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H J Anton

Publications and source records attributed to H J Anton.

11 recordsLinked to original sources
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

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↗
PubMed1979

[The statement of nuclear volume, DNA content and nuclear form in tissue sections (author's transl)].

15 days after amputation of the forelimb of young postmethamorphic Triturus vulgaris DNA-content and volume of the nuclei of the mesodermal blastema cells have been investigated in longitudinal sections of 2 microns in thickness by Feulgen-photometric and electronic determination of area. Discrimination of the DNA-synthesis phase was carried out using microautoradiography after "in vivo" labeling with tritiated thymidine. Volume and DNA-content of the nuclear sections have been found to be positive correlated. The DNA-synthesising part of the population shows characteristic differences to the mean value of volume and DNA-content of the remaining population. The factor circumference 2/area is suitable to characterize the differentiation degree of cells.

Animals↗
PubMed1979

[Cell activation and nuclear volume (author's transl)].

Freezing dried semithin sections (1 micron) coloured with nuclear fast red are suited for determination of volume and activation state of cells and nuclei by means of electronic image analysis. Additional investigations of the proteinsynthesis with help of autoradiographs after incorporation of tritiated amino acids affirm the informations. Magnification of the nucleus together with a simultaneous increase of the proteinsynthesis per unit volume characterize the Stratum basale near the amputation level as the most active area of the regeneration epidermis. The cell volume is correlated with the alterations of the nuclear volume. Determination of the mean relative volume of nuclei with aid of measurements of nuclei sections suffices to get informations about cell activity.

Animals↗
PubMed1977

[Methods to prepare histological microautoradiographs for evaluation by automatic image analysis (author's transl)].

A prerequisite for automatic image analysis of histoautoradiographs is the arrangement of the silver grains within the same plane of focus. This can be obtained by semi thin sections of 1 micrometer in thickness. A sufficient contrast for the determination of the nuclear areas and the overlying silver grains at the same time can be reached by staining the preparations with Kernechtrot or Feulgen nucleal reaction. If a higher image contrast is desired sections measuring 2 micrometer or more in thickness may be subjected to the autoradiographic procedure without removing the resin.

Animals↗
PubMedDate not supplied

[Vitamin A--a probe in the study of growth, differentiation and morphogenesis].

Scientific work on vitamin A research has started more than one hundred years ago. The information accumulated thus far has already been published in thousands of original papers, review articles, monographic series and books. The overall result of these investigations can be concentrated in the title of the present review. Vitamin A and its analogues, the retinoids, participate directly in several physiological functions, such as vision, growth, development and differentiation. These compounds have also found useful application in the cure of several serious dermatological diseases and in cancer therapy. Their activities are also widely exploited to study embryogenesis, teratogenesis and carcinogenesis. Recent advances ascribe to retinoic acid properties, which render it a putative candidate for the first vertebrate morphogen. These developments, in combination with progress made in the study of homeo box genes, open new ways towards elucidating the mode of action of retinoids at the molecular level. It is tempting to speculate that, understanding enough about the basic biology of retinoid action, might be beneficially exploited for the betterment of the mankind.

Animals↗