Apoptosis inhibition and ornithine decarboxylase superinduction as early epigenetic events in morphological transformation of Syrian hamster embryo cells exposed to 2-methoxyacetaldehyde, a metabolite of 2-methoxyethanol

We have conducted a study to determine the carcinogenic potential of ethylene glycol monomethyl ether (EGME), a member of the glycol ether family, as compared to its reactive metabolite 2-methoxy-acetaldehyde (MALD). Since disruption of equilibrium between cell proliferation and cell death is thought to play a key role in multistage carcinogenesis, we investigated, in Syrian hamster embryo (SHE) cells exposed to various doses of EGME and MALD, impairment in apoptosis rate and in ornithine decarboxylase (ODC) metabolism. The activity of this rate-limiting enzyme of polyamine biosynthesis is closely related to cell proliferation and cell transformation. At the end-point, comparative action of the two products on SHE cell morphological transformation frequency was evaluated. One-stage exposure of SHE cells to 2 mM EGME and 200 microM MALD for 5 h did not change basal apoptotic level, whereas 0.16 microM phorbol ester (TPA) decreased it. Using two-stage exposure protocol (1 h xenobiotic followed by 5 h TPA), MALD strongly inhibited apoptosis more than did TPA alone; the parent compound EGME did not have any effect on TPA inhibiting action. Western blotting analysis showed that sequential treatment (MALD/TPA) increased Bcl-2 oncoprotein expression, whereas Bcl-XL and Bax proteins were not changed. The same staged exposure of SHE cells to MALD/TPA strongly induced ODC activity, and the rate was higher than that obtained with TPA alone: this was accompanied by an increase of ODC protein level. This ODC superinduction was not observed with EGME/TPA treatment. In long-term SHE-cell morphological transformation assay, staged exposure to MALD (800 microM or 1 mM for 24 h) followed by TPA applications increased the number of transformed colonies at the seventh day. Such early cooperative events as apoptosis inhibition and ODC superinduction, followed by the increase of SHE-cell transformation frequency, are highly indicative of a carcinogenic potential for the metabolite, MALD.

Effect of aluminum on superoxide dismutase activity in the adult rat brain

Male rats were treated daily with an intraperitoneal injection of 15 mg aluminum (Al chloride)/kg body weight for 17 d, in order to study the effects on superoxide dismutase (SOD) activities in the brain (cortex). No significant difference between control and treated animals was registered in the Cu/Zn and Mn SOD activities in the gray matter of the cortex. High Al levels were found in the plasma, the spleen, and the liver of the treated animals in comparison to the controls, but not in the cortex homogenates (gray matter). In addition, Al induced a significant decrease in food ingestion and weight gain.

Surgical repair of patellar luxation in llamas: 7 cases (1980-1996)

OBJECTIVE

To evaluate anatomy of the stifle in llamas and determine outcome of llamas that underwent surgery for repair of patellar luxation.

DESIGN

Anatomic and retrospective study.

ANIMALS

6 llamas with unilateral patellar luxation and 1 llama with bilateral luxations.

PROCEDURE

6 stifles from llama cadavers were dissected to determine anatomy. Medical records were reviewed to identify history, procedure, outcome, and complications of llamas that underwent surgery.

RESULTS

6 llamas had lateral patellar luxation (including the llama with bilateral luxations), and 1 had medial patellar luxation. Six llamas had a history of trauma before onset of clinical signs. Two llamas underwent tibial tuberosity transposition, but luxation recurred in both and 1 had problems with breakage of implants. The other 5 llamas underwent imbrication and release procedures; however, luxation recurred in 4 of the 5. Surgery was repeated in 2 llamas, with successful outcomes.

CLINICAL IMPLICATIONS

Results suggest that imbrication and release procedures may be useful for correction of patellar luxation in llamas without other bony abnormalities. However, long (20 cm) imbrication and release incisions are needed for a successful outcome. Use of a sling after surgery, to allow a gradual return to weight bearing and exercise, may also be important.

Glycol ethers induce death and necrosis in human leukemia cells

Ethylene glycol ethers are common solvents. Some isomers are toxic for the reproduction and immunity functions of humans and laboratory animals and are antileukemic for rodents. The health hazards of ethylene glycol ethers may result from their ability to induce cell death in various organs or tissues. To study this possibility, the human leukemia cell lines HL-60, Molt3, and K562 were treated with ethylene glycol ethers. 2-Ethoxyethanol and 2-butoxyethanol were selected because they are among the most commonly used ethelyne glycol ethers, but little is known about their individual toxicity. Cell death was detected by trypan blue uptake, flow cytometry, DNA electrophoresis, and poly(ADP-ribose) polymerase proteolysis. The treatments lasted up to 72 h with doses ranging from 1 to 20 mM, which are high relative to the concentrations found in biological fluids of exposed workers. The highest dose of 2-butoxyethanol (20 mM) induced apoptosis in Molt3 cells after 72 h incubation. Other treatments had no effect, induced necrosis, or blocked the cells in the G1 phase of the cell cycle.

Two-stage exposure of Syrian-hamster-embryo cells to environmental carcinogens: superinduction of ornithine decarboxylase correlates with increase of morphological-transformation frequency

As part of environmental toxicology, it is important to assess both the carcinogenic potential of xenobiotics and their mode of action on target cells. Since dysregulation of ornithine decarboxylase (ODC), a rate-limiting enzyme of polyamine biosynthesis, is considered as an early and essential component in the process of multistage carcinogenesis, we have studied the mode of ODC induction in Syrian-hamster-embryo(SHE) cells stage-exposed to carcinogens and to non-carcinogens. One-stage (5 hr) treatment of SHE cells with 50 microM clofibrate (CLF), a non-genotoxic carcinogen, or with 0.4 microM benzo(a)pyrene (BaP), a genotoxic carcinogen, slightly decreased basal ODC activity. Using the 2-stage exposure, 1 hr to carcinogen, then replacement by TPA for 5 hr, the ODC activity was higher than that obtained with TPA alone. This ODC superinduction was not observed when SHE cells were similarly pre-treated with non-carcinogenic compounds. Several environmental chemicals, pesticides, solvents, oxidizers and drugs were investigated with this SHE cell model. With one-stage exposure, some xenobiotics decreased basal ODC activity, while for others ODC changes were not noticeable. With 2-stage exposure (chemical followed by TPA), all carcinogens amplified the TPA-inducing effect, resulting in ODC superinduction. Comparative studies of the action of carcinogens and of non-carcinogens, using 2-stage exposure protocols, clearly show a close relationship between ODC induction rate and morphological transformation frequency.

Cardiovascular responses to orthostatic tests after a 42-day head-down bed-rest

Cardiovascular responses to orthostatic tests were studied before and after a prolonged 42 day-head-down bed-rest (HDBR;-6 degrees) experiment simulating a long duration space flight. Seven men participating in the experiment underwent stand tests (10 min) and lower body negative pressure (LBNP) tests (5 min at -25, -35, -45 mmHg). Heart rate variability and spontaneous baroreflex response slope (SBS) were analysed to assess autonomic nervous system responses. Changes in plasma volume (PV) were assessed at the end of HDBR. At the end of HDBR, four subjects could not complete the stand tests and one could not complete the LBNP test. A higher stressed heart rate with standing (+ 44% before and + 57% after HDBR) and LBNP exposure (+ 19% before and + 34% after HDBR) were observed. A decrease in blood pressure (BP) reflecting a reduced vasomotor response was only observed with standing (mean BP + 21% before and -8% after HDBR); LBNP was less sensitive probably because it was performed 6 h after the stand test. The PV decreased by 10.6%. A decline in spectrum total power reflecting a reduced variance of RR-interval, a decrease in parasympathetic activity and an increase in sympathetic one were observed at the end of HDBR. The reduced parasympathetic indicator and SBS would suggest that the vagal nerve component of the cardiovascular control had been diminished. Except for a lower BP when standing after HDBR, no significant difference was observed between finishers and non-finishers. Autonomic nervous system changes including reduced vasomotor responses constituted important contributors to the orthostatic intolerance observed here and after space flights. Some autonomic and PV changes seemed to be opposite to those observed with training and would suggest a role of reduced physical activity in cardiovascular changes induced by HDBR.

Alteration in methyl-methanesulfonate-induced poly(ADP-ribosyl)ation by 2-butoxyethanol in Syrian hamster embryo cells

The effects of 2-butoxyethanol (2-BE) on poly(ADP-ribosyl)ation were studied in Syrian hamster embryo (SHE) cells by measuring the cellular concentrations of the polymer poly(ADP-ribose) (pADPr) and of NAD+, the substrate of poly(ADP-ribose) polymerase (PARP). As biotransformation pathways of ethylene glycol ethers involve NAD+-dehydrogenases, it was hypothesized that 2-BE could reduce poly(ADP-ribosyl)ation by consuming NAD+. As a result DNA repair could be altered, which would explain that 2-BE had been shown to potentiate the effects of clastogenic substances such as methyl-methanesulfonate (MMS). In this study, the effects of 2-BE on MMS-induced pADPr metabolism were analyzed. The results indicated that: (i) 2-BE (5 mM) by itself did not influence significantly pADPr or NAD+ levels. (ii) 2-BE inhibited pADPr synthesis in MMS (0.2 mM)-pretreated cells, without any change in NAD+ concentrations. (iii) MMS treatment, which rapidly increased pADPr levels, also affected the poly(ADP-ribosyl)ation system as a secondary effect by damaging cell structures. Membrane permeabilization, which occurred at concentrations >1 mM MMS, led to a dramatic leakage of cellular NAD+ resulting in a strong reduction in pADPr levels. (iv) A bleomycin pulse (100 microM) applied after MMS and/or 2-BE treatment confirmed that 2-BE reduced poly(ADP-ribosyl)ation capacities of MMS-treated cells, though the glycol ether had no effect alone. This study confirmed that the inhibition of pADPr synthesis could be responsible for the synergistic effects of 2-BE with genotoxic substances. The mechanism of this inhibition cannot be explained by a lack of NAD+ at the concentrations of 2-BE tested.

Dysregulation of ornithine decarboxylase activity, apoptosis and Bcl-2 oncoprotein in Syrian hamster embryo cells stage-exposed to di(2-ethylhexyl)phthalate and tetradecanoylphorbol acetate

Perturbations of cell proliferation and death are considered as essential events in the process of carcinogenesis. Thus, two parameters, ornithine decarboxylase (ODC), an enzyme closely related to cell proliferation and transformation, and apoptotic phenomenon are profoundly modified. Using Syrian hamster embryo (SHE) cells, we have examined in the framework of two-stage carcinogenesis (initiation-promotion) the effects of a non-genotoxic [diethylhexylphthalate (DEHP)] or genotoxic [benzo[a]pyrene (BaP)] carcinogen or a non-carcinogenic compound [phthalic anhydride (AP)] on these parameters. Immunoreactive Bcl-2 and Bcl-xL proteins were also investigated following two-stage exposures. Whereas exposures to BaP, DEHP or AP alone did not provoke any modification of ODC activity, the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), strongly increased it. Using two-stage exposure protocol (xenobiotics first, then replacement by TPA-promoter), the ODC activity was higher than that obtained with TPA alone. This superinduction of ODC activity was observed only with the carcinogenic compounds DEHP and BaP. Following the same exposure protocol, spontaneous cellular apoptosis was decreased. Furthermore, Bcl-2 oncoprotein was also upregulated approximately 8- and 11-fold for BaP and DEHP respectively; meanwhile Bcl-xL protein rate did not change. The non-carcinogenic compound AP slightly inhibited spontaneous SHE cell death without ODC superinduction. Exogenous polyamines, putrescine, spermidine and spermine diluted in the medium did not inhibit spontaneous apoptosis. Although inhibition of apoptosis was not specific of carcinogenic compound, both superinduction of ODC activity and inhibition of apoptosis via Bcl-2 upregulation, may cooperate during early stages of the carcinogenic process.

Glutathione reductase, selenium-dependent glutathione peroxidase, glutathione levels, and lipid peroxidation in freshwater bivalves, Unio tumidus, as biomarkers of aquatic contamination in field studies

The aim of this study was to evaluate the usefulness of antioxidant parameters in the freshwater bivalve, Unio tumidus, as biomarkers of exposure to pollutants and to study their potential interest in predicting toxicity. Selenium-dependent glutathione peroxidase (Se-GPx), non-selenium-dependent glutathione peroxidase (non-Se-GPx), glutathione reductase (GRd), catalase, and superoxide dismutase (SOD) activities; reduced (GSH) and oxidized (GSSG) glutathione levels; and lipid peroxidation were measured in the gills and digestive glands of Unio. Control mussels were encaged and transplanted for 15 and 30 days to sites where the contamination of sediments was analyzed, along a river receiving domestic and industrial sources of pollution. After 15 days of exposure, all antioxidant parameters of the bivalves transferred to the most polluted sites had strongly decreased compared with control values. This was particularly true for Se-GPx and GRd activities, which were inhibited by 60 and 80% in the two tissues, and for GSH levels (80% reduction in the gills and 60% in digestive glands). These decreases were associated in the gills with lipid peroxidation (measured by malondialdehyde content) and with a high level of contamination of sediments by polycyclic aromatic hydrocarbons and polychlorinated biphenyls. In the mussels exposed at the least polluted sites, the same parameters decreased in the gills, but to a lesser extent: 50% for Se-GPx and 32% for GRd activities, and 45% for GSH levels. The gills appeared more sensitive than the digestive glands. After 30 days of exposure, while Se-GPx, GRd, and GSH remained reduced, a significant induction of non-Se-GPx and catalase activities was recorded in the gills, which reflected an adaptation of the transplanted species to their unsafe environment. All the results indicated that antioxidant defense components, namely, Se-GPx, GRd, and GSH, are sensitive parameters that could be useful biomarkers for the evaluation of contaminated aquatic ecosystems. The relationship between the degree of deficiency of antioxidant defenses and lipid peroxidation suggests that these parameters could also be biomarkers for toxicity.

Effects of peroxisome proliferators and 12-O-tetradecanoyl phorbol-13-acetate on intercellular communication and connexin43 in two hamster fibroblast systems

Effects of 12-O-tetradecanoyl phorbol 13-acetate (TPA) and the hepatic peroxisome proliferators (HPPs) clofibrate, methyl clofenapate (MCP), di(2-ethylhexyl)phthalate (DEHP) and mono(2-ethylhexyl)phthalate (MEHP) were studied in 2 gap junctional intercellular communication (GJIC) systems, metabolic cooperation in V79 cells and microinjection/dye transfer in Syrian hamster embryo (SHE) cells and V79 cells. TPA inhibited GJIC in both systems but was considerably more potent in V79 cells. SHE cells showed a rapid and transient inhibition of GJIC after exposure to HPPs, with maximal inhibition occurring at 5-15 min. The transient inhibition could be caused by metabolization of the compounds. Clofibrate and MEHP produced strong inhibition of metabolic cooperation in V79 cells at high concentrations, while the effect of MCP and DEHP was lower. However, DEHP, MEHP and clofibrate strongly inhibited dye transfer in V79 cells after a 30 min exposure. Clofibrate also showed a dose- and time-dependent effect on dye transfer in V79 cells. The phosphorylation status of the gap junction protein connexin43 (Cx43) changed minimally in SHE cells after exposure to TPA or HPPs. Cx43 from V79 cells was strongly affected by TPA, but not by HPPs. Immunofluorescence of Cx43 disappeared in both cell types when they were exposed to TPA and MEHP, but not to the other HPPs. Thus, there is no direct correlation between the inhibition of GJIC and changes in the phosphorylation status of Cx43 or the appearance of Cx43 in immunofluorescence experiments. The discrepancies may partly be explained by binding of accessory proteins to Cx43. We point out sequences that may be involved in such binding.

Cardiovascular and hormonal changes induced by a simulation of a lunar mission

BACKGROUND

This is the first simulation of a 14-d lunar mission including 6 d on the Moon.

HYPOTHESIS

We hypothesized that a lunar gravity simulation in the middle of a head-down tilt (HDT) might result in some reversal of body fluid/hormonal responses, and influence cardiovascular deconditioning.

METHODS

Six men (28 +/- 2.5 yr) were placed in bed rest (BR): in (HDT) (-6 degrees) to simulate microgravity during the travel (two 4-d periods), and in head-up tilt (HUT) (+10 degrees) (6-d period) to simulate lunar gravity (1/6 g). Muscular exercise was performed during the HUT period to simulate 6 h of lunar EVA. Heart rate variability (HRV) and hormonal responses were studied.

RESULTS

An orthostatic arterial hypotension was observed after the BR (tilt test) in 4 of the 6 subjects. Plasma volume measured at D14 decreased by -11.1% (vs. D-3, sitting position). A decrease in atrial natriuretic peptide (26 +/- 3.5 pg.ml-1 (D14) vs. 37.9 +/- 3.5 pg.ml-1 (D-3, sitting) and an increase in plasma renin activity (198 +/- 9.2 mg.L-1.min-1 (D14) vs. 71 +/- 9.2 mg.L-1.min-1 (D-3, sitting) were observed during the BR, more pronounced in HUT at 7:00 p.m. Sympathetic-parasympathetic balance (HRV) at rest showed a decrease in parasympathetic indicator and an increase in sympathetic indicator in BR (p < 0.05), without differences within HDT and HUT periods.

CONCLUSION

These changes were mostly similar to those reported in spaceflights, and HDT. Although the exposure to 1/6 g with exercise modified some hormonal and body fluid responses, this partial gravity simulation was not sufficient to prevent the decrease in orthostatic tolerance observed here as well as after Apollo lunar missions.

Comparative effects of clofibrate and methyl clofenapate on morphological transformation and intercellular communication of Syrian hamster embryo cells

The Syrian hamster embryo (SHE) cell system was used to evaluate the ability of two hepatocarcinogenic structurally related peroxisome proliferators (PPs) to induce morphological transformation (MT) of SHE colonies and to inhibit gap junctional intercellular communication (GJIC). Clofibrate and methyl clofenapate (MCP), which was shown to be a more active PP and a more potent carcinogen in vivo than clofibrate, were compared. MCP appeared slightly more active in vitro than clofibrate in affecting MT and GJIC of SHE cells. The morphological transformation of SHE colonies was induced by 50 microM MCP, against 100 microM clofibrate. Moreover, 50 microM MCP potentiated the transforming effects of both benzo[a]pyrene and 12-O-tetradecanoylphorbol-13-acetate. The inhibition of GJIC, measured by transfer of lucifer yellow, was transient and occurred at concentrations inducing morphological transformation. MCP inhibited dye transfer at 50 microM and the inhibition lasted up to 24 h at 100 microM. Inhibition of communication lasted only 4 h with clofibrate and occurred at a higher concentration (175 microM). This study showed that both the SHE cell transformation and dye transfer assays were able to display the different activities of the two PPs, even though the difference in potency observed was smaller than in vivo. It also revealed interactions between non-genotoxic carcinogens and the ability of the SHE cell transformation assay to detect these combined effects.

Orthostatic tests after a 4-day confinement or simulated weightlessness

Besides microgravity, inactivity is likely to play a role in the cardiovascular deconditioning after space flights and weightlessness simulations. The aim of the study was to compare the effects of a 4-day head-down bed rest (HDBR) (-6 degrees) and a 4-day confinement (C) on cardiovascular responses to orthostatic stress. Eight male subjects underwent head-up tilt (HUT) (+60 degrees) and lower-body negative pressure (LBNP) (-20, -30, -40 and -50 mmHg) before (D-1) and at the end (R1) of each situation. Blood pressure, heart rate variability (HRV) and spontaneous baroreflex slope (SBS) were determined. The HDBR reduced orthostatic tolerance, as five subjects presented orthostatic hypotension during the HUT at R1, compared with two subjects at D-1. These same two subjects presented orthostatic hypotension after confinement. The main findings, after HDBR, included reductions in RR interval and total spectral power and a decrease in the parasympathetic indicator (PNS) in favour of a decrease in vagal tone; the increase in the sympathetic indicator (SNS) was not significant. After confinement, the RR interval was also significantly reduced and PNS decreased, but not significantly. RR interval and PNS were further reduced during HUT and LBNP, reflecting a withdrawal of parasympathetic activity. SBS was reduced after HDBR (P < 0.05) and confinement (P = 0.05), with a further reduction during HUT and LBNP without difference between D-1 and R1. This experiment showed that a 4-day HDBR leads to impaired baroreflex function and changes in autonomic balance, which may contribute to orthostatic intolerance. Although less significant, similar patterns of changes in the autonomic nervous system were observed after confinement, suggesting an influence of the inactivity in cardiovascular deconditioning.

The genotoxicity of iron and chromium in electroplating effluents

Electroplating effluents were tested for their genotoxicity with the micronucleus test on newt larvae. The metallic content of the tested samples was responsible for the induction of micronuclei in red blood cells (RBC). Then, iron (Fe3+), chromium (Cr3+, Cr6+) and zinc (Zn2+) which were identified in these samples, were tested either separately or combined, at their concentrations in the electroplating effluents. Fe3+ induced a high level of micronuclei at 12.5 and 25 mg/l (nominal concentrations). Both soluble and non-soluble forms of iron were responsible for these genotoxic effects. At lower concentrations (0.6 and 4.5 mg/l) Fe3+ was not systematically genotoxic. Zinc could not be considered genotoxic on newt. Cr3+ gave negative responses, but exposure to Cr6+ (1 mg/l) could result in a significant number of micronucleated RBC in some cases. The most dramatic genotoxic effects were registered when Fe3+ and Cr6+ were combined. This study demonstrates that interactions between pollutants and the effects of non-soluble chemicals on aquatic vertebrates and invertebrates can no longer be neglected.

Nongenotoxic carcinogens: development of detection methods based on mechanisms: a European project

While the accumulation of genetic changes in a somatic cell is considered essential for the genesis of a cancer, it has become clear that not all carcinogens are genotoxic, suggesting that some carcinogens indirectly participate in the generation of genetic changes during carcinogenesis. A European project funded by the European Community was thus conceived to study mechanisms of nongenotoxic aspects of carcinogenesis. Two main strategical approaches were adapted: (i) to study whether and how Syrian hamster embryo (SHE), Syrian hamster dermal (SHD) and BALB/c 3T3 cell transformation systems simulate in vivo carcinogenesis, and to examine whether they can detect nongenotoxic carcinogens; (ii) to study, refine and validate mechanisms-based end-points for detection of nongenotoxic carcinogens. For mechanisms-based research, the proposed end-points included gap junctional intercellular communication (GJIC) inhibition, altered expression of critical genes, immortalization and aberrant cell proliferation. We also selected model compounds commonly usable for various endpoints. Our major results can be summarized as follows: (1) SHE and BALB/c 3T3 transformation systems reflect both genotoxic and nongenotoxic carcinogenic events; they detect not only genotoxic but also many although not all, nongenotoxic carcinogens. This is further supported by the fact that both genotoxic and nongenotoxic carcinogens were able to immortalize SHD cells. (2) Many nongenotoxic carcinogens, although not all, inhibit GJIC in vitro as well as in vivo. Mechanistic studies suggest an important role of blocked GJIC in carcinogenesis and that different mechanisms are involved in inhibition of the communication by different agents used. However, inhibition of GJIC is not a prerequisite for the enhancement (or induction) of transformation of SHE or BALB/c 3T3 cells. (3) Among compounds examined, there was a good correlation between induction of micronuclei and cell transformation in SHE cells while no such correlation was found between the induction of cell transformation and ornithine decarboxylase activity. (4) Two transgenic mouse mutation assays (lacI and lacZ) were established and validated. The genotoxin dimethylnitrosamine was shown to be mutagenic to the liver in both assays. Ortho-anisidine, a bladder-specific carcinogen that was inactive in standard rodent genetic toxicity assays was uniquely mutagenic to the bladder of the transgenic mice. The peroxisome proliferator methyl clofenipate was established as nonmutagenic to the liver of both transgenic mice. That eliminated DNA damage as a cause of the liver tumours produced by this chemical and weakened the idea that induced cell division leads to mutation induction. (5) With an in vitro DNA replication model, it was found that DNA damage induced by genotoxic agents can be responsible for inhibition of DNA replication, while certain nongenotoxic agents such as phorbol esters increase DNA replication. (6) An attempt to use structure-activity relationship for subfamilies of nongenotoxic carcinogens, e.g., receptor-mediated carcinogens, has been initiated with some promising results. Our results support the idea that there are multiple nongenotoxic mechanisms in carcinogenesis, and that working hypothesis-oriented approaches are encouraged rather than simple screening of chemicals in developing test systems for the detection of nongenotoxic carcinogens.

Effects of 28-day head-down tilt with and without countermeasures on lower body negative pressure responses

This study was performed to determine the effects of 28 d of head-down tilt (HDT) (simulated weightlessness) on cardiovascular responses to orthostatic stress induced by lower body negative pressure (LBNP) (before, during, and after HDT) and +60 degrees head-up tilt (before and after HDT) in 12 subjects. Half of them underwent countermeasures (CM) of regular muscular exercise (isometric and isokinetic training) and LBNP sessions (-30 mm Hg) as generally performed during spaceflight; the other six were a control group (C). The countermeasure effect on the orthostatic responses to LBNP and tilt test was assessed by studying the changes after HDT in the two groups. Essentially, blood pressure was better maintained in group CM in the tilt test after HDT (MBP at the end of the tilt vs. baseline value: +16% (CM); -19% (C)). LBNP and muscular exercise may have contributed to this improvement. One of the probable contributing factors is the relative conservation of plasma volume, at the end of HDT, in group CM (-2.2%), compared to group C (-11.2%). Transcranial Doppler (TCD) recordings of middle cerebral artery (MCA) velocities permitted indirect evaluation of cerebral blood flow changes during the orthostatic tests. MCA velocities decreased significantly although slightly (-7 to -12%) during LBNP sessions without changes along the HDT showing that the cerebral circulation was well preserved in each group. On the other hand, subjects undergoing presyncopal symptoms presented a drop in MCA velocities, suggesting a decrease in cerebral blood flow.

Mutagenicity of ethylene glycol ethers and of their metabolites in Salmonella typhimurium his-

Ethylene glycol ethers, their aldehyde and their acid metabolites were evaluated for their mutagenicity with the Ames test. The Salmonella typhimurium his- tester strains TA 97a, TA 98, TA 100 and TA 102 were used with and without rat S9 mix. Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol n-butyl ether and their corresponding aldehyde and acid derivatives were tested up to 10(-4) mol/plate (around 10 mg/plate) or up to cytotoxic concentrations. All tested substances gave negative results with TA 98, TA 100 and TA 102 either with or without S9 mix. In contrast, ethylene glycol n-butyl ether (EGBE) and the aldehyde metabolite of ethylene glycol monomethyl ether, methoxyacetaldehyde (MALD), displayed mutagenic potency in strain TA 97a with and without S9 mix at high concentrations. A significant number of revertants was obtained from 19 mumol/plate EGBE (2.2 mg/plate) and from 34 mumol/plate MALD (2.5 mg/plate). At these concentrations the level of revertants reached up to 7-fold and 3-fold the control values for EGBE and MALD respectively.

Synergistic effects of chlordane and TPA in multistage morphological transformation of SHE cells

The cyclodiene pesticide chlordane has been reported to be a non-genotoxic carcinogen in rodents. The effects of chlordane on SHE cell transformation were investigated in this study. It appeared that chlordane exhibited a weak transforming activity when applied repeatedly at 8 micrograms/ml. No effect resulted from the combination of benzo[a]pyrene-chlordane. In contrast, chlordane in the range 5-20 micrograms/ml and 12-O-tetradecanoylphorbol-13-acetate (TPA) (0.1 micrograms/ml) highly potentiated each other when applied sequentially. The synergistic effects could be inhibited by dexamethasone. These results led us to study the genotoxicity of chlordane on SHE cells: no DNA adduct formation could be detected in SHE cells treated with chlordane at a concentration potentiating the transforming effect of TPA. We also confirmed that this pesticide markedly inhibited intercellular communication between SHE as well as V79 cells. These results support literature data on the non-genotoxicity of chlordane. Overall, this study highlights the fact that interaction between-non genotoxic carcinogens may enhance the transformation frequency of SHE cells. Thus, combined effects must be taken into account in the evaluation of carcinogenic risk.

Femoral flow response to lower body negative pressure: an orthostatic tolerance test

The objective was to check, during a lower body negative pressure (LBNP) test, new vascular parameters for the detection of orthostatic intolerance induced by head-down-tilt (HDT) and spaceflight.

METHODS

The lower-limb volume flow and vascular resistance were evaluated by Doppler ultrasound. The HDT population consisted of two groups: control [6 subjects resting in a HDT (-6 degrees) position for 28 d] and countermeasure (6 subjects also in HDT for 28 d, but with repeated LBNP and exercise). The LBNP orthostatic test (four steps: -20, -30, -40, -50 mm Hg, of 3 min each) was performed before, during, and after the HDT. For the 14-d spaceflight (Antares) the cosmonaut underwent the LBNP test (10 min at -25 mm Hg and 10 min at -45 mm Hg), at preflight (3 times), inflight (day 11), and postflight (twice).

RESULTS

HDT--As the LBNP pressure decreased, the femoral blood flow decreased and the lower-limb vascular resistances increased in both HDT groups. In the control group the femoral flow was less reduced, at each of the 4 levels of depressure (p < 0.01). The amplitude of the leg vascular resistances was reduced at -40 mm Hg, and at -50 mm Hg, on HDT day 15 in both groups (before LBNP, after 1 week's exercise for the countermeasure group), and on post-HDT day 1 (p < 0.01) only in the control group. The femoral vascular resistance response had completely recovered in the countermeasure group on post-HDT day 1. During the post-HDT tilt table test, all 6 controls had a drop in blood pressure of 20 mm Hg (4 subjects) or 10 mm Hg (2 subjects); 3 had pre-syncopal symptoms. The HDT countermeasure subjects had neither any clinical signs of orthostatic intolerance nor any blood pressure drop. 14d-Spaceflight--During the flight, the cosmonaut did not use any countermeasures (exercise, LBNP). On flight day +11, and on postflight day 3, the femoral vascular resistance response to LBNP was decreased as observed in the control group on HDT day +15 and post HDT. On postflight day 7, the femoral response had completely recovered. The middle cerebral flow response to the various pre-, in-, and postflight LBNP tests consisted of a slight decrease of the cerebral flow together with resistances of comparable amplitude (-10 to -20%) to those measured during the same LBNP test in the HDT control group.

CONCLUSION

The femoral hemodynamics are much more disturbed than the cerebral ones in vascular deconditioning. The assessment of the lower limb vascular reactivity will be of interest in predicting orthostatic intolerance, and checking the efficiency of counter-measures.

The environmental risks of industrial waste disposal: an experimental approach including acute and chronic toxicity studies

The toxicity of 15 leachates of various solid industrial wastes accepted in an engineered landfill has been studied. A cost-effective battery of tests allowing evaluation of acute and chronic toxicity, as well as genotoxicity, and investigations on different trophic levels in the aquatic environment has been used. Acute toxicity was tested on bacteria (Microtox assay with Photobacterium phosphoreum) and microcrustaceans (Daphnia magna immobilization assay). A growth inhibition test of microalgae was carried out on Raphidocelis subcapitata. A 28-day chronic test with Daphnia magna was used to detect effects on reproduction. Genotoxicity was evaluated by means of the Ames test conducted on the crude aqueous phase and also on the concentrated fractions of water-extractable micropollutants (liquid-liquid and freeze-dried extracts). Chemical analyses of leachates were carried out simultaneously. The toxicity varied greatly between the different wastes. Toxic effects were observed in the short and/or in the long term. Four samples were potentially genotoxic. In most cases, toxicity registered could not be correlated with results of the chemical analyses. This study demonstrates the usefulness of associating a toxicological monitoring with chemical analyses in waste management.

[Orthostatic hypotension after space flight]

Cardiovascular changes occur during spaceflight. Because of the loss of hydrostatic pressure there is, during weightlessness, a fluid shift of extra- and intra-vascular volumes to the upper part of the body. This provokes objective and subjective symptoms, especially in the first days of spaceflight. The fluid shift is perceived by baroreceptors as a relative central hypervolaemia and induces neuro-hormonal mechanisms which provoke a real hypovolaemia. Cardiovascular deconditioning exists during spaceflight with the following symptoms when astronauts return to earth: decreased orthostatic tolerance with possible tendency towards spontaneous syncope and decreased effort capacity. The mechanisms of orthostatic intolerance are not well known. Several factors are probably involved, including hypovolaemia, modifications of the venous system, baroreflex changes, etc. Various countermeasures have been tested in microgravity simulations on the ground, then in flight.

An attempt to improve the SOS chromotest responses

The SOS Chromotest was carried out on leachates of ten industrial wastes with the standard procedure and a miniaturized version with microplates. The two methods gave identical results in nine samples (eight negative and one positive). A simple additional manipulation is described for the identification of the false positive response that is frequently observed with complex mixtures. It involves challenging the SOS Chromotest bacteria with samples (having previously shown a positive genotoxic response) just before the enzymatic activities (i.e. beta-galactosidase and alkaline phosphatase) are estimated colorimetrically. This additional step eliminates discrepancies between the results for the standard and the miniaturized procedures.

Regional intravenous guanethidine blocks in algodystrophy

Five-hundred-thirteen regional intravenous guanethidine blocks were carried out in 125 cases of algodystrophy (118 adults), after failure of other treatments in 120 cases (Group I) and without previous treatments in 5 (Group II). A positive result occurred in 85 cases of Group I (71%) and in the 5 cases of Group II, after 4.5 +/- 1.7 blocks. In Group I the results did not differ significantly between upper (33 cases) and lower (87 cases) limb or in regard to sex, age, duration of disease, nature of previous treatments. The presence of psychic disorders was accompanied by less frequent (p less than 0.02) positive results. The tolerance was satisfactory in 85.6% of cases: 22 moderate side effects authorized a continuation of the blocks, 22 serious ones indicated interruption, especially one case of thrombophlebitis and another one of very transitory acute ischaemia. The risk of intolerance was significantly raised (p less than 0.02) by age. The regional guanethidine blocks seemed to be a good treatment for algodystrophy after failure of other treatments.

[Treatment of algodystrophy by regional sympathetic blocks with guanethidine (410 blocks in 98 patients). Preliminary results]

In a preliminary retrospective study, 418 regional sympathetic blocks with guanethidine administered as treatment of 103 cases of algodystrophy gave 70 p. cent of positive results versus 55 p. cent in case of psychic disorders. The tolerance was correct in 85 p. cent but was decreased by old age.

Replacement of the anterior cruciate ligament. A comparison of autografts and allografts in dogs

To compare the efficacy of allograft versus autograft replacement of the anterior cruciate ligament, 15 dogs had the ligament cut and replaced 1 month later: 11 dogs received a frozen bone-ligament-bone allograft cruciate ligament, while 4 dogs received a standard autogenous replacement with iliotibial band. Three of 11 allograft dogs developed postoperative infections and were removed from the study; and two of the remaining eight allograft ligaments were absent at autopsy. All the autograft ligaments were present. From serial clinical and radiographic examinations, there were no differences observed in the two groups. Autopsy studies at 4 months, however, showed an increased inflammatory, pannus-like reaction about the origins and insertions of the six allograft ligaments as compared with the four autografts. The ligament hydroxyproline uptake was lower in the allograft group, averaging 60 percent of the contralateral unoperated on control versus equal to the control in the autograft group. The tensile strength of the allografts reached only 17 percent of the control value versus 41 percent for the autografts. Lymphocytotoxicity testing at 1 month revealed a donor-specific antibody response in 4 of 8 allograft dogs; however, no histologic evidence of immune response was observed in the ligaments. The synovial fluid leukocyte count was elevated in the allograft group at 4 months. The increased synovial leukocyte counts and joint cartilage erosion, the decreased strength and metabolic activity of the grafts, and the evidence of an immune response in the allograft dogs do not support implantation of cadaver cruciate ligaments clinically at this time.

An in vitro study of the structural properties of deep-frozen versus freeze-dried, ethylene oxide-sterilized canine anterior cruciate ligament bone-ligament-bone preparations

The effect of two preparation and storage methods on the structural properties of canine anterior cruciate ligament (ACL) bone-ligament-bone preparations was determined. In Group 1, one knee joint from each dog was tested after storage at -70 degrees for eight to 12 weeks. In Group 2, one knee joint from each dog was sterilized using ethylene oxide, freeze-dried, and then stored at room temperature for four to five weeks prior to mechanical testing. In both groups, the contralateral joint was tested fresh and used as a control. The bone-ligament-bone preparations were loaded in tension until failure and the load at failure, stiffness, and maximum elongation were measured. No preparation method caused a significant decline in breaking strength. In both groups, however, there was a significant increase in elongation at failure noted in the test specimens. This was accompanied, in Group 1 (deep-frozen), by a significant decrease in stiffness in the test joints. A similar trend toward decreased stiffness was observed in the test joints from Group 2 (freeze-dried).

Limb preservation in dogs with primary bone tumors

This article presents methods currently used for limb preservation in dogs with primary bone sarcomas. Emphasis is placed on diagnosis, proper patient selection, and perioperative management.

Interest of dynamic tests in acute ecotoxicity assessment in algae

Sorption of toxics by algae may be important and occurs very early. Thus, a decrease of the experimental toxic concentrations in the medium results in understating toxicity when tests are conducted under static conditions. In this work, two different methods of exposure of algae (Chlorella vulgaris) are studied, the static test and the pseudodynamic test. Acute effects (biological and analytical effects) of inorganic compounds (Cu2+, Cd2+, Pb2+, Cr6+) have been evaluated for 96 hr of exposure; in each case, IC50 is much lower in the dynamic condition than in the static one. The percentage of reduction varies from 55 to 75% after 96 hr. Accumulation of metal by chlorellae is greater when testing by the pseudodynamic way, with Cu2+ and Pb2+. But in the case of Cd2+ and Cr6+, the concentration factors are similar in the two kinds of exposure. These results point out the advantage of the pseudodynamic test, of which the methodology is very easy, for a more realistic assessment of acute ecotoxicity in these organisms.

Accumulation of cadmium in a freshwater food chain experimental model

The study of food chain contamination in nature or in the laboratory requires precise definitions of some terms. A simplified model of a freshwater food chain has been elaborated to try to point out hazards related to the presence of cadmium in the aquatic environment. Three different species belonging to various trophic levels, but to the same aquatic systems were used. The required biological and analytical criteria are described. The time course of the experiment was 34 days starting with a 10-day contamination of the first trophic level (algae). The algae were then separated, washed with fresh medium, and given to the second trophic level (daphnids) to eat for 20 days. The third trophic level (fish) was then introduced for 4 days as a scavenger. The methodology was designed to determine the accumulation of cadmium by daphnids and then fish from the algal source. The results show a high direct bioaccumulation of cadmium in algae. The indirect bioaccumulation of daphnids was of the same order of magnitude, but for fish it was smaller. Nevertheless the cadmium transfer from daphnids to fish was obvious.

[Interest of some biological criteria in studying daphnids contaminated by cadmium nitrate (author's transl)]

Three biological criteria were studied on daphnids after 28 days of contamination with three different concentrations of cadmium (5, 10, 15 micrograms/l), such as mortality, dry weight and reproduction rate relative to general metabolic state of the crustacea. The value of Cl50-28 exceed 15 micrograms/l for dry weight and mortality determinations, on the other hand it is only 10 micrograms/l for reproduction rate. The latter appears as the most sensible criteria.