Xenopus Metamorphosis Research Articles

The visual pigment system of Xenopus laevis: Tadpoles and adults

Meтoдoм экcтpaгиpoвaния ycтaнoвлeнo, хтo cиcтeмa пигмeитoв ceтхaтки aиypaнa Xenopus, oбитaющeгo иcклюхитeльнo в вoдe, нe являeтcя пocтoяинoй B тeхeниe eгo жизиeннoгo циклa. Ceтхaтки лихинoк coдepжaт кaк пopфиpoпcии, тaк и poдoпcин, иo y взpocлых ocoбeй имeeтcя тoлькo или глaвным oбpaзoм пopфиpoпcии. Этo oзнaхaeт, хтo мeтaмopфoзa Xenopus, B oтлихиe oт нeкoтopых дpyгих aнypaн, coпpoвoждaeтcя cмeиoй A 1-пигмeнтa иa A- 2пигмeнт. Для aиypaнa, oбитaющeгo тoлькo в вoдe, зтo пpoтивopeхит тoмy, хтo мoжнo oжидaть, ocнoвывaяcь нa eгo oбpaзa жизни. Oбьяcнeниe зтoмy мoжeт быть дaнo, нe иcхoдя из их нacтoящeгo oбpaзe жизни, иo из их звoлюции; т.e. мoжиo пpeдпoлaгaть, хтo Xenopus, ceйхac живoтнoe вoдянoe, пpoиcхoдит oт cyхoпyтных пpeдкoв. Poдoпcин, быть мoжeт, pyдимeнт, yкaзывaющий нa пpoщлoe, cкopee, хeм гoвopящий o пpиcпocoблeнии к тeпepящним ycлoвиям жизни.

XENOPUS LAEVIS AND DEVELOPMENTAL BIOLOGY

XENOPUS LAEVIS AND DEVELOPMENTAL BIOLOGY

The lateral line system at metamorphosis in Xenopus laevis (Daudin)

ABSTRACT Marked changes in the anatomy of the lateral line system occur during the metamorphosis of Xenopus. The distribution of rows differs in larva and adult and the orientation and number of organs are modified at metamorphosis. Larval plaques are functional, as shown by recording from their nerves. Two classes of cells with polarized cilia are present in the tadpole well before the orientation of individual organ plaques is rearranged at metamorphosis. The topography of the skin surface around individual plaques changes at metamorphosis. This change may reduce the directional sensitivity of organs. Myelinated inhibitory axons in the lateralis nerve are found only when the tadpole matures. This change takes place at a time when the adult method of locomotion is developed.

Spontaneous and induced metamorphosis inXenopus larvae at low temperature

In premetamorphicXenopus larvae mortality is not influenced by lowering the temperature from 22° to 8.5° C, but it rises dramatically below 8.5° C. At 10° C complete inhibition of spontaneous metamorphosis occurs only in premetamorphic larvae; beyond stage 56 cold treatment only delays the metamorphic changes.In cold-arrested premetamorphic larvae thyroxine and TSH elicit metamorphic responses. Since the responding capacity of the larval tissues to thyroxine is not affected, blockage of spontaneous metamorphosis at low temperature must result from the inhibition of the hypothalamic center.

Phagocytosis of melanin granules by connective tissue cells during the tissue disintegration of metamorphosis in Xenopus

Phagocytosis of melanin granules by cells of the connective tissue (histiocytes, macrophages) was observed in larvae ofXenopus laevis. Their participation in reduction of tissues is not of significant importance.

Wirksamkeit schilddrüsenhemmender Stoffe auf die Xenopusmetamorphose

A number of the compounds which had been shown byAstwood, in experiments on the rat, to have an action on the thyroid, were investigated for their inhibitory effect on the metamorphosis of Xenopus. The same compounds which had been proved to be active in the rat, were also shown, with few exceptions (e. g. p-amino-benzoic acid), to be active in Xenopus. On the other hand several substances which were not active in the rat (e. g. ammonium thiocyanate, thioacetamide) were active in Xenopus. Several of the compounds whichAstwood had described as not especially active or even inactive, proved to be particularly active. N-allylthiourea is about 10–20 times, and N-benzoylthiourea up to 200 times more active than thiourea or thiouracil. Ammonium thiocyanate and thioacetamide, which were found byAstwood to be inactive, showed a higher activity in Xenopus than potassium thiocyanate, which is active in the rat. The possible reasons for these big differences in activity in the rat and in Xenopus are discussed.