Basic concepts and practical equations on osmolality: Biochemical approach

Nourishing Physical Productivity and Performance On a Warming Planet - Challenges and Nutritional Strategies to Mitigate Exertional Heat Stress

PURPOSE OF REVIEW: Climate change is predicted to increase the frequency and severity of exposure to hot environments. This can impair health, physical performance, and productivity for active individuals in occupational and athletic settings. This review summarizes current knowledge and recent advancements in nutritional strategies to minimize the impact of exertional-heat stress (EHS). RECENT FINDINGS: Hydration strategies limiting body mass loss to < 3% during EHS are performance-beneficial in weight-supported activities, although evidence regarding smaller fluid deficits (< 2% body mass loss) and weight-dependent activities is less clear due to a lack of well-designed studies with adequate blinding. Sodium replacement requirements during EHS depends on both sweat losses and the extent of fluid replacement, with quantified sodium replacement only necessary once fluid replacement > 60-80% of losses. Ice ingestion lowers core temperature and may improve thermal comfort and performance outcomes when consumed before, but less so during activity. Prevention and management of gastrointestinal disturbances during EHS should focus on high carbohydrate but low FODMAP availability before and during exercise, frequent provision of carbohydrate and/or protein during exercise, adequate hydration, and body temperature regulation. Evidence for these approaches is lacking in occupational settings. Acute kidney injury is a potential concern resulting from inadequate fluid replacement during and post-EHS, and emerging evidence suggests that repeated exposures may increase the risk of developing chronic kidney disease. Nutritional strategies can help regulate hydration, body temperature, and gastrointestinal status during EHS. Doing so minimizes the impact of EHS on health and safety and optimizes productivity and performance outcomes on a warming planet.

Optimizing lentiviral vector formulation conditions for efficient ex vivo transduction of primary human T cells in chimeric antigen receptor T-cell manufacturing

BACKGROUND AIMS

Chimeric antigen receptor (CAR) T-cell products are commonly generated using lentiviral vector (LV) transduction. Optimal final formulation buffer (FFB) supporting LV stability during cryostorage is crucial for cost-effective manufacturing.

METHODS

To identify the ideal LV FFB composition for ex vivo CAR-T production, primary human T cells were transduced with vesicular stomatitis virus G-protein (VSV-G) -pseudotyped LVs (encoding a reporter gene or an anti-CD19-CAR). The formulations included phosphate-buffered saline (PBS), HEPES, or X-VIVOTM 15, and stabilizing excipients. The functional and viral particle titers and vector copy number were measured after LV cryopreservation and up to 24 h post-thaw incubation. CAR-Ts were produced with LVs in selected FFBs, and the resulting cells were characterized.

RESULTS

Post-cryopreservation, HEPES-based FFBs provided higher LV functional titers than PBS and X-VIVOTM 15, and 10% trehalose-20 mM MgCl2 improved LV transduction efficiency in PBS and 50 mM HEPES. Thawed vectors remained stable at +4°C, while a ≤ 25% median decrease in the functional titer occurred during 24 h at room temperature. Tested excipients did not enhance LV post-thaw stability. CAR-Ts produced using LVs cryopreserved in 10% trehalose- or sucrose-20 mM MgCl2 in 50 mM HEPES showed comparable transduction rates, cell yield, viability, phenotype, and in vitro functionality.

CONCLUSION

A buffer consisting of 10% trehalose-20 mM MgCl2 in 50 mM HEPES provided a feasible FFB to cryopreserve a VSV-G -pseudotyped LV for CAR-T-cell production. The LVs remained relatively stable for at least 24 h post-thaw, even at ambient temperatures. This study provides insights into process development, showing LV formulation data generated using the relevant target cell type for CAR-T-cell manufacturing.

Heart failure related fatigue: An exploratory analysis of serum osmolality from the national health and nutrition examination survey

BACKGROUND

Fatigue is a prominent symptom of heart failure (HF). However, underlying mechanisms remain poorly understood. Fluid volume status has been suggested as a physiologic mechanism of HF-related fatigue. Serum osmolality may fluctuate with changes in volume status associated with neurohormonal dysregulation. The relationship of fatigue to serum osmolality has not been assessed in adults with HF.

OBJECTIVES

Describe the relationship between serum osmolality and fatigue in adults with HF.

METHODS

We analyzed two waves of cross-sectional data from the National Health and Nutrition Examination Survey (2015-2016 and 2017-2018). Adults who self-reported having HF without select co-morbid conditions known to contribute to fatigue were included. Data were weighted to provide US national estimates, and complex sample design used for analyses. Sequential logistic regression was used to isolate the effect of serum osmolality on the odds of having fatigue.

RESULTS

Data from the sample represented 1.4 million Americans with HF (58.5 % male; median age 68 years), of whom 1,001,589 (67.9 %) reported fatigue. Participants with fatigue had lower serum osmolality compared to those without fatigue (t = -3.04, p = .009). Higher serum osmolality was associated with 8.8 % lower odds of experiencing fatigue when controlling for sex and body mass index (OR = 0.912, p = .007, CI 0.857 - 0.972).

CONCLUSIONS

HF-related fatigue is associated with lower serum osmolality. Low serum osmolality may indicate excess volume and the presence of a heightened neurohormonal response, both of which may influence fatigue. Alternatively, serum osmolality may directly affect other physiologic changes that may contribute to fatigue.

Necrostatin-1 protects corneal epithelial cells by inhibiting the RIPK1/RIPK3/MLKL cascade in a benzalkonium chloride-induced model of necroptosis

PURPOSE

Benzalkonium chloride (BAC) is commonly used as a preservative in ophthalmic medications, despite its potential to induce chemical injury. Extensive research has demonstrated that BAC can lead to adverse effects, including injuries to the ocular surface. Our study aimed to elucidate the underlying mechanism of necroptosis induced by BAC.

METHODS

Human corneal epithelial (HCE) cells and mouse corneas were subjected to chemical injury, and the necrostatin-1 (Nec1) group was compared to the dimethylsulfoxide (DMSO) group. The extent of damage to HCE cells was assessed using CCK-8 and flow cytometry. Hematoxylin and eosin staining, as well as fluorescein sodium staining, were used to detect and characterize corneal injury. The activation of inflammatory cytokines and necroptosis-related proteins and genes was evaluated using Western blotting, immunofluorescence staining, and quantitative RT‒PCR.

RESULTS

In our study, the induction of necroptosis by a hypertonic solution was not observed. However, necroptosis was observed in HCE cells exposed to NaOH and BAC, which activated the receptor-interacting protein kinase 1 (RIPK1) - receptor-interacting protein kinase 3 (RIPK3) - mixed lineage kinase domain-like protein (MLKL) signaling pathway. In mouse corneal tissues, BAC could induce necroptosis and inflammation. The administration of Nec1 mitigated the inflammatory response and ocular surface damage caused by BAC-induced necroptosis in our experimental models. Furthermore, our in vivo experiments revealed that the severity of necroptosis was greater in the 3-day group than in the 7-day group.

CONCLUSIONS

Necroptosis plays a role in the pathological development of ocular surface injury caused by exposure to BAC. Furthermore, our study demonstrated that the administration of Nec1 could mitigate the pathological effects of necroptosis induced by BAC in clinical settings.

Arrhythmogenic Potential of Myocardial Edema: The Interstitial Osmolality Induces Spiral Waves and Multiple Excitation Wavelets

Myocardial edema is a common symptom of pathological processes in the heart, causing aggravation of cardiovascular diseases and leading to irreversible myocardial remodeling. Patient-based studies show that myocardial edema is associated with arrhythmias. Currently, there are no studies that have examined how edema may influence changes in calcium dynamics in the functional syncytium. We performed optical mapping of calcium dynamics on a monolayer of neonatal rat cardiomyocytes with Fluo-4. The osmolality of the solutions was adjusted using the NaCl content. The initial Tyrode solution contained 140 mM NaCl (1T) and the hypoosmotic solutions contained 105 (0.75T) and 70 mM NaCl (0.5T). This study demonstrated a sharp decrease in the calcium wave propagation speed with a decrease in the solution osmolality. The successive decrease in osmolality also showed a transition from a normal wavefront to spiral wave and multiple wavelets of excitation with wave break. Our study demonstrated that, in a cellular model, hypoosmolality and, as a consequence, myocardial edema, could potentially lead to fatal ventricular arrhythmias, which to our knowledge has not been studied before. At 0.75T spiral waves appeared, whereas multiple wavelets of excitation occurred in 0.5T, which had not been recorded previously in a two-dimensional monolayer under conditions of cell edema without changes in the pacing protocol.

Association between serum osmolality and risk of in-hospital mortality in patients with intracerebral hemorrhage

Aim

This study aimed to analyze the association between serum osmolality and the risk of in-hospital mortality in intracerebral hemorrhage (ICH) patients.

Methods

In this retrospective cohort study, data of a total of 1,837 ICH patients aged ≥18 years were extracted from the Medical Information Mart for Intensive Care-IV (MIMIC-IV). Serum osmolality and blood urea nitrogen (BUN)-to-creatinine (Cr) ratio (BCR) were used as the main variables to assess their association with the risk of in-hospital mortality in ICH patients after first intensive care unit (ICU) admission using a univariable Cox model. Univariable and multivariable Cox regression analyses were applied to explore the associations between serum osmolality, BCR, and in-hospital mortality of ICH patients. Hazard ratio (HR) and 95% confidence intervals (CIs) were calculated.

Results

The median survival duration of all participants was 8.29 (4.61-15.24) days. Serum osmolality of ≥295 mmol/L was correlated with an increased risk of in-hospital mortality in patients with ICH (HR = 1.43, 95%CI: 1.14-1.78). BCR of >20 was not significantly associated with the risk of in-hospital mortality in ICH patients. A subgroup analysis indicated an increased risk of in-hospital mortality among ICH patients who were women, belonged to white or Black race, or had complications with acute kidney injury (AKI).

Conclusion

High serum osmolality was associated with an increased risk of in-hospital mortality among ICH patients.

Two-photon microscopy of acoustofluidic trapping for highly sensitive cell analysis

We combine two-photon-excited fluorescence microscopy and acoustofluidic trapping in a spherical microchamber to in vitro study cells and cell clusters three-dimensionally close to in vivo conditions. The two-photon microscopy provides the in-depth 3D analysis of the spherical microchamber dimensions as well as the positions of trapped samples therein with high spatial precision and high temporal resolution enabling even tracking of the fast moving particles. Furthermore, optical sectioning allows to gather information of individual cells in trapped cell clusters inside the chamber. We demonstrate real-time monitoring of osmosis in A549 lung cells and red blood cells as one possible biomedical application. The observed osmosis reduced the cell membrane diameter by approximately 4 μm in the A549 cells and by approximately 2 μm in the red blood cells. Our approach provides an important optical tool for future investigations of cell functions and cell-cell interactions avoiding wall-contact inside an acoustofluidic device.

Recognizing Complications in Youth With Diabetes Admitted With Diabetic Ketoacidosis Versus Hyperglycemic Hyperosmolar State

INTRODUCTION

We compare in-hospital complications in youth with isolated diabetic ketoacidosis (DKA) to youth with hyperosmolarity.

METHOD

We reviewed medical records of youth (1-20 years) admitted over two years with DKA, hyperglycemic hyperosmolar state (HHS), and hyperosmolar DKA. We evaluated outcomes, including hospital length of stay, altered mental status (AMS), and acute kidney injury (AKI).

RESULTS

Of 369 admissions, 334 had isolated DKA, 32 had hyperosmolar DKA, and three had isolated HHS. Hyperosmolar youth had longer length of stay, larger initial fluid boluses, more frequent pediatric intensive care unit admissions, and increased risk of AKI and AMS. The odds of AKI were positively associated with serum osmolality and negatively associated with new-onset diabetes mellitus (DM) compared with established DM.

CONCLUSIONS

In youth with DM, hyperosmolarity increases acute complications compared with isolated DKA. Larger-scale studies are needed to identify ways to prevent acute complications in youth experiencing hyperglycemic emergencies.

Osmolality in oral supplements drives ileostomy output: Defining the Goldilocks zone

BACKGROUND

Patients with an ileostomy often have impaired quality of life, sodium depletion, secondary hyperaldosteronism, and other organ-specific pathologies. The osmolality of oral supplements influences ileostomy output and increases sodium loss. We hypothesized the existence of an osmolality range in which fluid absorption and secondary natriuresis are optimal.

METHODS

This was a single-center, quasi-randomized crossover intervention study, including patients with an ileostomy and no home parenteral support. After an 8-h fasting period, each patient ingested 500 mL of 3-18 different oral supplements and a standardized meal during the various intervention periods, followed by a 6-h collection of ileostomy and urine outputs. The primary outcome was 6-h ileostomy output.

RESULTS

A total of 14 ileostomy patients with a median age of 65 years (interquartile range 38-70 years) were included. The association between osmolalities (range 5-1352 mOsm/kg) and ileostomy output forecasted an S-curve. A linear association between osmolality of oral supplements (range 290-600 mOsm/kg) and ileostomy output was identified and assessed with a mixed-effects model. Ileostomy output increased by 57 g/6 h (95% confidence interval (CI) 21-94) when the oral supplement osmolality increased by 100 mOsm/kg (p = 0.005).

CONCLUSION

Osmolality in oral supplements correlated with ileostomy output. Our results indicate that patients with an ileostomy may benefit from increased ingestion of oral supplements with osmolalities between 100 and 290 mOsm/kg. We define this range as the Goldilocks zone, equivalent to optimal fluid and electrolyte absorption.

Osmolality and Tonicity of Isotonic Beverages

This study aimed to measure and compare the osmolality and tonicity of isotonic beverages that can be bought on the Slovenian market. The main goal was to examine how good is the agreement between the measured osmolalities of the beverages and the requirements for isotonic beverages set up by EFSA. Osmolalities were measured with an osmometer using the freezing point depression method. Afterwards, two complementary methods for the observation of tonicity were developed. Erythrocytes were exposed to standard NaCl solutions of different osmolalities to observe their influence on the volume and shape of cells following the turbidity of the solution and the morphology of erythrocytes. These two methods enabled us to determine whether standard solutions were hypo-, iso-, or hypertonic. In this way, we found that the osmolality of 12 out of the 18 investigated isotonic beverages was in the range of 270-330 mOsm/kg, as required by EFSA. However, six samples did not meet this criterion and should therefore not have the label "isotonic" or be described as such. The measurements of turbidity of solutions indicated that most isotonic beverages exhibit a lower tonicity than standard NaCl solutions of identical osmolality. However, examination of the erythrocytes in isotonic beverages showed that the measurements were additionally complicated by the low pH values of these beverages. Finally, by demonstrating how different components of isotonic beverages pass through the erythrocyte membranes, we found that even isoosmolal beverages are often not isotonic, as the concentration of actively transported sugars in these beverages is relatively high.

Impacts of dietary fat on multi tissue gene expression in the desert-adapted cactus mouse

Understanding the relationship between dietary fat and physiological responses is crucial in species adapted to arid environments where water scarcity is common. In this study, we present a comprehensive exploration of gene expression across five tissues (kidney, liver, lung, gastrointestinal tract, and hypothalamus) and 19 phenotypic measurements, investigating the effects of dietary fat in the desert-adapted cactus mouse ( Peromyscus eremicus ). We show impacts on immune function, circadian gene regulation, and mitochondrial function for mice fed a lower-fat diet compared to mice fed a higher-fat diet. In arid environments with severe water scarcity, even subtle changes in organismal health and water balance can affect physical performance, potentially impacting survival and reproductive success. The study sheds light on the complex interplay between diet, physiological processes, and environmental adaptation, providing valuable insights into the multifaceted impacts of dietary choices on organismal well-being and adaptation strategies in arid habitats.

Long-term health outcomes associated with hydration status

Body water balance is determined by fundamental homeostatic mechanisms that maintain stable volume, osmolality and the composition of extracellular and intracellular fluids. Water balance is maintained by multiple mechanisms that continuously match water losses through urine, the skin, the gastrointestinal tract and respiration with water gains achieved through drinking, eating and metabolic water production. Hydration status is determined by the state of the water balance. Underhydration occurs when a decrease in body water availability, due to high losses or low gains, stimulates adaptive responses within the water balance network that are aimed at decreasing losses and increasing gains. This stimulation is also accompanied by cardiovascular adjustments. Epidemiological and experimental studies have linked markers of low fluid intake and underhydration - such as increased plasma concentration of vasopressin and sodium, as well as elevated urine osmolality - with an increased risk of new-onset chronic diseases, accelerated aging and premature mortality, suggesting that persistent activation of adaptive responses may be detrimental to long-term health outcomes. The causative nature of these associations is currently being tested in interventional trials. Understanding of the physiological responses to underhydration may help to identify possible mechanisms that underlie potential adverse, long-term effects of underhydration and inform future research to develop preventative and treatment approaches to the optimization of hydration status.

The U-shaped association between serum osmolality and 28-day mortality in patients with sepsis: a retrospective cohort study

BACKGROUND

Sepsis is a recognized global health challenge that places a considerable disease burden on countries. Although there has been some progress in the study of sepsis, the mortality rate of sepsis remains high. The relationship between serum osmolality and the prognosis of patients with sepsis is unclear.

METHOD

Patients with sepsis who met the criteria in the Medical Information Mart for Intensive Care IV database were included in the study. Hazard ratios (HRs) and 95% confidence intervals (CIs) were determined using multivariable Cox regression. The relationship between serum osmolality and the 28-day mortality risk in patients with sepsis was investigated using curve fitting, and inflection points were calculated.

RESULTS

A total of 13,219 patients with sepsis were enrolled in the study; the mean age was 65.1 years, 56.9 % were male, and the 28-day mortality rate was 18.8 %. After adjusting for covariates, the risk of 28-day mortality was elevated by 99% (HR 1.99, 95%CI 1.74-2.28) in the highest quintile of serum osmolality (Q5 >303.21) and by 59% (HR 1.59, 95%CI 1.39-1.83) in the lowest quintile (Q1 ≤285.80), as compared to the reference quintile (Q3 291.38-296.29). The results of the curve fitting showed a U-shaped relationship between serum osmolality and the risk of 28-day mortality, with an inflection point of 286.9 mmol/L.

CONCLUSION

There is a U-shaped relationship between serum osmolality and the 28-day mortality risk in patients with sepsis. Higher or lower serum osmolality is associated with an increased risk of mortality in patients with sepsis. Patients with sepsis have a lower risk of mortality when their osmolality is 285.80-296.29 mmol/L.

Identifying Baseline Predictors of Selective Laser Trabeculoplasty Effectiveness: An Alternative Mathematical Approach

BACKGROUND

Selective laser trabeculoplasty (SLT) emerges as a first-line treatment for newly diagnosed open-angle glaucoma and ocular hypertension. However, the interindividual response to SLT considerably varied. Large-scale clinical investigations concerning predictive factors for SLT effectiveness are limited. This study aimed to identify baseline predictors of the percentage intraocular pressure (IOP)-lowering effectiveness of SLT using an alternative mathematical approach.

METHODS

Mathematical equations of IOP under the steady state of aqueous humour flow were formulated. The conclusive equation integrates physiological variables, including trabecular outflow facility, uveoscleral outflow fraction, plasma protein concentration, albumin/globulin ratio, mean arterial pressure, episcleral venous pressure, and plasma osmolarity. The equation was employed to estimate the percentage of IOP reduction following SLT and subsequently subjected to global sensitivity analysis to determine significant predictors of the IOP-lowering effect of SLT using the Monte Carlo simulation of 8,192 samples.

RESULTS

In the current model, a 50% improvement in the trabecular outflow facility impacted by SLT is associated with a mean percentage IOP reduction of 16.6%. Lower baseline trabecular outflow facilities were the strongest predictors, showing a correlation with greater effectiveness of SLT in terms of percentage of IOP reduction. The second most influential factor includes baseline uveoscleral outflow fraction, followed by baseline episcleral venous pressure. Specifically, lower baseline uveoscleral outflow fraction and episcleral venous pressure were found to be correlated with increased effectiveness of SLT. Baseline levels of plasma protein concentration, albumin/globulin ratio, mean arterial pressure, and plasma osmolarity have minimal impact on SLT success or failure.

CONCLUSION

This study identifies baseline trabecular outflow facilities as the strongest predictor of SLT effectiveness. The results suggested that pre-SLT medical treatment that augments uveoscleral outflow and/or trabecular outflow facilities could compromise the effectiveness of subsequent SLT in terms of percentage IOP reduction compared to those who never received pre-SLT medication.

Variable domain mutational analysis to probe the molecular mechanisms of high viscosity of an IgG1 antibody

Subcutaneous injection is the preferred route of administration for many antibody therapeutics for reasons that include its speed and convenience. However, the small volume limit (typically ≤ 2 mL) for subcutaneous delivery often necessitates antibody formulations at high concentrations (commonly ≥100 mg/mL), which may lead to physicochemical problems. For example, antibodies with large hydrophobic or charged patches can be prone to self-interaction giving rise to high viscosity. Here, we combined X-ray crystallography with computational modeling to predict regions of an anti-glucagon receptor (GCGR) IgG1 antibody prone to self-interaction. An extensive mutational analysis was undertaken of the complementarity-determining region residues residing in hydrophobic surface patches predicted by spatial aggregation propensity, in conjunction with residue-level solvent accessibility, averaged over conformational ensembles from molecular dynamics simulations. Dynamic light scattering (DLS) was used as a medium throughput screen for self-interaction of ~ 200 anti-GCGR IgG1 variants. A negative correlation was found between the viscosity determined at high concentration (180 mg/mL) and the DLS interaction parameter measured at low concentration (2-10 mg/mL). Additionally, anti-GCGR variants were readily identified with reduced viscosity and antigen-binding affinity within a few fold of the parent antibody, with no identified impact on overall developability. The methods described here may be useful in the optimization of other antibodies to facilitate their therapeutic administration at high concentration.

Serum osmolality was non-linearly associated with the risk of all-cause and cardiovascular mortality in patients with diabetes

AIMS

This study aimed to evaluate the relationship between both low and high osmolarity and the risk of all-cause and cause-specific mortality in diabetic population.

METHODS

All participants were included from the National Health and Nutrition Examination Survey 1999-2014. Baseline serum osmolality was determined from laboratory tests and cause of death from national death records. HRs and 95% CIs for all-cause mortality and cardiovascular mortality in diabetes were estimated using Cox proportional regression analysis. The non-linear relationship was explored using restricted cubic splines regression.

RESULTS

Among 7622 individuals with diabetes, 1983 (12.4%) died during a total of 3.26 thousand person-years of follow-up. Compared with the reference category (281-284 mmol/kg), the multivariable-adjusted HRs and 95% CIs for all-cause mortality were 1.27 (1.16-1.40; p<0.001) in the lowest osmolality category (<201 mmol/kg) and 1.18 (1.09-1.28; p<0.001) in the highest osmolality category (>312 mmol/kg). Restricted cubic splines results showed that serum levels of osmolality had a U-shaped association with the risk of all-cause mortality, and L-shaped relationship with the risk of cardiovascular death.

CONCLUSIONS

Both low osmolality and high osmolality were predictive of increased all-cause mortality in patients with diabetes, supporting a U-shaped relationship. Also, a lower serum osmolality increased the risk of cardiovascular mortality.

Blood pressure and renal function responses in workers exposed to lead for up to six years

The Study for Promotion of Health in Recycling Lead (SPHERL) assessed the blood pressure (BP) and renal function (RF) responses for up to 6 years in the workers without previous occupational lead exposure. BP was the average of five consecutive readings and the estimated glomerular filtration rate was derived from serum creatinine (eGFRcrt) and cystatin C (eGFRcys). Blood lead (BL) was measured by inductively coupled plasma mass spectrometry (detection limit 0.5 μg/dL). The statistical methods included multivariable-adjusted mixed models and interval-censored Cox regression analysis. The 234 workers analyzed were on average 28.5 years old and included 91.9% men. The baseline BL concentration was 4.35 μg/dL and increased 3.17-fold over follow-up (median: 2.03 years; range: 0.92-6.45 years). The changes in BP and RF were not significantly correlated with the follow-up-to-baseline BL ratio (p ≥ .51 and p ≥ .18, respectively). The fully-adjusted changes in systolic/diastolic BP associated with a doubling of BL were -0.25/-0.12 mm Hg (CI: -0.94 to 0.44/-0.66 to 0.42 mm Hg). Accordingly, the incidence of stage-1 or -2 hypertension was not associated with the BL change (p ≥ .063). Similarly, the changes in eGFRcrt and eGFRcys associated with a 3-fold BL increment were not significant, amounting to -0.70 mL/min/1.73 m2 (CI: -1.70 to 0.30 mL/min/1.73 m2 ) and -1.06 mL/min/1.73 m2 (-2.16 to 0.03 mL/min/1.73 m2 ). In conclusion, the BP and RF responses to an over 3-fold BL increment were small and not significant confirming the safety of modern lead-handing facilities operating under current safety rules.

Meta-analysis of the Boyle van 't Hoff relation: Turgor and leak models explain non-ideal volume equilibrium

There has been much recent attention paid to the interaction of cell volume, its regulation, and the molecular biology of the cell. Cells are generally assumed to behave as linear osmometers, with their water volume linearly proportionate to the inverse of osmotic pressure as described by the Boyle van 't Hoff (BvH) relation. This study evaluates the generality of this and other long-standing assumptions about cell responses to anisotonic conditions. We present alternative models that account for osmoregulation including mechanical resistance to volumetric expansion (the turgor model) and ion-osmolyte leakage (the leak model). To evaluate the generality of the BvH relation and determine the suitability of alternative models, we performed a comprehensive survey of the literature and a careful analysis of the resulting data, and then we used these data to compare among models. We identified 137 articles published from 1964 to 2019 spanning 14 animal species and 26 cell types and determined the BvH relation is not an appropriate general model but is adequate when restricted to the hypertonic region. In contrast, models that account for either mechanical resistance or ion-osmolyte leakage fit well to almost all collected data. The leak model has fitted parameters that are in the same range as the current literature estimate, while the turgor model typically requires an elastic modulus value of one or multiple orders of magnitude larger than literature values. However, confirmation of the underlying mechanism of osmotic regulation is required at the cell-specific level and cannot be assumed a priori.

4D Bioprinting via Molecular Network Contraction for Membranous Tissue Fabrication

Generation of thin membranous tissues (TMT), such as the cornea, epidermis, and periosteum, presents a difficult fabrication challenge in tissue engineering (TE). TMTs consist of several cell layers that are less than 100 µm in thickness per layer. While traditional methods provide the necessary resolution for TMT fabrication, they require significant handling and incorporation of several layers is limited. Extrusion bioprinting offers precise control over deposition of different biomaterials and cell populations within the same construct but lacks the resolution to generate biomimetic TMTs. For the first time, a 4D bioprinting strategy that allows for the generation of cell-laden TMTs is developed. Anionic gelatin methacrylate (GelMA) hydrogels are treated with cationic poly-l-lysine (PLL), which induces charge attraction, microscale network collapse, and macroscale hydrogel shrinking. The impact of shrinking on hydrogel properties, print resolution, and cell viability is presented. Additionally, this work suggests that a novel mechanism is occurring, where PLL exhibits a contractile force on GelMA and PLL molecular weight drives GelMA shrinking capabilities. Finally, it is shown that this phenomenon can occur while maintaining an encapsulated cell population. These findings address a critical barrier by generating macroscale tissue structures with their microscale TMT counterparts in the same print.

The Ins and Outs of IV Fluids in Hemodynamic Resuscitation

OBJECTIVES

Concise definitive review of the physiology of IV fluid (IVF) use in critically ill patients.

DATA SOURCES

Available literature on PubMed and MEDLINE databases.

STUDY SELECTION

Basic physiology studies, observational studies, clinical trials, and reviews addressing the physiology of IVF and their use in the critically ill were included.

DATA EXTRACTION

None.

DATA SYNTHESIS

We combine clinical and physiologic studies to form a framework for understanding rational and science-based use of fluids and electrolytes.

CONCLUSIONS

IVF administration is among the most common interventions for critically ill patients. IVF can be classified as crystalloids or colloids, and most crystalloids are sodium salts. They are frequently used to improve hemodynamics during shock states. Many recent clinical trials have sought to understand which kind of IVF might lead to better patient outcomes, especially in sepsis. Rational use of IVF rests on understanding the physiology of the shock state and what to expect IVF will act in those settings. Many questions remain unanswered, and future research should include a physiologic understanding of IVF in study design.

Comprehensive Evaluation of Inflammatory Biomarkers and Osmolarity to Distinguish Simple and Complex Febrile Seizures in Children

With limited sample sizes and varying study outcomes regarding complete blood count (CBC)-associated biomarkers and their febrile seizure (FS) classification, along with limited research on osmolarity, this study aims to evaluate CBC-associated biomarkers, including osmolarity, for a comprehensive view of their diagnostic value. This single-center retrospective study used data from 364 children (aged 5-60 months) diagnosed with FS. The patients were categorized into simple FS (n = 221) and complex FS (n = 143) groups. CBC and biochemical tests, including sodium, potassium, chloride, glucose, blood urea nitrogen, and C-reactive protein levels, were evaluated. The neutrophil-to-lymphocyte ratio (NLR), mean platelet volume-to-lymphocyte ratio, and osmolarity were calculated and compared between FS types and the number of seizures. Receiver operating characteristic (ROC) curve analysis was conducted to assess the predictive utility of these markers. Inflammatory markers, including NLR, were ineffective in predicting FS types. Complex FS cases exhibited a significantly lower osmolarity than simple FS cases. The area under the ROC curve for osmolarity to distinguish complex FS was 0.754, while other markers did not reach the desired threshold of 0.700. Including osmolarity in the classification of FS has clinical applicability. Physicians may consider osmolarity as an additional tool to aid in clinical decision-making.

Role of Crystalloids in the Perioperative Setting: From Basics to Clinical Applications and Enhanced Recovery Protocols

Perioperative fluid management, a critical aspect of major surgeries, is characterized by pronounced stress responses, altered capillary permeability, and significant fluid shifts. Recognized as a cornerstone of enhanced recovery protocols, effective perioperative fluid management is crucial for optimizing patient recovery and preventing postoperative complications, especially in high-risk patients. The scientific literature has extensively investigated various fluid infusion regimens, but recent publications indicate that not only the volume but also the type of fluid infused significantly influences surgical outcomes. Adequate fluid therapy prescription requires a thorough understanding of the physiological and biochemical principles that govern the body's internal environment and the potential perioperative alterations that may arise. Recently published clinical trials have questioned the safety of synthetic colloids, widely used in the surgical field. A new clinical scenario has arisen in which crystalloids could play a pivotal role in perioperative fluid therapy. This review aims to offer evidence-based clinical principles for prescribing fluid therapy tailored to the patient's physiology during the perioperative period. The approach combines these principles with current recommendations for enhanced recovery programs for surgical patients, grounded in physiological and biochemical principles.

Disrupted Pediatric Diabetes Trends in the Second Year of the COVID-19 Pandemic

Context

Increases in incident cases of pediatric type 1 (T1D) and type 2 diabetes (T2D) were observed during the first year of the COVID-19 pandemic.

Objective

This work aimed to identify trends in incidence and presentation of pediatric new-onset T1D and T2D during the second year of the COVID-19 pandemic.

Methods

A retrospective chart review was conducted. Demographics, anthropometrics, and initial laboratory results from patients aged 0 to 21 years who presented with new-onset diabetes to a pediatric tertiary care center were recorded.

Results

The incident cases of T1D (n = 46) and T2D (n = 46) in 2021-2022 (second year of the pandemic) were consistent with the incident cases of T1D (n = 46) and T2D (n = 53) in 2020 to 2021 (first year of the pandemic). Compared to the incident cases of diabetes in the prepandemic years, in the second year, the incident cases of T1D increased 48%, and the incident cases of T2D increased 188%. In the second year of the pandemic, incident cases of T2D represented half (50%) of all newly diagnosed pediatric diabetes cases. Patients with T2D were more likely to present in diabetic ketoacidosis, though this was not statistically significant (P = .08).

Conclusion

The increase in incident cases of pediatric T1D and T2D observed during the first year of the COVID-19 pandemic persisted during the second pandemic year. This suggests that despite pediatric vaccination efforts and return to social in-person activities, we may continue to see effects of the pandemic on pediatric diabetes trends.

Cerebrospinal fluid biomarkers provide evidence for kidney-brain axis involvement in cerebral malaria pathogenesis

Introduction

Cerebral malaria is one of the most severe manifestations of malaria and is a leading cause of acquired neurodisability in African children. Recent studies suggest acute kidney injury (AKI) is a risk factor for brain injury in cerebral malaria. The present study evaluates potential mechanisms of brain injury in cerebral malaria by evaluating changes in cerebrospinal fluid measures of brain injury with respect to severe malaria complications. Specifically, we attempt to delineate mechanisms of injury focusing on blood-brain-barrier integrity and acute metabolic changes that may underlie kidney-brain crosstalk in severe malaria.

Methods

We evaluated 30 cerebrospinal fluid (CSF) markers of inflammation, oxidative stress, and brain injury in 168 Ugandan children aged 18 months to 12 years hospitalized with cerebral malaria. Eligible children were infected with Plasmodium falciparum and had unexplained coma. Acute kidney injury (AKI) on admission was defined using the Kidney Disease: Improving Global Outcomes criteria. We further evaluated blood-brain-barrier integrity and malaria retinopathy, and electrolyte and metabolic complications in serum.

Results

The mean age of children was 3.8 years (SD, 1.9) and 40.5% were female. The prevalence of AKI was 46.3% and multi-organ dysfunction was common with 76.2% of children having at least one organ system affected in addition to coma. AKI and elevated blood urea nitrogen, but not other measures of disease severity (severe coma, seizures, jaundice, acidosis), were associated with increases in CSF markers of impaired blood-brain-barrier function, neuronal injury (neuron-specific enolase, tau), excitatory neurotransmission (kynurenine), as well as altered nitric oxide bioavailability and oxidative stress (p < 0.05 after adjustment for multiple testing). Further evaluation of potential mechanisms suggested that AKI may mediate or be associated with CSF changes through blood-brain-barrier disruption (p = 0.0014), ischemic injury seen by indirect ophthalmoscopy (p < 0.05), altered osmolality (p = 0.0006) and through alterations in the amino acids transported into the brain.

Conclusion

In children with cerebral malaria, there is evidence of kidney-brain injury with multiple potential pathways identified. These changes were specific to the kidney and not observed in the context of other clinical complications.

Association of serum osmolality with all-cause and cardiovascular mortality in US adults: A prospective cohort study

BACKGROUND AND AIMS

The association between serum osmolality, an effective indicator of body hydration status, and long-term mortality in the general population remains undetermined. The present study aimed to investigate the association of serum osmolality with long-term all-cause and cardiovascular mortality among adults in the United States.

METHODS AND RESULTS

This cohort study used data from the National Health and Nutrition Examination Survey (NHANES) 2007-2014. Participants were linked to National Death Index mortality data from the survey date through December 31, 2019. Cox proportional hazards regression model was used to calculate hazard ratios (HRs) and 95% CIs, and restricted cubic spline (RCS) regression was conducted. A total of 18312 US adults were included. During a median follow-up of 8.7 years, 1353 total deaths occurred, including 379 cardiovascular deaths. After multivariable adjustments, compared with the 3rd quartile (Q3) of serum osmolality, participants in the 1st (Q1) and 4th (Q4) quartiles were at a significantly higher risk of all-cause mortality (HR 1.41 [95% CI, 1.14-1.75] and 1.29 [95% CI, 1.04-1.61], respectively). RCS revealed a nonlinear relationship of serum osmolality to all-cause and cardiovascular mortality, with an inflection point of 278 mmol/kg.

CONCLUSION

In the nationally representative cohort of US adults, serum osmolality was nonlinearly associated with all-cause and cardiovascular mortality. The risk of mortality was lowest around an osmolality of 278 mmol/kg. These findings suggest the importance of serum osmolality management for long-term health outcomes.

Consensus document on the management of hyponatraemia of the Acqua Group of the Spanish Society of Endocrinology and Nutrition

INTRODUCTION

Hyponatremia is the most prevalent electrolyte disorder in the outpatient and inpatient settings. Despite this frequency, hyponatremia, including severe hyponatremia, is frequently underestimated and inadequately treated, thus highlighting the need to produce consensus documents and clinical practice guidelines geared towards improving the diagnostic and therapeutic approach to it in a structured fashion.

MATERIAL AND METHODS

Members of the Acqua Group of the Spanish Society of Endocrinology and Nutrition (SEEN) met using a networking methodology over a period of 20 months (between October 2019 and August 2021) with the aim of discussing and developing an updated guideline for the management of hyponatraemia. A literature search of the available scientific evidence for each section presented in this document was performed.

RESULTS

A document with 8 sections was produced, which sets out to provide updated guidance on the most clinically relevant questions in the management of hyponatraemia. The management of severe hyponatraemia is based on the i.v. administration of a 3% hypertonic solution. For the management of chronic euvolemic hyponatraemia, algorithms for the initiation of treatment with the two pharmacological therapeutic options currently available in Spain are presented: urea and tolvaptan.

CONCLUSIONS

This document sets out to simplify the approach to and the treatment of hyponatraemia, making it easier to learn and thus improve the clinical approach to hyponatremia.

Influence of Na+ disorder on cytoplasmic conductivity and cellular electromagnetic (EM) energy absorption of human erythrocytes (PONE-D-21-36089)

Cytoplasmic conductivity of human erythrocytes may be significantly disturbed by the composition of the external suspending media. Effects of external NaCl on cytoplasmic conductivity of human erythrocyte (Human Red Blood Cells, HRBC) were investigated in a simple NaCl system. Using thermodynamic theory cytoplasmic conductivities could be calculated from internal [K+], [Na+], [Cl-] and [HCO3-]. Effect of cell volume and cell water changes were introduced and allowed for using the Debye-Hückel-Onsager relation and Walden's rule of viscosity. Cell volume and cell water change of HRBCs were measured in suspending isotonic solutions with conductivities from 0.50 S m-1 up to hypertonic solutions of conductivity of 2.02 S m-1 at selected temperatures of 25°C (standard benchmark temperature) and 37°C (physiological temperature). In isotonic solutions, cytoplasmic conductivity of human erythrocyte decreases with rise in the external media ionic concentration and vice versa for hypertonic solutions. The HRBC is capable of rapidly regulating its volume (and shape) over quite a wide range of osmolality. Specific Absorption Rate (SAR, 900 MHz) values (W kg-1) of electromagnetic radiation are below safe limits at non-physiological 25°C but above legal limits at 37°C [National Council on Radiation Protection and Measurements, NCRP]. However, at 37°C under both hypertonic [Na+] and isotonic but low [Na+], SAR increases further beyond legal limits.

Osmotic Contribution of Synthesized Betaine by Choline Dehydrogenase Using In Vivo and In Vitro Models of Post-traumatic Syringomyelia

Introduction

Syringomyelia (SM) is a debilitating spinal cord disorder in which a cyst, or syrinx, forms in the spinal cord parenchyma due to congenital and acquired causes. Over time syrinxes expand and elongate, which leads to compressing the neural tissues and a mild to severe range of symptoms. In prior omics studies, significant upregulation of betaine and its synthesis enzyme choline dehydrogenase (CHDH) were reported during syrinx formation/expansion in SM injured spinal cords, but the role of betaine regulation in SM etiology remains unclear. Considering betaine's known osmoprotectant role in biological systems, along with antioxidant and methyl donor activities, this study aimed to better understand osmotic contributions of synthesized betaine by CHDH in response to SM injuries in the spinal cord.

Methods

A post-traumatic SM (PTSM) rat model and in vitro cellular models using rat astrocytes and HepG2 liver cells were utilized to investigate the role of betaine synthesis by CHDH. Additionally, the osmotic contributions of betaine were evaluated using a combination of experimental as well as simulation approaches.

Results

In the PTSM injured spinal cord CHDH expression was observed in cells surrounding syrinxes. We next found that rat astrocytes and HepG2 cells were capable of synthesizing betaine via CHDH under osmotic stress in vitro to maintain osmoregulation. Finally, our experimental and simulation approaches showed that betaine was capable of directly increasing meaningful osmotic pressure.

Conclusions

The findings from this study demonstrate new evidence that CHDH activity in the spinal cord provides locally synthesized betaine for osmoregulation in SM pathophysiology.

Supplementary Information

The online version of this article contains supplementary material available 10.1007/s12195-022-00749-5.

Effect of high-flow nasal cannula therapy on thirst sensation and dry mouth after extubation: A single-centre prospective cohort study

OBJECTIVES

Little is known regarding the association between the type of oxygen therapy and thirst sensation after extubation. This study aimed to assess the effect of post-extubation high-flow nasal cannula on thirst.

RESEARCH METHODOLOGY/DESIGN AND SETTING

This single-centre prospective cohort study included 100 ventilated patients. After extubation, patients received either high-flow nasal cannula (n = 19) or conventional oxygen therapy (n = 81). Thirst intensity was evaluated by a self-reporting numeric rating scale, and dry mouth was defined objectively using an oral moisture checking device.

MAIN OUTCOME MEASURES

The primary outcome was thirst intensity 24 hours post-extubation. Secondary outcomes were thirst intensity at 4 hours post-extubation and prevalence of dry mouth at 4 hours and 24 hours post-extubation.

RESULTS

At 24 hours post-extubation, the median (interquartile range) thirst intensity was 5 (1, 7) in the high-flow nasal cannula group and 5 (4, 6) in the conventional oxygen group. After adjustment, high-flow nasal cannula therapy was significantly associated with lower thirst intensity (adjusted odds ratio, 0.14; 95 % confidence interval (CI) 0.04-0.49; P = 0.002). At 4 hours post-extubation, high-flow nasal cannula was also associated with lower thirst intensity (adjusted odds ratio, 0.19; 95 % CI, 0.06-0.60; P = 0.005). The number of patients with dry mouth was not significantly different between the two groups (high-flow vs conventional oxygen therapy, 42.1 % vs 30.9 % [4 hours after extubation]; 47.4 % vs 34.6 % [24 hours after extubation]).

CONCLUSIONS

High-flow nasal cannula therapy was associated with lower thirst intensity than conventional oxygen therapy following extubation. However, there was no significant difference in the prevalence of dry mouth.

Possibility to use the different sizes and colors of carrots for the production of juices - comparison of bioactive compounds, nutritional quality, pro-health properties, and sensory evaluation

BACKGROUND

Carrot is a popular vegetable consumed by people of all age groups and is used in various food products because of its high nutritional content, especially vitamin A.

RESULTS

In the present study, colorful fresh carrot juices of 12 carrot varieties were investigated for in vitro antidiabetic, anti-aging, and anti-obesity activities with antioxidant potential by ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and FRAP (ferric reducing ability of plasma) assays. The studied juices were also compared for physicochemical characteristics: titratable acidity, pH, pectin content, total soluble solids, dry mass, ash, viscosity, turbidity, osmolality, and color. The results of the study showed that normal purple carrot juice exhibited the best activities in all biological and antioxidant tests, except for anti-α-glucosidase activity. Normal purple carrot juice also had the highest total mineral content with elevated results for titratable acidity, pH, total soluble solids, dry mass, ash, viscosity, and osmolality.

CONCLUSION

Purple carrot juices demonstrated elevated health-promoting activities and could be used in blended beverage recipes to attract children's attention. The results of sensorial characteristics (appearance, color, and taste) of juices, however, showed that people are more familiar with orange carrot products. © 2022 Society of Chemical Industry.

The accuracy of serum osmolarity calculation in small children

Background

Serum osmolality can be measured (Omeas) or calculated (Ocal). Many formulas for Ocal have been already published, but data regarding the most accurate equation in small babies is not available. Thus, we aim to compare Omeas and Ocal obtained by different formulas in newborns and small children.

Methods

The study included 280 serum samples taken from children, from the first day of life to 2 years (mean age 8.2 ± 7.6 months) treated in the University Children's Hospital in Krakow. The serum osmolality was measured by osmometer and calculated by 8 common formulas.

Results

The mean value of Omeas (2 8 5 .8 ± 5 .1 mOsm/kgH2O) was significantly different as compared to the mean values of Ocal (p< 0.01) for all formulas, except Ocal obtained by the formula: 1.86*(N a + K) +1.15*Glu + Urea + 14. According to Bland-Altman analysis, this formula showed the best performance for estimating osmolality. In children under 3 months of life Passing-Bablok regression indicated both systematic and proportional error for results obtained by each formula compared to the measured values.

Conclusions

To calculate osmolarity in children aged between 3 months and 2 years old the following equation: 1 .86*(N a + K) + 1.1 5*G lu+ U rea+ 14 might be used, whereas serum osmolality in children up to 3 month of life should be measured.

Public and occupational health risks related to lead exposure updated according to present-day blood lead levels

Lead is an environmental hazard that should be addressed worldwide. Over time, human lead exposure in the western world has decreased drastically to levels comparable to those among humans living in the preindustrial era, who were mainly exposed to natural sources of lead. To re-evaluate the potential health risks associated with present-day lead exposure, a two-pronged approach was applied. First, recently published population metrics describing the adverse health effects associated with lead exposure at the population level were critically assessed. Next, the key results of the Study for Promotion of Health in Recycling Lead (SPHERL; NCT02243904) were summarized and put in perspective with those of the published population metrics. To our knowledge, SPHERL is the first prospective study that accounted for interindividual variability between people with respect to their vulnerability to the toxic effects of lead exposure by assessing the participants' health status before and after occupational lead exposure. The overall conclusion of this comprehensive review is that mainstream ideas about the public and occupational health risks related to lead exposure urgently need to be updated because a large portion of the available literature became obsolete given the sharp decrease in exposure levels over the past 40 years.

Sex-specific issues of central and peripheral arginine-vasopressin concentrations in neurocritical care patients

BACKGROUND

Arginine-Vasopressin (AVP) is a nonapeptide that exerts multiple functions within the central nervous system and in the blood circulation that might contribute to outcome in critically ill patients. Sex differences have been found for mental and physical effects of AVP. For example, stress response and response due to hemorrhage differ between males and females, at least in animal studies. Data on humans -especially on AVP within the central nervous system (CNS)-are scarce, as cerebrospinal fluid (CSF) which is said to represent central AVP activity, has to be collected by means of invasive procedures. Here we present data on 30 neurocritical care patients where we simultaneously collected blood, CSF and saliva to analyze concentrations in the central and peripheral compartments.

PATIENTS AND METHODS

30 neurocritical care patients were included (13 male, 13 postmenopausal female, 4 premenopausal female) with a median age of 60 years. CSF, plasma and saliva were obtained simultaneously once in each patient and analyzed for AVP concentrations. Correlations between the central compartment represented by CSF, and the peripheral compartment represented by plasma and saliva, were identified. Relations between AVP concentrations and serum sodium and hematocrit were also determined.

RESULTS

In the whole patient collective, only very weak to weak correlations could be detected between AVP plasma/CSF, plasma/saliva and CSF/saliva as well as between AVP concentrations in each of the compartments and serum sodium/hematocrit. Regarding the subgroup of postmenopausal females, a significant moderate correlation could be detected for AVP in plasma and CSF and AVP CSF and serum sodium.

CONCLUSION

Absolute concentrations of AVP in central and peripheral compartments did not show sex differences. However, correlations between AVP plasma and CSF and AVP CSF and serum sodium in postmenopausal females indicate differences in AVP secretion and AVP response to triggers that deserve further examination.

Diagnostic and therapeutic approach to hypernatremia

Hypernatremia occurs when the plasma sodium concentration is greater than 145 mmol/L. Depending on the duration, hypernatremia can be differentiated into acute and chronic. According to severity: mild, moderate and threatening hypernatremia. Finally, depending on pathogenesis, hypernatremia can be defined as hypervolemic, hypovolemic, and euvolemic. Acute hypervolemic hypernatremia is often secondary to increased sodium intake (hypertonic NaCl and NaHCO₃ solutions). Instead, chronic hypervolemic hypernatremia may be an expression of primary hyperaldosteronism. Euvolemic hypernatremia occurs in diabetes insipidus: depending on the underlying pathogenesis, it can be classified into two basic types: neurogenic (or central) and nephrogenic. The neurogenic form may be triggered by traumatic, vascular or infectious events; the nephrogenic form may be due to pharmacological causes, such as lithium, or non-pharmacological ones, such as hypokalemia. For hypovolemic hypernatremia, possible explanations are renal or extrarenal losses. The main goal of treatment of hypernatremia is the restoration of plasma tonicity. In particular, if the imbalance has occurred acutely, rapid correction improves the prognosis by preventing the effects of cellular dehydration; if hypernatremia has developed slowly, over a period of days, a slow correction rate (no more than 0.4 mmol/L/h) is recommended.

Effect of vasopressin V2-receptor antagonist tolvaptan on syndrome of inappropriate antidiuresis (SIAD) after transsphenoidal pituitary surgery: recovery of measured osmolality

Background

Delayed hyponatremia after pituitary surgery can be treated with the V2-receptor antagonist, oral tolvaptan. We investigated the pharmacological effect of oral tolvaptan against SIAD in patients with hyponatremia after pituitary surgery.

Methods

Thirty-nine patients with pituitary adenoma treated by endoscopic transsphenoidal surgery developed SIAD according to the major guidelines, and 7 patients (17.9%) were treated with tolvaptan. Tolvaptan was administrated orally half a tablet (3.75 mg) once in the first two cases, and half a tablet twice in the other five cases. Serum osmolality, urinary osmolality, urinary sodium concentration, urinary volume, and serum sodium and potassium concentration were evaluated before administration, and after the last oral administration of tolvaptan. Serum osmolality and urine osmolality were physically measured.

Results

Serum sodium concentration was significantly increased from 132.1 ± 4.0 to 143.0 ± 2.9 mmol/L (mean ± standard deviation, n = 7, P < 0.001). Serum osmolality was significantly increased from 266.3 ± 7.7 to 289.6 ± 6.7 mOsm/kg (n = 7, P < 0.001). Urine osmolality was significantly reduced from 607.1 ± 240.4 to 262.7 ± 115.6 mOsm/kg (n = 7, P = 0.01). Urinary sodium concentration was significantly decreased from 121.3 ± 48.4 to 36.9 ± 35.0 mOsm/kg (n = 7, P = 0.001). Urine output (24-hour including the first administration) was significantly increased from 1384.2 ± 550.7 to 3291.3 ± 1710.9 mL/day (n = 6, P = 0.026).

Conclusions

Oral tolvaptan administration corrects SIAD after pituitary surgery. Hyponatremia after pituitary surgery was confirmed to be due to SIAD.

Natraemia variations induced by acute dialysis in critically ill patients: a database study

Natraemia is often abnormal in critically ill patients and may change rapidly during renal replacement therapy (RRT). This database study in a single intensive care unit (ICU) evaluated natraemia before and after the first RRT session for acute kidney injury. Of 252 patients who required RRT in 2018-2020, 215 were included. Prevalences were 53.9% for hyponatraemia (≤ 135 mmol/L) and 3.7% for hypernatraemia (> 145 mmol/L). Dialysate sodium was ≥ 145 mmol/L in 83% of patients. Median dialysis sodium gradient was 12 mmol/L, with a value above 16 mmol/L in 25% of patients. Median natraemia increased from 135 before to 140 mmol/L after RRT, the median hourly increase being faster than recommended, at 1.0 mmol/L [0.2-1.7]. By multivariate analysis, the only variable significantly associated with the RRT-induced natraemia change was the dialysis sodium gradient [odds ratio, 1.66; 95% confidence interval 1.39-2.10]. Pearson's correlation coefficient between the gradient and the natraemia change was 0.57. When performing RRT in ICU patients, in addition to the haemodynamic considerations put forward in recommendations, the dialysis sodium gradient deserves careful attention in order to control natraemia variations. Studies to devise a formula for predicting natraemia variations might prove helpful to confirm our results.

Demystifying hyponatremia: A clinical guide to evaluation and management

Hyponatremia (serum sodium <135 mEq/L) is a frequent electrolyte abnormality complicating the clinical care of hospitalized patients. Hyponatremia has been associated with an increased risk of mortality. Hyponatremia can be seen in patients with euvolemia, hypovolemia, or hypervolemia. Evaluation of hyponatremia relies on clinical assessment and estimation of serum sodium, urine electrolytes, and serum and urine osmolality in addition to other case-specific laboratory parameters. In addition, point-of-care ultrasonography is an important adjunct to physical assessment in estimation of volume status. Understanding the pathophysiology of the underlying process can lead to a timely diagnosis and appropriate management of hyponatremia.

Hyponatremia in horses with septic pneumopathy

Background

Hyponatremia is common in horses with bacterial pleuropneumonia, but no further characterization of this abnormality has been reported.

Objectives

Describe admission plasma sodium concentration ([Na]) in horses with septic pneumopathy and evaluate any association of plasma [Na] with markers of systemic inflammation.

Animals

Medical records of horses >1 month of age that between 2008 and 2021 had a transtracheal aspirate (TTA) performed, abnormal TTA cytology, positive TTA culture, pulmonary disease on ultrasonography, radiography or both, and plasma [Na] assessed by direct ion‐selective‐electrode (dISE). Horses with concurrent diarrhea or azotemia were excluded.

Methods

Clinical and clinicopathological variables of interest between hypo‐ and normonatremic horses were compared. Spearman correlation and Fisher exact tests were used to identify significant associations (P < .05).

Results

Twenty of 35 horses had hyponatremia (median, 132 mmol/L; 25‐75th interquartile range [IQR], 129.7‐133.1 mmol/L; reference range, 134.2‐138.4 mmol/L). A higher proportion of horses with systemic inflammatory response syndrome (SIRS) had hyponatremia (P = .01). Hyponatremic patients had higher mean plasma fibrinogen concentration (461 ± 160.5 mg/dL; P = .01) and higher rectal temperature (38.8 ± 0.7°C; P = .02) than normonatremic horses. Negative correlations were found between plasma [Na] and fibrinogen (P = .001; ρ = −0.57) concentrations and between plasma [Na] and rectal temperature (P = .001; ρ = −0.51). Presence or absence of pleural effusion did not influence severity of hyponatremia. Mean duration of hospitalization was longer (P = .04) in hyponatremic horses (9.8 ± 6.6 days).

Conclusions and Clinical Importance

Hyponatremia at admission is associated with the presence of inflammation, SIRS, and with longer duration of hospitalization.

Serum Osmolarity and Vasopressin Concentration in Acute Heart Failure-Influence on Clinical Course and Outcome

Neurohormone activation plays an important role in Acute Heart Failure (AHF) pathophysiology. Serum osmolarity can affect this activation causing vasopressin excretion. The role of serum osmolarity and vasopressin concentration and its interaction remain still unexplored in AHF. The objective of our study was to evaluate the relationship of serum osmolarity with clinical parameters, vasopressin concentration, in-hospital course, and outcomes in AHF patients. The study group consisted of 338 AHF patients (male (76.3%), mean age of 68 ± 13 years) with serum osmolarity calculated by the equation: 1.86 × sodium [mmol/L] + (glucose [mg/dL]/18) + (urea [mg/dL]/2.8) + 9 and divided into osmolarity quartiles marked as: low: <287 mOsm/L, intermediate low: 287−294 mOsm/L, intermediate high: 295−304 mOsm/L, and high: >304 mOsm/L. There was an increasing age gradient in the groups and patients differed in the occurrence of comorbidities and baseline clinical and laboratory parameters. Importantly, analysis revealed that vasopressin presented a linear correlation with osmolarity (r = −0.221, p = 0.003) and its concentration decreased with quartiles (61.6 [44.0−81.0] vs. 57.8 [50.0−77.3] vs. 52.7 [43.1−69.2] vs. 45.0 [30.7−60.7] pg/mL, respectively, p = 0.034). This association across quartiles was observed among de novo AHF (63.6 [55.3−94.5] vs. 58.0 [50.7−78.6] vs. 52.0 [46.0−58.0] vs. 38.0 [27.0−57.0] pg/mL, respectively, p = 0.022) and was not statistically significant in patients with acute decompensated heart failure (ADHF) (59.5 [37.4−80.0] vs. 52.0 [38.0−74.5] vs. 57.0 [38.0−79.0] vs. 50.0 [33.0−84.0] pg/mL, respectively, p = 0.849). The worsening of renal function episodes were more frequent in quartiles with higher osmolarity (4 vs. 2 vs. 13 vs. 11%, respectively, p = 0.018) and patients that belonged to the quartiles with low and high osmolarity were characterized more often by incidence of worsening heart failure (20 vs. 9 vs. 10 vs. 22%, respectively, p = 0.032). There was also a U-shape distribution in relation to one-year mortality (31 vs. 19 vs. 23 vs. 37%, respectively, p = 0.022). In conclusion, there was an association of serum osmolarity with clinical status and both in-hospital and out-of-hospital outcomes. Moreover, the linear dependence between vasopressin concentration and serum osmolarity in the AHF population was identified and was driven mainly by patients with de novo AHF which suggests different pathophysiological paths in ADHF and AHF de novo.

Dysnatremia in Gastrointestinal Disorders

The primary solute of the milieu intérieur is sodium and accompanying anions. The solvent is water. The kidneys acutely regulate homeostasis in filtration, secretion, and resorption of electrolytes, non-electrolytes, and minerals while balancing water retention and clearance. The gastrointestinal absorptive and secretory functions enable food digestion and water absorption needed to sustain life. Gastrointestinal perturbations including vomiting and diarrhea can lead to significant volume and electrolyte losses, overwhelming the renal homeostatic compensatory mechanisms. Dysnatremia, potassium and acid-base disturbances can result from gastrointestinal pathophysiologic processes. Understanding the renal and gastrointestinal contributions to homeostatis are important for the clinical evaluation of perturbed volume disturbances.

Interspecies Diversity of Osmotic Gradient Deformability of Red Blood Cells in Human and Seven Vertebrate Animal Species

Plasma and blood osmolality values show interspecies differences and are strictly regulated. The effect of these factors also has an influence on microrheological parameters, such as red blood cell (RBC) deformability and aggregation. However, little is known about the interspecies differences in RBC deformability at various blood osmolality levels (osmotic gradient RBC deformability). Our aim was to conduct a descriptive–comparative study on RBC osmotic gradient deformability in several vertebrate species and human blood. Blood samples were taken from healthy volunteers, dogs, cats, pigs, sheep, rabbits, rats, and mice, to measure hematological parameters, as well as conventional and osmotic gradient RBC deformability. Analyzing the elongation index (EI)–osmolality curves, we found the highest maximal EI values (EI max) in human, dog, and rabbit samples. The lowest EI max values were seen in sheep and cat samples, in addition to a characteristic leftward shift of the elongation index–osmolality curves. We found significant differences in the hyperosmolar region. A correlation of mean corpuscular volume and mean corpuscular hemoglobin concentration with osmoscan parameters was found. Osmotic gradient deformability provides further information for better exploration of microrheological diversity between species and may help to better understand the alterations caused by osmolality changes in various disorders.

Derivation And Validation Of A New Formula For Plasma Osmolality Estimation

BACKGROUND

Plasma osmolality is a physic and chemical property of interest in emergency medicine. This magnitude can be measured at the laboratory, but it is usually estimated with equations. A huge variety of formulas for calculating osmolality have been published, most of them relying on sodium, urea and glucose. The purpose of this study is to develop a new equation for plasma osmolality calculation. In addition we assess the new equation in a sample of healthy individuals.

METHODS

We used results of sodium, potassium, glucose, urea and osmolality recovered from our patient's database. Multivariate lineal regression was carried-out, considering sodium and potassium as separated variables and as unique variable. In a second phase the obtained equations were tested in a sample of healthy blood-donors. Osmolality was measured by freezing point depression.

RESULTS

In the first phase, 1362 plasma determinations for sodium, potassium, glucose, urea and osmolality were analyzed. All of included variables had a significant correlation with measured osmolality, being the highest correlation with sodium plus potassium and the lowest one was with potassium alone. The formulas obtained for the osmolality estimation were 1.86*Na+1.6*(Glucose/18)+1.12*(Urea/6)+21 (A) and 1.88*(Na+K)+1.59*(Glucose/18)+1.08*(Urea/6)+10.6 (B). Assess of the new equations in a sample of healthy individuals showed better results than equations previously published. The lowest difference versus measured osmolality was produced by formula B.

CONCLUSION

The equations produced in this study perform better in the estimation of plasma osmolality than previously published formulas. We recommend introducing formula B in the clinical chemistry routine.

Root-TRAPR: a modular plant growth device to visualize root development and monitor growth parameters, as applied to an elicitor response of Cannabis sativa

BACKGROUND

Plant growth devices, for example, rhizoponics, rhizoboxes, and ecosystem fabrication (EcoFAB), have been developed to facilitate studies of plant root morphology and plant-microbe interactions in controlled laboratory settings. However, several of these designs are suitable only for studying small model plants such as Arabidopsis thaliana and Brachypodium distachyon and therefore require modification to be extended to larger plant species like crop plants. In addition, specific tools and technical skills needed for fabricating these devices may not be available to researchers. Hence, this study aimed to establish an alternative protocol to generate a larger, modular and reusable plant growth device based on different available resources.

RESULTS

Root-TRAPR (Root-Transparent, Reusable, Affordable three-dimensional Printed Rhizo-hydroponic) system was successfully developed. It consists of two main parts, an internal root growth chamber and an external structural frame. The internal root growth chamber comprises a polydimethylsiloxane (PDMS) gasket, microscope slide and acrylic sheet, while the external frame is printed from a three-dimensional (3D) printer and secured with nylon screws. To test the efficiency and applicability of the system, industrial hemp (Cannabis sativa) was grown with or without exposure to chitosan, a well-known plant elicitor used for stimulating plant defense. Plant root morphology was detected in the system, and plant tissues were easily collected and processed to examine plant biological responses. Upon chitosan treatment, chitinase and peroxidase activities increased in root tissues (1.7- and 2.3-fold, respectively) and exudates (7.2- and 21.6-fold, respectively). In addition, root to shoot ratio of phytohormone contents were increased in response to chitosan. Within 2 weeks of observation, hemp plants exhibited dwarf growth in the Root-TRAPR system, easing plant handling and allowing increased replication under limited growing space.

CONCLUSION

The Root-TRAPR system facilitates the exploration of root morphology and root exudate of C. sativa under controlled conditions and at a smaller scale. The device is easy to fabricate and applicable for investigating plant responses toward elicitor challenge. In addition, this fabrication protocol is adaptable to study other plants and can be applied to investigate plant physiology in different biological contexts, such as plant responses against biotic and abiotic stresses.

Pediatric Diabetes on the Rise: Trends in Incident Diabetes During the COVID-19 Pandemic

Context

The effects of the coronavirus disease 2019 (COVID-19) pandemic on the incident cases of pediatric type 1 diabetes (T1D) and type 2 diabetes (T2D) are not clear.

Objective

To identify trends in incidence and presentation of pediatric new-onset T1D and T2D during the COVID-19 pandemic.

Methods

A retrospective chart review was conducted. Demographics, anthropometrics, and initial laboratory results from patients ages 0 through 21 years who presented with new-onset diabetes to a pediatric tertiary care center were recorded.

Results

During the pandemic, incident cases of pediatric T1D increased from 31 in each of the prior 2 years to 46; an increase of 48%. Incident cases of pediatric T2D increased by 231% from 2019 to 2020. The number of incident cases of pediatric T2D increased significantly more than the number of incident cases of pediatric T1D (P = 0.009). Patients with T2D were more likely to present in diabetic ketoacidosis (DKA), though this was not statistically significant (P = 0.093). Severe DKA was higher compared with moderate DKA (P = 0.036) in incident cases of pediatric T2D. During the pandemic, for the first time, incident cases of T2D accounted for more than one-half of all newly diagnosed pediatric diabetes cases (53%).

Conclusions

There were more incident pediatric T1D and T2D cases as well as an increase in DKA severity in T2D at presentation during the COVID-19 pandemic. More importantly, incident T2D cases were higher than the incident T1D during the pandemic. This clearly suggests a disruption and change in the pediatric diabetes trends with profound individual and community health consequences.

Two-year responses of renal function to first occupational lead exposure

Introduction

Whether in advanced countries lead exposure still contributes to renal impairment is debated, because blood lead (BL) level is declining toward preindustrial levels and because longitudinal studies correlating renal function and BL changes over time are scarce.

Methods

The Study for Promotion of Health in Recycling Lead (SPHERL) evaluated the 2-year renal function responses in 251 workers (mean age, 29.7 years) transiting from environmental to occupational exposure. Main study end point was the estimated glomerular filtration rate (eGFR) derived from serum creatinine (eGFRcrt), cystatin C (eGFRcys), or both (eGFRcc). BL level was measured by inductively coupled plasma mass spectrometry (detection limit 0.5 μg/dl).

Results

In the follow-up, mean baseline BL level of 4.13 μg/dl increased 3.30-fold. In fully adjusted mixed models, additionally accounting for the within-participant clustering of the 1- and 2-year follow-up data, a 3-fold BL level increment was not significantly correlated with changes in eGFR with estimates amounting to −0.86 (95% CI: −2.39 to 0.67), −1.58 (−3.34 to 0.18), and −1.32 (−2.66 to 0.03) ml/min per 1.73 m² for eGFRcrt, eGFRcys, or eGFRcc, respectively. Baseline BL level and the cumulative lead burden did not materially modify these estimates, but baseline eGFR was a major determinant of eGFR changes showing regression to the mean during follow-up. Responses of serum osmolarity, urinary gravity, or the urinary albumin-to-creatinine ratio (ACR) were also unrelated to the BL level increment. The age-related decreases in eGFRcrt, eGFRcys, and eGFRcc were −1.41, −0.96, and −1.10 ml/min per 1.73 m², respectively.

Conclusion

In the current study, the 2-year changes in renal function were unrelated to the increase in BL level. However, given the CIs around the point estimates of the changes in eGFRcc and eGFRcys, a larger study with longer follow-up is being planned.

The Influence of Polyols on the Process Kinetics and Bioactive Substance Content in Osmotic Dehydrated Organic Strawberries

In recent years, an increasing interest in reducing sugar consumption has been observed and many studies are conducted on the use of polyols in the osmotic dehydration process to obtain candied or dried fruits. The studies in the literature have focused on the kinetics of the process as well as the basic physical properties. In the scientific literature, there is a lack of investigation of the influence of such polyol solutions such as sorbitol and mannitol used as osmotic substances during the osmotic dehydration process on the contents of bioactive components, including natural colourants. Thus, the aim of the study was to evaluate the impact of polyols (mannitol and sorbitol) in different concentrations on the process kinetics and on chosen physical (colour and structural changes) as well as chemical (sugars and polyol content, total anthocyanin content, total polyphenol content, vitamin C, antioxidant activity) properties of osmotic-dehydrated organic strawberries. Generally, the results showed that the best solution for osmotic dehydration is 30% or 40% sorbitol solutions, while mannitol solution is not recommended due to difficulties with preparing a high-concentration solution and its crystallization in the tissue. In the case of sorbitol, the changes of bioactive compounds, as well as colour change, were similar to the sucrose solution. However, the profile of the sugar changed significantly, in which sucrose, glucose, and fructose were reduced in organic strawberries and were partially replaced by polyols.

Effects of osmolality and solutes on the morphology of red blood cells according to three-dimensional refractive index tomography

Phosphate-buffered saline (PBS) and Alsever's solution (AS) are frequently used as media in blood-related studies, while 0.9% normal saline (NS) is frequently used in transfusion medicine. Despite the frequent use, the effects of these solutions on the shape and volume of red blood cells (RBCs) have not been reported. We collected blood samples from five healthy adults and used three-dimensional refractive index tomography to investigate the changes in the morphology of RBCs caused by changes in osmolality and solutes at the single-cell level. After diluting 2 μL of RBCs 200-fold with each solution (PBS, AS, and 0.9% NS), 40 randomly selected RBCs were microscopically observed. RBC shape was measured considering sphericity, which is a dimensionless quantity ranging from 0 (flat) to 1 (spherical). RBCs in plasma or AS showed a biconcave shape with a small sphericity, whereas those in 0.9% NS or PBS showed a spherical shape with a large sphericity. Moreover, we confirmed that sodium chloride alone could not elicit the biconcave shape of RBCs, which could be maintained only in the presence of an osmotic pressure-maintaining substance, such as glucose or mannitol. Although 0.9% NS solution is one of the most commonly used fluids in hematology and transfusion medicine, RBCs in 0.9% NS or PBS are not biconcave. Therefore, as the debate on the use of NS continues, future clinical studies or applications should consider the effect of glucose or mannitol on the shape of RBCs.