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Biomedical subjects

R Felix

Publications and source records attributed to R Felix.

At least 865 records · Page 48Linked to original sources
PubMed1977

The effect of pyrophosphate and diphosphonates on calcium transport in red cells.

The effect of 0.5 mM pyrophosphate (PPi), disodium ethane-4-hydroxy-1,1-diphosphonate (EHDP) and disodium dichloromethane diphosphonate (Cl2MDP) on the ATP-dependent Ca2+ extrusion from the human red cell ghosts was studied. PPi and Cl2MDP had no effect, when introduced into the cells or added outside to the medium. EHDP slightly increased the calcium concentration in the released cells and slightly decreased the rate constant of the calcium transport, having opposite effects when it was inside or outside the cells. PPi and the 2 diphosphonates were not found to move easily across the red cell membrane.

Biological Transport, Active↗
PubMed1977

[Current radionuclear methods in the diagnosis of regional myocardial circulation disorders].

Among nuclear medical diagnostic procedures a distinction can be made between non-invasive and invasive methods. The non-invasive methods serve either to image the still viable myocardium ("cold spot" technique) or for direct visualization of recently infarcted myocardial tissue ("hot spot" technique). These methods have the advantage of simple handling and good reproducibility. Side effects and risks are thus far unknown. Improvement of local dissolution should be aimed at in the future and wound greatly increase diagnostic and topographic security. The invasive procedures always require catheterization of the coronary arteries. This is the reason why they can be performed only with coronary arteriography. The Xenon "wash out" technique permits, with some restrictions, quantitative measurement of the regional flow rate. The "inflow technique" permits determination of perfusion distribution. The possibilities of the "double-radionuclide" scintigramm are discussed. For measurement of activity distribution, sationary detectors are generally preferred. In the case of the time-activity curves with the Xenon "wash out" technique, single detectors offer certain advantages.

Blood Flow Velocity↗
PubMed1977

Aggregation of calcium oxalate crystals: effect of urine and various inhibitors.

The influence of various factors on aggregation of calcium oxalate crystals in vitro was determined. Aggregation was assessed by filtering the crystal suspension and measuring the flow rate through a filter. 10% urine completely inhibited aggregation. Orthophosphate and magnesium at concentrations occuring in urine had no effect. Citrate had no effect at 10(-4) M ,but did inhibit at 10(-3) M. The latter effect is probably due to calcium binding. Pyrophosphate and disodium dichioromethylene diphosphonate (C12MDP) inhibited strongly at 10(-4) M, disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) at 10(-5) M, whereas pentanemonophosphonate had no effect. Uromucoid also did not show any inhibitory activity. Studies by means of heat inactivation, ultrafiltration and fractionation on DEAE-cellulose and gel-filtration indicated that the inhibitory activity was heterogenous and that the major part was larger than 10 000 daltons.

Calcium↗
PubMed1977

[Consideration of inhomogeneities in irradiation planning. 2. Influence of inhomogeneities on the shape of the depth dose curve in water with 42 MeV X-rays (author's transl)].

With 42 MeV high-energy radiation, inhomogeneities such as bones, fat, plaster or palacos have no particular influence upon the depth dose curve in water because of the relatively insignificant differences of their atomic numbers, and there is no need to consider them in calculation of the focal dose. Metallic inhomogeneities, however, their effective atomic numbers being relatively high, show a different behaviour in 42 MeV X-ray bremsstrahlung: Just behing the metallic inhomogeneity an increase of the dose as compared to water is to be seen (e.g. directly behind a metallic plate, 4.5 mm thick, the augmentation of the dose amounts to 17%). This difference between 42 MeV X-ray bremsstrahlung and 60Co gamma rays (see part I of the present study) in the shape of the depth dose curve following permeation of metal by the radiations is due to enhanced pair formation within the high-energy radiation of 42 MeV photons.

Adipose Tissue↗
PubMed1977

[Consideration of inhomogeneities in irradiation planning. 3. Influence of inhomogeneities on the shape of the depth dose curve in water with electronic radiation of different energies (author's transl)].

For electron beams the shift of the depth dose curve in water produced by an inhomogeneity with density rho2 and thickness d is to be calculated from Vcalc-d(rho1 -1). Because of additional energy losses by bremsstrahl production, this calculable value Vcalc has to be corrected by means of a factor K to be found experimentally. In the case of larger atomic numbers (metallic plate), and most intensely in the lower energy range from 10 to 20 MeV the loss of dosage on account of inhomogeneities is particularly high due to elastic scattering of electrons (e.g. 86% by a 4.5 mm metallic plate with 10 MeV electronic radiation).

Adipose Tissue↗
PubMed1977

[Local ventricular wall motion, local myocardial flow, and blood flow distribution in a poststenotic myocardial region in patients with coronary heart disease (author's transl)].

In 10 patients with coronary heart disease, local ventricular wall motion, local poststenotic flow, and distribution of myocardial perfusion were determined in the underperfused myocardium before and after 8 mg of Oxyfedrin intravenously. In 8 of the 10 patients there was a uniform reaction consisting of an improvement of wall motion, increase in flow, and homogeneity of flow distribution. These parallel changes of local wall movement and local blood flow in a poststenotic underperfused part of the myocardium can most probably be explained by the positively inotropic action of Oxyfedrin with a consecutive increase in blood flow. The results show that a therapeutic affect in patients with a coronary stenosis less than 60% in the left descending artery can be obtained with a positively inotropic substance.

Adult↗
PubMed1977

[Alterations of pulmonary vessels in congenital heart disease. A summarized differential diagnostic table (author's transl)].

Roentgen signs of congenital heart disease are demonstrated by plain p. a. chest films and kymograms. Diagnostic critieria are discussed which cause increased, decreased, or minimal altered pulmonary blood flow. This simple diagnostic method in combination with the clinical symptom of cyanosis allows differentiation of congenital heart disease prior to catheter examination.

Cyanosis↗
PubMed1976

Aggregation of hydroxyapatite crystals.

A system to study the aggregation of hydroxyapatite crystals was developed. The effect of several factors (Ca2+ x Pi product, Ca2+/Pi ratio, pH, and various substances) were tested. Pb2+, Zn2+, Mg2+ and methyleneblue had only small effects; citrate inhibited aggregation. Pyrophosphate was a strong inhibitor and the diphosphonates disodium ethane-1-hydroxy-1,1-diphosphonate and disodium dichloromethylene diphosphonate were even more potent. The monophosphonate pentanemonophosphonate had no effect. Potent inhibition also occurred with glycosaminoglycans: heparin greater than hyaluronic acid greater than dermatan sulfate greater than chondroitin 4-sulfate greater than chondroitin 6-sulfate. Urine also showed high inhibitory activity. The inhibition of heparin but not that of hyaluronic acid, PPi or urine was abolished by egg white lysozyme. The effects described might be relevant in the normal mineralization process as well as in the mechanisms leading to pathological calcification, such as urinary stone formation.

Binding Sites↗
PubMed1976

Disaggregation of hydroxyapatite crystals.

A system has been developed to measure quantitatively the disaggregation of hydroxyapatite crystals. Disaggregation was induced by pyrophosphate, ethane-1-hydroxy-1,1-diphosphonate, dichloromethylene diphosphonate, haparin and citrate. Hyaluronic acid stimulated aggregation at low concentrations and disaggregation at high concentrations. Lactate had no effect. The possible role disaggregation might play in the resorption of calcified tissues in vivo id discussed.

Binding Sites↗
PubMed1976

Pyrophosphatase and ATPase of isolated cartilage matrix vesicles.

Some of the characteristics of the pyrophosphatase and ATPase activities studied in isolated cartilage matrix vesicles were found to be similar to those already reported for the solubilized and purified bone alkaline phosphatase. Thus, the pH optimum of the pyrophosphatase activity responded similarly to changes in the concentration of Mg2+, Ca2+, and PPi. Further, the ATPase activity was not activated by Ca2+ in the presence of an optimal Mg2+ concentration. It is proposed that a function of the alkaline phosphatase of matrix vesicles in vivo is to hydrolyze the substrates PPi, ADP, and ATP, which are known inhibitors of calcium phosphate precipitation.

Adenosine Triphosphatases↗
PubMed1976

[Pathological perfusion scintigram of the myocardium in angina pectoris patients with normal coronary angiograms (author's transl)].

In patients aged 24 to 45 years with angina pectoris, pathological changes in the exercise electrocardiogram and a normal coronary angiogram, a disturbance of the pattern of myocardial perfusion could be demonstrated in addition by scintigraphy. The cause of this disturbance of myocardial perfusion is unknown. Myocardial scintigraphy is indicated (1) to demonstrate an otherwise undetectable disturbance in the blood flow of the myocardium with a morphologically normal coronary system, (2) in subtotal coronary stenosis before the decision to perform a coronary bypass operation is made, (3) in cases of anginal syndrome with normal coronary angiograms.

Adult↗
PubMed1976

The effect of several diphosphonates on acid phosphohydrolases and other lysosomal enzymes.

Diphosphonates are known to inhibit bone resorption in tissue culture and in experimental animals. This effect may be due to their ability to inhibit the dissolution of hydroxyapatite crystals, but other mechanisms may be important. Since lysosomal enzymes have implicated in the process of bone resorption, we have examined the effect of several phosphonates and of a polyphosphate (P20,2) on lysosomal hydrolases derived from rat liver and rat bone. Dichloromethylene diphosphonate strongly inhibited acid beta-glycerophosphatase (EC 3.1.3.2) and acid p-nitrophenyl phosphatase (EC 3.1.3.2) and to a lesser degree (in descending order) acid pyrophosphatase (EC 3.1.3.-), arylsulfatase A (EC 3.1.6.1), deoxyribonuclease II(EC 3.1.4.6) and phosphoprotein phosphatase (EC 3.1.3.16) of rat liver. Inhibition of acid p-nitrophenyl phosphatase and arylsulfatase A was competitive. Ethane-1-hydroxy-1, 1-diphosphonate did not inhibit any of these enzymes, except at high concentrations. Neither dichloromethylene diphosphonate nor ethane-1-hydroxy-1, 1-diphosphonate had any effect on beta-glucuronidase (EC 3.2.1.31), arylesterase (EC 3.1.1.2) and cathepsin D (EC 3.4.23.5). Of several other phosphonates tested only undec-10-ene-1-hydroxy-1, 1-diphosphonic acid inhibited acid p-nitrophenyl phosphatase strongly, the polyphosphate (P20, I) had little effect. Acid p-nitrophenyl phosphatase in rat calvaria extract behaved in the same way as the liver enzyme and was also strongly inhibited by dichloromethylene diphosphonate, but not by ethane-1-hydroxy-1, 1-diphosphonate. It is suggested that the inhibition of bone resorption by dichloromethylene diphosphonate might be due in part to a direct effect of this diphosphonate on lysosomal hydrolases.

Acid Phosphatase↗
PubMed1976

[The reliability of myocardial scintigraphy with thallium201, A comparison with lacvocardiography and perfusion scintigraphy (author's transl)].

Eighteen patients were investigated by laevocardiography, perfusion scintigraphy and with a 201thallium scan. In four patients with normal contractility of the left ventricle, normal uptake of 202thalium was found in every patient. Hypokinesia of the anterior wall or apex of the ventricle showed normal uptake on the 201thallium scintigram in four out of five patients. It follows that it is not usually possible to diagnose hypokinetic mural portions on 201thallium scintigrams without quantitative analysis. Our experience up to date with areas of akinesia has shown that it is possible to demonstrate areas of scarring (as negative contrast) in seven out of nine cases.

Angiocardiography↗
PubMed1976

Role of matrix vesicles in calcification.

The role of matrix vesicles in the calcification process was investigated in vitro. Isolated vesicles were unable to transport calcium actively. The ATPase activity was not stimulated by calcium in the presence of an optimal magnesium concentration. At a physiological substrate concentration of pyrophosphate, the pyrophosphatase had a pH optimum around 7.0. The vesicles nucleated calcium phosphate precipitation independently of the presence of hydrolyzable phosphate compounds. It is suggested that vesicles induce calcification by nucleating calcium phosphate precipitation and through the local destruction of pyrophosphate, a crystallization inhibitor.

Biological Transport, Active↗