Biomedical subjects

V Mitchell

Publications and source records attributed to V Mitchell.

16 recordsLinked to original sources

PubMed1992

GABAergic afferents modulate proenkephalin mRNA expression in the guinea pig hypothalamic magnocellular dorsal nucleus.

The proenkephalin (PE) gene expression within Met-enkephalin (ME) neurons of the guinea pig magnocellular dorsal nucleus (MDN) was measured following activation of GABAergic transmission by aminooxyacetic acid treatment (AOAA). A combination of preembedding ME immunocytochemistry and PE in situ hybridization was used to investigate PE mRNA and enkephalin immunoreactivity levels. In perikarya of the MDN, chronic AOAA-treatment resulted in an important decline in PE mRNA signal (-128%). In double-labeled neurons, the PE mRNA decrease was associated to an increase in ME immunoreactivity. These results indicate that the increase in ME immunoreactivity in the MDN following AOAA-treatment is not due to a rise in PE gene transcription. This study provides additional morphological evidence supporting a role for GABA in modulating the enkephalinergic hypothalamoseptal tract of the guinea pig.

Aminooxyacetic Acid↗

PubMed1992

Localization of mu opioid receptors on the membranes of nerve endings and tanycytes in the guinea-pig median eminence by electron microscopic radioautography.

The high density of opioid-containing nerve endings in the median eminence together with the absence of direct effects of opioids upon pituitary suggest a local action of opioids in the median eminence. The aim of this work was to address the occurrence of mu-opioid binding sites in the median eminence at the electron microscopic level, using the highly selective radioligand [125I]FK 33-824. mu-Opioid receptors were labeled in vitro on slightly prefixed slices of mediobasal hypothalamus. The labeling was essentially detected in the external part of the median eminence. Most of the silver grains overlaid membrane appositions. Two overall types of appositions were concerned: nerve terminal-nerve terminal or nerve terminal-tanycyte. Detailed analysis of the silver grain distribution indicated that mu receptors were observed on membranes of different types of nerve endings but also of tanycytes. All the binding sites were localized out of synaptic junctions since the median eminence is totally devoid of these structures. Our results suggest that in the median eminence, opioid peptides have a paracrine and/or autocrine action occurring at least via mu receptors located on nerve terminals but also on tanycytes.

Animals↗

PubMed1992

Continuous subarachnoid infusion of 0.125% bupivacaine for analgesia during labour.

We have studied 20 primiparous women requesting pain relief for labour, to determine the feasibility of subarachnoid infusions of bupivacaine for analgesia. A 28-gauge catheter was inserted into the subarachnoid space through a modified 22-gauge Sprotte needle. After a bolus dose of up to 1.5 ml of 0.25% bupivacaine, a continuous infusion of 0.125% bupivacaine was commenced. If analgesia became inadequate, additional 0.5-ml boluses of 0.25% bupivacaine were given (mean number of top-ups 2.8; range 0-6). Persistent perineal pain occurred in four women and this was relieved by 0.5% hyperbaric bupivacaine. Analgesia was good or excellent in 15 of 20 mothers within 10 min and in 19 of 20 within 30 min, and it remained good or excellent throughout labour and delivery. Motor block was complete in three of the women who needed hyperbaric 0.5% bupivacaine. There were no difficulties with insertion of the catheter, no episodes of significant hypotension (systolic arterial pressure less than 100 mm Hg) or postdural puncture headache. Seven mothers delivered their babies vaginally, eight required assistance with forceps and five needed a Caesarean section.

Adolescent↗

PubMed1992

Comparison of fiberendoscopy and Watson capsule for small intestinal biopsy in infants and children.

We analyzed the results of 607 small bowel biopsies performed over a seven-year period: 284 biopsies were obtained using a fiberendoscope and 323 biopsies using a Watson capsule. Three to six specimens were removed during endoscopy. The biopsy fragments obtained with the fiberendoscope were deeper than those obtained with the Watson capsule (p less than 0.0001) and were more often located in the duodenum (p less than 0.0001). The failure rate of the fiberendoscope biopsies (1%) was lower than for the Watson capsule biopsies (9%) (p less than 0.0001). Multiple biopsies increased the diagnostic value of fiberendoscopy which was 95% versus 85% for Watson capsule. The mean duration of the endoscopic procedure recorded in 30 children was 6.5 min for four to six samples, i.e. 1.5 min per biopsy specimen. Fiberendoscopy appears to be an efficient and safe method for performing small bowel biopsies in infants and children.

Adolescent↗

PubMed1992

Combination of immunocytochemistry and in situ hybridization in the same semi-thin sections: detection of Met-enkephalin and pro-enkephalin mRNA in the hypothalamic magnocellular dorsal nucleus of the guinea pig.

We describe a procedure for combining pre-embedding peroxidase immunocytochemistry with pre-embedding autoradiographic in situ hybridization in the same vibratome sections of paraformaldehyde-fixed brain tissue. The simultaneous detection of Met-enkephalin (Met-enk)-immunoreactive product and pro-enkephalin (PE) mRNA in neurons of the magnocellular dorsal nucleus (MDN) in the guinea pig hypothalamus was carried out as a model for this procedure. Vibratome slices were processed for Met-enk immunodetection followed by the incubation with a 45-base synthetic oligonucleotide complementary to PE mRNA labeled with 35S. Tissues were embedded in araldite, cut into semi-thin sections, and processed for autoradiography. Many neurons double labeled for Met-enk and PE mRNA were viewed in the MDN. The histological quality and the spatial resolution of both signals were optimized, since precise intracellular localization of hybridization sites was possible. This method allows simultaneous study of peptide immunoreactivity and mRNA expression levels in neurons within the same semi-thin sections. It may be useful for a variety of quantitative analyses, and might also be extended to ultrastructural analysis.

Animals↗

PubMed1991

GABA and enkephalin in the lateral septum of the guinea pig: light and electron microscopic evidence for interrelations.

Tract tracing techniques combined with immunohistochemistry in rats and guinea pigs have demonstrated the existence of a hypothalamo-lateral septum enkephalinergic pathway. Numerous enkephalinergic nerve endings encompass cell bodies located in the lateral septum. The present immunocytochemical study, at light and electron microscopic levels, was undertaken in the guinea pig brain to determine whether the contacted perikarya contain gamma-aminobutyric acid (GABA). The antisera against GABA revealed the presence of immunoreactive cell bodies throughout the lateral septum. At the light microscopic level, most GABA neurons appeared round while others were oval with one or two emerging dendrites. Ultrastructurally, cell bodies displayed a moderate number of organelles and a pale nucleus with frequent indentations of the nuclear envelope. The precise relationship between GABA neurons and enkephalinergic terminals was examined by means of a double-immunostaining method showing that 60% of cell bodies receiving synaptic inputs from enkephalinergic afferents contained GABA. These results show that the hypothalamo-septal enkephalinergic pathway prominently innervates GABA-containing neurons and also provide anatomical basis suggesting a disinhibitory role for this enkephalinergic tract.

Animals↗

PubMed1991

Use of human keratinocytes cultured on fibrin glue in the treatment of burn wounds.

Keratinocytes isolated from a small skin biopsy and cultured according to the method of Rheinwald and Green (Cell 1975, 6: 331) are able to undergo rapid expansion in vitro and have been used successfully in the treatment of burn wounds. One of the inconveniences of this method involves the transfer of the epidermal sheet from the culture flask onto the wound bed. One way to facilitate this process is to use fibrin glue (Biocol) as a culture bed for the keratinocytes. Burns are then grafted by simply placing the sheet of fibrin glue and keratinocytes onto the wound bed. This process has been successful in two patients, permanently covering areas of 720 cm2 and 5342 cm2. The newly formed epidermis was fully differentiated and histologically normal after 1 year. The efficiency of this improved, faster procedure could lead to a new approach in the treatment of extensive burn wounds.

Adult↗

PubMed1990

Effects of inhibition of GABA catabolism by aminooxyacetic acid on enkephalinergic neurons--immunocytochemical and ultrastructural study in the enkephalinergic hypothalamoseptal tract of the guinea-pig.

The immunocytochemical and ultrastructural features within [Met]enkephalin neurons of the guinea-pig hypothalamoseptal tract were investigated under chronic inhibition of GABAergic catabolism. This was achieved by raising the brain GABA concentration with aminooxyacetic acid which inhibits GABA-transaminase, the enzyme responsible for the catabolism of GABA. Guinea-pigs were injected intraperitoneally with 10 or 20 mg/kg per day aminooxyacetic acid for two, four or eight days and killed 16 h post-dose. Repeated injections of aminooxyacetic acid produced a great increase in immunoreactivity for GABA in nerve endings surrounding enkephalinergic perikarya in the magnocellular dorsal nucleus of the guinea-pig. Extensive immunocytochemical studies stressed the increase and redistribution of the immunoreaction for [Met]enkephalin in the perikarya of the magnocellular dorsal nucleus under such GABAergic activation. Quantitative and statistical analyses showed that administration of aminooxyacetic acid for eight days significantly increased the intensity of labelling within stimulated perikarya (P less than 0.001). A concomitant accumulation of immunopositive large granules in the enkephalinergic boutons of the lateral septum was observed. In the same way, ultrastructural changes in enkephalinergic cell bodies were analysed and reflected disturbances in the biosynthetic and digestive activities of enkephalinergic perikarya. We postulate that chronic inhibition of the GABAergic catabolism leads to modification in the metabolism of enkephalinergic neurons and to an inhibitory action of GABA on the [Met]enkephalin release from nerve endings. This study give morphological support to the complex functional interactions between GABA and opioid peptide transmitter system.

Aminooxyacetic Acid↗

PubMed1990

A clinical trial of two parenteral nutrition solutions in neonates.

Sixty eight neonates requiring total or supplemental parenteral nutrition in the first week of life were randomly allocated either Vamin 9 glucose (n = 34) or MB233G (n = 34) in a double blind trial. Twenty infants were withdrawn: four because they died before 5 days of age and 16 because the amino acids were required for less than the five days of the trial. The solutions were isocaloric (1.6 MJ/l, 380 kcal/l) and with the same nitrogen content (2.79 g/l) and were infused at rates and volumes determined by clinical staff on the basis on the infants, clinical condition and serum electrolyte biochemistry. There was an excess of deaths in the group treated with Vamin 9 glucose particularly related to babies weighing greater than or equal to 1000 g. Infants less than 1000 g receiving the Vamin 9 glucose preparation required amino acids for twice as long. There was no significant difference between the weight losses or head circumference during the study period. Plasma aminograms in the group receiving Vamin 9 glucose showed concentrations of phenylalanine, tyrosine, proline, serine, and aspartic acid to be significantly higher than the reference range. Multiple regression analysis suggested that phenylalanine was the primary abnormality. The intravenous amino acid preparation MB233G maintained the plasma aminogram of newborn infants within the reference range of normal newborn infants.

Amino Acids↗

PubMed1989

Use of antithrombotic drugs in the treatment of acute ischemic stroke: a survey of neurologists in practice in the United States.

In an attempt to determine the opinions and practices of neurologists regarding the use of antithrombotic drugs in the treatment of acute ischemic stroke, we conducted a survey of 349 randomly selected neurologists from throughout the United States. Responses were received from 247 (71%), and 219 identified themselves as primary or consulting physicians for patients with acute ischemic stroke. During the previous 12 months, these 219 physicians estimated that they had seen a total of 14,636 patients within 24 hours of acute ischemic stroke, and 22% of these patients were treated with heparin. The most frequently reported indications were prevention of recurrent cerebral embolism (82% of physicians) and progressing stroke (70%). Despite the frequent use of heparin, only 6.4% of neurologists felt that it has been shown to be effective, and 16.4% felt that it has been shown to be of no value. The primary concern about the use of heparin was lack of proven efficacy in 48% and safety concerns in 41%. Results of a future trial testing the efficacy of antithrombotic drugs would be useful for most neurologists in their management of patients with acute or progressing ischemic stroke.

Acute Disease↗

PubMed1988

GABA axon terminals in synaptic contact with enkephalin neurons in the hypothalamus of the guinea pig. Demonstration by double immunocytochemistry.

By using a method combining pre-embedding immunoperoxidase staining for enkephalin and postembedding immunocolloidal gold labeling for gamma-aminobutyric acid (GABA) it has been demonstrate that many GABAergic boutons made synapses on enkephalin-reacting soma in the magnocellular dorsal nucleus of the guinea pig hypothalamus. The gold particles revealing the presence of GABA were essentially located over the small clear vesicles and mitochondria present in these GABAergic nerve endings. All the synapses observed were symmetrical. Taking into account the great number of these nerve endings, we conclude for a strong regulatory role of GABA on enkephalin-containing cells of the magnocellular dorsal nucleus.

Animals↗

PubMed1988

Catecholamine innervation of enkephalinergic neurons in guinea pig hypothalamus: demonstration by an in vitro autoradiographic technique combined with a post-embedding immunogold method.

To study the relationship between the catecholamine (CA) nerve endings and the enkephalinergic cell bodies in the magnocellular dorsal nucleus (MDN) of guinea pig hypothalamus, double-labeling experiments were performed on the same tissue section at the electron microscopic level. An in vitro autoradiographic (ARG) method for [3H]-norepinephrine (NE) or [3H]-dopamine (DA) was combined with a post-embedding immunogold cytochemical technique for Met-enkephalin (Met-enk) in colchicine-treated animals. Hypothalamic slices (450 micrograms) were perfused with [3H]-NE or [3H]-DA at the fluid-gas interface, then fixed by immersion with glutaraldehyde and osmic acid. Semi-thin sections processed from the thickness of the slices showed adequate penetration of the tracers to all parts of the tissue. Frontal sections permitted visualization of some CA-uptake structures distributed around the cells. At the ultrastructural level, preservation appeared good on about 60% of the thickness of slices, and [3H]-CA structures were easily distinguished. Ultra-thin sections were successively incubated with Met-enk and colloidal gold-labeled antisera, followed by ARG processing. At the electron microscopic level, the good integrity of the tissue made possible visualization of [3H]-CA nerve terminals making synaptic contacts with enkephalinergic perikarya. These results provide morphological evidence for direct catecholaminergic control of enkephalinergic neurons of the MDN.

Animals↗

PubMed1988

[Intestinal biopsy: fiberscopy or Watson's capsule?].

We compared the results of 100 fiberendoscopic small bowel biopsies (F) with those of 100 Watson capsule biopsies (W). Three to 6 specimens were obtained during endoscopy. The F biopsy fragments were deeper than the W biopsies (P less than 0.001). The F biopsies were more often located in the duodenum than the W biopsies. The failure rate of the F biopsies (3%) was lower than for the W biopsies (12%): P less than 0.02. Multiple biopsies increased the diagnostic value of fiberendoscopy, which was 85% in our experience versus 77% for Watson capsule. The duration of the endoscopic procedure, available in 15 children, was 6.5 min for 4 to 6 samples, i.e. 1.5 min by specimen. Small bowel fiberendoscopy appears to be a safe and accurate method for performing small bowel biopsies in infants and children.

Adolescent↗

PubMed1985

Lives of women who became autonomous.

We examine the lives and growth processes of women who have achieved considerable development of personality. Subjects of study are seven women in a longitudinal sample who, at ages 42-45, are classified by the Loevinger Sentence Completion Test at the highest ego-levels. As a way of describing their lives, all seven are analyzed in terms of Levinson's model of male development, one case is presented in terms of Gilligan's model of female development, another in terms of Loevinger's general model, and linkages among theories are observed. Characteristics of Loevinger's autonomous stage are illustrated and the extent to which they are gender-related is discussed. Findings show that women with very different personalities, problems, and ways of life can attain a high level of ego-development; that their lives tend not to have been orthodox or easy; and that theories of adult development are useful but uneven in application.

Adaptation, Psychological↗

PubMed1978

Personality.

Explore the source record for details and available documents.

Career Choice↗

PubMedDate not supplied

Precise diagnosis of infection in burn wound biopsy specimens. Combination of histologic technique, acridine orange staining, and culture.

This study developed a rapid manual histologic technique on burn wound biopsy specimens for an early diagnosis of infection. A total of 86 biopsy specimens were processed using this rapid manual method, acridine orange fluorescent staining for the detection of microorganisms, and a quantitative culture for the identification and counting of bacteria in adjacent homogenized biopsy specimens. Use of these three techniques has shown their complementarity for the evaluation of sepsis in burn wound patients. The histologic study allowed a classification of the depth of bacterial involvement 4 hours after specimen collection, whereas the acridine orange fluorescent staining was useful for quantitative evaluation of infection in the same delay. Thus a rapid therapeutic decision can be made while waiting for the results of quantitative culture and sensitivity tests, which require 24 to 48 hours. We propose routine monitoring of burned patients consisting of these three tests performed simultaneously on each biopsy specimen.

Acridine Orange↗