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P S Thomas

Publications and source records attributed to P S Thomas.

At least 19 recordsLinked to original sources
PubMed1992

Purification, primary structure, bacterial expression and subcellular distribution of an oocyte-specific protein in Xenopus.

This study defines a novel Xenopus laevis protein (P100) that has recently been shown to be recognized by scleroderma patient sera. Using a combination of differential solubility in detergents, hydroxyapatite chromatography and one-dimensional PAGE, P100 was purified to apparent homogeneity and the amino acid sequence was obtained. An oligonucleotide derived from this sequence was used to clone P100 cDNA through a polymerase-chain-reaction cloning strategy. The entire P100 cDNA sequence was determined, identifying a novel 83,000-Da protein. Two alleles for P100 were transcribed in the oocyte, with only one predicted amino acid change between them. Bacterial expression of a clone containing the entire P100 coding region produced a protein that migrated at a mass 15% greater than that predicted from the amino acid sequence, indicating an aberrant electrophoretic mobility. The mRNA transcript for P100 was only expressed during the previtellogenic stages of oogenesis (stages I and II) and was absent from other Xenopus tissues. Similarly, the P100 protein was found only in Xenopus oocytes and was localized to the cytoplasm of these cells. P100 irreversibly bound single-stranded-DNA--cellulose but not double-stranded-DNA--cellulose. These data demonstrate the presence of a novel oocyte-specific protein in Xenopus.

Amino Acid Sequence↗
PubMed1992

Tobacco smoke releases performed mediators from canine mast cells and modulates prostaglandin production.

The role of an extract of tobacco smoke in activating mast cells was studied. With the use of isolated, canine mast cells as a model, we found that cigarette smoke solution (CSS) induced the release of the performed mediators histamine and tryptase from these cells in an energy- and temperature-dependent, non-cytotoxic manner. There was no requirement for extracellular calcium. Nicotine tartrate did not reproduce the effect of CSS. Interestingly, mast cells produced little prostaglandin D2 (PGD2) in response to the CSS, and there was a concentration-related inhibition of calcium ionophore A23187-induced PGD2 synthesis. This suggests at least two mechanisms acting on the mast cell: tobacco smoke can directly activate mast cells to release performed mediators and can simultaneously inhibit prostaglandin production. These observations suggest a mechanism by which mast cells may participate in the bronchospastic and proinflammatory changes seen in the lungs and airways of smokers.

Animals↗
PubMed1992

Prostaglandin D2 production and identification of prostaglandin H synthase within canine mast cell granule.

We have identified the presence of functional prostaglandin H synthase (PGH synthase, E.C. 1.14.99.1, or cyclooxygenase) within canine mast cell granules by demonstrating the generation of prostaglandin (PG) D2 from isolated and purified granules incubated with substrate as arachidonic acid or stimulated with calcium ionophore, A23187. This confirms the presence of both enzyme and substrate within the granule. Localization of PGH synthase to the granule was confirmed by immunoblotting of the pure granule preparation and by immunocytochemistry using the whole cell. In functional studies, colchicine, a microtubule polymerization inhibitor, caused a fall of up to 70%, both in the amount of histamine released and in the amount of PGD2 generated. This suggests either that functional PGH synthase is closely associated and coactivated with granules or that there is an independent association of this enzyme with the microtubule system. Release of the preformed and newly formed mediators of the mast cell appear to be closely linked, and prevention of degranulation may therefore attenuate the effects of both classes of mediators.

Animals↗
PubMed1992

Dog mastocytoma cells produce transforming growth factor beta 1.

Transforming growth factor-beta (TGF beta) promotes deposition of extracellular matrix and is associated with fibrotic conditions both in experimental animals and in humans. Although a role for mast cells has been suspected in the pathogenesis of fibrosis, no potent mediator capable of stimulating fibroblast growth or extracellular matrix deposition has been identified in mast cell supernatants. We report here the constitutive production of TGF beta 1 by four dog mastocytoma cell lines. TGF beta 1 was identified by characteristic biologic activity, blockade of biologic effect by specific neutralizing antibody, and by recognition of a band with the appropriate migration by western blot. TGF beta 1 mRNA, but not TGF beta 2 or TGF beta 3 mRNA, was also produced constitutively by all four cell lines. Quantitation by bioassay revealed baseline TGF beta secretion of approximately 1 ng/10(6) cells over 48 h. Stimulation of mastocytoma cells with phorbol ester increased the rate of release of TGF beta 1, most markedly in the first 30 min after stimulation, without increasing TGF beta 1 mRNA. Dog mastocytoma cells produced TGF beta 1 primarily in a latent form, inactive until treated with acid. Both pure TGF beta 1 and TGF beta-containing mastocytoma cell-conditioned media inhibited mitogenesis and proliferation in dog mastocytoma cell lines, suggesting that mast cell tumor lines would not grow preferentially based on their ability to produce TGF beta. These studies may make possible further investigation of the mechanism by which mast cells contribute to the induction of fibrosis.

Animals↗
PubMed1991

La/SSB ribonucleoprotein levels increased in transformed cells.

Autoantibodies to the La/SSB ribonucleoprotein are commonly found in patients with Sjögren's syndrome. Previous studies have shown that La/SSB accumulates in cells shortly after viral infection. We have extended these studies by investigating levels of the La/SSB antigen in virally and spontaneously transformed cell lines (contact-insensitive and tumourigenic) relative to their non-transformed counterpart cell lines (contact-sensitive and non-tumourigenic). Transformed BALB/3T12-3 and KNRK fibroblasts were visibly brighter by immunofluorescence assay than non-transformed BALB/3T3 and NRK fibroblasts respectively, when reacted with anti-La/SSB specific sera. This was confirmed by flow cytometry, as La/SSB levels were elevated in the transformed counterparts of the same cell lines. An anti-Sm monoclonal antibody and normal human serum reacted with these cell lines failed to show a significant increase by flow cytometry. Finally, a two-fold increase in the La/SSB antigen was demonstrated in cell lysates of these cell lines by a capture ELISA. These data show that La/SSB is elevated in transformed cell lines compared with non-transformed counterpart cell lines and suggest that this increase is not restricted to viral transformation.

Animals↗
PubMed1991

An oral treatment for lead toxicity.

Chronic lead poisoning has traditionally been treated by parenteral agents. We present a case where a comparison of ethylene diaminetetra-acetic acid was made with 2,3-dimethyl succinic acid (DMSA) which has the advantage of oral administration associated with little toxicity and appeared to be at least as efficacious.

Administration, Oral↗
PubMed1991

Heterogeneity of intact granules purified from canine mastocytoma cell lines.

We investigated the observation that some mast cells exhibit asynchronous release of granule-associated neutral proteases. Intact mast cell granules were isolated, purified, and studied with respect to their histamine, neutral protease, and proteoglycan content. Studies of two canine mastocytoma cell lines demonstrated differences in storage and packaging of granules within one of the cell lines (G) with respect to the neutral proteases and density, resulting in two distinct subpopulations of granules. By use of identical techniques no such differences were found in the other cell line (BR). These observations suggest that granule subpopulations in some mast cells may have a role in the differential release of mediators.

Animals↗
PubMed1990

Atrial natriuretic peptide in primary pulmonary hypertension.

Plasma levels of atrial natriuretic peptide (ANP) were determined during cardiac catheterization in nine patients with primary pulmonary hypertension (PPH) and the effect of prostacyclin infusion via a right heart catheter studied. The role of hypoxia on the release of ANP was investigated in a control group of six normal subjects who underwent an acute hypoxic challenge. Patients showed the typical haemodynamic changes of primary pulmonary hypertension with elevation of mean (SD) pulmonary artery pressure, 71.3 (13.8) mmHg, and low cardiac index, 1.9 (0.5) l.min-1.m-2. Plasma ANP was also elevated; mean pulmonary artery plasma ANP was 96.3 (77.6) pmol.l-1 in PPH patients compared with mean venous plasma ANP of 8.9 (5.6) pmol.l-1 in normal subjects. Prostacyclin infusion in PPH patients and hypoxic challenge in normal subjects did not significantly alter plasma ANP levels. The elevated levels of ANP in PPH are due to the altered haemodynamics secondary to increased pulmonary vascular resistance and may be responsible for the lack of peripheral oedema seen in this condition.

Adult↗
PubMed1990

Pain clinic #15. Treatment of sciatic nerve causalgia following pelvic fracture.

Direct injury to the sciatic nerve may occur in patients who sustain acetabular/pelvic fractures. Sciatic nerve causalgia has been noted in patients who suffer posterior wall acetabular fracture with or without ipsilateral hip dislocation. Sympathetic nervous system dysfunction is considered the primary cause for this syndrome, although some investigators suggest central nervous system involvement. This report documents the treatment results of three patients suffering from sciatic nerve causalgia who were referred to the Pain Treatment Center during the past year. In each case, diagnosis was confirmed by sympathetic blockade. Treatment regimens varied and included nerve blocks, cryoanalgesia techniques, and transcutaneous electrical nerve stimulation therapy. The syndrome was relieved in these patients within four to six weeks. Patients were followed for six months after initial treatment.

Adolescent↗
PubMed1978

Achondrogenesis.

Explore the source record for details and available documents.

Dwarfism↗
PubMed1978

Hypochondroplasia.

Clinical, radiological, and genetic features are described in 3 patients with hypochondroplasia. Early recognition of this disorder is possible from the abnormal body proportions with short limbs and lumbar lordosis without facial stigmata of achondroplasia. Radiological confirmation is possible provided a full skeletal survey is made. Two of our patients had a large head.

Cartilage Diseases↗
PubMed1978

The "mandibular mantle"--a sign of rickets in very low birth weight infants.

Mandibular periosteal new bone formation (the "mandibular mantle") is described in very low birth weight infants with other signs of severe metabolic bone disease. In infants with onset of dyspnoea and apnoea, between two and three months of age, this mandibular change suggests that the lung disorder is of skeletal, rather than pulmonary origin and aids in differentiation therefore, from the Mikity-Wilson Syndrome (pulmonary dystmaturity).

Bone Development↗