Biomedical subjects
Publications and source records attributed to D Thomas.
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In vitro study of spiramycine action on C. psittaci and C. trachomatis demonstrates that this antibiotic is active in a concentration similar to that found in the serum of patients who have received an injection of 4 g. However, it should be noted that even with a higher dose, few inclusions are still present. On the other hand, the action of spiramycine on mice infected with C. psittaci is highly efficient. The difference between the in vitro results and the excellent in vivo results could be explained by an important accumulation of antibiotic in the tissue.
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The literature is reviewed in the light of 6 cases of Takayasu's disease with cardiac manifestations. Whilst the cardiac manifestations of Takayasu's disease are most often due to the effects of hypertension, there nevertheless exist specifically cardiac lesions: coronary, valvular and myocardial. Coronary lesions, typically ostial, a veritable extension of aortic disease, may also effect the vessels themselves. The course is generally grave but surgery has been performed in a number of cases. Aortic insufficiency is usually moderate and without haemodynamic consequences and is the most frequent valve lesion, others being rare. Direct myocardial involvement with the possibility of arrhythmias or conduction disturbances is also rare, as are pericardial and endocardial lesions.
In 1974 changes in dyspnea, lung function, and pneumoconiotic radiographic abnormalities were recorded among the 1,015 Quebec chrysotile miners and millers surveyed in 1967-1968. The aim was to relate these changes to dust exposure--age, smoking, and earlier health status being taken into account. Dyspnea and lung function were assessed in 722 men, and for 277 recent radiographs were read separately by three experts for changes in the parenchyma and pleura. Each measure was analyzed independently for men without any abnormality when first seen (eligible for "attack") and for others (eligible for progression/regression). Age significantly influenced the rate of attack of pleural abnormality and the rates of attack and progression of dyspnea and lung function decline. Smoking had comparatively minor effects. The only associations with exposure were for progression of parenchymal change (one reader), and for progression of dyspnea. These essentially negative findings are similar to those obtained in a previous longitudinal survey of radiographs from the same workforce.
The authors have applied a xeroradiographic method to the measurement of Achilles' tendon thickness in familial hypercholesterolemia. They have not found a significant increase of the thickness, unless patients with xanthomas were included. Statistical value of the method is thus contested.
The pattern of theophylline metabolites in plasma was studied in 9 preterm neonates of 28-35 weeks gestation. In infants not exposed to corticosteroids prenatally, metabolite formation was dependent on gestational age, postnatal age and/or duration of theophylline therapy. Infants prenatally exposed to betamethasone clearly showed evidence of demethylation and oxidation of theophylline during the first week of life, indicating prenatal activation of the hepatic monooxygenase enzyme system. Preliminary half-life data suggests that activation of hepatic metabolism may not affect initial elimination of theophylline.
A multivariate discriminant analysis of potential risk factors for the progression of visual field defects was performed in 70 patients with chronic open-angle or low-tension glaucoma. Male sex, low diastolic blood pressure and diabetes mellitus were found to be significant risk factors. When the patients with low-tension glaucoma were excluded, a high mean intraocular pressure was identified as a risk factor. It was concluded that there is no reliable way to predict future visual field loss in patients with glaucoma.
Not all patients who undergo splenectomy for idiopathic thrombocytopenic purpura (ITP) respond to operation. This may be due to the presence of an accessory spleen. This is a report of three patients who underwent successful accessory splenectomy after relapse of their disease. Each patient initially experienced a complete response to splenectomy, but recurrence occurred months to years later. All of the patients had persistent Howell-Jolly bodies on peripheral blood smear, yet two of the patients had complete and sustained remissions of their disease after accessory splenectomy. Intraoperative localization of an accessory spleen may be exceedingly difficult in the patient who has undergone a previous operation. However, localization of accessory splenic tissue is greatly facilitated by use of a sterile isotopic detector probe intraoperatively after the injection of technetium-99m-labeled red blood cells. Given the morbidity and mortality rates of refractory ITP, patients who have a relapse after, or who fail to respond to, splenectomy should be evaluated for the presence of an accessory spleen, even if Howell-Jolly bodies are present on peripheral blood smear.
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Human haemoglobin was immobilized by cross-linking with glutaraldehyde as soluble polymers and artificial membranes. Effects of pH and 2,3-diphosphoglycerate on oxygen binding and cross-linking were studied with haemoglobin immobilized in both the oxy and deoxy states. The cooperativity is suppressed and the affinity is increased when compared with native haemoglobin. Haemoglobin immobilized in the oxy state exhibited a higher oxygen affinity than that immobilized in the deoxy state. The alkaline Bohr effect is not significantly different from that of native haemoglobin. The 2,3-diphosphoglycerate influence on oxygen binding was reduced by one third with immobilization. In order to separate the chemical and the "conformation freezing' effects on the properties of immobilized haemoglobin, glutaraldehyde-modified haemoglobin in oxy and deoxy states was produced. Oxygen binding was studied and chemical modifications were checked by electrophoresis and gel filtration. This chemically modified haemoglobin without polymerization and without intra-chain bridging exhibits a behaviour similar to that of cross-linked soluble polymers or membranes of haemoglobin.
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The right anterior oblique ventriculographs of 20 patients with obstructive cardiomyopathy were reviewed, and the images obtained during systole were divided into three groups: (1) bilocular left ventricular cavity with midventricular stenosis; (2) obliteration of the ventricle reduced to its infra-sigmoidal portion, with atrophy or even amputation of the apical portion; and (3) subnormal image. Haemodynamically, the most common abnormality (5/8 patients) in group 1 was the presence of a gradient in the basal state. In group 2, this gradient was only found in 2/8 patients, but the left ventricular telediastolic pressure was much higher in the basal state or after stimulation than in group 1. Haemodynamic changes were moderate in group 3. The abnormalities in left ventricular telediastolic pressure in this type of cardiomyopathy are interpreted as reflecting disorders in compliance which would then be maximal in group 2. This study is part of an attempt to classify the various characteristics of the left ventricle with the view of identifying some forms amenable to surgical treatment.
The present report gives preliminary results of a new sensitive method for potentiometric determination of oestradiol-17 beta in solution, as an application of the competitive enzyme-linked immunoassay technique. Anti-oestradiol-17 beta antibodies are immobilized on a pig skin gelatin membrane, which is incubated with peroxidase-labelled steroid and oestradiol. After fixation of the membrane onto the sensor of an iodide sensitive electrode, the enzymatic activity was evaluated in the presence of hydrogen peroxide and iodides, the electrode potential being a function of hapten concentration in the solution. The purpose of this preliminary work was to determine the optimized conditions for specificity and sensitivity of the antibody-coated membrane in the presence of peroxidase-labelled oestradiol and oestradiol, and to eliminate possible interferences due to adsorption or ionic fixation of enzyme-labelled steroid. The first tests carried out with oestradiol standard solutions gave satisfactory results at levels ranging from 57 pmol/l to 9.2 nmol/l, suggesting that this new procedure should find application in the determination of oestradiol-17 beta in biological fluids.
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Rhodopseudomonas capsulata chromatophores were immobilized with a co-crosslinking method. Immobilization was used as a tool for a defined modification of the chromatophore environment to study ATP production over a long period of time. The light-induced phosphorylation of ADP as a function of time was studied with chromatophores under different conditions: (a) native chromatophores with and without the hexokinase ATP-trapping system; (b) immobilized chromatophores without hexokinase, with the enzyme added in the bulk solution and with the enzyme co-immobilized in the matrix. The overall amount of ATP produced as a function of ADP concentration was studied for native and immobilized chromatophores. The global phosphorylation performed was also studied as a function of the amount of biological material used. The results can be explained by an effect of the ATP/ADP ratio. The results given by the immobilization show that the important point is not the ATP/ADP ratio in the bulk solution but the ratio value in the microenvironment of the chromatophore itself.
Computer interpretation of electrocardiograms was developed twenty years ago and is now routinely performed in the United States, where 9 different programs are being used. Depending on diagnosis and program, computer interpretation shows an 80-100% correlation with human interpretation. The systems provide an aid to diagnosis in preventive medicine and in hospitals without cardiologists, but since interpretations are standardized they are also useful in cardiology units, where they can be used to build up data banks, compare repeat ECGs with clinical findings and thus ultamately perfect electrocardiographic criteria. The use of this technique in Europe remains limited. In France, only two centers possess routine equipment. This feable diffusion is partly due to the cost of computer analysis, which can only compete with that of human interpretation if each system performs a sufficient number of ECGs.