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Hiroyuki Yamamoto

Publications and source records attributed to Hiroyuki Yamamoto.

116 records · Page 7Linked to original sources
PubMed2002

Mutated alleles of the rod and cone Na-Ca+K-exchanger genes in patients with retinal diseases.

PURPOSE: To study the possible involvement of the rod (SLC24A1) and cone (SLC24A2) Na-Ca+K exchanger (NCKX) genes in retinal diseases. METHODS: DNA was collected from unrelated patients with retinal disease, mainly from North America. A human genomic library was screened with the cone NCKX cDNA, and hybridizing clones were sequenced to determine the genomic organization of the SLC24A2 gene. The single-strand conformation polymorphism (SSCP) technique and direct sequencing were used to screen the patients' DNA for mutations in SLC24A1 and SLC24A2. The effect of selected missense changes on protein function was tested by measuring potassium-dependent Na-Ca exchange of the mutant proteins expressed in insect cells. RESULTS: Twenty-seven novel sequence changes were found in the rod NCKX gene, 21 of which are unlikely to be pathogenic, because they did not cosegregate with the disease or did not affect conserved regions of the protein. Of the remaining six, two were frameshift mutations found in one patient each. If translated, these alleles would encode nonfunctional proteins. Three of the six possibly pathogenic mutations were missense changes located in conserved regions, and their protein functions were assayed. Only one (Ile992Thr) had a significantly low level of exchanger function, but it was found in two unrelated patients who were heterozygotes with different retinal diseases, and this mutation could not be unequivocally associated with either disease. The last of the six changes is likely to create a new splice acceptor site. The genomic organization of the cone NCKX gene was determined, and it contained 11 exons with a few splice variants. Fifteen novel sequence changes were identified in the cone exchanger gene in patients with a cone dysfunction or degeneration. Only three of these sequence changes, all missense changes found in heterozygous patients, were considered possibly pathogenic. Functional analysis showed only a slight reduction in the activity of the corresponding mutant proteins. CONCLUSIONS: Although variant alleles of the rod and cone NCKX genes were found, none could be definitively associated with a specific retinal disease. The human phenotype associated with mutant exchanger alleles remains unknown.

Alleles↗
PubMed2002

[A case of follicular lymphoma derived from the conjunctiva].

BACKGROUND: Follicular lymphoma, derived from ocular adnexa as defined by World Health Organization Classification of neoplastic diseases of the hematopoietic and lymphoid tissues, is quite rare in Japan. CASE: A 65-year-old woman visited our clinic for treatment of a conjunctival tumor in the left eye. FINDINGS: Incisional biopsy revealed that the lesion was a lymphoma with well-defined follicles, and it was L 26(CD20) and BCL-2 positive immunohistochemically. Flow cytometric analysis showed that more than 70% of the cells were double positive for CD10 and CD20. Southern blot hybridization demonstrated gene rearrangement bands in the immunoglobulin gene JH region. The chromosome had a translocation t(14, 18) (q32, q21). Systemic evaluation detected no other lymphoma. CONCLUSION: The lesion was a follicular lymphoma derived from conjunctival tissue. Additional examinations such as flow cytometric analysis, gene analysis, and chromosome examination were useful for differential diagnosis of marginal zone B cell lymphoma of mucosa associated lymphoid tissue type and benign reactive lymphoid hyperplasia.

Aged↗
PubMedDate not supplied

Quinone cross-linked polysaccharide hybrid fiber.

The present article describes the synthesis of the N-(Lys-Gly-Tyr-Gly)-chitosan using the water-soluble active ester method, the preparation of the N-(Lys-Gly-Tyr-Gly)-chitosan-gellan hybrid fibers, and the reinforcement of the hybrid fibers by enzymatic cross-linking between the N-grafted peptides chains of chitosan. The cationic polysaccharide chitosan was treated with Boc-Lys(Z)-Gly-Tyr(Bzl)-Gly (4-hydroxyphenyl)dimethylsulfonium methyl sulfate ester in DMF-0.15 M acetic acid to incorporate the peptides into the side chain amino groups of chitosan followed by the acidic removals of the Z and Bzl groups. The degrees of N substitution were estimated to be 2.0 and 10 molar % by changing the molar ratios of the amino groups of the parent chitosan and the active ester. The resulting cationic N-(Lys-Gly-Tyr-Gly)-chitosan was spun into the hybrid fibers with the anionic polysaccharide gellan in water. The tensile strengths of the N-(Lys-Gly-Tyr-Gly)-chitosan hybrid fibers were superior to those of the original chitosan-gellan fibers. The mechanical strengths of the hybrid fibers further increased upon enzymatic oxidation using tyrosinase. Based on these results, we concluded that the covalent cross-linking due to the enzyme oxidation between the grafted peptides significantly contributed to reinforcement of the polysaccharide hybrid fibers. The present results afford a new methodology for the reinforcement achieved by the polymer modification inspired by a biological process.

Benzoquinones↗
PubMedDate not supplied

Cytologic features of atypical polypoid adenomyoma of the endometrium. A case report.

BACKGROUND: In 1981, Mazur reported the histologic characteristics of atypical polypoid adenomyoma (APA) of the endometrium. Although most APAs of the endometrium are considered to show benign behavior, there is a small associated risk of the development of adenocarcinoma. The histology of APA of the endometrium is well defined, but the cytologic features of the lesion have not yet been clarified. CASE: A 28-year-old nulligravida with hypermenorrhea had an exophytic, polypoid mass arising from the posterior uterine wall on ultrasonography and magnetic resonance imaging. The results of endometrial smear and biopsy were normal. Transcervical total resection of the tumor was performed with a resectoscope. Frozen sections of the sample suggested APA of the endometrium, and the permanent sections confirmed the diagnosis. The tumor stump/resection plane smears revealed overlapping, highly atypical glandular cells with enlarged, hyperchromatic nuclei; squamous metaplastic cells; and abundant, spindled smooth muscle cells on a clear background, effectively reflecting the epithelial and mesenchymal cell components of the lesion. CONCLUSION: Endometrial smear and biopsy are inaccurate methods for the diagnosis of APA of the endometrium because of limited sampling. Tumor stump/resection plane cytology appears to be useful for detecting APA of the endometrium.

Actins↗
PubMedDate not supplied

Differential roles of alterations of p53, p16, and SMAD4 expression in the progression of intraductal papillary-mucinous tumors of the pancreas.

Intraductal papillary-mucinous tumors (IPMTs) of the pancreas are characterized by dilated pancreatic ducts and ductules that are lined by tall columnar mucin-producing neoplastic epithelial cells. IPMTs have been suggested to be distinct neoplasms with a less aggressive phenotype than that of conventional ductal adenocarcinomas of the pancreas. Molecular mechanisms underlying tumorigenesis of IPMTs are beginning to be characterized. Allelic losses have frequently been detected at 9p, 17p, and 18q, suggesting that inactivation of tumor suppressor genes at these loci play a role in tumorigenesis of IPMTs. Using immunohistochemistry, we analyzed 38 IPMTs, including 9 hyperplasia, 16 adenoma, and 13 carcinoma tissues, for expression of p53, Ki-67, p16, and SMAD4. Nuclear p53 expression was observed in 5 (38%) of 13 carcinoma tissues but not in hyperplasia or adenoma tissues. Partial loss of p16 expression was observed in 9 (56%) and 12 (92%) of the 16 adenoma and 13 carcinoma tissues, respectively. Partial loss of p16 expression was observed even in adenomas with mild atypia. Partial loss of SMAD4 expression was observed in 6 (38%) and 12 (92%) of the 16 adenoma and 13 carcinoma tissues, respectively. The SMAD4 negative index was significantly higher in invasive carcinomas than in non-invasive carcinomas. Our results suggest that loss of p16 is an early event and p53 alteration is a late event during the progression of IPMTs. SMAD4 inactivation appears to be an early event but also involved in invasive tumor growth. Our results suggest that these alterations accumulate during the progression of IPMTs, reflecting results of analysis of allelic losses that showed a stepwise accumulation of genetic changes during progression.

Adenocarcinoma, Mucinous↗