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Progress in Retinal and Eye Research Mar 2022Hyperosmotic tear stimulates human corneal nerve endings, activates ocular immune response, and elicits dry-eye symptoms. A soft contact lens (SCL) covers the cornea... (Review)
Review
Hyperosmotic tear stimulates human corneal nerve endings, activates ocular immune response, and elicits dry-eye symptoms. A soft contact lens (SCL) covers the cornea preventing it from experiencing direct tear evaporation and the resulting blink-periodic salinity increases. For the cornea to experience hyperosmolarity due to tear evaporation, salt must transport across the SCL to the post-lens tear film (PoLTF) bathing the cornea. Consequently, limited salt transport across a SCL potentially protects the ocular surface from hyperosmotic tear. In addition, despite lens-wear discomfort sharing common sensations to dry eye, no correlation is available between measured tear hyperosmolarity and SCL-wear discomfort. Lack of documentation is likely because clinical measurements of tear osmolarity during lens wear do not interrogate the tear osmolarity of the PoLTF that actually overlays the cornea. Rather, tear osmolarity is clinically measured in the tear meniscus. For the first time, we mathematically quantify tear osmolarity in the PoLTF and show that it differs significantly from the clinically measured tear-meniscus osmolarity. We show further that aqueous-deficient dry eye and evaporative dry eye both exacerbate the hyperosmolarity of the PoLTF. Nevertheless, depending on lens salt-transport properties (i.e., diffusivity, partition coefficient, and thickness), a SCL can indeed protect against corneal hyperosmolarity by reducing PoLTF salinity to below that of the ocular surface during no-lens wear. Importantly, PoLTF osmolarity for dry-eye patients can be reduced to that of normal eyes with no-lens wear provided that the lens exhibits a low lens-salt diffusivity. Infrequent blinking increases PoLTF osmolarity consistent with lens-wear discomfort. Judicious design of SCL material salt-transport properties can ameliorate corneal hyperosmolarity. Our results confirm the importance of PoLTF osmolarity during SCL wear and indicate a possible relation between PoLTF osmolarity and contact-lens discomfort.
Topics: Blinking; Contact Lenses, Hydrophilic; Cornea; Dry Eye Syndromes; Humans; Osmolar Concentration; Tears
PubMed: 34597771
DOI: 10.1016/j.preteyeres.2021.101012 -
International Journal of Molecular... Oct 2020Abiotic stresses cause plant growth inhibition, damage, and in the most severe cases, cell death, resulting in major crop yield losses worldwide. Many abiotic stresses...
Abiotic stresses cause plant growth inhibition, damage, and in the most severe cases, cell death, resulting in major crop yield losses worldwide. Many abiotic stresses lead also to oxidative stress. Recent genetic and genomics studies have revealed highly complex and integrated gene networks which are responsible for stress adaptation. Here we summarize the main findings of the papers published in the Special Issue "ROS and Abiotic Stress in Plants", providing a global picture of the link between reactive oxygen species and various abiotic stresses such as acid toxicity, drought, heat, heavy metals, osmotic stress, oxidative stress, and salinity.
Topics: Droughts; Metals, Heavy; Osmotic Pressure; Plant Development; Plant Physiological Phenomena; Plants; Reactive Oxygen Species; Salinity; Stress, Physiological
PubMed: 33050128
DOI: 10.3390/ijms21207433 -
Investigative Ophthalmology & Visual... Feb 2021Aquaporins (AQPs) facilitate transmembrane osmotic water transport and may play a role in iris fluid conductivity, which is implicated in the pathophysiology of...
PURPOSE
Aquaporins (AQPs) facilitate transmembrane osmotic water transport and may play a role in iris fluid conductivity, which is implicated in the pathophysiology of glaucoma. In this study, we compared the iris expression of AQPs and aqueous osmolality between primary angle closure glaucoma (PACG), primary open-angle glaucoma (POAG), and nonglaucoma eyes.
METHODS
AQP1-5 transcripts from a cohort of 36 PACG, 34 POAG and 26 nonglaucoma irises were measured by quantitative real-time PCR. Osmolality of aqueous humor from another cohort of 49 PACG, 50 POAG, and 50 nonglaucoma eyes were measured using an osmometer. The localization of AQP1 in both glaucoma and nonglaucoma irises was determined by immunofluorescent analysis.
RESULTS
Of the five AQP genes evaluated, AQP1 and AQP2 transcripts were significantly upregulated in both PACG (3.48- and 8.07-fold, respectively) and POAG (3.12- and 11.58-fold, respectively) irises relative to nonglaucoma counterparts. The aqueous osmolalities of PACG (303.68 mmol/kg) and POAG (300.79 mmol/kg) eyes were significantly lower compared to nonglaucoma eyes (312.6 mmol/kg). There was no significant difference in expression of AQP transcripts or aqueous osmolality between PACG and POAG eyes.
CONCLUSIONS
PACG and POAG eyes featured significant increase in AQP1 and AQP2 expression in the iris and reduced aqueous osmolality compared to nonglaucoma eyes. These findings suggest that the iris may be involved in altered aqueous humor dynamics in glaucoma pathophysiology. Because PACG did not differ from POAG in both properties studied, it is likely that they are common to glaucoma disease in general.
Topics: Adult; Aged; Aquaporin 2; Aqueous Humor; Blotting, Western; Female; Gene Expression Regulation; Glaucoma, Angle-Closure; Glaucoma, Open-Angle; Humans; Intraocular Pressure; Male; Middle Aged; Osmolar Concentration; RNA
PubMed: 33616622
DOI: 10.1167/iovs.62.2.34 -
Age and Ageing Oct 2023Hydration is a fundamental aspect of clinical practice and yet it is an under-researched topic, particularly in older people, leading to many areas of uncertainty. There...
Hydration is a fundamental aspect of clinical practice and yet it is an under-researched topic, particularly in older people, leading to many areas of uncertainty. There are two types of dehydration; hypertonic, which is a water deficit, and isotonic, which is a deficit of both water and salt. Individual clinical signs and bedside tests are poor diagnostic tools, making dehydration difficult to identify. However, the diagnostic value of a holistic clinical approach is not known. The gold-standard clinical test for dehydration is serum osmolality, but this cannot diagnose isotonic dehydration and may delay diagnosis in acute situations. Salivary osmolality point-of-care testing is a promising and rapid new diagnostic test capable of detecting both hypertonic and isotonic dehydration in older people, but further evidence to support its clinical utility is needed. Daily fluid requirements may be less than previously thought in adults, but the evidence specific to older people remains limited. Hydration via the subcutaneous route is safer and easier to initiate than the intravenous route but is limited by infusion speed and volume. Prompting older adults more frequently to drink, offering a wider selection of drinks and using drinking vessels with particular features can result in small increases in oral intake in the short-term. The ongoing clinically-assisted hydration at end of life (CHELsea II) trial will hopefully provide more evidence for the emotive issue of hydration at the end of life.
Topics: Humans; Aged; Dehydration; Water; Osmolar Concentration; Death
PubMed: 37847795
DOI: 10.1093/ageing/afad193 -
Channels (Austin, Tex.) Dec 2020TRPC3 is a Ca-permeable cation channel commonly activated by the G-protein coupled receptors (GPCR) and mechanical distortion of the plasma membrane. TRPC3-mediated Ca... (Review)
Review
TRPC3 is a Ca-permeable cation channel commonly activated by the G-protein coupled receptors (GPCR) and mechanical distortion of the plasma membrane. TRPC3-mediated Ca influx has been implicated in a variety of signaling processes in both excitable and non-excitable cells. Kidneys play a commanding role in maintaining whole-body homeostasis and setting blood pressure. TRPC3 is expressed abundantly in the renal vasculature and in epithelial cells, where it is well positioned to mediate signaling and transport functions in response to GPCR-dependent endocrine stimuli. In addition, TRPC3 could be activated by mechanical forces resulting from dynamic changes in the renal tubule fluid flow and osmolarity. This review critically analyzes the available published evidence of the physiological roles of TRPC3 in different parts of the kidney and describes the pathophysiological ramifications of TRPC3 ablation. We also speculate how this evidence could be further translated into the clinic.
Topics: Animals; Calcium; Humans; Kidney; Osmolar Concentration; Signal Transduction; TRPC Cation Channels
PubMed: 32787494
DOI: 10.1080/19336950.2020.1804153 -
PloS One 2024Urine osmolality is used throughout research to determine hydration levels. Prior studies have found black individuals to have elevated urine creatinine and osmolality,... (Observational Study)
Observational Study
Urine osmolality is used throughout research to determine hydration levels. Prior studies have found black individuals to have elevated urine creatinine and osmolality, but it remains unclear which factors explain these findings. This cross-sectional, observational study sought to understand the relationship of self-reported race to urine creatinine and urine osmolality after accounting for age, socioeconomic status, and fluid intake. Data from 1,386 participants of the 2009-2012 National Health and Nutrition Examination Survey were utilized. Age, poverty-to-income ratio (PIR), urine flow rate (UFR), fluid intake, estimated lean body mass (LBM), urine creatinine, and urine osmolality were measured. In a sex-specific manner, black and white participants were matched on age, dietary moisture, UFR, and PIR. Urine creatinine was greater in black men (171 mg/dL) than white men (150 mg/dL) and greater in black women (147 mg/dL) than white women (108 mg/dL) (p < .001). Similarly, urine osmolality was greater in black women than white women (723 vs. 656 mOsm/kg, p = .001), but no difference was observed between white and black men (737 vs. 731 mOsm/kg, p = .417). Estimated LBM was greater in black men (61.8 kg) and women (45.5 kg) than in white men (58.9 kg) and women (42.2 kg) (p≤.001). The strongest correlate of urine osmolality in all race-sex groups was urine creatinine (Spearman ρ = .68-.75). These results affirm that individuals identifying as black produce higher urine creatinine concentrations and, in women, higher urine osmolality after matching for age, fluid intake, and socioeconomic status. The findings suggest caution when comparing urine hydration markers between racial groups.
Topics: Humans; Female; Male; Creatinine; Osmolar Concentration; White People; Adult; Middle Aged; Black or African American; Cross-Sectional Studies; Social Class; Nutrition Surveys; Aged; Age Factors; Drinking
PubMed: 38820483
DOI: 10.1371/journal.pone.0304803 -
Nature Jul 2022To impart directionality to the motions of a molecular mechanism, one must overcome the random thermal forces that are ubiquitous on such small scales and in liquid...
To impart directionality to the motions of a molecular mechanism, one must overcome the random thermal forces that are ubiquitous on such small scales and in liquid solution at ambient temperature. In equilibrium without energy supply, directional motion cannot be sustained without violating the laws of thermodynamics. Under conditions away from thermodynamic equilibrium, directional motion may be achieved within the framework of Brownian ratchets, which are diffusive mechanisms that have broken inversion symmetry. Ratcheting is thought to underpin the function of many natural biological motors, such as the FF-ATPase, and it has been demonstrated experimentally in synthetic microscale systems (for example, to our knowledge, first in ref. ) and also in artificial molecular motors created by organic chemical synthesis. DNA nanotechnology has yielded a variety of nanoscale mechanisms, including pivots, hinges, crank sliders and rotary systems, which can adopt different configurations, for example, triggered by strand-displacement reactions or by changing environmental parameters such as pH, ionic strength, temperature, external fields and by coupling their motions to those of natural motor proteins. This previous work and considering low-Reynolds-number dynamics and inherent stochasticity led us to develop a nanoscale rotary motor built from DNA origami that is driven by ratcheting and whose mechanical capabilities approach those of biological motors such as FF-ATPase.
Topics: DNA; Facilitated Diffusion; Hydrogen-Ion Concentration; Molecular Motor Proteins; Motion; Movement; Osmolar Concentration; Proton-Translocating ATPases; Stochastic Processes; Temperature; Thermodynamics
PubMed: 35859200
DOI: 10.1038/s41586-022-04910-y -
Andrology Jan 2022Terminally differentiated mammalian sperm are exposed to gradients of viscosity, pH, and osmolality both in the male and female reproductive tract during their perilous... (Review)
Review
BACKGROUND
Terminally differentiated mammalian sperm are exposed to gradients of viscosity, pH, and osmolality both in the male and female reproductive tract during their perilous journey to quest the ovum. The complex physicochemical factors play an integral role in preparing sperm for the fertilization process.
OBJECTIVES
To elucidate the influence of the reproductive tract microenvironment especially viscosity, pH, and osmolality in regulating sperm functional and fertilization competence.
MATERIALS AND METHODS
The data used in this review were collected from the research papers and online databases focusing on the influence of viscosity, pH, and osmolality on sperm function.
DISCUSSION
The gradients of viscosity, pH, and osmolality exist across various segments of the male and female reproductive tract. The changes in the viscosity create a physical barrier, pH aid in capacitation and hyperactivation, and the osmotic stress selects a progressive sperm subpopulation for accomplishing fertilization. The sperm function tests are developed based on the concept that the male genotype is the major contributor to the reproductive outcome. However, recent studies demonstrate the significance of sperm genotype-environment interactions that are essentially contributing to reproductive success. Hence, it is imperative to assess the impact of physicochemical stresses and the adaptive ability of the terminally differentiated sperm, which in turn would improve the outcome of the assisted reproductive technologies and male fertility assessment.
CONCLUSION
Elucidating the influence of the reproductive tract microenvironment on sperm function provides newer insights into the procedures that need to be adopted for selecting fertile males for breeding, and ejaculates for the assisted reproductive technologies.
Topics: Animals; Cellular Microenvironment; Female; Fertility; Genitalia; Humans; Hydrogen-Ion Concentration; Male; Osmolar Concentration; Sperm-Ovum Interactions; Spermatozoa; Viscosity
PubMed: 34420258
DOI: 10.1111/andr.13102 -
ELife Nov 2021Two neural circuits control the release of vasopressin in response to eating and drinking before there are any detectable changes in blood water levels.
Two neural circuits control the release of vasopressin in response to eating and drinking before there are any detectable changes in blood water levels.
Topics: Drinking; Osmolar Concentration; Water
PubMed: 34792465
DOI: 10.7554/eLife.74551 -
JBRA Assisted Reproduction Mar 2023The objective of our study was to compare the osmolality in sequential and single step culture media, used for in vitro human embryo culture, covered with mineral oil... (Observational Study)
Observational Study
OBJECTIVE
The objective of our study was to compare the osmolality in sequential and single step culture media, used for in vitro human embryo culture, covered with mineral oil and paraffin, in dry and humid incubators.
METHODS
We performed a prospective observational study. A total of 120 Petri dishes, with 960 droplets of culture media, were evaluated. Each dish was prepared with 4 droplets of single step medium and sequential medium. Sixty dishes were covered with mineral oil and 60 with paraffin oil. Half were incubated in a dry incubator and half in a humid. Osmolality was measured on days 1, 3, 5, 7. ANOVA test was performed for statistical analysis.
RESULTS
Osmolality results for single step and sequential medium, that were covered with both mineral and paraffin oil and placed in the dry incubator, significantly increased throughout the study time (D7>D5>D3). In the humid incubator, the results were similar for all periods. Osmolality was significantly lower in humid incubator, in all periods, when droplets were covered with both oils. When both culture media were placed in the humid incubator, no variation was detected, using both oils. However, when single step medium was placed in the dry incubator, covered with mineral oil, we observed a higher osmolality than the covered with paraffin oil.
CONCLUSIONS
TWe can conclude that humid incubator is better for maintaining osmolality and paraffin oil protect single step media from evaporation in dry incubator.
Topics: Humans; Mineral Oil; Embryo Culture Techniques; Reproductive Techniques, Assisted; Oils; Osmolar Concentration; Culture Media; Fertilization in Vitro
PubMed: 35389044
DOI: 10.5935/1518-0557.20210123