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Biomedical subjects

A Lenaers

Publications and source records attributed to A Lenaers.

At least 55 records · Page 3Linked to original sources
PubMed1977

Cardiac output monitoring during the acute phase of myocardial infarction: accuracy and precision of the thermodilution method.

A triple human catheter was used for the determination of cardiac output during the acute phase of moycardial infarction in 23 patients. The correlation coefficient between thermodilution and the Fick method was 0.91. Precision of the method assessed by multiple repeated determinations was 4.8 or 5.6%. Quadruplicate determinations allowed to detect variations of cardiac output in the range of 0.465 1/min. Variation between two successive determinations of more than 9.4% can probably be attributed to a technical error.

Acute Disease↗
PubMed1977

Influence of short-term physical training on exercise tolerance after myocardial infarction.

14 patients with stabilized myocardial infarction were submitted to a functional evaluation before and after 3 sessions of interval training on the bicycle ergometer. With submaximal exercise, myocardial load decreases after short-term training, the heart rate and the blood pressure--heart rate product being significantly lower for the same oxygen consumption. Maximal working capacity, expressed in watts or oxygen consumption, increases significantly after short-term training, the benefit being one-third of that obtained after 6 weeks' training. These early changes in functional capacity are positively correlated with those obtained by a more prolonged rehabilitation program. Leg muscular blood flow during submaximal and maximal exercise tends to increase after short-term training, although this change is not systematic and thus not significant.

Adult↗
PubMed1977

Segmental analysis of Ti-201 stress myocardial scintigraphy.

Thallium-201 scintigraphy of the exercised myocardium was performed in 70 male patients admitted for coronary arteriography and left-ventricular angiography. Left ventricular scintigrams were collected in left lateral, left anterior oblique (65 degrees, 45 degrees, and 25 degrees), and anterior views, and the images were divided into eight segments: apical, anteroseptal, anterior, antero-lateral, posterolateral, posterior, inferior, and posteroseptal. A correlative study between segmental hypoperfusion on scintigram and coronary-artery stenosis visualized by contrast artriorgraphy allowed selection of specific segments for each main coronary artery. Hypoactivity in the apical and posterior segments did not appear reliable. Using selected segments, we were able to identify LAD disease in 84%, LCx disease in 49%, and RCA disease in 79% of documented significant stenosis, with specificity of 95%, 89%, and 88%, respectively. Coronary-artery disease could be detected in 95% of patients having more than 50% coronary-artery stenosis, with 93% specificity. In most cases, patients with two-vessels disease and three-vessel disease could not be distinguished from each other. Multiple-vessel disease suggested by segmental analysis of myocardial scinitgrams after exercise was confirmed artriographically in 88% of the patients, but 52% with scintigrams suggesting signle-vessel disease had, in fact, multiple-vessel disease.

Adult↗
PubMed1976

Surface maps and myocardial scanning at rest and during exercise: comparison with coronary angiography.

The observations of surface electromaps recorded at rest and during exercise in two examplative cases are reported: the first one deals with a normal man while the second refers to a patient suffering from an old inferior myocardial infarction with bouts of angina pectoris; these surface maps are compared with myocardial scanning also performed at rest and during exercise. Special attention is devoted to the possible relation of the above described, non-invasive, techniques to the anatomical description of coronary lesions as demonstrated by coronary angiography. A close relationship is found between the surface potential distribution pattern and the area of hypofixation observed on the scan as far as the presumed location of ischemic myocardial tissue is concerned.

Adult↗
PubMed1976

[Reproductibility of the true measurement of blood volume, cardiac output, mean pulmonary circulation time and pulmonary blood volume by radiocardiography].

Radiocardiography provides a simple method of measurement of blood volume, cardiac output, mean pulmonary circulation time, and pulmonary blood volume. The use of a computer allows the results to produced immediately provided that the circulating blood volume is measured during the test anpd that the radiocardiographic tracing is analysed by an entirely automatic method. The reproducibity of the results given by this automatic method has been studied in 35 patients, two measurements being made at 20 minute intervals. The standard deviation of the percentage difference between consecutive measurements was 5.8% for the blood volume, 10.4% for the cardiac output, 8.8% for the mean pulmonary circulation time, and 9.7% for the pulmonary blood volume.

Adolescent↗
PubMed1975

Type III procollagen and collagen in skin.

A form of collagen, containing three alpha chains of type III, can be extracted from foetal calf, calf and rat skin under physiological conditions. This native collagen was purified by DEAE-cellulose chromatography and then was analysed by polyacrylamide gel electrophoresis which showed it consisted of several high molecular weight components, the size of gamma components and larger species. Prior reduction in dithiothreitol dissociated these large polymers into two components: the minor one migrated between the alpha1 (I) and alpha2 chains while the predominant one migrated between the alpha and beta chains. These two monomers were isolated by CM-cellulose chromatography. The minor one, which eluted between the alpha1 and alpha2 chains, had a molecular weight of approx. 95 000; its amino acid composition was similar to that of alpha1(III). The major one eluted in the alpha1 region and had a molecular weight of approx. 120 000; its amino acid composition, while similar to that of the alpha1(III) chain, differed in detail, and it is presumed to be a pro-alpha1(III) chain. Following pepsin digestion, the native collagen remained as a disulfide-bonded trimer which dissociated into only one component, a1(III), when denatured in dithiothreitol. These results suggest that the original, extracted protein consisted primarily ofa precursor form of type III collagen. This procollagen did not polymerize when heated at 37 degrees C and did not form the usual segment long spacing aggregates under suitable conditions. It was not modified by incubation with a purified procollagen peptidase preparation. This appears to be the first example of the isolation of type III (pro)collagen by extractive methods, without resorting to tissue digestion by proteolytic enzymes.

Amino Acids↗
PubMed1974

Calf tendon procollagen peptidase: its purification and endopeptidase mode of action.

The procollagen peptidase activity of calf tendon has been purified. The enzyme has a high degree of specificity for native procollagen and converts both pro alpha1 and alpha2, to alpha1 and alpha2, respectively. The purified enzyme is an endopeptidase which excises the amino terminal peptide extensions of the precursor chains in block; the molecular size and amino-acid composition of the excised peptides compare favorably with those predicted in previous reports. Antisera to the enzyme and to procollagen have been prepared and have been used to characterize the enzyme, the enzymatically excised peptides, and the enzyme-peptide complex in reaction mixtures.

Amino Acids↗
PubMed1971

Procollagen peptidase: an enzyme excising the coordination peptides of procollagen.

A heritable connective tissue disorder of cattle, dermatosparaxis, is characterized by an extreme fragility of the skin and the presence of additional peptides at the N-terminal extremities of the collagen alpha chains, p-alpha(1) and p-alpha(2). The existence of an enzyme activity is demonstrated in normal connective tissues that is capable of cleaving these additional N-terminal peptides from dermatosparaxic collagen. The activity is demonstratable with dermatosparaxic collagen in solution, as well as with reconstituted dermatosparaxic collagen fibrils polymerized in vitro. It has a pH optimum of about 7.0 and is inhibited by EDTA and mercaptoethanol. Differences in K(m) and V(max) values exist depending on the substrate utilized, i.e., p-alpha(1) or p-alpha(2); and the presence of additional amounts of one substrate, p-alpha(1), alters the concentration requirement for the second substrate, p-alpha(2). The product of the excision reaction with p-alpha(1) as substrate is an equimolar amount of normal alpha(1) monomer; the product when p-alpha(2) is substrate is an equimolar amount of normal alpha(2) monomer. The enzyme is present in normal calf skin, tendon, aorta, cartilage, and lung; it can be demonstrated in the skin of rats and humans. The enzyme activity is absent in dermatosparaxic connective tissues, thus suggesting that dermatosparaxis is caused by the absence of a normal enzyme function rather than by the production of an abnormal collagen.

Animals↗