Tsuyoshi Yoshitake

Reduced expression of apoptosis-related antigens in thymuses from patients with myasthenia gravis

Expression of the apoptosis-related antigens, Fas and BM-1, in thymuses from patients with myasthenia gravis (MG) was examined using immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). Fas antigen was markedly decreased in lymphoid follicles in thymuses from patients with MG, but was expressed diffusely in the remaining thymus tissues and in neonatal thymuses. BM-1 antigen was not expressed in the lymphoid follicles or other parts of the thymus. Fas mRNA was also decreased to various degrees in the thymuses from MG patients. Therefore, Fas antigen may play an important role in autoimmune diseases including MG.

CYTOKERATIN EXPRESSION IN NORMAL HUMAN THYMUS AT DIFFERENT AGES

Subsets of thymic epithellal cells were examined Immuno‐histochemically to determine whether or not their pheno‐types change during thymic growth and at early involution in terms of cytokeratin (CK) expression. Five monoclonal antibodies specific for CK4, CK8, CK13, CK18 and CK19 were used and applied for 16 neonatal, three Infantile and one adult thymus speeimen, which had been obtained at autopsy, that were normal macroscopically and microscopicaily. CK4, CK8, CK13, CK18 and CK19 were expressed simultaneously in the cortex, medulla and subcapsular area with the exception of CK4, which showed expression on the adult thymus. Light and electron microscopy showed that CK8 and CK19 expression was overlapped. Thus, It was thought that CK8 and CK19 formed complexes in the cytoplasm of thymic epithelial cells. The Immunoreactivity to CK4, CK13 and CK18 were attenuated or disappeared In the subcapsular area during the early involution stage. Interestingly, two patterns of CK18 expression were observed in the neonatal and Infantile thymus tissues, which Indicated that the thymic microenvironment was changeable even under normal conditions.

Significance of various anticoagulation therapies during use of a left ventricular assist device.

A multicomparative study to establish adequate anticoagulation therapy for left ventricular assist devices was undertaken by administrating various anticoagulants: heparin, a prostacyclin analogue combined with a protease inhibitor; thromboxane A2 synthetase inhibitor; or a protease inhibitor alone. Our investigation suggested that combined administration of prostacyclin analogue and protease inhibitor (FUT-175) is ideal anticoagulation therapy from the point of blood coagulation and fibrinolysis. Currently, however, sole administration of FUT-175 is adequate anticoagulation therapy during clinical use of left ventricular assist devices.

Ideal anticoagulation for use with a left ventricular assist device.

To establish ideal anticoagulation therapy for use with a left ventricular assist device, a study was done administering various anticoagulants: heparin, argatroban, a prostacyclin analogue combined with a protease inhibitor, or a protease inhibitor alone. Cardiac asisting by LVAD without any anticoagulants results in marked activation of blood coagulation or fibrinolysis. Administration of argatroban, as well as heparin, produces a bleeding tendency. Administration of a protease inhibitor (nafamostat mesilate, FUT-175) as a sole anticoagulant induces activation of the blood coagulation system to some extent, but it is within acceptable limits. Combined administration of a prostacyclin analogue (PG) and FUT-175 is most effective in maintaining balanced blood coagulation and fibrinolysis.

Thymic epithelial cells expressed unusual follicular dendritic cell markers: Thymic extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue

Described herein is a case of thymic extranodal marginal zone B‐cell lymphoma of mucosa‐associated lymphoid tissue. Using immunohistochemical double staining it was found that most of the thymic lymphoid follicles in this case possessed cytokeratin‐positive and follicular dendritic cell (FDC) marker‐positive cells. Moreover, using immunoelectron microscopy it was confirmed that some of the double‐positive cells were thymic epithelial cells. The candidate of cytokeratin subtype expressed on the double‐positive cells was cytokeratin 1 (CK1), which was expressed only by the epithelium of Hassalls corpuscles in thymuses from age‐matched patients with myasthenia gravis. The present case indicates a possibility that some thymic epithelial cells become FDC, although it was uncertain whether they were derived from the epithelia of Hassalls corpuscles or whether they were at the same differentiation stage as Hassalls corpuscles.

A case of encapsulated noninvasive thymoma (stage I) with myasthenia gravis showing metastasis after a 2-year dormancy

We herein describe a case of thymoma in which metastasis to the left lower visceral and parietal pleura was noticed after a 2-year dormancy. A closer examination revealed no evidence that the metastatic tumors were of lymph node origin. The initial thymoma was well encapsulated, and thus it was thought that the development of metastasis might have reflected a sudden rapid growth of the thymoma cells after a 2-year period of inactivity.

A new improved biodegradable tracheal prosthesis using hydroxy apatite and carbon fiber.

A new biodegradable tracheal prosthesis was developed using hydroxyapatite rings as the artificial tracheal cartilage, a carbon fiber tube as the tracheal tube; it was then implanted into the cervical trachea in dogs. Morphologic examination revealed that the hydroxyapatite ring was anchored firmly to the tracheal cartilage by ingrowth of cartilaginous tissue into the macropores of the hydroxyapatite.

Danger of urokinase as an anticoagulant with left ventricular assist devices.

The sole administration of urokinase causes no initial prolongation of activated partial thromboplastin time (A-PTT), but thereafter produces serious progressive prolongation of A-PTT; it also causes a progressive, severe decrease in fibrinogen levels and alpha 2-plasmin inhibitor activity by depletion. The antithrombogenicity of urokinase is not caused by prevention of blood coagulation system activation by antithrombin effect, but by secondary fibrinolysis by plasmin. Consequently, the administration of urokinase as a sole anticoagulant results in activation of coagulation and fibrinolysis, and, as a result, induces disseminated intravascular coagulation. Therefore, it is concluded that administration of urokinase is an inadequate anticoagulation therapy unless it is combined with other antithrombin agents.

Focal thymic hyperplasia in an adult: report of a case.

We report herein an unusual case of a 35-year-old Japanese man who underwent thoracotomy for a mass in the mediastinum which was found to be a well circumscribed localized tumor within the thymus. Focal thymic hyperplasia in adults is extremely rare and the clinicopathological features of this case were particularly interesting and posed great difficulty in establishing a diagnosis.

A comparative histological and immunohistochemical study of thymomas with and without myasthenia gravis

Because myasthenia gravis (MG) is frequently associated with thymoma, in this study the histological patterns of thymomas from 11 patients with MG (group A) were compared with those from 8 patients without MG (group B). An immunohistochemical examination was also conducted to determine whether the thymoma associated with MG is the site where autoantibodies are produced or secreted. Lymphoid follicles (LFs) and medullary differentiation (MD) were histologically evident only in group A in 4 and 5 patients, respectively, but were completely absent in group B. Moreover, an elevated serum antiacetylcholine receptor antibody titer was found in group A. Typical LFs were histologically and phenotypically similar to the lymph follicles seen in reactive lymph nodes. The number of cells expressing the B-cell antigen differed between groups A and B in terms of IgM- or IgD-bearing cells in the mantle zones and LNI-positive cells in the germinal centers of Us. Thus, it is thought that LFs consist of B cells under stimulatory conditions and that these B cells may have the potential to produce autoantibodies in MG; however, since the differentiation of these Ig-bearing cells to plasma cells was hardly evident, the thymoma itself is possibly not the site of autoantibody production or secretion in patients with MG.