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Biomedical subjects

H Saiga

Publications and source records attributed to H Saiga.

48 records · Page 3Linked to original sources
PubMed1985

Two genes in Balbiani ring 2 with metabolically different 75S transcripts.

Balbiani ring 2 (BR2) in salivary glands of Chironomus pallidivittatus and C. tentans (two sibling species of the subgenus Camptochironomus) is a favoured model system for studies of gene organization and transcript formation. Here we show that BR2 is more complex than hitherto believed, containing two 75S RNA-producing genes, BR2a and BR2b, present in different 35-40 kb blocks of DNA. The transcripts hybridizing to two different repeat units originating in BR2 differ in size. Further support for the presence of two genes comes from RNA studies during experimentally induced BR2 regression. The amounts of BR2a RNA per cell remain more or less constant throughout the course of the experiment, whereas the BR2b RNA decreases considerably. Under normal conditions there is 5-6 times more BR2a RNA than BR2b RNA. This ratio increases 3-fold under experimental conditions. BR2a and BR2b, although partially homologous, contain repeat units with characteristic differences. BR2a contains a repeat unit that is much more similar to a BR1 repeat than it is to the BR2b repeat. The possibility is discussed that a Balbiani ring in general represents an integrated set of active genes rather than a singe gene.

Journal Article↗
PubMed1984

Nucleotide sequence of the 5'-terminal coding region for pre-rRNA and mature 17S rRNA in Tetrahymena thermophila rDNA.

The 5'-terminus of 35S pre-rRNA and mature 17S rRNA of Tetrahymena thermophila was mapped on cloned rDNA fragments by S1 nuclease protection experiments. A single site for transcription initiation was observed when pre-rRNA prepared by three different methods was used as RNA probe. These mapping results were unambiguously confirmed by sequencing the 5'-terminal region of in vitro capped 35S pre-rRNA. DNA sequence analysis of about 520 nucleotides upstream of the transcription initiation site revealed several distinct sets of highly conserved repeat sequences. In addition, the 840 nucleotides downstream of the transcription initiation site (+ 1) was determined and shown to include the 5'-terminus of the 17S rRNA coding region at position + 647. A region surrounding the position + 195 contains an inverted repeat sequence which could be the structural basis for the recently described premature transcription termination event in this organism (Kister et al. (1983) Nucl. Acids Res. 11, 3487-3502).

Animals↗
PubMed1983

A histopathologic study of benign and malignant lymphoepithelial lesions of the parotid gland.

Twenty-three cases of benign and malignant lymphoepithelial lesions without Sjögren's syndrome were examined: 21 were classical benign lymphoepithelial lesions, and were mostly found in males older than 50 years of age. The other two cases were identified as undifferentiated carcinoma arising from benign lymphoepithelial lesion (8.7%; 2/23). Histologically, this carcinoma is characterized by the formation of cell nests of variable size and by marked lymphoplasmacytic infiltrations into the stromal tissue. In immunofluorescence, an increase of plasma cells containing IgA and IgG was noted in the marginal areas of carcinoma cell clusters. Electron microscopy disclosed that the carcinoma was composed of poorly differentiated cells with occasional squamous differentiation. No dysplastic characteristics were found in the infiltrating lymphocytic components. These two cases of carcinoma were found in middle-aged females.

Adult↗
PubMed1982

Histopathologic studies of undifferentiated carcinoma of the parotid gland.

Five-hundred-fifty-five primary epithelial tumors of parotid gland origin were examined. Eighteen cases could be defined undifferentiated carcinomas, constituting 3.2% of the total number or 10.2% of 176 malignant tumors. The undifferentiated carcinomas could be divided on the basis of the cell size into two types: (1) Small-cell type (12/18; 66.7%); the tumor cells were as large as, or slightly larger than lymphocytes. The cytoplasm was scanty with dark chromatin. Mitotic figures were numerous. The tumor cells in the periphery of the cell clusters exhibited a palisading arrangement. Electron microscopy revealed that these cells were rich in tonofilaments and connected by desmosomes. (2) Large-cell type (6/18; 33.3%); the carcinoma cells were roughly twice as large as those of the small-cell carcinoma. The tumor cells were spheroidal or spindle in shape with rich and clear cytoplasm. Many of the tumor-cell clusters showed macroalveolar structures, suggesting the possibility that this type occurred as a variant of poorly differentiated adenocarcinoma or epidermoid carcinoma. Clinicopathologically, there was no sex difference in the total number of the undifferentiated carcinomas, but the large-cell carcinomas were frequently encountered in females (83.3%). As to the age distribution, the carcinomas were found frequently in middle-aged patients from 30-49 years (66.7%). Many of the tumors were 2-4.9 cm at their greatest diameter (55.6%). Tumor mass less than 1.9 cm could not be found.

Adult↗
PubMed1982

Histopathologic studies of basal cell adenoma of the parotid gland.

Five-hundred-thirty-one cases of primary epithelial tumors of the parotid gland were examined. The incidence of basal cell adenomas was 7.5% (40 cases). The tumors could be classified histologically into these subtypes: basal cell (21/40; 42.5%); tubular, (13/40; 32.5%); trabecular (4/40; 10.0%); and papillary (2/40; 5.0%). The pattern of classic basal cell adenoma predominated in the basal-cell type but was also seen in varying degrees in the latter three types with a reciprocal transition. Accordingly, it could be suggested that tubular, trabecular, and papillary types are variants of basal cell adenoma. The higher incidence of basal cell adenomas in our survey could be accounted for by this categorization. Histologically, basal cell adenomas presented various features; (1) cystic formation (26/40; 65.0%), being most frequently seen in tubular and trabecular types; (2) adenoid cystic pattern (4/40; 10.0%); (3) elastosis in the stromal tissues (2/40; 5.0%). Basal cell adenomas were clinicopathologically compared with 291 cases of pleomorphic adenomas. Basal cell adenomas were seen more often in female patients, (60.0%), as were pleomorphic adenomas (68.4%). They were observed more frequently in patients over 50 years of age and the average was ten years higher than for pleomorphic adenoma. The tumor size tended to be smaller (below 2 cm at the greatest diameter) than pleomorphic adenomas.

Adenoma↗
PubMed1982

Determination of the transcription initiation site of Tetrahymena pyriformis rDNA using in vitro capping of 35S pre-rRNA.

Approximately 700 nucleotide sequences surrounding the transcription initiation site were determined with a cloned rDNA fragment of Tetrahymena pyriformis and the transcription initiation site was localized on these sequences using purified 35S pre-rRNA. A considerable portion of the 35S pre-rRNA was found to be capped in vitro. The 32P-labeled, capped 35S pre-rRNA, on nucleus P1 protection mapping, gave the protection band which is identical in size with that obtained with bulk 35S pre-rRNA. Both reverse transcription extension and nuclease P1 mapping localized the 5'-end of the 35S pre-rRNA at the same adenine nucleotide, 496 base pairs upstream from the HindIII site of the cloned rDNA fragment. Furthermore, sequencing of the 5'-terminal region of the in vitro capped 35S pre-rRNA unambiguously confirmed the above result. The strategy adopted in the present experiment could serve as a general procedure for determining the transcription initiation point even in cases where the concentration of the primary transcript is low.

Animals↗
PubMed1981

Localization of putative transcription initiation site on the cloned rDNA fragment of Tetrahymena pyriformis.

A DNA fragment (1.4 Kb) which codes for 5' region of 35S ribosomal precursor RNA (pre-rRNA) in Tetrahymena pyriformis was cloned with pBR322. The fragment was cleaved from the central part of the palindromic rDNA with restriction endonuclease KpnI and HindIII, and ligated to the larger moiety of pBR322 DNA-HindIII-BamHI fragment together with lambda DNA-KpnI-BamHI fragment through trimolecular ligation. The analysis of R-loop formed between KpnI-linearized recombinant plasmid and 35S pre-rRNA revealed a DNA:RNA hybrid region of 465 +/- 30 base pairs in length. Considering the contraction of DNA:RNA hybrids relative to DNA duplexes (Philippsen et al., J. Mol. Biol., 123, 387-404, 1978), the size of the hybrid region was corrected to about 490 base pairs. Alternatively, the size of DNA which was protected against nuclease S1 due to hybrid formation with 35S pre-rRNA was estimated to be 490 nucleotides long. These data indicate that the transcription initiation site is localized at about 490 base pairs from the HindIII site of the cloned rDNA fragment.

Animals↗
PubMed1981

Histopathologic studies on carcinoma in pleomorphic adenoma of the parotid gland.

Five-hundred-eighteen cases of primary epithelial tumors of the parotid gland were examined. The incidence of carcinomas in pleomorphic adenoma was 9.3% (48 cases). In addition to cellular atypism, the following histological findings were thought to be important criteria for the diagnosis of carcinomas: (1) capsular invasion, (2) infiltration into adjacent organs, (3) proliferation of atypical cells within fibrous tissues and chondroid matrix in the area of pleomorphic adenoma, (4) vascular involvement, and (5) mitotic figures. Pleomorphic adenomas (282 cases) were found predominantly in females (70.8%), at the age of 30 to 49 (48.2%), whereas carcinomas in pleomorphic adenoma were more often found in males (70.8%) and at the ages over 50 (43.8%). Histologic types were composed mostly of undifferentiated carcinoma (56.2%) and adenocarcinoma (37.5%). The prognosis of the carcinomas, especially the undifferentiated type, was generally poor; about 45% of the cases either experienced recurrence or died within five years. Electron microscopy on this undifferentiated carcinoma revealed characteristic filamentous structure in the carcinoma cells, resembling that observed in myoepithelial cells. It was assumed that the undifferentiated carcinoma cells were of myoepithelial origin.

Adenoma, Pleomorphic↗
PubMed1979

Properties of in vitro transcription by isolated Xenopus oocyte nucleoli.

Some properties of in vitro transcription by isolated Xenopus oocyte nucleoli were described. When incubated with labeled RNA precursors, Xenopus oocyte nucleoli exhibited prolonged incorporation of radioactivity into RNA. The synthetic activity was exclusively due to type I RNA polymerase as revealed by its insensitivity to low and high doses of alpha-amanitin. The size of the in vitro transcript was mostly larger than 28S at 10 minute incubation and became smaller as incubation proceeded. When [gamma-32P]ATP was included in the reaction mixture, 32P radioactivity was incorporated into RNA suggesting the possible initiation of transcription in this system. However, analysis of the terminal nucleotide of the transcript revealed that the incorporation of radioactivity from [gamma-32P]ATP was not due to the initiation of transcription but due to polynucleotide kinase activity in the nucleolar preparation. These results demonstrate that the incorporation of radioactivity from [gamma-32P] labeled nucleoside triphosphates cannot necessarily be regarded as an index of the initiation of transcription.

Amanitins↗