Cryobiology
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'''Cryobiology''' is the branch of [[biology]] that studies the effects of low [[temperature]]s on living things. The word cryobiology is derived from the Greek words "cryo" = cold, "bios" = life, and "logos" = science. It means the science of life at low temperature. In practice, cryobiology is the study of biological material or systems at temperatures below normal. Materials or systems studied may include [[protein]]s, [[cells]], [[tissues]], [[organs]], or whole [[organisms]]. Temperatures may range from moderately [[Hypothermia|hypothermic]] conditions to [[cryogenic]] temperatures.
== Definitions/Distinctions ==
;[[Cryobiology]]: is the study of [[life]] at low [[temperature]]s.
;[[Cryogenics]]: is the branch of [[physics]] and [[engineering]] that studies the production and use of very low [[temperature]]s. Cryogenics is not cryonics, although people often confuse them.
;[[Cryonics]]: is the low temperature preservation of humans and animals in a damaged state with the intention of future revival. Cryonics is not part of mainstream cryobiology because cryonics still depends heavily on speculative future technology.
==Major areas of study in cryobiology==
At least 6 major areas of study in cryobiology can be identified:
#Study of cold-adaptation of [[microorganism]]s, [[plant]]s (= cold hardiness), [[invertebrate]]s, and [[animal]]s (= [[hibernation]]).
#Cryopreservation of cells, tissues, [[gamete]]s, and [[embryo]]s of animal and human origin for (medical) purposes of long-term storage. This usually requires the addition of substances which protect the cells during freezing and thawing ([[cryoprotectant]]s).
#Preservation of organs under hypothermic conditions for transplantation.
#Lyophilization ([[Freeze drying|freeze-drying]]) of [[pharmaceutical]]s.
#[[Cryosurgery]], a (minimally) invasive approach for the destruction of unhealthy tissue using cryogenic gases/fluids.
#Physics of [[supercooling]], [[ice]] [[nucleation]]/growth and mechanical engineering aspects of [[heat transfer]] during cooling and warming.
==Historical background==
[[Image:Robert Boyle.jpg|thumb|right|100px|Boyle]]
Cryobiology history can be traced back to antiquity. As early as in [[2500 BC]] low temperatures were used in Egypt in medicine. The use of cold was recommended by [[Hippocrates]] to stop bleeding and swelling. With the emergence of modern [[science]], [[Robert Boyle]] studied the effects of low temperatures on animals.
In 1949 [[spermatozoon|sperm]] was [[cryopreservation|cryopreserved]] for the first time by a team of scientists led by [[Christopher Polge]] (1926-2006). This led to a much wider use of [[cryopreservation]] today, with many [[organ (anatomy)|organs]], [[Biological tissue|tissues]] and [[cell (biology)|cell]]s routinely stored in low [[temperature]]s. Large organs such as [[heart]]s are usually stored and transported, for short times only, at cool but not freezing temperatures for [[Organ transplant|transplantation]]. Cell suspensions (like [[blood]] and [[semen]]) and thin tissue sections can sometimes be stored almost indefinitely at [[liquid nitrogen]] temperature ([[cryopreservation]]). Human sperm, eggs and [[embryo]]s are routinely stored in [[fertility]] research and treatments. In the early 2000s a baby was born from a cryopreserved egg fertilized by a cryopreserved sperm.
[[Cryosurgery]] (= intended and controlled tissue destruction by ice formation) was carried out by James Arnott in 1845 in an operation on a patient with [[cancer]]. Although not very widespread, cryosurgery has its benefits. [[Hypothermia]], e.g. during [[heart surgery]] on a "cold" heart (generated by cold perfusion without any ice formation) allows for much longer operations and improves recovery rates for patients.
==Applied cryobiology==
Cryobiology as an [[applied science]] is primarily concerned with low temperature preservation. [[Hypothermia|Hypothermic]] storage is typically above 0°C but below normothermic (32°C to 37°C) mammalian temperatures. Storage by [[cryopreservation]], on the other hand, will be in the −80°C to −196°C temperature range. [[organ (anatomy)|Organ]]s, and [[Tissue (biology)|tissue]]s are more frequently the objects of hypothermic storage, whereas single cells have been the most common objects cryopreserved.
A rule of thumb in hypothermic storage is that every 10°C reduction in temperature is accompanied by a 50% decrease in [[Aerobic exercise|oxygen consumption]]<ref>{{cite journal | author=Raison JK | title=The influence of temperature-induced phase changes on the kinetics of respiratory and other membrane-associated enzyme systems.
| journal=J Bioenerg | volume=4 | issue=1 | year=1973 | pages=285–309 | pmid=4577759 | doi=10.1007/BF01516063
}}</ref>. Although [[Hibernation#Hibernating_animals|hibernating animals]] have adapted mechanisms to avoid [[Metabolism|metabolic imbalance]]s associated with hypothermia, hypothermic organs and tissues being maintained for [[Organ transplant|transplantation]] require special preservation solutions to counter [[acidosis]], depressed [[Na+/K+-ATPase|sodium pump]] activity and increased intracellular [[calcium]]. Special organ preservation solutions such as [[Viaspan]] (University of Wisconsin solution), [[Histidine-tryptophan-ketoglutarate|HTK]], and Celsior have
been designed for this purpose<ref>{{cite journal | author=Mühlbacher F, Langer F, Mittermayer C | title=Preservation solutions for transplantation | journal=Transplant Proc | volume=31 | issue=5 | year=1999 | pages=2069–70 | pmid=10455972 | doi=10.1016/S0041-1345(99)00265-1}}</ref>. These solutions also contain ingredients to minimize damage by [[Radical (chemistry)|free radicals]], prevent [[edema]], compensate for [[Adenosine triphosphate|ATP]] loss, etc.
Cryopreservation of cells is guided by the "Two-Factor Hypothesis" of American cryobiologist Peter Mazur, which states that excessively rapid cooling kills cells by intracellular ice formation and excessively slow cooling kills cells by either [[electrolyte]] [[toxicity]] or mechanical crushing<ref>{{cite journal | author=Mazur P | title=The role of intracellular freezing in the death of cells cooled at supraoptimal rates | journal=Cryobiology | volume=14 | issue=3 | year=1977 | pages=251–72 | pmid=330113 | doi=10.1016/0011-2240(77)90175-4}}</ref>. During slow cooling ice forms extracellularly, causing water to [[osmosis|osmotically]] leave cells, thereby [[dehydration|dehydrating]] them. Intracellular ice can be much more damaging than extracellular ice.
For [[red blood cell]]s the optimum cooling rate is very rapid (nearly 100°C per second), whereas for [[stem cell]]s the optimum cooling rate is very slow (1°C per minute). [[Cryoprotectant]]s, such as DMSO ([[dimethyl sulfoxide]]) and [[glycerol]], are used to protect cells from [[freezing]]. A variety of cell types are protected by 10% DMSO<ref>{{cite journal | author=Hunt CJ, Armitage SE, Pegg DE | title=Cryopreservation of umbilical cord blood: 1. Osmotically inactive volume, hydraulic conductivity and permeability of CD34(+) cells to dimethyl sulphoxide | journal=Cryobiology | volume=46 | issue=1 | year=2003 | pages=61–75 | pmid=12623029 | doi=10.1016/S0011-2240(02)00180-3}}</ref>. Cryobiologists attempt to optimize cryoprotectant concentration (minimizing both ice formation and toxicity) as well as cooling rate. Cells may be cooled at an optimum cooling rate to a temperature between −30°C and −40°C before being plunged into [[liquid nitrogen]].
Slow cooling methods rely on the fact that cells contain few [[Nucleation|nucleating]] agents, but contain naturally-occurring vitrifying substances that can prevent ice formation in cells that have been moderately dehydrated. Cryobiologists are increasingly using mixtures of cryoprotectants for full [[vitrification]] (zero ice formation) in preservation of cells, tissues and organs. Vitrification methods pose a challenge in the requirement to search for cryoprotectant mixtures that can minimize toxicity.
== Scientific societies ==
The '''[[Society for Cryobiology]]''' was founded in 1964 to bring together those from the biological, medical and physical sciences who have a common interest in the effect of low temperatures on biological systems. As of 2007 the Society for Cryobiology had approximately 280 members from around the world, and one half of them are [[United States|US]] based. The purpose of the Society is to promote scientific research in low temperature biology, to improve scientific understanding in this field, and to disseminate and apply this knowledge to the benefit of mankind. The Society organizes an [[Academic conference|annual scientific meeting]] dedicated to all aspects of low-temperature biology. This international meeting offers opportunities for presentation and discussion of the most up-to-date research in cryobiology as well as reviewing specific aspects through symposia and workshops. Members are also kept informed of news and forthcoming meetings through the Society newsletter, News Notes. The 2008-2009 President of the Society for Cryobiology is Barry J. Fuller.
The '''Society for Low Temperature Biology''' was founded in 1964 and became a [[Charitable organization|Registered Charity]] in 2003 ([[Charity Commission]] for England & Wales No. 1099747) with the purpose of promoting research into the effects of low temperatures on all types of organisms and their constituent cells, tissues and organs. As of 2006 the Society for Low Temperature Biology had approximately 130 (mostly British and European) members and holds at least one Annual General Meeting. The program usually includes both a [[symposium]] on a topical subject and a session of free communications on any aspect of low temperature biology. Recent symposia have included long-term stability, preservation of aquatic organisms, cryopreservation of embryos and [[gamete]]s, preservation of plants, low temperature [[microscopy]], [[vitrification]] (glass formation of aqueous systems during cooling), [[freeze drying]] and [[Biomedical tissue|tissue banking]]. Members are informed through the Society Newsletter, which is presently published 3 times a year. The 2005-2006 Chair of the Society for Low Temperature Biology has been Tiantian Zhang <ref>[http://www.beds.ac.uk/research/lirans/cryobiology/msc-cryobiology Tiantian Zhang]</ref>.
A list of additional scientific societies (mostly using "applied" cryobiology) can be found [http://www.sputtek.de/links1.htm here].
== Journals ==
''CRYOBIOLOGY'', (publisher: [[Elsevier]]) is the foremost scientific publication in this area, with approximately 60 refereed contributions published each year. Articles concern any aspect of low temperature biology and medicine (e.g. freezing, [[Freeze drying|freeze-drying]], hibernation, cold tolerance and adaptation, [[cryoprotectant|cryoprotective compounds]], medical applications of reduced temperature, [[cryosurgery]], [[hypothermia]], and perfusion of organs).
''CRYO LETTERS'' is an independent UK based rapid communication journal which publishes papers on the effects produced by low temperatures on a wide variety of biophysical and biological processes, or studies involving low temperature techniques in the investigation of biological and [[ecology|ecological]] topics.
''CELL PRESERVATION TECHNOLOGY'' is a [[peer-reviewed]] quarterly [[scientific journal]] published by [[Mary Ann Liebert, Inc.]] dedicated to the diverse spectrum of preservation technologies including [[cryopreservation]], dry-state ([[Cryptobiosis#Anhydrobiosis|anhydrobiosis]]), [[vitrification|glassy-state]] and hypothermic maintenance.
== Notes ==
<references />
==See also==
* [[Cryogenics]]
* [[Cryonics]]
* [[Cryopreservation]]
* [[Cryoprotectant]]
* [[Cryosurgery]]
* [[Cryptobiosis]]
* [[Freezing]]
* [[Freeze drying]]
* [[Hibernation]]
* [[Hypothermia]]
* [[Institute for Problems of Cryobiology and Cryomedicine]]
* [[Organ transplant]]
* [[Perfusion]]
* [[Tissue Engineering]]
* [[Vitrification]]
==External links==
* [http://www.societyforcryobiology.org/mc/page.do Society for Cryobiology]
* [http://www.SLTB.info Society for Low Temperature Biology]
* [http://www.elsevier.com/locate/cryo CRYOBIOLOGY]
* [http://www.cryoletters.org CryoLetters]
* [http://www.liebertpub.com/publication.aspx?pub_id=110 Cell Preservation Technology]
* [http://www.CRYO2006.org 43rd Annual Meeting of the Society for Cryobiology in association with the Society for Low Temperature Biology, July 23 - 27, 2006, Hamburg, Germany]
* [http://www.CRYO2007.org 44th Annual Meeting of the Society for Cryobiology, July 28 - August 1, 2007, Lake Louise, Canada]
* [http://cryo2008.uncc.edu/ 45th Annual Meeting of the Society for Cryobiology, July 20 - 23, 2008, Charlotte, NC, USA]
* [http://www.phys.unsw.edu.au/~jw/cryoblurb.html Cellular cryobiology and anhydrobiology]
* [http://www.scq.ubc.ca/?p=337 An overview of the science behind cryobiology at the Science Creative Quarterly]
[[Category:Cryobiology| ]]
[[bg:Криобиология]]
[[de:Kryobiologie]]
[[fa:سرمازیستشناسی]]
[[fr:Cryobiologie]]
[[ko:저온생물학]]
[[is:Lághitalíffræði]]
[[it:Criobiologia]]
[[he:קריוביולוגיה]]
[[ja:低温生物学]]
[[pt:Criobiologia]]
[[tr:Kriyobiyoloji]]
[[uk:Кріобіологія]]