Genotoxicity of 1,3-dichloro-2-propanol in the SOS chromotest and in the Ames test. Elucidation of the genotoxic mechanism

1,3-Dichloro-2-propanol (1,3-DCP-OH, glycerol dichlorohydrin) is of great importance in many industrial processes and has been detected in foodstuffs, in particular in soup spices and instant soups. It has been shown to be carcinogenic, genotoxic and mutagenic. Its genotoxic mechanisms are, however, not yet entirely understood. We have investigated whether alcohol dehydrogenase (ADH) catalysed activation to the highly mutagenic and carcinogenic 1,3-dichloroacetone or formation of epichlorohydrin or other genotoxic compounds play a role for mutagenicity and genotoxicity. In our studies, no indications of ADH catalysed formation of 1,3-dichloropropane could be found, although we could demonstrate a clear activation by ADH in the case of 2-chloropropenol. Formation of allyl chloride could also be excluded. We found, however, clear evidence that epichlorohydrin formed chemically in the buffer and medium used in the test is responsible for genotoxicity. No indication was found that enzymatic formation of epichlorohydrin plays a role. Additional mutagenicity and genotoxicity studies with epichlorohydrin also confirmed the hypothesis that genotoxic effects of 1,3-DCP-OH depend on the chemical formation of epichlorohydrin.     

Hybridization selections, using immobilized driver DNA, to enrich for clones unique to a library

We have developed a technique which allowed us to isolate sex-specific repeats of chickens (Gallus g. domesticus) from a genomic library originally containing one sex-specific repeat clone per 300 clones. Using this plus/minus selection method, we were able to enrich a sub-library in which the sex-specific repetitive clones made up over half of the population (170-fold increase in representation). This enrichment technique used hybridization kinetics to collect clones which are bound (plus selection) or not bound (minus selection) to their respective driver DNAs immobilized on nitrocellulose paper. Plus selections enriched for repetitive sequences and removed from the library most unique sequences as well as vectors containing no inserted sequences. These plus-selected sub-libraries were enriched for repetitive clones, yet still contained sequences representing as little as 10(-4) of the genome. Minus selection removed repetitive sequences shared between the driver and the library. When a plus-selected sub-library was minus selected, the doubly selected sub-library was enriched in repetitive sequences present in the library but not the minus driver.     

Multiple epitope labeling by the exclusive use of alkaline phosphatase conjugates in immunohistochemistry

 Here we demonstrate a simple and reliable multiple epitope labeling technique based exclusively on the alkaline phosphatase (AP) enzyme-linked visualization method. AP is functionally blocked by ethylenediaminetetraacetic acid (EDTA), which allows the repeated use of AP conjugates in immunohistochemistry with different substrates. We found that reactivation of AP function following EDTA incubation is dependent on EDTA concentration and incubation time. While incubation times of up to 2 h in 0.25 M EDTA, pH 6, exhibit a resumption of AP enzyme function, more than 2 h of incubation irreversibly blocks AP enzyme activity. Surprisingly, EDTA incubation also results in considerable but not complete inhibition of antibody crossreactivity during immunohistochemistry. Thus, this technique is suitable for single-layer, multiple-staining experiments with AP-linked primary antibodies or multilayer labeling with antibodies of various species for sequential staining rounds. We demonstrate the applicability of this technique in immunohistochemistry by double-labeling experiments using the monoclonal antibodies anti-glial fibrillary acidic protein, anti-leucocyte common antigen, anti-CD43/CD45RA (pan-human leucocyte), and anti-migration inhibitory factor-related protein-8 in combination with an in situ nick translation assay to characterize differentiating antigens of apoptotic cells in human glioblastoma paraffin sections. Accepted: 2 April 1998     

Management of adverse events associated with bosutinib treatment of chronic-phase chronic myeloid leukemia: expert panel review

Bosutinib, a BCR-ABL1 tyrosine kinase inhibitor (TKI), has been available for several years as a treatment for chronic-, accelerated-, and blast-phase chronic myeloid leukemia (CML), for patients with resistance or intolerance to prior therapy. In 2017, the BFORE trial demonstrated efficacy of bosutinib as first-line treatment in adult patients with newly diagnosed chronic-phase chronic myeloid leukemia (CP-CML). The most common adverse events (AEs) of any grade in bosutinib-treated patients in BFORE were diarrhea, nausea, thrombocytopenia, increased alanine aminotransferase, and increased aspartate aminotransferase, consistent with the most commonly reported AEs in earlier studies. To balance the efficacy and tolerability of treatment to optimize patient adherence with medications, treating physicians commonly use various strategies such as initiating treatment at a lower dose, dose reduction, or dose interruption, depending on the type and severity of the AEs and the clinical setting. In light of the recent data from first-line treatment, an expert panel of hematologists reviewed management strategies for the use of bosutinib in treatment of CP-CML and made the recommendations reported here. Although the panel focused on first-line treatment, the principles can be for the most part extended to bosutinib use in later lines of treatment. Recommendations include advice regarding prophylaxis and management for diarrhea. The panel also considered optimum timing for referral to a specialist for specific AEs. Across the commonly occurring AEs, the panel highlighted the importance of education and communication with patients about anticipated AEs.     

A dye-binding induced conformational transition of poly-(methacrylic acid) by Auramine O in aqueous solutions. I. Experimental results

Binding of auramine O to poly-(methacrylic acid) (PMA) has been established over a large range of C⁰_p/C⁰_d values using spectroscopic methods (UV absorption and visible fluorescence emission spectra), equilibrium and sedimentation dialysis, potentiometric and viscosimetric titrations. All the results show qualitative agreement with those obtained previously with the system crystal violet-PMA although the binding seems to be less strong for auramine O than for crystal violet. From dialysis experiments binding isotherms were obtained at three different degrees of neutralization α'; at α' = 0.10 the results could be fitted to a Langmuir isotherm but at α' equal to 0.40 and 0.65 deviations with respect to such an isotherm occur. The results of potentiometric and viscosimetric titrations confirm that the conformational transition which the dye-free PMA exhibits upon ionization is affected by the dye binding. The region in which the conformational transion occurs is broadened and is less sharply defined in the presence of auramine O.     

A study of the evolution of repeated DNA sequences in primates and the existence of a new class of repetitive sequences in primates.

A new class of lowly repetitive DNA sequences has been detected in the primate genome. The renaturation rate of this sequence class is practically indistinguishable from the renaturation rate of single-copy sequences. Consequently, this lowly repetitive sequence class has not been previously observed in DNA renaturation rate studies. This new sequence class is significant in that it might occupy a major fraction of the primate genome.Based on a study of the thermal stabilities of DNA heteroduplexes constructed from human DNA and either bonnet monkey or galago DNAs, we are able to compare the relative mutation rates of repetitive and single-copy sequences in the primate genome. We find that the mutation rate of short, interspersed repetitive sequences is either less than or approximately equal to the mutation rate of single-copy sequences. This implies that the base sequence of these repetitive sequences is important to their biological function.We also find that numerous mutations have accumulated in interspersed repeated sequences since the divergence of galago and human. These mutations are only recognizable because they occur at specific sites in the repeated sequence rather than at random sites in the sequence. Although interspersed repetitive sequences from human and galago can readily cross-hybridize, these site-specific mutations identify them as being two distinct classes. In contrast, far fewer site-specific mutations have occurred since the divergence of human and monkey.