RESUMEN
BACKGROUND/OBJECTIVES: Iron deficiency and anemia may impair athletic performance, and iron supplements are commonly consumed by athletes. However, iron overload should be avoided because of the possible long-term adverse health effects. METHODS: We investigated the iron status of 170 male and female recreational runners participating in the Zürich marathon. Iron deficiency was defined either as a plasma ferritin (PF) concentration <15 microg/l (iron depletion) or as the ratio of the concentrations of transferrin receptor (sTfR) to PF (sTfR:log(PF) index) of > or =4.5 (functional iron deficiency). RESULTS: After excluding subjects with elevated C-reactive protein concentrations, iron overload was defined as PF >200 microg/l. Iron depletion was found in only 2 out of 127 men (1.6% of the male study population) and in 12 out of 43 (28.0%) women. Functional iron deficiency was found in 5 (3.9%) and 11 (25.5%) male and female athletes, respectively. Body iron stores, calculated from the sTfR/PF ratio, were significantly higher (P<0.001) among male compared with female marathon runners. Median PF among males was 104 microg/l, and the upper limit of the PF distribution in males was 628 microg/l. Iron overload was found in 19 out of 127 (15.0%) men but only 2 out of 43 in women (4.7%). Gender (male sex), but not age, was a predictor of higher PF (P<0.001). CONCLUSIONS: Iron depletion was present in 28% of female runners but in <2% of males, whereas one in six male runners had signs of iron overload. Although iron supplements are widely used by athletes in an effort to increase performance, our findings indicate excess body iron may be common in male recreational runners and suggest supplements should only be used if tests of iron status indicate deficiency.
Asunto(s)
Anemia Ferropénica/epidemiología , Ejercicio Físico/fisiología , Ferritinas/sangre , Sobrecarga de Hierro/epidemiología , Hierro de la Dieta/metabolismo , Hierro/sangre , Carrera/fisiología , Adulto , Anemia Ferropénica/sangre , Atletas , Femenino , Humanos , Deficiencias de Hierro , Sobrecarga de Hierro/sangre , Hierro de la Dieta/administración & dosificación , Masculino , Estado Nutricional , Prevalencia , Receptores de Transferrina/metabolismo , Factores SexualesRESUMEN
The aim of this study was to investigate whether the washout length between glycemic response tests influences their reliability. A total of 3 men and 12 women performed eight identical blood glucose tolerance tests: four tests on consecutive days (short interval) and four tests spread over 20-30 days, with 5-10 days between the tests (long interval). No difference was observed in the coefficient of variation (P=0.32) of the incremental area under the blood glucose response curve between the short and long interval, and there was no drift within the short (P=089) and long interval (P=0.20). The first test did not differ from any of the subsequent tests (P>0.99). In conclusion, glycemic response testing on consecutive days does not seem to influence the variability of glycemic response tests compared with longer intervals and it does not cause any data drift under conditions of earlier diet and habitual exercise control. In addition, familiarization trials do not seem to be necessary for glycemic response tests.
Asunto(s)
Glucemia/análisis , Prueba de Tolerancia a la Glucosa/métodos , Insulina/sangre , Área Bajo la Curva , Estudios Cruzados , Carbohidratos de la Dieta/administración & dosificación , Carbohidratos de la Dieta/metabolismo , Femenino , Índice Glucémico , Humanos , Masculino , Factores de Tiempo , Adulto JovenRESUMEN
A borehole in the Callovo-Oxfordian clay rock in ANDRA's underground research facility was sampled during 1 year and chemically analyzed. Diffusion between porewater and the borehole solution resulted in concentration changes which were modeled with PHREEQC's multicomponent diffusion module. In the model, the clay rock's pore space is divided in free porewater (electrically neutral) and diffuse double layer water (devoid of anions). Diffusion is calculated separately for the two domains, and individually for all the solute species while a zero-charge flux is maintained. We explain how the finite difference formulas for radial diffusion can be translated into mixing factors for solutions. Operator splitting is used to calculate advective flow and chemical reactions such as ion exchange and calcite dissolution and precipitation. The ion exchange reaction is formulated in the form of surface complexation, which allows distributing charge over the fixed sites and the diffuse double layer. The charge distribution affects pH when calcite dissolves, and modeling of the experimental data shows that about 7% of the cation exchange capacity resides in the diffuse double layer. The model calculates the observed concentration changes very well and provides an estimate of the pristine porewater composition in the clay rock.
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Silicatos de Aluminio/análisis , Aniones , Cationes , Agua/análisis , Adsorción , Algoritmos , Carbonato de Calcio/análisis , Química/métodos , Arcilla , Difusión , Diseño de Equipo , Geología/métodos , Concentración de Iones de Hidrógeno , Iones , Modelos Químicos , Modelos EstadísticosRESUMEN
The gastric parietal cell is responsible for the secretion of HCl into the lumen of the stomach mainly due to stimulation by histamine via the cAMP pathway. However, the participation of several other receptors and pathways have been discovered to influence both stimulation and inhibition of acid secretion (e.g., cholinergic). Here we examine the role of phosphoinositide 3-kinase (PI3K) in the modulation of acid secretion. Treatment of isolated gastric glands and parietal cells with the PI3K inhibitor, LY294002 (LY), potentiated acid secretion in response to histamine to nearly the maximal secretion obtained with histamine plus phosphodiesterase inhibitors. As cAMP levels were elevated in response to histamine plus LY, but other means of elevating cAMP (e.g., forskolin, dbcAMP) were not influenced by LY, we posited that the effect might require activation of G-protein-coupled histamine H(2) receptors, possibly through the protein kinase B pathway (also known as Akt). Study of downstream effectors of PI3K showed that histaminergic stimulation increased Akt phosphorylation, which in turn was blocked by inhibition of PI3K. Expression studies showed that high expression of active Akt decreased acid secretion, whereas dominant-negative Akt increased acid secretion. Taken together, these data suggest stimulation with histamine increases the activity of PI3K leading to increased activity of Akt and decreased levels of cAMP in the parietal cell.
Asunto(s)
Ácido Gástrico/metabolismo , Mucosa Gástrica/metabolismo , Histamina/metabolismo , Células Parietales Gástricas/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Receptores Histamínicos H2/metabolismo , Transducción de Señal , 1-Metil-3-Isobutilxantina/farmacología , Aminopirina , Androstadienos/farmacología , Animales , Carbacol/farmacología , Forma de la Célula , Células Cultivadas , Agonistas Colinérgicos/farmacología , Cromonas/farmacología , AMP Cíclico/metabolismo , Relación Dosis-Respuesta a Droga , Factor de Crecimiento Epidérmico/metabolismo , Mucosa Gástrica/citología , Mucosa Gástrica/efectos de los fármacos , Mucosa Gástrica/enzimología , Antagonistas de los Receptores H2 de la Histamina/farmacología , Morfolinas/farmacología , Mutación , Técnicas de Cultivo de Órganos , Células Parietales Gástricas/efectos de los fármacos , Células Parietales Gástricas/enzimología , Inhibidores de Fosfodiesterasa/farmacología , Inhibidores de las Quinasa Fosfoinosítidos-3 , Fosforilación , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Pirimidinonas/farmacología , Conejos , Receptores Histamínicos H2/efectos de los fármacos , Factores de Tiempo , Transducción Genética , WortmaninaRESUMEN
OBJECTIVE: To determine the glycemic index (GI) dependence on the training state of healthy adult males. SUBJECTS AND DESIGN: Young, adult males of normal body mass index and normal glucose tolerance were tested twice with a 50 g reference glucose solution and twice with a breakfast cereal containing 50 g of available carbohydrates in a randomized order. Ten subjects were sedentary (SE), 12 were moderately trained (MT) and 12 were endurance trained (ET). Blood glucose, insulin and glucagon were measured. RESULTS: The GI differed significantly between SE and ET subjects (P=0.02, mean difference: 23 GI units, 95% CI=3-42 GI units). The GI of the MT subjects was intermediary, but did not differ significantly from the SE or ET subjects. The insulin index did not differ significantly between the groups (P=0.65). CONCLUSION: The GI of the commercially available breakfast cereal depended on the training state of the healthy males. The training state is the first reported factor influencing the GI that is subject specific rather than food specific.
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Glucemia/metabolismo , Carbohidratos de la Dieta/metabolismo , Glucagón/metabolismo , Índice Glucémico , Insulina/sangre , Aptitud Física/fisiología , Adolescente , Adulto , Antropometría , Área Bajo la Curva , Estudios Cruzados , Carbohidratos de la Dieta/administración & dosificación , Grano Comestible/metabolismo , Prueba de Tolerancia a la Glucosa , Humanos , Masculino , Consumo de OxígenoRESUMEN
Aquifer samples from the precipitation zone of an in situ iron and manganese removal plant that was operated for 10 years were analyzed for iron and manganese minerals. Measurements were performed by various chemical extraction techniques (5 M HCI, 0.008 M Ti(III)-EDTA, 0.114 M ascorbic acid), X-ray diffraction and Mössbauer spectroscopy. Chemical extractions showed that iron was precipitated as ferric oxides, whereas manganese was not oxidized but deposited as Mn(II) probably within carbonates. The ferric oxides in particular accumulate preferentially in the smaller grain- size fractions. This tendency was observed to a lesser extent for manganese. X-ray diffraction and Mössbauer spectroscopy showed that the ferric oxides were mainly crystalline (goethite, 50% to 100% of the iron). Ferrihydrite was found as well, but only as a minor fraction (< or = 12%). Pure manganese minerals were not found by X-ray diffraction. The precipitated amounts of iron (5 to 27 micromol/g Fe as ferric oxide) and manganese (1 to 4 micromol/g Mn) during 10 years operation of the treatment plant agree with values that were estimated from operational parameters (9 to 31 micromol/g Fe and 3 to 6 micromol/g Mn). Considering the small amounts of precipitated iron and manganese, no long-term risks of clogging of the aquifer are expected.
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Hierro/química , Manganeso/química , Purificación del Agua/métodos , Abastecimiento de Agua , Hierro/análisis , Manganeso/análisis , Tamaño de la Partícula , Suelo , Análisis Espectral , Difracción de Rayos XRESUMEN
A concentration response study was performed to clarify whether vasoactive drugs, routinely used in intensive care patients, inhibit oxygen radical production of neutrophils. Moreover, in a cell-free system, it was investigated whether these drugs exert free radical scavenging properties. Vasoactive agents were incubated with neutrophils from healthy human volunteers, which were stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP) and by opsonized zymosan to produce oxygen radicals, detected by chemiluminescence measurements. Sympathomimetics (epinephrine greater than norepinephrine, dopamine and dobutamine) as well as phosphodiesterase-inhibitors (amrinone and enoximone) inhibited FMLP-induced and zymosan-induced oxygen radical production of neutrophils in a concentration-dependent and drug-specific fashion. With the exception of amrinone, FMLP-induced chemiluminescence of neutrophils was impaired nearly 10-fold more markedly than zymosan-induced chemiluminescence. Glyceryl trinitrate, nifedipine and prostacyclin had no effect on oxygen radical production of neutrophils. In the cell-free system, epinephrine, norepinephrine, dopamine, amrinone and enoximone demonstrated oxygen free radical scavenging properties. This study shows that vasoactive drugs, frequently used in the clinical setting, may suppress oxidative burst after FMLP-receptor stimulation. As demonstrated in the cell-free system, this suppression was, at least in part, due to oxygen radical scavenging.
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Neutrófilos/efectos de los fármacos , Neutrófilos/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Vasoconstrictores/farmacología , Vasodilatadores/farmacología , Bloqueadores de los Canales de Calcio/farmacología , Radicales Libres , Humanos , Mediciones Luminiscentes , Nitroglicerina/farmacología , Inhibidores de Fosfodiesterasa/farmacología , Prostaglandinas/farmacología , Simpatomiméticos/farmacologíaRESUMEN
Despite their beneficial effects on cardiovascular derangements in patients with severe sepsis, high doses of sympathomimetics might contribute to an impaired neutrophil function. This study was conducted to examine whether various sympathomimetics [(-)-epinephrine (EPI), dopamine (DA) and dobutamine (DOB)] differ in their potency to suppress the formation of oxygen radicals by neutrophils and whether this potency correlates with their affinity to or intrinsic activity for beta-2 adrenoceptors (beta-2 AR). Oxygen radical production of human neutrophils was induced by N-formyl-methionyl-leucyl-phenyl-alanine and detected by chemiluminescence measurements. Dose-response curves for the inhibition of chemiluminescence by sympathomimetics were measured in the absence and presence of 0.1 microM CGP 20,712 A (1-[2(3-carbamoyl-4-hydroxy phenoxy)-ethylamino]-3-[4-(1-methyl-4-trifluoromethyl-2-imidazolyl) phenoxy]-2-propanol methanesulfonate) and 0.1 microM ICI 118,551 (erythro-(+/-)-1-(7-methylindan-4-yloxy)-3 isopropylaminobutan-2-ol hydrochloride) to selectively antagonize beta-1 AR and beta-2 AR, respectively. Inhibition of chemiluminescence of neutrophils by EPI was approximately 100-fold more potent than that by DA and DOB. Only the inhibition curve by EPI exhibited two components, one at nanomolar and one at micromolar concentrations. The nanomolar component was sensitive against beta-2 AR blockade, whereas the micromolar one was insensitive against both beta AR antagonists. Dose-response curves for DA and DOB exhibited a simple hyperbolic shape at micromolar concentrations and were insensitive against both beta AR antagonists. Maximum inhibition by DA and DOB was equipotent to that by EPI. However, the EC50 for DA was much lower than its dissociation constants, KD, assayed in membrane preparations by radioligand binding, whereas the EC50 of DOB matched KD. This difference could not be explained by a different efficiency of signal transduction, which was determined in receptor-coupled adenylate cyclase activity and which only showed a slightly higher efficiency of DA (51%) than of DOB (34%). Therefore, sympathomimetics were also investigated in a cell-free system, in which chemiluminescence was generated by horseradish peroxidase with hydrogen peroxide as substrate. Surprisingly, all of the sympathomimetics suppressed chemiluminescence with micromolar concentrations. We conclude that sympathomimetics with high affinity and high intrinsic activity (EPI) inhibit neutrophil function via occupation of beta-2 AR, whereas sympathomimetics with low affinity (DA) or low intrinsic activity (DOB) may act by direct scavenging of oxygen radicals.
Asunto(s)
Dobutamina/farmacología , Dopamina/farmacología , Epinefrina/farmacología , Neutrófilos/efectos de los fármacos , Receptores Adrenérgicos beta 2/efectos de los fármacos , Estallido Respiratorio/efectos de los fármacos , Simpatomiméticos/farmacología , Adenilil Ciclasas/metabolismo , Animales , Sistema Libre de Células , Humanos , Técnicas In Vitro , Mediciones Luminiscentes , N-Formilmetionina Leucil-Fenilalanina/farmacología , Ensayo de Unión Radioligante , Ratas , Especies Reactivas de Oxígeno/metabolismo , Receptores Adrenérgicos beta 1/efectos de los fármacosRESUMEN
The effects of the commercially available ketamine preparation (Ketanest), the ketamine racemate and of the two enantiomers, the R(-)-racemate and the S(+)-racemate, as well as its drug-free solvent were examined by N-formyl-methionyl-leucyl-phenylalanine-(FMLP)- and zymosan-induced oxygen radical production of polymorphonuclear cells (PMN). The racemate and the two enantiomers of ketamine suppressed FMLP- and zymosan-induced chemiluminescence of PMN in a dose-dependent fashion to the same extent. Therefore suppression of chemiluminescence of PMN by ketamine does not result from a specific receptor interaction.