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Biomedical subjects

R A Clark

Publications and source records attributed to R A Clark.

At least 199 records · Page 11Linked to original sources
PubMed1992

An audit of acute asthma admissions to a respiratory unit.

A criterion based audit was performed on 90 admissions with acute asthma to a specialist respiratory unit using the guidelines set by the British Thoracic Society. Three main areas were audited including: documentation of severity markers in the case notes on admission, acute treatment given on admission, and further investigations performed. Case notes were found to be deficient in documentation of objective severity markers such as peak expiratory flow rate (52% recorded) and blood gases (72% recorded), as well as subjective markers such as speech (27%), air entry (58%) and exhaustion (4%). Of the total 90 admissions, 78% were identified as having at least three out of five objective markers for acute severe asthma. Most of these severe cases (93%) were given corticosteroids but none were prescribed greater than 35% concentration of inspired oxygen. The majority of admissions had a chest radiograph (87%), and 56% had measurement of serum potassium. These results show that even in a specialised respiratory unit, guidelines such as those produced by the British Thoracic Society are not in general being adhered to. It also indicates that assessment of severity is inadequate, particularly for peak flow measurement, and that management is deficient in established treatments such as the use of high flow oxygen. As a result of the audit, a severity marker stamp for the case notes along with guidelines for treatment have been implemented in order to improve the quality of care delivered to patients admitted with acute asthma.

Acute Disease↗
PubMed1992

Intramarital illegitimacy.

Discovering cases of children born to married women by men not their husbands is generally difficult. Legal involvements with regard to paternity, divorce and litigious paranoids also have applicability to cases of pregnancy by donor insemination. The child's right to information regarding paternity is the same in both types of cases, and is relevant with respect to matters of heredity as well as, in some cases, counselling and psychotherapy.

Adult↗
PubMed1992

Diagnostic imaging in cancer.

Screening chest radiographs do not reduce mortality from lung cancer. Should an incidental noncalcified pulmonary parenchymal nodule be discovered, chest CT will demonstrate one third of such patients to, in fact, have the multiple nodules of metastatic disease. CT is very helpful to guide fine needle aspiration biopsy of lung lesions and to assist in evaluation for resectability. MR can be helpful in special circumstances, including the definition of the extent of paravertebral, superior sulcus, and diaphragmatic lesions. Endorectal ultrasound is not sensitive enough to function as a screening tool for prostate cancer but is used routinely to guide biopsies. CT and MR are rarely helpful in staging this disease. Given the highly characteristic trait of bone metastasis in prostate cancer, a bone scan is mandatory in all patients. Double contrast barium enema can be used as an adjunct or alternative to sigmoidoscopy for colorectal cancer screening, in the preoperative evaluation of patients, and in postoperative surveillance. CT and MR can detect macroscopic adenopathy and liver metastases; CT is generally the preferred study. Screening mammography can have a major impact in reducing breast cancer mortality. It is recommended that a baseline study be obtained at age 35. Annual or biannual examinations should commence at age 40. Any palpable lesion, whether or not it is demonstrated mammographically, must be subjected to biopsy. Ultrasound is the most useful initial imaging study for evaluating pelvic masses. MR will, on occasion, identify the origin of a mass not determinable from ultrasound scan. MR is particularly valuable to identify parametrial spread (inoperability) of cervical cancer, and has been underused for this purpose. Surgery remains the mainstay for the staging of ovarian and endometrial cancer, although CT can be helpful to identify macroscopic relapse, ascites, or liver metastases. Bone scan and liver CT remain the standard procedures for detecting metastases in these respective organ systems. MR can be invaluable in the imaging of epidural metastasis and spinal cord compression in patients with vertebral metastatic disease. Contrast-enhanced MR is more sensitive than contrast-enhanced CT for detecting brain metastases, but the latter remains a useful tool. Chest CT can improve the detection of pulmonary metastases when this is of crucial importance.

Biopsy, Needle↗
PubMed1991

Assembly of the neutrophil respiratory burst oxidase. Protein kinase C promotes cytoskeletal and membrane association of cytosolic oxidase components.

Activated human polymorphonuclear neutrophils (PMNs) convert molecular oxygen into superoxide anion, a process known as the respiratory burst, through the activity of a latent multicomponent NADPH-dependent oxidase. Components of this respiratory burst oxidase include the membrane-bound cytochrome b558 and the cytosolic factors p47-phox and p67-phox. We initiated these studies based on three observations: 1) that stimulation of PMN oxidase activity is associated with translocation of the cytosolic oxidase components to the plasma membrane; 2) that p47-phox is phosphorylated during PMN activation and that there is a sequential relationship between phosphorylation of p47-phox in the cytosol and appearance of the phosphoprotein in the membran; and 3) that the predicted amino acid sequences of p47-phox and of p67-phox contain regions of homology to the SH3 or A domain of the src family of tyrosine kinases, a region found in a variety of proteins which interact with the cytoskeleton or the subplasmalemmal cytoskeleton. Thus the purpose of our studies was to examine the role of protein kinase C (PKC)-dependent phosphorylation in the stimulus-induced association of p47-phox and p67-phox with the plasma membrane and the cytoskeleton. Using the PKC activator phorbol myristate acetate (PMA) as the agonist, we found that activation of the respiratory burst oxidase was associated with translocation of cytosolic p47-phox and p67-phox to the plasma membrane as well as redistribution of p47-phox to the Triton-insoluble cytoskeleton. Furthermore, the PKC inhibitor staurosporine inhibited phosphorylation of p47-phox, interrupted the redistribution of cytosolic oxidase factors, and blocked PMA-induced generation of superoxide anion. Taken together these results indicate that PKC-dependent phosphorylation of p47-phox correlates with association of p47-phox with the cytoskeleton and with translocation of p47-phox and p67-phox to the plasma membrane, with the ensuing assembly of an active superoxide-generating NADPH-dependent oxidase.

Alkaloids↗
PubMed1991

Growth factors.

Explore the source record for details and available documents.

Animals↗
PubMed1991

A cytosolic inhibitor of human neutrophil elastase and cathepsin G.

The neutrophil serine proteinases elastase and cathepsin G produce connective tissue injury, the extent of which depends on the balance between these enzymes and their inhibitors. The most important of these inhibitors is alpha 1-proteinase inhibitor, a member of a superfamily of homologous proteins known as serpins. Neutrophil cytosol inhibited the activities of human neutrophil elastase and cathepsin G in a dose-dependent fashion. To demonstrate formation of an enzyme-inhibitor complex, we combined 125I-elastase or 125I-cathepsin G with neutrophil cytosol or alpha 1-proteinase inhibitor and analyzed the products by polyacrylamide gel electrophoresis. Unbound elastase and cathepsin G each migrated to an apparent molecular weight of 25 kDa. In the presence of cytosol from neutrophils both radiolabeled enzymes migrated with a relative size of 68 kDa, whereas in the presence of alpha 1-proteinase inhibitor the relative size was 85 kDa. Enzyme-inhibitor complexes were stable in sodium dodecyl sulfate at 100 degrees C but were dissociated by hydrolysis in ammonium hydroxide (1.5 mol/L) at 37 degrees C. Formation of each complex was prevented by pretreatment of elastase or cathepsin G with diisopropylfluorophosphate, indicating that the inhibitor binds to the active site of the enzyme. Exposure of either alpha 1-proteinase inhibitor or neutrophil cytosol to the myeloperoxidase-H2O2-halide system prevented complex formation, suggesting the presence of an oxidizable amino acid at the binding site of the inhibitor. By electrophoretic analysis, the molecular weight of the cytosolic inhibitor was 43 kDa and neutrophils contained approximately 1 attomol of inhibitor per cell. The isoelectric points of the elastase and cathepsin G inhibitor were 5.5-5.9 and inhibitors of the two proteinases coeluted using size exclusion chromatography. These data demonstrate that human neutrophil cytosol contains a single serpinlike protein that inhibits elastase and cathepsin G. The inhibitor may be important in protecting the intracellular environment from proteolytic injury during degranulation.

Ammonium Hydroxide↗
PubMed1991

Measurement of normal human airways response to beta-adrenoceptor stimulation using a forced oscillation technique.

The purpose of the present study was to evaluate the responsiveness of normal human airways to beta-adrenoceptor stimulation using a forced oscillation technique. Seven normal volunteers (aged 25 +/- 2 year) were studied on three occasions, separated by weekly intervals, using a single-blind randomized design. On day 1, subjects were given cumulative doses of inhaled salbutamol (100, 200, 500, 1000 micrograms); and identical placebo was given on the other two visits. Respiratory oscillation impedance (Ros) was measured at baseline and 15 min after each dose increment. The coefficients of variation (CV) for short-term intra-individual variability on each placebo day were 7.5 and 9.5, and 9.6% for long-term variability (measured over all three visits). The 95% confidence values (2SD) for the change in Ros required to exclude natural variability were 0.39, 0.50 and 0.53 cmH2O l-1 s, respectively. There was a small fall in Ros in response to salbutamol although the mean maximum change (0.46 cmH2O l-1 s) was not significant (by ANOVA). Thus, the change in Ros (sensitivity) was no greater than the 95% confidence value for natural variability (reproducibility). Regression analysis also showed no evidence of a dose-response relationship for Ros.

Adrenergic beta-Agonists↗
PubMed1991

MR imaging of periosteal and cortical changes of bone.

The changes seen in the periosteum and cortical bone are fundamental radiographic features of bone disease. The basic radiographic findings used for diagnosis of bone lesions (patterns of cortical destruction and of periosteal new bone formation) can be well identified with magnetic resonance (MR) imaging. The authors used comparative radiographic, computed tomographic, and MR images to illustrate patterns of periosteal reaction (simple, laminated, spiculated, Codman triangle), geographic and permeative cortical destruction, cortical erosion, cortical expansion and continuity, and intraosseous and extraosseous calcification. The only feature not well demonstrated by MR imaging is pattern or extent of soft-tissue calcification. Although MR images are not required for diagnosis of most peripheral bone lesions, when they are obtained, these fundamental diagnostic features should not be ignored.

Bone Diseases↗
PubMed1991

Pathogenesis of pulmonary fibrosis in interstitial lung disease. Alveolar macrophage PDGF(B) gene activation and up-regulation by interferon gamma.

Alveolar macrophages are believed to be central in orchestrating the fibrotic response in interstitial lung disease (ILD). To test the hypothesis that macrophages from patients with ILD were dedicated to growth factor production and that this was independent of other indices of macrophage activation, we measured the mRNA of the B chain of PDGF and TGF-beta, as well as HLA-DR-alpha in alveolar macrophages from patients with ILD and from normal control subjects. When alveolar macrophages were examined immediately after lavage, cells from patients with ILD had increased PDGF(B) but similar TGF-beta and HLA-DR-alpha mRNA when compared with control subjects. Discoordinate regulation of these genes was observed when alveolar macrophage PDGF(B) mRNA increased while TGF-beta and HLA-DR-alpha mRNA decreased after culture for 24 h. This response was not disease-related as these changes were similar in cells from patients with ILD and from control subjects. Because a lymphocytic alveolitis is present in many cases of ILD, we asked whether interferon gamma (IFN-gamma) modulated the activation of these genes. In both the patients and the control subjects, PDGF(B) and HLA-DR-alpha, but not TGF-beta, mRNA were increased after incubation with IFN-gamma. These results indicate that PDGF(B) mRNA may be increased in alveolar macrophages in ILD and that PDGF(B), TGF-beta, and HLA-DR-alpha are independently regulated genes in alveolar macrophages, but that IFN-gamma increases both PDGF(B) and HLA-DR-alpha mRNA. We speculate that IFN-gamma induced PDGF(B) gene activation may be an important mechanism by which lymphocytes promote pulmonary fibrosis.

Adult↗
PubMed1991

Neutrophil nicotinamide adenine dinucleotide phosphate oxidase assembly. Translocation of p47-phox and p67-phox requires interaction between p47-phox and cytochrome b558.

Two of the cytosolic NADPH oxidase components, p47-phox and p67-phox, translocate to the plasma membrane in normal neutrophils stimulated with phorbol myristate acetate (PMA). We have now studied the translocation process in neutrophils of patients with chronic granulomatous disease (CGD), an inherited syndrome in which the oxidase system fails to produce superoxide due to lesions affecting any one of its four known components: the gp91-phox and p22-phox subunits of cytochrome b558 (the membrane-bound terminal electron transporter of the oxidase), p47-phox, and p67-phox. In contrast to normal cells, neither p47-phox nor p67-phox translocated to the membrane in PMA-stimulated CGD neutrophils which lack cytochrome b558. In one patient with a rare X-linked form of CGD caused by a Pro----His substitution in gp91-phox, but whose neutrophils have normal levels of this mutant cytochrome b558, translocation was normal. In two patients with p47-phox deficiency, p67-phox failed to translocate, whereas p47-phox was detected in the particulate fraction of PMA-stimulated neutrophils from two patients deficient in p67-phox. Our data suggest that cytochrome b558 or a closely linked factor provides an essential membrane docking site for the cytosolic oxidase components and that it is p47-phox that mediates the assembly of these components on the membrane.

Biological Transport↗
PubMed1991

Methodology in anti-emetic trials.

Major progress in the ability to control chemotherapy-induced emesis has been made over the past 10 years. One of the several factors contributing to this improved control has been the development of accurate assessment methodology. The application of proper study methodology fostered the identification of active single agents and led to the formation of effective anti-emetic combinations. In this communication, important areas in anti-emetic study evaluation will be outlined. Proper methodology includes selection of agents or regimens that have a good rationale for study. Patient, chemotherapy, and anti-emetic factors must be controlled or standardised in good trial design, and the evaluation techniques for determining the amount of emesis or of nausea must be performed using reliable and valid methods. The statistical design employed and number of patients entered in the trial should be determined based on achievable and relevant goals.

Adult↗
PubMed1990

Immunochemical and electrophoretic analyses of phosphorylated native and recombinant neutrophil oxidase component p47-phox.

Human polymorphonuclear neutrophils (PMNs) possess a potent oxygen-dependent microbicidal system that depends on the activity of a stimulus-activated multicomponent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. Patients with chronic granulomatous disease (CGD) lack activity of this oxidase and consequently suffer severe and frequent infections. Components of the oxidase include both membrane-bound factors (most notably, cytochrome b559, which is absent in the X-linked form of CGD) and at least two cytosolic factors, one or the other of which is absent in autosomal CGD. Patients with CGD, particularly the autosomal type, have defective phosphorylation of proteins in the 44 to 48 Kd range. A polyclonal antiserum (B-1) that recognizes cytosolic oxidase components of 47 and 67 Kd was used to identify phosphoproteins in a cell-free oxidase system. Two-dimensional gel electrophoresis showed the identity of the 47-Kd cytosolic protein (p47-phox) recognized by B-1 and the cationic 47-Kd protein that is phosphorylated in normal but not p47-phox-deficient CGD cytosol during activation of the NADPH-dependent oxidase. All full-length and C-terminal recombinant p47-phox proteins augmented the superoxide-generating capacity of the cell-free system and were phosphorylated when added to cytosol from normal subjects or from a patient with p47-deficient autosomal CGD. These studies provide compelling evidence that the 47-Kd cationic protein that is a substrate for phosphorylation during the activation of PMNs is, in fact, p47-phox, a cytosolic protein previously shown to be critical for normal activity of the NADPH-dependent oxidase of PMNs.

Autoradiography↗
PubMed1990

Two cytosolic components of the neutrophil NADPH oxidase, P47-phox and P67-phox, are not flavoproteins.

Two cytosolic proteins, p47-phox and p67-phox, have been shown to be essential components of the NADPH-dependent oxidase of human neutrophils, although the specific role of each of these proteins in the multicomponent electron transport complex is undetermined. The superoxide-generating activity of this oxidase can be reproduced in a cell-free system, combining cytosol and membranes from unstimulated neutrophils in the presence of fatty acid and NADPH. In the present studies, cytosol was treated with myristic acid, arachidonic acid, or sodium dodecyl sulfate in the absence of membranes and the resultant precipitate collected by centrifugation and analyzed. Both p47-phox and p67-phox precipitated in the presence of fatty acid. However, neither FAD nor FMN was localized in the precipitates, even though substantial amounts of p47-phox and p67-phox precipitated. These results suggest that neither p47-phox nor p67-phox is a flavoprotein and that neither, therefore, is the oxidase component which accepts electrons from NADPH.

Arachidonic Acid↗
PubMed1990

Cloning of a 67-kD neutrophil oxidase factor with similarity to a noncatalytic region of p60c-src.

Chronic granulomatous diseases (CGDs) are characterized by recurrent infections resulting from impaired superoxide production by a phagocytic cell, nicotinamide adenine dinucleotide phosphate (reduced) (NADPH) oxidase. Complementary DNAs were cloned that encode the 67-kilodalton (kD) cytosolic oxidase factor (p67), which is deficient in 5% of CGD patients. Recombinant p67 (r-p67) partially restored NADPH oxidase activity to p67-deficient neutrophil cytosol from these patients. The p67 cDNA encodes a 526-amino acid protein with acidic middle and carboxyl-terminal domains that are similar to a sequence motif found in the noncatalytic domain of src-related tyrosine kinases. This motif was recently noted in phospholipase C-gamma, nonerythroid alpha-spectrin (fodrin), p21ras-guanosine triphophatase-activating protein (GAP), myosin-1 isoforms, yeast proteins cdc-25 and fus-1, and the 47-kD phagocyte oxidase factor (p47), which suggests the possibility of common regulatory features.

Amino Acid Sequence↗
PubMed1990

Subsensitivity of beta-adrenoceptor responses in asthmatic patients taking regular low dose inhaled salbutamol.

Tremor (Tr), chronotropic (HR) and metabolic (K, Glu) responses to cumulative doses of inhaled salbutamol (100 micrograms to 4000 micrograms) were compared in an age and sex matched group of 7 normal (N) and asthmatic (A) subjects. Comparison of regression lines between groups showed differences in HR and K. This was also reflected in attenuation of maximum responses in group A, for HR and K. These results show subsensitivity of chronotropic and hypokalaemic responses in patients with asthma, which may reflect tachyphylaxis from the effects of long term inhaled salbutamol therapy.

Administration, Inhalation↗