RESUMEN
PURPOSE: Prior studies exploring the reliability of peak fat oxidation (PFO) and the intensity that elicits PFO (FATMAX) are often limited by small samples. This study characterised the reliability of PFO and FATMAX in a large cohort of healthy men and women. METHODS: Ninety-nine adults [49 women; age: 35 (11) years; [Formula: see text]O2peak: 42.2 (10.3) mL·kg BM-1·min-1; mean (SD)] completed two identical exercise tests (7-28 days apart) to determine PFO (g·min-1) and FATMAX (%[Formula: see text]O2peak) by indirect calorimetry. Systematic bias and the absolute and relative reliability of PFO and FATMAX were explored in the whole sample and sub-categories of: cardiorespiratory fitness, biological sex, objectively measured physical activity levels, fat mass index (derived by dual-energy X-ray absorptiometry) and menstrual cycle status. RESULTS: No systematic bias in PFO or FATMAX was found between exercise tests in the entire sample (- 0.01 g·min-1 and 0%[Formula: see text]O2peak, respectively; p > 0.05). Absolute reliability was poor [within-subject coefficient of variation: 21% and 26%; typical errors: ± 0.06 g·min-1 and × / ÷ 1.26%[Formula: see text]O2peak; 95% limits of agreement: ± 0.17 g·min-1 and × / ÷ 1.90%[Formula: see text]O2peak, respectively), despite high (r = 0.75) and moderate (r = 0.45) relative reliability for PFO and FATMAX, respectively. These findings were consistent across all sub-groups. CONCLUSION: Repeated assessments are required to more accurately determine PFO and FATMAX.
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Metabolismo de los Lípidos , Consumo de Oxígeno , Oxígeno/metabolismo , Tejido Adiposo/metabolismo , Adiposidad , Adolescente , Adulto , Anciano , Análisis de Varianza , Sesgo , Calorimetría/métodos , Calorimetría/normas , Capacidad Cardiovascular , Interpretación Estadística de Datos , Prueba de Esfuerzo , Femenino , Humanos , Masculino , Persona de Mediana Edad , Oxidación-Reducción , Reproducibilidad de los ResultadosRESUMEN
Since 2013, this journal has promoted the publication of thematic reviews (Taylor in Eur J Appl Physiol 113:1634, 2013), where leading groups were invited to review the critical literature within each of several sub-topics. The current theme is historically based, and is focussed on estimating the metabolic rate in humans. This review charts the development of our understanding of those methods, from the discovery of oxygen and carbon dioxide, to the introduction of highly sophisticated modern apparatus to examine the composition of expired gas and determine respiratory minute volume. An historical timeline links the six thematic vignettes on this theme. Modern advances have greatly enhanced data collection without significant decrements in measurement accuracy. At the same time, however, conceptual errors, particularly steady-state requirements, are too often ignored. Indeed, it is recognised that we often neglect the past, leading to errors in research design, experimental observations and data interpretation, and this appears to be increasingly prevalent within the open-access literature. Accordingly, the Editorial Board, in recognition of a widening gap between our experimental foundations and contemporary research, embarked on developing a number of thematic review series, of which this series is the first. The intent of each accompanying overview is to introduce and illuminate seminal investigations that led to significant scientific or intellectual breakthroughs, and to thereby whet the appetite of readers to delve more deeply into the historical literature; for it is only when the foundations are understood that we can best understand where we are now, and in which directions we should head.
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Metabolismo Basal , Fisiología/historia , Animales , Calorimetría/historia , Calorimetría/métodos , Calorimetría/normas , Historia del Siglo XVIII , Historia del Siglo XIX , Historia del Siglo XX , Historia del Siglo XXI , Humanos , Espirometría/historia , Espirometría/métodos , Espirometría/normasRESUMEN
Criterion data for total energy expenditure (TEE) in elite rugby are lacking, which prediction equations may not reflect accurately. This study quantified TEE of 27 elite male rugby league (RL) and rugby union (RU) players (U16, U20, U24 age groups) during a 14-day in-season period using doubly labelled water (DLW). Measured TEE was also compared to estimated, using prediction equations. Resting metabolic rate (RMR) was measured using indirect calorimetry, and physical activity level (PAL) estimated (TEE:RMR). Differences in measured TEE were unclear by code and age (RL 4369 ± 979; RU 4365 ± 1122; U16, 4010 ± 744; U20, 4414 ± 688; U24, 4761 ± 1523 Kcal day- 1). Differences in PAL (overall mean 2.0 ± 0.4) were unclear. Very likely differences were observed in RMR by code (RL 2366 ± 296; RU 2123 ± 269 Kcal day- 1). Differences in relative RMR between U20 and U24 were very likely (U16, 27 ± 4; U20, 23 ± 3; U24, 26 ± 5 Kcal kg- 1 day- 1). Differences were observed between measured and estimated TEE, using Schofield, Cunningham and Harris-Benedict equations for U16 (187 ± 614, unclear; - 489 ± 564, likely and - 90 ± 579, unclear Kcal day- 1), U20 (- 449 ± 698, likely; - 785 ± 650, very likely and - 452 ± 684, likely Kcal day- 1) and U24 players (- 428 ± 1292; - 605 ± 1493 and - 461 ± 1314 Kcal day- 1, all unclear). Rugby players have high TEE, which should be acknowledged. Large inter-player variability in TEE was observed demonstrating heterogeneity within groups, thus published equations may not appropriately estimate TEE.
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Calorimetría/métodos , Metabolismo Energético , Fútbol Americano/fisiología , Adolescente , Calorimetría/normas , Óxido de Deuterio/farmacocinética , Humanos , Masculino , Isótopos de Oxígeno/farmacocinética , Adulto JovenRESUMEN
Interaction thermodynamics between warfarin, a very popular anticoagulant, and Sudlow I binding site of human (HSA) or bovine (BSA) serum albumin have been examined in strictly controlled experimental conditions (HEPES buffer 50â¯mM, pH 7.4 and 25⯰C) by means of isothermal titration calorimetry (ITC), fluorescence spectrometry (FS) and frontal analysis capillary electrophoresis (FA/CE). Each technique is based on measurements of a different property of the biochemical system, and then the results allow a critical discussion about the suitability of each approach to estimate the drug-protein binding parameters. The strongest interaction step is properly evaluated by the three assayed approaches being the derived binding constants strongly consistent: from 4â¯×â¯104 to 7â¯×â¯104 for HSA and from 0.8â¯×â¯105 to 1.2â¯×â¯105 for BSA. Binding enthalpy variations also show consistent results: -5.4 and -5.6â¯Kcal/mol for HSA and -4.3 and -3.7â¯Kcal/mol for BSA, as measured by ITC and FS, respectively. Further high order interaction events for both albumins are detected only by FA/CE.
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Anticoagulantes/sangre , Calorimetría/métodos , Electroforesis Capilar/métodos , Albúmina Sérica Bovina/metabolismo , Albúmina Sérica Humana/metabolismo , Espectrometría de Fluorescencia , Warfarina/sangre , Anticoagulantes/química , Sitios de Unión , Calibración , Calorimetría/normas , Electroforesis Capilar/normas , Humanos , Unión Proteica , Conformación Proteica , Estándares de Referencia , Reproducibilidad de los Resultados , Albúmina Sérica Bovina/química , Albúmina Sérica Humana/química , Espectrometría de Fluorescencia/normas , Relación Estructura-Actividad , Termodinámica , Warfarina/químicaRESUMEN
OBJECTIVES: The laboratory mouse is presently the most common model for examining mechanisms of human physiology and disease. Housing temperatures can have a large impact on the outcome of such experiments and on their translatability to the human situation. Humans usually create for themselves a thermoneutral environment without cold stress, while laboratory mice under standard conditions (≈20° C) are under constant cold stress. In a well-cited, theoretical paper by Speakman and Keijer in Molecular Metabolism, it was argued that housing mice under close to standard conditions is the optimal way of modeling the human metabolic situation. This tenet was mainly based on the observation that humans usually display average metabolic rates of about 1.6 times basal metabolic rate. The extra heat thereby produced would also be expected to lead to a shift in the 'lower critical temperature' towards lower temperatures. METHODS: To examine these tenets experimentally, we performed high time-resolution indirect calorimetry at different environmental temperatures on mice acclimated to different housing temperatures. RESULTS: Based on the high time-resolution calorimetry analysis, we found that mice already under thermoneutral conditions display mean diurnal energy expenditure rates 1.8 times higher than basal metabolism, remarkably closely resembling the human situation. At any temperature below thermoneutrality, mice metabolism therefore exceeds the human equivalent: Mice under standard conditions display energy expenditure 3.1 times basal metabolism. The discrepancy to previous conclusions is probably attributable to earlier limitations in establishing true mouse basal metabolic rate, due to low time resolution. We also found that the fact that mean energy expenditure exceeds resting metabolic rate does not move the apparent thermoneutral zone (the lower critical temperature) downwards. CONCLUSIONS: We show that housing mice at thermoneutrality is an advantageous step towards aligning mouse energy metabolism to human energy metabolism.
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Regulación de la Temperatura Corporal , Calorimetría/métodos , Vivienda para Animales/normas , Temperatura , Animales , Calorimetría/normas , Humanos , Masculino , Ratones , Ratones Endogámicos C57BLRESUMEN
In reference dosimetry the aim is to establish the absorbed dose to water, D w, under reference conditions. However, existing dosimetry protocols are not always applicable for rapidly emerging new treatment modalities. For primary standard dosimetry laboratories it is generally not feasible to acquire such modalities. Therefore it is strongly desired that D w measurements with primary standards can be performed on-site in clinical beams for the new treatment modalities in order to characterize and calibrate detectors. To serve this need, VSL has developed a new transportable water calorimeter serving as a primary D w standard for (60)Co and MV-photons including MRI incorporated treatment equipment. Special attention was paid to its operation in different beam geometries and beam modalities including the application in magnetic fields. The new calorimeter was validated in the VSL (60)Co beam and on-site in clinical MV-photon beams. Excellent agreement of 0.1% was achieved with previous (60)Co field calibrations, i.e. well within the uncertainty of the previous calorimeter, and with measurements performed in horizontal and vertical MV-photon beams. k Q factors, determined for two PTW 30013 ionization chambers, agreed very well with available literature data. The relative combined standard uncertainty (k = 1) for D w measurements in (60)Co and MV-photons is 0.37%. Calibrations are carried out with a standard uncertainty of 0.42% and k Q -factors are determined with a relative standard uncertainty of 0.40%.
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Calorimetría/instrumentación , Imagen por Resonancia Magnética/métodos , Dosis de Radiación , Radioterapia/métodos , Calibración , Calorimetría/métodos , Calorimetría/normas , Imagen por Resonancia Magnética/instrumentación , Fotones/uso terapéuticoRESUMEN
The absolute dose delivered to a dynamically scanned sample in the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter anticipated to be established as a primary standard for synchrotron dosimetry. The calorimetry was compared to measurements using a free-air chamber (FAC), a PTW 31 014 Pinpoint ionization chamber, and a PTW 34 001 Roos ionization chamber. The IMBL beam height is limited to approximately 2 mm. To produce clinically useful beams of a few centimetres the beam must be scanned in the vertical direction. In practice it is the patient/detector that is scanned and the scanning velocity defines the dose that is delivered. The calorimeter, FAC, and Roos chamber measure the dose area product which is then converted to central axis dose with the scanned beam area derived from Monte Carlo (MC) simulations and film measurements. The Pinpoint chamber measures the central axis dose directly and does not require beam area measurements. The calorimeter and FAC measure dose from first principles. The calorimetry requires conversion of the measured absorbed dose to graphite to absorbed dose to water using MC calculations with the EGSnrc code. Air kerma measurements from the free air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. The two ionization chambers are secondary standards requiring calibration with kilovoltage x-ray tubes. The Roos and Pinpoint chambers were calibrated against the Australian primary standard for air kerma at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Agreement of order 2% or better was obtained between the calorimetry and ionization chambers. The FAC measured a dose 3-5% higher than the calorimetry, within the stated uncertainties.
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Calorimetría/métodos , Dosis de Radiación , Dosímetros de Radiación/normas , Calibración , Calorimetría/normas , Grafito , Humanos , Radioterapia/instrumentación , Radioterapia/métodos , Estándares de Referencia , Sincrotrones , Rayos XRESUMEN
The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm(-2), and at a dose rate of about 0.15 Gy min(-1), results of calorimetric measurements of absorbed dose to water, D(w), were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D(w) and D(wK) were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D(w) uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D(w), it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams.
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Calorimetría/normas , Grafito/efectos de la radiación , Rayos X , Absorción de Radiación , Calibración , Calorimetría/instrumentación , Radiometría/métodosRESUMEN
BACKGROUND: Successful ITC experiments require conversion of cell reagent (titrand M) to product and production or consumption of heat. These conditions are quantified for 1:1 binding, M+X â MX. METHODS: Nonlinear least squares is used in error-propagation mode to predict the precisions with which the key quantities - binding constant K, reaction enthalpy ΔH°, and stoichiometry number n - can be estimated over a wide range of the dimensionless quantity that governs isotherm shape, c=K[M]0. The measurement precision σq is estimated from analysis of water-water blanks. RESULTS: When the product conversion exceeds 90%, the parameter relative standard errors are proportional to σq/qtot, where the total heat qtot ≈ ΔH° [M]0V0. Specifically, σK/K×qtot/σq ≈ 25 for c=10(-3)-10, ≈ 11 c(1/3) for c=10-10(4). For c>1, n and ΔH° are more precise than K; this holds also at smaller c for the product n×ΔH° and for ΔH° when n can be held fixed. Use of as few as 10 titrant injections can outperform the customary 20-40 while also improving productivity. CONCLUSION: These principles are illustrated in experiment design using the program ITC-PLANNER15. GENERAL SIGNIFICANCE: Simple quantitative guidelines replace the "c rules" that have dominated the literature for decades.
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Compuestos de Bario/química , Calorimetría/normas , Cloruros/química , Éteres Corona/química , Programas Informáticos , Calor , Cinética , Análisis de los Mínimos Cuadrados , Nitratos/química , Proyectos de Investigación , Temperatura , TermodinámicaRESUMEN
To extend the dosimetric reference system to field sizes smaller than 2 cm × 2 cm, the LNE-LNHB laboratory is studying an approach based on a new dosimetric quantity named the dose-area product instead of the commonly used absorbed dose at a point. A graphite calorimeter and a plane parallel ion chamber with a sensitive surface of 3 cm diameter were designed and built for measurements in fields of 2, 1 and 0.75 cm diameter. The detector surface being larger than the beam section, most of the issues linked with absolute dose measurements at a point could be avoided. Calibration factors of the plane parallel ionization chamber were established in terms of dose-area product in water for small fields with an uncertainty smaller than 0.9%.
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Calorimetría/instrumentación , Calorimetría/métodos , Calorimetría/normas , Estudios de Factibilidad , Grafito , Radiometría/instrumentación , Radiometría/métodosRESUMEN
For a conscientious interpretation of thermodynamic parameters (Gibbs free energy, enthalpy and entropy) obtained by isothermal titration calorimetry (ITC), it is necessary to first evaluate the experimental setup and conditions at which the data were measured. The data quality must be assessed and the precision and accuracy of the measured parameters must be estimated. This information provides the basis at which level discussion of the data is appropriate, and allows insight into the significance of comparisons with other data. The aim of this article is to provide the reader with basic understanding of the ITC technique and the experimental practices commonly applied, in order to foster an appreciation for how much measured thermodynamic parameters can deviate from ideal, error-free values. Particular attention is paid to the shape of the recorded isotherm (c-value), the influence of the applied buffer used for the reaction (protonation reactions, pH), the chosen experimental settings (temperature), impurities of protein and ligand, sources of systematic errors (solution concentration, solution activity, and device calibration) and to the applied analysis software. Furthermore, we comment on enthalpy-entropy compensation, heat capacities and van't Hoff enthalpies.
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Calorimetría/métodos , Proteínas/química , Proteínas/metabolismo , Programas Informáticos , Termodinámica , Tampones (Química) , Calorimetría/normas , Exactitud de los Datos , Procesamiento Automatizado de Datos/métodos , Entropía , Ligandos , Unión Proteica , Protones , Reproducibilidad de los ResultadosRESUMEN
Despite its importance and all the considerable efforts made, the progress in drug discovery is limited. One main reason for this is the partly questionable data quality. Models relating biological activity and structures and in silico predictions rely on precisely and accurately measured binding data. However, these data vary so strongly, such that only variations by orders of magnitude are considered as unreliable. This can certainly be improved considering the high analytical performance in pharmaceutical quality control. Thus the principles, properties and performances of biochemical and cell-based assays are revisited and evaluated. In the part of biochemical assays immunoassays, fluorescence assays, surface plasmon resonance, isothermal calorimetry, nuclear magnetic resonance and affinity capillary electrophoresis are discussed in details, in addition radiation-based ligand binding assays, mass spectrometry, atomic force microscopy and microscale thermophoresis are briefly evaluated. In addition, general sources of error, such as solvent, dilution, sample pretreatment and the quality of reagents and reference materials are discussed. Biochemical assays can be optimized to provide good accuracy and precision (e.g. percental relative standard deviation <10 %). Cell-based assays are often considered superior related to the biological significance, however, typically they cannot still be considered as really quantitative, in particular when results are compared over longer periods of time or between laboratories. A very careful choice of assays is therefore recommended. Strategies to further optimize assays are outlined, considering the evaluation and the decrease of the relevant error sources. Analytical performance and data quality are still advancing and will further advance the progress in drug development.
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Bioensayo/normas , Exactitud de los Datos , Descubrimiento de Drogas , Calorimetría/normas , Bases de Datos Factuales , Electroforesis Capilar/normas , Fluorescencia , Inmunoensayo/normas , Ligandos , Espectroscopía de Resonancia Magnética/normas , Preparaciones Farmacéuticas/metabolismo , Sensibilidad y Especificidad , Resonancia por Plasmón de Superficie/normasRESUMEN
BACKGROUND: Intestinal absorption capacity is considered to be the best method for assessing overall digestive intestinal function. Earlier reference values for intestinal function in healthy Dutch adults were based on a study that was conducted in an inpatient metabolic unit setting in a relatively small series. The present study aimed to readdress and describe the intestinal absorption capacity of healthy adults, who were consuming their usual (Western European) food and beverage diet, in a standard ambulatory setting. METHODS: Twenty-three healthy subjects (aged 22-60 years) were included in the analyses. Nutritional intake (energy and macronutrients) was determined with a 4-day nutritional diary. Subsequently, mean faecal losses of energy (by bomb calorimetry), fat, protein and carbohydrate were determined following a 3-day faecal collection. Finally, intestinal absorption capacity was calculated from the differences between intake and losses. RESULTS: Mean (SD) daily faeces production was 141 (49) g (29% dry weight), containing 891 (276) kJ [10.7 (1.3) kJ g(-1) wet faeces; 22.6 (2.5) kJ g(-1) dry faeces], 5.2 (2.2) g fat, 10.0 (3.8) g protein and 29.7 (11.7) g carbohydrates. Mean (SD) intestinal absorption capacity of healthy subjects was 89.4% (3.8%) for energy, 92.5% (3.7%) for fat, 86.9% (6.4%) for protein and 87.3% (6.6%) for carbohydrates. CONCLUSIONS: The present study provides normative values for both stool nutrient composition and intestinal energy and macronutrient absorption in healthy adults on a regular Dutch diet in an ambulatory setting. Intestinal energy absorption was found to be approximately 90%.
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Calorimetría/métodos , Calorimetría/normas , Ingestión de Energía , Absorción Intestinal/fisiología , Adulto , Registros de Dieta , Carbohidratos de la Dieta/administración & dosificación , Grasas de la Dieta/administración & dosificación , Proteínas en la Dieta/administración & dosificación , Heces/química , Femenino , Voluntarios Sanos , Humanos , Masculino , Persona de Mediana Edad , Países Bajos , Evaluación Nutricional , Valores de Referencia , Adulto JovenRESUMEN
Nowadays, the absorbed dose to water for kilovoltage x-ray beams is determined from standards in terms of air-kerma by application of international dosimetry protocols. New standards in terms of absorbed dose to water has just been established for these beams at the LNE-LNHB, using water calorimetry, at a depth of 2 cm in water in accordance with protocols. The aim of this study is to compare these new standards in terms of absorbed dose to water, to the dose values calculated from the application of four international protocols based on air-kerma standards (IAEA TRS-277, AAPM TG-61, IPEMB and NCS-10). The acceleration potentials of the six beams studied are between 80 and 300 kV with half-value layers between 3.01 mm of aluminum and 3.40 mm of copper. A difference between the two methods smaller than 2.1% was reported. The standard uncertainty of water calorimetry being below 0.8%, and the one associated with the values from protocols being around 2.5%, the results are in good agreement. The calibration coefficients of some ionization chambers in terms of absorbed dose to water, established by application of calorimetry and air-kerma based dosimetry protocols, were also compared. The best agreement with the calibration coefficients established by water calorimetry was found for those established with the AAPM TG-61 protocol.
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Calorimetría/normas , Internacionalidad , Dosis de Radiación , Agua , Calibración , Estándares de Referencia , Incertidumbre , Rayos XRESUMEN
Microcalorimetry is frequently used as a high throughput predictive method in order to screen different formulations for their storage stability. However, the predictive power of measuring unfolding temperatures (Tm), although studied for the stability of proteins under stress, has not been investigated systematically for long term stability of pharmaceutical proteins yet. In this study, the microcalorimetric Tm is evaluated as a predictive tool for long term stability of 24 liquid formulations of Granulocyte Colony Stimulating Factor. Those were tested with respect to the effect of different buffer salts in different concentrations, different pH values, and the effect of two excipients: polysorbate 80 and hydroxy propyl-ß-Cyclodextrin. Formulations were first ranked based on the measured Tm. The same formulations were then ranked based on a long term stability study at 2-8 °C for a period of up to 24 months. For this study, standard analytical methods were used to assess both physical and chemical stabilities of the formulations on long term. Microcalorimetric Tm based ranking was then compared with the long term stability ranking. Determining Tm turned out to be a successful predictive tool to select good formulations and exclude bad ones with an acceptable low degree of error. In particular, physical long term stability at a storage temperature of 2-8 °C was better predicted by just measuring Tm than by conducting stress studies at elevated temperatures.
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Calorimetría/normas , Química Farmacéutica/normas , Factor Estimulante de Colonias de Granulocitos/química , Calorimetría/métodos , Química Farmacéutica/métodos , Estabilidad de Medicamentos , Predicción , Factores de TiempoRESUMEN
A primary standard for the absorbed dose rate to water in a 6°Co radiation field has been newly established at the National Metrology Institute of Japan. This primary standard combines the calorimetric measurements using a graphite calorimeter with the ionometric measurements using a thick-walled graphite cavity ionisation chamber. The calorimeter is operated in the constant temperature mode using AC Wheatstone bridges. The absorbed dose rate to water was determined to be 12 mGy s⻹ at a point of 1 m from the radiation source and at a water depth of 5 g cm⻲. The uncertainty on the calibration coefficient in terms of the absorbed dose to water of an ionisation chamber using this standard was estimated to be 0.39 % (k=1).
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Calorimetría/instrumentación , Calorimetría/normas , Radioisótopos de Cobalto/análisis , Grafito/efectos de la radiación , Radiometría/instrumentación , Radiometría/normas , Agua/química , Radioisótopos de Cobalto/normas , Japón , Dosis de Radiación , Estándares de Referencia , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Agua/normasRESUMEN
The use of whole-room calorimetry (WRC) in young children can increase our understanding of children's energy balance. However, studies using WRC in young children are rare due to concerns about its feasibility. To assess the feasibility of WRC in young children, forty children, aged 46 years, were asked to follow a graded activity protocol while in a WRC. In addition, six children participated in two additional resting protocols to examine the effect of diet-induced thermogenesis on resting energy expenditure (REE) measures and the reliability of REE measurement. Refusals to participate and data loss were quantified as measures of practical utility, and REE measured after an overnight fast and after a 90-min fast were compared. In addition, both were compared to predicted BMR values using the Schofield equation. Our results showed that thirty (78·9 %) participants had acceptable data for all intensities of the activity protocol. The REE values measured after a 90-min fast (5·07 (SD 1·04) MJ/d) and an overnight fast (4·73 (SD 0·61) MJ/d) were not significantly different from each other (P= 0·472). However, both REE after an overnight fast and a 90-min fast were significantly higher than predicted BMR (3·96 (SD 0·18) MJ/d) using the Schofield equation (P= 0·024 and 0·042, respectively). We conclude that, with a developmentally sensitive approach, WRC is feasible and can be standardised adequately even in 4- to 6-year-old children. In addition, the effect of a small standardised breakfast, approximately 90 min before REE measurements, is likely to be small.
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Metabolismo Basal , Calorimetría/normas , Metabolismo Energético , Actividad Motora , Descanso , Calorimetría/métodos , Niño , Preescolar , Dieta , Ingestión de Energía , Ayuno , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , TermogénesisRESUMEN
PURPOSE: Isothermal microcalorimetry (IMC) has recently been reported as a new method to rapidly detect urinary tract pathogens (UTP). However, further application of microcalorimetry in the clinical setting requires a standardized procedure. An important step toward such standardization is to use a reproducible growth medium. In this study, we investigated the potential of artificial urine in combination with microcalorimetry for detection of common UTP. METHODS: A microcalorimeter equipped with 48 channels was used. Detection was accomplished, and growth was monitored for four bacterial strains in artificial urine at 37 °C by measuring metabolic heat flow (µW = µJ/s) as a function of time. The strains were Escherichia coli, Proteus mirabilis, Enterococcus faecalis, and Staphylococcus aureus. RESULT: Bacterial growth was detected after 3-32 h with decreasing inoculums down to 1 CFU. The gram-negative strains grew and were detected faster than their gram-positive counterparts. The growth rates the different strains were 0.75 ± 0.11 for E. coli, 0.74 ± 0.10 for E. faecalis, 1.31 ± 0.04 for P. mirabilis, and 0.56 ± 0.20 for S. aureus. The shape of individual heat flow curves was characteristic for each species independent of its initial concentration. CONCLUSIONS: IMC allows rapid detection of UTP in artificial urine. Clearly, different heat flow patterns enable accurate pathogen differentiation. UTP detection after only 4 h is realistic. The rapid detection of UTP tested in standardized artificial urine proves the diagnostic potential of IMC and warrants further microcalorimetric studies in the clinical setting of urinary tract infections.
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Calorimetría/normas , Infecciones Urinarias/diagnóstico , Infecciones Urinarias/microbiología , Orina/microbiología , Animales , Enterococcus faecalis/aislamiento & purificación , Escherichia coli/aislamiento & purificación , Humanos , Pruebas de Sensibilidad Microbiana , Proteus mirabilis/aislamiento & purificación , Estándares de Referencia , Staphylococcus aureus/aislamiento & purificación , Infecciones Urinarias/orinaRESUMEN
Isothermal titration calorimetry (ITC) is one of the most interesting methods for the characterization of the interaction mechanisms of cyclodextrins (CDs) with drugs. In this review we explain how to conduct ITC experiments correctly for CD-guest interactions, how to choose an accurate fitting model for the titration curve and how to interpret carefully the ITC results. Finally, the use of ITC for the characterization of CD-containing nanoparticles is discussed.
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Calorimetría/métodos , Ciclodextrinas/química , Portadores de Fármacos/química , Modelos Químicos , Preparaciones Farmacéuticas/química , Termodinámica , Calorimetría/normas , Interacciones Farmacológicas , Estructura Molecular , Nanopartículas , Propiedades de Superficie , VolumetríaRESUMEN
The precision with which the dissociation constant, K(D), can be obtained from isothermal titration calorimetry depends on, among other factors, the concentrations of the interacting species. The so-called c value-the ratio of analyte concentration to K(D)-should fall in the range of 1 to 1000 for reliable K(D) determination. On the basis of simulated, noise-free data, Biswas and Tsodikov [5] recently suggested an optimal c value of 5 to 20. By contrast, we find an optimum at c > 40 on determining the K(D) confidence intervals through simulations containing noise levels typical of state-of-the-art microcalorimeters.