Biomedical subjects

M Stewart

Publications and source records attributed to M Stewart.

At least 307 records · Page 17Linked to original sources

PubMed1991

Cloning and sequencing of rat plectin indicates a 466-kD polypeptide chain with a three-domain structure based on a central alpha-helical coiled coil.

We have determined the complete cDNA sequence of rat plectin from a number of well-characterized overlapping lambda gt11 clones. The 4,140-residue predicted amino acid sequence (466,481 D) is consistent with a three-domain structural model in which a long central rod domain, having mainly an alpha-helical coiled coil conformation, is flanked by globular NH2- and COOH-terminal domains. The plectin sequence has a number of repeating motifs. The rod domain has five subregions approximately 200-residues long in which there is a strong repeat in the charged amino acids at 10.4 residues that may be involved in association between plectin molecules. The globular COOH-terminal domain has a prominent six-fold tandem repeat, with each repeat having a strongly conserved central region based on nine tandem repeats of a 19-residue motif. The plectin sequence has several marked similarities to that of desmoplakin (Green, K. J., D. A. D. Parry, P. M. Steinert, M. L. A. Virata, R. M. Wagner, B. D. Angst, and L.A. Nilles. 1990. J. Biol. Chem. 265:2,603-2,612), which has a shorter coiled-coil rod domain with a similar 10.4 residue charge periodicity and a COOH-terminal globular domain with three tandem repeats homologous to the six found in plectin. The plectin sequence also has homologies to that of the bullous pemphigoid antigen. Northern blot analysis indicated that there is a significant degree of conservation of plectin genes between rat, human, and chicken and that, as shown previously at the protein level, plectin has a wide tissue distribution. There appeared to be a single rat plectin gene that gave rise to a 15-kb message. Expression of polypeptides encoded by defined fragments of plectin cDNA in E. coli has also been used to localize the epitopes of a range of monoclonal and serum antibodies. This enabled us to tentatively map a sequence involved in plectin-vimentin and plectin-lamin B interactions to a restricted region of the rod domain.

Amino Acid Sequence↗

PubMed1991

Noninvasive cerebral optical spectroscopy for monitoring cerebral oxygen delivery and hemodynamics.

OBJECTIVE: To present an algorithm for noninvasive measurement of cerebral oxygen saturation (cerebral oximetry) and cerebral hemodynamics with near infrared spectroscopy. DESIGN: In vitro correlation of oximetry measurements with reference measurements; illustrative cases of hemodynamic and oximetric recordings. SETTING: Tertiary care neuroscience ICU. PATIENTS: Brain-injured patients with a prolonged, decreased level of consciousness chosen as illustrative examples. INTERVENTIONS: Two-channel multiple wavelength diffuse infrared transmission spectroscopy was interfaced with the scalp using adhesive. Transmission data were collected with gross superficial-to-deep spatial resolution. Saturation calculation based on the deep signal was observed longitudinally in the patient. With the same technology, arterial input and cerebral response functions, generated by iv tracer bolus, were deconvoluted to measure mean cerebral transit time. MEASUREMENTS AND MAIN RESULTS: A positive linear regression fit between diffuse transmission oximetry and measured blood oxygen saturation over the range 23% to 99% (r2 = .98, p less than .001) was noted. CONCLUSIONS: The approach used overcomes previously identified difficulties with cerebral oximetry, and demonstrates excellent in vitro correlation. The technique can be performed clinically without difficulty. A simultaneous measure of mean cortical transit time is possible.

Brain↗

PubMed1991

Cerebral oxygen metabolism measured during hypothermic circulatory arrest: a case report.

Infrared transmission spectroscopy was used to detect changes in cerebral oxy- and deoxyhemoglobin attenuation of infrared light in a patient undergoing circulatory arrest at 15 degrees C. Wavelength specific attenuation was used to determine hemoglobin oxygen saturation in the cerebral vasculature using a previously described paradigm. The fate of the residual oxygenated hemoglobin in the cerebrovascular compartment was followed during 15 min of circulatory arrest at 15 degrees C, and cerebral oxygen metabolism was identified as the progressive desaturation of this hemoglobin. The aggregate arterial and venous saturation fell from a normal value of 70% to an abnormally low value of 50%. Reperfusion resulted in near normalization of cerebrovascular oxygen saturation over 5 min, but evidence of persistent mild desaturation below prearrest baseline followed reperfusion. This case demonstrates both continued cerebral oxygen metabolism under hypothermic, circulatory arrest conditions and a cerebral oxygen delivery-consumption mismatch during reperfusion.

Journal Article↗

PubMed1991

Reversal of unconsciousness by use of naloxone in a profoundly mentally handicapped epileptic.

The reversal of a state of impaired consciousness in a known epileptic following a period of prolonged post-ictal unconsciousness (with flexor response to nociceptive stimuli) was achieved by use of 0.4 mg naloxone intravenously. This decision was based on the similarity of the individuals clinical presentation to that seen in cases of opiate overdose. The implications of this dramatic clinical intervention are discussed.

Adult↗

PubMed1991

Behaviour of severely malnourished children in a Jamaican hospital.

The behaviour of 18 children with severe malnutrition between the ages of six and 24 months was observed. They were compared with 21 age-matched adequately nourished children in hospital with other diseases, and were given regular developmental assessments with the Griffiths test. On admission to hospital the malnourished children were less active and more apathetic than the controls when alone in their cots, while the controls were more distressed. When given toys, initially the malnourished children explored them less, using fewer play actions and touching fewer toys. These differences were not present on recovery. Initial behaviour did not predict later developmental levels.

Brain Damage, Chronic↗

PubMed1991

Macromolecular structure and aggregation states of Helicobacter pylori urease.

Urease purified from Helicobacter pylori by differential ultracentrifugation and fast pressure liquid chromatography was composed of subunits with apparent molecular weights (MrS) of 66,000 and 30,000. Electron microscopy of this purified material demonstrated that it formed disc-shaped macromolecular aggregates that were approximately 13 nm in diameter and 3 nm thick. Images of both negatively stained and shadowed preparations indicated that the discs tended to stack to form pairs and then these pairs further aggregated to form four-disc stacks. This stacking of subunits explains the heterogeneity observed previously in the molecular weight of urease preparations. In some negatively stained preparations there were also some smaller (approximately 8-nm-diameter) annular units present, which may represent individual urease units or possibly an aggregate of one of the two subunits from which urease is constructed.

Helicobacter pylori↗

PubMed1991

Nuclear factor 1 activates the feline leukemia virus long terminal repeat but is posttranscriptionally down-regulated in leukemia cell lines.

A recombinant feline leukemia virus (FeLV) proviral clone (T17T-22) with a long terminal repeat (LTR) which differs from prototype FeLV by a point mutation within a conserved nuclear factor 1 (NF1)-binding motif in the LTR enhancer domain was found to be poorly expressed after DNA transfection. The NF1 point mutation reduced in vitro protein binding as assessed by gel shift analysis and reduced promoter activity significantly (2- to 10-fold). However, the degree of promoter impairment due to the NF1 site mutation varied according to cell type and was least severe in a feline leukemia cell line (T3) which had low levels of nuclear NF1 DNA-binding activity. Low NF1 DNA-binding activity was observed in three FeLV-induced leukemia cell lines (T3, T17, and FL74) and in murine F9 embryonal carcinoma cells. While similar levels of NF1 gene mRNA transcripts were detected in all cell lines, Western immunoblot analysis of F9, T17, and FL74 but not T3 nuclear extracts revealed very low levels of nuclear NF1 protein. These results indicate that NF1 activity is down-regulated in FeLV-induced leukemia cells by diverse posttranscriptional mechanisms. We suggest that NF1 down-regulation may be an important characteristic of target cells susceptible to FeLV transformation in vivo and may provide the selective pressure which favors duplication of the LTR core enhancer sequence in T-cell leukemogenic FeLV variants.

Animals↗

PubMed1991

Regional cerebrovascular oxygen saturation measured by optical spectroscopy in humans.

Regional cerebrovascular oxygen saturation, a quantitative measure of hemoglobin saturation in the combined arterial, venous, and microcirculatory compartments of the brain, can be measured noninvasively with near infrared spectroscopy. We assessed the sensitivity of this aggregate saturation to cerebral hypoxia during transient cerebral hypoxic hypoxia in seven human subjects. Regional cerebrovascular oxygen saturation measured over the middle frontal gyrus and analog electroencephalogram were recorded. We compared the time to achieve two end points: the earliest paroxysmal burst of theta-delta background slowing and a cerebrovascular oxygen saturation of less than 55%. Saturation fell below 55% prior to the electroencephalographic change (p less than 0.05). In a related effort, we also compared spectroscopically measured regional cerebrovascular oxygen saturation with an estimate of this value calculated from arterial and cerebral mixed venous saturation in nine patients. A positive linear relation (n = 68, R2 = 0.55, s = 4.2) was noted.

Adult↗

PubMed1991

Body dysmorphic disorder and the DSM-IV: the demise of dysmorphophobia.

Dysmorphophobia is a controversial term. It is not a phobia, reliable data on it are few, and many authors write about it without attempting to define it. DSM-III-R introduced the term "body dysmorphic disorder" to describe a non-psychotic condition in which there is pathological preoccupation with physical appearance and with the intention of replacing the term "dysmorphophobia". However, psychiatrists continue to use the word dysmorphophobia, often unaware that it may have several distinct meanings. This article, 1. demonstrates the current confusion in terminology, 2. elaborates on DSM-III-R's concept of body dysmorphic disorder, and 3. suggests refinements for the DSM-IV description.

Adolescent↗

PubMed1991

The Nithsdale schizophrenia surveys. VIII: Do relatives want family intervention--and does it help?

Sixty-three relatives of 52 schizophrenics living at home were offered a package of treatments by professionals working in an everyday NHS setting: educational seminars, relatives' groups, and family meetings. Thirty-two relatives refused intervention. Of the 31 relatives who agreed, 14 attended neither the educational seminars nor the relatives' groups. Seventeen relatives had a mean of ten treatment sessions, but there was little change in their level of expressed emotion after intervention. The number of patients who relapsed was the same in the 18 months before and after intervention, although the total number of relapses fell after intervention.

Adolescent↗

PubMed1991

The Scottish survey of old long-stay in-patients.

A total of 2605 old long-stay patients, defined as those admitted to hospital before the age of 65 years and in hospital more than six years, were identified in psychiatric hospitals serving 83% of the Scottish population. The bed occupancy was 59 per 100,000 of the general population, with a range among hospitals of 19-123 per 100,000. Of all patients, 64% were schizophrenic and 15% had organic brain disease; most patients were male, single and over 60 years of age; 41% had been in hospital more than 30 years; 61% had either florid psychotic symptoms or symptoms of a deficit state in marked or severe degree, and the rehabilitation potential for 70% was low. An increasing prevalence of deficit symptoms in schizophrenics was associated with increasing length of stay in hospital; the difference was most marked between those admitted before and after 1953.

Adult↗

PubMed1991

Epirubicin at two dose levels with prednisolone as treatment for advanced breast cancer: the results of a randomized trial.

Two hundred eleven patients with advanced breast cancer were randomized to receive either epirubicin (E) 50 mg/m2 and prednisolone (LEP) or E 100 mg/m2 and prednisolone (HEP). The intended treatment consisted of 16 courses of LEP or eight courses of HEP given at 3-weekly intervals. Reasons for stopping treatment early included progressive disease, stable disease without symptomatic improvement, or severe toxicity deemed intolerable by either the patient or physician. Toxicity was recorded at 3-weekly and response at 9-weekly intervals using the World Health Organization (WHO) criteria of response and toxicity. Two hundred nine patients were eligible for analysis, 98% of whom have been followed for more than a year. One hundred four patients received LEP and 105 HEP. Significantly worse myelosuppression, alopecia, nausea and vomiting, and mucositis were seen in the high-dose arm (P less than or equal to .001). More patients in the LEP arm stopped treatment before the fourth course than in the HEP arm, and the commonest reason for stopping was progressive disease. A similar median number of courses was given in each arm. There was a significantly higher response in the HEP arm (HEP - complete response [CR] + partial response [PR] = 41%, LEP - CR + PR = 23%). Despite this, no statistically significant differences was seen in overall survival or progression-free interval. The median survival for HEP and LEP was 44 and 46 weeks, respectively.

Adult↗

PubMed1991

Nuclear envelope dynamics and nucleocytoplasmic transport.

We have combined structural, biochemical and recombinant DNA methods to explore molecular interactions involved in nuclear envelope assembly dynamics and nucleocytoplasmic transport. Electron microscopy has established the overall architecture of the envelope and the relationship between nuclear pores, lamina fibres and pore-connecting fibrils. The lamin proteins that constitute the lamina resemble intermediate filament proteins, and assemble and disassemble during mitosis in response to phosphorylation. Lamins have been expressed in E. coli to facilitate structural investigations and the exploration of interaction sites with other envelope components. Disruption of envelopes has shown that nuclear pores are constructed from a central cylinder with cytoplasmic and nucleoplasmic rings. Examination of envelopes transporting gold-labelled nucleoplasmin has indicated that the transport pathway is complex and probably involves ring components in addition to the central cylinder. Molecular motors may be involved in changes in pore shape to enable transport and in the translocation mechanism.

Animals↗

PubMed1991

Molecular basis of myosin assembly: coiled-coil interactions and the role of charge periodicities.

Complementation of alternating zones of positive and negative charge in the myosin rod enables molecules to interact in a number of ways. This accounts for the complexity of the molecular organisation of thick filaments. However, directed mutagenesis of expressed LMM cDNA indicated that charge zone complementation is not a major driving force in myosin polymerisation. Instead, it probably serves to prevent unfavourable interaction geometries.

Electrochemistry↗

PubMed1991

Expression in Escherichia coli of human lamins A and C: influence of head and tail domains on assembly properties and paracrystal formation.

We have expressed in Escherichia coli cDNA corresponding to human lamins A and C, together with a number of fragments produced using site-specific mutagenesis. The proteins produced in this way were characterised both biochemically and ultrastructurally, and appeared to retain their native conformation. Crosslinking showed that all fragments formed 4-chain molecular dimers ('tetramers') analogous to those formed by intact intermediate filament proteins. Shadowed preparations showed the presence of rod-like particles that closely resembled those observed for other intermediate filament proteins and their proteolytically prepared rod domains. Moreover, the expressed lamins and a series of fragments in which different domains had been deleted formed paracrystals similar to those observed with native material. Deletion of either the N- or C-terminal non-helical domains altered the solubility and aggregation properties of the expressed protein, indicating that both domains have a role in lamin assembly.

Cloning, Molecular↗

PubMed1991

Expression in Escherichia coli of fragments of the coiled-coil rod domain of rabbit myosin: influence of different regions of the molecule on aggregation and paracrystal formation.

We have expressed in Escherichia coli a cDNA clone corresponding broadly to rabbit light meromyosin (LMM) together with a number of modified polypeptides and have used this material to investigate the role of different aspects of molecular structure on the solubility properties of LMM. The expressed material was characterized biochemically and structurally to ensure that it retained the coiled-coil conformation of the native molecule. Full-length recombinant LMM retained the general solubility properties of myosin and, although soluble at high ionic strength, precipitated when the ionic strength was reduced below 0.3 M. Constructs in which the 'skip' residues (that disrupt the coiled-coil heptad repeat) were deleted had solubility properties indistinguishable from the wild type, which indicated that the skip residues did not play a major role in determining the molecular interactions involved in assembly. Deletions from the N terminus of LMM did not alter the solubility properties of the expressed material, but deletion of 92 residues from the C terminus caused a large increase in solubility at low ionic strength, indicating that a determinant important for interaction between LMM molecules was located in this region. The failure of deletions from the molecule's N terminus to alter its solubility radically suggested that the periodic variation of charge along the myosin rod may not be as important as proposed for determining the strength of binding between molecules and thus the solubility of myosin.

Amino Acid Sequence↗

PubMed1991

Travelling for earlier surgical treatment: the patient's view.

As part of the northern region's programme within the national waiting list initiative, schemes have been funded to test the feasibility and acceptability of offering patients the opportunity to travel further afield in order to receive earlier treatment. A total of 484 patients experiencing a long wait for routine surgical operations in the northern region were offered the opportunity to receive earlier treatment outside their local health district; 74% of the patients accepted the offer. The initiative was well received by the participating patients and the majority stated that if the need arose on a future occasion they would prefer to travel for treatment rather than have to wait for lengthy periods for treatment at their local hospital. These findings, interpreted in the light of the National Health Service reforms introduced in April 1991, suggest that for some types of care, patients would welcome greater flexibility in the placing of contracts, not merely reinforcement of historical patterns of referral.

Adolescent↗

PubMed1991

Medical audit--why children attend out-patient clinics.

Ten thousand new out-patient referrals are made each year to the out-patient department of the Royal Belfast Hospital for Sick Children. A prospective study of a random sample of 295 (4%) of these children was undertaken to determine their reason for referral and the outcome of their attendance. The stated reason for referral was for investigation/diagnosis (45%), therapeutic advice (47%) or parental reassurance (6%). Non-attenders (10%) could not be predicted from the referral letter. Twenty-four per cent were found to have no abnormality. Significantly more children referred for parental reassurance and infants were included in this category. Less than half (45%) had investigations performed. These were mainly non-invasive with plain x-rays and urinalysis accounting for 44%. Consultant medical staff saw 53% of new referrals and requested more investigations but were less likely to review patients. The information obtained is used to suggest ways in which more rational use of hospital resources might be achieved without decreasing the standard of care to these children.

Ambulatory Care Facilities↗