Effect of vitamin A on lens regeneration in pigs

679-685Intraperitoneal injections of vitamin A (0.5 ml of 1500 IU/ml) to lentectomized pigs on alternate days up to 60th day after lentectomy induced lens regeneration in not only 10 days old young ones but also in 40 and 100 days old pigs. Lens regeneration did not occur even in a single case of control groups. In shape, size, transparency and histological features regenerated lenses were similar to normal intact lenses. The experimental model is the first to show that mitogenic and dedifferentiate activity of vitamin A can induce iris pigmented epithelial cells to trans-differentiate into new lens in pigs

Stage dependent effects of vitamin A excess on limbs during ontogenesis and regeneration in tadpoles of the toad Bufo melanostictus Schneider

Effects of variable treatments with vitamin A excess on ontogenesis and regeneration of hind limbs in toad tadpoles were investigated. In tadpoles at spatula/paddle stage of limb development right leg was kept intact and regeneration initiated in the left leg by amputation through shank. Following this, group A was reared in water from day 0 to 15 and groups B, C and D were kept in vitamin A solution during days 0-15, 3-15 and 0-3, respectively. In group A development of both intact limbs and regenerates was normal. In group B, foot morphogenesis was suppressed in intact limbs whose entire myogenic mesoderm also became necrotic; regeneration in the operated limbs proceeded only up to blastema stage. In group C, morphogenesis of intact limbs was not affected but histogenesis was relatively retarded and regenerates did not develop beyond blastema stage. In group D, foot morphogenesis was suppressed in the intact limbs but in them cartilage and muscle differentiation was normal. Regenerates however, ' developed in all cases and were well formed. , Vitamin A treatment induced many supernumerary regenerates in groups B and D which, in the former group remained blastema-like outgrowths but in the latter developed into well formed limbs. Differential effects observed on intact and regenerating limbs were related to their respective specific developmental stages at the time and duration of exposure to the vitamin; the stage of limb mesodermal differentiation and morphogenesis during ontogeny and regeneration susceptible to vitamin A could be identified. Developing anuran limb is suggested as a suitable system for investigations on the mechanisms of vitamin A teratogenesis

Increase in developmental potencies of blastema of rgenerating limbs in toad tadpoles exposed to vitamin A excess

During our investigations on the effects of viamin A excess on limb regeneration in anuran tadpoles certain very interesting results have been obtained which contradict the old view that the blastema differentiates only into the structures distal to the level of its origin. --- In experiments, spatula stage hind limbs of the toad Bufo melanostictus tadpoles were amputated through presumptive shank region. The control tadpoles were maintained in ordinary water and the experimental group of such operated tadpoles was immersed in 15 I.U./ml solution of vitamin A palmitate for first 3 days after amputation and then were transferred to ordinary water for the remaining 12 days of the experiment.--- In the control group regeneration of the amputated limbs occurred in 100% cases and all regenerates were completely normal. The regenerated part in each case consisted of only the structures which had been removed distal to the level of amputation. In the experimental group also regeneration occurred in 100% cases and the regenerates were normal in morphology but they differed from the controls in two respects: (i) in 37.5% cases more than one limb regenerated from the same stump; (ii) in all cases regenerates consisted of not only the structures distal to the level of amputation but also the structures proximal to this level including thigh region and the stump portion of the shank. In a number of cases even girdle-like structures had been formed at the level of amputation.--- It is suggested that the exposure of the regenerating limbs in the preblastemic period to vitamin A led to formation of blastemas with greater potency than usual. This resulted in formation of the entire limb from these blastemas and not only the structures actually removed by amputation. This treatment probably also neutralized the so called restrictive or distalizing influence of the stump on the blastema

Forelimb regeneration at wrist level in adults of skipper from Rama cyanophlyctis (Schneider) & its improvement by vitamin A treatment

This article does not have an abstract

The ‘‘Third Eye’’— A new concept of trans-differentiation of pineal gland into median eye in amphibian tadpoles of <i>Bufo melanostictus</i>

671-678Median third eye was found to develop from transplanted pineal gland of external gill stage tadpoles in the recipient 5 toe stage tadpoles of Bufo melanostictus. Pineal gland along with a bit part of brain tissue of the donor external gill stage tadpole was cut out and transplanted into a pit made between two lateral eyes of 5 toe stage recipient tadpoles. Half of the operated tadpoles were treated with vitamin A (15 IU/ml.) for 15 days. Median ‘‘third eye’’ was found to develop in the both untreated and vitamin A ·treated tadpoles. However, vitamin A increased the percentage of the development of median eyes. Morphological and histological study revealed that newly transformed median eyes were similar to that of normal functional eyes. A stalk like structure developed which connects the median eye to the brain. The median third eye could not develop when pineal gland of 5 toe stage mature tadpole was transplanted into the tadpole of the same age

Trans-differentiation of iris pigmented epithelial cells of <i style="">Euphlyctis cyanophlyctis</i> tadpoles into lens <i style="">in vitro</i>

17-25Meshed pigmented iris epithelium along with neural retina of tadpoles of the frog Euphlyctis cyanophlyctis were found to undergo dedifferentiation and subsequently transdifferentiate into lens in culture medium. During lag period, depigmentation (dedifferentiation) occurred in many cells. When culture became confluent 3-4 weeks after seeding tiny lens like structures differentiated from foci of cultured pigmented iris epithelium cells. The percentage of lens formation was higher in vitamin A treated cases. The culture system appears to be a suitable for investigating the changes occurred during trans-differentiation of pigmented epithelial cells into lens

Effect of Emblica officinalis (Gaertn) on lens regeneration in the frog, Rana cyanophlyctis (Schneider)

157-162Emblica officinalis (Amla) accelerated cell proliferation and dedifferentiation of pigmented epithelial cells of dorsal iris and consequently induced lens regeneration in R.cyanophlyctis. Further it enhanced the percentage of lens regeneration not only in young tadpoles but also is adult frogs. Lens regeneration ability declined with the age of animals in both control as well as treated groups

<span style="font-size:11.0pt;mso-bidi-font-size: 10.0pt;font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language:AR-SA" lang="EN-GB">Plasticity and reprogramming of differentiated ocular tissue of tadpoles of the frog, <i style="mso-bidi-font-style:normal">Euphlyctis cyanophlyctis</i> under the influence of vitamin A</span>

23-28<span style="mso-bidi-font-size: 9.0pt" lang="EN-GB">Present study has shown that differentiated cell types may loose their definitive characteristics and acquire features of another specialized cell type. Young (3 toe stage) and mature (5 toe stage) tadpoles of the frog, Euphylictis cyanophlyctis were employed as experimental animals. Experiments were completed in two phases: in the first part of experiment, lenses were extracted from right eye balls of tadpoles and treated with vitamin A; in the second part of the experiment, meshed lentectomized eye ball tissues were implanted into the pit made on mid lateral position of the tail of young and mature tadpoles and were treated with vitamin A. The results obtained gave clear evidence of plasticity and reprogramming of terminally differentiated ocular tissue into lens, retina and even complete eye. Vitamin A was found to be good model for accelerating the reprogramming of differentiated ocular tissue in anuran frog tadpoles. </span