Different States Of Hydration Research Articles

Synthonic Modeling of Quercetin and Its Hydrates: Explaining Crystallization Behavior in Terms of Molecular Conformation and Crystal Packing

Hydrated structures of a specific compound can often have different physiochemical properties compared to the anhydrous form. Therefore, being able to predict and understand these properties, especially the stability, is critical. In this study quercetin, a flavonoid molecule, is modelled in three different states of hydration to gain an understanding of the effect of water molecules on the structure, packing and conformation energetics of the three forms. Conformational analysis and modelling of intermolecular interactions (synthonic modelling) have been performed. It was found that in the anhydrous form hydrogen bonding is the strongest type of interaction while in the two hydrate structures, the incorporation of water within the lattice leads to the formation of hydrogen bonds between the quercetin and water molecules. Within hydrates quercetin molecules adopt a more planar conformation which allows them to pack more closely by strong π-π stacking interactions, thus resulting in a higher relative stability. The modelling results highlight the importance of water in the stabilization of the lattice and explain the preferential nucleation of the dihydrate form. It is further demonstrated how synthonic modelling can be a predictive tool for the product’s properties, leading to more efficient product design and faster development.

Characterization of the dielectric properties of biological tissues using mixture equations and correlations to different states of hydration

The aim of this study was to characterize the hydration fractions of biological tissues and to model these accurately from mixture equations. Hydration fractions, better known as volume fractions, are based on quantification of tissue hydration and accurate knowledge about the physiological composition of tissue fluids. Data on weight loss percentages for excised muscle and adipose tissue from a previous study were utilized for this purpose. The Bruggeman and Maxwell Garnett equations were then used to characterize the dielectric properties of the tissues in terms of mixtures of dry biological constituents and physiological saline solutions. It is shown that these models are accurate in modelling in vivo and ex vivo tissue in different states of hydration. This is based on precise knowledge of the physiological composition of biological fluids and their corresponding percentage contents.

Characterization of the dielectric properties of biological tissues and their correlation to tissue hydration

The aim of this paper was to investigate the correlation between the dielectric properties of biological tissues and their different states of hydration. Measurements were conducted on rat muscle and fat tissues both in vivo and ex vivo, in different states of dehydration through a loss on drying technique. Dielectric parameters were observed as a function of frequency from 500 MHz to 50 GHz by utilizing an open-ended coaxial probe at constant room temperature of 25° C. By observing which dehydration fractions fall within in vivo values, it was deduced that ex vivo samples are reliable in representing the dielectric parameters of in vivo samples, under certain controlled hydration conditions whereas, further analysis should be conducted for tissue characterized by low water content.

Time-Resolved Infrared Reflectance Studies of the Dehydration-Induced Transformation of Uranyl Nitrate Hexahydrate to the Trihydrate Form.

Uranyl nitrate is a key species in the nuclear fuel cycle. However, this species is known to exist in different states of hydration, including the hexahydrate ([UO2(NO3)2(H2O)6] often called UNH), the trihydrate [UO2(NO3)2(H2O)3 or UNT], and in very dry environments the dihydrate form [UO2(NO3)2(H2O)2]. Their relative stabilities depend on both water vapor pressure and temperature. In the 1950s and 1960s, the different phases were studied by infrared transmission spectroscopy but were limited both by instrumental resolution and by the ability to prepare the samples for transmission. We have revisited this problem using time-resolved reflectance spectroscopy, which requires no sample preparation and allows dynamic analysis while the sample is exposed to a flow of N2 gas. Samples of known hydration state were prepared and confirmed via X-ray diffraction patterns of known species. In reflectance mode the hexahydrate UO2(NO3)2(H2O)6 has a distinct uranyl asymmetric stretch band at 949.0 cm(-1) that shifts to shorter wavelengths and broadens as the sample desiccates and recrystallizes to the trihydrate, first as a shoulder growing in on the blue edge but ultimately results in a doublet band with reflectance peaks at 966 and 957 cm(-1). The data are consistent with transformation from UNH to UNT as UNT has two inequivalent UO2(2+) sites. The dehydration of UO2(NO3)2(H2O)6 to UO2(NO3)2(H2O)3 is both a structural and morphological change that has the lustrous lime green UO2(NO3)2(H2O)6 crystals changing to the matte greenish yellow of the trihydrate solid. The phase transformation and crystal structures were confirmed by density functional theory calculations and optical microscopy methods, both of which showed a transformation with two distinct sites for the uranyl cation in the trihydrate, with only one in the hexahydrate.

Evaluation of hydration status calculated from differences in venous and capillary plasma dilution during stepwise crystalloid infusions: A randomized crossover study in healthy volunteers

Background and objectiveA mini volume loading test (mVLT) was proposed for estimating hydration status and interstitial fluid accumulation during stepwise infusion of crystalloids. The method is based on both the transcapillary reflux model and the hypothesis that when subjects are dehydrated, venous plasma dilution induced by a fluid challenge is higher than in the capillaries, and that difference is diminished when the fluid challenge is given to more hydrated individuals. Our objective was to test that hypothesis by evaluating the veno-capillary dilution difference during mVLT in subjects with different hydration status. Materials and methodsIn a prospective randomized crossover study, three mini fluid challenges were given to 12 healthy volunteers on two occasions. The subjects were either dehydrated or hydrated before the experiments. ResultsIn dehydrated subjects only, capillary plasma dilution was significantly lower than venous (P=0.015, 0.005 and 0.006) after each mini fluid challenge. ConclusionsVeno-capillary dilution difference during mVLT depends on the hydration status. The mVLT method could possibly discriminate between the different states of hydration.

MR diffusion tensor imaging of normal kidneys.

To assess the feasibility of diffusion tensor imaging (DTI) of normal kidneys and the influence of hydration state. Ten healthy volunteers underwent renal DTI after fasting for 12 hours and 4 hours, without fasting, and following water diuresis. Medullary and cortical apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured and compared in the four different states of hydration. DTI was performed with a 3T magnetic resonance imaging (MRI) system using fat-saturated single-shot spin-echo echo planar imaging sequence. ADC of normal cortex (2.387 ± 0.081 × 10(-3) mm(2) /s) was significantly higher (t = 20.126, P = 0) than that of medulla (1.990 ± 0.063 × 10(-3) mm(2) /s). The FA value of normal cortex (0.282 ± 0.017) was significantly lower (t = -42.713, P = 0) than that of medulla (0.447 ± 0.022). The ADC and FA values of the left renal cortex (2.404 ± 0.082 × 10(-3) mm(2) /s, 0.282 ± 0.017) and medulla (2.002 ± 0.081 × 10(-3) mm(2) /s, 0.452 ± 0.024) were not significantly different (P > 0.05) from those of right renal cortex (2.369 ± 0.080 × 10(-3) mm(2) /s, 0.283 ± 0.018) and medulla (1.978 ± 0.039 × 10(-3) mm(2) /s, 0.443 ± 0.019). Values for ADC (×10(-3) mm(2) /s) and FA in the 12-hour fasting, 4-hour fasting, nonfasting, and water diuresis states were 2.372 ± 0.095 and 0.278 ± 0.018, 2.387 ± 0.081 and 0.282 ± 0.017, 2.416 ± 0.051 and 0.279 ± 0.023, 2.421 ± 0.068, and 0.270 ± 0.021, respectively, in cortex, 1.972 ± 0.084 and 0.438 ± 0.014, 1.990 ± 0.063 and 0.447 ± 0.022, 2.021 ± 0.081 and 0.450 ± 0.031, 2.016 ± 0.076 and 0.449 ± 0.028, respectively, in medulla. The ADC and FA values in different hydration states were not significantly different (P > 0.05). DTI of normal kidneys is feasible with reproducible ADC and FA values independent of hydration states.

Trehalose and Vitreous States: Desiccation Tolerance of Dormant Stages of the CrustaceansTriopsandDaphnia

Several aquatic organisms are able to withstand extreme desiccation in at least one of their life stages. This is commonly known as "anhydrobiosis." It was often thought that to tolerate such a desiccated state required high amounts of compatible solutes such as the nonreducing disaccharide trehalose, which protects cellular structures by water replacement and glass formation. Trehalose levels of dormant eggs and cysts of five freshwater crustaceans (Daphnia magna, Daphnia pulex, Triops longicaudatus, Triops cancriformis, and Triops australiensis) were observed in different states of hydration and dehydration. Although trehalose was detected in all species, the concentration was under 0.5% of the dry weight (0.05 μg/μg protein), and no change between the different states was observed. Differential scanning calorimetry (DSC) measurements indicated that dried cysts of all Triops species were in a glassy state, supporting the vitrification hypothesis. No indication for a vitreous state was found in dried resting eggs of Daphnia.

Diffusion-weighted MRI sequences (DW-MRI) of the kidney: normal findings, influence of hydration state and repeatability of results

This study was performed to determine the apparent diffusion coefficient (ADC) of the normal kidney using diffusion-weighted magnetic resonance imaging (DW-MRI) sequences and to analyse both the changes due to hydration state and results repeatability. Ten volunteers underwent DW-MRI imaging of the kidneys with a breath-hold single-shot spin-echo planar imaging (SE-EPI) sequence in the axial and coronal planes with b values of 300, 500, 800 s/mm(2), in different states of hydration. Urine osmolarity (OsmU) and sodium excretion (NaU) were measured at the time of each examination. ADC maps were created for all b values, and ADC values were calculated and compared between different states of hydration. In five subjects, the protocol was conducted twice to test data repeatability. ADC values were lower with higher b values (3.00 vs. 2.47 vs. 1.99 x 10(-3) mm(2)/s with b values of 300, 500, 800 s/mm(2), respectively). ADC values in different hydration states were not statistically different. Measurements were reproducible. OsmU and NaU were statistically different in the different states of hydration (p<0.01). ADC values significantly decrease with higher b values. Average ADC values in the normal kidney are reproducible. Hydration state does not significantly influence mean ADC values.

Trehalose and anhydrobiosis in tardigrades – evidence for divergence in responses to dehydration

To withstand desiccation, many invertebrates such as rotifers, nematodes and tardigrades enter a state known as anhydrobiosis, which is thought to require accumulation of compatible osmolytes, such as the non-reducing disaccharide trehalose to protect against dehydration damage. The trehalose levels of eight tardigrade species comprising Heterotardigrada and Eutardigrada were observed in five different states of hydration and dehydration. Although many species accumulate trehalose during dehydration, the data revealed significant differences between the species. Although trehalose accumulation was found in species of the order Parachela (Eutardigrada), it was not possible to detect any trehalose in the species Milnesium tardigradum and no change in the trehalose level has been observed in any species of Heterotardigrada so far investigated. These results expand our current understanding of anhydrobiosis in tardigrades and, for the first time, demonstrate the accumulation of trehalose in developing tardigrade embryos, which have been shown to have a high level of desiccation tolerance.

Walking by Ixodes ricinus ticks: intrinsic and extrinsic factors determine the attraction of moisture or host odour

Spontaneous walking by Ixodes ricinus nymphs in the horizontal plane was investigated within choice arenas to test whether these ticks move preferentially up a humidity gradient, and whether they are attracted towards host odour, specifically volatile substances from the back of a dog's ear. Responses by ticks with high and low fat contents and in different states of hydration were compared. Ticks with higher energy reserves were more likely to walk horizontally over short distances. Only if they were slightly dehydrated were they more likely to walk towards fully saturated air than drier air, and only if the atmosphere was sufficiently wet were they likely to walk towards odour secreted by host skin. It seems that, under certain circumstances, ticks of this ambushing species will move short distances towards host odour.

Imaging structured water and bound polysaccharide on mica surface at ambient temperature.

The presence of a water layer on the surface of muscovite mica under ambient conditions is well established. The water molecules are well ordered and seem to be oriented, leading to an icelike monolayer (probably ferroelectric) in epitaxial relation with the mica surface. We have imaged and characterized the height and contact angle of ordered water layer(s) formed by wetting and de-wetting processes on mica surfaces at different states of hydration by tapping mode atomic force microscopy. Implications that the presence of such an ordered water layer may have for imaging of biological samples are also discussed, with consideration of data for the polysaccharide hyaluronan.

Nanostructure of Nafion ® membranes at different states of hydration : An IR and Raman study

117 and 112 grades of H + Nafion ® membranes were studied using near-IR FT Raman scattering, IR absorption and ATR techniques. Tested membranes were as received, n water molecules per –HSO 3 groups ( n(117 I)∼10, n(112 I)∼2), equilibrated in water at RT ( n(117 II)∼20) or at 100°C ( n(112 II)∼16), air dried at 80°C (117 III grade, n∼1) and 110°C (117 IV grade, n∼3×10 −1) and completely dried over P 2O 5 (117 V). Infrared (ATR) and Raman spectra show that whatever the water uptake, Nafion ® (117 and 112) skeleton retains the helical zigzag conformation of the polytetrafluoroethylene (PTFE) and that the (CF 2CF 2) links prevail on the fluorocarbon part of the side-pendant chains. Comparison with PTFE allows for the calculation of the crystallinity degree of Nafion ® membranes. Two ν 2 bending OH vibrations are observed at 1650 (water, acid water) and 1720 cm −1 (weakly-hydrated H 3O + ion). After drying, H 3O +⋯SO 3 − interactions become visible and explain why the OH stretching massif shifts towards smaller wave numbers. At 80°C (117 III), sub-maximum at 2980 cm −1 is assigned to H 3O + hydrogen bonded to SO 3 − groups. The acid water ν 2 band disappears while the H 3O + band persists. In Nafion ® 117 IV, almost all the water content is eliminated and many sulfonic groups are undissociated. Formation of the hydrated cluster follows from the helical conformation of the (CF 2) n backbone and from the relative position of adjacent chains.

A CRYSTAL-CHEMICAL APPROACH TO THE COMPOSITION AND OCCURRENCE OF VANADIUM MINERALS

We introduce a crystal-chemical approach to the composition and occurrence of vanadium minerals. Here, the structure of a mineral is divided into two parts: the structural unit with bonds of higher bond-valence, and the interstitial complex, [ [m] M + a [n] M 2+ b [l] M 3+ c (H 2 O) d (H 2 O) e (OH) f ] (a+2b+3c−f)+ , which connects the structural units to form a continuous structure. Average coordination numbers of oxygen in structural units of vanadium minerals are in the range [2.75] to [4]. There are characteristic ranges of average O-coordination numbers for specific structural units, and these values can be used to calculate the range of Lewis basicities of structural units in vanadium minerals. The characteristic Lewis basicities explain why some interstitial cations occur, and some do not occur, with a specific structural unit. Furthermore, the maximum and minimum number of interstitial transformer (H 2 O) groups can be predicted. The occurrence of different states of hydration in vanadium minerals is rationalized via bond-valence theory. Here, Lewis basicities and effective Lewis acidities of structural components in vanadium minerals can explain detailed structural changes during dehydration. The average basicity of a structural unit is independent of the average O-coordination number, and can be compared to structural units in minerals with different interstitial cations and hydration states. With increasing polymerization, there is a decrease in the average basicity of the structural unit. Examination of the conditions of crystallization of vanadate minerals and synthetic phases shows that the average basicity of the structural unit correlates with the pH of the environment of crystallization. The average basicity of aqueous species in a solution correlates linearly with the pH at the maximum concentration of the species in solution.

Differential expression of individual UT-A urea transporter isoforms in rat kidney.

The rat renal urea transporter UT-A includes four mRNA isoforms: UT-A1, UT-A2, UT-A3, and UT-A4. This study detected by rapid amplification of cDNA ends (RACE), primer extension, and ribonuclease protection assay (RPA) a single transcription start site for UT-A1, UT-A3, and UT-A4, distinct from the one for UT-A2 and identified by 3'-RACE new transcripts of UT-A1, UT-A2, and UT-A3, characterized by alternative 3' untranslated sequences (UTR). Expression of an alternative 3'UTR resulted in UT-A1 and UT-A2 transcripts that are approximately 400 bp shorter than the original cDNA. These mRNA isoforms (UT-A1b and UT-A2b) were present in low abundance in the inner medulla. Expression of an alternative 3'UTR for UT-A3 resulted in a 3.5 kb transcript (UT-A3b), which is 1.5 kb longer than the original UT-A3 cDNA. UT-A3b mRNA was easily detected by Northern hybridization in the inner medulla. This study examined whether different states of hydration induce homogeneous changes in mRNA expression of individual UT-A isoforms in the kidney. Analysis of UT-A1, UT-A1b, UT-A2, UT-A2b, UT-A3, and UT-A3b mRNA expression in rat kidney revealed that water deprivation markedly increases the relative abundance of UT-A2, UT-A2b, UT-A3, and UT-A3b mRNA in renal inner medulla, whereas UT-A1 and UT-A1b remain almost unchanged. The conclusion is that differential expression of individual UT-A mRNA isoforms occurs in the kidney and probably involves multiple regulatory mechanisms.

In situ rehydration of perfluorosulphonate ion-exchange membrane studied by AFM

Nafion ® is a commercially available perfluorosulphonate cation exchange membrane commonly used as a perm-selective separator in chlor-alkali electrolysers and as the electrolyte in solid polymer fuel cells. This usage arises because of its high mechanical, thermal and chemical stability coupled with its high conductivity and ionic selectivity, which depend strongly on the water content. The membrane was therefore studied in different states of hydration obtained by placing the membrane and atomic force microscope (AFM) in a specially constructed environmental chamber to control the humidity. Tapping mode phase imaging was successfully used to identify the hydrophobic and hydrophilic regions of Nafion. The images support a cluster model for the hydrophilic regions of Nafion at humidities of (9–34)±2%. The clusters have a range of sizes from 5 to 30 nm, significantly larger than the ∼4 nm structures proposed from X-ray studies, which is probably due to the formation of cluster agglomerates. Phase images were interpreted semi-quantitatively in terms of energy loss, typically 3 kJ m −2, and the number and size of energy dissipative features. The number of clusters decreased while the average cluster size increased with increasing humidity.

Hydration of Nafion® studied by AFM and X-ray scattering

Nafion® is a commercially available perfluorosulphonate cation exchange membrane commonly used as a perm-selective separator in chlor-alkali electrolysers and as the electrolyte in solid polymer fuel cells. This usage arises because of its high mechanical, thermal and chemical stability coupled with its high conductivity and ionic selectivity, which depend strongly on the water content. The membrane was therefore studied in different states of hydration with two complementary techniques: atomic force microscopy (AFM) and small angle X-ray scattering (SAXS) combined with a maximum entropy (MaxEnt) reconstruction. Tapping mode phase imaging was successfully used to identify the hydrophobic and hydrophilic regions of Nafion. The images support the MaxEnt interpretation of a cluster model of ionic aggregation, with spacings between individual clusters ranging from 3 to 5 nm, aggregating to form cluster agglomerates with sizes from 5 to 30 nm. Both techniques indicate that the number density of ionic clusters changes as a function of water content, and this explains why the bulk volumetric swelling in water is observed to be significantly less than the swelling inferred from scattering measurements.

Study of lichens with different state of hydration by the combination of low temperature scanning electron and confocal laser scanning microscopies.

The use of techniques such as low temperature scanning electron microscopy (LTSEM) and confocal laser scanning microscopy (CLSM) allows the study of lichen thalli in different states of hydration and also near the natural state. The spatial organization of desiccated thalli, with reduced, very compact algal layers, is different from that of hydrated ones. Sometimes, the observation with transmission electron microscopy (TEM) of photobiont pyrenoids from desiccated thalli reports pyrenoids with a central part of a weak stained matrix lacking pyrenoglobuli, named "empty zones". "Empty zones" are not distinguishable with LTSEM and do not present immunolabelling with rubisco antibody in TEM. These zones could be originated by an expansion process during rehydration produced in chemical fixation.

Magnetic resonance in the assessment of renal function.

The kidneys are the most important organs to maintain homeostasis. In the assessment of renal functional disorders laboratory tests offer only indirect hints on location of the disease; radionuclide nephrography is hampered by low spatial resolution and radiologic methods provide only limited quantitative information. The MRI technique with fast pulse sequences and renally eliminated contrast agent has the capability of combining both anatomic and functional information. This article gives an overview on functional MRI of the kidneys with its possibilities and limitations. The clinical application of functional MRI allows a better understanding of some pathologic conditions such as urinary tract obstruction, renal insufficiency, effects of extracorporeal shock wave lithotripsy, different states of hydration, effects of drugs, vascular disorders, and effects of transplantation.

Influence of different states of hydration on injured tissue (bowel anastomosis) in a rat model

Sixty-three rats were divided into four groups according to the amount of IV fluid administered. To test the hypothesis that the swelling in inflammation, which is caused mainly by edema, is an autonomic process and is not influenced by the state of hydration of the experimental animal, we performed a standard jejunal anastomosis in a rat model and measured the amount of water (tritium) and sodium in the anastomosis and a corresponding length of jejunum without an anastomosis, which served as a control. In spite of availability or lack of a large amount of water and sodium, the proportion of these elements to dry tissue in the different groups remained the same. Because there was no statistically significant weight gain or loss between the different hydration groups and total body water also did not change significantly, we conclude that infusion of even very large or small amounts of fluid does not change the state of hydration of the animal. We postulate that, at least in the healthy rat, the kidneys are able to protect the body and the anastomosis from overhydration or dehydration, and the anastomosis/inflammation itself is autonomic with regard to the state of hydration of the animal.

MRI anatomy of the rat kidney at 1.5 T in different states of hydration.

The objective of this study was to determine correlation between structural anatomy and surface coil spin-echo MR imaging of the rat kidney and the effect of hydration state on MR signal intensities of the cortex and medulla. Twelve rats were studied in a pilot study with a 3-inch surface coil in a 1.5 T magnet under five different states of hydration. Serum and urine osmolality measurements were obtained immediately prior to each scan. Signal intensity measurements were made from both T1- and T2-weighted images of the cortex and medulla of both kidneys in each state of hydration. Gross and histological anatomy of the rat kidneys was correlated with the MR images. Four distinct layers were detected in vivo on MRI images of the rat kidney; these correlated with the histological layers. T1-weighted cortico-medullary differentiation was most pronounced at 48 h dehydration; T2 cortico-medullary differentiation was greatest at 72 h of dehydration. We concluded that different parts of the mammalian nephron can be identified by MR imaging and that cortico-medullary differentiation is affected by the hydration state of the animal.