Biomedical subjects

T Ohta

Publications and source records attributed to T Ohta.

At least 955 records · Page 53Linked to original sources

PubMed1991

Methionyl-tRNA synthetase gene from an extreme thermophile, Thermus thermophilus HB8. Molecular cloning, primary-structure analysis, expression in Escherichia coli, and site-directed mutagenesis.

The gene for the methionyl-tRNA synthetase (MetRS) from an extreme thermophile, Thermus thermophilus HB8, was cloned and sequenced. By expression of the T. thermophilus MetRS gene in Escherichia coli cells, thermostable MetRS was overproduced and purified to homogeneity by heat treatment and one-step column chromatography. The amino acid sequence of T. thermophilus MetRS showed low identities (approximately 25%) with those of MetRSs from E. coli, and cytoplasm and mitochondria of Saccharomyces cerevisiae. However, the amino acid residues in the binding sites for ATP and the anticodon and the 3' terminus of tRNA(Met) are highly conserved among the four MetRSs. T. thermophilus MetRS has a zinc finger-like sequence with all the three cysteine residues and a histidine residue. By site-directed mutagenesis of one of the cysteine residues (Cys127) of T. thermophilus MetRS, the SH group was found to be important for methionyl-tRNA synthesis. Just upstream of the structural gene for T. thermophilus MetRS there is a short open reading frame which codes for a methionine-rich peptide and is partly overlapped with an alternative terminator/antiterminator structure, suggesting that transcription of this gene is regulated by attenuation. Further upstream a region contains a nucleotide sequence homologous to that of the 5' half of T. thermophilus initiator tRNA(Met).

Amino Acid Sequence↗

PubMed1991

Negative supercoiling of DNA facilitates an interaction between transcription factor IID and the fibroin gene promoter.

Transcription of the fibroin gene can be reconstituted with partially purified components from HeLa cells. Transcription factors IIB, IID, and IIE and RNA polymerase II are required for accurate initiation of transcription. Linear and relaxed closed circular DNA show a similar level of template activity. However, transcription of closed circular DNA is stimulated when negative supercoils are introduced by the addition of DNA topoisomerase II and supercoiling factor purified from the posterior silk gland of Bombyx mori. Dissection of transcription into pre- and postinitiation steps by the use of Sarkosyl reveals that DNA supercoiling promotes formation of a preinitiation complex. Furthermore, order of addition experiments suggest that DNA supercoiling facilitates a functional binding of transcription factor IID to the promoter.

Cell Nucleus↗

PubMed1991

Initial stages of sperm-egg fusion in the freshwater teleost, Rhodeus ocellatus ocellatus.

The morphology of spermatozoa and the initial stages of sperm-egg fusion at fertilization were investigated ultrastructurally in the rose bitterling, Rhodeus ocellatus ocellatus. Each spermatozoon is composed of a spherical head without an acrosome, two centrioles, a large mitochondrion, and a flagellum. Freeze-fracture of spermatozoa illustrates that specialized arrays of intramembranous particles (IMPs) are present on the protoplasmic facing (PF) surface of the head plasma membrane at the portion slightly in front of the centrioles. The specialized arrays, whose functions are uncertain, are parallelogram-like in shape. The distribution of the particles is random and less compact in other areas of the head plasma membrane. The number of particles on the PF surface is larger than that on the extracellular facing (EF) surface. The complementary structures of the specialized arrays are also found on a similar portion of the EF surface. An ultrastructural study clearly shows fusion of gamete plasma membranes at the initial stages of sperm entry into the egg. Membrane fusion is first observed in eggs fixed 10 seconds after insemination in fresh water. The fusion site is the microvillus membrane of a sperm entry site on the egg and the head membrane of the spermatozoon. The plasma membrane fusion of gametes is discussed relative to the distribution of the IMPs and the fusion site.

Animals↗

PubMed1991

On kynureninase activity.

1) In Mg-deficient rats, kynureninase activity is decreased. 2) p-Hydroxyphenylpyruvate inhibits kynureninase activity. 3) -SH groups in the apoenzyme of kynureninase play a very important role in the enzymatic reaction. 4) 3-Hydroxykynurenine may be a very important regulative metabolite in the 3-hydroxykynurenine----xanthurenic acid pathway.

Animals↗

PubMed1991

Production of monoclonal antibodies specific for human bone gamma-carboxyglutamic acid containing protein.

Murine monoclonal antibodies specific for human bone gamma-carboxyglutamic acid containing protein (BGP) were produced against BGP purified from young adult human long bones. The amino acid composition of purified protein corresponds with that of human BGP, and Western blot analysis revealed that the antibodies reacted most intensely with the cytoplasm of osteoblasts and less intensely with the cytoplasm of osteocytes, but did not react with any other cells, such as chondrocytes, or osteoclasts. Because of their ability to react with routinely processed tissue sections and their marked reactivity with human osteoblastic cells, the antibodies are expected to be a useful tool for studying the process of ossification in human bones and for the immunohistochemical diagnosis of human osteogenic tumours.

Amino Acids↗

PubMed1991

Mucin-histochemical and immunohistochemical profiles of epithelial cells of several types of hepatic cysts.

Epithelial cells of several types of hepatic cysts were examined by mucin histochemistry and immunohistochemically. There were some differences in mucus and antigenic expression among the hepatic cysts examined. Epithelial cells of non-parasitic simple cysts and adult-type polycystic liver showed similar mucin-histochemical and immunohistochemical features, and were characterized by little mucin and weak immunoreactivities to several antibodies examined. Epithelial cells of hepatic hilar cysts were characterized by much mucin and moderate immunoreactivities to carbohydrate antigen 19-9 (CA 19-9), carcinoembryonic antigen (CEA) and epithelial membrane antigen (EMA). Epithelial cells of ciliated hepatic foregut cysts were characterized by much mucin and immunoreactivities to actin and tubulin which were positive in cilia. Epithelial cells of biliary cystadenoma were characterized by much mucin and moderate to strong immunoreactivities to cytokeratins CAM5.2 and AE1 and 3 as well as to CA 19-9, CEA, EMA and DU-PAN-2. Epithelial cells of biliary cyst-adenocarcinoma were characterized by much mucin and moderate to strong immunoreactivities to cytokeratins CAM5.2 and AE1 and 3 as well as to CA 19-9, CEA, EMA and DU-PAN-2. These differences in epithelial mucus and antigenic expression among several types of hepatic cysts may reflect differences in their origin and biological characteristics. These differences may be helpful in the differential diagnosis of hepatic cysts in small biopsy specimens.

Antigens↗

PubMed1991

Multigene families and the evolution of complexity.

Higher organisms are complex, and their developmental processes are controlled by the sequential expression of genes that often form multigene families. Facts are surveyed on how functional diversity of genes is related to duplication of genes or segments of genes, by emphasizing that diversity is often enhanced by alternate splicing and proteolytic cleavage involving duplicated genes or gene segments. Analyses of a population genetics model for the origin of gene families suggest that positive Darwinian selection is needed for acquiring gene families with desirable functions. Based on these considerations, examples that show acceleration of amino acid substitution relative to synonymous change during evolutionary processes are surveyed. Some of such examples strongly suggest that positive selection has worked. In other cases it is difficult to judge whether or not acceleration is caused by positive Darwinian selection. As a general pattern, acceleration of amino acid substitution is often found to be related to gene duplication. It is thought that complexity and diversity of gene function have been advantageous in the long evolutionary course of higher organisms.

Animals↗

PubMed1991

A new nonoperative method of percutaneous transgastric fistulo-drainage for an intractable external pancreatic fistula--a case report.

The external pancreatic fistula is a well-known complication of pancreatectomy and is conventionally classified as either a partial fistula or a total fistula. A partial fistula usually closes spontaneously and operative intervention is rarely needed, whereas, a total fistula on the other hand, very often does not close and may therefore require surgical intervention. We report herein, a case of an intractable total pancreatic fistula following pancreatoduodenectomy which was successfully repaired by a new non-operative method of percutaneous transgastric fistulo-drainage (PTFD). This technique, performed under the control of a two-way X-ray television system, is safe and considered useful for the treatment of an intractable total pancreatic fistula. In the future, this may be the method of choice for the management of such refractory total pancreatic fistulae.

Adult↗

PubMed1991

The results and problems of extensive radical surgery for carcinoma of the head of the pancreas.

Since 1973, 152 patients with pancreatic carcinoma have undergone surgery in our clinic, including 110 with carcinoma of the head of the pancreas. Of these 110 patients, resections were performed on 43 (39.1 per cent), 33 (30 per cent) of whom underwent a curative resection based on macroscopic evidence. Six of the patients who underwent macroscopic curative resection survived for five years, giving a five-year survival rate of 36.5 per cent by the Kaplan-Meier method after excepting 6 operative deaths. We compared the extent of pancreatic cancer by constructing survival curves according to the General Rules published by the Japan Pancreas Society. There was no statistical difference in survival based on tumor size or stage, however, there was a significant difference in the survival curves of so and se, being the absence or presence of the anterior capsule of the pancreas, rpo and rpe, being the absence or presence of invasion of the retroperitoneal tissue; ew(-) and ew(+) being the absence or presence of invasion at the surgical margin of resection, or n0 and n1 being the extent of lymph node metastasis. The results of this comparison suggest that extended radical pancreatectomy may be indicated for the treatment of pancreatic cancer as the standard radical operation for pancreatic cancer may miss tumors which have spread to the retroperitoneum and extrapancreatic nerve plexus.

Carcinoma↗

PubMed1991

Histomorphological study on the minor duodenal papilla.

The morphological characteristics of the minor duodenal papilla were studied histologically using surgically resected specimens according to the presence or absence of an opening of the accessory pancreatic duct in 30 patients (22 with a ductal opening and 8 without such an opening) who had undergone pancreatoduodenectomy within the past 4 years. The following results were found: 1) The minor duodenal papilla was composed fundamentally of the accessory pancreatic duct, pancreatic tissue of the dorsal pancreas which penetrated the duodenal proper muscular tunics and the surrounding fibrous connective tissue. 2) In those specimens with a ductal opening, smooth muscle fiber bundles derived from the duodenal proper muscular tunics surrounded the accessory pancreatic duct and seemed to possess sphincter action similar to that of Oddi sphincter muscles. 3) In those specimens without a ductal opening, the accessory pancreatic duct terminated blindly in the minor duodenal papilla which was comprised mostly of pancreatic tissue and seemed to have no sphincter muscles. 4) Islet cells in the pancreatic tissue of the minor duodenal papilla were rich in B-cells which were round to ovoid in shape and sharply outlined.

Ampulla of Vater↗

PubMed1991

Clinicopathological studies on solid and cystic tumors of the pancreas.

Three cases of pancreatic tumor in two females (case 1, case 3) and one male (case 2) were reported. Macroscopically cases 1 and 3, which were surrounded by a thick fibrous capsule, developed toward the outside of the pancreas and the cut surface showed mainly cystic degenerative areas filled with necrotic and hemorrhagic materials. In contrast with these two cases, case 2 was buried in the pancreatic tissue and the cut surface showed cystic degenerative areas in its center with a thick fibrous capsule and tumor cell nests invading beyond the capsule to the parenchyma of the pancreas. Microscopically each tumor was identical. The solid areas on the periphery were composed of sheets of polygonal uniform cells subdivided by delicate fibrovascular stalks. Near the degenerative areas, tumor cells lay on a delicate fibrovascular core in one or two layers, with pseudopapillary patterns. Mitotic figures were very rare. All three cases demonstrated immunoreactivity for alpha-1-antitrypsin, but not for islet hormones, tumor markers nor neuron-specific enolase. Although electronmicroscopically, zymogen granules were detected in cases 2 and 3, and annulate lamellae in cases 1 and 3, ductal cell character features were not so developed. From the above, these tumors were diagnosed as solid and cystic tumors of the pancreas. Furthermore, it was suggested that they differentiated in the direction of acinar cells.

Adolescent↗

PubMed1991

Clinicopathological study of pancreatic carcinoma with particular reference to the invasion of the extrapancreatic neural plexus.

A clinicopathological study of 44 ductal carcinomas of the head of the pancreas revealed 39 with retroperitoneal invasion, of which 27 showed extrapancreatic plexus involvements. The second portion of the plexus pancreaticus capitalis was the most frequent site of invasion. A statistically significant correlation was found between neural invasion in the pancreatic tissue and plexus invasion, but no clear correlation was found between plexus invasion and lymphatic invasion or tumor size. Even small-sized tumors (t1) showed plexus invasion. The cases with plexus invasion had a statistically higher incidence of lymph-node involvement around the superior mesenteric artery than those without plexus invasion. These results indicate that complete dissection of extrapancreatic plexus around the superior mesenteric artery, including lymph nodes and soft tissue, could prolong the survival of patients with ductal carcinoma of the pancreas, even in cases of small-sized carcinomas.

Humans↗

PubMed1991

Patterns of neural and plexus invasion of human pancreatic cancer and experimental cancer.

Specimens from four patients who underwent resection of cancer of the pancreatic head were examined histologically by serial sections to study the patterns of extrapancreatic nerve plexus invasion of cancer. To understand the mode of neural invasion and its specificity for pancreatic cancer, we also examined retropancreatically transplanted virus-induced rabbit papilloma (VX2) cells in six rabbits. Histological evaluation of the specimens from patients revealed neural invasion near the primary lesion, where cancer cells broke the perineurium and showed communication of cancer cells between the inside and outside of the perineurium. Tumor cells found distant from the primary cancer were confined to the perineurium, grew in a continuous pattern, and followed the branches of nerves. When the rabbit's VX2 cells were implanted into the retropancreatic region of recipient rabbits we also observed neural invasion. This study shows that neural invasion is a common, but not a specific, feature of pancreatic cancer, and it suggests that en bloc excision of the retropancreatic tissue, including fat tissue and the extrapancreatic nerve plexus, should be the basic procedure of radical surgery in the treatment of pancreatic cancer.

Animals↗

PubMed1991

Surgical treatment of pancreatic cancer. The Japanese experience.

Since 1973, 194 patients with pancreatic carcinoma have undergone surgery in our clinic, including 134 with carcinoma of the head of the pancreas. Of these 134 patients, resections were performed on 61 (45.5%), 49 (36.6%) of whom underwent a curative resection based on macroscopic evidence. Seven of the patients who underwent macroscopic curative resection survived for five years, giving a five-year survival rate of 26.4% by the Kaplan-Meier method after excepting seven operative deaths. We compared the extent of pancreatic cancer by constructing survival curves according to the General Rules published by the Japan Pancreas Society. There was no statistical difference in survival based on tumor size or stage; however, there was a significant difference in the survival curves of so and se, being the absence or presence of the anterior capsule of the pancreas; rpo and rpe, being the absence or presence of invasion of the retroperitoneal tissue; ew(-) and ew(+), being the absence or presence of invasion at the surgical margin of resection; and n0 and n1, being the extent of lymph node metastasis. The results of this comparison suggest that extended radical pancreatectomy may be indicated for the treatment of pancreatic cancer, since the standard radical operation for pancreatic cancer may miss tumors that have spread to the retroperitoneum and extrapancreatic nerve plexus.

Adult↗

PubMed1991

Atypical depressive symptoms possibly predict responsiveness to phototherapy in seasonal affective disorder.

Phototherapy was administered to 24 depressed patients with seasonal affective disorder (SAD), of which 62%, 24%, and 14%, respectively, showed improvements of greater than or equal to 50%, 25-50%, and less than 25% based on the Hamilton rating scale for depression for SAD (HAMSAD). No patients showed aggravation or side effects. Although the improvement rate in HAMSAD correlated significantly with the pretreatment severity of atypical symptoms of depression, it did not correlate with that of typical symptoms. This suggests that phototherapy is a useful treatment in SAD and that responsiveness to phototherapy in SAD can possibly be predicted by the atypical depressive symptoms before treatment.

Adolescent↗

PubMed1991

Tea tannin components modify the induction of sister-chromatid exchanges and chromosome aberrations in mutagen-treated cultured mammalian cells and mice.

The modifying effects of tannin components extracted from green tea and black tea on mutagen-induced SCEs and chromosome aberrations were studied. These tannin components did not affect spontaneous SCEs and chromosome aberrations in cultured Chinese hamster cells. The frequency of SCEs and chromosome aberrations induced by mitomycin C (MMC) or UV was enhanced by the posttreatment with tea tannin components. When cells were post-treated with tea tannin components in the presence of metabolic enzymes of rat liver (S9 mix), the modifying effects on the induction of SCEs and chromosome aberrations by mutagens were complicated. MMC- and UV-induced SCEs and chromosome aberrations were suppressed by the posttreatment with tea tannin components at low concentrations (less than or equal to 6.7 micrograms/ml) with S9 mix. At a high concentration of tea tannin components (20 micrograms/ml) with S9 mix, a co-mutagenic effect was observed. The modifying effects of tea tannin components were shown to occur in the G1 phase of the cell cycle. In cells from a patient with xeroderma pigmentosum (XP) and a normal human embryo, MMC-induced SCEs were suppressed by the posttreatment with tea tannin components in the presence of S9 mix, and enhanced in the absence of S9 mix. On the other hand, tea tannin components modified SCE frequencies in UV-irradiated normal human cells but not in UV-irradiated XP cells. Our results suggested that tea tannin components themselves inhibited DNA-excision repair and resulted in a co-mutagenic effect, while in the presence of S9 mix metabolites of tea tannin components promoted DNA-excision repair activity and resulted in an antimutagenic effect. MMC-induced chromosome aberrations in mouse bone marrow cells were suppressed by the pretreatment with green tea and black tea tannin mixture.

Animals↗

PubMed1991

Rotenone induces aneuploidy, polyploidy and endoreduplication in cultured Chinese hamster cells.

The clastogenic potential of rotenone, an insecticide, was investigated in cultured Chinese hamster cells. Rotenone induced aneuploidy (hypodiploidy and hyperdiploidy), polyploidy, and endoreduplication, but not structural chromosome aberrations. The highest frequency of polyploidy and endoreduplication was 58.8% and 3.0%, respectively, when cells were treated with rotenone at 1.0 microgram/ml for 30 h.

Aneuploidy↗

PubMed1991

Acute pancreatitis associated with anomalous union of the pancreaticobiliary ductal system.

Between 1978 and 1989, 13 of 48 patients with anomalous union of the pancreaticobiliary ductal system (AUPBD) were diagnosed as having acute pancreatitis. We have studied the clinical, radiologic, and surgical features of these 13 patients. A transient rise in the intraductal pressure of the pancreatic duct during an episode of abdominal pain is responsible for pancreatitis in patients with AUPBD. This rise in the intraductal pressure must be due to bile reflux into the pancreatic duct when an abnormally long common channel is blocked by cholelithiasis, protein plug, or dysfunction of the sphincter of Oddi. The pancreatitis resolves when the common channel obstruction is removed, and bile and pancreatic juice flow easily into the duodenum. We believe that this phenomenon is responsible for acute relapsing pancreatitis. It is our belief that the pancreas appears almost normal during symptom-free intervals.

Acute Disease↗