Reduction of spontaneous somatic mutation frequency by a low-dose X irradiation of Drosophila larvae and possible involvement of DNA single-strand damage repair

The third instar larvae of Drosophila were irradiated with X rays, and the somatic mutation frequency in their wings was measured after their eclosion. In the flies with normal DNA repair and apoptosis functions, 0.2 Gy irradiation at 0.05 Gy/min reduced the frequency of the so-called small spot (mutant cell clone with reduced reproductive activity) compared with that in the sham-irradiated flies. When apoptosis was suppressed using the baculovirus p35 gene, the small spot frequency increased four times in the sham-irradiated control group, but the reduction by the 0.2-Gy irradiation was still evident. In a non-homologous end joining-deficient mutant, the small spot frequency was also reduced by 0.2 Gy radiation. In a mutant deficient in single-strand break repair, no reduction in the small spot frequency by 0.2 Gy radiation was observed, and the small spot frequency increased with the radiation dose. Large spot (mutant cell clone with normal reproductive activity) frequency was not affected by suppression of apoptosis and increased monotonically with radiation dose in wild-type larvae and in mutants for single- or double-strand break repair. It is hypothesized that some of the small spots resulted from single-strand damage and, in wild-type larvae, 0.2 Gy radiation activated the normal single-strand break repair gene, which reduced the background somatic mutation frequency.     

A simple device for spot counting in photomicrographs or electron micrographs.

A simple apparatus for spot counting in photomicrographs or electron micrographs is described, consisting of an illuminator on which the photographic print in placed and a counting pen. By making small holes in the photograph with the specially designed spring-loaded counting pen, the spot counted can be clearly located by the light from the illuminator falling through the hole, whereas a microswitch built into the counting pen makes an electronic counting system to move one digit.     

不同激光照射方法对周围神经再生的影响

为研究不同半导体激光照射方法对周围神经损伤的影响,将96只家兔随机分为3周,6周,9周,12周4个观察期组,每个观察期组又随机分为不同照射方法的治疗组和对照组。建立动物模型后,各照射组在术后1d开始照射治疗,激光功率为10mw,每次照射10rain,每天一次,连续照射10d。照射治疗A组对准损伤神经吻合部位进行照射,照射治疗B组照射家兔L5、L6脊髓节段,照射治疗c组在对准吻合处进行照射同时还要照射L5、L6脊髓节段,对照组激光输出功率为零。实验结果表明低能量半导体激光照射能促进轴突再生,改善再生神经功能,以同时照射损伤周围神经部位和相应脊髓节段效果最为显著。     

Optimization of laser beams in FRAP experiments of microscopical objects

In fluorescence recovery after photobleaching (FRAP) experiments the sample is irradiated on a small spot, the diameter of which must be related to the sample size and the diffusion constant to be measured. This paper considers the conventional FRAP set-up where a laser beam is directed through a microscope vertical illuminator to the sample. The requirements of an intermediate optical system producing a Gaussian beam with a waist of given radius in the microscope object plane are considered, and the optical parameters determined.     

Dose rate and oxygen consumption rate in mice confined in a small holder during exposure to 2450 MHz microwave radiation

Summary The average dose rate and oxygen consumption rate of an individual mouse in a small holder during exposure to 2450 MHz CW microwave radiation are determined. The environmental conditions are 24° C temperature, 55% relative humidity, and 78 ml/min airflow. A forward power of 1.7 W resulted in the average dose rates of 31.0 mW/g, and 23.6 mW/g respectively, for the animals irradiated in the small, and the large holders. The results support the hypothesis that previously observed reduction in microwave energy absorption during irradiation is due to the orientation and positioning of the animal's body with respect to the microwave field. Relatively higher rate of oxygen consumption of the tightly confined sham-irradiated animals in comparison to that of the animals in the large holder is observed. Although a decrease in oxygen consumption rate is observed during exposure for the microwave irradiated animals in the small holder, the magnitude of this decrease is not more than that of the animals irradiated in the large holder. Thus the lack of reduction in the absorption of microwave energy is not compensated by a correspondingly large decrease in oxygen consumption, resulting in a larger heat load and perhaps larger stress to animals confined in the small holder.     

Morphology of the male reproductive system,sperm ultrastructure and γ-irradiation of the red palm weevil Rhynchophorus ferrugineus Oliv. (Coleoptera: Dryophthoridae)

In the present study we describe the morphology of the male reproductive apparatus and sperm ultrastructure of the red palm weevil – an invasive pest of several palm tree species – as well as the most important steps of spermatogenesis. The reproductive apparatus consists of a pair of testes (each formed by two lobes) a long tube-like accessory gland, a prostate gland and a small accessory gland. Characteristic features of the sperm are 90–100 μm total length, 10 μm nucleus, two mitochondrial derivatives, two accessory bodies, one well-developed puff-like structure and a typical insect 9+9+2 flagellar axoneme. One of the methods used for the biological control of pests is the Sterile Insect Technique (SIT), for the evaluation of which we make a preliminary comparison of the sperm ultrastructure of non-irradiated and irradiated weevils (at a dose of 80 Gray).     

Abnormal distribution of double strand breaks in DNA after direct action of ionizing energy

Experiments on purified DNA irradiated under circumstances which maximize direct absorption of ionizing energy in the DNA suggest that double strand breaks to the DNA helix are caused when energy depositions in spheres of comparable size to the diameter of the DNA helix exceed a threshold energy of between 70 and 100 eV. Evidence is also presented that shows that these events can lead to non-random patterns of double strand breakage within the molecule which are manifested as an excess of small fragments of DNA.     

Radio frequency electromagnetic exposure: Tutorial review on experimental dosimetry

Radio frequency (RF) dosimetry is the quantification of the magnitude and distribution of absorbed electromagnetic energy within biological objects that are exposed to RF fields. At RF, the dosimetric quantity, which is called the specific absorption rate (SAR), is defined as the rate at which energy is absorbed per unit mass. The SAR is determined not only by the incident electromagnetic waves but also by the electrical and geometric characteristics of the irradiated subject and nearby objects. It is related to the internal electric field strength (E) as well as to the electric conductivity and the density of tissues; therefore, it is a suitable dosimetric parameter, even when a mechanism is determined to be “athermal.” SAR distributions are usually determined from measurements in human models, in animal tissues, or from calculations. This tutorial describes experimental techniques that are used commonly to determine SAR distributions along with the SAR limitations and unresolved problems. The methods discussed to obtain point, planar, or whole-body averaged SARs include the use of small E-field probes or measurement of initial rate of temperature rise in an irradiated object. © 1996 Wiley-Liss, Inc.     

Investigation of the potential for mitotic recombination in the mouse

A variation of the mouse spot test is described that is designed to distinguish between spots of altered coat colour that arise by reciprocal mitotic recombination and those caused by somatic mutation or non-disjunction. Mouse fetuses that were heterozygous for two, linked coat colour genes were irradiated (1.5 Gy X-rays) in utero at 10.25-10.50 days post coitum (p.c.) or left untreated. Subsequently, the coats were classified for the presence of spots of altered colour. The irradiated embryos were heterozygous for the linked genes pink-eyed dilution (p) and albino (c) and were produced by both the repulsion and coupling crosses. Half of the reciprocal recombination events between the centromere and the proximal marker (p), in heterozygotes with p and c in repulsion, should produce twin spots. No such twin spots would be expected from a similar event in the coupling heterozygotes. The coats of 238 irradiated and 208 untreated repulsion heterozygotes plus 107 irradiated and 314 untreated coupling heterozygotes were classified for spots. One irradiated, repulsion heterozygote had a diffuse twin spot that was only recognisable by microscopic examination of the hairs. We conclude that if the treatment described induces mitotic recombination in the mouse, it does so with low efficiency.     

Partitioning of P1 plasmids by gradual distribution of the ATPase ParA

Recently, it has been reported that prokaryotes also have a mitotic-like apparatus in which polymerized fibres govern the bipolar movement of chromosomes and plasmids. Here, we show evidence that a non-mitotic-like apparatus that does not form polymerized filaments carries out plasmid partitioning. P1 ParA, which is a DNA-binding ATPase protein, was found to be distributed through the whole nucleoid and formed a dense spot at the centre of the nucleoid. The fluorescent intensity of the ParA spot blinked, and then the spot gradually migrated from the midcell to a cell quarter position. Such distribution was not observed in anucleate cells, suggesting that the nucleoid could be a matrix for gradual distribution of ParA. Plasmid DNA constantly colocalized at the spot of ParA and migrated according to spot migration and separation. Thus, the gradient distribution of ParA determines the destination of partitioning plasmids and may direct plasmids to the cell quarters.     

Effects of 60 Hz electric and magnetic fields on maturation of the rat neopallium

This study was undertaken to determine the effects of extremely low frequency (ELF; 60 Hz) electromagnetic (EM) fields on somatic growth and cortical development, as well as biochemical and morphological maturation, of the rat neopallium. On the fifth day of pregnancy, female rats were put in pairs into plastic cages that were housed in a specially constructed apparatus for irradiation under three separate sets of combination and intensity: 1) 1 kV/m and 10 gauss; 2) 100 kV/m and 1 gauss; and 3) 100 kV/m and 10 gauss. The dams were exposed for 23 h daily, from days 5 through 19 postconception after which they were returned to cages outside the exposure apparatus until they littered. The neonates were culled to eight pups per litter. At 0 (birth), 5, 12, and 19 days postnatally, they were killed for biochemical and morphological studies. Another group of pregnant rats was sham-exposed in an identical apparatus, which was not energized, and the pups were used as controls. The irradiated rats exhibited no physical abnormalities, nor did they show brain deformities such as swelling or herniation following exposure to ELF-EM fields. There was no difference in somatic growth between control and exposed rats, but a small reduction in cortical weight was observed in rats exposed at 1 kV/m and 10 gauss, and 100 kV/m and 1 gauss, respectively. Biochemical measurements of DNA. RNA, protein, and cerebroside concentrations indicated that among the three separate exposures, only the neopallium of rats exposed at 1 kV/m and 10 gauss showed a small reduction in DNA level, as well as small reductions in RNA and protein levels. No changes were noticed in cerebroside levels in any exposed animals, and there were no differences in protein/DNA and cerebroside/DNA ratios between control and exposed rats. Morphological observations did not reveal any detectable alterations in the irradiated rats. These results indicate that exposure to ELF-EM fields caused minimal or no changes in somatic growth and cerebral development of the rat. © 1993 Wiley-Liss, Inc.     

UV-microbeam irradiations of the mitotic spindle: spindle forces and structural analysis of lesions

Mitotic PtK1 spindles were UV irradiated (285 nm) during metaphase and anaphase between the chromosomes and the pole. The irradiation, a rectangle measuring 1.4 x 5 microns parallel to the metaphase plate, severed between 90 and 100% of spindle microtubules (MTs) in the irradiated region. Changes in organization of MTs in the irradiated region were analyzed by EM serial section analysis coupled with 3-D computer reconstruction. Metaphase cells irradiated 2 to 4 microns below the spindle pole (imaged by polarization optics) lost birefringence in the irradiated region. Peripheral spindle fibers, previously curved to focus on the pole, immediately splayed outwards when severed. We demonstrate via serial section analysis that following irradiation the lesion was devoid of MTs. Within 30 s to 1 min, recovery in live cells commenced as the severed spindle pole moved toward the metaphase plate closing the lesion. This movement was concomitant with the recovery of spindle birefringence and some of the severed fibers becoming refocused at the pole. Ultrastructurally we confirmed that this movement coincided with bridging of the lesion by MTs presumably growing from the pole. The non-irradiated half spindle also lost some birefringence and shortened until it resembled the recovered half spindle. Anaphase cells similarly irradiated did not show recovery of birefringence, and the pole remained disconnected from the remaining mitotic apparatus. Reconstructions of spindle structure confirmed that there were no MTs in the lesion which bridged the severed spindle pole with the remaining mitotic apparatus. These results suggest the existence of chromosome-to-pole spindle forces are dependent upon the existence of a MT continuum, and to a lesser extent to the loss of MT initiation capacity of the centrosome at the metaphase/anaphase transition.     

Enhancement of monoclonal antibody production in CHO cells by exposure to He–Ne laser radiation

This study tested the effectiveness of laser biostimulation in small-scale cultures in vitro. We investigated the response of recombinant CHO cells, which are used for the production of monoclonal antibody, to low level laser radiation. The cells were irradiated using a 632.8 nm He–Ne laser in a continuous wave mode at different energy doses. We incubated the irradiated cells in small batch cultures and assessed their proliferation and productivity at various time intervals. Compared to untreated cells, the irradiated cells showed a significant increase in antibody production. Moreover, the results showed that laser irradiation did not affect viability and slightly enhanced proliferation rate.     

Thermodynamics in the present progressive mode and its role in the context of the origin of life.

The origin and evolution of biological organizations proceeding on Earth are put in a nonequilibrium thermodynamic framework within a cosmological context. The dynamic process responsible for chemical evolution leading to the origin of biological being depends upon consumer-dominating thermodynamics, in which the heat sink is taken to be active in extracting heat energy from a body at a higher temperature. Consumer-dominating thermodynamics follows from the fact that when a small hot body contacts a cold heat sink, it decreases the temperature at the possible fastest rate. The fastest temperature drop, when applied to chemical products being synthesized through the energy supplied from an external heat source, is selective in keeping only those products that can decrease the temperature at the fastest rate among the available alternatives. Synthesis of small organic molecules in the small ice grains in interstellar diffuse clouds irradiated by ultraviolet radiation is a representative case of consumer-dominating thermodynamics, in which diffuse clouds serve as cold heat sinks in the cosmological context. Another case of consumer-dominating thermodynamics predominant on Earth especially in the perspective of the origin and evolution of life is with submarine hydrothermal vents, in which the surrounding cold seawater constantly serves as the cold heat sink.     

Protein-protein recognition and interaction hot spots in an antigen-antibody complex: free energy decomposition identifies "efficient amino acids"

The molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) method was applied to the study of the protein-protein complex between a camelid single chain variable domain (cAb-Lys3) and hen egg white lysozyme (HEL), and between cAb-Lys3 and turkey egg white lysozyme (TEL). The electrostatic energy was estimated by solving the linear Poisson-Boltzmann equation. A free energy decomposition scheme was developed to determine binding energy hot spots of each complex. The calculations identified amino acids of the antibody that make important contributions to the interaction with lysozyme. They further showed the influence of small structural variations on the energetics of binding and they showed that the antibody amino acids that make up the hot spots are organized in such a way as to mimic the lysozyme substrate. Through further analysis of the results, we define the concept of "efficient amino acids," which can provide an assessment of the binding potential of a particular hot spot interaction. This information, in turn, can be useful in the rational design of small molecules that mimic the antibody. The implications of using free energy decomposition to identify regions of a protein-protein complex that could be targeted by small molecules inhibitors are discussed.     

Die Chloroplastendrehung beiMougeotia

Summary Mougeotia cells with chloroplasts oriented in profile have been irradiated with small spots of monochromatic red polarized light in order to induce chloroplast movement.In these experiments, four factors have been varied: 1. the orientation of the vibration plane of the light in relation to the cell axis, 2. the localization of the spot, i. e. irradiation of the chloroplast or the cytoplasm, 3. the spot size, and 4. the duration of the irradiation.As a result of our experiments, we conclude that the photoreceptor molecules responsible for the light-induced chloroplast movement are localized in the cytoplasm.As the photoreceptor of this reaction is the well known phytochromesystem, we may assume that also in other plants the phytochrome is localized in the cytoplasm rather than in the chloroplast.

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Mit 9 Textabbildungen     

Oncogenic transformation by fractionated doses of neutrons

Oncogenic transformation was assayed after C3H 10T1/2 cells were irradiated with monoenergetic neutrons; cells were exposed to 0.23-, 0.35-, 0.45-, 5.9-, and 13.7-MeV neutrons given singly or in five equal fractions over 8 h. At the biologically effective neutron energy of 0.45 MeV, enhancement of transformation was evident with some small fractionated doses (below 1 Gy). When transformation was examined as a function of neutron energy at 0.5 Gy, enhancement was seen for cells exposed to three of the five energies (0.35, 0.45, and 5.9 MeV). Enhancement was greatest for cells irradiated with 5.9-MeV neutrons. Of the neutron energies examined, 5.9-MeV neutrons had the lowest dose-averaged lineal energy and linear energy transfer. This suggests that enhancement of transformation by fractionated low doses of neutrons may be radiation-quality dependent.     

Glyptothorax pantherinus, a new species of catfish (Teleostei: Sisoridae) from the Noa Dehing River, Arunachal Pradesh, India

Glyptothorax pantherinus, a new sisorid catfish species, is described from the Noa Dehing River of Arunachal Pradesh, India. The new species can be distinguished from its congeners by the following combination of characters: mottled skin; a well-developed obtuse leaf-shaped thoracic adhesive apparatus with no central depression, unculiferous ridges of the apparatus not extending anteriorly onto the gular region, and the ridges uninterrupted except for the posterior-most region; one bean-shaped cream-coloured spot on either side of the dorsal-fin origin; ventral surface of the simple rays of the paired fins are plaited marginally and distally.     

Design idea for a microwave energy coupler in biomedical field

The use of microwave radiation for biomedical purposes has been increasing in recent years. Among the most important applications are localized hyperthermia, non-invasive diagnosis and monitoring of cardiovascular system parameters and characterization of biological tissues.For all these purposes the design of suitable electro-magnetic (e.m.) energy couplers is of fundamental importance. In this paper a new structure is suggested and assessed for a direct contact microwave applicator. The proposed radiating system is obtained using the microstrip transmission lines technique and its principal characteristics are very small sizes and weight, together with good matching and sufficiently defined and small irradiated value.     

Small-world network approach to identify key residues in protein-protein interaction

We show that protein complexes can be represented as small-world networks, exhibiting a relatively small number of highly central amino-acid residues occurring frequently at protein-protein interfaces. We further base our analysis on a set of different biological examples of protein-protein interactions with experimentally validated hot spots, and show that 83% of these predicted highly central residues, which are conserved in sequence alignments and nonexposed to the solvent in the protein complex, correspond to or are in direct contact with an experimentally annotated hot spot. The remaining 17% show a general tendency to be close to an annotated hot spot. On the other hand, although there is no available experimental information on their contribution to the binding free energy, detailed analysis of their properties shows that they are good candidates for being hot spots. Thus, highly central residues have a clear tendency to be located in regions that include hot spots. We also show that some of the central residues in the protein complex interfaces are central in the monomeric structures before dimerization and that possible information relating to hot spots of binding free energy could be obtained from the unbound structures.