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Biomedical subjects

S Takai

Publications and source records attributed to S Takai.

At least 199 records · Page 11Linked to original sources
PubMed1995

Renal carcinogenesis in the Eker rat.

The Eker rat hereditary renal carcinoma is an excellent example of a Mendelian dominant predisposition to a specific cancer in an experimental animal. We recently reported that a germline insertion in the rat homologue of the human tuberous sclerosis (TSC2) gene gives rise to the dominantly inherited cancer in the Eker rat model. The function of the TSC2/Tsc2 gene product (called "tuberine" in the human case) is not yet understood, although it contains a short amino acid sequence homologous to the ras family GTPase-activating proteins (GAP3). In the study, we isolated subtracted cDNA clones having increased expression in Eker renal carcinoma cells, using a modified representational difference analysis method to search for additional genes specifically involved in renal carcinogenesis. Here we identified four genes: the third component of the complement (C3) gene, the fos-related antigen I (fra-1) gene, an unknown gene (designated as being expressed in renal carcinoma: erc) and the calpactine I heavy-chain (Annexin II) gene.

Animals↗
PubMed1995

A new retroviral vector for detecting mutations and chromosomal instability in mammalian cells.

A retroviral vector carrying both forward (neo) and backward (herpes simplex virus thymidine kinase or HSV-TK gene) selection markers was constructed as a substrate for mutational assay in mammalian cells. The cells infected with this virus are first selected with G418, mutagenized and then selected with the anti-herpes drug acyclovir (ACV). Since HSV-TK, but not the host TK, is capable of converting ACV to a toxic metabolite, cells retaining the intact HSV-TK gene fail to survive, while the cells carrying a mutated HSV-TK gene or which have lost the gene can form colonies in the presence of ACV, making it possible to detect the genetic defects in a positive manner. It is also possible to discriminate between small mutations and large deletions by checking the presence of the linked marker, neo. As a model experiment, we prepared an uncloned pool of rat fibroblast cells (CREF) infected with this virus and irradiated them with increasing doses of ultraviolet light. Dose-dependent increases in the number of ACV-resistant colonies were observed. Structural analysis of the HSV-TK gene in these clones revealed point mutations or small deletions in the majority of the cases. Since it requires no pre-existing genetic markers in the host cells, this system may be used for a wide variety of mammalian cells and provides a useful tool to assess both their susceptibility to various mutagens and their genomic instability.

Acyclovir↗
PubMed1995

Assignment of the human TIM proto-oncogene to 7q33-->q35.

The human transforming gene TIM has been mapped to human chromosome 7 region q33-->q35 by fluorescence in situ hybridization with R-banded chromosomes. Rearrangements within this region have been reported to occur in acute myeloid leukemia cells.

Acute Disease↗
PubMed1995

Identification of virulence-associated antigens and plasmids in Rhodococcus equi from patients with AIDS.

Rhodococcus equi is an emerging opportunistic pathogen of human immunodeficiency virus-infected patients. However, little is known about the characteristics of R. equi isolates from humans. This study characterized the plasmid content, expression of a virulence-associated antigen, and mouse virulence of 19 R. equi isolates from patients with and without AIDS. EcoRI digestion patterns and Southern, Western, and virulence analyses of these isolates with cryptic plasmids allowed definition of a new category of R. equi. Isolates from patients with AIDS tended either to be virulent and have 15- to 17-kDa antigens and an 85-kb plasmid (10(6) bacteria needed for lethality) or have intermediate virulence (10(7) bacteria needed for lethality) and one of four distinct large plasmids that share DNA homology and express a 20-kDa antigen. Most of the non-AIDS isolates were avirulent (> 10(8) bacteria needed for lethality) and did not express any of these antigens.

AIDS-Related Opportunistic Infections↗
PubMed1995

Pathogenesis of Rhodococcus equi infection in mice: roles of virulence plasmids and granulomagenic activity of bacteria.

Virulence of Rhocococcus equi ATCC 33701 and its plasmid-cured derivative ATCC 33701P- was compared in BALB/c and C3H/HeJ mice in terms of bacterial growth kinetics and histological changes in the liver, spleen and lungs, and humoral immune responses. Injection with a sublethal dose of 10(6) ATCC 33701 in mice resulted in microabscess formation after rapid multiplication in the liver and spleen by day 4, and then the bacteria were gradually eliminated with the formation of granuloma and the production of specific antibodies against 15- to 17-kDa antigens of the virulent bacteria. By contrast, ATCC 33701P- was avirulent as shown by early elimination of viable bacteria and no evidence of net multiplication in the organs. Histopathological changes consisted of only slight, transient infiltration of neutrophils and macrophages in the liver. Although live ATCC 33701P- did not evoke any humoral or histological responses in the mice, a large inoculum (10(8)) of killed ATCC 33701 and ATCC 33701P- resulted in the formation of granuloma in the liver and accelerated extramedullary hemopoiesis in the spleen. These results suggest that the pathogenesis of R. equi infection involves at least two important virulence determinants, both of which play critical roles in the disease: one is the virulence plasmid, which is required for R. equi to resist and grow within host cells; and the other is the granulomagenic activity that is related to the lipids and nature of the cell wall of the species, which induces the characteristic pathological changes.

Actinomycetales Infections↗
PubMed1995

Identification of virulent Rhodococcus equi by amplification of gene coding for 15- to 17-kilodalton antigens.

During a survey of the prevalence of virulent Rhodococcus equi at horse-breeding farms by plasmid and protein profiles, cryptic plasmids of various sizes were found in 66 (3.8%) of 1,725 isolates from feces of horses and 129 (5.9%) of 2,200 isolates from soil. Twenty-two isolates, which contained cryptic plasmids of different sizes, were found by plasmid profiles, and their protein profiles and mouse pathogenicities were examined. Of the 22 isolates, 7 were virulent R. equi, contained both virulence and cryptic plasmids, and expressed 15- to 17-kDa antigens. The remaining 15 isolates were avirulent and did not express the antigens: 6 strains contained cryptic plasmids of two different sizes and 9 strains contained cryptic plasmids of various sizes. A PCR assay was developed for the rapid identification of virulence plasmids of R. equi. Oligonucleotide primers, derived from the sequence of a gene coding for the 15- to 17-kDa virulence-associated antigens of R. equi, amplified a 564-bp product from all the tested isolates harboring a virulence plasmid. This PCR product hybridized with virulence plasmid DNA in the Southern hybridization assay. Virulence plasmid-cured derivatives and all of the tested isolates harboring cryptic plasmids only were negative. The PCR is a rapid, sensitive, and specific test for the identification of virulent R. equi from environmental isolates compared with standard techniques, such as plasmid and protein profiles and the mouse pathogenicity test, and is considered to be a useful tool for epidemiological studies.

Animals↗
PubMed1995

A case of repeated painless thyroiditis followed by Graves' disease.

A fifty-year-old woman was admitted to our hospital because of palpitation and general fatigue. She had received hemithyroidectomy for thyroid papillary adenocarcinoma at 28 years of age. She had experienced episodes of repeated painless thyroiditis five times over the last 12 years. At her sixth episode of thyrotoxicosis, she was suspected to have Graves' disease and admitted to our hospital. Laboratory findings revealed thyrotoxicosis with positive thyroid stimulating antibody and high radioactive iodine uptake, i.e. Graves' disease. Painless thyroiditis often relapses but rarely develops into Graves' disease. This is a rare case in which repeated painless thyroiditis was followed by Graves' disease. The relation between painless thyroiditis and Graves' disease is discussed.

Female↗
PubMed1994

Overexpression of ERK, an EPH family receptor protein tyrosine kinase, in various human tumors.

The ERK gene has been isolated as a genomic DNA encoding a part of the receptor protein-tyrosine kinase which belongs to the EPH subfamily. We previously identified a partial complementary DNA (cDNA) encompassing the catalytic domain of ERK from the expression library of human gastric cancer with an antiphosphotyrosine antibody. Using this cDNA as a probe, the cDNAs encoding mature ERK protein were isolated. The putative mature ERK protein, a total of 967 deduced amino acid residues, showed high homology with chicken Cek5 (92.5%) and mouse Nuk (99.1%). Chromosomal in situ hybridization revealed that human ERK cDNA is localized to chromosome 1p34-35. In Northern blot analysis of normal human tissues, the ERK gene was ubiquitously expressed mainly in cells of epithelial origin but not in the brain. Studies on RNAs from 76 human tumor tissues and cell lines showed that ERK is expressed at higher levels in various tumors of epithelial origin than in corresponding normal tissues, most frequently in gastric cancers (12 of 16, 75.0%). Overexpression of ERK was also detected in one osteosarcoma cell line. These findings suggest that ERK plays some significant role in carcinogenesis in the stomach and other tissues.

Amino Acid Sequence↗
PubMed1994

Ki-ras and c-myc oncogene expression measured by coamplification polymerase chain reaction.

Ki-ras and c-myc oncogene mRNA in carcinoma tissue was quantitatively detected by the coamplification polymerase chain reaction. After the reverse transcription of the mRNA mixture with random hexanucleotide primer the coamplification polymerase chain reaction of the oncogene and the internal standard beta-actin cDNA was done. The amount of oncogene mRNA was calculated from the coamplified product ratio. Ki-ras expression in a human gastric cancer strain H-111 was estimated to 5 percent of beta-actin. The expression of c-myc mRNA in colorectal carcinoma tissue was observed to be ten to one hundred times higher than normal mucosa. Gene expression was compared numerically in mole/liter without using hybridization and radioactive probes.

Actins↗
PubMed1994

Molecular cloning of the human histamine H1 receptor gene.

The human histamine H1 receptor gene, an intron-lacking gene, was isolated with bovine H1 receptor cDNA [Yamashita, M., Fukui, H., Sugama, K., Horio, Y., Ito, S., Mizuguchi, H., and Wada, H. (1991) Proc. Natl. Acad. Sci. USA 88, 11515-11519] used as a probe. The receptor protein deduced from the nucleotide sequence of this gene was composed of 487 amino acid residues with a calculated Mr of 55,781 and possessed characteristic properties of GTP binding protein-coupled receptors. At the 5' flanking region of the human H1 receptor gene, we located potential TATA box and CACCC sequences, AP1 binding site-like sequences, glucocorticoid responsive element-like sequences, and other binding sequences for inducers. Northern blot analysis showed that H1 receptor mRNAs visualized as two bands with 3.0-kilobase and 3.5-kilobase nucleotides were expressed in peripheral tissues such as placenta, lung, skeletal muscle, and kidney and that only one species with 3.5-kilobase nucleotides was present in the brain. H1 receptor mRNA was most abundant in the placenta. The human H1 receptor gene was mapped to the chromosome 3p25 by the fluorescence in situ hybridization method.

Amino Acid Sequence↗
PubMed1994

Mapping of the human C3G gene coding a guanine nucleotide releasing protein for Ras family to 9q34.3 by fluorescence in situ hybridization.

C3G, a human guanine nucleotide releasing protein for Ras protein, was mapped to human chromosome 9q34.3 by fluorescence in situ hybridization with R-banded chromosomes. C3G was originally identified as one of the CRK-binding proteins, similar to c-abl (9q34.1). Our result suggests that the downstream factors of Crk are localized in close proximity on chromosome 9.

Chromosome Banding↗
PubMed1994

Isolation and mapping of cosmid markers on human chromosome 22, including one within the submicroscopically deleted region of DiGeorge syndrome.

A genomic cosmid library was constructed from a Chinese hamster/human hybrid cell containing human intact chromosome 22 as its only human component. Of 1000 cosmids with inserts derived from human chromosome 22, 191 were tested for restriction fragment length polymorphisms (RFLPs). As a result, 64 clones detected RFLPs, including five variable number of tandem repeats systems. Of the remaining 127 cosmids, 111 detected a single copy sequence on human chromosome 22. Five somatic cell hybrids allowed us to assign all of the 64 polymorphic cosmids and 44 non-polymorphic cosmids to four different regions of human chromosome 22. In two patients with DiGeorge syndrome, one of the cosmids that had been sublocalized to 22pter-q11 detected hemizygosity. These 108 cosmid markers regionally assigned to human chromosome 22 should be useful for the construction of long-range physical maps and the identification of genetic alterations on the chromosome.

Animals↗