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Biomedical subjects

D E Scott

Publications and source records attributed to D E Scott.

At least 55 records · Page 3Linked to original sources
PubMed1989

Correlative scanning-immunoelectromicroscopic analysis of neuropeptide localization and neuronal plasticity in the endocrine hypothalamus.

Thirty-two Sprague-Dawley rats were divided into four groups, eight rats per group. Animals were hypophysectomized with removal of both the pars distalis and the neural lobe of the neurohypophysis. Groups of eight rats were euthanized 1, 2, 4 and 8 weeks following hypophysectomy and prepared for routine scanning electron microscopy (SEM) and correlative immunoelectron microscopy employing antisera against arginine vasopressin (AVP). Eight normal rats served as controls. In experimental rats that survived one to eight weeks posthypophysectomy, remarkable neuroanatomical alterations were notable in the median eminence and adjacent third cerebral ventricular lumen. In contrast to normal control rats, large numbers of neurites were observed with SEM to insinuate from the lateral recess into the cerebral ventricular lumen and as early as one week following hypophysectomy they overgrew the apical surfaces of ependymal cells that constitute the lining of the cerebral ventricle. Immunoelectron microscopy revealed that a significant proportion of these neurites were magnocellular in origin in that they harbored AVP-positive neurosecretory vesicles. In addition to large numbers of invading magnocellular neurites, neuronal perikayria with apparent axosomatic synapses were observed to emerge upon the thick feltwork of invading axons, the latter of which appeared to freely terminate within the ventricular lumen. AVP-positive axon profiles were, in addition, seen to terminate upon the basal lamina of portal perivascular spaces in the zona externa of the median eminence. These data are consistent with the idea that following hypophysectomy (to include high stalk section of the neurohypophyseal system), that there is rapid, and dynamic sprouting and regrowth of AVP-positive axons into the adjacent third cerebral ventricular lumen and to the contact zone of the median eminence as well. This phenomenon may represent a compensatory physiological response to injury of the neurohypophyseal system characterized by a highly plastic neuroanatomical reorganization of magnocellular elements which appear to utilize the CSF of the third cerebral ventricle as a functional terminus for the neurocisternal secretion of AVP which ultimately enters the systemic circulation.

Animals↗
PubMed1987

The fetal baboon median eminence as a circumventricular organ: I. Transmission electron microscopy.

This investigation has focused upon a set of neuroanatomical correlates that underscore functional changes in the median eminence of the fetal baboon Papio anubis. Eight fetal primate brains were harvested at mid-gestation (100 days post-coitus) and prepared for routine light and transmission election microscopic examination following ventriculo-cisternal perfusion with high osmolarity aldehyde fixatives. The median eminence and other adjacent circumventricular organs (CVO) were blocked and embedded in epon. Routine transmission electron microscopic examination revealed discreet regional differentiation and zonal maturation of the fetal baboon median eminence at 100 days post-coitus. The ependymal and hypendymal zones were anatomically separate from the underlying fibrous and palisade zones of the median eminence. The dominant cell type of the ependymal and hypendymal zones were tanycytes whose apical surfaces constituted the floor of the third cerebral ventricle. The distal processes of tanycytes terminated upon the abluminal basal lamina of well developed perivascular spaces in the contact zone of the fetal median eminence. Numerous axon profiles that harbored both dense core and microvesicles were also observed to terminate upon the system of perivascular spaces that contained numerous fenestrated capillaries. Sharing this common perivascular system were cells of the pars tuberalis that contained numerous secretory inclusions. These data strongly suggest that by mid-gestation the fetal primate median eminence is highly differentiated and may be capable of a wide range of functional activities in response to changes in the maternal-placental environment. The ultrastructural correlates of an active neuroendocrine axis are apparent at this period of development.

Animals↗
PubMed1986

Hypothalamic neuroendocrine correlates of cutaneous burn injury in the rat: I. Scanning electron microscopy.

Rats were given a standard scald burn on 60% of the body surface or only a sham burn and were sacrificed at intervals from 6 hr to 14 days later. Serum thyroxine (T4), free thyroxine index (FT4I) and triiodothyronine (T3) were depressed compared to values in respective shams as early as 6 hr post-burn. T4 and FT4I were less depressed on post-burn days (PBD) 2-3 than on PBD 1 and then exhibited a further fall. T3 remained depressed through PBD 14. Pineal melatonin content was elevated at 6 hr and fell to the normal daytime range in subsequent samples. The ventral portion of the diencephalon was prepared for scanning electron microscopy. Only in the burned rats and beginning on PBD 2, large numbers of supraependymal neurons (SEN) appeared in the ventricular space attached to the inferior walls and floor of the third cerebral ventricle. Transmission electron microscopy was used to confirm the neuronal nature of the SEN. Viewed by scanning electron microscopy, these persisted through PBD 14. SEN were interconnected by cables of their neurites exhibiting varicosities on individual neurites as they passed over perikarya of other SEN. Some SEN were seen to be only partially emerged from the underlying tissue and others were seen to send a thick process into the hypothalamic tissue. These observations indicate that after peripheral injury there is marked plasticity of the brain in an area thought to control the endocrine systems that show abnormalities after such a peripheral injury. The timing, location and nature of these anatomic changes indicate the possibility that at least some aspects of central nervous orchestration of the endocrine metabolic response to injury may be related to the emergence of a neuronal system receiving or sending messages through the cerebrospinal fluid and/or through new neurite circuits along the surface of the third ventricular wall. These structures may appear in response to initial primary hormonal changes and/or may play a role in maintaining the post-injury hormonal milieu manifested in part by a subsequent second fall in serum T4.

Animals↗
PubMed1986

Parent satisfaction with children's medical care. Development, field test, and validation of a questionnaire.

Research on both adult patients and parents of pediatric patients has demonstrated that satisfaction with medical encounters predicts such important outcomes as compliance with medical regimen. The authors developed a questionnaire to measure parent satisfaction with children's medical encounters, administered it to 104 parents of pediatric patients (field trial 1), and revised it. The revised Parent Medical Interview Satisfaction Scale (P-MISS) was then tested on a new sample of parents whose medical visits were videotaped (field trial 2). On field trial 2, the P-MISS showed a high alpha reliability (0.95). The four factor-based subscales identified by field trial 1 showed high alpha reliabilities on field trial 2: physician communication with the parent (0.81); physician communication with the child (0.93); distress relief (0.85); and adherence intent (0.86). With the exception of the distress relief subscale, the subscales appear to measure distinct dimensions of satisfaction. Objective ratings of physicians' interpersonal skills to parents during medical interviews correlated significantly with parents' total satisfaction scores as well as with all four satisfaction subscale scores, providing preliminary evidence of the construct validity of the P-MISS.

Adolescent↗
PubMed1985

Fetal hypothalamic transplants in diabetic rats analysed by scanning electron microscopy.

Adult male Brattleboro rats with chronic diabetes insipidus underwent stereotaxic surgery wherein minced fragments of anterior hypothalamus from fetal rats, 17 days post-coitus, were stereotaxically positioned into the lumen of the host third cerebral ventricle. Host rats with fetal donor tissue were killed at various times following surgery and were prepared for correlative scanning-transmission electron microscopy. Examination with this technique revealed the presence of large neurografts which grew to occupy the entire lumen of the host third ventricle. Grafts were well vascularized and in addition exhibited remarkable numbers of supraependymal, cerebrospinal fluid-contacting neurons. The physical emergence of this cell line in proximity to viable grafts is discussed with respect to the biochemical influences that a neuropeptide producing fetal transplant has upon a peptide-deficient host.

Animals↗
PubMed1984

Fetal hypothalamic transplants: neuronal and neurovascular interrelationships.

This investigation is one of a series aimed at developing an understanding of the neuroanatomical correlates of neuronal and vascular interactions that occur between heterografts of normal fetal hypothalamic tissue transplanted into the third cerebral ventricle of adult Brattleboro rats with homozygous autosomal diabetes insipidus (DI). Rapid vascular invasion of fetal neurografts occurred within 3 days and arose from the mantle plexus of portal capillaries in the underlying host median eminence. Host vessels also invaded from the periventricular stratum and preoptic area. In the ventral regions of heterografts neurites were observed to terminate upon perivascular spaces that surrounded local capillaries. Despite the development of apparently normal neurovascular zones, none of the DI host recipients demonstrated an amelioration of polydipsia or polyuria characteristic of diabeties insipidus.

Angiography↗
PubMed1984

The neuroanatomical and neurovascular organization of normal fetal hypothalamic explants in the third cerebral ventricle of Brattleboro rats with homozygous diabetes insipidus.

This investigation has combined microangiography, immunocytochemistry, coupled with transmission and scanning electron microscopy to discuss the neuroanatomical interactions that occur in the brains of Brattleboro rats with diabetes insipidus, following stereotaxic placement of normal fetal hypothalamic fragments into the third cerebral ventricle. Following surgical placement of 17 day post-coitus hypothalamic fragments, host rats with chronic autosomal homozygous diabetes insipidus were killed and their brains were prepared for analysis. A significant degree of explants (68%) flourished and grew in the lumen of the third cerebral ventricle of recipient hosts. Explants were rapidly invaded by host vessels from two routes. Vessels arose from the underlying mantle plexus of portal capillaries which remained fenestrated in the lower one-third of the explants and developed neurovascular (neurohemal) zones. The second source of vessels arose from bed capillaries of the adjacent paraventricular nucleus and adjacent hypothalamus. In contrast to vessels arising from the contact zone, these latter vessels remained unfenestrated. Small clusters of immunocytochemically positive neurons (neurophysin positive) were seen throughout the explants. Numerous healthy magnocellular neurons harboring numerous dense core vesicles and exhibiting multiple axosomatic and axodendritic synapses were seen throughout the neuropil of explants. Axon profiles were noted to terminate upon the abluminal basal lamina of perivascular spaces surrounding fenestrated capillaries in the lower one third of explants. None of the host animals exhibited physiological return to normal parameters of urine output, drinking behavior, and/or urine osmolarity. However the growth and development of explants in the third cerebral ventricle of DI hosts coupled with the emergence of bonafide neurovascular zones supports a potential anatomical substrate for the central delivery of neuropeptide hormones in this experimental model.

Animals↗
PubMed1984

Neuronal and neurovascular integration following transplantation of the fetal hypothalamus into the third cerebral ventricle of adult Brattleboro rats. Neurological transplants: I.

This investigation has confronted some very basic questions of neurobiology and specifically deals with the neurovascular and neuroanatomical interactions that occur between graft and host following neural transplantation. Host Long-Evans rats with chronic autosomal diabetes insipidus (DI) received stereotaxic implants of normal 17 day post-coitus fetal hypothalamic fragments from the rostral (anterior) hypothalamus of normal Long-Evans pups. Following stereotaxic surgery DI hosts were killed 60 or 90 days later and their brain prepared for correlative microangiography-immunocytochemistry coupled with transmission electron microscopy. Explants were rapidly invaded by host vessels from several routes. (1) Vessels appeared to arise from portal capillaries in the underlying median eminence and (2) from adjacent vessels from the paraventricular nucleus and surrounding endocrine hypothalamus and (3) possibly from intrinsic vessels of the graft. The former remained fenestrated and established bonafide neurovascular zones in the ventral regions and in actively growing explants. Small clusters of arginine vasopressin-positive fibers and neurophysin positive neurons were noted throughout the parenchyma of explants. Despite the presence of neurosecretory neurons and neurovascular (neurohemal) zones, none of the host rats exhibited a physiological return to normal parameters of water balance. However the active growth and development of explants in the third cerebral ventricle of DI host rats coupled with emergence of neurovascular zones lends support to a potential model for analyzing the development of anatomical substrates for the central delivery of neuropeptide hormones.

Animals↗
PubMed1981

Age related changes in the endocrine hypothalamus: I. Tanycytes and the blood-brain-cerebrospinal fluid barrier.

The fine structural organization of the floor of the third cerebral ventricle (dorsum of the median eminence of the hypothalamus) of 2 normal adult mice Fisher 344 rats was compared and contrasted with that of 2 aged rats 30 months old. Closely juxtaposed tanycytes (specialized ependymal cells) of normal young adults in the lower walls and floor of the third ventricle. In contrast, tanycytes in aged rats demonstrated significant intracellular separations, with only fine cytoplasmic processes remaining to interlink them. The phenomenon of mechanical separation between tanycytes in aged animals is discussed with respect to a potential impairment in the integrity of the blood-brain-cerebrospinal fluid barrier.

Aging↗
PubMed1980

Fetal hypothalamic transplants in the third ventricle of the adult rat brain. Correlative scanning and transmission electron microscopy.

Blocks of anterior hypothalamus were transplanted from 19 day-old fetuses of Wistar/Lewis rats into the third ventricle of adult male Brattleboro rats. Physiological changes in graft recipients and in sham-operated animals were monitored daily. Twenty days after surgery, the graft recipients and sham-operated animals were killed and their brains examined by correlative scanning and transmission electron microscopy. Host animals that exhibited both decreased polydipsia and increased urine concentration were found to have viable grafts within the third ventricle. The observed physiological changes suggested that synthesis and release of vasopressin occurred in the transplanted neurons. Grafts were well vascularized by vessels arising from the host hypothalamus. Neurons, with perikarya ranging from 8 to 30 micron in diameter, glial cells, and neurites were located throughout the transplants. A neurohemal contact zone, similar to that normally seen in the median eminence, could not be demonstrated in the grafts. The absence of complete glial and ependymal barriers indicates a relatively close association between cells in the transplants and the cerebrospinal fluid. A large increase in supraependymal neurons and their processes, including an eruption of neurons through the floor of the third ventricle in one animal, was observed in graft recipients but not in sham-operated animals.

Animals↗
PubMed1980

Simultaneous monoamine histofluorescence and neuropeptide immunocytochemistry: I. Localization of catecholamines and gonadotropin-releasing hormone in the rat median eminence.

Adjacent tissue sections through the rat median eminence were examined for the distribution of gonadotropin-releasing hormone (GnRH) and catecholamines (CA). A simultaneous visualization technique was employed for this correlative neuroanatomical analysis. At rostral and mid-central levels of the median eminence the majority of GnRH terminals do not appear in coexistence with CA terminals; the latter were confined to the outer-most 10 micrometers of the median eminence while the densest concentration of GnRH terminals was located internal to this layer. However, individual GnRH fibers appeared to penetrate the outer CA zone wherein they were found in juxtaposition to portal capillaries. At caudal levels of the median eminence, there was an extensive overlap of CA and GnRH varicosities adjacent to the tubero-infundibular sulcus. In addition, numerous GnRH terminals were seen adjacent to portal vessels. The differences in the positions of CA and GnRH terminals between rostral and caudal median eminence may provide a morphological basis for the hypothesis of separate regulatory mechanisms for CA upon GnRH secretion at these two levels of the median eminence.

Animals↗
PubMed1979

The tanycyte of the rat median eminence. I. Synaptoid contacts.

The present ultrastructural study proves the existence of nerve terminals closely apposed to the plasmalemmata of tanycytes in the rat median eminence. Several of these "axo-tanycytic" endings display remarkable accumulations of agranular endoplasmic reticulum in the form of pleomorphic vesicles which are closely apposed on either side of the plasma membrane of each cell compartment. Some of these vesicular profiles give the impression of structural continuity across both membrane systems. This phenomenon is discussed in the context of being a potential substratum for communication between both cell compartments.

Animals↗
PubMed1978

Ultrastructural localization of radiolabelled L-dopa in the endocrine hypothalamus of the rat.

Light and electron microscopic autoradiography has been employed to define the neuroanatomical patterns of uptake and binding of radiolabelled L-dopa in the endocrine hypothalamus of the rat. A dorsomedial continuum of arcuate and periventricular neurons selectively sequester 3HL-dopa 20 min following its intraventricular infusion. By 40 and 60 min following the infusion labelling of neurons is minimal and supports the notion of rapid degradation. Other cell compartments such as tanycytes demonstrate uptake of 3H L-dopa. The ultrastructural localization and distribution of radiolabelled L-dopa (or its metabolites) in the rodent hypothalamus is discussed with respect to mechanisms and cell compartments involved in neuroendocrine regulatory processes.

Animals↗