WordNet

(of a solution) the extent to which a solution has a higher osmotic pressure than some other
(of living tissue) in a state of abnormally high tension; "hypertonic muscle tissue"
(of a solution) having a higher osmotic pressure than a comparison solution

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/08/29 18:12:33」(JST)

wiki en

[Wiki en表示]

"Hypotonic" redirects here. For the muscular disease, see Hypotonia.

Effect of different solutions on blood cells

Micrographs of osmotic pressure on red blood cells

Tonicity is a measure of the osmotic pressure gradient (as defined by the water potential of the two solutions) of two solutions separated by a semipermeable membrane. It is commonly used when describing the response of cells immersed in an external solution. Like osmotic pressure, tonicity is influenced only by solutes that cannot cross the membrane, as only these exert an osmotic pressure. Solutes able to freely cross the membrane do not affect tonicity because they will always be in equal concentrations on both sides of the membrane.

There are three classifications of tonicity that one solution can have relative to another. The three are hypertonic, hypotonic, and isotonic.^[1]

Hypertonicity[edit source | edit]

Hypertonic refers to a greater concentration. In biology, a hypertonic solution is one with a higher concentration of solutes on the outside of the cell. When a cell is immersed into a hypertonic solution, the tendency is for water to flow out of the cell in order to balance the concentration of the solutes.

When plant cells are in a hypertonic solution, the flexible cell membrane pulls away from the rigid cell wall, but remains joined to the cell wall at points called plasmodesmata. The cell takes on the appearance of a pincushion, and the plasmodesmata almost cease to function because they become constricted: a condition known as plasmolysis. In plant cells the terms isotonic, hypotonic and hypertonic cannot strictly be used accurately because the pressure exerted by the cell wall significantly affects the osmotic equilibrium point.

A hypertonic solution is used in osmotherapy to treat cerebral hemorrhage.^{[citation needed]}

Hypotonicity[edit source | edit]

Hypotonic refers to a lesser concentration. A hypotonic solution has a lower concentration of solutes in its surroundings, so in an attempt to balance concentrations, water will rush into the cell, causing swelling. ^[2]

Some organisms have evolved intricate methods of circumventing hypotonicity. For example, saltwater is hypertonic to the fish that live in it. They need a large surface area in their gills in contact with seawater for gas exchange, thus they lose water osmotically to the sea from gill cells. They respond to the loss by drinking large amounts of saltwater, and actively excreting the excess salt. This process is called osmoregulation.

Isotonicity[edit source | edit]

An isotonic solution is one in which its effective osmole concentration is the same as the solute concentration of another solution with which it is compared. This occurs, for example, when the concentration of both water and total solute molecules are the same in an external solution as in the cell content. Water molecules diffuse through the plasma membrane in both directions, and as the rate of water diffusion is the same in each direction that cell will neither gain nor lose water.

For example, the osmolarity of Normal saline, 9 grams NaCl dissolved in water to a total volume of one litre, is a close approximation to the osmolarity of NaCl in blood, i.e. Normal saline is almost isotonic to blood plasma.

References[edit source | edit]

^ Sperelakis, Nicholas (2011). Cell Physiology Source Book: Essentials of Membrane Biophysics. Academic Press. p. 288. ISBN 978-0-12-387738-3.
^ "Definition — hypotonic". The Free Dictionary. Retrieved 23 August 2012.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. S状結腸鏡検査および大腸内視鏡検査のための前処置 bowel preparation for flexible sigmoidoscopy and colonoscopy
2. Chapter 4B：対向流のメカニズム chapter 4b countercurrent mechanism
3. Chapter 9B：腎臓の水分排泄と再吸収 chapter 9b renal water excretion and reabsorption
4. Chapter 5B：集合管 chapter 5b collecting tubules
5. 利尿剤誘発性低ナトリウム血症 diuretic induced hyponatremia

English Journal

The Effects of RegM on Stress Responses in Brucella melitensis.

Dong H1, Liu W, Peng X, Wu Q.
Current microbiology.Curr Microbiol.2015 May;70(5):730-4. doi: 10.1007/s00284-015-0782-1. Epub 2015 Feb 4.
Brucella melitensis is a facultative intracellular pathogen. The regM gene encodes a sensory transduction protein kinase in B. melitensis 16M, and genes orthologous to regM have been found to exist in many bacterial species. However, little is known about the regulation function of this gene in Bruc
PMID 25648428

Molecular and functional characterization of seven Na(+)/K(+)-ATPase β subunit paralogs in Senegalese sole (Solea senegalensis Kaup, 1858).

Armesto P1, Infante C2, Cousin X3, Ponce M1, Manchado M4.
Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology.Comp Biochem Physiol B Biochem Mol Biol.2015 Apr;182:14-26. doi: 10.1016/j.cbpb.2014.11.011. Epub 2014 Dec 5.
In the present work, seven genes encoding Na(+),K(+)-ATPase (NKA) β-subunits in the teleost Solea senegalensis are described for the first time. Sequence analysis of the predicted polypeptides revealed a high degree of conservation with those of other vertebrate species and maintenance of important
PMID 25483323

Caenorhabditis elegans OSM-11 signaling regulates SKN-1/Nrf during embryonic development and adult longevity and stress response.

Dresen A1, Finkbeiner S1, Dottermusch M1, Beume JS1, Li Y1, Walz G2, Neumann-Haefelin E3.
Developmental biology.Dev Biol.2015 Apr 1;400(1):118-31. doi: 10.1016/j.ydbio.2015.01.021. Epub 2015 Jan 29.
The Nrf family of transcription factors is critical for stress defense and detoxification. In Caenorhabditis elegans, the Nrf protein ortholog SKN-1 mediates this conserved stress response and promotes longevity. Moreover, SKN-1 is well known for its essential functions during C. elegans embryogenes
PMID 25637691

Japanese Journal

11-3 Biophysical skin effects of extemporaneous peloids from "Hervideros De Cofrentes Spa" natural mineral water according to their maturity time

CARBAJO José Manuel,Fernandez-TORAN Miguel Angel,CORVILLO Iluminada,AGUILERA Lourdes,MEIJIDE Rosa,CARRETERO Maria Isabel,MARAVER Francisco
日本温泉気候物理医学会雑誌 77(5), 507-508, 2014
… The main objective of the present study was to determine the in situ biomechanical behaviour of skin in response to the use of three muds manufactured with a hyperosmotic Spring "Hervederos de Cofrentes" water, Valencia, Spain. …
NAID 130004719508

Subarachnoid Hemorrhage After an Ischemic Attack Due to a Bacterial Middle Cerebral Artery Dissecting Aneurysm: Case Report and Literature Review

SAITO Atsushi,KAWAGUCHI Tomohiro,HORI Emiko,KANAMORI Masayuki,NISHIMURA Shinjitsu,SANNOHE Seiya,KAIMORI Mitsuomi,SASAKI Tatsuya,NISHIJIMA Michiharu
Neurologia medico-chirurgica 54(3), 196-200, 2014
… The diagnosis was cerebral ischemia and she was conservatively treated with hyperosmotic fluids. …
NAID 130003383224

α-Tubulin is Rapidly Phosphorylated in Response to Hyperosmotic Stress in Rice and Arabidopsis

Ban Yoshinori,Kobayashi Yuhko,Hara Tomomi [他],HAMADA Takahiro,HASHIMOTO Takashi,TAKEDA Shin,HATTORI Tsukaho
Plant and cell physiology 54(6), 848-858, 2013-06-01
NAID 10031184129