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Biomedical subjects

M Walters

Publications and source records attributed to M Walters.

At least 19 recordsLinked to original sources
PubMed1992

Functional erythroid promoters created by interaction of the transcription factor GATA-1 with CACCC and AP-1/NFE-2 elements.

We have investigated interactions between the erythroid transcription factor GATA-1 and factors binding two cis-acting elements commonly linked to GATA sites in erythroid control elements. GATA-1 is present at all stages of erythroid differentiation, is necessary for erythropoiesis, and binds sites in all erythroid control elements. However, minimal promoters containing GATA-1 sites are inactive when tested in erythroid cells. Based on this observation, two erythroid cis elements, here termed CACCC and AP-1/NFE-2, were linked to GATA sites in minimal promoters. None of the elements linked only to a TATA box created an active promoter, but GATA sites linked to either CACCC or AP-1/NFE-2 elements formed strong erythroid promoters. A mutation of T to C at position -175 in the gamma-globin promoter GATA site, associated with hereditary persistence of fetal hemoglobin (HPFH), increased expression of these promoters in both fetal and adult cells. A construct bearing the beta-globin CACCC element was more active in adult and less active in fetal erythroid cells, when compared with the gamma-globin CACCC element. These studies suggest that erythroid control elements are formed by the interactions of at least three transcription factors, none of which functions alone.

Animals↗
PubMed1991

Characterization of a DNA binding activity in DNAse I hypersensitive site 4 of the human globin locus control region.

A portion of the beta-globin Locus Control Region (LCR), which included DNAse I hypersensitive site 4 (HS4), was analyzed for its interactions with nuclear extracts and its contribution to LCR activity in a functional assay. In gel retardation assays, a short fragment from HS4 formed complexes with nuclear extracts from both erythroid and nonerythroid cells, and a core protected sequence 5'GACTGGC3' was revealed by DNAse I protection and methylation interference studies. This sequence resembles the binding sites of CCAAT-family members. Purified CP-2 but not CP-1 was shown to bind this HS4 sequence in a gel shift reaction, suggesting that the HS4 binding activity shares some sequence specificity with the CCAAT-factor family. Utilizing a transient expression assay in murine erythroleukemia cells, steady-state RNA levels were measured from pairs of LCR constructs linked to distinguishable beta-globin reporter genes. A short DNA fragment from HS4 which included the binding site for this novel binding activity accounted for most of the contribution to high level expression made by the entire HS4 region.

Animals↗
PubMed1991

POSSUM: a scoring system for surgical audit.

POSSUM, a Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity, is described. This system has been devised from both a retrospective and prospective analysis and the present paper attempts to validate it prospectively. Logistic regression analysis yielded statistically significant equations for both mortality and morbidity (P less than 0.001). When displayed graphically zones of increasing morbidity and mortality rates could be defined which could be of value in surgical audit. The scoring system produced assessments for morbidity and mortality rates which did not significantly differ from observed rates.

Aged↗
PubMed1988

Isolation of a chemotactic protein for neutrophils from human ovarian follicular fluid.

Human follicular fluid was found to contain a factor chemotactic for human neutrophils. This chemotactic activity was shown to be heat labile and trypsin sensitive. Gel permeation chromatography experiments indicate that the chemotactic protein has an approximate molecular weight of 100 kd. Isoelectric focussing suggests an isoelectric point for this protein of around 5.8. The biologic and clinical significance of this apparently unique chemotactic protein remains to be determined.

Body Fluids↗
PubMed1987

Reduced serum tricyclic levels due to gel separators.

Sixty-three blood samples were obtained from 48 subjects taking tricyclic antidepressants. Samples were simultaneously collected in Becton-Dickinson Vacutainer tubes for measurement of serum and plasma tricyclic antidepressant concentrations. Serum was drawn into red stopper tubes (without gel separator) and into speckled stopper serum separator tubes (with gel separator), while plasma was collected in green stopper tubes (heparinized). Imipramine, desipramine, amitriptyline, and nortriptyline concentrations were all significantly lower in serum separator samples than in either plasma or red stopper serum collection tubes. Serum and plasma concentrations were similar.

Antidepressive Agents, Tricyclic↗
PubMed1985

Bronchial challenge with room temperature isocapnic hyperventilation. A comparison with histamine challenge.

We evaluated isocapnic hyperventilation with room temperature gas (IHV) as a test of bronchial hyperreactivity and compared it with histamine challenge (HC) in three groups of subjects: normal subjects, known mild asthmatic patients, and patients referred to the pulmonary clinic for a chief complaint of dyspnea. Physical examination at the time of evaluation was negative in all subjects. When the criterion for a positive reaction to IHV was a decrease in FEV1 of 10 percent or greater, and the criterion for a positive reaction to HC was a PD20 (concentration of inhaled histamine necessary to decrease FEV1 by at least 20 percent) of less than 10 mg/ml, the specificity of both tests was 100 percent. The sensitivity of both tests as evaluated from the known asthmatic patients was also 100 percent. Among the dyspneic patients, eight of 30 reacted to both IHV and HC, two of 30 reacted to HC alone, and eight of 30 reacted to IHV alone. It was concluded that IHV compares favorably with HC as a test of bronchial hyperreactivity, patients with clinical histories highly suggestive for asthma might not need to undergo bronchial challenge testing, and neither HC nor IHV when used alone is able to identify all of the hyperreactive patients.

Adolescent↗
PubMed1979

Postnatal support.

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Child Health Services↗
PubMed1976

Characterization of an adenylate cyclase system sensitive to histamine H2-receptor excitation in cells from dog gastric mucosa.

A method of preparing viable cells from dog gastric mucosa is described. Cyclic AMP in these cells is elevated by histamine and 4-methyl histamine but 2-methyl histamine is only a weak agonist. The effects on cyclic AMP levels are inhibited competitively by metiamide and burimamide which give apparent KBvalues of 3.5x10-7 M and 2.3x10-6 M, respectively. These values are similar to those reported for other histamine H2-receptor systems. The H1-receptor antagonists, mepyramine and chlorpheniramine, have no inhibitory effect on the histamine induced elevation of cyclic AMP: promethazine inhibits the system but not by a competitive mechanism. It is concluded that the histamine stimulated adenylate cyclase system is probably located in the parietal cell component.

Adenylyl Cyclase Inhibitors↗
PubMed1973

Comex 1972.

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Asia↗