution of the neuronal perikarya and processes labeled for the enzyme are similar to those of the catecholaminergic neurons previously identified by histofluorescence. These findings indicate that specific neurons in the human fetus have at least one of the enzymes necessary for the biosynthesis of catecholamines and that cross‐species reactivity exists between antiserum produced to the bovine tyrosine hydroxylase and human tissues.
Development of rat Merkel cells
Authors: English Kathleen B. , Burgess Paul R. , Norman Dolores Kavka‐Van 
Published: December 2004

AbstractThe ultrastructure of Merkel cells and cutaneous nerves was examined in fetal, newborn, and 7‐day‐old rats. The earliest observation of cells having some, but not all, of the features of mature Merkel cells was at 16 days gestation in snout skin. These early presumptive Merkel cells resembled the neighboring keratocytes, except that they contained dense‐cored vesicles scattered in the cytoplasm. Presumptive Merkel cells were seen only in the epidermis, although a careful search was made of the dermis. Developing neurons were not observed to penetrate the epidermal basal lamina when presumptive Merkel cells were first seen. The earliest observation of identifiable nerve axons in the snout epidermis was at 17–17 1/2 days gestation. Study of the presumptive Merkel cells through successively older gestational stages showed that the cells became innervated and progressively developed the characteristics of adult Merkel cells. We suggest that Merkel cells arise from keratocyte‐like precursors in rat epidermis, at a time when skin nerves may still be several micrometers away.