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PubMedDate not supplied

[Relative genetic effectiveness of fission neutrons in inducing various types of recessive mutation in Drosophila melanogaster].

The RCR-analysis of 53 gamma-Ray- and neutron-induced vg recessive mutations of Drosophila melanogaster combined with complementation assay with the vg[nw83b27] deletion mutation is used to detect precisely the RGE values of neutrons (0.85 MeV) under the chromosome and point (at the DNA level) mutation induction. Simultaneously, the induction-kinetics of gamma-ray- and neutron-induced macrodeletion as well as recessive lethal mutations in the X-chromosome were studied. The results obtained have shown that all genetic end-points increase linearly with gamma-ray or neutron dose. Thereby, the efficacy of neutrons is found to be twice (and more) as large as that of gamma-rays under the all macro- and micro-aberration mutation induction (macrodeletions and recessive lethals in the X-chromosome, multilocus deletions and intragenic deletions as well). Unlike that, the RGE of neutrons are more than twice as low as that of gamma-rays under the gene/point mutation induction. This feature of neutrons have been predicted as far back as in the early days of the radiation genetics (N.W. Timofeeff-Ressovsky, K.G. Zimmer, 1938), but experimentally supported at the DNA level just now.

Animals↗
PubMed1981

Enhanced frequency of chromosome aberrations in lymphocytes of male compared with female muntjacs after X-ray irradiation in vitro.

Recently, there has been considerable interest in the study of radiation-induced dicentrics and other chromosome aberrations in phytohaemagglutinin (PHA)-stimulated blood lymphocytes of various mammals, including man, with the aim of establishing a proper biological dosimetry for the assessment of genetic radiation hazards in human. These studies have revealed that the radiosensitivity of lymphocytes differs between species and even between individuals of the same species, but the cause(s) of these variations still remains unclear. The life-shortening response to whole-body X-ray irradiation is influenced by both age and sex of the individuals, but although age has been shown to have effects on chromosome aberration yields, in vitro, the influence of sex on the sensitivity of lymphocyte chromosomes to radiation-induced damage has not been reported. It is generally thought that sex does not influence the aberration yield within the limitation of measurements used in such studies. However, we report here a study of X-ray induced chromosome aberration in lymphocytes of Indian muntjac, in which the yield of dicentrics was found to be consistently greater in male than in female lymphocytes.

Animals↗
PubMedDate not supplied

[Molecular genetics of radiation-induced chromosome breaks in a gene area in Drosophila: "position" effect of gene mutation?].

On the sample of 43 gamma-ray and neutron-induced inversion or translocation exchanges with the vestigial (vg) phenotype, the molecular cytogenetic analysis of distribution of exchange breakpoints on the molecular map of Drosophila vg region (subsection 49D3-4 on the polytene chromosome 2R) was performed using hybridisation in situ technique. Simultaneously, PCR-assay of DNA alterations in all exons and introns (except for intron 4) of the vg gene for 18 mutants with exchange breakpoints outside of the gene was carried out. The results obtained by these molecular genetic techniques have shown that 1) radiation-induced breaks under chromosome exchanges with the vg phenotype were regularly located inside of the vg gene (19 cases out of 43 studied ones or 44.2%) passing through the large introns; 2) breakpoints were frequently flanked by deletions of the gene as whole (3 exchanges) or of its major part (3 exchanges); 3) many of the breaks (18/43 or 41.8%) are situated outside (distal or proximal) of the gene although such mutants have got the vg phenotype; 4) 2/3 (12/18 or 66.7%) vg mutants with the breakpoint outside of gene show the intragenic DNA lesions (microdeletions, microinversions) occurring obviously independently and simultaneously with the neighbor chromosome breaks; 5) only each third vg mutant with break outside of the gene (6/18 or 33.3%) have the unchanged gene subregions under study and presents obviously the result of "position effect" which appear to manifest itself for a distance of 2-30 kb (more near and farther locations of the proximal and distal breakpoints, respectively, relative to the vg gene). Our findings showing regular induction of the multiple genetic lesions (chromosome breaks and mutations of the adjacent genes) on the both ends of chromosome exchange induced by single track produced by gamma-rays or neutrons were discussed as a scientific basis for the conceptually new approaches to the assessment of both genetic damage numbers in the cell genome with chromosome exchange (the multiple genetic lesions) and radiation genetic risk (our molecular genetic approach showing the need for an increase of risk levels at least on a factor of 3 for the heritable chromosome alterations detected by the ordinary cytogenetic monitoring).

Animals↗
PubMed1977

Second malignant tumors after cancer in childhood.

Studies were made of the development of second malignant tumors in children treated at the Sidney Farber Cancer Institute. In 1973 a retrospective analysis identified second cancers in 15 of 410 patients who survived a childhood cancer. During the period 5-24 years after diagnosis of the first cancer, the cumulative probability of developing a new cancer was 12%. This frequency was approximately 20-fold higher than the expected rate for the general population. Prospective study of the series since 1973 has identified a second primary cancer in five additional patients. The majority of second cancers were in the field of prior radiotherapy, and were attributable to the oncogenic effect of radiation. Genetic susceptibility factors were identified in individual patients.

Adolescent↗
PubMed1985

[Assessment of the genetic risk of radiation by irradiation data from laboratory mammals].

An attempt has been made to assess quantitatively genetic risk of radiation for man based on mammalian (mostly mouse) data and using the direct method proposed by UNSCEAR. The parameter employed was induction of reciprocal translocations. Two assumptions were made: human radiosensitivity equals that of the mouse; and dose-response is linear. From observations with acute gamma irradiation the estimate of risk per 10(-2) Gy was as follows: 39 translocation heterozygotes are expected among one million F1 conceptions, 5 cases of multiple congenital anomalies, 25 abortions recorded and 49 unrecorded. Chronic gamma irradiation at dose rates of 1.3 X 10(-5), 1.7 X 10(-4) and 1.0 X 10(-4) Gy/min was 3 to 10 times less effective. Exposure to 4.2 GeV deuterons proved inferior in effectiveness to gamma irradiation. Chronic exposure to 4.1 MeV neutrons delivered at 8 X 10(-4) Gy/min showed 7 times the effectiveness of chronic gamma irradiation. Administration of tritiated water (from 37 to 37 X 10(2) kBq/g b.w.) to rats entailed a risk of the same order of magnitude as external chronic gamma irradiation. Reduction of genetic risk was achieved by pretreatment with either AFT-, ATP-serotonin mixtures or the molecular combinations, Adeturon and Cytriphos. Study of interspecies differences in genetic radiosensitivity showed decline in the following order: rat-rabbit-mouse-Syrian hamster. A dose-rate effect was most clearly seen in the rat, and least clearly in the rabbit. In female mice, examination of oocyte depletion indicated primary follicles to be highly susceptible to acute gamma irradiation; decrease in sensitivity was observed beginning with stage 4. Chronic gamma irradiation was found to be less effective.

Adenosine Triphosphate↗
PubMed2002

A bentazon and sulfonylurea sensitive mutant: breeding, genetics and potential application in seed production of hybrid rice.

The use of a thermosensitive genic male sterility (TGMS) system in two-line hybrid rice breeding is affected greatly by the sterility instability of TGMS lines caused by temperature fluctuation beyond their critical temperatures for fertility reversion. To prevent seed production from self contamination, we have developed a system to secure seed purity using a herbicide-sensitive TGMS mutant, M8077S, obtained by radiation. Genetic analysis, using the F(1), F(2) and F(3) populations derived from this mutant and other normal varieties, revealed that bentazon lethality/sensitivity was controlled by a single recessive gene, which was named bel. The mutant can be killed at the seedling stage by bentazon at 300 mg/l or higher, a dosage that is safe for its F(1) hybrids and all other normal varieties. This mutant is also sensitive to all the tested sulfonylurea herbicides. Response of segregating plants to these two types of herbicide indicated that sulfonylurea sensitivity was also controlled by bel. By crossing this mutant with Pei-Ai 64S, an F(2) population was developed for genetic mapping. Surveying the two DNA pools from sensitive and non-sensitive F(2) plants identified four markers that were polymorphic between the pools. The putative linked markers were then confirmed with the F(2) population. The bel locus was located on chromosome 3, 7.1 cM from the closest microsatellite marker RM168. Phenotypic analysis indicated that the bel gene had no negative effect on agronomic traits in either a homozygous or heterozygous status. The mutant M8077S is valuable in the development of a TGMS breeding system for preventing impurity resulting from temperature fluctuation of the TGMS. Several two-line hybrid rice crosses using this system are under development.

Journal Article↗
PubMed1982

Absence of correlation between the chromosomal radiosensitivity of peripheral blood lymphocytes and stem-cell spermatogonia in mammals.

To evaluate the reliability of quantitative extrapolation of radiation-induced chromosomal damage from somatic cells to germ cells, data on the effects of several biological and physical factors on the chromosomal radiosensitivity of blood lymphocytes and stem-cell spermatogonia have been collected from the literature. The results show that most of the factors considered, such as chromosomal constitution, age, genetic constitution, species, sampling time and dose fractionation, had differential effects on the induction of chromosomal aberrations in both systems. These differential effects can easily be explained in terms of the biological differences between in-vitro-stimulated peripheral blood lymphocytes and stem-cell spermatogonia. It is concluded that only direct experiments on germ cells of higher primates and man can be used for a quantitative estimation of human genetic radiation risks arising from structural chromosomal aberrations.

Aging↗
PubMed1977

[Gonadal dosis in intravenous urography and voiding cystourethrography of children (athor's transl)].

Measurements of gonadal doses of 92 children during intravenous urography and voiding cystourethrography are reported. The high deviation of doses in the testes is discussed. The application of a lead protector for the testes is demanded to decrease exposure by a factor 15 in the central beam and a factor 1.3-2 in scattered radiation. By choice of spot film radiography instead of large radiography the ovarian dose is reduced to a factor 7-40. The gonadal dose is clearly lower if 70 mm technique instead of large film technique is used. A correlation between area ionisation product and gonadal dose could not be found; therefore the genetic radiation dose cannot be calculated by data recorded as required by law.

Child↗
PubMed1998

10 years of Genomics, chromosome 21, and Down syndrome.

During the first 10 years of Genomics (1987-1997), the molecular structure of human chromosome 21 (HC21) has been intensively investigated. Due to its small size and involvement in Down syndrome, it continues to serve as a model in the development of "genomics technologies." Increasingly more detailed genetic, radiation hybrid, physical, and transcription maps, in addition to NotI restriction and chromosomal breakpoint maps, of HC21 have been developed, and approximately 10% of its genes have been cloned. These maps have been vital in the localization of loci for 15 monogenic disorders to HC21, and 10 of these genes have been identified and characterized. The genetic maps have aided in the detailed elucidation of the origin of the supernumerary HC21 in trisomy 21 from investigations of recombination and nondisjunction events. Mouse models of Down syndrome, with partial trisomy 16, the mouse chromosome principally syntenic to HC21, have been created and initially characterized. A substantial number of the above studies related to the molecular mapping, gene cloning, and infrastructure of HC21 were published in Genomics (e.g., approximately 30% of papers describing HC21 maps were published here). The future goals of genomic analysis of HC21 will be the determination of its complete nucleotide sequence and the identification and functional analysis of all of its genes. These advances will help to provide a molecular explanation of the pathophysiology of Down syndrome and aid in the identification of genes for monogenic and polygenic disorders that map on this chromosome. Novel therapeutic interventions for Down syndrome and the monogenic and polygenic disorders that map to HC21 will be designed and tried based on the knowledge of the disease pathogenesis resulting from the genomic analysis.

Animals↗
PubMed1975

Compartments and cell flows within the mouse haemopoietic system. I. Restricted interchange between haemopoietic sites.

Two chromosomally distinguishable haemopoietic cell populations were injected into lethally irradiated syngeneic recipients. The presence or absence of the T(14;15)6Ca reciprocal translocation (indicated by T6 marker chromosomes) did not affect the proliferation of a population. Wide disparities were found in the proportions of the two donor cell populations between animals and between the right and left femora of individual animals. This suggest (i) that there is, at most, a very limited interchange of proliferating cells and their precursors between the marrow of different bones; and (ii) that the number of clones proliferating in the bone marrow at any one time must be rather small; there was evidence that this number depended in part on the number of haemopoietic cells injected. Exchange between the mitotically active cell populations of spleen, thymus, lymph nodes and bone marrow was also limited, as shown by significant disparities in the proportions of the two donor populations proliferating in the different tissues of individual mice.

Animals↗
PubMed1976

[Mutagenic effect of radiation on mice subjected to gamma irradiation during the embryonic period. I. Frequency of reciprocal translocations in the spermatocytes of mice subjected to gamma-irradiation at different stages of embryogenesis].

The frequency of reciprocal translocations was investigated in spermatocytes of mice gamma-irradiated at doses of 100 or 200 r at 4,5; 8,5; 10,5; 11,5 and 13,5 days of embryonic development, and in spermatocytes of adult males whose spermatogonia were irradiated. The cytological analysis of 41 males that were irradiated at a dose of 200 r at 4,5 days of embryogenesis showed that 2 males had a high frequency of reciprocal translocations in both testes (on the average 20,6 and 28,8%). In the testes of other males of this group translocations were not detected. It is highly probably that the testes of these 2 males were heterozygous for reciprocal translocations. The yield of reciprocal translocations in spermatocytes of males irradiated at 8,5--13,5 days of embryogenesis was very low, and was only 0,67 +/- 0,2 x 10(-5) on the average per 1 r per cell, whereas for adult mice it was 12,5 +/- 3,0 x 10(5) per 1 r per cell.

Animals↗