Protocol for sodium depletion and measurement of sodium appetite in mice.

Sodium appetite is a state that motivates animals to consume normally unappetizing concentrations of sodium. Here we describe a protocol to induce sodium appetite in mice by furosemide-induced diuresis and measure sodium intake using volumetric drinking tubes. This protocol induces sodium appetite rapidly and can be used to assess the effect of various treatments on sodium appetite. This protocol does not require electronic equipment and can be implemented easily. For complete details on the use and execution of this protocol, please refer to Park et al. (2020).

Despite increasing aldosterone, elevated potassium is not necessary for activating aldosterone-sensitive HSD2 neurons or sodium appetite.

Restricting dietary sodium promotes sodium appetite in rats. Prolonged sodium restriction increases plasma potassium (pK), and elevated pK is largely responsible for a concurrent increase in aldosterone, which helps promote sodium appetite. In addition to increasing aldosterone, we hypothesized that elevated potassium directly influences the brain to promote sodium appetite. To test this, we restricted dietary potassium in sodium-deprived rats. Potassium restriction reduced pK and blunted the increase in aldosterone caused by sodium deprivation, but did not prevent sodium appetite or the activation of aldosterone-sensitive HSD2 neurons. Conversely, supplementing potassium in sodium-deprived rats increased pK and aldosterone, but did not increase sodium appetite or the activation of HSD2 neurons relative to potassium restriction. Supplementing potassium without sodium deprivation did not significantly increase aldosterone and HSD2 neuronal activation and only modestly increased saline intake. Overall, restricting dietary sodium activated the HSD2 neurons and promoted sodium appetite across a wide range of pK and aldosterone, and saline consumption inactivated the HSD2 neurons despite persistent hyperaldosteronism. In conclusion, elevated potassium is important for increasing aldosterone, but it is neither necessary nor sufficient for activating HSD2 neurons and increasing sodium appetite.

Optogenetic Stimulation of Type I GAD65+ Cells in Taste Buds Activates Gustatory Neurons and Drives Appetitive Licking Behavior in Sodium-Depleted Mice.

Mammalian taste buds are comprised of specialized neuroepithelial cells that act as sensors for molecules that provide nutrition (e.g., carbohydrates, amino acids, and salts) and those that are potentially harmful (e.g., certain plant compounds and strong acids). Type II and III taste bud cells (TBCs) detect molecules described by humans as "sweet," "bitter," "umami," and "sour." TBCs that detect metallic ions, described by humans as "salty," are undefined. Historically, type I glial-like TBCs have been thought to play a supportive role in the taste bud, but little research has been done to explore their role in taste transduction. Some evidence implies that type I cells may detect sodium (Na+) via an amiloride-sensitive mechanism, suggesting they play a role in Na+ taste transduction. We used an optogenetic approach to study type I TBCs by driving the expression of the light-sensitive channelrhodopsin-2 (ChR2) in type I GAD65+ TBCs of male and female mice. Optogenetic stimulation of GAD65+ TBCs increased chorda tympani nerve activity and activated gustatory neurons in the rostral nucleus tractus solitarius. "N neurons," whose NaCl responses were blocked by the amiloride analog benzamil, responded robustly to light stimulation of GAD65+ TBCs on the anterior tongue. Two-bottle preference tests were conducted under Na+-replete and Na+-deplete conditions to assess the behavioral impact of optogenetic stimulation of GAD65+ TBCs. Under Na+-deplete conditions GAD65-ChR2-EYFP mice displayed a robust preference for H2O illuminated with 470 nm light versus nonilluminated H2O, suggesting that type I glial-like TBCs are sufficient for driving a behavior that resembles Na+ appetite.SIGNIFICANCE STATEMENT This is the first investigation on the role of type I GAD65+ taste bud cells (TBCs) in taste-mediated physiology and behavior via optogenetics. It details the first definitive evidence that selective optogenetic stimulation of glial-like GAD65+ TBCs evokes neural activity and modulates behavior. Optogenetic stimulation of GAD65+ TBCs on the anterior tongue had the strongest effect on gustatory neurons that responded best to NaCl stimulation through a benzamil-sensitive mechanism. Na+-depleted mice showed robust preferences to "light taste" (H2O illuminated with 470 nm light vs nonilluminated H2O), suggesting that the activation of GAD65+ cells may generate a salt-taste sensation in the brain. Together, our results shed new light on the role of GAD65+ TBCs in gustatory transduction and taste-mediated behavior.

Sodium Status and Replacement in Children and Adults Living with Cystic Fibrosis: A Narrative Review.

Patients with cystic fibrosis (CF) have a two- to four-fold higher sodium chloride sweat content compared with healthy controls. This high sweat salt loss increases the risk for electrolyte disturbances, associated with subacute or chronic complications. Sodium status therefore needs to be adequately monitored and salt intake adjusted to individual needs. The lack of current evidence to formulate specific recommendations and assess sodium status is reflected in a variability of recommendations in international guidelines. This narrative review presents an overview of the current evidence. Infants with CF in particular are at risk for severe sodium deficiency, potentially leading to metabolic alkalosis due to low intake and high sweat losses. More research on the assessment of sodium status and efficacy of sodium chloride supplements in the population of patients with CF, especially given the changing era of CF transmembrane conductance regulator modulatory treatment, is warranted.

Cortisol and Aldosterone Responses to Hypoglycemia and Na Depletion in Women With Non-Classic 21-Hydroxylase Deficiency.

BACKGROUND: Non-classic 21-hydroxylase deficiency is usually diagnosed in post-pubertal women because of androgen excess. Indication of systematic steroid replacement therapy is controversial because the risk of acute adrenal insufficiency is unknown. In order to specify this risk we evaluated the cortisol and aldosterone secretions in response to appropriate pharmacologic challenges. METHODS: In this prospective case-control non-inferiority study we investigated 20 women with non-classic 21-hydroxylase deficiency carrying biallelic CYP21A2 mutations and with serum 17-hydroxyprogesterone (17OHP) >10 ng/mL after stimulation with Synacthen® (tetracosactrin) and 20 age- and body mass index-matched healthy women with 17OHP after Synacthen® <2 ng/mL. Each participant underwent sequentially an insulin tolerance test to evaluate cortisol secretion and a sodium depletion test, obtained by oral administration of 40 mg of furosemide under low sodium diet (<20 mmol during 24 hours), to evaluate renin and aldosterone secretion. FINDINGS: The peak serum cortisol concentration after insulin hypoglycemia was lower in patients than in controls (mean difference -47 ng/mL, 90% CI, -66, P = 0.0026). A peak serum cortisol above a cutoff value of 170 ng/mL was obtained in all controls but only in 55% of patients (P = 0.0039). Twenty-four hours after sodium depletion, blood pressure, plasma sodium, potassium, and serum aldosterone concentrations were comparable between the two groups, but patients had higher stimulated renin concentrations than controls (P = 0.0044). INTERPRETATION: Patients with non-classic 21-hydroxylase deficiency frequently display partial cortisol insufficiency and compensated defect in aldosterone secretion. Their clinical management should systematically include assessment of adrenal functions.

Dysfunction of the endothelium and constriction of the isolated rat's middle cerebral artery in low sodium environment in the presence of vasopressin.

Hyponatraemia, a water-electrolyte disorder diagnosed in patients with subarachnoid haemorrhage (SAH), increases a risk of persistent vasospasm. In majority of cases, hyponatraemia results from inappropriate secretion of vasopressin (AVP). The effect of AVP-associated hyponatraemia on cerebral vasculature is unknown. The present study aimed to elucidate the role of AVP in the response of the middle cerebral artery (MCA) of the rat to hyponatraemia. Isolated, cannulated, and pressurized rat MCAs were perfused/superfused with physiological (Na+  = 144 mmol/L) buffer or low-sodium (Na+  = 121 mmol/L) buffer containing either AVP or angiotensin II (ANG II). ANG II was used to check if the effect of low plasma sodium concentration combined with AVP on the MCA tone is unique to vasopressin. At physiological Na+ concentration, vasopressin (1.4 × 10-11  mol/L) or angiotensin II (10-9  mol/L) resulted in relaxation of the MCA. Substitution of low-sodium for the normal sodium buffer with the same concentration of AVP, resulted in the constriction of the MCA. This effect was absent after removal of the endothelium, administration of vasopressin V1 receptor antagonist or concomitant inhibition of endothelin-1 receptors and synthesis of thromboxane A2. In contrast, no constriction of the MCA in low-sodium buffer was observed when AVP was replaced with ANG II. Our data suggest that presence of vasopressin and low sodium ion concentration results in the change of endothelium phenotype from pro-vasodilatory to pro-vasoconstrictory. This phenomenon may be an overlooked factor contributing to vasospasm in SAH patients with hyponatraemia caused by inappropriate antidiuretic hormone secretion (SIADH).

Acute body sodium depletion induces skin sodium mobilization in female Wistar rats.

NEW FINDINGS: What is the central question of this study? Can Na+ depletion mobilize Na+ from the skin reservoir in ovariectomized rats? Does oestrogen replacement change the amount and the dynamics of skin Na+ storage? Is the reduced salt appetite after Na+ depletion in ovariectomized rats with oestrogen replacement related to changes in the skin Na+ ? What is the main finding and its importance? This work demonstrated that acute body Na+ depletion induced by frusemide mobilized the osmotically inactive skin Na+ reservoir to become osmotically active. Oestrogen treatment decreased the induced Na+ intake in ovariectomized rats but did not modulate the inactive Na+ reservoir in control conditions or its mobilization induced by Na+ depletion. ABSTRACT: Oestradiol, which is an important hormone for water and electrolyte balance, also has a role in the inhibition of induced Na+ appetite. Sodium can be stored in the skin in osmotically active or inactive forms, and this skin Na+ reservoir may be involved in the control of body Na+ levels during physiopathological challenges. In this study, we investigated whether the effect of sodium depletion by frusemide can mobilize Na+ from the skin reservoir and whether oestradiol replacement changes or mobilizes the Na+ reserves in the skin. Ovariectomized Wistar rats were treated with vehicle or oestradiol for 7 days to evaluate the effects of oestrogen on the hydroelectrolyte balance, intake responses and skin Na+ and water content in basal conditions. Furthermore, the effects of oestrogen were evaluated after 24 h frusemide-induced whole-body Na+ depletion. Oestradiol-replaced rats exhibited reduced water intake without any significant changes in salt intake, Na+ excretion or water and Na+ skin content in basal conditions. After sodium depletion, both vehicle- and oestradiol-treated rats exhibited an increase in the osmotically active skin Na+ , which was associated with a decrease of the inactive skin Na+ reservoir. Oestrogen decreased the hypertonic saline intake induced by Na+ depletion, but it was not associated with any significant changes in the skin Na+ reservoir. Thus, sodium depletion is able to change the inactive-active skin Na+ reservoir balance. However, the oestrogenic modulation of sodium appetite after Na+ depletion is probably not related to the action of this hormone in the skin Na+ reservoir balance.

Whole body sodium depletion modifies AT1 mRNA expression and serotonin content in the dorsal raphe nucleus.

Angiotensin II (Ang II) acts on Ang II type 1 (AT1) receptors located in the organum vasculosum and subfornical organ (SFO) of the lamina terminalis as a main facilitatory mechanism of sodium appetite. The brain serotonin (5-HT) system with soma located in the dorsal raphe nucleus (DRN) provides a main inhibitory mechanism. In the present study, we first investigated the existence of Ang II AT1 receptors in serotonergic DRN neurones. Then, we examined whether whole body sodium depletion affects the gene expression of the AT1a receptor subtype and the presumed functional significance of AT1 receptors. Using confocal microscopy, we found that tryptophan hydroxylase-2 and serotonin neurones express AT1 receptors in the DRN. Immunofluorescence quantification showed a significant reduction in 5-HT content but no change in AT1 receptor expression or AT1/5-HT colocalisation in the DRN after sodium depletion. Whole body sodium depletion also significantly increased Agtr1a mRNA expression in the SFO and DRN. Oral treatment with the AT1 receptor antagonist losartan reversed the changes in Agtr1a expression in the SFO but not the DRN. Losartan injection into either the DRN or the mesencephalic aqueduct had no influence on sodium depletion-induced 0.3 mol L-1 NaCl intake. The results indicate the expression of Agtr1a mRNA in the DRN and SFO as a marker of sodium depletion. They also suggest that serotonergic DRN neurones are targets for Ang II. However, the function of their AT1 receptors remains elusive.

Increased locomotor activity in estrogen-treated ovariectomized rats is associated with nucleus accumbens dopamine and is not reduced by dietary sodium deprivation.

Estrogens are well known to increase locomotor activity in laboratory rodents; however, the underlying mechanism remains unclear. We used voluntary wheel running by female rats as an index of locomotor behavior to investigate this issue. We first determined whether the estrogen-induced increase in locomotion was susceptible to inhibition by a physiological challenge, and next whether it was associated with dopaminergic activation in the central reward area, nucleus accumbens. Ovariectomized rats were given estradiol or the oil vehicle and housed in cages with or without running wheels. All rats were given regular rodent chow for 1 week, a sodium-deficient diet for the next week, and then were returned to a regular diet for another week. At the end of the last week, all rats were killed, brains were extracted and dopamine levels in the nucleus accumbens were measured. As expected, estradiol treatment increased distance run. Surprisingly, dietary sodium deprivation further increased running, but this appeared to be related to experience with wheel running, rather than to sodium deprivation, per se. Dopamine was greater in the nucleus accumbens of estradiol-treated rats that ran compared to all other groups. Thus, the estrogen-induced increase in locomotion is a robust phenomenon that is not inhibited by a body sodium challenge and is associated with elevated levels of dopamine in reward pathways. These findings raise the possibility that the estrogen-induced increase in locomotor activity, which occurs during a hormonal milieu conducive to reproduction, may reflect mate-seeking behavior and, thereby, maximize reproductive success.

Na restriction activates epithelial Na channels in rat kidney through two mechanisms and decreases distal Na+ delivery.

KEY POINTS: Dietary Na restriction, through the mineralocorticoid aldosterone, acts on epithelial Na channels via both fast (24 h) and slow (5-7 days) mechanisms in the kidney. The fast effect entails increased proteolytic processing and trafficking of channel protein to the apical membrane. It is rapidly reversible by the mineralocorticoid receptor antagonist eplerenone and is largely lost when tubules are studied ex vivo. The slow effect does not require increased processing or surface expression, is refractory to acute eplerenone treatment, and is preserved ex vivo. Both slow and fast effects contribute to Na retention in vivo. Increased Na+ reabsorption in the proximal tubule also promotes Na conservation under conditions of chronic dietary Na restriction, reducing Na+ delivery to the distal nephron. ABSTRACT: Changes in the activity of the epithelial Na channel (ENaC) help to conserve extracellular fluid volume. In rats fed a low-salt diet, proteolytic processing of ENaC increased within 1 day, and was almost maximal after 3 days. The rapid increase in the abundance of cleaved αENaC and γENaC correlated with decreased urinary Na+ excretion and with increased ENaC surface expression. By contrast, ENaC activity, measured ex vivo in isolated cortical collecting ducts, increased modestly after 3 days and required 5 days to reach maximal levels. The mineralocorticoid receptor antagonist eplerenone reversed the increase in cleaved γENaC and induced natriuresis after 1 or 3 days but failed to alter either ENaC currents or Na+ excretion after 7 days of Na restriction. We conclude that Na depletion, through aldosterone, stimulates ENaC via independent fast and slow mechanisms. In vivo, amiloride-induced natriuresis increased after 1 day of Na depletion. By contrast, hydrochlorothiazide (HCTZ)-induced natriuresis decreased gradually over 7 days, consistent with increased ability of ENaC activity to compensate for decreased Na+ reabsorption in the distal convoluted tubule. Administration of amiloride and HCTZ together increased Na+ excretion less in Na-depleted compared to control animals, indicating decreased delivery of Na+ to the distal nephron when dietary Na is restricted. Measurements of creatinine and Li+ clearances indicated that increased Na reabsorption by the proximal tubules is responsible for the decreased delivery. Thus, Na conservation during chronic dietary salt restriction entails enhanced transport by both proximal and distal nephron segments.

Flattening of a generalization gradient following a retention interval: Evidence for differential forgetting of stimulus features.

In two experiments, rats received exposure to a compound consisting of a solution of salt plus a distinctive flavor (A), followed by an injection of furo-doca to induce a salt need. Experiment 1, established that this procedure successfully generated a preference for flavor A in a subsequent choice test between A and water. Experiment 2 used this within-event learning effect to investigate generalization, testing the rats with both A and a novel flavor (B). For different groups the interval between the training phase and the test phase was varied. Subjects tested immediately after training showed a steep generalization gradient (i.e., a strong preference for A, and a weak preference for B). Subjects given a 14-day retention interval showed a flattened gradient, a reduced level of preference for A and an enhanced preference for B. These results are interpreted in terms of changes in stimulus representations over the retention interval that act to reduce the effectiveness of the distinctive features of stimuli (the features that are necessary to ensure discrimination between them).

Sodium Carbonate is Saltier Than Sodium Chloride to Sodium-Depleted Rats.

In a series of behavioral experiments in the 1960s, G.R. Morrison identified several unique features of the taste of Na2CO3 to rats; namely, it is 1) considerably more intense than NaCl at isomolar concentrations, 2) avoided at 10 times lower concentrations than NaCl to thirsty rats, 3) preferred at 10 times lower concentrations than NaCl in sodium-depleted rats. He also demonstrated its qualitatively similarity to NaCl. In Experiment 1, we confirmed and extended many of Morrison's observations. Rats were injected with furosemide on 3 occasions to stimulate a sodium appetite. After each depletion, rats were given a brief-access taste test in a lickometer presenting, in random order, water and 7 concentrations of salt. One test used NaCl (0.028-0.89 M, quarter log steps), another used Na2CO3, and the third used Na2CO3, but at a tenfold lower concentration range (0.0028-0.089 M). Rats licked NaCl in an inverted-U shaped concentration-response function peaking at 0.158-0.281 M. As Morrison's results predicted, rats licked Na2CO3 in nearly identical fashion, but at a tenfold lower concentration range (peak at 0.0158-0.028 M). In a second experiment, furosemide-treated rats were repeatedly tested with the lower Na2CO3 range but mixed in the epithelial sodium channel blocker amiloride at various concentrations (3-300 µM, half log steps). Amiloride reduced licking for Na2CO3 and shifted the peak response rightward up to about half a log unit. Thus, this "super-saltiness" of Na2CO3 to rats is at least partly amiloride-dependent.

Aldosterone-Sensing Neurons in the NTS Exhibit State-Dependent Pacemaker Activity and Drive Sodium Appetite via Synergy with Angiotensin II Signaling.

Sodium deficiency increases angiotensin II (ATII) and aldosterone, which synergistically stimulate sodium retention and consumption. Recently, ATII-responsive neurons in the subfornical organ (SFO) and aldosterone-sensitive neurons in the nucleus of the solitary tract (NTSHSD2 neurons) were shown to drive sodium appetite. Here we investigate the basis for NTSHSD2 neuron activation, identify the circuit by which NTSHSD2 neurons drive appetite, and uncover an interaction between the NTSHSD2 circuit and ATII signaling. NTSHSD2 neurons respond to sodium deficiency with spontaneous pacemaker-like activity-the consequence of "cardiac" HCN and Nav1.5 channels. Remarkably, NTSHSD2 neurons are necessary for sodium appetite, and with concurrent ATII signaling their activity is sufficient to produce rapid consumption. Importantly, NTSHSD2 neurons stimulate appetite via projections to the vlBNST, which is also the effector site for ATII-responsive SFO neurons. The interaction between angiotensin signaling and NTSHSD2 neurons provides a neuronal context for the long-standing "synergy hypothesis" of sodium appetite regulation.

Towards a geography of omnivory: Omnivores increase carnivory when sodium is limiting.

Towards understanding the geography of omnivory, we tested three hypotheses that predict the proportion of animal tissue consumed: the sodium limitation hypothesis predicts that omnivores increase animal consumption in Na-poor environments because Na bioaccumulates from plants to predators; thus, heterotrophs are Na-rich sources. The nitrogen limitation and habitat productivity hypotheses use the same logic to predict more animal consumption in N-poor and productive environments respectively. Omnivory is a common trophic strategy, but what determines the balance of plant and animal tissue omnivores consume is relatively unexplored. Most of what we know comes from single populations at local scales. Here we quantitatively test these three hypotheses at a large geographic scale and across 20 species of omnivorous ants. We tested each hypothesis using N stable isotopes (δ15 N) to quantify the degree of carnivory in ant populations in 20 forests that span 12° latitude from Georgia to Maine, USA. We used the difference in δ15 N between 20 ant conspecifics in 10 genera between two paired forests (10 pairs of 20 forests) that consisted of a coastal and inland forests on the same latitude to determine if the proportion of animal tissue consumed could be predicted based on Na, N or net primary productivity. Sodium gradients accounted for 18% of the variation in δ15 N, 45% if one outlier ant species was omitted. In contrast, the nitrogen limitation and habitat productivity hypotheses, which predict more animal consumption in N-poor and more productive environments respectively, failed to vary with δ15 N. Our results reveal a geography of omnivory driven in part by access to Na.

The Perceptual Characteristics of Sodium Chloride to Sodium-Depleted Rats.

Three experiments assessed potential changes in the rat's perception of sodium chloride (NaCl) during a state of sodium appetite. In Experiment 1, sodium-sufficient rats licking a range of NaCl concentrations (0.028-0.89M) in 15s trials showed an inverted U-shaped concentration response function peaking at 0.281M. Depleted rats (furosemide) showed an identical function, merely elevated, suggesting altered qualitative or hedonic perception but no change in perceived intensity. In Experiment 2, sodium-depleted rats were tested with NaCl, sodium gluconate, and potassium chloride (KCl; 0.028-0.89M) similar to Experiment 1. KCl was licked at the same rate as water except for a slight elevation at 0.158; sodium gluconate and NaCl were treated similarly, but rats showed more licking for hypertonic sodium gluconate than hypertonic NaCl. Sodium-depleted rats were also tested with NaCl mixed in amiloride (10-300 µM). Amiloride reduced licking but did not alter the shape of the concentration-response function. Collectively, these results suggest that transduction of sodium by epithelial sodium channels (which are blocked by amiloride and are more dominant in sodium gluconate than NaCl transduction) is crucial for the perception of sodium during physiological sodium depletion. In Experiment 3, sodium-deplete rats were tested with NaCl as in Experiment 1 but after taste aversion conditioning to 0.3M NaCl or sucrose. Rats conditioned to avoid NaCl but not sucrose failed to express a sodium appetite, strongly suggesting that NaCl does not undergo a change in taste quality during sodium appetite-rats show no confusion between sucrose and NaCl in this paradigm.

Enamel alteration following tooth bleaching and remineralization.

The purpose of this study was to compare the effects of professional tooth whitening agents containing highly concentrated hydrogen peroxide (with and without laser activation), on the enamel surface; and the potential of four different toothpastes to remineralize any alterations. The study was performed on 50 human molars, divided in two groups: treated with Opalescence(®) Boost and Mirawhite(®) Laser Bleaching. Furthermore, each group was divided into five subgroups, a control one and 4 subgroups remineralized with: Mirasensitive(®) hap+, Mirawhite(®) Gelleѐ, GC Tooth Mousse™ and Mirafluor(®) C. The samples were analysed by SEM/3D-SEM-micrographs, SEM/EDX-qualitative analysis and SEM/EDX-semiquantitative analysis. The microphotographs show that both types of bleaching cause alterations: emphasized perikymata, erosions, loss of interprizmatic substance; the laser treatment is more aggressive and loss of integrity of the enamel is determined by shearing off the enamel rods. In all samples undergoing remineralization deposits were observed, those of toothpastes based on calcium phosphate technologies seem to merge with each other and cover almost the entire surface of the enamel. Loss of integrity and minerals were detected only in the line-scans of the sample remineralized with GC Tooth Mousse™. The semiquantitative EDX analysis of individual elements in the surface layer of the enamel indicates that during tooth-bleaching with HP statistically significant loss of Na and Mg occurs, whereas the bleaching in combination with a laser leads to statistically significant loss of Ca and P. The results undoubtedly confirm that teeth whitening procedures lead to enamel alterations. In this context, it must be noted that laser bleaching is more aggressive for dental substances. However, these changes are reversible and can be repaired by application of remineralization toothpastes.

Low extracellular sodium promotes adipogenic commitment of human mesenchymal stromal cells: a novel mechanism for chronic hyponatremia-induced bone loss.

Hyponatremia represents an independent risk factor for osteoporosis and fractures, affecting both bone density and quality. A direct stimulation of bone resorption in the presence of reduced extracellular sodium concentrations ([Na(+)]) has been shown, but the effects of low [Na(+)] on osteoblasts have not been elucidated. We investigated the effects of a chronic reduction of extracellular [Na(+)], independently of osmotic stress, on human mesenchymal stromal cells (hMSC) from bone marrow, the common progenitor for osteoblasts and adipocytes. hMSC adhesion and viability were significantly inhibited by reduced [Na(+)], but their surface antigen profile and immuno-modulatory properties were not altered. In low [Na(+)], hMSC were able to commit toward both the osteogenic and the adipogenic phenotypes, as demonstrated by differentiation markers analysis. However, the dose-dependent increase in the number of adipocytes as a function of reduced [Na(+)] suggested a preferential commitment toward the adipogenic phenotype at the expense of osteogenesis. The amplified inhibitory effect on the expression of osteoblastic markers exerted by adipocytes-derived conditioned media in low [Na(+)] further supported this observation. The analysis of cytoskeleton showed that low [Na(+)] were associated with disruption of tubulin organization in hMSC-derived osteoblasts, thus suggesting a negative effect on bone quality. Finally, hMSC-derived osteoblasts increased their expression of factors stimulating osteoclast recruitment and activity. These findings confirm that hyponatremia should be carefully taken into account because of its negative effects on bone, in addition to the known neurological effects, and indicate for the first time that impaired osteogenesis may be involved.

Safety and Efficacy of Low-osmolarity ORS vs. Modified Rehydration Solution for Malnourished Children for Treatment of Children with Severe Acute Malnutrition and Diarrhea: A Randomized Controlled Trial.

World Health Organization-recommended rehydration solution for malnourished children (ReSoMal) for rehydrating severe acute malnourished children is not available in India. In present study, 110 consecutive children aged 6-59 months with severely acute malnourishment and acute diarrhea were randomized to low-osmolarity oral rehydration solution (ORS) (osmolarity: 245, sodium: 75) with added potassium (20 mmol/l) or modified ReSoMal (osmolarity: 300, sodium: 45). In all, 15.4% of modified ReSoMal group developed hyponatremia as compared with 1.9% in low-osmolarity ORS, but none developed severe hyponatremia or hypernatremia. Both groups had equal number of successful rehydration (52 each). Both types of ORS were effective in correcting hypokalemia and dehydration, but rehydration was achieved in shorter duration with modified ReSoMal.

Hyponatremia in cancer patients.

Hyponatremia is the most frequent electrolyte disorder in hospitalized patients but also a well known poor prognostic factor in cancer patients. Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is often misdiagnosed by oncologist because of difficulties in the interpretation of laboratory tests. Etiology is heterogeneous but the predominant cause is represented by the unbalance between excessive presence of water and serum sodium deficiency. Ectopic production of arginine vasopressin (AVP) develops more frequently in small cell lung cancer but it is not so rare in other malignancies. Neurological impairment may range from subclinical to life-threating symptoms depending by the rate of serum sodium deficiency. Appropriate diagnosis is essential to set a proper therapy. When hyponatremia is caused by SIADH, hypertonic saline infusion is indicated for acute presentation whereas fluid restriction is preferred in case of chronic asymptomatic evolution. Other options include vaptans, vasopressin receptor antagonists, targeted specifically for the correction of euvolemic hyponatremia. The aim of this brief report is to provide concise and specific informations for the management of SIADH in oncology clinical practice.

Moniliform deformation of retinal ganglion cells by formaldehyde-based fixatives.

Protocols for characterizing cellular phenotypes commonly use chemical fixatives to preserve anatomical features, mechanically stabilize tissue, and stop physiological responses. Formaldehyde, diluted in either phosphate-buffered saline or phosphate buffer, has been widely used in studies of neurons, especially in conjunction with dyes and antibodies. However, previous studies have found that these fixatives induce the formation of bead-like varicosities in the dendrites and axons of brain and spinal cord neurons. We report here that these formaldehyde formulations can induce bead formation in the dendrites and axons of adult rat and rabbit retinal ganglion cells, and that retinal ganglion cells differ from hippocampal, cortical, cerebellar, and spinal cord neurons in that bead formation is not blocked by glutamate receptor antagonists, a voltage-gated Na(+) channel toxin, extracellular Ca(2+) ion exclusion, or temperature shifts. Moreover, we describe a modification of formaldehyde-based fixatives that prevents bead formation in retinal ganglion cells visualized by green fluorescent protein expression and by immunohistochemistry.