RESEARCHES ON ZEBRA FISH

By SREEREMYA.S, M.philLecturer, Dept.Of Biotechnology

Mercy College,Palakkad

Zebra fish

WELFARE OF ZEBRA FISH• This report aims to improve the welfare of zebrafish by: • o facilitating understanding of zebrafish behaviour and thus a better

appreciation of their requirements; • o highlighting current potential welfare and ethical concerns relating to

the breeding, supply, housing and care of zebrafish; • o arriving, where possible, at consensus based on available evidence

and sound scientific argument for appropriate environmental and care conditions for keeping zebrafish in the laboratory environment;

• o providing recommendations for improving health, welfare and egg quality, for reducing the potential for stress and suffering, and for reducing the number of animals used;

• o in areas where current knowledge is sparse or inconclusive, stimulating discussion and research to identify ‘good practice’.

Natural geographic range and habitat

• The exact current natural geographic range of the zebrafish is still far from clear. Engeszer et al (2007) state that data from original collections of these fish suggests a range extending from Pakistan in the west to Myanmar (Burma) in the east, and from Nepal in the north to the Indian state of Karnataka in the south. However, they caution that given the historical nature of many of these records, along with the possibility that specimens may have been misidentified (particularly with regard to their presence in the most extremes of this distribution) this suggested range may not be an entirely accurate reflection of their true present day distribution.

• They can typically be found in standing or slow-moving bodies of water, such as pools, ponds, lakes, ditches or rice paddies and would appear to be a floodplain rather than a true riverine species (Vargesson 2007, Delaney et al 2002, Spence et al 2006a). Field studies have found zebrafish at sites that are silt-bottomed and well-vegetated, with shallow and relatively clear water where they appear to occupy the whole of the vertical water column (Engeszer et al 2007, Spence et al 2007).

• More than just pets• Covered with iridescent scales and black

stripes, zebrafish (Danio rerio) are popular in home aquariums. However, these little one- to two-inch fish, natives of India’s Ganges River, are also helping biomedical researchers learn about how our hearts develop and function—and what can make them fail.

Developing zebra fish embryo

How is your heart like that of a zebrafish?

• Though distantly related, human and zebrafish hearts have much in common. Both are muscles designed to pump oxygen-carrying blood through the body. In both cases, the heart is made up of chambers with valves that ensure blood flows in the correct direction. And, in both cases, the heart pumps in a regular, rhythmic, way. The rhythmic beating of the heart in part depends on specialized heart muscle cells called myocytes that are normally a highly organized part of the heart’s structure.

• The zebrafish offers several distinct advantages as a genetic and embryonic model system to study cardiovascular disease. One major advantage is that zebrafish are vertebrates that can be used

for unbiased and whole-genome forward genetic screens. • This allows the identification of novel genes that are required for cardiovascular

development. In addition, the function of unknown genes, identified by expression or interaction screens, can be investigated by various reverse genetic approaches.

• Zebrafish embryos are particular well suited for studying gene function during cardiovascular development, because zebrafish embryos are not completely dependent on a functional

cardiovascular system for their development. In• zebrafish embryos that lack blood circulation, oxygen can still enter the embryos and reach

all tissues by passive diffusion owing to the small size of the embryo. This feature permits the embryos to survive the initial phase of embryonic development and allows the analysis of embryos with severe cardiovascular defects. This is in contrast to avian and mammalian embryos, which die rapidly in the absence of a functional cardiovascular system. Besides the ease of identifying and studying genetic mutants, the optical transparency of zebrafish embryos has given new insights into various cellular aspects of cardiovascular development.

Can a zebrafish help solve medical mysteries?

• Because zebrafish hearts are so similar to our own, scientists are using the fish to study many aspects of heart disease, particularly the role of genetic mutations that might cause heart abnormalities.

• One disease, called familial hypertrophic cardiomyopathy (HCM), is the leading cause of sudden death in young athletes.

Can a zebrafish help solve medical mysteries?

• Scientists had been studying a collection of zebrafish mutants that developed heart abnormalities. The most severe of this collection was a defect named silent heart; embryos with this mutation had hearts that did not beat at all. Using molecular techniques, researchers found the gene that, when mutated, produces silent heart also encodes the zebrafish version of the troponin T protein. In the case of silent heart, they found the gene so mutated that it failed to make any useful troponin T, and that this affected the production of two other important heart proteins. The failure of this system of proteins created disorganized heart muscle cells (myocytes) that in turn failed to organize into a heart effective at circulating blood. In humans with HCM, myocytes are also disorganized, which can lead to an abnormal heartbeat, and in some cases, sudden death.

• Thus zebra fish is a major expeimental model used for studying about different scientific fields

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