Bursicon Hormone

Papers below will discuss about Bursicon Hormone. It was writen as a part to fulfill one of the requirements for Insect Physiology courses. Thanks to Dr. Alqarni for his guidance during the writing.
So What is bursicon hormone...how it is work to insect etc...you will find out hopefully below

Bursicon: a brief
Insects has provide themselves a protection , mechanical support, and an effective barrier to desiccation and infections by their exoskeleton, however during their immature stages they have to replace the exoskeleton, the process called as molting. On this process a new cuticle is synthesized and secreted then is hardened after the remains of the old cuticle are shed at ecdysis. Molting and ecdysis are regulated by at least six different hormones, one of them is Bursicon (Luo et all, 2005). Bursicon bioactivity is essential for tanning of the exoskeleton and for wing spreading behavior that occur in newly emerged adult insects (Van Loy et al., 2007)


The discovery story
In 1935 Gottfried Fraenkel discover a hormone that responsible in the poupation formation of blowflies, this hormone later called as ecdyson, which was released by the brain (Reynold, 1983 and Truman, 1973)
At this time people considered this hormone as a universal hormone that responsible for three consecutive stages: splitting and shedding of the old cuticle; stretching and expansion of the new cuticle, and sclerotization (darkening) (Seligman,1980) molting, including the tanning and (sclerotization). Much work on the mechanism of action of ecdyson has been proceed on this assumption (Reynold, 1983).
In other papers in the same year Fraenkel’s also found that the newly emerged of blowflies could be delayed for 24 hours or more by forcing them to dig in sawdust so preventing them to have space for expanding and spread their wing, the result they remained pale and shrunken. Here there might be some other agent that control the tanning. This situation lay in abeyance for 27 years (Seligman, 1980 and Reynold, 1983).
Finally in 1962, the hormone that responsible for tanning were discovered by Cotrell (1962) and Franklen and Hasio, (1962).
Discovery fact
The discovery of bursicon mechanism can be understood clearly in two explanation, First A newly emerge adult blowflies must dig their way to the surface, when they expose to the air, they will swallow the air and the hormone (Bursicon) will be released to the blood and tanning begin. Secondly When newly emerged blowflies were decapitated or ligatured about their necks within a few minutes of eclosion, the rest of the body did not darken, when blood from tanning flies was injected into recipients neck ligatured, the block on tanning was lifted (Reynold, 1983).

Functional aspect of Bursicon (Reynold, 1983)
1. Bursicon control insect sclerotization
2. Bursicon control cuticle plasticization
3. Bursicon control Cuticle Deposition
4. Bursicon control Cell death
5. Responsible in Diuresis (reduction in blood volume)
6. Have a role in tracheal air-filling

Chemical nature of Bursicon
Bursicon properties is consistent as a peptide. It is destroyed by the proteolytic enzymes trypsin and pronase also by heating (Reynold, 1983).
The purification of Bursicon has not meet success so far. Apparently the hormone is unstable when purified. Fraenklen et al. (1966) cit in. (Seligman, 1980) had try to purify partially the hormone from the tissue by using acrylamide gel electrophoresis and Bio-Gel columns.

Mode of action of Bursicon

Bursicon’s principle physiology effect is on tanning of the cuticle. The exact sclerotization process is not very well understood, but it is agreed that an important cellular control of tanning is exerted at the level of synthesis tanning substrate from tyrosine (Reynold, 1983). Bursicon does not appear to have any effect on the interaction between tanning substrate (N-acetyldopamine) and the proteins cuticle (Seligman, 1980).

Overview and Prospect
Bursicon is distributed throughtout the nervous system and is present in the brain neurosecretory cells and corpora cardiac, they only released to the blood just after the time of ecdysis, they release in a massive then quickly cleared from the circulation (Mordue, 1982 and Renold, 1983). Here the absolute concentration of the hormone is less important than the timing of release. Just after the insect uses eclosion hormone to ensure the ecdysis occurs, the bursicon meet correct time in cuticle timing. Tanning must be fast to minimize the period in which the insect become vulnerable from accident or predator, it must not occur too soon , because once the new cuticle has begun to stiffen , it becomes imposible to extract it from the exuvia or toinflate it ti its proper size (Reynold, 1983).

Reference
Luo, Ching-Wei , Elizabeth M. Dewey, Satoko Sudo, John Ewer, Sheau Yu Hsu, Hans-Willi Honegger, and Aaron J. W. Hsueh. 2005. Bursicon, the insect cuticle-hardening hormone, is a heterodimeric cystine knot protein that activates G protein-coupled receptor LGR2.PNAS February 22, 2005 vol. 102 no. 8
Mordue W.1982. Neurosecretory peptides and biogenic amines. In Neuropharmacology of insect.Pitman. London.329p.
Reynold, Stuart E. 1983. Bursicon in Endocrinology of insects Vol.1. Ed. Downer, Roger G.H. and Hans Laufer. Alan R. Liss, Inc. NewYork.707p
Truman, James W. 1973.Physiology of insect ecdysis.II. The assay and occurence of the eclosion hormone in the chinese oak, silkmoth Antheraea pernyi.Biol. Bull., 144 : 200—211. (February, 1973)
Van Loy, T.,Matthias B. Van Hiel, Hans Peter Vandersmissen, Jeroen Poels, Fernando Mendive, Gilbert Vassart, Jozef Vanden Broeck. Evolutionary conservation of bursicon in the animal kingdom, Gen. Comp. Endocrinol.(2007), doi:10.1016/j.ygcen.2006.12.004