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PubMed1996

Trigeminocerebellar projection to the paramedian lobule with emphasis on the climbing fibre zones: a retrograde tracing study in the rabbit.

Projections of the trigeminal sensory nuclear complex (TSNC) onto the cerebellar paramedian lobule (PML) were investigated by the retrograde horseradish peroxidase (HRP) and fluorescent tracers (FB, DY) technique in the rabbit. Following injections of the tracers into the various regions of different sublobules of PML, the retrograde labelling pattern in TSNC was analyzed, especially in relation to the climbing fibre zones identified by retrograde labelling in the inferior olive (Zimny et al., 1989). The present results indicate that projections are bilateral with a clear ipsilateral preponderance. The major projections originate mainly from the dorsolateral and ventromedial regions of the principal trigeminal nucleus (Vp) except its caudal pole. Prominent input is also derived from the rostral (Vir) and caudal (Vic) pars interpolaris of the spinal trigeminal nucleus (Vsp). The cells of origin of the projections are present throughout the entire length of Vir with preference to dorsolateral and dorsal location. In Vic they tend to be distributed in the medial regions of its rostral half. Afferents form the pars oralis (Vo) of Vsp are moderate and arise mainly from the dorsomedial and dorsal regions in its caudal one-third. Projections from the pars caudalis (Vc) of Vsp and the mesencephalic trigeminal nucleus (Vmes) are absent. A topography exists in the trigeminocerebellar projections, however, no clear-cut evidence was obtained for a topical relationship between distribution of neurones in TSNC and projections sites in PML. On the other hand, certain correspondence could be found between subdivisions of TSNC and climbing fibre zones in PML. While zones C3 and C2-lateral appear to receive no trigeminal afferents, zone C1 is supplied by fibres from Vir and Vic. All subdivisions of TSNC project zones C2, D1 and D2. In sublobule f, medial (Dm) and lateral (Dl) composite zone D1 + D2 receive projections from Vic, or Vp and Vir, respectively. The present report provides new detailed data on the trigeminocerebellar system in the rabbit.

Animals↗
PubMed1997

Cortical, thalamic, and amygdaloid projections of rat temporal cortex.

The cortical, thalamic, and amygdaloid connections of the rodent temporal cortices were investigated by using the anterograde transport of iontophoretically injected biocytin. Injections into area Te1 labeled axons and terminals in the ventral regions of the dorsal and ventral subnuclei of the medial geniculate complex, area Te3, the rostrodorsal part of area Te2, and the ventrocaudal caudate putamen. No amygdaloid labeling was observed. Thalamic projections from Te2 targeted the lateral posterior nucleus, the dorsal part of the dorsal subnucleus of the medial geniculate complex, and the peripeduncular nucleus. Corticocortical projections mainly terminated in the dorsal perirhinal cortex, but moderately dense projections were observed in medial and lateral peristriate cortex, and only light projections were observed to Te1 and Te3. Projections to these isocortical regions terminated in layers I and VI. Amygdaloid projections targeted the ventromedial subdivision of the lateral nucleus and the adjacent part of the anterior basolateral nucleus. Area Te3 was observed to project to the ventrolateral parts of the dorsal and ventral subnuclei of the medial geniculate complex, the dorsal perirhinal cortex, rostral Te2, and Te1. In the amygdala, labeled fibers and terminals were concentrated in the dorsolateral subdivision of the lateral nucleus. These data confirm that areas Te1 and Te3 are hierarchically organized cortical areas connected with auditory relay nuclei in the thalamus. Area Te2, in contrast, appears to be weakly connected with Te1 and Te3 but is heavily connected with the peristriate cortex and tectorecipient thalamic nuclei. Te2 appears to be a visually related cortical area. The data also indicate that projections from Te2 and Te3 target different subregions of the lateral nucleus and that Te2, but not Te3, projects to the basolateral nucleus.

Amygdala↗
PubMed1997

Projections from the subdivisions of the fastigial nucleus to the vestibular complex and the prepositus hypoglossal nucleus in the albino rat: an anterograde tracing study using biocytin.

Differential projections from the subdivisions of the fastigial nucleus to the vestibular complex and the prepositus hypoglossal nucleus were investigated by an anterograde tracing method using biocytin in the albino rat. The caudomedial subdivision of the nucleus projected ipsilaterally to the dorsal and medial parts of the superior vestibular nucleus (Su Ve), the dorsomedial part of the lateral vestibular nucleus (LVe), and the dorsal parts of the medial (MVe) and spinal (Sp Ve) vestibular nuclei, and projected contralaterally to the ventrolateral corners of the Su Ve and LVe, the ventral part of the MVe, and the lateral part of the Sp Ve. The bilateral prepositus hypoglossal nuclei received sparse projections from the caudomedial subdivision. The middle subdivision of the fastigial nucleus projected ipsilaterally to the dorsal and/or ventral parts of the Su Ve, the dorsomedial pats of the LVe and Sp Ve, and the dorsolateral part of the MVe, and projected contralaterally to the dorsal margin of the Su Ve, the ventrolateral part of the LVe, and the lateral part of the Sp Ve. The dorsolateral protuberance of the fastigial nucleus projected ipsilaterally to the dorsal margin of the Su Ve, the dorsomedial part of the LVe, the dorsal or lateral parts of the Sp Ve, and the lateral part of the MVe, and projected contralaterally to the ventrolateral part of the LVe and the lateral part of the Sp Ve. The subnuclei x, y, and f, interstitial nucleus of the vestibular nerve, and the infracerebellar nucleus received bilateral or ipsilateral fastigiovestibular projections.

Animals↗
PubMed1981

Incomplete projection, a new defense mechanism--an experience in Japan.

Through my clinical experiences, the symptom which is explained as a defense mechanism, projection, seems to be divided into complete (Freud) and incomplete one. One is the patient who accepts the symptom which is quite unfamiliar (Projection) and the other, as I tried to explain in this paper, accepts the symptom as rather familiar. The patient who shows the incomplete projection could not project his own inner anxiety completely into the outside world, which results as a guilty feeling even having projective symptoms. The idea of incomplete projection is a useful way to understand clinically the patient and also I found that the patient who shows the symptom of projection sometimes has the incomplete type of projection through the course of psychotherapy.

Adult↗
PubMed1994

Achieving sustained quantifiable results in an interdepartmental quality improvement project.

BACKGROUND: In the mid-1980s Beth Israel Hospital Boston began a participatory management approach that encourages all members of the organization to improve productivity, efficiency, and quality through interdepartmental and intradepartmental project teams. The CT [computerized tomography]-Nursing-Transport Team, the hospital's first quality improvement project Team, grew out of an organizational challenge to solve an interdepartmental problem. The goal of the project was to have inpatients arrive on time for their scheduled CT-Scan appointment. Prior to the project's inception, over 50% of all inpatients scheduled for CT-Scans arrived more than 20 minutes late. METHODS: The team learned the Juran quality improvement methodology, using just-in-time training. The methodology consists of four major steps: problem definition and organization, the diagnostic journey, the remedial journey, and holding the gains. The team used many quality improvement tools including flow-charting, checksheets, histograms, Pareto charts, run charts, and brainstorming to find the root causes of the problem and achieve results. RESULTS: The team members collected data and flowcharted the complexity of the CT appointment and patient pick-up process to pinpoint the root causes of delays. They found that three floors accounted for a majority of the delays and that four reasons for delays explained two-thirds of the problem. Additionally, as nurses and CT technologists flowcharted the process, they found that they used a different definition of "on-call" and that misconceptions existed about the scan and the preparation for it. When transporters were included on the team, the team discovered that delays occurred in a pattern and that communication with central transport was poor and inconsistent. After the team made changes in break times, equipment, communication, planning, and timing, the late patient arrivals dropped dramatically--more than 80% of patients arrived within five minutes of a scheduled appointment. One year after the project team stopped meeting, close to 70% of patients continue to arrive within five minutes of their scheduled appointment time, despite increased volume and no additional scanners. CONCLUSION: The success of the project reinforced many well-known quality improvement conditions for success. These include (1) choosing a project that is "high pain, high drain," (2) having a committed project leader who can keep the team effort going, (3) using data to lead the team to the root cause of a problem by pointing out where, when, and why the problems occur, (4) utilizing flow-charting and shadowing to understand the process from a fresh perspective, and (5) holding well-facilitated meetings with a defined purpose, ground rules, and meaningful agenda.

Boston↗
PubMed2001

Perceived value and outcomes of residency projects.

Residency program directors' attitudes toward residency projects were studied. A questionnaire about the residency project experience was mailed in January 2000 to 446 pharmacy practice residency program and specialty residency program directors in the program database of the American Society of Health-System Pharmacists. Recipients responded to opinion statements on a 5-point scale. Responses to the opinion statements were separated into seven categories for analysis. A total of 278 usable questionnaires were returned, for a raw response rate of 63.6%. During the preceding three years, residency directors had served as primary advisors on 917 projects; 171 had served as advisor on at least one of every type of project allowed in the accreditation standards. Of the 917 projects, 364 were presented at national professional meetings, 124 were published, and 484 were believed to have resulted in a positive change in pharmacy services. There were no significant differences in total response scores among any of the subgroups analyzed. There was strong agreement that residency projects were valuable and should continue to be part of the residency program experience. The directors' views of the importance of original research as a project option were more neutral. Overall residency program directors had positive perceptions of the value of residency projects to both residents and institutions and believed that they should continue to be a requirement of residency programs.

Administrative Personnel↗
PubMed1991

Origins of the Human Genome Project.

The Human Genome Project has become a reality. Building on a debate that dates back to 1985, several genome projects are now in full stride around the world, and more are likely to form in the next several years. Italy began its genome program in 1987, and the United Kingdom and U.S.S.R. in 1988. The European communities mounted several genome projects on yeast, bacteria, Drosophila, and Arabidospis thaliana (a rapidly growing plant with a small genome) in 1988, and in 1990 commenced a new 2-year program on the human genome. In the United States, we have completed the first year of operation of the National Center for Human Genome Research at the National Institutes of Health (NIH), now the largest single funding source for genome research in the world. There have been dedicated budgets focused on genome-scale research at NIH, the U.S. Department of Energy, and the Howard Hughes Medical Institute for several years, and results are beginning to accumulate. There were three annual meetings on genome mapping and sequencing at Cold Spring Harbor, New York, in the spring of 1988, 1989, and 1990; the talks have shifted from a discussion about how to approach problems to presenting results from experiments already performed. We have finally begun to work rather than merely talk. The purpose of genome projects is to assemble data on the structure of DNA in human chromosomes and those of other organisms. A second goal is to develop new technologies to perform mapping and sequencing. There have been impressive technical advances in the past 5 years since the debate about the human genome project began. We are on the verge of beginning pilot projects to test several approaches to sequencing long stretches of DNA, using both automation and manual methods. Ordered sets of yeast artificial chromosome and cosmid clones have been assembled to span more than 2 million base pairs of several human chromosomes, and a region of 10 million base pairs has been assembled for Caenorhabditis elegans by a collaboration between Washington University and the Medical Research Council laboratory in Cambridge, U.K. This project is now turning to sequencing C. elegans DNA as a logical extension of this work. These are but the first fruits of the genome project. There is much more to come.

Europe↗
PubMed2006

Increasing aging and advocacy competency: the intergenerational advocacy pilot project.

The Council on Social Work Education's (CSWE) Strengthening Aging and Gerontology Education for Social Work (SAGE-SW) project, funded by the John A. Hartford Foundation partnered with the National Committee to Preserve Social Security and Medicare (NCPSSM) to develop an Intergenerational Policy and Advocacy Project (IAP). This curriculum pilot project, based on a community organization model, was conducted with 13 baccalaureate social work (BSW) and master's social work (MSW) programs across the country and 122 students. The project was one method to pursue CSWE SAGE-SW's efforts to infuse aging content into social work foundation curricula, to support intergenerational teaching, to strengthen social work advocacy skills, and to provide social work students with positive experiences working with older adults. Pilot sites were asked to carry out the project as part of an existing course foundation or field practicum course. Project activities included collaboration with a variety of community agencies, holding issues or "town hall" forums in order to educate community members about critical policy issues affecting older adults; making contacts and establishing relationships with local, state and/or federal legislators; and conducting assessments of the service needs of older adults in the students' communities. Questionnaires, feedback, pre-post evaluations as well as brief accounts of each project are presented. Participants considered the IAP to be a successful project in terms of the objectives of increasing awareness and competency among social work students of aging issues and of promoting intergenerational linkages between older people and social work students.

Aged↗
PubMed1978

Effects of type of target, cognitive ability, and age on projection.

It was hypothesized that older and more cognitively developed children would be less likely to use both attributive and contrast projection. Real and ambiguous target figures were used to assess the effect of the type of target on projection. 30 boys and 31 girls between the ages of 7 yr., 10 mo. and 14 yr., 10 mo. predicted a favored classmate's preferences in each of several categories. They also predicted the preferences of an unfavored classmate and of favored and unfavored ambiguous targets. These predictions were compared with the subjects' own preferences to measure attributive and contrast projection. Type of target affected the amount of projection. There was significantly more contrast projection onto ambiguous targets (dolls) than onto real targets (classmates). There was significantly more attributive than contrast projection for the real targets only. A significant negative correlation of -.26 (df = 59) was obtained between age and contrast projection onto the real targets. There were no significant correlations between the other measures of projection and the indices of cognitive ability, including age.

Achievement↗
PubMed2000

Selecting clinical quality improvement projects: getting a bigger return for your investment.

An urban medical center developed and implemented a process for selecting clinical quality-improvement projects. The process was designed to select projects that would deliver greater returns than had previous projects. The four-step process involved: (1) establishing project selection criteria, (2) identifying potential projects, (3) assigning points and ranking projects, and (4) selecting projects based on rank and available resources. This process won physician commitment and secured administrative support. It identified projects that had unprecedented success in improving clinical outcomes, increasing patient satisfaction, and reducing cost.

Critical Pathways↗
PubMed1991

The effects of lower lateral cartilage excision on nasal tip projection.

Nasal tip projection is an important defining feature of the nasal profile. Loss of projection is often the bane of the rhinoplastic surgeon. While augmentation techniques for maintaining or increasing tip projection are useful in selected patients, the majority of rhinoplasties rely on excision of cartilage, particularly cartilage of the cephalic border of the lower lateral crura, to produce the desired cosmetic result. The purpose of this study was to measure the effects of lower lateral cartilage excision on nasal tip projection resulting from three common forms of nasal tip surgery. These techniques included cephalic border resection without vertical dome division, cephalic border resection with vertical dome division, and cephalic border resection with dome division and suture reapproximation of the mesial crura, the so-called "Goldman tip." Despite the fact that overall excellent results were obtained and loss of projection was rarely a noticeable feature, a measurable loss of projection can be seen in all but one case in this series. Although loss of tip projection is usually acceptable due to the masking effect, the concurrent reduction in dorsal nasal height, loss of projection must be anticipated in excisional techniques of the lower lateral cartilage.

Cartilage↗
PubMed1996

Organization of hindlimb nerve projections to the rat spinal cord: a choleragenoid horseradish peroxidase study.

The aim of the present study has been to investigate the projections of hindlimb muscle afferent fibers to the spinal cord with particular emphasis on the ventral horn and the column of Clarke. Following transections of the appropriate ventral roots, injections of the B-subunit of cholera toxin conjugated to horseradish peroxidase were made into the tibial, peroneal, hamstring, superior gluteal, femoral, and obturator nerves in one group of adult rats. In another group of rats, similar experiments were done with intact ventral roots in order to map the location in the ventral horn of the motoneuron cell columns supplying each investigated nerve. An extensive overlap was found for the different nerve projections to Rexed's laminae V-VII. A somatotopic organization of the nerve projections was seen in the lamina IX cell groups of the ventral horn as well as in the column of Clarke, even though an overlap existed. The densest primary afferent projection from each injected nerve was to its homonymous motoneurons. Only a small to moderate overlap between the projections of the tributary branches of the sciatic nerve was found in the ventral horn, whereas the obturator and femoral nerve projections showed more profound overlap. In the column of Clarke, hindlimb nerves innervating distal muscles projected medially, and nerves innervating proximal muscles projected laterally.

Animals↗
PubMed1996

Comparative morphology of three types of projection-identified pyramidal neurons in the superficial layers of cat visual cortex.

The morphology and dendritic organization of corticocortical neurons in the superficial layers of area 18 that project to area 17 were studied by intracellular injection of lucifer yellow in the fixed-slice preparation. This corticocortical population contains primarily standard pyramidal cells, but occasional nonpyramidal, modified, fusiform, star, and inverted pyramidal cells were also seen. All cell types were present throughout layer 2 and in the upper and middle parts of layer 3. Standard pyramidal cells were found exclusively in lower layer 3. The mean somatic area of the area 17 projecting neurons was 251 microns 2. The width of basal dendritic fields was correlated to cell size for standard pyramidal cells but not for the other cell types. Next, the morphology and dendritic organization of the area 17 projecting neurons were compared to the pyramidal cells of the local horizontal patch networks and of the callosal system. The depth profile of the area 17 projecting and callosal pyramidal groups was virtually identical, peaking at 400 microns from the pial surface, whereas the local patch pyramidal group peaked at 281 microns. The local patch, area 17 projecting, and callosal pyramidal cells displayed increasingly larger mean somatic areas and basilar dendritic field width measurements. The number of basal dendritic branch points was greatest for callosal cells, and it was indistinguishable between local patch and area 17 projecting neurons. In the tangential plane, circular dendritic fields were observed on all callosal cells, but they were found on only approximately half of the local patch and area 17 projecting neurons. The remaining local patch and area 17 projecting neurons displayed mediolaterally and anteroposteriorly elongated basal dendritic fields, respectively.

Animals↗
PubMed1996

Differential central projections of vestibular afferents in pigeons.

The question of whether a differential distribution of vestibular afferent information to central nuclear neurons is present in pigeons was studied using neural tracer compounds. Discrete tracing of afferent fibers innervating the individual semicircular canal and otolith organs was produced by sectioning individual branches of the vestibular nerve that innervate the different receptor organs and applying crystals of horseradish peroxidase, or a horseradish peroxidase/cholera toxin mixture, or a biocytin compound for neuronal uptake and transport. Afferent fibers and their terminal distributions within the brainstem and cerebellum were visualized subsequently. Discrete areas in the pigeon central nervous system that receive primary vestibular input include the superior, dorsal lateral, ventral lateral, medial, descending, and tangential vestibular nuclei; the A and B groups; the intermediate, medial, and lateral cerebellar nuclei; and the nodulus, the uvula, and the paraflocculus. Generally, the vertical canal afferents projected heavily to medial regions in the superior and descending vestibular nuclei as well as the A group. Vertical canal projections to the medial and lateral vestibular nuclei were observed but were less prominent. Horizontal canal projections to the superior and descending vestibular nuclei were much more centrally located than those of the vertical canals. A more substantial projection to the medial and lateral vestibular nuclei was seen with horizontal canal afferents compared to vertical canal fibers. Afferents innervating the utricle and saccule terminated generally in the lateral regions of all vestibular nuclei in areas that were separate from the projections of the semicircular canals. In addition, utricular fibers projected to regions in the vestibular nuclei that overlapped with the horizontal semicircular canal terminal fields, whereas saccular afferents projected to regions that received vertical canal fiber terminations. Lagenar afferents projected throughout the cochlear nuclei, to the dorsolateral regions of the cerebellar nuclei, and to lateral regions of the superior, lateral, medial, and descending vestibular nuclei.

Animals↗
PubMed1997

Organisation of the reticular thalamic projection to the intralaminar and midline nuclei in rats.

This study examines the projection of the reticular thalamic nucleus to the classic "nonspecific" dorsal thalamic nuclei of rats. Individual nuclei of the intralaminar (central-lateral, paracentral, central-medial, parafascicular) and the midline (reuniens/rhomboid, parataenial) nuclear groups, together with the reticular nucleus itself, were injected with the neuronal tracers biotinylated dextran or fluorescent latex microspheres (red or green). Reticular cells projecting to the intralaminar and midline nuclei are limited largely to the rostral pole of the nucleus. Within the rostral pole, most reticular cells projecting to the intralaminar and midline nuclear groups are found in largely distinct sectors; cells that project to the intralaminar nuclei tend to lie more laterally, whereas those projecting to the midline nuclei lie more medially within the pole. Among the individual nuclei of both the intralaminar and midline nuclear groups, however, the segregation is far less distinct. For instance, the reticular cells that project to the intralaminar central-lateral, central-medial, paracentral, and parafascicular nuclei are intermixed completely on the lateral edge of the rostral pole. After separate injections of different colored latex microspheres into individual intralaminar nuclei, the incidence of double-labelled reticular cells is about 37%, a percentage much higher than among the "specific" dorsal thalamic nuclei (< 1%). All the above-mentioned results refer to the reticular labelling seen on the side ipsilateral to the injection. After separate injections into the intralaminar central-medial nucleus, the midline nuclei, and the reticular nucleus itself, we also see a very small group of reticular cells labelled on the contralateral side. In general, our results indicate that the reticular projection to the intralaminar and midline nuclei is far more diffuse than the reticular projection to the specific dorsal thalamic nuclei.

Afferent Pathways↗
PubMed1997

GABA- and glycine-immunoreactive projections from the superior olivary complex to the cochlear nucleus in guinea pig.

Retrograde transport of horseradish peroxidase was combined with immunocytochemistry to identify the origins of potential gamma-aminobutyric acid (GABA) -ergic and glycinergic inputs to different subdivisions of the cochlear nucleus. Projection neurons in the inferior colliculus, superior olivary complex, and contralateral cochlear nucleus were examined, but only those from the superior olivary complex contained significant numbers of GABA- or glycine-immunoreactive neurons. The majority of these were in periolivary nuclei ipsilaterally, with a sizeable contribution from the contralateral ventral nucleus of the trapezoid body. Overall, 80% of olivary neurons projecting to the cochlear nucleus were immunoreactive for GABA, glycine, or both. Most glycine-immunoreactive projection neurons were located ipsilaterally, in the lateral and ventral nuclei of the trapezoid body and the dorsal periolivary nucleus. This suggests that glycine is the predominant neurotransmitter used by ipsilateral olivary projections. Most GABA-immunoreactive cells were located bilaterally in the ventral nuclei of the trapezoid body. The contralateral olivary projection was primarily GABA-immunoreactive and provided almost half the GABA-immunoreactive projections to the cochlear nucleus. This suggests that GABA is the predominant neurotransmitter used by contralateral olivary projections. The present results suggest that the superior olivary complex is the most important extrinsic source of inhibitory inputs to the cochlear nucleus. Individual periolivary nuclei differ in the strength and the transmitter content of their projections to the cochlear nucleus and may perform different roles in acoustic processing in the cochlear nucleus.

Animals↗
PubMed1997

Amygdalo-hypothalamic projections in the lizard Podarcis hispanica: a combined anterograde and retrograde tracing study.

The cells of origin and terminal fields of the amygdalo-hypothalamic projections in the lizard Podarcis hispanica were determined by using the anterograde and retrograde transport of the tracers, biotinylated dextran amine and horseradish peroxidase. The resulting labeling indicated that there was a small projection to the preoptic hypothalamus, that arose from the vomeronasal amygdaloid nuclei (nucleus sphericus and nucleus of the accessory olfactory tract), and an important projection to the rest of the hypothalamus, that was formed by three components: medial, lateral, and ventral. The medial projection originated mainly in the dorsal amygdaloid division (posterior dorsal ventricular ridge and lateral amygdala) and also in the centromedial amygdaloid division (medial amygdala and bed nucleus of the stria terminalis). It coursed through the stria terminalis and reached mainly the retrochiasmatic area and the ventromedial hypothalamic nucleus. The lateral projection originated in the cortical amygdaloid division (ventral anterior and ventral posterior amygdala). It coursed via the lateral amygdalofugal tract and terminated in the lateral hypothalamic area and the lateral tuberomammillary area. The ventral projection originated in the centromedial amygdaloid division (in the striato-amygdaloid transition area), coursed through the ventral peduncle of the lateral forebrain bundle, and reached the lateral posterior hypothalamic nucleus, continuing caudally to the hindbrain. Such a pattern of the amygdalo-hypothalamic projections has not been described before, and its functional implications in the transfer of multisensory information to the hypothalamus are discussed. The possible homologies with the amygdalo-hypothalamic projections in mammals and other vertebrates are also considered.

Amygdala↗
PubMed1997

Quantitative and neurogenic analysis of the total population and subpopulations of neurons defined by axon projection in the superficial dorsal horn of the rat lumbar spinal cord.

The total neuron population of the superficial dorsal horn (SDH), i.e., laminae I and II, was quantitated in Nissl preparations of spinal segment L1 in the rat. Subpopulations of the SDH, defined by axon projection, were quantitated following strategic intraspinal injections of dual retrograde tracers (Fluoro-Gold and true blue). These methods were used in conjunction with [3H]thymidine (delivered in utero) autoradiography for neurogenic pattern analysis. Following stereological correction, each dorsal horn in spinal segment L1 contained 11 neurons in lamina I and 42.6 neurons in lamina II per 10-microm transverse section. Neurons with long projections, i.e., neurons with projections rostral to spinal segment T5, were only slightly more numerous in lamina I than in lamina II. These neurons made up 34% of the total neuron population in lamina I and 7.0% in lamina II. Most of these neurons did not demonstrate descending connections, and many (presumed supraspinal projection neurons) did not demonstrate short, ascending, intersegmental connections. Neurons with short propriospinal projections, i.e., neurons with connections caudal to spinal segment T5, made up approximately half of the total neuron population in both lamina I and lamina II: 55% and 52%, respectively. Of these, 79% had both short ascending and descending projections; the remaining 21% had only descending projections. Neurons that were not labeled with retrograde tracers (presumed local circuit cells) represented 11% of the neurons in lamina I and 41% in lamina II. Neurogenesis in the SDH proceeded along an axon-length gradient, whereby neurons with the longest axons completed neurogenesis first, and those with the shortest completed neurogenesis last. The generation of both propriospinal and supraspinal projection neurons began on embryonic day 13 (E13). Nearly equal numbers of neurons in this group were generated in laminae I and II through E14. On E15, neuron production slowed in lamina I and accelerated in lamina II as local circuit neurons and the remaining propriospinal neurons were generated. Neuron production ceased simultaneously in both lamina I and lamina II on E16.

Animals↗