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Biomedical subjects

M E Smith

Publications and source records attributed to M E Smith.

At least 181 records · Page 10Linked to original sources
PubMed1994

Sulfate metabolism of rat P0 glycoprotein: some observations.

It has been known for some time that P0, the major intrinsic protein in PNS myelin, contains sulfate. The position of sulfate has been described for beef PNS myelin, but rat PNS myelin differs somewhat from that of the beef, therefore an investigation of the location of sulfate in rat P0 was undertaken. Weanling rat nerves were incubated with [3H] amino acid mixture and [35S]O4, and purified myelin was prepared, and the proteins separated on polyacrylamide gels. The bulk of the [35S]O4 was incorporated into P0, but smaller peaks of sulfate label were found in the higher molecular weight proteins. With tunicamycin in the incubation mixture, sulfate incorporation was inhibited. Incubation of the labeled myelin mixture with endo F or glycanase resulted in total loss of sulfate label on P0, therefore all of the [35S]O4 was incorporated into the oligosaccharide chain, with none on the polypeptide. Castanospermine and deoxymannojirimycin inhibited [35S]O4 incorporation into P0, but no inhibition was exerted by swainsonine. These results indicate that sulfate resides in the core of the oligosaccharide chain, with none in the terminal region. Such a structure would correlate with the lack of an HNK-1 epitope, absent in the rat, but found in P0 of many species.

Animals↗
PubMed1994

POMC neuropeptides and their receptors in the neuromuscular system of wobbler mice.

The pro-opiomelanocortin-derived peptides, beta-endorphin (beta-EP), ACTH and alpha-MSH act in concert to promote synaptogenesis and nerve growth in the neuromuscular system. Immunocytochemistry was used to detect the peptides in triceps muscles of normal developing and adult mice and in adult wobbler mice with motor neurone disease. Immunoreactivity for beta-EP and alpha-MSH/ACTH was present in some intramuscular motor nerves. There was a significantly higher proportion of immunoreactive nerves in the muscles of the developing and the diseased mice than in the normal adults. ACTH and beta-EP receptors were revealed using autoradiography. Specific binding sites for 125I-labelled ACTH and 125I-labelled beta-EP were present in some fibres in all muscles examined. There were significantly higher proportions of fibres exhibiting specific beta-EP and specific ACTH binding sites in the muscles of the developing and the diseased mice compared to the muscles of normal adults. It seems likely that the high incidence of immunoreactive nerves and of muscle fibres with the peptide receptors in the developing and diseased mice reflects the trophic actions of the peptides in the neuromuscular system.

Adrenocorticotropic Hormone↗
PubMed1994

Upregulation of the pro-opiomelanocortin gene in motoneurons after nerve section in mice.

In the normal adult mouse a few of the ventral horn motoneurones were slightly immunoreactive for the pro-opiomelanocortin (POMC)-derived peptides beta-endorphin (beta-EP) and alpha-melanotropin (alpha-MSH). After unilateral section of the sciatic nerve the incidence of immunoreactive cells and the intensity of staining increased in both the ipsilateral and the contralateral ventral horns. The proportion of cells which expressed the peptides reached a maximum at approximately 24 h after nerve section, and thereafter declined, but the proportion was still higher than normal at 7 days after the section. Using histochemical in situ hybridization with cDNA oligonucleotide probes for POMC transcript regions which encode for adrenocorticotropin (ACTH) 4-11 and beta-endorphin 1-8, POMC mRNA was detected in very few motoneurones in unoperated or sham operated mice. After unilateral sciatic nerve section increases in the proportion of cells which expressed the POMC mRNA were seen in both the ipsilateral and contralateral ventral horns. The increase, like that seen for peptide immunoreactivity, was maximum at around 24 h and thereafter declined but at 7 days after the section the proportion of POMC mRNA-positive cells had returned to normal. Thus injury to the motoneurones is accompanied by synthesis of POMC-derived peptides via upregulation of the POMC gene in the motoneurone.

Animals↗
PubMed1994

Structural characterisation of Na2ZrO3.

A combination of X-ray and electron diffraction, electron microscopy and solid-state nuclear magnetic resonance (NMR) has been used to elucidate the structure and the ordering of Na2ZrO3. The diffraction data confirm a monoclinic crystal structure. A sample prepared by a conventional solid-state reaction of the components is shown by both X-ray diffraction and electron microscope imaging to have an extremely high concentration of planar defects associated with stacking disorder of the planes along the c-axis. The incidence of these defects is significantly reduced in a sample recrystallised from a bismuth oxide flux. NMR indicates that the local coordinations are well defined in both samples but with some sharpening of the spectra from the recrystallised sample indicative of the increase of long-range order. The 23Na magic angle spinning (MAS) NMR spectra clearly show three distinct sites with widely differing quadrupolar interaction parameters that can be related to the known site symmetries. Two distinct oxygen resonances are observed in the MAS NMR spectrum from an 17O-enriched sample while the static 91Zr NMR spectrum can be simulated with one set of interaction parameters.

Magnetic Resonance Spectroscopy↗
PubMed1994

Nurses' responses to patient anger: from disconnecting to connecting.

Caring for angry patients can be a threatening experience. Grounded theory research was used to explore female nurses' reactions and feelings as the recipients of patient anger. The data were collected by interviewing nine female registered nurses in two hospitals in south-western Nova Scotia. The participants were asked to discuss their feelings and responses to an intense encounter with an angry patient. Anger was defined as a multi-dimensional concept with negative cogitations. The concept of self-efficacy emerged as the major area of concern for the participants. The findings suggest that when the threat to self was high, nurses managed anger situations by disconnecting from the angry patient. Low or controllable threats were generally managed by connecting with the angry patient.

Adaptation, Psychological↗
PubMed1994

Acrodermatitis chronica atrophicans: a case report and review of the literature.

We report a 55-year-old woman with acrodermatitis chronica atrophicans (ACA) and a peripheral sensory neuropathy. ACA is an uncommon late cutaneous manifestation of Lyme disease, which follows disseminated Borrelia burgdorferi infection. This is the second published case from the U.K. since serological diagnosis has been available. In this patient the diagnosis was confirmed by serology using a sensitive enzyme-linked immunosorbent assay and immunoblotting techniques. B. burgdorferi DNA was demonstrated in the affected skin using the polymerase chain reaction, although staining and cultures for the organism were negative. Recommended treatment of ACA is with oral doxycycline 100 mg twice daily for 28 days, but our patient did not respond well to this regimen. She was therefore treated with ceftriaxone intravenously for 21 days, which resulted in a rapid symptomatic and clinical response.

Acrodermatitis↗
PubMed1994

Retinoblastoma.

Retinoblastoma (RB) is the most common intraocular malignancy of childhood, occurring in approximately 1 in 20,000 live births. It arises from pluripotential retinal progenitor cells. Mutations of the RB1 gene interfere with regulation of the cell cycle. Patients who harbor a germinal mutation of the RB1 gene are at risk for the development of second, non-ocular tumors.

Child, Preschool↗
PubMed1994

Upregulation of the POMC gene in rats by a neurotoxicant which targets motoneurones.

Immunocytochemistry and histochemical in situ hybridisation were used to detect POMC-derived peptides (beta-endorphin and alpha-MSH) and POMC mRNA respectively, in the lumbar spinal cord of adult rats. In normal rats the incidence of ventral horn cells which expressed the peptides or mRNA was negligible. However after treatment with IDPN a neurotoxicant which targets the motoneurones the peptides and POMC mRNA were detectable in over 65% of ventral horn motoneurones. After treatment with 1,3 DNB a neurotoxicant which does not target motoneurones immunostaining for the peptides and mRNA was negligible. Thus chemical intoxication of the motoneurones causes upregulation of the POMC gene.

Animals↗
PubMed1994

A whole-person sampler for assessing numbers of host-seeking adult mosquitoes.

The whole-person bag sampler (WPBS) is a human-baited drop-net mosquito trap for evaluating an individual's exposure to nuisance mosquitoes. A diagram of WPBS construction is given, with results from field tests. Trap operator exposures of 2, 4, and 8 min did not result in a corresponding increase in mosquitoes caught in the WPBS, although simultaneous captures using a sweep net or Nasci aspirator increased with the sample duration. The person baiting and operating the trap did not have a significant effect on number of mosquitoes captured. Taxonomic diversity of adult mosquitoes collected with WPBS and CO2-baited traps was similar, with Aedes vexans predominant in the study areas.

Aedes↗
PubMed1993

Upregulation of the pro-opiomelanocortin gene in spinal motoneurones in muscular dystrophy in mice.

Pro-opiomelanocortin (POMC) mRNA was detected in motoneurones of mice using histochemical in situ hybridization and cDNA oligonucleotide probes for the adrenocorticotropin (ACTH) 4-11 and beta-endorphin 1-8 regions of POMC. Staining for POMC mRNA was negligible in motoneurones in normal adult mice but in dystrophic mice the mRNA was present in > 60% of the ventral horn cells. It is concluded that neuropathic change in motoneurones is accompanied by upregulation of the POMC gene and synthesis of POMC-derived peptides.

Adrenocorticotropic Hormone↗
PubMed1993

Phagocytosis of myelin by microglia in vitro.

Previous experiments from this laboratory have shown that peritoneal macrophages in culture will phagocytize myelin. Myelin preopsonized with myelin antibodies is phagocytized to a much greater extent than untreated myelin, indicating that macrophages ingest myelin by an Fc receptor. The present work was undertaken to determine the characteristics of myelin phagocytosis by microglia, the resident macrophages of the central nervous system. Microglia isolated from 4-5 day primary cultures of newborn rat brains were shown to bind and phagocytize myelin labeled in the lipids by 14C-acetate. Both binding and phagocytosis as shown by the appearance of 14C-cholesterol ester were greatly increased if labeled myelin was preopsonized with antiserum to myelin basic protein or galactocerebroside. Both preopsonized and untreated myelin were phagocytized more actively by microglia than by peritoneal macrophages under the same culture conditions. Microglia cultured in the presence of GM-CSF showed slightly increased cholesterol ester production from opsonized myelin, but the effect of GM-CSF was significantly greater than myelin pretreated with control serum (34% increase) or untreated myelin (154% increase). There was no significant effect of GM-CSF on myelin phagocytosis by peritoneal macrophages. Cerebrospinal fluid containing immunoglobulin drawn from rabbits with acute EAE also opsonized myelin to increase phagocytosis by microglia, as has been previously shown with peritoneal macrophages. These results indicate that microglia may actively participate in myelin destruction in demyelinating diseases where myelin antibodies or a source of GM-CSF may be present.

Animals↗
PubMed1993

Clinical worsening in multiple sclerosis is associated with increased frequency and area of gadopentetate dimeglumine-enhancing magnetic resonance imaging lesions.

It is now well established that clinically stable patients with relapsing-remitting multiple sclerosis have ongoing disease activity when evaluated by serial gadolinium-enhanced (Gd-DTPA) magnetic resonance imaging (MRI) scans. Despite this, the relationship between clinical disease and MRI lesions, though suspected, has not been extensively documented. The relationship between Gd-DTPA MRI lesions and clinical disease was examined in this study of 9 patients with mild relapsing-remitting multiple sclerosis (Expanded Disability Status Scale [EDSS] < 3.5) who had 24 to 37 monthly Gd-DTPA MRI scans, neurological examinations, and EDSS score assignments. The area and frequency of Gd-DTPA lesions were examined during months with and without clinical worsening as measured by EDSS. Forty-one episodes of clinical worsening were noted during the study. A significant association was observed between these periods of clinical worsening and MRI parameters, including increases in total number, number of new lesions, and the total area of enhancement. Logistic regression analysis showed a significant effect of the number and area of Gd-DTPA MRI lesions on both the onset and continuation of clinical worsening, confirming an important relationship between clinical disease and an increase in cerebral Gd-DTPA MRI activity. A relationship with long-term disability was suggested, but cannot be confirmed without longer follow-up of these patients.

Adult↗