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At least 127 records · Page 7Linked to original sources
PubMed1996

Distribution of descending projections from primary auditory neocortex to inferior colliculus mimics the topography of intracollicular projections.

To ascertain whether the auditory neocortex also innervates the central nucleus of the inferior colliculus (CNIC) and not only its dorsal (DCIC) and external (ECIC) cortices, the anterograde tracers Phaseolus vulgaris-leucoagglutinin (PHA-L) and biotinylated dextran (BD) were injected into the primary auditory neocortex of albino rats (Te1), and labeled corticocollicular fibers were studied via light and electron microscopy. Axons from discrete regions of Te1 form two rostrocaudally oriented laminar plexuses of terminal fibers in the ipsilateral inferior colliculus (IC) and one in the contralateral IC. The first ipsilateral plexus, located in the medial half of the IC, has a dorsomedial to ventrolateral orientation, parallel to the isofrequency planes of the IC; is continuous through the CNIC and DCIC; and extends into the rostral ECIC. The second plexus is located in the deep layers of the lateral ECIC. These two plexuses meet caudally and ventrally, at the border between the CNIC and the lateral ECIC. The plexus in the contralateral IC is less dense and shorter than the two ipsilateral plexuses and is symmetric to the medial plexus. The thickness of the three plexuses is correlated with the size of the injection site, and their mediolateral and dorsoventral positions change as the injection site in Te1 is displaced rostrocaudally, with more caudal injections resulting in more dorsolateral medial plexuses and more dorsomedial lateral plexuses. Furthermore, the ventromedial border of the IC receives nontopographic, convergent projections from wide regions of rostral portions of Te1. The distribution of these corticocollicular plexuses mimics the topography of previously described intracollicular fibers. Electron microscopy shows that, in all three subdivisions of the ipsilateral IC, corticocollicular fibers form small boutons with features generally associated with excitatory transmission; i.e., they contain round synaptic vesicles and form asymmetric synapses with thin dendritic shafts and spines. These results demonstrate that the auditory corticocollicular projections innervate more extensive regions of the IC than were previously observed. Although peripheral regions receive the densest projection, the entire IC appears to be the target of corticofugal input.

Animals↗
PubMed1997

Metamorphic remodeling of the primary olfactory projection in Xenopus: developmental independence of projections from olfactory neuron subclasses.

In adult Xenopus, the nasal cavity is divided into separate middle (MC) and principal (PC) cavities; the former is used to smell water-borne odorants, the latter air-borne odorants. Recent work has shown that olfactory neurons of each cavity express a distinct subclass of odorant receptors. Moreover, MC and PC axons project to distinct regions of the olfactory bulb. To examine the developmental basis for this specificity in the olfactory projection, we extirpated the developing MC from early metamorphic (stage 54-57) tadpoles and raised the animals through metamorphosis. In most lesioned animals, the MC partly regenerated. Compared with the unlesioned side, reduction of the region of the glomerular layer of the olfactory bulb receiving MC afferents ranged from 70% to 95%. PC afferents did not occupy regions of the olfactory bulb deprived of MC afferents. These results support a model in which intrinsic cues in the olfactory bulb control the projection pattern attained by ingrowing olfactory axons.

Animals↗
PubMed1999

Optimal gradient waveform design for projection imaging and projection reconstruction echoplanar spectroscopic imaging.

The use of modulated B0 projection gradient waveforms is proposed for magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) to shape the k-space sampling density function to match the profile of an applied reconstruction window function. This allows for a time-efficient means of maximizing the signal-to-noise ratio when, for example, a low-pass spatial filter, designed to reduce k-space truncation artifacts and corresponding point-spread function sidelobe energies, is implemented. Both the two-dimensional (2D) and 3D cases are investigated. To create the projection gradient waveforms, a design method is developed that uses nonlinear constrained optimization (NLCO) to minimize the variance of the reconstruction noise. The design is subject to both equality and inequality constraints, which include the maximum gradient magnitude and slew rate. It is shown that NLCO can also be applied to twisting the projection trajectories for purposes of reducing the data acquisition time while still maintaining the desired sampling density. Applications to 1H MRSI are investigated via simulations. Advantages and limitations of the new sampling schemes are discussed.

Brain Chemistry↗
PubMed1981

Olivocerebellar projections to the pyramis and copula pyramidis in the rat: differential projections to parasagittal zones.

The organization of the olivocerebellar projection to the pyramis and copula pyramidis in the rat has been studied with the use of microinjections of horseradish peroxidase (HRP). These injections were made in different mediolateral positions along the width of this lobule. The objective was to determine the subnuclear origin of parasagittal zones of olivary innervation. The results indicate that six zones of varying width can be distinguished, each of which receives a different olivary projection. Injections in the pyramis in succeedingly more lateral positions resulted in retrograde labeling of the lateral part of the caudal medial accessory olive (MAO), nucleus beta of the MAO, and a slightly more rostral part of the lateral MAO. Injections in the copula pyramidis result in retrograde labeling of the lateral part of the dorsal accessory olive (DAO), the intermediate part of the MAO, and the caudal tip of the principal olive. In very few of the experiments was there labeling of more than one subnuclear locus within the inferior olivary complex. These results suggest that parasagittal zones within the pyramis and copula pyramidis of the rat cerebellum receive highly ordered and differential projections from the inferior olivary complex.

Afferent Pathways↗
PubMed1987

Development of brainstem and cerebellar projections to the diencephalon with notes on thalamocortical projections: studies in the North American opossum.

The North American opossum is born in a very immature state, 12 days after conception, and climbs into an external pouch where it remains attached to a nipple for an extended period of time. We have taken advantage of the opossum's embryology to study the development of brainstem and cerebellar projections to the diencephalon as well as the timing of diencephalic projections to somatosensory motor areas of neocortex. The techniques employed included immunocytochemistry for serotonin, the retrograde and orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase, and the selective impregnation of degenerating axons. Our results suggest that serotoninergic axons, presumably from the dorsal raphe and superior central nuclei, are present in the diencephalon at birth. Axons from the bulbar reticular formation, the vestibular complex, the trigeminal sensory nuclei, and the dorsal column nuclei reach at least mesencephalic (and probably diencephalic) levels by postnatal day (PND) 3, whereas those from the cerebellar nuclei may not grow into comparable levels until PND 5. The dorsal column and cerebellar nuclei innervate the ventral nuclei of the thalamus by estimated postnatal day (EPND) 17 and all of the diencephalic nuclei supplied in the adult animal by EPND 26. Diencephalic axons enter ventrolateral (face) areas of presumptive somatosensory motor cortex by PND 12, but do not reach dorsomedial (limb) regions until EPND 21. At both ages, diencephalic axons are limited to the cortical subplate and marginal zone; they do not innervate an identifiable internal granular layer until considerably later. Our results suggest that axons from the brainstem and cerebellum grow into the diencephalon early in development, but that they do not influence the cerebral cortex until relatively late. When the results of the present study are compared with those reported previously on the development of ascending spinal (Martin et al., '83) and corticofugal (Martin et al., '80; Cabana and Martin, '85b,c) projections, it appears that specific components of major somatosensory and motor circuits develop according to different timetables.

Animals↗
PubMed1987

Organization of subcortical pathways for sensory projections to the limbic cortex. II. Afferent projections to the thalamic lateral dorsal nucleus in the rat.

Afferent projections to the thalamic lateral dorsal nucleus were examined in the rat by the use of retrograde axonal transport techniques. Small iontophoretic injections of horseradish peroxidase were placed at various locations within the lateral dorsal nucleus, and the location and morphology of cells of origin of afferent projections were identified by retrograde labeling. For all cases examined, subcortical retrogradely labeled neurons were most prominent in the pretectal complex, the intermediate layers of the superior colliculus, and the ventral lateral geniculate nucleus. Labeled cells were also seen in the thalamic reticular nucleus and the zona incerta. Within the cerebral cortex, labeled cells were prominent in the retrosplenial areas (areas 29b, 29c, and 29d) and the presubiculum. Labeled cells were also seen in areas 17 and 18 of occipital cortex. Peroxidase injections in the dorsal lateral part of the lateral dorsal nucleus result in labeled neurons in all of the ipsilateral pretectal nuclei, but especially those that receive direct retinal afferents. Labeled cells were also seen in the ventral lateral geniculate nucleus and the rostral tip of laminae IV-VI of the superior colliculus. In contrast, peroxidase injections in ventral medial portions of the lateral dorsal nucleus result in fewer labeled pretectal cells, and these labeled cells are found exclusively in the pretectal nuclei that do not receive retinal afferents. Other labeled cells following injections in the rostral and medial portions of the lateral dorsal nucleus are seen contralaterally in the medial pretectal region and nucleus of the posterior commissure, and bilaterally in the rostral tips of laminae IV and V of the superior colliculus. Camera lucida drawings of HRP labeled cells reveal that projecting cells in each pretectal nucleus have a characteristic soma size and dendritic branching pattern. These results are discussed with regard to the type of sensory information that may reach the lateral dorsal nucleus and then be relayed on to the medial limbic cortex.

Afferent Pathways↗
PubMed1992

Development of the olivocerebellar projection in the rat: II. Matching of the developmental compartmentations of the cerebellum and inferior olive through the projection map.

A transient biochemical parcellation has been observed by immunocytochemical methods, during the perinatal development of both the inferior olive and the cerebellum. In the present study, we sought a relationship between this developmental compartmentation and the organization of the olivocerebellar projection. In the inferior olive, a transient parvalbumin immunoreactivity restricted to the dorsal cap of the medial accessory olive is observed around birth. The climbing fiber projection of the dorsal cap was identified in the cerebellum of newborn rats based on its parvalbumin immunoreactivity. The pattern of this projection, restricted to lobules IX and X of the vermis, and to the flocculus, is indistinguishable from that of the adult medial accessory olive, which was previously described from axonal tracing experiments. The parvalbumin immunoreactive climbing fibers were followed between birth and postnatal day 7. In the caudal vermis, Purkinje cell subpopulations can be identified between embryonic day 20 and postnatal day three, on the basis of their differential immunostaining with an antibody directed against a specific peptide, PEP 19. In lobule X, the parvalbumin immunoreactive climbing fibers form two sagittal bands on each side of the midline, one medial and one lateral. The medial parvalbumin immunoreactive climbing fiber band is coextensive with a PEP 19 negative Purkinje cell cluster, indicating a clear relationship between the biochemical parcellations of the cerebellum and inferior olive.

Animals↗
PubMed1993

Geometry of the projection of the visual field onto the superior colliculus of the wallaby (Macropus eugenii). II. Stability of the projection after prolonged rearing with rotational squint.

At about the time of eye opening, one eye of seven tammar wallaby pouch young was surgically rotated about the optic axis by approximately 90 degrees. In adulthood the projection of the visual field through the rotated eye onto the contralateral superior colliculus was mapped electrophysiologically. Although apparently distorted, the projection could be coherently re-rotated mathematically to a reasonable copy of the normal projection from the opposite eye of the same animal, including details such as regional variations of the magnification factor. The same was true of three adult animals in which the eye rotation was done after anaesthesia immediately before the electrophysiological mapping. In animals in which the visual field seen through one eye, the other being normal, was rotated for the entire period of visual experience, there was no sign of compensation or rearrangement of the topographic map. Retinocollicular synaptic connections appear unmoved by such discordant visual experience.

Animals↗
PubMed1995

The efferent projections of the periaqueductal gray in the rat: a Phaseolus vulgaris-leucoagglutinin study. I. Ascending projections.

This study has examined the ascending projections of the periaqueductal gray in the rat. Injections of Phaseolus vulgaris-leucoagglutinin were placed in the dorsolateral or ventrolateral subregions, at rostral or caudal sites. From either region, fibers ascended via two bundles. The periventricular bundle ascended in the periaqueductal and periventricular gray matter. At the posterior commissure level, this bundle divided into a dorsal component that terminated in the intralaminar and midline thalamic nuclei, and a ventral component that supplied the hypothalamus. The ventral bundle formed in the deep mesencephalic reticular formation and supplied the ventral tegmental area, substantia nigra pars compacta, and the retrorubral field. The remaining fibers were incorporated into the medial forebrain bundle. These supplied the lateral hypothalamus and forebrain structures, including the preoptic area, the nuclei of the diagonal band, and the lateral division of the bed nucleus of the stria terminalis. The dorsolateral subregion preferentially innervated the centrolateral and paraventricular thalamic nuclei and the anterior hypothalamic area. The ventrolateral subregion preferentially innervated the parafascicular and central medial thalamic nuclei, the lateral hypothalamic area, and the lateral division of the bed nucleus of the stria terminalis. Although the dorsolateral and ventrolateral subregions gave rise to differential projections, the projections from both the rostral and caudal parts of either subregion were similar. This suggests that the dorsolateral and ventrolateral subregions are organized into longitudinal columns that extend throughout the length of the periaqueductal gray. These columns may correspond to those demonstrated in recent physiological studies.

Animals↗
PubMed1995

Spinovestibular projections in the rat, with particular reference to projections from the central cervical nucleus to the lateral vestibular nucleus.

Projections from the spinal cord to the vestibular nuclei were examined following injections of Phaseolus vulgaris-leucoagglutinin, cholera toxin subunit B, or biotinylated dextran at various levels of the spinal cord in the rat. Labeled terminals were abundant after injections of the tracers into the C2 and C3 segments containing the central cervical nucleus. Labeled terminals were seen in the descending vestibular nucleus and the parvocellular, magnocellular, and caudal parts of the medial vestibular nucleus throughout its rostrocaudal extent. Labeled terminals were most numerous in the lateral vestibular nucleus throughout its rostrocaudal extent. The projections from the central cervical nucleus to the vestibular nuclei were exclusively contralateral to the cells of origin because the axons of the central cervical nucleus neurons cross in the spinal cord. Following tracer injections in the cervical enlargement, many labeled terminals were seen in the magnocellular part of the medial vestibular nucleus, but a few were seen in the lateral and the descending vestibular nucleus. Injections into more caudal segments resulted in sporadic terminal labeling in the magnocellular part of the medial vestibular nucleus, the descending vestibular nucleus, and the caudal part of the lateral vestibular nucleus. The results indicate that primary neck afferent input relayed at the central cervical nucleus is mediated directly to the contralateral vestibular nuclei. It is suggested that this projection serves as an important linkage from the upper cervical segments to the lateral vestibulospinal tract in the tonic neck reflex.

Animals↗
PubMed1983

Afferent projections from the brainstem to the three floccular zones in cats. I. Climbing fiber projections.

The cat's flocculus can be divided into 3 zones on the basis of differences in their efferent projection sites. In the present study, climbing fiber projections from the inferior olive to each zone of the flocculus were studied by means of retrograde axonal transport of horseradish peroxidase (HRP). Following large injections of HRP into the flocculus, labeled cells appear in the dorsal cap and the ventrolateral outgrowth of the principal olive. No HRP-labeled somata are present in other parts of the inferior olive. Following microinjections of HRP into the rostral of caudal zones of the flocculus, labeled cells appear in the ventrolateral outgrowth and the rostral part of the dorsal cap, while, after injections into the middle zone, labeled cells are found in the caudal part of the dorsal cap. These findings show that there exists zonal organization in the climbing fiber projections to the flocculus; the rostral and caudal zones receive climbing fiber afferents from the ventrolateral outgrowth and the rostral part of the dorsal cap, while the middle zone receives those from the caudal part of the dorsal cap.

Afferent Pathways↗
PubMed1985

Modification of the projection from the sensory cortex to the motor cortex following the elimination of thalamic projections to the motor cortex in cats.

Examination of the projection from area 2 of the sensory cortex to the motor cortex revealed substantial changes following lesion of the ventrolateral nucleus of the thalamus. These observed changes were as follows. (1) The polarity of the evoked potentials elicited by area 2 stimulation reversed in the depth of the motor cortex whereas in normal animals, there was no reversal. (2) The amplitude of area 2-elicited EPSPs in the motor cortical neurons became greater following the lesion of VL. (3) The shape of the observed EPSPs was characterized by multiple peaks whereas in normal animals, the EPSPs were generally smooth and monophasic. (4) Neurons receiving a short-latency input from area 2 were distributed throughout the depths of the motor cortex whereas in normal animals, they were located only in the upper layers (layers II and III). (5) Intracellular injection of HRP revealed that the neurons receiving short-latency input were not restricted to typical stellate type cells, but also included bipolar or bitufted neurons with elongated cell bodies and polarized arborizations. These neurons were located in the superficial (II and III) as well as in the deep (V) layer. It is concluded that the elimination of thalamic input resulted in the reinforcement of the corticocortical input to the motor cortex. The subsequently observed corticocortical projection extended to neurons did not originally innervated by the association fibers. The results suggested that functional recovery following thalamic lesion is partly due to reorganization of projections from the sensory cortex to the motor cortex.

Animals↗
PubMed1983

Interhemispheric nigrostriatal projections in the rat: bifurcating nigral projections and loci of crossing in the diencephalon.

The organization of interhemispheric nigrostriatal projections in the rat was studied with (1) a double labeling technique combined with a histofluorescence method for monoamines and with (2) horseradish-peroxidase (HRP) as a tracer. Each animal received an injection of Fast Blue (FB) into the caudate nucleus (NC) of one hemisphere and an injection of Nuclear Yellow (NY) into the NC of the other hemisphere. Brains were processed according to the sucrose-potassium phosphate-glyoxylic acid (SPG) method in order to identify monoaminergic neurons. About 5% of the neurons which were labeled by either of the tracers in the substantia nigra (SN) ipsilateral to the injection site were also labeled in the contralateral SN. Most of these interhemispherically projecting SN-neurons were monoaminergic. A small number of neurons in either SN was labeled with both fluorescent tracers. This suggests that bifurcating, monoaminergic neurons in the SN project to both NC. In the second experiment, rats received a unilateral injection of HRP into NC. After a survival time of several hours the animals were perfused and the brains were processed using benzidine-dihydrochloride. Fibers crossing the hemisphere were found within the massa intermedia of the thalamus and within the inferior thalamic peduncle. The results are discussed with respect to a possible functional role of interhemispheric nigrostriatal connections.

Animals↗
PubMed1997

Direct vasoactive intestinal polypeptide-containing projection from the suprachiasmatic nucleus to spinal projecting hypothalamic paraventricular neurons.

In mammals, photoperiodic information is conveyed from the retina to the pineal through a polysynaptic pathway, which includes the suprachiasmatic nucleus (SCN), the paraventricular nucleus of the hypothalamus (PVN), the spinal preganglionic neurons and, finally, the superior cervical ganglion. Precise data on the site in the PVN or which SCN transmitters are involved in the transmission of information in this pathway is lacking. In the present experiment we investigated whether SCN efferents containing vasoactive intestinal polypeptide (VIP) innervate PVN neurons that project to the spinal cord. A combination of retrograde tracing and immunocytochemistry with the aid of a confocal laser scanning microscope allowed us to assess possible interaction of SCN efferents and spinal cord projecting neurons in the PVN. Approximately 30% of identified autonomic projecting neurons in the dorsal PVN and 40% in the ventral PVN received VIP innervation mainly on their dendrites. These results provide further evidence for the involvement of SCN-derived VIP in the transmission of circadian information to the pineal.

Animals↗
PubMed1998

A model for adolescent-targeted HIV/AIDS services: conclusions from 10 adolescent-targeted projects funded by the Special Projects of National Significance Program of the Health Resources and Services Administration.

This article describes a model of service for youth living with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) and youth at high risk for HIV, based on the lessons learned from a set of innovative service projects funded by the Health Resources and Services Administration Special Projects of National Significance (SPNS) Program. Although each project has a unique focus, all collectively seek to enroll youth with HIV into care through new or existing HIV service networks, and direct recruitment via street outreach and other similar methods. The use of various outreach methods tends to yield different patterns of engagement of youth in services. An ideal approach may use a combination of complementary outreach methods. Data at both the national and local levels point to five major elements that capture the innovations of the collective service model: (a) peer-youth information and dissemination; (b) peer-youth advisory groups; (c) peer-youth outreach and support; (d) professional, tightly linked medical social support networks; and (e) active case management and advocacy, for individual clients as well as the programs themselves, to link the various components together. One of the most important factors in the model's success is that youth and professionals share an equal partnership in all stages of program design, planning, and implementation. Youth and professionals each share their expertise in a dynamic process. In addition, active case management is crucial, not only to ensure that clients receive needed services, but also to ensure that the programs themselves run in a coordinated, tightly linked way. Given needs of adolescent clients and existing adult-oriented service networks, the use of active case management and the active participation of youth in the services system are critical.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Results of a humanitarian otologic and audiologic project performed outside of the United States: lessons learned from the "Oye, Amigos!" project.

From 1989 to 1993, "Oye, Amigos!" a combined group of hearing health and other medical professionals performed 18 humanitarian medical and audiologic trips to Tepic, Nayarit, Mexico. The group saw 1500 patients, issued over 800 hearing aids, and performed 150 surgeries on 123 patients. Our tympanoplasty success rate, defined as an intact tympanic membrane, was 41% during the first 2 years of the project but increased to 74% during the last 3 years. Two hundred eighteen patients who were candidates for surgery did not return for care. We present the lessons learned from the surgical care and overall management of this project, and present suggestions to improve future projects.

Adolescent↗
PubMed1999

Serum cholesterol ester fatty acids in 7- and 13-month-old children in a prospective randomized trial of a low-saturated fat, low-cholesterol diet: the STRIP baby project. Special Turku coronary Risk factor Intervention Project for children.

To evaluate changes that occur in serum cholesterol ester fatty acid composition during the transition from typical infant feeding to a more adult type of nutrition, this study compared the effects on serum cholesterol ester fatty acids of breast milk or formula at the age of 7 mo with effects caused by 6-mo dietary intervention in 137 children. The intervention [Special Turku coronary Risk factor Intervention Project for children (STRIP baby project)] aimed at a reduction of saturated fat intake to 10% of energy after the age of 1 y without purposefully influencing total fat intake. Nutrient intakes were calculated from 3-d food records. At the age of 7 mo, i.e. before dietary education began, milk type markedly influenced dietary and serum cholesterol ester fatty acid composition (mean serum cholesterol ester 16:0 in breastfed vs formula-fed infants, 13.7% vs 12.0%, respectively, p < 0.001; serum cholesterol ester 18:2n-6 50.6% vs 57.6%, p < 0.001). At the age of 13 mo the calculated fat intake of the intervention and control children differed markedly but serum cholesterol ester fatty acid compositions in all children resembled closely those measured in 7-mo-old breastfed infants, e.g. at the age of 13 mo the relative proportions of 18:2n-6 were 49.9% and 51.1% in previously formula-fed intervention and control children, respectively, and 50.3% and 50.1% in previously breastfed intervention and control children, respectively. In conclusion, serum cholesterol ester fatty acid composition reflected differences in dietary fat quality (breast milk or formula) at the age of 7 mo, whereas dietary intervention as applied in the STRIP baby project had only a minimal effect.

Breast Feeding↗
PubMed1977

The effects of a finite number of projection angles and finite lateral sampling of projections on the propagation of statistical errors in transverse section reconstruction.

The dependence of noise amplification on the nuber of projection angles and on the lateral sampling interval of projections is presented. It is shown that about 1-5D/d angles and a sampling interval of about 0-5d are required in order that the data be efficiently utilized. D is the linear dimension of the reconstruction region and d is the linear dimension of the cells into which the reconstruction region is subdivided (resolution length). Values for noise amplification are given for various combinations of projection angles and lateral sampling intervals.

Information Theory↗