T e host-graft-versus reaction to homotransplanted skin was studied in Triturus cristatus carnifex Laur., in adult males and females which had received the following treatments: (1) total body X -ray irradiation (one dose of 1600 r). (2) 1600 r X-ray irradiation of the splenic area, after shielding of the remaining body surface. In previous experiment the animals had been splenectomized at different time-intervals, after skin homotransplants: the results, compared with those presently obtained,...
The regenerative power of the optic lobe was studied in 70 young metamorphosed specimens of Xenopus laevis. The experimental animals were grouped as follows: Group I: more than 80% of the volume of the optic lobe was removed. Group II: 30% to 50% of the volume of the optic lobe was ablated. Group III: less than 30% of the optic lobe was ablated. The results showed than the regenerative capacity of the midbrain in metamorphosed specimens is very low. Only when the ablation of the optic lobe was inferior...
Unilateral ablation of the midbrain was performed in 27 tadpoles of Xenopus laevis (Daudin) at stage 47 (according to Nieuwkoop and Faber). Their brain was implanted in the anterior chamber of the eye of adult specimens of Rana esculenta L. and was fixed at 10-20-30 days after the operation. In some cases we observed that the implanted brain displayed a regenerative capacity which, although much less ineffective than in vivo, led to the regeneration of a new mesencephalic wall. In the partially...
Removal of the whole midbrain was performed in larvae of Rana dalmatina at stage 32 and of Rana esculenta at stage 33 (according to Manelli and Margaritora). The results show that the regeneration of the mesencephalon and particularly of the optic tectum is possible also from non-mesencephalic regions and is accomplished by pluripotent elements the determination and differentiation of which take place during the regenerative process.
In a previous paper by one of us (Filoni and Oberti, 1968), the poor regenerative capacity of the optic tectum in adult specimens of Xenopus laevis was reported. The right optic lobe had been removed by suction; since this technique causes connectival proliferation at the healing site, it was decided to repeat the experiment by operating the animals in two different ways to ascertain the effective regenerative power of the midbrain. The right optic lobe of adult Xenopus laevis was removed either...
The regeneration of the midbrain following to the ablation of the right optic lobe has been studied in larvae of Rana esculenta at stage 32 (according to Manelli and Margaritora). The results were in agreement with those previously obtained with other species of Amphibia anoura; they demonstrated that the regenerative process causes the neoformation of an optic lobe which is like that of the control side, both in volume and histological structure.
Two types of homoplastic transplants have been made in adult Amphibia Urodela (Triturus cristatus carnifex Laur.): i) skin was transplanted from a donor animal to an acceptor animal. 2) skin was transplanted to an acceptor, which functioned as a tem porary guest, and successively returned to the donor animal. In this last case a remarkable proliferation of the epidermal layer in the “returned skin” was observed. The explanations for the different reactions of histocompatibility, which were found...
The M.S.T. and the histocompatibility of skin transplants in adult specimens of Triturus cristatus carnifex Laur. was studied under different experimental conditions: (1) homotransplantation (2) homotransplantation on temporary hosts which had been X-ray treated (2450r) and injected with a spleen suspension obtained from the skin donor animals, followed by retrotransplantation to these donor animals The skin presented a slightly altered histological structure after the period on the temporary...
The treatment of specimens of flatworms (Dugesia gonocephala s.l.) (Platyhelminthes, Turbellaria, Tricladida) with very diluted copper solutions shows initially an increase of dopamine-like activity and thereafter a complete paralysis of the same. The morphological substrate of such an activity consists in evident damages with copper-soaking of neurons. These data are in accordance with the high sensibility towards copper ions obtained in the nigro-striatal dopaminergic system of higher Vertebrates....
Motor patterns under different stimuli related to the functional role of the brain in Dugesia gonocephala s.l. The motor system of flatworms, with its dopaminergic-cholinergic interactions, seems to be very close to the extrapyramidal system of Mammalia (Man also). We have investigated the threshold dose of apomorphine and amphetamine, related to the histological regeneration of brain in different experimental conditions, i.e. cranial and caudal fragments of operated animals, unoperated or half-brain...
The histology of normal and regenerated optic lobes was examined in young specimens of Xenopus laevis by applying the Golgi-Cox method. In the operated animals the unilateral ablation of the optic lobe has been performed at the early larval stages (48-51) and at the later larval stages (55-56), according to Nieuwkoop and Faber. From our observations we drew the following conclusions: 1) The histological features of the optic tectum of Xenopus laevis are essentially similar to those of other Anurans....
Fifty larvae of Xenopus laevis at stage 48 (according to Nieuwkoop and Faber) were submitted to tail amputation. Either 50% or 70% of the tail was cut off. The animals were sacrificed from the 30th to the 40th day after the operation, when they had reached stage 56-57. The study of the regenerated tail demonstrated that the histological structure of the neo-formed spinal cord is very similar to that of control animals, although the volume is clearly reduced. The regenerated spinal cord is constituted...
A morphological and histochemical study focused on synaptic receptors of Dugesia gonocephala s.l. (Platheminthes, Turbellaria, Tricladida) has been conducted in 90 specimens. Special concern was given to the synaptic function of a reference zone closest to the eyes. The motor pattern of Dugesia was investigated administering different drugs acting on dopaminergic systems either stimulating (l-dopa, apomorphine, piribedil), or blocking (haloperidol), or depleting monoamine containing neurons like...
In order to establish if the antithyroid substance 4(6)-propyl-2-thiouracil (PTU) directly affects the regenerative process of the optic tectum, larval Xenopus laevis at stage 48 (according to Nieuwkoop and Faber, 1956) were submitted to ablation of the right optic lobe and reared in 0.01 % PTU solution. The regenerative process of the optic tectum were compared with controls reared in water. The results obtained demonstrated that the PTU has no direct effect either on the proliferative phase or...
The biological effects of X-rays and sulphur mustard on the thymus of young rats were compared. The results can be summarized as follows: 1) after X-irradiation the thymus presents a remarkably altered histological picture (high percentage of picnotic lymphocytes, mitotic inhibition, alteration of the cortico-medullary boundary) but it has a rather rapid recovery with a maximum of the mitotic activity at the 5th day after irradiation. 2) The treatment with sulphur mustard caused delayed histological...
Skin fragments (6x4 mm) from adult Triturus marmoratus Latr. were grafted on the dorsal side of adult Triturus cristatus carnifex Laur. The recipient newts were divided into four batches: 1) non-treated (control specimens); 2) X-ray irradiated (1250 r); 3) X-ray irradiated (2450 r); 4) X-ray irradiated (2450 r) and injected with a spleen suspension from the donor. From the results it was apparent that: 1) in non-irradiated allografts an early histoincompatibility reaction develops (day 15); 2) the...
Behavioural and morphological observations have been conducted in specimens of flatworms (Dugesia gonocephala s.l.) treated with different ions such as zinc, lead, gold and silver. A copper-like activity of lead, gold and silver can be excluded; zinc-treated specimens show loss of motility comparable to the akinetic-end-phase described during copper exposure; the initial stage of copper-induced hyperkinesias probably depends upon a dopamine-like stimulation, specific to this ion.
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