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PubMed1984

Spinally projecting neurons in the dorsal column nuclei: distribution, dendritic trees and axonal projections. A retrograde HRP study in the cat.

The distribution, dendritic trees and axonal courses of spinally projecting cells in the dorsal column nuclei were studied after labelling by retrograde HRP transport. The region of densest distribution was at the base of the two nuclei and in the area between them, extending for about 2 mm caudally from the obex. Only very few cells were found inside the cell cluster regions of the nuclei, where their dendrites had a free stellate form. The great majority, lying between, deep, or rostral to the cluster regions, also had a stellate form, except where they impinged on the boundaries of the cluster regions or on other nuclear borders; the spread of dendrites was dramatically restricted at such boundaries, often leading to a fusiform appearance in transverse sections which however was not evident in the parasagittal plane. No justification was therefore found for subdividing the population on morphological grounds. Axons of these cells descended ipsilaterally in either the medial part of the dorsolateral fascicle or in the adjacent lateral part of the cuneate fascicle, at cervical levels, and probably in about equal numbers. Most axons destined for the DLF followed a deep caudolateral trajectory, while many destined for the DC had a more dorsal or lateral course. Collateral branches were seen within the nuclei but could not be followed far. The fact that few if any cells lying in the region of maximum distribution of the spinally projecting cells were labelled following injections of HRP into the thalamic ventroposterior nucleus emphasizes that they form a distinctive entity within this medullary nuclear complex, and that any axon branches they give into the contralateral brainstem must have some other destination than the VPL. Two other groups of neurons were labelled by HRP implants into the dorsal columns - one in the ventrolateral medullary reticular formation, and the other in the nucleus of the solitary tract.

Afferent Pathways↗
PubMed1981

Compressed retinotectal projection in hamsters: fewer ganglion cells project to tectum after neonatal tectal lesions.

After partial ablation of the superior colliculus (tectum) in neonatal hamsters, the whole extent of the visual field comes to be represented in a compressed map on the remaining tectal fragment. However, the total volume of tectal tissue in which retinotectal fibers arborize is less than normal. These observations suggests that the retinal ganglion cells which arborize in this reduced volume might arise throughout the whole extent of the retina but be fewer in number than normal. Alternatively, the ganglion cells which project to the tectum might be normal in number but reduced in terminal arbor size. To distinguish between these possibilities, we have used tectal injections of horseradish peroxidase to label retinal ganglion cells which project to the tectum. The numbers of labelled cells per mm2 of retina were counted in selected regions. In hamsters with small lesions, which left 80--85% of the tectum intact, the density of labelled retinal ganglion cells was normal. However, in hamsters with larger lesions, the density of labelled cells was significantly lower than normal.

Animals↗
PubMed1988

An ultrastructural study of the projections from the midbrain periaqueductal gray to spinally projecting, serotonin-immunoreactive neurons of the medullary nucleus raphe magnus in the rat.

In this triple-label, electron microscopic study in the rat, a lesion of the midbrain periaqueductal gray (PAG) was made so that the distribution and targets of degenerating PAG terminals could be identified in the medullary nucleus raphe magnus (NRM). Spinally projecting NRM neurons were identified by the retrograde transport of wheat germ agglutinin-horseradish peroxidase from the cervical cord. We also used immunocytochemistry to define the subpopulation of NRM neurons which were serotonin-immunoreactive. We report that both serotonergic and non-serotonergic neurons of the medulla, which project to the spinal cord, receive monosynaptic inputs from the PAG.

Animals↗
PubMed1989

Subpallidal-pedunculopontine projections but not subpallidal-mediodorsal thalamus projections contribute to spontaneous exploratory locomotor activity.

The contribution of the pedunculopontine nucleus to exploratory locomotion was investigated in rats. Locomotor activity recorded in a standard open-field apparatus was increased more than two-fold when wooden panels were inserted. This novelty-elicited locomotion was reduced significantly when procaine was injected bilaterally into the pedunculopontine nucleus but not when procaine was injected bilaterally into the mediodorsal thalamus, a second major projection site of the subpallidal area. These results support observations from earlier studies implicating hippocampal-accumbens-subpallidal-pedunculopontine projections in exploratory locomotion.

Animals↗
PubMed1986

Quantification of branched neuronal projections labelled by retrograde fluorescent tracing. A study of olivo-cerebellar projections.

A method for estimating the number of branched and unbranched neurones projecting from a nucleus to two target sites is presented, based on the retrograde transport of fluorescent tracers. The method initially involves stereological corrections for the size of cytoplasm and nuclei respectively labelled by the two tracers. A second correction is applied to account for doubly labelled cells whose cytoplasm, but not nuclei, are in the plane of section. Finally, the detection rates of the two tracers are determined and appropriate corrections are applied. The projection from the medial accessory olive to the cerebellar vermis was studied using true blue and diamidino yellow to illustrate the method. Application of the method increased the number of branched neurones detected by 18.5%. Of the total increase, 48.4% was due to the correction for size, 9.2% to the correction for doubly labelled cells with nuclei outside the plane of the section and 42.4% to the correction for detection rates. There was no significant masking of one tracer by another, but true blue enhanced the fluorescence of diamidino yellow.

Amidines↗
PubMed1995

Reduction of transiently expressed acetylcholinesterase activity in developing thalamocortical projections does not affect the mature pattern of basal forebrain projections to visual cortex.

Experiments tested the hypothesis that acetylcholinesterase (AChE) activity, expressed transiently in developing thalamocortical projections, serves to limit the growth of basal forebrain cholinergic projections into thalamocortical recipient zones. Newborn rats were subjected to enucleation, a procedure that eliminates transient AChE activity in developing visual cortex. After 3-8 weeks survival, AChE histochemical techniques revealed no alteration in the pattern of AChE positive basal forebrain axons in visual cortex. These data indicate that transient AChE activity in developing sensory cortex does not limit ingrowth of basal forebrain cholinergic axons.

Acetylcholinesterase↗
PubMed1986

The relationship between descending serotonin projections and ascending projections in the nucleus raphe magnus: a double labeling study.

The nucleus raphe magnus and rostral parts of the nucleus raphe obscurus were found to have extensive efferent projections: a major ascending non-serotonergic (5-HT) projection through the median forebrain bundle, and a descending system consisting of both 5-HT and non-5-HT neurons. Differences in the localizations of their cells of origin suggest that they form two distinct efferent systems from the caudal medullary raphe nuclei.

Animals↗
PubMed1988

The locus of optic nerve head representation in the retinotopic projection over nucleus geniculatus lateralis ventralis and nucleus griseum tectalis in the chick also lacks a retinal projection.

Recently we have demonstrated the presence of a gap in the avian retinotectal projection, that corresponds with the locus of retinotopic representation of the elongated optic nerve head. The present report describes an equivalent gap in the optic neuropiles of the avian ventral geniculate nucleus and griseum tectalis formation, detected after filling optic terminals anterogradely from the contralateral eye with peroxidase. A projection-less strip appears at the expected retinotopic position in both grisea intersecting radially all the strata of the corresponding neuropiles. It is speculated that a common synaptogenetic mechanism must account for these gaps.

Animals↗
PubMed1983

Multi-dimensional treatment planning: II. Beam's eye-view, back projection, and projection through CT sections.

Three features of a fully three-dimensional treatment planning program are presented: (1) The beam's-eye-view provides the user with an accurate reproduction of anatomic features from the viewpoint of a treatment source. The source can be moved to any feasible position relative to the patient, permitting a choice which allows sensitive organs to be excluded from the beam. In this view a field defining aperture can readily be designed. (2) Back-projection of such an aperture shows the parts of the original transverse CT sections, or reconstructed sagittal or coronal sections, which may be covered by the selected beam. (3) Projection through the CT data from any desired origin provides an alignment film simulation which can be used to confirm accuracy of treatment, as well as help establish anatomic relationships relative to the margins of a treatment field.

Computers↗
PubMed1999

Alabama coronary artery bypass grafting Cooperative Project: baseline data. Alabama CABG Cooperative Project Study Group.

BACKGROUND: The Alabama Cooperative CABG Project is a statewide process-oriented analysis of coronary artery bypass grafting (CABG). The purpose of this report is to present the first information generated by this analysis, which will serve as a baseline for subsequent quality improvement projects. METHODS: Medical records of Medicare beneficiaries from Alabama, a comparison state, and a national random sample who had isolated CABG between July 1, 1995, and June 30, 1996, were examined. Fifty-six demographic, procedural, and outcome variables were abstracted. Quality indicators identified by the Alabama Quality Assurance Foundation Study Group included: internal mammary artery use, prescription of aspirin at discharge, duration of postoperative intubation, use of intraaortic balloon pump, readmission to intensive care unit, hospital readmission within 30 days, return to the operating room for bleeding, and in-patient mortality. Benchmark performance rates for quality indicators reflecting care processes were calculated. RESULTS: Alabama, the comparison state, and the national sample consisted of 4,092, 2,290, and 1,119 patients, respectively. The processes of care and outcome, including risk-adjusted mortality, for CABG across the state of Alabama are generally similar to other states and nationwide samples. However, there was considerable variation at the local hospital level in Alabama for each quality indicator. CONCLUSIONS: The data provide a "snapshot" of practice patterns for CABG in Alabama. A specific quality indicator (duration of intubation) was identified as a focus for statewide improvement. Hospital-specific variations in quality indicators suggested opportunities for improvement in other indicators at a number of hospitals.

Aged↗
PubMed1998

Direct projections from the periaqueductal gray to pontine micturition center neurons projecting to the lumbosacral cord segments: an electron microscopic study in the rat.

Direct projections from the periaqueductal gray (PAG) to the pontine micturition center neurons directly projecting to the lumbosacral cord segments were observed electron microscopically in the rat by a double labeling method. Biotinylated dextran amine (BDA) was injected into the PAG and horseradish peroxidase (HRP) was injected into the lumbosacral cord segments. After injection of BDA into the ventrolateral part of the PAG, many BDA-labeled axons were seen light microscopically in Barrington's nucleus; a moderate number of them were found in the pontine tegmental region just ventral to Barrington's nucleus (D-region [Ding, Y-Q., Takada, M., Tokuno, H. and Mizuno, N., J. Comp. Neurol., 357 (1996) 318-330]). On the other hand, after injection of BDA into the dorsolateral part of the PAG, only a few BDA-labeled axons were seen in Barrington's nucleus or the D-region. BDA-labeled axon terminals were electron microscopically confirmed to be in synaptic contact with HRP-labeled dendrites and somata in Barrington's nucleus and the D-region. The results indicate that the ventrolateral part of the PAG is implicated in regulation of the micturition reflex.

Animals↗
PubMed1999

Direct projections from the medial preoptic area to spinally-projecting neurons in Barrington's nucleus: an electron microscope study in the rat.

Direct projections from the medial preoptic area (MPO) to the pontine micturition center neurons directly projecting to the lumbosacral spinal cord were revealed electron microscopically in the rat by a double labeling method. Biotinylated dextran amine (BDA) was injected into the MPO and horseradish peroxidase (HRP) was injected into the lumbosacral cord segments. At light microscopic level, BDA-labeled presumptive axon terminals completely overlapped with HRP-labeled neurons in Barrington's nucleus. Electron microscopic observation showed that some BDA-labeled axon terminals made synaptic contacts with dendrites of HRP-labeled neurons in Barrington's nucleus. The present results indicated that the MPO may be involved in the modulation of the pontine micturition reflex in the rat.

Animals↗
PubMed2000

Beta-endorphin-, adrenocorticotrophic hormone- and neuropeptide y-containing projection fibers from the arcuate hypothalamic nucleus make synaptic contacts on to nucleus preopticus medianus neurons projecting to the paraventricular hypothalamic nucleus in the rat.

The nucleus preopticus medianus is known to be situated in a key site in pathways regulating the paraventricular hypothalamic nucleus. To investigate the innervation pattern to nucleus preopticus medianus neurons by afferent fibers containing beta-endorphin, adrenocorticotrophic hormone and neuropeptide Y, a retrograde tracing method was combined with immunohistochemistry for these peptides in the rat. In the first experiment with injection of a retrograde tracer in the nucleus preopticus medianus, retrogradely labeled neurons were found in many regions throughout the brain. Among these, the arcuate hypothalamic nucleus contained a number of retrogradely labeled neurons showing immunoreactivity to the neuropeptides examined. About 20%, 20% and 40% of retrogradely labeled arcuate hypothalamic nucleus neurons showed beta-endorphin, adrenocorticotrophic hormone and neuropeptide Y immunoreactivity, respectively. About 18% and 57% of retrogradely labeled neurons in the nucleus tractus solitarius and ventrolateral medulla, respectively, were immunoreactive to neuropeptide Y. There were many more neuropeptide Y-immunoreactive projections to the nucleus preopticus medianus from the arcuate hypothalamic nucleus than those from the medulla. None of the retrogradely labeled neurons in the medulla showed immunoreactivity to beta-endorphin or adrenocorticotrophic hormone. In the second experiment with injection of a retrograde tracer in the paraventricular hypothalamic nucleus, electron microscopic observation revealed that retrogradely labeled neurons in the nucleus preopticus medianus were in synaptic contact with beta-endorphin-, adrenocorticotrophic hormone- and neuropeptide Y-immunoreactive axon terminals. The present finding indicates that nucleus preopticus medianus neurons projecting to the paraventricular hypothalamic nucleus are innervated by beta-endorphin-, adrenocorticotrophic hormone- and neuropeptide Y-containing arcuate hypothalamic nucleus neurons in addition to being innervated by neuropeptide Y-containing catecholaminergic medullary neurons which have been reported in our previous study.

Adrenocorticotropic Hormone↗
PubMed1999

Identification of an efferent projection from the paraventricular nucleus of the hypothalamus terminating close to spinally projecting rostral ventrolateral medullary neurons.

The paraventricular nucleus of the hypothalamus is increasingly being viewed as an important site for cardiovascular integration because of its connections to regions in the brain and spinal cord which are known to be important in cardiovascular control. Like the vasomotor neurons of the rostral ventrolateral medulla, descending axons from paraventricular neurons can be identified that form synapses on sympathetic preganglionic neurons in the thoracic spinal cord. The purpose of this study was to determine whether paraventricular axons project to the rostral ventrolateral medulla and whether they are closely apposed to reticulospinal neurons in this region. Descending paraventricular axons were labelled with biotin dextran amine, while rostral ventrolateral medullary neurons were retrogradely labelled from the spinal cord with wheatgerm agglutinin conjugated to horseradish peroxidase. This revealed, within the rostral ventrolateral medulla, paraventricular axon and terminal varicosities closely apposed to and apparently contiguous with retrogradely labelled spinally projecting neurons. Thus our study at the light microscopical level has shown the potential for the paraventricular nucleus to directly influence rostral ventrolateral reticulospinal neurons. We suggest these connections, if confirmed by electron microscopy, could be one means by which activation of paraventricular neurons elicits alterations in blood pressure.

Animals↗
PubMed1999

Excitatory projections from the anterior hypothalamus to periaqueductal gray neurons that project to the medulla: a functional anatomical study.

The present study was designed to investigate the organization of excitatory projections from regions of the anterior hypothalamus that are known to co-ordinate autonomic and sensory functions to medullo-output neurons in the periaqueductal gray. The induction of Fos protein was used to identify neurons in the periaqueductal gray that were activated synaptically by chemical stimulation at sites in the anterior hypothalamus from which either increases or decreases in arterial blood pressure were evoked (pressor sites and depressor sites, respectively). This was combined with retrograde tracing using fluorescent latex microspheres from sites in the medulla. When compared to control animals, neuronal activation at pressor sites in the anterior hypothalamus evoked Fos-like immunoreactivity in significantly more neurons in all but one sub-division of the periaqueductal gray (P at least < 0.05). The majority of Fos-positive neurons following a pressor response were located in the caudal half of the periaqueductal gray where significantly more neurons contained Fos-like immunoreactivity in lateral than in any other sub-division (P < 0.01). In all but two of 14 subdivisions of the periaqueductal gray, the numbers of neurons that expressed Fos-like immunoreactivity following stimulation at depressor sites in the anterior hypothalamus were not significantly different from controls. When neuronal activation at pressor or depressor sites in the anterior hypothalamus was combined with retrograde tracing from the rostral ventrolateral medulla, nucleus raphe magnus and/or nucleus raphe obscurus the majority of double-labelled neurons were located in the caudal half of the periaqueductal gray. Comparisons between the numbers of double-labelled neurons that resulted from different combinations of hypothalamic and medullary injection sites revealed that neuronal activation at pressor sites in the anterior hypothalamus combined with retrograde tracing from the rostral ventrolateral medulla resulted in the greatest numbers of double-labelled neurons. The identification of double-labelled neurons indicates that medullo-output neurons in the periaqueductal gray receive excitatory inputs predominantly from pressor compared to depressor sites in the anterior hypothalamus. These results are discussed in relation to the roles of the different longitudinal columns of the periaqueductal gray, and the organisation of their projections to the medulla, in the co-ordination of autonomic and sensory functions.

Animals↗
PubMed1999

Do superior colliculus projection zones in the inferior pulvinar project to MT in primates?

In order to determine the relationship of superior colliculus inputs to thalamic neurons projecting to the middle temporal visual area (MT), injections of wheat germ agglutinin conjugated with horseradish peroxidase were placed in the superior colliculus of three owl monkeys, with injections of Fast Blue in the MT. The locations of labelled terminals and neurons in the posterior thalamus were related to four architectonically distinct nuclei of the inferior pulvinar (Stepniewska & Kaas, Vis. Neurosci. 14, pp.1043-1060, 1997). Fast Blue injections in the MT labelled neurons largely in the medial nucleus of the inferior pulvinar. A few labelled neurons were found in the adjoining central medial nucleus of the inferior pulvinar, as well as in the lateral pulvinar and the dorsal lateral geniculate nucleus. Superior colliculus inputs were most dense in the posterior and medial nuclei of the inferior pulvinar. There were sparser inputs to the central lateral nucleus of the inferior pulvinar, locations in the lateral and medial pulvinar, and the dorsal lateral geniculate nucleus. The results indicate that the medial nucleus of the inferior pulvinar, the major projection zone to the MT, does not receive a significant input from the superior colliculus.

Animals↗
PubMed1999

The Berkeley Drosophila Genome Project gene disruption project: Single P-element insertions mutating 25% of vital Drosophila genes.

A fundamental goal of genetics and functional genomics is to identify and mutate every gene in model organisms such as Drosophila melanogaster. The Berkeley Drosophila Genome Project (BDGP) gene disruption project generates single P-element insertion strains that each mutate unique genomic open reading frames. Such strains strongly facilitate further genetic and molecular studies of the disrupted loci, but it has remained unclear if P elements can be used to mutate all Drosophila genes. We now report that the primary collection has grown to contain 1045 strains that disrupt more than 25% of the estimated 3600 Drosophila genes that are essential for adult viability. Of these P insertions, 67% have been verified by genetic tests to cause the associated recessive mutant phenotypes, and the validity of most of the remaining lines is predicted on statistical grounds. Sequences flanking >920 insertions have been determined to exactly position them in the genome and to identify 376 potentially affected transcripts from collections of EST sequences. Strains in the BDGP collection are available from the Bloomington Stock Center and have already assisted the research community in characterizing >250 Drosophila genes. The likely identity of 131 additional genes in the collection is reported here. Our results show that Drosophila genes have a wide range of sensitivity to inactivation by P elements, and provide a rationale for greatly expanding the BDGP primary collection based entirely on insertion site sequencing. We predict that this approach can bring >85% of all Drosophila open reading frames under experimental control.

Alleles↗