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Biomedical subjects

D Thomas

Publications and source records attributed to D Thomas.

At least 775 records · Page 43Linked to original sources
PubMed1986

Aromatic hydroxylations in peroxidations by haemoglobin systems.

The catalytic activity of haemoglobin on aromatic substrates was studied in three systems: NADH-methylene blue-haemoglobin, ascorbic acid-haemoglobin, and red blood cells. Aniline and phenol but not acetanilide or p-toluidine are hydroxylated by haemoglobin. Dealkylations are not observed. Hydroxylations are postulated to be intermediate reactions in peroxidations catalysed by haemoglobin. The lifetime of the products depends on the presence of electron donors, such as NADH or ascorbic acid, in the medium. In the red blood cells where endogenous electron donors are recycled, levels of the products are higher and their lifetime is longer. This could have implications on drug metabolism by haemoglobin, as haemoglobin is present in large quantities in the organism.

Animals↗
PubMed1986

Piroxicam versus naproxen in the treatment of painful shoulder.

A double-blind, parallel trial of 40 patients with chronic shoulder pain was carried out to compare alleviation of pain and improvement in mobility after treatment with 20 mg piroxicam each morning or 250 mg naproxen twice daily. During the 3-week study, patients also underwent conservative treatment of therapeutic exercise. Piroxicam was better than naproxen at relieving pain at night, but time, rather than a drug effect, seemed responsible for the improvement in shoulder abduction. No difference between the drugs was demonstrated regarding their effect on pain on active movement of the shoulder and external rotation.

Double-Blind Method↗
PubMed1986

[Digitized intravenous angiography in Takayasu's disease. Apropos of 44 cases].

Forty-four patients with Takayasu's disease were investigated by digitised intravenous angiography (DIVA) during a diagnostic and pretherapeutic work up (N = 29) or at surgery (N = 15); the aim of this retrospective study was to assess the role of DIVA in the investigation of this condition. The patients were 36 women, 6 men and 2 children; the average age was 31 years. The intravenous injections were performed in a central vein in 74% and in a peripheral vein in 26% of patients; the average amount of contrast medium injected was 140 ml per investigation (32 g of iodine %). Depending on the site of the lesions, the distribution of the 43 successfully investigated patients was as follows: Type I: 13 (20%), Type II: 6 (14%), Type III: 12 (28%), Type IV: 12 (28%). In the group of patients managed medically (N = 14) no other angiographic investigations were considered. In the group with an indication for surgery or percutaneous angioplasty (N = 15), the procedure was carried out without further angiography in 13 cases; in 2 patients the imaging of the distral vessels was inadequate and complementary angiography was required. All postoperative controls (N = 15) but one were satisfactory. These results show that DIVA is sufficiently reliable for it to be considered as an investigation of first intent in patients with suspected Takayasu's disease. The investigation is well tolerated and can be repeated when necessary to determine the optimal time for surgery. Arterial angiography should seem only to be indicated when the venous approach has failed, which was rare in this series.

Adolescent↗
PubMed1986

Intravenous digital subtraction angiography in Takayasu's disease. A report of 32 cases.

IVDSA appears to be a reliable method and should therefore be considered as a first step examination when Takayasu's disease is suspected. The simplicity and safety of the method provide a rationale for the use of this technique in Takayasu's disease. Therapeutic decisions can usually be obtained without further radiological investigation, and conventional arteriography has to be performed only when data obtained with IVDSA are insufficient. In these rare cases, conventional arteriography aims at the investigation of a particular area. The site of arterial puncture can be precisely guided by IVDSA.

Adolescent↗
PubMed1986

The reactions of SacI, PvuII and EcoRI endonucleases.

A new approach to the mechanism study of DNA restriction is suggested. It is based on enzymatic hydrolysis of DNA in the presence of organic solvent. We found that in the presence of DMSO (10% v/v), the superhelical cleavage of pBR322 DNA by restriction endonucleases SacI and EcoRI proceeds with extensive accumulation of an intermediate, the single-nicked circular DNA, while with PvuII endonuclease the superhelical form is converted directly to the linear form.

DNA↗
PubMed1986

[Surgery of acquired heart valve diseases in France: developments in a 10-year period. A multicentric study].

A multicenter study compares the surgery of acquired valvular diseases in France in 1974 and 1984. This study concerns etiology, surgical procedures and postoperative results within 3 months after operation. 2718 observations issued from 20 medical and surgical centers are divided in 2 groups: the first includes 856 patients who underwent surgical operation in 1974, the other group with 1862 patients was operated on in 1984. Significant differences may be observed. The mean age is higher in 1984 (55 vs. 47 years); the rheumatismal etiology decreases from 50.2% in 1974 to 35.1% in 1984; the degenerative and dystrophic causes increase from 13.8% in 1974 to 32.9% in 1984; while the monovalvular mitral lesion is more frequent (42%) than the aortic one (32.7%) in 1974, the proportion is reversed in 1984 where 47% aortic and 34.5% mitral lesions are found; the number of surgical treatments of mitral stenoses in 1984 is half of those in 1974, but the number of surgically treated aortic stenoses and mitral regurgitations is double of those in 1974; the preoperative examination includes left-side heart catheterization in 81.1% and coronary angiography in 64% of surgically treated patients en 1984, the respective percentages en 1974 being 57.8% and 16.1%. In 1974, 27.6% of patients are in a preoperative functional stage I or II, in contrast to 42.8% in 1984. Mitral commissurotomy represents 29.3% of mitral surgery in 1974 (25.6% of them with closed operation), the respective percentage in 1984 being only 10.5% (2.5% of them with closed heart operation).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

[Coronary stenosis after radiotherapy. Clinical study of 5 cases and review of the literature].

Coronary artery stenosis is one of the possible complications of radiotherapy to the mediastinum. Although less frequent than pericardial disease, anatomopathological studies have shown it not to be uncommon. Five cases with different clinical presentations are reported and the 30 previously described cases are reviewed. Radiotherapy was performed for Hodgkin's disease in 70% of cases and for carcinoma of the breast in 10% of cases. The average delay before onset of the symptoms was 4 years but in some cases delays of up to 10 years were observed. The most common presentation was an inaugural myocardial infarction (50 to 60% of cases). In other cases, angina of effort or typical spastic angina was observed. The coronary lesions were mainly proximal single artery stenosis affecting especially the left anterior descending artery. The typical histological appearances of the stenosis were intimal and sometimes adventicial fibrosis, occasionally associated with medial hyaline sclerosis. However, atherosclerotic lesions were also commonly present. This observation raises the question of the role of irradiation in the development of precocious atherosclerosis by coronary endothelial damage. This hypothesis is supported by the results of experimental studies and by the fact that several autopsy reports showed that the atheroma only developed in the irradiated zone. In addition, although the most demonstrative cases are those of young patients of 30 to 35 years of age, the responsibility of radiotherapy in the development or coronary pathology of older patients cannot be excluded, especially when none of the classical coronary risk factors are present.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Increased frequency of adenocarcinoma of the uterine cervix in young women in Los Angeles County.

By hypothesizing that oral contraceptives (OC's) might have a carcinogenic effect on glandular cells of the cervix if given during periods of active metaplasia (e.g., postmenarchal adolescence), an increasing rate of cervical adenocarcinoma was predicted in young women who had been teenagers when OC's were introduced roughly 20 years ago. Secular trends for cervical carcinomas in non-Hispanic whites were examined by age, histologic type, and social class by using data from the Los Angeles County population-based tumor registry. Between 1972 and 1982, the frequency of invasive cervical adenocarcinoma in women under 35 years of age increased from about 2 to about 5 annually, amounting to an average rate of change of 8% per year (P less than .01). There was essentially no trend for women over 35 years old; the frequency of other invasive carcinomas (and of squamous carcinoma in situ) decreased at average rates of about 3% per year in women under 35 years of age and decreased more rapidly in older women. The increase in adenocarcinoma, unlike risk from cervical cancer generally, was most striking among young women residing in middle-to-upper income neighborhoods, who were the first to use OC's; in this subgroup the average rate of increase was 16% per year (P less than .05). These findings are compatible with our hypothesis and merit further study.

Adenocarcinoma↗
PubMed1986

Phase II study of low-dose methotrexate in advanced osteosarcoma followed by escalation after disease progression: a study of the Soft Tissue and Bone Sarcoma Group of the European Organization for Research on Treatment of Cancer.

Twenty-seven patients with osteosarcoma and measurable metastases were treated with low-dose methotrexate (LDMTX) (80 mg/m2), followed by high-dose methotrexate (HDMTX) (7.5 g/m2) after disease progression in 14 patients. LDMTX was administered on Days 1, 8, and 15; if response or stable disease occurred, it was repeated on Days 29 and 43. If response occurred by Day 57, LDMTX was continued every 2 weeks until disease progression. If stable disease occurred by Day 57, the patient crossed over (optional) to HDMTX. HDMTX was given weekly during the first 3 weeks and continued once every 14 days until disease progression. Twenty-five of the patients were evaluable for response. Three patients (12%) achieved complete remission, with durations of 5, 14, and 34 weeks, respectively. The time to disease progression from the start of treatment was 19, 28, and 42 weeks. Twelve patients (48%) had stable disease, with a median duration of 7.5 weeks (range, 6-20). Ten patients (40%) had disease progression. In general, toxicity with LDMTX was mild. The most frequent toxic effect was stomatitis. Twelve of 14 patients who crossed over to HDMTX were evaluated for response. Six patients had stable disease and six had disease progression. We conclude that the results achieved with LDMTX seem inferior to the results achieved with HDMTX described in the literature.

Adolescent↗
PubMed1986

Risk factors for invasive cervical cancer among Latinas and non-Latinas in Los Angeles County.

A case-control study among white women in Los Angeles County was conducted to investigate etiologic factors that might explain the high rates of invasive cervical cancer among Latinas. Two hundred patients with invasive squamous cell carcinoma of the uterine cervix and matched (age, sex, preferred language, and neighborhood) controls were interviewed, 98 pairs in English and 102 pairs in Spanish. Seven factors were found to contribute independently and significantly (P less than .01) to risk, each after adjustment for the other six: years since last Pap smear, years of education (protective), frequency-years douching, pack-years of smoking, years of barrier contraceptive use (protective), number of sexual partners before age 20, and recognized episodes of genital warts. An eighth variable, interval in years between menarche and first intercourse, was the second variable to enter the stepwise logistic regression analysis but lost its statistical significance when sexual partners before age 20 entered the model. Together, these eight variables accounted for almost 99% of the risk. There were no significant interactions between any of these variables and age, language of interview, or birth in a Latin country. There was no increased risk associated with use of oral contraceptives, either before or after adjustment for the other significant factors. Compared to English-speaking controls, Spanish-speaking controls smoked less, douched less, had fewer sexual partners before 20, and had essentially the same average interval between menarche and first intercourse and the same average number of episodes of genital warts; however, they had had a longer interval since their last Pap smear, fewer years of barrier contraceptive use, and fewer years of education. Education, presumably a correlate of an inadequately measured etiologic risk factor (possibly papillomavirus infection), was responsible for the greatest difference in risk between the Spanish- and English-speaking cases.

Adolescent↗
PubMed1986

[Essential and iatrogenic gingival hyperplasia. Its morphology and significance].

11 specimens were carried out in patients with idiopathic gingival hyperplasia (3 cases), gravidic hyperplasia (1 case), iatrogenic hyperplasia (5 cases after cyclosporin A administrated in patients with cardiac grafts, 2 cases after treatment by Adalat). By optic microscopy, the deep collagen base is thickened, associated sometimes to an inflammatory process. By histoenzymology, the fibroblasts have high activities of their oxidative enzymes and also of the enzymes of protein synthesis. The electron microscopy corroborates the numerous globular fibroblasts with well-developed rough endoplasmic reticulum. These results prove the main role of fibroblasts in these lesions and the etiopathogenesis of this hyperplasia is discussed.

Adolescent↗
PubMed1986

Effects of high-calcium and/or high-sodium diet on basal and angiotensin II-stimulated blood pressure in the spontaneously hypertensive rat.

Direct conscious blood pressure (BP) was measured via indwelling femoral cannula to evaluate the effects of chronic diet supplements with Na, Ca or both, offered to 3-week-old weanling spontaneously hypertensive rats (SHR). Despite similar food intakes, body weights were reduced within 1-2 weeks on high-Ca diets. Blood pressure was unchanged by 5.5 weeks of diet treatments. However, irrespective of concomitant Na supplement, more prolonged treatment with the high-Ca diet completely abolished the further increase in BP between the 9th and 12th weeks of age, which was noted in the rats fed the normal or high-Na diets. Angiotensin-stimulated BP was attenuated by high-Ca diets regardless of diet Na, similar to basal readings. These weight and pressure effects of Ca were not reproduced by high-Na diet alone. For all four groups, BP was directly and significantly correlated with body weight, both at 9 and 12 weeks of age. These studies demonstrate the potential role of growth retardation in the antihypertensive action of oral Ca loading in young rats.

Angiotensin II↗
PubMed1986

Competitive strategy in the hospital industry.

Porter recently developed a framework for applying effective strategies in an increasingly competitive business environment. His framework can be adapted to the health care industry and can serve as a tool for success.

Costs and Cost Analysis↗
PubMed1986

The nature and role of disturbances in calcium metabolism in genetic hypertension.

Abnormalities in Ca metabolism in genetic hypertension have been suggested by studies of the spontaneously hypertensive rat and of humans with essential hypertension. A state of relative Ca deficiency in genetic hypertension was previously hypothesized to explain the reduced serum ionized Ca, increased serum parathyroid hormone levels, and the association between oral Ca loading and mild reduction in blood pressure. Renal Ca leak, reduced intestinal Ca absorption, and diminished Ca intake were further postulated to account for the Ca deficient state. This hypothesis, however, is not supported by the following lines of evidence in genetic hypertension: the absence of fasting hypercalciuria owing to intrinsic tubular defects, increased net Ca absorption in vivo despite greater Ca retention before and during established hypertension, increased intracellular free Ca concentrations, the failure to aggravate the hypertension by 50% reduction in dietary Ca intake, and the failure to ameliorate the hypertension by maneuvers that augment Ca balance (parenteral Ca administration, a high Mg diet, and 1,25-dihydroxyvitamin D3 injections). The available literature may be explained by the alternative hypothesis that genetic hypertension is characterized by generalized membrane defects in Ca regulation, resulting in a relative increase in cytosolic free Ca. The mechanism (or mechanisms) and physiological consequences of the disturbances in Ca homeostasis, however, remain to be defined.

Animals↗
PubMed1986

[Thymoma and pregnancy. Apropos of a case].

A case of thymoma associated with pregnancy is reported. This association is extremely rare (8 described cases) and the clinical outcome is most frequently unfavorable for the mother. The diagnosis was given by a standard chest X-ray performed routinely post-partum. Sixteen months after total surgical extirpation of the tumor and adjunctive radiotherapy the patient is still in complete remission. The presented case is discussed with reference to a review of literature.

Adult↗
PubMed1985

Experimental evidence for multistability in a photobiochemical system.

The kinetic behavior of a typical Hill reaction catalyzed by thylakoids and using the oxidized form of 2,6-dichloroindophenol (DCPIPox) as the artificial electron acceptor, is considered. Here, the light absorption process and the reduction of DCPIPox are autocatalytically coupled, leading to the occurrence of multiple steady states with respect to either the acceptor concentration or the incident light intensity. Experimental evidence is presented for both cases and the emergence of autocatalysis is discussed. The effect of the spatial arrangement on the global behavior of the system described is emphasized.

2,6-Dichloroindophenol↗
PubMed1985

3 beta, 17 beta-hydroxysteroid dehydrogenase of Pseudomonas testosteroni. Kinetic evidence for the bifunctional activity at a common catalytic site.

3 beta, 17 beta-Hydroxysteroid dehydrogenase (3 beta 17 beta HSDH) is an NAD-dependent dehydrogenase which has a double specificity for the 3- and 17-positions on the steroid skeleton. When dehydroepiandrosterone (DHEA) is used as steroid substrate, and the assay coupled with ketosteroid-isomerase, the two reactions occur alternately and each reaction on the 3-position produces a chromophoric molecule. These two reactions can follow one another without dissociation of the coenzyme from the enzyme binding site. This is confirmed by competition experiments with another dehydrogenase.

17-Hydroxysteroid Dehydrogenases↗