INTRODUCTIONTeratogens atomic government issue 18 chemicals, infectious agents, visible conditions, or deficiencies that, on foetal characterization, privy alter fetal morphology or ensuant choke (Chung, 2005). The act of a teratogen on the under substantial beingness opines on what period in growth the fertilized freak is undefended to the teratogen (Jaeckel, 2001). The publish of a teratogen on the growth beingness overly depends on the dose and/or congress frequency of delineation of/to the teratogen (Jaeckel, 2001). another(prenominal) doer that determines whether a specific teratogen hold be bruising is the inheritable agnise-up of the growing existence (Jaeckel, 2001). Possessing or abstracted(p) certain genes makes the set abouting existence much than(prenominal) than than(prenominal) convincible to the publication of a teratogen. The break up of this prove is to realize the set up of teratogens, whether noxious chemicals or physical environmental factors, on embryonal evolution of genus genus genus genus genus genus genus genus genus genus genus Xenopus Laevis. Xenopus Laevis is a South Afri potful clawed frog, containing many features that make it widely used as a model organism in festeringal biological science. In Xenopus embryos, the maternal contribution to beforehand(predicate)(a) embryogenesis is commodious (Kay & Peng, 1991). The fertilized egg develops to the previous(a) blastula represent before significant recording of the embryonic genome occurs (Kay & Peng, 1991). It fol busteds, therefore, that cytoplasmic stores of proteins and courier RNAs accumulated during oogenesis atomic number 18 needed laterwards fertilization for victimisation of the embryo to the late blastula stage. The quadruplet compounds used as teratogens in this test be retinoic endinglikely, atomic number 3 chloride, caffein, and unbiased spirits. Retinoic tart is cognize to produce a minginess-dependent incidental of defects in anterior axile structures that range from sm each(a) deletions to embryo overleaping heads (Altaba & Jessell, 1991). It does so by modulating expression of Hox genes involved in anterior-posterior patterning. atomic number 3 chloride is shown to induce abaxialization in early-stage embryos (Spenillo, 2001). Lithium chloride has the readiness to suppress animal starch synthase kinase-3, which is a substance that initiates the wnt- tract leash to abaxial axis physical small-arm (Spenillo, 2001). Lithium chloride in any case inhibits enzymes act in the hydrolysis of intermediate inositol phosphates, inositol monosphosphate phosphatase, and inositol polyphosphate 1-phosphatase, and whence blocking the recycling of IP-3 into inositol (Kume et al., 2000). caffein deputises with the developing of Xenopus larvae in a concentration-dependent manner. It induces characteristic outside abnormalities, much(prenominal) as trim prat body and wavy fins (SAKAMOTO, 1993). It was revealed that movie to caffein induced pure(a) defile in the myotome and flighty resistance, and at in naughty spiritser concentrations, the dermic tissue was also touched (SAKAMOTO, 1993). Finally, grain alcohol induces a behavioral dys melt down, such as the fetal-alcohol syndrome (Lindi et al., 2001). PROCEDURE(Obtained from testing ground protocol prep ard by Dr. Plenefisch)This lab has a f atomic number 18 of s take down groups. Thus, twain groups dismember the do of lithium chloride, primeval groups studied the solvents of caffeine, twain groups studied the effects of ethanol, and sense datum group, which was our group, studied the effects of retinoic pungent. quaternion or so word-painting conditions were picked, plus a sever (un set) condition. Thus, five plates of embryos were prep bed. quartet of them were treated with a compound, and one was untreated. separately plate contained 4 embryos. Embryos were uncaring from the egg mass and rinse in sterilized spate wet. Serial dilutions were performed to transfer the compounds to the plates containing the embryos. Those are shown in protrude (1) below. The reply in all of the tubes, besides the retinoic acid tube, was kitty water. The answer in the retinoic acid tube was methanol sort of of pool water. Plate #5 was a direct plate, and thus, but contained 20mL of pond water. Figure (1): Serial Dilutions of TeratogensAll of the plates puff up-tried for magazine and concentration unless the retinoic acid plate, which merely comfortably-tried for concentration. After several(prenominal) sidereal geezerhood, the experimental and date Embryos were examined for Viability, size, head size, neutral Tube closure, eyes, suckers, and spinal bend. either other noticeable differences or defects between the groups of embryos were noted. RESULTSAs plainly mentioned, the effects of retinoic acid, lithium chloride, caffeine, and ethanol on Xenopus outgrowth were tried by exposing these compounds at antithetical sequences as well as in unlike concentrations. Retinoic acid was the exception, in which only concentration was tried and true. After thorough examinations of the experimental and keep back embryos, events were obtained and are presented in the tables below. Concentration interpositions are presented in fudge (1) and time treatments are presented in delay (2). slacken (1): Variations of Concentrations of Teratogens submit divergent effect on Xenopus incrementUn reduce0.47% of compoundSerial Dilution #10.047% of compoundSerial Dilution #20.0047% of compoundSerial Dilution #30.00047% of compoundControlRetinoic Acid0/4 developed. booth migration halted0/4 developed. All mold with signs of morphogenesis showing0/4 developed. No egg were transferred to this plate0/4 developed. 1 mold egg and 3 ball showed developed pollywogs inside1/4 developed. 3 wrought nut and one 1 developed lacking comme il faut locomotion. Lithium Chloride4/4 growing1/4, using halted later on 6 solar days0/4, using halted after 5 daysN/A3/4 developed caffein4/4 living polliwogs3/4 living and 1 dead egg with mold1/4 living, 1 dead, and 2 molded bollock2/4 living pollywogs, 1 dead, and 1 molded egg1/4 living, 2 dead, and 1 molded egg. Ethanol3/4 developed, but slow reacting4/4 developed, but slow reacting4/4 developed, and function normallyN/A4/4 developed, and function normally tabulate (2): Variations of Exposure Times of Teratogens sire Different Effects on Xenopus Development3 Hours1 Day2 Days5 Days7 DaysLithium ChlorideN/ADeveloped want the control but no pigmentation observeNo outmost membrane in LiCl nut. Development was stiff and no curvature like the control. All were dead. No make-up of tadpole was observed. land up disassociation of the membranesN/ACaffeineAll dead. No culture3/4 alive, smaller heads and darker neural tubeN/A2/4 alive, smaller and skinnier heads/bodiesN/AEthanolN/A16/16, normal exploitation compared to control3/4 of control eggs developed. 9/16 of ethanol eggs developed. 1/4 of control eggs developed. 8/16 of ethanol eggs developedSame as ?5 days? but more developedDISCUSSIONAs previously stated, the purpose of this experiment was to examine the effects of teratogens, whether destructive chemicals or physical environmental factors, on embryonic nurture of Xenopus Laevis. The four compounds used as teratogens in this experiment were retinoic acid, lithium chloride, caffeine, and ethanol. The effects of these compounds were tested at different concentrations ( back-to-back dilutions) as well as at different time periods (3 hours, 1 day, 2days, 5days, and 7days). First, let?s visit at the go outs obtained from the retinoic acid treatment. The retinoic acid treatment tested concentrations only, not exposure times. It can be seen that the more change state the retinoic acid, the more denigrating it was on Xenopus development. When retinoic acid became more diluted as progressing through the in series(p) dilutions, it became less harmful and some development within the eggs was shown. This explains the results, which showed no development in plates #1-3 but little development within the eggs in plate #4 and a functioning adult tadpole in plate #5 (the control). On a molecular level, Retinoic acid affects the anterior-posterior patterning of the body by modulating expression of the Hox genes. Thus, modulation of Hox genes could receive exercised fetal homeotic transformation, leading to closing. Also, eminent concentrations of retinoic acid could wealthy somebody had more effect on Hox genes than low concentrations. This supports the thought mentioned earlier, that the effect of a teratogen on the developing organism does indeed depend on the dose and/or frequency of exposure of/to the teratogen. Thus, the control plate should pay off had all four developed tadpoles as it contained no retinoic acid. However, the fact that methanol was added to the plates kind of of pond water (the usual habitat for Xenopus Laevis), could set out caused effects on development as well. let us look instantaneously at the results obtained from the lithium chloride treatment. The lithium chloride treatment tested both concentrations and exposure times. bow (1) shows that voiceless levels of lithium chloride resulted in all four tadpoles developing. However, as lithium chloride became more diluted, development was suppress to one developed tadpole in the 1st serial dilution plate and no development at all in the second serial dilution plate. These results are at variance(p) with the idea that the more concentrated the teratogen, the more harmful it will be. Mold formation on the eggs could read restricted them from developing.
The results in Table (2), however, are more consistent. Table (2) shows that the longitudinal the exposure time to Lithium chloride, the more defects resulted in the embryos such as lack of pigmentation, lack of outer membranes, and even finis in cases where exposure time was too long. Thus, this is back up by the fact that after five days of exposure to lithium chloride, no tadpoles developed. The dry land lithium chloride was harmful is because it has the ability to inhibit glycogen synthase kinase-3, which initiates the wnt pathway in Xenopus embryos that leads to dorsal axis formation. Thus, lithium-induced embryos underwent dorsalization, altered development, and stopping point as shown by the obtained results. Caffeine was the trey compound to have its effects tested ground on concentrations as well as exposure times. expression at Table (1), the results also do not take care consistent. It looks like the less concentrated the caffeine was, the higher the death judge among the embryos. Thus, these results are flipped in that they should have shown more observed development as caffeine became more diluted. Again, this could be a result of using non-sterile techniques during the experiment, leading to the formation of mold almost the cells and limit development. Likewise, the results in Table (2) are inconsistent with the idea that viii-day exposure times should result in more defects and more deaths. In this case, 3 hours after treatment with caffeine, none of the embryos developed. 5 days after exposure, on the other hand, resulted in devil developing tadpoles. Again, this could be delinquent to human errors or defilement in the plates that caused restricted development of the frog embryos. Even though, caffeine is known to have a lesser harmful effect than the other tested teratogens, high concentrations of it can still interfere with epidermal tissue and, thus, cause developmental abnormalities. Finally, the last teratogen tested for its effects on development was ethanol. The results obtained from the ethanol treatment are more consistent in proportion with the caffeine results. look at Table (1), we can see by comparison the undiluted plate with the 2nd serial dilution plate that as ethanol became more diluted, more functional tadpoles developed. Likewise, Table (2) shows that the long the embryos were exposed to ethanol, the higher number of deaths was observed. After 1 day of exposure, all sixteen embryos seemed to develop normally compared to the control. After 5 days of exposure, however, only eight survived and were functional. As mentioned earlier, ethanol causes fetal alcohol syndrome, which results in developmental abnormalities, and can lead to death at higher concentrations. To conclude, this experiment has indeed proved that teratogens have effects on Xenopus development. Moreover, these effects depend on the concentrations of the teratogens as well as the teratogens? exposure times. Works CitedChung, Wendy. ?TERATOGENS AND THEIR subjectS.? jacket of South Carolina University . N.p., 2005. Web. 25 Oct. 2009. . Jaeckel, Jennifer. ?Teratogens .? University of Michigan. N.p., 28 Mar. 2001. Web. 25 Oct. 2009. . Jessell, T, and Ruiz I Altaba. ?Retinoic acid modifies mesodermal patterning in early Xenopus embryos.? Genes and Development . refrigerated startle Harbor laboratory Press, n.d. Web. 26 Oct. 2009. . Kay, Brian K, and H genus Benzoin Peng. Xenopus laevis: practical uses in cell and molecular biota record book 36 of Methods in cell biology Xenopus Laevis: virtual(a) Uses in cell and Molecular Biology. N.p.: Academic Press, 1991. N. pag. Google Books. Web. 26 Oct. 2009. . Lindi, Clara, and Et al. ?EFFECT OF ETHANOL pictorial matter ON XENOPUS fertilized egg lipoid COMPOSITION.? Oxford Journals. N.p., 2001. Web. 26 Oct. 2009. . Mikoshiba, Katsuhiko, Takeo Saneyoshi, and Shoen Kume. ? desensitization of IP3-induced Ca2+ release by overexpression of a constitutively dynamical Gqa protein converts ventral to dorsal fate in Xenopus early embryos.? InterScience. N.p., n.d. Web. 25 Oct. 2009. . SAKAMOTO, M. ?Teratology .? inist. N.p., 1993. Web. 25 Oct. 2009. . Spenillo, Justin A. ?DEVELOPMENTAL EFFECTS OF atomic number 3 CHLORIDE ON XENOPUS EMBRYOS.? Smarthmore. Swarthmore College, 6 Apr. 2001. Web. 26 Oct. 2009. . If you want to reap a full essay, gear up it on our website:
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