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Biomedical subjects

W E Smith

Publications and source records attributed to W E Smith.

At least 73 records · Page 4Linked to original sources
PubMed1992

Direct spectroscopic determination of functional sulphydryl groups on intact cell surfaces by surface-enhanced resonance Raman scattering.

Semi-quantitative and direct determination of labelled sulphydryl groups on the surface of intact erythrocytes has been accomplished for the first time with surface-enhanced resonance Raman scattering (SERRS). The method, which involves the use of citrate-reduced silver colloids, is sensitive and selective. A 10(-8) M effective concentration of picomole quantities of sulphydryl groups was determined in the presence of the normally overwhelming signal from haemoglobin. This seminal study suggests that SERRS may be applied to other in situ, site-directed labelling experiments.

Cell Membrane↗
PubMed1992

Gold concentrations in blood fractions of patients with rheumatoid arthritis treated with Myocrisin.

Gold levels in the plasma and blood cells of patients treated with the gold drug Myocrisin (sodium aurothiomalate) were determined by atomic absorption spectrometry. There is a correlation between whole blood gold and plasma gold concentrations which is different for smokers and non-smokers. Most cellular gold is associated with the membrane and is present in concentrations approximately equivalent to the number of reactive sulphydryl groups on the exofacial surface of the cell. Since gold would be expected to react with SH groups and since these groups are vital for cellular function, a possible role for gold in modifying cellular metabolism is indicated.

Arthritis, Rheumatoid↗
PubMed1992

Antioxidant effects of angiotensin-converting enzyme (ACE) inhibitors: free radical and oxidant scavenging are sulfhydryl dependent, but lipid peroxidation is inhibited by both sulfhydryl- and nonsulfhydryl-containing ACE inhibitors.

With an assay that generates free radicals (FR) through photooxidation of dianisidine sensitized by riboflavin, 4 x 10(-5) M captopril, epicaptopril (SQ 14,534, captopril's stereoisomer), zofenopril, and fentiapril [all sulfhydryl (-SH)-containing angiotensin-converting enzyme (ACE) inhibitors] were shown effective scavengers of nonsuperoxide free radicals whereas non-SH ACE inhibitors were not. Captopril was a more effective FR scavenger at pH 5.0 than at pH 7.5. Captopril (2 x 10(-5) M) also scavenged the other toxic oxygen species hydrogen peroxide and singlet oxygen and inhibited microsomal lipid peroxidation. Finally, captopril reduced the amount of superoxide anion-radical detected after neutrophils in whole blood were activated with zymosan, probably by inhibiting leukocyte superoxide production.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Estimation of the spatio-temporal correlations of biological electrical sources from their magnetic fields.

Quasi-static electromagnetic systems, such as those found in biological systems, produce electric and magnetic fields whose temporal and spatial correlations reflect the source correlations in a straightforward manner. These fields can be noninvasively measured, providing information about the coherence properties of the source, which may directly represent ordered physiological processes of the organism. The description "biocoherence" will be adopted here to refer to the manifestation of the coherence in the magnetic measurements of these sources due solely to physiological processes. In this paper a general formulation linking the spatial and temporal coherence of measurable magnetic fields with the corresponding spatial and temporal coherence of the inaccessible current sources is derived in the quasi-static model. A method for reconstructing the spatial and temporal coherence of the source distribution is then presented. Such coherence maps would be useful descriptors of physiological processes occurring over time and space, and would represent more information than an image of the current sources frozen in time, or even a temporal sequence of such images.

Electroencephalography↗
PubMed1992

Spin echo nuclear magnetic resonance studies on intact erythrocytes: changes in cellular metabolism as a consequence of carbimazole therapy.

OBJECTIVE: Because the exact mechanism of action of carbimazole is uncertain, nuclear magnetic resonance (NMR) spectroscopy was used to investigate cellular changes in erythrocytes from Graves' patients following a course of carbimazole therapy. DESIGN: NMR spectroscopy was carried out using intact erythrocytes obtained from Graves' patients prior to and at 2 and 12 months after carbimazole treatment. The data were correlated with thyroid hormone and antibody levels. PATIENTS: Twenty patients (four males; 16 females) with newly diagnosed and previously untreated Graves' disease were enrolled into the study. Assessments were made prior to the commencement of therapy and after 2 and 12 months on treatment. Of the 20 patients assessed at 0 and 2 months only 12 completed the study. MEASUREMENTS: The oxidation-reduction balance of erythrocyte glutathione was measured directly using 1H spin echo NMR spectroscopy of intact cells. Thyroid hormone and antibody levels were measured using reported methods. RESULTS: At 2 and 12 months a significant (P < 0.01) oxidation of the erythrocyte glutathione was observed. Of the four thyroid related markers (T3, T4, TRAb and TSH) assessed in this study both T3 (P < 0.001) and TRAb (P < 0.001) were observed to correlate with the NMR observed changes in glutathione. However, in-vitro experiments indicated that carbimazole does not affect red cell glutathione directly. CONCLUSIONS: A model is presented which uses the hydrated iodium cation (I+), the natural product of T4 conversion to T3, as a chemical oxidant which can produce the observed clinical alteration in intracellular glutathione in ex-vivo erythrocytes. It is suggested that a major factor in the action of carbimazole in Graves' disease may be to stimulate the function of the deiodinase enzymes.

Adult↗
PubMed1992

Action of sodium aurothiomalate on erythrocyte membrane.

The number of sulphydryl groups on the erythrocyte membrane has been assessed as a function of nutritional status for two groups of patients, one receiving non-steroidal anti-inflammatory drugs (NSAIDs) and the other receiving sodium aurothiomalate (Myocrisin). The patients receiving NSAIDs had a significantly higher number of sulphydryl groups in both the glucose depleted and glucose activated states than the patients receiving sodium aurothiomalate. The study focuses on the hexose transport protein where there is a specific binding site for gold using the two sulphydryl residues on helices 11 and 12 of the protein. The data suggest that the strong binding of gold to the erythrocyte membrane occurs via thiol pairs rather than by isolated sulphydryl groups and that there are possibly two further binding sites for gold on the membrane, the identities of which are still unclear.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1992

Evidence for oxidative stress in unstable angina.

OBJECTIVE: To determine whether unstable angina, which is characterised by recurring episodes of myocardial ischaemia and reperfusion, is associated with oxidative stress (that is, where there is an imbalance between oxidants, such as free radicals, which are in excess and antioxidants). DESIGN: Between group comparison of patients with unstable angina, stable angina, and healthy controls. SETTING: The coronary care unit and cardiac investigation ward of a regional cardiology centre. PATIENTS: Twenty five consecutive patients admitted to the coronary care unit with unstable angina. Twenty five consecutive patients admitted to the cardiac investigation ward (patients with stable angina undergoing coronary angiography) were used as controls for the presence of atherosclerosis, drug treatment, and smoking habit. Thirty eight healthy controls (hospital staff and patients admitted for minor surgical procedures who were otherwise healthy) were also studied. MAIN OUTCOME MEASURES: Thiobarbituric acid related substances (TBARS) in plasma and plasma reduced thiol (PSH) as indicators of oxidative damage to lipids and proteins respectively were measured. Coronary angiography was performed in all patients with stable angina and roughly half of those with unstable angina. RESULTS: Mean (SEM) plasma TBARS in unstable angina and stable angina were 9.95 (0.36) nmol/ml and 9.14 (0.28) nmol/ml respectively (p = 0.08). Mean plasma TBARS in healthy controls were 8.09 (0.21) nmol/ml (p < 0.05 compared with both angina groups). Mean (SEM) PSH concentration in unstable angina was 4.21 (9) nmol/ml and in stable angina was 4.85 (9) nmol/ml (p < 0.05). Mean PSH in healthy controls was 5.64 (8) nmol/ml (p < 0.001 compared with both angina groups). The extent of coronary artery disease, use of medication, and smoking habit were not significantly different between the angina groups. CONCLUSIONS: Biochemical indicators of oxidative stress are more abnormal in unstable than stable angina. This is in keeping with experimental evidence that episodes of ischaemia and reperfusion lead to generation of free radicals and toxic oxygen species and depression of endogenous antioxidant activity. The clinical significance of this finding remains to be determined, although, experimentally, free radicals and toxic oxygen species have adverse effects on myocardial contractile function, myocardial electrical stability, endothelial mediated vasodilatation, and coagulation.

Adult↗
PubMed1991

Clinical analysis in intact erythrocytes using 1H spin echo NMR.

A new method of clinical analysis based on 1H spin echo NMR spectroscopy is presented. It is capable of providing information on six metabolites within viable erythrocytes, directly and without any preparative procedures prior to analysis except for cell separation and washing. Erythrocytes from patients with rheumatoid arthritis and Graves' disease are compared with cells obtained from healthy volunteers. The NMR detectable species in the cytosol of the cells are glutathione, ergothioneine, choline, creatine, glycine, lactate and to a lesser extent alanine and valine. Significant differences are observed between the ergothioneine pools in the rheumatoid group (P less than 0.01) compared to the control group. The glutathione: di-glutathione ratio can be assessed from the ratio, g2 to g4, taken from different signals in the glutathione molecule. The total concentration of glutathione present is easily assessed qualitatively but is more difficult to quantitate.

Adult↗
PubMed1991

A sensitive assay of transthyretin (prealbumin) in human cerebrospinal fluid in nanogram amounts by ELISA.

A sensitive ELISA method for determining transthyretin (prealbumin) in human cerebrospinal fluid (CSF) is described. The method utilizes goat antihuman transthyretin antibody (IgG fraction) for capture and peroxidase conjugated antibody for color development. The assay has a linear range of 1-4 ng transthyretin added per well. The within-day and between-day coefficients of variation are 5.1 and 6.1%, respectively. The concentration of transthyretin in CSF (ranging from 5 to 20 mg per L) correlated significantly with the corresponding serum concentrations (range 170-420 mg/l). This suggests that synthesis of transthyretin in the brain and peripheral tissues is under similar biological control in normal subjects. The transthyretin concentrations in CSF did not correlate with total CSF protein concentration or age of the subject.

Adult↗
PubMed1990

Oxidative damage in chronic heart failure: protection by captopril through free radical scavenging?

The pathogenesis of heart failure is not yet fully understood. In animal models there is some evidence to suggest a role for free radicals (FRs). We have investigated malondialdehyde - LM in plasma of patients with heart failure and found it to be raised when compared to controls. We present data to show that Captopril, a drug with an ACE inhibitory effect is a FR scavenger both in vitro and ex-vivo in patients with heart failure.

Aged↗
PubMed1990

An NMR compatible model for solid tumour.

An NMR model for the study of drug interactions with solid tumour is described. It is based on the use of packed cells in a simple medium. The system is capable of dealing with cellular biochemistry at a molecular level through experiments conducted in a homogeneous field by 1H spin-echo NMR spectroscopy. However, through a simple imaging technique, it is also possible to introduce a spatial element into the chemistry of the packed cells. The use of these complementary NMR methods are illustrated by the action of the cytotoxic agent doxorubicin on cellular glycolysis. A pattern of signals observed in a homogeneous field experiment following oxidative stress are duplicated in the imaging experiment to illustrate the toxins' ability to penetrate the model tumour.

Antineoplastic Agents↗
PubMed1990

Free radical scavenging: a potentially beneficial action of thiol-containing angiotensin converting enzyme inhibitors.

Free radical (FR) scavenging may be a therapeutically useful adjunctive property of angiotensin converting enzyme (ACE) inhibitors. In this study we have shown that SH-containing ACE inhibitors (captopril, epicaptopril, zofenopril) are potent FR scavengers at a concentration of 4 x 10(-5) M whereas non-SH ACE inhibitors (enalaprilat, quinaprilat and perindoprilat) have no FR-scavenging activity at this concentration. Furthermore, the SH-containing agents preferentially scavenged general radicals rather than superoxide radicals, i.e. suggesting that these drugs would be effective in quenching the culprit FR in ischaemia/reperfusion injury.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1990

Concentration and reactivity of the sulphydryl group population on the membrane of intact erythrocytes in patients with rheumatoid arthritis.

The sulphydryl population on erythrocyte membrane is shown to vary as a function of the nutritional status of the cell. When an assay based on reaction with Ellman's reagent and controlled conditions were used the mean values (SEM) for the sulphydryl population on the membranes of normal erythrocytes incubated overnight in the presence and absence of glucose were found to be 3.29 (0.27) and 2.56 (0.25) million sulphydryl functions per cell respectively. Under identical conditions rheumatoid erythrocytes incubated in the presence and absence of glucose were found to have a significantly lower sulphydryl population--1.54 (0.08) and 1.15 (0.08) million respectively. The predominant concentrations of sulphydryl groups on the membrane are found at sites on the transmembrane proteins and, in particular, on the hexose transport protein. By influencing the nutritional status of the cells significant differences in activity between the normal and diseased state have been identified and these may have a role in the aetiology of rheumatoid arthritis by altering the response of cells to oxidative stress.

Arthritis, Rheumatoid↗
PubMed1990

The effect of carbimazole therapy on interleukin 2, interleukin 2 receptors and free radicals.

Levels of Interleukin 2 (IL2), IL2 receptors (IL2R) and free radical scavengers were measured in 25 Graves' disease patients prior to and following an 8 week course of Carbimazole therapy in an attempt to understand the mechanism by which the drug acts on the immune system. In untreated Graves' patients IL2R levels were elevated and IL2 levels reduced. Free radical scavengers were also reduced in these patients. Following treatment IL2R levels fell and IL2 levels rose. Levels of the free radical scanvengers also rose. It is not clear whether it is the fall in IL2R levels or the rise in the level of free radical scavengers (implying a reduction in free radical activity) which is responsible for the rise in IL2.

Carbimazole↗