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T T Sun

Publications and source records attributed to T T Sun.

At least 109 records · Page 6Linked to original sources
PubMed1991

Relative proliferative rates of limbal and corneal epithelia. Implications of corneal epithelial migration, circadian rhythm, and suprabasally located DNA-synthesizing keratinocytes.

An important element of the recently proposed limbal stem cell model is that corneal epithelial cells migrate centripetally. The driving force for this migration is unknown, although it has been suggested that limbal epithelium, proliferates at a higher rate than central corneal epithelium, thus creating a population pressure toward the central cornea. This hypothesis was tested by measuring the relative proliferative rates of limbal and central corneal epithelia using 3H-thymidine autoradiographic techniques. The results indicate that, in both the New Zealand white rabbit and SENCAR mouse, the labeling index (LI) of limbal epithelium is actually lower than that of central corneal epithelium. This difference in LI persists throughout the circadian rhythm cycle. These results suggest that population pressure per se cannot be responsible for the centripetal migration of corneal epithelium and raise the possibility that preferential desquamation of central corneal epithelium may "draw" peripheral cells toward the central cornea. In both epithelia, the LI peak precedes the mitotic index (MI) peak during circadian cycle by 4-6 hr. These data therefore are in close agreement with earlier results on several nonocular stratified epithelia but contradict an earlier suggestion that the LI and MI peaks of corneal epithelium coincide. Finally, although most of the 3H-thymidine incorporating cells in central cornea may appear to be suprabasally located, they are only partially displaced into the suprabasal compartment. In most cases, such cells are still connected with the basement membrane through a thin stalk of cytoplasm. Since corneal epithelium rests on an exceptionally flat and rigid substratum, an increase in cellular volume in DNA-synthesizing cells may not be tolerated well in an already crowded basal layer. This may explain why an unusually large proportion of DNA-synthesizing cells are expelled preferentially into either a "second tier basal layer" or into the suprabasal compartment.

Animals↗
PubMed1990

Appearance of the keratin pair K3/K12 during embryonic and adult corneal epithelial differentiation in the chick and in the rabbit.

Sequential expression of the K3/K12 keratin pair was studied during epithelial corneal differentiation, using monoclonal antibodies coupled with electrophoretic analysis. In the chick embryo, K12 appears on day 12, while K3 is present at least from day 11. By contrast, in the rabbit embryo, the expression of K12 (at 17 days) precedes that of K3 (at 21 days). In the adult rabbit, K3 is expressed without K12 in part of the limbus. Thus, within the corneal-type keratin pair, either the acidic or the basic partner appears first, according to the developmental stage or the species.

Animals↗
PubMed1990

Large scale purification and immunolocalization of bovine uroplakins I, II, and III. Molecular markers of urothelial differentiation.

The differentiation of mammalian urothelium culminates in the formation of asymmetrical unit membrane (AUM). Using gradient centrifugation and detergent wash, we purified milligram quantities of AUMs which, interestingly, contained three major proteins (15, 27, and 47 kDa) that appeared to be identical to the three immunoaffinity purified, putatively AUM-associated proteins that we described earlier (Yu, J., Manabe, M., Wu, X.-R., Xu, C., Surya, B., and Sun, T.-T. (1990) J. Cell Biol., 111, 1207-1216). Peptide mapping and immunoblotting established that these three proteins were distinct molecules. Using monospecific antibodies to these three proteins, we showed that they were all restricted to the superficial urothelial cells and were AUM-associated. The 27- and 15-kDa proteins were detected exclusively on the luminal side of mature, apical AUMs. In contrast, epitopes of the 47-kDa protein were detected on both sides of apical AUMs suggesting a transmembranous configuration. These results (i) provide the strongest evidence thus far that AUM contains three major proteins (the 27-kDa uroplakin I, 15-kDa uroplakin II, and 47-kDa uroplakin III) which form an extremely insoluble complex, (ii) suggest that uroplakin II, like uroplakin I (Yu, J., Manabe, M., Wu, X.-R., Xu, C., Surya, B., and Sun, T.-T. (1990) J. Cell. Biol. 111, 1207-1216), translocates from one side of the membrane to another during AUM maturation, (iii) indicate that uroplakin III may play a different structural role than uroplakins I and II in AUM formation, and (iv) establish the three uroplakins as markers for an advanced stage of urothelial differentiation.

Animals↗
PubMed1990

Radioimmunotherapy of human colorectal carcinoma xenografts using 90Y-labeled monoclonal antibody CO17-1A prepared by two bifunctional chelate techniques.

Monoclonal antibody CO17-1A, which has specificity for colorectal and pancreatic carcinomas, was radiolabeled with the pure beta emitter, 90Y, by either the cyclic diethylenetriaminepentaacetic acid (DTPA) anhydride technique or by a site-specific bifunctional chelate technique using 1-(p-aminobenzyl)DTPA (p-NH2-Bz-DTPA). Female nude mice bearing SW 948 human colorectal carcinoma xenografts were given injections i.v. of 90Y-labeled monoclonal antibody CO17-1A at dosages of 100, 150, and 200 muCi/25 g body weight. Unlabeled CO17-1A (100 micrograms/25 g body weight) was coadministered. In animals receiving 90Y-CO17-1A prepared by the cyclic DTPA anhydride technique, tumor volume was unchanged from base line at a dose of 200 microCi/25 g. As the dosage of 90Y-CO17-1A increased, the rate of tumor growth decreased, but all experimental animals in this group died between 14 and 21 days. In contrast, CO17-1A radiolabeled with 90Y by the site-specific p-NH2-Bz-DTPA bifunctional chelate technique produced a maximum tumor volume reduction of 87% in the 200 microCi/25 g group by day 15, and no deaths were noted in any of the 90Y-CO17-1A-treated groups for 71 days. Dose-response curves again showed increased tumoricidal effects with increased dosages of 90Y-CO17-1A. S-2-(3-Aminopropylamino)ethylphosphorothioic acid, commonly known as WR-2721, is a radioprotective drug which has been shown to protect against bone marrow depression in irradiated humans. No protection was observed when WR-2721 was used as an adjunct to treatment with 90Y-CO17-1A prepared by either the cyclic DTPA anhydride technique or the site-specific p-NH2-Bz-DTPA technique. When the site-specific p-NH2-Bz-DTPA technique was used, the reduction in WBC and hemoglobin levels correlated with increasing bone marrow toxicity at higher doses. We conclude that CO17-1A labeled with 90Y via the site-specific p-NH2-Bz-DTPA technique has potential for radioimmunotherapy of human colorectal carcinoma.

Amifostine↗
PubMed1990

Label-retaining cells reside in the bulge area of pilosebaceous unit: implications for follicular stem cells, hair cycle, and skin carcinogenesis.

Inconsistent with the view that hair follicle stem cells reside in the matrix area of the hair bulb, we found that label-retaining cells exist exclusively in the bulge area of the mouse hair follicle. The bulge consists of a subpopulation of outer root sheath cells located in the midportion of the follicle at the arrector pili muscle attachment site. Keratinocytes in the bulge area are relatively undifferentiated ultrastructurally. They are normally slow cycling, but can be stimulated to proliferate transiently by TPA. Located in a well-protected and nourished environment, these cells mark the lower end of the "permanent" portion of the follicle. Our findings, plus a reevaluation of the literature, suggest that follicular stem cells reside in the bulge region, instead of the lower bulb. This new view provides insights into hair cycle control and the possible involvement of hair follicle stem cells in skin carcinogenesis.

Animals↗
PubMed1990

Microcystic adnexal carcinoma. An immunohistochemical comparison with other cutaneous appendage tumors.

Since its initial description, microcystic adnexal carcinoma (MAC) of the skin has been controversial. In particular, it features keratin production of the type seen in some pilar neoplasms , and has been thought to pursue partial follicular differentiation. Diagnostically, MAC may be difficult to separate from desmoplastic trichoepithelioma (DTE) in superficial biopsy specimens. We studied 12 MACs, 22 malignant eccrine acrospiromas, 7 sudoriferous syringometaplasias, 6 syringomas, 5 DTEs, and 40 other benign pilar neoplasms immunohistochemically. Paraffin sections and antibodies to "hard" (pilar) keratins. epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), Leu-M1, and S100 protein were employed. The MACs exhibited reactivity for hard keratin subclasses AE 13 and AE 14, EMA, CEA, and Leu-M1. Desmoplastic trichoepitheliomas expressed positivity for AE 14, EMA, and Leu-M1 focally, but lacked the other specified markers. Syringomas and malignant acrospiromas displayed EMA, CEA, and AE 14 reactivity, and 5 syringometaplastic lesions were AE 14-reactive. Benign pilar tumors aside from DTEs were reactive only for AE 13, AE 14, or both. These data indicate that MAC exhibits an immunophenotype that is a "hybrid" of those seen in pure sweat glandular and follicular neoplasms, and suggest that it may indeed show combined pilar and sudoriferous differentiation. Based on these results, it also appears that immunohistochemical analysis may be useful in the diagnostic separation of MAC and DTE.

Adenoma, Sweat Gland↗
PubMed1990

Comparison of limbal and conjunctival autograft transplantation in corneal surface reconstruction in rabbits.

Destruction of corneal surface was created in one eye of 24 rabbits by n-heptanol corneal epithelial debridement and surgical removal of limbal zone. One month later, the animals were equally subdivided into three groups of eight for limbal transplantation, conjunctival transplantation, and control without transplantation. During a 6-month postoperative follow-up, all corneas in the control group showed progressive vascularization and conjunctivalization. All corneas with limbal transplantation showed progressive decrease of vascularity, verified by fluorescein angiography. In contrast, all but one of the eight corneas of conjunctival transplantation showed progressive vascularization (P = 0.01). More important, the resultant epithelia showed corneal phenotype in limbal transplantation, but remained conjunctival in conjunctival transplantation, as verified by monoclonal antibodies AM-3, APSM-1, and AE-5. These results support the concept of the limbal location of corneal epithelial stem cells, and indicate that complete destruction of the limbal zone resulted in corneal vascularization and conjunctivalization, and that limbal transplantation has a better efficiency than conjunctival transplantation in restoring such destroyed corneal surface.

Animals↗
PubMed1990

Uroplakin I: a 27-kD protein associated with the asymmetric unit membrane of mammalian urothelium.

The luminal surface of mammalian urothelium is covered with numerous plaques (also known as the asymmetric unit membrane or AUM) composed of semi-crystalline, hexagonal arrays of 12-nm protein particles. Despite the presumed importance of these plaques in stabilizing the urothelial surface during bladder distention, relatively little is known about their protein composition. Using a mouse mAb, AE31, we have identified a 27-kD protein that is urothelium-specific and is differentially expressed in superficial umbrella cells. This protein (pI approximately 5.8) partitions into the detergent phase during Triton X-114 phase separation. Pulse-chase experiments using cultured bovine urothelial cells showed that this protein is synthesized as a 32-kD precursor that is processed through a 30-kD intermediate, to the mature 27-kD form. In cytoplasmic vesicles containing immature AUM, the AE31 epitope is detected in patches on the cytoplasmic side, but in mature, apical AUM it is detected exclusively on the luminal side. This suggests an unusual translocation of the AE31 epitope during AUM maturation; more data are required, however, to substantiate this interpretation. Immunoaffinity purification of the 27-kD protein results in the copurification in approximately molar ratio of a 15-kD protein, as well as a small and variable amount of a 47-kD protein. Immunoblotting data indicate that these three proteins are immunologically distinguishable. This copurified 15-kD protein is relative basic (pI approximately 8.0). Like the 27-kD protein, it is urothelium-specific and is present mainly in the umbrella cells. Together, our data indicate that a 27-kD protein is urothelial plaque-associated (uroplakin I). Based on complex formation data, we provisionally name the 15-kD protein uroplakin II; additional data will be required to determine whether this and the 47-kD protein are integral parts of AUM. The identification of these AUM-associated and -related proteins, plus the availability of a culture system capable of synthesizing and processing some of these molecules, offer new opportunities for studying the detailed structure, assembly, and function of asymmetrical unit membrane.

Animals↗
PubMed1990

Assessing the differentiation state of cultured bovine urothelial cells: elevated synthesis of stratification-related K5 and K6 keratins and persistent expression of uroplakin I.

Although significant progress has recently been made in culturing mammalian urothelial cells, relatively little is known about their biochemical differentiation. In this paper, we assessed the differentiation state of cultured bovine urothelial cells by analyzing their keratins and a cell surface marker, uroplakin I. Urothelial cells were serially cultured either in a serum-free medium, or in a serum-containing medium in the presence of 3T3 feeder cells, with similar results. Despite their stratified appearance, both normal urothelium and cultured urothelial cells synthesize mainly K8, K18 and K19, keratins that are typically seen in simple epithelia. However, cultured urothelial cells synthesize a greatly increased amount of K5 and K6 keratins, which are usually expressed by stratified epithelia but present only in trace amounts in normal urothelium. These data indicate that, as far as keratin synthesis is concerned, cultured urothelial cells undergo an altered pattern of differentiation towards a more 'stratified phenotype'; this unusual finding has interesting implications for urothelial evolution. In the meantime, many superficial cells in cultured urothelial colonies make uroplakin I, a 27 x 10(3) Mr protein subunit of the asymmetrical unit membrane (AUM) characteristic of urothelial (superficial) umbrella cells. These results indicate that cultured urothelial cells undergo, at least in part, AUM biogenesis. Cultured urothelial cells thus provide a useful experimental model system for studying certain early steps of AUM formation.

Animals↗
PubMed1990

Ultrasonographic diagnosis of fetal cystic hygroma.

Prenatal diagnosis of seven cases of fetal cystic hygroma was characterized by multiloculated cystic mass with septated appearance in relation to the fetal head and neck, as well as various degree of lymphedema and peritoneal effusion and no direct communication with the central nervous system. Karyotype studies were performed in four cases and a composite of karyotypes from literatures is presented. The sonographic appearances and cytogenetic analyses will provide the significant framework needed for accurate prenatal diagnosis and genetic counseling.

Adult↗
PubMed1989

Existence of slow-cycling limbal epithelial basal cells that can be preferentially stimulated to proliferate: implications on epithelial stem cells.

Despite the obvious importance of epithelial stem cells in tissue homeostasis and tumorigenesis, little is known about their specific location or biological characteristics. Using 3H-thymidine labeling, we have identified a subpopulation of corneal epithelial basal cells, located in the peripheral cornea in a region called limbus, that are normally slow cycling, but can be stimulated to proliferate in response to wounding and to a tumor promotor, TPA. No such cells can be detected in the central corneal epithelium, suggesting that corneal epithelial stem cells are located in the limbus. A comparison of various types of epithelial stem cells revealed a common set of features, including their preferred location, pigment protection, and growth properties, which presumably play a crucial role in epithelial stem cell function.

Animals↗
PubMed1989

Expression of keratin 5 as a distinctive feature of epithelial and biphasic mesotheliomas. An immunohistochemical study using monoclonal antibody AE14.

In previous biochemical analyses, keratin 5 (Mr 58,000) has been detected in most mesotheliomas with epithelial component but not in pulmonary adenocarcinomas (Blobel et al., Am J Pathol 121: 235-247, 1985). In the present study, we have characterized a monoclonal antibody, AE14, as being selectively specific for keratin 5 (apart from the reactivity with certain hair proteins) as shown by immunoblotting of gel-electrophoretically separated proteins from various tissues. Immunohistochemical screening of a variety of normal human tissues, using immunoperoxidase microscopy on cryostat sections, revealed the binding of this antibody to the basal, immature cells of stratified squamous epithelia, to basal cells of pseudostratified epithelia, to some myoepithelial cells, thymic reticulum cells, certain pancreatic duct cells, as well as a variable subpopulation of mesothelial cells of the pleura and the peritoneum. In 12/13 epithelial and biphasic mesotheliomas of the pleura, heterogeneous but extended staining with antibody AE14 was seen whereas 21 pulmonary adenocarcinomas were negative or, in six of these cases, showed staining of only a few cells. Among carcinomas from other sites, colonic adenocarcinomas and renal cell carcinomas were negative whereas limited staining was found in some pancreatic adenocarcinomas. It is suggested that antibody AE14 may be useful, as a defined polypeptide-specific reagent, in the histologic distinction between mesotheliomas and most adenocarcinomas. Furthermore, the expression patterns of keratin 5 as detected by antibody AE14 in various normal and malignant epithelial tissues are discussed, particularly their relation to processes of squamous metaplasia and their indication of phenotypic tumor heterogeneity.

Adenocarcinoma↗
PubMed1989

Expression of hair-related keratins in a soft epithelium: subpopulations of human and mouse dorsal tongue keratinocytes express keratin markers for hair-, skin- and esophageal-types of differentiation.

The dorsal surfaces of mammalian tongues are covered with numerous projections known as filiform papillae whose morphology varies in different species. Using a panel of monoclonal antibodies to keratins as probes, we have established that, in both human and mouse, the interpapillary epithelia express mainly the "esophageal-type" keratins, while the papillary epithelia express "skin-type" keratins as well as some keratins reacting with a monoclonal antibody (AE13) to hair keratins. The AE13-reactive proteins of the mouse were found to be very similar to those of authentic mouse hair keratins. However, the corresponding protein of human tongue appears to be different from all known human keratins. This protein has a MW of 51K; it is relatively acidic; it is sulfhydryl-rich, as revealed by iodoacetic acid-induced charge and apparent size shift; it shares an epitope with all the known acidic human hair keratins; and it is associated with keratin fibrils in vivo. This protein may therefore be regarded as a novel type I "hard" keratin. These data establish that mammalian dorsal tongue epithelia can be divided into at least three compartments that undergo mainly "esophageal-", "skin-" and "hair"-types of differentiation. Different keratin filaments, e.g., those of the esophageal- and hair-types, exhibit strikingly different degrees of lateral aggregation, which can potentially account for the different physical strength and rigidity of various cellular compartments. Our data also suggest the possibility that variations in papillary structure in human and mouse may arise from different spatial arrangements of specific keratinocytes, and/or from the expression of specialized hair-related keratins.

Animals↗
PubMed1989

Association of a basic 25K protein with membrane coating granules of human epidermis.

Keratinocytes of the upper granular layers contain unique round-to-oval granules, 100-500 nm in diameter, in their peripheral cytoplasm. These granules (known as membrane coating granules [MCG], or lamellar granules) fuse with the apical cell surface of uppermost granular cells and discharge their contents into the intercellular space, where they are believed to play a role in establishing the permeability barrier of the epidermis and possibly in regulating the orderly desquamation of terminally differentiated keratinocytes. Using two monoclonal antibodies originally prepared against hair follicle antigens, we have identified a 25K epidermal protein in association with both MCG-like granules in the peripheral cytoplasm of granular cells as well as MCG-derived intercellular material. This protein is relatively basic (pI greater than 8), largely aqueous soluble, methionine deficient, and is relatively abundant in epidermis (comprising up to approximately 0.1% of soluble proteins). Its distribution is restricted to the granular layer of keratinized (cornified) stratified squamous epithelia. The identification of this protein component opens new avenues for studying the molecular mechanisms underlying the establishment of permeability barrier and/or regulation of desquamation.

Animals↗
PubMed1989

Basement membrane heterogeneity and variation in corneal epithelial differentiation.

We have previously shown that the expression of a major 64-Kda keratin (K3) in corneal epithelium is site-related. It is found suprabasally in limbal epithelium, but uniformly (basal cells included) in central corneal epithelium. In the present study, we used a panel of antibodies against various components of corneal epithelial basement membrane to investigate a possible correlation between basement membrane heterogeneity and differential (basal vs. suprabasal) K3 keratin expression. One of these antibodies, AE27, stains human conjunctival basement membrane weakly, limbal basement membrane heterogeneously, and central corneal basement membrane strongly. Basal cells resting on basement membrane that stains strongly with AE27 tend to stain with monoclonal antibody AE5, which recognizes keratin K3. Basal cells on basement membrane staining weakly with AE27 tend not to stain with AE5. No such correlation exists between AE5 staining and type IV collagen, which is detectable immunohistochemically in conjunctival and limbal basement membrane, but not in corneal basement membrane overlying Bowman's layer. These results suggest that basement membrane of human corneal/conjunctival epithelium can be divided into at least three domains: the conjunctival basement membrane (type IV collagen-positive, AE27-weak), the limbal basement membrane (type IV collagen-positive, AE27-strong), and corneal basement membrane (type IV collagen-negative, AE27-strong). The results also raise the possibility that basement membrane heterogeneity may play a functional role in regulating keratin expression and other aspects of differentiation of corneal epithelium; more experiments are needed to test this hypothesis.

Animals↗
PubMed1989

Transient synthesis of K6 and K16 keratins in regenerating rabbit corneal epithelium: keratin markers for an alternative pathway of keratinocyte differentiation.

Cultured rabbit corneal epithelial cells undergo three distinct stages of growth and differentiation characterized by the sequential appearance of K5/K14 keratin markers for basal keratinocytes, K6/K16 keratin markers for "hyperproliferative" keratinocytes, and K3/K12 keratin markers for corneal-type differentiation. Analyses of [35S]methionine-labeled, newly synthesized keratins revealed that K6/K16 are synthesized only briefly when the cells undergo exponential growth, and their synthesis is suppressed when the cells reach confluence and switch to synthesizing K3/K12. Transient synthesis of K6/K16 was also observed in vivo during corneal epithelial regeneration. Although K6/K16 expression in general correlates well with cellular growth, drug-induced inhibition of corneal epithelial growth and related data on human epidermal keratinocytes indicate that these two events are dissociable. These results establish clearly for the first time a reciprocal relationship, on a protein level, between the synthesis of K6/K16 and a differentiation-related keratin pair, K3/K12. Such a relationship strongly suggests a competitive mechanism controlling the synthesis of these two major classes of keratins in the suprabasal compartment. Our results also indicate that although hyperproliferation is usually accompanied by K6/K16 expression, the reverse is not always true. Taken together, the data suggest that K6/K16 are synthesized, perhaps by default, as an alternative suprabasal keratin pair under conditions that are nonpermissive for keratinocytes to express their normal, differentiation-related keratin pairs.

Animals↗
PubMed1988

Preclinical assessment of 90Y-labeled monoclonal antibody CO17-1A, a potential agent for radioimmunotherapy of colorectal carcinoma.

Monoclonal antibody CO17-1A was radiolabeled with 90Y using the cyclic DTPA anhydride technique and administered intravenously to athymic nude mice bearing SW 948 human colorectal carcinomas. The tumor specificity of 90Y-CO17-1A was improved by coadministration of 100 micrograms of the unlabeled antibody per animal and by purification using HPLC instead of column gel filtration chromatography. Absorbed radiation dose estimates for 90Y-CO17-1A were calculated. The radiation dose to the bone marrow will limit the amount of 90Y-CO17-1A that can be administered for cancer therapy.

Animals↗