Changes In Hydration Research Articles

Venous dilation effect of hot towel (moist and dry heat) versus hot pack for peripheral intravenous catheterization: a quasi-experimental study

BackgroundHeat application before peripheral intravenous catheterization is recommended for venous dilation. Hot pack application enlarges the venous diameter in healthy adults; however, hot towels (moist and dry heat) are used often in some medical cases. However, it is unclear whether hot towel application promotes venous dilation better than hot pack application. This study compared the venous dilation effect of using a hot towel (moist and dry heat) to a hot pack before applying the tourniquet at an access site for peripheral intravenous catheterization.MethodsEighty-eight healthy females aged 18–29 years were recruited for this quasi-experimental study. They underwent three types of heat applications (hot pack, moist hot towel, and dry hot towel [moist hot towel wrapped in a dry plastic bag], all of which were warmed to 40 ± 2 °C and performed for 7 min) to their forearm and tourniquet application for 30 s after each heating. Venous diameter and depth were measured using ultrasonography, and venous palpability and visibility (venous assessment score) was observed as venous dilatation effects. In addition, the skin temperature, stratum corneum hydration, and subjective evaluation of the warmth were measured.ResultsThere were no significant differences in venous diameter and assessment scores after intervention between the dry hot towel and the hot pack groups, and the effect size was negligible (Cohen’s d < 0.20). However, these measurements were significantly lower for the moist hot towel than for the other two heat applications (P < .001). Although there was no significant difference in skin temperature and warmth rating score between the dry hot towel and the hot pack, these were significantly lower for the moist hot towel than for the other two heat applications (P < .001). The amount of change in stratum corneum hydration of the dry hot towel was not significantly different from that of the hot pack; however, that of the moist hot towel was significantly larger than that of the other two heat applications (P < . 001.)ConclusionsA method in which a towel warmed in hot water is wrapped in a dry barrier may be an alternative to a hot pack.Trial registrationThis study was registered with University Hospital Medical Information Network in Japan (Registration No.: UMIN000048308. Registered on July 7, 2022).

Influence of in situ ettringite formation on the rheological properties of quartz suspensions

Cement suspensions are subject to hydration processes causing dissolution of cement clinker, precipitation of hydration products and changes in the ion content of the carrier liquid. These mechanisms take place in parallel and control the workability of cement suspensions. The precipitation of nano-granular ettringite is currently believed to be one of the key influencing factors for rheological properties of fresh cement suspensions. In order to quantify the effect of ettringite precipitation from other precipitation or dissolution processes onto the rheological behaviour, a model suspension consisting of quartz powder and in situ formed ettringite is used, enabled by implementing a new upscalable synthesis route of ettringite. The quantity of formed ettringite in the model suspension is varied and derived qualitatively from X-ray diffraction as well as quantitatively from inductively coupled plasma optical emission spectrometry and thermogravimetric analysis. The influence of the ettringite content on the rheological properties is determined and linked to the specific surface of the formed ettringite particles. This allows a quantification of the controlling mechanism of ettringite and the dependency of these mechanisms on particle properties. The correlation of the results to a reference suspension without ettringite verifies the statement of influence.

Biomolecular condensates in kidney physiology and disease.

The regulation and preservation of distinct intracellular and extracellular solute microenvironments is crucial for the maintenance of cellular homeostasis. In mammals, the kidneys control bodily salt and water homeostasis. Specifically, the urine-concentrating mechanism within the renal medulla causes fluctuations in extracellular osmolarity, which enables cells of the kidney to either conserve or eliminate water and electrolytes, depending on the balance between intake and loss. However, relatively little is known about the subcellular and molecular changes caused by such osmotic stresses. Advances have shown that many cells, including those of the kidney, rapidly (within seconds) and reversibly (within minutes) assemble membraneless, nano-to-microscale subcellular assemblies termed biomolecular condensates via the biophysical process of hyperosmotic phase separation (HOPS). Mechanistically, osmotic cell compression mediates changes in intracellular hydration, concentration and molecular crowding, rendering HOPS one of many related phase-separation phenomena. Osmotic stress causes numerous homo-multimeric proteins to condense, thereby affecting gene expression and cell survival. HOPS rapidly regulates specific cellular biochemical processes before appropriate protective or corrective action by broader stress response mechanisms can be initiated. Here, we broadly survey emerging evidence for, and the impact of, biomolecular condensates in nephrology, where initial concentration buffering by HOPS and its subsequent cellular escalation mechanisms are expected to have important implications for kidney physiology and disease.

Thirstiness, body hydration and thickened water: A study about their relationship

When liquids are thickened to swallow safely, thirstiness sensation might not be quenched. In this study, we investigated how drinking water, thickened water, or not drinking influences body hydration and thirstiness sensation. Forty-one healthy participants attended four 3 h sessions with different stimulus provided: nothing, water, thickened water A (gum-based thickener), or thickened water B (starch-based thickener). The hydration status (oral moisture and urinary osmolality), self-reported dimensions (thirst sensation, dry mouth sensation, and desire to drink), and hunger feeling were measured at 0, 90, and 180 min, respectively; after 180 min, water was administered ad libitum. The results show no significant changes in oral mucosa hydration over time. The urine osmolality values showed differences in body hydration depending on whether they had ingested water and on the type of thickened water (lower for thickener B). Thirstiness, dry mouth, and the desire to drink water after having the stimuli differed significantly from when no stimuli were given. Low liking was related to longer consumption time and more swallows, especially for thickened water B. At the end of the study, beyond the differences among three behavioral clusters, ad libitum water intake increased if no stimulus or thickened water B were administered. Hunger sensation varied over time, but not among stimuli. In conclusion, in the fast situation (no drink), thickened water helped maintain body hydration, although compared to water it were more disliked and, in comparison with water, right after their consumption did not decrease the dry mouth sensation. Therefore, although thickeners seem effective for hydrating and calming thirstiness, their poor liking needs to be improved in the design of dysphagia thickeners to improve their diet adherence.

Osmolytes Modulate Photoactivation of Phytochrome: Probing Protein Hydration.

Phytochromes are bistable red/far-red light-responsive photoreceptor proteins found in plants, fungi, and bacteria. Light-activation of the prototypical phytochrome Cph1 from the cyanobacterium Synechocystis sp. PCC 6803 allows photoisomerization of the bilin chromophore in the photosensory module and a subsequent series of intermediate states leading from the red absorbing Pr to the far-red-absorbing Pfr state. We show here via osmotic and hydrostatic pressure-based measurements that hydration of the photoreceptor modulates the photoconversion kinetics in a controlled manner. While small osmolytes like sucrose accelerate Pfr formation, large polymer osmolytes like PEG 4000 delay the formation of Pfr. Thus, we hypothesize that an influx of mobile water into the photosensory domain is necessary for proceeding to the Pfr state. We suggest that protein hydration changes are a molecular event that occurs during photoconversion to Pfr, in addition to light activation, ultrafast electric field changes, photoisomerization, proton release and uptake, and the major conformational change leading to signal transmission, or simultaneously with one of these events. Moreover, we discuss this finding in light of the use of Cph1-PGP as a hydration sensor, e.g., for the characterization of novel hydrogel biomaterials.

Combined Bipolar Radiofrequency and Non-Crosslinked Hyaluronic Acid Mesotherapy Protocol to Improve Skin Appearance and Epidermal Barrier Function: A Pilot Study.

Age-associated changes in epidermal hydration, pigmentation, thickness and cell renewal influence skin appearance and can lead to laxity, dryness and poor skin tone. The aim of this pilot study was to assess the synergistic effects of a new bipolar radiofrequency plus non-crosslinked hyaluronic acid (HA) mesotherapy protocol compared with radiofrequency alone on skin appearance and markers of epidermal function. This prospective, single-center, split-face pilot study recruited women aged 25-65 years with dryness and laxity of the facial skin defined by a trans-epidermal water loss (TEWL) value of ≥26 g/m2/h. Subjects were treated with a bipolar radiofrequency device on both sides of the face. This was immediately followed by needle hyaluronic acid (HA) treatment on one side of the face with 2.5 mL of a non-crosslinked HA. Photographic documentation, analysis of epidermal barrier function parameters, and high frequency (HF) ultrasound analysis were performed prior to treatment and at 28 days. Twenty female subjects with a mean age of 46 (range 29 to 54) years and dry and lax facial skin were included. TEWL was reduced and skin hydration improved to a greater extent with the combined radiofrequency plus mesotherapy protocol compared with radiofrequency alone (-5.8% vs. +3.9% and +23.1% vs. +1.0%, respectively). The combined protocol was also associated with greater improvements in melanin (-7.5% vs. -1.5%) and erythema values (-7.2% vs. +3.0%), respectively. Ultrasound measures of epidermal thickness and epidermal density were greater after the combined protocol compared with radiofrequency alone (12.0% vs. 5.6% and 57.7% vs. 7.1%, respectively). Both treatments were well-tolerated. The combined bipolar radiofrequency and HA mesotherapy protocol provided greater improvements in skin hydration, firmness and tone compared with radiofrequency alone. The combination treatment was also associated with greater epidermal thickness and density and increased keratinocyte differentiation suggesting a synergistic effect of both treatments on epidermal homeostasis and barrier function. Both treatments were well-tolerated and led to improvements in facial appearance.

Thermal modulation of skin friction at the finger pad

Preliminary human studies show that reduced skin temperature minimises the risk of mechanically induced skin damage. However, the mechanisms by which cooling enhances skin tolerance to pressure and shear remain poorly understood. We hypothesized that skin cooling below thermo-neutral conditions will decrease kinetic friction at the skin-material interface. To test our hypothesis, we measured the friction coefficient of a thermally pre-conditioned index finger pad sliding at a normal load (5N) across a plate maintained at three different temperatures (38, 24, and 16 °C) in 8 healthy young adults (29±5y). To quantify the temperature distribution of the skin tissue, we used 3D surface scanning and Optical Coherence Tomography to develop an anatomically representative thermal model of the finger. Our group-level data indicated that the sliding finger with thermally affected tissues (up to 8 mm depth) experienced significantly lower frictional forces (p<0.01) at plate temperatures of 16 °C (i.e. 32% decrease) and 24 °C (i.e. 13% decrease) than at 38 °C, respectively. This phenomenon occurred consistently across participants (i.e. N = 6/8, 75%) and without large changes in skin hydration during sliding. Our complementary experimental and theoretical results provide new insights into thermal modulation of skin friction that can be employed for developing thermal technologies to maintain skin integrity under mechanical loading and shearing.

In-Season Longitudinal Hydration/Body Cell Mass Ratio Changes in Elite Rugby Players.

Hydration status has a direct role in sports performance. Bioelectrical Impedance Vector Analysis (BIVA) and Urine Specific Gravity (USG) are commonly used to assess hydration. The study aims to identify the sensitivity and relationship between BIVA and USG in a field sports setting. BIVA and USG measurements were conducted five times throughout one rugby season. 34 elite male rugby players (25.1 ± 4.4 years; 184.0 ± 7.8 cm; 99.9 ± 13.4 kg) were enrolled. Differences over time were tested using one-way repeated measures ANOVA, and Bonferroni's post-hoc test was applied in pairwise comparisons. Resistance-reactance graphs and Hotelling's T2 test were used to characterize the sample and to identify bioelectrical changes. A repeated measures correlation test was conducted for BIVA-USG associations. Two clear trends were seen: (1) from July to September, there was a vector shortening and an increase of the phase angle (p < 0.001); and (2) from December to April, there was a vector lengthening and a decrease of the phase angle (p < 0.001). USG reported neither changes nor correlation with BIVA longitudinally (p > 0.05). Vector variations indicated a body fluid gain (especially in the intracellular compartment) and a body cell mass increase during the preseason, suggesting a physical condition and performance improvement. During the last months of the season, the kinetic was the opposite (fluid loss and decreased body cell mass). Results suggested that BIVA is sensitive to physiological changes and a better option than USG for assessing hydration changes during a rugby sports season.

Variations in the Protein Hydration and Hydrogen-Bond Network of Water Molecules Induced by the Changes in the Secondary Structures of Proteins Studied through Near-Infrared Spectroscopy.

This study investigated how the secondary structural changes of proteins in aqueous solutions affect their hydration and the hydrogen-bond network of water molecules using near-infrared (NIR) spectroscopy. The aqueous solutions of three types of proteins, i.e., ovalbumin, β-lactoglobulin, and bovine serum albumin, were denatured by heating, and changes in the NIR bands of water reflecting the states of hydrogen bonds induced via protein secondary structural changes were investigated. On heating, the intermolecular hydrogen bonds between water molecules as well as between water and protein molecules were broken, and protein molecules were no longer strongly bound by the surrounding water molecules. Consequently, the denaturation was observed to proceed depending on the thermodynamic properties of the proteins. When the aqueous solutions of proteins were cooled after denaturation, the hydrogen-bond network was reformed. However, the state of protein hydration was changed owing to the secondary structural changes of proteins, and the variation patterns were different depending on the protein species. These changes in protein hydration may be derived from the differences in the surface charges of proteins. The elucidation of the mechanism of protein hydration and the formation of the hydrogen-bond network of water molecules will afford a comprehensive understanding of the protein functioning and dysfunctioning derived from the structural changes in proteins.

Evaluation of Changes in Hydration and Body Cell Mass with Bioelectrical Impedance Analysis after Exercise Program for Rheumatoid Arthritis Patients.

Rheumatoid arthritis (RA) is a debilitating disease that can result in complications such as rheumatoid cachexia. While physical exercise has shown benefits for RA patients, its impact on hydration and body cell mass remains uncertain. The presence of pain, inflammation, and joint changes often restrict activity and make traditional body composition assessments unreliable due to altered hydration levels. Bioelectrical impedance is a commonly used method for estimating body composition, but it has limitations since it was primarily developed for the general population and does not consider changes in body composition. On the other hand, bioelectrical impedance vectorial analysis (BIVA) offers a more comprehensive approach. BIVA involves graphically interpreting resistance (R) and reactance (Xc), adjusted for height, to provide valuable information about hydration status and the integrity of the cell mass. Twelve women with RA were included in this study. At the beginning of the study, hydration and body cell mass measurements were obtained using the BIVA method. Subsequently, the patients participated in a six-month dynamic exercise program encompassing cardiovascular capacity, strength, and coordination training. To evaluate changes in hydration and body cell mass, the differences in the R and Xc parameters, adjusted for height, were compared using BIVA confidence software. The results showed notable changes: resistance decreased after the exercise program, while reactance increased. BIVA, as a classification method, can effectively categorize patients into dehydration, overhydration, normal, athlete, thin, cachectic, and obese categories. This makes it a valuable tool for assessing RA patients, as it provides information independent of body weight or prediction equations. Overall, the implementation of BIVA in this study shed light on the effects of the exercise program on hydration and body cell mass in RA patients. Its advantages lie in its ability to provide comprehensive information and overcome the limitations of traditional body composition assessment methods.

Investigating oil solubilization into nonionic micelles by Raman multivariate curve resolution

AbstractHydrophobic hydration, whereby water spontaneously structures around hydrophobic and amphiphilic molecules, plays a key role in the process of surfactant micelle formation and micellar oil solubilization. Using vibrational Raman multivariate curve resolution spectroscopy, we characterized changes in the hydrophobic hydration occurring within nonionic alkylphenol ethoxylate surfactant Tergitol NP‐12 micelles as a function of oil solubilization. We report trends in the changes of hydrophobic hydration depending on the chain length of the oil as well as the presence of a halogen atom in the oil chemical structure. Changes in hydrophobic hydration directly correlate to changes in the physical properties of the micellar solution, including cloud point and micelle hydrodynamic diameter. We compare hydrophobic hydration of Tergitol NP‐12 to nonionic linear alkyl ethoxylate surfactant Makon TD‐12 and ionic sodium dodecyl sulfate and observe similar trends; the molecular structure of the oil has the largest impact on the hydrophobic hydration. We believe these studies contribute to a fundamental understanding of the importance of hydrophobic hydration in surfactant and oil aggregates, especially as it relates to micellar oil solubilization, and provide insight into how the molecular solubilizate can impact micellar structure, size, and stability.

Water consumption patterns impact hydration markers in males working in accordance with the National Institute for Occupational Safety and Health recommendations

The impact of water consumption bolus volume and frequency on hydration biomarkers during work in the heat is unknown. In a randomized, crossover fashion, eight males consumed either 500 mL of water every 40 min or 237 mL of water every 20 min during 2 hr of continuous walking at 6.4 kph, 1.0% grade in a 34 °C/30% relative humidity environment, followed by 2 hr of rest. Hydration biomarkers and variables were assessed pre-work, post-work, and after the 2 hr recovery. There were no differences in body mass between trials at any time point (all p > 0.05). Percent change in plasma volume during work was not different when 237 mL of water was repeatedly consumed (−1.6 ± 8.2%) compared to 500 mL of water (−1.3 ± 3.0%, p = 0.92). Plasma osmolality was maintained over time (p = 0.55) with no difference between treatments (p = 0.21). When consuming 500 mL of water repeatedly, urine osmolality was lower at recovery (205 ± 108 mOsmo/L) compared to pre-work (589 ± 95 mOsmo/L, p < 0.01), different from repeatedly consuming 237 mL of water which maintained urine osmolality from pre-work (548 ± 144 mOsmo/L) through recovery (364 ± 261 mOsmo/L, p = 0.14). Free water clearance at recovery was greater with repeated consumption of 500 mL of water (1.2 ± 1.0 mL/min) compared to 237 mL of water (0.4 ± 0.8 mL/min, p = 0.02). Urine volume was not different between treatments post-work (p = 0.62), but greater after 2 hr of recovery when repeatedly consuming 500 mL of water compared to 237 mL (p = 0.01), leading to greater hydration efficiency upon recovery with repeated consumption of 237 mL of water (68 ± 12%) compared to 500 mL (63 ± 14%, p = 0.01). Thirst and total gastrointestinal symptom scores were not different between treatments at any time point (all p > 0.05). Body temperatures and heart rate were not different between treatments at any time point (all p > 0.05). Drinking larger, less frequent water boluses or drinking smaller, more frequent water boluses are both reasonable strategies to promote adequate hydration and limit changes in body mass in males completing heavy-intensity work in the heat.

Molecular insight on hydration of protein tyrosine phosphatase 1B and its complexes with ligands

Knowledge of hydration and the role of solvent in protein–ligand (P-L) binding is essential for rational drug design. In this direction, a complete description of P-L binding requires a clear understanding of the change in protein and ligand hydration states when they form a complex. In the present work, we investigated the 3D-hydration of protein tyrosine phosphatase 1B (PTP1B) in the unbound and bound states and changes in this process occurring upon the complex formation with 2HB1 and 2QBP inhibitors as an example. To this end, we have used a simplified version of the site density functional theory - the three-dimensional reference interaction site model. The obtained data indicate that both the ligands and PTP1B in unbound state are well-hydrated. Upon complex formation, the ligands experience significant dehydration, while the level of PTP1B hydration changes little. Moreover, the hydrated state of P-L complex remains practically the same as for liganded PTP1B itself. In this case, some of the waters are partly “collectivized” by the protein and the ligand, i.e., solvent molecules will be shared by PTP1B and 2HB1/2QBP. The active site pocket of the protein was also found to be well-hydrated. P–L binding results in partial dehydration of the pocket, which is connected with the displacement of part of the water from the pocket by the ligand. The results show the presence of two/seven waters inside the pocket for PTP1B-2HB1/2QBP. Location of the most tightly bound two/three waters in the PTP1B-2HB1/2QBP complex is coinsiding with the PDB data. Among tightly bound waters, only two molecules are “bridging” ones, i.e., forming simultaneously H-bonds with pocket residues and ligands. In addition, all possible H-bonds between the ligand, pocket amino acid residues and water are discussed for both complexes. The data obtained are necessary for understanding the molecular mechanisms of the PTP1B functioning and the creation of selective regulators of its activity.

The Physiology of Migraine and its Prevention by Nutrition

Migraine is a genetic condition associated with hypersensitive sensory neurons, more sensory neuronal connections, and different electrical properties than a non-migraine brain[1, 2]. Migraineurs waste 50% more sodium in their urine than typical subjects[3]. The most prominent migraine related genetic variants are associated with critical ionic channels that operate the brain’s electrical functions: action potential, resting potential, the delivery of neurotransmitters, and the resetting of membrane potential[4, 5]. Migraineurs’ brains are very sensitive to electrolyte imbalance as a result of channelopathy[6-8] and because of carbohydrate sensitivity. Migraineurs tend to end up with metabolic syndrome. In this paper I present case studies based on findings in a Facebook migraine group with over thirteen thousand migraine members, who have been able to abort and prevent all of their migraines while also tapering off of all of their migraine medications, by applying only nutritional and hydration changes.1. Ambrosini, A. and J. Schoenen, The electrophysiology of migraine. Curr Opin Neurol, 2003. 16(3): p. 327-31. 2. Tso, A.R., et al., The anterior insula shows heightened interictal intrinsic connectivity in migraine without aura. Neurology, 2015: p. 1043-50. 3. Campbell, D.A., E.M. Tonks, and K.M. Hay, An Investigation of the Salt and Water Balance in Migraine. British Medical Journal, 1951: p. 1424-1429. 4. Science, W.I.o. The Human Gene Database. GeneCards: The Human Gene Database 2017 [cited 2017 1/28/2017]; The Human Genome Database]. Available from: http://www.genecards.org . 5. Liu, H., et al., Resting state brain activity in patients with migraine: a magnetoencephalography study. The Journal of Headache and Pain, 2015. 16(1): p. 42. 6. Lee, J.-Y. and M. Kim, Current Issues in Migraine Genetics. J Clin Neurol, 2005. 1(1): p. 8-13. 7. Catterall, W.A., et al., Inherited Neuronal Ion Channelopathies: New Windows on Complex Neurological Diseases. The Journal of Neuroscience, 2008. 28(46): p. 11768-11777. 8. Longo, D.L., et al., Harrison's Manual of Medicine 18th Edition. 2013, New York: McGraw Hill Medical. Not funded This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Set-on-demand 3D Concrete Printing (3DCP) construction and potential outcome of shotcrete accelerators on its hardened properties

Set-on-demand 3D Concrete Printing (3DCP) construction is a new method of handling printable concrete mixes to reduce the pumping and transport issues of 3DCP. In this method, rapid stiffening of a flowable mix is achieved near the nozzle by the chemical intervention of the accelerators. The literature on the set-on-demand 3DCP and the effect of the accelerators on the hardened properties of printed concrete is limited. Keeping in view the literature gap, the first part of this study presents a brief overview of the material handling issues when stiff mixes are used for printing and discusses the opportunities offered by set-on-demand 3DCP to mitigate these issues. Then this study selects a shotcrete set accelerator as a case study to tune the rheology of a self-compacting mortar for a set-on-demand 3DCP process and investigates the effects on the hardened properties. The experimental results showed that the set accelerator improved the compressive and flexural properties by 290% and 233% on the first day of concrete age and then slightly reduced these properties at the later ages (3, 7, and 28 days). Shotcrete accelerator remarkably changed the hydration kinetics by modifying hydration phases and produced new profile peaks in the calorimetry test. The change of hydration was reflected in the ultrasonic pulse velocity and X-ray diffraction test results.

Nutritional Status of Coronary Artery Disease Patients-Preliminary Results.

Malnutrition is a condition that negatively impacts the clinical outcomes of numerous diseases. The aim of this study was to assess the nutritional status of coronary artery disease (CAD) patients and to investigate its relationship with the main clinical aspects of CAD. 50 CAD patients undergoing coronary angiography were enrolled in this study. The nutritional status assessment was based on Nutritional Risk Score 2002 (NRS 2002), body mass index (BMI), and bioelectrical impedance analysis (BIA) measurements. The analysis showed a moderate inverse correlation between NRS 2002 and BIA phase angle measured at 50 kHz (R: -0.31; p = 0.03) and Z200/5 parameter (R: 0.34; p = 0.02). The analysis of CAD clinical parameters showed a significant correlation between NRS 2002 and Canadian Cardiovascular Society (CCS) class (R: 0.37; p = 0.01). Left ventricle ejection fraction (LVEF) was correlated with BMI (R: 0.38; p = 0.02), however further BIA revealed hydration changes as LVEF was correlated to intracellular (ICF) and extracellular fluid (ECF) proportion: positively with ICF (R: 0.38; p = 0.02) and negatively with ECF (R: -0.39; p = 0.02). NRS 2002 and BIA are valuable tools for nutritional status assessment in CAD patients. Malnutrition is related to the severity of CAD symptoms, particularly in women. Maintaining proper nutritional status can have a potentially important role in this group of patients.

Quantitative evaluation of transdermal drug delivery patches on human skin with in vivo THz-TDS.

Transdermal drug delivery (TDD) has been widely used in medical treatments due to various advantages, including delivering drugs at a consistent rate. However, variations in skin hydration can have a significant effect on the permeability of chemicals. Therefore, it is essential to study the changes in skin hydration induced by TDD patches for better control of the delivery rate. In this work, in vivo terahertz (THz) spectroscopy is conducted to quantitatively monitor human skin after the application of patches with different backing materials and propylene glycol concentrations. Changes in skin hydration and skin response to occlusion induced by other patches are investigated and compared. Our work demonstrates the potential application of in vivo THz measurements in label-free, non-invasive evaluation of transdermal patches on human skin and further reveals the mechanism behind the effect.

The role of protein-membrane electrostatic interactions in the adaptive gating cycle of MscS.

Bacterial mechanosensitive channels MscS and MscL directly respond to tension in the cytoplasmic membrane. It appears not to be a coincidence that both channels are anchored to membrane lipids with positively charged residues primarily at the cytoplasmic interface of the inner membrane, leaving the periplasmic side of the barrel the freedom to move and tilt. The functional cycle of MscS involving opening ↔ closing and inactivation ↔ recovery transitions relies on two prominent anchors, R46 and R74, that reside at the level of cytoplasmic phosphates. WT MscS exhibits voltage-dependent inactivation and recovery, showing deeper inactivation and slower recovery under depolarizing voltages (+60 mV) compared to hyperpolarizations (−60 mV). Substitutions of both R46 and R74 with poor interfacial anchors (A or D) result in no expression, whereas G, I, L, or V substitutions express but produce non-functional channels. Patch-clamp experiments showed that polar substitutions in positions 46 and 74, which maintain H-bonding capability to lipid phosphate groups (N, Q, S), preserve expression, activation, voltage-dependence of inactivation and recovery, as well as osmotic rescuing. Aromatic (W, Y) substitutions produce channels that completely lack voltage sensitivity of inactivation and recovery, but are otherwise functional. Insertion of periplasmic anchors (R or W) in flexible N-terminal segments (positions 3-21) did not produce strong phenotypes, however, the A22R substitution, which faces outer-leaflet phosphates, abolishes inactivation without affecting opening. These data show that the inactivation and recovery transitions are sensitive to the polarity of the cytoplasmic ends of TM1 and TM2 and are likely associated with the change of hydration near these segments which can be altered by voltage. The insertion of a periplasmic anchor (R22) restrains the position of the TM1-TM2 pair of helices, which require a higher degree of freedom during inactivation.

Deadly acceleration in dehydration of Eucalyptus viminalis leaves coincides with high-order vein cavitation.

Xylem cavitation during drought is proposed as a major driver of canopy collapse, but the mechanistic link between hydraulic failure and leaf damage in trees is still uncertain. Here, we used the tree species manna gum (Eucalyptus viminalis) to explore the connection between xylem dysfunction and lethal desiccation in leaves. Cavitation damage to leaf xylem could theoretically trigger lethal desiccation of tissues by severing water supply under scenarios such as runaway xylem cavitation, or the local failure of terminal parts of the leaf vein network. To investigate the role of xylem failure in leaf death, we compared the timing of damage to the photosynthetic machinery (Fv/Fm decline) with changes in plant hydration and xylem cavitation during imposed water stress. The water potential at which Fv/Fm was observed to decline corresponded to the water potential marking a transition from slow to very rapid tissue dehydration. Both events also occurred simultaneously with the initiation of cavitation in leaf high-order veins (HOV, veins from the third order above) and the analytically derived point of leaf runaway hydraulic failure. The close synchrony between xylem dysfunction and the photosynthetic damage strongly points to water supply disruption as the trigger for desiccation of leaves in this hardy evergreen tree. These results indicate that runaway cavitation, possibly triggered by HOV network failure, is the tipping agent determining the vulnerability of E. viminalis leaves to damage during drought and suggest that HOV cavitation and runaway hydraulic failure may play a general role in determining canopy damage in plants.

Potential of mean force conformational energy maps for disaccharide linkages of the Burkholderia multivorans exopolysaccharide C1576 in aqueous solution

Potential of Mean Force Ramachandran energy maps in aqueous solution have been prepared for all of the glycosidic linkages found in the C1576 exopolysaccharide from the biofilms of the bacterial species Burkholderia multivorans, a member of the Burkholderia cepacian complex that was isolated from a cystic fibrosis patient. C1576 is a rhamnomannan with a tetrasaccharide repeat unit. In general, for the four linkage types in this polymer, hydration did not produce dramatic changes in the Ramachandran energy surfaces, with the 3-methyl-α-d-rhamnopyranose-(1→3)-α-d-rhamnopyranose case exhibiting the greatest hydration change, with the global minimum energy conformation shifting by more than 80° in ψ. However, hydration did reduce the rigidity of all the linkages, increasing the overall flexibility of this polysaccharide.