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Biomedical subjects

K Vyska

Publications and source records attributed to K Vyska.

At least 37 records · Page 2Linked to original sources
PubMed1985

Use of 3-fluoro-deoxyglucose for the assessment of cerebral perfusion and glucose transport. I. Theory.

A new model is described applying dynamic positron emission tomography (dPET) and 3-fluoro-deoxyglucose (3FDG) to the measurement of local cerebral perfusion and glucose transport across the blood-brain-barrier (BBB). The model takes advantage of 3FDG being practically not metabolized in brain and being transported back from tissue into the circulation. Simultaneous registration of tracer concentration in blood and tissue by dPET permits the in vivo determination of the Michaelis-Menten constant (K) and maximal velocity (V) for 3FDG and glucose transport across the BBB as well as the determination of local perfusion rate. Values obtained in normal cortex using this method were K = 6.3 mumol/g and V = 2.46 mumol/g min. Local perfusion rate ranged between 0.8 and 0.98 ml/min g.

Blood-Brain Barrier↗
PubMed1985

Use of 3-fluoro-deoxyglucose for the assessment of cerebral perfusion and glucose transport. II. Evaluation of patients undergoing EC-IC bypass surgery.

Dynamic positron emission tomography (dPET) and 3-fluoro-deoxy-glucose (3FDG) have been applied to the followup of selected patients undergoing extracranial-intracranial (EC-IC) bypass surgery. To determine glucose transport across the blood-brain-barrier and local perfusion rate a new mathematical model has been used. Immediately following EC-IC surgery, dPET shows an increase in perfusion of approx. 7 ml/min 100g over both the operated and the contralateral hemispheres indicative of reversal of interhemispheric steal. Followup studies show reduction of local perfusion rate combined with an improvement of glucose transport rates. This finding suggests improvement of cerebral metabolic capacity following improvement of perfusion suggestive of longterm beneficial effects of EC-IC bypass.

Blood-Brain Barrier↗
PubMed1983

Minimal cardiac transit times--a sensitive parameter reflecting changes in cardiac volume-to-flow ratios.

Minimal cardiac transit times (MTTs) are differences between times of appearance of the indicator at consecutive segments of the cardiopulmonary circulation. The MTTs are shown to be directly proportional to the quotient of volume to flow. The relationship of the cardiac MTTs to ventricular ejection fraction was derived. Utilizing this technique the ejection fractions of the left and right ventricles in 72 normal individuals were calculated. Theoretical aspects of measuring cardiac MTTs were related to experience of clinical application and confirmed its usefulness.

Cardiac Output↗
PubMed1983

Myocardial imaging and metabolic studies with [17-123I]iodoheptadecanoic acid in patients with idiopathic congestive cardiomyopathy.

In twenty patients with primary congestive cardiomyopathy (COCM) the patterns of accumulation and washout of the fatty acid analogue [17-123I]iodoheptadecanoic acid (I-123 HA) were studied. In contrast to patients with ischemic heart disease, where reduced I-123 HA accumulation was correlated with stenosis of the main coronary arteries, thus usually involving larger wall segments, the patients with COCM concentrated I-123 HA heterogeneously in small spotty segments throughout the entire left-ventricular myocardium. The regional washout half-times varied between 15.1 and 116.2 min. It seems that in patients with severe COCM the elimination half-times are more prolonged than in early stages of the disease. There was no correlation between the regional uptake and the elimination half-times. Sequential myocardial imaging with I-123 HA appears useful for noninvasively diagnosis of COCM.

Cardiomyopathies↗
PubMed1982

Flow cytometry of human testicular tissue.

Flow cytometry of testicular tissue from autopsies showed differences in the proportion of substained spermatozoa (1 CA), spermatids (1 CB), diploid 2C nuclei and premeiotic spermatozoa in the 4 C class. The evaluation of the histograms was performed with computer assistance. Healthy accident cases or those delivered in forensic medicine furnished the control values. Patients with hepatic cirrhosis showed a nearly complete loss of the haploid class, while cases with fatty degeneration of the liver demonstrated a reduction. Circulatory insufficiency in cases of acute shock resulted in an increase in the 4C values of meiotic prophase I and a decrease of spermatids. Spermatozoa were normal in these cases. After prolonged shock a nearly complete breakdown of spermatogenesis was observed. In cases of atherosclerosis an irregular degree of reduction was seen. Cancer patients showed a reduction of spermatogenesis in correlation to therapy.

Adult↗
PubMed1982

Demonstration of decreased functional activity of visual cortex by [11 C]methylglucose and positron emission tomography.

A hemorrhagic infarction which caused left hemiparesis and homonymous hemianopia was demonstrated as a hypodense lesion on the first CT; 2 weeks later it was hyperdense and enhanced after injecting meglumine. Positron emission tomography with [11C]methyl-D-glucose also revealed the ischemic lesion, but also marked decrease of glucose uptake in the visual cortex, which indicated decreased functional activity.

Adult↗
PubMed1981

Organization of highly purified calf thymus DNA. I. Cleavage into subunits and release of phosphopeptides.

DNA (N-DNA) prepared under conditions eliminating the exposure of chromatin to cytoplasmic components exhibits some special properties not observed for DNA prepared by standard methods (S-DNA).N-DNA, having a sedimentation coefficient of 24.7 S and a firmly bound protein content of 0.7%, can be cleaved (in contrast to S-DNA) by treatment with chelating agents, into stable subunits having a mean molecular weight of about 500 000. This cleavage was shown to be an ordered process which involved no enzymatic or shear degradation. It was accompanied by the release of phosphopeptides. The analyses of these phosphopeptides revealed the presence of two main fractions. One contained phosphoserine and glycine (Mr about 1400), and the other contained phosphoserine, glycine, alanine, glutamic and aspartic acids (Mr about 900). The amount of released phosphopeptides could be correlated to the extent of cleavage.

Animals↗
PubMed1981

Relationship between the purity and molecular weight of calf thymus DNA.

The molecular weight and purity of calf thymus DNA, prepared by different procedures of isolation, were determined. The highest molecular weight was obtained by the method of Blin and Stafford (12 x 10(7)). This DNA contained 17% protein. The further purification of this DNA led both to increase of purity and to reduction of the molecular weight. The relationship between molecular weight and achieved purity was found to be a monotonic sigmoid-shape function ranging between the molecular weights of 12 x 10(7) and 12 x 10(6) and between the purities of 17 and 0.7% protein. After achieving this highest level of purity (0.7% protein content), despite repetition of the purification cycles, no further increase of purity or reduction of the molecular weight was achieved. The use of [14C]T4 bacteriophage DNA as internal standard demonstrated that the reduction of the molecular weight does not result from an artifact, such as shear or enzymatic degradation, but that the high-molecular-weight calf thymus DNA preparation must be considered to consist of either aggregates of small subunits stabilized by laterally attached proteins or of tandemly joined units connected by protein or peptide linkers.

Animals↗
PubMed1981

[Studies of cardiac metabolism with 123I-labelled fatty acids and 11C-methylglucose (author's transl)].

To characterize externally detectable changes in the myocardial metabolism of free fatty acids (FFA) and glucose, which are associated with ischemia and cardiomyopathy, omega-123I-heptadecanoic acid (stearic acid analogue), 75Br-phenylpentadecanoic acid, and 3-0-11C-methyl-D-glucose were used as indicators. It could be demonstrated that in the metabolism of free fatty acids at least two different patho-physiological situations may exist. Disturbances in the mechanism of the accumulation of free fatty acids lead to a decrease of the amount of the free fatty acids which are available for energy production (these disturbances can be recognized as indicator accumulation defects). Disturbances associated with the mechanism of free fatty acid catabolism lead to a decrease of the ability of the myocardial cell to utilize the free fatty acids (these disturbances can be recognized as changes in indicator elimination rates). Whereas in ischaemic heart disease, the areas with altered FFA accumulation correlate with the areas of altered FFA-elimination, no correlation was found in the case of cardiomyopathy. The 11C-methylglucose seems to be an excellent indicator for the in-vivo assessment of the function of transport system in the myocardial cell membrane.

Animals↗
PubMed1981

In vivo assessment of phagocytic properties of Kupffer cells.

Three-compartment analysis was used to assess the kinetics of phagocytosis of Tc-99m-labeled human serum albumin microparticles (Tc-99m HSA-MM) in human Kupffer cells in vivo. The tracer turnover in these phagocytic cells could be described by a monoexponential accumulation with a two-stage elimination phase. Three-compartment analysis of the Tc-99m HSA-MM kinetics allowed us to quantify tracer attachment, phagocytosis, and degradation in Kupffer cells. The calculated time course of phagocytosis in ten control subjects proved to be identical to that of phagocytosis of various test substances in mouse macrophage monolayers (1). In addition, an impairment of particle turnover at the macrophage membrane, a significantly diminished (p less than 0.01) phagocytosis rate of the tracer, was observed in ten patients with various tumors.

Adult↗
PubMed1980

[Global and regional changes of cardiopulmonary blood volume under continuous work load (author's transl)].

The present study describes a method for the continuous determination of global and regional stress-induced alterations of cardiopulmonary blood volumes in normals, trained athletes and patients with latent cardiac insufficiency. In contrast to normals and athletes there is an increase of the total cardiac blood volume in the cardiac patients. There are also significant differences in blood volume changes of the left lung between normals and athletes on the one hand and the cardiac patients on the other. The method is simple and non-hazardous; it permits the observation of the obviously different adaptation of the cardiopulmonary system during exercise in normals, athletes and cardiac patients.

Adaptation, Physiological↗
PubMed1980

Myocardial imaging and metabolic studies with [17-123I]iodoheptadecanoic acid.

After intravenous administration of the stearic acid analogue [17-123I]iodoheptadecanoic acid (I-123 HA), myocardial metabolism was studied in ten normal individuals, eight patients with coronary artery disease and three patients with congestive heart failure. High-quality images were obtained in sequential scintigraphy of I-123 metabolically bound in myocardial tissue. Infarcted zones as well as ischemic regions are indicated by reduced tracer uptake. Iodine-123 in the blood pool and interstitial space consists mainly of radioiodide that is liberated by fatty-acid metabolism and was corrected for. Using the proposed correction not only are the images improved but the uptake and elimination of the I-123 in the myocardial cells can be followed. The average disappearance half-time of I-123 HA from the myocardium of normal persons was 24 +/- 4.7 min. In patients with coronary artery disease significant differences between myocardial regions were observed.

Adult↗
PubMed1979

[Study of minimal cardiac transit times in normal persons during beta-sympathicolysis (author's transl)].

The effects of single equipotent doses of Propranolol and Carazolol on cardiac haemodynamics of normal persons were investigated in a placebo-controlled double-blind study by radiocardiographic measurements of minimal cardiac transit times (MTTs). 90 min after oral application of 40 mg Propranolol a significant (p less than 0.005) prolongation of MTTs between the right auricle and the aortic root by 25% could be observed. A corresponding effect after treatment with 5 mg Carazolol was not recognizable (p greater than 0.05). Both substances strongly reduced the heart rate. The negative chronotropic effects of both beta-blockers were indistinguishable (p greater than 0.05).

Adrenergic beta-Antagonists↗
PubMed1978

Comparative evaluation of fatty acids labeled with C-11, Cl-34m, Br-77, and I-123 for metabolic studies of the myocardium: concise communication.

Various long-chain fatty acids have been labeled with C-11, Cl-34m, Br-77, and I-123 and evaluated for their potential application in measuring myocardial metabolism in vivo. Comparative studies of the kinetics of accumulation and clearance from the heart muscle of mice indicate that the extraction of omega-halofatty acids is more efficient than that of alpha-halofatty acids. Among the omega-halofatty acids, the highest uptake is observed for the 17-iodoheptadecanoic acid, which shows an extraction behavior almost identical to that of [1-11C] palmitic acid, although with a higher radioactivity level in blood due to the release of free iodide.

Animals↗