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PubMed1982

Infant mortality: world estimates and projections, 1950-2025.

Although the infant mortality rate is considered 1 of the preferred indicators for describing both demographic conditions and the overall and social economic well-being of a country, comparable and consistent estimates and projections of infant mortality for all countries of the world have been lacking. In an attempt to improve this situation, the UN Population Division, with the support and encouragement of the UN Children's Fund and the assistance of the World Health Organization and the UN regional commissions, has recently completed a comprehensive project which provides estimates and projections of infant mortality for all world countries for the period 1950-2025. This article reviews the estimates and projections produced by this project. The various sources and the quality of the data, as well as the methods employed to estimate current and past levels of infant mortality and to project future trends, are reviewed and evaluated. The article concludes with a discussion of the results vis-a-vis the goals set for infant mortality by the World Population Plan of Action and the International Development Strategy for the 3rd UN Development Decade.

Data Collection↗
PubMedDate not supplied

The Appalachian Rural Health Project in Chautauqua County, N.Y., 1973-78.

The Appalachian Regional Commission awarded a 5-year grant to the Chautauqua County Department of Health to establish primary health care services to medically underserved rural areas of the county. Four clinics were opened at various stages as the project grew.What began as an open system multidisciplinary approach to the delivery of primary health care changed abruptly to a closed system in March 1976, when the county medical society members voiced a strong objection to the rural health project. Among other assertions, the medical society claimed that the clinics of the project were "too costly and unnecessary as they now exist." Equally strong voices of community people demanded that the project be allowed to operate. An unprecedented public hearing was held and, as a result, a compromise plan was developed that permitted the medical services of the clinics to be continued, but most of the multidisciplinary components devoted to social development were eventually dropped.By September 30, 1978, when the project grant ended, three of the four clinics had been taken over on a private basis by physicians who had previously been assigned to the clinics and supported by the project.The effects of grassroots support and power of the people in a community in determining their health rights and needs were demonstrated and documented in this pioneer program. It is anticipated that the Chautauqua County experience may be a helpful model in planning other projects that attempt to institute change in the health care delivery system in underserved rural areas.

Appalachian Region↗
PubMed1993

A plan for the mouse genome project. Joint NIH/DOE Mouse Working Group.

The National Center for Human Genome Research and the Department of Energy convened a committee of geneticists and biologists who use the laboratory mouse in their research programs. Their responsibility was to identify goals and guidelines for completing the genetic and physical maps of the mouse genome. The motivation for convening this group was to make certain that existing and anticipated research projects together represent a comprehensive program for addressing the Five Year Goals of the Human Genome Project. Three meetings were held: the first addressed the contributions that the mouse can make to the Human Genome Project; the second meeting reviewed the status of the genetic map, gene mapping research, and genome informatics; and the final meeting evaluated the status of the physical map and physical mapping research. The committee then prepared a report that reviewed the status of the mouse genome project and made recommendations concerning areas of research emphasis. The resulting Request For Applications entitled 'Mapping the Mouse Genome with Emphasis on Technology Development' (RFA: HG-92-002) is an important mechanism for coordinating mouse genome research and accomplishing the goals of the mouse genome project. Progress towards complete genetic and physical maps has been impressive. The genetic map should be completed on schedule, and ongoing physical mapping projects are promising. Given rapid progress on these maps, the Working Group proposed expanding the focus of the mouse genome effort to begin planning comprehensive approaches for characterizing the function of the large number of genes that will soon be mapped and eventually sequenced.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

[Pedalo--a community project for mothers of infants in St. Gallen-Rotmonten].

The "Pedalo" pilot project has been in the trial phase in St. Gallen's Rotmonten Quarter for a year and a half now. It was developed by a group of women residents of the quarter. Having the backing and support of the ZEPRA executive committee, the objective of the project is to reunite mothers with one or several small children and offer them support and guidance in everyday and crisis situations. The project is designed as a grassroots effort with a preventative character, working hand in hand with trained laypersons within Rotmonten and joining forces with other support organizations and agencies of the City of St. Gallen as needed (catalyst and coordination function). The model for the "Pedalo" meeting place was the Dutch intervention project Moeders informeren moeders (MIM, "Mothers Inform Mothers"). This project idea was adopted by a group of mothers who had previously taken the initiative in their own neighborhood. Today, "Pedalo" essentially provides for a meeting place, in addition to organizing ad-hoc events or campaigns in the neighborhood. Since the beginning of the trial phase the project has been supported by public funding and private donations.

Female↗
PubMedDate not supplied

Measurement of preoperative and postoperative nasal tip projection and rotation.

OBJECTIVE: To measure the effect of columellar struts and cephalic trim on tip projection and tip rotation using digitized photographs. METHODS: Using photographs of 62 patients who underwent external rhinoplasty, we retrospectively analyzed nasal tip projection (the Goode method) and rotation (nasolabial angle) before and after surgery. A cartilaginous strut was used in 36 patients, whereas 26 patients did not receive a strut. Patients were categorized into 4 subgroups, depending on the placement of a strut (placement, strut+ vs nonplacement, strut-) and the removal of the cephalic margin (removal, cephalic+ vs nonremoval, cephalic-) of the lateral crus: strut-/cephalic-, n = 17; strut+/cephalic-, n = 23; strut-/cephalic+, n = 9; strut+/cephalic+, n = 12. RESULTS: Nasal tip projection, measured with the Goode method, increased from 0.58 to 0.60 (P = .02) in the strut+ group; in the strut- group, nasal tip projection did not change significantly. Nasolabial angle increased from 93.96 degrees to 100.92 degrees in the strut+/cephalic- group and from 88.30 degrees to 95.06 degrees in the strut+/cephalic+ group. Removal of the cephalic margin alone (strut-/cephalic+) hardly affected tip rotation (P = .05). CONCLUSIONS: The external rhinoplasty approach did not lead to a decrease in nasal tip projection. A cartilaginous strut slightly increased nasal tip projection and also increased nasal tip rotation. This effect was accentuated by the removal of the cephalic margin of the lateral crus.

Female↗
PubMed1977

Nasal projection.

The challenge of enduring tip projection is met with the use of a septal cartilage graft between the medial crura. With suturing, a "sandwich" is created composed of the two medial crura and the graft between them. The sandwich can be trimmed as necessary, in accordance with the surgeon's taste requirements for good tip profile and projection. The graft allows much more projection than from the medial crura alone. We describe the Goldman technique of rim incisions, delivery of the lower lateral cartilages, bisection of each, and then creation of the sandwich. The technique has been performed on more than 40 patients, in most of whom the results have remained successful more than six months postoperatively. The results indicate excellent fixation of the projected tip with maintenance of position, strength, and form. The indications for this tip technique are the classical ones for medial crura projection, such as hypoplastic tip cartilages, short columella revision rhinoplasty, and most importantly, the increase of real projection not attained by simple rotation.

Cartilage↗
PubMed1991

Nasal tip projection. Quantitative changes following rhinoplasty.

Fifty-one patients were enrolled in a study and underwent primary rhinoplasty. Serial nasal tip projection measurements were made preoperatively, intraoperatively, and 6 months postoperatively. Actual changes in measured nasal tip projection were evaluated with respect to preoperative goals and specific procedures used to accomplish these goals in the nasal tip. Several useful observations are made from these data: (1) The most important components of nasal tip projection in the postsurgical nasal tip are the medial crura, their attachment to the caudal septum, and the presence of additional cartilaginous grafts placed between the medial crura or beneath the crural feet. (2) Actual nasal tip projection will decrease postoperatively, unless measures to increase the length and strength of the medial crural segment are taken (ie, McCollough-modified Goldman tip procedure, cartilage struts, plumping grafts, etc), regardless of the preoperative goal. (3) The double-dome unit procedure is effective in narrowing the wide or bulbous lobule but alone does not permanently increase nasal tip projection. (4) Conservative tip procedures, such as a complete strip, result in decreased nasal tip projection and should therefore be used in patients in whom retrodisplacement of the nasal tip is the intended result.

Adult↗
PubMed1996

Glutamate and aspartate immunoreactive neurons of the rat basolateral amygdala: colocalization of excitatory amino acids and projections to the limbic circuit.

The basolateral amygdala has projections to several structures that take part in the limbic cortico-striato-pallido-thalamic circuit, including the prefrontal cortex, ventral striatum, and mediodorsal thalamic nucleus. The present investigation used a technique that combines retrograde tract tracing with immunohistochemistry for glutamate and aspartate to determine if amygdaloid neurons projecting to different targets in the limbic circuit can be distinguished on the basis of their content of excitatory amino acids. Cell counts revealed that at least 85-95% of the neurons in the basolateral nucleus projecting to the prefrontal cortex or ventral striatum were pyramidal cells that exhibited glutamate or aspartate immunoreactivity. Colocalization studies indicated that 94-100% of aspartate-immunoreactive neurons in the basolateral nucleus were also glutamate positive and that 92-94% of glutamate-immunoreactive neurons were also aspartate positive. A small number of glutamate-positive pyramidal neurons in the anterior subdivision of the cortical nucleus were found to project to the mediodorsal thalamic nucleus. However, the great majority of amygdaloid neurons with projections to the mediodorsal nucleus did not exhibit glutamate or aspartate immunoreactivity. The absence of glutamate and aspartate immunoreactivity in these cells suggests that these neurons do not use excitatory amino acids as neurotransmitters. The finding of high levels of glutamate and aspartate in basolateral amygdaloid neurons projecting to the prefrontal cortex and ventral striatum is consistent with previous reports indicating that these neurons may use excitatory amino acids as neurotransmitters, but is not a definitive criterion for this determination.

Amygdala↗
PubMed1996

Comparison of cerebellothalamic and pallidothalamic projections in the monkey (Macaca fuscata): a double anterograde labeling study.

To address the question of segregated projections from the internal segment of the globus pallidus (GPi) and the cerebellar nuclei (Cb) to the thalamus in the monkey, we employed a double anterograde labeling strategy combining the anterograde transport of horseradish peroxidase conjugated to wheat germ agglutinin (WGA-HRP) with biotinylated dextran amine (BDA) transport. The tissue was processed sequentially for WGA-HRP, and then BDA immunohistochemistry using two different chromogens. Since the two labels were easily distinguishable on the same histological section, the interrelationship between the cerebellar and pallidal projection systems could be directly evaluated. We found that both the cerebellothalamic and pallidothalamic label consisted of dense plexuses of labeled fibers and swellings in a patch-like configuration. The patches or foci of labeling were distributed either as dense single label or as interdigitating patches of double label. We found dense single label in the central portion of the ventral anterior nucleus pars principalis (VApc) and the ventral lateral nucleus pars oralis (VLo) following the GPi injections or in the central portion of the ventral posterior lateral nucleus pars oralis (VPLo) and nucleus X (X) following the cerebellar nuclei injections. Complementary interdigitating patches of WGA-HRP and BDA labeling were found primarily in transitional border regions between thalamic nuclei. On occasion, we found overlap of both labels. We observed a gradient pattern in the density of the pallidothalamic and cerebellothalamic projections. The pallidothalamic territory included VApc, VLo, and the ventral lateral nucleus pars caudalis (VLc), with the density of these projections decreasing along an anterior to posterior gradient in the thalamus. Occasional patches of pallidal label were found in VPLo and nucleus X. Conversely, the density of cerebellothalamic projections increased along the same gradient, with the cerebellothalamic territory extending anteriorly beyond the cell-sparse zones of VPLo, X, and VLc to include VLo and VApc also. These data suggest that although the cerebellar and pallidal projections primarily occupy separate thalamic territories, individual thalamic nuclei receive differentially weighted inputs from these sources.

Animals↗
PubMed1996

Organization of projections from the basomedial nucleus of the amygdala: a PHAL study in the rat.

The organization of axonal projections from the basomedial nucleus of the amygdala (BMA) was examined with the Phaseolus vulgaris leucoagglutinin (PHAL) method in adult male rats. The anterior and posterior parts of the BMA, recognized on cytoarchitectonic grounds, display very different projection patterns. Within the amygdala, the anterior basomedial nucleus (BMAa) heavily innervates the central, medial, and anterior cortical nuclei. In contrast, the posterior basomedial nucleus (BMAp) sends a dense projection to the lateral nucleus, and to restricted parts of the central and medial nuclei. Extra-amygdalar projections from the BMA are divided into ascending and descending components. The former end in the cerebral cortex, striatum, and septum. The BMAa mainly innervates olfactory (piriform, transitional) and insular areas, whereas the BMAp also innervates inferior temporal (perirhinal, ectorhinal) and medial prefrontal (infralimbic, prelimbic) areas and the hippocampal formation. Within the striatum, the BMAa densely innervates the striatal fundus, whereas the nucleus accumbens receives a heavy input from the BMAp. Both parts of the BMA send massive projections to distinct regions of the bed nuclei of the stria terminalis. Descending projections from the BMA end primarily in the hypothalamus. The BMAa sends a major input to the lateral hypothalamic area, whereas the BMAp innervates the ventromedial nucleus particularly heavily. Injections were also placed in the anterior cortical nucleus (COAa), a cell group superficially adjacent to the BMAa. PHAL-labeled axons from this cell group mainly ascend into the amygdala and olfactory areas, and descend into the thalamus and lateral hypothalamic area. Based on connections, the COAa and BMAa are part of the same functional system. The results suggest that cytoarchitectonically distinct anterior and posterior parts of the BMA are also hodologically distinct and form parts of distinct anatomical circuits probably involved in mediating different behaviors (for example, feeding and social behaviors vs. emotion-related learning, respectively).

Amygdala↗
PubMed1996

Gracile, cuneate, and spinal trigeminal projections to inferior olive in rat and monkey.

In the cat, somatosensory nuclei send substantial projections to the inferior olive, where they terminate in a somatotopic fashion. Although the organization of the cat inferior olive has been used to interpret data from other species, published data suggest this organization may not occur universally. The present study investigated whether the inferior olive in albino rats and cynomolgus monkeys receives the same brainstem somatosensory inputs, whether these inputs are organized somatotopically and, if so, how the organization compares with that in the cat. Projections from the gracile, cuneate and spinal trigeminal nuclei were labeled with wheat germ agglutinin conjugated to horseradish peroxidase or with biotinylated dextran. The results were compared with data from cats (Berkley and Hand [1978] J. Comp. Neurol. 180:253-264). In the rat and monkey, the gracile, cuneate and spinal trigeminal nuclei all project to the contralateral inferior olive, where each nucleus has a distinct preferred terminal field. As in the cat, projections to the medial accessory olive and caudal dorsal accessory olive did not terminate in a precisely organized fashion. Projections to the rostral dorsal accessory olive, however, formed a clear somatotopic map. These somatotopic maps differed from those in the cat in that input from the trigeminal nucleus was confined rostrally, so that the caudal end only received input from the gracile and cuneate nuclei. These data indicate that similar organizational principles characterize the somatosensory projections to the inferior olives of the three species. Nevertheless, distinct species differences occur with regard to the details of this organization.

Animals↗
PubMed1996

Comparison of projection neurons in the pontine nuclei and the nucleus reticularis tegmenti pontis of the rat.

Dendritic features of identified projection neurons in two precerebellar nuclei, the pontine nuclei (PN) and the nucleus reticularis tegmenti pontis (NRTP) were established by using a combination of retrograde tracing (injection of fluorogold or rhodamine labelled latex micro-spheres into the cerebellum) with subsequent intracellular filling (lucifer yellow) in fixed slices of pontine brainstem. A multivariate analysis revealed that parameters selected to characterize the dendritic tree such as size of dendritic field, number of branching points, and length of terminal dendrites did not deviate significantly between different regions of the PN and the NRTP. On the other hand, projection neurons in ventral regions of the PN were characterized by an irregular coverage of their distal dendrites by appendages while those in the dorsal PN and the NRTP were virtually devoid of them. The NRTP, dorsal, and medial PN tended to display larger somata and more primary dendrites than ventral regions of the PN. These differences, however, do not allow the differentiation of projection neurons within the PN from those in the NRTP. They rather reflect a dorso-ventral gradient ignoring the border between the nuclei. Accordingly, a cluster analysis did not differentiate distinct types of projection neurons within the total sample. In both nuclei, multiple linear regression analysis revealed that the size of dendritic fields was strongly correlated with the length of terminal dendrites while it did not depend on other parameters of the dendritic field. Thus, larger dendritic fields seem not to be accompanied by a higher complexity but rather may be used to extend the reach of a projection neuron within the arrangement of afferent terminals. We suggest that these similarities within dendritic properties in PN and NRTP projection neurons reflect similar processing of afferent information in both precerebellar nuclei.

Animals↗
PubMed1997

Projection from the cerebellar lateral nucleus to precerebellar nuclei in the mossy fiber pathway is glutamatergic: a study combining anterograde tracing with immunogold labeling in the rat.

The pontine nuclei (PN) and the nucleus reticularis tegmenti pontis (NRTP) are sources of an excitatory projection to the cerebellar cortex via mossy fibers and a direct excitatory projection to the cerebellar nuclei. These precerebellar nuclei, in turn, receive a feedback projection from the cerebellar nuclei, which mostly originate in the lateral nucleus (LN). It has been suggested that the feedback projection from the LN partially uses gamma-aminobutyric acid (GABA) as a transmitter. We tested this hypothesis by using a combination of anterograde tracing (biotinylated dextran amine injection into the LN) and postembedding GABA and glutamate immunogold histochemistry. The pattern of labeling in the PN and the NRTP was compared with that of cerebellonuclear terminals in two other target structures, the parvocellular part of the nucleus ruber (RNp) and the ventromedial and ventrolateral thalamus (VM/VL). The projection to the inferior olive (IO), which is known to be predominantly GABAergic, served as a control. A quantitative analysis of the synaptic terminals labeled by the tracer within the PN, the NRTP, and the VL/VM revealed no GABA immunoreactivity. Only one clearly labeled terminal was found in the RNp. In contrast, 72% of the terminals in the IO were clearly GABA immunoreactive, confirming the reliability of our staining protocol. Correspondingly, glutamate immunohistochemistry labeled the majority of the cerebellonuclear terminals in the PN (88%), the NRTP (90%), the RNp (93%), and the VM/VL (63%) but labeled only 5% in the IO. These data do not support a role for GABAergic inhibition either in the feedback systems from the LN to the PN and the NRTP or within the projections to the RNp and the VM/VL.

Animals↗
PubMed1997

Association of serotonin-like immunoreactive axons with nociceptive projection neurons in the caudal spinal trigeminal nucleus of the rat.

Serotoninergic projections to the spinal dorsal horn are implicated in the modulation of nociceptive transmission. However, morphological evidence indicating that serotoninergic projection fibers make synapses on nociceptive neurons in the medullary dorsal horn is still meager. Thus, we examined whether axonal varicosities with serotonin (5-HT)-like immunoreactivity (5-HT-LI) might make synapses on nociceptive projection neurons in the caudal spinal trigeminal nucleus (Vc) of the rat. Projection neurons were retrogradely labeled with tetramethylrhodamine-dextran amine (TMR-DA) or wheat germ agglutinin-horseradish peroxidase (WGA-HRP) that was injected into the parabrachial or thalamic region. Vc neurons in which c-fos protein-like immunoreactivity (Fos-LI) was induced by subcutaneous injection of formalin into the lip were considered nociceptive. Vc neurons in direct contact with axonal varicosities that bind isolectin I-B4 were also considered nociceptive. Triple labeling for 5-HT, TMR-DA, and Fos as well as that for 5-HT, TMR-DA, and I-B4 were done by using the immunofluorescence and fluorescence histochemical techniques. Confocal laser-scanning microscopy revealed that axonal varicosities with 5-HT-LI were in close apposition to TMR-DA-labeled neurons showing Fos-LI in lamina I and the outer part of lamina II (lamina IIo), and that both axonal varicosities with 5-HT-LI and those binding I-B4 were in close apposition to single neuronal profiles labeled with TMR-DA. The presumed nociceptive neuronal profiles in close apposition to axon terminals with 5-HT-LI were mainly those of laminae I and II neurons as well as dendrites of lamina III neurons. Electron microscopy confirmed that axon terminals with 5-HT-LI and those with I-B4 binding activity in laminae I and II made synapses on somatic and dendritic profiles that were labeled with WGA-HRP. The results indicate that serotoninergic neurons project directly on nociceptive projection neurons in the Vc.

Animals↗
PubMed1997

Sensitive period for lesion-induced reorganization of intracortical projections within the vibrissae representation of rat's primary somatosensory cortex.

Previous experiments from this laboratory demonstrated that intracortical connections in lamina IV of the rat primary somatosensory cortex (SI) are most dense outside the patches of cytochrome oxidase (CO) staining that correspond to the mystacial vibrissae. This pattern of intracortical connections becomes apparent on postnatal day 4 (P-4), at least 2 days after the appearance of the vibrissae-related pattern of thalamocortical afferents. Transection of the infraorbital nerve (ION) on the day of birth (P-0) disrupts both the CO and intracortical projection patterns. This series of experiments was undertaken to determine whether the patterning of either thalamocortical afferents or intracortical projections defines the end of the period over which peripheral damage can alter intracortical projections in lamina IV of SI. The infraorbital nerve (ION) was transected in different cohorts of rats on P-1 through P-5, and animals were allowed to survive > or =45 days, at which time biotinylated dextran amine (BDA) injections were made into the SI. After 7 days, animals were killed, and alternate cortical sections were processed for the demonstration of BDA or CO. Transection of the ION on P-1 or P-2 altered the patterning of both CO and intracortical connections in the SI. In contrast, cutting the ION on P-3 left the pattern of CO densities in the SI intact, but significantly altered the patterning of intracortical connections. Transection of the nerve on P-5 resulted in qualitatively and quantitatively normal patterns of both CO densities and BDA-labelled intracortical projections. These results indicate that the establishment of a stable barrel pattern in layer IV of the SI is not sufficient for normal adult patterning of intracortical projections in this lamina. However, once the mature pattern of intracortical projections in layer IV is established, ION lesions can no longer alter it.

Aging↗
PubMed1998

Projection and innervation patterns of individual thalamic reticular axons in the thalamus of the adult rat: a three-dimensional, graphic, and morphometric analysis.

The gamma-aminobutyric acid-ergic thalamic reticular nucleus (Rt), which carries matching topographical maps of both the thalamus and cortex and in which constituent cells can synaptically communicate between each other, is the major extrinsic source of thalamic inhibitions and disinhibitions. Whether all the Rt axonal projections into the thalamus are similarly organized and have common projection and innervation patterns are questions of great interest to further our knowledge of the functioning of the Rt. The present study provides architectural and morphometric data of individual, anterogradely labeled axonal arbors that arose from distinct parts of the Rt. One hundred twenty-seven Rt neurons from all regions of Rt were marked juxtacellularly with biocytin or Neurobiotin in urethane-anesthetized adult rats. Eighteen two-dimensional and 14 three-dimensional reconstructions of single tracer-filled Rt neurons were made from serial, frontal, horizontal, or sagittal sections. Both the somatodendritic and axonal fields of tracer-filled Rt cells were mapped in three dimensions and illustrated to provide a complementary stereotaxic reference for future studies. Most marked units projected to a single nucleus of the anterior, dorsal, intralaminar, posterior, or ventral thalamus. Axons emerging from cells in distinct sectors of the Rt projected to distinct nuclei. Within a sector, neurons with separate dendritic fields innervated separate regions either in a single nucleus or into different but functionally related thalamic nuclei. Neurons with an overlap of their dendritic fields gave rise either to overlapping axonal arborizations or, more rarely, to distinct axonal arbors within two different thalamic nuclei implicated in the same function. In rare instances, an Rt axon could project within these two nuclei. Thalamic reticular axons commonly displayed a single well-circumscribed arbor containing a total of about 4,000 +/- 1,000 boutons. Every arbor was composed of a dense central core, which encompassed a thalamic volume of 5-63 x 10(6) microm3 and was made up of patches of maximal innervation density (10 +/- 4 boutons/tissue cube of 25 microm each side), surrounded by a sparse component. The metric relationships between the Rt axonal arbors and the dendrites of their target thalamocortical neurons were determined. Both the size and maximal innervation density of the axonal patches were found to fit in with the somatodendritic architecture of the target cells. The Rt axonal projections of adult rats are thus characterized by their (1) well-focused terminal field with a patchy distribution of boutons and (2) parallel organization with a certain degree of divergence. The role of the Rt-mediated thalamic inhibition and disinhibition may be to contrast significant with nonrelevant ongoing thalamocortical information.

Animals↗
PubMed1998

Nigrothalamic projections and nigrothalamocortical pathway to the medial agranular cortex in the rat: single- and double-labeling light and electron microscopic studies.

Although the rat medial agranular cortex (AGm) has been implicated in a variety of motor functions, the source of the afferents impinging upon thalamic neurons projecting to the AGm is not directly known. The main purpose of this study was to determine whether the AGm is a major recipient of the nigrothalamocortical pathway. This issue was addressed by two sets of experiments. First, the organization of the nigrothalamic projections was studied by light and electron microscopy following injections of the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) into the pars reticulata of the substantia nigra (SNR). The major finding of this study was the disclosure of a heretofore unknown projection to the rostromedial part of the ventral anterior-ventral lateral complex (VAL). This projection originates exclusively from the ventral portion of the SNR and is comparable in strength to the well-known nigrothalamic projection to the ventromedial nucleus (VM). Electron microscopic examination revealed differences in the synaptic organization of nigral terminals in the VAL and the VM. A large proportion of the labeled terminals in the VAL was involved in axosomatic synapses, whereas, in the VM, the axosomatic synapses were rare, and 67% of nigral terminals were found in contact with thin dendrites. To assess a possible disynaptic nigrothalamocortical pathway to the AGm, a double-labeling strategy combining PHA-L injections in the SNR and pressure injections of the retrograde tracer, cholera toxin subunit B (CTB) in the AGm was employed. The greatest density of CTB-labeled neurons was found in the rostral and central portion of the VAL, coincident with the nigrothalamic labeling originating from the ventral SNR. Electron microscopic analysis confirmed that some of the PHA-L-labeled terminals established synaptic contacts with the CTB-labeled cell bodies and large dendrites. In conclusion, our findings indicate that there exist two different nigrothalamocortical pathways through the motor thalamus in the rat. The SNR-VAL-AGm cortical projection may play a role in oculomotor functions, whereas the SNR-VM-cortical pathway has been implicated in arousal mechanisms.

Animals↗
PubMed1998

Cortical projections of the parvocellular laminae C of the dorsal lateral geniculate nucleus in the cat: an anterograde wheat germ agglutinin conjugated to horseradish peroxidase study.

The areal and laminar distributions of the projection from the parvocellular part of laminae C of the dorsal lateral geniculate nucleus (Cparv) were studied in visual cortical areas of the cat with the anterograde tracing method by using wheat germ agglutinin conjugated to horseradish peroxidase. A particular objective of this study was to examine the central visual pathways of the W-cell system, the precise organization of which is still unknown. Because the Cparv in the cat is said to receive W-cell information exclusively from the retina and the superior colliculus, the results obtained would provide an anatomical substrate for the W-cell system organization in mammals. The results show that the cortical targets of the Cparv are areas 17, 18, 19, 20a, and 21a and the posteromedial lateral suprasylvian (PMLS) and ventral lateral suprasylvian(VLS) areas. In area 17, the projection fibers terminate in the superficial half of layer I; the lower two-thirds of layer III, extending to the superficial part of layer IV; and the deep part of layer IV, involving layer Va. These terminations form triple bands in area 17. The projection terminals in layer I are continuous, whereas those in layers III, IV, and Va distribute periodically, exhibiting a patchy appearance. In areas 18 and 19, the projection fibers terminate in the superficial half of layer I and in the full portions of layers III and IV, forming double bands. In these areas, the terminals in layer I are continuous, whereas those in layers III and IV distribute periodically, exhibiting a patchy appearance. In area 20a, area 21a, PMLS, and VLS, projection fibers terminate in the superficial part of layer I, in part of layer III, and in the full portion of layer IV, although they are far fewer in number than those seen in areas 17, 18, and 19. The present results demonstrate that the Cparv fibers terminate in a localized fashion in both the striate and the extrastriate cortical areas and that these W-cell projections are quite unique in their areal and laminar organization compared with the X- and Y-cell systems.

Animals↗