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At least 667 records · Page 37Linked to original sources
PubMed1988

Maintenance energy requirements of laying hens: a comparison of measurements made by two methods based on indirect calorimetry.

1. The aims of this study were to compare maintenance metabolisable energy requirement estimates obtained in laying hens by two methods of respiration calorimetry, to investigate the changes in the heat production and energy retention of laying hens associated with temporarily reduced energy intake and to demonstrate the errors caused by using inappropriate values of net efficiency of energy utilisation (k) when extrapolating to maintenance energy requirement from a range of energy retention values. 2. One of the methods used regression of a range of energy retentions on energy intakes, followed by interpolation of zero energy retention; the other method employed extrapolation to zero energy retention from a single level of energy intake and retention. 3. Maintenance energy requirements derived from the two methods were similar. There was no indication that repeated temporary reduction of energy intake for the regression method gave a reduced value for maintenance energy requirement. The main potential advantage of the single-point method is therefore rapidity. 4. The single-point method relies for accuracy either on fixing an energy intake near the expected maintenance or on having a very accurate value for k. For example, the error attributable to using an assumed net efficiency (k) value of 0.7 when the true value was 0.8 was shown to vary between 0 if energy retention was measured at the equilibrium point and about 70 kJ/kgW0.75 d, or +15%, if energy retention was measured in the fasted state. 5. Stability of heat production and energy intake was approached after 2 d of reduced energy intake.

Animals↗
PubMed1985

X-ray diffractometry and calorimetry studies of structural modifications induced by gamma-irradiation in phosphatidylcholine multilamellar liposomes.

Experimental results are reported on structural and thermodynamic modifications induced by gamma-irradiation in model membranes. Differential scanning calorimetry (DSC) and X-ray diffraction were used to study the different phases and associated transitions of dipalmitoylphosphatidylcholine after 60Co gamma-irradiation. Changes were observed in the shape of calorimetric peaks and in the corresponding enthalpy. The repetition distance of the layers increases while the distances related to the aliphatic chains decrease as a function of gamma-irradiation time. Moreover, an increase in the hexagonal symmetry with increasing dose was detected. No disappearance of a pre-transition was detected even at high doses.

Calorimetry↗
PubMed2002

Maturity degree of composts from municipal solid wastes evaluated by differential scanning calorimetry.

Differential scanning calorimetry (DSC) in association with chemical analysis was applied to assess the maturity reached by the organic fraction of Municipal Solid Wastes (MSW) subjected to composting processes with manual and fixed aeration and sampled at different composting times. Thermograms showed that the difference in the treatments, i.e., the manual aeration and the fixed aeration, had no relevant effect on the stabilization and maturation of OM in the substrates. Common thermal effects observed were: a low temperature endotherm assigned to dehydration and/or loss of peripheral polysaccharides chains; a medium temperature exotherm assigned to loss of peptidic structures, and a high temperature exotherm assigned to oxydation and polycondensation of aromatic nuclei of the molecule. Results obtained suggest that in the experimental conditions used, a shorter time of composting (about 30 d) appears adequate, in order to limit the extended mineralization of OM, whereas a prolonged composting time (up to 132 d) would produce a compost of poor quality with high ash content and low OM content.

Biodegradation, Environmental↗
PubMed2002

[Measurement and differentiation method of carbon in municipal solid waste incineration (MSWI) bottom ash using differential scanning calorimetry (DSC)].

In this study, Differential Scanning Calorimetry (DSC) is applied to speciation and evaluation of carbon in Municipal Solid Waste Incineration (MSWI) bottom ash. This innovative recognition approach highlights and quantifies different types of carboned materials in bottom ash: Labile Organic Carbon (LOC) and Refractory Carbon (RC). The Labile Organic Carbon contains small molecules unburnt or decomposed and volatile. This organic material (LOC) is oxidized at medium temperatures (between 300 and 325 degrees C). The Refractory Carbon contains Elementary Carbon (EC) and Resistant Organic Carbon (ROC) in the form of complex molecules of high molecular weight. This is oxidized at high temperatures (between 435 and 470 degrees C).

Calorimetry, Differential Scanning↗
PubMed2005

Changes in leukemic cell nuclei revealed by differential scanning calorimetry.

Using differential scanning calorimetry we analyzed the thermal profiles of nuclei from normal and B-cell chronic lymphocytic leukemia mononuclear cells. Intact nuclear fraction of normal mononuclear cells is characterized by four thermal transitions, i.e., at 60, 70, 83 and 103 degrees C. Leukemic nuclear samples revealed the transitions at 67 and 83 degrees C, however, in more aggressive stage of the disease additional thermal peaks at 76 and 93 degrees C were observed. Our very preliminary results revealed that mononuclear cell nuclear fraction from blood of patients responding to the used therapy, i.e., cladribine alone or its combination with mitoxantrone and cyclophosphamide indicates decrease (or even loss) of transition at 93 degrees C concomitant with increase of transition at 76 degrees C. A complementary study showed that in mononuclear cells of patients who appeared to be sensitive to chemotherapy the decrease of antiapoptotic Bcl-2 protein expression and signs of apoptotic morphology were observed.

Aged↗
PubMed2002

Product inhibition study on carbonic anhydrase using spectroscopy and calorimetry.

Kinetic and thermodynamic studies have been made on the effect of the p-nitrophenol product on the activity of bovine carbonic anhydrase in 50 mM Tris buffer pH 7.5, at 300K using UV spectrophotometry and isothermal titration calorimetry (ITC). A competitive inhibition was observed for p-nitrophenol as a product of the enzymatic reaction. A graphical fitting method was used for determination of the binding constant and enthalpy of inhibitor binding using ITC data. The dissociation binding constant was 0.10mM by the microcalorimetric method, which is in good agreement with the value of 0.11mM for the inhibition constant obtained from the spectrophotometric method.

Animals↗
PubMed1996

Interaction of myosin subfragment 1 with F-actin studied by differential scanning calorimetry.

The thermal unfolding of the myosin subfragment 1 (S1) and of filamentous actin (F-actin) in their strong complex obtained in the presence of ADP was studied by differential scanning calorimetry (DSC). It is shown that in the acto-S1 complexes S1 and F-actin melt separately, and thermal transitions of each protein can be easily followed. Interaction of S1 with F-actin significantly increases S1 thermal stability and also affects the thermal stability of F-actin. Although S1 unfolds at much lower temperature than F-actin, the molecules of S1 remain bound to F-actin even after full denaturation. Under these conditions S1 may induce cross-linking between actin filaments. It is concluded that DSC studies on the acto-S1 complexes offer a new and promising approach to investigate the structural changes which occur in the myosin head and in F-actin due to their interaction.

Actins↗
PubMed2004

Flow calorimetry--a useful tool for determination of immobilized cis-epoxysuccinate hydrolase activity from Nocardia tartaricans.

Bacterial cells Nocardia tartaricans with cis-epoxysuccinate hydrolase activity were entrapped in hardened calcium pectate gel by a commercial high performance encapsulator. This enzyme (in a single step reaction with no formation of side products) was used to hydrolyze disodium cis-epoxysuccinate to a pure enantiomer--disodium L-(+)-tartrate. Activities of this enzyme were determined using flow calorimetry. The validity of this method was corroborated by HPLC and isotachophoresis. The immobilized biocatalyst has activity (75.8 U/mgdry) able to convert disodium cis-epoxysuccinate to disodium tartrate at 94% yield in 5.5h. Immobilization of N. tartaricans in hardened calcium pectate gel beads had a positive effect on the activity of cis-epoxysuccinate hydrolase, storage stability, yield, and time of bioconversion.

Calorimetry↗
PubMed2004

Quantifying low amorphous or crystalline amounts of alpha-lactose-monohydrate using X-ray powder diffraction, near-infrared spectroscopy, and differential scanning calorimetry.

Efficient and accurate quantification of low amorphous and crystalline contents within pharmaceutical materials still remains a challenging task in the pharmaceutical industry. Since X-ray powder diffraction (XRPD) equipment has improved in recent years, our aim was 1) to investigate the possibility of substantially lowering the detection limits of amorphous or crystalline material to about 1% or 0.5% w/w respectively by applying conventional Bragg Brentano optics, combined with a fast and simple evaluation technique; 2) to perform these measurements within a short time to make it suitable for routine analysis; and 3) to subject the same data sets to a partial least squares regression (PLSR) in order to investigate whether it is possible to improve accuracy and precision compared to the standard integration method. Near-infrared spectroscopy (NIRS) and differential scanning calorimetry (DSC) were chosen as reference method. As model substance, alpha lactose monohydrate was chosen to create calibration curves based on predetermined mixtures of highly crystalline and amorphous substance. In contrast to DSC, XRPD and NIRS revealed an excellent linearity, precision, and accuracy with the percent of crystalline amount and a detectability down to about 0.5% w/w. Chemometric evaluation (partial least squares regression) applied to the XRPD data further improved the quality of our calibration.

Calorimetry, Differential Scanning↗
PubMed2004

A rapid micro quantification method of paracetamol in suppositories using differential scanning calorimetry.

This study adopts Differential Scanning Calorimetry (DSC) to analyze the thermal properties of samples (2.5-4.0 mg) from the tip, middle, and base sections of individual paracetamol suppositories, which were sampled carefully using a stainless steel scalpel. The contents of paracetamol present in the samples obtained from these sections were determined from the enthalpies of fusion of paracetamol and expressed as % w/w paracetamol to allow comparison of the amount of paracetamol found in each section. The tip, middle, and base sections contained 10.1+/-0.2%, 10.1+/-0.2%, and 10.3+/-0.2% w/w paracetamol, and are statistically similar (One-way anova; p>0.05). This indicates that the preparation technique adopted produces high quality suppositories in terms of content uniformity. The contents of paracetamol in the 120-mg paracetamol suppositories determined by DSC and UV spectrophotometry were statistically equivalent (Students's t-test; p>0.05), 120.8+/-2.6 mg and 120.8+/-1.5 mg, respectively, making DSC a clear alternative method for the measurement of content of drug in suppositories. The main advantages of the method are that samples of only 2.5-4.0 mg are required and the procedure does not require an extraction process, which allows for the analysis to be completed rapidly. In addition, it is highly sensitive and reproducible, with the lower detection limit at 4.0% w/w paracetamol, which is about 2.5 times lower than the content of paracetamol (10% w/w) present in our 120-mg paracetamol suppositories and commercial paracetamol suppositories, which contained about 125 mg paracetamol. Therefore, this method is particularly suited for determination of content uniformity in individual suppositories in quality control (QC) and in process quality control (PQC).

Acetaminophen↗
PubMedDate not supplied

Isothermic titration calorimetry to study CMCs of neutral surfactants and of the liposome-forming bolaamphiphile dequalinium.

Isothermic titration calorimetry was used to measure the heat of micelle formation (molar enthalpy of transfer of surfactants monomers from water into micellar aggregates. The problems associated with the estimation of the CMC and the whole therodynamic profile of micellization of surfactants via Gibbs-Helmholtz-Equation are discussed. CMC's of octylthioglucoside and the peculiar bolaamphilphile dequalinium which concentrates in mitochondria are measured. In contrast to earlier reports, no CMC of dequalinium could be found inspite of extensive systematic measurements.

Anti-Infective Agents, Local↗
PubMed2005

On the feasibility of water calorimetry with scanned proton radiation.

Water calorimetry is considered to be the most direct primary method to realize the physical quantity gray for absorbed dose to water. The Swiss Federal Office of Metrology and Accreditation (METAS) has routinely operated a water calorimeter as primary standard for photon radiation since 2001. Nowadays, cancer therapy with proton radiation has become increasingly important and is a well established method. In the framework of the ProScan project conducted by the Paul Scherrer Institute (PSI), the spot-scanning technique is prepared for the subsequent application in hospitals, and adjusted to the recent findings of clinical research. In the absence of primary standards for proton radiation, the metrological traceability is assured by calibrating secondary standards in 60Co radiation and correcting with calculated beam quality correction factors. It is internationally recognized that the development of primary standards for proton radiation is highly desirable. In a common project of PSI and METAS, it is investigated whether a modified version of the water calorimeter in operation at METAS is suitable as primary standard for scanned proton radiation. A feasibility study has been conducted to investigate the linear energy transfer (LET) dependence of the heat defect and the influence of the time and space structure of the scanned beam on the homogeneity and stability of the temperature field in the water calorimeter. Simulations are validated against experimental data of the existing calorimeter used with photon radiation and extended to scanned proton radiation.

Calorimetry↗
PubMed2006

Continuous indirect calorimetry--a laboratory simulation of a new method for non-invasive metabolic monitoring of patients under anaesthesia or in critical care.

A method was tested which permits continuous real time monitoring of O(2) uptake in patients attached to a breathing system. The method is an indirect calorimetry technique which uses fresh gas rotameters for control, regulation and measurement of the gas flows into the system, with continuous sampling of mixed exhaust gas. Testing of this approach was conducted using a lung gas exchange simulator, in order to determine its accuracy and precision under controlled conditions, when compared to a range of simulated O(2) uptake values. The overall mean bias (standard error) was -1.3 mL min(-1) (0.3) and the standard deviation was 6.5. The performance of the method was found to be consistent across a wide range of fresh gas flow rates and O(2) concentrations from 30 to 80%. The method warrants in vivo testing under clinical conditions.

Calorimetry↗
PubMed1986

Comparison of the doubly labeled water (2H2(18)O) method with indirect calorimetry and a nutrient-balance study for simultaneous determination of energy expenditure, water intake, and metabolizable energy intake in preterm infants.

The doubly labeled water method was compared with indirect calorimetry and a nutrient-balance study for simultaneous determination of rates of CO2 production, energy expenditure, and water intake over 5 days in four preterm infants. Additionally, metabolizable energy (ME) intake estimated using the isotope procedure (as energy expenditure plus an estimate for energy deposition based on weight gain), was compared to ME intake measured in the balance study. Compared to values obtained by traditional methods, calculated CO2 production, energy expenditure, and water intake differed by -1.4 +/- 4.8% (SD), +0.3 +/- 2.6%, and +5.7 +/- 1.4%, respectively; the difference in water intake was significant (p less than 0.05). Calculated ME intakes were 5.3 +/- 19.3% less than measured intakes, but the difference was not significant. These findings indicate that the doubly labeled water method can provide accurate information on rates of CO2 production, energy expenditure, and water intake in preterm infants, but individual estimates of ME intake may be subject to substantial error.

Calorimetry, Indirect↗
PubMed1988

Energy expenditure from minute-by-minute heart-rate recording: comparison with indirect calorimetry.

Total daily energy expenditure (TDEE) and energy expended in activity (EAC) were estimated by the minute-by-minute heart-rate method in 22 (16 men, 6 women) individually calibrated subjects and compared with values obtained by whole-body indirect calorimetry. Subjects followed four activity protocols during the 22 h in the calorimeter; no exercise (n = 6) and 2 (n = 5), 4 (n = 4), and 6 (n = 6) 30-min bouts of exercise on a bicycle ergometer at varying intensities. There were no statistically significant differences between the two methods in TDEE or EAC in any of the sex or protocol groupings. The regression of TDEE by heart rate on TDEE in the calorimeter was y = 0.92x + 1.0 MJ; (r = 0.87, SEE = 0.91 MJ). The heart-rate method also follows the varying activity patterns of individuals and can be used to closely estimate the TDEE and EAC of even small (n = 4-6) groups of subjects. In the present measurements, it gave a maximum error of TDEE for individuals of +20% and -15%.

Adult↗
PubMed1989

Energy expenditure in underweight free-living adults: impact of energy supplementation as determined by doubly labeled water and indirect calorimetry.

The effect of energy supplementation was evaluated in six underweight adults under free-living conditions. Customary energy intake (EI) over 4 wk and estimated body composition were defined. Then for 12 wk subjects were fed their customary EI under controlled conditions to assure stable energy reserve. Finally, intake was increased by a mean of 720 kcal/d for 8 wk adjusted to increase body fat from 9 to 18%. Body weight (means +/- SD) increased from 55.2 +/- 3.4 to 57.0 +/- 4.2 kg. Body fat gain was highly variable ranging from 0.6 to 3.8 kg. Energy expenditure (EE) by the factorial and doubly labeled water methods did not change. Fat storage accounted for 66% of the supplemental energy; 237 kcal/d remained unaccounted for. EE by the factorial method, which uses indirect calorimetry or isotopic measurements, were highly correlated (r = 0.8; p less than 0.01). Under the conditions of this study EI does not affect EE. The labeled water method permits the evaluation of energy expenditure in free-living conditions.

Body Composition↗
PubMed1990

Comparison of substrate utilization by indirect calorimetry during cyclic and continuous total parenteral nutrition.

Five male adult home patients were studied in a randomized order under continuous (24 h/d) and nocturnal cyclic (15 h/d) isocaloric, isonitrogenous total parenteral nutrition (TPN). They received 2626 +/- 265 total kcal/d as 60% dextrose and 40% lipids; the 3-h lipid infusion was followed by the dextrose amino acid infusion on both regimens. Substrate oxidation was measured by indirect calorimetry during four periods on the fourth day of each regimen. During cyclic TPN net lipogenesis occurred with a nonproteic respiratory quotient (npRQ) greater than 1 during dextrose amino acid infusion followed by net lipolysis with an npRQ less than 1 during the nonnourishing phase. In contrast, during continuous TPN net lipogenesis persisted with an npRQ greater than 1 over the 21 h of dextrose amino acid infusion. During the 3-h lipid infusion, fat oxidation was observed during both regimens but was more pronounced during cyclic TPN (p less than 0.05). As a consequence, 24-h lipid oxidation was higher and 24-h dextrose utilization lower during cyclic vs continuous TPN (p less than 0.05). These results suggest that cyclic TPN when alternating between substrate storage and oxidation, mimics the physiological pattern of oral feeding.

Adult↗
PubMed1991

Comparative continuous-indirect-calorimetry study of two carbohydrates with different glycemic indices.

Six healthy young men were studied by indirect calorimetry for 6 h after eating a meal composed of glucose or manioc starch (equivalent to 50 g dextrose). Blood was drawn every 30 min for 6 h to measure plasma glucose, free fatty acid (FFA), and insulin concentrations. The glycemic index of the starch was 57%. Plasma insulin and glucose concentrations were significantly higher from 150 to 210 min and FFA concentrations remained significantly lower from 210 to 360 min after starch than after glucose. Carbohydrate oxidation rose from a similar initial concentration for glucose and starch, to a constant concentration until 200 min before becoming significantly higher for the starch load until the end of the test. Total glucose oxidation was significantly higher with starch. Total fat oxidation did not differ after the two loads. A negative correlation was found between glucose oxidation and plasma FFA concentrations. Use of low-glycemic-index carbohydrates increases carbohydrate oxidation because of lower plasma FFA concentrations and fat oxidation.

Absorption↗