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Biomedical subjects

D S Reid

Publications and source records attributed to D S Reid.

At least 37 records · Page 2Linked to original sources
PubMed1991

Ionic diffusion in frozen starch gels.

Quality changes in food frozen by different conditions and at different storage temperatures were demonstrated using a model system. A frozen starch gel represents a frozen food matrix, and ions in the external medium represent the reactant molecules. We determined the effective diffusion rates of Zn+2 ions into frozen starch gel cylinders that were frozen at different freezing rates. The diffusion was performed at -8 degrees and -15 degrees C. The amounts of ion diffused were determined by atomic absorption, whilst the structure of the frozen samples could be simultaneously determined by scanning electron microscopy. The effective diffusion rates were found to correlate with the amount of unfrozen portion of the samples. This suggests that ions move mainly through the unfrozen portion around the ice crystals. Fast- and slow-frozen samples exhibited significantly different effective diffusion rates at -15 degrees C, which might be due to differences in size and orientation of ice crystals. Zn+2 ions moved slower at -15 degrees C than at -8 degrees C.

Crystallization↗
PubMed1991

Studies of reaction kinetics in relation to the Tg' of polymers in frozen model systems.

The rates of diffusion-controlled processes in a frozen system can be influenced by the presence of glassy states. One characteristic of cryostabilization by this mechanism is a change in the temperature dependence of reaction rates at the Tg' of the system. The cryostabilization behavior of solutes such as maltodextrin, carboxymethylcellulose (CMC), and sucrose was studied. Three different model reaction systems (enzyme hydrolysis, protein aggregation, and non-enzymatic oxidation) were used. Maltodextrin had a consistent pattern of cryostabilization behavior at temperatures ranging from -3 degrees C to -20 degrees C for all three model systems. Significant retardation effects were evident in the temperature range corresponding to its glassy states. Sucrose did not show a stabilizing effect in the non-proteinaceous model system (the non-enzymatic oxidation reaction). This could partly be due to the absence of the glassy state, since the storage temperatures were above its Tg'. However, in the protein aggregation model system, sucrose was an excellent stabilizer in protecting actomyosin from aggregation. This may be explained by a "solute exclusion" mechanism. CMC did not show any stabilizing effect in the protein aggregation and non-enzymatic oxidation model systems studied, even though it has a Tg' as high as that of maltodextrin. These results demonstrated that although the presence of a glassy state may well have a retarding effect on the rates of diffusion processes, just knowing the Tg' of a polymer is not sufficient for prediction of its stabilization effect in a frozen system.

Actomyosin↗
PubMed1991

Effect of solute on the nucleation and propagation of ice.

Using the emulsion technique, we have studied nucleation of ice in aqueous solutions containing silver iodide or Pseudomonas syringae. Using a Differential Scanning Calorimeter (DSC), we determined characteristic temperatures of nucleation, and also rates of nucleation at selected temperatures. The freezing point depression induced by added solute is linearly related to the lowering of both homogeneous and heterogeneous nucleation temperature. Nucleation kinetics depend on a fifth power function of the temperature. Solute is found to affect the parameters of this relationship in different ways, dependent upon the nature of the catalytic site for ice nucleation. We have also studied the effect of composition on the linear propagation velocity (LPV) of ice in undercooled solutions contained in a U-tube. We have determined velocities in a range of concentrations of sugar solution at the same undercooling, and also as a function of undercooling. The role of added polymer has also been investigated. It is affected by the sugar concentration.

Calorimetry, Differential Scanning↗
PubMed1991

Salmonella: a rare cause of subacute effusive-constrictive pericarditis.

A 36 year old woman had emergency pericardectomy because of subacute effusive-constrictive pericarditis. The pericardial fluid and tissue culture showed that this was caused by infection with Salmonella enteritidis. Cardiac involvement with salmonella does not usually present in such an aggressive manner and it has not previously been reported to cause this rare type of cardiac constriction.

Acute Disease↗
PubMed1991

Melanoma metastatic to breast.

A patient presented with an unusual case of a breast mass. History and meticulous physical examination led to the diagnosis of metastatic melanoma, which was confirmed by biopsy. The differential diagnosis of metastasis to breast is discussed.

Adult↗
PubMed1990

Reduction in ST segment elevation after thrombolysis predicts either coronary reperfusion or preservation of left ventricular function.

The usefulness of a reduction in ST segment elevation to predict coronary reperfusion in myocardial infarction remains uncertain. ST segment changes and angiographic findings were compared in 45 patients soon after thrombolysis. The percentage ST segment change 3 hours after treatment (in the lead showing the greatest initial ST elevation) was compared with the TIMI perfusion grade (thrombolysis in myocardial infarction trial) obtained between 90 minutes and 3 hours after treatment. Global ejection fraction and regional wall motion were assessed by cineventriculography (11 (5) days (mean (SD))) and by gated blood pool imaging (44 (11) days). Prediction of coronary patency by a reduction of greater than 25% in ST segment elevation 3 hours after thrombolytic treatment had a sensitivity of 97% but a specificity of only 43%. Where the ST segment elevation was reduced by greater than 25% the global ejection fraction was well maintained whether or not the infarct vessel was patent. In patients with a reduction of less than 25% in ST elevation, the ejection fraction was significantly lower and regional wall motion abnormality more severe. Reduction in ST elevation of greater than 25% within 3 hours of thrombolysis indicates either a patent infarct artery or preservation of left ventricular function. When the ST segment elevation does not fall by greater than 25% persistent coronary occlusion is likely (predictive accuracy 86%) and is associated with a lower ejection fraction. These patients may benefit from further treatment or additional interventions.

Adult↗
PubMed1988

Coupling of redox indicator dyes into an enzymatic reaction cycle.

The spectral properties of ten redox indicator dyes were evaluated with the aim of finding the optimal choice for coupling to enzymatic reactions with high sensitivity for the production of the reduced form. Eight of the dyes were selected for coupling into a reaction cycle formed by yeast alcohol dehydrogenase with substrates ethanol and nicotinamide adenine dinucleotide (NAD+) and diaphorase with substrates reduced nicotinamide adenine dinucleotide (NADH, produced by the prior reaction) and the oxidized form of the respective dye. Two of the dyes exhibited decreased absorption on reduction, whereas all (eight) tetrazolium dyes increased in their absorption substantially upon reduction. Bis-tetrazolium dyes had a significantly higher molar extinction coefficient (up to 23,000 M-1.cm-1) than mono-tetrazolium dyes (down to 8000 M-1.cm-1). Kinetically, most dyes could be reduced with NADH (and diaphorase), but the rate of reduction varied considerably among the dyes with nitroblue tetrazolium (NBT) and tetranitroblue tetrazolium (TNBT) being the fastest. Therefore, NBT and TNBT seem to be the most suitable for fast response.

Alcohol Dehydrogenase↗
PubMed1987

Prevention of tolerance to nitroglycerin patches by overnight removal.

This investigation assesses the extent of tolerance development with nitroglycerin patches and whether tolerance might be prevented by overnight patch removal. On commencing therapy, active patches significantly prolonged exercise time (3.5 hours after patch application) in comparison with placebo, with an accompanying reduction in ST-segment depression at maximal common workload. Patients then received continuous or 12-hour-daily intermittent patch therapy, in a double-blind fashion, for 7 days. Exercise testing was repeated before and after active patch application, on the eighth day of each treatment phase. During continuous therapy, beneficial effects on exercise time and ST depression were abolished. By contrast, during intermittent therapy, prolongation of exercise time and reduction in ST-segment depression still occurred, on testing 3.5 hours after active patch application. These results confirm previous studies showing a high degree of tolerance during continuous therapy with nitroglycerin patches and suggest that tolerance can be prevented by 12-hour-daily intermittent therapy.

Administration, Cutaneous↗
PubMed1987

Flecainide--an intravenous infusion regimen.

An intravenous infusion regimen for flecainide was studied in 12 patients. Therapeutic drug levels were rapidly established and maintained throughout the 48-h infusion period. Two patients were withdrawn because of possible drug related problems, but in general the regimen seemed both effective and well tolerated.

Aged↗
PubMed1987

Gravitational and magnetic activation methods applied to cultured cells (LK 35.2).

Monoclonal antibody 10.2-16 is directed toward the mouse class II major histocompatibility complex gene product 1-Ak expressed on the cell line LK35.2. Instead of activating cells by fluorophor we used (acrylamide-coated) heavy and magnetic microspheres of 0.6 micron in radius. These microspheres are chemically coupled (carbodiimide method) with the antibody toward the surface antigen. The cells are observed through a microscope with horizontal alignment, as they sediment in a (temperature controlled) tube with square cross-section. Stokes Law allows the determination of the density of cells (first alone) using viscosity and density of Dulbecco's modified Eagle's Medium together with the observed mean sedimentation velocity (66 microns/min) and a mean diameter of 10 microns. We found a density of 1.0558 +/- 0.0028 g/cm3 at 10 degrees C. Independently, thinly coated, heavy (and magnetizable) microspheres with the cited antibody are attached to cells and observed likewise. The increased sedimentation velocity permits us to show that the cells were fully covered with microspheres (290 per cell). A magnetic field gradient opposing gravity moved these cells against gravity with two different mean velocities, 340 microns/min and 850 microns/min. The higher velocity resulted in 290 particles per cell, the lower one in 130 particles per cell. The limits for the expansion of this method to smaller particle sizes (down to 10 nm) are evaluated.

Antibodies, Monoclonal↗
PubMed1987

Effect of aryl 4-guanidinobenzoates on the acrosin activity of human spermatozoa.

Certain aryl 4-guanidinobenzoates (AGs; inhibitors of proteinases, including the sperm enzyme acrosin) have been shown to be more potent vaginal contraceptives in rabbits and less toxic than nonoxynol-9, the active ingredient of most marketed vaginal contraceptive formulations. To determine if these AGs can contact sperm and inhibit acrosin when mixed with the entire human ejaculate for a short period of time (roughly imitating clinical conditions), the inhibitors were added to semen at various concentrations for 2 min, after which the seminal plasma and unbound inhibitor were removed from the sperm by Ficoll centrifugation. Subsequently, the total arginine amidolytic activity of the spermatozoa was determined spectrophotometrically after a combined treatment that resulted in extraction, proacrosin activation, and reaction with substrate. Dose-response curves were prepared. All AGs studied were effective inhibitors of the amidolytic activity under these conditions, with ED50 values (the dose levels at which half of the acrosin associated with 10(6) sperm is inhibited) ranging from 10(-5) to 10(-7) M. To determine the effect on the proteolytic activity of individual spermatozoa, the experiment was repeated with 4'-acetamidophenyl 4-guanidinobenzoate (AGB), and the protease released from the sperm was measured by the gelatin-plate assay. The inhibition results were similar to those obtained by extraction of the spermatozoa and measurement of amidolytic activity. Thus, when mixed with the human ejaculate, AGs interact rapidly with spermatozoa to inhibit both their arginine amidolytic and proteolytic activity (probably due primarily or only to inhibition of acrosin) and remain bound even after removal of the seminal plasma. These data encourage further study of the compounds for contraceptive purposes.

Acrosin↗
PubMed1987

The effect of thrombolytic therapy with anisoylated plasminogen streptokinase activator complex on the indicators of myocardial salvage.

The role of anisoylated plasminogen streptokinase activator complex (APSAC) in acute myocardial infarction, in effecting thrombolysis, in limiting infarct size and in preserving myocardial function, was assessed by comparing APSAC and placebo in a double-blind, randomised trial. Between October 1984 and April 1985, 43 patients (mean age 57.3 years) with evolving infarctions (19 anterior/24 inferior) were randomised. All patients received treatment within 3 hours of the onset of pain. Patients over 70 years of age or with contraindications to thrombolytic therapy were excluded. Response to therapy was assessed by comparing reductions in summated ECG R wave amplitude and changes in QRS score at 24 hours and 7 days in the leads with ST abnormalities on admission. Radionuclide ejection fractions (EF) were performed 2 to 6 months after infarction. Evidence of successful reperfusion was based on non-invasive parameters. Mean time to peak cardiac enzyme release was shorter in the active treatment group, indicating effective thrombolysis (11.5 hours vs 17.6 hours; p less than 0.01). No differences were found in R wave reduction or QRS score at either 24 hours or 7 days, between active and placebo groups in total or when divided by infarct site. No difference was seen between the EFs of the groups in total or between inferior infarct groups. The mean EF of the treated anterior group was higher than that of the untreated group (p less than 0.05). Successful thrombolysis was seen in the actively treated group. Evidence of myocardial salvage and preservation was seen among treated patients with anterior infarcts only.

Adult↗
PubMed1986

Percutaneous removal of a fractured right heart catheter from the apex of the right ventricle.

A 58-year-old woman underwent right and left heart catheterization for suspected ischaemic heart disease with ventricular tachycardia. During the procedure a Bourassa catheter fractured and lodged at the right ventricular apex. Under general anaesthesia and radiographic screening the fragment was removed using a bronchoscopy biopsy forceps via the jugular vein after other methods had failed. This case highlights the need for familiarity with several techniques for the removal of such fragments.

Cardiac Catheterization↗
PubMed1986

Amiodarone pulmonary toxicity: clinical and subclinical features.

In a prospective study of lung function of 34 patients taking amiodarone, 24 showed no functional changes but 10 developed a sustained fall in CO transfer factor (TLCO) exceeding 15 per cent. These patients had on average received a higher dose of drug in the first three months of treatment. Seven showed no clinical or radiographic changes and TLCO improved with reduction in drug dose. The other three patients developed florid clinical and radiographic features of amiodarone pulmonary toxicity. All three had impaired TLCO before receiving amiodarone. During the course of the prospective study amiodarone pulmonary toxicity was diagnosed in four other patients. Lung tissue was examined in five of the seven patients with clinical toxicity and showed alveolar wall thickening, exudation and interstitial and intra-alveolar fibrosis with prominent 'foamy' macrophages. Electron microscopy of macrophages showed numerous lysosomal multilamellar bodies, which were demonstrated by energy dispersive X-ray analysis to contain iodine, a constituent of the amiodarone molecule. Two of the patients with clinical toxicity died of respiratory failure; the other five showed gradual improvement on withdrawal of the drug and treatment with corticosteroids. Subsequent withdrawal of steroids was associated with clinical and/or functional deterioration in five patients. A separate autopsy study of the lungs of eight patients dying during treatment with amiodarone, but without clinically-recognised toxicity, showed that an alveolitis had been present in two and prominent 'foamy' macrophages were seen in the lungs of six patients. We conclude that clinical and subclinical effects of amiodarone on the lung are common. The clinical syndrome may be easily misdiagnosed as pulmonary oedema. Subclinical changes in lung function are usually reversible, but whether they herald clinical toxicity if treatment is continued without modification is not established. The presence of 'foamy' macrophages may simply reflect exposure to the drug rather than clinically-important toxicity.

Adult↗
PubMed1986

Absorption of phenylbutazone from a paste formulation administered orally to the horse.

The absorption pattern of phenylbutazone was studied in five horses during administration of the drug in a paste formulation on days 1, 5, 8 and 12 of a 12-day dosing schedule. Since two or more plasma concentration peaks were usually obtained following each oral dose, it was concluded that phasic absorption was a particular feature of the oil:water formulation of the product. Possible causes of this unusual absorption pattern are discussed and the therapeutic implications of both phasic absorption and the recorded values of Cmax, tmax and AUC024 for phenylbutazone and its active metabolite oxyphenbutazone are considered.

Absorption↗