Oogenesis in Macrotrachela quadricornifera (Rotifera,Bdelloidea)

Bdelloids reproduce via obligate apomictic parthenogenesis. Oogenesis occurs through two subsequent equational divisions, with the extrusion of two polar bodies. Although the morphology of the bdelloid reproductive apparatus has been previously described, the eutely of the germarium has never been investigated. We studied oogenesis in Macrotrachela quadricornifera by assessing: (1) the constancy of oocyte number, (2) chromosome number and size, and (3) the DNA content of oocytes and blastomeres. Oocyte number at birth is constant and determines maximal fertility. We found a chromosome number of 5, in which two homologous pairs can be recognized. The genome size of the species is 0.75 picograms.     

Comparison of five strains of a parthenogenetic species,Macrotrachela quadricornifera (Rotifera,Bdelloidea)

Five clonal populations belonging to the parthenogenetic species Macrotrachela quadricornifera were analyzed electrophoretically. The populations stemmed from samples collected from different environments paired geographically: water bodies (C, P, F) and terrestrial mosses (Ml, M2). The six enzymes considered were: leucine amino peptidase (LAP), arginine phosphokinase (APK), glucose phosphate isomerase (PGI), and esterases (EST) and malic enzyme (ME). The results are interpreted under the assumption that bdelloid rotifers have a diploid chromosome set. A genetic interpretation of the banding patterns was attempted. A relatively high degree of enzymatic polymorphism among the strains was found. Only 27% of alleles are shared by all strains. The relationship among the strains was examined by single-link cluster analysis: we can distinguish moss and water populations, regardless of their geographic origins, and in accord with the results of a life-history traits study on the same strains. The differences in life-history parameters among the five strains may be due not only to phenotypic plasticity induced by the environment, but to real genetic divergence.     

Egg size and offspring fitness in a bdelloid rotifer

To test if the quality of offspring is affected by egg size and whether it increases with the amount of resources allocated to an individual egg, we compared the offspring hatched from small and large eggs of Macrotrachela quadricornifera(Rotifera, Bdelloidea). Differently sized eggs were obtained by feeding mothers with different food concentrations. Large eggs were expected to provide better offspring in terms of (1) development time of the embryos, (2) age at first reproduction of the juveniles and (3) recovery after desiccation of the newborns. The comparison between offspring hatched from large vs. small eggs of the same bdelloid species revealed that animals hatched from large eggs had shorter embryonic development and earlier age at first reproduction than animals hatched from small eggs. In contrast, the capacity to survive stress, like desiccation, was not affected by egg size. Thus, offspring hatched from larger eggs had shorter generation times, but were not favoured under harsh circumstances.     

Monte Carlo mixture model of lifetime cancer incidence risk from radiation exposure on shuttle and international space station

Estimating uncertainty in lifetime cancer risk for human exposure to space radiation is a unique challenge. Conventional risk assessment with low-linear-energy-transfer (LET)-based risk from Japanese atomic bomb survivor studies may be inappropriate for relativistic protons and nuclei in space due to track structure effects. This paper develops a Monte Carlo mixture model (MCMM) for transferring additive, National Institutes of Health multiplicative, and multiplicative excess cancer incidence risks based on Japanese atomic bomb survivor data to determine excess incidence risk for various US astronaut exposure profiles. The MCMM serves as an anchor point for future risk projection methods involving biophysical models of DNA damage from space radiation. Lifetime incidence risks of radiation-induced cancer for the MCMM based on low-LET Japanese data for nonleukemia (all cancers except leukemia) were 2.77 (90% confidence limit, 0.75-11.34) for males exposed to 1 Sv at age 45 and 2.20 (90% confidence limit, 0.59-10.12) for males exposed at age 55. For females, mixture model risks for nonleukemia exposed separately to 1 Sv at ages of 45 and 55 were 2.98 (90% confidence limit, 0.90-11.70) and 2.44 (90% confidence limit, 0.70-10.30), respectively. Risks for high-LET 200 MeV protons (LET=0.45 keV/micrometer), 1 MeV alpha-particles (LET=100 keV/micrometer), and 600 MeV iron particles (LET=180 keV/micrometer) were scored on a per particle basis by determining the particle fluence required for an average of one particle per cell nucleus of area 100 micrometer(2). Lifetime risk per proton was 2.68x10(-2)% (90% confidence limit, 0.79x10(-3)%-0. 514x10(-2)%). For alpha-particles, lifetime risk was 14.2% (90% confidence limit, 2.5%-31.2%). Conversely, lifetime risk per iron particle was 23.7% (90% confidence limit, 4.5%-53.0%). Uncertainty in the DDREF for high-LET particles may be less than that for low-LET radiation because typically there is very little dose-rate dependence. Probability density functions for high-LET radiation quality and dose-rate may be preferable to conventional risk assessment approaches. Nuclear reactions and track structure effects in tissue may not be properly estimated by existing data using in vitro models for estimating RBEs. The method used here is being extended to estimate uncertainty in spacecraft shielding effectiveness in various space radiation environments.     

EVA dosimetry in manned spacecraft

Extra Vehicular Activity (EVA) will become a large part of the astronaut's work on board the International Space Station (ISS). It is already well known that long duration space missions inside a spacecraft lead to radiation doses which are high enough to be a significant health risk to the crew. The doses received during EVA, however, have not been quantified to the same degree. This paper reviews the space radiation environment and the current dose limits to critical organs. Results of preliminary radiation dosimetry experiments on the external surface of the BION series of satellites indicate that EVA doses will vary considerably due to a number of factors such as EVA suit shielding, temporal fluctuations and spacecraft orbit and shielding. It is concluded that measurement of doses to crew members who engage in EVA should be done on board the spacecraft. An experiment is described which will lead the way to implementing this plan on the ISS. It is expected that results of this experiment will help future crew mitigate the risks of ionising radiation in space.     

Syntheses and Synergistic Activity of Some Pyrethrum Synergists from Dillapiole

In a search for alternative pyrethrum synergists, dillapiole, one of the chief constituents of Indian dill (Anethum sowa Roxb.) seed oil has been converted into a number of derivatives. Syntheses of 16 such compounds, their spectrometric characterization and factors of synergism towards Pyrethrins against Tribolium castaneum Herbst. are being reported. Some of these compounds showed superior activity to piperonyl butoxide, the most commonly used pyrethrum synergist.     

Musculature of two bdelloid rotifers, Adineta ricciae and Macrotrachela quadricornifera: organization in a functional and evolutionary perspective

Organization of muscles in microinvertebrates has often been studied to answer functional questions and understand phylogenetic relationships among taxa. In this study, the musculature of two bdelloid species, Adineta ricciae and Macrotrachela quadricornifera , was illustrated, and their organization was compared with other rotifer taxa to generate possible hypotheses of evolutionary relationships among Rotifera. The two species share a common habitat but differ from each other in feeding and locomotion. A. ricciae feeds on the biofilm by scraping it, is unable to swim, and slides on the head cilia using the foot to propel over the substratum. M. quadricornifera feeds by filtration, can swim, and advances by looping in a leech-like motion. Their musculature, stained with TRITC-phalloidin, was observed using confocal laser scanning microscopy. Major differences between the two species were observed in the muscles of head and foot, possibly reflecting differences in their life style. Muscles of the trunk were similarly arranged: circular muscles surrounded longitudinal bands, which were inserted at different points on the body wall. In both bdelloids, circular muscles of the trunk were incomplete ventrally, a condition also present in Seison and in soft-bodied monogononts from benthos. Within rotifers, circular muscles in the form of complete rings are present in acanthocephalans and in soft-bodied planktonic monogononts but are absent in loricate monogononts, which generally possess dorsoventral bands. The diversity of muscle organization among rotifers was interpreted and discussed.     

Microbe-I: fungal biota analyses of the Japanese experimental module KIBO of the International Space Station before launch and after being in orbit for about 460 days

In addition to the crew, microbes also find their way aboard the International Space Station (ISS). Therefore, microbial monitoring is necessary for the health and safety of the crew and for general maintenance of the facilities of this station. Samples were collected from three sites in the Japanese experimental module KIBO on the ISS (air diffuser, handrail, and surfaces) for analysis of fungal biota approximately 1 year after this module had docked with the ISS. Samples taken from KIBO before launch and from our laboratory were used as controls. In the case of KIBO, both microbe detection sheet (MDS) and swab culture tests of orbital samples were negative. The MDS were also examined by field emission-scanning electron microscopy; no microbial structures were detected. However, fungal DNAs were detected by real-time PCR and analyzed by the clone library method; Alternaria sp. and Malassezia spp. were the dominant species before launch and in space, respectively. The dominant species found in specimens from the air conditioner diffuser, lab bench, door push panel, and facility surfaces on our laboratory (ground controls) were Inonotus sp., Cladosporium sp., Malassezia spp., and Pezicula sp., respectively. The fungi in the KIBO were probably derived from contamination due to humans, while those in our laboratory came from the environment (e.g., the soil). In conclusion, the cleanliness in KIBO was equivalent to that in a clean room environment on the ground.     

Genomics in space life sciences

Since the early days of manned spaceflight, hazardous effects of the space environment on living organisms have been disputed. With the continuous manning of the International Space Station, the planned Chinese space station, and renewed interest in returning to the Moon and sending manned flights to Mars, identifying and addressing the potential outcomes of long-term space exposures is critically important.     

Detection of space radiation-induced double strand breaks as a track in cell nucleus

To identify DNA damage induced by space radiations such as the high linear energy transfer (LET) particles, phospho-H2AX (γH2AX) foci formation was analyzed in human cells frozen in an International Space Station freezer for 133 days. After recovering the frozen sample to the earth, the cells were cultured for 30 min, and then fixed. Here we show a track of γH2AX positive foci in them by immuno-cytochemical methods. It is suggested that space radiations, especially high LET particles, induced DSBs as a track. From the formation of the tracks in nuclei, exposure dose rate was calculated to be 0.7 mSv per day as relatively high-energy space radiations of Fe-ions (500 MeV/u, 200 keV/μm). From the physical dosimetry with CR-39 plastic nuclear track detectors and thermo-luminescent dosimeters, dose rate was 0.5 mSv per day. These values the exposed dose rate were similar between biological and physical dosimetries.     

Cytoglobin is a stress-responsive hemoprotein expressed in the developing and adult brain.

Cytoglobin (Cygb) is a novel tissue hemoprotein relatively similar to myoglobin (Mb). Because Cygb shares several structural features with Mb, we hypothesized that Cygb functions in the modulation of oxygen and nitric oxide metabolism or in scavenging free radicals within a cell. In the present study we examined the spatial and temporal expression pattern of Cygb during murine embryogenesis. Using in situ hybridization, RT-PCR, and Northern blot analyses, limited Cygb expression was observed during embryogenesis compared with Mb expression. Cygb expression was primarily restricted to the central nervous system and neural crest derivatives during the latter stages of development. In the adult mouse, Cygb is expressed in distinct regions of the brain as compared with neuroglobin (Ngb), another globin protein, and these regions are responsive to oxidative stress (i.e., hippocampus, thalamus, and hypothalamus). In contrast to Ngb, Cygb expression in the brain is induced in response to chronic hypoxia (10% oxygen). These results support the hypothesis that Cygb is an oxygen-responsive tissue hemoglobin expressed in distinct regions of thenormoxic and hypoxic brain and may play a key role in the response of the brain to ahypoxic insult.     

Study on genotoxic effects of the space environment: a comparison between experienced cosmonauts and unexposed Russian twins

The molecular analysis of T-lymphocytes from experienced cosmonauts and seven pairs of unexposed twins was performed [M. Khaidakov, D. Young, H. Erfle, A. Mortimer, Y. Voronkov, B.W. Glickman, Molecular analysis of mutations in T-lymphocytes from experienced soviet cosmonauts, Environ. Mol. Mutagen, 30 (1997) 21–30; J. Curry, G. Bebb, J. Moffat, D. Young, M. Khaidakov, A. Mortimer, B.W. Glickman, Similar mutant frequencies observed between monozygotic twins, Human Mutation, 9 (1997) 445–451]. Hprt mutant frequencies (MF) in both datasets were considerably higher (38.0±14.6×10⁻⁶ in cosmonauts, and 18.5±8.9×10⁻⁶ in twins) than in the background Western control (8–12×10⁻⁶), [A.D. Tates, F.J. van Dam, H. van Mossel, H. Shoemaker, J.C.P. Thijssen, V.M. Woldring, A.H. Zwinderman, A.T. Natarajan, Use of the clonal assay for the measurement of frequencies of HPRT mutants in T-lymphocytes from five control populations, Mutation Res., 253 (1991) 199–213; R.F. Branda, L.M. Sullivan, J.P. O'Neill, M.T. Falta, J.A. Nicklas, B. Hirsch, P.M. Vacek, R.J. Albertini, Measurement of HPRT mutant frequencies in T-lymphocytes from healthy human populations, Mutation Res., 285 (1993) 267–279]. The distribution of mutations by class in the twin dataset was essentially similar to the background Western control, whereas cosmonaut samples demonstrated a significant excess of splice errors and complex mutations. The distribution of base substitutions showed similar trends in both the cosmonaut and twin samples, which are quite distinct compared to those seen in the Western control. The differences observed between cosmonaut and twin samples (a 2-fold higher MF and an excess of complex mutations in cosmonaut mutational spectra) could be an indication of possible effects of the space environment. However, these changes could also be age-related because the twin group was, on average, 17 years younger. Moreover, very similar patterns of base substitution distribution in both datasets suggest the involvement of certain region-specific factors reflected in mutational spectra. In order to discriminate between occupation and region-specific factors contributing to mutagenesis, an additional study involving trainees and cosmonauts with recent long-term flight experience is required.     

Evaluation of the Protective Activities of a Late Embryogenesis Abundant (LEA) Related Protein,Cor15am,during Various Stresses in Vitro

Arabidopsis Cor15am is a late embryogenesis abundant (LEA) related protein that has been shown to exhibit cryoprotective activity in vitro. In this study, we further investigated the mechanisms by which Cor15am protects substrates from inactivation. Although Cor15am did not exhibit refolding activity, it showed protective activity against various stresses in vitro. This might be attributable to the activity of Cor15am in attenuating the aggregation of the substrates. Our data indicate that Cor15am functions as a protectant against various stresses by preventing protein aggregation.     

Anhydrobiosis quotient: a novel approach to evaluate stability in desiccated bacterial cells

Aim:  The major objective of this study was the development of a methodology to quantify the anhydrobiotic ability of bacteria and its application to evaluate the stability of desiccated bacterial cells using the biocontrol agent Tsukamurella paurometabola C-924 as a model of anhydrobiote.
Methods and Results:  Tsukamurella paurometabola C-924 was desiccated by spray-drying. Samples of desiccated cells were stored at several temperatures and viability and residual moisture were measured at different intervals of time. The term anhydrobiosis quotient (ε) was defined, and a scale of anhydrobiotic ability for classifying micro-organisms in terms of tolerance to desiccation was established (1 ≤  ε  ≤ 15). The anhydrobiosis quotient was used to evaluate the stability of the anhydrobiotic cells. As a main result, changes in the anhydrobiosis quotient at several temperatures were fitted using a reparameterized Weibull model, which was found to be robust for the prediction of the stability at 4°C.
Conclusions:  A novel methodology was developed to evaluate the desiccated state in bacteria. The anhydrobiosis quotient allows the quantitative estimation of the anhydrobiotic ability, and the mathematical model developed allows the prediction of the desiccated state of bacterial populations.
Significance and Impact of the Study:  The new methodology could be applied in studying the anhydrobiosis state of bacterial populations as a predictive tool for industrial and environmental microbiology.     

Stress-related variation in antioxidative enzymes activity and cell metabolism efficiency associated with embryogenesis induction in isolated microspore culture of triticale (<Emphasis Type="Italic">x Triticosecale</Emphasis> Wittm.)

Isolated microspore cultures of two spring triticale (x Triticosecale Wittm.) cultivars were used to examine the effect of various stress treatments (either high—32°C or low—5°C temperature with or without nitrogen/carbohydrate starvation) applied to excised anthers on the effectiveness of microspore embryogenesis induction. To quantify the effects of pretreatment conditions, the activity of antioxidative enzymes (catalase, peroxidase and superoxide dismutase) together with respiration rate and heat emission were measured. It was observed that heat shock treatment applied as the only one stress factor increased the activity of antioxidative enzymes which suggests intensive generation of reactive oxygen species. Such pretreatment effectively triggered microspore reprogramming but drastically decreased microspore viability. After low temperature treatment, the activity of antioxidative enzymes was similar to the control subjected only with the stress originated from the transfer to in vitro culture conditions. This pretreatment decreased the number of microspores entering embryogenesis but sustained cell viability and this effect prevailed in the final estimation of microspore embryogenesis effectiveness. For both, low- and high-temperature treatments, interaction with starvation stress was beneficial increasing microspore viability (at 5°C) or efficiency of embryogenesis induction (at 32°C). The latter treatment significantly reduced cell metabolic activity. Physiological background of these effects seems to be different and some hypothetical explanations have been discussed. Received data indicate that in triticale, anther preculture conditions could generate oxidative stress and change the cell metabolic activity which could next be reflected in the cell viability and the efficiency of microspore embryogenesis.     

Chlorophyll budget in a productive tropical pond: algal production,sedimentation, and grazing by microzooplankton and rotifers

Chlorophyll a and pheopigment standing stocks and fluxes were used during a two weeks colonization experiment in a productive tropical pond (Layo, Côte d'Ivoire) in order to establish a chlorophyll budget. The experiment started from an azoïc state (the pond was dried, limed and progressively filled with ground water). Algal production was the only input to the phytoplanktonic system, while grazing and algal sedimentation were the main outputs. Chlorophyll a reflected the algal biomass, and degradation pigments were considered as an index of grazing by zooplankton (here, protozoans and rotifers). An estimation of the input through the algal growth rate was performed for the two main biological events observed during the study. The first algal bloom, with a large picoplankton participation, was mainly regulated by microzooplankton (increase of the peak) and rotifers (decrease of the peak). The second bloom (exclusively nanoplankton) was regulated by rotifers (increase) and by sedimentation of living cells (decrease). This last process was related to a sudden exhaustion of ammonia in the water column. Because of the time-lag between algal proliferation and zooplanktonic bloom, the phytoplanktonic biomass was able to be adjusted according to the availability of nutrients. This self-regulation took the form of sinking of active algal cells, resulting in a transient reduction of the food available for rotifers. This process had drastic consequences in these shallow waters, since a major part of the phytoplankton produced was removed from the pelagic system. For an optimal exploitation of the natural resources of an aquaculture pond, a study of the equilibrium nutrients-phytoplankton-zooplankton would provide a basis for artificial intervention, with a view to limit the impact of this mode of natural regulation.