[Aortic root redissection associated with the use of gelatin-resorcin-formalin glue following surgical treatment for acute type A aortic dissection; report of a case]

A late redissection case of the aortic root after total arch replacement for acute Stanford type A aortic dissection was reported. A 55-year-old male was treated with total arch replacement for acute Stanford type A aortic dissection. The aortic valve was bicuspid valve, and the right coronary leaflet was prolapsed because of the dissection of right and non coronary cusp. Resuspension of the commissure and the fixation of the dissected aortic wall with gelatin-resorcin-formalin (GRF) glue was performed during the operation. The initial postoperative course was uneventful and the patient discharged 52 days after the operation. Redissection of aortic root was pointed out on the computed tomography (CT) 3.5 years after the operation. As the second operation, the aortic root replacement was performed. Coronary artery bypass for right coronary artery was simultaneously performed with right internal thoracic artery because the right coronary ostium was stenotic and showed ischemic change on electrocardiogram monitor during the operation. The redissection was seen on the right coronary sinus, which was fixed by the GRF glue during the first operation. The pathological study showed the migration of macrophages and the tear of the fibrous tissue. These findings was thought to be associated with the use of the GRF glue. Careful use of the GRF glue for the fixation of the dissected aorta during the surgical treatment for the Stanford type A aortic dissection was thought to be important.

[Primary pericardial malignant mesothelioma with incomplete endocardial cushion defect; report of a case]

Primary pericardial malignant mesothelioma is rare tumor and its prognosis is quite poor due to its late presentation and difficulty of complete resection. We describe a rare case of primary pericardial malignant mesothelioma in a 46-year-old female with incomplete endocardial cushion defect (ECD). Incidentally, we found 2 masses in the pericardial spaces after pericardiectomy. We have successfully removed these 2 masses en bloc and performed a total repair of incomplete ECD. Pathologically, these masses were a primary pericardial malignant mesothelioma. This patient is doing well 4 months after surgery without any evidence of recurrence despite reported poor prognosis of "primary pericardial malignant mesothelioma".

Incidence and recurrence rates of colorectal adenomas estimated by annually repeated colonoscopies on asymptomatic Japanese

BACKGROUND

Whereas high recurrence rates of colorectal adenomas after polypectomy are widely recognised, little is known of the natural incidence in those with no neoplastic lesions initially. It is also known that single colonoscopy has a significant miss rate.

AIMS

To elucidate the incidence and recurrence rates of colorectal neoplasms from a large cohort of asymptomatic Japanese patients on the basis of annually repeated colonoscopies.

METHODS

A total of 6225 subjects (4659 men and 1566 women) participating in an annual colonoscopic screening programme and completing three or more colonoscopies were analysed during the 14 year period between 1988 and 2002. Patients were divided into three groups according to the findings of the initial two colonoscopies: 4084 subjects with no neoplasm, 1818 with small adenomas <10 mm, and 323 with advanced lesions, including carcinoma in situ, severe dysplasia, or large adenomas > or =10 mm. Mean age at the second colonoscopy was 48.8 years.

RESULTS

For all types of colorectal neoplasms, the incidence rate in those with no initial neoplasm was 7.2%/year whereas recurrence rates in those with small adenomas and advanced lesions were 19.3% and 22.9%/year, respectively. For advanced colorectal lesions, the incidence rate was 0.21%/year whereas recurrence rates in those with small adenomas and advanced lesions were 0.64% and 1.88%/year, respectively. Colorectal neoplasms were in general more likely to develop in males and older subjects.

CONCLUSIONS

Although recurrence rates after polypectomy were elevated, the incidence rates in subjects with no neoplastic lesions initially were quite high.

Ganglioside/calmodulin kinase II signal inducing cdc42-mediated neuronal actin reorganization

Cell surface glycoconjugates are thought to mediate cell-cell recognition and play roles in neuronal development and functions. We demonstrated here that exposure of neuronal cells to nanomolar levels of gangliosides Neu5Acalpha 8Neu5Acalpha 3Galbeta 4GlcCer, Galbeta 3GalNAcbeta 4(Neu5Acalpha 8Neu5Acalpha 3)Galbeta 4GlcCer (GD1b), Neu5Acalpha 3Galbeta 3GalNAcbeta 4(Neu5Acalpha 8Neu5Acalpha 3)Galbeta 4GlcCer (GT1b) or its oligosaccharide portion induced a rapid and transient activation of Ca2+/calmodulin-dependent protein kinase II (CaM-KII) in the subplasmalemma. Galbeta 3GalNAcbeta 4(Neu5Acalpha 3)Galbeta 4GlcCer (GM1), GalNAcbeta 4(Neu5Acalpha 3)Galbeta 4GlcCer, Neu5Acalpha 3Galbeta 4GlcCer, Neu5Acalpha 3Galbeta 3GalNAcbeta 4(Neu5Acalpha 3)Galbeta 4GlcCer (GD1a), and Neu5Acalpha 8Neu5Acalpha 3Galbeta 3GalNAcbeta 4(Neu5Acalpha 8Neu5Acalpha 3)-Galbeta 4GlcCer were ineffective. GT1b and GD1b stimulated transient elevation of bulk cytosolic Ca2+ levels while GM1 slightly elevated the levels and GD1a did not. Thus, the cytosolic Ca2+ elevation by the gangliosides may trigger the CaM-KII activation. The treatment was accompanied by peripheral actin polymerization and filopodia formation in NG108-15 cells and primary hippocampal neurons, but not in glial cells. CaM-KII inhibitors blocked both CaM-KII activation and the subsequent filopodia formation. A small G-protein cdc42 was a potential downstream target of CaM-KII activated by the gangliosides. These results suggest that oligosaccharides of the gangliosides serve as potential regulators of the filopodia formation in neuronal cells by triggering the activation of CaM-KII followed by cdc42 up-regulation via a cell surface receptor-like component. The filopodia formation induced by the gangliosides may have a physiological relevance because long-term exposure of hippocampal neurons to GT1b oligosaccharide induced advanced dendritogenesis. Furthermore, exposure of cerebellar neurons to GT1b oligosaccharide facilitated CaM-KII-dependent dendritic outgrowth and branch formation of cerebellar Purkinje neurons, in which actin isoforms were localized to motile structures in dendrites. Thus, the ganglioside/CaM-KII signal plays a role in modulating dendritic morphogenesis by inducing cdc42-mediated actin reorganization.

Wear properties of Ti and Ti-6Al-7Nb castings for dental prostheses

Titanium has been increasingly applied to dental prostheses because of its biocompatibility. However, application remains limited, due to the low strength and poor wear resistance of unalloyed titanium. The purpose of this study is to evaluate the wear resistance of high-strength Ti-6Al-7Nb alloy castings for dental application. Test specimens were cast from commercially pure titanium (CP-Ti grades 2 and 3) and Ti-6Al-7Nb alloy ingots, and subjected to a wear test simulating the occlusal loading pattern. Wear resistance was evaluated by the weight loss during the test. Ti-6Al-7Nb alloy was found to exhibit lower weight loss than CP-Ti. Moreover, scanning electron microscopic (SEM) observation after the test revealed that the worn surface of Ti-6Al-7Nb alloy is much smoother than that of CP-Ti. These results indicate that Ti-6Al-7Nb alloy castings can be used to produce dental prostheses of improved wear resistance and mechanical strength.

Extracellular carbohydrate-signal triggering camp-dependent protein kinase-dependent neuronal actin-reorganization

Cell surface glycoconjugates are thought to mediate cell-cell recognition and to play roles in neuronal development and functions. We demonstrated here that exposure of neuronal cells to nanomolar levels of glyco-chains with an N-acetylgalactosamine (GalNAc) residue at the non-reducing termini (GalNAc-S) such as GalNAcbeta4(Neu5Acalpha3)Galbeta4GlcCer (GM2) ganglioside, its oligosaccharide portion, GalNAcbeta4Galbeta4GlcCer (Gg(3)) Cer, GalNAcalpha3GalNAcbeta3Galalpha4Galbeta4GlcCer (Gb(5)) Cer (Forssman hapten) and alpha1-4 linked oligomers of GalNAc, induced a rapid and transient activation of cAMP-dependent protein kinase (PKA) in subplasmalemma. The treatment was accompanied by peripheral actin polymerization and filopodia formation in NG108-15 cells and primary cultured hippocampal neurons, but not in glial cells. A cAMP-dependent protein kinase (PKA) selective inhibitor and an adenylate cyclase inhibitor blocked both PKA activation and the subsequent filopodia formation. A small GTPase cdc42 was a potential downstream target of GalNAc-S-activated PKA. These results suggest that extracellular GalNAc-S serve as potential regulators of the filopodia formation in neuronal cells by triggering the activation of PKA followed by cdc42 up-regulation via a cell surface receptor-like component. Filopodia formation induced by GalNAc-S may have a physiological relevance because long-term exposure to GalNAc-S enhanced F-actin-rich dendrite generation of primary cultured hippocampal neurons, and PKA-dependent dendritic outgrowth and branch formation of primary cultured cerebellar Purkinje neurons, in which actin isoforms were localized to motile structures in dendrites. These findings provide evidence for a novel GalNAc/PKA-signaling cascade in regulating some neuronal maturation.

Effect of heat treatment with the mould on the super-elastic property of Ti-Ni alloy castings for dental application

Tensile property of Ti-50.85Ni (mol %) alloy castings was investigated quantitatively in relation to the thermal behavior accompanied with phase transformation to evaluate the effect of heat treatment after casting with the mould in air. The heat treatment temperature was 713 or 773 K, and the period was 0.9, 1.8, or 3.6 ks. Apparent proof stress of the castings decreased with increasing period of heat treatment, and the decrease was larger with the treatment at 773 K. Residual strain also decreased by the heat treatment, however, it was low with the treatment for relatively short period, i.e. 713 K-0.9 and 1.8 ks, and 773 K-0.9 ks treatments. From the thermal behavior measured by differential scanning calorimetry (DSC), the ascent in the transformation temperatures and the increase in the thermal peak height appeared to influence the changes in the tensile property. These changes by heat treatment were believed to be effective to utilize more flexibility, less stress and less permanent deformation in dental castings.

Bending property and phase transformation of Ti-Ni-Cu alloy dental castings for orthodontic application

Bending property of Ti-Ni-Cu alloy castings was investigated in a three-point bending test for orthodontic application in relation to the phase transformation. The compositions of the alloys were Ti-50.8Ni and Ti-40.8Ni-10.0Cu (mol %), and four cross-sectional shapes of the specimens were selected. Heat treatment was performed at 713, 753 or 793 K for 1.8 ks. The bending load changed by the cross-sectional size and shape mainly because of the difference in the moment of inertia of area, but the load-deflection relation did not differ proportionally in the unloading process. The difference between the load values in the loading and the unloading processes was relatively small for Ti-Ni-Cu alloy. With respect to the residual deflection, there was no significant difference between Ti-Ni and Ti-Ni-Cu alloys with the same treatment condition. The load values in the loading and the unloading processes decreased by each heat treatment for Ti-Ni alloy; however, the decrease in the load values for Ti-Ni-Cu alloy was not distinct. It is proved that Ti-Ni-Cu alloy castings produce effective orthodontic force as well as stable low residual deflection, which is likely to be caused by the high and sharp thermal peaks during phase transformation.

Effects of the antiplatelet agent TA-993 and its metabolite MB3 on the hemorheological properties of rat and human erythrocytes

In the present study, we investigated the effects of the antiplatelet agent TA-993 and its metabolite MB3 on the hemorheological properties of rat and human erythrocytes in comparison with ticlopidine and aspirin. TA-993 and MB3 concentration-dependently lowered the viscosity of rat erythrocyte suspensions. TA-993 and MB3 inhibited both the hypotonic hemolysis of human erythrocytes and the mechanical hemolysis of rat erythrocytes induced by turbulent flow. Treatment of rats with TA-993 (10 mg/kg/day po) for 10 days significantly increased blood filterability, but ticlopidine and aspirin did not show this effect. TA-993 and MB3 enhanced the interaction of 1-anilino-8-naphthalene sulfonate (ANS), a hydrophobic probe, with human erythrocyte ghosts and reduced the fluorescence polarization in 1,6-diphenyl 1,3,5-hexatriene (DPH, a fluidity probe)-labeled human erythrocyte ghosts. TA-993 and MB3 induced aggregation of liposome suspensions prepared from acidic phospholipids. These findings suggest that TA-993 and MB3 may affect the erythrocyte membrane by interacting with acidic phospholipids and thus improve the hemorheological properties.

Modulation of event-related potentials in normal human subjects by visual divided attention to spatial and color factors

We investigated how visual event-related potentials (ERPs) are modulated by visual divided attention using an S1-S2 paradigm. Stimulus S2 consisted of non-target stimuli (Stimulus 1, 2, 3) and a target stimulus (Stimulus 4). The spatial/color factor was compared between S1 and S2: same/same (Stimulus 1); same/different (Stimulus 2); different/same (Stimulus 3); and different/different (Stimulus 4). The P1/N1 (90 approximately 150 ms) showed significantly greater amplitude in Stimulus 3 than in Stimuli 1 and 2. The N2 (230 approximately 290ms) showed significantly greater amplitude in Stimulus 2 than in Stimuli 1 and 3. We assumed that the P1/N1 was related to spatial attention, enhanced by alterations to the spatial factor, and that the N2 was related to color attention, enhanced by alterations to the color factor.

[A case of Vernet's syndrome due to varicella-zoster virus infection]

We report a 73-year-old man who suffered from an acute onset of dysphagia, cough, hoarseness and left facial and occipital pain. On the 44 days of illness, he was admitted to our clinic. A neurological examination revealed left IX, X and XI cranial nerve palsy. The diagnosis of Vernet's syndrome due to varicella-zoster virus (VZV) infection was made, based on the high titers of VZV antibody in serum. Magnetic resonance imaging revealed a unique nodular lesion with gadolinium enhancement at the medial side of the left jugular foramen. Clinical symptoms improved with intravenous high dose pulse methylprednisolone therapy. The clinical course suggests that the inflammation extended from the left X cranial nerve ganglion.

Angiographic features at ischemia- or infarct-related sites in patients with acute coronary syndrome: morphology changing in a relatively short time

OBJECTIVES

Coronary cineangiography was reviewed in patients with acute coronary syndrome to investigate whether angiographic features at identifiable ischemia- or infarct-related lesions can change in terms of luminal diameter and morphology in a short period after development, and whether the amount of thrombus with/without underlying ruptured plaque is the major determinant.

METHODS

The present study included 72 patients with unstable angina, 118 with acute myocardial infarction (< 1 month after onset) and 137 with old myocardial infarction (> or = 1 month after onset). The coronary angiographic findings were compared with those from patients with stable effort angina. The groups of patients were subdivided into two groups based on whether antiplatelet and/or anticoagulant therapy, or fibrinolytic therapy with subsequent anticoagulant agents (antiplatelet and/or anticoagulant, or fibrinolytic therapy) were administered. The morphologies of the ischemia- or infarct-related lesions were classified as totally occlusive, simple (Type I lesion) or complex. Complex lesions were further subdivided into Type IIa lesions indicative of the presence of thrombus accumulation with/without an underlying ruptured atheromatous plaque, e.g., narrowing with irregular, poorly defined or hazy borders, sharp leading or trailing edges that overhang or are perpendicular to vessel walls, and globular endoluminal negative images, Type IIb lesions with two or more serial, closely spaced narrowings together with multiple irregularities, and Type IIc lesions indicative of the presence of some parts of ruptured plaque with a smaller amount of thrombus, e.g., luminal narrowing with extraluminal contrast pooling, single or paired short thin linear radiolucencies with/without a variable degree of outpouching, and narrowing with definite outpouching with/without radiolucency, and Type IId lesions showing narrowing with morphology not included in Type IIa-IIc lesions. The coronary angiographic findings were related to the elapsed time before the coronary angiographic study, and whether each patient underwent antiplatelet and/or anticoagulant, or fibrinolytic therapy.

RESULTS

Ischemia- or infarct-related lesions were totally occlusive in 9.7% of patients with unstable angina, 40.7% of those with acute myocardial infarction and 21.9% of those with old myocardial infarction. Total occlusion was significantly more prevalent in patients with acute myocardial infarction than in those with stable effort angina (23.9%, p < 0.05), and total occlusion was more frequent in patients without antiplatelet and/or anticoagulant, or fibrinolytic drugs (50.6% vs 17.1%, p < 0.01). The presence of total occlusion decreased with time after development, and the decrease was more significant with the use of antiplatelet and/or anticoagulant, or fibrinolytic drugs. Type IIa morphology was significantly prevalent immediately after the initial episode, and Type IIa and IIc morphologies increased in the late period, and were more frequent with the use of antiplatelet and/or anticoagulant, or fibrinolytic drugs.

CONCLUSIONS

The severity of the luminal diameter at ischemia- or infarct-related lesions sites can progress or even regress in a relatively short period in patients with acute coronary syndrome, and the amount of accumulated thrombus with/without underlying ruptured plaque is a major determinant of luminal diameter narrowing and angiographic morphology.

A radiation hybrid map of mouse genes

A comprehensive gene-based map of a genome is a powerful tool for genetic studies and is especially useful for the positional cloning and positional candidate approaches. The availability of gene maps for multiple organisms provides the foundation for detailed conserved-orthology maps showing the correspondence between conserved genomic segments. These maps make it possible to use cross-species information in gene hunts and shed light on the evolutionary forces that shape the genome. Here we report a radiation hybrid map of mouse genes, a combined project of the Whitehead Institute/Massachusetts Institute of Technology Center for Genome Research, the Medical Research Council UK Mouse Genome Centre, and the National Center for Biotechnology Information. The map contains 11,109 genes, screened against the T31 RH panel and positioned relative to a reference map containing 2,280 mouse genetic markers. It includes 3,658 genes homologous to the human genome sequence and provides a framework for overlaying the human genome sequence to the mouse and for sequencing the mouse genome.

[A case of thoracic vertebral tuberculosis associated with pulmonary sarcoidosis]

A 56-year-old woman was admitted to our hospital, on October 10, 1999 because of tingling numbness of the Th3 area and paraparesis. Her medical history included the diagnosis of pulmonary sarcoidosis which had responded to steroid therapy. On radiographic examination, a Th2 compression fracture and gadolinium enhanced areas were shown in MRI. We diagnosed vertebral sarcoidosis and restarted steroid therapy. Next day, she had no paresis and she was discharged after 20 days. However, the patient returned to our hospital with recurrence of the same pain and paraparesis on January 1, 2000, and spinal fusion of the Th2-3 was performed by a transpleural anterolateral approach using a block of iliac bone as a graft. Histology and cultural studies of tissue revealed tuberculosis. There is a diagnostic dilemma, "sarcoidosis or tuberculosis?", but it is necessary to be aware of this at the time of the initial diagnosis.

Fluvastatin inhibits O2- and ICAM-1 levels in a rat model with aortic remodeling induced by pressure overload

Upregulation of intercellular adhesion molecule-1 (ICAM-1) expression is suggested to play an important role in the pathogenesis of vascular remodeling. The aim of the present study was to investigate the effects of the 3-hydroxy-3-methylglutaryl (HMG) CoA reductase inhibitor fluvastatin on superoxide anion (O2-) production and ICAM-1 expression in a rat model with vascular remodeling induced by pressure overload. Two weeks after aortic banding, marked increases in O2- production and ICAM-1 protein levels were observed in the aorta. O2- formation and ICAM-1 immunoreactivity were mainly increased in the endothelium and adventitia of the aorta in banded rats. Oral administration of fluvastatin prevented both these changes and the development of perivascular fibrosis and increased the expression of endothelial nitric oxide synthase. Cholesterol and lipid peroxide levels in serum did not change in the banded rats. Thus the beneficial effects of fluvastatin seen in this study as well as its cholesterol-lowering effect may contribute to attenuate the atherosclerotic process.

Fission yeast tor1 functions in response to various stresses including nitrogen starvation, high osmolarity, and high temperature

A target of rapamycin (TOR) protein is a protein kinase that exerts cellular signal transduction to regulate cell growth in response to extracellular nutrient conditions. In the Schizosaccharomyces pombe genome database, there are two genes encoding TOR-related proteins, but their functions have not been analyzed. Here we report that one of the genes, referred to as tor1+, is required for sexual development induced by nitrogen starvation. Ste11 is a key transcription factor for the initiation of sexual development. The expression of ste11+ is normally regulated in tor1- cells; and overexpression of ste11+ hardly rescues the defect in fertility in tor1-. Upon nitrogen starvation, tor1+ cells promote two rounds of the cell cycle to become arrested at the G1 phase before initiation of sexual development. The tor1- cells do not promote such a cell cycle, suggesting that Tor1 is necessary for the response to nitrogen starvation. The tor1- cells show no growth or very slow growth under various stress conditions, including external high pH, high concentrations of salts or sorbitol, and high temperature. These results suggest that Tor1 is necessary for any response to a wide range of stresses. The vegetative growth of tor1- cells is inhibited by rapamycin, although tor1+ cells are resistant to the drug. The tor1- cells are hypersensitive to fluphenazine and cyclosporin A, which specifically inhibit calmodulin and calcineurin, respectively.

[Drug-induced interstitial pneumonia associated with inhalation of fibrinolysin-deoxyribonuclease (ElaseR)]

A 73-year-old man was referred to our department because of sputum production and fever. He had under-gone a total laryngectomy for laryngeal cancer. His chest radiograph showed patchy ground-glass shadows in both lung fields. He was treated with antibiotics for pneumonia, but his symptoms continued, and the size of the patchy shadows in the chest radiograph increased. Inhalation therapy with ElaseR had been started from one day before fever arose. Withdrawal of ElaseR treatment resolved his symptoms. We therefore suspected drug-induced interstitial pneumonia. Transbronchial lung biopsy specimens showed infiltration of lymphocytes in the alveolar septa and thickening of those septa. A bronchoalveolar lavage revealed an increased number of lymphocytes, and the CD4/CD8 ratio was 0.3. A drug lymphocyte stimulation test (DLST) with peripheral blood lymphocytes was strongly positive (S.I. 2127%) for ElaseR. The anti-nuclear antigen (ANA) was detected (x640), and the anti-single strand DNA antibody titer was also high (123.4 IU/ml). About 10 weeks after the withdrawal of ElaseR, the infiltrative shadows and the abnormal laboratory findings improved spontaneously. On the basis of these findings, we arrived at a diagnosis of drug-induced interstitial pneumonia associated with inhalation of ElaseR.

New technique for producing hybridoma by using laser radiation

BACKGROUND AND OBJECTIVE

With conventional methods, cell fusion rate is extremely low, and fusion of two specific cells is not possible. We developed a new method for inducing cell fusion under the microscope by using a microprocessing device by laser.

STUDY DESIGN/MATERIALS AND METHODS

Under a microscope, the target cells were irradiated with laser beams for trapping. Then, the trapped cells were transferred and placed in contact with the corresponding cells, which were also fixed by laser beam. The pulse laser beams are focused on the contact surface to cut small perforations for mutual communication of the cytoplasms.

RESULTS

The fusion rate of mouse myeloma cells was 38%. The rate of hybridoma production of myeloma cell and lymphocyte was 2%. We confirmed the proliferation of the newly formed hybridoma in HAT medium and the production of immunoglobulin G.

CONCLUSION

This new cell fusion method is characterized by production of hybridomas of target cells, lower cell toxicity, and a high rate of hybrid production.

Super-elastic property of Ti-Ni alloy for use in dentistry

The super-elasticity of Ti-Ni alloy was investigated in tensile and bending tests to evaluate the mechanical properties of the castings and heat treatment effect on the bending properties of the wires for new clinical applications of the alloy in prosthodontics and orthodontics. In terms of the tensile properties of the castings, apparent proof stress increased and elongation decreased with the small increase in nickel content or with the decrease in titanium purity. This result suggests that precise control of the materials is indispensable to utilize the super-elasticity in dental cast appliances. In terms of the bending properties of Ti-Ni alloy wires, low residual deflection and small load/deflection ratio were obtained by the second heat treatment between 733 and 813 K, which was found to be suitable for the shape memory treatment of orthodontic appliances. Moreover, the functional force was changeable within this treatment temperature range.

Establishment of a mouse thymic epithelial cell line, IT-76MHC and a brief review on cultured thymic epithelial cells

Interactions between thymocytes and thymic stromal cells are essential for thymocyte differentiation, but little evidence has been presented to directly show in vivo functions or interactions of the stromal cells. Among the stromal cells, the thymic epithelial cell has been considered to have profound effect on thymocyte differentiation and maturation. The calcium-depleted medium, originally developed for the culture of mouse epidermal cells, was applied for the culture of the mouse thymic epithelial cells, and successfully, an epithelial cell line, IT-76MHC was obtained from the mouse thymus. IT-76MHC cells were identified as distinct mouse thymic epithelial cells by 1/ mosaic-like arrangement, 2/ presence of well-developed desmosome and 3/ tonofilaments, 4/ positivity for cytokeratin, and 5/ induced expression of MHC class I and II by IFN-gamma treatment. IGF-1, IGF-2, oxytocin and vasopressin were also detected immunohistochemically in IT-76MHC cells. Furthermore, the IT-76MHC thymic epithelial cells, when injected intrathymically in the allogeneic mouse, prolonged the survival of skin graft from the same donor strain that IT-76MHC cells were derived. These results demonstrate that the thymic epithelial cell line IT-76MHC produces modest thymocyte survival factors as well as a growth suppressor, and that IT-76MHC cells have the ability to induce transplantation tolerance probably through their expression of MHC class I and II molecules. Taken altogether, the IT-76MHC thymic epithelial cells have been proved to be useful tools to better understand the in vivo functions of thymic epithelial cells, and to gain a deep insight into their involvement in the critical selection process of thymocytes which still remains obscure. Finally and additionally, literatures so far reported on thymic epithelial cells in culture, especially lines and clones, are reviewed and their identity as well as their functions are discussed.