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.     

Feeding and anhydrobiosis in bdelloid rotifers: a preparatory study for an experiment aboard the International Space Station

Abstract. Here we report the effect of food concentration on the recovery from anhydrobiosis of a bdelloid rotifer, Macrotrachela quadricornifera . Cohorts were either starved, or fed high or low concentrations of food, before being dried and their subsequent recovery rates determined. The rotifers starved for 3 d before anhydrobiosis recovered in significantly higher proportion, and those fed lower food concentration recovered better than those fed higher food concentration. In addition, starvation did not decrease the recovery of other bdelloid species ( Philodina roseola and Adineta sp. 1) which were either fed or starved before anhydrobiosis. These results suggest that a successful recovery from anhydrobiosis is not dependent on prior resource level supplied to the bdelloids. However, the lack of resources might not be the only factor in a successful recovery from anhydrobiosis. Observations using scanning electron microscopy of fed individuals of M. quadricornifera entering anhydrobiosis showed that some food remained in the digestive tract. Thus, we propose that the negative effect of rich food may be due to a purely mechanical effect and may be interfering with a proper folding of the rotifer body at the onset of anhydrobiosis. This contribution results from studies carried out in preparation for biological experiments scheduled on the International Space Station (ISS).     

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.     

Novel method for evaluating the health condition of mice in space through a video downlink

Clarification of the criteria for managing animal health is essential to increase the reliability of experiments and ensure transparency in animal welfare. For experiments performed in space, there is no consensus on how to care for animals owing to technical issues, launch mass limitation, and human resources. Some biological processes in mammals, such as musculoskeletal or immune processes, are altered in the space environment, and mice in space can be used to simulate morbid states, such as senescence acceleration. Thus, there is a need to establish a novel evaluation method and evaluation criteria to monitor animal health. Here, we report a novel method to evaluate the health of mice in space through a video downlink in a series of space experiments using the Multiple Artificial-gravity Research System (MARS). This method was found to be more useful in evaluating animal health in space than observations and body weight changes of the same live mice following their return to Earth. We also developed criteria to evaluate health status via a video downlink. These criteria, with “Fur condition” and “Respiratory” as key items, provided information on the daily changes in the health status of mice and helped to identify malfunctions at an early stage. Our method and criteria led to the success of our missions, and they will help establish appropriate rules for space experiments in the future.     

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.     

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.     

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.     

Characterization of fungi isolated from the equipment used in the International Space Station or Space Shuttle

As a part of a series of studies regarding the microbial biota in manned space environments, fungi were isolated from six pieces of equipment recovered from the Japanese Experimental Module “KIBO” of the International Space Station and from a space shuttle. Thirty‐seven strains of fungi were isolated, identified and investigated with regard to morphological phenotypes and antifungal susceptibilities. The variety of fungi isolated in this study was similar to that of several previous reports. The dominant species belonged to the genera Penicillium, Aspergillus and Cladosporium, which are potential causative agents of allergy and opportunistic infections. The morphological phenotypes and antifungal susceptibilities of the strains isolated from space environments were not significantly different from those of reference strains on Earth.     

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.     

Investigations of a simulated geomagnetic field experienced by the International Space Station on attentional performance

We have previously reported that the exposure to an abnormal magnetic field simulating the one encountered by the International Space Station (ISS) orbiting around the Earth may enhance autonomic response to emotional stimuli. Here we report the results of the second part of that study which tested whether this field also affects cognitive functions. Twenty-four volunteers participated in the study, 12 exposed to the natural geomagnetic field and 12 to the magnetic field encountered by ISS. The test protocol consisted of a set of eight tests chosen from a computerized test battery for the assessment of attentional performance. The duration of exposure was 90 min. No effect of exposure to ISS magnetic field was observed on attentional performance.     

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.     

Accumulation of a tumor suppressor p53 protein in rat muscle during a space flight

We previously reported that the space environment consisting of microgravity and space radiation induced an increased level of p53 protein, a tumor suppressor gene product, in rat skin. Here, we report the increase of p53 protein in the muscles of rats that traveled into space. Rats were divided into three groups. The first group remained on earth (VC), and did not show any change in p53 protein level. The second group made a 14-day flight into space on the Second Spacelab Life Science (SLS-2) Mission (F). The third group was experimentally subjected to the same kinds of stress as those in the second group without making a space flight (SC). F and SC rats were sacrificed on day zero (F-0, SC-0) and day nine (F-9, SC-9) after return from space. F-0 rats showed a 1.5-fold increase in p53 protein level compared with that of SC-0 rats, whereas, F-9 rats showed a 1.35-fold increase in p53 protein compared with that of SC-9 rats. These results suggest that the accumulation of cellular p53 protein induced by space environments occurs not only in rat skin cells, but also in rat muscle cells.     

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.     

Dehydration-regulated processing of late embryogenesis abundant protein in a desiccation-tolerant nematode

Late embryogenesis abundant (LEA) proteins occur in desiccation-tolerant organisms, including the nematode Aphelenchus avenae, and are thought to protect other proteins from aggregation. Surprisingly, expression of the LEA protein AavLEA1 in A. avenae is partially discordant with that of its gene: protein is present in hydrated animals despite low cognate mRNA levels. Moreover, on desiccation, when its gene is upregulated, AavLEA1 is specifically cleaved to discrete, smaller polypeptides. A processing activity was found in protein extracts of dehydrated, but not hydrated, nematodes, and main cleavage sites were mapped to 11-mer repeated motifs in the AavLEA1 sequence. Processed polypeptides retain function as protein anti-aggregants and we hypothesise that the expression pattern and cleavage of LEA protein allow rapid, maximal availability of active molecules to the dehydrating animal.