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Biomedical subjects

I Wadsö

Publications and source records attributed to I Wadsö.

At least 19 recordsLinked to original sources
PubMed1992

Effects of pH-variations on the kinetics of growth and energy metabolism in cultured T-lymphoma cells: a microcalorimetric study.

The progression of T-lymphoma cells (CCRF-CEM) growing in suspension has been monitored during long term (12-28 h) batch experiments using microcalorimetry. In parallel with the calorimetric measurements, changes in cell concentration, pH, p(O2) and concentrations of the main energy sources (glucose and glutamine) were determined. The overall metabolic rate per cell (as reflected by the heat production rate per cell, Pcell) and the growth rate decreased with time. These changes could be attributed solely to the decrease in pH of the medium until the total heat production, Q, exceeded 1.2 J per ml (corresponding to an incubation time of 20 h of a batch having an initial cell concentration of 1 x 10(6) cells per ml). The lowering of p(O2) to a level of 0.02 mmol/l or the decrease in concentrations of glucose and glutamine to 7.7 and 1.3 mmol/l, respectively, did not influence Pcell or the growth pattern. No "crowding effect" was observed for the cells in the investigated concentration range (0.6-1.3) x 10(6) cells per ml.

Calorimetry↗
PubMed1991

Cell growth experiments using a microcalorimetric vessel equipped with oxygen and pH electrodes.

A method is described for simultaneous measurements of heat production rate, oxygen activity and pH, using a 3-ml stirred microcalorimetric titration/perfusion vessel fitted with a polarographic oxygen sensor and a combination pH-electrode. Heat production rate (+/- 0.3 microW), pH (+/- 0.01) and oxygen concentration (+/- 4 mumol/l) could be measured without any cross interference between the three signals. Results from measurements on suspensions of T-lymphoma cells and E. coli are presented.

Calorimetry↗
PubMed1990

Microcalorimetric investigations of animal cells.

Calorimetric measurements on living animal cells normally involve determination of heat production rates under essentially isothermal conditions. Experiments are usually performed by use of twin heat conduction microcalorimeters. Combination of results from calorimetric measurements and analytical determinations lead to valuable thermochemical information. But in most studies conducted so far, the calorimeters are used solely as analytical tools, "process monitors". Experiments are easy to perform but several critical experimental parameters should be taken into account.

Animals↗
PubMed1990

Prediction of the cytotoxic effects of some antineoplastic drugs on cultured T-lymphoma cells by microcalorimetry.

The effects on T-lymphoma cells of the antineoplastic drugs Ara-C, cisplatin, vinblastine, chlorambucil and prednimustine were studied by microcalorimetry and a conventional viability assay. The heat production rate for cells was measured immediately after drug treatment and was compared with the change in cell concentration during the following generation time. The results of the microcalorimetric observations were correlated with cell death. Such correlations varied considerably for the different drugs, in particular between chlorambucil and the other drugs investigated.

Antineoplastic Agents↗
PubMed1988

The potential use of microcalorimetry in predictive tests of the action of antineoplastic drugs on mammalian cells.

The effect of methotrexate (MTX) on cultured T-lymphoma cells in a growing suspension was measured by microcalorimetry. The effect of the drug could be observed within 2 h after its injection into the calorimetric vessel. A dose-response curve was constructed from the calorimetric results obtained with final concentrations of MTX in the range of 0.02-2.00 microM. In another series of experiments calorimetric values were determined after 8 h of MTX-cell interaction. These data were correlated with values for cell counts during an 18 h period following the removal of the drug. A clear correlation was found between the calorimetric and cytotoxicity data. Calorimetric results obtained within 8 h of MTX-cell interaction appear to be of value in predicting the antineoplastic effect of the drug.

Animals↗
PubMed1986

Microcalorimetric measurements on tissue cells attached to microcarriers in stirred suspension.

Vero cells growing on microcarriers in stirred suspension were observed calorimetrically using a vessel designed for use with the LKB 'BioActivity Monitor'. Rates of formation of carbon dioxide and lactate were followed in parallel. The results showed that the power and rate of lactate formation could be correlated to both cell number and amount of protein, while the rate of carbon dioxide formation was slightly better correlated to cell number. The power per cell was 27.4 +/- 2.1 pW. Only 33% of this power could be accounted for by the formation of lactate and carbon dioxide.

Animals↗
PubMed1986

A microcalorimetric study of heat production in resting skeletal muscle from human subjects.

Different microcalorimetric techniques have been compared for the assessment in vitro of the total metabolic activity of resting skeletal muscle. Human fibre bundles were suspended in Krebs-Ringer-phosphate buffer containing glucose and insulin and the heat evolution was continuously monitored for 2-6 h. Palmitate as substrate was also tested. The power signals declined rapidly when a static calorimetric method (A) was used. Two different perfusion methods (B, C) gave higher power values. Long-lasting steady states were observed with method C, where the sample was contained in a cage acting as a stirrer. Significant differences were found for fibre bundles from different human muscles as well as age- and sex-related differences. The heat production in samples from the rectus abdominis muscle (method B), 0.73 mW/g muscle wet wt., was significantly higher than for the obliquus internus muscle, 0.44 mW/g, and the vastus lateralis muscle, 0.55 mW/g, but not different from the heat production value of vastus medialis, 0.66 mW/g. In method C particularly, the fibre bundles are believed to be in adequate contact with the surrounding medium. With the use of a multi-channel calorimeter it is possible to perform up to four experiments simultaneously, e.g. involving the calorigenic effects of pharmacological substances. The technique provides a new approach for detailed studies of muscle metabolism in physiological and pathological conditions.

Adolescent↗
PubMed1986

Thermochemistry of the interaction between peptides and vancomycin or ristocetin.

The thermodynamics of the interaction between the glycopeptide antibiotics vancomycin and ristocetin and bacterial peptidoglycan peptide analogs have been studied by means of a microcalorimetric titration technique. From results of the calorimetric measurements, changes in Gibbs energies, enthalpies, entropies and heat capacities for the binding reactions have been calculated. The derived thermodynamic data have been discussed on the basis of stereochemical data available for the interaction of acetyl-D-alanyl-D-alanine with each of the two antibiotics. The significance of entropic factors connected with conformational changes of the antibiotics is stressed.

Calorimetry↗
PubMed1986

Thermochemical characterization of T-lymphoma cells under non-growing conditions.

Cultured T-lymphoma cells, CCRF-CEM, were studied under non-growing conditions by microcalorimetry. A new stirred reaction vessel, mainly designed for biological experiments, was used. The calorimetric results were interpreted by use of known enthalpy data and an assumed net reaction scheme. Of the thermal power measured, 75% could be accounted for by formation of lactate and bicarbonate from the glucose in the medium. It is suggested that the residual power comes from oxidation of intracellular material.

Adenosine Triphosphate↗
PubMed1984

Calorimetric determination of the partition coefficient for chlorpromazine hydrochloride in aqueous suspensions of dimyristoylphosphatidylcholine vesicles.

Lipid suspensions containing from 0.1 to 0.2% by weight dimyristoylphosphatidylcholine were mixed in a flow calorimeter with equal volumes of chlorpromazine hydrochloride at concentrations ranging from 6 X 10(-5) to 1.2 X 10(-4) M. The vesicle bilayer volume fraction of the suspension was determined by density measurements. Linear relationships were obtained between heat production per ml suspension and chlorpromazine concentration at each level of lipid volume. Using phase partitioning as a model, the values of the partition coefficient and the enthalpy change were found to be K'c = 1300 and delta H = -30 kJ X mol-1 at 25 degrees C. Heat outputs at slightly higher concentrations of chlorpromazine increased less than linearly because of repulsive forces between neighboring chlorpromazine cations absorbed in the bilayer phase. At still higher concentrations the slope increased again but partition coefficients became variable, which indicated a change in the nature of the interaction. In batch calorimeter titrations at higher concentrations a sharp increase in heat output was observed at the critical micelle concentration of chlorpromazine (4 mM) and a final leveling off at 6 mM. Enthalpies of dilution of chlorpromazine obtained in separate experiments were large and endothermic, but no break in the curve could be detected at the critical micelle concentration.

Calorimetry↗
PubMed1984

Design and testing of a new microcalorimetric vessel for use with living cellular systems and in titration experiments.

A new microcalorimetric vessel primarily intended for use with living cellular systems and in titration experiments has been designed and tested. The vessel, which forms a modular system, fits into an ampoule measuring cylinder of the LKB 'BioActivity Monitor'. It can be used with different sample cups, volume 1-3 ml, and can be equipped with different types of stirrer and sample holders for cellular materials. Experiments can be performed with or without medium perfusing through the vessel. Small quantities of reagents can be added to the sample compartment during the measurements. Stepwise calorimetric titrations can be performed by an automatic procedure. Test experiments reported include results of measurements with human T-lymphoma cells in stirred suspension and melanoma cells adhered to a polystyrene film in a stirred perfusing medium. Results from titration experiments where N-acetyl-D-alanine was bound to ristocetin A are reported, delta G degree' = -16.5 +/- 0.2 kJ mol-1 and delta H degree' = -32.1 +/- 0.4 kJ mol-1.

Calorimetry↗
PubMed1984

Heat production in human blood lymphocytes. A methodological study.

Heat production rates (thermal power) in peripheral blood lymphocytes from healthy subjects were determined under some defined experimental conditions in an attempt to establish by microcalorimetry a basal metabolic reference range for lymphocytes in the non-activated state. The effects of cell isolation method, the presence of other types of blood cells, cell concentration, temperature, pH and type of suspension medium on the rate of heat production by lymphocytes were evaluated. The results indicate that microcalorimetry is suitable for monitoring the metabolism of these cells with good precision in the physiological range of cell concentration.

Basal Metabolism↗
PubMed1982

Heat production by adipocytes from obese subjects before and after weight reduction.

Microcalorimetry has been employed to measure the heat production by adipocytes obtained by percutaneous biopsy from lean subjects and from obese subjects before and after weight reduction. Cellular heat production was significantly lower in obese than in lean subjects. After weight reduction cellular heat production increased in fat cells from the obese subjects but was still significantly lower than in cells from control subjects. A number of variables reflecting uptake and mobilization of depot fat have measured and correlated to the heat production values in the obese subjects. The findings are consistent with the view that a decreased total metabolic activity might contribute to the development or perpetuation of obesity.

Adipose Tissue↗
PubMed1982

A test and calibration process for microcalorimeters used as thermal power meters.

A test and calibration process for microcalorimeters is described. The method has been developed with particular reference to instruments used for measurements of thermal power produced by suspensions of living cells. The process investigated is the hydrolysis of triacetin in imidazole/acetic acid buffer. The power levels are regulated by changing the buffer composition. The power will decrease slowly and very nearly linearly with time. Five test solutions, power levels 7-90 microW X ml-1, have been characterized at 37 degrees C and one of them at 25 degrees C (13 microW X ml-1). The power values for these reaction mixtures can be accurately calculated (+/- 0.5%) as a function of time during extended reaction periods, about 20 h or more.

Buffers↗
PubMed1982

Simultaneous determination of delta G, delta H and delta S by an automatic microcalorimetric titration technique. Application to protein ligand binding.

A methodological study has been made with a syringe titration unit attached to an LKB batch microcalorimeter. The precision and accuracy of the instrument assembly have been evaluated by neutralization reactions and by dilution of sucrose solutions. As an example, heat quantities on the order of 10 mJ accompanying the addition of 10 microliter titrant solution could be determined with an accuracy of better than 1%. A stepwise titration procedure was used to characterize the binding of indole-3-propionic acid to alpha-chymotrypsin. The following thermodynamic data were obtained (25 degrees C, acetate buffer, pH 5.80): delta G0=-18.46 +/- 0.17 kJ X mol-1, delta H0=-15.26 +/- 0.20 kJ X mol-1, delta S0 = 10.85 +/- 1.21 JK-1 X mol-1.

Calorimetry↗
PubMed1982

Heat production in different populations of human blood cells exposed to immune complexes in vitro: the importance of the Fc parts of immunoglobulins and the influence of active complement.

By use of a batch microcalorimeter of the thermopile type, heat production was measured in isolated populations of human peripheral blood cells exposed to defined immune complexes formed in vitro. It was found that most of the heat production recorded in whole blood after admixture of immune complexes occurs in the granulocytes. Under these conditions small but constantly higher activation values were found in the absence of active complement. It was shown that complexes consisting of antigen and F(ab)2 fragments prepared from the specific antibodies were able to initiate heat production in the cells only in the presence of active complement. These experiments indicate that immune complexes are able to induce increased heat production in the cells either by binding to Fc receptors or by activation of complement through the alternative pathway and subsequent binding of the generated C3b to C3b receptors on the heat-producing cells.

Antigen-Antibody Complex↗