Karyotypes of Chironomus Meigen (Diptera: Chironomidae) species from Africa.

The karyotypes of six African Chironomus species (Chironomus alluaudi Kieffer, 1913, Chironomus transvaalensis Kieffer, 1923, Chironomus sp. Nakuru, Chironomus formosipennis Kieffer, 1908, Chironomus prope pulcher Wiedemann, 1830, Chironomus sp. Kisumu) were investigated; four of these karyotypes were described for the first time (Chironomus sp. Nakuru, Chironomus formosipennis, Chironomus prope pulcher, Chironomus sp. Kisumu). Of the six Chironomus karyotypes, three had "pseudothummi" cytocomplex chromosome arms combinations AE CD BF G (Chironomus alluaudi, Chironomus transvaalensis, Chironomus sp. Nakuru), two had "thummi"cytocomplex arms combinations AB CD EF G (Chironomus formosipennis, Chironomus prope pulcher), and one had "parathummi"armcombinations AC BF DE G (Chironomus sp. Kisumu). Thus, three of the ten main cytocomplexes known were detected in Africa. Detailed photomaps of all chromosome arms, with the exception of arms B and G, were prepared for the karyotypes of Chironomus alluaudi, Chironomus transvaalensis, Chironomus sp. Nakuru, Chironomus prope pulcher; the karyotypes of Chironomus formosipennis, Chironomus sp. Kisumucould only be fragmentarily mapped. Endemic African banding sequences were characteristic for most of the chromosomal arms in all species studied. However, basic sequences, which can be present in different Chironomus species on different continents (Wülker, 1980; Kiknadze et al. 2008), were also detected also in several African species (Chironomus alluaudi, Chironomus sp. Nakuru, and Chironomus formosipennis). The banding sequences of African species studied allow discussion of the derivation of modern banding patterns from hypothetical species, living before separation of cytocomplexes and continents.

[Chromosomal variability in natural populations of Chironomus cingulatus Meigen (Diptera, Chironomidae)].

Chromosomal polymorphism has been investigated in 7 natural populations from West Europe, West Siberia and Sakha Republic (Yakutia). The pool of polytene chromosome banding sequences of this species includes 15 banding sequences. The chromosomal polymorphism has been revealed in 5 of chromosomal arms. The most polymorphic is the arm B, there are 4 banding sequences in it. There are 3 banding sequences in the arm A. The arms D, E and G have 2 banding sequences. No chromosome rearrangements have been found in the arms C and F. The populations of Chironomus cingulatus differ clearly in the number and frequencies of banding sequences. This is evidence of that different gene sequences are adaptive in different populations.

[Geographic differentiation of genomic DNA of Chironomus plumosus (Diptera, Chironomidae) in natural holarctic populations].

Using RAPD markers, polymorphism and differentiation of genomic DNA was examined in seven natural populations of Chironomus plumosus from Europe, Siberia, and North America. All these populations showed high polymorphism of genomic DNA. The Palearctic and Nearctic populations of this species were not statistically significantly different in the genomic DNA polymorphism level. The genetic distance (GD), which characterizes the extent of intraspecific differentiation of population genetic structure, was determined among the natural populations of C. plumosus. The genetic distance was on average 0.0245. It was demonstrated that genetic structures of the Palearctic and Nearctic populations of C. plumosus was differentiated to a higher extent than in Palearctic. However, the genetic distances between the populations from different zoogeographical zones (0.313) did not exceed the level characteristic of the among-population differences, which do not disturb the species genetic integrity.

[The geographic varyability of the polytene chromosome banding sequence of non-biting midje Chironomus pseudothummi str. (Diptera, Chironomidae)].

The karyotypes and chromosomal polymorphism of Chironomus pseudothummi were investigated in different parts of its range. It was established that chromosomal variability in the natural populations of this species was represented mainly by the inversion polymorphism of arm G. Only rare and unique inversions were found as heterozygous in arms C, D, and E. In total, the 14 banding sequences of polytene chromosomes form the banding sequences pool of Ch. pseudothummi. Geographic differences in distribution of chromosomal banding sequences throughout the range were established. The presence of banding sequences pstG1 and pstG2 is characteristic of European populations. Banding sequence pstG1 was completely vanished with simultaneous increase in frequency of pstG2 and appearance of new inversion banding sequence pstG3 in Siberian populations. The differences in the set of the rare and unique inversions in arms C, D, and E between west-European and west-Siberian populations were revealed.

[The chromosomal polymorphism and divergence of populations in Chironomus nuditarsis Str. (Diptera, Chironomidae)].

The karyotype structure and chromosomal polymorphisms were investigated in 6 natural and 2 laboratory populations of Chironomus nuditarsis from Europe and Asia. The pool of rearranged polytene chromosome banding sequences of this species was determined that includes 16 inversion banding sequences and sequences with giant DNA-knobs (ndtG1k, ndtG2k). Obvious differences were demonstrated in the level of chromosomal polymorphism between European and Asian (Siberian) populations: the former were highly polymorphic, while the latter were practically monomorphic. It was suggested to consider the Siberian populations as marginal one. Cytogenetic distances between populations of C. nuditarsis as well between C. nuditarsis and the related species C. plumosus were estimated. The data obtained show that chromosomal rearrangements play a very important role in cytogenetic divergence of populations.

[Divergence patterns of banding sequences in different polytene chromosome arms reflect relatively independent evolution of different genome components].

Divergence patterns of the banding sequences from the chromosomal arms A, C, D, E, and F were compared in 63 species of the genus Chironomus. Evaluation of the number of breakpoints between the pairs of inverted banding sequences and the analysis of the lengths of the conserved segments in the chromosomal arms in the chironomid species examined showed that different arms evolved relatively independently and at different rates. No direct correlation between the arm length and the breakpoints number was observed. The length of the conservative segment was not fixed, but was arm-specific. Robustness and fidelity of the estimates of phylogenetic relationships between the species examined increased with the arm number, i.e., with the genome proportion included in the analysis.

[Divergence of the polytene chromosome banding sequences as a reflection of evolutionary rearrangements of the genome linear structure].

Banding sequences of five chromosomal arms (A, C, D, E, and F), accounting for about 70% of the total genome size in 63 Chironomus species, were used as phylogenetic markers to analyze divergence patterns of the linear genome structure during the evolution. The number of chromosomal breakpoints between the pairs of banding sequences compared served as a measure of divergence. It was demonstrated that the greater the divergence between the species compared, the higher the number of chromosomal breakpoints and the smaller the size of the conserved chromosomal regions. A banding sequences comparison in sibling species demonstrated a lower number of chromosomal breakpoints; the breakpoint number was maximum in a comparison of the banding sequences in the subgenera Chironomus and Camptochironomus. The use of the number of chromosomal breakpoints as a divergence measure provided establishment of phylogenetic relationships between 63 Chironomus species and discrimination of sibling species groups and cytocomplexes on a phylogenetic tree.

[Variation and divergence of multilocus genome markers in the species of the genus Chironomus (Diptera, Chironomidae)].

Variation and divergence patterns of the multilocus genome markers in twelve Chironomus species belonging to the plumosus and piger sibling-species groups were examined by use of polymerase chain reaction with random primers (RAPD method). The chironomid species showed high levels of the RAPD markers polymorphism. The genetic distances (GD) were determined between the species within the group of closely related species, as well as between the species from different groups. The estimates obtained characterized the divergence levels between the sibling species (GD = 0.739) and morphologically distinct species (GD = 0.935). Comparison of the variation and divergence levels of the RAPD markers with those for the other genome markers, namely, the enzyme-coding genes and chromosomes (gene linkage groups) have demonstrated different divergence rates for different genome components during speciation of Chironimids.

[Karyotype structure in species of Propsilocerus genus (Diptera, Chironomidae)].

Karyotype structure and polytene chromosome banding patterns were studied in two Orthocladiinae siblings--Propsilocerus akamusi (China) and Propsilocerus jacuticus (Russia). Both species have haploid number of chromosome typical for Orthocladiinae (n = 3). An unusual structure of centromeric regions was observed in all three chromosomes of karyotypes in both species. Photomaps of polytene chromosomes are presented. A comparison of karyotypes of P. akamusi and Propsilocerus jacuticus revealed a high level of homology in their banding sequences, however, the presence of fixed paracentric inversions in chromosomal arms IR, IIR, IIIR of Propsilocerus jacuticus has shown a clear-cut phylogenetic divergence. No chromosomal polymorphism was found in both species.

[The functional morphology of polytene chromosomes in the midge Chironomus pilicornis F. from the permafrost zone reservoirs]. / Funktsional'naia morfologiia politennykh khromosom khironomidy Chironomus pilicornis F. iz vodoemov kriolitozony.

The karyotype and chromosomal polymorphism of Chironomus pilicornis from the reservoirs of Yakutian permafrost zone are described. In the Yakutian populations, of 10 inversion sequences 11 genotypical combinations of these were registered. The level of inversion heterozygosity is 50-70%, but in several populations it makes only 11-29%. In comparison with the Scandinavian populations, significant functional modifications of chromosomal morphology were found. They are associated with the increase in centromeric heterochromatin amount, facultative chromocentre formation, and the appearance of numerous B-chromosomes and nucleoli, including the facultative ones. A possible adaptive significance of such functional modifications conditioned by climate peculiarities is discussed.

[Karyotype of the midge Chironomus heterodentatus Konstantinov from the group Obtusidens (Diptera, Chironomidae)]. / Kariotip komara-zvontsa Chironomus heterodentalis Konstantinov iz gruppy Obtusidens (Diptera, Chironomidae).

The karyotype of Chironomus heterodentatus, belonging to the obtusidens-group described by Konstantinov from the Volga in 1956, was studied in detail. Combinations of chromosomal arms are AB, CD, EF and G (cytocomplex thummi). The Ch. heterodentatus karyotype cleary differs from those of other members of the obtusidens-group with a species-specific banding pattern in arms A, B, C and D. Chromosomal polymorphism on homo- and heterozygous inversions was found in arms, A, B, D, E and G. 19 inversion banding sequences and their 27 genotypic combinations have been recorded. The shortest arm G is highly polymorphic. Heterozygotes on the Balbiani ring activity were found in arm G along with homo- and heterozygotes on inversions. B-chromosomes with a frequency equal to 2.7-25.0% were recorded in some Volga populations.

The modifying effect of nitrites, nitrates and increased temperature on 14C metabolism.

The paper deals with the experimental findings regarding the effects of non-radiational factors, such as sodium nitrite and nitrate and increased temperature, on the metabolism kinetics of 14C inorganic and organic compounds (14C-sodium bicarbonate, 14C-glucose) in conditions of long-term internal exposure to the nuclide. The authors determined the time which elapses before the steady state is achieved as well as the maximum concentration, the accumulation factor and the dose strength. At a concentration of 3 g/l, nitrites and nitrates were shown to produce no significant modifying effect on the kinetics of 14C metabolism. In hyperthermic conditions, 14C metabolism proved to be more intensive. The findings reported herein may have practical applications in setting up hygienic norms and evaluating the hazards of 14C accumulation in the environment.

[Delayed effects of acute radiation injuries by radioactive carbon (14C-glycine)]. / Otdalennye éffekty ostrykh radiatsionnykh porazhenii radioaktivnym uglerodom (14C-glitsinom).

A study was made of late biological effects of radioactive carbon (14C-glycine) applied in acute doses. The course of radiation sickness, at its acute stage, is similar to that of acute radiation sickness caused by external gamma-irradiation. The recovery is slow, and the disease becomes chronic exhibiting metabolism disturbances and early death of animals. Radioactive carbon has a pronounced blastomogenic action.

[Biological action of radioactive carbon. Biological effects of large amounts of radioactive carbon (14C-glycine)]. / Biologicheskoe deistvie radioaktivnogo ugleroda. Biologicheskie éffekty bolshikh kolichestv radioaktivnogo ugleroda (14C-glitsina).

In experiments on CBA X C57B16 mice a study was made of the acute effects of radiocarbon (14C-glycine) administered intraperitoneally in doses of 130, 60, 30 and 15 mBq/animal (the total cumulative doses absorbed within the body were, at an average, 29.5, 14.2, 7.1 and 3.6 Gy, respectively). In the first group, the animals developed grave radiation affections (50% death, average life-span of 17.6 days); in the second group, the affection was less serious, and in the third and fourth groups, the affection was light. A mean tissue absorbed dose in the died animals was 6-11 Gy.

Genetic effects of radiocarbon in reproductive cells of male mice.

The genetic effect of incorporated radiocarbon was studied after single, long-term (33 days) and chronic (6 and 12 months) treatment of male mice (CBA X C57B1) F1 with [14C]glucose. The genetic effect in male germ cells was estimated by 3 tests: DLM frequency in post- and pre-meiotic cells, RT frequency in stem spermatogonia and frequency of abnormal sperm heads. Absorbed doses in the gonads were: 0.22, 0.50 and 1.01 Gy, after a single exposure; 0.74 and 1.47 Gy, after long-term exposures; and 0.006 and 0.031 Gy, after chronic exposure for 6 months; and 0.013 and 0.066 Gy, for 12 months. The results suggest that DLM frequency in post-meiotic cells increased linearly with increasing the dose of 14C single and long-term exposures at a dose of 1.47 Gy only. A chronic treatment with [14C]glucose induced no increase in DLM frequency. RT frequency in stem spermatogonia was statistically significantly higher than the control level after the single and long-term exposure to 14C. A comparison of the results with the results of external single and chronic gamma-irradiation allows the conclusion that the relative genetic efficiency of radiocarbon as compared with that of gamma-rays is about 1.

[Reaction of mouse hematopoietic stem cells on gamma-irradiation and exposure to tritium oxide]. / Reaktsiia gemopoéticheskikh kolonieobrazuiushchikh kletok myshei na gamma-obluchenie i vozdeistvie okisi tritiia.

In experiments on 600 mice, relative biological effectiveness of tritium oxide was compared to that of gamma-radiation (137Cs) with respect to the response of CFUc. It was shown that RBE of tritium oxide was 1 within the dose range from 0.8 to 0.4 Gy.

Kinetics of metabolism of organic and inorganic 14C compounds.

Results of experimental studies on the dynamics of metabolism of various inorganic (NA2CO3, K2CO3, CaCO3) and organic (glucose, glycine, palmitic and succinic acids, ethanol and methanol) compounds of 14C after its single and long-term administration into the organism of rats are presented. The values of the corresponding rates of accumulation of 14C and the onset of the state of equilibrium after long-term administration of the radionuclide were elucidated for a number of compounds. Results of the studies can find practical application in norm-setting. The corresponding rate of accumulation in man of 14C taken in the diet was determined by extrapolation of the experimental data. It was found to be approximately 30. The state of practical 14C equilibrium in man occurs approximately 11/2 years after the beginning of the intake.

Endomitosis in grasshoppers. I. Nuclear morphology and synthesis of DNA and RNA in the endopolyploid cells of the inner parietal layer of the testicular follicle.

Changes in chromosome number (n-16n) due to somatic polyploidization were observed in the inner parietal layer cells (IPLCs) of the testicular follicle in 30 grasshopper species. A distribution into a geometrical series originating from the diploid value was established for the chromosome number of most of the nuclei of the IPLCs. However, nuclei with chromosome numbers of n, 3n, 5n, 7n were also found. POLYPLOId cells showed morphological patterns indicative of classical endomitosis. Endometaphase was most frequently encountered in the IPLCs. At this stage, the chromosomes were sufficiently condensed so that they were individually identifiable and their numbers could be counted. A Feulgen stain-positive fibrillar halo around the central part of chromosomes produced a lampbrush-like appearance. It was shown that the presence of many endometaphases in the IPLCs was not correlated with intense chromosome replication. 3H-thymidine incorporation data as well as cytophotometric DNA measurements did not demonstrate any appreciable DNA synthesis in the IPLCs. However, these cells were found to incorporate intensely 3H-uridine, especially in the endometaphase stage. Based on these data a reconsideration of the morphological patterns of endomitosis is suggested. The chromosomes of endopolyploid cells are considered as suitable models for studies of the functional organization of actively transcribed, individually visible chromosomes.

Radiocarbon (14C) migration and metabolism kinetics (a review).

Radiocarbon (14C) introduced into the biosphere as a result of nuclear explosions and operation of nuclear power stations has upset the equilibrium existing in nature. The increase in 14C concentration in the biosphere is a problem of considerable hygienic and social importance, since 14C affects all living organism in the world. This paper presents data on 14C migration and metabolism kinetics. Radiocarbon metabolism kinetics depends on the form of the chemical compound metabolized. Inorganic 14C compounds are metabolized relatively fast. Organic 14C compounds (carbohydrates, fats and proteins) are retained longer in the body. Differences in the metabolism kinetics of differents 14C compounds lead to the formation of unequal irradiation doses in various organs and tissues. In establishing standards for admissible 14C intake, one should take into consideration the kind of chemical compound in which the element is incorporated.

[Formation of endopolyploid cells with the morphology of classic endomitosis during ontogenesis of the desert locust, Schistocerca gregaria (Forskal) (Orthoptera)]. / Formirovanie éndopoliploidnykh kletok s morfologiei klassicheskogo éndomitoza v ontogeneze pustynnoi saranchi Schistocerca gregaria (Forskal) (Oortoptera).

The morphological observations of cells of the basal region of seminal follicles, studies of 3H-thymidine and 3H-uridine incorporation and results of cytophotometric DNA determination have shown that during the larval development the cells which have morphological features of classical endomitosis in the differentiated state are reproduced. Their reproduction and polyploidization takes place in the definite, morphologically delineated zone in the basal region of seminal follicle. From the latter zone these cells migrate in the middle zone where they function. At the same time changes in their morphology are observed: cell flattening, chromatin loosening in the nuclei, appearance of morphologically distinct chromosomes. The level of 3H-uridine incorporation increases.