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Biomedical subjects

R Kremer

Publications and source records attributed to R Kremer.

At least 73 records · Page 4Linked to original sources
PubMed1984

[Cardiac valvular surgery after 65 years of age].

252 symptomatic patients aged 65-79 underwent surgery between 1970 and 1982 for heart valve lesions. Hospital mortality was 11.8%. Analysis of the short and long term results justifies cardiac surgery in elderly patients with valve disease.

Actuarial Analysis↗
PubMed1983

Left atrial myxoma causing fluttering of the anterior mitral leaflet.

This report describes the M-mode echocardiographic features of a left atrial myxoma, before and after excision of the tumor. Preoperative M-mode echocardiogram demonstrated fine diastolic fluttering of the anterior leaflet of the mitral valve which disappeared after surgery. Preoperative aortography and minutious examination of the aortic valve during operation excluded any associated lesion of the aortic valve. The fluttering of the anterior mitral valve is probably related to turbulent blood flow around the tumor prolapsing between mitral leaflets during diastole.

Aortic Valve Insufficiency↗
PubMed1982

Characterization of the rabbit renal receptor for native parathyroid hormone employing a radioligand purified by reversed-phase liquid chromatography.

Iodinated native bovine parathyroid hormone (bPTH(1-84)) was separated from uniodinated hormone by reversed-phase liquid chromatography techniques after lactoperoxidase labeling. Analysis of iodinated residues after enzymatic digestion indicated that the major labeled product was largely monoiodinated on the sole tyrosine residue. This material retained full bioactivity in an in vitro renal adenylate cyclase assay. Binding of 125I-bPTH(1-84) to rabbit renal membranes at 4 degrees C was proportional to membrane protein concentration and was saturable and dissociable. Radioligand binding was inhibited by concentrations of unlabeled bPTH(1-84) required to stimulate adenylate cyclase in the same membrane preparation but was not inhibited by non-PTH peptides other than adrenocorticotropin at high concentrations (greater than 10 microM). Synthetic NH2-terminal analogues of bPTH(1-84) all elicited approximately equivalent inhibition of radioligand binding which was, however, less potent than unlabeled bPTH(1-84), suggesting a role for the carboxyl region of the molecule in the interaction of bPTH(1-84) with its receptor. Activity of the NH2-terminal agonists was similar to bPTH(1-84) in stimulating adenylate cyclase. Although substitution in sequence position one, of serine in human PTH(1-34) for alanine in bPTH(1-34), reduced activity in the adenylate cyclase assay, inhibition of 125I-bPTH(1-84) binding by both peptides and by an analogue of bPTH(3-34) was equivalent, consistent with a minimal contribution of the first 2 residues for receptor binding of the NH2-terminal region of PTH. The results illustrate the utility of the radiolabeled preparation of native bPTH we have developed and emphasize the importance of probing the PTH receptor with an intact hormone to maximize information concerning the mechanism of PTH action.

Animals↗
PubMed1982

Parathyroid hormone stimulates mammalian renal 25-hydroxyvitamin D3-1 alpha-hydroxylase in vitro.

We have shown that parathyroid hormone (PTH) stimulates 25-hydroxyvitamin D2-1 alpha-hydroxylase activity in mitochondrial preparations of guinea pig kidney in vitro.1,25-[3H]dihydroxyvitamin D3 produced from 25-[3H]hydroxyvitamin D3 was identified by both normal phase and reversed-phase high pressure liquid chromatography. Enzyme stimulation by PTH was dose-dependent, peaked after 15 minutes of incubation with hormone and was maximal at concentrations of approximately 10(-10) M PTH-(1-84) and PTH-(1-34). This guinea pig renal model therefore permits direct examination of hormonal regulation of the mammalian enzyme in vitro.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1979

[Radiocompetitive dosage of 25 hydroxyvitamin D and 24, 25-dihydroxyvitamin D in geriatrics. Study of seasonal variations].

Dosages of 25 (OH) D and of 24, 25 (OH) 2 D in the plasma were done in March and October in 26 women more than 70 years old, hospitalized in a semi-chronic disease hospital of the Paris area. Eleven young adults, studied in June, served as control. There was a significant decrease of 25 (OH) D and 24,25 (OH) 2 D in older individuals (pL 0,001). In march, the levels of 25 (OH) D and 24,25 (OH) 2 D were respectively 2,7 +/- 1,6 mg/ml and 0,88 +/- 0,53 mg/ml. In October the level of 25 (OH) D (5,8 +/- 2,6 mg/ml) were significantly higher (p L 0,01) whereas the level of 24,25 (OH) 2 D did not vary (0,84 +/- 0,58 mg/ml). These results are in agreement with those obtained in England. The underline the relative deficit vitamin D in older individuals. The constant decrease of 24, 25 (OH) 2 D remained unexplained.

Aged↗
PubMed1978

A simple and specific competitive protein binding assay for 24,25-dihydroxyvitamin D in human serum.

A sensitive and specific competitive protein binding assay for 24,25-dihydroxyvitamin D was developed using rat kidney cytosol as the binding protein. It also included a chromatographic step on a Sephadex LH 20 column to separate the metabolite specifically. The average value for 24, 25-dihydroxyvitamin D in serum in 19 male and female healthy subjects aged from 20 to 40 was found to be 8.24 +/- 0.34 ng/ml (1.98 +/- 0.08 . 10(-8) mol/l) mean +/- S.D. In hepatic insufficiencies the levels are higher (14.15 +/- 3.59 ng/ml) than in normal subjects. A comparison between 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D levels was made.

Adult↗
PubMed1978

[Radiocompetitive estimation of 25-hydroxyvitamin D in human serum (author's transl)].

A radiocompetitive estimation of 25-hydroxyvitamin D in human serum is described. After extraction, a stage of purification by chromatography on a Sephadex LH 20 column permits separation of 25-hydroxyvitamin D from Vitamin D and other metabolites. The reaction of radiocompetition uses as tracer tritiated 25-hydroxycholecalciferol and as source of binding protein, rat renal cytosol. The characteristics of the binding protein and the presence in human plasma of significant quantities of 24,25-dihydroxyvitamin D render necessary the chromatographic stage. This technic permits one to measure simply and specifically 25-hydroxyvitamin D in the human serum, of which normal levels (average +/- standard deviation) are 12.88 +/- 5.42 microgram/l 3.2.10(-8) + 1.35.10(-8) mol/l).

Adult↗
PubMed1975

[Conduction disorders in aortic valve diseases].

Among 304 cases of aortic valvulopathies studied for surgical selection, the authors have found a high incidence of conduction disturbances (16% in aortic stenosis and 18,4% in aortic regurgitation). The conduction defects are mostly intraventricular among stenosis isolated or associated to regurgitation and mostly atrio-ventricular among pure aortic insufficiencies. The highest incidence (30%) being found in patients with bacterial endocarditis acute or healed. The incidence of conduction disturbances increases with age, with the presence of valvular calcifications, of left ventricular strain or failure, of coronary insufficiency and angina... practically with the duration and the severity of the valvular disease. Surgical risk is heavier and natural prognosis poorer in valvulopathies with conduction disturbances. But these disturbances never contraindicates surgery : it is sometimes necessary to insert a pacemaker with or without valvular replacement mostly in aortic stenosis with infrahisian conduction defects. During hemodynamic investigation of such cases one must be ready to stimulate the heart, particularly during right heart catheterization of patients with complete left bundle branch block.

Adult↗
PubMed1975

[Orgainc tricuspid pathology in rheumatic valvulopathies].

Surgical observations show that organic tricuspid lesions are not uncommon: 3.2% among cases of valvular surgery, 9.5% among patients with combined mitral and aortic replacements. Pure stenosis is relatively rare (7 cases) but easy to diagnose: this lesion plays a protective role on pulmonary parenchyma. There is no symptom due to congestive lungs and few pulmonary post-operative complications among these patients. Organic tricuspid insufficiency, isolated or associated to stenosis is more frequent (18 cases) but more difficult to diagnose before surgery. There seems to be no protection of the pulmonary circulation. Pulmonary arterial hypertension, clinical and radiological features of congestive lungs and post-operative pulmonary complications are usual.

Adult↗
PubMed1975

[Rupture of the mitral chordae tendinae].

Twenty-seven cases of ruptured chordae tendineae have been discovered during surgery for mitral regurgitation (9,3 %) : the highest incidence of ruptured chordae tendineae has been found among pure mitral insufficiency (36 %). In thirteen cases, the rupture was isolated, without any other valvular lesion. The syndrome described as characteristic of rupture was present in one third of our patients : isolated cases do not differ clinically from the others but for a more frequent acute evolution. In pure or predominant mitral regurgitation, surgery seems needed when clinical aggravation, acute or progressive, cannot be explained by arrhythmia, anaemia, pulmonary embolism, hyperthyroidism.

Adult↗