PubMed Health⌕ Search

Biomedical subjects

T T Sun

Publications and source records attributed to T T Sun.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of a keratinocyte-specific extracellular epitope of desmoglein. Implications for desmoglein heterogeneity and function.

Despite the presumed importance of desmoglein, a 160-kDa glycoprotein, in desmosome formation and its possible involvement in certain blistering skin diseases, the precise location and function of this protein have not yet been firmly established. We describe here the characterization of a new monoclonal antibody, AE23, against an extracellular epitope of desmoglein. Both the AE23 epitope and another epitope, defined by the previously characterized DG3.4 antibody, reside on a 160-kDa human epidermal desmoglein as evidenced by their identical solubility profile, their coexistence in a 130-kDa desmoglein degradative product, their coadsorption by an AE23 immunoaffinity column, and the identical changes in the two antigens' electrophoretic mobility after air oxidation and deglycosylation. The AE23 epitope is resistant to various endoglycosidases, suggesting that sugar moieties are not involved. Characterization of several proteolytic fragments of this epidermal desmoglein enabled us to map the DG3.4 epitope to a 96-kDa intracellular domain and the AE23 epitope to an extracellular domain flanked by the plasma membrane and the distal N-glycosylation site(s). However, these two epitopes do not always coexist on the same desmoglein molecule. For example, tissue surveys showed that although the DG3.4 epitope is present in the desmogleins of all epithelial cell types, the AE23 epitope is limited to normal keratinocytes. Moreover, electron microscopic localization data indicate that whereas the DG3.4 epitope is detected in the submembranous plaques of desmosomes, the AE23 epitope is present in the intercellular space of both desmosomal and nondesmosomal areas. These results raise the possibility that there exist several biochemically closely related isoforms of desmoglein, one (AE23+/DG3.4+) restricted to epidermal desmosomes, one (AE23+/DG3.4-) uniformly distributed along the keratinocyte cell surface, and another (AE23-/DG3.4+) present in desmosomes of simple epithelia and basal cells of cultured keratinocytes. The uniform distribution of at least one desmoglein-related antigen in the intercellular space of keratinocytes coupled with the realization that different isoforms of desmogleins form a subfamily of cadherins suggest that desmoglein(s) may play a more general role in keratinocyte adhesion than previously appreciated.

Animals↗
PubMed1992

Simultaneous ectopic pregnancy with intra-uterine gestation after in vitro fertilization and embryo transfer.

A case of combined intra-uterine and tubal ectopic pregnancy is described following in vitro fertilization and the transfer of two four-cell and one two-cell embryos. This phenomenon is known to be related to ovarian stimulation by gonadotropin therapy, and there is an increased risk with tubal disease. Techniques applied at the time of embryo transfer, the use of culture medium with 50% fetal cord serum to convey the embryos to the uterus, the catheterization method, and the position of the patient during transfer are presented. The risk of multiple pregnancies and combined intra-uterine and ectopic gestations increases with numbers of transfers and large volume of transfer medium. We would therefore recommend that after IVF-ET treatment in women with tubal disease, intensive care should be taken in the early follow-up period to rule out the possibility of ectopic pregnancy. In this case, a viable ongoing intra-uterine pregnancy was confirmed after surgery for right ampullary ectopic pregnancy. And a 2,925 g male in excellent condition was delivered by Cesarean section without complications.

Adult↗
PubMed1992

Interaction of trichohyalin with intermediate filaments: three immunologically defined stages of trichohyalin maturation.

"Trichohyalin" is a 220-kD protein found in trichohyalin granules that are present as major differentiation products in the medulla and inner root sheath cells of human hair follicles. It was unclear whether this protein served as an intermediate filament precursor in the inner root sheath or as an intermediate-filament-associated (matrix) protein. We have produced a panel of monoclonal antibodies (AE15-17) to this protein and used them to trace its fate during inner root sheath differentiation. These studies have allowed us to define three immunologically distinct forms of this trichohyalin protein. They are 1) the AE15-positive form, which is found throughout all trichohyalin granules; 2) the AE16-positive form, which is localized as discrete punctae on the surface of trichohyalin granules; and 3) the AE17-positive, intermediate-filament-bound form, which associates with the inner root sheath filaments with a regular, 400-nm periodicity. From these results we suggest that the 220-kD trichohyalin protein is an intermediate-filament-associated protein that may play a role in the lateral aggregation, precise alignment, and stabilization of inner root sheath filament bundles.

Animals↗
PubMed1992

Expression of K12 keratin in alkali-burned rabbit corneas.

The healing of alkali-injured corneas is characterized by the persistence of polymorphonuclear leukocytes (PMN) in tissues and recurrent corneal epithelial defects. It has been suggested that the proteolytic enzymes secreted by PMN may account in part for the recurrent epithelial defects in the alkali-burned corneas. Cytoplasmic keratins, which form intracellular intermediate filaments, participate in the formation of hemidesmosomes and play a key role in the focal adhesion of epithelial cells to the basement membranes. The K3/K12 keratin pair is a major constituent of differentiated and stratified corneal epithelium. We have recently cloned the cDNA encoding the rabbit K12 keratin. In the present study we examined the expression of K12 keratin during the healing of alkali-burned rabbit corneas by slot-blot and in situ hybridization. Our results indicate that in normal cornea K12 keratin is equally expressed in all cell layers of stratified corneal epithelium and suprabasal layers of limbal epithelium, but not in bulbar conjunctival and other epithelia, i.e., lens, iris, and retinal pigment epithelium. The basal cells of the detached regenerating epithelium of the injured cornea express a very low level of K12 keratin. These observations are consistent with the notion that defective expression of K3/K12 keratins may play a role in the abnormal attachment of the regenerating epithelium to the basement membrane.

Animals↗
PubMed1992

Identification of an 85-100 kDa glycoprotein as a cell surface marker for an advanced stage of urothelial differentiation: association with the inter-plaque ('hinge') area.

Although bladder cancers account for almost 5% of all human cancer deaths, little is known about the biochemistry of urothelial differentiation. We have recently identified three major protein subunits ('uroplakins') of asymmetric unit membranes (AUM), which form rigid-looking plaques covering up to 70% of the apical surface of urothelial superficial (umbrella) cells. The ordinary-looking plasma membranes that interconnect these plaques are believed to be functionally specialized, serving as flexible but durable 'hinges'. Whether these hinge membranes are biochemically unique is unknown. Using a new monoclonal antibody (AE32) we have identified an 85-100 kDa glycoprotein (UGP85) which appears to be urothelium-specific. In both normal urothelium and cultured urothelial colonies this cell surface protein is associated mainly with superficial cells, suggesting that its expression is differentiation dependent. Results from in vitro translation experiments indicated that this glycoprotein contains a core polypeptide of about 55 kDa. Using immunogold localization techniques, we showed that in cultured urothelial colonies--which are known to lack mature AUM plaques--UGP85 is distributed relatively uniformly on the apical surface of some differentiated cells. However, in superficial cells of normal urothelium UGP85 is mainly associated with the hinge areas. These results raise the possibility that UGP85 is a plasma membrane component which can be excluded, to varying extents, from the plaque region as 12 nm protein particles are assembled into a tightly packed paracrystalline AUM structure. The identification of UGP85 provides the first evidence that the hinge areas interconnecting the urothelial plaques are biochemically distinguishable from the plasma membranes of the relatively undifferentiated urothelial cells of the lower cell layers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Comparison of five bifunctional chelate techniques for 90Y-labeled monoclonal antibody CO17-1A.

Monoclonal antibody CO17-1A was radiolabeled with 90Y by five bifunctional chelate techniques. Radiation absorbed dose estimates for normal organs and tumor were calculated for each preparation based on timed tissue distribution studies in nude mice bearing SW 948 human colorectal carcinoma xenografts. The cyclic DTPA anhydride technique was inferior to the four other techniques studied. Data for SCN-Bz-DTPA and SCN-Bz-Mx-DTPA, which were conjugated to epsilon-lysyl amino groups, were similar to those for NH2-Bz-DTPA and NH2-Bz-Mx-DTPA, which were conjugated site specifically to oligosaccharides.

Animals↗
PubMed1991

Transient expression of mouse hair keratins in transfected HeLa cells: interactions between "hard" and "soft" keratins.

Although it has been shown previously that an acidic (type I) "soft" keratin can interact with many basic (type II) "soft" keratins to form 10-nm intermediate filaments, it has been unclear whether "soft" keratins are compatible with the "hard" keratins typically found in hair and nail. To address this issue and to generate more structural information about hard keratins, we have isolated and sequenced a cDNA clone that encodes a mouse hair basic keratin (b4). Our sequence data revealed new information regarding the structural conservation of hard keratins as a group, being significantly different from soft keratins. Using expression vectors containing appropriate cDNA inserts, we studied the expression of this basic (b4) as well as an acidic (a1) mouse hair keratin in HeLa cells. The expression of these alien hair keratins in the transfected cells was surveyed using a panel of monoclonal and polyclonal antibodies. Our results indicated that the basic and acidic hair keratin readily incorporated into the existing endogenous soft keratin network of HeLa cells. Overproduction of hair keratin, however, occasionally led to the formation of cytoplasmic aggregates containing both hard and soft keratins. These data suggest that although small amounts of newly synthesized hair keratins can incorporate into the "scaffolding" of the preformed soft keratin filament network, possibly through dynamic subunit exchange, overproduction of hard keratins can lead to the partial collapse of the soft keratin network. These observations, along with the deduced amino acid sequence data, support and extend the concept that hard and soft keratins, although closely related, are divergent enough to justify their being divided into two separate subgroups.

Animals↗
PubMed1991

Interaction of filaggrin with keratin filaments during advanced stages of normal human epidermal differentiation and in ichthyosis vulgaris.

Filaggrin is a histidine-rich, basic protein whose name was first proposed based on its ability to aggregate intermediate filaments in vitro. Based on this in vitro observation, it has generally been assumed that filaggrin functions in vivo as a matrix protein which causes keratin filaments to become densely packed in the terminally differentiated cornified cells. Inconsistent with this view however, is the well-known observation that keratin aggregation appears to proceed normally in the affected epidermis of ichthyosis vulgaris patients despite a greatly reduced quantity of filaggrin. To address this issue, we used immuno-electron microscopy to localize filaggrin and its cross-reactive precursor, profilaggrin, in human and mouse epidermis, as well as in ichthyosis vulgaris epidermis. We found that the localization of filaggrin in lower cornified cells correlates precisely with the formation of aggregated keratin filaments, and the disappearance of filaggrin in upper cornified cells correlates precisely with the loosening of keratin filaments. Furthermore, we showed that, even in ichthyosis vulgaris, small amounts of filaggrin/profilaggrin are present as electron-dense deposits associated with keratin filaments in the granular cells, and that the localization of this small amount of antigen again correlates with the aggregation state of keratin filaments. These data strongly suggest that filaggrin is indeed involved in filament aggregation in vivo.

Animals↗
PubMed1991

Regional heterogeneity in human corneal and limbal epithelia: an immunohistochemical evaluation.

The authors studied the distribution of specific keratins within the superior, inferior, medial, and lateral regions of human limbus and cornea to determine whether the limbal epithelium exhibits regional heterogeneity in its microstructure. A corneal epithelial basic keratin (K3), recognized by monoclonal antibody AE5, was immunohistochemically undetectable in the basal layers of the limbus in these four regions, but was seen in all layers in the central cornea. The pattern of immunostaining with another monoclonal antibody, AE1, which recognizes several acidic keratins, was complementary to AE5 staining in that AE1 recognized a similar heterogeneity in the limbal epithelial cells. AE1 immunoreacted with the basal cells of the limbus, but not those of the central corneal epithelium. Limbal characteristics, as defined by AE1-positive and AE5-negative staining, extended deeply into peripheral cornea in the superior and inferior regions, but to a lesser extent in the lateral and medial regions. The broader regions of epithelium with limbal characteristics in the superior and inferior regions raises the possibility that these regions play an important role in corneal epithelial maintenance and wound healing.

Aged↗
PubMed1991

Simultaneous ectopic pregnancy with intrauterine gestation after in vitro fertilization and embryo transfer.

A case of combined intrauterine and tubal ectopic pregnancy is described following in vitro fertilization and the transfer of two four-cell and one two-cell embryos. This phenomenon is known to be related to ovarian stimulation by gonadotropin therapy, and there is an increased risk with tubal disease. Techniques applied at the time of embryo transfer, the use of culture medium with 50% fetal cord serum to convey the embryos to the uterus, the catheterization method, and the position of the patient during transfer are presented. The risk of multiple pregnancies and combined intrauterine and ectopic gestations increases with increasing numbers of transfers and large volume of transfer medium. We would therefore recommend that after IVF-ET treatment in women with tubal disease, intensive care should be taken in the early follow-up period to rule out the possibility of ectopic pregnancy. In this case, a viable ongoing intrauterine pregnancy was confirmed after surgery for right ampullary ectopic pregnancy. And a 2925gm male in excellent condition was delivered by cesarean section without complications.

Adult↗
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↗