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Biomedical subjects

D Thomas

Publications and source records attributed to D Thomas.

At least 703 records · Page 39Linked to original sources
PubMed1988

Results of serial coronary angiography in patients with homozygous familial hypercholesterolaemia.

We studied the progression of coronary angiographic findings in a series of 10 patients with homozygous familial hypercholesterolaemia. All patients had medical treatment; six had additional surgical treatment. They were followed over a period of 2-10 years (mean follow-up five years). Three types of evolution were observed: (a) normal coronary angiography with no development of any lesion over a period of eight years in two young patients; (b) regression of proximal coronary stenoses in three patients, and (c) progression of coronary angiographic status in five patients. A different evolution of proximal and distal segment lesions was observed; while more than two-thirds of proximal segments stenoses improved and no proximal lesion increased with a 45% decrease in plasma cholesterol level, no improvement was obtained at the distal level. Distal lesions tended to increase and new lesions appeared in spite of a major plasma cholesterol level reduction. When early treatment results in a cholesterol plasma level decrease of more than 45% and a level of about 4 g l-1 over a very long period of time, the coronary prognosis may be good.

Adolescent↗
PubMed1988

Age-related changes in angiotensin II-stimulated proximal tubule fluid reabsorption in the spontaneously hypertensive rat.

The development of hypertension in the spontaneously hypertensive rat (SHR) up to 8 weeks of age involves sodium retention with reduced fractional sodium excretion. Since angiotensin II (Ang II) directly stimulates proximal tubular sodium transport, we investigated age-related changes in proximal reabsorption (Jv), using shrinking split-drop micropuncture before and after enalaprilat in SHR at 5, 7 and 12 weeks of age and in age-matched Wistar-Kyoto rats (WKY). Control values for Jv were higher in the SHR than in WKY at 5 weeks, but lower at 7 and 12 weeks, consistent with an early phase of sodium retention. Enalaprilat reduced mean Jv by approximately 15% in all WKY groups, indicating the extent of Ang II-stimulated transport. In the SHR there was an age-dependent reduction in the effect of enalaprilat on Jv, and by 12 weeks no Ang II stimulation could be detected. Age-related changes in proximal tubular reabsorption could contribute to sodium retention in the young SHR and may reflect a more general pattern of inherited transport defects.

Aging↗
PubMed1988

Stability fluctuations of plasmid-bearing cells: immobilization effects.

The maintenance of the plasmid vectors pTG201 and pTG206 (which both carry the Pseudomonas putida xylE gene) and pB lambda H3 in Escherichia coli hosts was studied in free and immobilized continuous cultures. pTG201, containing the strong lambda PR promoter, was more quickly lost than plasmid pTG206, containing the tetracycline resistance gene promoter. The instability of pTG201 seems to be related to high expression of the cloned xylE genet. Fluctuations in the proportion of pTG201-containing cells were observed in the free system, suggesting the appearance of adaptive descendants (with and without plasmid) from the initial strains. The loss of plasmid vectors from E. coli cells and the fluctuations in the proportion of plasmid-containing cells could be prevented by immobilizing plasmid-containing bacteria in carrageenan gel beads.

Catechol 2,3-Dioxygenase↗
PubMed1988

SAM2 encodes the second methionine S-adenosyl transferase in Saccharomyces cerevisiae: physiology and regulation of both enzymes.

In Saccharomyces cerevisiae the SAM1 and SAM2 genes encode two distinct forms of S-adenosylmethionine (AdoMet) synthetase. In a previous study we cloned and sequenced the SAM1 gene (D. Thomas and Y. Surdin-Kerjan, J. Biol. Chem. 262:16704-16709, 1987). In this work, the SAM2 gene was isolated by functional complementation of a yeast double-mutant strain, and its identity was ascertained by gene disruption. It has been sequenced and compared with the SAM1 gene. The degree of homology found between the two genes shows that SAM1 and SAM2 are duplicated genes. Using strains disrupted in one or the other SAM gene, we have studied the regulation of their expression by measuring the steady-state level of mRNA after growth under different conditions. The results show that the expression of the two SAM genes is regulated differently, SAM2 being induced by the presence of excess methionine in the growth medium and SAM1 being repressed under the same conditions. The level of mRNA in the parental strain shows that it is not the sum of the levels found in the two disrupted strains. This raises the question of how the two AdoMet synthetases in S. cerevisiae interact to control AdoMet synthesis.

Amino Acid Sequence↗
PubMed1988

Long-term vasodilator therapy of chronic aortic insufficiency. A randomized double-blinded, placebo-controlled clinical trial.

Although vasodilator drugs acutely reduce regurgitation and improve cardiac performance in aortic insufficiency, their long-term effects on left ventricular size and function are uncertain. Consequently, we performed a double-blinded, placebo-controlled trial using hydralazine in 80 minimally symptomatic patients who had clinically stable, moderate-to-severe aortic insufficiency. Patients randomized to hydralazine displayed a progressive reduction in left ventricular end-diastolic volume index (LVEDVI) measured by radionuclide angiography, the predetermined end point of the study. At 24 months, mean LVEDVI had been reduced by 30 +/- 38 ml/m2, an 18% reduction from baseline. In contrast, LVEDVI changed minimally in patients randomized to placebo, and the intergroup differences over time were statistically significant (p less than 0.03). The hydralazine group also experienced reductions in left ventricular end-systolic volume index and increases in ejection fraction that were significantly different (both p less than 0.01) from changes in placebo-treated patients. These findings show that long-term treatment with hydralazine reduces the volume overload in aortic insufficiency and suggest that such therapy may have a beneficial effect on the natural history of the disease.

Administration, Oral↗
PubMed1988

Allograft versus autograft bone in scoliosis surgery.

The results of a study of the use of autograft versus allograft bone in the surgery of idiopathic adolescent scoliosis are presented. Two groups of patients, matched for age, sex, level and angle of curve, received bone grafts, 20 patients having autogenous bone from the iliac crest and the other 20 having donor bone from a bone bank. Both groups had otherwise identical posterior fusions and Harrington instrumentation. There was no difference between the two groups in a blind, radiographic assessment of bone graft mass at six months, nor in maintenance of the curve correction over the same period. No major operative complications nor failures of instrumentation were encountered. There was, however, a marked reduction in operative time and blood loss in the patients receiving donor bone and also a much lower incidence of late symptoms relating to the operative sites. We conclude that, even in the presence of adequate iliac crest, the use of bank bone is superior for grafting in idiopathic scoliosis surgery.

Adolescent↗
PubMed1988

Characterization of a ferritin isolated from the midgut epithelial cells of a homopteran insect, Philaenus spumarius L.

Crystalline accumulations of ferritin-like particles are present within the cytoplasma and the nucleus in midgut epithelial cells of the homopteran Philaenus spumarius. A structural study at the electron microscope level reveals that these particles have the morphological characteristics of the ferritin molecule: crystals have a face-centered cubic structure with a lattice parameter of 14 +/- 1 nm; negatively stained isolated particles have the appearance of ferritin; on rotary-shadowed particles 3 axes of symmetry are clearly seen; image processing performed on selected molecules demonstrates a 4-fold symmetry. A semiquantitative electron microprobe analysis effected on aggregates of microcrystals in thin sections reveals a high atomic ratio Fe/P. Analyzed by SDS-PAGE, the protein subunit has a molecular weight of 18,600. The amino acid composition of the protein bears the general characteristics of the ferritin molecule in terms of polar and nonpolar residues. But in terms of sequences, this protein displays a strong dissimilarity to rat liver ferritin as demonstrated with a common amino acid index test and with immunoelectrophoresis experiments.

Animals↗
PubMed1988

[Prenatal diagnosis of an adenomatoid malformation of the lung. Apropos of 2 cases].

Two cases of pulmonary cystic adenomatoid malformation are presented. The first case presented with bilateral pulmonary cystic involvement associated with oligoamnios and feto-placental anasarca. A peculiar feature of this case was the elevated level of alphafetoprotein in the amniotic fluid. In the second case, the pulmonary involvement was limited to one lobe. There was coexistent aplasia of the diaphragm. Premature rupture of the amniotic membranes necessitated a therapeutic abortion at 21 weeks of pregnancy. In connection with these two cases, a discussion based on the data in the literature.

Adolescent↗
PubMed1988

[Remote results of aortic valve replacement with the St. Jude medical prosthesis].

The St Jude Medical prosthesis on the aortic valve was evaluated in a 7-year prospective study which involved 49 patients. Survivors were followed up for 2,577 patient-months, meaning a mean follow-up of 5 years per patient and a minimum follow-up of 4 years per patient. The overall survival rate at 6 years was 79.6 +/- 5.7 p. 100. All deaths occurred during the first two years, and none of them was ascribable to the prosthesis. The left ventricular systolic and diastolic echocardiographic diameters were significantly greater in the patients who died. The linear rate of thromboembolic accidents was 0.93 p. 100 per patient-year, and that of accidents due to anticoagulants was 3.26 p. 100 per patient-year. The probability of freedom from all complication at 6 years was 71 +/- 9 p. 100. In the totality of patients, 10.2 p. 100 required pacemaker implantation; these patients had aortic stenosis exclusively, and all were alive at 7 years. The quality of live, assessed during consultations, was altered in one-half of the survivors. The good results obtained with the St Jude Medical prosthesis are marred by a high initial mortality rate, notably in patients with left ventricular enlargement, by the frequency of accidents due to anticoagulants and by the mediocre quality of life of survivors.

Actuarial Analysis↗
PubMed1988

[Development of left ventricular function following aortic valve replacement].

Changes in left ventricular function were evaluated in twelve patients with aortic valve stenosis and in eleven patients with aortic valve regurgitation in order to find out whether the results obtained soon after aortic valve replacement persisted over a long period. All patients had been provided with a St-Jude Medical valve. Evaluation included electrocardiography, radiography of the chest, phonocarotidography and echocardiography and was performed preoperatively, then three months and five years on average in each patient after surgery. In patients with aortic valve stenosis, the left ventricular mass clearly regressed during the first three months (p less than 0.01) and continued to regress, albeit not significantly, over five years. In patients with aortic valve regurgitation, the left ventricular volume and mass regressed significantly during the first three months and remained normal for five years. No significant variation in systolic performance was observed in both groups. In spite of good overall results, 26 p. 100 of the patients had an unfavourable long-term outcome as they developed major left ventricular dilatation. Nos prosthesis dysfunction was observed, and the St Jude Medical valve caused little obstruction. Thus, with this little obstructive prosthesis the postoperative improvement obtained persisted for five years in most cases of aortic valve stenosis or regurgitation.

Aortic Valve Insufficiency↗
PubMed1987

[Left ventricular insufficiency in chronic obstructive bronchopneumopathies. A cause to look for: dilated cardiomyopathy].

Dilated cardiomyopathy was observed in 2 patients with chronic obstructive lung disease. This association raises first a diagnostic problem: the low specificity of clinical, radiographic and electrocardiographic signs makes it difficult to diagnose a left ventricular failure in such patients. Echocardiography is useful, but right and left heart catheterization and coronary arteriography are needed to establish the diagnosis of dilated cardiomyopathy and exclude other causes of left cardiac failure. The cause-effect relationship between the 2 diseases is not easy to evaluate. It is studied here in the light of the different mechanisms suggested to explain the repercussions function and notably the interactions between ventilation and right and left ventricular function. However, the association of the 2 diseases seems to be fortuitous. Their reciprocal repercussions, notably in the field of haemodynamics, are unquestionable and make the overall prognosis worse.

Aged↗
PubMed1987

SAM1, the structural gene for one of the S-adenosylmethionine synthetases in Saccharomyces cerevisiae. Sequence and expression.

Saccharomyces cerevisiae contains two genes, SAM1 and SAM2, encoding functional S-adenosylmethionine synthetases. The gene SAM1 was isolated by functional complementation of a double mutant of S. cerevisiae, and its identity was confirmed by gene disruption. The cloned gene was used to probe wild type chromosomal DNA, and two regions hybridizing with SAM1 were found, one of which is the SAM1 region. The DNA sequence of SAM1 is reported. The translation product shows a high homology with the one deduced from the sequence of the MetK gene encoding the SAM synthetase of Escherichia coli.

Amino Acid Sequence↗