Effects of extracellular environment on the osmotic signal transduction involved in activation of motility of carp spermatozoa
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The mechanism by which a hypo-osmotic shock activates motility of carp spermatozoa was studied. The direct role of osmolality at the axoneme was investigated after demembranation of spermatozoa with Triton X-100 and reactivation in various ionic or anionic solutions containing Mg-ATP: demembranated spermatozoa remain motile in solutions of osmolality up to 550 mOsm kg-1 while non-demembranated spermatozoa are immotile when osmolality rises above 250 mOsm kg-1 with the same salt solutions as well as in non-ionic solutions. Suspension in hypo-osmotic saline solutions triggered the swelling of native carp spermatozoa. No motility or swelling occurred above 200-300 mOsm kg-1 and this osmolality is probably that of the cytosol. The swelling of carp spermatozoa is the result of an entrance of water but this was not affected by pCMBS, an inhibitor of the aquaporin CHIP28, or by various inhibitors of the co-transport of water with ions. Various pharmacological agents that affect the motility of different sperm species had no effect on carp sperm motility when used under similar conditions. However, prolonged exposure to a solution devoid of K+ or Cl- affects the activation of motility in a reversible manner, suggesting that these ions have a role in the perception or transduction of the osmotic signal. Altering the concentration of intracellular second messengers such as Ca2+ and cAMP, and the pH did not affect the motility of carp spermatozoa. However, DMSO at 1-20% (400-3200 mOsm kg-1) affects the motility of carp spermatozoa 3-4 min after mixing. These results show that the activation signal of carp sperm motility differs from that known for spermatozoa of other species of fish such as trout. Our results indicate that the activation mechanism may involve a co-transport of ions or specific 'stretch-activated channels' that are sensitive to osmotic pressure.Keywords:
Osmole
Osmotic concentration
Five adult asthmatics completed five standardized exercise tests while inhaling aerosols with different osmolarities. The nebulized solutions were 2% NaCl (osmolarity = 616 mosm), 4% NaCl (osmolarity = 1232 mosm), 6.1% dextrose (osmolarity = 308 mosm = isoosmolar), 24.4% dextrose (osmolarity = 1232 mosm) and distilled water (osmolarity = 0). All the patients had EIA. During the study all conditions, except the osmolarity of the inhaled aerosols were kept constant. There was no statistical difference in the response to the exercise on the five days, the fall in PEF being 22.8% after exercise while inhaling 2% NaCl, 17.8% after inhaling 4% NaCl, 16.2 after inhaling 6.1% dextrose, 24.8% after inhaling 24.4% dextrose and 21.6% after exercise while inhaling nebulized distilled water, respectively. It is concluded that the osmolarity of the inhaled aerosol is of little or no importance in exercise-induced asthma.
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Distilled water
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I read with interest the article by Williams et al. (1) discussing the effects of lactated Ringer’s solution and normal saline on serum osmolality. In the introduction to the article, the authors state that the “measured osmolality of normal saline is similar to the calculated osmolarity of 308 mOsm/L.” However, according to Weast (2), the osmolarity of a 0.9% sodium chloride solution is actually 287 mOsm/kg. How do the authors explain this discrepancy? A smaller difference in osmolality between the two solutions (33 mOsm/kg) instead of their larger assumed difference 54 mOsm/kg) may explain why the difference in obtained serum osmolality between the two solutions was small. Kenneth M. Swank MD
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ABSTRACT Objectives: The present guidelines of the American Academy of Pediatrics recommend that osmolarity not exceed 450 mOsm/kg (or approximately an osmolarity of 400 mOsm/L) for breast milk or infant formulae, to minimize the risk factors for necrotizing enterocolitis. A commercial protein supplement has been developed to meet special protein requirements (4.0–4.5 g · kg −1 · day −1 ) of infants with a birth weight <1000 g. Because its effect on osmolarity has not been systematically studied, we characterized the effects of fortification on the osmolarity of human milk (HM). Methods: Osmolarity of fresh and processed HM was measured at baseline, after fortification with a commercial HM fortifier and after further supplementation with additional protein increasing in 0.5‐g steps up to 4.0 g. Measurements were performed immediately after adding fortifier and/or protein and after 24 hours. In addition, changes in osmolarity were determined after adding therapeutic additives such as iron, multivitamin supplement, and calcium‐phosphorus capsules. Results: Native HM samples (n = 84) had 297 mOsm/L, (median; 95% confidence interval 295–299 mOsm/L). Adding HM fortifier increased osmolarity up to 436 mOsm/L (95% confidence interval 431–441 mOsm/L). Additional protein supplementation increased osmolarity by 23.5 mOsm/L per 0.5‐g step, up to a maximum of 605 mOsm/L. Pasteurization decreased osmolarity by 20–30 mOsm/L ( P < 0.001), and storage for 24 hours slightly increased osmolarity (by 11.5 mOsm/L P = 0.0002). Therapeutic additives increased osmolarity up to 868 mOsm/L. Conclusions: Adding HM fortifier and additional protein to HM increased osmolarity to >400 mOsm/L and therefore above the recommended threshold. Because of the excessive increase in osmolarity combinations of HM + fortifier and additional protein should not be applied together with multivitamins or other additives.
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Aim. To determine the effects of hemodialysis (HD) on tear osmolarity and to define the blood biochemical tests correlating with tear osmolarity among patients with end stage renal disease (ESRD). Material-Method. Tear osmolarity of ESRD patients before and after the hemodialysis program was determined as well as the blood biochemical data including glucose, sodium, potassium, calcium, urea, and creatinine levels. Results. Totally 43 eyes of 43 patients (20 females and 23 males) with a mean age of 53.98 ± 18.06 years were included in the study. Tear osmolarity of patients was statistically significantly decreased after hemodialysis (314.06 ± 17.77 versus 301.88 ± 15.22 mOsm/L, p = 0.0001). In correlation analysis, pre-HD tear osmolarity was negatively correlated with pre-HD blood creatinine level (r = -0.366, p = 0.016). Post-HD tear osmolarity was statistically significantly correlated with the post-HD glucose levels (r = 0.305 p = 0.047). Tear osmolarity alteration by HD was negatively correlated with creatinine alteration, body weight alteration, and ultrafiltration (r = -0.426, p = 0.004; r = -0.365, p = 0.016; and r = -0.320, p = 0.036, resp.). There was no correlation between tear osmolarity and Kt/V and URR values. Conclusion. HD effectively decreases tear osmolarity to normal values and corrects the volume and composition of the ocular fluid transiently. Tear osmolarity alteration induced by HD is correlated with body weight changes, creatinine alterations, and ultrafiltration.
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Ultrafiltration (renal)
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I read with interest the article by Williams et al. (1) discussing the effects of lactated Ringer’s solution and normal saline on serum osmolality. In the introduction to the article, the authors state that the “measured osmolality of normal saline is similar to the calculated osmolarity of 308 mOsm/L.” However, according to Weast (2), the osmolarity of a 0.9% sodium chloride solution is actually 287 mOsm/kg. How do the authors explain this discrepancy? A smaller difference in osmolality between the two solutions (33 mOsm/kg) instead of their larger assumed difference 54 mOsm/kg) may explain why the difference in obtained serum osmolality between the two solutions was small. Kenneth M. Swank MD
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Sperm washing
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Background : Infusion of high‐osmolarity parenteral nutrition (PN) formulations into a peripheral vein will damage the vessel. In this study, the authors developed a refractometric method to predict PN formulation osmolarity for patients receiving PN. Methods : Nutrients in PN formulations were prepared for Brix value and osmolality measurement. Brix value and osmolality measurement of the dextrose, amino acids, and electrolytes were used to evaluate the limiting factor of PN osmolarity prediction. A best‐fit equation was generated to predict PN osmolarity (mOsm/L): 81.05 × Brix value – 116.33 ( R 2 > 0.99). To validate the PN osmolarity prediction by these 4 equations, a total of 500 PN admixtures were tested. Results : The authors found strong linear relationships between the Brix values and the osmolality measurement of dextrose ( R 2 = 0.97), amino acids ( R 2 = 0.99), and electrolytes ( R 2 > 0.96). When PN‐measured osmolality was between 600 and 900 mOsm/kg, approximately 43%, 29%, 43%, and 0% of the predicted osmolarity obtained by equations 1, 2, 3, and 4 were outside the acceptable 90% to 110% confidence interval range, respectively. When measured osmolality was between 900 and 1,500 mOsm/kg, 31%, 100%, 85%, and 15% of the predicted osmolarity by equations 1, 2, 3, and 4 were outside the acceptable 90% to 110% confidence interval range, respectively. Conclusions : The refractive method permits accurate PN osmolarity prediction and reasonable quality assurance before PN formulation administration.
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Brix
Refractometry
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