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Biomedical subjects

K Takasu

Publications and source records attributed to K Takasu.

At least 19 recordsLinked to original sources
PubMed2001

Facile and stereoselective access to nonracemic tricyclic cyclobutanes by asymmetric intramolecular Michael-aldol reaction: thermodynamic equilibrium and activation by iodonium ion.

Intramolecular Michael-aldol reactions of (-)-phenylmenthyl enoates tethered to cycloalkanone affords tricyclic cyclobutanes with high degrees of diastereochemical control. Kinetic and thermodynamic studies revealed that the Michael-aldol reaction is reversible under conditions in which trimethylsilyl iodide is used in the presence of hexamethyldisilazane at ambient temperature. Different levels of diastereoselectivity are observed when this cyclization process is carried out under kinetic vs thermodynamic conditions. Finally, an influence of added iodonium donors on the reaction rate has been noted.

Journal Article↗
PubMed2000

Novel intramolecular (4 + 1) and (4 + 2) annulations of halopolyenes by cascade radical reaction

Free radical reaction of vinyl iodides having dinenoate function in the presence of tributyltin hydride or tris(trimethylsilyl)silane caused a sequential cyclization reaction to produce (4 + 1) and (4 + 2) annulated compounds by means of a cascade radical reaction. Stereogenic centers of the cascade reaction were highly controlled. On the contrary, the cathodic electrolysis of the vinyl iodides afforded monocyclic compounds.

Journal Article↗
PubMed2000

Total synthesis of (+/-)-culmorin and (+/-)-longiborneol: an efficient construction of Tricyclo[6.3.0.0(3,9)]undecan-10-one by intramolecular double Michael addition.

The treatment of 4-[(5E)-6-methoxycarbonyl-5-hexenyl]-3, 4-dimethyl-2-cyclopenten-1-one (5) with LHMDS, TMSI-HMDS, Bu(2)OTf-HMDS, or TMSCl-NEt(3)-ZnCl(2) caused the intramolecular double Michael addition to afford tricyclo[6.3.0.0(3, 9)]undecan-10-one 12 in high yields with perfect stereoselectivity. The methodology was further elaborated to achieve efficient total syntheses of (+/-)-culmorin (1) and (+/-)-longiborneol (2). The common precursor 13 of them was obtained from 14 in 94% yield as a single isomer by the treatment with LHMDS. After the conversion of 13 into the corresponding acid 24 by hydrolysis, oxidative decarboxylation using S-(1-oxido-2-pyridinyl)-1,1,3, 3-tetramethylthiouronium hexafluorophosphate (HOTT, 27), followed by the Birch reduction, stereoselectively afforded (+/-)-culmorin (1). (+/-)-Longiborneol (2) was synthesized from 24 by the standard transformation. Additionally, the treatment of 24 with Pb(OAc)(4) led to 28 via uncommon migration. Its structure was determined by X-ray analysis after the transformation into the diketone 29.

Computer Graphics↗
PubMed2000

Primary malignant melanoma of the male urethra.

BACKGROUND: We describe a rare case of malignant melanoma originating from the male urethra. METHODS/RESULTS: This case, which presented a tan-colored lesion at the distal urethra on urethroscopy, was considered as transitional cell carcinoma by transurethral biopsy. Pathologic examination of widely resected urethra revealed scattering cells, which included melanin granules in cytoplasm, and then immunohistochemical stains established the diagnosis as amelanotic melanoma. Although partial penectomy and inguinal lymph node dissection were subsequently performed, 7 months later, total cystourethrectomy was required because of multifocal recurrence at the residual urethra. CONCLUSIONS: In cases of amelanotic melanoma, it should be noted that a lack of melanin granules in tumor cells may lead pathologists and urologists to a misdiagnosis due to the histologic non-specific appearance. With respect to surgical management, of significance is the fact that malignant melanoma may progress multifocally along the total urethra; therefore, total urethrectomy should be considered as radical surgery for the primary site, even if the tumor is confined to the distal urethra.

Humans↗
PubMed2000

[Papillary adenocarcinoma of the prostate: report of 3 cases].

We report here 3 cases of papillary adenocarcinoma of the prostate. In all 3 cases, the tumors were discernible on cystourethroscopy and transurethral biopsy established the diagnosis, whereas no significant finding was found on digital rectal examination. Although androgen deprivation therapy was administered in all cases, different surgical procedures were employed according to the stage in each case. In case 1, since the papillary tumor was confined within the prostatic urethra, complete resection was accomplished by transurethral resection (TUR). In case 2, since pelvic lymph nodes metastases were found, local radiation therapy was added. In case 3, since the patient had vesical invasion of tumor total cysto-prostatectomy was performed. Papillary adenocarcinoma of the prostate originates from the prostatic duct, resulting in existence at the "central portion" of the prostate gland. Cystourethroscopy and transurethral biopsy is helpful for diagnosis of this disease, whereas rectal digital examination is useless. As a surgical procedure for the primary site, TUR may be efficient for tumors confined within the prostatic urethra, although more extensive surgery may be necessary for those with a more invasive profile.

Adenocarcinoma, Papillary↗
PubMed1998

Immunohistochemical evidence of the mesothelial histogenesis of a uterine adenomatoid tumor.

We present rare case of a uterine adenomatoid tumor. In order to characterize the diversity of immunoreactive antigens associated with mesothelial differentiation, we immunohistochemically examined the tumor's epithelioid and myofibromatoid components, as well as the biphasic pattern of its adenomatoid changes. Immunostaining of tumor cells was positive for high- and low-molecular-weight cytokeratins and vimentin. Specific immunoreactions with antibodies against desmin, alpha-actin, and the S-100 protein also were observed. The present adenomatoid tumor can be explained in terms of various transformations and typical alterations in mesothelioma cells: (1) the mesothelial cells had differentiated to epithelial and stromal components, concomitant with the presence of predominant reactive foci; (2) intermediate cells expressed different types of cytoskeletal intermediate filament proteins (IMPs); and (3) the patterns of fibromatoid and leiomyoid differentiation resembled those of a benign mesothelioma of the ovarian or oviductal peritoneum. Our immunohistochemical investigations indicated that the present tumor exhibited the histogenesis of a true mesothelioma, an adenomatoid mesothelioma.

Actins↗
PubMed1997

[Immunohistochemical study of thymidine phosphorylase in uterine cervical intraepithelial neoplasia].

Studies have shown that thymidine phosphorylase (TdRPase) activity in various tumors is higher than that in normal tissues. We studied the immunohistochemical localization of TdRPase in uterine cervical intraepithelial neoplasia (CIN) using monoclonal antibody against TdRPase. Sixty-nine patients were studied: CIN 1, 14; CIN 2, 15; CIN 3 (severe dysplasia), 23; CIN 3 (carcinoma in situ), 17. Immunoreactivity for TdRPase was found in 29% of CIN 1, 40% of CIN 2, 70% of CIN 3 (severe dysplasia), and 88% of CIN 3 (carcinoma in situ), showing increasing incidence with the progression of tumor grade. Furthermore, in higher grade tumor, more immunoreactive cells were found with increased intensity of immunoreaction. Both nucleus and cytoplasm of atypical cells showed immunoreactivity in most TdRPase positive cases, while either nucleus or cytoplasm was positive in a few cases. The stromal tissues were negative for the antibody except 3 cases of CIN 3 (carcinoma in situ) in which the stromal tissues adjacent to the tumor was positive. Our data suggest that immunoreactivity of TdRPase in CIN may correlate with the grade of CIN.

Biomarkers, Tumor↗
PubMed1995

Three cases of primary hyperparathyroidism associated with nonmedullary thyroid carcinoma.

Nonmedullary thyroid carcinoma was diagnosed in three of nine cases of primary hyperparathyroidism. In all three cases, diagnosis of primary hyperparathyroidism was made before that of thyroid carcinoma. In the first case, follicular carcinoma was incidentally detected during parathyroidectomy. In the second case, thyroid tumor was discovered during imaging studies for hyperparathyroidism. Papillary carcinoma and ectopic parathyroid was diagnosed postoperatively. In the third case, a thyroid lesion had been mistaken for a putative parathyroid lesion, but the diagnosis of papillary carcinoma was obtained. These cases suggest that preoperative examination for hyperparathyroidism should be carefully evaluated, considering possible concomitant thyroid lesions.

Adenocarcinoma↗
PubMed1994

Presacral epidermal cyst found in an adult male with a high CEA content: report of an unusual case.

A 63-year-old Japanese man presented with constipation, having noticed flat stools for several years. Digital examination of the rectum, followed by barium enema, colono-fiberscopy, computed tomography (CT), and magnetic resonance imaging (MRI) revealed an oval mass located between the retrorectal and presacral space without any mucosal lesion. This mass had narrowed the rectal lumen by compressing the rectum anteriorly. Although the plasma levels of the tumor markers were within the normal range, those of the tumor contents were elevated with a carcinoembryonic antigen (CEA) of 118 ng/mL, while the alpha-fetoprotein (AFP) value was 1 ng/mL. The tumor was completely extirpated through an abdominal incision, and there has been no evidence of recurrence thus far. Histological examination showed that the tumor wall was made of keratinized stratified squamous epithelium without any cutaneous adnexal structure, and hence it was diagnosed as an epidermal cyst. CEA was identified in these benign epithelial cells by immunoperoxidase staining using a monoclonal antibody. To the best of our knowledge, there have been only four other cases with a presacral epidermal cyst documented in the Japanese literature, all of whom were female. Our patient is the first reported case of an adult male with a presacral epidermal cyst.

Carcinoembryonic Antigen↗
PubMed1994

[An autopsy case of adenosquamous cell carcinoma of the extrahepatic bile duct with endobronchial mass obstructing the left main bronchus and masquerading as asthma].

A 65-year-old male was admitted with diagnosis of bronchial asthma. On admission, he was orthopneic, cyanotic and distressed. Marked hypoxemia with PaO2 of 31.1 mmHg was noted, but no obvious localized airway obstruction on plain chest X-ray film could be detected. These was minimal response to intensive treatment with steroid in addition to various bronchodilators on the presumed diagnosis of bronchial asthma. Two weeks later, chest X-ray disclosed complete atelectasis of the left lung. Stenosis of the left main bronchus with enlarged mediastinal lymph nodes on chest CT was suggested. Endoscopic examination disclosed complete obstruction of the left main bronchus just beyond the carina and polypoid tumors in the right main bronchus and basal segment bronchus. The biopsy specimens revealed squamous cell carcinoma. Chemotherapy with CDDP and VDS resulted in disappearance of atelectasis after one week and marked relief of respiratory distress. Four months later, at the completion of irradiation therapy, an abdominal tumor associated with pain appeared and bone scintigram showed multiple bone metastases. After four times chemotherapy including CDDP, hypercalcemia and renal hypofunction developed, and the patient died. Autopsy disclosed a tumor in the extrahepatic bile duct, cystic lesions of the pancreas and swelling of subcarinal lymph nodes, but no tumorous lesion in the lung and endobronchial tissue. Histological examination of the extrahepatic bile duct tumor revealed adenosquamous cell carcinoma, with predominantly squamous cell carcinoma. Other metastatic lesions consisted of squamous cell carcinoma. These findings are compatible with pulmonary metastases of adenosquamous cell carcinoma of the extrahepatic bile duct.

Aged↗
PubMed1992

Tyrosine-7 in human class Pi glutathione S-transferase is important for lowering the pKa of the thiol group of glutathione in the enzyme-glutathione complex.

Previously, we reported the importance of Tyr7 for the catalytic activity of human class Pi glutathione S-transferase [Kong et al. (1992) Biochem. Biophys. Res. Comm., 182, 1122]. As an extension of this study, we investigated the pH dependence of kinetic parameters of the wild-type enzyme and the Y7F mutant. The replacement of Tyr7 with phenylalanine was found to alter the pH dependence of Vmax and Vmax/KmCDNB of the enzyme for conjugation of GSH with 1-chloro-2,4-dinitrobenzene (CDNB). The pKa of the thiol of GSH in the wild-type enzyme-GSH complex was estimated to be about 2.4 pK units lower than that in the Y7F-GSH complex. Tyr7 is thus considered to be important for catalytic activity in lowering the pKa of the thiol of GSH in the enzyme-GSH complex.

Amino Acid Sequence↗
PubMed1992

Metastatic renal cell carcinoma to the pituitary gland presenting with hypopituitarism.

A 57-year-old man with pituitary metastasis from renal cell carcinoma is reported. He underwent right nephrectomy and total pancreatectomy for renal cell carcinoma and its pancreatic metastasis, respectively. Imaging studies showed an intrasellar mass lesion. The examination revealed panhypopituitarism, diabetes insipidus and bitemporal hemianospia. Metastatic renal cell carcinoma was diagnosed by the biopsy of the pituitary tumor. Metastatic renal cell carcinoma to the pituitary gland, which is extremely rare, appears to have unique features of presenting with hypopituitarism and visual disturbance more frequently than other metastatic pituitary tumors.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

[A case report of the limited form Wegener's granulomatosis].

The classical from of Wegener's granulomatosis (WG) is a necrotizing granulomatous angiitis that involves the upper and lower airways, and kidneys. A limited form of WG is characterized by pulmonary lesions identical to those of classical form WG without renal involvement. The authors report a case of limited form WG. A 58-year-old Japanese woman was admitted because of an abnormal pulmonary shadow. Pathological examination revealed granulomatous angiitis consistent with WG. No other organ involvement was found. The pulmonary shadow improved with cyclophosphamide therapy. The patient is now well and without evidence of exacerbation of the disease 18 month after the discharge.

Cyclophosphamide↗
PubMed1990

[Cytological and immunocytochemical study of prostatic carcinoma cell in voided urine. Usefulness of prostate-specific antigen in cytology specimen].

The presence of prostatic carcinoma cells in voided urine was seldom noticed and these cells might be hardly distinguished from transitional cell carcinoma cells of the urinary tracts on the Papanicolaou-stained slides. We investigated the cytological findings and the localizations of prostate-specific antigen (PSA) in 7 cases of prostatic carcinomas (4 adenocarcinomas, 2 squamous cell carcinomas, and 1 undifferentiated carcinoma) which showed tumor cells in voided urine. The cytological findings of each histological types were as follows: adenocarcinoma cells were observed in small clusters of round or columnar cells with eccentric nuclei and prominent nucleoli with occasion, squamous cell carcinoma cells were characteristically well-differentiated keratinizing ones varying in shape and in staining reaction, and undifferentiated carcinoma cells were polyhedral and large ones with dense cytoplasm. After destaining of the Papanicolaou-stained slides, the positivity for PSA was demonstrated by immunocytochemical stain with PSA antiserum in cytoplasms of the tumor cells of 6 cases except for 1 undifferentiated carcinoma. We recognized that immunocytochemical detection of PSA was a useful mean in cytological detection for prostatic carcinomas in voided urine.

Adenocarcinoma↗