Changes In Osmolality Research Articles

An update review on hemodynamic instability in renal replacement therapy patients.

Hemodynamic instability in patients undergoing kidney replacement therapy (KRT) is one of the most common and essential factors influencing mortality, morbidity, and the quality of life in this patient population. Decreased cardiac preload, reduced systemic vascular resistance, redistribution of fluids, fluid overload, inflammatory factors, and changes in plasma osmolality have all been implicated in the pathophysiology of hemodynamic instability associated with KRT. A cascade of these detrimental mechanisms may ultimately cause intra-dialytic hypotension, reduced tissue perfusion, and impaired kidney rehabilitation. Multiple parameters, including dialysate composition, temperature, posture during dialysis sessions, physical activity, fluid administrations, dialysis timing, and specific pharmacologic agents, have been studied as possible management modalities. Nevertheless, a clear consensus is not reached. This review includes a thorough investigation of the literature on hemodynamic instability in KRT patients, providing insight on interventions that may potentially minimize factors leading to hemodynamic instability.

Postpartum Hypernatremia with Extrapontine Rhabdomyelinolysis: A Case Report.

Hypernatremia (serum sodium>160 meq/L) present with diverse neurological manifestations, ranging from flaccid paralysis to impaired cognition, encephalopathy, and even deep coma. Osmotic demyelination refers to changes in brain cells because of an acute change in plasma osmolality. It is further divided into two types, i.e., central pontine myelinolysis (CPM) and extrapontine myelinolysis (EPM). Patients with EPM, besides spasticity, may also present with other movement disorders such as catatonia, parkinsonism, and dystonia. We present a case of a postpartum woman bought to the emergency department by her relatives in an unconscious state. In view of poor sensorium (Glasgow coma scale < 7), she was intubated and received mechanical ventilatory support. On admission, computed tomography ofthebrain was normal, and the patient was transferred to the intensive care unit (ICU) for further management. The preliminary work-up in the ICU showed hypernatremia (serum sodium of 182 mEq/L) with hyper-osmolality (359 mOsm/kgH2O). She was managed as per the ICU protocol for hypernatremia. During her ICU stay, her sensorium improved, but she developed flaccid paralysis and was quadriplegic. Thus, a tracheostomy was performed, and she was weaned from the ventilator. After ventilator weaning, she was transferred to the ward for further rehabilitation. During rehabilitation, the patient was able to sit and takefoodorally.To date, only a few cases are reported in postpartum women with acute severe hypernatremia caused by high-grade fever and loss of body fluids leading to extra-pontine demyelination and flaccid paralysis. This case highlightsthat prompt recognition and appropriate intervention can improve the outcomes in these patients.

Feedback linking cell envelope stiffness, curvature, and synthesis enables robust rod-shaped bacterial growth

Bacterial growth is remarkably robust to environmental fluctuations, yet the mechanisms of growth-rate homeostasis are poorly understood. Here, we combine theory and experiment to infer mechanisms by which Escherichia coli adapts its growth rate in response to changes in osmolarity, a fundamental physicochemical property of the environment. The central tenet of our theoretical model is that cell-envelope expansion is only sensitive to local information, such as enzyme concentrations, cell-envelope curvature, and mechanical strain in the envelope. We constrained this model with quantitative measurements of the dynamics of E. coli elongation rate and cell width after hyperosmotic shock. Our analysis demonstrated that adaptive cell-envelope softening is a key process underlying growth-rate homeostasis. Furthermore, our model correctly predicted that softening does not occur above a critical hyperosmotic shock magnitude and precisely recapitulated the elongation-rate dynamics in response to shocks with magnitude larger than this threshold. Finally, we found that, to coordinately achieve growth-rate and cell-width homeostasis, cells employ direct feedback between cell-envelope curvature and envelope expansion. In sum, our analysis points to cellular mechanisms of bacterial growth-rate homeostasis and provides a practical theoretical framework for understanding this process.

Effect of Lactate Minimum Speed-Guided Conditioning on Selected Blood Parameters of Horses

During exercise, equines can suffer severe water and electrolyte imbalances depending on the intensity and duration. In this sense, conditioning aims to promote adaptations to the organism in order to maintain cardiovascular and thermoregulatory stability during exertion. This study aimed to evaluate the effect of conditioning guided by lactate minimum speed (LMS) test on the blood osmolality of horses. We hypothesized that after conditioning the blood osmolality would vary less during exercise and that LMS could be used in equine conditioning program. Ten Arabian horses were evaluated before (ET 1) and after (ET 2) 6 weeks of conditioning. The conditioning intensity was established from the LMS during ET 1. The blood was obtained at rest and during the ETs. An increase in LMS and a decrease in lactate were seen in individual horses; however, these differences were not significant at a group level. No change in blood osmolality was observed when comparing the ETs. The plasma volume remained unchanged in ET 2. The conditioning guided by LMS improved the animals’ fitness, which was evidenced by the lower lactate production in ET 2. The fact that the osmolality kept unchanged proves the effectiveness of the osmotic blood balance during exercise, as its control involves the interaction of different systems. Body adaptations occurred with conditioning, providing greater homeostasis control since the plasma volume remained stable in ET 2. It was concluded that the LMS test can be used to define an effective equine conditioning program even though some adjustments are still necessary.

Extend the Survival of Human Sperm In Vitro in Non-Freezing Conditions: Damage Mechanisms, Preservation Technologies, and Clinical Applications.

Preservation of human spermatozoa in vitro at normothermia or hypothermia maintaining their functions and fertility for several days plays a significant role in reproductive biology and medicine. However, it is well known that human spermatozoa left in vitro deteriorate over time irreversibly as the consequence of various stresses such as the change of osmolarity, energy deficiency, and oxidative damage, leading to substantial limitations including the need for semen examinations, fertility preservation, and assisted reproductive technology. These problems may be addressed with the aid of non-freezing storage techniques. The main and most effective preservation strategies are the partial or total replacement of seminal plasma with culture medium, named as extenders, and temperature-induced metabolic restriction. Semen extenders consist of buffers, osmolytes, and antioxidants, etc. to protect spermatozoa against the above-mentioned adverse factors. Extended preservation of human spermatozoa in vitro has a negative effect on sperm parameters, whereas its effect on ART outcomes remains inconsistent. The storage duration, temperature, and pre-treatment of semen should be determined according to the aims of preservation. Advanced techniques such as nanotechnology and omics have been introduced and show great potential in the lifespan extension of human sperm. It is certain that more patients will benefit from it in the near future. This review provided an overview of the current knowledge and prospects of prolonged non-freezing storage of human sperm in vitro.

Dicarbonyl/L-xylulose reductase (DCXR) producing xylitol regulates egg retention through osmolality control in Caenorhabditis elegans

ABSTRACT To support life, the osmolality of the cellular fluid is tightly regulated by various means, including osmolyte control. Dicarbonyl/L-xylulose reductase (DCXR) is a highly conserved enzyme reducing L-xylulose to xylitol, which serves as an effective osmolyte in various mammalian and human tissues such as lung epithelium, sperm, and lens. DHS-21 is the only DCXR ortholog in Caenorhabditis elegans, and DCXR null mutant worms accumulate eggs in the uterus. However, it has been unknown how and why the mutant worms impair egg retention. In this study, we tested whether the egg-retention in dhs-21 (jh129), the DCXR null mutant worm, is sensitive to changes in osmolarity. Low osmolality reverted the egg retention phenotype of dhs-21(jh129), while high osmolarity aggravated it. Also, knock-down of either one of osr-1, osm-7, or osm-11, osmoregulatory genes, also rescued egg-retention phenotypes of the null mutants. The study indicates that DCXR functions in fluid homeostasis by regulating cellular osmolality in C. elegans and provides insights into DCXR-involved clinical conditions, such as congenital cataracts and malfunctioning lung and kidney.

The effects of feeding and transport length on the welfare of white rhinoceroses (Ceratotherium simum simum) during long-distance translocations: a preliminary study.

Translocation is a valuable conservation tool, but poses significant risks for the transported rhinoceroses. Interventions reducing these risks are required to ensure positive welfare during transportation. The aim of this study was to evaluate the effect of journey duration and feeding during the transport of white rhinoceroses (Ceratotherium simum simum). A total of 32 animals were transported by road during two events, five days apart. Fifteen rhinoceroses in the first transport event (37.0 ± 2.4 hr duration) were not fed, while 17 rhinoceroses in the second event (32.2 ± 1.5 hr duration) were offered lucerne. Blood samples were collected at capture and after transport for the evaluation of changes in serum clinical chemistry analytes. The Wilcoxon rank-sum test was used to compare differences between the groups. In all rhinoceroses, transport resulted in changes in serum electrolyte, metabolite and enzyme concentrations, indicating a loss in total body water, nutritional shifts, stress and fatigue. Fed rhinoceroses, transported over a shorter time, displayed greater changes in osmolality (p < 0.006), serum sodium and chloride concentrations (p = 0.005 and = 0.001, respectively) indicating a greater degree of total body water loss than non-fed rhinoceroses. Feeding and a shorter transport duration reduced, but did not prevent, nutritional challenges. A greater increase in the muscle enzymes CK and AST (p = 0.027 and = 0.001, respectively), indicated greater fatigue in non-fed rhinoceroses transported over a longer time. Further work to distinguish the effects of feeding and journey duration is required to better understand the role feeding may play in mitigating welfare challenges during rhinoceros translocation.

Changes in the expression of certain osmosensitive channel and transporter genes in primary hepatocytes of air-breathing catfish, Clarias magur: A strategy to adapt under osmotic stress

Environmental salinity/osmolarity is an important abiotic ecological factor that affects several metabolic activities of aquatic organisms. Air-breathing magur catfish (Clarias magur) frequently encounter a wide range of external osmolarity changes in their natural habitats as well as internal osmolarity due to the absorption of amino acids and other metabolites through the intestine. The major objective of the present investigation was to demonstrate the influences of anisotonicity exposure on the expression of certain isoforms of aquaporin (AQP) channels (aqp7, 8, and 11), taurine transporter (TauT, slc6a6), urea transporter (UT1, slc14a1) and Na+-K+-ATPase (NKA, atp1a1, and atp1b1) transporter genes, and their translated protein products in the primary hepatocytes of magur catfish. These genes are known to play major roles in cellular volume regulation and water homeostasis under osmotic stress. Exposure of primary hepatocytes to hypertonic medium (+40 mOsmol/L) for a period of 48 h resulted in a significant increase in the expression of aqp7, aqp8, aqp11, slc6a6, slc14a1, atp1a1, and atp1b1 genes, as evidenced by a rise in the levels of both mRNAs of all the above-mentioned genes, and also their translated protein products compared to isotonic controls. However, exposure of primary hepatocytes to hypotonic medium (_40 mOsmol/L) for the same period led to a significant decrease in mRNA levels for aqp7, aqp8, aqp11, slc6a6, and slc14a1 genes, and also their translated protein products compared to isotonic controls as a consequence of downregulation of corresponding genes. Interestingly, NKA enzyme activity in primary hepatocytes was found to increase significantly after exposure to both hypertonic and hypotonic media. Hypertonicity induced the genes for α- and β-subunits of this enzyme both at transcriptional and translational levels. In contrast, hypotonicity induced only the atp1a1 gene and the expression of corresponding translated protein without causing any changes in the expression of the atp1b1 gene. Thus, it may be contemplated that osmotic stress, which results due to anisotonicity of the external environment or in the body fluids, leads to differential expression of different osmosensitive channels such as AQPs, and transporters such as TauT, UT1, UT2, and NKA in hepatic cells of magur catfish and work in coordination to defend the osmotically-induced changes of cellular volume. These regulatory responses of channels and transporters could be one of the vital molecular mechanisms that may have evolved in this catfish to defend against the osmotically-induced stresses.

Amyloid [Formula: see text] (1-42) peptide impairs mitochondrial respiration in primary human brain microvascular endothelial cells: impact of dysglycemia and pre-senescence.

Diabetes increases the risk of Alzheimer's disease (AD). We investigated the impact of glucose concentrations on the β-amyloid (Aβ)-induced alteration of mitochondrial/cellular energetics in primary human brain microvascular endothelial cells (HBMECs). HBMECs were grown and passaged in media containing 15mmol/l glucose (normal) based on which the glucose levels in the media were designated as high (25mmol/L) or low (5mmol/L). HBMECs were treated with Aβ (1-42) (5µmol/l) or a scrambled peptide for 24h and mitochondrial respiratory parameters were measured using Seahorse Mito Stress Test. Aβ (1-42) decreased the mitochondrial ATP production at normal glucose levels and decreased spare respiratory capacity at high glucose levels. Aβ (1-42) diminished all mitochondrial respiratory parameters markedly at low glucose levels that were not completely recovered by restoring normal glucose levels in the media. The addition of mannitol (10mmol/l) to low and normal glucose-containing media altered the Aβ (1-42)-induced bioenergetic defects. Even at normal glucose levels, pre-senescent HMBECs (passage 15) displayed greater Aβ (1-42)-induced mitochondrial respiratory impairments than young cells (passages 7-9). Thus, hypoglycemia, osmolarity changes, and senescence are stronger instigators of Aβ (1-42)-induced mitochondrial respiration and energetics in HBMECs and contributors to diabetes-related increased AD risk than hyperglycemia.

Efficacy of hypertonic saline in treatment of corneal edema: A randomized crossover trial

BackgroundTo determine the efficacy of sodium chloride (NaCl) 5% drops in comparison to 6% ointment and study tear Osmolarity as an objective measure correlating with clinical findings in the treatment of corneal edema. MethodsThis is a prospective, randomized, interventional, open-label, crossover study of 40 eyes of 40 patients with corneal edema due to Bullous keratopathy and Fuchs endothelial dystrophy. Subjects were divided into 2 groups by simple randomization: group A received NaCl 5% drops and group B received NaCl 6% ointment. Both treatments were administered four times daily for seven days. Subsequently, after a 1-week wash-out period, switch over of treatment was done. Central corneal thickness (CCT) and tear osmolarity were primarily efficacy variables. ResultsBaseline parameters were comparable. The median reduction in CCT from baseline (706.7 ± 58.41 μm), at 6 hours with NaCl 5% drops was 23 μm (-27, 74) and that with NaCl6% ointment was 37.5 μm (-7, 85). The reduction in CCT was more with 6% ointment (p = 0.013). The difference in reduction in CCT between two treatments at one week was not statistically significant, although there was a substantial reduction in thickness with each treatment individually. The change in tear osmolarity from the baseline at 2 Hours with both NaCl5% drops and 6% ointment was significant, and it remained so till 6 h. Side-effects such as stickiness, stinginess, blurring, and foreign body sensation were more with 6% eye ointment. ConclusionTopical NaCl 6% eye ointment in QID dosage is more effective than NaCl 5% drops in the medical management of corneal edema. In patients symptomatically intolerant to ointment, NaCl 5% eye drops may be prescribed as an effective option.

Renal Deletion of LRRC8/VRAC Channels Induces Proximal Tubulopathy.

Volume-regulated anion channels (VRACs) are heterohexamers of LRRC8A with LRRC8B, -C, -D, or -E in various combinations. Depending on the subunit composition, these swelling-activated channels conduct chloride, amino acids, organic osmolytes, and drugs. Despite VRACs' role in cell volume regulation, and large osmolarity changes in the kidney, neither the localization nor the function of VRACs in the kidney is known. Mice expressing epitope-tagged LRRC8 subunits were used to determine the renal localization of all VRAC subunits. Mice carrying constitutive deletions of Lrrc8b-e, or with inducible or cell-specific ablation of Lrrc8a, were analyzed to assess renal functions of VRACs. Analysis included histology, urine and serum parameters in different diuresis states, and metabolomics. The kidney expresses all five VRAC subunits with strikingly distinct localization. Whereas LRRC8C is exclusively found in vascular endothelium, all other subunits are found in the nephron. LRRC8E is specific for intercalated cells, whereas LRRC8A, LRRC8B, and LRRC8D are prominent in basolateral membranes of proximal tubules. Conditional deletion of LRRC8A in proximal but not distal tubules and constitutive deletion of LRRC8D cause proximal tubular injury, increased diuresis, and mild Fanconi-like symptoms. VRAC/LRRC8 channels are crucial for the function and integrity of proximal tubules, but not for more distal nephron segments in spite of their larger need for volume regulation. LRRC8A/D channels may be required for the basolateral exit of many organic compounds, including cellular metabolites, in proximal tubules. Proximal tubular injury likely results from combined accumulation of several transported molecules in the absence of VRAC channels.

A propensity score-based, comparative study assessing humid and dry time-lapse incubation, with single-step medium, on embryo development and clinical outcomes.

Does culture in a high relative humidity atmosphere improve clinical outcomes when using a time-lapse integrated incubator and single-step culture medium? Using an integrated time-lapse system and single-step culture medium, culture in a high relative humidity atmosphere increases the likelihood of embryos, especially those subjected to preimplantation genetic testing for aneuploidies, to achieve a pregnancy compared to those cultured in dry conditions. The use of a humid atmosphere inside incubators can reduce changes in culture media osmolality, which has been reported to have a significant effect on embryo quality and morphokinetics. Studies assessing the effect of humid culture (HC) in clinical outcomes are, however, scarce and inconclusive, mostly due to a high variability in culture conditions and reduced sample size. Retrospective cohort study performed over 1627 ICSI cycles performed during 3 consecutive years in which embryo cohorts were cultured in a time-lapse incubator with three dry and three humidified chambers, and using single-step culture medium. Clinical outcomes were compared between treatments in which embryo cohorts were cultured in either humid (n = 833) or dry (n = 794) conditions. The study includes autologous treatments, with (N = 492) and without (N = 372) preimplantation genetic testing for aneuploidies (PGT-A) and ovum donation treatments (N = 763), performed in three university-affiliated private IVF centres. Stimulation, oocyte pickup and fertilization were performed according to the standard procedures of the clinic. All embryo cohorts were cultured in the same model of time-lapse incubator, distributed to either a dry or humidified chamber, while the rest of the culture variables remained equal. The population was weighted by the inverse probability of treatment to control for all measured confounders. The association between HC and the main outcome was assessed by logistic regression over the weighted population. The E-value was reported as a way of considering for unmeasured confounders. Differences in embryo development and other secondary outcomes between the study groups were assessed by Pearson Chi-squared test, ANOVA test and Kaplan-Meier survival analysis. An univariable logistic regression analysis, weighted by the inverse probability of treatment, determined that embryos cultured in humid conditions are more likely to achieve a clinical pregnancy than those cultured in dry conditions (odds ratio (OR) = 1.236 (95% CI 1.009-1.515), P = 0.041, E = 1.460). Through stratification, it was determined that said effect is dependent on the type of treatment: no improvement in clinical pregnancy was present in ovum donation or autologous treatments, but a statistically significant positive effect was present in treatments with preimplantation genetic testing (OR = 1.699 (95% CI 1.084-2.663), P = 0.021, E = 1.930). Said increase does not relate with an improvement in later outcomes. Differences were also found in variables related to embryo developmental morphokinetics. The retrospective nature of the study makes it susceptible to some bias linked to the characteristics of the treatments. To lessen the effect of possible biases, cases were weighted by the inverse probability of treatment prior to the evaluation of the outcome, as means to assess for measured confounders. In addition, the E-value of the weighted OR was calculated as a sensitivity analysis for unmeasured confounders. A randomized prospective study could be performed for further assessing the effect of humid conditions in clinical outcome. These results support that embryo culture under conditions of high relative humidity contributes to optimize clinical results in undisturbed culture in a time-lapse incubator with single-step medium. To our knowledge, this is the largest study on the matter and the first performing a propensity score-based analysis. This work was supported by the ''Centro para el Desarrollo Tecnologico Industrial'' from the Spanish Ministry of Science, Innovation, and Universities (CDTI-20170310) and Generalitat Valenciana and European Social Fund (ACIF/2019/264). None of the authors have any competing interest to declare. N/A.

Decapod egg membranes: powerful barriers or regulatory structures?

Osmoregulatory abilities and mechanisms of adults and larvae of decapod crustaceans have been extensively investigated. However, how embryos carried by their mothers can deal with changing or extreme salinities is less understood. The egg membranes are believed to isolate embryos from a challenging environment, although osmoregulatory ability has been demonstrated in early developing embryos (naupliar stage) of two crabs. To establish whether embryos are isolated by their membranes and/or are able to osmoregulate, we measured the survival and volume change over 48 h of oocytes and embryos in different stages of three carideans (Betaeus lilianae, Palaemon macrodactylus and P. argentinus) and the brachyuran Neohelice granulata, subjected to different salinities. In addition, we recorded osmolality changes in homogenates of the same stages in P. argentinus and N. granulata after 2 h of exposure and mapped the presence of putative sites of ions exchange in the membrane of all species. High mortality, when it occurred, was associated with low salinity and mortality variation with the stage of development depended on the species. All species precipitated silver salts in or under the egg envelope, with a different pattern between carideans and the brachyuran. Changes in osmolality and egg volume after hypo- or hyper-osmotic salinity challenges indicate that eggs are not fully isolated by their membranes, and that some osmoregulatory mechanisms are in play to maintain developmental homeostasis. We suggest that egg membranes can participate in osmoregulation by selectively transporting ions to an intramembrane space, with differences between carideans and brachyurans.

Pikeperch (Sander lucioperca) spermatozoa motility and volume regulation under different osmotic and ionic conditions.

Pikeperch (Sander lucioperca) is a highly profitable commercial species whose economic value has greatly increased in the last decade. As in other species, the quality of spermatozoa in this species is a principal feature inherent in fertilization success and efficient natural and artificial reproduction. The capacity of fish spermatozoa to be activated and tolerate environmental changes (in osmolality, ion composition, external pH, temperature, etc.) during the motility period contributes to fertilization success. In this study, we investigated the effects of environmental osmolality and ion composition on spermatozoa motility. To determine if the activation mechanism is affected by sperm quality parameters, we measured semen characteristics such as semen volume, spermatozoa concentration, seminal fluid osmolality and ion composition, and spermatozoa lipid composition. An additional parameter of sperm quality reflecting spermatozoa osmoresistance, the swelling rate, was measured by the nephelometry method. We detected that sperm samples with the highest content of palmitic (C16:0) and palmitoleic (C16:1) acids showed the lowest motility activation under the studied conditions, suggesting that these fatty acids are possible markers for the determination of spermatozoa quality in fish. Our results show that pikeperch spermatozoa can be activated under different osmotic conditions and that cell swelling always accompanies motility. However, spermatozoa sustain their volume under hypotonic conditions when motility is not initiated, suggesting that pikeperch spermatozoa activation is mainly controlled by ion composition rather than the osmolarity of the surrounding medium.

What Is the Optimal Speed of correction of the Hyperosmolar Hyperglycemic State in Diabetic Ketoacidosis? An Observational Cohort Study of U.S. Intensive Care Patients

ObjectiveThe international guidelines for the treatment of diabetic ketoacidosis (DKA) advise against rapid changes in osmolarity and glucose; however, the optimal rates of correction are unknown. We aimed to evaluate the rates of change in tonicity and glucose level in intensive care patients with DKA and their relationship with mortality and altered mental status. MethodsThis is an observational cohort study using 2 publicly available databases of U.S. intensive care patients (Medical Information Mart for Intensive Care-IV and Electronic Intensive Care Unit), evaluating adults with DKA and associated hyperosmolarity (baseline Osm ≥300 mOsm/L). The primary outcome was hospital mortality. The secondary neurologic outcome used a composite of diagnosed cerebral edema or Glasgow Coma Scale score of ≤12. Multivariable regression models were used to control for confounding factors. ResultsOn adjusted analysis, patients who underwent the most rapid correction of up to approximately 3 mmol/L/hour in tonicity had reduced mortality (n = 2307; odds ratio [OR], 0.21; overall P < .001) and adverse neurologic outcomes (OR, 0.44; P < .001). Faster correction of glucose levels up to 5 mmol/L/hour (90 mg/dL/hour) was associated with improvements in mortality (n = 2361; OR, 0.24; P = .020) and adverse neurologic events (OR, 0.52; P = .046). The number of patients corrected significantly faster than these rates was low. A maximal hourly rate of correction between 2 and 5 mmol/L for tonicity was associated with the lowest mortality rate on adjusted analysis. ConclusionBased on large-volume observational data, relatively rapid correction of tonicity and glucose level was associated with lower mortality and more favorable neurologic outcomes. Avoiding a maximum hourly rate of correction of tonicity >5 mmol/L may be advisable.

OzTracs: Optical Osmolality Reporters Engineered from Mechanosensitive Ion Channels.

Interactions between physical forces and membrane proteins underpin many forms of environmental sensation and acclimation. Microbes survive osmotic stresses with the help of mechanically gated ion channels and osmolyte transporters. Plant mechanosensitive ion channels have been shown to function in defense signaling. Here, we engineered genetically encoded osmolality sensors (OzTracs) by fusing fluorescent protein spectral variants to the mechanosensitive ion channels MscL from E. coli or MSL10 from A. thaliana. When expressed in yeast cells, the OzTrac sensors reported osmolality changes as a proportional change in the emission ratio of the two fluorescent protein domains. Live-cell imaging revealed an accumulation of fluorescent sensors in internal aggregates, presumably derived from the endomembrane system. Thus, OzTrac sensors serve as osmolality-dependent reporters through an indirect mechanism, such as effects on molecular crowding or fluorophore solvation.

The impact of modified fluid gelatin 4% in a balanced electrolyte solution on plasma osmolality in children-A noninterventional observational study.

Intravenous fluids for perioperative infusion therapy should be isotonic to maintain the body fluid homeostasis in children. Modified fluid gelatin 4% in a balanced electrolyte solution has a theoretical osmolarity of 284 mosmol L-1 , and a real osmolality of 264 mosmol kg H2 O-1 . Because both values are lower than those of 0.9% saline or plasma, gelatin would be expected to be hypotonic in-vitro and in-vivo. We thus hypothesized that the infusion of gelatin would be expected to decrease plasma osmolality. We performed an in-vitro experiment and an in-vivo study to evaluate the impact of gelatin on the osmolality in children. In the in-vitro experiment, full blood samples were diluted with gelatin 4% or albumin (50 g L-1 ) from 0% (pure blood) to 100% (pure colloid), and the osmolality was measured by freezing-point depression. In the in-vivo study, blood gas analyses from children undergoing major pediatric surgery were collected before and after gelatin infusion, and the osmolality was calculated by a modified version of Zander's formula. In the in-vitro experiment, 65 gradually diluted blood samples from five volunteers (age 25-55 years) were analyzed. The dilution with gelatin caused no significant changes in osmolality between 0% and 100%. Compared with gelatin, the osmolality in the albumin group was significantly lower between 50% and 100% dilution (p < .05). In the in-vivo study, 221 children (age 21.4 ± 30 months) were included. After gelatin infusion, the osmolality increased significantly (mean change 4.3 ± 4.8 [95% CI 3.7-4.9] mosmol kg H2 O-1 ; p < .01) within a normal range. Gelatin in a balanced electrolyte solution has isotonic characteristics in-vitro and in-vivo, despite the low theoretical osmolarity, probably caused by the (unmeasured) negative charges in the gelatin molecules contributing to the plasma osmolality. For a better evaluation of the (real) tonicity of gelatin-containing solutions, we suggest to calculate the osmolality (mosmol kg H2 O-1 ) using Zander's formula. ClinicalTrials.gov (ID: NCT02495285).

Serum and urine osmolality: 8 hours, 24 hours and 1-month sample stability

Objectives The body of literature varies significantly regarding serum and urine osmolality stability. Therefore, our aim was to investigate the stability of serum and urine osmolality at different temperatures (room temperature (RT) 4–8 °C, −20 °C) and time conditions (8 h, 24 h, 1 month). Methods The stability study was conducted following the CRESS guidelines, including 40 serum and urine samples. Samples were aliquoted into three aliquots and stored as follows: primary tube stored at RT for 8 h; two capped aliquots stored at 4–8 °C for 8 h and 24 h; one aliquot stored at −20 °C for 1 month. To minimize imprecision error, serum and urine osmolality were measured by the freezing point depression method in triplicate on OSMOMAT 3000 (Gonotech, Germany) analyzer. Percentage difference (PD%) against baseline measurement was calculated. Deviations were assessed against a reference change value of 5.0%. Results The PD% for serum and urine osmolality was below 2.0% for all time/temperature conditions. For serum samples: primary tube after 8 h at RT PD% (95% CI) = 0.0% (−0.3, 0.2%); 8 h at 4–8 °C PD% (95% CI) = −0.4% (−0.7, 0.0%); 24 h at 4–8 °C PD% (95% CI) = −0.7% (−0.7, −0.6%); 1 month at −20 °C PD% (95% CI) = −2.1% (−2.4, −1.5%). For urine samples: after 8 h at RT PD% (95% CI) =0.6% (0.2, 0.9%); 8 h at 4–8 °C PD% (95% CI) = −0.2% (−0.5, 0.1%); 24 h at 4–8 °C PD% (95% CI) = −0.2% (−0.5, 0.0%); 1 month at −20 °C PD% (95% CI) = −2.0% (−3.0, −1.0%). Conclusions Changes in osmolality for tested conditions for serum and urine samples, were within acceptance criteria. Reflex and add-on osmolality testing can be performed within the same day in samples kept at RT for 8 h in primary tube and within 24 h, in aliquoted refrigerated samples, without compromising the reliability of test results. For longer storage, samples should be kept at −20 °C.

Osmoregulation and the Hypothalamic Supraoptic Nucleus: From Genes to Functions.

Due to the relatively high permeability to water of the plasma membrane, water tends to equilibrate its chemical potential gradient between the intra and extracellular compartments. Because of this, changes in osmolality of the extracellular fluid are accompanied by changes in the cell volume. Therefore, osmoregulatory mechanisms have evolved to keep the tonicity of the extracellular compartment within strict limits. This review focuses on the following aspects of osmoregulation: 1) the general problems in adjusting the “milieu interieur” to challenges imposed by water imbalance, with emphasis on conceptual aspects of osmosis and cell volume regulation; 2) osmosensation and the hypothalamic supraoptic nucleus (SON), starting with analysis of the electrophysiological responses of the magnocellular neurosecretory cells (MNCs) involved in the osmoreception phenomenon; 3) transcriptomic plasticity of SON during sustained hyperosmolality, to pinpoint the genes coding membrane channels and transporters already shown to participate in the osmosensation and new candidates that may have their role further investigated in this process, with emphasis on those expressed in the MNCs, discussing the relationships of hydration state, gene expression, and MNCs electrical activity; and 4) somatodendritic release of neuropeptides in relation to osmoregulation. Finally, we expect that by stressing the relationship between gene expression and the electrical activity of MNCs, studies about the newly discovered plastic-regulated genes that code channels and transporters in the SON may emerge.

Hydration Status in Men Working in Different Thermal Environments: A Pilot Study.

The aim of this study was to determine the effects of different seasons of the year and the time of day (before work vs. after work) on hydration status in men. The study involved sixty foresters who spent most of the work outdoors. During three seasons of the year (summer, autumn, and winter), indices of hydration status (body mass (BM) and percentage change of BM, total body water (TBW) and percentage change of TBW, serum osmolality (Sosm) and percentage change of Sosm, urine osmolality, urine-specific gravity (USG), urine color, and thirst) were determined before work on the first day (time point 1 used as baseline), immediately after work on the first day (time point 2), and before work on the following day (time point 3). USG decreased at time point 2 compared to time point 1 (p < 0.001) and time point 3 (p = 0.03). At time point 2 (p = 0.002) in winter and time point 3 in autumn (p = 0.049), serum osmolality was higher than in summer. In conclusion, the differences in hydration status depended on the time of day and season. A large percentage of foresters come to work inadequately hydrated, especially in colder seasons compared to summer.