Effect of an overground walking training on gait performance in healthy 65- to 80-year-olds.

The aim of this study was to examine the effect of an individualized overground walking interval training on gait performance [i.e., speed and energy cost (C(w))] in healthy elderly individuals. Twenty-two older adults were assigned to either a training group (TG; n=12, 73.4+/-3.9yr) or a non-training control group (CG; n=10, 70.9+/-9.6yr). TG participated in a 7-week individualized walking interval training at intensities progressing from 50 to 100% of ventilatory threshold (T (VE)). Aerobic fitness [maximal oxygen uptake (V O(2max)) and T (VE)], preferred walking speed (PWS), gross and net C(w) (GC(w) and NC(w), respectively) and relative effort (%V O(2max)) at PWS measured before training (PWS(1)) were assessed prior and following the intervention. All outcomes were measured on a treadmill. Significant improvements in GC(w) (-8%; P=0.007), NC(w) (-12%; P=0.003), relative effort (%V O(2max): -12%; P<0.001) and PWS (+12%; P<0.001) were observed in TG but not in CG (P>0.71). V O(2max) and T (VE) remained unchanged in both groups (P>0.57). Changes in GC(w) at PWS(1) (difference between GC(w) at PWS(1) measured pre and post intervention) were inversely correlated with changes in PWS (difference between pre and post PWS; r=-0.67; P=0.02). The decreased C(w) at PWS(1), with no concomitant improvement in aerobic fitness, represents the main contributing factor for the reduction of the relative effort at this speed. This also allows elderly people to increase their PWS post training. Therefore, the present walking training may be an effective way to improve walking performance and delay mobility impairment in older adults.

Cardio-pulmonary interaction in premature newborn with nasal continuous positive airways pressure (n-CPAP) respiratory assistance evaluated with echocardiography

Introduction: Nasal continuous positive airways pressure (n-CPAP) is an effective treatment in premature infants with respiratory distress. The cardio-pulmonary interactions secondary to n-CPAP are well studied in adults, but less well described in premature infants. We postulated that there could be important interactions with regard to the patent ductus arteriosus (PDA). Methods: Prospective study, approved by the local ethic committee. Premature infants less than 32 weeks gestation, _7 days-old, needing n-CPAP for respiratory distress, but without the need of additional oxygen were included in the study. Every patient had a first echocardiography with n-CPAP and then n-CPAP was retrieved. 3 hours later the echocardiography was repeated by the same investigator and then the patient replaced on n-CPAP. Results: 14 premature newborn were included, mean gestational age of 28 _ 2 weeks, mean weight 1.1 _ 0.3 Kg and height 39 _ 3 cm. Echocardiographic measurements are depicted in Table 1. Significant finding were observed between measurement on n- CPAP or without n-CPAP: on end diastolic left ventricular diameter (12.8 _ 1.6 mm vs. 13.5 _ 2 mm), on end systolic left ventricular diameter (8.4 _ 1.3 mm vs. 9.1 _ 1.5 mm), left atrium diameter (8.9 _ 2.2 mm vs. 10.4 _ 2.5 mm), maximal velocity on tricuspid valve (46 _ 10 cm/s vs. 51 _ 9 cm/s), calculated Qp (3.7 _ 0.8 L/min/m2 vs. 4.3 _ 0.8 L/min/m2). Only three patients have demonstrated a PDA during the study. Conclusion: Positive end expiratory pressure (Peep) has hemodynamic effects which are: reduction of systemic and pulmonary venous return as shown by the changes on tricuspid valve inflow,on the calculated Qp and finally on the diameter of the left atrium and left ventricle.We found in premature infants the same hemodynamic effects than those described in adults but with lower Peep values. This could be due to the particular elasticity and weakness of the thoracic wall of premature infants. Interestingly the flow through a PDA seems also to be diminished with Peep, but the number of patients is insufficient to conclude. Further investigation will be needed to better understand these interactions. Table 1. Echocardiographic measurement (mean (SD)). With n-CPAP Without n-CPAP p value RV ED diameter (mm) 6.3 (1.7) 6.04 (1.1) NS LV ED diameter (mm) 12.8 (1.6) 13.5 (2.0) _0.05 LV ES diameter (mm) 8.4 (1.3) 9.1 (1.5) _0.05 SF (%) 34 (5) 33 (6) NS Ao valve diameter (mm) 7.4 (1.3) 7.4 (1.2) NS LA diameter (mm) 8.9 (2.2) 10.4 (2.5) _0.05 Vmax Ao (cm/s) 70 (16) 71 (18) NS Vmax PV (cm/s) 69 (15) 72 (16) NS Vmax TV (cm/s) 46 (10) 51 (9) _0.05 Vmax MV (cm/s) 53 (17) 54 (18) NS Qp (L/min/m2) 3.7 (0.8) 4.3 (0.8) _0.05 Qs (L/min/m2) 4.0 (0.8) 4.0 (0.7) NS Qp/Qs 0.92 (0.14) 1.09 (0.23) _0.05 RV: right ventricle, LV: left ventricle, ED: end diastolic, ES: end systolic, SF: shortening fraction,Ao: aortic valve, LA: left atrium,Vmax: maximum Doppler Velocity, Qp: pulmonary output, Qs: systemic output, NS: non significant.

Neuroprotection in cerebral ischemia with XG-102, a new peptide inhibitor of JNK

Abstract Stroke or cerebrovascular accident, whose great majority is of ischemic nature, is the third leading cause of mortality and long lasting disability in industrialised countries. Resulting from the loss of blood supply to the brain depriving cerebral tissues of oxygen and glucose, it induces irreversible neuronal damages. Despite the large amount of research carried out into the causes and pathogenic features of cerebral ischemia the progress toward effective treatments has been poor. Apart the clot-busting drug tissue-type plasminogen activator (tPA) as effective therapy for acute stroke (reperfusion by thrombolysis) but limited to a low percentage of patients, there are currently no other approved medical treatments. The need for new therapy strategies is therefore imperative. Neuronal death in cerebral ischemia is among others due to excitotoxic mechanisms very early after stroke onset. One of the main involved molecular pathways leading to excitotoxic cell death is the c-Jun NH2-terminal kinase (JNK) pathway. Several studies have already shown the efficacy of a neuroprotective agent of a new type, a dextrogyre peptide synthesized in the retro inverso form (XG102, formerly D-JNKI1), which is protease-resistant and cell-penetrating and that selectively and strongly blocks the access of JNK to many of its targets. A powerful protection was observed with this compound in several models of ischemia (Borsello et al. 2003;Hirt et al. 2004). This chimeric compound, made up of a 10 amino acid TAT transporter sequence followed by a 20 amino acids JNK binding domain (JBD) sequence from JNK inhibitor protein (JIP) molecule, induced both a major reduction in lesion size and improved functional outcome. Moreover it presents a wide therapeutic window. XG-102 has proved its powerful efficacy in an occlusion model of middle cerebral artery in mice with intracérebroventricular (i.c.v.) injection but in order to be able to consider the development of this drug for human ischemic stroke it was therefore necessary to determine the feasibility of its systemic administration. The studies being the subject of this thesis made it possible to show a successful neuroprotection with XG-102 administered systemically after transient mouse middle cerebral artery occlusion (MCAo). Moreover our data. provided information about the feasibility to combine XG-102 with tPA without detrimental action on cell survival. By combining the benefits from a reperfusion treatment with the effects of a neuroprotective compound, it would represent the advantage of bringing better chances to protect the cerebral tissue. Résumé L'attaque cérébrale ou accident vasculaire cérébral, dont la grande majorité est de nature ischémique, constitue la troisième cause de mortalité et d'infirmité dans les pays industrialisés. Résultant de la perte d'approvisionnement de sang au cerveau privant les tissus cérébraux d'oxygène et de glucose, elle induit des dommages neuronaux irréversibles. En dépit du nombre élevé de recherches effectuées pour caractériser les mécanismes pathogènes de l'ischémie. cérébrale, les progrès vers des traitements efficaces restent pauvres. Excepté l'activateur tissulaire du plasminogène (tPA) dont le rôle est de désagréger les caillots sanguins et employé comme thérapie efficace contre l'attaque cérébrale aiguë (reperfusion par thrombolyse) mais limité à un faible pourcentage de patients, il n'y a actuellement aucun autre traitement médical approuvé. Le besoin de nouvelles stratégies thérapeutiques est par conséquent impératif. La mort neuronale dans l'ischémie cérébrale est entre autres due à des mécanismes excitotoxiques survenant rapidement après le début de l'attaque cérébrale. Une des principales voies moléculaires impliquée conduisant à la mort excitotoxique des cellules est la voie de la c-Jun NH2terminal kinase (JNK). Plusieurs études ont déjà montré l'efficacité d'un agent neuroprotecteur d'un nouveau type, un peptide dextrogyre synthétisé sous la forme retro inverso (XG-102, précédemment D-JNKI1) résistant aux protéases, capable de pénétrer dans les cellules et de bloquer sélectivement et fortement l'accès de JNK à plusieurs de ses cibles. Une puissante protection a été observée avec ce composé dans plusieurs modèles d'ischémie (Borsello et al. 2003;Hirt et al. 2004). Ce composé chimérique, construit à partir d'une séquence TAT de 10 acides aminés suivie par une séquence de 20 acides aminés d'un domaine liant JNK (JBD) issu de la molécule JNK protéine inhibitrice. (JIP), induit à la fois une réduction importante de la taille de lésion et un comportement fonctionnel amélioré. De plus il présente une fenêtre thérapeutique étendue. XG-102 a prouvé sa puissante efficacité dans un modèle d'occlusion de l'artère cérébrale moyenne chez la souris avec injection intracerebroventriculaire (i.c.v.) mais afin de pouvoir envisager le développement de ce composé pour l'attaque cérébrale chez l'homme, il était donc nécessaire de déterminer la faisabilité de son administration systémique. Les études faisant l'objet de cette thèse ont permis de montrer une neuroprotection importante avec XG-102 administré de façon systémique après l'occlusion transitoire de l'artère cérébrale moyenne chez la souris (MCAo). De plus nos données ont fourni des informations quant à la faisabilité de combiner XG-102 et tPA, démontrant une protection efficace par XG-102 malgré l'action nuisible du tPA sur la survie des cellules. En combinant les bénéfices de la reperfusion avec les effets d'un composé neurooprotecteur, cela représenterait l'avantage d'apporter des meilleures chances de protéger le tissu cérébral.

Energy expenditure before and during energy restriction in obese patients.

Twenty-four hour energy expenditure (24 EE), resting metabolic rate (RMR), spontaneous physical activity and body composition were determined in 7 obese patients (5 females, 2 males, 174 +/- 9% IBW, 38 +/- 2% fat mass) on 2 different occasions: before weight reduction, and after 10 to 16 weeks on a hypocaloric diet as outpatients, the recommended energy intake varying from 3500 to 4700 kJ/day depending on the subject. Mean body weight loss was 12.6 +/- 1.9 kg, ie 13% of initial body weight, 72% being fat. Twenty-four hour energy expenditure (24 EE) was measured in a respiration chamber with all the subjects receiving 10418 kJ/d before weight reduction and an average of 3360 +/- 205 kJ/d while on the diet. When expressed in absolute values, both 24 EE and RMR decreased during the hypocaloric diet from 9819 +/- 442 to 8229 +/- 444 and from 7262 +/- 583 to 6591 +/- 547 kJ/d respectively. On the basis of fat-free-mass (FFM), 24 EE decreased from 168 +/- 6 to 148 +/- 5 kJ/kg FFM/d whereas RMR was unchanged (approximately 120 kJ/kg FFM/d). Approximately one half of the 24 EE reduction (1590 kJ/d) was accounted for by a decrease in RMR, the latter being mainly accounted for by a reduction in FFM. Most of the remaining decline in 24 EE can be explained by a decreased thermic effect of food, and by the reduced cost of physical activity mainly due to a lower body weight. Therefore, there seems little reason to evoke additional mechanisms to explain the decline in energy expenditure during dieting.

Effect of weight reduction in moderately overweight patients on recorded ambulatory blood pressure and free cytosolic platelet calcium.

Although platelet cytosolic calcium has been shown to decrease during pharmacological treatment of hypertension, there is no evidence that cytosolic calcium also falls during a nonpharmacological reduction in blood pressure. To provide such evidence, we examined prospectively the relation between platelet cytosolic calcium and ambulatory blood pressure during weight reduction in moderately overweight (body mass index [BMI] greater than 25), mildly hypertensive individuals. The experimental group (responders: BMI reduction greater than 5%) consisted of 19 patients who lost 8.5 +/- 2.9 kg (mean +/- SD, p less than 0.05) during a 10-week hypocaloric diet, whereas the control group (nonresponders: BMI reduction less than 5%) consisted of 12 patients who showed no relevant change in body weight (-2.0 +/- 1.3 kg) during the same period of time. The moderate weight loss of the responders decreased blood pressure by 14/5 mm Hg (p less than 0.05), as measured by ambulatory monitoring, which renders a placebo effect unlikely. This nonpharmacological reduction in blood pressure was accompanied by a proportional 11% decrease (p less than 0.05) in platelet cytosolic calcium and also by significant (p less than 0.05) decreases in plasma catecholamines and serum cholesterol. These findings establish the concept of a nonpharmacological reduction in free cytosolic platelet calcium in humans and add further evidence suggesting a link between intracellular calcium homeostasis and blood pressure regulation.

IL28B polymorphisms predict reduction of HCV RNA from the first day of therapy in chronic hepatitis C.

Background & Aims: Single nucleotide polymorphisms (SNPs) associated with IL28B influence the outcome of peginterferon-alpha/ribavirin therapy of chronic hepatitis C virus (HCV) infection. We analyzed the kinetics of HCV RNA during therapy as a function of IL28B SNPs.Methods: IL28B SNPs rs8099917, rs12979860, and rs12980275 were genotyped in 242 HCV treatment-naive Caucasian patients (67% genotype 1, 28% genotype 2 or 3) receiving peginterferon-alpha 2a (180 mu g weekly) and ribavirin (1000-1200 mg daily) with serial HCV-RNA quantifications. Associations between IL28B polymorphisms and early viral kinetics were assessed, accounting for relevant covariates.Results: In the multivariate analyses for genotype 1 patients, the T allele of rs12979860 (T(rs12979860)) was an independent risk factor for a less pronounced first phase HCV RNA decline (log(10) 0.89 IU/ml among T carriers vs. 2.06 among others, adjusted p <0.001) and lower rapid (15% vs. 38%, adjusted p = 0.007) and sustained viral response rates (48% vs. 66%, adjusted p <0.001). In univariate analyses, Trs12979860 was also associated with a reduced second phase decline (p = 0.002), but this association was no longer significant after adjustment for the first phase decline (adjusted p = 0.8). In genotype 2/3 patients, Trs12979860 was associated with a reduced first phase decline (adjusted p = 0.04), but not with a second phase decline.Conclusions: Polymorphisms in IL28B are strongly associated with the first phase viral decline during peginterferon-alpha/ribavirin therapy of chronic HCV infection, irrespective of HCV genotype. (C) 2011 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Oxygen uptake of isolated toad skin epithelium: micromeasurement and effect of ionic acclimation.

Oxidative metabolism of isolated toad skin epithelium (Bufo viridis) was investigated in vitro under open-circuit conditions using the spectrophotometric oxyhemoglobin micromethod. This highly sensitive technique has been adapted for studying several epithelia in parallel and for detecting possible regional variations of oxygen uptake in individual epithelium. Changes in the proportion of mitochondria-rich cells (MRC) by ionic acclimation affected oxidative metabolism under nontransporting condition. After acclimation of animals to either NaNO3 or NaCl solutions (100 mmol/l, for greater than 2 wk), the number of MRC per square millimeter in epithelia from nonacclimated and NaNO3- and NaCl-acclimated animals was 350 +/- 113, 460 +/- 196, and 107 +/- 52, respectively. O2 uptake of nonacclimated and NaNO3-acclimated epithelia was significantly higher than that of NaCl-acclimated epithelia (i.e., 0.89 and 0.90 vs. 0.57 nmol O2.h-1.mm-2, respectively). The correlation established between O2 uptake and number of MRC allowed evaluation of the respiration rate of one single MRC, i.e., approximately 1 pmol O2/h. The lowest mitochondrial oxidative activity was found in the epithelia from NaCl-acclimated toads where the uncoupler 2,4-dinitrophenol (50 mumols/l) had the highest relative stimulatory effect (+114%). Acetazolamide (50 mumols/l), a potent inhibitor of carbonic anhydrase mainly present in the MRC, reduced selectively by 31% O2 uptake of the MRC-rich epithelia (NaNO3 acclimated). O2 uptake increased significantly by approximately 80% when basolateral pH increased from 5.8 to 7.8, but did not depend on apical pH. These findings indicate that under nontransporting (open-circuit) conditions, aerobic metabolism of the isolated toad skin epithelium is related to the density and/or characteristics of the MRC.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of plasma alanine aminotransferase during vigabatrin treatment.

In 9 drug-resistant patients with partial seizures treated with vigabatrin, gamma-vinyl GABA (VGB), alanine aminotransaminase (ALAT) activity in plasma was significantly reduced. Comparison of in vitro with in vivo measurements led us to conclude that this reduction is mainly an in vivo phenomenon, perhaps due to cross-enzyme inhibition. The assessment of two biological variables linked with ALAT, glucose and alanine levels under fasting conditions, failed to show any significant metabolic alterations. VGB is an effective drug for partial epilepsy. Our observations do not suggest that reduced ALAT activity is of clinical concern.

Inactivation des pathogènes des produits sanguins labiles: entre enjeux financiers et conséquences possibles à long terme [Pathogen reduction of blood components: from financial issues to possible long-term consequences].

Pathogen inactivation of blood products represents a global and major paradigm shift in transfusion medicine. In the next near future, it is likely that most blood products will be inactivated by various physicochemical approaches. The concept of blood safety will be challenged as well as transfusion medicine practice, notably for donor selection or biological qualification. In this context, it seems mandatory to develop analytical economic approaches by assessing costs-benefits ratio of blood transfusion as well as to set up cohorts of patients based on hemovigilance networks allowing rigorous scientific analysis of the benefits and the risks of blood transfusion at short- and long-term.

Bitumens in the late Variscan hydrothermal vein-type uranium deposit of Pribram, Czech Republic: Sources, radiation-induced alteration, and relation to mineralization

The late Variscan (275-278 Ma) Pribram uranium deposit is one of the largest known accumulations of uraniferous bitumens in hydrothermal veins. The deposit extends along the northwestern boundary of the Central Bohemian pluton (345-335 Ma) with low-grade metamorphosed Late Proterozoic and unmetamorphosed Cambrian rocks. From a net uranium production of 41,742 metric tons (t), more than 6,000 t were extracted from bitumen-uraninite ores during 43 years of exploration and mining. Three morphological varieties of solid bitumen are recognized: globular, asphaltlike, and cokelike. While the globular bitumen is uranium free, the other two types are uraniferous. The amount of bitumen in ore veins gradually decreases toward the contact with the plutonic body and increases with depth. Two types of bitumen microtextures are recognized using high-resolution transmission electron microscopy: amorphous and microporous, the former being less common in uraniferous samples. A lower Raman peak area ratio (1,360/1,575 cm(-1)) in mineralized bitumens (0.9) compared with uranium-free samples (2.0) indicates a lower degree of microtextural organization in the latter The H/C and O/C atomic ratios in uranium-free bitumens (0.9-1.1 and 0.09, respectively) are higher than those in mineralized samples (H/C = 0.3-0.8, O/C = 0.03-0.09). The chloroform extractable matter yield is Very low in uranium-free bitumens (0.30-0.35% of the total organic carbon,TOC) and decreases with uranium content increase. The extracted solid uraniferous bitumen infrared spectra show depletion in aliphatic CH2 and CH3 groups compared to uranium-free samples. The concentration of oxygen-bearing functional groups relative to aromatic bonds in the IR spectra of uranium-free and mineralized bitumen, however, do not differ significantly. C-13 NMR confirmed than the aromaticity of a uraniferous sample is higher (F-ar = 0.61) than in the uranium-free bitumen (F-ar = 0.51). Pyrolysates from uraniferous and nonuraniferous bitumens do not differ significantly, being predominantly cresol, alkylphenols, alkylbenzenes, and alkylnaphthalenes. The liquid pyrolysate yield decreases significantly with increasing uranium content. The delta(13)C Values of bulk uranium-free bitumens and low-grade uraniferous, asphaltlike bitumens range from -43.6 to 52.3 per mil. High-grade, cokelike, uraniferous bitumens are more C-13 depleted (54.5 to -58.4 parts per thousand). In contrast to the very light isotopic ratios of the high-grade uraniferous cokelike bitumen bulk carbon, the individual n-alkanes and isoprenoids (pristane and phytane) extracted from the same sample are significantly C-13 enriched. The isotopic composition of the C13-24 n-alkanes extracted from the high-grade uraniferous sample (delta(13)C = -28.0 to 32.6 parts per thousand) are heavier compared with the same compounds in a uranium-free sample (delta(13)C = 31.9 to 33.8 parts per thousand). It is proposed that the bitumen source was the isotopically light (delta(13)C = 35.8 to 30.2 parts per thousand) organic matter of the Upper Proterozoic host rocks that were pyrolyzed during intrusion of the Central Bohemian pluton. The C-13- depleted pyrolysates were mobilized from the innermost part of the contact-metamorphic aureole, accumulated in structural traps in less thermally influenced parts of the sedimentary complex and were later extracted by hydrothermal fluids. Bitumens at the Pribram deposit are younger than the main part of the uranium mineralization and were formed through water-washing and radiation-induced polymerization of both the gaseous and liquid pyrolysates. Direct evidence for pyrolysate reduction of uranium in the hydrothermal system is difficult to obtain as the chemical composition of the original organic fluid phase was modified during water-washing and radiolytic alteration. However, indirect evidence-e.g., higher O/C atomic ratios in uranium-free bitumens (0.1) relative to the Upper Proterozoic source rocks (0.02-0.05), isotopically very light carbon in associated whewellite (delta(13)C = 31.7 to -28.4 parts per thousand), and the striking absence of bitumens in the pre-uranium, hematite stage of the mineralization-indicates that oxidation of organic fluids may have contributed to lowering of aO(2) and uraninite precipitation.

Comparison of antibiotic drops placed in the conjunctival cul-de-sac to antibiotic ointment applied to the lid margin in reduction of bacterial colonization on the lid margin.

PURPOSE: To compare the efficacy of antibiotic drops placed in the conjunctival cul-de-sac to antibiotic ointment applied to the lid margin in reduction of bacterial colonization on the lid margin. METHODS: A randomized, prospective, single-masked study was conducted on 19 patients with culture-proven colonization of bacteria on the lid margins. Ophthalmic eligibility criteria included the presence of > or =50 colony-forming units/mL (CFU/mL) of bacteria on both right and left lids. Each patient received one drop of ofloxacin in one eye every night for one week, followed by one drop once a week for one month. In the same manner, each patient received bacitracin ointment (erythromycin or gentamicin ointment if lid margin bacteria were resistant to bacitracin) to the lid margin of the fellow eye. Quantitative lid cultures were taken at initial visit, one week, one month, and two months. Fifteen volunteers (30 lids) served as controls. Lid cultures were taken at initial visit, one week, and one month. RESULTS: Both antibiotic drop and ointment reduced average bacterial CFU/mL at one week and one month. Average bacterial CFU/mL reestablished to baseline values at two months. There was no statistically significant difference between antibiotic drop and ointment in reducing bacterial colonization on the lid margin. CONCLUSION: Antibiotic drops placed in the conjunctival cul-de-sac appear to be as effective as ointment applied to the lid margins in reducing bacterial colonization in patients with > or =50 CFU/mL of bacteria on the lid margins.

Oxygen isotope compositions of iron oxides from high-grade BIF-hosted iron ore deposits of the Central Hamersley Province, Western Australia: Constraints on the evolution of hydrothermal fluids

The Hamersley province of northwest Australia is one of the world's premier iron ore regions with high-grade martite-microplaty hematite iron ore deposits mostly hosted within banded iron formation (BIF) sequences of the Brockman Iron Formations of the Hamersley Group. These high-grade iron ores contain between 60 and 68 wt percent Fe, and formed by the multistage interaction of hydrothermal fluids with the host BIF formation. The oxygen isotope compositions of magnetite and hematite from BIF, hydrothermal alteration assemblages, and high-grade iron Ore were analyzed from the Mount Tom Price, Paraburdoo, and Charmar iron ore deposits. The delta(18)O values of magnetite and hematite from hydrothermal alteration assemblages and high-grade iron ore range from -9.0 to -2.9 per mil, a depletion of 5 to 15 per mil relative to the host BIF. The delta(18)O values are spatially controlled by faults within the deposits, a response to higher fluid flux and larger influence the isotopic compositions by the hydrothermal fluids. The oxygen isotope composition of hydrothermal fluids (delta(18)O(fluid)) indicates that the decrease in the (18)O content of iron oxides was due to the interaction of both basinal brines and meteoric fluids with the original BIF. Late-stage talc-bearing ore at the Mount Tom Price deposit formed in the presence of a pulse of delta(18)O-enriched basinal brine, indicating that hydrothermal fluids may have repeatedly interacted with the BIFs during the Paleoproterozoic.