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Biomedical subjects

C A Heckman

Publications and source records attributed to C A Heckman.

33 records · Page 2Linked to original sources
PubMed1984

Changes in cell-substratum adhesion and nuclear-cytoskeletal anchorage during cytodifferentiation of BeWo choriocarcinoma cells.

Changes in the substratum anchorage of cells and nuclei were examined during methotrexate (MTX)-induced cytodifferentiation of BeWo human choriocarcinoma cells. During this process cytotrophoblast-like cells (CTLs) transform into giant mono- and multinucleated syncytiotrophoblast-like cells (STLs). Cells treated with MTX for 24 h exhibited significantly faster rates of substratum detachment by EDTA, trypsin-EDTA, EDTA-glycine, and DMSO than did uninduced controls. The decrease in cell-substratum adhesiveness occurred prior to the onset of morphological transformation. By 48 h, when morphological transformation was first observed, there had occurred a marked change in nuclear-cytoskeletal anchorage to the substratum, as evidenced by a difference in sensitivity of Triton-extracted STL and CTL monolayers to detachment by KI. STL monolayers were completely detached within 5 min of exposure to 0.3 M KI, while CTL monolayers remained firmly attached to the substratum for at least 3 h. KI-extracted residues were examined by electron microscopy and found to consist of nuclear shells attached to intermediate filaments. When cytoskeletal residues and KI-extracted proteins of STL and CTL cells were compared by two-dimensional polyacrylamide gel electrophoresis (PAGE), qualitative and quantitative differences were seen in a number of minor components. Thus the sensitivity of STL nuclear-cytoskeletal monolayers to removal by KI, an effective actin depolymerizing agent, may involve changes in the organization, stability, or interactions of actin with other components of the cytoskeletal framework.

Cell Adhesion↗
PubMed1984

Behavioral anomalies of highly malignant respiratory tract epithelial cells.

In previous work, we undertook a comparison of cells from three highly malignant in vitro epithelial lines with cells from three lines showing little or no evidence of tumorigenicity, to see if consistent structural perturbations were present. Cells from highly malignant lines showed common anomalies in the organization of the lamellar cytoplasm. The objective of the present studies was to determine whether these anomalies were correlated with common adhesive or motile properties of the cells. The cells were cultured in a special chamber on the stage of an inverted microscope, and their movements were recorded by a time-lapse video process. Cells selected at the 24.0-hr interval after plating were subjected to a progressive analysis of movement by entering their sequential positions on the digitizing tablet of a Videoplan image analyzer. For each frame analyzed, representing a 15-min real-time interval, the distance traveled and the angle of travel relative to a fixed axis were measured, and the extent of contact between the subject cell and its neighbors was estimated. For the great majority of cells, the direction of translocative movement was random. The mean velocities were in the range of 17 to 60 mum/hr and tended to be greater for cells from the highly malignant lines. Although the frequency of cell-cell contact varied little among lines, the frequency of cells overlapping during contact was much greater for lines of high malignant potential than for lines of negligible tumorigenicity. Striking differences were observed in the behavior of cells plated on glass and plastic substrata. While cells from lines of negligible tumorigenicity adhered well to both substrates, cells from all of the three highly malignant lines became rounded or formed spheroidal masses when plated on glass surfaces. The results indicated that gradations of adhesive, although not necessarily motile, properties were correlated with gradations of tumorigenicity in these epithelial model systems.

Animals↗
PubMed1983

Organ and species specificity of epithelial growth.

Previous work in this laboratory demonstrated that rat respiratory airway epithelial cells grown from tissue explants undergo concurrent division and differentiation in culture. In the present studies, this model system has been used to optimize conditions for epithelial growth, with the goal of facilitating the culture of epithelium from other organs and species. Fibroblasts appeared to limit the expansion of epithelial outgrowths; their growth was controlled by using delipidated serum, rather than serum, in the culture media, with addition of adrenergic antagonists. In nonsupplemented media, rat tracheal fibroblasts doubled in number in about 3 d. The doubling time was slowed to more than 9 d by the serum substitution in conjunction with the alpha-antagonist phenoxybenzamine. Rat tracheal epithelial cultures maintained under identical conditions doubled in less than 4 d, so that a growth advantage of threefold was achieved. The combination of conditions also seemed to inhibit growth of fibroblasts from other species. However, even when the problem of fibroblast overgrowth was obviated, the respiratory airway epithelia of the mouse, hamster, and marmoset failed to show self-sustaining growth in culture. The rat epithelium continued to grow for over 6 wk. A number of other organs from the rat, notably esophagus, skin, and salivary gland, showed self-sustaining growth after removal of explants. Although epithelial outgrowths were formed by explants from certain organs of the hamster, only those from the kidney and thyroid continued to grow after removal of the tissue explants. Therefore, growth failure in cultured epithelia, quantitatively defined, is common and frequently unrelated to the problem of fibroblast overgrowth. The rat seems to be the species of choice for studies on the isolated epithelia from most organ sites.

Animals↗
PubMed1982

Pathogenesis of lesions induced in rat lung by chronic tobacco smoke inhalation.

Lesions were induced in the lungs of specific-pathogen-free F344 rats by chronic tobacco smoke exposure. Animals exposed to 7 cigarettes/day were killed after 1, 1.5, or 2 years of exposure. Parallel lifetime exposures induced pulmonary tumors in 9% of the animals. In serially killed animals, four types of lesions were found: 1) perivascular or peribronchiolar accumulation of lymphoreticular cells. 2) fibrotic and cellular enlargement of peribronchiolar septa, 3) type II cell hyperplasia with septal fibrosis, and 4) air-space enlargement (emphysema). However, emphysema occurred only in animals exposed to a higher (10 cigarettes) dose of tobacco smoke. Ultrastructural studies showed all of the focal lesions to be infiltrated by cells typical of the inflammatory response. The type II hyperplastic and peribronchiolar alveolar lesions involved larger portions of the parenchyma in fibrotic changes but differed in structure, location, and frequency. The incidence of the peribronchiolar alveolar lesions was temporally related to tumor incidence.

Animals↗
PubMed1980

Classification of cultured mammalian cells by shape analysis and pattern recognition.

We have developed a method for classifying cultured cells on the basis of shape characteristics. High-resolution optical information on three-dimensional shape was obtained by anodic oxide interferometry. Each interference order formed in a cell was considered as a closed figure; measurement of 37 mathematical descriptors was carried out for each figure. The individual cells were classified according to the values of their descriptors. We used standard principles of pattern recognition, such as hierarchical cluster analysis and nearest neighbor analysis, as a basis for ordering the cells into groups. Alternatively, linear discriminant functions could be used, but they provided only a slight improvement in correct classification of the cells. We anticipate that the method will be appropriate for classification of cultured cell lines and for determination of the magnitude and direction of cell shape changes implicated in various biological processes.

Cell Line↗
PubMed1980

Ultrastructural characteristics of carcinogen-induced nondysplastic changes in tracheal epithelium.

Nondysplastic hypotrophic and metaplastic epithelial alterations induced by dimethylbenz(a)anthracene in isogenic tracheal transplants were studied by light and electron microscopy 3--24 months after cessation of a 4-week carcinogen exposure. Hypotrophic epithelium observed at all time points was characterized by the presence of nonciliated cells that adopted either cuboidal or squamous shapes, forming simple or bistratified epithelia. Most of these cells, as well as some metaplastic cells, exhibited features of mucin-secreting cells. The metaplastic epithelia showed nonkeratinizing squamous metaplasia, closely related to transitional metaplasia, and keratinizing squamous metaplasia, which presented either an atrophic or an acanthotic epithelium. Although many of these epithelia showed morphologic features of normal stratified epithelia, several nonkeratinizing squamous metaplasias and acanthotic keratinizing squamous metaplasias exhibited some irregularities, probably representing very early atypical ultrastructural features (ie, perinuclear concentration of tonofilament bundles, the presence of dark and clear basal epithelial cells, interruptions and alterations of the basal lamina). These features were not observed in a group of early squamous metaplasias studied for comparative purposes 2 weeks after cessation of dimethylbenz(a)anthracene exposure, which were characterized by a combination of degenerative phenomena and increased cell proliferation.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

Ultrastructural characteristics of carcinogen-induced dysplastic changes in tracheal epithelium.

Squamous metaplasias with various degrees of atypia, carcinomas in situ, and microinvasive carcinomas produced in rat tracheal transplants by a 4-week exposure to demethylbenz(a)anthracene were studied 12-96 weeks after cessation of carcinogen exposure. In addition to the classical nuclear and cytoplasmic indicators of atypism, the squamous metaplasias with slight and moderate atypia were characterized by the presence of glycogen in the spinous layer, atypical composite keratohyalin granules in the granular layer, and in most cases an orthokeratinized horny layer. The squamous metaplasias with severe atypia showed an increased secretory activity and a decreased number of desmosomes. Carcinomas in situ were characterized by numerous intracellular and extracellular microcysts filled with secretory material identified by histochemical techniques as containing neutral glycoproteins and sialomucins. Microinvasive carcinoma showed similar characteristics, with an increase in polylobulated nuclei and appearance of multilaminar ergastoplasm. An outstanding feature in all these lesions was the presence of dark fusiform epithelial cells. They were observed in the middle layers in the squamous metaplasias with severe atypia and appeared in all layers of the carcinomas in situ.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

Regulation of ether lipids and their precursors in relation to glycolysis in cultured neoplastic cells.

Tumors typically show high rates of glycolysis and elevated levels of ether lipids, particularly the alkyldiacylglycerols; thus, we investigated the relationship between ether lipid accumulation and glucose metabolism in a neoplastic cell line (B2-1). The B2-1 cells grown in 5.5 mM galactose in the absence of glucose produced very low levels of alkyldiacylglycerols, triacylglycerols, lactic acid, and dihydroxyacetone-P. Increasing concentrations of glucose caused a progressive increase in lactic acid, dihydroxyacetone-P, and up to a ten-fold increase in alkyldiacylglycerols and triacylglycerols. Glucose supplements also caused an increased incorporation of [9,10-3H]palmitic acid into alkyldiacylglycerols and triacylglycerols. These metabolic changes appeared to be independent of altered growth rates of the cells. The addition of hexadecanol along with glucose to the cultures resulted in a shorter lag and a more rapid rate of accumulation of alkyldiacylglycerols; hexadecanol supplements alone had no effect. The extent of uptake and oxidation of hexadecanol was similar in both the glucose and galactose-grown cells. These results indicate that the levels of alkyldiacylglycerols in neoplastic cells can be regulated by the extent their precursors are formed from glucose.

Animals↗
PubMed1978

Respiratory tract epithelium in primary culture: concurrent growth and differentiation during establishment.

Studies of cellular function in the respiratory tract lining have traditionally been limited by the small tissue mass and functional diversity of the epithelium. Recent improvements in culture conditions have permitted long-term maintenance of epithelial cells derived from the upper respiratory tract of rats. The present study determined the extent to which proliferation and differentiation took place in such epithelial cell cultures. The labelling index obtained after 3H-dThd administration was approximately 100-fold higher than that of the quiescent epithelium in vivo; therefore, a large proportion of the cells were probably in the cycling population. Ultrastructural studies showed that features unique to the specialized mucous secretory cells and ciliated cells were lost rapidly with entry of these cells into the in vitro environment. With long-term maintenance, the cultures were reorganized into a stratified epithelium containing large, squamous, apical cells and small basal cells. The ultrastructural appearance of basal cells in vitro was nearly identical to that of basal cells in vivo. Squamous cells were frequently joined by tight junctions. Because hemicysts originated by detachment of squamous cells from the basal layers but not from adjacent squamous cells, they were considered to indicate stratification in the cultures. The proliferative and differentiative status of the mucociliary epithelium was altered by in vitro conditions, and came to resemble that of early squamous metaplasia in the respiratory tract epithelium.

Animals↗
PubMed1975

Association of tissue factor activity with the surface of cultured cells.

Tissue factor occurs in a dormant state on the surface of cultured normal human fibroblasts and WISH 1 amnion cells. The activity of undisturbed monolayers or cells lifted with brief trypsin treatment (0.125 per cent trypsin for 1 min) increases up to 60-fold upon prolonged digestion with dilute trypsin (0.0025 per cent trypsin for 30 min); activity appears subsequent to cell detachment. Up to 70 per cent of the total cellular tissue factor becomes active under these conditions and is released from the cells. The ruthenium red staining coat of the cells is lost during detachment, but cell viability (more than 90 per cent exclude trypan blue) and cell morphology do not change during the subsequent development of tissue factor activity. Furthermore, less than 10 percent of four intracellular enzymes and less than 20 per cent of two plasma membrane enzymes are released during this period of time. We therefore conclude that cells in culture do have tissue factor activity, that it exists in a latent form, and that total cell disruption is not necessary for this activity to initiate blood coagulation.

Amnion↗