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Biomedical subjects

W D Stewart

Publications and source records attributed to W D Stewart.

At least 19 recordsLinked to original sources
PubMed1996

Graft-versus-host reaction affecting lesional skin but not normal skin in a patient with piebaldism.

A case of graft-vs.-host disease (GVHD) arising solely within an area affected by piebaldism is described. The patient, a 35-year-old woman with a single hypopigmented patch on the right leg present since birth, had received an allogeneic bone marrow transplant (BMT) from an HLA-identical sibling donor, for treatment of a myelodysplastic syndrome (MDS). Beginning on day +38 post-BMT, the patch developed changes which were histologically consistent with GVHD. Syngeneic mixed epidermal cell-lymphocyte reaction (MECLR) testing of tissue from the patch, and from adjacent normal skin, showed differences which suggest that piebaldism-affected skin is immunologically different from normal skin. These findings may offer new insight into the pathophysiology of this disorder.

Adult↗
PubMed1995

Eosinophilic ulcer of the oral mucosa.

BACKGROUND: The eosinophilic ulcer is a rare lesion of the oral mucosa that has been infrequently described in the literature. OBJECTIVE: We attempted to characterize the history, demographics, clinical features, histologic features, pathogenesis, and treatment of the eosinophilic ulcer. METHODS: We observed three new cases of eosinophilic ulcer and reviewed the English-language literature. RESULTS: Eosinophilic ulcer occurs in any age group, without sex preference. The most common site in the oral cavity is the tongue, and the average size at diagnosis is 1.6 cm2. These lesions are often ulcerated, may be tender, and are sometimes multiple. The histologic features are characteristic but likely represent a spectrum of related disorders. Most eosinophilic ulcers will resolve spontaneously within a month. Recurrences are uncommon (< 15%). CONCLUSION: The eosinophilic ulcer is a benign, self-limited, reactive process of the oral mucosa of unknown origin. Its histologic features are characteristic but may be confused with atypical histiocytic granuloma and angiolymphoid hyperplasia with eosinophilia or, more importantly, lymphoma. This condition most likely represents a spectrum of related disorders with overlapping clinical and histologic features. After the diagnosis has been histologically confirmed, conservative management is suggested.

Adolescent↗
PubMed1992

Eccrine syringofibroadenomatosis: a clinical and histologic study and review of the literature.

A 56-year-old man had an 11-year history of a psoriasiform eruption of the palms, soles, and shins. An examination revealed well-demarcated patches and plaques of erythematous, fissured, and hyperkeratotic skin with focal erosions. There was no clinical evidence of ectodermal dysplasia. On histologic examination these lesions proved to be eccrine hamartomas that consisted of anastomosing cords and strands of cuboidal epithelial cells with well-formed ducts and a fibrovascular mucinous stroma. Eccrine ductal origin was indicated by histopathologic, histochemical, immunopathologic, and electron microscopic evaluation. These multiple palmoplantar eccrine hamartomas, unassociated with ectodermal dysplasia, represent a sporadic hamartomatous condition that is best designated as "eccrine syringofibroadenomatosis."

Adenofibroma↗
PubMed1991

A 12-month treatment of severe psoriasis with acitretin: results of a Canadian open multicenter study.

Both etretinate and its principal metabolite, acitretin, are efficacious in the treatment of psoriasis. Because patients with severe psoriasis often require chronic therapy, this study was undertaken to determine the efficacy, tolerability, and safety of acitretin in patients on continuous treatment for 12 months. The initial daily dose of 50 mg was taken for 4 weeks. Thereafter the dose was increased or decreased by 10 mg at monthly intervals (10 to 70 mg) to produce the optimal response with minimal toxicity. Seventy percent of the patients who completed 12 months of treatment showed marked improvement. All patients experienced adverse reactions; dry lips, hair loss, skin peeling, pruritus, and nail disorders were the most frequent. Fourteen patients were withdrawn from the study because of one or more intolerable adverse reactions.

Acitretin↗
PubMed1991

Performance characteristics for an immunoassay.

In the United States of American the medical device amendments of 1976 established a comprehensive system for regulation of medicaldevices intended for human use. One provision of the amendmentsestablishes three categories (classes) of devices depending on the regulatory controls needed to provide reasonable assurance of safety and effectiveness. The categories are as follows: Class I, General Controls; Class II, Performance Standards; and Class III, Premarket Approval. The performance characteristics of an immunology device that requires premarket approval (CLASS III) may be viewed as an extension of successfully completed scientific and laboratory investigations. Clinical trials of the device establish analyte levels in well-defined populations of healthy and diseased individuals and provide an estimate of the central tendency of analyte range. The performance characteristics of an immunoassay kit are established by laboratory studies, these studies include but are not limited to the following studies: reproducibility, recovery, linearity, stability, specificity, and sensitivity.

Antibodies↗
PubMed1989

Pilot study of etretinate in psoriatic arthritis.

A 2-center pilot study compared clinical and laboratory outcomes in 40 patients with psoriatic arthritis before and after treatment for 8 to 24 weeks with the vitamin A derivative, etretinate. The number of tender joints fell from 22.0 +/- 8.75 before treatment to 11.44 +/- 8.50 after treatment (p = .000). The duration of morning stiffness was 101.95 +/- 62.45 min before therapy and 44.53 +/- 82.10 min after treatment (p = 0.0004). Similar highly clinically and statistically significant improvement was seen in all clinical outcome measures and in the erythrocyte sedimentation rate. Primarily mucocutaneous side effects were seen in 39/40 patients and resulted in treatment termination before 24 weeks in 9 patients.

Arthritis↗
PubMed1988

Insertion sequence IS2 in the cyanobacterium Chlorogloeopsis fritschii.

A cloned DNA fragment, previously demonstrated to encode ribulose bisphosphate carboxylase/oxygenase (RuBisCO) of Chlorogloeopsis fritschii strain CCAP1411/1b, is shown also to include the entire transposable element, IS2, normally a resident in the Escherichia coli genome. Southern-blot hybridisation experiments confirm the presence of IS2 in the C. fritschii genome. This finding adds a new and unrelated species to the known host range of this element and provides evidence of genetic transfer between the Gram-negative E. coli and cyanobacteria. This may also have significance in relation to the nucleotide sequence rearrangements known to occur adjacent to RuBisCO and nif genes in other nitrogen-fixing cyanobacteria.

Base Sequence↗
PubMed1986

Proline inhibits N2-fixation in Anabaena 7120.

The uptake and metabolism of proline by Anabaena 7120 is demonstrated. Uptake is linear over the first hour and it appears that the rate of proline oxidation is sufficient to account for growth is suggested by the finding that exogenous proline represses heterocyst differentiation and inhibits nitrogen fixation in Anabaena 7120, without affecting growth rate.

Cyanobacteria↗
PubMed1985

Studies on the regulation and function of the Klebsiella pneumoniae ntrA gene.

The ntrA gene from Klebsiella pneumoniae has been cloned and the product identified as a 76-kDal acidic polypeptide. An ntrA::lacZ fusion was used to demonstrate that expression of ntrA is not controlled by the nitrogen regulation (ntr) system and is independent of the nitrogen status of the cell. Studies with multicopy plasmids carrying ntrA and rpoD suggest that the ntrA product competes with the rpoD product (sigma 70 of RNA polymerase) in mediating transcription initiation by RNA polymerase at ntrA-dependent promoters. No significant homology between ntrA and rpoD was detected by Southern blotting.

Bacterial Proteins↗
PubMed1984

Purification and characterization of thioredoxin from the N2-fixing cyanobacterium Anabaena cylindrica.

Thioredoxin has been purified to homogeneity from the cyanobacterium Anabaena cylindrica. The protein consists of a single polypeptide chain with a relative molecular mass of about 11 680 which has two cysteine residues (residues 31 and 34) in the sequence-Cys-Gly-Pro-Cys- and an isoelectric point at pH 4.55. The N-terminal amino acid sequence of 39 residues shows distinct homologies with the sequences of Escherichia coli and Corynebacterium nephridii thioredoxins. Anti-(A. cylindrica thioredoxin) antiserum was used to quantify the thioredoxin which constituted about 0.22% of the soluble protein in cell-free extracts of N2-fixing, NO3- -grown or NH4+-grown A. cylindrica. Activation of fructose-1,6-bisphosphatase of A. cylindrica, activation of glutamine synthetase and NADP+-dependent malate dehydrogenase of the green alga Scenedesmus obliquus but not of A. cylindrica, and deactivation of glucose-6-P dehydrogenase of the cyanobacterium Anabaena variabilis were all achieved using the same thioredoxin species. No other thioredoxin species were detected in extracts of A. cylindrica when examined for the activation of these enzymes.

Amino Acid Sequence↗
PubMed1984

Multiple melanomas occurring in a patient with xeroderma pigmentosum.

Xeroderma pigmentosum (XP) is associated with an increased frequency of cutaneous malignancies including malignant melanoma. We report a patient who developed eleven primary melanomas and numerous highly atypical nevi in addition to the basal cell carcinomas and squamous cell carcinomas more commonly seen in patients with XP.

Adult↗
PubMed1984

The effect of suspended particulate material on cyanobacteria--cyanophage interactions in liquid culture.

The effect of the lytic phage LPP-DUN1 on the cyanobacterium Plectonema boryanum has been investigated in batch and in continuous cultures in the presence and absence of silt. In batch culture Plectonema without added phage grew normally; the presence of phage caused rapid lysis of the cyanobacterium and the addition of silt prevented lysis by the phage. In continuous culture the numbers of cyanobacterial cells and phage particles oscillated in a reciprocal manner, but the addition of silt damped down the oscillations in Plectonema biomass without decreasing the numbers of phage particles isolated from the cultures. The presence of silt thus appears to protect the cyanobacterium from lysis by phage, although the total numbers of phage particles are relatively unaffected by the silt, at least in the short-term.

Bacteriophages↗
PubMed1983

The role of specific cations in regulation of cyanobacterial glutamine synthetase.

Purified glutamine synthetase from the cyanobacterium Anabaena cylindrica required a divalent cation for activity. Maximum biosynthetic activity required Mg2+ (25 mM when supplied alone). Co2+ and Mn2+ each supported up to 20% of this activity; 12 other cations tested were ineffective. At 2.5 - 10 mM Mg2+, 0.1 mM Co2+ or ethylene glycol-bis-(beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA) stimulated GS activity to maximum rates; other divalent cations (particularly Mn2+) inhibited Mg2+-dependent activity. At 5 mM Mg2+ the Kappm for NH+4 (0.05 mM) was 20-fold lower than at 25 mM Mg2+; added Co2+ did not markedly alter this low Km for NH+4; this could be physiologically important.

Ammonia↗
PubMed1982

Nitrogenase activity and membrane electrogenesis in the cyanobacterium Plectonema boryanum.

The relationships between nitrogenase activity (acetylene reduction) and the transplasmalemma proton electrochemical potential gradient (delta muH+) have been investigated using the non-heterocystous filamentous cyanobacterium Plectonema boryanum. By selectively modifying the chemical (delta pH) and electrical (delta psi) components of delta muH+ under conditions in which the size of the ATP pool remained unaffected, nitrogenase activity was found to be dependent on, or regulated by delta psi. When the ATP pool decreased, concomitant with a decreased internal pH (pHi) the requirement for delta psi was modified. The observed reduction in the intracellular ATP pool and the decreased ATP:ADP ratio also correlated with an inhibition of nitrogenase activity. The data are consistent with a model in vivo in which reductant supply to nitrogenase is regulated by, or dependent on an energised plasmalemma and where there is a fine balance between the supply of reductant and ATP for nitrogenase activity. The correlation observed between delta psi and nitrogenase activity extends our previous observations using the heterocystous cyanobacterium Anabaena variabilis.

Adenosine Diphosphate↗
PubMed1981

Characterization of the transport of potassium ions in the cyanobacterium Anabaena variabilis Kütz.

Interrelationships between potassium-ion transport and transplasmalemma electrical-potential difference (delta psi m) have been investigated in Anabaena variabilis (ATCC 29413) by measuring K+ translocation and membrane potential in parallel. At pH 7.0, 5 mmol . dm-3 external K+, there was a thirtyfold accumulation of K+. The K+ equilibrium potential was lower (more negative) than the measured membrane potential by up to 20 mV, (delta psi K+ = -90 mV; delta psi m = -70 mV to -75 mV, respectively). Dark pretreatment and low temperature (4 degrees C) reduced internal K+ and depolarized delta psi m. External pH affected K+ translocation and membrane potential; delta psi m was hyperpolarized at high external pH; transplasmalemma K+ fluxes and internal K+ concentration were also increased at high pH. The effects of pH upon delta psi m, coupled with the finding that the membrane potential was relatively insensitive to external K+, suggest that delta psi m is unlikely to be due primarily to a diffusion potential of K+, but that the membrane potential is maintained by an electrogenic proton-extrusion mechanism. There was no close (obligate) link between K+ transport and changes in delta psi m. Carbonylcyanide m-chlorophenylhydrazone decreased K+ fluxes, internal K+ and delta psi m when added in amounts up to 100 mumol . dm-3. However, delta psi K+ was always more negative than delta psi m. Valinomycin up to concentrations of 50 mumol . dm-3 increased transplasmalemma K+ fluxes by up to 300%, while changes in delta psi m were negligible. Internal K+ was unaffected by valinomycin. N,N'-Dicyclohexylcarbodiimide at concentrations up to 100 mumol . dm-3, reduced K+ flux rates and caused a hyperpolarization of delta psi m. These observations suggest that delta psi m is primarily due to electron transport reactions at the plasmalemma and that K+ transport is energy-dependent. In the presence of dicyclohexylcarbodiimide, internal K+ redistributed in accordance with the membrane potential, suggesting that passive uniport in response to delta psi m (i.e. secondary active transport) is not usually important but may operate when primary active mechanisms are blocked.

Biological Transport, Active↗