Biomedical subjects

L Trón

Publications and source records attributed to L Trón.

At least 37 records · Page 2Linked to original sources

PubMed1999

[Positron emission tomography ia an effective tool in modern oncology].

A total of 399 positron emission tomography (PET) examinations were carried out with a GE 4096 Plus PET scanner during the past 5 years on patients referred to the National Institute of Oncology in Budapest. The majority (n = 316) of these investigations were performed with the use of [18F]-fluorodezoxyglucose (FDG) to map the glucose metabolism; [11C]-methionine PET was indicated in 79 cases to detect protein transport and metabolism. The perfusion tracer [15O]-butanol was applied in only 4 cases to answer certain oncology-related, differential diagnostic questions. The oncological examinations were related to primary diagnostics, staging/restaging and therapy monitoring. In the staging/restaging and therapy monitoring of known tumours, conclusive results were achieved in 81-82% of the cases by using either FDG or [11C]-methionine as tracer. The concordant numerical data indicated that the PET investigation provides a definite answer to the question of the presence or absence of viable tumour tissue, with similar effectivity in any of the above indications, no matter whether FDG or [11C]-methionine is used. The search for occult primary tumours was the most frequent indication within the primary diagnostics: 10 (37%) primaries were localized by using FDG PET in the 27 investigated cases. This is a remarkably high value, especially in view of the failure of all the conventional diagnostic procedures carried out prior to the PET investigations. Application of PET may be indicated in all cases when the ultimate question is a non-invasive estimation of viable tumorous tissue.

Fluorodeoxyglucose F18↗

PubMed1999

[Evaluation of the nature of brain tumors using methods of nuclear medicine].

FDG-PET studies permit an assessment of the degree of brain tumour malignancy and detection of tumour recurrence. MIBI-SPECT also affords promising results in this respect. In this work, the diagnostic value of MIBI-SPECT was compared with that of FDG-PET for the determination of primary brain tumours malignancy and the detection of recurrent brain tumours. SPECT and PET examination were carried out within a week in 14 patients (12 males, 2 females, mean age: 40 years, range 16-61 years) with brain tumours. Seven patients had a primary tumour, and in a further 7 MRI or the clinical signs and symptoms let to a suspicion of tumour recurrence. All tumours were verified histologically to be gliomas of grades I-IV. The SPECT and PET images were analysed visually and semiquantitatively. In 3 of the investigated 7 primary glioma patients, there was a visibly enhanced MIBI-positive cases, only one had an increased FDG uptake. In 4 of the 7 tumour recurrence cases, either the MIBI or the FDG uptake was visibly increased. All of these were histologically high-grade gliomas. In the remaining low grade tumours (primary of recurrent), neither MIBI nor FDG revealed a pathologically increased uptake. The intensity of radiopharmaceutical uptake at the site of the tumours was visually and semiquantitatively higher for MIBI that for FDG. It is concluded that MIBI-SPECT is a valuable and simple tool for evaluation of the biological characteristics of brain tumours, showing increased uptake of MIBI according to the malignancy and tumour recurrence of brain tumours.

Animals↗

PubMed1999

[Improvement of myocardial perfusion following left ventricular resection].

Left ventricular aneurysm had detected at the 55-year-old woman after extensive anterior myocardial infarction in association with progressive ventricular dilatation and symptoms of heart failure. Coronary angiogram revealed a serious lesion in the proximal segment of the left anterior descending coronary branch with a poor run off tract. 18FDG-PET and 99mTc-MIBI-SPECT investigation were performed in order to differentiate the scarred regions from the viable myocardial segments. Taking into consideration the results an aneurysm resection was performed without revascularisation procedure. After the surgery not only the ejection fraction and the left ventricular dilatation had improved but the tissue perfusion in the segments surrounding the resected aneurysm had also showed a significant increase at the follow up MIBI-SPECT imaging.

Coronary Angiography↗

PubMed1999

Radiation myelopathy with partial functional recovery: PET evidence of long-term increased metabolic activity of the spinal cord.

Postoperative telecobalt irradiation was performed with a biologically effective extrapolated response dose of 165 Gy2 delivered to the spinal cord of a papillary thyroid cancer patient. Incomplete cervical transection developed, followed by a gradual functional improvement, which is still continuing 8 years after radiotherapy. Between the 6th and 8th years of the clinical course, positron emission tomography investigations demonstrated an increased 18F-deoxyglucose accumulation and (15)O-butanol perfusion, but negligible 11C-methionine uptake in the irradiated spinal cord segment. We suggest that the increased metabolism and perfusion, and the lack of detectable protein synthesis may be related to the increased energy demands of action potential conduction, due to the higher than normal density of sodium channels along demyelinated axons displaying restored conduction.

Adult↗

PubMed1999

Preparation and primary evaluation of [11C]CSC as a possible tracer for mapping adenosine A2A receptors by PET.

A 11C labeled selective adenosine A2A antagonist, (E)-8-(3-chlorostyryl)-1,3-dimethyl-7-[11C]methylxanthine [11C]CSC) was prepared by the reaction of (E)-8-(3-chlorostyryl)-1,3-dimethylxanthine and [11C]methyl iodide. The decay-corrected radiochemical yield was 32.3% with a radiochemical purity of 99%, a specific activity of 1.85-5.55 GBq/mumol and a preparation time of 1 h. A primary evaluation of [11C]CSC as a potential tracer for mapping adenosine A2A receptors by positron emission tomography (PET) is also presented. Biodistribution and autoradiographic studies were carried out on Swiss mice and domestic rabbits. In mice the lung showed the highest uptake at 10 min after i.v. injection, followed by the liver, kidney, heart and brain. Inside the brain a high level of radioactivity accumulated in the striatum, in accordance with previous findings on the specific spatial distribution of A2A adenosine receptors and also in the medulla oblongata. Dynamic PET studies on rabbits showed a fast brain uptake of CSC, reaching a maximum in less then 2 min. On the basis of competition experiments with the unlabeled ligand [11C]CSC proves to bind specifically to the appropriate receptor.

Animals↗

PubMed1998

[Multiple endocrine neoplasia-type medullary thyroid carcinoma in three generations of a family].

The familial accumulation of a multiple endocrine neoplasia (MEN) type 2a medullary thyroid carcinoma, is described based on the retrospective analysis of a family history. The proband was characterized by medullary carcinoma (MC) combined with phaeochromocytoma, her child had been shown to suffer from MC. In the third generation of the family C-cell hyperplasia and bilateral adrenal hyperplasia occurred. It is shown that in order to arrive at a correct decision as regards the therapy to be used, modern laboratory tests (serum calcitonin, CEA-analysis) and diagnostic imaging methods (ultrasound, computer tomography, magnetic resonance imaging, positron emission tomography, metaiodobenzylguanidine scintigraphy) should be used. It is emphasized that the available therapeutic means (surgery, radiotherapy, nuclear medicine) have to be carefully selected and, if necessary, combined. In medullary thyroid carcinoma associated tumours in other endocrine organs should be expected to occur. Family screening using blood chemical and genetic tests are recommended in asymptomatic cases, since their surgical treatment can in this way lead to complete recovery.

Adult↗

PubMed1998

Cerebral effects of a single dose of intravenous vinpocetine in chronic stroke patients: a PET study.

The effects of vinpocetine (Cavinton) on the cerebral glucose metabolism of chronic stroke patients are studied with positron emission tomography. The regional and global cerebral metabolic rates of glucose (CMRglu) and the kinetic constants related to them are quantified before and after single-dose intravenous vinpocetine treatment. These measurements are completed with transcranial Doppler sonography and single photon emission computed tomography to explore the possible mechanisms underlying the resulting changes in glucose uptake and metabolism in the brain. The authors' findings indicate that a single-dose vinpocetine treatment, although it does not affect significantly the regional or global metabolic rates of glucose, improves significantly the transport of glucose (both uptake and release) through the blood-brain barrier in the whole brain, the entire contralateral hemisphere, and in the brain tissue around the infarct area of the symptomatic hemisphere. These changes are in accord with increased blood flow in the entire contralateral hemisphere as well as decreased blood flow velocity and increased peripheral vessel resistance in the entire symptomatic hemisphere.

Aged↗

PubMed1997

[Image fusion of different tomographic methods (PET/CT/MRI) effectively contribute to therapy planning].

Image fusion (and image registration) is a fundamental topic of three-dimensional (3D) medical image processing. The need to register different imaging modalities arises for several reasons: some anatomical details, especially soft tissues, are more easily seen in MRI than CT images, but the bony structures are better visualised by CT. The visualisation of any morphological volume with a functional data set which may come from SPECT or PET is a very important method both for research purposes and for routine diagnostics. Our developed programs allowing us to solve image fusion tasks also contained some free available softwares. These packages helped us to start additional software development for more advanced applications having elaborated this way the informatical background of multimodality image processing. This paper presents three oncological applications of the image fusion: PET-CT-MRI registration for 3D radiotherapy planning, PET-MRI registration in planning surgery and metastasis localization. All these registration processes were solved by the landmark-matching registration method.

Decision Making↗

PubMed1997

[11C-methionine: an effective radio-tracer for PET scan in the detection of tumors of low proliferating capacity].

11C-methyl-methionine is available at the PET Center of University Medical School Debrecen since June, 1996. The first 5 oncological examinations were indicated for clinically suspected recurrent/residual tumorous tissue of low-grade/low proliferative capacity, following the negative or inconclusive results of previous 18F-deoxyglucose (FDG) examinations. In these situations, the methionine examinations provided conclusive results in 4 cases (out of the total of 5 examinations). On the basis of published data and own experience, the authors recommend methionine PET investigations for diagnosis, differential diagnosis and therapy monitoring of tumours of low-grade/low proliferative capacity following inconclusive results of previous FDG examination.

Adult↗

PubMed1997

[Cerebral positron emission tomographic study in systemic lupus erythematosus].

The cerebral glucose metabolism in eight patients with systemic lupus erythematosus (SLE) and in five healthy controls were examined by positron emission tomography (PET) using 18-F-labeled deoxy-glucose (FDG) as tracer. One of the eight patients had no abnormality by magnetic resonance imaging (MRI), three of them had cerebral atrophy and four patients had multiple white matter hyperintensities and vascular infarcts in the striatum as assessed by MRI. With FDG-PET, inhomogeneous multifocal cerebral glucose hypometabolism was detected, more frequently in the temporal lobe of right hemisphere. The PET findings did not correlate always with the neurological symptoms. Abnormalities in brain metabolism can be detected more frequently by PET, than morphological changes by MRI, indicating the involvement of the central nervous system.

Adult↗

PubMed1997

[Prediction of the result of high-risk coronary bypass surgery by positron emission tomography].

Coronary angiography revealed three-vessel disease in a 56-year-old male with two previous myocardial infarctions. Coronary bypass surgery was initially ruled out by cardiac surgeon because of the poor left ventricular function (EF: 23%), despite moderate viability signs during conventional isotope techniques. Positron emission tomography with 18FDG indicated a large periinfarction area of hibernating myocardium. Accordingly, coronary bypass grafting was performed. Postoperatively, the symptoms disappeared, the left ventricular wall motion abnormalities (with the exception of the scarred region demonstrated by PET) improved, and the global left ventricular function increased significantly. This case and the role of cardiac PET study for prediction of the result of revascularization are discussed.

Coronary Angiography↗

PubMed1997

Flow cytometric determination of intracellular free potassium concentration.

A flow cytometric assay has been developed for determination of intracellular free potassium concentration ([K+]i). Investigated cells, loaded with the fluorescent pH indicator 2',7bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF), are incubated in the presence of nigericin, and the intracellular pH is measured. The ionophore maintains the same ratio value [H+]/[K+] on both sides of the cytoplasmic membrane, so [K+]i can be evaluated from the measured intracellular pH (pHi) and the known parameters of the buffer. Application of the method revealed that the intracellular potassium concentration is significantly higher in lymphocytes than in proliferating cells of HUT-78, U266, and JY cell lines. A surprisingly low (60 mM) [K+]i concentration was observed with sperm cells of common carp. This method allows measurements on individual cells, provides data of excellent statistics, and still does not require large amounts of material. These features offer remarkable advantages over other techniques used for intracellular K+ measurements, such as steady-state fluorescence, atom absorption photometry, or energy-dispersive x-ray analysis.

Animals↗

PubMed1997

Role of extracellular and intracellular pH in carp sperm motility and modifications by hyperosmosis of regulation of the Na+/H+ exchanger.

Recently developed flow cytometric methods (Trón et al.: Mol Immunol 27:1307-1311, 1990) to measure the intracellular pH (pHi) and intracellular potassium concentration in mammalian cells by using the fluorescent pH-indicator dye 2',7bis-(2-carboxyethyl)-5 (and-6)-carboxyfluorescein (BCECF) were adopted for measuring these parameters in carp sperm. The intracellular potassium concentration of the carp sperm was 62.4 +/- 5.3 mM. This is very similar to the potassium concentration of the seminal plasma (87 +/- 16 mM), and it suggests a depolarized state of the sperm cell in the semen. An average pHi value of 7.06 +/- 0.11 was obtained by measuring sperm samples taken from ten animals. Changes in the ionic composition of the environment did not alter pHi. Sperm motility was initiated by transferring the cells to an environment of 110 mOsm osmolality. This hypoosmotic shock induced fast changes in the membrane structure that could be reversed by restoring physiologic osmolality. Activation was accompanied by a fast alkalinization of the sperm cells. This pH change was amiloride sensitive, suggesting the involvement of the Na+/H+ exchanger in the activation process. Alkalinization of acid-loaded sperm cells depended on the osmolality of the environment. Equilibrium pHi of these cells in hyperosmotic buffers was substantially lower relative to cells in an isoosmotic environment. Effects of the extracellular and intracellular pH on carp sperm motility were also examined. Extracellular pH below 5.5 abolished sperm motility completely. Alkaline extracellular pH did not alter the duration of sperm motility even at extreme values (pHe = 9.6). Duration of the flagellar motion did not depend on the pHi between values of 6.5 and 8.5; however, it was significantly reduced both below and above this range. No motility was observed below pHi = 6.0 or above pHi = 9.5 with a 10 min incubation time at these pH values prior to activation. Effects of the extracellular and intracellular pH on sperm motility were partially reversible.

Animals↗

PubMed1997

[First Hungarian experiences with positron emission tomography (PET) studies. Members of the PET working group].

Diagnostic investigations commenced on the 28th of June 1994 in Hungary's and Central Europe's first PET Centre at the University Medical School of Debrecen. The Centre is equipped with a GE 4096 Plus whole body PET scanner. A metabolic tracer, 18F-deoxy-D-glucose (FDG), was used in the investigations. During the first 15 months 249 PET investigations were made in the Centre of which 242 were diagnostic and 7 normal subjects served as control for the patient studies with brain scans. The number of oncological indications (intra- and extracranial tumours, Hodgkin's lymphomas) was n = 105 (43.4% of the 242 diagnostic examinations), neurological investigations (without intracranial tumours) formed the dominant group (n = 117; 48.3%), whereas the number of cardiological indications was 20 (8.3%). The oncological studies included those of intracranial tumours (n = 76; 31.4%); thyroid tumours (n = 9; 3.7%); Hodgkin's lymphomas (n = 7; 2.9%) and other extracranial tumours (n = 13; 5.4%). The distribution of different neurological and psychiatric investigations was as follows: localization of focal epileptogen zone (n = 60; 24.8%); differential diagnosis of dementias (n = 30; 12.4%); exploration of cerebrovascular diseases (n = 10; 4.1%); and other neurological diseases (n = 17; 7.0%). The main objective of the cardiological PET investigations was the exploration of viable myocardium. The present paper overviews both the procedures (including administrative issues, as well) and the results of the first 249 FDG-PET investigations.

Aged↗

PubMed1996

[Positron emission tomography: foundations and applications].

Positron emission tomography (PET) is a non-invasive biomedical imaging technique whereby the distribution of biological tracer molecules, labelled by positron emitting isotopes, in the living body can be studied quantitatively. As theoretically an metabolically active molecule can be labelled, the technique is applicable to the measurement of any biochemical or physiological process in proper anatomical context. The introduction of PET has revolutionised the exploration of normal physiological functions. With the help of technique, among others, anatomical structures underlying mental functions can be localised in the human brain, the receptor architecture of the nervous system can be mapped, or the kinetics of pharmacons can be properly measured and modelled. In the clinical practice, PET has proven to be a uniquely useful diagnostic technique in neurology, psychiatry, cardiology, and oncology in establishing primary diagnosis and differential diagnosis, designing therapeutic interventions as well as assessing their efficacy. Hungary's and Central European region's first PET center has been established at the University Medical School in Debrecen.

Humans↗

PubMed1996

Intracellular pH does not affect drug extrusion by P-glycoprotein.

The intracellular pH (pH(i)) of cells exhibiting multidrug resistance (MDR) related to the expression of the P-glycoprotein (Pgp) is often more alkaline than that of the parental cells, as also observed for the KB-V1/KB-3-1 system in this paper. The possible role of an elevated pH(i) in Pgp-related MDR has been investigated by shifting back the pH(i) of the MDR+ cells to a more acidic value using the mobile proton ionophore carbonylcyanide m-chlorophenylhydrazone (CCCP). The influence of CCCP-evoked delta pH(i) on relative daunorubicin (DNR) accumulation was similar in the case of several Pgp positive and negative cell lines, in view of flow cytometric and radioactive drug accumulation studies and measuring DNR levels in the medium in a flow-through system. Our data argue against a significant effect of pH(i) on Pgp pumping efficiency. However, an indirect connection between pH(i) regulation and the MDR phenotype is suggested by the fact that acidification of the external medium in the presence of verpamil could be observed exclusively in MDR+ cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1996

Regional glucose metabolic rates in the human brain: a PET study.

With the purpose of determining the regional cerebral glucose metabolic rates (rCMRglu) in the normal human brain in resting state, we measured with PET and FOG, as the tracer, the distribution of regional radioactivity levels in the brains of seven young healthy volunteers. The individual brain images were stereotactically standardised with the help of a computerised brain atlas. In the next steps, the global cerebral glucose metabolic rate (gCMRglu) in the individual subjects was normalised to 34 mumol/ 100 g/min, followed by the averaging of the stereotactically standardised and metabolically normalised brain images across the subject population. In the final step, on the basis of high precision anatomical information, three-dimensional (3-D) volumes-of-interest (VOI's), covering over thirty anatomical structures in the brain, were created and the rCMRglu values inside the VOI's were determined in the averaged image. The present measurements of the rCMRglu values are in outstanding agreement with those determined in earlier quantitative PET-FDG studies, demonstrating that stereotactically standardised and metabolically normalised images of regional radioactivity distributions in the brain can be used for quantitative determination of rCMRglu values.

Adult↗

PubMed1995

Flow cytometric determination of absolute membrane potential of cells.

Membrane potential measurements using fluorescent membrane potential indicator dyes report on relative changes but usually do not result in an absolute value of the measured parameter. The method developed in this paper is based on the assumption that the negatively charged bis-oxonol distributes across the cytoplasmic membrane according to the Nernst equation. It is further supposed that the fluorescence intensity measured from a given stained cell is a single-value function of the intracellular dye concentration. The protocol suggested incorporates the construction of a calibration curve (fluorescence intensity measured from stained cells vs. extracellular dye concentration). This allows the evaluation of the membrane potential in millivolts using fluorescence readings of the cells both in the depolarized state and in the state of interest. Good agreement was found between absolute membrane potential data of human peripheral blood lymphocytes by our method and results of parallel patch clamp measurements.

Animals↗