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1

The origin of syncytial muscle fibres in the myotomes of Xenopus laevis ? a revision

100%
Kielbowna L., Daczewska M.
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issue 1-2
39-44
EN
During the early stages of myogenesis in X. laevis, the primary myoblasts (of mesodermal origin) differentiate simultaneously, in each myotome, into mononucleate myotubes. At later stages mesenchymal cells appear in intermyotomal fissures and then in the myotomes between myotubes and contribute to the formation of syncytial muscle fibres. The pathway of mesenchymals cell during myogenesis was described in X. laevis by monitoring the incorporation of 3H-thymidine. 3H-thymidine was incorporated in the nuclei of mesenchymal cells in intermyotomal fissures of younger myotomes and then in those of older myotomes between the myotubes revealing the proliferation of mesenchymal cells. As expected, nuclei of differentiating mononucleate myotubes did not incorporate 3H-thymidine. At later stages of myogenesis the myotubes were found to contain two classes of nuclei: large nuclei of the primary myoblasts (of myotomal origin) and smaller nuclei originating from secondary myoblasts of mesenchymal origin. TEM and autoradiographic analyses confirm that mulinucleate myotubes in X. laevis arise through fusion of secondary myoblasts with mononucleate myotubes.
2

VariousDNAcontent in myotube nuclei during myotomal myogenesis in Hymenochirus boettgeri (Anura: Pipidae)

100%
Daczewska M., Saczko J.
Folia Biologica
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2003
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vol. 51
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issue 3-4
151-157
EN
During myotomal myogenesis in Hymenochirus boettgeri primary myoblasts differentiate into morphologically and functionally mature, mononucleate myotubes. Further muscle development in the studied species is due to fusion of mesenchymal cells with the latter, resulting in the presence of two classes of nuclei in the myotube: large of myotomal origin and small of mesenchymal origin. Densitometric measurements of DNA content revealed that the myotube nuclei at stages 35 reached values close to 4C DNA (3, 3C DNA), while at a later stage (42) the values were equal to 4C. Conversely, the secondary myoblast nuclei following the fusion with the myotube at stage 42 had 2C DNA ? a content comparable to that found in erythrocyte nuclei. PCNA (Proliferating Cell Nuclear Antigen) ? marker of S-phase of cell cycle, detected in the myotube nuclei (at stages 35, 42) appears during DNA replication.
3

Effect of thyroxine on some digestive enzymes of the adult male toad, Bufo melanostictus

75%
Bhattacharyya S. K., Chaki K. K., Miasrak K. K.
Folia Biologica
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2002
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vol. 50
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issue 1-2
83-90
EN
Thyroxine is known to play an important role during the developmental process of amphibians. The present work is designed on the hypothesis that a functional relationship exists between the thyroid gland and digestive physiology in the adult toad. Three doses of thyroxine (25 mug/100 g; 50 mug/100 g; 100 mug/100 mug body weight) were orally dministered daily to the adult male toad, Bufo melanostictus and changes in -amylase, pepsin, trypsin, and esterase activities of the different zones of the digestive tract, pancreas and liver were observed. The observations were made on 7, 15, and 30 days of thyroxine treatment. The result shows that the dose of 25 mug increases the enzyme activities in the gastrointestinal tract, liver and pancreas of 7 days treatment. However, prolonged treatment with all the doses shows little effect on these enzymes. The pattern of changes in the enzymatic activities in the digestive tract of the adult male toads show more advanced compartmentalization than that of fishes. It is also found that site-specific enzyme production is not pronounced in this amphibious vertebrate. It is proposed that a positive functional relationship between thyroxine and digestive enzymes exists in the adult male toad.
4

Nitric oxide production by cells infiltrating amphibian skin grafts. j

75%
Jozkowicz A., Plytycz B.
Folia Biologica
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1997
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vol. 45
73-78
EN
In vivo injection of the edible frog Rana esculenta with NOS inhibitor, L-NMMA caused prolongation of skin allograft and xenograft viability, statistically significant only in the latter case. In the present studies skin allo- and xenografts at the latent or rejection phase were excised from the hosts (Bufo bufo, R. temporaria, and R. esculenta) and incubated in vitro for 24 hrs in a medium only or in the presence of competitive (L-NMMA, L-NAME, L-aminoguanidyne) and noncompetitive (dexamethasone and cycloheximide) inhibitors of NO synthesis. In some experiments graft infiltrating cells were washed out and cultured separately from the respective skin fragments. The nitrite level was measured in the culture supernatant using Griess reagent. The nitrite level was negligible in the control skins, autografts, and xenografts depleted of graft infiltrating cells, as well as in allo- and xenografts excised at the rejection phase. In the case of grafts excised at the latent phase, the nitrite amount was substantial in supernatant from allografts and significantly higher in xenografts. A high level of nitrite was also present in supernatants from graft infiltrating cells. It is concluded that the NO contributes to some stages of the rejection process of the anuran skin grafts, this contribution being especially significant in the case of xenografts. The main source of this agent are graft infiltrating phagocytic cells.
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