Formation of multiple ependymas in the regenerating optic lobe of larvae of the Egyptian toad, Bufo regularis Reuss

In the regenerating optic lobe of Bufo regularis larvae, secondary ependymas were formed in both the dorsal part (optic tectum) and ventral region (tegmentum) of the lobe concerned. These secondary ependymas were frequently observed in the rostral and caudal tectal regions after complete excision of the tectum. Most of the multiple ependymal structures were formed by self-organization of groups of undifferentiated cells migrating from the primary ependyma lining the optic tectum. Others split off from the primary ependyma, but remained in contact with it. The observations emphasize the wide range of possibilities of the cells produced by the larval tectal ependyma in response to partial or total excision of the tectum. The results suggest that cells of ependymal origin, in regenerating tectum, are capable of self-organization to complete ependymal tubes in the absence of direct with the primary ependyma.     

Amputation level and hind limb regeneration in larvae of the Egyptian toad Bufo regularis Reuss: length, volume and rate

Study of the influence of the amputation level on regeneration length and volume and on the rate of regeneration of the hind limbs of a larval stage of Bufo regularis revealed that, during dedifferentiation and blastema accumulation and growth, the parts regenerating from proximal and distal amputation levels were almost the same length and volume, and grew at the same rate, irrespective of the amputation level. During blastema differentiation and morphogenesis, however, there were significant length, volume and elongation rate differences between parts regenerating from different amputation levels. The results also demonstrated that there was a strong positive correlation between regeneration length and volume, but that the elongation rate was not correlated to regeneration volume.     

Regeneration of the optic tectum in larval stages of Bufo regularis Reuss after partial and total excision

The right optic tectum of four larval stages of Bufo regularis was subjected to partial and total excision to determine the regenerative capacity of the optic tectum. Intense regenerative capacity can be observed at stage 50; the regenerated part grows to a considerable size and its structure is comparable to that of the intact part. This regenerative capacity gradually diminishes and from stage 55 onwards the decrease is pronounced. At stage 57 regenerative capacity is severly reduced and the regenerated part, if present, always has an anomalous structure.     

Local motion processing in the optic tectum of the Japanese toad,Bufo japonicus

Summary The results of previous behavioral studies can be so interpreted that the prey-catching behavior in the toad is elicited if there is a local motion restricted with-in a small part of the visual field, while it is suppressed if there is a global motion over a large part of the visual field. This has led us to design experiments to answer a specific question (yet a very essential one for understanding neural processes underlying this behavior): Are there local motion detectors in the toad's visual system that are not activated by global motion over a large part of the visual field but are activated by local motion confined within a smaller part of it? The present study showed that (1) the majority of the toad's tectal neurons exhibit properties of the local motion detectors as defined above, and (2) these properties can be explained from the receptive field structure revealed in the present experiments. Based on these results, we suggest that the tectal local motion detectors are essential for the detection and localization of small moving prey-objects in the natural environment while ignoring the large moving objects or the self-induced motion of the visual field.Abbreviations ERF excitatory receptive field - G1-5 group 1–5 neurons     

Aflatoxin-B1 inhibition of spermatogenesis in the toad Bufo regularis

Aflatoxin-B1 was injected in a dose of 0.01 mg/50 g body weight into the dorsal lymph sac of male toads (Bufo regularis) to evaluate its effect on the testes. After three and six weeks' treatment the diameters of the seminiferous tubules were significantly reduced. Furthermore, spermatogenic cells were almost completely absent. The histological evidence also showed complete suppression of spermatogenesis. It is suggested that one or several AFB1 metabolites may be responsible for suppression of spermatogenesis in the given toads, through inhibition of testicular androgenic activity.