Mutagenicity of sodium azide and its metabolite azidoalanine in Drosophila melanogaster

The mutagenic and toxic activities of sodium azide (NaN(3) ) and its organic metabolite L-azidoalanine [N(3)-CH(2)-CH(NH)(2)-COOH] were examined in the different stages of spermatogenesis in Drosophila melanogaster. Both azide and azidoalanine were toxic to the injected males, but azidoalanine was significantly less toxic than sodium azide. Following the injection with 0.2 microl of these compounds in the hemocoel of young adult wild-type males, the minimum concentrations of these compounds with complete toxic effects (zero survival) were 40 mM sodium azide and 160 mM azidoalanine. Sex-linked recessive lethals were scored by the Muller-5 method in three successive broods, representing sperms (brood A), spermatids (brood B), and a compiled group of meiotic and premeiotic germ cell stages (brood C). The results provide strong experimental evidence that azidoalanine is significantly (p<0.01) mutagenic to all stages of spermatogenesis in Drosophila melanogaster. Sodium azide, however, was not significantly (p>0.05) mutagenic and did not increase the rate of sex-linked recessive lethals over those produced by the control group injected with 0.45% NaCl. These results indicate the requirement of metabolic activation of azide in Drosophila as a prerequisite for its mutagenic effects.     

Radioprotective effect of six chemicals against X-ray-induced genetic damage in D. melanogaster

In Drosophila melanogater six chemicals were tested for radioprotectiveeffect against X-ray-induced genetic damage such as sex-linked recessive lethals and autosomal translocations using Oster's ring-X chromosome stock. A 2-day brood pattern was followed to score the damage induced at different spermatogenic stages separately. In all cases the chemicals were injected before X-irradiation. 10-mM solution of reduced glutathione (GSH) provided statistically significant protection against sex-linked recessive lethals in all broods. In translocation tests this chemical reduced the frequency in all broods but the result is not statistically significant. Cysteamine (MEA) did not show any protective effect but the frequency of lethals was slightly reduced in the first and fourth broods. 2-Aminoethyl isothiuronium Br·HBr (AET) showed a statistically significant protective effect when the data of the replicate experiments were pooled. Negative results were obtained for 5-hydroxytryptamine (5-HT) in sex-linked lethal tests. Aminoethyl phosphorothioate (AEPT) reduced the frequencies of both sex-linked lethals and autosomal translocations in all broods consistently but the results are not statistically significant. In tests for both lethals and translocations the reduction was largest in the stages with highest radiosensitivity. N(3-Aminopropyl)aminoethyl phosphorothioate (3AP-AEPT) gave no protection.     

Isozyme polymorphisms maintained by lethal loci in inbred strains of Aedes triseriatus

We analyzed the progeny of brother-sister matings of two inbred strains of the treehole mosquito, Aedes triseriatus, at several isozyme loci to determine which factors were maintaining heterozygosity at these loci after prolonged inbreeding. The triseriatus Kramer (TK) lines were polymorphic for the Odh and Hbd loci after 12 generations of full-sib mating, and the triseriatus Vero Beach (TV) lines were polymorphic for the Odh, Hk-4, Pgm, and Hbd loci after 14 generations of full-sib mating. Genetic analysis of 22 TK F13 matings and nine TV F15 matings showed that heterozygosity was enforced by lethal loci to which all the polymorphic isozyme loci were linked. The lethal loci formed a balanced lethal system. We determined the relative positions and map distances of lethals and enzyme loci.     

The relationship between radiation-induced and transposon-induced genetic damage during Drosophila spermatogenesis

The combined effect of transposon mobility and X-rays on X-linked recessive lethals and dominant lethals was measured in the germ line of F₁ male hybrids in the P-M system of hybrid dysgenesis. X-linked lethal mutation rate was measured in the chromosome derived from the P-strain father of the M × P cross. Mutations induced in irradiated dysgenic males were compared to those of unirradiated males, as well as to irradiated nondysgenic males derived from M × M crosses. Three four-day broods of sperm were tested for both X-linked lethals and dominant lethals. X-linked lethal mutation rate in dysgenic control males was 6.38%, 6.36% and 4.55% in broods 1, 2 and 3 respectively, thus showing a decrease in older males. The mutation rate in the same broods of irradiated, nondysgenic control males was 3.66%, 4.46% and 6.38%, respectively. The rate obtained in dysgenic irradiated males was 10.33, 11.16 and 7.97 in the same 3 broods. These results demonstrate that when X-rays and P element mobility were and 7.97 in the same 3 broods. These results demonstrate that when X-rays and P element mobility were combined as a source of mutagenesis, a strickly additive effect on genetic damage was observed in the first two broods of sperm which represent primarily mature sperm and spermatids respectively. The third brood, representing mostly spermatocytes showed a less than additive effect, probably due to germinal selection. In contrast, the induction of dominant lethals showed a clearly synergistic effect in the last two Broods of sperm tested, when X-rays and transposon mobility were combined. The X-ray component of dominant lethlity in brood 1, representing mostly mature spermatozoa, was negative, indicating a lower than expected lethality induced by X-irradiation in the presence of P element mobility. The X-ray-induced component of dominant lethality, was expressed as the per cent of embryo lethality after adjusting the results obtained with each brood of sperm from nondysgenic and dysgenic males to their respective unirradiated controls. These values were 32.3%, 30.5% and 64.7% for brood 1, 2 and 3 respectively from nondysgenic males, and 14.1%, 56.1% and 71.4% for the same broods from dysgenic males. Thus the differential effect of X-rays in sperm broods 1, 2 and 3 was −18.2, +25.6 and +6.7% respectively. These results suggest that the synergistic effect may be due to the common component of X-ray and P element-induced genetic damage, namely chromosome breaks, and that the interaction of these lesions resulted in a greater than additive number of of unrestitude chromosome breaks and nonviable chromosomal rearrangements.     

Species comparisons concerning radiation-induced dominant lethals and chromosome aberrations

After X-irradiation of post-meiotic stages, male mice, guinea-pigs, rabbits and golden hamsters differed both in general sensitivity to the induction of dominant lethals, and in the relative sensitivity of the various spermatogenic stages. Guinea-pigs were the least sensitive, and hamsters had a different stage sensitivity pattern, with mature sperm the most sensitive stage.     

Genotoxic damage induced by isopropanol in germinal and somatic cells of Drosophila melanogaster

Isopropanol (isopropyl alcohol, 2-propanol, IPA) is a volatile solvent widely used in domestic or industrial environments and reported as innocuous in various test systems. The aim of this work was to search for in vivo genotoxic effects of IPA in Drosophila melanogaster, studying its ability to induce nondisjunction (ND) in females, sex linked recessive lethals (SLRL) in males, and somatic mutation and/or recombination (SMART) in larvae. Treatments were acute (60min) and were administered via inhalation. IPA had low toxicity in adult flies (75% IPA mortality index, MI=12.7% (females) and 2.6% (males)) and larvae (MI=14.3%, 75% IPA). Female fertility was severely affected during the first 24h (brood I, BI) after treatment, but, afterwards, control values were recovered. IPA induced a 50-fold increase of ND (%) in 24h old females, and a six-fold rise in 4-5 d old BI offspring. Nondisjunction frequencies (%) in the offspring of broods II to V (24h in each case) were similar to control values. IPA doses of 25% and 50% (v/v), tested in 24h old females, showed a significant dose-dependent increase of ND(%)in BI only, with control values in subsequent broods. Flies gave normal offspring when kept in regular media for 24h before mating. The eye spot test (SMART) showed a significant increase at 50% IPA (p<0.05, m=2), but the response was not dose-dependent. IPA failed to induce SLRL in any of the spermatogenesis stages tested. These findings suggest that the main effect of IPA is to induce chromosomal malsegregation; IPA must be present at the resumption of M-phase I after fertilization, to exert these effects. The alcohol does not affect DNA directly, but perturbations of the nuclear membrane may be responsible for induction of ND.     

Progeny selection for agronomic characters in early generations of a potato breeding programme

 Repeatabilities of progeny means, and the univariate cross prediction method were used to study the effectiveness of progeny selection for agronomically important characters in early generations of potato (Solanum tuberosum L.) breeding. The study was based on 90 progenies (72 crosses+18 selfs) evaluated for three successive generations, i.e. seedling, first clonal and second clonal generations. Repeatabilities of progeny means were measured as correlation coefficients between generations. In the univariate cross prediction method, progeny means and within-progeny standard deviations were used to calculate the proportions of clones exceeding the target values, and correlation coefficients between generations for predicted and observed proportions of clones, were calculated. Population means varied from generation to generation. Correlation coefficients between generations for progeny means for most of the characters were significant, but moderate. These were higher than the correlation coefficients between predicted and observed proportions of clones exceeding the target values. The possibility of using progeny means as a selection parameter to reduce the number of genotypes to be examined in later stages by rejecting the poor crosses in seedling generation is discussed. Received: 8 January 1997/Accepted: 28 February 1997     

Modification of radiation-induced genetic damage in Drosophila melanogaster male germ cells with nucleic acid precursors II. Effects on post-meiotic cells

Following the observation that the nucleoside pre-treatment reduced the radiation-induced dominant lethality in the post-meiotic germ cells, similar experiments were conducted using the same treatment conditions to study the influence of the nucleoside(s) pre-treatment on the radiation-induced (1.2 kR) incidence of sex-linked recessive lethals and translocation events in the post-meiotic male germ cells of 1-day-old D. melanogaster. The nucleoside pre-treatment reduced the translocation frequency (not statistically significant) and the lethal mutation frequency (statistically significant) in the post-meiotic cells (pre-injection DNA synthesis cells) especially in the mature sperms sampled in brood a (br a). The radio-protective effect of the nucleosides on the mature sperms was confirmed using 7-day-old virgin males and different radiation doses (2.4 kR and 3.6 kR).The frequency of lethal mutation was lowest when irradiation was preceded by the injection of an equimolar solution of thymidine (TdR), deoxyadenosine (AdR), deoxycytidine (CdR) and deoxyguanosine (GdR). However, when the nucleosides were injected after irradiation (within 10–30 min) there was no change in the yield of radiation-induced lethals.The possible mechanisms for the radioprotective action of the nucleosides in the post-meiotic germ cells such as (a) “protection” by a radiochemical action of nucleosides competing for short-lived radicals that might otherwise cause damage to DNA and (b) biochemical-physiological mechanisms such as metabolic events increasing the radioresistance of the cells, providing excess energy for repair or favoring and partaking in the DNA repair synthesis were discussed. Further studies were felt necessary to elucidate this phenomenon.     

Dose-response relationships and R.B.E. values of dominant lethals induced by X-rays and 1.5 MeV neutrons in prophase-1 oocytes and in mature sperm of the two-spotted spider mite Tetranychus urticae Koch (acari, tetranychidae)

Mature sperm and prophase-1 oocytes of Tetranychus urticae Koch were irradiated with 250-kVp X-rays or 1.5 MeV fast neutrons. The X-ray doses ranged from 0.5 to 24.0 krad, and those of the fast neutrons from 0.1 to 16.0 krad. The genetic endpoint measured was lethality, expressed in the stages from egg to adulthood in the F1 progeny. The frequency of recessive lethals in female germ cells was estimated by comparing survival of fertilized versus unfertilized F1 eggs, after irradiation with the same dosage. X-Rays induce dominant lethals in prophase-1 oocytes by the action of both single hits on single targets and multiple hits on multiple targets. 1.5-MeV neutrons induce these effects predominantly by the action of multiple tracks on multiple targets. Dominant lethals were induced in mature sperm by X-rays and by fast neutrons by the action of both single hits on single targets and multiple hits on multiple targets. Both for prophase-1 oocytes and for mature sperm the low R.B.E. value corresponded with the relatively large multiple-target component of induction of dominant lethals by fast neutrons. The nature of dominant lethality in relation to the kinetochore organization of the chromosome is discussed. A non-linear trend in the dose--effect relationship was observed for both X-rays and fast neutrons for the estimated frequency of recessive lethals induced in prophase-1 oocytes. X-Rays were more effective than neutrons in inducing recessive lethals in prophase-1 oocytes at doses lower than 3 krad.     

长爪沙鼠脑底动脉Willis环变异缺失遗传特性分析及脑缺血模型高发群体的初步培育

目的研究长爪沙鼠脑底动脉Willis环遗传特性,并定向培育脑缺血高发种群。方法通过对5代定向培育的长爪沙鼠高发群动物共398只动物的右侧颈总动脉结扎模型进行观察,比较长爪沙鼠亲代与子代间脑底动脉Willis环的变异缺失类型,探求其遗传特性,并根据该遗传特性将Willis环后交通支缺失且前交通支缺失或细小的同类型的长爪沙鼠父母所生的子代雌雄个体配对繁殖,定向培育长爪沙鼠半脑缺血模型高发生率种群。结果当双亲的Willis环类型一致时,其子代大部分与其父母一致;而当双亲的Willis环类型不一致时,Willis环前交通支与母亲一致率为60.4%,前交通支与父亲的一致率为48.2%,两者的差异有显著性意义（P=0.015）。长爪沙鼠半脑缺血模型高发生率种群定向培育5代后,行单侧颈总动脉结扎时,一侧脑缺血造模成功率由F1代的40%提高到F5代的75%。结论长爪沙鼠脑底动脉Willis环变异有明显的遗传性,初步培育出了长爪沙鼠半脑缺血模型高发生率种群。     

On the prospects of using balanced sex-linked lethals for insect pest control

Summary A new method is suggested for controlling species of insect pests in which the female is heterogametic. This method, involving the use of balanced lethals on the Z chromosome, causes the death of females in the embryonic stage. The method has already been tested in practical sericulture for the production of entirely male progeny of the silkworm. The method requires the construction of two strains of the pest, one carrying two balanced nonallelic but closely located lethals on the Z chromosome, and another with two other pairs of lethals of the same type. In the hybrid progeny from the crosses between the two strains, 100% of the female embryos would die, thus making it possible to release only males without any laborious procedure for sex discrimination. In the progeny from the crosses between the released males and females from the natural population, again 100% of females would die, but the males would survive and when they mated — 62.5% of the female progeny would die. This rate would decline to 34.4 and 16.6% in the sons and grandsons respectively. The repeated release of hybrid males would lead to a progressive increase, with each successive generation, in the percentage of female mortality in the natural population until its total extinction.     

Mutagen sensitivity of Drosophila melanogaster. VI. Evidence from the excision-defective mei-9AT1 mutant for the timing of DNA-repair activity during spermatogenesis

The sex-linked recessive lethal test has been used to compare mutation induction by ethyl methanesulfonate and methyl methanesulfonate in spermatogenic stages of the DNA repair-deficient mei-9AT1 mutant and a repair-proficient control strain. For both agents, the data demonstrate that induced mutation rates are similar in both strains for the meiotic and post-meiotic broods. Conversely, for spermatogonial broods, the data indicate that the excision-deficient strain exhibits a 4-8 fold increase in induced mutation rate in comparison to the excision-proficient control strain. These experiments suggest that the low mutability of gonial cells normally observed for these agents is due to effective excision-repair processes which function until the commencement of meiosis. From alkylation mutagenesis experiments with repair-deficient E. coli strains, we note that the mei-9 strain exhibits pleiotropic mutant phenotypes very similar to those displayed by the uvr D mutant. By analogy with these studies, we speculate that mei-9, like uvr D, is deficient in a DNA unwinding protein.     

Mutagenicity of hycanthone in Drosophila melanogaster

The schistosomicidal agent hycanthone was tested for mutagenicity in Drosophila melanogaster. The compound was administered either by injection into adult males or by larval feeding. The following types of genetic damage were measured:(1) complete and mosaic sex-linked recessive lethal mutations; (2) II–III translocations; and (3) dominant lethals.In postmeiotic germ cells, especially in late spermatids, a pronounced increase was found in the frequency of sex-linked recessive lethals, both completes and mosaics. By contrast, translocations and dominant lethals were not induced.     

Analysis of mutagen specificity Drosophila melanogaster

The previously reported difference between the mutational spectra of hydrazine (HZ) and hydroxylamine (HA) was confirmed for one selected locus (miniature) at which hydrazine produces no mutations in treated late larval spermatogonia or premeiotic spermatocytes sampled by 3 days' progeny. The genetically effective dose was measured in most experiments by the production of v mutants, and in a few by the production of sex-linked lethals. In a total of over 37 000 X-chromosomes (16 000 from previous, and over 21 000 from present experiments) treatment with HZ yielded no m mutation, but 90 v mutations. After treatment with genetically equivalent doses of HA, m and v mutations were about equally frequent. The ratio of visible mutations at the v locus to lethals on the X-chromosomes was exceptionally high after either treatment. So was the ratio of m mutations to lethals after treatment with HA.     

Allelic composition and genetic background effects on transgene expression and inheritance in white clover

Allelic composition and genetic background effects on GUS expression and inheritance using a chimeric (cauliflower mosaic virus 35Sp:uidA) transgene were investigated in white clover as a prelude to transgenic cultivar development. Stable expression and Mendelian inheritance of the uidA transgene was observed over two generations when the uidA transgene was maintained in a heterozygous state. Transgenic backcross progeny (BC1) were intercrossed to produce segregating F2 populations. GUS-positive F2 plants were test-crossed with a non-transgenic control plant to determine whether individuals were heterozygous or homozygous for the transgene. Both expected and distorted segregation ratios were observed. Distortion of the segregation ratio was not caused by transgene inactivation or rearrangement, but was influenced by genetic background. BC1, BC2 and F2 populations were found to have similar levels of uidA gene expression. Quantification of GUS expression from progeny of high and low GUS expressing plants indicate that it is possible to alter transgene expression through selection. No difference was found between the level of expression for F2 plants homozygous or heterozygous for the transgene. These results indicate that F2 plants, homozygous for a transgene, might be used to develop a transgenic cultivar. However, progeny testing to determine the influence of genetic background is a prerequisite to such a development.     

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.     

Influence of maternal age on incidence of pupal diapause in the flesh fly, Sarcophaga bullata

ABSTRACT. Females of the flesh fly, Sarcophaga bullata Parker, produce an increasingly higher number of diapausing progeny in successive broods. Though a maternal effect completely eliminates the capacity for diapause in the first brood of females with an embryonic and larval history of short day, diapause is restored at low levels in later broods. Exposure to long daylength at the onset of adult life does not alter the diapause response of later broods, thus suggesting that the age effect cannot be modified by daylength manipulation. The age response implies that changes in maternal physiology exert an important regulatory control on the diapause fate of the pupa.     

Digoxin effect and imprinting in the unicellular Tetrahymena

Treatment with digoxin increased, whereas treatment with ouabain decreased, the growth rate of Tetrahymena, but the progeny generations showed an increased mitotic rate after both treatments. A single exposure to digoxin or ouabain accounted for a more than twofold increase in the incorporation (binding) of the cardiac glycosides in the progeny generations.     

Mutagenesis at the ad-3A and ad-3B loci in haploid UV-sensitive strains of Neurospora crassa. IV. Comparison of dose-response curves for MNNG, 4NQO and ICR-170 induced inactivation and mutation-induction

The genetic effects of MNNG, 4NQO and ICR-170 have been compared on 5 different UV-sensitive strains and a standard wild-type strain of Neurospora crassa with regard to inactivation and the induction of forward-mutations at the ad-3A and ad-3B loci. Whereas all UV-sensitive strains (upr-1, uvs-2, uvs-3, uvs-5 and uvs-6) are more sensitive to inactivation by MNNG and ICR-170 than wild-type, only uvs-5 shows survival comparable to wild-type after 4NQO treatment, all other strains are more sensitive to 4NQO. In contrast to the effects on inactivation, a wide variety of effects were found for the induction of ad-3A and ad-3B mutations: higher forward-mutation frequencies than were found in wild-type were obtained after treatment with MNNG or 4NQO for upr-1 and uvs-2, no significant increase over the spontaneous mutation frequency was found with uvs-3 after MNNG, 4NQO or ICR-170 treatment; mutation frequencies comparable to that found in wild-type were obtained with uvs-6 after MNNG, 4NQO or ICR-170 treatment and with upr-1 after ICR-170 treatment. Lower forward-mutation frequencies than were found in wild-type were obtained with uvs-2 after ICR-170 treatment and with uvs-5 after MNNG, 4NQO or ICR-170 treatment. These data clearly show that the process of forward-mutation at the ad-3A and ad-3B loci is under genetic control by mutations at other loci (e.g. upr-1, uvs-2, uvs-3, uvs-5 and uvs-6) and that the effect is markedly mutagen-dependent.     

Characteristics of circle of Willis variations in the mongolian gerbil and a newly established ischemia-prone gerbil group

Mongolian gerbils (Meriones unguiculatus) have an incomplete circle of Willis (CoW), as a result of which approximately 30-40% of these animals develop focal cerebral ischemia after unilateral carotid occlusion (UCO). There are four types of patterns of the anterior and posterior communicating arteries (ACoAs and PCoAs, respectively) of the CoW and they determine the severity of the ischemic symptoms. We used 398 gerbils from five generations, including a selectively bred ischemia-prone group, to investigate post-UCO ischemic symptoms and possible correlations of ACoA and PCoA patterns between parents and their progeny. We observed that if the parents had complete ACoAs, their progeny also had complete ACoAs, and we found significant differences when the parents' ACoAs were incomplete: in 60.4% of offspring the type of ACoA was consistent with that of the mother and in 48.2% it was consistent with that of the father. The severity of the neurological symptoms after UCO was significantly related to the patterns of the ACoAs when PCoAs were absent. The proportion of UCO ischemia in gerbils with incomplete ACoAs was significantly higher than in those with complete ACoAs. After selectively breeding five generations, the proportion of UCO ischemia increased from 40% in the F1 animals to 75% in the F5 animals. Our results suggest that variations in the CoW are genetic and demonstrate that we successfully established an ischemia-prone group of gerbils.