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Biomedical subjects

H Sakamoto

Publications and source records attributed to H Sakamoto.

At least 577 records · Page 32Linked to original sources
PubMed1993

Amplified genes in cancer in upper digestive tract.

Gene amplification in stomach and oesophageal cancers was reviewed. In stomach cancers, two receptor type tyrosine kinases, c-erbB-2 and K-sam, are frequently amplified and overexpressed. c-erbB-2 seems to be preferentially amplified in well-differentiated, and K-sam in poorly-differentiated, gastric adenocarcinomas. 11q13 genes are amplified in about 50% of the oesophageal cancers. These genes include hst-1, int-2 and cyclin D/prad1, all of which are mapped to chromosome 11 at band q13. Although hst-1 and int-2 are usually not expressed despite amplification, elevated transcription of the cyclin D gene is accompanied by its amplification, suggesting a role of a G1 cyclin in oesophageal carcinogenesis.

ErbB Receptors↗
PubMed1993

Innervation of the anteromedial muscle bundles of the gluteus medius.

The independent anteromedial muscle bundles situated lateral to the nerve to tensor fasciae latae were examined in 13 human pelvic halves. Each of these independent muscle layers was shown not to be an independent muscle but part of gluteus medius. On the basis of its innervation, tensor fasciae latae is closely related to the most anteromedial muscle layer of gluteus medius. From their pattern of innervation, these anteromedial bundles may be considered as a continuation of gluteus medius rather than as completely independent. Furthermore, tensor fasciae latae is closely related to the most anteromedial of these bundles.

Buttocks↗
PubMed1993

[Gonadotropin receptor system and its signal transduction pathway].

Recent advances in genetic studies have elucidated structure of gonadotropin receptors. This transmembrane receptor contains seven transmembrane domains and induces multiple biological changes in granulosa/theca cells resulting in follicular maturation in women. The signal transduction involves G protein mediated systems, cAMP mediated systems and phospholipase C systems. This paper reviews recent advances in gonadotropin receptor system and its signal transduction pathway.

Amino Acid Sequence↗
PubMed1992

Control of Drosophila Sex-lethal pre-mRNA splicing by its own female-specific product.

Drosophila melanogaster somatic sexual differentiation is accomplished by serial function of the products of sex-determination genes. Sex-lethal (Sxl), is one such gene. It is functionally expressed only in female flies. The sex-specific expression of this gene is regulated by alternative mRNA splicing which results in either the inclusion or exclusion of the translation stop codon containing third exon. Although previous genetic and molecular analyses suggest that functional Sxl expression is maintained by a positive feedback loop, where the female-specific Sxl product promotes the synthesis of its own female-specific mRNA, the mechanistic details of such regulation have remained unclear. We have developed a cotransfection system using Drosophila cultured (Kc) cells in which Sxl primary transcripts are expressed with or without the female specific Sxl product. Here we show that the female-specific Sxl product induces the synthesis of its own female-specific mRNA by negative control of male-specific splicing. Deletion, substitution, and binding experiments have demonstrated that multiple uridine-rich sequences in the introns around the male-specific third exon are involved in the splicing regulation of Sxl pre-mRNA.

Animals↗
PubMed1992

Establishment of a highly sensitive and specific exon-trapping system.

We have established a highly sensitive and specific exon-trapping system (SETS) with a specific plasmid vector in which an exon in a given DNA segment is identified by its ability to remain as a mature mRNA after splicing. The SETS provides us with the isolation of possible exons rapidly and easily from DNA fragments in chromosomal regions of more than 300 kilobase pairs. Genomic DNA fragments were partially digested and subsequently cloned into plasmid pMHC2, an exon-trapping vector we have constructed. These constructs were transfected into COS-7 cells, and consequent RNA transcripts were spliced in the cells. The resulting mature mRNA was harvested and amplified by using reverse transcription-PCR. Possible exons can be recognized by the sizes of PCR products and cloned into a plasmid vector. The SETS provides a direct means of cloning exons from genomic DNA of more than 300 kilobase pairs within a short period of time. Using this system, we have screened 300-kilobase-pair genomic DNA segments derived from human chromosome 11q13. Human chromosome 11q13 may contain genes responsible for human cancers, because DNA amplification is observed in several malignant tumors. We have successfully identified exon 2 of the HST1 gene and additional transcribed sequences.

Base Sequence↗
PubMed1992

Expressions of receptor gene for hepatocyte growth factor in kidney after unilateral nephrectomy and renal injury.

The renal expressions of the receptor gene (c-met) for hepatocyte growth factor (HGF) were examined in unilateral nephrectomy (UNX), renal ischemia or folic acid administration. The levels of c-met mRNA were increased rapidly in all rat models at 6h after the operations. On the other hand, the expression of c-met mRNA in a kidney cell line (MDCK cells) was down-regulated for 8 h after HGF addition, indicating that c-met mRNA induction in rat models may be independent of the stimulated production of HGF. The stimulated expression of c-met in these models suggest that HGF may play an important role in renal hypertrophy after UNX and regeneration after ischemic or nephrotoxic injury.

Animals↗
PubMed1992

Binding of the Drosophila transformer and transformer-2 proteins to the regulatory elements of doublesex primary transcript for sex-specific RNA processing.

Sex-specific alternative processing of double-sex (dsx) precursor messenger RNA (pre-mRNA) is one of the key steps that regulates somatic sexual differentiation in Drosophila melanogaster. By transfection analyses using dsx minigene constructs, we identified six copies of the 13-nucleotide sequences TC(T/A)(T/A)C(A/G)ATCAACA in the female-specific fourth exon that act as the cis elements for the female-specific splicing of dsx pre-mRNA. UV-crosslinking experiments revealed that both female-specific transformer (tra) and transformer-2 (tra-2) products bind to the 13-nucleotide sequences of dsx pre-mRNA. These results strongly suggest that the female-specific splicing of dsx pre-mRNA is activated by binding of these proteins to the 13-nucleotide sequences.

Animals↗
PubMed1992

Establishment and characterization of human uterine leiomyosarcoma heterotransplanted into nude mice.

Human uterine leiomyosarcoma is a rare gynecological malignancy with a generally poor prognosis. We have established a human uterine leiomyosarcoma tumor line in nude mice, designated UTS-1, and describe the characteristics of this tumor. The UTS-1 tumor doubled in 12.1 days and retained the histological characteristics of leiomyosarcoma, even after 14 serial generations. Ultrastructurally, the tumor is characterized by nuclear pleomorphism typical of smooth muscle, intracytoplasmic filaments with dense bodies, a relative paucity of micropinocytotic vesicles, and an incomplete external lamina. Immunohistochemically, the UTS-1 cells reacted with antibodies against vimentin, desmin, smooth-muscle actin and myosin, but not with antibodies against keratin, CEA and S-100 protein. Serum levels of AFP, CA125, CEA and SCC ranged within normal limits in tumor-bearing mice. The serum level of immunosuppressive acidic protein correlated well with an activity of the tumor. Estrogen and progesterone receptors were not detected in the tumor. Chromosomal analysis showed a human karyotype with some marker chromosomes and a modal number of 85 chromosomes. The UTS-1 tumor should prove a useful model to explore the biological characteristics and treatment of human uterine leiomyosarcoma.

Animals↗
PubMed1992

Bordetella pertussis adenylate cyclase toxin. Structural and functional independence of the catalytic and hemolytic activities.

The Bordetella pertussis calmodulin-dependent adenylate cyclase (CyaA) is a 1706-residue-long toxin, endowed with hemolytic activity. We have constructed B. pertussis mutant strains producing modified CyaAs devoid of adenylate cyclase activity. Our results show that such modified CyaAs display hemolytic activity identical to the wild-type toxin, thus demonstrating that the hemolytic activity is independent of the adenylate cyclase activity. Furthermore, B. pertussis and Escherichia coli strains producing CyaA lacking the catalytic domain (residues 1-373) were constructed. The truncated protein exhibits hemolytic activity comparable to the wild-type toxin, thus establishing that the carboxyl-terminal 1332 residues alone are endowed with hemolytic activity. Together, these findings show that adenylate cyclase and hemolytic activities are located in two distinct regions of the molecule (respectively, approximately amino acids 1-400 and 401-1706) and that the two regions of CyaA are functionally independent.

Adenylate Cyclase Toxin↗
PubMed1992

K-sam-related gene, N-sam, encodes fibroblast growth factor receptor and is expressed in T-lymphocytic tumors.

We recently reported the isolation of the K-sam complementary DNA (cDNA), which was amplified preferentially in poorly differentiated types of stomach cancer and codes for one of the heparin-binding growth factor or fibroblast growth factor (FGF) receptor families. The K-sam-related gene, N-sam (NCC-IT-cell-derived sam), was isolated by screening of the cDNA libraries of human immature teratoma cells, NCC-IT. Sequence analysis of the N-sam cDNAs showed that N-sam encodes a human FGF receptor, the FLG protein. N-sam was expressed in lymphocytic leukemia/lymphoma cells, predominantly in the thymic T-cell phenotype. In a T-cell leukemia line, MOLT3, N-sam mRNA expression was markedly enhanced by 12-O-tetradecanoylphorbol-13-acetate treatment and was also up-regulated by basic FGF exposure. These results indicate that N-sam expression is regulated during T-cell ontogeny and modulated by its putative ligand exposure. The results also suggested that interaction between immature T-cell and marrow or thymic interstitial cells might be mediated by N-sam and basic FGF stored in the extracellular matrix of stromal cells.

Base Sequence↗
PubMed1992

Discriminative affinity labelling of opioid receptors by enkephalin and morphiceptin analogues containing 3-nitro-2-pyridinesulphenyl-activated thiol residues.

The thiol groups of leucinthiol, cysteamine and cysteine incorporated into opioid peptides enkephalin and morphiceptin were activated by the 3-nitro-2-pyridinesulphenyl (Npys) group to form mixed disulphides highly reactive to a free thiol. Enkephalin analogues containing Npys-leucinthiol or -cysteine at positions 4, 5 and 6 exhibited high affinities for both mu and delta receptors, while morphiceptin analogues containing Npys-cysteine at positions 4 and 5 showed relatively weak affinity only for mu receptors. When these S-activated opioid peptides were incubated with rat brain membrane preparations, it was found, by binding assay using radiolabelled and non-labelled [D-Ala2,MePhe4,Gly-ol5]enkephalin, that they label mu opioid receptors in a dose-dependent manner. The concentrations required to label half of the receptors were 0.2-2 microM for enkephalins and 10-30 microM for morphiceptins. These results suggested that the thiol group labelled by S-activated enkephalins and morphiceptins is present in the ligand binding site of receptor protein, but not in GTPase-binding protein.

Affinity Labels↗
PubMed1992

Hepatocyte growth factor is a paracrine factor for renal epithelial cells: stimulation of DNA synthesis and NA,K-ATPase activity.

The expressions of mRNAs of hepatocyte growth factor (HGF) and its receptor (c-met) and its effects were examined in cultured renal epithelial cell lines (OK, LLCPK1, and MDCK cells) and rat mesangial cells in primary culture. Northern blot analysis revealed the presence of HGF mRNA in mesangial cells, but not in epithelial cells. c-met mRNA was detected in epithelial cells, but not in mesangial cells. HGF stimulated [3H]-thymidine incorporation (DNA synthesis) dose-dependently in OK and LLCPK1 cells, but not in MDCK and mesangial cells. Ouabaine sensitive rubidium uptake (Na,K-ATPase activity) was stimulated by 63% with HGF (10 ng/ml) treatment for 16hr in MDCK cells. The results suggest that HGF is produced in the kidney, at least in mesangial cells and works on epithelial cells to stimulate the proliferation and/or to modify cell functions in a paracrine manner.

Animals↗
PubMed1992

Stratificational relationship among the main nerves from the dorsal division of the sacral plexus and the innervation of the piriformis.

In order to comprehend more completely the morphology of the nerves to the piriformis, it is necessary to obtain a detailed understanding of the relationship of the origin and the course of these nerves from the dorsal division of the sacral plexus, with reference to the superior and inferior gluteal nerves. Twelve of seven human pelvic halves were carefully dissected in order to examine the origins of the nerves from the dorsal division of the sacral plexus. Six of these pelvic halves were further dissected under a stereomicroscope to examine the nerves to the piriformis. 1. The origin of the superior gluteal nerve was more proximal and dorsal in the sacral plexus than that of the inferior gluteal nerve. 2. The superior gluteal nerve consisted of a thick cranial part and a thin caudal part; the former continued as the inferior branch of the nerve, and the latter, the superior branch. The cranial and caudal parts crossed before reaching the glutei medius and minimus. 3. The nerves to the piriformis arose from three main nerves from the dorsal division of the sacral plexus: 1) the caudalmost root of the superior gluteal nerve, 2) the caudal roots of the inferior gluteal nerve and 3) the common peroneal nerve. Considering the stratificational relationship among the main nerves from the dorsal division of the sacral plexus, the piriformis appears to be composed of parts from different muscle layers.

Buttocks↗
PubMed1992

Muscles of the pelvic outlet in the fowl (Gallus gallus domesticus) with special reference to their nerve supply.

The manner of innervation of the pelvic outlet muscles in fowl (Gallus gallus domesticus) was examined in detail in four male pelvic halves. The segmental arrangement of the nerve supply in the sacral and pudendal plexuses was compared to that of Lacertilia and Urodela as a basis for a morphological analysis of the pelvic outlet muscles. From the viewpoint of innervation, the pelvic outlet muscles of fowl are classified into two groups: a sphincter muscle group and a levator muscle group. These two groups are closely related to the ventral muscles of the pelvic limb. In contrast to the morphology of pelvic outlet muscles in lacertilians, in fowl the caudal muscle element does not contribute to the formation of these muscles.

Animals↗
PubMed1992

Localization of HstI transcripts to the apical ectodermal ridge in the mouse embryo.

The HstI gene is a transforming gene, coding for a protein of the fibroblast growth factor family (Sakamoto et al., 1986). Previous RNA hybridization studies with the mouse homolog demonstrated the presence of a 3.0-kb transcript in Day 11 and 14 mouse embryos. Here we detect a 3.0-kb transcript in the limb and body of the dissected Day 11 mouse embryo. PCR amplification using HstI-specific primers also showed comparable results. In order to localize the HstI transcripts during development, corresponding HstI cDNA was isolated, and an HstI-specific region was used as a probe for in situ hybridization analysis. Serial sections of embryos from Day 8 (early-somite stages) through Days 9, 10, 11, and 12 of gestation were examined. With the antisense probe, a signal was detected in the Day 11 and 12 embryo, where it was localized to the apical ectodermal ridge (AER) of the limb bud. This structure is well known for its role in promoting the distal outgrowth of the developing limb bud. Signal was detected in both fore- and hindlimbs during the period of rapid distal growth. This restricted localization suggests a role for HstI in normal embryogenesis, including outgrowth of the limb bud.

Animals↗