Surface Circular Photogalvanic Effect in Tl-Pb Monolayer Alloys on Si(111) with Giant Rashba Splitting

We have found that surface superstructures made of "monolayer alloys" of Tl and Pb on Si(111), having giant Rashba effect, produce non-reciprocal spin-polarized photocurrent via circular photogalvanic effect (CPGE) by obliquely shining circularly polarized near-infrared (IR) light. CPGE is here caused by injection of in-plane spin into spin-split surface-state bands, which is observed only on Tl-Pb alloy layers, but not on single-element Tl nor Pb layers. In the Tl-Pb monolayer alloys, despite their monatomic thickness, the magnitude of CPGE is comparable to or even larger than the cases of many other spin-split thin-film materials. The data analysis has provided the relative permittivity $\epsilon^{\ast}$ of the monolayer alloys to be $\sim$ 1.0, which is because the monolayer exists at a transition region between the vacuum and the substrate. The present result opens the possibility that we can optically manipulate spins of electrons even on monolayer materials

cDNA cloning of rat major AP endonuclease (APEX nuclease) and analyses of its mRNA expression in rat tissues.

APEX nuclease is a mammalian DNA repair enzyme having apurinic/apyrimidinic (AP) endonuclease, 3'-5'-exonuclease, DNA 3' repair diesterase and DNA 3'-phosphatase activities. It is also a redox factor (Ref-1), stimulating DNA binding activity of AP-1 binding proteins such as Fos and Jun. In the present paper, a cDNA for the enzyme was isolated from a rat brain cDNA library using mouse Apex cDNA as a probe and sequenced. The rat Apex cDNA was 1221 nucleotides (nt) long, with a 951-nt coding region. The amino acid sequence of rat APEX nuclease has 98.4% identity with mouse APEX nuclease. Using the rat Apex cDNA as a probe for Northern blot analysis, the size of rat Apex mRNA was shown to be approximately 1.5 kb. Its expression was compared in 9 rat organs on postnatal days 7 and 28. Although Apex mRNA was expressed ubiquitously, the levels varied significantly, suggesting organ- or tissue-specific expression of the Apex gene. The highest level was observed in the testis, relatively high levels in the thymus, spleen, kidney and brain, and the lowest level in the liver. The level of expression at postnatal day 28, with the exception of the testis, was almost the same as or lower in respective organs than that at postnatal day 7. Postnatal developmental changes of Apex mRNA expression in the testis and thymus were further studied. The expression in testis was markedly increased on postnatal days 21 and 28. The expression in thymus increased once at postnatal day 14, and then decreased. The developmental changes of Apex mRNA expression in testis and thymus suggest that APEX nuclease is involved in processes such as recombinational events.</p

Clinical study on polypoid lesions of the colon

1986年4月から1990年2月末までの間に岡山大学医学部附属病院三朝分院で経験した早期大腸癌を含む大腸ポリープ90例（107病変）を対象に，年齢，臨床症状，便潜血反応，病変存在部位について検討を行い，以下の成績を得た。(1)大腸検査総数の22.4％にポリープが発見された。ポリープの77％は腺腫，5％は腺癌（早期癌）であった。(2)便潜血反応はポリープ例の75.9％に陽性であり，右側大腸ポリープでの陽性率は高かったが，S状結腸および直腸ポリープでは70％程度であった。(3)若年者では右側結腸にポリープが発見されることは稀であるが，50才以上では18％程度に認められた。高齢者では右側結腸も内視鏡で検査することが重要である。(4)免疫学的便潜血検査法の導入により大腸ポリープの発見効率が改善するものと考え られた。This report is concerned with clinical study on 90 patients with polypoid lesions (107 lesions) which we have encountered in Misasa Hospital, Okayama University in the past 4 years. Following results were obtained : (1) Polypoid lesions were detected in 90 (22.4%) and advanced adenocarcinoma (mostly resectable) in 22 (5.5%) of 402 patients who were examined by sigmoidoscopy and barium enema ; (2) Histological examination of the polypoid lesions showed adenoma in 77.2%, hyperplastic polyp in 8.7%, inflammatory polyp in 7.6%, neurinoma in 0.3% and early cancer (adenocarcinoma) in 5.4% ; (3) It was impossible to differentiate benign and malignant polypoid lesions on the basis of endoscopic and X-ray findings alone ; (4) Forty-two percent of the polypoid lesions was detected in the sigmoid colon, 30% in the rectum, 16.8% in the descending colon, 9.3% in the ascending colon, 0.9% in the caecum ; (4) Patients younger than 50 years of age showed only one polypoid lesion in the right hemicolon, whereas elder patients showed as many as 17 polypoid lesions ; (5) Among the 90 patients with polypoid lesions, 40 presented with abdominal pain, 20 with no symptoms (annual health check-up), 17 with irregular bowel habits, and 10 with melena ; (6) Among the 90 patients, occult blood in stool was positive in 75.8% with a lower positive rate in the lesions of the sigmoid and rectum ; (7) Among 5 asymptomatic patients with lesions and with a negative hemoccult test, 3 patients with a polypoid lesion were examined because of the patients' request, 1 patient with a polypoid lesion because of a positive family history, and the remaining 1 patient in a search for the primary lesion of the metastatic liver cancer ; (8) Among patients with a positive hemoccult test, the detection rate of polypoid lesions was 41.9% with use of an immunological method, whereas it was 19.7% with use of a chemical method. In conclusion, (1) detection of colonic polypoid lesions can lead to the detection of early cancer, although only histological examination can confirm the accurate diagnosis ; (2) a hemoccult test in stool with an immunological method is an effective method for screening asymptomatic colonic polypoid lesions, although it must be admitted that negative results may occasionally occur ; (3) macroscopic observation of the stool mass is important before sampling, because lesions of the sigmoid colon or the rectum may show scanty blood only on the limited area of the surface of the stool ; (4) patients elder than 50 years of age should be examined more carefully for the whole colon preferably with an endoscope, because they show a high incidence of small polypoid lesions in the right hemicolon

Error-Prone Translesion DNA Synthesis by Escherichia coli DNA Polymerase IV (DinB) on Templates Containing 1,2-dihydro-2-oxoadenine

Escherichia coli DNA polymerase IV (Pol IV) is involved in bypass replication of damaged bases in DNA. Reactive oxygen species (ROS) are generated continuously during normal metabolism and as a result of exogenous stress such as ionizing radiation. ROS induce various kinds of base damage in DNA. It is important to examine whether Pol IV is able to bypass oxidatively damaged bases. In this study, recombinant Pol IV was incubated with oligonucleotides containing thymine glycol (dTg), 5-formyluracil (5-fodU), 5-hydroxymethyluracil (5-hmdU), 7,8-dihydro-8-oxoguanine (8-oxodG) and 1,2-dihydro-2-oxoadenine (2-oxodA). Primer extension assays revealed that Pol IV preferred to insert dATP opposite 5-fodU and 5-hmdU, while it inefficiently inserted nucleotides opposite dTg. Pol IV inserted dCTP and dATP opposite 8-oxodG, while the ability was low. It inserted dCTP more effectively than dTTP opposite 2-oxodA. Pol IV's ability to bypass these lesions decreased in the order: 2-oxodA > 5-fodU~5-hmdU > 8-oxodG > dTg. The fact that Pol IV preferred to insert dCTP opposite 2-oxodA suggests the mutagenic potential of 2-oxodA leading to A:T→G:C transitions. Hydrogen peroxide caused an ~2-fold increase in A:T→G:C mutations in E. coli, while the increase was significantly greater in E. coli overexpressing Pol IV. These results indicate that Pol IV may be involved in ROS-enhanced A:T→G:C mutations

Experimental model of chronic pancreatitis, a review - Does it really exist?

Experimental model of pancreatitis is mandatory for elucidating the pathobiology of the disease and also to see the response of a novel treatment. In addition, the need for an animal model of chronic pancreatitis is further strengthened by the relative inaccessibility and paucity of the human pancreatitis tissue. Whereas various models of acute pancreatitis and also of exocrine pancreatic tumor have been described, chronic pancr-eatitis has not been consistently reproduced in experimental animals. Many researchers attempted to establish an experimental model of chronic pancreatitis either by partially obstructing the drainage of pancreatic secretion in dogs and cats or by feeding alcohol to dogs and rats with and without temporary occlusion of the biliopancreatic duct or by surgically inducing ischaemia in the pancreas of the dogs. But, none of these models is identical with human disease. A consistently reproducible model of human chronic pancr-eatitis probably does not exist. In this expanding era of molecular biology which promises us to enhance greatly our understanding of this disease, a right experimental model of chronic pancreatitis is still in progress.疾患の実験モデルの作成は,その疾患の病因,病態の解明,さらに治療法の開発のために重要である｡筆者らの一人は厚生省難治性膵疾患調査研究班の班員として,慢性膵炎の病態の解明や治療法の開発に関する研究を行っており,その研究の一環として,慢性膵炎の実験モデルの作成を現在行っている｡そこで,これまで報告されている慢性膵炎の実験モデルについて概要を報告した｡種々の動物や方法でヒト慢性膵炎に病因,病態,組織像が類似するモデルの作成が試みられてきたが,そのすべてが合致するような慢性膵炎モデルは確 立されてはいない｡近年の分子生物学的研究の進歩は著しく,実験モデルへの応用が種々なされている現在,より簡便で再現性のある慢性膵炎モデルの作成が望まれるところである

Detection and analyses by gel electrophoresis of cisplatin-mediated DNA damage.

DNA damage induced by cis-diamminedichloroplatinum (II) (cisplatin: cis-DDP), an anticancer drug, was studied in vitro by monitoring the drug-induced conformational change of pUC18 plasmid DNA, the sensitivity to some restriction enzymes of the damaged DNA and the sequence-dependent termination of DNA synthesis caused by cisplatin. Closed circular, superhelical pUC18 DNA was treated at 37 degrees C for 16 h with various concentrations of cisplatin. Cisplatin-dose-dependent conformational change due to unwinding of the treated DNA was detected by agarose gel electrophoresis. To analyze the base-specificity of the cisplatin damage, the measurement for sensitivity of cisplatin-treated DNA to various types of restriction enzyme and sequence gel analysis of the treated DNA were conducted. The results suggested that cisplatin attacked preferentially the sequence of GG &#62; AG &#62; GNG in the order. In the present assay condition, the cisplatin/DNA nucleotide ratios required for the DNA damage detection were roughly 0.025 for the conformational analysis, 0.001 or more for the restriction enzyme analysis, and less than 0.001 for the sequence gel analysis. By using the present method, it was demonstrated that the cisplatin-mediated DNA damage was inhibited by NaCl, KCl, CaCl2 or MgCl2 at their nearly physiological concentrations, and by reducing agents such as thiourea and 2-mercaptoethanol in the reaction mixture.</p

Radically Different Thioredoxin Domain Arrangement of ERp46, an Efficient Disulfide Bond Introducer of the Mammalian PDI Family

SummaryThe mammalian endoplasmic reticulum (ER) contains a diverse oxidative protein folding network in which ERp46, a member of the protein disulfide isomerase (PDI) family, serves as an efficient disulfide bond introducer together with Peroxiredoxin-4 (Prx4). We revealed a radically different molecular architecture of ERp46, in which the N-terminal two thioredoxin (Trx) domains with positively charged patches near their peptide-binding site and the C-terminal Trx are linked by unusually long loops and arranged extendedly, forming an opened V-shape. Whereas PDI catalyzes native disulfide bond formation by the cooperative action of two mutually facing redox-active sites on folding intermediates bound to the central cleft, ERp46 Trx domains are separated, act independently, and engage in rapid but promiscuous disulfide bond formation during early oxidative protein folding. Thus, multiple PDI family members likely contribute to different stages of oxidative folding and work cooperatively to ensure the efficient production of multi-disulfide proteins in the ER

Peplomycin-induced DNA repair synthesis in permeable mouse ascites sarcoma cells.

DNA repair synthesis induced in permeable mouse ascites sarcoma cells by peplomycin, an antitumor antibiotic, was studied. Mouse ascites sarcoma (SR-C3H/He) cells were permeabilized with a low concentration of Triton X-100 in an isotonic condition. Permeable cells were treated with an appropriate concentration of peplomycin to introduce single-strand breaks in permeable cell DNA. DNA repair synthesis in peplomycin-treated permeable cells was measured by incubating the cells with four deoxynucleoside triphosphates in an appropriate buffer system. The DNA repair synthesis was enhanced by ATP and NaCl at near physiological concentrations. More than 90% of DNA synthesis in the present system depended on the peplomycin-treatment. The repair nature of the DNA synthesis was confirmed by a BrdUMP density shift technique. The repair patches were largely completed and ligated in the presence of ATP. Analyses using selective inhibitors for DNA polymerases showed that both DNA polymerase Beta and aphidicolin-sensitive DNA polymerases (DNA polymerase alpha and/or delta) were involved in the repair DNA synthesis.&#60;/P&#62;</p