Larvengestalt und Eingeweide-Situs beim Alpenmolch (Triturus alpestris) nach halbseitiger UV-Bestrahlung von Neurula- und Nachneurula-Keimen

Abstract

Neurulae and postneurulae ofTriturus alpestris (up toHARRISON stage 29) were irradiated with mixed ultraviolet light from the left, right, dorsal or ventral side, respectively. The duration of treatment ranged from 1-600 seconds. Visible effects occurred already after a 5 sec irradiation. Embryos and larvae showed defects of histological and external features. In this paper "inversions" are distinguished from "partial inversions". In "inversions" the curvature of the gut and the liver sinus (or, in some cases, only the latter) are inverted. "Partial inversions" include all cases of lesser expression. The frequency of total and partial inversions of the digestive system depends on the duration, the stage and the side of irradiation. The frequency of total and partial inversions after dorsal, ventral and right side irradiation is not markedly higher than it is in normal controls (an exception are partial inversions of the gut after treatment within a certain dose range). Irradiation of the left side leads to a marked increase of partial inversions in all age classes. A significant increase (p<0.001) of total inversions occurs only after treatment in early stages (HARRISON 15-17) with high doses. A maximum of inversions of the digestive tract at low doses is still to be proven. The frequency of the experimentally elicited situs inversus viscerum decreases during neurulation. Inversions of the heart are less frequent than are inversions of the gut. The results are not in agreement with the hypothesis of a mechanical curving of the gut discussed bySPEMANN; rather, they indicate an influence from irradiation disturbance to the morphogenetic determination processes.

On the biological basis of human laterality: II. The mechanisms of inheritance

“…Physical interference can also influence asymmetries. Treatment with X-rays increases the percentage of situs inversus in newts , as does unilateral ultraviolet radiation (von Kraft, 1968a) and also electric current (von Kraft, 1968b). If plaice larvae are prevented from settling by agitation of the water, metamorphosis does not occur, and they remain symmetrical (Agassiz, in Osborn, 1894).…”

Is there a maturational left-right gradient for brain functions?

“…Of primary importance for the development of later organ asymmetry is a specific process of determination, which starts with gastrulation and finishes during neurulation. During this "determination phase" (von Kraft 1971a) the embryo is still morphologically completely bilaterally symmetrical and shows no apparent left-right gradient of development This is also true for a subsequent "post-determination phase" (von Kraft 1971a), in which influencing the future organ asymmetry is no longer possible (von Woellwarth 1950;Wehrmaker 1969;von Kraft 1968a;1970;1971c, 1973.…”

Symmetry and Asymmetry in the Development of Inner Organs in Parabiotic Twins of Amphibians (Urodela)

“…At least in Urodeles it was shown that all kinds of transient form s between the norm al situs and the situs inversus can occur, so that a continuous situs spectrum can be achieved (von Kraft, 1968a(von Kraft, , 1969b(von Kraft, , 1970(von Kraft, , 1971b . For different reasons the am phibian em bryo was preferred as an experim ental model, and most experiments on organ asym m etry and the left±right problem in organ ogenesis have been perform ed with these animals (Oppenheim er, 1974).…”