Biomedical subjects

V Mitchell

Publications and source records attributed to V Mitchell.

8 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↗

PubMed1978

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