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W M Cowan

Publications and source records attributed to W M Cowan.

At least 55 records · Page 3Linked to original sources
PubMed1982

Some observations on hypothalamo-amygdaloid connections in the monkey.

The projections of the hypothalamus to the amygdala have been studied autoradiographically in a series of eleven cynomolgus monkeys (Macaca fascicularis) in which injections of [3H]amino acids had been made in different regions of the caudal two-thirds of the hypothalamus. The most prominent projection arises from the ventromedial nucleus of the hypothalamus and terminates most heavily in the medial, magnocellular division of the central nucleus. Injections confined to the ventromedial nucleus also result in labeling of the piriform cortex, the periamygdaloid cortex, the anterior amygdaloid area, the medial amygdaloid nucleus and the parvocellular divisions of both the basal and basal accessory nuclei. All these projections are bilateral (although the contralateral component is much smaller) and show evidence of a rostro-caudal topographic organization. Isotope injections that involve the caudal part of the lateral hypothalamic area label projections to the medial division of the central amygdaloid nucleus, to the medial and cortical nuclei and to the anterior amygdaloid area. When such caudally placed injections also involved the lateral mamillary nucleus, the lateral division of the central amygdaloid nucleus was additionally labeled. Although the medial mamillary nucleus does not project to the amygdala, there is evidence for a minor projection from the supramamillary region to the medial amygdaloid nucleus. The ventral tegmental area appears to project to the lateral division of the central nucleus and the medial portion of the substantia nigra has a small projection to both divisions of the central nucleus. All of these projections reach the amygdala by way of the so-called ventral amygdalofugal pathway, but at least some of the fibers that arise in the ventromedial nucleus run in the stria terminalis.

Afferent Pathways↗
PubMed1982

The morphology and connections of the posterior hypothalamus in the cynomolgus monkey (Macaca fascicularis). I. Cytoarchitectonic organization.

The cytoarchitectonic organization of the posterior hypothalamus of the cynomolgus monkey (Macaca fascicularis) was analyzed in Nissl, Golgi, acetylcholinesterase, and reduced silver preparations. The region consists of a number of cell masses that differ considerably in their discreteness and in the homogeneity of their neuronal populations. The nuclei identified include: the medial mamillary nucleus (in which at least three distinct subdivisions can be recognized--a pars medialis, a pars lateralis, and a pars basalis); the small-celled nucleus intercalatus; the large-celled lateral mamillary nucleus; a single premamillary nucleus; the tuberomamillary nucleus; the posterior hypothalamic nucleus; the caudal extension of the lateral hypothalamic area; the supramamillary area; and the paramamillary nucleus (which appears to correspond to the nucleus of the ansa lenticularis of other workers). As a basis for the subsequent experimental study of the efferent connections of the posterior hypothalamus, the location of each of these cell masses is described and illustrated in a series of low-power photomicrographs, as are the form and distribution of the resident neuronal populations of the various components of the mamillary complex as seen in Golgi preparations.

Animals↗
PubMed1982

The morphology and connections of the posterior hypothalamus in the cynomolgus monkey (Macaca fascicularis). II. Efferent connections.

The efferent connections of the posterior hypothalamus have been analyzed autoradiographically in a series of eight cynomolgus monkey (Macaca fascicularis) brains with injections of 3H-amino acids in different regions of the mamillary complex and the surrounding areas. The medial mamillary nucleus was found to project through the mamillothalamic tract to the ipsilateral anteroventral, anteromedial, and interanteromedial nuclei, and by way of the mamillotegmental tract principally to the deep tegmental nucleus (of Gudden). It also appears to contribute fibers to the medial forebrain bundle, some of which reach as far rostrally as the medial septal nucleus. The lateral mamillary nucleus projects through the mamillothalamic tract bilaterally upon the anterodorsal nuclei of the thalamus, and through the mamillotegmental system to the dorsal tegmental nucleus; it also appears to contribute fibers to the medial forebrain bundle. The supramamillary area has extensive ascending and descending connections that are distributed with the medial forebrain bundle to the hypothalamus and rostral midbrain; in addition, it gives rise to an unusually well-defined projection to field CA2 of the hippocampus and to a narrow zone overlying the outer part of the granule cell layer and the adjoining part of the molecular layer of the dentate gyrus. We have not been able to distinguish the connections of the posterior hypothalamic nucleus from those of the caudal part of the lateral hypothalamic area: they both appear to contribute substantially to the ascending components of the medial forebrain bundle, and through its descending projection to the tegmental fields of the midbrain, the nucleus centralis superior of the raphe complex, the locus coeruleus, and the central gray as far caudally as the facial nerve. Their further projections to the spinal cord were not examined. Viewed broadly, and in the light of previous work, our observations confirm, once again, the constancy of the connections of the hypothalamus in the mammalian brain, and the pivotal position that the posterior hypothalamus occupies in the elaborate system of connections that links the limbic areas of the forebrain with the complex of structures that Nauta has aptly designated the "midbrain limbic region."

Animals↗
PubMed1982

The medial forebrain bundle of the rat. II. An autoradiographic study of the topography of the major descending and ascending components.

The medial forebrain bundle (MFB) is a complex fiber system that courses through and partly arises and partly terminates within the lateral preoptic and lateral hypothalamic areas. It consists mainly of thin fibers and may be comprised of as many as 50 descending and ascending components of varying lengths and of different origins and/or destinations (Nieuwenhuys et al., '82). With the aid of an an atlas of the MFB and the surrounding brain areas in the rat presented in the preceding paper (Nieuwenhuys et al., '82), the position and topographic relationships of some 21 components of the bundle have been analyzed in detail, in brains that had been prepared for autoradiography following injections of tritiated amino acids into a number of structures that are known to contribute fibers to the MFB. From this analysis it is clear that most of the labeled components occupy specific and rather constant positions within the MFB. For example, the ascending components are largely confined to the dorsal half of the bundle; those arising from the medial preoptic area and the various hypothalamic nuclei are distributed rather diffusely over much of the MFB; and the descending components that arise from the olfactory tubercle and the magnocellular preoptic nucleus are confined to restricted parts of the bundle. These findings indicate that the neurons which occupy different parts of the lateral hypothalamic area probably receive distinctive inputs, and to a first approximation these are likely to be determined principally by their position within the MFB.

Amygdala↗
PubMed1982

The sprouting of septal afferents to the dentate gyrus after lesions of the entorhinal cortex in adult rats.

The projection of the septum to the dentate gyrus has been demonstrated autoradiographically and the pattern of acetylcholinesterase (AChE) staining in the dentate gyrus has been mapped histochemically, in a series of normal young adult rats and in a group of animals in which the entorhinal cortex had been ablated or its efferents to the dentate gyrus interrupted, some weeks earlier. It is clear from this material that the normal disposition of the septal projection to the dentate gyrus differs significantly from the pattern of AChE staining; however, in the denervated region of the molecular layer in the experimental animals there is a marked increase in the density of the septal projection which precisely coincides with the zone of intensification of AChE staining. It follows from this that although the distribution AChE does not accurately reflect the organization of the septo-dentate projection in normal animals, the intensification of AChE staining provides a good indication of the reorganization which occurs in this pathway following entorhinal deafferentation.

Acetylcholinesterase↗
PubMed1982

A note on the transneuronal transport of wheat germ agglutinin-conjugated horseradish peroxidase in the avian and rodent visual systems.

While using horseradish peroxidase conjugated to the plant lectin wheat germ agglutinin (WGA-HRP) as an anterograde marker to label the developing retinofugal projection in the chick, we have found that a significant amount of the tracer can escape from the axons and axon terminals of retinal ganglion cells and be subsequently taken up and transported both anterogradely and retrogradely by neighboring neurons and/or axon terminals. The release and uptake of the tracer appears to be nonspecific, and is particularly striking at embryonic stages; at these stages there is also appreciable uptake of the WGA-HRP by ependymal cells and by radial glial processes. Subsequent experiments in rats have shown that as early as 2 days after an injection of WGA-HRP into an eye there is clear labeling of geniculo-cortical axons in the striate cortex. Since WGA-HRP is being used increasingly in neuroanatomical studies, it is now clear that when interpreting the results of experiments with this marker the possibility of transneuronal labeling must be borne in mind, and especially after relatively long post-labeling survival periods. At the same time the secondary transport of WGA-HRP may, in certain neural systems, provide a useful tool for analyzing second-order connections.

Age Factors↗
PubMed1982

Production and characterization of monoclonal antibodies against the "brain-specific" proteins 14-3-2 and S-100.

We have raised mouse hybridomas that secrete monoclonal antibodies against bovine brain-specific proteins 14-3-2 and S-100, and we have characterized the antibodies by immunoperoxidase and immunofluorescence methods in sections and in tissue cultures of rat brain. One monoclonal antibody to 14-3-2 (E8.F9) has been found to react strongly with bovine 14-3-2 and with rat neuron-specific enolase in an enzyme-linked immunosorbent assay (ELISA) and to react weakly with rat nonneuronal enolase. This pattern of specificity is reflected in strong neuronal labeling and occasional weak glial labeling in immunocytochemical preparations. After appropriate tissue fixation, E8.F9 could be shown to be localized primarily to the cytoplasm of neurons; with less adequate fixation nuclear labeling was also seen. A monoclonal antibody to the calcium binding protein S-100 (G12.B8) reacted strongly with bovine S-100 in an ELISA and with the major protein bands in electrophoretically separated S-100. In immunocytochemical preparations G12.B8 labeled the cytoplasm of astrocytes. Both antibodies are of the IgG1 subclass. Because of its specificity, the antibody against the S-100 protein promises to be useful as an immunological marker for astrocytes in the adult animal and in mature tissue cultures of brain cells. Although it has been thought that the generally low levels and relatively late appearance of S-100 during ontogeny may restrict its usefulness as a marker for developing astrocytes, preliminary immunocytochemical evidence indicates that G12.B8 selectively labels radial glial cells and astrocytes or astrocyte precursors as early as, or even earlier than, antibodies against the glial fibrillary acidic protein. The antibody against neuron-specific enolase is likely to be of limited use as a neuronal marker because of its crossreactivity with nonneuronal enolase.

Animals↗
PubMed1981

A scanning electron microscope study of the in vitro development of dissociated hippocampal cells.

Cultures of dissociated hippocampal neurons from 18-day-old rat fetuses were examined by scanning electron microscopy after periods between one hour and 20 days following plating on a poly-L-lysine coated substrate. Cell attachment was virtually complete within one hour after plating, and at that stage many cells could be seen which had started to extend processes with broad growth cones. By four hours in culture, process formation was well advanced and some cells had already assumed a pyramidal configuration. After 16 hours in culture, numerous contacts were seen between neighboring growth cones, and this frequently led to fasciculation of the interacting fibers. During the next three weeks the cell bodies enlarged considerably and rounded-up, and two distinct types of processes became evident: large, rapidly tapering dendrite-like processes and finer, essentially uniform-diametered processes that resemble axons. In most of the older cultures a dense plexus of processes was formed, and many of the finer processes appeared to have "bouton-like" swellings as they traversed the upper surfaces of the neuronal perikarya. Non-neuronal elements, which comprised only about 5% of the cells initially plated, rapidly proliferated in our cultures and within three to six days formed a confluent monolayer beneath the neurons.

Animals↗
PubMed1981

Observation on the development of the striatum in mice and rats.

The morphology and development of the striautum (caudate-putamen) have been examined in normal and reeler mice of the C57 BL/6J strain and in Sprague-Dawley rats. The striatum of an adult mouse contains approximately 690,000 neurons on each side and of these about 97% are medium-sized cells and just under 3% are large cells. In adult rats the percentage of large- and medium-sized neurons is about the same, but the total number of neurons is in excess of 1,500,000. Tritiated (3H) thymidine autoradiographic studies indicate that neuronogenesis in the mouse striatum occurs both in the neuroepithelium of the ventricular zone and in the underlying subventricular zone, between the 12th day of gestation and the first few days postnatally, with the peak period of neuronogenesis being on the 14th and 15th embryonic day. In both mice and rats striatal neurons are generated along three distinct gradients: from caudal to rostral, from lateral to medial, and from ventral to dorsal. The large neurons are among the earliest cells generated. A major proportion of the medium-sized neurons is also generated during this period, but proliferation of these neurons continues for at least several days. In the immediate postnatal period there appears to be some turnover of neurons in the striatum, some cells degenerating while others are still being formed. Cell counts indicate that in the rat there may be as many as 2,000,000 neurons in the striatum at postnatal day 4, but that this number is reduced to the adult figure by day 8.

Animals↗
PubMed1981

Evidence that the early postnatal restriction of the cells of origin of the callosal projection is due to the elimination of axonal collaterals rather than to the death of neurons.

By using two fluorescent dyes that are retrogradely transported along axons, we have been able to demonstrate that many of the neurons in the parietal region of the rat cerebral cortex that can be labeled from the contralateral hemisphere early in postnatal development, persist well beyond the period when the callosal projection normally becomes restricted. This indicates that the major factor in the progressive restriction of the callosal projection is the withdrawal or degeneration of axon collaterals, rather than the selective death of many of the cells that initially project to the opposite side.

Animals↗
PubMed1981

Evidence for collateral projections by neurons in Ammon's horn, the dentate gyrus, and the subiculum: a multiple retrograde labeling study in the rat.

Although it has been recognized for some years that each cytoarchitectonic field of Ammon's horn and the subiculum gives rise to a specific pattern of cortical and subcortical projections, it has not been clear whether these various projections arise from different populations of neurons within each field or whether they arise as collaterals from an essentially homogeneous population of cells. We have examined this problem, and the related issue of the origin of the commissural and ipsilateral associational projections of the dentate gyrus, by injecting retrogradely transported fluorescent dyes into two or more of the relevant projection fields in adult rats and subsequently examining the brains for doubly or triply labeled neurons. It is clear from these experiments that at least two of the known efferent projections of field CA1 (to the septum and to the entorhinal cortex) arise from the same pyramidal neurons and also that the commissural, ipsilateral associational, septal, and subicular projections of the other major field of Ammon's horn--field CA3--similarly are due to collaterals. Double-labeling experiments also indicate that at least 80% of the cells in the deep hilar region of the dentate gyrus give rise to both an ipsilateral (associational) and a crossed (or commissural) projection to the dentate granule cells. In contrast, the projection neurons in the dorsal part of the subiculum form a quite heterogeneous population; cells that project to both the septum and the entorhinal area are intermingled with others that project to one or the other area but not to both. The cortical and cortico-subcortical connections of the hippocampal formation thus appear to be quite different from those of the neo-cortex, and the existence of such an extensive system of collateral projections clearly has important consequences for studies of the development of the hippocampus and of its response to selective deafferentation.

Afferent Pathways↗
PubMed1980

The effects of neonatal 6-hydroxydopamine treatment on morphological plasticity in the dentate gyrus of the rat following entorhinal lesions.

Lesions of the entorhinal cortex, which is the major source of afferents to the outer two thirds of the molecular layer of the dentate gyrus, induce an expansion of the commissural projection, which is normally restricted to the inner third, and an intensification of acetylcholinesterase staining in the outer portion of the layer; these changes are thought to be due to the sprouting of the commissural fibers and certain cholinergic afferents to the dentate gyrus, respectively. We have studied these sequelae of entorhinal lesions in young adult rats which had been treated with 6-hydroxydopamine (6-OHDA) as neonates, in order to determine whether in the absence of its normal noradrenergic input, morphological plasticity in the dentate gyrus would be altered either in magnitude or extent. In animals treated with 6-OHDA, the levels of noradrenaline in the hippocampal formation were reduced by 93%. Despite this, there was clear evidence for an expansion of the commissural projection following entorhinal lesions, as judged both autoradiographically and in Timm-stained material. Similarly, the intensification of acteylcholinesterase staining in the outer part of the molecular layer appeared as marked as after comparable lesions in untreated animals. From these observations it would appear that in the dentate gyrus, at least, morphological plasticity does not require the presence of an intact noradenergic innervation.

Acetylcholinesterase↗
PubMed1980

Jerzy E. Rose.

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Bibliographies as Topic↗
PubMed1980

Subcortical afferents to the hippocampal formation in the monkey.

The distribution of neurons in the basal telencephalon, the diencephalon, and the brainstem that project to the hippocampal formation has been analyzed in mature cynomolgus monkeys (Macaca fascicularis) by the injection of horseradish peroxidase into different rostro-caudal levels of the hippocampal formation. After injections which involve Ammon's horn, the dentate gyrus, and the subicular complex, retrogradely labeled neurons are found in the following regions: in the amygdala (specifically in the anterior amygdaloid area, the basolateral nucleus, and the periamygdaloid cortex); in the medial septal nucleus and the nucleus of the diagonal band; in the ventral part of the claustrum; in the substantia innominata and the basal nucleus of Meynert; in the rostral thalamus (specifically in the anterior nuclear complex, the laterodorsal nucleus, the paraventricular and parataenial nuclei, the nucleus reuniens, and the nucleus centralis medialis); in the lateral preoptic and lateral hypothalamic areas, and especially in the supramammillary and retromammillary regions; in the ventral tegmental area, the tegmental reticular fields, the raphe nuclei (specifically in nucleus centralis superior and the dorsal raphe nucleus), in the nucleus reticularis tegmenti pontis, the central gray, the dorsal tegmental nucleus, and in the locus coeruleus.

Afferent Pathways↗