Gonadal sex differentiation and early ovarian/testicular development in cultured Pacific bluefin tuna, Thunnus orientalis (Temminck et Schlegel).

Pacific bluefin tuna (PBT), Thunnus orientalis, is one of the most important species for aquaculture in Japan. Recently, the reduction in muscle fat content associated with sexual maturation in farmed PBT has become a serious problem. To develop technologies for inducing sterility, detailed and reliable data on gonadal development in PBT are needed. Here, we demonstrated the process of gonadal sex differentiation, and of early ovarian and testicular development during the immature stages in PBT. Gonadal sex differentiation was first characterized by the formation of the ovarian cavity in female and of the efferent ducts in male 57 days post hatching (dph). The gonads then differentiated into ovaries or testes according to the genotypic sex until 83 dph. During this period, primordial germ cells, oogonia, and type-A spermatogonia were solitarily distributed in the gonads, and the number of germ cells did not differ between sexes. After gonadal sex differentiation, gonads of PBTs developed in a sexually dimorphic manner: proliferation and differentiation of germ cells occurred earlier in the ovaries than in the testes. The oogonia in ovaries formed cysts at 185 dph, but the type-A spermatogonia were solitarily distributed in testes at this stage, and cysts of type-A spermatogonia were first observed at 247 dph. Moreover, the oogonia entered meiosis and differentiated into chromatin-nucleolus stage oocytes until 247 dph, and subsequently into peri-nucleolus stage oocytes until 285 dph, whereas the type-A spermatogonia differentiated into type-B spermatogonia, spermatocytes, spermatids, and spermatozoa from 446 dph onwards. We believe the results of this study provide the necessary basis for future studies on sterile PBT production.

A resected case of focal autoimmune pancreatitis with pancreatic duct wall thickening representing periductal lymphoplasmacytic infiltrate.

This case revealed that branch pancreatic duct wall thickening by endoscopic ultrasonography represented periductal lymphoplasmacytic infiltrate as a characteristic histopathological finding of autoimmune pancreatitis, which may help in the diagnosis of autoimmune pancreatitis. An 80-year-old man was referred because fluorodeoxyglucose-positron emission tomography for lung cancer indicated abnormal uptake in the pancreatic head. Computed tomography showed an enhanced mass with cystic structures in the pancreatic head. Magnetic resonance cholangiopancreatography revealed mild dilatation of the main pancreatic duct in the pancreatic body with no strictures. Endoscopic ultrasonography demonstrated a lobulated heterogeneous hypoechoic mass in the pancreatic head. A branch pancreatic duct with wall thickening connected the mass to the main pancreatic duct. An intraductal neoplasm filling and spreading into the branch pancreatic duct was considered, and surgery was performed. Histopathologically, the mass consisted of marked inflammatory cell infiltration, storiform fibrosis, and obliterative phlebitis. The branch pancreatic duct with wall thickening revealed a band-like inflammatory cell infiltration with mainly lymphocytes and plasma cells beneath the normal pancreatic duct epithelium. Immunohistological staining revealed abundant IgG4-positive plasma cells (> 10 cells/HPF) in the inflammatory cell infiltration. The definite diagnosis was type 1 focal autoimmune pancreatitis.

Emphysematous cystitis in a patient with type 2 diabetes mellitus.

A 62-year-old woman with a history of poorly controlled type 2 diabetes mellitus was admitted to our hospital with a 3-week history of mild fever, vomiting, and anorexia. Abdominal computed tomography (CT) showed bilateral hydronephrosis and gas accumulation in the urinary bladder wall and left ureter. Laboratory tests showed leukocytosis and elevated C-reactive protein level. Urine culture showed heavy growth of Escherichia coli. The final diagnosis was emphysematous cystitis. The patient was treated with systemic antibiotics and drainage using a urethral catheter. The clinical and radiographic findings resolved rapidly, and she was discharged from the hospital on day 28. Emphysematous cystitis is a relatively rare urinary tract infection associated with gas formation, and has the potential for a serious outcome if untreated. Early detection by imaging studies such as CT is important in providing prompt treatment and favorable clinical outcome.

Multifocal granular cell tumors of the gastrointestinal tract: Immunohistochemical findings compared with those of solitary tumors.

Granular cell tumors (GCT) are infrequently found in the gastrointestinal tract (GIT), and only four previous reports have described lesions occurring simultaneously in different sites. The present case of 11 GCT, located in the esophagus, stomach, colon and pericolic adipose tissue, occurred in a 50-year-old Japanese woman. All GCT appeared histologically benign and there was no sign of recurrence at 3 years after surgery. Immunohistochemical analysis and comparison between this case of multifocal GCT and six cases of solitary benign GCT of the GIT, which were taken from the files of the Department of Pathology at Kitasato University (1986-2000), demonstrated the follow-ing: (1) all diffusely expressed S-100, DCC and bcl-2, and (2) median labeling indices for Ki-67, cyclin D1, p53 (Pab1801), and p21WAF1/CIP1 of 4%, 24%, 1% and 28%, respectively, for the multifocal tumors, and 3.5%, 23%, 1% and 29%, respectively, for the solitary lesions, with no significant difference between the two groups. Thus, the expression of cyclin D1 and p21WAF1/CIP1 may be involved in the tumorigenesis of both types of GCT. The present case emphasizes the need to evaluate the entire GIT when a single GCT is identified. Multifocal lesions should be treated conservatively by local excision because, as with the solitary tumors, they exhibit a benign biological behavior, consistent with their low Ki-67 immunoreactivity.

A case of mixed connective tissue disease presenting with nephrotic syndrome.

A 70-year-old woman was admitted to our hospital for the treatment of diffuse scleroderma and marked edema in the lower extremities. Renal biopsy revealed membranous change, interstitial nephritis, and intimal hyperplasia of the small arteries. The patient was diagnosed as having mixed connective tissue disease (MCTD) presenting with nephrotic syndrome (NS). She responded well to a combination treatment consisting of methylprednisolone (m-PSL) pulse therapy, oral PSL, and cyclosporine A (CsA). We speculated on the actual pathogenesis of NS in this case of MCTD.