Search PubMed⌕ Search

Biomedical subjects

T Tamaoki

Publications and source records attributed to T Tamaoki.

At least 145 records · Page 8Linked to original sources
PubMed1983

Primary structures of human alpha-fetoprotein and its mRNA.

DNA complementary to human alpha-fetoprotein (AFP)mRNA was cloned in the plasmid pBR322. Analysis of three overlapping cDNA clones revealed most of the nucleotide sequence of AFP mRNA, and the remaining nucleotides at the 5' end of the mRNA were elucidated from a cloned genomic DNA fragment. The amino acid sequence was deduced from the nucleotide sequence, which revealed 19 amino acids in the signal sequence and 590 amino acids in mature AFP. There are 15 regularly spaced disulfide bridges, which generate a folding structure having three repeating domains. There is one potential N-glycosylation site, Asn-Phe-Thr, in the amino acid sequence. In comparison with mouse AFP, 66% of the amino acid sequence was conserved, with the highest identity (72%) in domain 3, followed by domain 2 (67%) and domain 1 (59%). In comparison with human albumin, a 39% conservation of primary structure was found. Again, the similarity was the highest in domain 3 and the lowest in domain 1. Human AFP and human albumin are similar in overall structure, but certain parts of the molecules differ significantly in their predicted secondary structure.

Amino Acid Sequence↗
PubMed1983

[Structure and expression of alpha-fetoprotein gene--current progress in research].

alpha-Fetoprotein (AFP) is of great biological and medical interest because its concentration in the serum often increases drastically in association with the development of hepatomas and germ cell tumors. Thus, studies of mechanisms of regulation of AFP synthesis may contribute to our understanding of normal and neoplastic growth processes. This article will review recent advances in the study of the structure, expression and regulation of the AFP gene in normal and malignant cells.

Albumins↗
PubMed1982

Expression and methylation of the mouse alpha-fetoprotein gene in embryonic, adult, and neoplastic tissues.

Expression of the mouse alpha-fetoprotein gene in embryonic, adult, and neoplastic tissues was assessed by RNA dot hybridization using 32P-labeled alpha-fetoprotein cDNA as probe, alpha-fetoprotein mRNA was present in high levels in total RNA from yolk sac endoderm, fetal liver, and an alpha-fetoprotein-producing hepatoma. In contrast, this mRNA was greatly depleted in total RNA from yolk sac mesoderm and essentially absent in brain, adult liver, and a non-alpha-fetoprotein-producing hepatoma. These results indicated that alpha-fetoprotein gene expression was controlled primarily at the transcriptional level. The presence of the modified base, 5-methylcytosine, in the alpha-fetoprotein gene was studied by comparing hybridization patterns obtained by Southern blot analysis of DNA cleaved with the restriction endonuclease isoschizomers Msp I and Hpa II. The gross sequence organization and reiteration frequency of the alpha-fetoprotein gene were invariant among the DNA samples, whereas, in each case, there was a positive correlation between hypomethylation of six CCGG (Hpa II) sites in the alpha-fetoprotein gene and expression of this gene. These Hpa II sites were distributed throughout a large portion of the alp]a-fetoprotein gene. Patterns of cytosine methylation in this gene were established before day 15 of gestation in yolk sac endoderm and mesoderm.

Animals↗
PubMed1982

Control of HLA-DR antigen gene expression at the pretranslational level: comparison of an HLA-DR-positive B lymphoblastoid cell line and its HLA-DR-negative variant.

An HLA-DR-positive human B lymphoblastoid cell line, T5-1, and its HLA-DR negative variant, 6.1.6, were studied to elucidate mechanisms resulting in the nonexpression of HLA-DR genes in 6.1.6. The cell lines were labeled with 35S-methionine in vivo, their proteins immunoprecipitated with a monoclonal HLA-DR-specific antibody, and their two-dimensional gel electrophoresis patterns compared. The T5-1 map showed DR-antigen heavy and light chains, while the 6.1.6 map showed neither chain. When the cells were labeled in the presence of tunicamycin, the two-dimensional map of T5-1 showed nonglycosylated heavy and light chains of DR antigen while that of 6.1.6 did not. RNA was extracted from T5-1 and 6.1.6 cells and translated in rabbit reticulocyte lysates. Two-dimensional gel analysis of the immunoprecipitated proteins from T5-1 revealed spots which were identified as HLA-DR light chain and I invariant on the basis of their precipitation by monoclonal and specific allo- and heteroantibodies, and their molecular weight and pI values. These spots were absent in the 6.1.6 maps, indicating that 6.1.6 has no detectable translatable messenger RNA for HLA-DR light chains. The addition of dog pancreas microsomes to the T5-1 cell-free translation mixture resulted in an increase in the molecular weight of the precursor HLA-DR proteins consistent with glycosylation. Together with earlier cell fusion studies showing that DR structural genes were intact in 6.1.6, these data suggested that the lesion in 6.1.6 is an alteration in a regulatory element required for transcription of DR genes or mRNA processing.

B-Lymphocytes↗
PubMed1982

Synthesis of alpha-fetoprotein by the pre-implantation and post-implantation bovine embryo.

The synthesis of alpha 1-fetoprotein (AFP) was measured by radioimmunoassay in tissues and fluids of 19 bovine embryos (14-46 days of gestation) and in tissue cultures of 4 pre-implantation embryos (17-27 days) by incorporation of radioactive methionine. AFP was first detected in Day-14 trophoblasts and secretion of AFP into allantoic fluid occurred by Day 16. Embryonic tissues and fluids in pre-implantation and post-implantation embryos contained levels of AFP that were 550 to 1 500 000 times higher than those found in maternal serum (3.9-298 000 compared with 0.07-0.25 ng/mg protein). High levels of AFP were also found in uterine fluid which suggested significant transfer of this protein from the early post-implantation conceptus. The major sites of AFP synthesis were yolk sac and fetal liver. It is concluded that the synthesis of bovine AFP is not initiated by events associated with implantation.

Animals↗
PubMed1982

Tetrocarcins, new antitumor antibiotics. 3. Antitumor activity of tetrocarcin A.

Tetrocarcin A, isolated from a Micromonospora culture showed activity against experimental i.p. inoculated tumors such as Ehrlich carcinoma, MH134 hepatoma, B16 melanoma. But it was not active against solid tumors such as sarcoma 180 and Ehrlich carcinoma. It was marginally active against the growth of solid Lewis lung carcinoma without prolonging the life span of the tumor-bearing mice. It was active against P388 leukemia (i.v.-i.v. system). It did not show myelosuppression and nephrotoxicity in mice. DNA and protein synthesis of P388 cells in culture were more significantly suppressed than RNA synthesis by tetrocarcin A.

Aminoglycosides↗
PubMed1982

Gilvocarcins, new antitumor antibiotics. 4. Mode of action.

The mode of action of gilvocarcins was studied. Gilvocarcins V, M and A possessed antibacterial activities decreasing in that order. Gilvocarcin V inhibited DNA synthesis in Bacillus subtilis through strong interaction with DNA and resulting cleavage. Gilvocarcin M showed interaction with DNA and a small change in DNA mobility upon electrophoresis in agarose gel, while gilvocarcin A showed no interaction with DNA, thus reflecting their relative biological activities.

Aminoglycosides↗
PubMed1982

Tetrocarcins E1, E2, F and F-1, new antibiotics. Fermentation, isolation and characterization.

New components of tetrocarcins (E1, E2, F and F-1) were found in the culture broth of Micromonospora chalcea KY 11091 that was known to produce tetrocarcins A, B and C. Tetrocarcin F-1 consisted of tetronolide and nitro sugar (tetronitrose). Tetrocarcins E1 and E2 consisted of F-1 and deoxy sugar (L-digitoxose). Tetrocarcin F consisted of F-1 and two deoxy sugars (their structures were not yet determined). They all showed antibacterial activities against Gram-positive bacteria and the specific activity decreased with decrease in the numbers of deoxy sugars attached to the aglycone.

Aminoglycosides↗
PubMed1982

Synthesis and secretion of alpha-fetoprotein and acute-phase alpha 2-macroglobulin by Zajdela rat ascites hepatoma.

Zajdela rat ascites hepatoma cells have been reported to be 'nonsecretors' of alpha-fetoprotein (AFP). Because of the potential of such cells in the study of defective secretory mechanisms of AFP and other serum proteins, we concluded a detailed investigation of the production of AFP in Zajdela cells growing in vivo. Three approaches were used: radioimmunoassay of intracellular and extracellular AFP and assays of AFP mRNA by molecular hybridization and cell-free translation. Radioimmunoassay showed that the AFP concentration in the hepatoma cells was extremely low (1.2 micrograms/g) as compared to known AFP-producing tissues such as fetal liver (600 micrograms/g). The assays of AFP mRNA by hybridization and translation supported the low level of AFP production in Zajdela cells, and we consider such cells to be poor producers of AFP and therefore not suitable for the study of defective mechanisms for AFP secretion. The Zajdela tumor cell intracellular concentration of acute-phase alpha 2-macroglobulin (AP alpha 2M) measured by radioimmunoassay was also found to be low (3.0 micrograms/g) compared to liver of Zajdela-bearing rats (80 micrograms/g). In view of these low levels of synthesis of AFP and AP alpha 2M in Zajdela hepatoma cells, little biological significance may be attached to the apparent nonsecretion of these onco-fetal proteins.

Animals↗
PubMed1982

Alphafetoprotein messenger RNA in human embryonal carcinoma grown in nude mice, and cloning of its complementary DNA.

Messenger RNA for human apha-fetoprotein (AFP) was partially purified from human testicular embryonal carcinoma grown in nude mice. DNA complementary to the mRNA was synthesized, tailed with oligo(dC) and inserted at the PstI site of the plasmid pBR322 tailed with oligo(dG). Escherichia coli strain LE392 was transformed with the chimeric plasmid and colonies were screened for human AFP mRNA sequences by hybridization with DNA complementary to mouse AFP mRNA (greater than 95% pure). Five colonies showed positive hybridization. The plasmid pHAF2, containing the largest insert, 900 nucleotides, was further characterized by hybrid-arrest of translation of AFP mRNA, restriction endonuclease mapping and partial nucleotide sequence analysis. It was found that the AFP complementary DNA (cDNA) sequence in pHAF2 corresponded to the 3'-end of AFP messenger RNA (mRNA), and showed a restriction map entirely different from that of mouse AFP cDNA clones previously reported.

Animals↗