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Biomedical subjects

A Ohashi

Publications and source records attributed to A Ohashi.

125 records · Page 7Linked to original sources
PubMed1979

Recognition of structure of 5-halogenated derivatives of ara-UTP by DNA polymerase gamma and reverse transcriptase.

This report deals with the test of a series of 5-halogenated derivatives of ara-UTP for the inhibition of DNA polymerase gamma and viral reverse transcriptase. The compounds newly synthesized and tested were; ara5-FUTP, ara5-C1UTP, ara5-BrUTP and ara5-IUTP. The results were: 1) All these compounds were inhibitory to DNA polymerase gamma and reverse transcriptase. The mode of inhibitions was, in all cases, competitive against dTTP. 2) Ki values for these inhibitors with DNA polymerase gamma were lower than those with reverse transcriptase. 3) Ara5-ClUTP was less inhibitory to reverse transcriptase than other derivatives.

Animals↗
PubMed1978

Inhibitory effect of 1-beta-D-arabinofuranosylthymine 5'-triphosphate and 1-beta-D-arabinofuranosylcytosine 5'-triphosphate on DNA polymerases from murine cells and oncornavirus.

This report compares the effect of the newly synthesized 1-beta-D-arabinofuranosylthymine 5'-triphosphate with 1-beta-D-arabinofuranosylcytosine 5'-triphosphate on the activity of DNA polymerases from mouse cells and oncornavirus. 1-beta-D-Arabinofuranosylthymine 5'-triphosphate inhibited all the activities of DNA polymerase alpha, beta, and gamma and viral DNA polymerase. The mode of inhibition of 1-beta-D-arabinofuranosylthymine 5'-triphosphate as well as 1-beta-D-arabinofuranosylcytosine 5'-triphosphate was competitive to the deoxynucleoside triphosphate with the same base. The inhibition constant (Ki) and the mode of inhibition of nucleotide incorporation varied with changes in the combination of the inhibitor, substrate(s), and enzyme species.

Animals↗
PubMed1976

Comparative studies of the effects of cyclic AMP, various hormones and chloramphenicol on the induction of delta-aminolevulinic acid synthetase and tyrosine aminotransferase in the organ-cultured chick embryo liver.

Induction of delta-aminolevulinic acid synthetase by allylisopropylacetamide in organ-cultured chick embryo liver was not appreciably influenced by any of cycli AMP, dibutyryl cyclic AMP, theophylline, glucose, insulin, glucagon, epinephrine, isoproterenol, and hydrocortisone, whereas the activity of tyrosine aminotransferase significantly increased in response to cyclic AMP and some of those hormones. Accumulation of delta-aminolevulinic acid synthetase in the cultured liver cytosol fraction was not appreciably increased by the addition of dibutyryl cyclic AMP or insulin to the incubation medium. Apparently the behaviors of the induction of delta-aminolevulinic acid synthetase in chick embryo liver in ovo and in vitro differ from those in the livers of adult chicken and rat. High concentrations of chloramphenicol suppressed significantly the allylisopropylacetamide-induced increase of delta-aminolevulinic acid synthetase as well as incorporation of 14C-leucine into proteins. The activity of tyrosine aminotransferase, however, was rather increased when relatively low concentrations of chloramphenicol were added to the medium.

5-Aminolevulinate Synthetase↗
PubMed1976

Studies on the conversion of the cytosol delta-aminolevulinate synthetase to the mitochondrial enzyme.

DELTA-Aminolevulinate (ALA) synthetase was induced in the rat by allylisopropylacetamide, and ALA synthetase in the liver cytosol fraction was partially purified. The cytosol ALA synthetase shows a molecular weight (M.W.) of about 600,000 by gel filtration and about 178,000 by sucrose density gradient centrifugation, whereas the mitochondrial enzyme gives M.W. about 110,000 by either method. In the presence of 0.25 M NaCl, however, the cytosol ALA synthetase showed M.W. 300,000--350,000 by gel filtration and gave M.W. 110,000 or a S value of 6.4 by centrifugation. Treatment of the cytosol ALA synthetase with papain or snake venom also yielded an entity which showed M.W. 110,000 by gel filtration as well as by sucrose density gradient centrifugation. When the 6.4 S enzyme once separated by centrifugation was combined with a fraction exhibiting about 4 S on centrifugation and was subsequently subjected to gel filtration, the ALA synthetase activity was recovered in the fraction corresponding to M.W. about 170,000. When the combination of the 6.4 S enzyme and a fraction of about 8 S was examined by gel filtration, the ALA synthetase activity was eluted showing M.W. about 250,000. The ALA synthetase in the cytosol fraction seems to exist as a complex composed of an ALA synthetase of M.W. 110,000 and a 4 S protein and an 8 S protein to form a larger size of the enzyme (M.W. 300,000) which further aggregates to give M.W. about 600,000. Physiologically, the complex may be subjected to a limited proteolysis so as to lose the capacity to form complex and aggregates, followed by incorporation of smaller sizes of the enzyme into the mitochondria.

5-Aminolevulinate Synthetase↗
PubMedDate not supplied

Safe percutaneous canalization of the biliary tree using a sheath in patients with malignant biliary stenosis.

BACKGROUND: Percutaneous canalization of the bile duct is essential for radiologic interventions of the biliary tract. This study discusses technical considerations for safe approaches for canalization of the bile duct when using a sheath. METHODS: During early and late periods, percutaneous canalization was performed in 104 patients and 79 patients with malignant biliary stenosis, respectively. The late period differed from the early period in that the bile duct was canalized with a previously placed sheath to prevent catheter dislodgement during the procedure. RESULTS: During the early and late periods, catheter dislodgement during canalization occurred in three of 104 patients (3%) and none of 79 patients (0%), respectively. The success rate of canalization without cholangioscopy in the late period (99%) was better than that in the early period (89%; p < 0.05). CONCLUSION: Placement of a sheath into the biliary tree increases the safety and success of canalization in patients with malignant stenosis.

Adult↗
PubMedDate not supplied

Catheter dislodgement of percutaneous transhepatic biliary drainage: identification of role of puncture sites and catheter sheath.

BACKGROUND: To identify the appropriate puncture points in the bile duct to avoid catheter dislodgement. METHODS: Percutaneous transhepatic biliary drainage catheters (n = 300) were placed in 242 patients. The frequency of dislodgement (complete dislodgement or bending of the catheter) was prospectively investigated. The puncture site of the bile duct was classified on the ultrasonographic findings as follows: Main-B3, main branch of the lateral inferior segment; peripheral-B3, peripheral branch of the lateral inferior segment; B2, lateral superior segment; left hepatic duct, proximal portion of the left hepatic duct; B8, anterior superior segment; B5, anterior inferior segment; B5 + 8, main bile duct of the anterior segment; B6, bile duct of posterior inferior segment; and right hepatic duct, proximal portion of the right hepatic duct. RESULTS: When a catheter without an outer sheath was used, catheter dislodgement in peripheral-B3 (2/11, 18%) was more common than in main-B3 (0/32, 0%; p < 0.05). In B5, catheter dislodgement (6/12, 50%) was more frequent than in B8 (3/20, 15%; p < 0.05) and in B6 (0/14, 0%; p < 0.005). When a catheter with an outer sheath was used, catheter dislodgement (2/207, 1%) was rare. CONCLUSION: Drainage from B5 and peripheral-B3 is associated with a high risk of dislodgement of the catheter. A catheter with an outer sheath was useful to prevent catheter dislodgement.

Adult↗
PubMedDate not supplied

Hyperechoic lines as a sonographic confirmatory sign during percutaneous transhepatic biliary drainage.

BACKGROUND: In ultrasonically guided percutaneous transhepatic biliary drainage, we often can recognize hyperechoic lines at the tip of the needle when the duct is penetrated successfully. We evaluated the frequency of this phenomenon and analyzed whether it was a useful sign for confirming successful bile duct puncture. METHODS: In 65 patients with biliary tract diseases, 84 catheters were placed in the course of 108 attempts at puncture. Results of puncture and the presence of hyperechoic lines were investigated prospectively. RESULTS: When the ultrasonographic findings showed hyperechoic lines, successful puncture was significantly more frequent than when the findings did not show hyperechoic lines (53/55, 96%, vs. 31/59, 53%; p < 0.0001). When we judged the hyperechoic lines as the sign of successful puncture, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 63%, 93%, 96%, 48%, and 71%, respectively. CONCLUSION: Hyperechoic lines are a useful confirmatory sign of successful puncture. However, absence of these lines was not invariably associated with unsuccessful puncture.

Aged↗
PubMedDate not supplied

Intraductal ultrasonography for evaluating the patency of biliary metallic stents: correlation with cholangioscopic findings.

BACKGROUND: This is the first study to correlate intraductal ultrasonography (IDUS) with cholangioscopy in evaluating the patency of biliary metallic stents. METHODS: The findings of IDUS (probe 2.0 mm in diameter and 20-MHz frequency) through a percutaneous transhepatic (n = 24) or transpapillary (n = 2) approach were retrospectively reviewed without other information. Criteria for IDUS are as follows: type 1, the inside of the stent is free; type 2, the inner edge is smooth; type 3, the inner edge is irregular; type 4, the inside of the stent is totally occupied; type 5, the solid echo is connected to the outside mass; type 2+D, a hypoechoic line is seen between the bile duct wall and the inside solid component and the inner edge of the bile duct wall is smooth; type 3+D, an irregular hypoechoic line is seen between the bile duct wall and the inside solid component. RESULTS: In the control group (n = 11), IDUS showed type 1 (n = 9) or type 2 (n = 2). In the occluded group (n = 15), when IDUS showed type 3 or 5, the patients (n = 5) required additional stents (n = 3), microwave coagulation of the tumor (n = 1), or transient external drainage (n = 1). When IDUS showed type 4 (n = 5), after washing, the findings changed to type 2+D (n = 4). When IDUS after washing showed a smooth inner edge (type 2+D), the patients were treated without additional stents more frequently than the other groups (eight of nine vs. two of six), a significant distinction (p < 0.05). CONCLUSION: IDUS is useful in assessing the patency of metallic stents. When the inside of the stent is totally occupied, however, examination after washing is necessary.

Aged↗
PubMedDate not supplied

Utility and limitations of intraductal ultrasonography in distinguishing longitudinal cancer extension along the bile duct from inflammatory wall thickening.

BACKGROUND: We wanted to distinguish wall thickening caused by cancer extension from that caused by inflammation after placing a biliary catheter on intraductal ultrasonography (IDUS). METHODS: We studied 51 patients with biliary tract malignancies who had undergone placement of biliary drainage catheters before IDUS. IDUS was performed from a transhepatic (n = 34) or transpapillary (n = 17) route with a thin-caliber ultrasonic probe (2.0 mm in diameter, 20-MHz frequency). At the hepatic side of the tumor, the thickness, asymmetry, outer margin, inner margin, and internal echoes of the bile duct wall were reviewed prospectively and correlated with the histologic findings of the surgically resected specimens in all cases. RESULTS: When IDUS showed wall thickening in a semicircular fashion, notched outer margin, rigid inner margin, papillary inner margin, and heterogeneous internal echoes, each finding had a positive predictive value for diagnosing cancer extension (100%, 100%, 83%, 100%, and 90%, respectively). When these factors were used as the diagnostic criteria of cancer extension, IDUS accurately demonstrated suitable surgical margins in 76% of all patients and 71% of patients with bile duct carcinoma. CONCLUSION: Wall thickening in a semicircular fashion, notched outer margin, rigid or papillary inner margin, and heterogeneous internal echoes are specific for cancer extension. However, surgical margins can be inaccurately assessed in some patients.

Aged↗
PubMedDate not supplied

Prediction of the histologic type of bile duct cancer by using intraductal ultrasonography.

BACKGROUND: Patients with papillary adenocarcinoma survive longer than do patients with other histologic types of bile duct tumors. We evaluated the usefulness of intraductal ultrasonography (IDUS) for predicting the histology. METHODS: Preoperative tumor assessment was performed by using IDUS through a percutaneous tract or the transpapillary route in 37 patients with extrahepatic bile duct cancer. In 30 of 37 patients, imaging results were compared prospectively with histologic findings in resected specimens. Probes 2.0 mm in diameter and 20 MHz in frequency were mainly used. When IDUS showed a "narrow-based polypoid pattern" or a "papillary surface pattern," the patients were judged as having papillary adenocarcinoma. RESULTS: The accuracy, sensitivity, and specificity of IDUS in predicting papillary adenocarcinoma were 90%, 89%, and 90%, respectively. When intraductal ultrasonography showed a papillary surface pattern or a narrow-based polypoid pattern, lymph node metastases and perineural invasion were rarely seen when compared with other patients with bile duct cancer (p < 0.05). CONCLUSION: IDUS is useful for assessing the histologic type of bile duct cancer.

Adenocarcinoma, Papillary↗
PubMedDate not supplied

The inhibitory effect of DL-alpha-tocopheryl ferulate in lecithin on melanogenesis.

Oral vitamin E (alpha-tocopherol) supplementation has been reported to improve facial hyperpigmentation. The compound of alpha-tocopherol and ferulic acid, also an antioxidant connected with an ester bond, alpha-tocopheryl ferulate (alpha-TF) can absorb ultraviolet (UV) radiation and thus maintain tocopherol in a stable state. Our aim was to determine whether alpha-TF can be applied to improve and prevent facial hyperpigmentation induced by UV as a whitening agent as well as an antioxidant. In this study, the effects of alpha-TF on melanogenesis were examined using cultured human melanoma cells and normal human melanocytes in vitro. alpha-TF solubilized in 0.5% lecithin inhibited melanization significantly at the concentration of 30 micrograms/ml compared with arbutin (100 micrograms/ml), kojic acid (100 micrograms/ml), ascorbic acid (600 micrograms/ml), and tranexamic acid (600 micrograms/ml). alpha-TF had no effect on the protein amounts of tyrosinase, TRP (tyrosinase related protein)-1, and TRP-2 of human melanoma cells exposed to UV radiation, but inhibited tyrosine hydroxylase activity. alpha-TF neither directly inhibited tyrosinase activity of the large granule fraction extracted from melanoma cells, nor modulated glycosylation of tyrosinase. These results suggest that alpha-TF may be a candidate for whitening agent which suppresses melanogenesis, possibly by inhibiting tyrosine hydroxylase activity in an indirect manner. Further, alpha-TF decreased the amount of 8-hydroxydeoxyguanosine produced indirectly through active oxygen species (AOS) in guinea pig skin exposed to 2 times the minimal erythema dose of UVB radiation, but did not suppress the direct formation of cyclobutane pyrimidine dimers and (6-4) photoproducts. Thus alpha-TF may reduce AOS-induced DNA damage and thereby contribute at least in part to suppressing or retarding skin cancer development.

8-Hydroxy-2'-Deoxyguanosine↗