Studies of the renal effects of angiotensin II receptor blockade: the confounding factor of acute water loading on the action of vasoactive systems.

The acute renal tubular effects of two pharmacologically distinct angiotensin II receptor antagonists have been evaluated in normotensive volunteers on various salt diets. In the first study, the renal response to a single oral dose of losartan (100 mg) was assessed in subjects on a low (50 mmol Na/d) and on a high (200 mmol Na/d) salt intake. In a second protocol, the renal effects of 50 mg irbesartan were investigated in subjects receiving a 100 mmol Na/d diet. Both angiotensin II antagonists induced a significant increase in urinary sodium excretion. With losartan, a modest, transient increase in urinary potassium and a significant increase in uric acid excretion were found. In contrast, no change in potassium and uric acid excretions were observed with irbesartan, suggesting that the effects of losartan on potassium and uric acid are due to the intrinsic pharmacologic properties of losartan rather than to the specific blockade of renal angiotensin II receptors. Assessment of segmental sodium reabsorption using lithium as a marker of proximal tubular reabsorption demonstrated a decreased distal reabsorption of sodium with both antagonists. A direct proximal tubular natriuretic effect of the angiotensin II antagonist could be demonstrated only with irbesartan. This apparent discrepancy allowed us to reveal the importance of acute water loading as a possible confounding factor in renal studies. The results of the present analysis show that acute water loading per se may enhance renal sodium excretion and hence modify the level of activity of the renin-angiotensin system expected from a given sodium diet. Since acute water loading is a common practice in clinical renal studies, this confounding factor should be taken into account when investigating the renal effects of vasoactive systems.

Mass conservative three-dimensional water tracer distribution from Markov chain Monte Carlo inversion of time-lapse ground-penetrating radar data

Time-lapse geophysical measurements are widely used to monitor the movement of water and solutes through the subsurface. Yet commonly used deterministic least squares inversions typically suffer from relatively poor mass recovery, spread overestimation, and limited ability to appropriately estimate nonlinear model uncertainty. We describe herein a novel inversion methodology designed to reconstruct the three-dimensional distribution of a tracer anomaly from geophysical data and provide consistent uncertainty estimates using Markov chain Monte Carlo simulation. Posterior sampling is made tractable by using a lower-dimensional model space related both to the Legendre moments of the plume and to predefined morphological constraints. Benchmark results using cross-hole ground-penetrating radar travel times measurements during two synthetic water tracer application experiments involving increasingly complex plume geometries show that the proposed method not only conserves mass but also provides better estimates of plume morphology and posterior model uncertainty than deterministic inversion results.

Measurement of absolute cell volume, osmotic membrane water permeability, and refractive index of transmembrane water and solute flux by digital holographic microscopy.

ABSTRACT. A dual-wavelength digital holographic microscope to measure absolute volume of living cells is proposed. The optical setup allows us to reconstruct two quantitative phase contrast images at two different wavelengths from a single hologram acquisition. When adding the absorbing dye fast green FCF as a dispersive agent to the extracellular medium, cellular thickness can be univocally determined in the full field of view. In addition to the absolute cell volume, the method can be applied to derive important biophysical parameters of living cells including osmotic membrane water permeability coefficient and the integral intracellular refractive index (RI). Further, the RI of transmembrane flux can be determined giving an indication about the nature of transported solutes. The proposed method is applied to cultured human embryonic kidney cells, Chinese hamster ovary cells, human red blood cells, mouse cortical astrocytes, and neurons.

Transport of a biocontrol Pseudomonas fluorescens through 2.5-m deep outdoor lysimeters and survival in the effluent water

Application of wild-type or genetically-modified bacteria to the soil environment entails the risk of dissemination of these organisms to the groundwater. To measure vertical transport of bacteria under natural climatic conditions, Pseudomonas fluorescens strain CHA0 was released together with bromide as a mobile tracer at the surface of large outdoor lysimeters. Two experiments, one starting in autumn 1993 and the other in spring 1994 were performed. Shortly after a heavy rainfall in late spring 1994, the released bacteria were detected for the first time in effluent water from the 2.5-m-deep lysimeters in both experiments, i.e. 210 d and 21 d, respectively, after inoculation. Only a 10−9 to 10−8 fraction of the inoculum was recovered as culturable cells in the effluent water, but a larger fraction of the CHA0 cells was in a non-culturable state as detected with immunofluorescence microscopy. As much as 50% of the mobile tracer percolated through the lysimeters, indicating that, compared with bromide, bacterial cells were retained in soil. In the second part of this study, persistence of CHA0 in groundwater microcosms consisting of lysimeter effluent water was studied for 380 d. Survival of the inoculant as culturable cells was better under anaerobic than under aerobic conditions. However, a large fraction of the cells became non-culturable in both cases. When the experiment was performed with filter-sterilized effluent water, the total count of introduced bacteria did not decline with time. In conclusion, the biocontrol strain was transported in low numbers to a potential groundwater level under natural climatic conditions, but could persist for an extended period in groundwater microcosms.

Ambient seismic noise monitoring of a clay landslide: Toward failure prediction

Given that clay-rich landslides may become mobilized, leading to rapid mass movements (earthflows and debris flows), they pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones, which could be detected by monitoring shear wave velocity variations. With this purpose in mind, the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

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.

Geochemical and H-O-Sr-Nd isotope evidence for magmatic processes and meteoric-water interactions in the basal complex of La Gomera, Canary Islands

The plutonic rocks of the Basal Complex of La Gomera, Canary Islands, Spain, were studied by means of major and trace element contents and by H-O-Sr-Nd isotope compositions in order to distinguish primary magmatic characteristics and late-stage alteration products. Deciphering the effects of alteration allowed us to determine primary, plume-related compositions that indicated D- and (18)O-depletion relative to normal upper mantle, supporting the conclusions of earlier studies on the plutonic rocks of Fuerteventura and La Palma. Late-stage alteration took place during the formation of the intrusive series induced by interaction with meteoric water. Inferred isotopic compositions of the meteoric water indicate that the water infiltrated into the rock edifice at a height of about 1500 m above sea level, suggesting the existence of a subaerial volcano which was active during the intrusive activity and that it has been either distroyed or remain buried by later volcanic and landslide events.

Population demography of an endangered lizard, the Blue Mountains Water Skink.

BACKGROUND: Information on the age structure within populations of an endangered species can facilitate effective management. The Blue Mountains Water Skink (Eulamprus leuraensis) is a viviparous scincid lizard that is restricted to < 40 isolated montane swamps in south-eastern Australia. We used skeletochronology of phalanges (corroborated by mark-recapture data) to estimate ages of 222 individuals from 13 populations. RESULTS: These lizards grow rapidly, from neonatal size (30 mm snout-vent length) to adult size (about 70 mm SVL) within two to three years. Fecundity is low (mean 2.9 offspring per litter) and is affected by maternal body length and age. Offspring quality may decline with maternal age, based upon captive-born neonates (older females gave birth to slower offspring). In contrast to its broadly sympatric (and abundant) congener E. tympanum, E. leuraensis is short-lived (maximum 6 years, vs 15 years for E. tympanum). Litter size and offspring size are similar in the two species, but female E. leuraensis reproduce annually whereas many E. tympanum produce litters biennially. Thus, a low survival rate (rather than delayed maturation or low annual fecundity) is the key reason why E. leuraensis is endangered. Our 13 populations exhibited similar growth rates and population age structures despite substantial variation in elevation, geographic location and swamp size. However, larger populations (based on a genetic estimate of effective population size) contained older lizards, and thus a wider variance in ages. CONCLUSION: Our study suggests that low adult survival rates, as well as specialisation on a rare and fragmented habitat type (montane swamps) contribute to the endangered status of the Blue Mountains Water Skink.

First day of an oil spill on the open sea: early mass transfers of hydrocarbons to air and water.

During the first hours after release of petroleum at sea, crude oil hydrocarbons partition rapidly into air and water. However, limited information is available about very early evaporation and dissolution processes. We report on the composition of the oil slick during the first day after a permitted, unrestrained 4.3 m(3) oil release conducted on the North Sea. Rapid mass transfers of volatile and soluble hydrocarbons were observed, with >50% of ≤C17 hydrocarbons disappearing within 25 h from this oil slick of <10 km(2) area and <10 μm thickness. For oil sheen, >50% losses of ≤C16 hydrocarbons were observed after 1 h. We developed a mass transfer model to describe the evolution of oil slick chemical composition and water column hydrocarbon concentrations. The model was parametrized based on environmental conditions and hydrocarbon partitioning properties estimated from comprehensive two-dimensional gas chromatography (GC×GC) retention data. The model correctly predicted the observed fractionation of petroleum hydrocarbons in the oil slick resulting from evaporation and dissolution. This is the first report on the broad-spectrum compositional changes in oil during the first day of a spill at the sea surface. Expected outcomes under other environmental conditions are discussed, as well as comparisons to other models.

Role of the renal circadian timing system in maintaining water and electrolytes homeostasis.

Many basic physiological functions exhibit circadian rhythmicity. These functional rhythms are driven, in part, by the circadian clock, an ubiquitous molecular mechanism allowing cells and tissues to anticipate regular environmental events and to prepare for them. This mechanism has been shown to play a particularly important role in maintaining stability (homeostasis) of internal conditions. Because the homeostatic equilibrium is continuously challenged by environmental changes, the role of the circadian clock is thought to consist in the anticipative adjustment of homeostatic pathways in relation with the 24h environmental cycle. The kidney is the principal organ responsible for the regulation of the composition and volume of extracellular fluids (ECF). Several major parameters of kidney function, including renal plasma flow (RPF), glomerular filtration rate (GFR) and tubular reabsorption and secretion have been shown to exhibit strong circadian oscillations. Recent evidence suggest that the circadian clock can be involved in generation of these rhythms through external circadian time cues (e.g. humoral factors, activity and body temperature rhythms) or, trough the intrinsic renal circadian clock. Here, we discuss the role of renal circadian mechanisms in maintaining homeostasis of water and three major ions, namely, Na(+), K(+) and Cl(-).

Expression quantitative trait locus mapping across water availability environments reveals contrasting associations with genomic features in Arabidopsis.

The regulation of gene expression is crucial for an organism's development and response to stress, and an understanding of the evolution of gene expression is of fundamental importance to basic and applied biology. To improve this understanding, we conducted expression quantitative trait locus (eQTL) mapping in the Tsu-1 (Tsushima, Japan) × Kas-1 (Kashmir, India) recombinant inbred line population of Arabidopsis thaliana across soil drying treatments. We then used genome resequencing data to evaluate whether genomic features (promoter polymorphism, recombination rate, gene length, and gene density) are associated with genes responding to the environment (E) or with genes with genetic variation (G) in gene expression in the form of eQTLs. We identified thousands of genes that responded to soil drying and hundreds of main-effect eQTLs. However, we identified very few statistically significant eQTLs that interacted with the soil drying treatment (GxE eQTL). Analysis of genome resequencing data revealed associations of several genomic features with G and E genes. In general, E genes had lower promoter diversity and local recombination rates. By contrast, genes with eQTLs (G) had significantly greater promoter diversity and were located in genomic regions with higher recombination. These results suggest that genomic architecture may play an important a role in the evolution of gene expression.

First aid in burn injuries with counterintuitive warm water improves outcome

Objective: Cooling is considered a panacea in burn injury. However, burn injuries are characterized by an ischemic zone prone to progression, a phenomenon that can substantially increase morbidity. Cold-induced vasoconstriction potentially aggravates ischemia and promotes progression. Therefore we compared the effect of warm (37°C) and cold (17°C) water on burn progression. Methods: The comb burn model creates 4 rectangular burned surfaces separated by 3 unburned interspaces that become necrotic if untreated. After heating in boiling water the template was applied for 60 seconds on 24 Wistar rats randomized into 3 groups: no treatment (CON); treatment for 20 minutes with cold water (17°C: CW) or warm water (37°C: WW). Burn progression in surface (planimetry) and Departmenth (histology), as well as microcirculatory perfusion (laser Doppler flowmetry) were assessed after 1h, as well as 1, 4, and 7 days. Results: Both CW and WW delayed burn progression without reducing the final burn Departmenth (deep dermis). In contrast, only WW but not CW increased dermal perfusion (81 ± 2% (WW) vs. 62 ± 2% (CW) and 63 ± 1% (CON), p< 0·05) already 1 hour after burn induction. The difference observed after one hour led to a complete flow recovery during the observation period and translated into increased interspace survival, respectively less necrosis with WW(65 ± 4% vs. 81 + 4% (CW) and 91 ± 2% (CON), p< 0·05) after 7 days. Conclusions: Application of warm water significantly improved dermal perfusion, increased interspace survival, and delayed burn progression.However it didn't alter the ultimate burn Departmenth of the actually burned area. Therefore, warm water can create a therapeutic window for targeted nonsurgical treatment of burn progression.