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Biomedical subjects

C F Shuler

Publications and source records attributed to C F Shuler.

53 records · Page 3Linked to original sources
PubMed1989

Effect of periodontal dressings on human gingiva fibroblasts in vitro.

In vitro cytotoxicity studies of periodontal dressings have not generally produced a result consistent with in vivo observations. These prior in vitro studies have not used human intraoral cell lines. We tested the effects of two eugenol containing and two non-eugenol periodontal dressings on cultured human gingival fibroblasts (HGF) (ATCC #1292). Replicate HGF cultures grown in microtiter plates were exposed to stock, 1:4 and 1:16 dilutions of extracts made from each of the four periodontal dressings. The HGF cultures were pulse labelled with tritiated thymidine (3HTdR) after 24, 48, and 72 hours. Incorporations of the labelled thymidine were measured using liquid scintillation counting and expressed as counts per minute. The results showed that undiluted extracts from all four periodontal dressings totally inhibited 3HTdR uptake (P less than 0.05). The 1:4 dilution of eugenol dressings inhibited 3HTdR uptake significantly more than non-eugenol dressings (P less than 0.05). Interestingly, at 72 hours the 1:16 dilution of the non-eugenol dressings caused significantly increased 3HTdR uptake which was not observed with the eugenol dressings. The present results suggest that the use of a human fibroblastic cell line for testing the effects of periodontal dressings may provide information about the relative biological effects of these dressings. Using this cell line, we have found that eugenol dressings inhibit fibroblast proliferation to a greater extent than non-eugenol dressings.

Cell Line↗
PubMed1988

Transformation of normal homologous cells by a spontaneously activated Ha-ras oncogene.

Several tumor-derived oncogenes have been shown to independently act as complete carcinogens following transfection into target cells from established tissue culture lines. However, the number and types of oncogenes required to transform primary cultures of normal mammalian cells is unclear. To clarify this issue in a simplified model system, we transfected genomic DNA from a naturally occurring rat tumor into NIH/3T3 cells as well as into early passage rat embryo fibroblasts. The 3T3 cells were transformed with high efficiency to malignant phenotypes; the rat embryo cells were transformed at lower frequencies following cotransfection with a selectable neomycin resistance marker and treatment with Geneticin (G418). The transformed rat cells had cancerous phenotypes as determined by in vitro, cytogenetic, and in vivo criteria. Moreover, the transformed mouse and rat cells contained new tumor DNA-derived nucleotide sequences homologous to the activated human Ha-ras oncogene. Elevated levels of Ha-ras-specific mRNA, as well as enhanced expression of the Mr 21,000 oncogene product, were detected in the transformed cells. Therefore, under well-defined experimental conditions, a spontaneously activated Ha-ras oncogene from a naturally occurring tumor was able to independently transform normal, homologous cells to a malignant phenotype.

Animals↗
PubMed1987

Identification of intermediate filament keratin proteins in parakeratinized odontogenic keratocysts. A preliminary study.

The keratin proteins were extracted from the epithelial lining of three odontogenic keratocyst specimens. Two of the specimens were from a patient with nevoid basal cell carcinoma syndrome; the third was a solitary lesion. Seven keratin proteins with molecular weights of 46, 48, 50, 52, 54, 58, and 59 kilodaltons were identified by SDS-polyacrylamide gel electrophoresis and immunoblotting with antikeratin antiserum. The reproducibility of the pattern of molecular markers implies a series of genetic events coincident with the characteristic pattern of epithelial differentiation.

Adult↗
PubMed1987

Keratin protein identification in dimethylbenzanthracene-induced hamster cheek-pouch squamous cell carcinomas.

Individual keratin proteins were identified in 10 DMBA induced squamous cell carcinomas (SCC) of the hamster cheek pouch. SDS-polyacrylamide gel electrophoresis of water-insoluble cytoskeletal extracts from the tumor tissue demonstrated alterations in the protein distribution normal for the site. Immunoblot analysis with a broad spectrum polyclonal antikeratin antiserum identified the keratins in the preparations and confirmed changes in their distribution in the tumor preparations. The major keratin species for all the tumor tissues ranged in molecular weight from 45 to 57kd. The normal tissues had keratins with molecular weights from 45 to 73kd. The absence of high molecular weight keratins was a prominent feature in all the cancers. The histologic appearance of the tumors was varied but the distribution of the keratins was not correlated with the various histologies. The results demonstrate that changes in keratin gene expression occur in DMBA-induced cheek-pouch carcinomas but the precise alterations in the keratin proteins from those seen normally are not predictable.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1986

Studies of androgen metabolism and action in cultured hair and skin cells.

In order to study the mechanism of action of androgen on pubic and scalp hair, we established these and skin epithelial cells in culture. Because 5 alpha-reductase has been suspected of playing a role in hair growth, we tested the possibility that these cells differ in their pattern of androgen metabolism. Furthermore, we tested the hypothesis that androgen exerts its distinctive effects on these hairs by differentially regulating keratin or DNA synthesis. Anagen hairs of men and women were plucked from the pubis or scalp vertex and were studied using an epithelial cell culture technique. DHT formation from [3H]T cultured skin cells increased in the following order: epidermal less than scalp less than pubic less than fibroblasts = 0.8:2.8:8.1:71%/mg DNA/min, respectively. Androstanediols were minor [3H]DHT metabolites of all these skin cell types. The only feature that distinguished among the cultured epithelial cells was the ratio of apparent 5 alpha-reductase (5 alpha-R) to 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activity: this was significantly greater (P less than 0.05) in cultured pubic hair cells than in scalp hair or epidermal cells. Cultured scalp and pubic hair cells resembled freshly plucked hair follicle cells in their keratin pattern. 46, 50, 56 and 58 kdalton bands constituted 99% of the total keratins. This keratin pattern and the polygonal cell shape were also similar to that of cultured epidermal cells. However, this keratin pattern was distinctly different from that of hair shafts which have 53 and 63 kdalton keratins. Dihydrotestosterone did not affect the keratin pattern, pattern of incorporation of [35S]cysteine or [35S]methionine, or rates of protein synthesis or cell proliferation in cultured hair cells. Although the higher apparent 5 alpha-R/17 beta-HSD ratio of cultured pubic than of scalp hairs is compatible with modulation of hair development by androgen, these studies militate against the possibility that androgens directly affect hair cell proliferation or protein synthesis in pubic or scalp hair.

17-Hydroxysteroid Dehydrogenases↗
PubMed1986

Embryogenesis of stratified squamous epithelium. I. Tissue-specific expression of keratin proteins.

Although several types of modified stratified squamous epithelia are present in the adult mammal, most are presumably derived from similar embryonic progenitors. Mechanisms responsible for region-specific specialization are poorly understood. To correlate epithelial diversification with the expression of tissue-specific markers, we analyzed keratin protein composition in four representative types of rat squamous epithelia from early embryonic through adult phases of development. Keratin subsets synthesized in palatal mucosa were qualitatively similar, but differed dramatically in relative abundance. Tongue mucosa synthesized a different, but consistent subset of keratins which also changed quantitatively throughout morphogenesis. In contrast, different keratin genes were sequentially expressed during histogenesis of backskin and footpad epidermis. These data indicate that tissue-specific keratin biosynthesis is genetically predetermined early in embryogenesis.

Animals↗
PubMed1986

Embryogenesis of stratified squamous epithelium. II. Developmental stage-specific immunoreactivity of keratins.

Throughout embryogenesis of the rat palate, from the early fetal to adult stages, a consistent subset of keratin proteins is synthesized in the epithelial lining cells. Although the relative abundance of particular keratins has been shown to vary with ongoing palatogenesis, the expression of finite keratins appears to be genetically predetermined. In order to preliminarily ascertain whether conformational changes accompanied intermediate filament 'maturation' from monomeric to polymeric keratin formation, we screened cytokeratins with polyclonal and monoclonal antibodies generated against adult-type keratins. Until epithelial stratification occurred on the 16th day of gestation, the keratin proteins were weakly immunoreactive. On the other hand, subsequent to epithelial thickening, adult-type immunoreactivity was initiated and progressed concomitantly with ongoing palatal development. These findings suggest that the cytokeratin intermediate filaments may progress through conformational 'maturation' during polymerization, and play a role in the eventual acquisition of the adult-type epithelial structure and function.

Animals↗
PubMed1981

In vitro epithelial cell outgrowth from oral leukoplakia.

The appearance of an epithelial cell outgrowth in vitro from biopsies of oral leukoplakia is compared with the histologic appearance of the lesion. Tissue samples from oral leukoplakia of 20 patients were cultured to allow the outgrowth of populations of epithelial cells. Adjacent tissue within the lesions was fixed for routine histology. Epithelial cell outgrowth was successful from biopsies possessing the histologic characteristics hyperkeratosis (14 of 20 cases), altered epithelial thickness (14 of 19 cases) and increased mitotic activity (1 of 4 cases). No epithelial cell outgrowth was observed from leukoplakia tissue possessing signs of epithelial dysplasia (0 of 2 cases).

Cells, Cultured↗
PubMed1979

Sister chromatid exchange induction resulting from systemic, topical, and systemic-topical presentations of carcinogens.

Chinese hamster cheek pouch mucosal cells were examined for in vivo sister chromatid exchange formation resulting from the exposure of animals to carcinogens presented in three manners: systemic, topical, and systemic-topical combination. The systemic presentation of cyclophosphamide (5 or 10 mg/kg) through i.p. injection resulted in an increase in sister chromatid exchanges from 4.8 to 9.9 per cell. Topical application of 7,12-dimethylbenz(a)anthracene (0.5% in mineral oil, 0.1 ml) resulted in an increase in the sister chromatid exchange frequency to 11.5/cell, as compared with a value of 5.0/cell in animals treated only with mineral oil. Systemic administration of 8-methoxypsoralen (0.5, 1, 2.5, or 5 mg/kg) through i.p. injection, followed by activation with topical near-ultraviolet light (3.75 x 10(4) ergs/sq mm at 365 nm) resulted in an increase in sister chromatid exchange, reaching 15.4/cell at 5 mg 8-methoxypsoralen per kg. Exposure of animals to 8-methoxypsoralen or near-ultraviolet light alone, but not in combination, did not produce an increase in sister chromatid exchange. Sister chromatid exchange frequencies in cheek pouch cells were also compared with sister chromatid exchange frequencies in marrow cells of identically treated animals to assess the importance of exposure mode and tissue specificity in sister chromatid exchange formation.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1978

Bromodeoxyuridine tablet methodology for in vivo studies of DNA synthesis.

5-Bromodeoxyuridine (BrdU) tablets with different physical characteristics are useful in a wide variety of studies requiring detection of DNA replication in vivo. These tablets can effect a high substitution of BrdU in DNA, thereby permitting sister chromatid differentiation in chromosomes stained with 33258 Hoechst alone or in conjunction with Giemsa. Baseline and cyclophosphamide-induced in vivo sister chromatid exchange frequencies in mouse spleen, marrow, and thymus were measured and found to be significantly greater than those in spermatogonia. Sister chromatid exchange analysis was also extended to mouse liver and to Chinese hamster and Armenian hamster marrow cells. Sister chromatid differentiation was observed in Armenian hamster meiotic tissue, and evidence for interhomolog chromatid exchange obtained.

Animals↗
PubMed1977

A simplified technique for in vivo analysis of sister-chromatid exchanges using 5-bromodeoxyuridine tablets.

A small tablet of 5-bromodeoxyuridine (BrdU), implanted subcutaneously in a mouse, provides sustained release of base analog sufficient to effect substitution of DNA throughout an entire replication period. As illustrated by studies of mouse bone-marrow and spleen cells in the presence or absence of cyclophosphamide, this depot method of BrdU administration greatly simplifies in vivo analysis of sister-chromatid-exchange formation.

Animals↗
PubMedDate not supplied

Conversion of premalignant human cells to tumorigenic cells by methylmethane sulfonate and methylnitronitrosoguanidine.

Nine human tumor cell lines derived from both epithelial and mesenchymal tumors exhibited either an anchorage-independent growth non-tumorigenic phenotype or an anchorage-independent tumorigenic phenotype. Transformed epithelial cell lines with the non-tumorigenic phenotype could be converted to a progressively growing tumor phenotype following treatment with either methylmethane sulfonate (MMS) or N-methyl-N'-nitro-N-nitro-soguanidine (MNNG). In contrast, sarcoma derived cell lines with a non-tumorigenic phenotype could be converted to a progressively growing tumor phenotype only with MNNG. SV40 immortalized HET-1A non-tumorigenic phenotype cells could be converted to a progressively growing tumorigenic phenotype, infrequently, when treated with MNNG, but not MMS. Progressively growing tumors produced by either MMS or MNNG treated non-tumorigenic phenotypes exhibited metastatic potential in nude mice. Chemically treated HET-1A cells acquired the ability to produce tumor in mice but the tumor did not exhibit metastatic potential. In contrast, populations of tumorigenic cells were not rendered more biologically aggressive after treatment with either MMS or MNNG; i.e., the latency period for tumor development was not accelerated and the tumors did not exhibit metastatic potential. These results suggest that the biological effects of MMS and MNNG on non-tumorigenic, tumorigenic and immortalized cell lines are phenotype specific.

Animals↗