scholarly journals Osmotic Regulation and Viability during Storage of Potato Microtubers Obtained in Vitro

2020 ◽  
Vol 9 (3) ◽  
Author(s):  
J. Gerardo Ortiz-Montiel ◽  
M. Teresa Ortiz-Melo ◽  
Yolanda Pozos-Ruiz ◽  
Rocio Reyero-Saavedra ◽  
Manuel Mandujano-Piña ◽  
...  
Keyword(s):  
Osmotic Regulation

Macromolecular crowding and confinement in cells exposed to hypertonicity

1994 ◽  
Vol 266 (4) ◽  
pp. C877-C892 ◽  
Author(s):  
M. M. Garner ◽  
M. B. Burg
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Cell Volume Regulation ◽  
Macromolecular Crowding ◽  
Inorganic Ions ◽  
Organic Osmolytes ◽  
Osmotic Regulation ◽  
Molecular Crowding ◽  
In Cells

The nonideal properties of solutions containing high concentrations of macromolecules can result in enormous increases in the activity of the individual macromolecules. It has been proposed that molecular crowding and confinement occur in cells and are major determinants of the activity of the proteins and other intracellular macromolecules. This concept has important implications for cell volume regulation because, under crowded conditions, relatively small changes in concentration, consequent to alterations of water content, lead to large changes in macromolecular activity. This review considers several aspects of macromolecular crowding and confinement, including: 1) the physical chemical principles involved; 2) in vitro demonstrations of the effects; 3) relation to water activity; 4) estimates of the actual intracellular activity of water and macromolecules; 5) relation to osmotic regulation in various types of cells, including bacteria, red blood cells, and complex nucleated cells; and 6) the relation to inorganic ions and organic osmolytes in cells stressed by hypertonicity. We conclude that, while there is compelling evidence for important effects of molecular crowding in vitro and in red blood cells, the role of macromolecular crowding and confinement in osmotic regulation of more complex cells is an open question that deserves the extensive attention it is currently receiving.

scholarly journals In vitro uses of biological cryoprotectants

2002 ◽  
Vol 357 (1423) ◽  
pp. 945-951 ◽  
Author(s):  
Peter J. Lillford ◽  
Chris B. Holt
Keyword(s):  
Crystal Growth ◽  
Freezing Point ◽  
Ice Nucleation ◽  
Active Species ◽  
Osmotic Regulation ◽  
Ice Crystal ◽  
Freezing Point Depression ◽  
Commercial Use ◽  
Crystal Growth Inhibition

Ice can be anything from a highly destructive agent in agriculture to a useful building material. Established industries are based on the known rules of physics and chemistry which allow some control of amounts of ice or ice crystal geometry. However, organisms have much more subtle requirements to maintain their delicate internal structure if they are to survive freezing. As a result they have selected specific molecules for freezing–point depression, osmotic regulation, ice nucleation and crystal growth inhibition. All these active species may have potential commercial use once they are identified, understood and produced at economic scales. We examine the progress made so far in extending biological subtlety into commercial processes, and look for prospects for further innovation.

scholarly journals Mechanistic basis for loss of water balance in green tree frogs infected with a fungal pathogen

2019 ◽  
Vol 317 (2) ◽  
pp. R301-R311 ◽  
Author(s):  
Nicholas C. Wu ◽  
Callum McKercher ◽  
Rebecca L. Cramp ◽  
Craig E. Franklin
Keyword(s):  
Water Balance ◽  
Water Uptake ◽  
Fungal Pathogen ◽  
Batrachochytrium Dendrobatidis ◽  
Osmotic Regulation ◽  
Water Fluxes ◽  
Uptake Rates ◽  
Osmotic Homeostasis ◽  
Ventral Skin

Chytridiomycosis, a lethal skin disease caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd), disrupts skin function of amphibians, interfering with ionic and osmotic regulation. To regulate fungal loads, amphibians increase their rate of skin sloughing. However, sloughing also causes a temporary loss of ionic and osmotic homeostasis due to disruption of the skin, a key osmoregulatory organ. The combined effects of increased sloughing frequency and chytridiomycosis contribute to the high rates of mortality from Bd infections. However, the mechanisms responsible for the loss of cutaneous osmotic regulation remain unknown. We measured the changes in whole animal water uptake rates, in vitro transcutaneous water fluxes across the ventral skin, and the mRNA expression of epithelial water transport proteins (aquaporins, AQPs) and junctional proteins in Bd-infected and uninfected Litoria caerulea skin. We hypothesize that infected frogs would show reduction/inhibition in cutaneous water transporters responsible for regulating water balance, and sloughing would exacerbate cutaneous water fluxes. We found that infected, nonsloughing frogs had an impaired rate of water uptake and showed increased rates of in vitro water efflux across the ventral skin. In uninfected frogs, the expression of AQPs and junction genes increased significantly with sloughing, which may assist in regulating cutaneous water movements and barrier function in the newly exposed skin. In contrast, infected frogs did not show this postsloughing increase in AQP gene expression. The combination of increased sloughing frequency, impaired water uptake rates, and increased rates of water loss likely contributes to the loss of osmotic homeostasis in frogs infected with Bd.

scholarly journals Osmotic regulation of cytokine synthesis in vitro.

1995 ◽  
Vol 92 (26) ◽  
pp. 12230-12234 ◽  
Author(s):  
L. Shapiro ◽  
C. A. Dinarello
Keyword(s):  
Osmotic Regulation ◽  
Cytokine Synthesis

In vivo and in vitro osmotic regulation of HSP-70 and prostaglandin synthase gene expression in kidney cells

1995 ◽  
Vol 269 (6) ◽  
pp. F854-F862 ◽  
Author(s):  
B. D. Cowley ◽  
M. J. Muessel ◽  
D. Douglass ◽  
W. Wilkins
Keyword(s):  
Water Movement ◽  
Mdck Cells ◽  
Renal Medulla ◽  
Kidney Cells ◽  
Mrna Levels ◽  
Osmotic Regulation ◽  
Hsp 70 ◽  
Prostaglandin Synthase

As a function of the urinary concentrating mechanism, the cells of the renal medulla are exposed to elevated and constantly varying osmolalities and adapt to this environment by selectively expressing certain mRNAs. We evaluated the expression and regulation of two RNAs that may be important in adaptation of rental medullary cells to hyperosmolality. We demonstrate selective, modulated expression in the renal medulla of heat shock protein HSP-70 mRNA and prostaglandin synthase-1 mRNA, with the abundance of these two mRNAs regulated in vivo in concert with changes in medullary sodium and urea. We also determined the abundance of these mRNAs in cultured kidney cells (MDCK) in response to an increase in extracellular osmolality due to selected osmotic agents. HSP-70 and prostaglandin synthase-2 mRNA levels increased when extracellular osmolality was increased to 400-600 mosmol/kg by the addition of NaCl. At 500 mosmol/kg this response was evident at 6 h, was maximal near 24 h, and persisted for a total of 90 days. Prostaglandin synthase-1 mRNA levels in MDCK cells were also increased after chronic exposure to extracellular osmolality. Increased extracellular osmolality caused by agents to which cells are impermeable caused increased levels of HSP-70 and prostaglandin synthase-2 mRNAs, whereas increased extracellular osmolality caused by agents to which cells are permeable did not; thus osmotic regulation involved osmotic water movement. We conclude that the abundance of HSP-70 and prostaglandin synthase-1 mRNAs in the renal medulla is regulated in response to renal medullary osmolality and suggest that this may also be true for other medullary mRNAs yet to be described.

scholarly journals Osmotic Regulation of Toad Bladder Responsiveness to Neurohypophyseal Hormones

1972 ◽  
Vol 60 (6) ◽  
pp. 665-678 ◽  
Author(s):  
Patrick Eggena
Keyword(s):  
Urinary Bladder ◽  
Water Movement ◽  
Plasma Osmolality ◽  
Bulk Water ◽  
Toad Bladder ◽  
Toad Urinary Bladder ◽  
Osmotic Regulation ◽  
Neurohypophyseal Hormones

The effect of dilution of the interstitial fluids on the responsiveness of the toad urinary bladder to antidiuretic hormones has been examined in vivo and in vitro. Toads were given periodic injections with vasopressin while in water so that their plasma osmolality fell below 190 mosmoles/kg H2O. The hydraulic conductivity of bladders which had been removed from the animal and fixed with 1% glutaraldehyde was 10-fold less in overhydrated toads than in normally hydrated controls. A similar inhibitory phenomenon was observed in in vitro studies, when the tonicity of Ringer's fluid in which the bladders were suspended was lowered from its isotonic value. Mannitol, but not urea, could be effectively substituted for one-half of the NaCl content of Ringer's fluid. In other experiments it has been shown that the responsiveness of the bladder to vasotocin is depressed during bulk water movement across the tissue. This "flux inhibition" was found to depend upon the velocity and the duration of water flow from mucosa to the serosa. It is suggested that the responsiveness of the toad bladder to antidiuretic hormones diminishes as the effective osmotic pressure of the interstitial fluids declines.

scholarly journals Effects of Ionic and Osmotic Strength on the Glucosyltransferase of Rhizobium meliloti Responsible for Cyclic β-(1,2)-Glucan Biosynthesis

1998 ◽  
Vol 64 (4) ◽  
pp. 1290-1297 ◽  
Author(s):  
Cheryl Ingram-Smith ◽  
Karen J. Miller
Keyword(s):  
Rhizobium Meliloti ◽  
Choline Chloride ◽  
Compatible Solutes ◽  
Ionic Character ◽  
Osmotic Regulation ◽  
High Concentrations ◽  
Glucan Synthesis ◽  
Ionic Solutes

ABSTRACT The cyclic β-(1,2)-glucans of Rhizobium meliloti andAgrobacterium tumefaciens play an important role during hypoosmotic adaptation, and the synthesis of these compounds is osmoregulated. Glucosyltransferase, the enzyme responsible for cyclic β-(1,2)-glucan biosynthesis, is present constitutively, suggesting that osmotic regulation of the biosynthesis of these glucans occurs through modulation of enzyme activity. In this study, we examined regulation of cyclic glucan biosynthesis in vitro with membrane preparations from R. meliloti. The results show that ionic solutes inhibit glucan synthesis, even when they are present at low concentrations (e.g., 10 mM). In contrast, neutral solutes (glucose, sucrose, and the compatible solutes glycine betaine and trehalose) were found to stimulate glucan synthesis in vitro when they were present at high concentrations (e.g., 1 M). Furthermore, high concentrations of these neutral solutes were shown to compensate for the inhibition of glucosyltransferase activity by ionic solutes. Consistent with their ionic character, the compatible solute potassium glutamate and the osmoprotectant choline chloride inhibited glucosyltransferase activity in vitro. The results suggest that intracellular ion concentrations, intracellular osmolarity, and intracellular concentrations of nonionic compatible solutes all act as important determinants of glucosyltransferase activity in vivo. Additional experiments were performed with an ndvA mutant defective for transport of cyclic glucans and an ndvB mutant that produces a C-terminal truncated glucosyltransferase. Cyclic β-(1,2)-glucan biosynthesis, although reduced, was found to be osmoregulated in both mutants. These results reveal that NdvA and the C terminus of NdvB are not required for osmotic regulation of cyclic β-(1,2)-glucan biosynthesis.

Ultrastructural Investigations of the Contractile Filaments of Amoebae

1974 ◽  
Vol 32 ◽  
pp. 188-189
Author(s):  
P.L. Moore
Keyword(s):  
Cytoplasmic Streaming ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Amoeboid Movement ◽  
Different Types ◽  
Chemical Conditions ◽  
Complete Interpretation

Previous freeze fracture results on the intact giant, amoeba Chaos carolinensis indicated the presence of a fibrillar arrangement of filaments within the cytoplasm. A complete interpretation of the three dimensional ultrastructure of these structures, and their possible role in amoeboid movement was not possible, since comparable results could not be obtained with conventional fixation of intact amoebae. Progress in interpreting the freeze fracture images of amoebae required a more thorough understanding of the different types of filaments present in amoebae, and of the ways in which they could be organized while remaining functional.The recent development of a calcium sensitive, demembranated, amoeboid model of Chaos carolinensis has made it possible to achieve a better understanding of such functional arrangements of amoeboid filaments. In these models the motility of demembranated cytoplasm can be controlled in vitro, and the chemical conditions necessary for contractility, and cytoplasmic streaming can be investigated. It is clear from these studies that “fibrils” exist in amoeboid models, and that they are capable of contracting along their length under conditions similar to those which cause contraction in vertebrate muscles.

Sign in / Sign up

Export Citation Format

Share Document