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Genes & Genetic Systems Dec 2002Bacteria have devised phosphotransfer signaling mechanisms for eliciting a variety of adaptive responses to their environment. These mechanisms are collectively referred... (Review)
Review
Bacteria have devised phosphotransfer signaling mechanisms for eliciting a variety of adaptive responses to their environment. These mechanisms are collectively referred to as two-component regulatory systems. Each system generally consists of a sensor protein histidine kinase, which is anchored in the cell membrane, and a cytoplasmic response regulator, whose activity is modulated by the sensor. Most response regulators are transcription factors. In this review, we briefly introduce the established concept on bacterial two-component regulatory systems, using the Agrobacterium VirA-VirG system as an example, and give the evidence for the existence of quite similar systems in higher plants, such as the signal transduction induced by the phytohormone cytokinin. The Arabidopsis CRE1 histidine kinase and its related proteins AHK2 and AHK3 perceive cytokinins in the environment and transduce a signal, presumably through the AHP bridge components that carry the histidine-containing phosphotransfer (HPt) domain, to the ARR1 response regulator that transcriptionally activates genes immediately responsive to cytokinins. In addition, this signal transfer process appears to participate in cross-talk with signaling systems that respond to daylight and another phytohormone, ethylene, through an intracellular pool of several ARR1-like molecular species and the AHP components.
Topics: Arabidopsis; Arabidopsis Proteins; Aspartic Acid; Bacterial Proteins; Cytokinins; DNA-Binding Proteins; Ethylenes; Histidine; Light; Osmosis; Signal Transduction; Transcription Factors; Virulence Factors
PubMed: 12589073
DOI: 10.1266/ggs.77.383 -
Kidney360 Sep 2021Overly rapid correction of chronic hyponatremia may lead to osmotic demyelination syndrome. European guidelines recommend a correction to ≤10 mEq/L in 24 hours to...
BACKGROUND
Overly rapid correction of chronic hyponatremia may lead to osmotic demyelination syndrome. European guidelines recommend a correction to ≤10 mEq/L in 24 hours to prevent this complication. However, osmotic demyelination syndrome may occur despite adherence to these guidelines.
METHODS
We searched the literature for reports of osmotic demyelination syndrome with rates of correction of hyponatremia ≤10 mEq/L in 24 hours. The reports were reviewed to identify specific risk factors for this complication.
RESULTS
We identified 19 publications with a total of 21 patients that were included in our analysis. The mean age was 52 years, of which 67% were male. All of the patients had community-acquired chronic hyponatremia. Twelve patients had an initial serum sodium <115 mEq/L, of which seven had an initial serum sodium ≤105 mEq/L. Other risk factors identified included alcohol use disorder (=11), hypokalemia (=5), liver disease (=6), and malnutrition (=11). The maximum rate of correction in patients with serum sodium <115 mEq/L was at least 8 mEq/L in all but one patient. In contrast, correction was <8 mEq/L in all but two patients with serum sodium ≥115 mEq/L. Among the latter group, osmotic demyelination syndrome developed before hospital admission or was unrelated to hyponatremia overcorrection. Four patients died (19%), five had full recovery (24%), and nine (42%) had varying degrees of residual neurologic deficits.
CONCLUSION
Osmotic demyelination syndrome can occur in patients with chronic hyponatremia with a serum sodium <115 mEq/L, despite rates of serum sodium correction ≤10 mEq/L in 24 hours. In patients with severe hyponatremia and high-risk features, especially those with serum sodium <115 mEq/L, we recommend limiting serum sodium correction to <8 mEq/L. Thiamine supplementation is advisable for any patient with hyponatremia whose dietary intake has been poor.
Topics: Demyelinating Diseases; Humans; Hyponatremia; Male; Middle Aged; Osmosis; Sodium; Syndrome
PubMed: 35373113
DOI: 10.34067/KID.0004402021 -
The Journal of General Physiology Apr 1992We apply the diagrammatic method developed by Hill (1977. Free Energy Transduction in Biology. Academic Press, New York) to analyze single-file water transport. We use... (Review)
Review
We apply the diagrammatic method developed by Hill (1977. Free Energy Transduction in Biology. Academic Press, New York) to analyze single-file water transport. We use this formalism to derive explicit expressions for the osmotic and diffusive permeabilities Pf and Pd of a pore. We first consider a vacancy mechanism of transport analogous to the one-vacancy pore model previously used by Kohler and Heckmann (1979. J. Theor. Biol. 79:381-401). (a) For the general one-vacancy case, we find that the permeability ratio can be expressed by Pf/Pd = (Pf/Pd)eqf(wA,wB), where the second factor is a function of the water activities in the two adjoining compartments A and B. As a consequence, the permeability ratio in general can effectively differ from its value at equilibrium. We also find that n - 1 less than or equal to (Pf/Pd)eq less than or equal to n, a result already proposed by Kohler and Heckmann (1979. J. Theor. Biol. 79:381-401). (b) When vacancy states are transient intermediates, the model can be reduced to a diagram consisting of only fully occupied states. Such a diagram resembles the one describing a no-vacancy mechanism of transport (c), but in spite of the similarity the expressions obtained for the permeability coefficients still retain the basic relationships of the original (a) nonreduced one-vacancy model. (c) We then propose a kinetic description of a no-vacancy mechanism of single-file water transport. In this case, the expressions derived for Pf and Pd are formally equivalent to those obtained by Finkelstein and Rosenberg (1979. Membrane Transport Processes. Vol. 3. C.F. Stevens and R.W. Tsien, editors, Raven Press, New York. 73-88.) A main difference with the vacancy mechanism is that here the permeability coefficients are independent of the water activities.
Topics: Biological Transport; Kinetics; Mathematics; Models, Biological; Osmosis; Water
PubMed: 1597681
DOI: 10.1085/jgp.99.4.645 -
Journal of Biomechanics Jan 2019Mounting evidence suggests that cells within soft tissues seek to maintain a preferred biomechanical state. Residual stress is defined as the stress that remains in a...
Mounting evidence suggests that cells within soft tissues seek to maintain a preferred biomechanical state. Residual stress is defined as the stress that remains in a tissue when all external loads are removed and contributes to tissue mechanohomeostasis by decreasing the transmural gradient of wall stress. Current computational models of pelvic floor mechanics, however, often do not consider residual stress. Residual strain, a result of residual stress can be quantitatively measured through opening angle experiments. Therefore, the objective of this study is to quantify the regional variations in opening angles along the murine female reproductive system at estrus and diestrus, to quantify residual strain in the maintenance state of sexually mature females. Further, evidence suggests that hydrophilic glycosaminoglycan/proteoglycans are integral to cervical remodeling. Thus, variations in opening angles following hypo-osmotic loading are evaluated. Opening angle experiments were performed along the murine reproductive system in estrus (n = 8) and diestrus (n = 8) and placed in hypo-osmotic solution. Measurements of thickness and volume were also obtained for each group. Differences (p < 0.05) in opening angle were observed with respect to region and loading, however, differences with respect to estrous stage were not significant. Thickness values were significant (p < 0.05) with respect to region only. The effects of both estrous cycle and region resulted in significant differences (p < 0.05) in observed volume. The observed regional differences indicate variation in the stress-free state among the reproductive system which may have implications for future computational models to advance women's reproductive health.
Topics: Animals; Biomechanical Phenomena; Cervix Uteri; Estrous Cycle; Female; Mice; Osmosis; Reproduction; Stress, Mechanical
PubMed: 30458959
DOI: 10.1016/j.jbiomech.2018.11.001 -
The Journal of General Physiology Jul 1959Melting point depression was used as an index of the water potential of rat tissues and serum. Organs removed from anesthetized rats were immediately frozen in liquid...
Melting point depression was used as an index of the water potential of rat tissues and serum. Organs removed from anesthetized rats were immediately frozen in liquid nitrogen and ground with mortar and pestle. Aliquots of the resulting frozen powder were suspended in chilled liquid silicone. While the suspension was vigorously stirred and warmed at a constant rate, the temperature of the melting mixture was measured. The melting curves of rat muscle, liver, heart, and brain were not significantly different from those of rat serum. The melting curve depression of whole kidney was greater than that of serum; this was demonstrated to be due to hypertonicity of the renal medullary area alone. It was demonstrated that autolysis will rapidly increase the depression of the melting curve of tissue. It is concluded that within the limits of the method used the melting point depression, and hence the water potential, of intracellular and extracellular fluids is the same.
Topics: Animals; Kidney; Osmosis; Permeability; Rats; Temperature; Water
PubMed: 13664925
DOI: 10.1085/jgp.42.6.1257 -
The Plant Cell Aug 2016
Topics: Arabidopsis Proteins; Osmosis; Osmotic Pressure; Starch; Stress, Physiological
PubMed: 27465025
DOI: 10.1105/tpc.16.00585 -
The Journal of Experimental Medicine May 1948The cytoplasm of cells of the liver and of the kidney is in large part occupied by bodies which respond to the water content of these cells and are modified by dissolved...
The cytoplasm of cells of the liver and of the kidney is in large part occupied by bodies which respond to the water content of these cells and are modified by dissolved substances in the surrounding fluid or by physical change such as freezing. These bodies, in part mitochondria but designated more broadly cytochondria, constitute an osmotic system within the cytoplasm of cells. When the specific gravity of liver or kidney tissue is used as an index of changes in the water content of tissue, swelling of cytochondria in general follows the intake of water but this relation may be modified by a variety of conditions. When liver that has been frozen and thawed is immersed in water, cytochondria become swollen though the containing cells diminish in size. Solutions of sodium and of potassium chloride isotonic with blood plasma cause delayed swelling of cells and cytochondria, greater with the potassium salt; solutions of calcium chloride of equal molar concentration cause immediate swelling of cells and cytochondria. The basophile material of the cytoplasm (ribonucleic acid and related substances) and the material that gives to mitochondria their characteristic stain are removed by immersion in water but their disappearance is retarded by isotonic solutions of sodium or of potassium chloride and further delayed by hypertonic solutions. When the intensity of staining reactions is diminished by the partial loss of basophile substance or of the distinctive mitochondrial material, these are found at the surfaces of the cytoplasmic bodies, held perhaps by adsorption. When water, isotonic solutions of sodium chloride, or Ringer's solution comes into contact with immersed liver, they remove basophile and mitochondrial material from a superficial zone and substances with similar staining reactions appear in the cytoplasm of cells at a deeper level. Osmotic changes in the cytoplasmic bodies may be reversible. When liver tissue which has been for a short time immersed in water is transferred to a solution that is approximately isotonic in relation to blood plasma, swollen cytochondria return in part or completely to their former size; but with continued immersion in water, this reversibility becomes increasingly less complete.
Topics: Cells; Cytoplasm; Isotonic Solutions; Kidney; Liver; Osmosis; Permeability; Ringer's Solution; Water
PubMed: 18912893
DOI: 10.1084/jem.87.5.425 -
Molecules (Basel, Switzerland) Sep 2019The advantages of peritoneal dialysis (PD) over hemodialysis (HD) are well-documented. Notwithstanding, only a small proportion of patients with end-stage renal disease... (Review)
Review
The advantages of peritoneal dialysis (PD) over hemodialysis (HD) are well-documented. Notwithstanding, only a small proportion of patients with end-stage renal disease (ESRD) are managed with PD. This may be related to the high glucose load that PD solutions in current use have on the patient. The effects of such excess glucose include the relatively early limitation of the ultrafiltration capacity of the peritoneal membrane, and the metabolic effects associated with hyperglycemia, e.g., decreased insulin sensitivity. This article describes the advantages that may be realized by the glucose-sparing effects of substituting part of the glucose load with other osmotically active metabolites, particularly L-carnitine. The latter is anticipated to have metabolic advantages of its own, especially as in PD patients, high plasma concentrations can be achieved in the absence of renal clearance. Besides its better biocompatibility, L-carnitine demonstrates anti-anemia action due to its effects on erythropoiesis, and positive effects on the longevity and deformability of erythrocytes. Observations from our trials on the use of carnitine-enriched PD solutions have demonstrated the effectiveness of L-carnitine as an efficient osmolyte in PD, and its favorable effect on the insulin sensitivity of the patients. The significance of these findings for future developments in the use of PD in the management of patients with ESRD is discussed.
Topics: Carnitine; Erythrocytes; Glucose; Humans; Kidney Failure, Chronic; Osmosis; Peritoneal Dialysis; Ultrafiltration
PubMed: 31547545
DOI: 10.3390/molecules24193449 -
The Science of the Total Environment Sep 2020The polyamide reverse osmosis (RO) membrane was modified with graphene oxide (GO), followed by polymerization of acrylic acid (used as an antiscalant) for the reduction...
The polyamide reverse osmosis (RO) membrane was modified with graphene oxide (GO), followed by polymerization of acrylic acid (used as an antiscalant) for the reduction of both biofouling and mineral scaling. After functionalization, the water contact angle reduced from 41.7 ± 4.5° for unmodified RO membrane to 24.4 ± 1.3° for the modified RO membranes, which showed that membrane hydrophilicity was significantly enhanced, in addition to the improvement in surface smoothness. The modified membranes were tested for their anti-scaling and anti-biofouling characteristics. When the mineral scaling test was performed using CaSO solution as feedwater, the permeate flux was reduced by only 3% as compared to the unmodified RO membrane which encountered up to 22% decline in flux by the end of the experiment. After the scaling test, the membrane surface was characterized by Scanning electron microscopy - energy-dispersive X-ray spectroscopy, Fourier transform infrared, and X-ray diffraction techniques. The results showed that the unmodified RO membrane was fully covered with gypsum precipitates. Whereas, the precipitates were detected only at the highly saturated zones of the water channel i.e. towards the exit of water flow. Additionally, the anti-bacterial test was performed through bacteriostasis rate determination, which showed that the modified membranes inhibited the growth of nearly 95% of the bacterial cells. Further experiments were also performed to investigate the inhibition of both scaling and biofouling by modified RO membranes. Thus, it was found that the polymer-modified GO coated RO membranes were able to diminish both gypsum scaling and biofilm formation demonstrating their potential to control different types of membrane fouling.
Topics: Acrylic Resins; Biofouling; Graphite; Membranes, Artificial; Minerals; Osmosis; Water Purification
PubMed: 32479964
DOI: 10.1016/j.scitotenv.2020.139500 -
Scientific Reports May 2019Though it is known that the water content of biological soft tissues alters mechanical properties, little attempt has been made to adjust the tissue water content prior...
Though it is known that the water content of biological soft tissues alters mechanical properties, little attempt has been made to adjust the tissue water content prior to biomechanical testing as part of standardization procedures. The objective of this study was to examine the effects of altered water content on the macro and micro scale mechanical tissues properties. Human iliotibial band samples were obtained during autopsies to osmotically adapt their water content. Macro mechanical tensile testing of the samples was conducted with digital image correlation, and micro mechanical tests using atomic force microscopy. Analyses were conducted for elastic moduli, tensile strength, and strain at maximum force, and correlations for water content, anthropometric data, and post-mortem interval. Different mechanical properties exist at different water concentrations. Correlations to anthropometric data are more likely to be found at water concentrations close to the native state. These data underline the need for adapting the water content of soft tissues for macro and micro biomechanical experiments to optimize their validity. The osmotic stress protocol provides a feasible and reliable standardization approach to adjust for water content-related differences induced by age at death, post-mortem interval and tissue processing time with known impact on the stress-strain properties.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Cadaver; Child; Child, Preschool; Elastic Modulus; Feasibility Studies; Female; Humans; Male; Materials Testing; Microscopy, Atomic Force; Middle Aged; Osmosis; Osmotic Pressure; Tendons; Tensile Strength; Water; Young Adult
PubMed: 31133713
DOI: 10.1038/s41598-019-44306-z