Pyridyl- and Pyridylperoxy Radicals – A Matrix Isolation Study

The three isomeric pyridyl radicals 2a–c were synthesised using flash vacuum pyrolysis in combination with matrix isolation and characterised by infrared spectroscopy. The IR spectra are in good agreement with spectra calculated using density functional theory methods. The reaction of the pyridyl radicals 2 with molecular oxygen leads to the formation of the corresponding pyridylperoxy radicals 3a–c. The peroxy radicals 3 are photolabile, and irradiation results in syn–anti isomerisation of 3a and 3b and ring expansion of all three isomers of 3.

A map of local adaptation in Arabidopsis thaliana

Local adaptation is critical for species persistence in the face of rapid environmental change, but its genetic basis is not well understood. Growing the model plant Arabidopsis thaliana in field experiments in four sites across the species' native range, we identified candidate loci for local adaptation from a genome-wide association study of lifetime fitness in geographically diverse accessions. Fitness-associated loci exhibited both geographic and climatic signatures of local adaptation. Relative to genomic controls, high-fitness alleles were generally distributed closer to the site where they increased fitness, occupying specific and distinct climate spaces. Independent loci with different molecular functions contributed most strongly to fitness variation in each site. Independent local adaptation by distinct genetic mechanisms may facilitate a flexible evolutionary response to changing environment across a species range.

GER1, a GDSL motif-encoding gene from rice is a novel early light- and jasmonate-induced gene

The reaction of the rice mutant HEBIBA differs from that of wild-type rice in that the mutant responds inversely to red light and is defective in the light-triggered biosynthesis of jasmonic acid (JA). Using the wild type and the HEBIBA mutant of rice in a differential display screen, we attempted to identify genes that act in or near the convergence point of light and JA signalling. We isolated specifically regulated DNA fragments from approximately 10 000 displayed bands, and identified a new early light- and JA-induced gene. This gene encodes an enzyme containing a GDSL motif, showing 38 % identity at the amino acid level to lipase Arab-1 in Arabidopsis thaliana. The GDSL CONTAINING ENZYME RICE 1 gene (GER1) is rapidly induced by both red (R) and far-red (FR) light and by JA. The results are discussed with respect to a possible role for GER1 as a negative regulator of coleoptile elongation in the context of recent findings on the impact of JA on light signalling.

Characterization of cytokine, growth factor receptor, costimulatory and adhesion molecule expression patterns of bone marrow blasts in relapsed childhood B cell precursor all

Relapse of childhood acute lymphoblastic leukaemia (ALL) comprises a leading challenge of investigation. Characterization of leukaemic cells regarding their potency to express growth factors and surface molecules can provide insight into their aberrant biology. Thus, we analyzed bone marrow blasts from 10 children with relapsed B cell precursor ALL. The gene and protein expression of essential haematopoietic growth factors (IL-2, IL-4, IL-7, IL-10, IL-15, IFN-gamma, G-CSFR), their corresponding receptors as well as the expression pattern of adhesion molecules (ICAM-1, CD58) and costimulatory proteins (CD40, CD40L, B7.1, B7.2, CD28, MHC-I and II) was analyzed by RT-PCR and flow cytometry. Constitutive gene expression was found for IL-7, IL-10, IL-15 and IFN-gamma and their corresponding receptors. Flow-cytometric analysis showed that IL-10R, IL-7Ralpha, IL-4Ralpha and the gamma(c)chain are constitutively expressed, and that some cells bear the G-CSFR. IL-10 and IL-15 protein-producing leukaemic cells were easily detectable. The neoplastic cells mainly lack B7.1, and ICAM-1 is mostly decreased. Furthermore, high CD40, and, surprisingly, CD40L expression could be found. These studies show that ALL cells are likely to be sensitive to many growth factors and some factors are produced by the neoplastic cell itself. The secretion of IL-10 by leukaemic cells, and the absence or downregulation of conventional adhesion and costimulatory molecules might represent an effective mechanism of escape of immune surveillance in relapsed ALL.

Expression analysis and characterization of alternatively spliced transcripts of human IL-7Ralpha chain encoding two truncated receptor proteins in relapsed childhood all

In the family of cytokines and cytokine receptors, alternative splicing of pre-mRNA is a frequently observed process that generates different protein isoforms from a single genetic locus. The splicing-derived cytokine receptor protein isoforms are mostly soluble receptors or show alterations in their cytoplasmic domain. It is possible that receptor abnormalities or a pathological ratio of different isoforms may contribute to leukaemia by circumventing normal growth factor control or altering the balance of proliferation and differentiation. IL-7 plays a critical role in early stages of both B and T cell maturation. Moreover, it stimulates the expansion of mature T cells including anti-tumour reactive cells as well as a number of T and B cell malignancies underlining its potential importance for deregulated lymphoid proliferation and leukaemogenesis. Here, we present detailed data on the expression of the interleukin 7 receptor alpha chain (IL-7Ralpha) in leukaemic cells from 210 children with acute lymphoblastic leukaemia (ALL) and describe two novel alternatively spliced transcripts of human IL-7Ralpha coding for truncated receptor proteins which are still capable of binding IL-7. IL-7Ralpha mRNA expression was more frequent in more mature pre-B ALL [91% (30/33)] than in common [81% (81/100)] or pro-B ALL [64% (18/28)], or even in T ALL [64% (29/45)]. These results are in concordance with flow cytometric analyses on the proportion of IL-7Ralpha bearing cells among total blast cell population. Our results lead us to assume that splicing derived IL-7Ralpha isoforms play a potential role in modulating IL-7 signal transduction and might be important for the pathogenesis of leukaemia.

Extensive alternative splicing of interleukin-7 in malignant hematopoietic cells: implication of distinct isoforms in modulating IL-7 activity

Interleukin-7 (IL-7) plays a pivotal role in early stages of normal B and T cell development. In addition, IL-7 stimulates the proliferation of both antitumor reactive cells and a number of T and B cell malignancies, underlining its significance for leukemogenesis. However, its exact role in the process of pathologic maturation of lymphocytes and regulation of the immune response is not completely understood. As alternative splicing of pre-mRNA has been shown to be involved in the control of gene expression, and splicing-derived protein isoforms with antagonistic activity have been found, we assessed the mRNA-expression of IL-7 and its previously described alternative splice variant lacking exon 4, IL-7delta4, in leukemic cells from children with acute lymphoblastic leukemia (ALL). PCR of full-length IL-7 cDNA enabling the competitive amplification of both variants led to the amplification of diverse unexpected PCR products. The sequence data demonstrated the existence of three additional in-frame splice variants resulting from exon skipping of exon 3 or exon 5 or both in combination with exon 4. We named these IL-7delta3/4, IL-7delta4/5, and IL-7delta3/4/5. Furthermore, three out-of-frame splice variants were identified, IL-7(-56bpExon2), IL-7delta4(-56bpExon2), and IL-7delta3/4/5(-56bpExon2), in which, in addition to the aforementioned exon skipping, 56 bp of the 3' end of exon 2 are omitted. Our results led us to assume that splicing-derived IL-7 isoforms play a potential role in modulating IL-7-mediated biologic effects. Further studies are required to clarify the significance of the diverse IL-7 protein isoforms for the regulation of IL-7 function and the pathogenesis of leukemia.

Guanine nucleotides and pertussis toxin reduce the affinity of histamine H3 receptors on AtT-20 cells

Agonist occupancy of high affinity histamine H3 receptors on AtT-20 cells induces increased ACTH release. However, the signal transduction process by which this occurs is presently unknown. As a first step in characterizing this pathway, we have examined the effects of a variety of nucleotides and nucleotide analogs on Na-methylhistamine binding to these receptors. Nonhydrolyzable guanine nucleotide analogs inhibit up to 40% of the [3H]Na-methylhistamine binding by increasing the dissociation rate of the ligand from the receptor and, thereby, reducing receptor affinity. Pertussis toxin also decreases the affinity of the H3 receptors and ADP ribosylates a 41 kDa protein. Neither GTP gamma S nor pertussis toxin change Bmax. These data indicate that the H3 receptors on these cells are coupled to a G protein of the Gi subclass.

High affinity histamine H3 receptors regulate ACTH release by AtT-20 cells

The distribution of high affinity histamine H3 receptors in various tissues from guinea pig has been determined using [3H]N alpha-methylhistamine binding. In the course of those studies, it was observed that the pituitary gland contains H3 receptors. Using this radioligand, we have now identified and characterized H3 receptors on' the AtT-20 cell line from a murine anterior pituitary tumor. This line has approximately 5000 high affinity (KD = 0.7 nM) H3 binding sites per cell. Competition binding with standard H1, H2 and H3 agents has confirmed that these sites are, indeed, H3 receptors. The H3 receptor specific agonist, (R)-alpha-methylhistamine increased the release of adrenocorticotropic hormone (ACTH) from AtT-20 cells in a dose- and time-dependent manner, while histamine and the H2 agonist dimaprit were significantly less potent. Furthermore, this response was blocked by thioperamide, an H3 receptor specific antagonist, but not by the H1 and H3 antagonists, chlorpeniramine and cimetidine. These results identify, for the first time, a cell line expressing H3 receptors and indicate that the high affinity histamine H3 receptor regulates ACTH release from that cell.

Characterization and tissue distribution of H3 histamine receptors in guinea pigs by N alpha-methylhistamine

We have used [3H]N alpha-methylhistamine to characterize H3-binding in the guinea pig brain and to study its tissue distribution. Kinetic and equilibrium binding experiments indicate a single class of high affinity sites in membranes isolated from guinea pig brain tissue (Kd = 0.4 nM, Bmax = 41 fmol/mg of protein). Competition binding experiments have confirmed that this ligand associates with H3-receptors and, under the conditions used in these experiments, does not bind to H1- or H2-receptors. Although there was some binding in the ileum and large intestine, H3-binding was found primarily in the central nervous system.

Embryotoxicity and mutagenicity of mycotoxins

Embryotoxicity: Aflatoxin B1 (AFB1), G1 (AFG1), and Patulin (PA) were investigated in NMRI mice for embryotoxic and teratogenic activity. These three mycotoxins were injected intraperitoneally or given orally on day 12 and 13 of pregnancy. AFB1 (15, 45, and 90 mg/kg ip or 45 mg/kg po) produced moderate retardation in fetal development and a dose-related increase of cleft palates, wavy ribs, and diaphragm changes. The effects after injection of AFG1 (45 to 90 mg/kg ip) were reduction of fetal weights, increase of diaphragm changes, and malformations of kidneys. PA (1, 25, 2, 5, and 3.75 mg/kg ip or 3.75 mg/kg po) was found to elevate the rate of cleft palates after 3.75 mg/kg. Dominant lethal assay: Neither PA (2, 5, and 5 mg/kg ip) nor AFB1 (15 and 45 mg/kg ip) increased the frequency of the dominant lethal mutations. Both mycotoxins showed no mutagenic activity in this test system. Cytogenetic studies: The capability of the three mycotoxins AFB1, AFG1, and PA to induce chromosome damages in vivo has been tested in the Chinese hamster by examination of bone marrow cells. The substances were tested in each of two oral doses (AFB1: 12, 5, and 25 mg/kg; 25 and 50 mg/kg; PA: 10 and 20 mg/kg). The present data show that the three mycotoxins induce chromosome aberrations in the following order of activity: PA greater than AFB1 greater than AFG1.

Mutagenicity testing of doxylamine succinate, an antinauseant drug

Doxylamine succinate (DA), a compound which was formerly used as an antinauseant during pregnancy, showed no substantial mutagenicity in mouse embryos following transplacental exposure. A small dose-dependent induction of chromosomal aberrations was found in mouse embryos on day 11 of gestation. No induction of sister chromatid exchanges (SCE) was found in embryos on day 11 of gestation. A micronucleus test with fetal blood on day 17 of gestation was negative. Additionally, DA was negative in Chinese hamster bone marrow in vivo (micronuclei) and in human lymphocyte cultures in vitro (SCE).

Central muscarinic cholinergic influences on ethanol sensitivity in long-sleep and short-sleep mice

Sensitivity to the hypnotic effects of ethanol was increased selectively by central administration of muscarinic agonists. Carbachol or oxotremorine, but not nicotine, i.c.v., enhanced hypnotic sensitivity to ethanol markedly, as measured by blood ethanol concentration at loss or righting response, in short-sleep (SS) but not long-sleep (LS) mice. Likewise, the acetylcholinesterase inhibitor, neostigmine, i.c.v., differentially enhanced hypnotic sensitivity to ethanol in these mouse lines. LS and SS mice were equally sensitive to the hypothermic effects of carbachol, neostigmine or oxotremorine i.c.v. The muscarinic antagonists, atropine or pirenzepine, i.c.v., were without effect on ethanol sensitivity, but these compounds antagonized muscarinic agonist-enhanced ethanol sensitivity in SS mice effectively. Pirenzepine, and M1 selective antagonist, produced a parallel shift in the oxotremorine dose-response curve, indicating that the enhanced hypnotic sensitivity to ethanol may be due to interaction of oxotremorine with M1 muscarinic receptors. This possibility was supported by the finding that atropine and pirenzepine which are known to have comparable affinities for M1 but not M2 receptors, had comparable potencies in antagonizing the action of oxotremorine or neostigmine. The results suggest that LS and SS mice differ genetically in neuronal processes activated by specific muscarinic agonists and are consistent with the hypotheses that ethanol acts in part via membrane receptor coupling to intracellular processes known to mobilize intracellular Ca++.

Brain neurotensin receptors in mice bred for differences in sensitivity to ethanol

The hypothesis that some of ethanol's acute effects are mediated via neurotensinergic systems was investigated by characterizing neurotensin (NT) receptors in mice (LS and SS) selectively bred for differences in sensitivity to ethanol. [3H]Neurotensin binding in brain membranes from both mouse lines was specific, saturable, reversible, and linear with protein concentrations. Subcellular localization studies showed specific NT binding to be concentrated in the microsomal/synaptosomal fractions. Scatchard analyses of [3H]NT binding indicated similar KD values for membranes from various brain regions of LS and SS mice. However, Bmax values in frontal cortex, cerebellum, and striatum were greater in SS than in LS mice. In competitive binding studies IC50 values were lower for NT8-13 than for NT1-13, and IC50 values for NT1-8, NT1-11, D-Trp11-NT, and D-Tyr11-NT were greater than 1000 nM. Association and dissociation rate constants for [3H]NT and resulting KD values (0.8 nM) were similar for LS and SS brain membranes. Ethanol, in vitro, had no effect on NT binding characteristics, but as expected various cations markedly increased KD values.

Experience with mutagenicity testing of new drugs: viewpoint of a regulatory agency

Quality and quantity of mutagenicity testing were analyzed for drugs with new active compounds which were submitted for registration in the Federal Republic of Germany from mid 1982 to mid 1986. A large variety of deficiencies was found, applying to selection and number of mutagenicity tests as well as to test performances. Only 65 out of the 144 drugs submitted for registration were tested sufficiently in the initial phase of registration. From 1982 to 1986 this situation has not been changed markedly. Inadequate test performance still remains the main reason for insufficient testing, leading in some cases to artificially positive results. For in vivo tests the selection of test species was mainly motivated by technical reasons and not by characteristics of the test compound. Most of the insufficiencies were eliminated during the second phase of registration. In some cases insufficient mutagenicity testing led to consequences concerning risk-benefit assessment of the drug and its regulation.

Neurotensin selectively alters ethanol-induced anesthesia in LS/Ibg and SS/Ibg lines of mice

Neurotensin (NT) differentially altered ethanol-induced anesthesia as measured by duration of loss of righting response or by blood ethanol levels producing loss of righting response in mice (LS and SS) which were selectively bred for differences in response to ethanol. At doses of 5-500 ng i.c.v., NT increased ethanol sensitivity in SS mice, but not in LS mice, as measured by blood ethanol concentrations at loss of righting response. At higher doses, 0.5-10 micrograms i.c.v., NT enhanced the sensitivity of both SS and LS mice to ethanol-induced anesthesia. The hypothermic effect of ethanol determined at loss of righting response was not altered in either LS or SS mice at low doses of NT, but at higher doses NT enhanced ethanol-induced hypothermia in both lines of mice. The altered anesthetic sensitivity was specific for ethanol in that NT did not alter pentobarbital-induced sleep time in either LS or SS mice and halothane anesthesia was altered slightly only in LS mice. NT analogues, N-acetyl-NT8-13, and [D-Trp11]-NT but not NT1-8 enhanced the anesthetic action of ethanol in SS mice. Bombesin, cholecystokinin sulfate, substance P, [D-Trp8, D-Cys14]-somatostatin and corticotropin releasing hormone (CRF) were not effective in enhancing ethanol-induced anesthesia in LS or SS mice. CRF appeared to decrease ethanol sensitivity in LS but not in SS mice. Beta-Endorphin (beta-END) markedly increased the ethanol sensitivity of SS and to a lesser extent of LS mice at relatively high doses, e.g. 0.5-1.0 micrograms i.c.v. The results of the present study indicate that differences in brain sensitivity of LS and SS mice to ethanol may be mediated by genetic differences in NT systems. Likewise, NT, and probably beta-endorphin, may interact with other neurochemical processes that are involved in the mechanism of ethanol-induced anesthesia and that differ genetically in LS and SS mice.

Species differences in mutagenicity testing. II. Sister-chromatid exchange and micronucleus induction in rats, mice and Chinese hamsters treated with cyclophosphamide

Comparative investigations of sister-chromatid exchange (SCE) and micronucleus induction in the bone marrow of rats, mice and Chinese hamsters with the cytostatic alkylating mutagen cyclophosphamide (CP) revealed remarkable species differences in their mutagenic responses. With both test systems the sensitivities of the three species can be ranked into the order rat greater than mouse greater than Chinese hamster. More explicit results were obtained with the SCE test than with the micronucleus test within the same dose range. This may be due to the influence of species-related differences in the cytotoxic response to CP in the micronucleus test. These results show that clearly different mutagenic responses in different test species may be obtained in standard assays even with a compound which is metabolized in a very similar manner in all animal species.

Species differences in mutagenicity testing: I. Micronucleus and SCE tests in rats, mice, and Chinese hamsters with aflatoxin B1

Three animal species used in in vivo mutagenicity testing--rats, mice and Chinese hamsters--were compared with respect to their mutagenic response to the mycotoxin aflatoxin B1 (AFB1). The micronucleus test and the SCE test with bone marrow cells were chosen as test methods, employing similar protocols for all species. The mutagenic potential of AFB1 was detected with rats and mice but not with Chinese hamsters. Rats were more susceptible to the mutagenic action of AFB1 than mice with regard to the effective dose. A difference in sensitivity between males and females was evident in rats and mice: male animals exhibited higher induced micronucleus frequencies than females, and a clear SCE-inducing effect was only detectable in male animals. These results are in agreement with those of in vitro and carcinogenicity studies. They may be due to metabolic differences between the species and sexes, predominantly differences in glutathione conjugation of the reactive AFB1 epoxide and in the formation of the metabolite aflatoxicol. Furthermore, it could be demonstrated that AFB1 seems to be a more potent inducer of micronuclei than of SCE. Since our results obtained with rats and mice were clearly positive, but with the Chinese hamster the mutagenic potential of AFB1 was not detectable with the test systems used, it can be concluded that the choice of an "inappropriate" test species may lead to a false negative judgment on the genotoxic potential of a test compound.

Influence of chronic ethanol uptake and acute acetaldehyde treatment on the chromosomes of bone-marrow cells and peripheral lymphocytes of Chinese hamsters

Chinese hamsters received 10% (v/v) ethanol as their only liquid supply during 46 weeks. At the end of the drinking period the rate of chromosomal aberrations was determined in cultured lymphocytes. The cultures were set up with the blood from the retro-orbital plexus. Bone-marrow metaphases of the same animals were analysed with regard to sister-chromatid exchanges (SCE) after implantation of BrdU tablets in vivo. No cytogenetic effects were found in either test system. Another group of Chinese hamsters received acetaldehyde at 0.01, 0.1 amd 0.5 mg/kg by i.p. injection, and bone-marrow metaphases were analysed with respect to SCE. The SCE frequencies were elevated by acetaldehyde at 0.5 mg/kg, but not by the lower doses.

Simultaneous exposure of Chinese hamsters to ethanol and cigarette smoke: cytogenetic aspects

Chinese hamsters (Cricetulus griseus) were treated with ethanol, with cigarette smoke and with both. During the experimental period of 12 weeks a control group of animals (c) received water ad libitum, another water drinking group received a cigarette smoke treatment during the last 4 weeks (S). Another group received 20% (v/v) ethanol during the whole experimental period as the only liquid supply (E), and one group with the same ethanol treatment was simultaneously treated with cigarette smoke during the last 4 weeks of the experiment (ES). The investigation of bone marrow cells after 12 weeks with regard to chromosomal aberrations and sister chromatid exchanges revealed no effects. A high mitotic activity was found in the smoke treated groups.

Chromosomal analysis in bone-marrow cells of Chinese hamsters after treatment with mycotoxins

Mycotoxins are ubiquitously occurring metabolites of moulds that grow on foodstuffs. They are able to cause toxic diseases in man and animals. Aflatoxin B1 (AFB1), aflatoxin G1 (AFG1) and platulin (PA) induce chromosomal damage in Chinese hamster bone-marrow cells. With respect to the number of induced aberrant mitoses the 3 mycotoxins can be ranked in the order PA greater than AFB1 greater than AFG1.

The influence of ethanol treatment of cytogenetic effects in bone marrow cells of Chinese hamsters by cyclophosphamide, aflatoxin B1 and patulin

Chromosomes were investigated from the bone marrow of Chinese hamsters which received 10% (v/v) ethanol as the only liquid supply for a period of 9 weeks. At the end of the ethanol drinking period 1 group of animals received 2 oral doses of 80 mg/kg cyclophosphamide (CP), a second group received 2 oral doses of 25 mg/kg aflatoxin B1 (AFB1), a third group 2 oral doses of 20 mg/kg patulin (PA). The 2 applications were separated by 24 h. The intake of ethanol had no effect on the bone marrow chromosomes, and had no potentiating effect on CP induced aberrations. 9 weeks consumption of 10% (v/v) ethanol revealed likewise no influence on the frequencies of chromosomal aberrations induced by the indirect mutagen AFB1. However, the rate of chromosomal aberrations induced by the direct mutagen PA was clearly suppressed in ethanol drinking animals.