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Biomedical subjects

A Kistler

Publications and source records attributed to A Kistler.

At least 37 records · Page 2Linked to original sources
PubMed1991

Altered differentiation of limb bud cells by transforming growth factors-beta isolated from bone matrix and from platelets.

A crude extract of demineralized bone matrix caused an altered differentiation of limb bud cells which was seen within 5 days in culture. Using this bioassay system we purified two factors to homogeneity and found that according to their N-terminal sequences they corresponded to TGF-beta 1 and TGF-beta 2 isolated from platelets. Biochemical analyses and biological studies (molecular mass determination, inactivation by reducing agents and proteases, antibody neutralization, competitive binding to TGF-beta receptors and influence on protein expression) provided additional evidence that the two proteins isolated from demineralized bone matrix were apparently identical to TGF-beta 1 and TGF-beta 2. Proteoglycan content, alkaline phosphatase activity and response of the cells to PTH stimulated adenylate cyclase were quantitatively changed by the factors. Culturing limb bud cells on polycarbonate membranes resulted in a rapid and extensive growth and differentiation of the cells to palpable tissue pieces. Relative to controls distinct cell and tissue morphology was observed macroscopically and in histological sections of these tissue pieces.

Alkaline Phosphatase↗
PubMed1990

Comparative teratogenicity of three retinoids: the arotinoids Ro 13-7410, Ro 13-6298 and Ro 15-1570.

Three retinoids of the arotinoid series, namely the free carboxylic acid Ro 13-7410, its ethyl ester Ro 13-6298, and the new arotinoid ethyl sulfone Ro 15-1570, were tested for their embryotoxic and teratogenic activity in rats. The retinoids were administered orally on either day 9 or 13 of gestation. Treatment on day 9 of gestation resulted mainly in malformations of the head and the trunk; whereas, on day 13 limb malformations were prominent. Ro 13-7410 and Ro 13-6298 were about 1000 times more embryotoxic and teratogenic than retinoic acid but induced a similar malformation pattern to retinoic acid. In contrast, the sulfur-containing arotinoid Ro 15-1570 was active at similar dose levels to retinoic acid but caused a peculiar malformation pattern on day 13 of gestation. This finding supports the hypothesis that the arotinoid ethyl sulfone Ro 15-1570 has unique biological properties, inducing no bone toxicity in adult rats and distinctly affecting limb development.

Abnormalities, Drug-Induced↗
PubMed1990

Teratogenicity of arotinoids (retinoids) in vivo and in vitro.

The effect of structural modifications on the arotinoid molecule, a new class of retinoids, on their teratogenicity in mice was studied. Animals were treated on days 8 and 9 of gestation, the most susceptible stages to retinoid-induced malformations in rodents. The teratogenic potency of the 13 arotinoids tested varied over a dose range of more than five orders of magnitude. Next, we tested whether the quantitative differences in the teratogenicity of these arotinoids correlates with their activity in high density (micromass) cultures of rat embryonic limb bud and midbrain cells. There was a good quantitative correlation between the in vivo teratogenicity and the in vitro activity in limb bud cells but no correlation was found in midbrain cells. Thus, the limb bud cell culture system may be useful for a preliminary testing to select non-teratogenic retinoids. For the risk assessment in humans, however, the in vitro results should be verified in animals studies.

Abnormalities, Drug-Induced↗
PubMed1990

Ontogenetic transition of wound healing pattern in rat skin occurring at the fetal stage.

Full-thickness excisional wounds were made in the dorsal skin of rat fetuses at day 16 and day 18 of gestation. A small patch of skin surrounding the open wound was cut out, mounted on a plastic ring and incubated in an organ culture system. In the presence of serum, the open wound in the day-16 fetal skin closed within three days of culture. During the wound-closure process, no new structures were formed in the wound space, and no conspicuous changes were noted in the histological architecture of the surrounding skin during culture, indicating that the wound closure may result from a centripetal movement of the surrounding skin only. In contrast, the size of the open wound in the day-18 fetal skin remained almost unchanged for one week, but a thin acellular network spread over the wound space within one day of culture. The predominant component of the network was cross-linked fibrin, as disclosed by scanning electron microscopy and sodium dodecylsulfate-polyacrylamide gel electrophoresis followed by immunoblotting. The network served as a scaffold for the ingrowth of fibroblast-like cells. These stage-dependent differences in fetal wound healing were consistent with an in vivo study showing that the day-16 wound was covered with the surrounding skin itself, whereas the day-18 wound was covered with newly formed epidermis and invaded by inflammatory cells. The present investigation strongly indicates the prenatal occurrence of a fetal-to-adult transition in the wound-healing pattern of rat skin.

Animals↗
PubMed1989

Effects of vitamin D derivatives on soft tissue calcification in neonatal and calcium mobilization in adult rats.

The activity of 18 vitamin D analogs on soft tissue calcification and growth impairment in neonatal rats and their effect on bone calcium mobilization, intestinal calcium absorption and binding to intestinal 1,25-dihydroxyvitamin D3 receptors in adult rats were compared. Depending on the chemical modification of the vitamin D parent compounds, they could be separated into active and inactive analogs. Cholecalciferol and ergocalciferol were similarly active, but epimerization of ergocalciferol at carbon 23 caused loss of activity. Hexafluorination at carbon 26 and 27 and the introduction of a double bond at carbon 22 or 23 had no or little effect on the activity. The loss of activity was caused by the introduction of a triple bond at carbon 23 and by hydroxylation at carbon 23, 26 or 28. The differentiation of human promyelocytic leukemia cells (HL-60) induced by these derivatives was used as a parameter for antitumour activity. All six analogs, which markedly affected calcium metabolism, were highly active in HL-60 cells. However, at least three derivatives were highly active in the antitumour test but failed to induce hypercalcemia. Thus, these results indicate that it could be possible to develop medically useful vitamin D derivatives devoid of hypercalcemic side-effects.

Animals↗
PubMed1989

Requirement of serum factors for wound closure of embryonic skin in vitro.

Forelimb buds of rat embryos at day 13 of gestation were cut and cultured in Dulbecco's modified Eagle medium. In the absence of serum, the epidermis did not cover the wound surface. In the presence of fetal calf serum or ultroser G, a serum substitute, epidermal wound closure appeared in a concentration-dependent manner within 1 day of culture. Cycloheximide, an inhibitor of protein synthesis, reversibly inhibited wound healing, demonstrating that protein synthesis was required for epidermal wound closure. Dialysis and fractionation of ultroser G indicated that high molecular weight factors (greater than 25,000 d) were required for epidermal wound closure.

Animals↗
PubMed1988

Wound healing in fetal limb organ culture.

The in vitro wound healing responses in whole-limb organ culture of fetal rats at day 19 of gestation were compared with the intrauterine wound repair. In vitro, after a skin incision was made in the lower forelimb, the subcutaneous tissue and the dermis regenerated. Reepithelialization appeared within two to five days. Thus, the wound healing was comparable to the intrauterine fetal wound repair. The whole limb organ culture may be a useful and suitable in vitro test system to study the mechanisms involved in fetal wound healing to search for compounds required in fetal skin regeneration and to test factors tht might influence it.

Animals↗
PubMed1987

Limb bud cell cultures for estimating the teratogenic potential of compounds. Validation of the test system with retinoids.

Mesenchyme cells, derived from embryonic limb buds, cultured at high cell density, multiply and differentiate into chondrocytes. Using alcian blue, a stain specific for cartilage proteoglycans, the degree of chondrogenesis can be visualized in the micromass cultures as well as quantified by extraction of the stain and spectrophotometric determination of its absorbance. In the presence of active retinoids chondrogenesis is concentration-dependently inhibited. For comparison of the activity of the various retinoids the concentration needed to reduce alcian blue staining by 50% was estimated. In order to validate whether the activity in limb bud cells can predict the teratogenic potential in vivo, the in vitro activity of 25 retinoids was compared with their in vivo teratogenicity observed mainly in rodents. For retinoids which were already in the biologically active form like those with a free carboxylic acid endgroup, there was a good quantitative correlation between the in vitro and in vivo activity. In contrast, the ethylester analog etretinate was slightly active and the ethylamine analog motretinide inactive in vitro but both were teratogenic in vivo. This finding may indicate that these retinoids were not metabolized to the active form in vitro. In conclusion, these results suggest that the limb bud cell culture system may be useful for a preliminary testing to select non-teratogenic retinoids. For the risk assessment in humans, however, the in vitro result should be verified in animal studies.

Animals↗
PubMed1986

Suppression by cyclohexanetriones of retinoic acid-induced cartilage degradation in vitro and teratogenicity in vivo.

In cultured fetal rat bones, cyclohexanetriones that stimulate prostaglandin synthesis inhibited retinoic acid-induced cartilage degradation in a dose-dependent manner. The inhibition by the cyclohexanetrione Ro 31-0521 was reversible, indicating that the effect was not due to cytotoxicity. Excess retinoic acid is teratogenic in rats and adversely affects the normal differentiation of various morphogenetic systems, depending on the time of administration. The following retinoic acid-induced malformations were suppressed by Ro 31-0521: malformations of long bones and of apical phalanges induced on days 13 and 15 of gestation, respectively; spina bifida and tail malformations induced on day 11 of gestation and cleft palate induced on day 15 of gestation. However, cleft palate and other head malformations including exencephaly induced by retinoic acid on day 11 of gestation were not suppressed but even increased by Ro 31-0521. At a high dose, Ro 31-0521 given alone on day 11 of gestation was embryolethal and teratogenic but was not on the tested other days, indicating that the cyclohexanetrione at specific stages and doses also interfered with normal morphogenesis like retinoic acid. Assuming that stimulation of prostaglandin synthesis is the main biological effect of the cyclohexanetriones, our findings suggest that prostaglandins may be involved in mediating retinoid action.

Abnormalities, Drug-Induced↗
PubMed1986

Structure-activity relationship of retinoids on lobuloalveolar differentiation of cultured mouse mammary glands.

The influence of 28 retinoids on the structural differentiation of mouse mammary glands in whole organ cultures was examined. Mammary glands from BALB/c mice pretreated with steroids (estradiol and progesterone) and cultured in the presence of lactogenic hormones (insulin, prolactin, hydrocortisone and aldosterone) differentiate into lobuloalveolar structures. These differentiation processes were inhibited by retinoic acid at 10(-6) M and by the arotinoid containing tetramethylated tetraline (Ro 13-7410) at 10(-10) M. The presence of this arotinoid for as little as 5 min, followed by incubation in control medium, irreversibly suppressed lobuloalveolar differentiation. After pre-incubation of mammary glands in control medium for 3 days, the arotinoids no longer suppressed the differentiation of lobuloalveolar structures. Structure-activity relationships of selected retinoids with marked differences in their biological activity were similar to those reported. The mouse mammary gland in whole organ culture may be a suitable and useful bioassay system for selecting retinoids which affect differentiation processes and may thus be helpful in the treatment of oncological diseases.

Aldosterone↗
PubMed1985

Teratogenesis and reproductive safety evaluation of the retinoid etretin (Ro 10-1670).

Reproduction and teratology studies were performed with etretin, the free acid analog of the retinoid etretinate. The lowest teratogenic dose of etretin in mice, rats and rabbits was 3, 15 and 0.6 mg/kg, respectively. In all three species, the lowest dose which was embryolethal, fetolethal or reduced the survivability of the pups during lactation was 2-3 times higher than the above doses. In rats, the lowest effective dose of etretin was 3 mg/kg in both the study for fertility and general reproductive performance and the peri- and postnatal study. The main adverse effect in these two experiments was a reduced survival of the F1-generation.

Abnormalities, Drug-Induced↗