[Study of the intra- and extracellular electrolyte content in Paramecia cultures carried out during a space flight (author's transl)]. / Etude de la teneur intra et extracellulaire des electrolytes dans les cultures de Paramecies réalisées pendant un vol spatial.

In the results of previous investigations we have already reported that cultures of Paramecium tetraurelia submitted to a space flight present a stimulation of their proliferative ability, an increase in cell volume and a decrease in dry weight and in total protein content. These results suggest changes of cell metabolism induced by the space environment. In order to confirm this hypothesis we have studied the concentration of extracellular electrolytes in the control and the in-flight culture media with respect to the intracellular content of the same electrolytes. These measures concern Na, Cl, K, P, Mg, Ca. In this paper we report the results of these analyses and note that if no differences are noted for Na and Cl between control and in-flight cultures, modifications in P, K, Ca and Mg levels are observed. Generally there is a higher concentration of these elements in the in-flight medium but, in contrast, a lower intracellular content is noted for in-flight Paramecia. We have established a double comparison: on the one hand between control and in-flight media and between control and in flight cells, on the other hand between media and cells. All these data suggest possible changes in the membrane permeability, or of the binding proteins in Paramecia cultivated in hypogravity.

Influence of sperm parameters on embryo quality.

OBJECTIVE: To evaluate the influence of sperm defects on embryo quality. DESIGN: Retrospective study. SETTING: In vitro fertilization center. PATIENTS: Embryo transfers (710) from IVF attempts for tubal disease (626) or male infertility (84). MAIN OUTCOME MEASURES: Embryo morphology as a function of causes of infertility, semen, and follicular growth parameters. Embryos were classified into three groups according to their morphology. RESULTS: Transfers of embryos with good morphology were associated to a higher pregnancy rate (34%) than those with intermediate (24%) and poor (10%) morphology. Transfers of embryos with a poor morphology were more frequent (26 of 84 versus 114 of 626) and those with a fair aspect were less frequent (24 of 84 versus 229 of 626) in male infertility than in tubal disease. Embryos with a poor morphology were associated with lower percentage of morphologically normal sperms (62% +/- 19% versus 67% +/- 18%; means +/- SD) and a higher percentage of abnormalities of the postacrosomial region (29% +/- 15% versus 18% +/- 7%). Moreover, sperms with counts < 10 x 10(6)/mL were associated with a lower percentage of embryos with good morphology (18% versus 37%) than sperms with counts > or = 10 x 10(6)/mL. CONCLUSION: Embryo quality is influenced by the semen quality and especially by sperm head abnormalities, suggesting an important role of the male gamete on the early stages of embryogenesis.

Relevance of acrosome function in the evaluation of semen in vitro fertilizing ability.

OBJECTIVES: To determine whether or not acrosome evaluation can enhance the prediction of IVF results when associated to conventional semen parameters. DESIGN: Acrosome reaction, sperm concentration, motility, and morphology were recorded in 131 semen samples from patients undergoing an IVF attempt. MAIN OUTCOME MEASURES: Spontaneous acrosome loss after a 24-hour incubation in B2 medium and after induction by calcium ionophore A23187 and phorbol ester, phorbol 12-myristate 13-acetate 4-O-methyl ether (TPA). RESULTS: Statistically significant differences between fertilization failures and successes were found for concentration, viability, spontaneous and induced acrosome reaction, and most parameters of motility and morphology. However, none of the parameters could predict > 64% of IVF results when studied alone. A progressive discriminant analysis allowed to predict up to 83% of IVF results, by classifying sperms through their normal forms, rapid motility, spontaneous acrosome loss, enlarged heads, multiflagellar forms, vitality, linear motility, and acrosome response to TPA. The other parameters, including concentration and response to calcium ionophore, had no additive value. CONCLUSION: The study of acrosome function, through spontaneous acrosome loss and response to TPA, is of great interest in clinical practice when associated to some parameters of motility and morphology. However, it appears that response to calcium ionophore, one of the most studied parameters, is of poor practical interest.

Antibiotic activity in space.

Environmental factors in space exert an influence on the behaviour of bacteria, particularly on their sensitivity to antibiotics. Thus, G. Taylor and S. Zaloguev observed that bacterial samples collected on the crew during flight in the Apollo-Soyouz Test Project Mission presented higher antibiotic resistance than controls. This paper presents the results of two experiments performed in 1982 and 1985 (Cytos 2 during the French-Soviet Mission and "Antibio" in the Biorack programme of the European Space Agency). The results show an increase of antibiotic resistance in bacteria growth in flight and a modification in the structure of the cell wall. All these modifications are transitory. Two hypotheses are put forward to explain the phenomenon.

Effects of gravity and cosmic rays on cell proliferation kinetics in Paramecium tetraurelia.

Space flights resulted in a stimulating effect on kinetics of proliferation in Paramecium tetraurelia. Additional experiments were performed in order to determine the origin of this phenomena. Paramecia were cultivated in balloon flights or in a slow clinostat, or were exposed to different levels of hypergravity. The results suggest that changes in cell proliferation rate are related to cosmic rays and to a direct effect of microgravity.

Space flight effects on Paramecium tetraurelia flown aboard Salyut 6 in the Cytos I and Cytos M experiments.

Results of the Cytos M experiment and complementary results of the Cytos I experiment flown aboard the Soviet orbital station Salyut 6 are shown. Space flight of Paramecia cultures resulted in a stimulating effect on cell proliferation, in a larger cell volume, in changes in cell dry weight, cell total protein and the electrolyte content of the culture media in which the organisms were grown. The assumption of a possible effect of weightlessness on membrane permeability is discussed.

Influence on cell proliferation of background radiation or exposure to very low, chronic gamma radiation.

Investigations carried out on the protozoan Paramecium tetraurelia and the cyanobacteria Synechococcus lividus, which were shielded against background radiation or exposed to very low doses of gamma radiation, demonstrated that radiation can stimulate the proliferation of these two single-cell organisms. Radiation hormesis depends on internal factors (age of starting cells) and external factors (lighting conditions). The stimulatory effect occurred only in a limited range of doses and disappeared for dose rates higher than 50 mGy/y.

Effects of space flight factors at the cellular level: results of the Cytos experiment.

Paramecium tetraurelia was cultivated aboard the Soviet orbital station Salyut 6. Each culture included one cell, bacterized culture medium, and two small glass tubes filled with a fixative. Cultures were kept at a low temperature before Soyouz-Salyut docking. Cultures were maintained at 25 degrees +/- 0.1 degree C in orbit and were fixed every 12 h. The space flight resulted in an increase in cell growth rate and in cell volume. Measurements of cell dry weight and total protein content favour a higher cell water content. Respective roles of cosmic rays and microgravity are discussed. Cytos results are compared to those of previous space experiments.

Study of minimal inhibitory concentration of antibiotics on bacteria cultivated in vitro in space (Cytos 2 experiment).

The aim of the Cytos 2 experiment, carried out during the French-Soviet manned flight in July 1982, was to study the bacteria's sensitivity to antibiotics cultivated in vitro during the orbital flight, using the bacterial method of minimal inhibitory concentration (MIC). Two species of bacteria were tested with various antibiotics: Staphylococcus aureus with Oxacillin, Chloramphenicol and Erythromycin; Escherichia coli with Colistin and Kanamycin. The results show an increase in resistance to antibiotics particularly strong in E. coli and weaker in Staphylococcus aureus. Considering these results, we think that there might be a relationship between the increase in resistance to antibiotics and a stimulating effect on growth rate by the factors of environmental space.

The CYTOS biological experiments carried out on the Soviet orbital station Salyut 6.

Two biological experiments (CYTOS programme) were performed aboard the Soviet orbital Station Salyut 6. For these experiments we have developed several original devices. In this paper we give the technical characteristics of this specialized hardware and the experimental methods used to carry out these experiments.

Effects of microgravity and hypergravity on the cell: investigations on Paramecium tetraurelia.

Previous space CYTOS experiments have shown that space flights resulted in an increase in growth of Paramecia cultures. Microgravity is the major factor responsible of this response: indeed the stimulatory effect disappeared in inflight cultures placed on a 1 g centrifuge aboard the Spacelab. On the other hand, exposure to different levels of hypergravity on Earth resulted in an opposite response, i.e. to a reduced cell growth rate. A possible mechanism of microgravity on paramecia is discussed.

Respective role of microgravity and cosmic rays on Paramecium tetraurelia cultured aboard Salyut 6.

Paramecium tetraurelia cultured aboard Salyut 6 have shown in increase in cell growth rate, cell volume, water content and changes in electrolyte content. Additional experiments, carried out in balloon flight and on earth, showed that the stimulating effect observed on cell proliferation is related to exposure to cosmic rays. Other changes seem to be due to a direct effect of microgravity on cell. Mechanism of gravity action on cell is discussed.

Preliminary results of Cytos 2 experiment.

Cytos 2 experiment, carried out during the French-Soviet manned flight (July 1982), has studied the antibiotics sensitivity of bacteria cultivated in vitro during the orbital flight. The results show an increase of the antibiotics resistance and a larger thickness of the cellular envelope for the inflight cells. The increase of antibiotics resistance can be related to a stimulating effect of space on the cell growth rate or to changes of the cellular envelope structure.

Theoretical and experimental investigations on the fast rotating clinostat.

We have investigated both theoretically and experimentally the validity of the fast rotating clinostat to simulate microgravity for a free swimming single-cell organism such as the paramecium. Computer simulations show that cells on suspension move as cells cultivated in space. However, rotated paramecia are still affected by gravity, as shown by the variations in the rate of paramecium rotation on their axis. Using a fast clinostat, which allows to investigate simultaneously twenty cultures, we have observed a stimulating effect on cell growth rate similar to that previously reported in space. All these results point towards the fact that the fast clinostat can reproduce some of the effects of microgravity on paramecia.

Effects of angular speed in responses of Paramecium tetraurelia to hypergravity.

The paper shows the results of investigations carried out in a single cell organism. Paramecium tetraurelia exposed to different gravitational levels. Hypergravity resulted in a decrease in cell growth rate. The responses depend on g level and angular speed of the centrifuge; furthermore they depend also on small short fluctuations in g levels, delta g, due to the swimming of the cells inside the culture tubes. Delta g depends on angular speed and size of the holding device. The inhibitory effect of hypergravity, for the same angular speed, increases with respect of the diameter of the culture tubes.

[Effects of hypergravity on Paramecium tetraurelia]. / Effets de l'hypergravité sur Paramecium tetraurelia.

Previous space experiments carried out in Paramecium tetraurelia have shown that exposure to microgravity results in an enhancement of cell multiplication. An opposite effect occurs when paramecia are exposed to hypergravity. Changes in cell growth rate observed in hypergravity cannot be ascribed to the bacteria present in the culture medium, the same effect being observed when paramecia grow in sterile medium.

Effect of sperm pre-treatments on the results of sub-zonal insemination (SUZI).

Follicular fluid and progesterone, which are present in the natural environment of oocytes, have been reported to induce the acrosome reaction and we compared their use in pretreatment of spermatozoa for human sub-zonal insemination (SUZI). Pre-treatment with follicular fluid (20% v/v) was associated with a higher fertilization rate than pre-incubation with progesterone (1 mmol/l) as assessed by both the embryos/injected oocytes rate (31.7 +/- 6.2% versus 13.5 +/- 5.9%, respectively; P < 0.01) and the male pronuclei/injected spermatozoon rate (10.5 +/- 3.3% versus 3.6 +/- 1.9%, respectively; P < 0.01). Since we have previously reported that pre-treatment with progesterone allowed a higher percentage of live-reacted spermatozoa to be obtained, these results suggest that either progesterone induces modifications of the plasma membrane, which prevent fusion with the oolema, or that follicular fluid not only induces the acrosome reaction but increases the fusion ability by compounds other than progesterone.

Selection and micro-injection of acrosome-reacted human spermatozoa.

A method of selection of acrosome-reacted human spermatozoa is described. Petri dishes were coated with GB24 antibody, specific to the inner acrosomal membrane. The acrosome-reacted spermatozoa were fixed on the antibody and could be removed by aspiration with a micro-pipette. They were then injected into the perivitelline space of hamster eggs in order to check their fertilizing ability. This selection allowed the fertilization rate to be significantly increased (24 versus 7% for control spermatozoa; P < 0.01). This method could enhance the results of human sub-zonal insemination.

Human sperm capacitation and in-vitro fertilization in a chemically defined and protein-free medium SMART1.

Media for sperm capacitation and in-vitro fertilization (IVF) are supplemented by proteins (albumin, globulins) extracted from human or animal sera, which raises the problem of potential contamination by pathogens. The present study aimed to evaluate the efficiency of a protein-free medium (SMART1, Bio-Media, Boussens, France) and to compare it with a human serum albumin (HSA) containing medium (FertiCult, FertiPro NV, Aalter, Belgium). In the first part of the study, media were compared for their ability to support human sperm functions. Total motility, progressive motility and rapid motility were no different between media after a 30 min and a 4 h incubation, but were significantly reduced using SMART1 after a 24 h incubation. However, the kinematic parameters (straight line velocity, mean path velocity, curvilinear velocity and mean amplitude of lateral head displacement) were significantly lower using SMART1, whatever the incubation time. The spontaneous acrosome reaction and the acrosome response to A23187 ionophore were similar in both media. In the second part of the study, media were compared in a randomized trial in 93 IVF attempts. No significant difference was found in the transfer per attempt rate (92 versus 87% respectively for SMART1 and FertiCult, NS) but the percentage of fertilized oocytes was significantly higher using SMART1 (65 versus 55% respectively for SMART1 and FertiCult, P < 0.01). The percentage of embryos with a fair morphology was identical in both media (30 versus 30% respectively for SMART1 and FertiCult, NS). In conclusion, despite a decrease in sperm kinematics, SMART1 medium allows an increase in fertilization rate and, since it is devoid of any human or animal compound, may be preferable for human use.