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Biomedical subjects

H J Anton

Publications and source records attributed to H J Anton.

At least 19 recordsLinked to original sources
PubMed2002

Urodelean amphibians in studies on microgravity: effects upon organ and tissue regeneration.

Results obtained from nine experiments performed onboard Russian biosatellites have shown that microgravity promotes tissue regeneration in the newt, Pleurodeles waltl. The effect has been reproduced in all flights and on a clinostat as well for eye tissues (lens and retina), limbs and tail. The effect was demonstrated in 1.5- to 2-fold increase in cell proliferation in the early stages of regeneration in space flight. Animals "flown" intact and operated after flight regenerated faster than control ones and showed long-lasting micro-"g" effect. The most recent experiment flew aboard the Bion-11 biosatellite. This test was performed for study on microgravity effect on neural retina regeneration after optic nerve lesioning in the newt. Obtained results confirmed our previous information about intensification of regenerative processes in detached neural retina in urodela exposed to simulated weightlessness (Grigoryan et al., 1998). In particular, we found the increase and activation of cell populations participating in neural retina restoration and maintenance of retinal structure. Our findings suggest that promoting effect of microgravity upon regeneration could be influenced by several factors, largely influenced by a response of the whole organism to changed gravity vector. We hypothesized the synthesis of the specific range of stress proteins induced by micro-"g" and their regulative role in cell proliferation. Such a hypothesis for the existence of "altered gravity stress proteins" is discussed.

Animals↗
PubMed1998

Influence of clinorotation and fettering stress on tail regeneration of Triturus vulgaris (Urodela).

Tail-amputated adult Triturus vulgaris, fettered in cuvettes of a fast-rotating clinostat were exposed to simulated weightlessness (60 rpm; equiv. to 10(-3)-10(-4) g), during a 14-day period. To feed and clean the animals rotation was stopped once a day for approx. 10 min. To test the influence of the fettering stress, a second series of animals was kept separately under normal earth conditions without rotation. A further control series was kept in a dark container without any handicap. While tail regeneration of the rotated animals was markedly accelerated, the fettered-only animals showed a considerably less marked acceleration effect. At the end of the 14-day period, all regenerates were reamputated together with an additional 5 mm of the tail stump. Although this second level of amputation was distant from the first, the regenerative growth rate of the rotated series was accelerated 123% in contrast to both the control and the fettered-only series. Our results demonstrate that the growth acceleration is induced by clinorotation. Fettering stress has no comparable influence. The growth promoting effect is not limited to the regenerating area.

Amputation, Surgical↗
PubMed1998

Microgravity effects on neural retina regeneration in the newt.

Data on forelimb and eye lens regeneration in urodeles under spaceflight conditions (SFC) have been obtained in our previous studies. Today, evidence is available that SFC stimulate regeneration in experimental animals rather than inhibit it. The results of control on-ground experiments with simulated microgravity suggest that the stimulatory effect of SFC is due largely to weightlessness. An original experimental model is proposed, which is convenient for comprehensively analyzing neural regeneration under SFC. The initial results described here concern regeneration of neural retina in Pleurodeles waltl newts exposed to microgravity simulated in radial clinostat. After clinorotation for seven days (until postoperation day 16), a positive effect of altered gravity on structural restoration of detached neural retina was confirmed by a number of criteria. Specifically, an increased number of Mullerian glial cells, an increased relative volume of the plexiform layers, reduced cell death, advanced redifferentiation of retinal pigment epithelium, and extended areas of neural retina reattachment were detected in experimental newts. Moreover, cell proliferation in the inner nuclear layer of neural retina increased as compared with control. Thus, low gravity appears to intensify natural cytological and molecular mechanisms of neural retina regeneration in lower vertebrates.

Animals↗
PubMed1996

Influence of longitudinal whole animal clinorotation on lens, tail, and limb regeneration in urodeles.

Two species of newts (Urodela) and two types of clinostats for fast clinorotation (60 rpm) were used to investigate the influence of simulated weightlessness on regeneration and to compare results obtained with data from spaceflight experiments. Seven or fourteen days of weightlessness in Russian biosatellites caused acceleration of lens and limb regeneration by an increase in cell proliferation, differentiation, and rate of morphogenesis in comparison with ground controls. After a comparable time of clinorotation the results obtained with Triturus vulgaris using a horizontal clinostat were similar to those found in spaceflight. In contrast, in Pleurodeles waltl using both horizontal and radial clinostats the results were contradictory compared to Triturus. We speculate that different levels of gravity or/and species specific thresholds for gravitational sensitivity could be responsible for these contradictory results.

Animals↗
PubMed1996

Regeneration of organs and tissues in lower vertebrates during and after space flight.

In this paper most important data obtained in studies on the effect of space flight conditions on regeneration in the adult newt are summarized. We demonstrate a phenomenon of synchronization of limb and lens regeneration and increase in its rate during and after space flight. We also describe a peculiarities of cell proliferation in lens, limb and tail regenerates and of the process of minced muscle regeneration.

Animals↗
PubMed1996

Evidence for S stage quiescence in regeneration blastema cells.

Working on the temporal structure of the S stage of regeneration blastema cells we have discovered that some blastema cells, containing a 3C quantity of DNA, do not incorporate radioactive thymidine, or that they proceed through the synthetic phase with a speed undetectable by a radioactive pulse. We report the identification of several short-term periods of quiescence for regeneration blastema cells in vivo, operating during the S stage of the cell cycle. Blastema cell smears from regenerating urodele forelimbs were used in this study. Combined microdensitometric scanning of Feulgen-stained nuclei and microradioautographic labelling of the same nuclei have been exploited to assess DNA replication. A total of 3,600 blastema cell nuclei were scanned, mapped on photographic film and subsequently processed for radioautography. It was found that 49.7% of the cells with a DNA content ranging between 2C and 4C were unlabelled after 1 h exposure to tritiated thymidine.

Amputation, Surgical↗
PubMed1994

Allografting of a nontransmissible, spontaneous dermal melanoma in the newt Triturus cristatus.

Regeneration-competent urodele Amphibia are highly resistant to spontaneous development of neoplasms, in comparison with other vertebrates which do not exhibit great regenerative power. This observation implies that at least one growth parameter of urodele cells might be subject to different developmental mechanisms than the cells of animals incapable of epimorphic regeneration. Therefore, keeping records concerning the incidence of tumors in urodeles and investigating those exceptional cases might prove invaluable in understanding the basic biological principles governing organ regeneration and carcinogenesis, and might therefore help in cancer therapy. The present report depicts a case of two spontaneous, dermal, melanoma-like tumors found in an adult newt Triturus cristatus. Both tumors were located in the pelvic region. Histological examinations and tumor transplantations were conducted. It was found that the tumors were melanomata. When allografted within the body cavity, their mass was progressively eliminated.

Animals↗
PubMed1993

Unilateral forelimb amputation affects protein synthesis in ipsilateral and contralateral spinal cord and spinal ganglia neurons of the newt in vivo.

The aim of this investigation was to analyze the effect of urodele limb amputation and blastema growth on the protein synthesis in spinal cord and spinal ganglia neurons corresponding to the 3rd and 4th spinal segment of young, postmetamorphic Triturus vulgaris, in vivo. Protein synthesis was studied on both trunk sides as a function of right forelimb amputation at the distal stylopodium, and blastema development, during a critical period of 22 days post amputation (dpa). Protein synthesis was assessed by counting silver grains on autoradiographs obtained after pulse labeling with tritiated phenylalanine. An electronic image analyzer was used to evaluate the results. During the period of observation, several statistically significant, yet moderate changes were observed in the protein synthesis of motor neurons. In contrast, the studied metabolic parameter exhibited considerable augmentation in sensory neurons and spinal nerve. The main results may be summarized as follows: (a) Limb amputation triggers protein synthesis in both ipsilateral and contralateral neural elements; (b) protein synthesis is higher on the ipsilateral than on the contralateral side; (c) as the aftermath of forelimb amputation, the 4th ipsilateral ganglion responds with an approximately 20% higher protein synthesis in comparison to the 3rd one; (d) peaks in protein synthesis are encountered mainly at two time points: 3 hpa and 14 dpa. Protein synthesis returns to control levels after 22 days of limb regeneration.

Amputation, Surgical↗
PubMed1991

Retinoic acid does not induce formation of cilia on the surface of wound epithelial cells in axolotls.

It has been reported that vitamin A palmitate induces the production of cilia on the epidermal cells of the regenerating axolotl limb, and the formation of crevices in the epidermal surface. The aim of the present investigation was to reexamine under well defined conditions the potential of retinoids to evoke the above described metaplastic changes. In order to achieve our purpose we administered axolotls with retinoic acid for 2, 4, 6, 8, and 10 days after limb amputation. The young regenerates were inspected by scanning electron microscopy (SEM). The data obtained showed that the external layer of the wound epithelium and of the stump epidermis as well was quite normal without any sign of cilia formation. In some cases, crevices were observed even in control animals.

Ambystoma↗
PubMed1990

Demonstration of sensory-motor innervation of postmetamorphic forelimb regenerates of Triturus alpestris (Urodela) on cryotome serial sections using horseradish peroxidase.

A method has been developed to obtain horseradish peroxidase-treated serial sections containing spinal cord as well as bilateral ventral and dorsal roots, dorsal root ganglia and spinal nerves. Young postmetamorphic newts (Triturus alpestris) served as experimental animals. After cryotome cross sectioning the forelimb region of the trunk, slices 80 microns in thickness were mounted serially with up to 15 sections per slide. This facilitated subsequent staining manipulations and made partial loss of sections less likely.

Animals↗
PubMed1990

Effect of vitamin A on wound epidermis during forelimb regeneration in adult newts.

The effects of vitamin A on blastemal epidermis were studied during the early postamputational period of forelimb regeneration in Triturus alpestris. Vitamin A was administered through oral intubation at a dose of 250 IU per gram of body weight per day. The results were evaluated by morphometry, histology, and autoradiography. After 7, 11 and 14 days of treatment, several alterations were observed in the wound epidermis: a) reversal of keratinization; fewer keratinized cells were counted in sections from vitamin A-treated limbs; b) decrease in the incorporation of tritiated thymidine, as judged by estimation of labeling indices; c) increased mitotic activity in the cells of the stratum germinativum, and in the middle layer of the epithelial cells, as well. The significance of these cellular effects is discussed against the relevant literature.

Animals↗
PubMed1990

Mitotic activity in the blastema and stump tissues of regenerating hind limbs of Xenopus laevis larvae after amputation at ankle level. An autoradiographic study.

Mitotic activity, as indicated by DNA synthesis, was studied by autoradiographic analysis along the proximodistal axis of regenerating limbs in the early and later larval stages 53 and 57 of Xenopus laevis. Wound-healing, dedifferentiation, blastema formation and growth phases were studied. Most of the various stump tissues, as well as the cell mass of the regeneration blastema, were involved. The study showed an increase in DNA synthesis in the stump tissues during their dedifferentiation as well as during blastema formation. The increase was confined mainly to the distal portion (close to the amputation level), so that a proximodistal gradient was discernible. This could be regarded as valid evidence of contribution of the severed stump tissues to the blastema cells. The mesenchymal blastema cells formed after amputation at stage 53 displayed higher mitotic activity than the fibrocytoid blastema cells formed at stage 57. Although the latter were more differentiated than the former, they still showed DNA replication and mitotic division.

Amputation Stumps↗
PubMed1988

Estimation of cell cycle parameters from double labeling experiments.

Double labeling of cell populations with radioactive thymidine yields two types of differently labeled nuclei. Their numbers and the number of unlabeled nuclei can be used to estimate doubling times, T, and S-phase lengths, S. As of yet, such estimations have been performed either for stationary populations in which proliferation and losses are in balance, or for exponentially growing populations in which all cells have the same cycle duration. We calculate S and T for the more general type of cell population with arbitrarily distributed frequencies of cycle durations. The calculations do not require more mathematical or computational effort. We obtain three main results: (i) The estimation of T and S does not require explicit knowledge of the frequency distribution of cycle durations; (ii) in particular, equivalent estimates for T and S are obtained for both types of growing cell populations without losses, one with arbitrarily distributed cycle durations and one with the same cycle duration for all cells; and (iii) for small labeling indices, the estimate for S from the general model approaches the S-phase length of a stationary population and the estimate for T from the general model approaches the generation time of a stationary population, multiplied by the constant factor 1n(2). These relationships are valuable tools for reinterpreting results derived under the assumption of stationarity, which are considerably easier to obtain.

Animals↗
PubMed1988

Autoradiographic evaluation of vitamin A effects on Triturus alpestris blastema cells.

Autoradiographic studies on Triturus alpestris regenerates treated with vitamin A palmitate for 4, 7, 11 and 14 days after amputation, reveal a considerable diminution in the percentage of cells duplicating DNA, as judged by measurements of labelling indices. Based on previous observations, that vitamin A promotes DNA-synthesis, mitosis and growth of regenerates, we conclude that the lower labelling indices calculated are due to an acceleration of S-phase processes, resulting in a concomitant reduction in its duration.

Animals↗
PubMed1988

Influence of vitamin A palmitate on the growth of regenerating Triturus alpestris forelimbs.

The objective of this investigation was to analyse the effects of vitamin A palmitate orally administered to young postmetamorphic Triturus alpestris on the growth of regenerates. Vitamin A was administered for 4, 7, 11 and 14 days after amputation at the middle of the right zeugopod. Growth of regenerates was evaluated on the basis of external size measurements and blastema cell proliferation. Calculation of the percentages of cells in each cell-cycle phase and estimation of mitotic indices during the period of drug administration were performed by microdensitometric scanning of Feulgen-stained nuclei and counting of chromosome configurations, respectively. Vitamin A was found to induce polyploidism, to enhance transition from G1- to S-phase cell nuceli, to prolong the duration of G2-phase to the detriment of S-phase and to promote mitotic activity in the mesenchyme cells. In accordance with the above, an acceleration in the growth rates of treated blastemas with respect to controls was observed.

Animals↗
PubMed1988

Vitamin A induced bilateral asymmetries in triturus forelimb regenerates.

After amputation of both forelimb of young, postmetamorphic Triturus alpestris through the middle of the zeugopod, the left and right regenerates grew asynchronously. As a result of oral administration of vitamin A palmitate (250 IU/gbw/day), from the 4th to the 13th dpa, the growth rate of the right regenerates was relatively higher than that of the left ones. Moreover, the percentage of skeletal abnormalities as well as proximodistal duplications (proximalizations), induced by vitamin A, was nearly twice as high in the right regenerates as compared to their left counterparts.

Aging↗