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PubMed2006

Ten-year experience with an emergency medicine resident research project requirement.

BACKGROUND: Controversy exists regarding the value and quality of required emergency medicine (EM) resident scholarly projects. OBJECTIVES: To describe the research designs and presentation rate at national scientific meetings and the publication rate of EM resident scholarly projects at a university-based residency program. METHODS: The authors reviewed the initial ten years (1993-2002) of resident scholarly projects from an EM residency program. Since the inception of the program, a formal research study has been required of all residents for residency graduation. Scholarly projects were reviewed and categorized by study design. Abstracts from the American Academy of Emergency Medicine (AAEM), American College of Emergency Physicians (ACEP), and Society for Academic Emergency Medicine (SAEM) annual meetings were searched to identify projects presented at any of these national meetings. A PubMed search for resident and faculty investigators was performed, and faculty and graduated residents were queried to identify all resident scholarly projects published in peer-reviewed journals. RESULTS: Eighty-seven residents produced 90 scholarly projects. Study designs were prospective data collection, 42 (47%); retrospective chart review, 38 (42%); survey, 5 (6%); animal, 4 (4%); and computer program development, 1 (1%). Of the 80 projects collecting patient data, 72 were conducted at a single center; 6, at two centers; and 2, at five centers each. Of the 42 prospective clinical studies, 27 (64%) were observational and 15 (36%) were interventional. Forty-six (51%) abstracts were presented at national meetings (SAEM, 20; ACEP, 19; AAEM, 3; and other, 4). Thirty-six (40%) of the projects have been published in peer-reviewed journals. Abstract presentation at national meetings (range, 13%-64% of projects per yr) and manuscript publication rates (range, 0-67% of projects per yr) were variable from year to year. CONCLUSIONS: Resident scholarly projects at one institution were equally likely to use a prospective or retrospective design, and most were conducted at a single center. More than half of the projects were presented at national research meetings, and more than a third were subsequently developed into manuscripts and published in peer-reviewed journals. When an original research study is required for satisfying the scholarly requirement for EM residency graduation, resident projects can contribute to the EM literature.

Abstracting and Indexing↗
PubMed1990

Projection subtypes of rat neostriatal matrix cells revealed by intracellular injection of biocytin.

Individual neostriatal-matrix spiny neurons were stained intracellularly with biocytin after intracellular recording in vivo, and their axons were traced into the globus pallidus (GP), entopeduncular nucleus (EP), and/or substantia nigra (SN). The locations of the neurons within the matrix compartment of the neostriatum (NS) were established by immunocytochemical counterstaining of sections containing the cell bodies using antibodies for calbindin-D28K. This allowed nearly complete visualization of the axonal projections of single NS neurons. On the basis of their intrastriatal axonal arborizations, matrix spiny neurons could be divided into 2 types. One type, which was the more common, had local axonal arborizations restricted to the region of the dendritic field, often with axon collaterals arborizing within the dendritic field of the cells of origin. A second, less common, cell type in the matrix had local axon collaterals distributed widely in the NS. Among matrix neurons with restricted local collateral fields, 3 subtypes could be distinguished on the basis of their efferent axonal projections. Type I cells projected only to the GP. Type IIa cells projected to the GP, EP, and SN pars reticulata. Type IIb cells projected to the GP and SN but not to the EP. The shapes and densities of the GP arborizations varied in the 3 cell types, with the cells projecting only to the GP (type I) projecting more heavily and filling a larger volume there than type II cells. The dendrites and intrastriatal axon collaterals of 3 subtypes were similar in morphology. The class of matrix spiny neurons with intrastriatal axon collaterals distributed widely in the NS were observed to project to the GP. Projections beyond the GP were not identified for this cell type, but could not be ruled out. Somatodendritic morphologies of neurons did not differ according to the projection site. These results demonstrate that NS matrix spiny cells are more heterogeneous in their efferent projection patterns than previously suspected on the basis of retrograde axonal tracing and immunocytochemical studies. As predicted by those previous studies, there is a class of matrix neurons that projects only to the GP. Presumably, these cells contain enkephalin. Cells projecting to the SN and EP, and so presumably containing substance P, give off a small projection to the GP, as well, and differ in their collateralization patterns within the 3 major target nuclei.

Animals↗
PubMed1995

General practitioner trainees' experience of undertaking audit projects: preliminary report from the west of Scotland region.

BACKGROUND: Departments of general practice increasingly provide formal teaching in audit. However, little is known about audit projects carried out by trainees in general practice. AIM: A study was undertaken to ascertain general practitioner trainees' experience of undertaking an audit project in the trainee year, with reference to their understanding of audit theory, perceived usefulness of the project in enhancing clinical knowledge, time taken to do the audit and practice team involvement in the project. METHOD: All 104 trainees in the west of Scotland region completing their trainee year on 31 July 1993 were sent a postal questionnaire that month. The replies to the questionnaire were analysed and compared with the audit project that each trainee had submitted in June 1993 as part of a pilot project for summative assessment. RESULTS: Responses were received from 103 trainees (99%). Seventy trainees (68%) felt strongly that their audit project was relevant to patient care but only 31 (30%) felt strongly that the project was a useful way of enhancing clinical knowledge of the disease process. Data collection was the most time consuming aspect of the audit project, 23% of trainees reporting taking a day or more to complete this stage. Trainees who chose their own audit project were more likely to complete two sets of data collection than those who had not chosen their own project. Seventy nine trainees (77%) indicated that trainers had been involved in their project and 51 trainees indicated that one of the other practice partners had been involved in their project. CONCLUSION: Performing an audit as a trainee is feasible in the time limit of the one year in general practice. The educational benefit appears to be limited to the knowledge of audit process, rather than to clinical knowledge. Audit projects of relevant size and complexity, involving appropriate members of the practice team, are to be encouraged, as is the development of an instrument for assessing trainee audit.

Education, Medical, Continuing↗
PubMed1999

Perirhinal cortex projections to the amygdaloid complex and hippocampal formation in the rat.

The differential efferent projections of the perirhinal cortex were traced by using anterograde and retrograde tracing techniques. The dorsal bank cortex (area 36) projected lightly to the lateral entorhinal cortex and more strongly to the lateral, posterolateral cortical, and posterior basomedial amygdaloid nuclei and amygdalostriatal transition zone. The ventral bank (dorsolateral entorhinal cortex) projected to the lateral entorhinal cortex, dorsal subiculum, and subfield CA1 and mainly targeted the basolateral amygdaloid nucleus. Corticocortical projections from the dorsal and ventral banks targeted different cortical areas. The fundus of the rhinal sulcus (area 35) projected to both lateral and medial entorhinal cortices, ventral subiculum, lateral and basolateral nuclei, and amygdalostriatal transition zone. Corticocortical projections targeted areas projected to by both dorsal and ventral banks and also by second somatosensory area, first temporal cortical area, and striate cortex. Neurons projecting to the lateral nucleus were distributed in all layers of the dorsal bank, wheras those projecting to CA1 and subiculum were found in superfical layers (mostly layer III) of the ventral bank. Projections to the basolateral nucleus arose from superfical layers (mostly layer II) of the fundus and deep layers of the ventral bank. Furthermore, projections to the amygdala mostly arose from rostral levels, whereas hippocampal projections primarily originated caudally. The rat perirhinal cortex is heterogeneous in its efferent connectivity, and distinct projections arise from the dorsal and ventral banks and fundus of the rhinal sulcus. The widespread cortical connectivity of the fundus suggests that only this part of the perirhinal cortex is similar to area 35 of the primate brain.

Amygdala↗
PubMed2002

Morphology and projection pattern of medial and dorsal pallial neurons in the frog Discoglossus pictus and the salamander Plethodon jordani.

In the frog Discoglossus pictus and the salamander Plethodon jordani, the morphology and axonal projection pattern of neurons in the medial and dorsal pallium were determined by intracellular biocytin labeling. A total of 77 pallial neurons were labeled in the frog and 58 pallial neurons in the salamander. Within the medial pallium (MP) of the frog, four types of neurons were identified on the basis of differences in their axonal projection pattern. Type I neurons have bilateral projections into telencephalic and diencephalic areas; type II neurons have bilateral projections to telencephalic areas and ipsilaterally descending projections to diencephalic regions; type III neurons have only intratelencephalic connections, and a single type IV neuron has ipsilaterally descending projections. The somata of the four types occupy four nonoverlapping zones. Neurons of the dorsal pallium (DP) project exclusively to the ipsilateral MP and to the dorsal edge of the lateral pallium. In the ventral MP of the salamander, neurons have mostly intratelencephalic projections. Neurons in the dorsal MP project bilaterally to diencephalic and telencephalic regions. Neurons in the medial DP project ipsilaterally to the MP, lateral septum, nucleus accumbens, medial amygdala, and the internal granule layer of the olfactory bulb. In five cases, fibers were found in the commissura hippocampi, but in only two cases could these fibers be followed toward the contralateral MP and septum. Neurons in the lateral DP had no contralateral projections; they projected to the ipsilateral MP and in eight cases to the ipsilateral septum as well. Based on similarities of cytoarchitecture and projection pattern in neurons of the MP and DP, it is proposed that both frogs and salamanders have an MP subdivided into a ventral and dorsal portion, and a DP subdivided into a medial and a lateral portion.

Animals↗
PubMed1977

Projections from the amygdaloid complex to the cerebral cortex and thalamus in the rat and cat.

Projections are described from the basolateral, lateral and anterior cortical nuclei of the amygdaloid complex, and from the prepiriform cortex, to several discrete areas of the cerebral cortex in the rat and cat and to the mediodorsal thalamic nucleus in the rat. These projections are very well-defined in their origin, and in their area of laminar pattern of termination. The basolateral amygdaloid nucleus can be divided into anterior and posterior divisions, based on cytoarchitectonic and connectional distinctions. In both the rat and cat the posterior division projects to the prelimbic area (area 32) and the infralimbic area (area 25) on the medical surface of the hemisphere. The anterior division projects more lightly to these areas, but also sends fibers to the dorsal and posterior agranular insular areas and the perirhinal area on the lateral surface. Furthermore, in the cat the perirhinal area is divided into two areas (areas 35 and 36) and the anterior division projects to both of these and also to a ventral part of the granular insular area; this last area is adjacent to, but separate from the auditory insular area and the second cortical taste area. In most of these areas, the fibers from the basolateral nucleus terminate predominantly in two bands: one in the deep part of layer I and layer II, and a heavier band in layer V (in the rat) or layers V and VI (in the cat). The lateral amygdaloid nucleus projects heavily to the perirhinal area, and also to the posterior agranular insular area. These fibers terminate predominantly in the middle layers of the cortex, although the cellular lamination in these two areas is relatively indistinct. The anterior cortical amygdaloid nucleus and the prepiriform cortex both project to the infralimbic area and the ventral agranular insular area, and the anterior cortical nucleus also projects to the posterior agranular area and the perirhinal area. In all of these areas, the fibers from these olfactory-related structures terminate in the middle of layer I. In the rat, the two divisions of the basolateral nucleus also project to the medial segment of the mediodorsal thalamic nucleus, with the anterior division projecting mainly to the posterior part of this segment and the posterior division to the anterior part. The endopiriform nucleus, deep to the prepiriform cortex, projects to the central segment of the mediodorsal nucleus; this may constitute the major olfactory input into the mediodorsal nucleus, since little or no projection could be demonstrated from the prepiriform cortex itself. Projections to the mediodorsal nucleus have not been found in the cat.

Afferent Pathways↗
PubMed1984

Subcortical projections of area MT in the macaque.

Area MT is a visuotopically organized area in extrastriate cortex of primates that appears to be specialized for the analysis of visual motion. To examine the full extent and topographic organization of the subcortical projections of MT in the macaque, we injected tritiated amino acids in five cynomolgus monkeys and processed the brains for autoradiography. The injection sites, which we identified electrophysiologically, ranged from the representation of central through peripheral vision in both the upper and lower visual fields and included, collectively, most of MT. Projections from MT to the superior colliculus are topographically organized and in register with projections from striate cortex to the colliculus. Unlike projections from striate cortex, those from MT are not limited to the upper layer of the stratum griseum superficiale but rather extend ventrally from the upper through the lower layer of the stratum griseum superficiale and even include the stratum opticum. Projections from MT to the pulvinar are organized into three separate fields. One field (P1) is located primarily in the inferior pulvinar but extends into a portion of the adjacent lateral pulvinar. The second field (P2) partially surrounds the first and is located entirely in the lateral pulvinar. The third and heaviest projection field (P3) is located posteromedially in the inferior pulvinar but also includes small portions of the lateral and medial pulvinar that lie dorsal to the brachium of the superior colliculus. While projections from MT to P1 and P2 are topographically organized, there appears to be a convergence of MT inputs to P3. Projections from MT to the reticular nucleus of the thalamus are located in the ventral portion of the nucleus, approximately at the level of the caudal pulvinar. There was some evidence that MT sites representing central vision project more caudally than do those representing peripheral vision. Projections from MT to the caudate, putamen, and claustrum are localized to small, limited zones in each structure. Those to the caudate terminate within the most caudal portion of the body and the tail. Similarly, projections to the putamen are always to its most caudal portion, where the structure appears as nuclear islands. Projections to the claustrum are located ventrally, approximately at the level of the anterior part of the dorsal lateral geniculate nucleus. Projections from MT to the pons terminate rostrally in the dorsolateral nucleus, the lateral nucleus, and the dorsolateral portion of the peduncular nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Topographic organization of the olivocochlear projections from the lateral and medial zones of the superior olivary complex.

By anterograde tracing using autoradiography, we have found topographic organizations in the projections of both medial and lateral olivocochlear (OC) systems in the cat. Lateral-zone injections show an ipsilateral cochleotopic projection pattern with more medial injections projecting more basally in the cochlea. In the contralateral cochlea, in contrast, the projections from all of the lateral-zone injections were predominantly to the apex. However, detailed analysis suggests the possibility that the contralateral lateral-zone projections may have the same cochleotopic organization as the ipsilateral projections but with a heavy bias toward the apex. Medial-zone injections show a pattern in which more dorsal regions project more basally in both cochleas. The ipsilateral projections of lateral OC neurons appear to connect regions with similar best frequencies but the projections of medial OC neurons do not. Summation of data from all of the injections in each zone indicates that lateral OC projections are relatively evenly distributed throughout the ipsilateral cochlea but are predominantly to the apex in the contralateral cochlea. Medial OC projections are predominantly to the middle and basal parts of the cochlea on both sides with contralateral projections somewhat more basal than ipsilateral projections.

Animals↗
PubMed1988

Projections of the retinorecipient pretectal nuclei in the pigeon (Columba livia).

We have used anterograde autoradiographic and retrograde HRP techniques to investigate the efferent connections of the retinorecipient pretectal nuclei in the pigeon. In the accompanying paper we identified these nuclei in the pigeon as the nucleus lentiformis mesencephali--pars lateralis and pars medialis, the tectal gray, the area pretectalis, and pretectalis diffusus. Although there are reports of a few of the projections of these nuclei, they had not previously been the subject of a detailed study. We found that different cell types in the lentiformis mesencephali, pars medialis and the lentiformis mesencephali, pars lateralis have descending projections to different targets. These targets include the inferior olive, the cerebellum, the lateral pontine nucleus, the nucleus papillioformis, the nucleus of the basal optic root, the nucleus mesencephalicus profundus, pars ventralis, the nucleus principalis precommissuralis, and the stratum cellulare externum. We found that a few cells in the lentiformis mesencephali project to the medial pontine nucleus, but that a much heavier projection arises from the nucleus laminaris precommissuralis, which is medial to the nucleus lentiformis mesencephali, pars medialis. The tectal gray has predominantly ascending projections to the diencephalon. The nuclei that it projects to are the nucleus intercalatus thalami, the nucleus of the ventral supraoptic decussation, the nucleus posteroventralis, the ventral lateral geniculate nucleus, the nucleus dorsolateralis medialis, and the nucleus dorsolateralis anterior. The tectal gray also projects topographically to layers 4 and 8-13 of the optic tectum. Area pretectalis has both ascending and descending projections. It has ipsilateral ascending projections to the nucleus dorsolateralis anterior, pars magnocellularis, the nucleus lateralis anterior, and the nucleus ventrolateralis thalami. It has ipsilateral descending projections to the central gray, the nucleus of the basal optic root, pars dorsalis, the lateral pontine nucleus, and the deep layers of the optic tectum. It has contralateral projections to the area pretectalis, the nucleus Campi Foreli, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch, the cerebellum, and the Edinger-Westphal nucleus. The efferent projections of pretectalis diffusus are limited. It projects contralaterally to the pretectalis diffusus, and ipsilaterally to the nucleus of the ventral supraoptic decussation, the lateral pons, and the cerebellum.4

Animals↗
PubMed1988

Specificity of sensory projections to the spinal cord during development in bullfrogs.

Sensory neurons in dorsal root ganglia of frogs project to areas of the spinal cord they do not normally innervate following removal of adjacent ganglia at tadpole stages (Frank and Westerfield, J. Physiol. (Lond.) 324:495-505, '82b). A possible explanation of this phenomenon is that sensory neurons project to wider areas of the spinal cord in tadpoles than in adult frogs and that partial deafferentation causes the retention of these widespread projections. Therefore, the specificity of sensory projections to the spinal cord in tadpoles was assessed by staining individual dorsal roots with horseradish peroxidase. Thoracic sensory neurons project to thoracic segments of the spinal cord and to the brainstem in tadpoles, like thoracic sensory neurons in adult frogs. They rarely arborize in the brachial region even at stages when no other sensory fibers arborize at this level. Furthermore, their projections are restricted to the dorsal horn at all stages. Conversely, hypoglossal sensory neurons, which project into the intermediate gray matter in the adult, also project to this area in tadpoles. The finding that sensory neurons in tadpoles only project to areas of the spinal cord that they innervate in the adult suggests that the novel projections observed following partial deafferentation of the spinal cord are actually induced by the operation. An additional finding was that forelimb afferents, which project to an area extending from the obex to midthoracic levels in adult frogs, arborize at rostral spinal levels and at thoracic levels several stages before they form projections to the region around their own dorsal root. These differences in the stages at which projections to different levels of the spinal cord develop suggest that local properties of the spinal cord may control the timing of sensory fiber arborization.

Afferent Pathways↗
PubMed1988

Origins of descending projections to the medulla oblongata and rostral medulla spinalis in the urodele Salamandra salamandra (amphibia).

Descending projections to the medulla oblongata and rostral medulla spinalis have been examined in the urodele Salamandra salamandra with retrograde horseradish peroxidase tracing. Ipsilateral projections originate from the striatum and the nucleus ventrolateralis thalami and reach the medulla oblongata. The ipsilateral nucleus praeopticus magnocellularis reaches the medulla spinalis. The rostral part of the nucleus tuberculi posterioris projects to the ipsilateral medulla oblongata; its caudal part projects further caudally. Tectal efferents and the efferents of the nucleus praetectalis profundus project bilaterally, the nucleus praetectalis superficialis, nucleus mesencephalicus nervi trigemini, torus semicircularis, nucleus Darkschewitsch, and nucleus fasciculi longitudinalis medialis project ipsilaterally to the medulla oblongata. The nucleus mesencephalicus nervi trigemini, nucleus fasciculi longitudinalis medialis, and tectal efferents reach the rostral medulla spinalis. The nucleus ruber projects mainly via the contralateral dorsolateral funiculus to the medulla spinalis. A largely crossed medullary projection arises in the nucleus dorsalis tegmenti pars anterior, a bilateral projection arises in the nucleus dorsalis tegmenti pars posterior, and an ipsilateral projection arises in the nucleus ventralis tegmenti pars anterior. Cerebellar and statoacoustic efferents descend to the medulla spinalis. The nucleus reticularis isthmi, superior, medius and inferior as well as the nucleus raphes exhibit spinal trajectories. The nucleus vestibularis magnocellularis projects bilaterally, the nucleus vestibularis medialis projects ipsilaterally spinalward. The supposed nucleus descendens nervi trigemini descends mainly contralaterally. A small spinal projection arises in the nucleus tractus solitarii. The results indicate that salamander brains display elaborate descending connections which are similar to those in other vertebrates despite their scarcely differentiated neuronal cytoarchitecture.

Animals↗
PubMed1989

Intrinsic connections of rat primary visual cortex: laminar organization of axonal projections.

The organization of local projections within the rat primary visual cortex (area 17) was investigated by tracing fibers with HRP in in vitro brain slices. The projections from different layers showed distinct laminar patterns. Layer 4 made a strong, topographically precise, projection to lower layer 2/3; weaker projections extended laterally and terminated diffusely in layer 2/3 but also ran vertically to layers 5 and 6. The connections of lower and upper layer 2/3 were reciprocal and point-to-point. Within layer 2/3, a large number of fibers ran horizontally and terminated at variable distances from the injection site without making terminal clusters. The main output from layer 2/3 was to layer 5. The most prominent projections from the upper half of layer 5 were to layers 2/3 and 6; lower layer 5, in contrast, made wide-ranging, clustered projections to layer 1, the bottom of layer 2/3, and the top of layers 4 and 5. The patches were 130-160 micron wide and spaced apart by 230-260 micron. The main projection that arose from the superficial layer 6 terminated in layer 4 above the injection site. In contrast, lower layer 6 made clustered projections to the layer 3/4 border, extending up to 2 mm in the coronal plane. The patches were 190-220 micron wide and spaced apart by 320-390 micron. Additional projections went to the layer 5/6 border and layers 1 and 2. These results indicate that geniculocortical input is processed through interlaminar connections that are topographically precise, widespread, or patchy. These connectivity patterns suggest a role for these connections in the transformation of functional maps between layers; focused projections preserve the architecture of the layers of origin, and diverging or patchy projections rearrange this organization and form new maps in the target layers (Lund: Annu. Rev. Neurosci. 11:253-288, '88). However, only a few interlaminar connections show one of these patterns in isolation, making it difficult to assign a single function to a particular connection. We, therefore, tentatively conclude that projections terminating in layers 1-4, with the possible exception of the connection between upper layer 6 and layer 4, transform functional maps. In contrast, the topographically precise projections from upper to lower layers preserve functional maps. The specific role of these connections in the construction of receptive field properties, however, is not known.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Neuropeptides and catecholamines in efferent projections of the nuclei of the solitary tract in the rat.

This study focuses on the involvement of catecholamines and nine different peptides in efferents of the nucleus of the solitary tract to the central nucleus of the amygdala, the bed nucleus of the stria terminalis, and different parabrachial and hypothalamic nuclei in the rat. A double-labeling technique was used that combines a protein-gold complex as the retrograde tracer with immunohistochemistry. Catecholaminergic projection neurons were the most numerous type observed and projected mainly ipsilaterally to all targets studied. Most projections arose from areas overlying the dorsal motor nucleus, mainly the medial nucleus. Neurons synthesizing somatostatin, met-enkephalin-Arg-Gly-Leu, dynorphin B, neuropeptide Y, and neurotensin projected to all structures examined. Somatostatin and enkephalin immunoreactive projection cells were the most numerous. They were located in close proximity to each other, including all subnuclei immediately surrounding the solitary tract, bilaterally. Most dynorphin and neuropeptide Y immunoreactive projection cells were found rostral to that of enkephalinergic and somatostatinergic projections, and mainly in the ipsilateral medial nucleus. Neurotensinergic projections were sparse and from dorsal and dorsolateral nuclei. Substance P and cholecystokinin contribute to parabrachial afferents. The location of substance P immunoreactive projection cells closely resembled that of enkephalinergic and somatostatinergic projections. Projecting cholecystokinin immunoreactive cells were observed in dorsolateral nucleus. Bombesin immunoreactive cells in dorsal nucleus projected to either the parabrachial or hypothalamic nuclei. No vasoactive intestinal polypeptide-containing cells were detected. Thus, most catecholaminergic and neuropeptidergic efferents originated from different populations of cells. It is proposed that catecholaminergic neurons constitute the bulk of solitary efferents and that they may contribute to autonomic neurotransmission. Peptidergic neurons mainly form other subgroups of projections and may play a role in modulating the physiological state of the target nuclei.

Animals↗
PubMed1993

Spinal neurogenesis and axon projection: a correlative study in the rat.

The purpose of the present study was to determine the relationship between the duration of a spinal neuron's neurogenic period and the length of its axon or level of projection. Spinal segment L1 was chosen for examination and neurons were divided into four projection groups: 1) supraspinal projection (SSp), 2) long ascending propriospinal (LAPr), 3) short ascending propriospinal (SAPr), and 4) descending propriospinal (DPr). To determine the duration of the neurogenic period for each group, 3H-thymidine was administered to fetal rats during the proliferative period for spinal neuroblasts on one of embryonic (E) days E13 through E16. Between 50 and 100 days after birth neurons in each group were labeled with the retrograde fluorescent tracer Fluoro-Gold. To demonstrate nerve cells with SSp projections, spinal cords were hemisected at spinal segment C3 in one group of animals and Fluoro-Gold was applied to the sectioned surface of the cord. Three additional sets of animals were used to label nerve cells with LAPr, SAPr, and DPr projections by injecting Fluoro-Gold into the gray matter at spinal segments C6, T12, and L5, respectively. Neurons labeled with both Fluoro-Gold and 3H-thymidine and neurons labeled with Fluoro-Gold alone in each animal in each group were counted and the data statistically analyzed. Results showed that within each spinal lamina neurons with different projections were generated, i.e., completed cell division, at significantly different rates. Neurons with the longest axons, those with SSP projections, were generated first. These were followed by those with LAPr projections, and finally those with SAPr and DPr projections. In most laminate there was no significant difference between the neurogenic periods of rostrally projecting short propriospinal (SAPr) neurons versus caudally projecting short propriospinal (DPr) neurons. It was concluded that the duration of the neurogenic period for a given group of neurons within each spinal lamina is inversely related to the distance between the nerve cell and its projection site regardless of the direction of its projection.

Animals↗
PubMed1995

Topographically specific hippocampal projections target functionally distinct prefrontal areas in the rhesus monkey.

The sources of ipsilateral projections from the hippocampal formation, the presubiculum, area 29a-c, and parasubiculum to medial, orbital, and lateral prefrontal cortices were studied with retrograde tracers in 27 rhesus monkeys. Labeled neurons within the hippocampal formation (CA1, CA1', prosubiculum, and subiculum) were found rostrally, although some were noted throughout the entire rostrocaudal extent of the hippocampal formation. Most labeled neurons in the hippocampal formation projected to medial prefrontal cortices, followed by orbital areas. In addition, there were differences in the topography of afferent neurons projecting to medial when compared with orbital cortices. Labeled neurons innervating medial cortices were found mainly in the CA1' and CA1 fields rostrally, but originated in the subicular fields caudally. In contrast, labeled neurons which innervated orbital cortices were considerably more focal, emanating from the same relative position within a field throughout the rostrocaudal extent of the hippocampal formation. In marked contrast to the pattern of projection to medial and orbital prefrontal cortices, lateral prefrontal areas received projections from only a few labeled neurons found mostly in the subicular fields. Lateral prefrontal cortices received the most robust projections from the presubiculum and the supracallosal area 29a-c. Orbital, and to a lesser extent medial, prefrontal areas received projections from a smaller but significant number of neurons from the presubiculum and area 29a-c. Only a few labeled neurons were found in the parasubiculum, and most projected to medial prefrontal areas. The results suggest that functionally distinct prefrontal cortices receive projections from different components of the hippocampal region. Medial and orbital prefrontal cortices may have a role in long-term mnemonic processes similar to those associated with the hippocampal formation with which they are linked. Moreover, the preponderance of projection neurons from the hippocampal formation innervating medial when compared with orbital prefrontal areas followed the opposite trend from what we had observed previously for the amygdala (Barbas and De Olmos [1990] (J Comp Neurol 301:1-23). Thus, the hippocampal formation, associated with mnemonic processes, targets predominantly medial prefrontal cortices, whereas the amygdala, associated with emotional aspects of memory, issues robust projections to orbital limbic cortices. Lateral prefrontal cortices receive robust projections from the presubiculum and area 29a-c and sparse projections from the hippocampal formation. These findings are consistent with the idea that the role of lateral prefrontal cortices in memory is distinct from that of either medial or orbital cortices. The results suggest that signals from functionally distinct limbic structures to some extent follow parallel pathways to functionally distinct prefrontal cortices.

Afferent Pathways↗
PubMed1987

Extension and retraction of axonal projections by some developing neurons in the leech depends upon the existence of neighboring homologues. II. The AP and AE neurons.

To assess the generality of our previous finding (Gao and Macagno, 1987) that segmental homologues play a role in the establishment of the pattern of axonal projections of the heart accessory HA neurons, we have extended our studies to two other identified leech neurons: the anterior pagoda (AP) neurons and the annulus erector (AE) motor neurons. Bilateral pairs of AP neurons are found in the first through the twentieth segmental ganglia (SG1 through SG20) of the leech ventral nerve cord. All AP neurons initially extend axonal projections to the contralateral periphery as well as longitudinal projections along the contralateral interganglionic connective nerves toward anterior and posterior neighboring ganglia. Although the peripheral projections are maintained by all AP neurons throughout the life of the animal, the longitudinal projections disappear in all but two segments: the AP neurons in SG1 maintain their anterior projections and extend them into the head ganglion, and those in SG20 maintain their posterior projections and extend them into SG21 and the tail ganglion. When single AP neurons are deleted anywhere along the nerve cord before processes begin to atrophy, however, the longitudinal projections are retained by their ipsilateral homologues in adjacent ganglia. The rescued processes appear to take over the projections of the deleted neurons. In cases where two or more AP neurons on the same side of the nerve cord are deleted from adjacent ganglia, a contralateral homologue sometimes extends projections to the periphery ipsilaterally or on both sides. We obtained similar results when we deleted single AE neurons from midbody ganglia. Thus, our experiments with three different identified neurons consistently show that the initial pattern of projections is the same in all ganglia, but that the existence of homologues in adjacent ganglia leads to the pruning of some of the initial projections. A consequence of this homologue-dependent process retraction is that neurons normally lacking neighboring homologues will have patterns of projections different from those neurons that do have such neighbors. Process loss by the HA, AP, and AE neurons may be the result either of competition for targets, inputs, or growth factors or of direct interactions among homologous cells.

Animals↗
PubMed2001

Effective planning and implementation of ecological rehabilitation projects: a case study of the regional municipality of Waterloo (Ontario, Canada).

The literature guides environmental planning and, specifically, how to use ecological rehabilitation projects to achieve long-term planning goals and landscape-scale environmental sustainability. There is, however, a perceived gap between principles in the literature and the use of them by practitioners involved in smaller-scale ecological rehabilitation projects. Using interviews with practitioners involved in 11 projects within the Regional Municipality of Waterloo, Ontario, Canada, we tested whether practitioners used five principles for effective planning and implementation of ecological rehabilitation that we derived from the literature. These five principles were: establishing political and ecological context, using ecologically appropriate objectives and practices, using comparative multidisciplinary and cross-scale approaches, using adaptive planning and implementation, and establishing good communication within and external to projects. Few projects followed all five principles, and practitioners indicated that they used three more project-specific principles: obtaining political/social support, promoting projects and changing attitudes about projects, and securing sufficient and persistent funding to maintain a project's life. While the literature emphasizes that ecological rehabilitation is only effective if projects are coordinated on a watershed basis, most practitioners focused solely on the goals of their specific project. The gap between literature and practice may arise because most practitioners are new to the field of ecological rehabilitation and still are focused on the methods involved. Time pressures force practitioners to obviate the literature and get projects started quickly, lest support evaporate. Complicating these difficulties is decreased support from federal and provincial governments for large-scale environmental planning. It is unclear whether ecological rehabilitation projects in Waterloo Region (at least) will ever become effective at promoting landscape-scale ecological goals or remain smaller-scale stop-gaps.

Animals↗
PubMed1984

The topography of the mesencephalic and pontine projections from the cingulate cortex of the rat.

A projection from the rat midline cortex to the midbrain and pons has been recognized for several years. The present study is a detailed analysis of this projection using the autoradiographic technique. Small injections of [3H]amino acids were placed within individual segments of the cingulate cortex in 68 rats. The resulting material reaffirmed the existence of the cingulo-brainstem projections and demonstrated that a precise topographical relationship exists between the cingulate cortex cells of origin and their termination fields within the brainstem. The most ventral and anterior segment of the cortex (IRaa) projects to the ventral periaqueductal gray, to the dorso-medial ventral pontine nuclei and to the lateral tegmental region. Conversely, the dorso-anterior cortex (IRca) projects to the superior colliculus, the dorso-lateral periaqueductal gray, and the medio-ventral ventral pontine nuclei. The intermediate anterior cortex projects to both dorsal and ventral periaqueductal gray, lightly to the superior colliculus, and to the medio-intermediate ventral pontine nuclei. The posterior half of the infraradiata (IR) cortex projects to the dorso-lateral periaqueductal gray, to the superior colliculus, and to the region of the ventral pontine nuclei slightly lateral to the terminal zone occupied by the anterior IR cortex. Increasingly dorsal segments of the IR beta cortex project to more increasingly ventral areas of the ventral nuclei. The posterior portion of the midline cortex (retrosplenial cortex, R) does not project to the dorsal midbrain, but it does topographically project to the ventral pontine nuclei, lateral to the terminal zone of the IR axons. Increasingly, posterior regions of the R cortex project to more lateral regions of the ventral nuclei, and increasingly, dorsal cells of the R cortex project to more dorsal regions of the ventral nuclei. These data demonstrate a very precise topography of brainstem projections which may underlie the visceral and somatic motor functions of the cingulate cortex, as well as the ability of the cingulate cortex to modulate sensory information and emotional behavior.

Animals↗