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T Masaki

Publications and source records attributed to T Masaki.

At least 181 records · Page 10Linked to original sources
PubMed1998

Novel mutations of the endothelin B receptor gene in patients with Hirschsprung's disease and their characterization.

Hirschsprung's disease (HSCR) is a congenital intestinal disease, characterized by the absence of ganglion cells in the distal portion of the intestinal tract. Recently, three susceptibility genes have been identified in HSCR, namely the RET protooncogene, the endothelin B (ETB) receptor gene (EDNRB), and the endothelin-3 (ET-3) gene (EDN3). To investigate whether mutations in EDNRB could be related with HSCR in non-inbred populations in Japan, we examined alterations of the gene in 31 isolated patients. Three novel mutations were detected as follows: two transversions, A to T and C to A at nucleotides 311 (N104I) and 1170 (S390R), respectively, and a transition, T to C at nucleotide 325 (C109R). To analyze functions of these mutant receptors, they were expressed in Chinese hamster ovary cells. S390R mutation did not change the binding affinities but caused the decreases in the ligand-induced increment of intracellular calcium and in the inhibition of adenylyl cyclase activity, showing the impairment of the intracellular signaling. C109R receptors were proved to be localized near the nuclei as an unusual 44-kDa protein with the extremely low affinity to endothelin-1 (ET-1) and not to be translocated into the plasma membrane. On the other hand, N104I receptors showed almost the same binding affinities and functional properties as those of the wild type. Therefore, we conclude that S390R and C109R mutations could cause HSCR but that N104I mutation might be polymorphous.

Adenylyl Cyclase Inhibitors↗
PubMed1998

High affinity binding of oxidized LDL to mouse lectin-like oxidized LDL receptor (LOX-1).

We cloned mouse LOX-1 cDNA to take advantage of a gene-targeting technique to clarify the role of LOX-1 in vivo. Mouse LOX-1 was composed of 363 amino acids and had a C-type lectin domain type II membrane protein structure. Mouse LOX-1 had triple repeats of the sequence in the extracellular "Neck domain," which is unlike human and bovine LOX-1. LOX-1 bound oxidized LDL with two classes of binding affinity in the presence of serum. The binding component with the higher affinity showed the lowest value of Kd among the known receptors for oxidized LDL. In the absence of serum, the high affinity component disappeared, suggesting that an unknown co-factor in serum is essential for efficient uptake of oxidized LDL by endothelial cells. A low concentration of unlabeled oxidized LDL displaced 125I-labeled oxidized LDL more efficiently in the presence of serum than in the absence of serum. The co-factor in the serum may be involved in the pathophysiology of atherosclerosis in addition to the oxidation of LDL.

Amino Acid Sequence↗
PubMed1998

pp60c-src activation in hepatocellular carcinoma of humans and LEC rats.

For the related Src kinases, a close correlation exists between elevated tyrosine kinase activity and cell transformation. However, the involvement of pp60c-src in hepatocellular carcinoma (HCC) remains obscure. The aim of this study was to evaluate whether pp60c-src tyrosine kinase activity is elevated in HCC. We analyzed the kinase activity of pp60c-src in normal liver tissue, chronic hepatitis liver tissue, and tumorous and adjacent nontumorous portions of HCC tissue from patients and Long-Evans cinnamon (LEC) rats that are known to develop liver cancer spontaneously. The kinase activity of pp60c-src was rarely detected in the normal human liver tissue and chronic hepatitis liver tissue, but it was elevated in tumorous and nontumorous portions of HCC tissue. Furthermore, the kinase activity of pp60c-src was significantly elevated in tumorous tissues compared with nontumorous tissues. The kinase activity of pp60c-src was also higher in poorly differentiated HCC. In addition, the kinase activity of pp60c-src increased proportionately with the development of HCC of LEC rats. Our results suggest that activation of the protooncogene product pp60c-src may play an important role in the malignant transformation of hepatocytes in human and LEC rats, and that it may be closely related to the histopathological grading of human HCC.

Animals↗
PubMed1998

Role of p53 and p21/WAF1 detection in patient selection for preoperative radiotherapy in rectal cancer patients.

BACKGROUND: Recent studies showed that p53 and p21 may play major roles in determining tumor radiosensitivity through the apoptosis pathway. The aim of this study was to investigate the predicting value of radiosensitivity in human rectal carcinoma. METHODS: p53 and p21/WAF1 expressions in formalin fixed, paraffin-embedded, preradiation biopsy samples from 49 patients with primary rectal carcinoma were analyzed immunohistochemically. p53 and p21 expressions and their relationships with histopathologic changes after radiation and other clinical features were evaluated. RESULTS: Expressions of p53 and p21/WAF1 were 49 and 28.6 percent, respectively. In 36.7 percent of total tumors, significant histopathologic effect can be observed. There was a significant inverse expression of p53 and p21. Most of the p53(+) or p21(-) tumors were radioresistant, and the majority of p53(-) or p21(+) tumors were radiosensitive. Tumors size in the radiosensitive, p53(-), or p21(+) group decreased more significantly than in radioresistant, p53(+), or p21(-) group (P < 0.01), and patients with radioresistant, p53(+), or p21(-) tumors had more local recurrence, more distant metastasis, and a shorter five-year survival rate than those with radiosensitive, p53(-), or p21(+) tumors, but without statistic significance. No statistically significant correlation can be observed between other tumor clinical features and radiosensitivity, p53, or p21 expressions. CONCLUSION: Immunohistochemistry detection of p53 and p21 expressions may be useful parameters for more radiosensitive patients selected for preoperative radiotherapy.

Adult↗
PubMed1998

Differential diagnosis of dysplasia-associated lesion or mass and coincidental adenoma in ulcerative colitis.

PURPOSE: This study was undertaken to investigate factors that influenced differential diagnosis of dysplasia-associated lesion or mass and coincidental adenoma in patients with ulcerative colitis. METHODS: Among 346 patients with ulcerative colitis who underwent colonoscopy between 1979 and 1995, 27 patients had macroscopic neoplastic lesions and were divided into two groups: those with dysplasia-associated lesion or mass (16 patients) and those with adenoma (11 patients), each being categorized by the presence and absence of dysplasia in the flat mucosa adjacent to the elevated lesions, respectively. RESULTS: Thirteen of 27 patients had dysplasia-associated lesion or mass detected by colonoscopic biopsy; 10 of these patients underwent colectomy, and all had dysplasia-associated lesion or mass in the colectomy specimens. Two patients whose biopsy findings were adenoma had an unsuspected dysplasia-associated lesion or mass in the operative specimens. In the remaining 12 patients, the macroscopic lesions were excised during colonoscopy because of clinical and colonoscopic evidence of adenoma. One of them was proved to have dysplasia-associated lesion or mass, and the other 11 were confirmed as having adenoma in the polypectomy specimens. Patients with dysplasia-associated lesion or mass were significantly younger (P < 0.05), had longer duration of ulcerative colitis (P < 0.01), and had more extensive disease (P < 0.005) than those with adenoma. The colonoscopic appearance was plaque-like in 13, sessile in 13, and pedunculated in 2 of the 28 lesions with dysplasia-associated lesion or mass, whereas it was plaque-like in only 1 and sessile or pedunculated in 15 of the 16 lesions with adenoma (P < 0.001). The mean size of the lesions that were considered to be dysplasia-associated lesions or mass and adenoma was 1.8 and 0.5 cm, respectively (P < 0.0001). CONCLUSIONS: Colonoscopic biopsy for detection of dysplasia in the flat mucosa adjacent to macroscopic neoplastic lesions is an appropriate preoperative approach to distinguish dysplasia-associated lesions or mass from adenomas in patients with ulcerative colitis. The statistically significant variables that influenced the differential diagnosis were age, duration of disease, extent, tumor size, and tumor colonoscopic appearance.

Adenoma↗
PubMed1998

A schwannoma of the cecum: case report and review of Japanese schwannomas in the large intestine.

A 66-year-old Japanese man had a positive fecal occult blood test at a regular check-up, and a large polypoid mass was detected in the cecum by barium enema study. Colonoscopy showed a submucosal tumor with ulcer protruding into the cecal lumen. A large-forceps biopsy specimen was taken from the bottom of the ulcer. With the tentative diagnosis of neurogenic tumor, ileocecal resection was performed. The tumor showed spindle-cell proliferation in a concentric or fascicular pattern. Immunohistochemically, the tumor cells were diffusely positive for S-100 protein, and they had intracytoplasmic periodic acid Schiff (PAS)-positive crystalloids. The mitosis count was low (about 1 per 20 high-power fields). The pathological diagnosis of this tumor was benign gastrointestinal schwannoma. A large number of schwannoma cases have been reported since 1910 when Verocay reported it as a true tumor that stemmed from Schwann cells and did not contain neuroganglion cells. However, gastrointestinal schwannomas are rare, and schwannomas of the large intestine are extremely rare. We reviewed 40 cases already reported in Japan and this present case in order to clarify the clinicopathological features of this tumor.

Aged↗
PubMed1998

Per anal suturing of a bleeding ulcer to achieve successful hemostasis of massive hemorrhage associated with ulcerative colitis: report of two cases.

We report herein the cases of two patients with ulcerative colitis complicated by massive hemorrhage who were successfully treated by per anal suturing of a bleeding ulcer. A 40-year-old woman and a 22-year-old man had suffered from extensive colitis for 8 and 2 years, respectively, and both followed a similar clinical course. They were admitted under emergency conditions and, despite treatment with intravenous high-dose prednisolone and thereafter with intraarterial injections of prednisolone, suffered several attacks of massive hemorrhage with hypovolemic shock. Emergency subtotal colectomy with ileostomy and rectal mucous fistula were performed, but recurrent massive hemorrhage occurred during the early postoperative period. Bleeding from a discrete ulcer in the rectum was subsequently located, and both patients underwent per anal suturing of the ulcer. No recurrent bleeding occurred thereafter, and an ileoanal anastomosis was performed several months later. Massive hemorrhage is a rare complication of ulcerative colitis which is most often resolved by subtotal colectomy without proctectomy. Although bleeding associated with ulcerative colitis usually occurs diffusely, these case reports serve to demonstrate that massive bleeding can also result from a discrete ulcer. We advocate that this condition be treated by an endoscopic or local hemostatic procedure.

Adult↗
PubMed1998

Posttranslational modifications of endothelin receptor type B.

Endothelin receptor type B (ETb) is one of the two ET receptor subtypes, both of which belong to the G protein-coupled receptor (GPCR) superfamily. The primary amino acid sequence of ETb, published in 1990, predicted potential posttranslational modifications of the receptor protein, and in the last couple of years, we and others presented direct experimental evidence for palmitoylation and phosphorylation of ETb. Functional evaluation of both substitution and deletion mutants indicated a negative role on the part of these modifications in the ligand binding capacities and cellular sequestrations of the receptors. At least one of them, palmitoylation, however, appears to be critically involved in the coupling with G proteins.

Journal Article↗
PubMed1998

Activation of two types of Ca2+-permeable nonselective cation channel by endothelin-1 in A7r5 cells.

1. In A7r5 cells loaded with the Ca2+ indicator fura-2, we examined the effect of a Ca2+ channel blocker SK&F 96365 on increases in intracellular free Ca2+ concentrations ([Ca2+]i) and Mn2+ quenching of fura-2 fluorescence by endothelin-1 (ET-1). Whole-cell patch-clamp was also performed. 2. Higher concentrations (> or = 10 nM) of ET-1 (higher [ET-1]) evoked a transient peak and a subsequent sustained elevation in [Ca2+]i: removal of extracellular Ca2+ abolished only the latter. A blocker of L-type voltage-operated Ca2+ channel (VOC) nifedipine at 1 microM reduced the sustained phase to about 50%, which was partially sensitive to SK&F 96365 (30 microM). 3. Lower [ET-1] (< or = 1 nM) evoked only a sustained elevation in [Ca2+]i which depends on extracellular Ca2+. The elevation was partly sensitive to nifedipine but not SK&F 96365. 4. In the presence of 1 microM nifedipine, higher [ET-1] increased the rate of Mn2+ quenching but lower [ET-1] had little effect. 5. In whole-cell recordings, both lower and higher [ET-1] induced inward currents at a holding potential of -60 mV with linear I-V relationships and reversal potentials close to 0 mV. The current at lower [ET-1] was resistant to SK&F 96365 but was abolished by replacement of Ca2+ in the bath solution with Mn2+. The current at higher [ET-1] was abolished by the replacement plus SK&F 96365. 6. In a bath solution containing only Ca2+ as a movable cation, ET-1 evoked currents: the current at lower [ET-1] was sensitive to Mn2+, whereas that at higher [ET-1] was partly sensitive to SK&F 96365. 7. These results indicate that in addition to VOC, ET-1 activates two types of Ca2+-permeable nonselective cation channel depending on its concentrations which differ in terms of sensitivity to SK&F 96365 and permeability to Mn2+.

Animals↗
PubMed1998

Desensitization of ET(A) endothelin receptor-mediated negative chronotropic response in right atria--species difference and intracellular mechanisms.

1. Desensitization of ET(A) endothelin receptor (ET(A)R) was compared between the rat and guinea-pig with regard to negative chronotropic response (NC) in the right atria (RA). 2. ET-1 (100 nM) produced distinct NC in the presence of BQ788 (300 nM), and positive chronotropic response (PC) in the presence of BQ123 (1 microM) in both species, showing that ETAR and ET(B) endothelin receptor (ET(B)R) mediate NC and PC, respectively. 3. Repetitive applications of ET-1 (50 nM) desensitized PC, and the second application only induced a strong NC in both species. Later applications of ET-1 produced virtually no response in the rat RA, whereas they produced BQ123-sensitive NCs repetitively in guinea-pig RA, exhibiting marked species difference in desensitization of ETAR-mediated NC. 4. Pretreatment with staurosporine (100 nM) prevented desensitization of ET(A)R in the rat RA altogether. However, phorbol 12-myristate 13-acetate (PMA, 300 nM) failed to induce, but rather hampered, desensitization of ET(A)R. 5. Partial amino acid sequencing of ET(A)Rs, spanning from the 2nd through the 4th intracellular loops, revealed that all the potential Ser/Thr phosphorylation sites, including a protein kinase C (PKC) site, are conserved among guinea-pigs, rats, rabbits, bovines and humans. 6. In guinea pig RA, pretreatment with okadaic acid (1 microg ml(-1)) and PMA did not facilitate desensitization of ET(A)R whereas these agents successfully desensitized ETAR during combined stimulation of beta-adrenoceptor and ET(A)R by isoproterenol (300 nM) and ET-1 (100 nM). 7. These results suggest that species differences in desensitization of ET(A)R are not caused by differences in the site(s) of, but caused by differences in the environment for phosphorylation of the receptor. Desensitization of ET(A)R appears to require phosphorylation of the receptor by PKC as well as a kinase stimulated by beta-adrenoceptor activation.

Animals↗
PubMed1998

GC/MS analysis of urinary excretion of 9alpha,11beta-PGF2 in acute and exercise-induced asthma in children.

BACKGROUND: 9Alpha,11beta-prostaglandin (PG) F2 is an initial metabolite of PGD2 which has a potent bronchoconstrictive activity. OBJECTIVES: We measured the urinary levels of 9alpha,11beta-PGF2 in asthmatic children to investigate its role in not only acute asthmatic attack in a time course study but also in exercise-induced asthma (EIA). METHODS: In the acute asthma study, 30 asthmatic children were examined. Urine samples were collected on the first, third, and sixth days. Urinary levels of 9alpha,11beta-PGF2 were measured with gas chromatography mass spectrometry using the electron impact method. In the exercise challenge study, 14 children with EIA and 14 children without EIA were studied. Urine samples were collected before exercise challenge, and at 1 h, and 5 h after exercise challenge. Urinary levels of 9alpha,11beta-PGF2 were measured. RESULTS: Elevated urinary levels of 9alpha,11beta-PGF2, which were observed on the first day when treatment was started in the hospital, were gradually decreased on the third day (P < 0.05), and on the sixth day (P < 0.01). A significant correlation between urinary levels of 9alpha,11beta-PGF2 and symptom scores (P < 0.005) was observed on the first day. In EIA, there was a significant increase in urinary levels of 9alpha,11beta-PGF2 at 1 h (P < 0.01) and at 5 h (P < 0.01) after exercise challenge, but not in the children without EIA. CONCLUSION: 9Alpha,11beta-PGF2 may be involved in the pathogenesis of acute and exercise-induced asthma in children.

Acute Disease↗
PubMed1998

Outcome of local excision for locally invasive rectal carcinomas with special reference to histological features at the invasive margin.

BACKGROUND: Several researchers reported promising results that local excision with or without postoperative chemo-radiation therapy is an alternative approach for sphincter preservation in patients with locally invasive rectal carcinomas. However, indications and long-term results have not yet been determined. METHODS: Demographic and pathological characteristics of eight patients with locally invasive tumors undergoing initially local excision were reviewed with reference to histological features at the invasive margin. RESULTS: All the tumors were well differentiated adenocarcinomas. In all but two tumors, the invasion was limited within the proper muscle layer. Radiation therapy was given preoperatively in one patient and postoperatively in two patients. Additional bowel resection was not attempted in these three cases. Among the remaining five patients, two received additional bowel resection with lymph node dissection. No lymph node metastasis was observed in these two patients. During the average follow-up period of 55 months, three patients had regional lymph node metastases at 7, 36 and 72 months, respectively. Another patient had regional lymph node and distant metastases at 5 months. Three out of five patients with moderate to severe grade of dedifferentiated histology at the invasive margin (H-inv) had regional lymph node metastases. On the other hand, one out of three patients with mild H-inv had lymph node metastases. CONCLUSIONS: H-inv may be useful as a clinical predictor of lymph node metastasis. However, more experience is needed to confirm the usefulness of H-inv in selecting invasive rectal cancer patients in whom local excision is safe and appropriate.

Adenocarcinoma↗
PubMed1998

Characteristics in primary signet-ring cell carcinoma of the colorectum, from clinicopathological observations.

BACKGROUND: The biological behavior of signet-ring cell carcinomas in colorectum tends to be worse than that of mucinous carcinomas. However, in previous studies, clinicopathological features of this disease have been somewhat ill-defined because various histological criteria of this disease were adopted. METHODS: We selected 11 cases of signet-ring cell carcinomas and 29 cases of mucinous carcinomas among 1595 consecutive colorectal carcinomas on defined criteria and compared clinicopathological and molecular biological features between these two types of carcinomas. RESULTS: Clinical staging of signet-ring cell carcinomas were far advanced and their prognosis tended to be worse than that of mucinous carcinomas. Furthermore, the incidence of K-ras mutations in signet-ring cell and mucinous carcinomas showed no difference between these two types of carcinomas. However, the incidence of K-ras mutation in these diseases was slightly lower than that in 30 ordinary colorectal carcinomas examined as a comparison. CONCLUSIONS: These results suggest that the carcinogenesis of signet-ring cell and mucinous carcinomas are different from that of ordinary colorectal carcinomas and that there may exist other genes related to malignancy of signet-ring cell carcinomas.

Adenocarcinoma, Mucinous↗
PubMed1998

Microsatellite instability is associated with the macroscopic configuration of neoplasms in patients with multiple colorectal adenomas.

BACKGROUND: The management of patients with multiple colorectal adenomas, 10-100 in number, is often troublesome clinically. To establish the reasonable management of such cases, genetic backgrounds should be made clear. METHODS: For a total of 19 adenomas and four carcinomas from four patients with multiple colorectal adenomas, we analyzed genetic instability at four selected microsatellite loci and screened exon 1-4 of the APC gene with special reference to macroscopic configurations of adenomas and carcinomas. RESULTS: RER-positive phenotypes were detected in none of 13 protruded type adenomas, two (33%) out of six superficial elevated type adenomas and two (50%) out of four carcinomas. We detected no mutation of exon 1-4 of the APC gene in any sample. In patients with multiple colorectral adenomas, the proportion of superficial elevated type adenomas exhibiting genetic instability was significantly higher than that of protruded type adenomas. CONCLUSIONS: The results suggested that RER-positive phenotype was an early event in tumorigenesis through superficial elevated type adenomas.

Adenoma↗
PubMed1998

The processing pathway of endothelin-1 production.

Production of endothelin (ET-1) is believed to be a three-step process, consisting of an initial proteolytic cleavage by signal peptidase of preproET-1, a second cleavage of proET-1 to big ET-1-Lys-Arg by dibasic amino acid-specific convertase and C-terminal trimming, and finally the processing of Big ET-1 to ET-1 by endothelin-converting enzyme (ECE). To clarify the relationships between the second processing step and the third, we introduced point mutation into ET-1 cDNA to replace the Arg in the -4 position of the recognition motifs of furin-like convertase in human preproET-1 (Arg49 or Arg89) by Gly. When mutant cDNAs were expressed in CHO-K1 cells, they failed to be processed at the mutated processing signal, suggesting the involvement of the enzyme with furin-like specificity in the processing at dibasic amino acid motifs. Co-transfection of mutant preproET-1 cDNA and ECE-1 cDNA revealed that cleavage at Arg92 is essential for cleavage by ECE-1 but that cleavage at Arg52 is not. Although without cleavage at Arg52 a high molecular weight form of ET-1, designated Large ET-1, is produced by processing by ECE-1, it did not evoke a Ca2+ transient in ETA receptor-expressing cells. In conclusion, the cleavage by furin-like convertase is essential for the production of active ET-1.

Animals↗
PubMed1998

Cysteine residues in the carboxyl terminal domain of the endothelin-B receptor are required for coupling with G-proteins.

We demonstrate that the human endothelin-B (ETB) receptor incorporates [3H]palmitic acid. Mutation of three putative palmitoylated cysteine residues (amino acids 402, 403 and 405) in the carboxyl terminus into serine residues (C2/3/5S) completely prevented palmitoylation of ETB. When expressed in CHO cells, C2/3/5S was localized on the cell surface, retained high affinity for ET-1 and ET-3, and was rapidly internalized when bound to the ligand. However, unlike the wild-type ETB, C2/3/5S transmitted neither an inhibitory effect on adenylate cyclase nor a stimulatory effect on phospholipase C, indicating a critical role of palmitoylation in the coupling with G-proteins, regardless of the G-protein subtype. Truncation of the carboxyl terminus, including all or a part of the three cysteine residues, gave palmitoylation-negative and -positive deletion mutants, delta 402 and delta 403. Despite the absence of the cytoplasmic tail, both delta 402 and delta 403 showed essentially the same features as C2/3/5S, except that delta 403 did transmit a stimulatory effect on phospholipase C via a pertussis toxin-insensitive G-protein, most likely a member(s) of the Gq family. These results indicated a differential requirement for the carboxyl terminus downstream from the palmitoylation site in the coupling with G-protein subtypes, i.e., it is required for the coupling with Gi but not for that with Gq.

Animals↗