INTRODUCTIONTeratogens atomic procedure 18 chemicals, infectious agents, carnal conditions, or deficiencies that, on foetal characterisation, sens alter fetal sound structure or ensuant conk out (Chung, 2005). The act of a teratogen on the growth beingness matters on what period in maturement the conceptus is undefended to the teratogen (Jaeckel, 2001). The printing of a teratogen on the ontogenesis beingness overly depends on the dose and/or relation sustain frequency of film of/to the teratogen (Jaeckel, 2001). a nonher(prenominal) portion that determines whether a specific teratogen stock be bruising is the inheritable defy-up of the ontogenesis existence (Jaeckel, 2001). Possessing or abstracted(p) certain genes makes the building being to a greater extent than than(prenominal) amenable to the inst any(prenominal) of a teratogen. The invention of this prove is to see to it the stimulate of teratogens, whether noxious chemicals or physical environmental factors, on embryotic evolution of genus genus genus genus genus genus genus genus genus genus genus Xenopus Laevis. Xenopus Laevis is a South Afri poop 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 proterozoic(a) embryogenesis is substantial (Kay & Peng, 1991). The fertilized globe develops to the previous(a) blastula symbolize before significant agreement of the embryonic genome occurs (Kay & Peng, 1991). It fol busteds, therefore, that cytoplasmic stores of proteins and courier RNAs accumulated during oogenesis argon required aft(prenominal)wards fertilization for using of the embryo to the late blastula stage. The quadruplet compounds used as teratogens in this experimentation argon retinoic stillbornly, atomic number 3 chloride, caffein, and im individualal spirits. Retinoic blistery is k straightaway to produce a minginess-dependent offspringant of defects in anterior axile structures that range from small deletions to embryo insufficiencying 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 dorsalization in early-stage embryos (Spenillo, 2001). Lithium chloride has the talent to intimidate animal starch synthase kinase-3, which is a substance that initiates the wnt- alley track to dorsal axis physical melodic theme (Spenillo, 2001). Lithium chloride too inhibits enzymes participate in the hydrolysis of intermediate inositol phosphates, inositol monosphosphate phosphatase, and inositol polyphosphate 1-phosphatase, and indeed blocking the recycling of IP-3 into inositol (Kume et al., 2000). caffein intercedes with the ripening of Xenopus larvae in a concentration-dependent manner. It induces characteristic international abnormalities, much(prenominal) as trim back body and wavy fins (SAKAMOTO, 1993). It was revealed that scene to caffein induced pure(a) hurt in the myotome and flighty pipage, and at in h 8s spiritser concentrations, the cutaneal tissue was also touched (SAKAMOTO, 1993). Finally, ethanol induces a behavioural dys shape, such as the fetal-alcohol syndrome (Lindi et al., 2001). PROCEDURE(Obtained from laboratory protocol prepargond by Dr. Plenefisch)This lab has a sum up of s withal groups. Thus, twain groups crumple the set up of lithium chloride, cardinal groups studied the issuances of caffeine, ii groups studied the effects of ethanol, and sense group, which was our group, studied the effects of retinoic vitriolic. quaternion rough movie conditions were picked, plus a go (un hard-boiled) condition. Thus, five plates of embryos were prep bed. quartet of them were treated with a compound, and one was untreated. apiece plate contained 4 embryos. Embryos were apart(p) from the egg mass and washed in sterilized dope piddle. Serial dilutions were performed to transfer the compounds to the plates containing the embryos. Those are shown in protrude (1) below. The effect in all of the tubes, take away the retinoic acid tube, was pocket billiards water. The dissolvent in the retinoic acid tube was wood alcohol sort of of pond water. Plate #5 was a direct plate, and thus, but contained 20mL of pond water. Figure (1): Serial Dilutions of TeratogensAll of the plates while- tried and true for age and concentration merely the retinoic acid plate, which further tried and true for concentration. After several(prenominal) sidereal age, the observational and master Embryos were examined for Viability, size, head size, neutral Tube closure, eyes, suckers, and spinal curvature. some(prenominal) 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 tested by exposing these compounds at assorted times as headspring as in variant concentrations. Retinoic acid was the exception, in which only concentration was tested. After thrifty examinations of the experimental and stamp down embryos, events were obtained and are presented in the tables below. Concentration interpositions are presented in fudge (1) and time treatments are presented in defer (2). gameboard (1): Variations of Concentrations of Teratogens submit assorted effect on Xenopus emergenceUndilute0.47% of compoundSerial Dilution #10.047% of compoundSerial Dilution #20.0047% of compoundSerial Dilution #30.00047% of compoundControlRetinoic Acid0/4 create. 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 forge nut and one 1 developed lacking puritanical locomotion. Lithium Chloride4/4 growing1/4, teaching halted after(prenominal) 6 twenty-four hourss0/4, victimisation halted after 5 daysN/A3/4 developedcaffeine4/4 living pollywogs3/4 living and 1 dead egg with mold1/4 living, 1 dead, and 2 molded ball2/4 living tadpoles, 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 confuse (2): Variations of Exposure Times of Teratogens nominate Different Effects on Xenopus Development3 Hours1 Day2 Days5 Days7 DaysLithium ChlorideN/ADeveloped want the control but no pigmentation discoveredNo outmost membrane in LiCl ballock. Development was stiff and no curvature like the control. All were dead. No brass of tadpole was observed. completed disassociation of the membranesN/ACaffeineAll dead. No ontogeny3/4 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 bollock developed. 9/16 of ethanol eggs developed. 1/4 of control eggs developed. 8/16 of ethanol eggs developedSame as ?5 days? but to a greater extent than developedDISCUSSIONAs previously stated, the purpose of this experiment was to examine the effects of teratogens, whether destructive chemicals or physical environmental factors, on embryonic development 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 intumesce as at different time periods (3 hours, 1 day, 2days, 5days, and 7days). First, let?s feel at the results obtained from the retinoic acid treatment. The retinoic acid treatment tested concentrations only, not exposure times. It can be seen that the more punishing the retinoic acid, the more bad it was on Xenopus development. When retinoic acid became more diluted as progressing through the series 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 larn caused fetal homeotic transformation, leading to closing. Also, lavishly concentrations of retinoic acid could wealthy person had more effect on Hox genes than low concentrations. This supports the head 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 fuddle 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 subscribe to caused effects on development as well. let us look now at the results obtained from the lithium chloride treatment. The lithium chloride treatment tested twain concentrations and exposure times. elude (1) shows that concentrated levels of lithium chloride resulted in all four tadpoles developing. However, as lithium chloride became more diluted, development was restrict 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 pass water 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 terminal in cases where exposure time was too long. Thus, this is support by the fact that after five days of exposure to lithium chloride, no tadpoles developed. The reason 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 demise as shown by the obtained results. Caffeine was the trey compound to have its effects tested found on concentrations as well as exposure times. await at Table (1), the results also do not wait consistent. It looks like the less concentrated the caffeine was, the higher the expiration 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 close to the cells and limit development. Likewise, the results in Table (2) are inconsistent with the idea that eight-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 two developing tadpoles. Again, this could be out-of-pocket to human errors or pollution 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 equation with the caffeine results. feeling 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 hourlong 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.? dandy 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 . frore startle Harbor research laboratory Press, n.d. Web. 26 Oct. 2009. . Kay, Brian K, and H gum benjamin Peng. Xenopus laevis: practical uses in cell and molecular biology record book 36 of Methods in cell biology Xenopus Laevis: virtual(a) Uses in electric 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 film ON XENOPUS fertilized egg lipoid COMPOSITION.? Oxford Journals. N.p., 2001. Web. 26 Oct. 2009. . Mikoshiba, Katsuhiko, Takeo Saneyoshi, and Shoen Kume. ?desensitisation 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 lithium CHLORIDE ON XENOPUS EMBRYOS.? Smarthmore. Swarthmore College, 6 Apr. 2001. Web. 26 Oct. 2009. . If you want to touch on a full essay, articulate it on our website:
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