Oxygen consumption in collagenase-liberated rat adipocytes in relation to cell size and age.

Oxygen consumption of collagenase-liberated rat adipocytes was measured by two different techniques: a microspectrophotometric method using hemoglobin as indicator of respiration and a technique using the oxygen electrode. These two completely different techniques gave similar values for oxygen consumption. With the spectrophotometric method, the oxygen consumption of single fat cells was determined. A close positive correlation (r = greater than 0.90) between oxygen consumption and fat cell size was observed in each tissue examined. With the oxygen electrode technique, oxygen consumption of adipocyte suspensions from young (40 days, 180 g) and old (90 days, 480 g) rats was examined. Fat cells of the suspensions were separated into classes of different size by a flotation technique. A significant positive correlation between fat cell size and oxygen consumption was observed in both young (r = 0.88) and old (r = 0.95) rats. However, the slope was much steeper in young rats. At a cell weight of 0.1 microgram the oxygen consumption was 0.364 and 0.086 microL O2/10(6) cells/min-1 in young and old rats, respectively. In the literature, a number of separate metabolic pathways have been found to be related positively to fat cell size and negatively to age. We conclude that these scattered metabolic observations are in agreement with integrated data on energy expenditure as evaluated from oxygen consumption. Estimations of the energy expenditure of adipose tissue indicates that this tissue is responsible for about 1% and 0.5% of the total energy expenditure in young and old rats, respectively.

Complications of Valve Lung Volume Reduction in a Case of Previous Pleurodesis.

Lung volume reduction with valves is increasingly used to treat selected patients with severe emphysema. The indications for this procedure have been previously described; however, its contraindications have not yet been conclusively established. This case highlights the potentially severe complications of endobronchial one-way valve placement in the setting of a previous pleurodesis.

Free conjunctival autologous graft for bleb repair and bleb reduction after trabeculectomy and nonpenetrating filtering surgery.

PURPOSE: To describe methods and outcomes of excisional revision of a filtering bleb (bleb revision) using free conjunctival autologous graft either for bleb repair or for bleb reduction after trabeculectomy and deep sclerectomy with an implant. METHODS: Retrospective medical records were reviewed for a consecutive non-comparative case series comprising patients who underwent excisional revision of a filtering bleb between May 1998-January 2001. Excisional revision using free conjunctival autologous graft (bleb revision) was performed either for bleb repair, to treat early and late leaks and hypotony with maculopathy, or for bleb reduction, to improve ocular pain, discomfort, burning, foreign body sensation, tearing, and fluctuations of visual acuity. The revision consisted of bleb excision and free conjunctival autologous graft. The bleb histopathology was analyzed in patients who underwent bleb repair. RESULTS: Sixteen patients were included in the study, consisting of nine patients who had a trabeculectomy and seven patients who had a deep sclerectomy with an implant. Bleb revision was necessary in 14 patients due to leaking filtering bleb (bleb repair), and in 2 patients due to bleb dysesthesia (bleb reduction). After a follow-up of 15.1 +/- 8.4 months, the mean intraocular pressure (IOP) rose from 7.8 +/- 6.3 mm Hg to 14.3 +/- 6.5 mm Hg, and the visual acuity from 0.4 +/- 0.3 to 0.7 +/- 0.3, with a P value of 0.008 and 0.03, respectively. The complete success rate at 32 months, according to the Kaplan-Meier survival curve, was 38.3%, and the qualified success rate was 83.3%. Four patients (25%) required additional suturing for persistent bleb leak. To control IOP, antiglaucoma medical therapy was needed for six patients (37.5%) and repeated glaucoma surgery was needed for one patient. CONCLUSION: Free conjunctival autologous graft is a safe and successful procedure for bleb repair and bleb reduction. However, patients should be aware of the postoperative possibility of requiring medical or surgical intervention for IOP control after revision.

Fluid-rock-strain feedbacks in extensional shear zones

La présence de fluide météorique synchrone à l'activité du détachement (Farmin, 2003 ; Mulch et al., 2007 ; Gébelin et al., 2011), implique que les zones de cisaillement sont des systèmes ouverts avec des cellules de convections à l'échelle crustale et un intense gradient géothermique au sein du détachement (Morrison et Anderson, 1998, Gottardi et al., 2011). De plus, les réactions métamorphiques liées à des infiltrations fluides dans les zones de cisaillement extensionnel peuvent influencer les paramètres rhéologiques du système (White and Knipe, 1978), et impliquer la localisation de la déformation dans la croûte. Dans ce manuscrit, deux zones de cisaillement infiltrées par des fluides météoriques sont étudiées, l'une étant largement quartzitique, et l'autre de nature granitique ; les relations entre déformation, fluides, et roches s'appuient sur des approches structurales, microstructurales, chimiques et isotopiques. L'étude du détachement du Columbia river (WA, USA) met en évidence que la déformation mylonitique se développe en un million d'années. La phase de cisaillement principal s'effectue à 365± 30°C d'après les compositions isotopiques en oxygène du quartz et de la muscovite. Ces minéraux atteignent l'équilibre isotopique lors de leur recristallisation dynamique contemporaine à la déformation. La zone de cisaillement enregistre une baisse de température, remplaçant le mécanisme de glissement par dislocation par celui de dissolution- précipitation dans les derniers stades de l'activité du détachement. La dynamique de circulation fluide bascule d'une circulation pervasive à chenalisée, ce qui engendre localement la rupture des équilibres d'échange isotopiques. La zone de cisaillement de Bitterroot (MT, USA) présente une zone mylonitique de 600m d'épaisseur, progressant des protomylonites aux ultramylonites. L'intensité de la localisation de la déformation se reflète directement sur l'hydratation des feldspaths, réaction métamorphique majeure dite de « rock softening ». Une étude sur roche totale indique des transferts de masse latéraux au sein des mylonites, et d'importantes pertes de volume dans les ultramylonites. La composition isotopique en hydrogène des phyllosilicates met en évidence la présence (1) d'une source magmatique/métamorphique originelle, caractérisée par les granodiorites ayant conservé leur foliation magmatique, jusqu'aux protomylonites, et (2) une source météorique qui tamponne les valeurs des phyllosilicates des fabriques mylonitiques jusqu'aux veines de quartz non-déformées. Les compositions isotopiques en oxygène des minéraux illustrent le tamponnement de la composition du fluide météorique par l'encaissant. Ce phénomène cesse lors du processus de chloritisation de la biotite, puisque les valeurs des chlorites sont extrêmement négatives (-10 per mil). La thermométrie isotopique indique une température d'équilibre isotopique de la granodiorite entre 600-500°C, entre 500-300°C dans les mylonites, et entre 300 et 200°C dans les fabriques cassantes (cataclasites et veines de quartz). Basé sur les résultats issus de ce travail, nous proposons un modèle général d'interactions fluide-roches-déformation dans les zones de détachements infiltrées par des fluides météoriques. Les zones de détachements évoluent rapidement (en quelques millions d'années) au travers de la transition fragile-ductile ; celle-ci étant partiellement contrôlée par l'effet thermique des circulations de fluide météoriques. Les systèmes de détachements sont des lieux où la déformation et les circulations fluides sont couplées ; évoluant rapidement vers une localisation de la déformation, et de ce fait, une exhumation efficace. - The presence of meteoric fluids synchronous with the activity of extensional detachment zones (Famin, 2004; Mulch et al., 2007; Gébelin et al., 2011) implies that extensional systems involve fluid convection at a crustal scale, which results in high geothermal gradients within active detachment zones (Morrison and Anderson, 1998, Gottardi et al., 2011). In addition, the metamorphic reactions related to fluid infiltration in extensional shear zones can influence the rheology of the system (White and Knipe, 1978) and ultimately how strain localizes in the crust. In this thesis, two shear zones that were permeated by meteoric fluids are studied, one quartzite-dominated, and the other of granitic composition; the relations between strain, fluid, and evolving rock composition are addressed using structural, microstructural, and chemical/isotopic measurements. The study of the Columbia River detachment that bounds the Kettle core complex (Washington, USA) demonstrates that the mylonitic fabrics in the 100 m thick quartzite- dominated detachment footwall developed within one million years. The main shearing stage occurred at 365 ± 30°C when oxygen isotopes of quartz and muscovite equilibrated owing to coeval deformation and dynamic recrystallization of these minerals. The detachment shear zone records a decrease in temperature, and dislocation creep during detachment shearing gave way to dissolution-precipitation and fracturing in the later stages of detachment activity. Fluid flow switched from pervasive to channelized, leading to isotopic disequilibrium between different minerals. The Bitterroot shear zone detachment (Montana, USA) developed a 600 m thick mylonite zone, with well-developed transitions from protomylonite to ultramylonite. The localization of deformation relates directly to the intensity of feldspar hydration, a major rock- softening metamorphic reaction. Bulk-rock analyses of the mylonitic series indicate lateral mass transfer in the mylonite (no volume change), and significant volume loss in ultramylonite. The hydrogen isotope composition of phyllosilicates shows (1) the presence of an initial magmatic/metamorphic source characterized by the granodiorite in which a magmatic, and gneissic (protomylonite) foliation developed, and (2) a meteoric source that buffers the values of phyllosilicates in mylonite, ultramylonite, cataclasite, and deformed and undeformed quartz veins. The mineral oxygen isotope compositions were buffered by the host-rock compositions until chloritization of biotite started; the chlorite oxygen isotope values are negative (-10 per mil). Isotope thermometry indicates a temperature of isotopic equilibrium of the granodiorite between 600-500°C, between 500-300°C in the mylonite, and between 300 and 200°C for brittle fabrics (cataclasite and quartz veins). Results from this work suggest a general model for fluid-rock-strain feedbacks in detachment systems that are permeated by meteoric fluids. Phyllosilicates have preserved in their hydrogen isotope values evidence for the interaction between rock and meteoric fluids during mylonite development. Fluid flow generates mass transfer along the tectonic anisotropy, and mylonites do not undergo significant volume change, except locally in ultramylonite zones. Hydration of detachment shear zones attends mechanical grain size reduction and enhances strain softening and localization. Self-exhuming detachment shear zones evolve rapidly (a few million years) through the transition from ductile to brittle, which is partly controlled by the thermal effect of circulating surface fluids. Detachment systems are zones in the crust where strain and fluid flow are coupled; these systems. evolve rapidly toward strain localization and therefore efficient exhumation.

The effect of continuous positive airway pressure on total cerebral blood flow in healthy awake volunteers.

PURPOSE: Continuous positive airway pressure (CPAP) is the gold standard treatment for obstructive sleep apnea. However, the physiologic impact of CPAP on cerebral blood flow (CBF) is not well established. Ultrasound can be used to estimate CBF, but there is no widespread accepted protocol. We studied the physiologic influence of CPAP on CBF using a method integrating arterial diameter and flow velocity (FV) measurements obtained for each vessel supplying blood to the brain. METHODS: FV and lumen diameter of the left and right internal carotid, vertebral, and middle cerebral arteries were measured using duplex Doppler ultrasound with and without CPAP at 15 cm H(2)O, applied in a random order. Transcutaneous carbon dioxide (PtcCO(2)), heart rate (HR), blood pressure (BP), and oxygen saturation were monitored. Results were compared with a theoretical prediction of CBF change based on the effect of partial pressure of carbon dioxide on CBF. RESULTS: Data were obtained from 23 healthy volunteers (mean ± SD; 12 male, age 25.1 ± 2.6 years, body mass index 21.8 ± 2.0 kg/m(2)). The mean experimental and theoretical CBF decrease under CPAP was 12.5 % (p < 0.001) and 11.9 % (p < 0.001), respectively. The difference between experimental and theoretical CBF reduction was not statistically significant (3.84 ± 79 ml/min, p = 0.40). There was a significant reduction in PtcCO(2) with CPAP (p = <0.001) and a significant increase in mean BP (p = 0.0017). No significant change was observed in SaO(2) (p = 0.21) and HR (p = 0.62). CONCLUSION: Duplex Doppler ultrasound measurements of arterial diameter and FV allow for a noninvasive bedside estimation of CBF. CPAP at 15 cm H(2)O significantly decreased CBF in healthy awake volunteers. This effect appeared to be mediated predominately through the hypocapnic vasoconstriction coinciding with PCO(2) level reduction. The results suggest that CPAP should be used cautiously in patients with unstable cerebral hemodynamics.

Effect of Vagus Nerve Stimulation in an Adult Patient with Dravet Syndrome: Contribution to Sudden Unexpected Death in Epilepsy Risk Reduction?.

We report on a patient who developed, from 5 months of age, multiple seizure types, including myoclonic, associated with severe psychomotor delay, leading to the diagnosis of Dravet syndrome. Over the years, he developed refractory epilepsy and was implanted with a vagus nerve stimulator at the age of 19. After 3 months, he experienced a progressive improvement of partial and generalized seizures, with a >90% reduction, and better alertness. This meaningful clinical improvement is discussed in the light of the sudden unexpected death in epilepsy risk, which is high in this setting, and seems remarkably diminished in our patient in view of the reduction of generalized convulsions.

Potential influence of the chemical composition of water on the stable oxygen isotope composition of continental ostracods

Many studies in continental areas have successfully used the oxygen isotope composition of fossil ostracod valves to reconstruct past hydrological conditions associated with large changes in climate. Yet, ostracods are known to crystallise their valves out of isotopic equilibrium for oxygen and they generally have higher 18O contents compared to inorganic calcite grown at equilibrium under the same condi- tions. A review of vital offsets determined for continental ostracods indicates that vital offsets might change from site to site, questioning a potential influence of environmental conditions on oxygen isotope fractionation in ostracods. Results from the literature suggest that pH has no influence on ostracod vital offset. A re-evaluation of results from Li and Liu (J Paleolimnol 43:111-120, 2010) suggests that salin- ity may influence oxygen isotope fractionation in ostracods, with lower vital offsets for higher salinities. Such a relationship was also observed for the vital offsets determined by Chivas et al. (The ostracoda- applications in quaternary research. American Geo- physical Union, Washington, DC, 2002). Yet, when results of all studies are compiled, the correlation between vital offsets and salinity is low while the correlation between vital offsets and host water Mg/Ca is higher, suggesting that ionic composition of water and/or relative abundance of major ions may also control oxygen isotope fractionation in ostracods. Lack of data on host water ionic composition for the different studies precludes more detailed examination at this stage. Further studies such as natural or laboratory cultures done under strictly controlled conditions are needed to better understand the potential influence of varying environmental condi- tions on oxygen isotope compositions of ostracod valves.

The oxygen concentrator : an appropriate technology for treating hypoxaemic children in developing countries

RÉSUMÉ L'Organisation Mondiale de la Santé (OMS) recommande d'administrer l'oxygène par concentrateurs dans les pays en voie de développement (PVD), les cylindres posant des problèmes logistiques et financiers trop importants. Cette technologie a été proposée aux enfants d'un hôpital sénégalais (Ndioum) qui présentaient les critères d'oxygénation de l'OMS. Les bénéfices cliniques et financiers ont été majeurs. En revanche, les connaissances des soignants sur les diverses techniques d'administration d'oxygène ainsi que les prestations du service de maintenance étaient insuffisantes. L'implantation de concentrateurs doit être encouragée dans les PVD, mais doit respecter une stratégie englobant enseignement, maintenance et suivi de l'opération. Diverses actions correctrices ont été entreprises à Ndioum où plusieurs concentrateurs fonctionnent désormais régulièrement. Summary: The World Health Organisation (WHO) recommends supplying oxygen in developing countries by concentra¬tors because cylinders pose considerable logistic and financial problems. This technology was employed to treat children in a hospital in Ndioum, Senegal, who met the WHO oxygenation criteria. There were clear clinical and financial benefits, but neither the nurses' knowledge of the various techniques of oxygen supply nor the maintenance service were satisfactory. The use of concentra¬tors should be encouraged in developing countries. A strategy including technical training, maintenance and monitoring should be adopted. Corrective actions were undertaken in Ndioum, and several concentrators are now being used on a regular basis.

Controls on ostracod valve geochemistry: Part 2. Carbon and oxygen isotope compositions

The stable carbon and oxygen isotope compositions of fossil ostracods are powerful tools to estimate past environmental and climatic conditions. The basis for such interpretations is that the calcite of the valves reflects the isotopic composition of water and its temperature of formation. However, calcite of ostracods is known not to form in isotopic equilibrium with water and different species may have different offsets from inorganic precipitates of calcite formed under the same conditions. To estimate the fractionation during ostracod valve calcification, the oxygen and carbon isotope compositions of 15 species living in Lake Geneva were related to their autoecology and the environmental parameters measured during their growth. The results indicate that: (1) Oxygen isotope fractionation is similar for all species of Candoninae with an enrichment in 18O of more than 30/00 relative to equilibrium values for inorganic calcite. Oxygen isotope fractionation for Cytheroidea is less discriminative relative to the heavy oxygen, with enrichments in 18O for these species of 1.7 to 2.30/00. Oxygen isotope fractionations for Cyprididae are in-between those of Candoninae and Cytheroidea. The difference in oxygen isotope fractionation between ostracods and inorganic calcite has been interpreted as resulting from a vital effect. (2) Comparison with previous work suggests that oxygen isotope fractionation may depend on the total and relative ion content of water. (3) Carbon isotope compositions of ostracod valves are generally in equilibrium with DIC. The specimens' δ13C values are mainly controlled by seasonal variations in δ13CDIC of bottom water or variation thereof in sediment pore water. (4) Incomplete valve calcification has an effect on carbon and oxygen isotope compositions of ostracod valves. Preferential incorporation of at the beginning of valve calcification may explain this effect. (5) Results presented here as well as results from synthetic carbonate growth indicate that different growth rates or low pH within the calcification site cannot be the cause of oxygen isotope 'vital effects' in ostracods. Two mechanisms that might enrich the 18O of ostracod valves are deprotonation of that may also contribute to valve calcification, and effects comparable to salt effects with high concentrations of Ca and/or Mg within the calcification site that may also cause a higher temperature dependency of oxygen isotope fractionation.

Oxidation and ubiquitination in neurodegeneration.

It is widely accepted that protein oxidation is involved in a variety of diseases, including neurodegenerative diseases. Especially during aging, a reduction in anti-oxidant defence mechanisms leads to an increased formation of free radical oxygen species and consequently results in a damage of proteins, including mitochondrial and synaptic ones. Even those proteins involved in repair and protein clearance via the ubiquitin proteasome and lysosomal system are subject to damage and show a reduced function. Here, we will discuss a variety of mechanisms and provide examples where cognition is affected and where repair mechanisms are no longer sufficient to compensate for a dysfunction of damaged proteins or even may become toxic. Next to physiological deficits, an accumulation of deficient proteins in aggresomes may occur and result in a formation of pathological hallmark structures typical for aging and disease. A major challenge is how to prevent aberrant oxidation, given that oxidation plays an essential role in aging and neurodegenerative diseases. Particularly interesting are the possibilities to reduce the formation of radical oxygen species leading to a dysfunction of protein repair and protein clearance, or to a formation of toxic byproducts accelerating neurodegeneration.