Changes In Total Water Research Articles

Water content changes in new multiple sclerosis lesions have a minimal effect on the determination of myelin water fraction values.

Myelin water fraction (MWF) is a histopathologically validated in vivo myelin marker. As MWF is the proportion of water with a short T2 relative to the total water, increases in water from edema and inflammation may confound MWF determination in multiple sclerosis (MS) lesions. Total water content (TWC) measurement enables calculation of absolute myelin water content (MWC) and can be used to distinguish edema/inflammation from demyelination. We assessed what influence changes in total water might have on MWF by calculating MWC values in new MS lesions. 3T 32-echo T2 relaxation data were collected monthly for 6 months from six relapsing-remitting MS participants. TWC was determined and multiplied with MWF images to calculate corrected MWC images. The effect of this water content correction was examined in 20 new lesions by comparing mean MWF and MWC over time. On average, at lesion first appearance, lesion TWC increased by 6.4% (p = .003; range: -1% to +21%), MWF decreased by 24% (p = .006; range: -70% to +12%), and MWC decreased by 20% (p = .026; range: -68% to +21%), relative to prelesion values. Average TWC in lesions then gradually decreased, whereas MWF and MWC remained low. The shape of the MWF and MWC lesion evolution curves was nearly identical, differing only by an offset. MWF mirrors MWC and is able to monitor myelin in new lesions. Even after taking into account water content increases, MWC still decreased at lesion first appearance attributed to demyelination.

Assessment of the impacts of climate variability on total water storage across Africa: implications for groundwater resources management

The links between climate variability, depicted by time series of oceanic indices, and changes in total water and groundwater storage are investigated across nine large aquifer basins of the African continent. The Gravity Recovery and Climate Experiment (GRACE) mission’s observations represent a remarkable tool that can provide insight into the dynamics of terrestrial hydrology in areas where direct in situ observations are limited. In order to evaluate the impact of interannual and multidecadal climate variability on groundwater resources, this study assesses the relationship between synoptic controls on climate and total water storage estimates from (i) GRACE from 2002 to 2013 and (ii) a two-variable climate-driven model that is able to reconstruct past storage changes from 1982 to 2011. The estimates are then compared to time series of groundwater levels to show the extent to which total water storage covaries with groundwater storage. Results indicate that rainfall patterns associated with the El Nino Southern Oscillation (ENSO) are the main driver of changes in interannual groundwater storage, whereas the Atlantic MultiDecadal Oscillation (AMO) plays a significant role in decadal to multidecadal variability. The combined effect of ENSO and AMO could trigger significant changes in recharge to the aquifers and groundwater storage, in particular in the Sahel. These findings could help decision-makers prepare more effective climate-change adaptation plans at both national and transboundary levels.

Seasonal variation in total water storage in California inferred from GPS observations of vertical land motion

GPS is accurately recording vertical motion of Earth's surface in elastic response to seasonal changes in surface water storage in California. California's mountains subside up to 12 mm in the fall and winter due to the load of snow and rain and then rise an identical amount in the spring and summer when the snow melts, the rain runs off, and soil moisture evaporates. We invert the GPS observations of seasonal vertical motions to infer changes in equivalent water thickness. GPS resolves the distribution of change in total water across California's physiographic provinces at a resolution of 50 km, compared to 200 km resolution from the Gravity Recovery and Climate Experiment. The seasonal surface water thickness change is 0.6 m in the Sierra Nevada, Klamath, and southern Cascade Mountains and decreases sharply to about 0.1 m east into the Great Basin and west toward the Pacific coast. GPS provides an independent inference of change in total surface water, indicating water storage to be on average 50% larger than in the NLDAS-Noah hydrology model, likely due to larger changes in snow and reservoir water than in the model.

Subduction fluxes of water, carbon dioxide, chlorine, and potassium

The alteration of upper oceanic crust entails growth of hydrous minerals and loss of macroporosity, with associated large‐scale fluxes of H2O, CO2, Cl−, and K2O between seawater and crust. This age‐dependent alteration can be quantified by combining a conceptual alteration model with observed age‐dependent changes in crustal geophysical properties at DSDP/ODP sites, permitting estimation of crustal concentrations of H2O, CO2, Cl−, and K2O, given crustal age. Surprisingly, low‐temperature alteration causes no net change in total water; pore water loss is nearly identical to bound water gain. Net change in total crustal K2O is also smaller than expected; the obvious low‐temperature enrichment is partly offset by earlier high‐temperature depletion, and most crustal K2O is primary rather than secondary. I calculate crustal concentrations of H2O, CO2, Cl−, and K2O for 41 modern subduction zones, thereby determining their modern mass fluxes both for individual subduction zones and globally. This data set is complemented by published flux determinations for subducting sediments at 26 of these subduction zones. Global mass fluxes among oceans, oceanic crust, continental crust, and mantle are calculated for H2O, Cl−, and K2O. Except for the present major imbalance between sedimentation and sediment subduction, most fluxes appear to be at or near steady state. I estimate that half to two thirds of subducted crustal water is later refluxed at the prism toe; most of the remaining water escapes at subarc depths, triggering partial melting. The flux of subducted volatiles, however, does not appear to correlate with either rate of arc magma generation or magnitude of interplate earthquakes.

Water compartmentalization and extracellular tortuosity after osmotic changes in cerebellum of Trachemys scripta.

1. Water compartmentalization in the turtle cerebellum subject to media of different osmolalities was quantified by combining extracellular diffusion analysis with wet weight and dry weight measurements. The diffusion analysis also determined the tortuosity of the extracellular space. 2. Isolated cerebella were immersed in normal, oxygenated physiological saline (302 mosmol kg-1), hypotonic saline (238 mosmol kg-1) and a series of hypertonic salines (up to 668 mosmol kg-1). The osmolality was varied by altering the NaCl content. 3. Extracellular volume fraction and tortuosity of the granular layer of the cerebellum were determined from measurements of ionophoretically induced diffusion profiles of tetramethylammonium, using ion-selective microelectrodes. The volume fraction was 0.22 in normal saline, 0.12 in hypotonic medium and 0.60 in the most hypertonic medium. Tortuosity was 1.70 in the normal saline, 1.79 in the hypotonic and 1.50 in the most hypertonic saline. 4. The water content, defined as (wet weight-dry weight)/wet weight, of a typical isolated cerebellum (including granular, Purkinje cell and molecular layers) was 82.9%. It increased to 85.2% in hypotonic saline and decreased to 80.1% in the most hypertonic saline. 5. Measurements of extracellular volume fraction and water content were combined to show that hypotonic solutions caused water to move from the extracellular to the intracellular compartment while hypertonic solutions caused water to move from the intracellular to extracellular compartment, with only a relatively small changes in total water in both cases. 6. These results suggest the use of the isolated turtle cerebellum as a model system for studying light scattering or diffusion-weighted magnetic resonance imaging.

Changes in the water and electrolyte content of skeletal muscles of the mouse during post-natal development

1. 1. A study was made of the changes in total water, sodium, chloride and potassium in the biceps brachii (BB), extensor digitorum longus (EDL) and soleus (SOL) muscles of the mouse durinf post-natal development. 2. 2. There was a decrease in the total water, sodium and chloride content in all three muscles. 3. 3. Potassium expressed per unit wet wt. increased in the BB and EDL during development, but in the SOL it increased and then decreased. On a dry tissues basis there was a decrease in potassium in all three muscles, the change was greatest in the SOL. 4. 4. There were significant differences between the three muscles in their electrolytes content at maturity. In the SOL potassium was less and sodium and chloride greater than in the BB and EDL. 5. 5. Differences were noted between the muscles in their time to reach maturity. The SOL took up to 12 weeks, while the BB took only 6 weeks.

Water balance of whole animal, muscle tissue, and muscle cells in the prosobranch gastropod, Acmaea scutum.

AbstractThe prosobranch limpet Acmaea scutum is found in both marine and estuarine environments. A number of parameters affect the water balance of this limpet. A. scutum has little control of total water content. Total water changes with season, size of animal, and salinity. Limpets from a marine environment, when immersed in experimental salinities for up to one week, are unable to regulate total body water. Estuarine limpets however, are able to regulate total body water in experimental salinities between 24 and 48 hours immersion. The ability to regulate water content between 24 and 48 hours is probably not important in the estuarine environment. Studies on the effect of field salinity on the water content of estuarine animals show that changes in field salinity of about 15% sea water resulted in significant changes in total body water.Water content of muscle tissue and muscle cells of marine A. scutum, like body water values, conform when external salinity is changed. Estimates of intracellular water per unit of muscle tissue (using inulin space as extracellular space) changed with external salinity from 79.3% at 50% sea water to 57.7% at 125% sea water.