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Biomedical subjects

T T Sun

Publications and source records attributed to T T Sun.

At least 163 records · Page 9Linked to original sources
PubMed1983

Epidermal stem cells.

Stem cells are by definition present in all self-renewing tissues and are believed to play a central role in cell growth and differentiation. Existing evidence suggests that a subpopulation of epidermal basal keratinocytes represents stem cells; however, these cells have never been positively identified. In this paper we review evidence that in monkey palm epidermis there exist two morphologically distinct subpopulations of basal keratinocytes that are spatially segregated. One population, located in the shallow rete ridges, is characterized by a cytoplasm filled with tonofilaments and a highly convoluted ("serrated") dermal-epidermal junction; these cells may play a role in anchoring the epidermis to the dermis. In contrast, the other population, located at the tips of deep rete ridges, is characterized by a "primitive" cytoplasm containing abundant melanosomes and a relatively flattened ("nonserrated") dermal-epidermal junction. Tritiated thymidine labeling experiments suggest that the nonserrated basal keratinocytes are slow-cycling; however, a highly proliferative population of keratinocytes can be identified immediately above these basal cells. These findings are consistent with the concept that the nonserrated basal keratinocytes may represent stem cells that give rise to suprabasally located, transient amplifying cells before undergoing terminal differentiation. Monkey palm epidermis provides a model system for further studies of primate epidermal stem cells.

Animals↗
PubMed1983

Keratin expression during normal epidermal differentiation.

The four major epidermal keratins (65-67K, 58K, 56K, and 50K) have been localized in various cell layers of normal human epidermis. Guinea pig antisera and mouse monoclonal antibodies were prepared against human epidermal keratins and were characterized with respect to their specificity to individual keratin polypeptides by the immunoblot technique. These antibodies were used to stain vertical frozen sections of skin, and to identify keratins extracted from serial, horizontal skin sections. The results indicate that: (1) a 65-67K keratin component is limited to the suprabasal layers, (2) a 58K keratin is present throughout the epidermis, (3) a 56K keratin appears to be made only in cells above the basal layer, possibly in the upper spinous or granular layer, and (4) a 50K keratin is present in all living layers but is largely eliminated during stratum corneum formation. The 65-67K and 56K keratins, which are characteristic of suprabasal, terminally differentiated keratinocytes, may be regarded as molecular markers of keratinization.

Antibodies, Monoclonal↗
PubMed1982

Correlation of specific keratins with different types of epithelial differentiation: monoclonal antibody studies.

We have prepared three monoclonal antibodies against human epidermal keratins. These antibodies were highly specific for keratins and, in combination, recognized all major epidermal keratins of several mammalian species. We have used these antibodies to study the tissue distribution of epidermis-related keratins. In various mammalian epithelia, the antibodies recognized seven classes of keratins defined by their immunological reactivity and size. The 40, 46 and 52 kilodalton (kd) keratin classes were present in almost all epithelia; the 50 kd and 58 kd keratin classes were detected in all stratified squamous epithelia, but not in any simple epithelia; and the 56 kd and 65-67 kd keratin classes were unique to keratinized epidermis. Thus the expression of specific keratin classes appeared to correlate with different types of epithelial differentiation (simple versus stratified; keratinized versus nonkeratinized).

Animals↗
PubMed1982

Immunolocalization of keratin polypeptides in human epidermis using monoclonal antibodies.

Three monoclonal antibodies (AE1, AE2, and AE3) were prepared against human epidermal keratins and used to study keratin expression during normal epidermal differentiation. Immunofluorescence staining data suggested that the antibodies were specific for keratin-type intermediate filaments. The reactivity of these antibodies to individual human epidermal keratin polypeptides (65-67, 58, 56, and 50 kdaltons) was determined by the immunoblot technique. AE1 reacted with 56 and 50 kdalton keratins, AE2 with 65-67 and 56-kdalton keratins, and AE3 with 65-67 and 58 kdalton keratins. Thus all major epidermal keratins were recognized by at least one of the monoclonal antibodies. Moreover, common antigenic determinants were present in subsets of epidermal keratins. To correlate the expression of specific keratins with different stages of in vivo epidermal differentiation, the antibodies were used for immunohistochemical staining of frozen skin sections. AE1 reacted with epidermal basal cells, AE2 with cells above the basal layer, and AE3 with the entire epidermis. The observation that AE1 and AE2 antibodies (which recognized a common 56 kdalton keratin) stained mutually exclusive parts of the epidermis suggested that certain keratin antigens must be masked in situ. This was shown to be the case by direct analysis of keratins extracted from serial, horizontal skin sections using the immunoblot technique. The results from these immunohistochemical and biochemical approaches suggested that: (a) the 65- to 67-kdalton keratins were present only in cells above the basal layer, (b) the 58-kdalton keratin was detected throughout the entire epidermis including the basal layer, (c) the 56-kdalton keratin was absent in the basal layer and first appeared probably in the upper spinous layer, and (d) the 50-kdalton keratin was the only other major keratin detected in the basal layer and was normally eliminated during s. corneum formation. The 56 and 65-67-kdalton keratins, which are characteristic of epidermal cells undergoing terminal differentiation, may be regarded as molecular markers for keratinization.

Antibodies, Monoclonal↗
PubMed1982

Production of L-[1-11C]valine by HPLC resolution.

Based on a recently developed analytical technique, preparative high-performance liquid chromatographic (HPLC) resolution of DL-[1-11C]valine has been achieved. A conventional reverse-phase HPLC column and a chiral mobile phase (aqueous solution of L-proline, cupric acetate, and sodium acetate) were used. The copper can be removed from the L-valine fraction by precipitation as the sulfide, and final purification by cation-exchange chromatography yields L-[1-11C]valine in a form that is acceptable for clinical positron tomographic studies. This purification method does not remove the L-proline introduced in the resolution process, but added L-proline did not affect the tissue distribution of L-[1-14C]valine in rats. We have produced up to 60 mCi of L-[1-11C]valine in an overall synthesis and resolution time of 50 min. This procedure should be adaptable to the rapid resolution of other C-11-labeled amino acid racemates.

Carbon Radioisotopes↗
PubMed1981

Enhancement of formation of the esophageal carcinogen benzylmethylnitrosamine from its precursors by Candida albicans.

Previous studies in Linxian, an area of China with a high incidence of esophageal carcinoma, showed that fungal infections are common in the esophageal epithelium of patients with either premalignant changes or early esophageal carcinoma. Fungi of the genus Candida were the most frequent invaders. In these areas nitrate and nitrite are often present in high concentrations in drinking water and staple grains. The present studies have established the ability of Candida albicans to augment the nitrosative formation of the esophagus-specific carcinogen, benzylmethylnitrosamine (NBMA; N-nitroso-N-methylbenzylamine). Stationary C. albicans cultures, with pH held at 6.8, were incubated with the precursors of NBMA, benzylmethylamine (BMA; N-methylbenzylamine) and NaNO(2). There was a significant increase in the amount of NBMA formed in these cultures, compared to precursors-only controls. The amount of NBMA synthesized depended on fungal cell number. Exponentially growing cultures were also able to cause NBMA formation. The identity of the NBMA was confirmed by high-performance liquid chromatographic coelution with authentic NBMA in three solvent systems and by mass spectroscopy. Boiled cells and conditioned medium in which cells had been incubated were not effective in enhancing nitrosation. Cultured Candida released acidic metabolites that reduced the pH of the medium when only a low concentration of buffer was present. Spontaneous nitrosation of BMA was enhanced under these acidic conditions. Thus, C. albicans infecting the esophageal epithelium could cause local formation of NBMA by both cell-mediated catalysis and extracellular decrease in pH.

Benzylamines↗
PubMed1981

Identification of mouse mammary epithelial cells by immunofluorescence with rabbit and guinea pig antikeratin antisera.

Few markers are available to identify the three types of mammary epithelial cells--ductal, alveolar, and myoepithelial--especially in pathological conditions and in cell cultures. We have used antisera to human keratins in immunofluorescence to facilitate the identification of the three mouse mammary epithelial cell types. In frozen tissue sections and primary cell cultures, a rabbit antikeratin antiserum specifically stained cytoplasmic filaments in all three types of epithelial cells. A guinea pig antiserum against the same keratin preparation, however, reacted preferentially with filaments in myoepithelial cells and readily detected this cell type in normal, dysplastic, and malignant mammary tissues and cell cultures. Neither antisera reacted with fibroblasts or any other mesenchymal cells. The combined use of the two antikeratin antisera thereby permits rapid surveys of tissue sections and cultures for the localization of not only all epithelial cells but also the subpopulation of myoepithelial cells. Moreover, when mammary cultures established from late-pregnant or lactating mice were stained simultaneously with guinea pig antikeratin and rabbit anticasein antisera, three populations of epithelial cells were mutually exclusive: those stained by anticasein antiserum, those stained by guinea pig antikeratin antiserum, and those stained by neither, consistent with properties of alveolar, myoepithelial, and ductal cells, respectively. These antisera thus offer a tool for studying different epithelial cell types during mammary development, tumorigenesis, and malignant progression.

Animals↗
PubMed1981

Expression of keratin and vimentin intermediate filaments in rabbit bladder epithelial cells at different stages of benzo[a]pyrene-induced neoplastic progression.

Rabbit bladder epithelium, grown on collagen gels and exposed to the chemical carcinogen benzo[a]pyrene, produced nontumorigenic altered foci as well as tumorigenic epithelial cell lines during 120-180 d in culture. Immunofluorescence studies revealed extensive keratin filaments in both primary epithelial cells and benzo[a]pyrene-induced altered epithelial foci but showed no detectable vimentin filaments. The absence of vimentin expression in these cells was confirmed by two-dimensional gel electrophoresis. In contrast, immunofluorescence staining of the cloned benzo[a]pyrene-transformed rabbit bladder epithelial cell line, RBC-1, revealed a reduction in filamentous keratin concomitant with the expression of vimentin filaments. The epithelial nature of this cell line was established by the observation that cells injected into nude mice formed well-differentiated adenocarcinomas. Frozen sections of such tumors showed strong staining with antikeratins antibodies, but no detectable staining with antivimentin antibodies. These results demonstrated a differential expression of intermediate filament type in cells at different stages of neoplastic progression and in cells maintained in different growth environments. It is apparent that the expression of intermediate filaments throughout neoplastic progression is best studied by use of an in vivo model system in parallel with culture studies.

Animals↗
PubMed1980

Human epithelial cells cultured from urine: growth properties and keratin staining.

Epithelial cells can be cultured from the urine of newborn infants, providing a simple, noninvasive biopsy method. We established such cultures by standard techniques from 44% of uncontaminated specimens obtained from newborn infants up to 1 week of age. There was an average of three colonies per milliliter of urine. Many cultures accomplished 15 to 25 population doublings in as many as five subcultures and yielded total potential culture sizes of 10(4) to 6 x 10(8) cells. Plating efficiency was high at each passage. The cultures displayed two morphologically distinct epithelial cell types. Immunofluorescent staining of keratin fibers in most of these cells further identified them as epithelial.

Blood↗
PubMed1980

The use of antikeratin antiserum as a diagnostic tool: thymoma versus lymphoma.

Indirect immunofluorescence staining in two thymomas, one case of thymic hyperplasia, 10 malignant lymphomas and three seminomas was done with an antibody prepared against keratins from human epidermis. Staining was observed only in the epithelial cells of the thymomas and thymic hyperplasia and correlated well with electron microscopic studies. Immunofluorescence staining of thymic tumors with antikeratin antibody provides a simple, specific, and sensitive method for distinguishing thymoma from lymphoma and seminoma. The method may also prove to be useful in other instances in the distinction between epithelial and nonepithelial tumors.

Adult↗
PubMed1980

Epithelialization of the corneal endothelium in posterior polymorphous dystrophy.

The unusual cell type present on the posterior corneal surface of posterior polymorphous dystrophy patients has been characterized. In addition to microvilli and desmosomes, these cells contain abundant 10 nm filaments which by immunofluorescent staining were shown to consist of keratin proteins, a marker for epithelial cells.

Cornea↗
PubMed1979

Keratin cytoskeletons in epithelial cells of internal organs.

An antiserum against human epidermal keratins was used to detect keratins in frozen sections of various rabbit and human tissues by indirect immunofluorescence. Strong staining was observed in all stratified squamous epithelia (epidermis, cornea, conjunctiva, tongue, esophagus, vagina, and anus), in epidermal appendages (hair follicle, sebaceous gland, ductal and myoepithelial cells of sweat glands), as well as in Hassall's corpuscles of the thymus, indicating that all contain abundant keratins. No staining by the antiserum was observed in fibroblasts, muscle of any type, cartilage, blood vessel, nerve tissue, iris or lens epithelium, or the glomerular or tubular cells of the kidney. In contrast, the antiserum stained the cells of most epithelia of the intestinal tract, urinary tract (urethra, bladder, ureter, collecting ducts of kidney), female genital tract (cervix, cervical glands, uterus, and oviduct), and respiratory tract (trachea and bronchi). Epithelial cells of the fine ductal system in the pancreas and submaxillary gland also stained well. When primary cultures of epithelial cells derived from bladder, intestine, kidney, and trachea were grown on glass coverslips and stained with anti-keratin, fiber networks similar to those of cultured keratinocytes were observed. These results show that keratins constitute a cytoskeleton in epithelial cells of diverse morphology and embryological origin. The stability of keratin filaments probably confers the structural strength necessary for cells covering a free surface. Keratin staining can be used to obtain information about the origin of cell lines.

Animals↗