Cytogenetic consequences of chronic irradiation in rodent populations inhabiting the Eastern Ural Radioactive Trace zone

Chromosome instability in bone-marrow cells and ⁹⁰Sr accumulation in the bone tissue are studied in rodents (Apodemus (Sylvaemus) uralensis Pall., 1811 and Apodemus agrarius Pall., 1771)* inhabiting the Eastern Ural Radioactive Trace (EURT) zone (Kyshtym radiation accident 1957) and adjacent areas of the Urals. Intensive mutagenic process in both species from impact plots (soil pollution by ⁹⁰Sr, 2322–16690 kBq/m²) is found. Significant positive correlation of the frequency of aberrant cells and the concentration of ⁹⁰Sr is shown. Possible causes of the lack of resistance to long-term mutagenic factors (over 100 generations in the 50 years since the accident), such as migration of animals and the specific configuration of the EURT zone (an extended narrow territory with a sharply falling gradient of radionuclide pollution), which considerably decrease the probability that certain changes will be fixed and inherited in a series of generations of rodents, are discussed.     

Accumulation of 90Sr in the bone tissue of the northern mole vole, living in the head part of the East Ural Radioactive Trace

Deposition of 90Sr in a bone tissue of the northern mole-vole (Ellobius talpinus Pallas, 1770) living in the head part of the East Ural Radioactive Trace (EURT) (density of pollution by 90Sr 37 MBq/m2 - 1000 Ci/km2) was investigated. Features of the rodent are digging (underground) way of life, family organization of settlements and weak migratory activity. Authentic (p < 0.01) interfamily distinctions in concentration 90Sr are revealed on the background of absence of sexual and are features of accumulation the radionuclides inside separate families, thus individual parameters differ in 7 times. It is established, that the level of accumilation of 90Sr is comparable with that in other species of small mammals in this territory. Age inversion of accumulation of 90Sr earlier found out in other species of mammals on the EURT is confirmed.     

Parameters of peroxide oxidation of lipids and the system of its regulation in the tissues of Ellobius talpinus Pall,living on the territory of the East Urals Radioactive Trace

The peroxide oxidation of lipids and the systems of its regulation was tested in Ellobius talpinus Pall, living on the territory of the East Urals Radioactive Trace with the 90Sr contamination density of 1000 Ci/km2. The degree of sensitivity of the examined tissues and organs was revealed, the most considerable parameters were defined for marking radiosensitivity of the taken species, as well as the complex of parameters, allowing classifying an animal as an inhabitant of the clean or the contaminated territory. The found changes are considered as compensatory mechanisms for forming of nonspecific resistance.     

90Sr and 137Cs in higher aquatic plants of some water basins on the East-Urals Radioactive Trace: species features of radionuclide concentration

The paper summarizes the results from radioecological studies of a number of water basins located on the East-Urals Radioactive Trace (EURT), as exemplified by the lakes Large Ighish, Small Ighish and Shablish which are included in the medium-distance and remote zone of the EURT. The lake Misyash which is situated in the opposite direction from the release vector and has been only contaminated due to global fallouts has been used as a control water basin. The current species composition of the high aquatic plants and species-specific concentration of 90Sr and 137Cs in them was studied, also, the radionuclide accumulation and discrimination coefficients were estimated.     

Cytogenetic effects in plant populations from the East Urals Radioactive Track

Mutation dynamics in generations was studied in natural populations of plants from the East Ural Radioactive Track (EURT, Kyshtym accident). The experiments were aimed at the investigation of the formation of genetic load in natural plant populations under conditions of prolonged radiation exposure. The main approach used in the study was the analysis of cytogenetic alteration, chlorophyll and gene mutations in plants exposed for more than 40 years to chronic beta-irradiation and in their progeny.     

Characteristics of natural radionuclide distribution in different organs of plants growing on territory with increased radiation background

We investigated wild-growing grassy plants such as Alhagi pseudalhagi, Zygophyllum, Juncus acutus and Argusia sibirica with the purpose of studying the mechanism of carry of radionuclides from ground in plants and an establishment most the common laws of distribution of radionuclides between different organs of plants. The results of the research show that the researched plants are mainly accumulated 40K. On a degree of accumulation, 226Ra occupies the second place, but 232Th doesn't participate almost in processes of carry from ground in plants. It is established that root systems of plants possesses unequal ability to absorb same radionuclides from the same ground. For example, the root system of Argusia sibirica is characterized by smaller ability to absorb 226Ra, but 40K is more accessible. It is shown that biological availability radionuclides in the given ground depends both on a kind of plants and on radionuclides. For example, Argusia sibirica, Zygophyllum show higher accumulating ability to 40K and in relation to 226Ra, Alhagi pseudalhagi and Juncus acutus are more sensitive. It is established that accumulating ability of stalks of different plants in relation to 40K are appreciably different. Distribution of radionuclides in seeds of plants has other character. Thus Alhagi pseudalhagi in the seeds had also certain amount of 232Th, and leaves Argusia sibirica in comparison with Zygophyllum have a high degree of accumulation as for 40K, so for 226Ra.     

Some morphological aspects of the synaptonemal complex in higher plants.

The synaptonemal complex is illustrated in electron micrographs from pollen mother cells (p.m.cs) of the following plants: Fritillaria lanceolata, Allium fistulosum, Tulbaghia violacea, Luzula purpurea, Phaedranassa viridiflora and the tulip cultivar Keiserkroon. The possibility that the lateral elements in synaptonemal complexes of plants are tubiform structures is discussed in relation to their fine structure and in the light of a deformity seen in them. An assessment of the evidence suggesting that both lateral and central elements in the complex are ribonucleoprotein structures is made. The effect of brief water treatment on the chromatin and synaptonemal complex at zygotene in p.m.cs of the Phaedranassa is discussed, particularly with reference to two precisely oriented axial strands then seen running between the lateral elements. Examination of stages of premeiotic interphase and early leptotene in p.m.cs of the Fritillaria, revealed that the axial cores laid down at leptotene are formed first in heterochromatic regions, which in this species are locked in chromocentres that persist until pachytene. Further, at leptotene the chromatin in these parts was singularly more decondensed (diffuse) than at any other period, including the premeiotic interphase, subsequent stages of meiosis and mitotic cycle in meristems. It is suggested that the diffuse state of the chromatin in chromocentres at the onset of leptotene, allows the necessary freedom of movement required to promote homologous pairing of the heterochromatic segments. Evidence of such a movement was indicated by a change in position of the nucleoli, which moved from a more central position at early premeiotic interphase to a peripheral one at the onset of leptotene, when they are seen adpressed to the nuclear envelope.     

Chiral mutagens: Cytogenetic effects on higher plants

The cytogenetic activity of chiral nitrosoalkilureas and their effect on winter soft wheat chromosomes (Triticum aestivum L.) have been investigated. A comparative analysis of the cytogenetic activity of the chiral nitrosoalkilureas—S(+)1-N-nitroso-1-N-methyl-3-N-sec-buthylurea (S(+)NMsBU) and R(−)-1-N-nitroso-1-N-methyl-3-N-sec-buthylurea (R(−)NMsBU)—on higher plants has been performed for the first time. According to the frequency of chromosome aberrations, stereoisomers S(+) are twice more active than stereoisomers R(−). In addition to the typical anaphase aberrations (fragments, bridges, and lagging chromosomes), other numerous mitosis pathologies have been found: C-mitosis, chromosome hyperspiralization and despiralization, unequal chromosome allocation between daughter nuclei, three-pole mitosis, etc. Such pathologies have not been found when treating with nitrosoethylurea and gamma rays.     

Some characteristics of nitrate reductase from higher plants

With respect to cofactor requirements, NADH, and FMNH₂ were equally effective as electron donors for nitrate reductase obtained from leaves of maize, marrow, and spinach, when the cofactors were supplied in optimal concentrations. The concentration of FMNH₂ required to obtain half-maximal activity was from 40- to 100-fold higher than for NADH. For maximal activity with the corn enzyme, 0.8 millimolar FMNH₂ was required. In contrast, NADPH was functional only when supplied with NADP:reductase and exogenous FMN (enzymatic generation of FMNH₂).

All attempts to separate the NADH₂- and FMNH₂-dependent nitrate reductase activities were unsuccessful and regardless of cofactor used equal activities were obtained, if cofactor concentration was optimal. Unity of NADH to FMNH₂ activities were obtained during: A) purification procedures (4 step, 30-fold); B) induction of nitrate reductase in corn seedlings with nitrate; and C) inactivation of nitrate reductase in intact or excised corn seedlings. The NADH- and FMNH₂-dependent activities were not additive.

A half-life for nitrate reductase of approximately 4 hours was estimated from the inactivation studies with excised corn seedlings. Similar half-life values were obtained when seedlings were incubated at 35° in a medium containing nitrate and cycloheximide (to inhibit protein synthesis), or when both nitrate and cycloheximide were omitted.

In those instances where NADH activity but not FMNH₂ activity was lost due to treatment (temperature, removal of sulfhydryl agents, addition of p-chloromercuribenzoate), the loss could be explained by inactivation of the sulfhydryl group (s) required for NADH activity. This was verified by reactivation with exogenous cysteine.

Based on these current findings, and previous work, it is concluded that nitrate reductase is a single moiety with the ability to utilize either NADH or FMNH₂ as cofactor. However the high concentration of FMNH₂ required for optimal activity suggests that in vivo NADH is the electron donor and that nitrate reductase in higher plants should be designated NADH:nitrate reductase (E.C. 1.6.6.1).

     

Radiation effects on the one locus-gametophytic system of self-incompatibility in higher plants

Summary A brief review is presented of the temporary and permanent effects which are usually observed after irradiation treatment of self-incompatible plants with a one locus-system of gametophytic incompatibility and attempts are made to demonstrate that the study and exploitation of such effects can lead to important advances in the fields of mutation breeding, radiobiology per se and biochemistry.The fact that irradiation treatment has only negative effects on the self-incompatibility system (inactivation of the incompatibility reaction and/or genetic losses at the S locus) is discussed in relation to the positive changes (formation of new specificities) which are observed during inbreeding. In this connection, the suggestion is made that the self-incompatible plant may perhaps be equipped with a switch system or a mutagenic mechanism which enables it to display a new specificity when this new specificity is needed for increasing the level of genetic polymorphism in the population to which the plant belongs.

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Zusammenfassung Es wird ein Überblick gegeben über die temporären und permanenten Nachwirkungen einer Strahlenbehandlung von selbstinkompatiblen Pflanzen mit gametophytischer Determination. Die Untersuchung und Auswertung solcher Effekte kann zu Fortschritten auf dem Gebiete der Mutationszüchtung, der allgemeinen Strahlenbiologie und der Biochemie beitragen.Die Tatsache, daß die Strahlenbehandlung lediglich negative Wirkungen hat (Inaktivierung der Inkompatibilitätsreaktion und/oder genetische Störungen am S-Locus), wird vergleichend diskutiert mit den positiven Änderungen (Auftreten neuer Spezifizitäten) bei anschließender Inzucht.Es wird in diesem Zusammenhang vorgeschlagen anzunehmen, daß die selbstinkompatible Pflanze möglicherweise mit einem Schalt-System oder einem mutagenen Mechanismus ausgerüstet ist, die sie in die Lage versetzen, eine neue Spezifizität zu entwickeln, wenn diese zur Erhöhung des Niveaus des genetischen Polymorphismus in der Population notwendig ist.

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This publication is contribution no. 482 of the Euratom Biology Division.     

几种高等水生植物的克藻效应研究

研究了五种高等水生植物(黑藻、金鱼藻、水花生、茭白、空心菜)对蛋白核小球藻、斜生栅藻生长的抑制作用。试验结果显示,各种受试植物均有不同程度的克藻效果,金鱼藻与黑藻的克藻作用最强,水花生的作用次之。克藻效果以受试植物与藻共培养最佳,其次为连续添加种植水,表明在植物的生长过程中其化感物质是连续释放且能迅速降解的,而黑藻干物质的浸提液所具有的克藻效应说明有些化感物质对一定温度和光照是较稳定的。     

Physiological effects of betalains upon higher plants

Red and yellow betalains isolated from red beetroots by means of gel filtration were strong inhibitors of indole-3-acetic acid oxidase; 50% inhibition was obtained at 5 × 10^?7 M and 3 × 10^?7 M respectively. Concentrations of 10^?4 M betanin had no effect upon ATP production in mitochondria. The red pigment relieved the inhibitory effects upon wheat root elongation caused by indole-3-acetic acid but not the inhibition caused by 2,4-dichlorophenoxyacetic acid.     

The chiral mutagens: cytogenetic effects on higher plants

The paper covers investigation of cytogenetic activity of chiral mutagens and their specific effects on the plant cells chromosomes of soft winter wheat (Triticum aestivum L.). Comparative analysis of cytogenetic activity of chiral NEU: S(+)1-N-nitroso- 1-N-methyl-3-N-sec-buthylureas (S(+)NMsBU) and R(-)1-N-nitroso- 1N-methyl-3-Nsec-buthylureas (R(-)NMsBU) on winter wheat was performed. As it was shown by the frequency of chromosomal aberrations the S(+) stereoisomer was twice more active than R(-). In addition to typical anaphase aberrations (fragments, bridges, lagging chromosomes) the numerous mitosis pathologies were revealed - K-mitoses, hyperspiralization and despiralization of chromosomes, unequal allocation of chromosomes between the daughter nuclei, mass fragmentation, nondisjunction and chromosome adhesion, three-pole mitoses, etc. Neither of the mentioned pathologies was observed under the action of NEU and gamma-rays.     

Does boron play only a structural role in the growing tissues of higher plants?

In species in which boron (B) mobility is limited, B deficiency only occurs in growing plant organs. As a consequence of the highly localized patterns of plant growth and the general immobility of B it has been extremely difficult to determine the primary function of B in plants. In species in which B is phloem mobile, the removal of B from the growth medium results in the depletion of B present in mature leaves. Thus, it is possible to develop mature leaves with increasingly severe levels of B depletion, thereby overcoming the complications of experiments based on growing tissues. Utilizing this approach we demonstrate here that B depletion of mature plum (Prunus salicina) leaves did not result in any discernible change in leaf appearance, membrane integrity or photosynthetic capacity even though B concentrations were reduced to 6-8 µg/g dwt, which is less than 30% of the reported tissue B requirement. Boron depletion, however, results in a severe disruption of plant growth and metabolism in young growing tissues. This experimental evidence and theoretical considerations suggest that the primary and possibly sole function of B, is as a structural component of growing tissues.