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At least 433 records · Page 24Linked to original sources
PubMed1983

Scanning electron microscopical investigation of the larval development and the morphological differentiation of the paraventricular organ (PVO) of the South African clawed toad Xenopus laevis Daudin.

The development and the differentiation of the surface of the paraventricular organ (PVO) in tadpoles of the South African Clawed Toad Xenopus laevis Daudin from stages 46 to 66 and one adult animal was studied by means of light microscopy, scanning and transmission electron microscopy. At the light microscopical level, the PVO is visible from stage 46 on. From stage 48 on the organ is divided into two parts, a narrow rostral one and a more flattened and broad caudal one. From stage 58 on the rostral part of the PVO lies in the sulcus organi paraventricularis similar to the caudal part which lies in the sulcus lateralis infundibuli. The position of the PVO on both sides of the third ventricle is unchanged over all stages studied. The growth of the organ is finished at stage 65. The structure of the surface of the rostral and the caudal part of the organ differs up to the stage of 57. From stage 58 on the surfaces of the two parts of the PVO assimilate by developing a network of fibers which is orientated transversally. The different cell types of the PVO which can be seen at the level of transmission electron microscopy are fully developed at stage 57 but their position does not correspond to that of the adult animal. There is no difference between the right and left half of the organ in all groups studied.

Animals↗
PubMed1980

A comparison of the effect of albendazole, cambendazole, and thiabendazole on the larval development of three hymenolepidid cestodes.

Flour beetles (Tribolium confusum) parasitized either by Hymenolepis diminuta, H. nana, or H. microstoma were fed continuously on flour mixed either with thiabendazole, cambendazole, or albendazole (drug concentration was always 10%) from day 1 (24 hr) to day 10 postinfection when the experiments were terminated. All drugs markedly inhibited the development of H. diminuta and H. nana. Populations of these species recovered from beetles fed anthelmintics were composed mostly of under-developed forms, many of which still retained the size and appearance of newly hatched oncospheres, whereas all the parasites recovered from the control beetles (fed only flour) reached full development. Parasites inhibited by cambendazole and albendazole recovered and reached full development within 9 days after treatment was terminated. Also, results were obtained which implied that some parasites were able to continue their development at a reduced rate in the presence of the drugs. Hymenolepis microstoma differed from the other species in its response to the drugs. Albendazole and thiabendazole had no effect on its development and it was only slightly inhibited by cambendazole. Larvae recovered from beetles fed the latter drug had all developed beyond the oncosphere stage but 3 to 5% of them repeatedly failed to reach full development. The drugs varied in their effects on the flour beetles. An average of 63% and 33% of those fed thiabendazole and cambendazole, respectively, died before the 10th day of infection. Albendazole, on the other hand, had no effect on beetle survival.

Albendazole↗
PubMed1980

The morphogenesis of microtriches in the tegument of Taenia hydatigena throughout its larval development.

An electron microscope study was made on the development of microtriches, basic cytoplasmic inclusions, rod-shaped bodies and lamellated bodies in the larva of T. hydatigena. In the initial stage of its development, the tegument contains rod-shaped bodies and spineless or branching microtriches. An electron-dense substance released from rod-shaped bodies constitutes the basic substance of the tegument. Lamellated, secretory bodies appear in the tegument at the time of a differentiation of the scolex anlage. We believe that contents of lamellated bodies are released to the external environment either by their fusion with surface channels or their secernment in microtriches of the scolex anlage. The released secretion cements microtriches of a less active bladder in order to produce a defence barrier against host cells. Microtriches which have completed their secernment in an environment containing the secretory substance, close up in a point composed of the electron dense substance released from rod-shaped bodies. At the stage of encystment, microtriches become detached from the cementing substance which then is deposited on the inner side of the cyst wall. Lamellated bodies vacuolate.

Animals↗
PubMed1994

Replication, expression, and fate of foreign DNA during embryonic and larval development of the African catfish (Clarias gariepinus).

The transfer of exogenous DNA in fish represents a powerful strategy to study the regulation of gene expression in vivo. The African catfish (Clarias gariepinus) was chosen for this study because of its scientific and economic importance due to its easy husbandry, its short developmental period, and its value as a protein source in Africa and Asia. Fertilized eggs (1- and 2-cell stage) were cytoplasmatically injected with either supercoiled or linearized plasmids harboring the fusion genes encoding beta-galactosidase (lacZ) or luciferase (Luc) without a promoter or fused to the promoter/enhancer of human cytomegalovirus (CMV). Replication of the exogenous DNA peaked at 4 hours (early gastrula) and again at 2 days (which corresponds to the developmental stage of yolksac resorption). Foreign DNA persisted during embryogenesis, and it was still detectable 8 months after injection. In vivo transient expression of both CMV fusion genes was mosaic and peaked within 24 hours after DNA injection. Transient expression of the luciferase reporter gene could be detected with a much higher sensitivity than the lacZ gene. These data establish African catfish as a suitable in vivo assay system, and they confirm the luciferase reporter gene as a high quality reporter gene in fish.

Animals↗