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Biomedical subjects

P Bogner

Publications and source records attributed to P Bogner.

36 records · Page 2Linked to original sources
PubMed1998

On the role of Na,K-ATPase: a challenge for the membrane-pump and association-induction hypotheses.

The regulation of cellular ion levels has been an important issue of cell physiology since the beginning of the century. A special interest was focused on the monovalent ions which are involved in several cellular functions; in fact, the maintenance of high K+ level inside the cells is one of the most basic life-phenomena. Regarding the regulation of monovalent ions in general, two opposing ideas emerged: one being the membrane theory and the other the sorption theory(ies). Today most scientists are familiar only with the membrane theory which involves the pump and leak hypothesis and only a few consider the predictions of the association-induction hypothesis which may be classified as one of the sorption theories. In the regulation of monovalent ions the Na,K-ATPase is a key-molecule according to the membrane theory but not considered that important by the association-induction hypothesis. In this paper, we present two simple experiments which demonstrate the possible role of this molecule in the regulation of cellular Na+, K+ homeostasis and also disprove the pump and leak hypothesis.

Animals↗
PubMed1997

[Method and use of intracranial cine MR imaging].

The authors introduce a dynamic, non-invasive MR method for the examination of liquorspaces and liquor flow in 221 patients. This method is suitable not only for a dynamic imaging of liquor-flow but also for the semi-quantitative evaluation of flow through the aqueduct. This later measurement can help to select the shuntresponsive NPH cases as well. Cine MR examination along with the routine protocol seems to be most helpful in the differential-diagnostics of different hydrocephalus cases.

Humans↗
PubMed1997

[Principles of functional MRI imaging and its possibilities in the study of cerebral cortex activation].

While MR imaging of anatomic structures has long been widely appreciated, the emergence of functional magnetic resonance imaging (FMRI) methods for localising brain activity has emerged in the beginning of the 90s. This new MRI technique produces images of activated brain regions by detecting the indirect effects of neural activity on local blood volume, flow and oxygen saturation, and it is a promising new tool for further understanding of the relationships among brain structure, function and pathology. The information revealed by FMRI is partially overlapping with PET and SPECT, but it is non-invasive and has a better spatial and temporal resolution. The authors briefly summarise the concept and basics of FMRI and demonstrate the first successful FMRI examination performed in Hungary. The potential role of FMRI in the clinical practice is presented.

Animals↗
PubMed1996

Albumin can reverse the release of potassium from human erythrocytes treated with the non-ionic detergent, Brij 58.

Exchange of erythrocyte intracellular (i/c) K+ for extracellular (e/c) Na+ in human erythrocytes treated with sub-CMC concentrations of the non-ionic detergent Brij 58 can be stopped by reincubation in serum or albumin containing solutions. The progressive equilibration of the K+ contents of detergent-treated human erythrocytes with the incubation medium was reversed by an albumin-mediated withdrawal of detergent molecules from the cell. Re-establishment of near normal [K+] in terms of K+/kg water proceeds in two ways: (i) a metabolism-dependent net accumulation of K+ ions; and (ii) a metabolism-independent shrinkage of erythrocytes, this being the more significant factor.

Adenosine Triphosphate↗
PubMed1996

Nuclear magnetic resonance relaxation parameters of muscle in malignant hyperthermia-susceptible swine.

RATIONALE AND OBJECTIVES: The malignant hyperthermia (MH) syndrome involves characteristic changes in metabolism that have a significant effect on the postmortem properties of muscle tissue. We investigated the 1H nuclear magnetic resonance (MR) relaxation parameters of muscle tissue from normal (MH-) and malignant hyperthermia-susceptible (MH+) swine taken before their death to identify whether postmortem metabolic differences would be accompanied by changes in relaxation parameters. METHODS: Muscle samples from 63 MH-susceptible swine were characterized by proton MR relaxation times (T1 and T2). The water content, pH, conducting, and the "subjective meat" quality were assessed in order to differentiate the meat into one of three groups: normal, pale-soft-exudative, and dark-firm-dry. RESULTS: The T2 relaxation of MH- and MH+ muscles was significantly different, but no significant changes were detected in the water content and corresponding T1 relaxation times. CONCLUSION: These data suggest that MH-susceptible swine can be distinguished from normal swine using nuclear MR relaxometry. The results of relaxation measurements and the multiexponential analysis of the T2 curves suggest a shift between the different water compartments during MH that might predict the increased water loss of muscle tissue after death.

Animals↗
PubMed1996

Postnatal changes in water content and proton magnetic resonance relaxation times in newborn rabbit tissues.

In the present study, using proton nuclear magnetic resonance relaxation (H1 NMR) measurements, an attempt was made to quantitate water fractions with different mobility in the skin, skeletal muscle, and liver tissues obtained from New Zealand white rabbit pups. Serial studies were carried out at the postnatal age of 0-1, 24, 48, and 72 h in pups nursed with their mothers and suckling ad libitum (group I) and in those pups separated from their mothers and completely withheld from suckling (group II). Tissue water content (desiccation method) and T1 and T2 relaxation times (H1 NMR method) were measured. Free, loosely bound, and tightly bound water fractions were calculated by applying multicomponent fits of the T2 relaxation curves. It was demonstrated that skin water content and T1 and T2 relaxation times decreased with age (p < 0.01), the decrease in T2 proved to be more pronounced in group II than in group I (p < 0.05). Muscle and liver water, and T1 and T2 relaxation times did not change with age in the suckling pups. In response to with-holding fluid intake muscle water remained constant, liver water increased paradoxically (p < 0.05). T1 relaxation time showed no consistent change in either tissues, whereas T2 relaxation time decreased significantly (muscle, p < 0.01) or tended to decrease (liver, p < 0.06). Using biexponential analysis fast and slow components of T2 relaxation curve could be distinguished that corresponded to the bound and free water fractions. Bound water accounted for 42-47%, 50-57%, and 34-40% of total tissue water in the skin, skeletal muscle, and liver, respectively, regardless of age and fluid intake. Triexponential fits of the T2 relaxation curve made possible the further partition of tissue water into tightly bound (fast component), loosely bound (middle component), and free (slow component) water fractions. In all tissues studied, loosely bound fraction predominated (skin, 48-64%; muscle, 54-65%; liver, 45-63%), followed by the free (skin, 26-45%; muscle, 23-32%; liver, 20-25%) and the tightly bound water fraction (skin, 6-14%; muscle, 10-16%; liver, 14-33%). Postnatal age and fluid intake had no apparent influence on this pattern of distribution. It is concluded that the majority of neonatal tissue water is motion-constrained. The free, the loosely bound, and the tightly bound water fractions appear to be interrelated and dependent on age, fluid intake, the tissues studied, and their hydration.

Animals↗
PubMed1995

Effect of non-lytic concentrations of Brij series detergents on the metabolism-independent ion permeability properties of human erythrocytes.

Subcritical micellar concentrations (sub-CMC) of Brij-series detergents alter ion movements between human erythrocytes and their environment when metabolism has been slowed down by incubation at zero degrees centigrade. The effect of nonhemolytic concentrations of detergents on the erythrocyte K+ and Na+ movements is described. Results indicate a significant difference in monovalent cation movements, depending on the number of hydrophilic polyoxyethylene units (n). There is an increasing loss of K+ and gain of Na+ as n increases from 4 to 20. Where n > or = 21, ion movements are not significantly different from those found in erythrocytes not exposed to detergents. The carbon chain length of the detergent fatty acid residue (10-18 carbons) appears to be relatively unimportant, but detergents with unsaturated (oleic acid) hydrophobic regions potentiate K+ release and Na+ uptake when compared to the corresponding saturated fatty acid (stearic acid). The erythrocyte stabilizing effect of detergents against hypo-osmotic shock correlates well with the increase of monovalent ion traffic and the mobility of membrane lipids revealed by fluorescence anisotropy measurements.

Adenosine Triphosphate↗
PubMed1994

Release of potassium, lipids, and proteins from nonionic detergent treated chicken red blood cells.

The plasma membrane of erythrocytes, as of other cells, is thought to act as the barrier responsible for maintaining intracellular gradients of most ions and small molecular species between the cell and its environment. Controlled application of the nonionic detergent Brij 58 effectively opened the erythrocyte plasma membrane, as judged by electron microscopy and lipid mobilization, but the cytoplasm maintained much of its integrity for about 30 min. Release of K+ correlated well with release of protein into the surrounding medium. The results demonstrate that permeabilization of the erythrocyte plasma membrane does not result in an instantaneous equilibration of small ions, such as K+, between the cell and its environment. A comparison was made between erythrocytes treated with Brij 58 and Triton X-100. The lipid and protein solubilizing actions of Triton X-100 were not as easily separable in time as those of Brij 58. The results of treatment of the erythrocytes with different types of nonionic detergents suggest that the membranolytic and cytoplasmic protein destabilizing actions of nonionic detergents correspond with their hydrophilic-lipophilic balance numbers (HLB values).

Animals↗
PubMed1994

Cation distribution in mammalian red blood cells: interspecies and intraspecies relationships between cellular ATP, potassium, sodium and magnesium concentrations.

The intracellular K+/Na+ ratio of erythrocytes of different mammalian species are known to differ markedly. These differences are sustained despite plasma potassium and sodium concentrations being almost identical, i.e. high [Na+] and low [K+], in all mammalian species. Conventional cell theory couples intracellular K+ and Na+ concentrations with Na+/K(+)-dependent ATPase activity. Ling's Association-Induction (AI) hypothesis couples intracellular K+ and Na+ concentrations with the concentration of ATP, by way of an inductive adsorption of both monovalent cations on the available terminal and lateral carboxyl groups of proteins. Based on the working hypothesis, different relationships are expected between the erythrocyte K+ and Na+ concentrations and ATP levels. Our results indicate that the intracellular ATP level in erythrocytes of different species corresponds with intracellular K+ and Na+ levels, K+/Na+ ratios and total K+ + Na+ levels. Similar relationships were revealed between the erythrocyte ATP and monovalent cation contents of different individual sheep.

Adenosine Triphosphate↗
PubMed1993

Relationship between cellular ATP, potassium, sodium and magnesium concentrations in mammalian and avian erythrocytes.

Intracellular K+/Na+ ratios of erythrocytes of various mammalian species are known to differ markedly. We have measured ATP, K+, Na+, Mg2+, H2O contents of erythrocytes of twelve mammalian and three avian species. Our results indicate that the intracellular ATP concentration in erythrocytes of different species is in close positive correlation with the K+/Na+ ratios (linear correlation coefficient, r = 0.852). Furthermore, ATP levels in erythrocytes of individual sheep with different potassium concentrations correspond with their K+/Na+ ratios (r = 0.747). Intracellular magnesium concentrations also correlate with ATP concentrations in erythrocytes of different species (r = 0.629) and in different sheep (r = 0.549).

Adenosine Triphosphate↗
PubMed1993

Relaxometry, animal biodistribution, and magnetic resonance imaging studies of some new gadolinium (III) macrocyclic phosphinate and phosphonate monoester complexes.

The Gd3+ complexes of three new phosphorus containing tetraaza macrocycles (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis (methylene ethylphosphonic acid), H4DOTEP; 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis (methylene phosphonic acid monoethylester), H4DOTPME; and the corresponding n-butyl ester, H4DOTPMB) were prepared and examined for possible use as MRI contrast agents. Although thermodynamically and kinetically less stable than Gd(DOTA)- in saline and HSA solution, the stability of these new macrocyclic complexes appears to be sufficiently high for in vivo applications. NMRD relaxivity profiles of the three complexes indicate that the number of inner sphere water molecules for these chelates is < or = 1 and that the more hydrophobic chelate, Gd(DOTPMB), binds to human serum albumin (HSA). Biodistribution studies of the radioactive 153Sm or 159Gd chelates in rats, gamma imaging of the 153Sm chelates in rats, and proton MRI studies of the nonradioactive Gd3+ chelates in rabbits all indicate that the DOTPMB complexes accumulate preferentially in the liver, spleen, and small intestines while the more hydrophilic DOTEP and DOTPME complexes appear to display renal clearances similar to other low molecular weight contrast agents.

Animals↗
PubMed1992

Isolation of prolyl-tRNA synthetase as a free form and as a form associated with glutamyl-tRNA synthetase.

Rat liver prolyl-tRNA synthetase was purified as a dimer of M(r) 60,000 subunits not associated with other aminoacyl-tRNA synthetases and as a form associated with glutamyl-tRNA synthetase. Proteolysis of the dimeric enzyme generated a less active form with M(r) 52,000 subunits and an inactive form with M(r) 40,000 subunits. A second species was isolated with polypeptides of M(r) 60,000 and 150,000. This form dissociated during gel filtration chromatography being partially resolved into the M(r) 150,000 and 60,000 components; glutamyl-tRNA synthetase was associated with the larger polypeptide and prolyl-tRNA synthetase with the smaller component. Antibodies against the M(r) 60,000 polypeptide reacted with the M(r) 60,000 and 150,000 polypeptides. Gel filtration of extracts revealed multiple forms of prolyl- and glutamyl-tRNA synthetase. Antibody against the M(r) 60,000 component detected the M(r) 60,000 and 150,000 polypeptides throughout the chromatogram; these forms could be partially separated by polyethylene glycol fractionation. The M(r) 150,000 and 60,000 polypeptides were detected by Western blot analysis of crude extracts prepared under several conditions. Antibody to prolyl-tRNA synthetase reacted with a M(r) 150,000 polypeptide of the aminoacyl-tRNA synthetase core complex identified previously as glutamyl-tRNA synthetase.

Amino Acids↗
PubMed1992

Stabilization of intercellular contacts in MDCK cells during Ca2+ deprivation. Selective effects of monocarboxylic acids on desmosomes.

Short-chain monocarboxylic acids (MCAs) selectively protect desmosomal junctions of MDCK cells from disruption by chelating agents and low calcium medium. This effect occurs in the millimolar concentration range and increases inversely with carbon chain length (formate > acetate = propionate > butyrate > isobutyrate > isovalerate). The relative activity of MCAs does not correlate with their overall hydrophobicity or ability to chelate ions, or their effectiveness in lowering cytosolic pH. It exhibits chemical specificity and is dependent upon postconfluency culture age. MCAs also inhibit cell rounding produced by low concentrations of aminocarboxylate-chelating agents. Their effect on cell rounding, but not on desmosomes, can be antagonized by okadaic acid. The possibility is discussed that MCAs may produce their effects by binding specifically to protein(s) associated with the desmosome of mature, fully polarized MDCK monolayers.

Animals↗
PubMed1992

Motional characteristics of K+ and Na+ in intact and sucrose-permeabilized rat lymphocytes.

Most, if not all, cells maintain an unequal distribution of Na+ and K+ against their environment. These two monovalent ions are in constant exchange between the cell and the extracellular space since both ions have proved to be permeable through the cell membrane. The distribution of Na+ and K+ in intact and "sucrose-permeabilized" rat lymphocytes were studied ("sucrose-permeabilization" means homogenization in isotonic sucrose solution). Both the intact and the permeabilized lymphocytes were incubated in Hanks' solution and then transferred into K+, Na(+)-free isotonic sucrose solution. Alternatively, the cells were incubated only in the sucrose solution or in Hanks' solution. The Na+ and K+ content of the cells were determined at the conclusion of each period of incubation in the same or different medium. We found that K+ did not equilibrate under any conditions in intact lymphocytes but Na+ responded to changes of the incubation media. In the permeabilized cells Na+ freely equilibrated with the extracellular medium while K+ did not, although its concentration decreased compared to that of intact cells.

Animals↗
PubMed1989

Paraproteins associated with low plasma sodium levels.

The mechanism of the maintenance of low plasma sodium levels seen in certain multiple myeloma cases has been attributed to the cationic nature of pathological immunoglobulins (paraproteins). This hypothesis was tested with equilibrium dialysis and polyacrylamide gel electrophoresis techniques. Citrated plasma samples and affinity chromatography purified paraproteins of three multiple myeloma patients with abnormally low plasma sodium levels were dialysed against 140 mmol/L NaCl solution at pH 7.4 for 24 hours. The electrophoresis of paraproteins was conducted under non-denaturing conditions. Low plasma sodium concentrations observed under the dialysis of the patients' plasma samples were in good agreement with earlier reports. However, the isolated paraproteins did not show any sodium exclusion during the dialysis experiment. The electrophoretic mobility of the paraproteins at pH 7.4 indicated that the isoelectric point of these molecules was below 7.4, so they cannot behave as cations at the pH of the blood. From these data it appears that the maintenance of low plasma sodium levels in certain IgG type myeloma cases cannot be explained by the previously postulated cationic nature of the paraproteins.

Amino Acids↗
PubMed1989

Release of hemoglobin and potassium from human red blood cells treated with Triton X-100 under the critical micellar concentration.

The action of detergents is thought to be connected primarily with micelle formation. However, detergent monomers can also effect biological systems. It was found in this study that human red blood cells can be disintegrated with Triton X-100 non-ionic detergent at a concentration of 0.007%, lower than the critical micellar concentration (CMC). The time dependent release of hemoglobin and potassium was detected at 37 degrees C and both were sigmoid in character. Although potassium was released faster than hemoglobin, a cooperative relationship between potassium and hemoglobin within the intact red blood cell is suggested by this observation.

Erythrocytes↗
PubMed1975

Effectiveness of audio-based instruction in medical pharmacology.

An audio-based method of instruction on the topic of diuretic drugs was compared with the lecture method using a random sample of 66 sophomore medical students. A cognitive test given to measure achievement as a result of the two treatments showed that the average score of 80 percent for the audio group was significantly higher (p smaller than 0.25) than the 75 percent for the lecture group. A comparison of the lowest quartile scores in each group revealed that the audio-based group also scored higher 13 points, p smaller than .05) than the lecture group; however, no difference was noted in the upper three quartile scores of the two groups. The amount of time spent studying did not appear to be a factor. A second test given to meausre attitudes toward the audio method showed strong positive views among students.

Achievement↗