Fluorescence polarization has been widely used for the studies on the molecular motion in solution and has been applied to immunoassays for proteins, therapeutic drug monitoring in clinical pharmacy, ...and assays for environmentally toxic compounds. Because fluorescence polarization is most readily applicable to the kinetic analysis of the binding reaction between a substance having small molecular mass and a receptor molecule, this method is easily applied to the analysis of carbohydrate–lectin binding. In this tutorial Thematic Review, we briefly introduce the principles of fluorescence polarization and some applications of fluorescence polarization technique to glycobiology.
Four 2-phenylbenzotriazole (PBTA)-type compounds (PBTA-4, PBTA-6, PBTA-7, and PBTA-8) were identified as major mutagens in blue cotton/rayon-adsorbed substances collected at sites below textile ...dyeing factories or municipal water treatment plants treating domestic waste and effluents from textile dyeing factories in several rivers in Japan. The main purpose of this study is to understand the basis of the roles of human cytochrome P450 (CYP) and
N-acetyltransferases (NATs) in genotoxic activation of PBTA derivatives. We compared the induction of
umuC gene expression as a measure of genotoxicity using
Salmonella typhimurium TA1535/pSK1002 (parental strain), NM2009 (bacterial
O-acetyltransferase-overexpressing strain) established in our laboratories. PBTA-4, PBTA-6, PBTA-7, and PBTA-8 induced the
umuC gene expression more strongly in the bacterial
O-acetyltransferase-overproducing strain than in the parental strain in the presence of rat S9 mix. We determined the activation of PBTA derivatives by cDNA-based recombinant (
Trichoplusia ni) systems expressing human or rat cytochrome P450 enzymes (P450 or CYP) and NADPH-P450 reductase using
S. typhimurium NM2009. The results showed that human recombinant CYP1A1 enzyme was much more active than CYP1A2 and CYP3A4 in the genotoxic activation of PBTA-4, PBTA-6, PBTA-7, and PBTA-8. Similarly, rat recombinant CYP1A1 enzyme catalyzed the activation of these chemicals at high rates. α-Naphthoflavone, a known inhibitor of CYP1A1, was found to inhibit genotoxic activation caused by PBTA derivatives. We further determined the activation of PBTA derivatives using
S. typhimurium NM6001 (human NAT1-expressing strain),
S. typhimurium NM6002 (human NAT2-expressing strain), and
S. typhimurium NM6000 (
O-AT-deficient parent strain) in the presence of S9 mix. PBTA-4 showed almost similar sensitivity in the NAT1-expressing strain and the NAT2-expressing strain, although NAT2-expressing strain exhibited relatively higher sensitivity to PBTA-6, PBTA-7, and PBTA-8 than NAT1-expressing strain. The results support the view that
O-acetylation by human NAT1 and NAT2 enzymes is involved in the genotoxic activation of PBTA compounds. These results demonstrate for the first time that human P4501A1 and NATs (NAT1 and NAT2) contribute significantly to the activation of PBTA-type compounds to genotoxic metabolites that induce
umuC gene expression in
S. typhimurium tester strains.
Background
Within the basic region‐helix‐loop‐helix (bHLH)‐PAS family of transcription factors, Arnt and Arnt2 play unique roles; these two factors not only heterodimerize with themselves, but also ...with other members of this family and they act as transcription regulators which bind to specific DNA elements. Whereas Arnt is broadly expressed in various tissues, the expression of Arnt2 is known to be limited to the neural tissues.
Results
To elucidate the function of Arnt2 in detail, we cloned the mouse Arnt2 gene and its gene structure was determined. We subsequently generated germ line Arnt2 mutant mice by gene targeting technology. Heterozygous Arnt2 mice were viable, but homozygous Arnt2 gene knockout mice died shortly after birth. Histological and immunological analyses revealed that the supraoptic nuclei (SON) and the paraventricular nuclei (PVN) are hypocellular. Moreover, secretory neurones identified by the expression of neurosecretory hormone such as arginine vasopressin, oxytocin, corticotrophin‐releasing hormone and somatostatin are completely absent in SON and PVN in the mutant Arnt2 mice. Consistent with these observations, prospective SON and PVN neurones which express Brn2 appeared around E13.5 in the mantle zone, but no neurones which expressed the neurosecretory hormones were found in the SON and PVN regions.
Conclusions
These data show that the transcription factor Arnt2 controls the development of the secretory neurones at the later or final stages of differentiation rather than at the beginning stage. Strikingly similar observations have been reported with the Sim1 deficient mice. Taken together, our results demonstrate that Arnt2 is an indispensable transcription factor for the development of the hypothalamus, and suggest that Arnt2 is an obligatory partner molecule of Sim1 in the developmental process of the neuroendocrinological cell lineages.
p53 mutation is one of the major results of ultraviolet (UV) radiation. UV photoproducts of cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidone (6–4) photoproducts (64PPs) also play an ...important role in skin cancer development. Atypical fibroxanthoma (AFX), which mimics malignant fibrous histiocytoma (MFH) histologically, occurs in the sun-exposed skin of the elderly, and therefore, an association with UV has long been suspected. Eighteen fibrohistiocytic skin lesions comprising AFX (n = 7), storiform-pleomorphic type MFH centered in the subcutis (superficial MFH; S-MFH; n = 4) and benign fibrous histiocytoma (BFH; n = 7) were used for immunohistochemical and molecular analysis. Eight cases of deep MFH (D-MFH) were also analyzed for UV photoproduct expression for the purposes of comparison. Immunohistochemically, the CPD scores of AFX (3.6 ± 0.4) were significantly higher than those of S-MFH (1.3 ± 0.8), D-MFH (0.8 ± 0.5), or BHF (1.4 ± 0.7); however, the 64PP scores were extremely low in all these tumors (AFX, 0.1 ± 0.1; S-MFH, 0.0 ± 0.0; D-MFH, 0.0 ± 0.0; and BHF, 0.0 ± 0.0). AFX, S-MFH, and BFH showed immunoexpression for p53 (2/7, 2/4, and 0/7), respectively. p53 mutations were detected in AFX (4/6; 67%) and S-MFH (1/4; 25%), but not in BFH (0/5; 0%) using polymerase chain reaction–single-strand conformation polymorphism, and all of the mutations in AFX were either C-T transitions or at dipyrimidine sites. In conclusion, AFX and S-MFH are both similar fibrohistocytic lesions; however, AFX has high immunoreactivity for CPDs compared with S-MFH, D-MFH, or BFH. These data suggest that CPDs may play an important role in the pathogenesis of AFX.
To the authors' knowledge, little is known regarding the relation between the proliferative ability and clinicopathologic parameters in skull base chordomas (SBCs) and nonskull base chordomas ...(NSBCs).
The authors investigated 122 conventional chordomas for their clinicopathologic parameters, proliferative ability (MIB-1 labeling index LI) and clinical outcome.
Primary NSBCs were found to affect more elderly patients and demonstrated a higher MIB-1 LI compared with primary SBCs. Mitosis was more commonly noted in recurrent NSBCs compared with primary NSBCs. Apoptosis was more frequent in elderly patients than in younger patients with regard to both SBCs and NSBCs. Apoptosis also was found to be correlated with necrosis in SBCs, suggesting a common factor for the two different types of cell death. Mucoid matrix was reported to be more abundant in NSBCs than in SBCs, and appeared to occur more often in elder NSBC patients compared with younger NSBC patients. This indicates that it is produced in the later stages of tumorigenesis. In SBCs, several clinicopathologic parameters were found to be correlated with MIB-1 LI. Among them, increased age, recurrence, and nuclear pleomorphism were the only independent factors found to indicate a higher MIB-1 LI. No such parameters were found in NSBCs. However, in these lesions, prognosis was significantly poorer in those cases with nuclear pleomorphism compared with those without.
The results of the current study suggest that nuclear pleomorphism is a prognostic indicator in NSBCs. The proliferative ability of SBCs appears to be closely associated with patient age, clinical status (recurrence), and nuclear pleomorphism.
To determine the cytochrome P450 (CYP) isoforms involved in the oxidation of propofol by human liver microsomes.
The rate constant calculated from the disappearance of propofol in an incubation ...mixture with human liver microsomes and recombinant human CYP isoforms was used as a measure of the rate of metabolism of propofol. The correlation of these rate constants with rates of metabolism of CYP isoform-selective substrates by liver microsomes, the effect of CYP isoform-selective chemical inhibitors and monoclonal antibodies on propofol metabolism by liver microsomes, and its metabolism by recombinant human CYP isoforms were examined.
The mean rate constant of propofol metabolism by liver microsomes obtained from six individuals was 4.2 (95% confidence intervals 2.7, 5.7) nmol min(-1) mg(-1) protein. The rate constants of propofol by microsomes were significantly correlated with S-mephenytoin N-demethylation, a marker of CYP2B6 (r = 0.93, P < 0.0001), but not with the metabolic activities of other CYP isoform-selective substrates. Of the chemical inhibitors of CYP isoforms tested, orphenadrine, a CYP2B6 inhibitor, reduced the rate constant of propofol by liver microsomes by 38% (P < 0.05), while other CYP isoform-selective inhibitors had no effects. Of the recombinant CYP isoforms screened, CYP2B6 produced the highest rate constant for propofol metabolism (197 nmol min-1 nmol P450-1). An antibody against CYP2B6 inhibited the disappearance of propofol in liver microsomes by 74%. Antibodies raised against other CYP isoforms had no effect on the metabolism of propofol.
CYP2B6 is predominantly involved in the oxidation of propofol by human liver microsomes.
Recent studies have shown that the use of cytokines such as granulocyte colony-stimulating factor (G-CSF) to ameliorate chemotherapy-induced myelosuppression may enhance the viability of tumour cells ...with functional receptors for these cytokines. In this study, therefore, we used murine bone marrow (BM) cells in an in vitro model in an attempt to determine whether topoisomerase inhibitors (camptothecin, etoposide and doxorubicin) induce myelosuppression (BM cell death) and whether novel treatments other than the administration of G-CSF can be used for rescue from myelosuppression. DNA fragmentation assay, ultrastructural analysis and cell cycle analysis demonstrated that these chemotherapeutic agents induced apoptosis in BM cells. We demonstrated in addition that enforced expression of the bcl-2 gene in BM cells by MPZenNeo (bcl-2) retroviral gene transfer increased resistance to the apoptosis induced by these agents. These findings suggest the possibility that enforced expression of the bcl-2 gene in BM cells using gene transfer techniques may enable rescue from chemotherapy-induced myelosuppression.
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