Formaldehyde, glyoxal, urethane, methyl carbamate, 2,3-butanedione, 2,3-hexanedione, ethyl acrylate, dibromoacetonitrile and 2-hydroxypropionitrile induce chromosome loss in Saccharomyces cerevisiae

Induction of mitotic chromosome loss could be demonstrated for the dialdehyde glyoxal, the diketones 2,3-butanedione and 2,3-hexanedione, ethyl and methyl carbamate, ethyl acrylate, dibromoacetonitrile, 2-hydroxypropionitrile and formaldehyde, but only when they were combined with subacute concentrations of propionitrile, which is a strong inducer of chromosomal malsegregation. The same chemicals did not induced mitotic chromosome loss when applied in pure form. However, glyoxal, ethyl acrylate, dibromoacetonitrile and formaldehyde when applied in pure form also induced mitotic recombination. Respiratory deficiency was induced, in the absence of propionitrile, by these recombinogenic agents and also by 2,3-hexanedione and 2-hydroxypropionitrile which are not recombinogenic.     

Induction of chromosome loss by mixtures of organic solvents including neurotoxins

Twenty-three aprotic polar solvents - 3 nitriles, 8 organic esters, 10 ketones and 2 lactones - and LiCl were tested in combination with propionitrile alone or a mixture of ethyl acetate and propionitrile for the induction of mitotic chromosome loss in the D61.M strain of the yeast Saccharomyces cerevisiae. Propionitrile and ethyl acetate are very potent inducers of chromosome loss. Mixtures of propionitrile and ethyl acetate induced chromosome loss at much higher frequencies than was observed with the pure chemicals. To test the potentiating effects of propionitrile or mixtures of propionitrile with ethyl acetate on other chemicals, they were used in concentrations that were at or below the level for induction of chromosome loss. Twenty chemicals when tested in pure form were negative or only marginally active in the test for chromosome loss. Except for amyl propionate and benzyl acetate, the same chemicals showed strong induction in combination treatments with the potentiating chemicals. All the ketones including the neurotoxic methyl ethyl ketone, 2-hexanone and 2.5-hexanedione induced high frequencies of chromosome loss. Only methyl ethyl ketone is capable of inducing high levels of chromosome loss when tested in the pure form at much higher concentrations. 1-Methyl-2-pyrrolidinone and gamma-valerolactone had previously been shown to induce chromosome loss only when the treatment at a growth-supporting temperature was interrupted by a cold shock within a narrow range of low temperatures which prevented growth. Both gave very strong induction in combination treatment performed at a continuous growth-supporting temperature. LiCl is a weak inducer of chromosome loss: strong induction can be achieved in combination treatments.     

The influence of solvent stress on MMS-induced genetic change in Saccharomyces cerevisiae

MMS induced mitotic recombination but not mitotic chromosome loss when tested in pure form in strain D61.M of Saccharomyces cerevisiae, confirming previous results of Albertini (1991), whereas in Aspergillus nidulans it also induced chromosomal malsegregation in addition to mitotic recombination (Käfer, 1988). However, induction of mitotic chromosome loss was observed in combination with strong inducers of chromosome loss such as the aprotic polar solvents ethyl acetate and to a lesser extent methyl ethyl ketone but not with γ-valerolactone and propionitrile. In addition to this, 4 solvents, dimethyl formamide, dimethyl sulfoxide, dioxane and pyridine, enhanced the MMS-induced mitotic recombination in strain D61.M. An enhancement of MMS-induced mitotic recombination and reverse mutation could be demonstrated for ethyl acetate and γ-valerolactone in yeast strain D7.     

The influence of solvent stress on MMS-induced genetic change in Saccharomyces cerevisiae

MMS induced mitotic recombination but not mitotic chromosome loss when tested in pure form in strain D61.M of Saccharomyces cerevisiae, confirming previous results of Albertini (1991), whereas in Aspergillus nidulans it also induced chromosomal malsegregation in addition to mitotic recombination (Käfer, 1988). However, induction of mitotic chromosome loss was observed in combination with strong inducers of chromosome loss such as the aprotic polar solvents ethyl acetate and to a lesser extent methyl ethyl ketone but not with γ-valerolactone and propionitrile. In addition to this, 4 solvents, dimethyl formamide, dimethyl sulfoxide, dioxane and pyridine, enhanced the MMS-induced mitotic recombination in strain D61.M. An enhancement of MMS-induced mitotic recombination and reverse mutation could be demonstrated for ethyl acetate and γ-valerolactone in yeast strain D7.     

Detection of induced mitotic chromosome loss in Saccharomyces cerevisiae--an interlaboratory study

The diploid yeast strain D61.M was used to study induction of mitotic chromosome loss. The test relies upon the uncovering and expression of multiple recessive markers reflecting the presumptive loss of the chromosome VII homologue carrying the corresponding wild-type alleles. The underlying 'loss event' is probably complex since the predicted centromere-linked lethal tetrad segregations for chromosome VII are not recovered. Instead, the homologue bearing the multiple recessive markers is patently homozygous. An interlaboratory study was performed in which 16 chemicals were tested under code in 2 laboratories. The results generated by the Berkeley and Darmstadt laboratories were in close agreement. Acetonitrile, ethyl acetate, 4-acetylpyridine, propionitrile and nocodazole were identified as potent inducers of mitotic chromosome loss. Acetone, dimethyl sulfoxide and 2-methoxyethyl acetate either elicited weak responses or yielded ambiguous results. Water, carbon tetrachloride, 4-fluoro-D,L-phenylalanine, amphotericin B, griseofulvin, cadmium chloride, ethyl methanesulfonate and methylmercury(II) chloride failed to induce chromosome loss. These data suggest that the system described herein represents a reliable assay for chemically induced chromosome loss in yeast.     

The detection of mitotic and meiotic chromosome gain in the yeast Saccharomyces cerevisiae: effects of methyl benzimidazol-2-yl carbamate, methyl methanesulfonate, ethyl methanesulfonate, dimethyl sulfoxide, propionitrile and cyclophosphamide monohydrate

The diploid yeast strain BR1669 was used to study induction of mitotic and meiotic chromosome gain by selected chemical agents. The test relies on a gene dosage selection system in which hyperploidy is detected by the simultaneous increase in copy number of two alleles residing on the right arm of chromosome VIII: arg4-8 and cup1S (Rockmill and Fogel. 1988; Whittaker et al., 1988). Methyl methanesulfonate (MMS) induced mitotic, but not meiotic, chromosome gain. Methyl benzimidazol-2-yl carbamate (MBC) and ethyl methanesulfonate (EMS) induced both mitotic and meiotic chromosome gain. Propionitrile, a polar aprotic solvent, induced only mitotic chromosome gain; a reliable response was only achieved by overnight incubation of treated cultures at 0 degrees C. MBC is postulated to act by binding directly to tubulin. The requirement for low-temperature incubation suggests that propionitrile also induces aneuploidy by perturbation of microtubular dynamics. The alkylating agents MMS and EMS probably induce recombination which might in turn perturb chromosome segregation. Cyclophosphamide monohydrate and dimethyl sulfoxide (DMSO) failed to induce mitotic or meiotic chromosome gain.     

Aneuploidy in Drosophila, IV. Inhalation studies on the induction of aneuploidy by nitriles

The Drosophila ZESTE system was used to monitor the induction of sex chromosome aneuploidy following inhalation exposure of adult females to four nitriles: acetonitrile, propionitrile, acrylonitrile and fumaronitrile. Acetonitrile and propionitrile were highly effective aneuploidogens, inducing both chromosome loss and chromosome gain following brief exposures to low concentrations of these chemicals, and these nitriles also induced rapid paralysis. Acrylonitrile-induced chromosome loss only but did not induce paralysis. Fumaronitrile, in contrast with the results reported in yeast, was ineffective in inducing chromosome loss or gain. Virtually all exceptional offspring induced by acetonitrile and propionitrile were recovered in the first sampled eggs, corresponding to treated mature oocytes. Additionally, the time interval between treatment and sampling was shown to be important, suggesting rapid loss or detoxification of the nitriles. Genetic analysis demonstrated that most aneuploids resulted from induced segregation errors during the first division of meiosis. Cold treatments were found to be ineffective in enhancing the effects of acetonitrile, suggesting important differences between the Drosophila and yeast aneuploidy detection systems. Possible mechanisms by which nitriles may disrupt chromosome segregation in Drosophila oocytes are considered.     

Effect of glyoxal pretreatment on radiation-induced genetic damage in Drosophila melanogaster

The effects of glyoxal and of glyoxal pretreatments on radiation-induced genetic damage were investigated in Drosophila melanogaster mature sperm, by means of sex-linked recessive and dominant lethality, reciprocal translocation and chromosome loss tests. In addition, the possible mutagenic effect of glyoxal was assessed in postmeiotic cells up to 7 days after treatment. The results obtained show: (1) the frequencies of recessive lethals after glyoxal treatment were within control values, (2) no clastogenic effect of glyoxal was observed, (3) glyoxal pretreatment did not modify the frequency of recessive lethals induced by X-rays, (4) after pretreatment with glyoxal a consistent, though not significant, increase was seen in the frequency of reciprocal translocations in 3 replicate experiments, (5) the yield of dominant lethals and of complete and partial chromosome loss induced by radiation was significantly increased by pretreatments with glyoxal. It is suggested that the increase of the frequency of genetic endpoints resulting from chromosome breakage, when glyoxal was administered prior to irradiation, could be ascribed to: (a) a sensitizing action of glyoxal to the clastogenic effect of ionizing radiation; (b) the formation of reactive species by the interaction of glyoxal with radiation; and/or (c) interference of glyoxal with the normal handling of radiation-induced lesions in mature postmeiotic male cells.     

Altered Fidelity of Mitotic Chromosome Transmission in Cell Cycle Mutants of S. CEREVISIAE

Thirteen of 14 temperature-sensitive mutants deficient in successive steps of mitotic chromosome transmission (cdc2, 4, 5, 6, 7, 8, 9, 13, 14, 15, 16, 17 and 20) from spindle pole body separation to a late stage of nuclear division exhibited a dramatic increase in the frequency of chromosome loss and/or mitotic recombination when they were grown at their maximum permissive temperatures. The increase in chromosome loss and/or recombination is likely to be due to the deficiency of functional gene product rather than to an aberrant function of the mutant gene product since the mutant alleles are, with one exception, recessive to the wild-type allele for this phenotype. The generality of this result suggests that a delay in almost any stage of chromosome replication or segregation leads to a decrease in the fidelity of mitotic chromosome transmission. In contrast, temperature-sensitive mutants defective in the control step of the cell cycle (cdc28), in cytokinesis (cdc3) or in protein synthesis (ils1) did not exhibit increased recombination or chromosome loss.--Based upon previous results with mutants and DNA-damaging agents in a variety of organisms, we suggest that the induction of mitotic recombination in certain mutants is due to the action of a repair pathway upon nicks or gaps left in the DNA. This interpretation is supported by the fact that the induced recombination is dependent upon the RAD52 gene product, as essential component in the recombinogenic DNA repair pathway. Gene products whose deficiency leads to induced recombination are, therefore, strong candidates for proteins that function in DNA metabolism. Among the mutants that induce recombination are those known to be defective in some aspect of DNA replication (cdc2, 6, 8, 9) as well as some mutants defective in the G2 (cdc13 and 17) and M (cdc5 and 14) phases of the mitotic cycle. We suggest that special aspects of DNA metabolism may be occurring in G2 and M in order to prepare the chromosomes for proper segregation.     

Comparison of chemically induced chromosome loss in a diploid, triploid, and tetraploid strain of Saccharomyces cerevisiae.

Triploid and tetraploid strains of Saccharomyces cerevisiae were constructed and the spontaneous loss during mitosis of one, two or three copies of chromosome VII was determined. In one strain, a triploid (VM2) in which expression of the recessive alleles can be observed only after loss of two copies of chromosome VII (3N-2), the spontaneous frequency of chromosome loss was lower than in the diploid D61.M. In another strain, a tetraploid (VM4) that also requires the loss of two copies of chromosome VII for observation (4N-2) of the recessive alleles, the spontaneous frequency was slightly higher than in the diploid D61.M. The spontaneous frequency of other genetic events (that is, mutation, recombination or chromosome breakage) were lower by 2-3 orders of magnitude than in the diploid strain D61.M. Induction of chromosome loss and other genetic events by nocodazole, ethyl acetate, hydroxyurea and ethyl methanesulfonate was determined in D61.M, VM2, and VM4, and the results were compared. Nocodazole and ethyl acetate induced chromosome loss in both the triploid and the tetraploid strains at lower concentrations than required in the diploid. These compounds also induced elevated frequencies of other genetic events in both the triploid and the tetraploid strains but not in the diploid. Hydroxyurea induced elevated frequencies of chromosome loss in the diploid and the tetraploid. Frequencies of chromosome loss in the triploid treated with hydroxyurea, although elevated, are based on observation of very few colonies of the correct phenotype. Ethyl methanesulfonate failed to induce chromosome loss in any of the three strains. Hydroxyurea and ethyl methanesulfonate did, however, induce very high frequencies of other genetic events.     

Chromosome aberrations induced by pyrolysates of carbohydrates in Chinese hamster V79 cells

The clastogenic activity of some pyrolysates of carbohydrates was examined in cultured Chinese hamster V79 cells. These pyrolysates include levoglucosan (LG-I), levoglucosenone (LG-II), furfural (FF), 5-(hydroxymethyl)-2-furfural (HMF), glyoxal (GL), methylglyoxal (MGL), 3-deoxy-D-glucosone (DG) and thiazolidine (TZ). LG-I did not induce a significant number of chromosome aberrations at doses up to 8000 micrograms/ml. In contrast, the related compound LG-II induced aberrations and reduced mitosis in a dose-dependent fashion at around 1/2000 of the LG-I doses. Both furan derivatives, FF and HMF, and both glyoxal derivatives, GL and MGL, induced a significant number of chromosome aberrations and a significant lowering of mitotic activity. Among these compounds, FF and MGL showed stronger clastogenic activity than HMF and GL, respectively. DG slightly but positively induced chromosome aberrations. TZ was one of the most potent clastogens among the compounds examined in this study, showing the highest incidence of aberrant cells with many exchanges at doses inducing a significant lowering of mitotic activity. The results of this study indicate the need for a re-evaluation of the thermal decomposition of carbohydrates as a source of genotoxic contaminants.     

The centriolar cycle in polykaryons containing prematurely condensed chromosomes or telophase-like nuclei]

In fused interphase-mitotic cells, either interphase nuclei are induced to premature chromosome condensation (PCC) or mitotic chromosomes are induced to telophase-like nuclei (TLN) formation. This study concerns structural and functional changes in centrioles of fused cells in which PCC or TLN are induced. Embryonic pig kidney cells were fused using a modified PEG-DMSO-serum method. Cell cycle period of the nuclei was determined before cell fusion using double-labeling autoradiography. Polykaryons containing desirable type of PCC or interphase nuclear combination in TLN were selected on the basis of isotope labeling after being embedded in epon. Selected cells were cut into serial sections and studied under electron microscope. The data obtained showed that centrioles at every interphase period undergo mitotic activation when their nuclei are induced to PCC. They acquire fibrillar halo and form half-spindles. Daughter centrioles at G1, S and G2 periods are also capable of mitotic activation when separated from their mother centriole. Inert centrioles were found in some cells with G1-PCC. When mitotic nuclei are induced to TLN formation, their centrioles also become inactivated. They lose fibrillar halo and mitotic spindles break down. Some mitotic centrioles develop features characteristic of interphase period such as satellites and vacuoles. Induced nuclear and centriolar changes are simultaneous and may be controlled by the same factor. Mitotic factor of mitotic cell partner which induces PCC may also induce interphase centrioles to mitotic activation. Degradation of the mitotic factor leading to TLN formation may also cause the loss of the mitotic activity of centrioles and disorganization of mitotic spindles.     

Association of Disomic Chromosome Loss with Ems-Induced Conversion in Yeast

Experimental tests with the yeast Saccharomyces cerevisiae of a previously proposed model suggesting a causal relationship between disomic chromosome loss (n + 1 → n) and centromere-adjacent mitotic gene conversion were performed. Disomic haploid cells heteroallelic at two loci on the left arm of chromosome III were exposed to ethyl methanesulfonate (EMS) under nonlethal conditions; EMS-induced prototrophic gene convertants were selected and tested for coincident chromosome loss. The principal results are: (1) The frequency of chromosome loss among EMS-induced gene convertants selected to arise near the centromere is markedly enhanced over basal levels and remains constant, independent of EMS exposure. There is little such enhancement among EMS-induced convertants selected to arise far from the centromere. (2) Chromosome loss is almost completely associated with induced conversion of the centromere-proximal allele at the centromere-adjacent heteroallelic locus. This result is identical to (and confirms) results found previously for spontaneous loss-associated conversion. (3) The conversion polarity at the centromere-adjacent locus among unselected (nonloss-associated) induced or spontaneous mitotic convertants is identical to that among meiotic convertants and markedly favors the contromere-distal allele. These findings are wholly consistent with, and strengthen, the hypothesis that structural involvement of centromeric regions in nearby recombinational events may interfere with proper segregational function and lead to mitotic chromosome loss.     

Detection of induced mitotic chromosome loss in Saccharomyces cerevisiae--an interlaboratory assessment of 12 chemicals

Induced mitotic chromosome loss was assayed using diploid yeast strain S. cerevisiae D61.M. The test relies upon the uncovering and expression of multiple recessive markers reflecting the presumptive loss of the chromosome VII homologue carrying the corresponding wild-type alleles. An interlaboratory study was performed in which 12 chemicals were tested under code in 2 laboratories. The results generated by the Berkeley and the Darmstadt laboratories were in close agreement. The solvents benzonitrile and methyl ethyl ketone induced significantly elevated chromosome loss levels. However, a treatment regime that included overnight storage at 0 degree C was required to optimize chromosome loss induction. Hence, these agents are postulated to induce chromosome loss via perturbation of microtubular assembly. Fumaronitrile yielded inconsistent results: induction of chromosome loss and respiratory deficiency was observed in both laboratories, but the response was much more pronounced in the Darmstadt trial than that observed in Berkeley. The mammalian carcinogens, benzene, acrylonitrile, trichloroethylene, 1,1,1-trichloroethane and 1,1,1,2-tetrachloroethane failed to induce chromosome loss but elicited high levels of respiratory deficiency, reflecting anti-mitochondrial activity. Trifluralin, cyclophosphamide monohydrate, diazepam and diethylstilbestrol dipropionate failed to induce any detectable genetic effects. These data suggest that the D61.M system is a reproducible method for detecting induced chromosome loss in yeast.     

Mitotic stability of yeast chromosomes: a colony color assay that measures nondisjunction and chromosome loss

A colony color assay that measures chromosome stability is described and is used to study several parameters affecting the mitotic maintenance of yeast chromosomes, including ARS function, CEN function, and chromosome size. A cloned ochre-suppressing form of a tRNA gene, SUP11, serves as a marker on natural and in vitro-constructed chromosomes. In diploid strains homozygous for an ochre mutation in ade2, cells carrying no copies of the SUP11 gene are red, those carrying one copy are pink, and those carrying two or more copies are white. Thus, the degree of red sectoring in colonies reflects the frequency of mitotic chromosome loss. The assay also distinguishes between chromosome loss (1:0 segregation) and nondisjunction (2:0 segregation). The most dramatic effect on improving mitotic stability is caused by increasing chromosome size. Circular chromosomes increase in stability through a size range up to approximately 100 kb, but do not continue to be stabilized above this value. However, linear chromosomes continue to increase in mitotic stability throughout the size range tested (up to 137 kb). It is possible that the mitotic stability of linear chromosomes is proportional to chromosome length, up to a plateau value that has not yet been reached in our synthetic constructions.     

Segregation of recessive phenotypes in somatic cell hybrids: role of mitotic recombination, gene inactivation, and chromosome nondisjunction.

Somatic cell hybrids heterozygous at the emetine resistance locus (emtr/emt+) or the chromate resistance locus (chrr/chr+) are known to segregate the recessive drug resistance phenotype at high frequency. We have examined mechanisms of segregation in Chinese hamster cell hybrids heterozygous at these two loci, both of which map to the long arm of Chinese hamster chromosome 2. To follow the fate of chromosomal arms through the segregation process, our hybrids were also heterozygous at the mtx (methotrexate resistance) locus on the short arm of chromosome 2 and carried cytogenetically marked chromosomes with either a short-arm deletion (2p-) or a long-arm addition (2q+). Karyotype and phenotype analysis of emetine- or chromate-resistant segregants from such hybrids allowed us to distinguish four potential segregation mechanisms: (i) loss of the emt+- or chr+-bearing chromosome; (ii) mitotic recombination between the centromere and the emt or chr loci, giving rise to homozygous resistant segregants; (iii) inactivation of the emt+ or chr+ alleles; and (iv) loss of the emt+- or chr+-bearing chromosome with duplication of the homologous chromosome carrying the emtr or chrr allele. Of 48 independent segregants examined, only 9 (20%) arose by simple chromosome loss. Two segregants (4%) were consistent with a gene inactivation mechanism, but because of their rarity, other mechanisms such as mutation or submicroscopic deletion could not be excluded. Twenty-one segregants (44%) arose by either mitotic recombination or chromosome loss and duplication; the two mechanisms were not distinguishable in that experiment. Finally, in hybrids allowing these two mechanisms to be distinguished, 15 segregants (31%) arose by chromosome loss and duplication, and none arose by mitotic recombination.     

Recombinogenic Conditions Influence Partner Choice in Spontaneous Mitotic Recombination

Mammalian common fragile sites are loci of frequent chromosome breakage and putative recombination hotspots. Here, we utilized Replication Slow Zones (RSZs), a budding yeast homolog of the mammalian common fragile sites, to examine recombination activities at these loci. We found that rates of URA3 inactivation of a hisG-URA3-hisG reporter at RSZ and non-RSZ loci were comparable under all conditions tested, including those that specifically promote chromosome breakage at RSZs (hydroxyurea [HU], mec1Δ sml1Δ, and high temperature), and those that suppress it (sml1Δ and rrm3Δ). These observations indicate that RSZs are not recombination hotspots and that chromosome fragility and recombination activity can be uncoupled. Results confirmed recombinogenic effects of HU, mec1Δ sml1Δ, and rrm3Δ and identified temperature as a regulator of mitotic recombination. We also found that these conditions altered the nature of recombination outcomes, leading to a significant increase in the frequency of URA3 inactivation via loss of heterozygosity (LOH), the type of genetic alteration involved in cancer development. Further analyses revealed that the increase was likely due to down regulation of intrachromatid and intersister (IC/IS) bias in mitotic recombination, and that RSZs exhibited greater sensitivity to HU dependent loss of IC/IS bias than non RSZ loci. These observations suggest that recombinogenic conditions contribute to genome rearrangements not only by increasing the overall recombination activity, but also by altering the nature of recombination outcomes by their effects on recombination partner choice. Similarly, fragile sites may contribute to cancer more frequently than non-fragile loci due their enhanced sensitivity to certain conditions that down-regulate the IC/IS bias rather than intrinsically higher rates of recombination.     

Hepatocyte cytotoxicity induced by hydroperoxide (oxidative stress model) or glyoxal (carbonylation model): prevention by bioactive nut extracts or catechins

Carbonyl and oxidative stress play important roles in the development of diabetic complications and have been shown to be augmented by various natural compounds and pharmacological agents. Nuts are a rich source of bioactive compounds and antioxidants and various beneficial health effects of nuts have been reported. This study was conducted to evaluate the cytoprotectiveness of various nut extracts and bioactive compounds found in nuts for decreasing cytotoxicity, lipid peroxidation and protein carbonylation in cell toxicity models of diabetes-related carbonyl (glyoxal) and oxidative stress (hydroperoxide). Methanol, ethyl acetate or water were used to prepare crude hazelnut and walnut extracts, which were then used to screen for in vitro cytoprotection of freshly isolated rat hepatocytes against these toxins. The order of protection by nut extracts against hydroperoxide induced cell death was: walnut methanolic extract>walnut aqueous extract>lipophilic walnut extract>hazelnut aqueous extract>hazelnut methanolic extract whereas the lipophilic hazelnut extract did not protect against cell death. The order of protection against lipid peroxidation was the same except for the hazelnut methanolic extract, which prevented lipid peroxidation better than the hazelnut aqueous extract. Catechin, epicatechin and epigallocatechin gallate (EGCG) were investigated for possible protective effects against carbonyl stress cell death and protein carbonylation in hepatocytes. Catechin protected against glyoxal induced cell death and protein carbonylation, and even elicited protection when added to hepatocytes 30 min after the addition of glyoxal. When catechin and epicatechin were compared for protectiveness against glyoxal induced carbonyl stress in hepatocytes, epicatechin protected more effectively than catechin against cell death and protein carbonylation at 120 min. Both compounds also elicited better protection when premixed with glyoxal before addition to hepatocytes, compared to not premixing with glyoxal. Our results suggest (a) that bioactive nut constituents in the non-lipophilic extracts were more effective than lipophilic extracts for cytoprotection against hydroperoxide induced oxidative stress, (b) catechin compounds under physiological conditions were likely effective at preventing glyoxal cytotoxicity by trapping glyoxal or reversing early stage carbonylation (Schiff base formation).     

Perturbation of the chromosomal binding of RCC1, Mad2 and survivin causes spindle assembly defects and mitotic catastrophe

Mitotic catastrophe is a form of cell death that results from aberrant mitosis. Currently, the mechanisms involved in this form of cell death remain poorly understood. We found that actinomycin D induces mitotic catastrophe with severe spindle assembly defects. We have studied the nature of three groups of chromosome binding proteins in mitotic cells treated with actinomycin D. We found that actinomycin D reduced the binding affinity of RCC1 to the mitotic chromosome, which led to a reduction of RanGTP level. In addition, Mad2 was not concentrated at the kinetochores, indicating that the mitotic spindle checkpoint was affected. Furthermore, the localization of survivin was altered in cells. These data suggested that chromosomal binding of the mitotic regulators such as RCC1, Mad2 and survivin is essential for mitotic progression. Mitotic chromosomes not only carry the genetic material needed for the newly synthesized daughter cells, but also serve as docking sites for some of the mitotic regulators. Perturbation of their binding to the mitotic chromosome by actinomycin D could affect their functions in regulating mitotic progression thus leading to severe spindle defects and mitotic catastrophe.     

Biological production of 2,3-butanediol

2,3-Butanediol (2,3-BDL), which is very important for a variety of chemical feedstocks and liquid fuels, can be derived from the bioconversion of natural resources. One of its well known applications is the formation of methyl ethyl ketone, by dehydration, which can be used as a liquid fuel additive. This article briefly reviews the basic properties of 2,3-BDL and the metabolic pathway for the microbial formation of 2,3-BDL. Both the biological production of 2,3-BDL and the variety of strains being used are introduced. Genetically improved strains for BDL production which follow either the original mechanisms or new mechanisms are also described. Studies on fermentation conditions are briefly reviewed. On-line analysis, modeling, and control of BDL fermentation are discussed. In addition, downstream recovery of 2,3-BDL and the integrated process (being important issues of BDL production) are also introduced.