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Biomedical subjects

K Segawa

Publications and source records attributed to K Segawa.

At least 73 records · Page 4Linked to original sources
PubMed1995

Ocular findings in a patient with Prader-Willi syndrome.

A 25-year-old woman is described whose clinical features included infantile hypotonia, obesity after infancy, intellectual impairment, dysmorphic facial features, short stature, small hands and feet, and abnormal dentition, which are typical of the Prader-Willi syndrome. The patient had almond-shaped eyes, spot-like hypopigmentation under the retina, and a polychromatic luster in the anterior and posterior subcapsular regions of both lenses. Using fluorescence fundus angiography, we identified choroid-transmitted fluorescence in the areas of spot-like hypopigmentation. Recordings of both electroretinogram and visual evoked potential were normal. Ophthalmologists should be aware of the characteristic features of Prader-Willi syndrome because some of the ocular disorders associated with this syndrome can be treated.

Adult↗
PubMed1994

Presence of p53 mutations in 3Y1-B clone 1-6: a rat cell line widely used as a normal immortalized fibroblast.

The 3Y1 cell line, established from a rat whole embryo, is widely used as a normal immortalized fibroblast. We analyzed p53 mutations in four clonal lines derived from the 3Y1 cell line; 3Y1-B clone 1-6, 3Y1-C and two clonal lines (3Y1 cl-3 and 3Y1 cl-6) which had been transformed by the human papilloma virus E6 gene. Polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) analysis and DNA sequencing showed that three clonal lines had a double mutation at codons 130 and 136 on the same allele and that the other clonal line, 3Y1 cl-3, had no mutations. 3Y1-B clone 1-6, which has been registered as the standard clonal line at the Japanese Cancer Research Resources Bank, demonstrated weak bands of the wild type allele, suggesting the existence of heterogeneous cell types in this "clonal" line. PCR-SSCP analysis of 25 subclones obtained by limiting dilution of 3Y1-B clone 1-6 cells revealed a mixture of two types of cells; 12 subclones showed only the bands of mutated allele, and 13 subclones showed both bands of the wild and mutated p53 alleles. These findings should be taken into consideration when using this cell line as a normal immortalized cell line.

Animals↗
PubMed1994

Stimulation of polyomavirus DNA replication by wild-type p53 through the DNA-binding site.

The tumor suppressor p53 possesses characteristics of a transcription factor; it binds to specific DNA sequences and activates transcription from various promoters. Here we found that murine wild-type p53 stimulated not only transcription but also polyomavirus (Py) DNA replication in a sequence-dependent manner. Oncogenic mutant p53, lacking the DNA-binding activity, showed no stimulation of Py DNA replication. Deletion of the N-terminal acidic transactivation domain of wild-type p53, which completely eliminated the ability to stimulate transcription, only impaired the function to stimulate Py DNA replication. The replication-stimulating activity of wild-type p53 was impaired by the deletion of the C-terminal oligomerization domain as well, without affecting the ability to stimulate transcription. The region responsible for the sequence-specific DNA-binding activity mapped to the central portion of the p53 molecule has a minimal activity. The results indicate that both the N-terminal and the C-terminal regions significantly contribute to the p53-mediated stimulation of Py DNA replication.

Amino Acid Sequence↗
PubMed1994

B cell mitogenic activity of sea squirt antigen.

The activity of sea squirt antigen, one of the allergy-inducing substances for humans, on murine and human lymphocytes was studied in vitro. Sea squirt antigen stimulated normal mouse spleen cells to proliferate, as detected by [3H]-TdR incorporation, in a dose-dependent manner. The responder cells are B cells because the response was reduced by the treatment of spleen cells with anti-immunoglobulin antibody and complement and passing through a nylon wool column, but not with anti-Thy-1 antibody and complement. Spleen cells of C3H/HeJ mice, which are lipopolysaccharide low responders, were also stimulated as well as spleen cells of C3H/HeN mice, suggesting that this response is not due to lipopolysaccharide in the antigen fraction. Sea squirt antigen stimulated not only proliferative response of B cells, but also polyclonal immunoglobulin production. Furthermore, sea squirt antigen also stimulated human lymphocytes to proliferate and to produce immunoglobulin. All these results suggest that sea squirt antigen has mitogenic activity on B cells, and this ability is concerned with the induction of allergic reaction.

Animals↗
PubMed1994

Lectin electron microscopic histochemistry of the pseudoexfoliative material in the skin.

PURPOSE: To investigate the hypothesis that pseudoexfoliation (PSX) syndrome is a systemic disorder, the authors studied the composition of glycoconjugates in the intraocular and extraocular PSX material at the electron microscopic level, using a panel of lectins as cytochemical probes. METHODS: The authors examined 8 lid skins, 11 trabecular tissues, and 3 cataractous lenses from human eyes with PSX syndrome. Tissues were processed for electron microscopical histochemistry and stained with PNA, RCA120, DBA, SBA, ConA, WGA, UEA-I, and Lotus, with an indirect lectin-colloidal gold technique. RESULTS: Both the intraocular and extraocular PSX materials manifested almost identical reactivity to lectins, which indicated that glycoconjugates in the PSX material contained with sugar residues of galactose (PNA, RCA120), alpha-mannose (ConA), and N-acetyl-D-glucosamine (WGA). On the other hand, it was indicated that sugar residues of N-acetyl-D-galactosamine (DBA, SBA) and fucose (UEA-I, Lotus) were absent. Granular inclusions and microfibrils in the capsule and ocular zonules were stained similarly and weakly. CONCLUSIONS: The intraocular and extraocular PSX materials contained the same sugar residues of glycoconjugates, which suggested that those materials had the same nature. This study, the first documentation of lectin-binding sites on the extraocular PSX material, supported the hypothesis of PSX syndrome as a systemic disorder.

Exfoliation Syndrome↗
PubMed1994

Localization of elastin in the normal and glaucomatous human trabecular meshwork.

PURPOSE: The extracellular materials (ECMs) in the trabecular meshwork (TM) are thought to play a crucial role in aqueous outflow resistance. Immunohistochemical localization of elastin, one of the major ECMs in the normal and glaucomatous human TM, was examined ultrastructurally. METHODS: Eight normal eye bank eyes and 16 trabeculectomy specimens of primary open angle glaucoma (POAG, 11 eyes from 8 cases), congenital glaucoma (2 eyes from 1 case), and juvenile glaucoma (3 eyes from 2 cases) were embedded in Lowicryl K4M at low temperature. The distribution of elastin was studied by the protein A-gold technique. RESULTS: In normals, the gold particles indicating the antigenic sites for elastin existed mainly in the central amorphous element of the elastic-like fibers, and a few gold particles were observed within the area containing fine granular-like material and fine fibrillar-like material. No labeling was observed in cellular materials or other ECMs. In congenital and juvenile glaucoma, labeling was similar to that observed in normals. In POAG specimens compared to normals, there was an increased amount of elastin-bound immunogold particles along the inner canal endothelium. The increased gold particles, which did not have a fibrillar arrangement and were not enclosed by electron-dense microfibrils, were found within the area containing fine fibrillar-like material. However, labeling within the elastic-like fibers was similar to that observed in normals. CONCLUSIONS: Under electron microscopy, elastin could be localized in the normal and glaucomatous human TM. The results of this investigation suggest that elastin may play an important role in the etiology of POAG.

Adult↗
PubMed1994

[The relationship between titrated acidity (mEq/l) and pH of human gastric juice: a study based on the data estimated by pH-meter].

The relationship between titrated acidity and pH was studied using the 3206 samples of human gastric juice, which were collected by the intragastric tube in the basal and gastrin stimulated conditions. The pH of samples subjected to the present study ranged from 0.95 and 6.9. The results showed that a certain value of pH did not always indicate an identical value of titrated acidity, and that the coefficient of variation was greater as pH value rose. As a whole, however, the acidity became lower with the increase of pH value. Thus, the relationship between pH and titrated acidity could be expressed closely as "Y = 369.19 - 424.09X + 203.66X2 - 48.29X3 + 5.57X4 - 0.25X5), where X = pH and Y = acidity. The conversion table from pH to acidity, which was calculated by this expression, was presented for the clinical use.

Adult↗
PubMed1994

Dominance of activated T cells and interleukin-6 in aqueous humor in Vogt-Koyanagi-Harada disease.

PURPOSE: To determine the immunopathologic role of the lymphocytes and lymphokines in aqueous humor (AH) of patients with Vogt-Koyanagi-Harada disease (VKH). METHODS: The distribution of leukocyte subsets in the peripheral blood and AH was examined using fluorescein isothiocyanate-conjugated monoclonal antibodies. The levels of lymphokines, such as interleukin-2 (IL-2) and interleukin-6 (IL-6), in the sera, AH, and cerebrospinal fluid from the patients with VKH were determined using an enzyme-linked immunosorbent assay. RESULTS: T cells constituted the majority of lymphocytes within AH. The value for CD4+ cells (helper/inducer T lymphocytes) in AH was 51.7% +/- 14.9% (mean +/- SD) and that for CD8+ cells (cytotoxic/suppressor T lymphocytes) was 31.1% +/- 13.0%. The percentage of HLA-DR+ cells (B lymphocytes, monocytes, macrophages, and activated T lymphocytes) in AH (50.8% +/- 24.9%) significantly exceeded (P < 0.001) that in blood (13.1% +/- 4.2%). The percentage of CD8+ cells in AH from three patients with the delayed type of VKH rose during their clinical course. The level of IL-6 was significantly elevated in AH from the patients with VKH. The level of IL-6 in AH correlated with the number of lymphocytes in AH, and it reflected the severity of the inflammatory response in AH of patients with VKH. The level of IL-2 in the sera, AH, and cerebrospinal fluid was in the normal range. CONCLUSIONS: Aqueous humor lymphocytes from the patients with VKH were more activated than were peripheral blood lymphocytes. IL-6 may play an important role as an inflammatory mediator in VKH. It may be useful to analyze the lymphocyte subsets and the levels of lymphokines, especially of IL-6, at the site of inflammation in uvea to improve the criteria for assessing the prognosis of VKH.

Adult↗
PubMed1993

Cyclin E enhances P53-mediated transactivation.

Plasmids expressing G1 and G2 cyclins were introduced into the Saos-2 cell system monitoring p53-mediated transactivation [(1993) Oncogene 8, 543]. Cyclin E, but not other cyclins, enhanced the p53-mediated transactivation about 2-fold. Co-transfection of a CDK2 expression plasmid caused a 30% increase in the extent of the p53-mediated transactivation. Moreover, the transfected p53 protein became phosphorylated coordinately with the enhanced transactivation. The close correlation between transactivation and p53 phosphorylation suggests that phosphorylation is involved in positive regulation for the transactivation by p53.

Cells, Cultured↗
PubMed1993

Comparative study on E6 and E7 genes of some cutaneous and genital papillomaviruses of human origin for their ability to transform 3Y1 cells.

E6 (or E7) genes of some genital and cutaneous human papillomaviruses (HPVs) were compared for their ability to transform cells of a rat fibroblastic line (3Y1) by using recombinant retroviruses. The E6 gene of genital cancer-associated HPV 16 or 18 was found to induce a characteristic morphological change, i.e., densely packed arrays of elongated cells forming swirl patterns. This change is the same as that induced by the E6 gene of cutaneous cancer-associated HPV 5, 8, or 47, which we described previously. The E6 gene of HPV 1 or 11, associated with benign tumor of cutaneous or genital tissue, respectively, induced no such change. The E6 genes of all these cutaneous and genital HPVs enhanced anchorage-independent growth of the target cells induced by E7 gene of HPV 16 or 18, and this enhancing activity of HPVs 16, 18, and 47 was stronger than that of HPVs 1 and 11. A distinct type of morphological transformation of 3Y1 cells, i.e., rounded miniaturized cells that were densely packed without forming any distinctive arrays, was found to be induced strongly by E7 genes of HPVs 16 and 18, weakly by E7 of HPVs 1 and 11, and not at all by E7 of HPV 47. The results suggest that the intensity of the morphological change induced by E6 genes, rather than E7 genes, is correlated to the risk of malignant conversion of the lesion with which the corresponding HPVs are associated.

Cell Line↗
PubMed1993

Escape from in vitro aging in SV40 large T antigen-transformed human diploid cells: a key event responsible for immortalization occurs during crisis.

A human diploid fibroblast strain MRC-5 was transfected with a replication origin-defective early region of SV40 containing the gene of large T antigen, and 48 clones of T antigen-transformed MRC-5 were isolated. Although T antigen prolonged the lifespan of MRC-5, all the transformed clones were still mortal. From two of the transformed MRC-5 clones, eight independent immortalized clones were obtained in triple experiments of immortalization. The transformed phenotypes of immortalized clones were widely varied and did not always retain those of the parental pre-immortalized clones. The immortalization occurred at the frequency of about 1-3 x 10(-7)/cell. From cell number and population doubling time of the immortalized clones, the immortalization was estimated to occur in or just before the crisis of parental mortal cells. The decreases of modal chromosome numbers and the loss of chromosomes 5 and 10 were found to be common in three independent immortalized clones examined. Thus, the escape from the cellular aging process seemed to be caused by certain genetic events including the loss of chromosomes at the end of lifespan in T antigen-transformed human diploid cells.

Aneuploidy↗
PubMed1993

Abrogation of p53-mediated transactivation by SV40 large T antigen.

p53 is known to bind specifically to the 44-bp human DNA sequence in an immunoprecipitation assay. We show here that the transcription of the reporter CAT gene linked with the herpesvirus thymidine kinase (tk) promoter containing the 44-base sequence is enhanced by mouse wild-type but not mutant-type p53 in F9 and p53-null Saos-2 cells. The p53-mediated transactivation was dramatically abrogated by introduction of SV40 large T antigen (SVLT) in Saos-2 cells in which p53 was clearly associated with SVLT. Furthermore, the p53-SVLT complex did not bind to the 44-base sequence at all. Thus, SVLT sequesters the transactivation function of the wild-type p53 by inhibiting the binding of p53 to the 44-base sequence. This is good evidence to show 'loss of functions' in the product of a tumor-suppressor oncogene by a dominant oncogene product at a molecular level.

Antigens, Polyomavirus Transforming↗
PubMed1993

Biological and biochemical activity of E7 genes of the cutaneous human papillomavirus type 5 and 8.

In contrast to the observed activity of the E7 genes of the genital high-risk human papillomavirus (HPV)16 and HPV18, E7s of the cutaneous high-risk HPV5 and HPV8 show no in vitro transforming activity in established rodent cells. We recently reported that the HPV8 E7 driven by the SV40 enhancer/promoter oncogenically transforms primary rat embryo fibroblast (REF) cells collaboratively with the EJras oncogene (Jpn. J. Cancer Res., 82, 1340-1343, 1991). To study the functional differences between cutaneous HPV5 and HPV8 E7s and genital HPV16 E7, we cloned each of the E7 open reading frames and tested their immortalizing and transforming activities, the binding ability of their products with retinoblastoma protein (RB) and their complementation activity of a RB-nonbinding adenovirus E1A mutant. In contrast to results with HPV16 E7, transfection of HPV5 and HPV8 E7s did not produce any G418-resistant colonies in primary baby rat kidney (BRK) cells. However, they induced morphological transformation of primary BRK cells as well as of primary REF cells when cotransfected with the EJras oncogene. The ras-cooperating activity of HPV8 E7 appears to be extremely low, since, unlike the case of HPV5 and HPV16 E7s, transformed BRK colonies induced by HPV8 E7 plus ras have had a very low survival rate. The in vitro RB binding experiment showed that HPV5 and 8 E7s are able to form complexes with RB protein with reduced affinities of about one fourth and one nineteenth that of HPV16 E7, respectively. Moreover, not only HPV16 E7 but also HPV5 and 8 E7s complemented a nontransforming adenovirus 5 E1A mutant (dl922/947) incapable of binding to RB in inducing E1A-specific transformed foci on primary BRK cells. Since both the activities, the ras-collaborative transformation and complementation of the inert E1A mutant by E7s, all correlate with in vitro RB binding affinity (HPV16 E7 > HPV5 E7 > HPV8 E7), it is likely that RB binding of HPV5 and HPV8 E7s is an integral part of the biological activities of these proteins.

Adenovirus E1A Proteins↗
PubMed1992

Ultrastructural alteration of cartilaginous fibril arrangement in the rat mandibular condyle as revealed by high-resolution scanning electron microscopy.

Three-dimensional alteration of fibrillar matrix in the rat mandibular condylar cartilage was investigated with a high-resolution scanning electron microscope (SEM) and it was determined whether alterations correlate with developing occlusion and advancing age. Two important SEM techniques of DMSO freeze-cracking and treatment with trypsin and hyaluronidase were employed to remove interfibrillar proteoglycans and disclose fibril arrangement. Our SEM investigation demonstrated that collagen fibrils in the fibrous zone covering hyaline-cartilaginous area in the condyle are thicker (50 to 80 nm in diameter) than the fibrils (30 to 50 nm in diameter) that predominantly constituted an interterritorial fibrillar matrix (IFM) in the area. While the thick fibrils had a distinct striation of about 55 nm periodicity, the thin fibrils had no distinguishable striation. The thick fibrils having a periodic striation of about 60 nm was found along with the thin fibrils, also in the IFM in the aged rats and in the deep IFM, but were considerably less than the thin fibrils. The fibrils in the fibrous zone and IFM were disorderly arranged at 19-day-insemination age. In 1-week-old rats whose incisors erupted, the fibrils constituting the fibrous zone altered from disordered to ordered arrangement. The IFM in these rats took the form of a network. Incorporation of small fibrillar bundles into the fibrillar network was seen in 2-week-old rats whose upper and lower first molars erupted. In 8-week-old rats whose molars had erupted completely, the IFM completely occupied by regularly oriented fibrils appeared additionally.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Multipotent marrow stromal cell line is able to induce hematopoiesis in vivo.

Several murine marrow stromal cells were established from murine bone marrow cultures. Stromal cell lines transfected with a tumor-inducing polyoma virus middle T antigen (MTAg) were inoculated into nude mice subcutaneously. KUSA-MTAg cells, one of these cell lines, led to the rapid local development of bone marrow consisting of trilineage hematopoietic cells and bone; other cell lines produced spindle cell sarcoma or hemangiosarcoma. These results suggested that a single stromal cell line, KUSA-MTAg cells, may induce hematopoietic stem cells or early progenitors of three lineages of hematopoietic cells in vivo. Interestingly, untransfected KUSA cells expressed three new mesenchymal phenotypes, osteocytes, adipocytes, and myotubes, after treatment with 5-azacytidine.

Adipose Tissue↗
PubMed1992

Antigen presentation by Toxoplasma-infected cells: antigen entry through cell membrane fusion.

The antigen presentation of cells infected by Toxoplasma gondii (T.g.) for MHC class-I-restricted cytotoxic T cells (CTL) was blocked by treating the T.g.-infected cells with the fungal antibiotic brefeldin A. Electron microscopic analysis of T.g.-infected murine and human-antigen-presenting cells (APC) prepared by the combination of quick-freezing with the deep-etching or freeze-substitution methods revealed that the outer membrane of T.g. fused with some parts of the vacuolar membranes of APC to build up channel-like structures. Work station and cytofluorometry studies detected 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) in cells infected by BCECF-labeled T.g., which strongly suggested the direct entry into cells of BCECF derived from T.g. These findings provide evidence that T.g. antigens enter the cytoplasm of APC through cell membrane fusion of T.g. and T.g.-infected APC, and that T.g.-infected APC present T.g. antigen for MHC class-I-restricted CTL through the endogenous pathway of antigen presentation.

Animals↗
PubMed1992

Retrospective evaluation of surgical intervention following chemo- and radiotherapy of maxillary sinus cancers.

During the past 15 years, 30 patients with squamous cell carcinomas of the maxillary sinus were treated by modified partial maxillectomy following chemo- and radiotherapy, taking care to preserve facial contour and function as far as possible. Follow-up evaluation showed that local recurrences, and regional lymph node and distant metastases were more frequent in T4 patients than in T3 patients. Evaluation of the histopathological effects of preoperative chemo- and radiotherapy at the time of surgery showed that T4 patients tended to have a poorer response to the treatment than T3 patients. Analysis according to the direction of primary tumor extension showed that the incidence of local recurrence was higher in the superolateral type, whereas that of regional lymph node metastasis was higher in the medial type. The cumulative 5-year survival was high (72.2%) in Stage III patients and low (22.5%) in Stage IV patients. The overall rate was 55.4%. The treatment produced relatively good outcomes in T3 patients but poor outcomes in T4 patients. These findings indicate that T4 carcinoma of the maxillary sinus must be managed initially by a combination of irradiation and multi-chemotherapeutic drugs, and then treated by more extensive surgical resection.

Adult↗