Cryobiology is the branch of hypothermic conditions to cryogenic temperatures.
- Areas of study 1
Cryopreservation in nature 2
- Bacteria 2.1
- Plants 2.2
- Invertebrates 2.3.1
- Vertebrates 2.3.2
Applied cryobiology 3
- Historical background 3.1
- Preservation techniques 3.2
- Cryobiology in humans 3.3
- Scientific societies 4
- Journals 5
- See also 6
- References 7
- External links 8
Areas of study
At least six major areas of cryobiology can be identified: 1) study of cold-adaptation of transplantation, 4) lyophilization (freeze-drying) of pharmaceuticals, 5) cryosurgery, a (minimally) invasive approach for the destruction of unhealthy tissue using cryogenic gases/fluids, and 6) physics of supercooling, ice nucleation/growth and mechanical engineering aspects of heat transfer during cooling and warming, as applied to biological systems. Cryobiology would include cryonics, the low temperature preservation of humans and mammals with the intention of future revival, although this is not part of mainstream cryobiology, depending heavily on speculative technology yet to be invented. Several of these areas of study rely on cryogenics, the branch of physics and engineering that studies the production and use of very low temperatures
Cryopreservation in nature
Many living organisms are able to tolerate prolonged periods of time at temperatures below the freezing point of water. Most living organisms accumulate cryoprotectants such as antinucleating proteins, polyols, and glucose to protect themselves against frost damage by sharp ice crystals. Most plants, in particular, can safely reach temperatures of −4 °C to −12 °C.
Three species of bacteria, Carnobacterium pleistocenium, Chryseobacterium greenlandensis. and Herminiimonas glaciei, have reportedly been revived after surviving for thousands of years frozen in ice. Certain bacteria, notably Pseudomonas syringae, produce specialized proteins that serve as potent ice nucleators, which they use to force ice formation on the surface of various fruits and plants at about −2 °C. The freezing causes injuries in the epithelia and makes the nutrients in the underlying plant tissues available to the bacteria. Listeria grows slowly in temperatures as low as -1.5 °C and persists for some time in frozen foods.
Many plants undergo a process called hardening which allows them to survive temperatures below 0 °C for weeks to months.
Nematodes that survive below 0 °C include Trichostrongylus colubriformis and Panagrolaimus davidi. Cockroach nymphs (Periplaneta japonica) survive short periods of freezing at -6 to -8 °C. The red flat bark beetle (Cucujus clavipes) can survive after being frozen to -150 °C. The fungus gnat Exechia nugatoria can survive after being frozen to -50 °C, by a unique mechanism whereby ice crystals form in the body but not the head. Another freeze-tolerant beetle is Upis ceramboides. See insect winter ecology and antifreeze protein. Another invertebrate that is briefly tolerant to temperatures down to -273 °C is the tardigrade.
For the wood frog (Rana sylvatica), in the winter, as much as 45% of its body may freeze and turn to ice. "Ice crystals form beneath the skin and become interspersed among the body's skeletal muscles. During the freeze, the frog's breathing, blood flow, and heartbeat cease. Freezing is made possible by specialized proteins and glucose, which prevent intracellular freezing and dehydration."  The wood frog can survive up to 11 days frozen at -4 °C.
Other vertebrates that survive at body temperatures below 0 °C include painted turtles (Chrysemys picta), gray tree frogs (Hyla versicolor), box turtles (Terrapene carolina - 48 hours at -2 °C), spring peeper (Pseudacris crucifer), garter snakes (Thamnophis sirtalis- 24 hours at -1.5 °C), the chorus frog (Pseudacris triseriata), Siberian salamander (Salamandrella keyserlingii - 24 hours at -15.3 °C), European common lizard (Lacerta vivipara) and Antarctic fish such as Pagothenia borchgrevinki. Antifreeze proteins cloned from such fish have been used to confer frost-resistance on transgenic plants.
Hibernating Arctic ground squirrels may have abdominal temperatures as low as −2.9 °C (26.8 °F), maintaining subzero abdominal temperatures for more than three weeks at a time, although the temperatures at the head and neck remain at 0 °C or above.
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, bull transplantation. Cell suspensions (like blood and semen) and thin tissue sections can sometimes be stored almost indefinitely in liquid nitrogen temperature (cryopreservation). Human sperm, eggs, and embryos are routinely stored in fertility research and treatments. Controlled-rate and slow freezing are well established techniques pioneered in the early 1970s which enabled the first human embryo frozen birth (Zoe Leyland) in 1984. Since then, machines that freeze biological samples using programmable steps, or controlled rates, have been used all over the world for human, animal, and cell biology – 'freezing down' a sample to better preserve it for eventual thawing, before it is deep frozen, or cryopreserved, in liquid nitrogen. Such machines are used for freezing oocytes, skin, blood products, embryo, sperm, stem cells, and general tissue preservation in hospitals, veterinary practices, and research labs. The number of live births from 'slow frozen' embryos is some 300,000 to 400,000 or 20% of the estimated 3 million in vitro fertilized births. Dr Christopher Chen, Australia, reported the world’s first pregnancy using slow-frozen oocytes from a British controlled-rate freezer in 1986.
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. Cryosurgery is not common.
Cryobiology as an applied science is primarily concerned with low-temperature preservation. 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 to −196 °C temperature range. Organs, and tissues 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 Viaspan (University of Wisconsin solution), HTK, and Celsior have been designed for this purpose. These solutions also contain ingredients to minimize damage by free radicals, prevent edema, compensate for 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. During slow cooling, ice forms extracellularly, causing water to osmotically leave cells, thereby dehydrating them. Intracellular ice can be much more damaging than extracellular ice.
For red blood cells, the optimum cooling rate is very rapid (nearly 100 °C per second), whereas for stem cells the optimum cooling rate is very slow (1 °C per minute). Cryoprotectants, such as dimethyl sulfoxide and glycerol, are used to protect cells from freezing. A variety of cell types are protected by 10% dimethyl sulfoxide. Cryobiologists attempt to optimize cryoprotectant concentration (minimizing both ice formation and toxicity) and cooling rate. Cells may be cooled at an optimum rate to a temperature between −30 and −40 °C before being plunged into liquid nitrogen.
Slow cooling methods rely on the fact that cells contain few nucleating agents, but contain naturally occurring vitrifying substances that can prevent ice formation in cells that have been moderately dehydrated. Some cryobiologists are seeking 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.
Cryobiology in humans
Cryopreservation in humans with regards to infertility involves preservation of embryos, sperm, or oocytes via freezing. Conception, in vitro, is attempted when the sperm is thawed and introduced to the 'fresh' eggs, the frozen eggs are thawed and sperm is placed with the eggs and together they are placed back into the uterus or a frozen embryo is introduced to the uterus. Vitrification has its glitches and is not as reliable or proven as freezing fertilized sperm, eggs, or embryos as traditional slow freezing methods because eggs alone are extremely sensitive to temperature. Many researchers are also freezing ovarian tissue in conjunction with the eggs in hopes that the ovarian tissue can be transplanted back into the uterus, stimulating normal ovulation cycles. In 2004, Donnez of Louvain in Belgium reported the first successful ovarian birth from frozen ovarian tissue. In 1997, samples of ovarian cortex were taken from a woman with Hodgkin’s lymphoma and cryopreserved in a (Planer, UK) controlled-rate freezer and then stored in liquid nitrogen. Chemotherapy was initiated after the patient had premature ovarian failure. In 2003, after freeze-thawing, orthotopic autotransplantation of ovarian cortical tissue was done by laparoscopy and after five months, reimplantation signs indicated recovery of regular ovulatory cycles. Eleven months after reimplantation, a viable intrauterine pregnancy was confirmed, which resulted in the first such live birth – a girl named Tamara.
Therapeutic 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.
The 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 2011-2012 president of the Society for Cryobiology was John H. Crowe.
The Society for Low Temperature Biology was founded in 1964 and became a gametes, preservation of plants, low-temperature microscopy, vitrification (glass formation of aqueous systems during cooling), freeze drying and tissue banking. Members are informed through the Society Newsletter, which is presently published three times a year.
Cryobiology (publisher: Elsevier) is the foremost scientific publication in this area, with about 60 refereed contributions published each year. Articles concern any aspect of low-temperature biology and medicine (e.g. freezing, freeze-drying, hibernation, cold tolerance and adaptation, 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 ecological topics.
Biopreservation and Biobanking (formerly 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 (anhydrobiosis), and glassy-state and hypothermic maintenance. Cell Preservation Technology has been renamed Biopreservation and Biobanking and is the official journal of International Society for Biological and Environmental Repositories.
- Maki LR, Galyan EL, Chang-Chien MM, Caldwell DR (1974). "Ice Nucleation Induced by Pseudomonas syringae". Applied Microbiology 28 (3): 456–459.
- Zachariassen KE, Kristiansen E (2000). "Ice nucleation and antinucleation in nature". Cryobiology 41 (4): 257–279.
- Food Safety Watch
- Scientist finds fungus gnats survive winter half-frozen | Alaskana | ADN.com
- Alaska beetles survive 'unearthly' temperatures
- ADW: Lithobates sylvaticus: INFORMATION
- Nation & World | Looking to frozen frogs for clues to improve human medicine | Seattle Times Newspaper
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- Mazur P (1977). "The role of intracellular freezing in the death of cells cooled at supraoptimal rates". Cryobiology 14 (3): 251–72.
- Hunt CJ, Armitage SE, Pegg DE (2003). "Cryopreservation of umbilical cord blood: 1. Osmotically inactive volume, hydraulic conductivity and permeability of CD34(+) cells to dimethyl sulphoxide". Cryobiology 46 (1): 61–75.
- "Freezing". Pacific Fertility Center. 2010. Retrieved 2010-02-28.
- "Livebirth after orthotopic transplantation of cryopreserved ovarian tissue" (PDF). J Donnez, M M Dolmans, D Demylle, P Jadoul, C Pirard, J Squifflet, B Martinez-Madrid, A Van Langendonckt. 2004. Retrieved 2015-01-02.
- Darwin, Mike (1991). "Cold War: The Conflict Between Cryonicists and Cryobiologists". Cryonics (Alcor Life Extension Foundation). Retrieved 2009-08-24.
- "Officers & Governors". Society for Cryobiology. Retrieved 2010-03-13.
- (Charity Commission for England & Wales No. 1099747)
- Society for Cryobiology
- Society for Low Temperature Biology
- Cell Preservation Technology
- Cellular cryobiology and anhydrobiology
- An overview of the science behind cryobiology at the Science Creative Quarterly