bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell death of motoneurons in the chick embryo spinal cord. VI. Reduction of naturally occurring cell death in the thoracolumbar column of terni by nerve growth factor
Authors: Oppenheim Ronald W. , Maderdrut Jerome L. , Wells David J.
Published: December 2004

A discrete preganglionic cell column (column of Terni, CT) in the caudal thoracolumbar (segments 21–23) spinal cord is first discernible in avian embryos on day 8 when it contains approximately 9,300 visceral motoneurons. By day 10 there are about 6,900 motoneurons in the thoracolumbar (sympathetic) CT and this number remains constant until at least day 15. Daily injections of nerve growth factor (NGF) (1–20 μg) on the chorioallantoic membrane from day 3 to day 9 produced a dose‐dependent increase in both the volume of the caudal thoracolumbar sympathetic ganglia and the number of motoneurons in the corresponding CT on day 10. The number and size of the neurons in the paravertebral sympathetic ganglia was also increased by NGF. Nerve growth factor decreased the number of pyknotic (dying) neurons in both the thoracolumbar sympathetic ganglia and the corresponding CT on days 8 and 10. The increased number of neurons in both the thoracolumbar sympathetic ganglia and the corresponding CT following chronic administration of NGF is the result of decreased cell death. The highest dose of NGF reduced naturally occurring cell death in the thoracolumbar CT by more than 60%. Daily injections of cytochrome C (20 μg) from day 3 to day 9 had no effect on either the volume of the sympathetic ganglia or the number of motoneurons in the CT on day 10

Daily injections of NGF (10–20 μg) from day 10 until day 14 increased the volume of (and the number of neurons in) the caudal thoracic sympathetic ganglia on day 15 but had no effect on the number of motoneurons in the corresponding CT. Nerve growth factor also had no effect on the number of motoneurons in either the somatic lateral motor column, the sacral (parasympathetic) CT, or the “abortive” visceral efferent column at the cervical level. Daily administration of NGF produced a similar increase in the volume of the dorsal root ganglia at the cervical, thoracic, and sacral levels. The reduction of cell death in the thoracolumbar CT by NGF is the result of neither a direct effect on spinal motoneurons nor an indirect effect of increased sensory innervation

Naturally occurring cell death of sympathetic preganglionic neurons is regulated by the size of their innervation field.
An afoveate area centralis in the chick retina
Authors: Morris Valerie B.
Published: December 2004

A specialization has been found in the nasal retina of late embryonic and newly hatched chicks of the domestic fowl. In whole mounts of the retina, there is a central node about 2 mm from the dorsal end of the optic disc and a set of structures radiating out from this node. This complex has been named the aster. sections of the retina show that the structures which form the aster lie in the inner nuclear layer. The specialization has been classed as an afoveate area centralis.
Histochemical evidence for sympathetic innervation of hair receptor afferents in cat skin
Authors: Roberts William J. , Levitt Gregg R.
Published: December 2004

The goal of the present study was to demonstate histochemically fine catecholamine‐containing sympathetic nerve fibers which might be associated with hair receptor afferent fibers in cat skin. Positive results would be consistent with the hypothesis that the sympathetically mediated desensitization of hair afferents, observed in this and earlier studies, is mediated by direct neurotransmitter release onto the afferent fibers.

Activity in single primary afferent fibers was recorded electrophysiologically during mechanical stimulation of hairs and electrical stimulation of the lumbar sympathetic trunk in anesthetized cats. The mechanical threshold for activation was seen to increase markedly during low‐frequencey sympathetic stimulation.

Fresh‐frozen sections of skin from cat hindleg were treated with glyoxylic acid for detection of fluorescent catecholamines. Fluorescent fibers were observed in association with hair follicles as well as with arterioles and arrector‐pili muscles. Subsequent silver staining of the identical skin sections revealed that the fine catecholamine‐containing fibers located near hair follicle were closely associated with hair receptor afferent fibers. The results are therefore consistent with the hypothesis that sympathetic modulation of hair receptor sensitivity is mediated by direct neurotransmitter release onto the afferent fibers.
Neurotensin: Topographical distribution of brain sites involoved in hypothermia and antinociception
Authors: Kalivas Peter W. , Jennes Lothar , Nemeroff Charles B. , Prange Arthur J.
Published: December 2004

When administered into the cerebroventricular system of the rat, neurotensin (NT) produces a variety of effects, including a decrease in colonic temperature and an increase in nociceptive threshold. The previous study described in detail the localization of immunohistochemical NT in the rat brain. In this study, bilateral injections of NT were made into 223 separate loci in the rat brain and a map was generated showing the brain regions where NT produced a decline in colonic temperature and an increase in hot plate response latency. It was found that some of the brain areas which contain immunohistochemically identified NT responded to locally administered NT. Further, most NT‐sensitive brain loci contain NT cell bodies as well as fibers.

Areas in the brain where NT produced an antinociceptive response were not the same areas where NT evoked hypothermia. An antinociceptive response was consistently produced after NT injection into the nucleus amygdaloideus centralis, rostral area praeoptica medialis, the ventral thalamus dorsomedial and medial to the lemniscus medialis, rostal mesencephalic periventricular gray, and medial pontine formatio reticularis. Less‐consistent antinociception was also observed in the mesencephalic formatio reticularis and the caudal diagonal band of Broca. Hypothermia was induced by NT in the area praeoptica medialis contiguous with the area anterior hypothalami, nucleus ventralis tegmenti (Tasi), floor of the fourth ventricle, and tractus spinalis nervi trigemini. Less profound hypothermia was also produced in the posterior hypothalamus. The fact that all these responsive brain areas contain NT indicates that the microinjection of NT may be mimicking the effects of endogenously released NT, thus supporting the possible physiological significance of NT as an endogenous modulator of body temperature or nociceptive sensory information.
The accessory motor nuclei of the trigeminal, facial, and abducens nerves in the rat
Authors: Székely George , Matesz Clara
Published: December 2004

The cobalt labeling technique was applied to the trigeminal, facial, and abducens roots in order to investigate the location and morphology of motoneurons of the main and accessory motor nuclei of these cranial nerves in the rat. On the basis of soma‐dendritic morphology, axonal trajectory, and tegmental location, three different accessory nuclei were distinguished in the brainstem. Neurons of the accessory nuclei of V and VII form a common club‐shaped nucleus extending between the main motor nuclei of V and VII. The Dendritic tree of these neurons is oriented in the dorsoventral direction and the axon invariably follows a dorsolaterally directed bent course. The accessory VI nucleus is located ventral and lateral to the main VI nucleus in the lateral tegmentum. The neurons have elongated perikarya, strong ventral and weak dorsal dendritic arbors, and the bent axonal course is directed dorsomedially. Neurons of the main VI nucleus have rounded perikarya and radial dendritic arborizations. Muscle groups innervated by the accessory and main motor nuclei have distinctly different functions.
An HRP study of the connections of the subfornical organ of the rat
Authors: Lind R. Wallace , van Hoesen Gray W. , Johnson Alan Kim
Published: December 2004

The connections of the subfornical organ (SFO) wer investigated by using the HRP technique. Injections into the SFO labeled neurons in the medial septum, but not in lateral septum nor in the diagonal band nucleus. Labeled cells were observed in the median preoptic nucleus, below the ependyma of the third ventricle, in the dorsal preoptic region near the anterior commissure, and diffusely throughout the medial preoptic and anterior bypothalamic areas.

Fibers were followed from the ventral stalk of the SFO. Precommissural fibers enter the median preoptic nucleus where many of them appear to terminate. Others continue on to the medial septum, the OVLT, the supraoptic nucleus, and the suprachiasmatic nucleus, HRP injections into the median preoptic nucleus labled many neurons in the SFO.

Postcommissural fibers reach the hypothalamus by descending along the walls of the ventricle in the subependymal space, by traveling in the columns of the fornix and the medial corticohypothalamic tract, or by passing through the paraventricular nucleus of the thalamus. Some postcommissural fibers turn rostrally and enter the median preoptic nucleus while others join precommissural fibers bound for the supraoptic nucleus. More caudally directed fibers appear to innervate the paraventricular nucleus of the hypothalamus and the medial preoptic and anterior hypothalamic areas. HRP injections into the paraventricular nucleus of the hypothalamus labeled neurons in the SFO.

These finding corroborate and extend previous work in describing neural connections between two brain regions that are important for fluid blance.
The afferent connections of the suprachiasmatic nucleus of the golden hamster with emphasis on the retinohypothalamic projection
Authors: Pickard Gary E.
Published: December 2004

The afferent connections of the hypothalamic suprachiasmatic nucleus (SCN) of the golden hamster were examined using horseradish peroxidase (HRP) as the retrograde tracer molecule. Unilateral iontophoretic deposition of HRP into the SCN labeled ganglion cells bilaterally in the retinae. The labeled ganglion cells all had large somata and were randomly distributed across the retina. A similar number were labeled in each retina, which contrasted with the findings from injections into the optic chiasm and lateral geniculate body. Chiasm and geniculate injections both labeled three classes of ganglion cell (small, large, and giant) predominantly in the contralateral retinae.

Telencephalic afferent projections to the SCN included the ventral subicular cortex and the septum. Notable diencephalic afferents included the dorsal lamina of the internal division of the ventral lateral geniculate nucleus (vLGN); the ipsilateral input was twice that of the contralateral projection. The same region of the vLGN was also noted to be reciprocally connected to the contralateral vLGN. The thalamic paraventricular nucleus was also heavily labeled but only ipsilaterally. Of functional significance, the SCN was discovered to innervate its contralateral homologue. Other less numerous afferents in the midbrain included the dorsal and median raphe nuclei and the dorsal nucleus of the lateral lemniscus.

The afferent projections to the SCN determined in this study are discussed in regard to the known physiological role of the SCN as part of the circadian clock system.
Somatotopic organization of vibrissae afferents in the trigeminal sensorynuclei of the rat studied by transganglionic transport of HRP
Authors: Arvidsson Jan
Published: December 2004

Transganglionic transport of horseradish peroxidase (HRP) has been used to study the cell bodies and central projections of neurons innervating the vibrissae in the rat. These can be grouped into five horizontal rows and one posterior vertical row. Twenty‐four to 48 hours after the nerves innervating different vibrissae were exposed to HRP, the trigeminal ganglia, brainstem, and upper cervical spinal cord were fixed by perfusion and serial sections were processed according to the tetramethylbenzidine technique.

The results revealed a tendency for somatotopic organization in the trigeminal ganglion of cell bodies innervating the different vibrissae. Corresponding termination areas in the trigeminal sensory nuclei showed a detailed pattern of organization replicating the peripheral organization of the vibrissae. In all trigeminal sensory nuclei the horizontal rows are represented in an inverted fashion from dorsal to ventral, i.e., the most dorsal row is represented most yentrally. In addition, the more anterior a vibrissa is located, the deeper is it represented in the rostral nonlaminated nuclei. The situation is reversed in the laminated nucleus caudalis. The posterior vertical row is represented most superficially in the rostral nonlaminated nuclei, but most deeply in the laminated nucleus caudalis. In nucleus cau dalis there are also rostrocaudal differences in the representation of differ ent vibrissae. Thus, the posterior vibrissae in a horizontal row have their main representations more caudally than the anterior vibrissae. The pos terior vertical row has its main representation most caudally, in the Cl segment.
Cortical connections of striate cortex in the owl monkey
Authors: Lin C.‐S. , Weller R. E. , Kaas J. H.
Published: December 2004

Injections of trkiated proline and horseradish peroxidase were used to study cortical connections of striate cortex in owl monkeys. All cases resulted in label in area 18 (V‐II) and the middle temporal visual area (MT). In most, but not all cases, label was also present in the dorsomedial visual area (DM). The connections between striate cortex and each of these three visual areas were retinotopic and reciprocal. Projections to V‐II, MT, and DM were concentrated in layers IV and III, while pyramidal cells in layers III, V, and VI of these areas projected back to striate cortex.
Functional role of regrowing pyramidal tract fibers
Authors: Reh Thomas , Kalil Katherine
Published: December 2004

When pyramidal tract axons are severed in the infant hamster, the damaged fiber? regrow via a new pathway to their normal terminal sites in the medulla and spinal cord and there form synaptic connections (Kalil and Reh, ′79, ′82). We studied the behavior of animals with infant and adult lesions of the medullary pyramid to determine the functional significance of the new pathway in maintaining normal motor behavior. Examination of behaviors normally mediated by the pyramidal tract, particularly the manipulation of sunflower seeds during feeding, revealed a correlation between the presence of the new tract and the preservation of function. Furthermore, in the adult animal with an infant lesion, the spared behaviors were lost when the new pathway was destroyed.
Exposure to lines of only one orientation modifies dendritic morphology of cells in the visual cortex of the cat
Authors: Tieman Suzannah Bliss , Hirsch Helmut V. B.
Published: December 2004

To determine whether selective exposure to lines of one orientation modifies the shape of the dendritic fields of cells in visual cortex, we examined the dendritic morphology of neurons in area 17 of five normally reared cats, five cats reared viewing only vertical lines, and three cats reared viewing only horizontal lines. Kittens were placed with their mothers into a totally dark room before their eyes had opened. Beginning at 4 weeks of age, the kittens were brought out for daily periods of exposure wearing masks that limited the vision of each eye to a field of three vertical lines or three horizontal lines. After a minimum of 170 hours of exposure, the animals were killed and blocks of visual cortex were impregnated by the Golgi‐Kopsch procedure and cut tangential to the pial surface. Complete neurons from layers III and IV were drawn with the aid of a camera lucida, and the orientations of the dendritic fields were analyzed using Sholl diagrams. In normal cats, the distributions of the orientations of dendritic fields were uniform, whereas in stripe‐reared cats, the distributions for the layer III pyramidal cells were shifted. The direction of this shift varied with the experience of the cat: In cats reared viewing only vertical lines, the dendritic fields were oriented orthogonal to the representation of the vertical meridian, and in cats reared viewing only horizontal lines, the fields were oriented parallel to the representation of the vertical meridian. In contrast, the distribution of dendritic orientations for the stellate cells was not affected by stripe‐rearing. These results demonstrate a morphological effect of early visual experience that is specific to the particular stimulus presented during rearing and suggest that (1) cortical cells differ in the degree to which they can be modified by such experience, and (2) the dendritic morphology of cortical neurons is related to their preferred orientations.
A horseradish peroxidase study of projections from the main and external cuneate nuclei to the cerebellum of the North American raccoon
Authors: Haring John H. , Rowinski Mark J.
Published: December 2004

Neurons of the raccoon main (MCN) and external (ECN) cuneate nuclei having terminal fields in the anterior lobe and paramedian lobule of the cerebellum were studied by means of the retrograde transport of horseradish peroxidase (HRP). In the MCN, neurons of the polymorphic regions, but not of the round cell clusters, were labeled following HRP injections of the anterior lobe. HRP‐labeled fusiform, triangular, and stellate cells were observed from 3–4 mm caudal to the obex to 2–3 mm rostral to it. The main body of labeled MCN neurons was located in the 1.25 mm immediately rostral to the obex, there forming a recognizable subnucleus in the ventral MCN. The ECN displayed uniform labeling from the anterior lobe with no particular cell type or nuclear region being labeled preferentially. A minor projection to the anterior lobe appeared to originate in the contralateral MCN and ECN. Injections of the paramedian lobule produced MCN labeling similar to that observed after anterior lobe injections, but the majority of labeled ECN neurons were found in the dorsomedial part of the nucleus.

In lobule V of the anterior lobe, sagittal zone c contained the greatest density of cuneocerebellar terminals as judged by the degree of retrograde labeling seen in neurons of both the MCN and ECN. This observation was consistent with evoked potentials recorded in the anterior lobe of the raccoon cerebellum.

The position of cuneocerebellar neurons in the ventrolateral MCN suggests that the bulk of the information being transferred to the cerebellumby the raccoon MCN is related to deep, rather than cutaneous, modalities.
An electron microscopic comparison of the medial interlaminar nucleus and the a laminae in the dorsal lateral geniculate nucleus of the cat
Authors: Wilson James R.
Published: December 2004

The medial interlaminar nucleus (MIN) of the cat's dorsal lateral ge‐niculate nucleus was studied under the light and electron microscopes and compared with the A laminae. At the light level, MIN has more axons and a lesser cell packing density than the A laminae. Examined at the electron microscopic level, MIN could not qualitatively be distinguished from the A laminae. When quantitative counts of the profiles containing synaptic ves‐icles were made, MIN had less F profiles and more RSD profiles per unit area than the A laminae. Structure/function correlations suggest that additional F terminals may mediate nondominant eye inhibition and/or a greater amount of inhibition on X‐cells versus Y‐cells.
Thalamic projections to visual areas of the middle suprasylvian sulcus in the cat
Authors: Tong Lillian , Kalil Ronald E. , Spear Peter D.
Published: December 2004

The thalamic afferents to two areas of the lateral suprasylvian visual cortex in the cat were studied by using retrograde transport of horseradish peroxidase (HRP). Injections were localized retinotopically with electro‐physiological recording. The posteromedial lateral suprasylvian area (PMLS) of Palmer et al. (78) receives afferents from the pulvinar (P), the posterior nucleus of Rioch (PN), the C‐laminae of the lateral geniculate nucleus (LGNd) and the centrolateral (CL), lateral posterior (LP), medial interlaminar (MIN) nuclei. The anteromedial lateral suprasylvian area (AMLS) receives affer‐ents from CL, P, LP, PN, MIN, and probably from the posterior nuclear group (PO), and the lateral dorsal (LD) and ventral anterior (VA) nuclei.

The LP‐pulvinar complex has been divided into four zones on the basis of connectivity: geniculate wing, pulvinar, the lateral division of LP, and the interjacent division of LP (Updyke, '77; Graybiel and Berson, '80; Guillery et al., '80). The locations of labeled cells in the present experiments suggest that both AMLS and PMLS receive afferents from each of the four zones, although differences exist in the strength of the projections.

While AMLS and PMLS receive afferents from many of the same nuclei (CL, P, LP, PN, and MIN), differences in their afferents also were noted. These differences are of three types. The first is that some nuclei project to only one of the cortical areas. PMLS alone receives input from the C‐laminae of the LGNd while AMLS alone receives probable input from PO, LD, and VA. The second difference is in the strength of the projection from some nuclei. AMLS receives a stronger projection from CL and P than does PMLS. The third difference concerns the pattern of distribution of neurons that project to each cortical area. Labeled cells in LP are dispersed after an AMLS injection, but are found in clusters or bands after a PMLS injection. Thus our results indicate that the thalamic afferents to AMLS and PMLS are in general similar: however, differences in input to AMLS and PMLS suggest that inputs to PMLS are predominantly visual while AMLS receives a broader spectrum of afferent information.
Distribution of dopamine‐, noradrenaline‐, and adrenaline‐containing cell bodies in the rat medulla oblongata: Demonstrated by the immunocytochemical localization of catecholamine biosynthetic enzymes
Authors: Armstrong David M. , Ross Christopher A. , Pickel Virginia M. , Joh Tong H. , Reis Donald J.
Published: December 2004

The immunocytochemical localization of the biosynthetic enzymes‐tyrosine hydroxylase (TH), dopamine‐beta‐hydroxylase (DBH), and phen‐ylethanolamine‐N‐methyltransferase (PNMT)‐was used to determine the cytological features and precise neuroanatomical location of catecholami‐nergic neurons in the medulla oblongata of rat. Perikarya labeled with TH were detected in two bilaterally symmetrical columns located in the ventrolateral and dorsomedial medulla. The distribution and the number of neuronal perikarya containing TH were the same as those containing DBH, except in the dorsal motor nucleus of the vagus at the level of the area postrema where the number of neurons immunocytochemically labeled for TH was considerably greater than those labeled for DBH. The detection of perikarya which show immunoreactivity for TH, used in the biosynthesis of dopamine, noradrenaline, and adrenaline, but not DBH, which converts dopamine to noradrenaline, suggests the existence of dopamine‐synthesiz‐ing neurons in the medulla.

Perikarya labeled with PNMT, used in the biosynthesis of adrenaline, were localized in more restricted regions corresponding to rostral subsets of the dorsal and ventral groups labeled for TH and DBH. Counts of neurons immunpcytochemically labeled for TH or PNMT were obtained in order to determine the relative ratio of neurons which contain the enzymes necessary for the synthesis of dopamine, noredrenaline, or adrenaline at various levels of the medulla. At the most caudal levels no PNMT labeled neurons were detected. Further rostral, PNMT‐labeled neurons were first detected in the ventrolateral medulla. At the level of the area postrema, the number of PNMT‐labeled neurons in the ventrolateral medulla was approximately half of the number of cells showing immunoreactivity for TH. In contrast, few PNMT‐labeled cells were detected in the dorsomedial medulla at the level of the area postrema compared to many neurons labeled for TH. At rostral medullary levels, in both the ventrolateral and the dorsomedial regions, the number of neurons labeled for TH and PNMT was essentially the same. Thus most, if not all, of the catecholaminergic neurons in the rostral medulla have PNMT, necessary for the synthesis of adrenaline.
Golgi studies on Purkinje cell development in the frog during spontaneous metamorphosis. III. Axonal development
Authors: Uray Nándor J. , Gona Amos G.
Published: December 2004

The development and organization of Purkinje cell axons and their collaterals was studied in the bullfrog using the Golgi‐Kopsch method. In the tadpole, axonal collaterals are few and usually unbranched. In the adult, however, intracortical axonal collaterals of Purkinje cells are more numerous, and they form a meager supraganglionic plexus and a more extensive infraganglionic plexus. In contrast to the pattern seen in higher vertebrates, these plexuses have a tendency to be distributed along the length of the cerebellar plate in both tadpoles and froglets. In addition, collateral branches that form intracortical plexuses apparently increase throughout the course of cerebellar development in this species.
Retinal degeneration in the pcd cerebellar mutant mouse. I. Light microscopic and autoradiographio analysis
Authors: LaVail Matthew M. , Blanks Janet C. , Mullen Richard J.
Published: December 2004

The Purkinje cell degeneration (pcd) mutant mouse rapidly loses cerebellar Purkinje cells between 3 and 5 weeks after birth and slowly loses retinal photoreceptor cells during the first year of life. In the present study, the retinal degeneration in the pcd mouse was analyzed by light microscopy and autoradiography throughout the first 15 months of age. By day 25 there is an abundance of pyknotic photoreceptor nuclei and many outer segments are clearly disorganized. Thereafter, as the photoreceptor cells are lost, their outer segments slowly become shorter and more variable in length; this slow change in length is explained by an almost proportional reduction in both rod outer segment renewal and disc shedding rates. At about 2 months of age, the rate of rod outer segment renewal is slightly less than half that in littermate controls, and the number of large phagosomes in pigment epithelial cells during the burst of disc shedding soon after light onset is one‐half or less than that seen in littermate controls. Between 2 and 10.5 months of age, the retina in the inferior hemisphere of the eye shows substantially more‐advanced photoreceptor degeneration than does the superior hemisphere, particularly in the far peripheral retina. A central‐toperipheral gradient of degeneration is conspicuous in the superior hemisphere; a similar but less obvious gradient of degeneration is also seen in the inferior hemisphere of the eye. Loss of photoreceptor cells and their synaptic terminals results in a predictable thinning of the outer synaptic layer. However, the inner nuclear layer shows no measurable thinning and the inner synaptic layer is reduced in thickness by only about 5–15%. Beginning at about 10 months of age, foci of thinned pigment epithelial cells are evident, and by 12 months there is some vascularization of the pigment epithelium by retinal capillaries.
Mesodiencephalic and other target regions of ascending spinal projections in the turtle, Pseudemys scripta elegans
Authors: Kunzle H. , Woodson W.
Published: December 2004

Ascending spinal projections were investigated in turtle Pseudemys scripta elegans following injections of radioactive amino acids into the spinal cord at various levels. Experiments using S35‐methionine were most successful in demonstrating various mesodiencephalic target areas.

Ascending projections from lumbar and cervical segments terminated predominantly in caudal and lateral reticular fields including the perihy‐poglossal complex. These spinal regions also projected for a lesser extent to rostrolateral and caudomedial reticular fields and to the nucleus (n.) raphe inferior. Afferents terminated consistently within the peritoral region, the optic tectal layers, the mesodiencephalic periventricular white matter, and the ovalis complex. Occasional labeling was noted in the diencephalic white matter adjacent to the optic tract, the n. supraopticus, and in the n. commissuralis anterior. Projections to the so‐called rostrolateral perirotundal complex following high cervical injections were less prominent following low cervical and lumbar injections. Cervical afferents terminated in a variable manner in the vestibular complex, the torus semicircularis n. centralis, the mesodiencephalic periventricular gray (griseum centrale, n. intersti‐tialis commissuralis posterior and hypothalamic areas), the n. suprapedun‐cularis, and the n. reuniens.
Modification of visual callosal projections in rats
Authors: Cusick C. G. , Lund R. D.
Published: December 2004

The effects of a variety of developmental manipulations on the distribution of the callosal pathway to visual cortex were examined by using the Fink Heimer technique in adult rats. First, the callosal projections in albino and pigmented rats were compared and found to be similar. The callosal pathway was limited in area 17 to a region adjoining its lateral border with area 18a. Second, dark‐reared rats were found to have normal callosal projections. Third, rats bilaterally enucleated at birth had expanded callosal inputs within area 17. Fourth, monocular enucleation at birth produced an expanded callosal pathway to area 17 contralateral to the enucleation and normal callosal projections to the opposite hemisphere. The expanded callosal inputs after enucleation showed a patchy distribution and usually avoided the most medial part of area 17. Fifth, a reduction in the callosal projections to the area 17/18a border was found after neonatal unilateral optic tract lesions. Sixth, expanded callosal inputs to area 17 were found following unilateral thalamic lesions at birth. The abnormal projection occupied mainly layers IV and III.

The results of the different experiments indicate that the detailed distribution of the visual callosal projection within area 17 depends heavily on the organization of the retinogeniculocortical pathways to each hemisphere.
The projections of the lateral geniculate nucleus of the squirrel monkey: Studies of the interlaminar zones and the S layers
Authors: Weber J. T. , Huerta M. F. , Kaas J. H. , Harting J. K.
Published: December 2004

Anterograde and retrograde tracing techniques were used to reveal that axons arising from neurons within the interlaminar zones and the S layers of the lateral geniculate nucleus of the squirrel monkey terminate within the supragranular layers of area 17. Specifically, our data indicate that the axons of the neurons housed within the S layers end in a patchlike fashion in cortical layers IIIa and IIIb, while neurons in the interlaminar zones project primarily to layer I. Both pathways may convey W‐cell information from the retina and the superior colliculus to the striate cortex.
Cytoarchitecture and visual receptive neurons in the wulst of the Japanese quail (Coturnix coturnix japonica)
Authors: Watanabe Masami , Ito Hironobu , Masai Hideo
Published: December 2004

The cellular organization of the Wulst was studied in Nissl‐ and Golgi‐stained brain sections in order to identify the visual receptive neurons. Golgi‐impregnated neurons were divided into four types according to their soma size, dendritic configuration, and density of spine distribution. Type I neurons, the largest cells in the Wulst, have long, straight dendrites with many spines. Type II neurons are medium‐sized cells with long, straight dendrites. These dendrites have numerous spines. Type III neurons are medium‐sized or small cells with spine‐free dendrites. Type IV neurons, the smallest cells in the Wulst, have short dendrites with sparse spines. The projections of the nucleus dorsolateralis anterior thalami pars lateralis (DLL) to the Wulst were determined by the Fink‐Heimer method. After lesions of the DLL, degenerating terminals are seen in a dorsolateral portion of the nucleus intercalatus hyperstriatum accessorium where the types II, III, and IV neurons are distributed. Postsynaptic elements to the DLL axons were identified by reconstruction of electron microscopic serial sections. Most of the postsynaptic elements were dendritic spines of the type II and IV neurons and a few were dendritic shafts of the type III neurons.
A developmental study of substance‐P, somatostatin, enkephalin, and serotonin immunoreactive elements in the spinal cord of the North American opossum
Authors: DiTirro F. J. , Martin G. F. , Ho R. H.
Published: December 2004

Substance‐P (SP), somatostatin (SOM), enkephalin (ENK), and serotonin (5‐HT) immunoreactive elements were studied in the spinal cord of the opossum at each 10‐mm snout‐rump (S‐R) length interval between 18 (newborn) and 127 mm (75 days after birth). The opossum is born 12 days after conception and undergoes a protracted postnatal development in an external pouch which makes it a good model for such a study. SP‐like immunoreactivity was detected in the newborn opossum; it was found within fibers located mainly in the dorsolateral marginal zone. SP‐like immunoreactive fibers soon become fairly abundant within presumptive laminae I, II, and X and were scattered within other areas of the spinal gray matter including the intermediolateral cell column. By 30 days after birth (57 mm S‐R length), the adult distribution was established. SOM‐like immunoreactivity was not detected within the spinal cord at birth. However, by postnatal day 5 (24 mm S‐R length) it was present in fibers which were numerous within the marginal zone and present within presumptive laminae I–III as well as in more ventral areas of the gray matter. By approximately postnatal day 30, evidence for SOM immunoreactivity was found within all areas of the spinal gray matter expected from studies of the adult opossum. ENK‐like immunoreactivity was present at birth within fibers of the dorsolateral marginal zone. By postnatal day 30 ENK immunoreactive fibers were found within most of the areas containing them in the adult animal, except for laminae I and II. ENK‐like immunoreactivity was not observed in laminae I and II until approximately postnatal day 50 (84 mm S‐R length). Fibers showing 5‐HT‐like immunoreactivity were remarkably abundant within the cervical marginal zone at birth but sparse at lumbosacral levels. They were found within laminae IV–Xby postnatal day 15 (35 mm S‐R length) and within the intermediolateral cell column by at least day 30. The adult distribution was not present until approximately 50 days after birth when 5‐HT‐like immunoreactivity was found within fibers of laminae I and II. Demonstration of SOM‐, ENK‐, and 5‐HT‐like immunoreactivities in neuronal somata of the spinal cord was age dependent.

Our results suggest that axons containing SP, SOM, ENK, and 5‐HT are present within the opossum's spinal cord very early in development and that they grow into specific spinal targets in an orderly sequence.
Developmental relationships between trigeminal ganglia and trigeminal motoneurons in chick embryos. II. Ganglion axon ingrowth guides motoneuron migration
Authors: Moody Sally A. , Heaton Marieta B.
Published: December 2004

In the chick embryo the trigeminal (V) sensory ganglion cells send axons into the metencephalon a few hours before the V motoneurons migrate from the midline to form a lateral nucleus adjacent to the ingrowing sensory axons. This relationship suggests that the ganglion axons may influence the initiation and direction of V motoneuron migration. In the present experiment the development of the ganglion axons was retarded by removing the neural crest anlage of the V ganglion. Subsequently, V ganglion cells which were derived from the ectodermal placode anlage sent axons into the metencephalon up to 2 days later than normal. The lateral migration of the V motoneurons was similarly delayed, commencing only after the central axons from the placodal ganglia penetrated the metencephalon. This study demonstrates that the presence of V ganglion perikarya alone is not sufficient to guide the appropriate migration of V motoneurons. This migration occurs only after the axons from the V sensory ganglion cells have penetrated the brainstem.
Development of order in the rat trigeminal system
Authors: Erzurumlu Reha S. , Killackey Herbert P.
Published: December 2004

The trigeminal system of the rat is characterized by a high degree of order. The pattern of the distribution of vibrissae follicles on the face is replicated at each synaptic station between face and somatosensory cortex (Belford and Killackey, '80). The present study details the development of the trigeminal nerve, its intrinsic organization, and its relationship with its peripheral and central targets. We have observed that at early embryonic ages (E12 and E13) the trigeminal ganglion neurons grow out in straight lines without crossing, and the distance between these neurons and their peripheral and central targets is very short. We have found that fibers reach the periphery before follicle formation is first detectable (E14). At all ages, the trigeminal fibers show a marked tendency to fasciculate. After the development of the pattern of vibrissae follicles on the face, the pattern of fasciculation within the nerve can be clearly related to the rows of vibrissae and the buccal pad. This peripherally related order in the nerve was experimentally verified by injecting horseradish peroxidase into the follicles of individual rows and selectively sectioning portions of the nerve. Further, we provide evidence that the discrete brainstem pattern reflecting vibrissae distribution develops after organization is detectable in the nerve and in a temporal sequence from lateral to medial, which replicates the developmental sequence of vibrissae follicles from ocular to nasal on the face. This sequence is detectable in both the distribution of afferent terminals as measured with succinic dehydrogenase histochemistry and of horseradish peroxidase back‐labeled trigeminothalamic relay cells. We interpret our results as suggesting that a number of factors may play a role in the establishment of specific neuronal topographies in the rodent trigeminal system.
Direct reciprocal connections between the bed nucleus of the stria terminalis and dorsomedial medulla oblongata: Evidence from immunohistochemical detection of tracer proteins
Authors: Sofroniew Michael V.
Published: December 2004

Connections between the bed nucleus of the stria terminalis and the dorsomedial medulla oblongata have been examined by immunohistochemical detection of the tracer proteins horseradish peroxidase (HRP) or wheatgerm agglutinin (WGA). Two sets of four rats received 0.2 or 0.4 μl of eithertracer injected into the dorsomedial medulla oblongata, were fixed by perfusion 48 hours later, and were processed for immunohistochemical detection of the tracers. Rats receiving HRP showed only a few single neurons retrogradely labelled in the ipsilateral bed nucleus, and some anterogradely labelled fibers. Rats receiving WGA showed a large number of retrogradely labelled neurons in the ipsilateral bed nucleus. Labelled neurons were most concentrated in a group in the central, dorsal, and lateral aspects of the nucleus at the level of the anterior commissure and just caudal to this. Just ventral to this group was a dense cluster of anterogradely labelled fibers. The retrogradely labelled neurons ranged from 12 to 20 μm in size and were multipolar. These findings indicate that there are direct reciprocal connections between the bed nucleus of the stria terminalis and the autonomic centers of the dorsomedial medulla oblongata and strengthen the concept that this nucleus is involved in forebrain integration of autonomic functions.
Origin of the rubrospinal tract in neonatal, developing, and mature rats
Authors: Shieh Jeng Yung , Leong Seng Kee , Wong Wai Chow
Published: December 2004

This investigation describes the origin of the rubrospinal tract in neo‐natal (1‐10 days old), developing (15‐20 days old), and mature (2‐4 months old) rats studied by using the horseradish peroxidase (HRP) method of tracing neuronal connections. HRP was administered in the cervical or lumbosacral segments of the spinal cord either in the crystal or solution form. The results showed that the rubrospinal tract extended to the lum‐bosacral part of the spinal cord at birth. There appeared to be no difference in the pattern of labelled rubrospinal (RS) neurons following the admin‐istration of HRP in the cervical or the lumbosacral cord segment of the neonatal, developing, and mature rats. In rats of these three age groups, labelled neurons were found bilaterally in the red nucleus, with a contra‐lateral predominance, and they were found in both the parvicellular and magnocellular portions of the red nucleus. There was a somatotopic ar‐rangement in the labelled RS neurons: Those projecting to the cervical cord segments were located in the dorsal and dorsomedial regions of the red nucleus and those projecting to the lumbosacral cord segments were located in the ventral and ventrolateral regions of the nucleus.
Ascending projections to the inferior colliculus following unilateral cochlear ablation in the neonatal gerbil, Meriones unguiculatus
Authors: Nordeen K. W. , Killackey H. P. , Kitzes L. M.
Published: December 2004

We evaluated the consequences of neonatal cochlear destruction upon ascending projections to the inferior colliculi. Unilateral cochlear ablations were performed in both neonatal and adult gerbils. Four to 12 months later, the inferior colliculus (IC) was examined physiologically and injected uni‐laterally with horseradish peroxidase (HRP). The number of labeled cells was determined bilaterally in all three divisions of cochlear nucleus (CN) and in the medial superior olive (MSO). In both experimental groups, trans‐ncuronal changes within the deafferented CN were greater in the ventral divisions than in the dorsal division. On the unoperated side the magnitude of projections from CN to the inferior colliculi was altered in animals le‐sioned as neonates. Following HRP injections into the IC on the unoperated side, the number of ipsi later ally labeled cells in CN (unoperated side) was significantly greater in the neonatal experimental group than in adult ex‐perimental and control animals. These anatomical changes were accom‐panied by increased ipsilaterally evoked excitatory activity recorded in the IC on the unoperated side. Following HRP injections into the IC on the ablated side, the number of contralaterally labeled cells in CN (unoperated side) was significantly reduced in animals lesioned as neonates as compared with control animals. The number of labeled cells in ipsilateral MSO was not significantly different across groups. Our interpretation is that unilat‐eral cochlear ablation in neonatal gerbils results in an increase in the magnitude of ipsilateral projections and a decrease in the magnitude of contralateral projections from CN on the unoperated side to the inferior colliculi. These data suggest that the normal pattern of innervation of the IC results, in part, from interactions among afferent projections.
Differentiation of granule cell dendrites in the dentate gyrus of the rhesus monkey: A quantitative golgi study
Authors: Duffy Charles J. , Rakic Pasko
Published: December 2004

The differentiation of granule cell dendrites in the dentate gyrus of the hippocampal region was studied in a series of developing fetal and postnatal rhesus monkeys whose brains were processed by the rapid Golgi method. The total combined lengths of dendrites, the total number of dendritic spines, and their density on the proximal, middle, and distal thirds of the dendritic shafts were determined at embryonic days 58, 95, 120, 153, term (165), postnatal days 3, 20, 60, 150, 365, and adults. At all ages examined, granule cells exhibited various levels of maturation with the more differentiated cells being situated in the superficial strata of the granular layer and the less mature cells lying in progressively deeper positions, thus conforming to the outside‐to‐inside spatiotemporal gradient of their genesis. Quanti‐tative analysis shows that, in this primate, hippocampal granule cells dif‐ferentiate mainly in the second half of gestation with all measured param‐eters attaining mature values by the time of birth. However, the analysis also reveals a transient phase of exuberant postnatal development which involves excessive dendritic branching, regional changes in dendritic length, overproduction of dendritic spines, and redistribution of spines within the molecular layer. After reaching peak values around the middle of the first year of life, these parameters decrease and in adult monkeys fall back to the neonatal level.
Cell death and changes in the retrograde transport of horseradish peroxidase in rubrospinal neurons following spinal cord hemisection in the adult rat
Authors: Goshgarian Harry G. , Koistinen Jeanne M. , Schmidt Eric R.
Published: December 2004

Most of the hypotheses that have been proposed to explain why the injured mammalian spinal cord is not capable of extensive regeneration have suggested that the internal milieu of the injured spinal cord is not conducive to repair. Relatively little attention has been directed toward neuronal cell death as being contributory to the minimal amount of spinal cord regeneration. The present study suggests that the availability of regenerating axons in the injured spinal cord may be limited by the death of axotomized supraspinal neurons in the adult mammal. Adult rats were subjected to a right spinal cord hemisection at T1 followed by a second, more rostral right hemisection at C2 Horseradish peroxidase (HRP) was injected into the rostral hemisection site to acquire information on the metabolic changes that occur in HRP‐labeled rubrospinal neurons after axotomy. In the experimental animals, a delay of 9‐219 days occurred between the two operations whereas there was no delay between the two procedures in the control animals. An analysis of neuronal counts indicated that although there was a statistically significant (P < 0.01) decrease in the number of labeled rubrospinal neurons in the contralateral red nucleus of the experimental animals compared to controls, there was also a smaller, yet significant (P < 0.01) increase in the number of nonlabeled neurons in the experimental animals. The mean total number (both labeled and nonla beled) of neurons in the experimental animals (2,269 ± 348 cells), however, was significantly lower (P < 0.01) than the mean total number of neurons in the control animals (3,473 ± 488 cells). Thus, it is concluded that extensive cell death occurs in the red nucleus of the adult rat following spinal cord hemisection.

The increase in the number of nonlabeled neurons coupled with an overall decrease in the intensity of the HRP reaction in labeled neurons of the experimental animals indicates that HRP retrograde transport is reduced in chronically axotomized rubrospinal neurons. This suggests that the retrograde axonal transport system may be used as an instrument to gauge the metabolic state of injured CNS neurons. This technique may enable us to gain a better understanding of degeneration and regeneration in the injured mammalian spinal cord.