Selective cytotoxic activity of new lipophilic hydroxytyrosol alkyl ether derivatives

Recent data suggest that hydroxytyrosol, a phenolic compound of virgin olive oils, has anticancer activity. This communication reports the synthesis of decyl and hexadecyl hydroxytyrosyl ethers, as well as the cytotoxic activity of hydroxytyrosol and a series of seven hydroxytyrosol alkyl ether derivatives against A549 lung cancer cells and MRC5 non-malignant lung fibroblasts. Hydroxytyrosyl dodecyl ether (HTDE) showed the highest selective cytotoxicity, and possible mechanisms of action were investigated; results suggest that HTDE can moderately inhibit glycolysis, induce oxidative stress, and cause DNA damage in A549 cells. The combination of HTDE with the anticancer drug 5-fluorouracil induced a synergistic cytotoxicity in A549 cancer cells but not in non-malignant MRC5 cells. HTDE also displayed selective cytotoxicity against MCF7 breast cancer cells versus MCF10 normal breast epithelial cells in the 1-30 μM range. These results suggest that the cytotoxicity of HTDE is more potent and selective than that of parent compound hydroxytyrosol.

Ether stress-induced Alzheimer-like tau phosphorylation in the normal mouse brain

Tau is reversibly hyperphosphorylated in the mouse brain by starvation or cold water swimming. Here, we report tau phosphorylation in the hippocampus of normal mouse after ether anesthesia, known to trigger typical stress reactions. Robust phosphorylation of tau was observed immediately and 10min after ether vapor exposure at Ser202/Thr205 and Thr231/Ser235, sites typically phosphorylated in Alzheimer brains. The phosphorylation levels returned to baseline by 1h. The most conspicuous and consistent change in the protein kinases studied was the inactivating phosphorylation of Ser9 of TPKI/GSK3beta in close correspondence with tau phosphorylation. These findings show that tau phosphorylation is a rapid physiological process integral to stress response system, and suggest involvement therein of TPKI/GSK3beta.

Effects of beacon on the rat pituitary-adrenocortical axis response to stress

Beacon is a peptide expressed in the rat hypothalamus and adrenal cortex, which is involved in the central regulation of feeding and inhibits basal and agonist-stimulated glucocorticoid secretion from adrenocortical cells. In vivo studies on beacon have not yet been carried out, and therefore we investigated the effects of a subcutaneous (sc) injection of beacon on the response of rat hypothalamo-pituitary-adrenal axis to stress. Handling and sc injection per se elicited a moderate increase in the plasma concentrations of ACTH and corticosterone, which was counteracted by beacon. Similarly, beacon dampened ACTH and corticosterone responses to ether stress. In contrast, beacon did not affect ACTH response to cold stress, although it was able to induce a moderate lowering in the corticosterone response. Taken together, these findings allow us to draw the following conclusions: i) beacon inhibits handling/injection- and ether stress-activated, but not cold stress-activated, neural mechanism(s) responsible for stimulation of ACTH secretion and the ensuing increase in corticosterone production; and ii) the beacon-induced dampening in corticosterone response to stress also involves a direct inhibitory effect on the adrenal-cortex secretory activity. The physiological relevance of beacon as endogenous anti-stress agent remains to be evaluated.

Secretory phospholipase A2 as a tumor-specific trigger for targeted delivery of a novel class of liposomal prodrug anticancer etherlipids

The use of many common clinically relevant chemotherapeutics is often limited due to insufficient delivery to the tumor and dose-limiting systemic toxicities. Therefore, therapeutics that specifically target tumor cells and are nontoxic to normal cells are required. Here, we report the development of a novel class of liposomes composed of lipid prodrugs, which use the increased secretory phospholipase A2 type IIA (sPLA2) activity of the tumor microenvironment as a trigger for the release of anticancer etherlipids (AEL). Treatment of sPLA2-secreting tumor cells in vitro with liposomes consisting of proAELs resulted in growth inhibition comparable with addition of the AELs alone. Using a specific sPLA2 inhibitor, we showed the low cytotoxicity of the nonhydrolyzed proAEL liposomes and have proven the sPLA2 dependency of the activation of proAELs to cytotoxic AELs. In addition, we showed that our proAEL liposomes circumvent the inherent hemolytic toxicities associated with the use of etherlipids, thereby allowing i.v. administration of such therapeutics as nontoxic prodrug liposomes. Furthermore, using a sPLA2-secreting human colon cancer xenograft model, we showed that the proAEL liposomes are capable of inducing a tumor growth delay in vivo. Taken together, these data support the validity of this novel tumor-selective liposomal prodrug delivery strategy. This new approach also provides a promising system for tumor-selective delivery and release of conventional chemotherapeutics encapsulated in the sPLA2-degradable prodrug liposomes.

Health effects of exposure to ethylene glycol monoethyl ether in female workers

Ethylene glycol monoethyl ether (EGEE) is a solvent commonly used in industry. To find the health effect of the solvent exposure in women, we did an investigation on 32 female workers exposed to EGEE in factories manufacturing photopolymer sensitization plate, and 20 subjects working in the same companies without potential exposure to the solvent. The mean age was 35.0 and 33.9 yr in the two groups, respectively. The mean concentration of the urinary metabolite (ethoxyacetic acid) was 120.87 mg/g creatinine (geometric mean) in the exposed group, and 2.71 mg/ g creatinine in the control group. Average RBC count and hemoglobin levels were normal in both groups. However, there were 2 subjects in the exposed group with an RBC count and hemoglobin concentration slightly lower than the standard. Out of 20 controls, 5 subjects reported irregular menstruation, and in comparison, 4 out of 32 exposed females had the same complaint. The most common health complaints were dizziness and swelling of the legs, with the same frequencies seen in both groups. Overall, our study suggests that although female workers were exposed to high concentrations of EGEE, subsequent health problems possibly due to such exposure were not significant.

[Morphological and functional characteristics of the lens histamine-containing structures at the early stages of chemical irritation of the eye]

The purpose of the present study was to determine, using the methods of light, fluorescence microscopy and cytospectrofluorometry, the morpho-functional changes in histaminergic structures of the lens as influenced by extrinsic chemical irritation of the eye (exposure to ether vapors). The experiments were conducted on 74 outbred male albino rats. Extremely fast simultaneous changes (demonstrated in all lens structures already 3 minutes after an irritation) were found in histamine content of the lens cells. According to the results of luminescence analysis, maximal increase in histamine content (by 53.3%) took place in the area of lens nucleus. In the cytoplasm of lens epitheliocytes, histamine content was increased by 22%, while in the cytoplasm of equatorial epithelial cells it was increased by 36.1%, and in the nuclei of central epithelial cells--by 26.4%. The data obtained suggests an existence of diffuse neurotransmission in the lens, that is not associated with neurons.

Comparative study of the effects of toluene, benzene, 1,1,1-trichloroethane, diethyl ether, and flurothyl on anxiety and nociception in mice

The main purpose of this study was to compare the effects of solvents from different chemical classes on anxiety and nociception. Independent groups of mice were exposed to air (control group), toluene (1000-4000 ppm), benzene (1000-4000 ppm), 1,1,1-trichloroethane (TCE, 2000-12000 ppm), diethyl ether (10,000-30,000) or flurothyl (200-600 ppm). After a 30-min exposure, animals were tested either in the anxiety paradigm conditioned defensive burying (CDB) test or in the hot plate test. All solvents but flurothyl produced anxiolytic-like actions being the order of potency toluene > benzene > TCE > diethyl ether. When tested in the hot plate paradigm, toluene and TCE increased nociception, benzene and diethyl ether had no effects, and flurothyl decreased nociception Additional groups of mice were conditioned to recognize the aversive stimulus (electrified prod) prior to toluene exposure and then tested in the CDB test. In unconditioned animals, toluene increased the number of shocks that mice received; however, when mice had previous experience in the CDB test, toluene lacked this effect. Taken together, these results show that inhalants have different effects with different potencies both in the CDB and in the hot plate tests. Additionally, data suggest that acute administration of toluene could impair learning.

Acute stress increases calcium current amplitude in rat hippocampus: temporal changes in physiology and gene expression

Activation of hippocampal glucocorticoid receptors in vitro increases calcium current amplitude through a process requiring DNA binding of receptor homodimers. We here investigated (i). whether similar increased calcium currents also occur following in vivo glucocorticoid receptor activation due to stress and (ii). if so, whether this can be explained by increased expression of calcium channel subunits. Rats were exposed to a novelty stress; some of the animals were pretreated with a glucocorticoid receptor antagonist. In subsequently prepared hippocampal slices, calcium currents were recorded from identified CA1 pyramidal neurons, after which RNA was collected, linearly amplified and hybridized with cDNA clones. Glucocorticoid receptor activation due to novelty exposure was associated with large total peak calcium currents and high-threshold noninactivating currents. Low-threshold calcium currents were not affected. Large total peak and noninactivating current amplitudes were also seen when animals received a more severe stressor, i.e. additional ether exposure. In the stressed groups, the total peak and high-threshold calcium current gradually increased with time resulting in a significant enhancement at >or=3 h after stress exposure. In the same cells, the summated (relative) RNA expression of various alpha1 calcium channel subunits was only transiently enhanced, prior to the functional changes. These data indicate that in vivo activation of glucocorticoid receptors due to stress gradually increases specific calcium current components. Prior to the functional change, increased expression of calcium channel subunits was observed, suggesting that the enhanced function could be explained by transcriptional regulation of the channels.

Neonatal inhalatory anesthetic exposure: reproductive changes in male rats

We investigated the effects of an inhalatory anesthetic (ethyl ether) during the neonatal period of brain sexual differentiation on the later fertility and sexual behavior of male rats. Animals were exposed to ethyl ether immediately after birth. At adulthood, body weight, testes wet weight, and plasma testosterone levels were not affected; however, neonatal exposure to ether showed alterations on male fertility: a decrease in the number of spermatids and spermatozoa, an increase in the transit time of cauda epididymal spermatozoa and a decrease in daily sperm production. An alteration of sexual behavior was also observed: decreased male sexual behavior and appearance of homosexual behavior when the male rats were castrated and pretreated with exogenous estrogen. Probably, the ether delayed or reduced the testosterone peak of the sexual differentiation period, altering the processes of masculinization and defeminization of the hypothalamus. Our results indicate that perinatal exposure to ethyl ether during the critical period of male brain sexual differentiation, acting as endocrine disruptors, has a long-term effect on the fertility and sexual behavior of male rats, suggesting endocrine disruption through incomplete masculinization and defeminization of the central nervous system.

Effect of non-peptide corticotropin-releasing factor receptor type 1 antagonist on adrenocorticotropic hormone release and interleukin-1 receptors followed by stress

Previous studies demonstrated that ether-laparotomy significantly increased iodine-125-labeled interleukin-1alpha ([125I]IL-1alpha) binding in the mouse anterior pituitary at 2 h after the onset of stress. Corticotropin-releasing factor (CRF) receptor antagonist, D-Phe CRF (12-41), abolished ether-laparotomy-induced increase in [125I]IL-1alpha binding in the pituitary, showing that CRF plays a pivotal role in the regulation of IL-1 receptors under stress conditions. In an attempt to define the effect of CRA 1000 (2-(N-(2-methylthio-4-isopropylphenyl)-N-ethylamino-4-(4-(3-fluorophenyl)-1,2,3,6-tetrahydropyridin-1-yl)-6-methylpyrimidine), a non-peptide CRF receptor type 1 antagonist on the regulation of hypothalamic-pituitary-adrenal (HPA) axis and IL-1 receptors in the mouse, we measured plasma adrenocorticotropic hormone (ACTH) and corticosterone levels, [125I]IL-1alpha binding and the expression of transcripts for type 1 IL-1 receptor (IL-1R1 mRNA) in the pituitary at 2 h after endotoxin lipopolysaccharide (LPS) treatment or ether-laparotomy stress with or without CRA 1000 pretreatment. A single injection of LPS dramatically increased plasma ACTH and corticosterone levels compared with saline injection. In contrast, plasma ACTH levels were significantly attenuated in response to one LPS injection following oral CRA 1000 pretreatment. LPS-induced plasma corticosterone levels tended to be lower after CRA 1000 pretreatment but it did not reach statistical significance. Ether-laparotomy stress significantly increased plasma ACTH and corticosterone levels at 2 h after the onset of stress and CRA 1000 pretreatment did not affect the peak ACTH and corticosterone levels following stress. Ether-laparotomy stress resulted in a robust increase in [125I]IL-1alpha binding and IL-1R1 mRNA levels in the pituitary. CRA 1000 pretreatment significantly decreased ether-laparotomy stress-induced IL-1R1 mRNA levels but did not affect [125I]IL-1alpha binding. Pretreatment with CRA 1000 without stress significantly increased [125I]IL-1alpha binding and IL-1R1 mRNA levels compared with those in vehicle pretreatment. These data demonstrate differential effects of CRA 1000 in HPA axis following endotoxin and ether-laparotomy stress and complex interactions between CRF and IL-1 receptors during stress.

Inhaled anesthetics have hyperalgesic effects at 0.1 minimum alveolar anesthetic concentration

We investigated the hyperalgesic (antianalgesic) effect of the inhaled anesthetics isoflurane, halothane, nitrous oxide, and diethyl ether, or the nonimmobilizer 1, 2-dichlorohexafluorocyclobutane at subanesthetic partial pressures (or, for the nonimmobilizer, subanesthetic partial pressures predicted from lipid solubility) in rats. Hyperalgesia was assessed as a decrease in the time to withdrawal of a rat hind paw exposed to heat. All four anesthetics, including nitrous oxide and diethyl ether, produced hyperalgesia at low partial pressures, with a maximal effect at 0.1 minimum alveolar anesthetic concentration (MAC) required to prevent response to movement in 50% of animals, and analgesia (an increased time to withdrawal of the hind paw) at 0. 4 to 0.8 MAC. The nonimmobilizer had neither analgesic nor hyperalgesia effects. We propose that inhaled anesthetics with a higher MAC-Awake (the MAC-fraction that suppresses appropriate responsiveness to command), such as nitrous oxide and diethyl ether, can be used as analgesics because patients are conscious at higher anesthetic partial pressures, including those which have analgesic effects, whereas anesthetics with a lower MAC-Awake do not produce analgesic effects at concentrations that permit consciousness.

IMPLICATIONS

The inhaled anesthetics isoflurane, halothane, nitrous oxide, and diethyl ether produce antianalgesia at subanesthetic concentrations, with a maximal effect at approximately one-tenth the concentration required for anesthesia. This effect may enhance perception of pain when such small concentrations are reached during recovery from anesthesia.

Simultaneous blockade of two glutamate receptor subtypes (NMDA and AMPA) results in stressor-specific inhibition of prolactin and corticotropin release

Many neurons express simultaneously two or more isotypes of glutamate receptors, so that pharmacological modulation of more than one receptor may be necessary to reveal the role of glutamate in mediating physiological processes. The present studies were aimed at evaluating involvement of endogenous glutamate in triggering plasma prolactin (PRL) and adrenocorticotropic hormone (ACTH) levels in response to three different stress stimuli (footshock, immobilization and ether stress). Blockade of glutamate receptor subtypes was achieved by the administration of the NMDA antagonist dizocilpine (MK-801, 0.2 mg/kg) and the selective AMPA antagonist GYKI 52466 (10 mg/kg). Rats were pretreated for 4-5 days and then exposed to stressful stimulation. Basal hormone levels were not affected by the antagonists. In male rats, combined, but not separate blockade of NMDA and AMPA/kainate subtypes of glutamate receptors prevented the rise in plasma PRL in response to footshock stress. In female rats, footshock-induced PRL release was inhibited even by separate blockade of NMDA receptors by dizocilpine, suggesting that the PRL system of females is more sensitive to the effect of NMDA antagonists than that of males. None of the treatments affected PRL release during immobilization or ether stress. Simultaneous blockade of NMDA and AMPA receptor subtypes resulted in a mild inhibition of immobilization-induced ACTH release without any effect on ACTH response to footshock or ether stress. The data suggest that involvement of glutamatergic pathways in neuroendocrine response during stress is selective for discrete stress stimuli and stress hormones. In addition a concerted action of glutamate on both NMDA and non-NMDA receptor subtypes is involved in the control of PRL release during footshock stress.

[The effect of electromagnetic radiation in the millimeter range on the development of disorders in the liver induced by ether anesthesia (experimental research)]

Rat experiments with ether anaesthesia (EA) indicate that EA induces enlargement of hepatic sinusoids, stasis and perivascular edema of the triad vessels and other changes in the liver. Right hypochondrium exposure to electromagnetic waves (4.76-5.08 mm) up to 20 days in rats given simultaneously ether anaesthesia showed that livers from the irradiated rats did not differ from control. Thus, millimetric wave radiation may prevent pathological alterations arising in white rat liver after ether anaesthesia.

Effects of C-type natriuretic peptide on pituitary-adrenal activation in rats

The effects of C-type natriuretic peptide (CNP) on the hypothalamo-pituitary-adrenal system response to different stressors was studied. Various doses of CNP (0.2, 2, 4 microg) were injected into the lateral cerebral ventricle of freely moving rats 30 min before stress and activation of the adrenal was measured by plasma corticosterone. CNP did not affect basal corticosterone secretion in the doses applied, but inhibited in a dose-dependent manner the increase in plasma corticosterone induced by ether stress, electric shock and restraint. CNP exerted a more profound inhibitory effect on the response to ether stress than on that to electric shock or restraint. These results suggest that CNP acts centrally and to a different extent on the responses to different stresses.

Characteristics of the proopiomelanocortin system in the outdoor-bred domestic gander. II. Seasonal and circadian rhythmicity; effect of ether stress and lipopolysaccharide administration

The responsiveness of the POMC system to exogenous stimuli and the diurnal and seasonal rhythmicity of ACTH and beta-endorphin (beta E) in plasma were studied in outdoor-reared domestic ganders. Plasma levels of ACTH- and beta E-like immunoreactivities were determined by direct and specific radioimmunoassays. In the first series of experiments immunoreactive (ir) ACTH and beta E were measured in the plasma of male domestic geese after 5 min of ether stress and after administration of 2 micrograms/kg lipopolysaccharide (LPS). Both ir-ACTH and ir-beta E levels increased 5 and 10 min after ether inhalation, but the increase in the ir-beta E concentration was only half that of the ir-ACTH. The plasma ir-ACTH levels were elevated after 60 and 120 min but not after 90 min of LPS administration: ir-beta E levels were unchanged at all time points. In a second series of experiments blood samples were taken on 30 March. 16 June, 4 August, and 27 October. On these days diurnal samplings were performed at 02:00, 06:00, 10:00, 14:00, 18:00, and 22:00 h. A two-way analysis of variance showed significant diurnal and seasonal changes for both hormones and significant interaction between the diurnal and seasonal levels. The highest daily mean values of the plasma ir-ACTH and ir-beta E concentrations were measured in June. The maximum of the ir-ACTH level was at 10:00 h in March and August, but at 22:00 h in June and October. The changes in ir-beta E concentrations paralleled those of ir-ACTH, but the changes did not reach statistical significance in every case.

Functional observational battery comparing effects of ethanol, 1,1,1-trichloroethane, ether, and flurothyl

Several recent reports have demonstrated that acute solvent exposure in animals produces a profile of neurobehavioral effects similar to that of classical CNS depressant drugs such as the barbiturates and ethanol. The present investigation further delineated the behavioral pharmacology of three solvents [1,1,1-trichloroethane (TCE), ether, and flurothyl] using a functional observational battery (FOB) composed of 21 qualitative and quantitative measures of behavior. The profiles of acute effects produced by TCE and ether were similar to one another and similar to the profile of effects produced by the IP administration of ethanol. This profile of depressant effects included changes in posture, decreased arousal, disturbances in gait, decreased forelimb grip strength, increased landing foot splay, and impaired psychomotor coordination. Flurothyl exposure also produced dose-related effects on many of the measures in the FOB; however, unlike the depressant vapors, flurothyl did not affect measures of muscle tone and equilibrium such as forelimb grip strength and landing foot splay, or measures of sensorimotor reactivity, including the touch response and tail pinch response. In addition, flurothyl produced handling-induced convulsions in some mice. Recovery from the acute effects of these vapors was rapid and began within minutes of removal from the exposure chamber. These results provide further evidence that exposure to certain solvents produces a profile of reversible effects qualitatively similar to that produced by depressant drugs and alcohol, and that the FOB can be used to compare and contrast profiles of depressant and excitatory effects of inhalants.

Regulation of stress-induced transcriptional changes in the hypothalamic neurosecretory neurons

Transcriptional changes in corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) gene expression were studied by in situ hybridization histochemistry using cRNA probes directed against intronic sequences. Acute ether stress resulted in a rapid induction of CRF and a delayed activation of vasopressin heteronuclear (hn)RNA in the parvocellular neurosecretory neurons within the paraventricular nucleus (PVN) of the hypothalamus. To explore possible molecular mechanisms regulating stress-related neuropeptide expression in vivo, the time-courses of stress-induced activation of different transcription factor classes were compared to that of changes in neuropeptide transcription. The peak of CRF transcription was parallel to that of cAMP response-element binding protein (CREB) phosphorylation but preceded the induction of c-fos and NGFI-B mRNAs and Fos protein. In contrast, AVP expression occurred in step with immediate-early gene (IEG) responses, suggesting involvement of different mechanisms underlying stress-induced neuropeptide responses. The interference of glucocorticoid hormones with stress-induced neuropeptide and transcription-factor responses has also been revealed in rats acutely or chronically pretreated with glucocorticoids. Acute dexamethasone injection did not prevent neuropeptide and transcription factor responses to either inhalation, whereas chronic corticosterone administration completely blocked IEG and neuropeptide induction in the stress-related neurosecretory neurons.

Stress through handling for vaginal screening, serotonin, and ACTH response to ether

The effect of duration of handling for vaginal smear screening on the adrenal weight and acute ACTH response to ether were examined in 4-day-cycling female rats, sacrificed at 97-103 days of age on diestrus-2 after evaluation of resistance to handling, thymus weight, and hypothalamic serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA). Prolonged handling paralleled increased resistance (behavioral response) to handling and adrenal weight but was inversely related to thymus weight. The hypothalamic 5-HT, 5-HIAA, and 5-HIAA/5-HT ratio, compared to controls with similar conditions of handling, were not modified after 2.5 min of ether despite the ACTH rise. In ether-stressed rats, the ACTH response to ether was lower after prolonged handling compared to short handling paralleling decreased thymus weight. In contrast, 5-HT, 5-HIAA, and the 5-HIAA/5-HT ratio were higher, paralleling increased resistance and adrenal weight. The results suggest chronic activation of the hypothalamo-pituitary-adrenal axis with positive serotonergic involvement after prolonged handling and resistance during vaginal screening and a negative implication of this activation on the acute ACTH response to ether.

Effects of antidepressants on thyroid stimulating hormone release in rats under ether stress

We found inhibitory effects of antidepressants (clomipramine, maprotyline, mianserin and zimelidine) and 5-hydroxytryptophan (5-HTP) on thyroid stimulating hormone (TSH) release induced by ether stress in freely moving rats. We confirmed that ether stress suppressed the plasma TSH levels after 30 min. We then injected intravenously 250 ng thyrotropin releasing hormone (TRH), 0.1 mg/kg clomipramine, 2.5 mg/kg maprotyline, 2.5 mg/kg mianserin, 0.5 mg/kg zimelidine and 25 mg/kg 5-HTP simultaneously. These materials blocked the influences on plasma TSH levels by the ether stress. Serotonergic antidepressants (clomipramine, zimelidine) and 5-HTP (precursor of serotonin) had a higher potency against the ether stress. These results suggest that antagonizing effects against the ether stress may involve the serotonergic system in the pituitary gland.

Hyperammonemia induced in rats by inhalation anesthesia with ether

Transient hyperammonemia was observed in rats after inhalation anesthesia with ether. The elevation of blood ammonia concentration induced by ether anesthesia was greatest in carbon tetrachloride injured and indomethacin-treated rats, but not observed in phenobarbital-treated rats. The results suggest interaction between ether metabolism and ammonia metabolism in the liver.

Serum prolactin response to ether stress in diabetic rats: opiate system contribution

Diabetes in streptozotocin-treated rats is associated with alterations in various neuroendocrine systems, including endogenous opioids. These changes are suggested to be responsible for the significant reduction in serum prolactin (PRL) response to a brief restraint stress in diabetic male rats, as compared with normoglycemic controls. The present study examines serum PRL response to ether exposure in diabetic male rats. The animals' response to ether stress, which is known to be related to the opioid system, was examined twice in each rat: shortly after cannula insertion (Day 1), and seven days later. In order to evaluate the opiate system involvement, the experiment was repeated on Day 1 and 7 after surgery in a group of rats which were pretreated with naltrexone (Nalt), an opioid receptor antagonist. Opioid receptor sensitization was also performed by prior acute morphine administration on Day 7 after cannulation surgery. Following adaptation to the cannulation, no difference in serum PRL response to ether stress was found between diabetic and normoglycemic rats. However, on Day 1 after surgery, a significant difference was found between the diabetic and control groups: the normoglycemic (control) group exposed to ether responded to the surgical stress by augmented serum PRL levels. This response was not recorded in the diabetic rats. Opioid receptor blockade by Nalt administration 30 min before ether exposure eliminated this difference. Opioid receptor sensitization by morphine pretreatment facilitated PRL secretion in normoglycemic rats exposed to either, while no effect could be distinguished in the diabetic group. It is therefore concluded that the streptozotocin-induced diabetic rats do not differ from normoglycemic ones in their ability to respond to acute ether stress by itself. However, enhanced PRL secretion induced by ether exposure under additional surgical stress, or by presensitization of the opioid receptors by morphine, is prevented in diabetic rats, probably due to diminished opioid receptor response.

The role of central corticoliberin in the ether stress-induced secretion of neurohypophyseal hormones and corticosterone in the rat

As corticotropin-releasing factor (CRF) and oxytocin (OXT) are released in response to various stressors and a role of CRF in stress-induced OXT secretion has been proposed by previous authors, the present experiments were scheduled to investigate the participation of the brain CRF system in the stress-evoked release of OXT, arginine-8-vasopressin (AVP) and corticosterone. CRF-antiserum (AS) was given into the lateral ventricle of the brain of Wistar male rats, and 24 h later, the injection was repeated 30 min prior to ether stress followed by decapitation in 5 min. Plasma OXT and AVP were measured by radioimmunoassay and corticosterone by fluorimetry. Ether stress increased the levels of corticosterone and OXT, but not that of AVP. CRF-AS alone did not change the secretion of these hormones. CRF-AS pretreatment blocked the corticosterone-releasing action of ether stress, whereas it exerted no influence on the stress-induced OXT secretion into the circulation. There was no effect of a combined application of CRF-AS and stress on the plasma AVP level. These results suggest that the central CRF system is involved in the ether stress-elicited corticosterone response, however CRF is unlikely to be connected with the regulation of OXT secretion under these experimental conditions.

Chemical mutagenesis testing in Drosophila. IX. Results of 50 coded compounds tested for the National Toxicology Program

Fifty chemicals were tested for mutagenic activity in post-meiotic and meiotic germ cells of male Drosophila melanogaster using the sex-linked recessive lethal (SLRL) assay. As in the previous studies in this series, feeding was chosen as the first route of administration. If the compound failed to induce mutations by this route, injection exposure was used. One gaseous chemical (1,3-butadiene) was tested only by inhalation. Those chemicals that were mutagenic in the sex-linked recessive lethal assay were further tested for the ability to induce reciprocal translocations. Eleven of the 50 chemicals tested were mutagenic in the SLRL assay. These included bis(2-chloroethyl) ether, 1,4-butanediol diglycidyl ether, 1-chloro-2-propanol, dimethyl methylphosphonate, dimethyl morpholinophosphoramidate, dimethyloldihydroxyethylene urea, 2,2-dimethyl vinyl chloride, hexamethylphosphoramide, isatin-5-sulfonic acid (Na salt), isopropyl glycidyl ether, and urethane. Five of these, including 1,4-butanediol diglycidyl ether, 2,2-dimethyl vinyl chloride, hexamethylphosphoramide, isopropyl glycidyl ether, and urethane, also induced reciprocal translocations.

Pituitary-adrenal response to ether vapor in the weanling animal: characterization of the inhibitory effect of glucocorticoids on adrenocorticotropin secretion

The hypothalamic-pituitary-adrenal axis is hyporesponsive to stimuli during early life in the rat. Once the adrenocortical response is established, failure to terminate the corticosterone (B) rise is evident after certain stressors, such as ether. The purpose of this study was 2-fold: 1) to investigate the B and ACTH response to ether vapor in young animals and 2) to test the ability of glucocorticoids to inhibit the ether ACTH-stimulated secretion in weanling animals. Rats aged 14, 18, and 25 d and adult rats were subjected to ether vapor for 3 min. Plasma was collected for B and ACTH determination by RIA at 0, 5, 15, 30, 60, and 120; min after ether exposure. Maximum B levels were observed at different times after exposure: 15 min in the adult and 30 min in the younger animals. In addition, B levels were significantly elevated at 60 min in the d 25 and d 18 rats compared with the adult (d 25 = 672.4 +/- 28.9, d 18 = 744.6 +/- 31.7, adult = 323.2 +/- 8.7 mol/L +/- SEM; d 25 = 23.3 +/- 1.0, d 18 = 25.8 +/- 1.1, adult = 11.2 +/- 0.3 micrograms/dL +/- SEM). The B delay observed in the younger animals was not due to a delayed ACTH response because maximal ACTH values were observed 5 min after ether exposure in all ages (d 14 = 21.9 +/- 4.8, d 18 = 35.8 +/- 21.3, d 25 = 82.01 +/- 16.5, adult = 98.9 +/- 25.2 x 10(-12) mol/L +/- SEM). However, in the d 25 rats the ACTH level remained significantly elevated 30 min after the ether vapor challenge (5 min = 86.9 +/- 25.2, 30 min = 61.8 +/- 4.8, 60 min = 15.3 +/- 4.1 x 10(-12) mol/L +/- SEM). The delay to return to resting ACTH levels was consistent with the time delay observed for the B release from the adrenal.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral and neuroendocrine effects of diethyl ether exposure in the mouse

Diethyl ether has diverse behavioral effects and is known for its ability to stimulate stress hormones, yet little is known of the concentrations in which these effects occur. To more fully characterize these effects, adult male NIH mice were exposed to a range of concentrations of ether (1000-30000 ppm) in an inhalation chamber and both behavioral and neuroendocrine responses were assessed. When responding was maintained under FI-60 s schedules of milk presentation, 30-min exposures to 1000 ppm ether resulted in minimal behavioral effects, 3000-10000 ppm increased rates of responding over two-fold and higher concentrations decreased responding almost completely. Five-min exposures to the same range of concentrations resulted in concentration-related effects which were smaller than those produced by 30-min exposures. Exposure to a similar range of concentrations in naive mice increased adrenocorticotrophic hormone (ACTH) and corticosterone levels in a time- and concentration-dependent manner. Five-min exposures to 10000 ppm ether increased levels of ACTH from a baseline of 25.95 pg/ml to 310.5 pg/ml but did not affect corticosterone. Thirty-min exposures to the full range of concentrations of ether, increased corticosterone from control levels of 70 ng/ml to 418 ng/ml at 30000 ppm, and increased ACTH from control levels of 19.13 pg/ml to 80.5 pg/ml at 30000 ppm, in a concentration-dependent manner. The increase in ACTH for 30-min exposures was not as large as that observed for 5-min exposures at 10000 ppm, nor was it as large as that seen for corticosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of different chronic intermittent stressors and acetyl-l-carnitine on hypothalamic beta-endorphin and GnRH and on plasma testosterone levels in male rats

Chronic stress affects the reproductive function by modifying the neuroendocrine homeostasis. The aim of the present study was to clarify the neuroendocrine and the gonadal changes following chronic intermittent stress in male rats and the action of a neuroactive drug, acetyl-l-carnitine (ALC). The effect of two different stressors, cold water swimming or ether, on central beta-endorphin (beta-EP) and GnRH contents, and on plasma testosterone levels was investigated. In addition, the response to an acute stress in chronically stressed rats, treated or untreated with ALC (10 mg/day/rat p.o.), was evaluated. The stressors were applied twice a day for 10 days, and rats were killed before, during and after the last stress session. Mediobasal hypothalamus (MBH) beta-EP and GnRH contents, and plasma testosterone levels were evaluated by radioimmunoassay. The following results were obtained: (1) both chronic swimming and ether stress caused a decrease in hypothalamic beta-EP contents; (2) MBH GnRH contents increased after chronic swimming stress but not after ether stress; (3) chronic swimming stress induced a twofold decrease in plasma testosterone levels, while no changes were observed after ether stress; (4) the treatment with ALC prevented the decrease in plasma testosterone levels after chronic swimming stress, and (5) acute stress in chronically stressed animals caused an increase in MBH-beta-EP. The present data showed that chronic swimming stress reduces the reproductive capacity and impairs the capacity to respond to the acute stress and that ALC modulates the hormonal changes to physical stress and prevents the antireproductive effect of chronic cold swimming.

Acetyl-L-carnitine effect on pituitary and plasma beta-endorphin responsiveness to different chronic intermittent stressors

The aims of the present study were: 1) to compare the effect of two different chronic intermittent stressors i.e. cold-swimming versus ether, on the pituitary opioidergic system; 2) to evaluate the response of pituitary and plasma beta-endorphin (beta-EP) to an acute stress in chronically stressed rats; and 3) to evaluate the effect of acetyl-l-carnitine treatment (10 mg/day/rat per os at night) on pituitary and plasma beta-EP changes induced by two different types of chronic stress. The stressors were applied twice a day for 10 days. Rats were killed either before, during or after the last swimming or ether stress session. beta-EP was measured by radioimmunoassay in anterior pituitary and in neurointermediate lobe extracts and in plasma. The following observations were made: 1) Chronic intermittent cold-swimming stress increased anterior pituitary contents and plasma beta-EP levels; 2) both chronic intermittent cold-swimming stress and ether stress caused an increase of neurointermediate lobe beta-EP contents; 3) as in control animals, rats exposed to chronic intermittent swimming stress reduced pituitary beta-EP contents and raised plasma beta-EP levels in response to the last acute swimming stress; 4) in contrast to control animals, rats exposed to chronic intermittent ether stress did not show any significant response of the pituitary-plasma opioidergic system to the last acute ether session; 5) the acetyl-l-carnitine treatment counteracted the changes evoked by chronic intermittent cold-swimming stress on the pituitary and plasma beta-EP levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of serotonin 5-HT1, 5-HT2, and 5-HT3 receptor antagonists on the prolactin response to restraint and ether stress

Serotonin (5-HT) appears to be involved in the central control of the prolactin (PRL) response to suckling and estrogen. Furthermore, 5-HT may participate in the mediation of stress-induced PRL release. In order further to elucidate the role of 5-HT and the type of 5-HT receptor(s) involved in the PRL response to stress, we investigated the effect of blockade of 5-HT1, 5-HT2 or 5-HT3 receptors on the restraint or ether stress-induced release of PRL in male rats. Pretreatment with the 5-HT1 + 2 receptor antagonist methysergide (0.5 or 2.5 mg/kg i.p.) inhibited or prevented the PRL response to restraint or ether stress. Pretreatment with the 5-HT2 receptor antagonists ketanserin or LY 53857 (0.5 or 2.5 mg/kg i.p.) inhibited the response to restraint or ether stress approximately 30 or 60%, respectively. Higher doses of both 5-HT2 receptor antagonists (10 mg/kg i.p.) had a minor inhibitory effect (5-30% for ketanserin and 50% for LY 53857). Prior intraperitoneal administration of the 5-HT3 receptor antagonists ICS 205-930 or GR 38032F (0.05-2.5 mg/kg i.p.) inhibited the restraint stress-induced PRL release dose-dependently. Both compounds inhibited the PRL response to ether stress, but only the effect of GR was dose-related. The maximal inhibitory effect (70% inhibition of the PRL response to restraint or ether stress) was obtained for both compounds at a dose of 0.1 mg/kg. We conclude that serotonergic neurons are involved in the mediation of the stress-induced PRL release by activation of 5-HT1, 5-HT2 as well as 5-HT3 receptors.

Effects of inhalation of ethyl-ether on glycemia and on some variables of intermediate metabolism in rats

The influence of a anesthetic, ethyl-ether, on arterial plasma levels of glucose, insulin and lipids was studied in starved Wistar rats. Ethyl-ether increased significantly (P < 0.05) glucose plasma levels, as a result not only of stress and of the release of catecholamines and glucocorticoids, but also of the decrease in the use of glucose by the tissues. Ethyl-ether did not change significantly the level of triglycerides, cholesterol and phospholipids. Insulin concentration was not increased, even when hyperglycemia was established. Ketonuria, acidosis and hypercapnia were increased. In these rats the administration of insulin produced a diminution in glycemia. The findings suggest that, under anesthesia with ether, the endocrine pancreas is incapable of recognizing glucose as a specific stimulus to promote the release of insulin.

Central circulation during halothane-diethyl-ether azeotrope and isoflurane anaesthesia in the pig

The fatal anaesthetic ratio (FAR) has been determined for halothane-diethyl-ether (HE) in pigs, and the central circulation during hypovolaemia has been investigated using a well-documented agent such as isoflurane as a standard. The fatal anaesthetic ratio for HE in pigs was (3.21/1.03) = 3.12. This is high compared to the FAR for halothane of 1.7. The central circulation was investigated in 12 pigs which were randomly allocated to either HE or isoflurance anaesthesia, respectively. Baseline values were recorded when they were stable at 1.3 MAC of the volatile anaesthetic used. The pigs were bled 30% of their blood volume, and measurements were made at 5 and 30 min. There was one significant difference between these groups in central circulation: the blood pressure was higher at baseline measurement in the HE group. At 5 min and 30 min, there were no significant differences between these groups. There was a general depression of central circulation without any sign of decreased contractility. HE anaesthesia is well tolerated during hypovolaemia in pigs.

Autoxidative injury with loss of cytochrome P-450 following acute exposure of rats to fasting and ether anaesthesia

1. Exposure of fasted rats (20 h) to ether anaesthesia for 4 min resulted in increased exhalation of alkanes, an indication of lipid peroxidation in vivo. 2. Liver and kidney of the fasted rats anaesthetized with ether showed immediate 4-fold increases in luminol-amplified chemiluminescence, reaching maxima 30 min later, indicating the production of reactive oxygen species. 3. Liver and kidney cytosols of the fasted anaesthetized rats similarly showed immediate 4-fold increases of thiobarbituric acid-reactive material (malondialdehyde and other lipid peroxidation breakdown products) which attained maxima 60 min later. 4. Total cytochromes P-450 of liver and kidney of rats were decreased to 25-30% of control values after 20 h fasting and 4 min of ether anaesthesia, but were restored to normal levels 2 h later. Cytochrome P450 I (EROD activity) was decreased to 35-44% of control values by the ether anaesthesia and was restored to 80% of normal levels 2 h later. 5. Diether ether is known to be metabolized by cytochrome P450 IIE1 which is induced by fasting and by diethyl ether, and is possibly involved in the observed radical production, lipid peroxidation, and loss of cytochromes P-450.

Sex differences in adrenocortical structure and function. XXVII. The effect of ether stress on ACTH and corticosterone in intact, gonadectomized, and testosterone- or estradiol-replaced rats

Studies were performed on the reactivity of the hypothalamo-pituitary-adrenocortical axis of intact, gonadectomized, and testosterone- or estradiol-replaced rats to standard ether stress. Plasma ACTH and corticosterone (B) levels, anterior pituitary ACTH, and adrenal B content were estimated 20 and 40 min after stress application and in unstressed animals. Ether stress resulted in an increase in plasma ACTH and B levels and in adrenal B content while pituitary ACTH content was notably lower when compared with unstressed rats. The response was markedly higher in female than in male rats. After orchiectomy and testosterone replacement, plasma ACTH and B responses to ether stress were similar to those observed in intact male rats. On the other hand, ovariectomized females responded to ether stress like intact males, while after estradiol replacement the pattern of plasma ACTH and B concentration and adrenal B content was similar to that in intact female rats. Thus, the higher responsiveness of the pituitary-adrenal cortex axis of female rats to ether stress depends on stimulatory or facilitatory effect of estradiol.

Chemical stress and GABAergic central system

1. The function of the gamma-aminobutyric acid (GABA)ergic system in certain areas of the rat brain was investigated after acute (30 sec) ether stress. 2. GABA endogenous concentrations, uptake of [3H]GABA and the activity of glutamate decarboxylase were measured in different brain areas. 3. After 30 sec of exposure to ether vapour, GABA concentration and total [3H]GABA uptake in the frontal cerebral cortex were increased. In contrast, stress increased GABA concentration in the hypothalamus, but reduced total [3H]GABA uptake. 4. Since the neuronal component of [3H]GABA uptake was increased in the frontal cerebral cortex this might be responsible for the increase in total [3H]GABA uptake. The increase in the endogenous concentration of GABA in the hypothalamus probably resulted from its enhanced synthesis because GAD activation was observed in the hypothalamus after stress. 5. In conclusion, the present study shows that acute ether stress induces rapid and quickly reversible changes in the GABAergic system according to the area of brain. The characteristics of these changes as related to their quick appearance and reversibility might suggest an effect upon neuronal activity due to acute stress exposure.

Sensitivity to ether anesthesia and to gamma-rays in mutagen-sensitive strains of Drosophila melanogaster

An ether-resistant strain of Drosophila melanogaster, Eth-29, has previously been found to be radiosensitive. Some mutagen-sensitive strains are known to be hypersensitive to X-rays in larvae. The correlation between sensitivities to ether anesthesia and to gamma-rays was examined in adult flies of 12 mutagen-sensitive strains and 6 control strains. A wide variation in sensitivities to ether anesthesia, gamma-ray knock-down and gamma-ray lethality was demonstrated. No correlation between DNA-repair capacity and ether sensitivity or gamma-ray knock-down sensitivity was shown. Only mei-9 and mus201, which are deficient in excision repair, as well as Eth-29 were found to be sensitive to gamma-ray lethality. These findings indicate that the targets for ether anesthesia, knock-down and lethality may be different. Lethality appears to be caused by DNA damage, while the other 2 endpoints appear not to be related to DNA damage.

Ethyl-oxide effects on a newly formed blood-brain barrier

The morphofunctional effects of ethyl-oxide, utilized as anaesthetic, on the optic tectum blood-brain barrier were investigated in hatching chick embryos (21st incubation day) and young chickens in which the barrier to the marker of vascular permeability horseradish peroxidase is complete after the 18th incubation day. Results indicate that ethyl-oxide administration produces horseradish peroxidase extravasation by opening the tight interendothelial junctions. The escape rate of the marker is higher in the tecta of hatching embryos than in those of chickens and in both horseradish peroxidase extravascular diffusion is more frequent at the level of vessel bifurcation than along the branchless vessel tracts.

In-vitro spin-trapping of free radicals produced during trichloroethylene and diethylether metabolism

Free-radical production during the metabolism of various xenobiotics represents a frequent mechanistic explanation for their toxicity. We tested the hypothesis of production of free radicals from two solvents, diethylether and trichloroethylene (TRI), and from two metabolites of TRI, namely trichloroethanol (TCE) and trichloroacetic acid (TCA). The formation of free radicals was detected by electron spin resonance spectroscopy (ESR), using a spin-trapping agent, alpha-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone (POBN). Two experimental models were used. The first was a chemical model using Fenton's reagent, a mixture of Fe(II)-chelator and H2O2, for which the normal reaction is OH. production, and the second, a preparation from rat liver and brain microsomes containing NADPH and achieving enzymatic oxidation of the solvents. After addition of diethylether, free-radical production was demonstrated under the two experimental conditions. This free radical probably derived from the parent molecule by hydrogen abstraction. TRI and TCE additions to the Fenton system suppressed normal OH. production whereas this production was increased after TCA addition. The addition of TCE to the microsomal preparations was followed by free-radical production which could derive either from the parent molecule or from other sources, e.g. from membrane degradation, with a preference for the first hypothesis because of the characteristics of the signal. This result was not observed after addition of TRI or TCA. In conclusion, these preliminary results confirm the validity of the hypothesis of production of free radicals from diethylether, but they are less consistent for TRI as this production was observed only after addition of TCE; this result is interesting, however, as TCE is considered to play a major role in the toxicity observed after TRI exposure in humans.

Residual effects of ether anesthesia on whole-body hemodynamics and organ blood flows in the rat

This study was designed to determine the short-term residual effects of ether anesthesia on hemodynamics and blood flow distribution in the rat. Eighteen male Sprague Dawley rats were instrumented and allowed to recover for at least 2 days before beginning the experiment. Using microspheres, cardiac output, and blood flow distribution were determined at five different periods: before ether anesthesia; at a surgical level of ether anesthesia; and 20 min, 1 hr, or 3 hr after cessation of anesthesia. Ether anesthesia initially decreased arterial pressure, increased cardiac index, and decreased total peripheral resistance. The residual effects of ether included progressive increases in arterial blood pressure and an increase in total peripheral resistance index. Cardiac index was returned to normal 1 hr after termination of anesthesia. Blood flow to the brain and heart increased during anesthesia and was significantly elevated 1 hr later. Other organs, including kidney, spleen, and intestine showed a decrease in blood flow during anesthesia, which persisted for at least 20 min. Thus, ether anesthesia produced acute and residual disturbances in hemodynamics and blood flow distribution, which may have an untoward influence on concomitant experimental observations.

Plasma concentration and vascular effect of beta-endorphin in spontaneously hypertensive and Wistar Kyoto rats

In order to find out whether beta-endorphin (beta-E) is involved in the development of hypertension, we performed two series of experiments. Firstly, spontaneously hypertensive rats (SHR) and their normotensive Wistar Kyoto controls (WKY) were submitted to ether stress. Plasma concentrations of beta-endorphin-like immunoreactivity (beta-EI), adrenocorticotropin (ACTH) and alpha-melanotropin (alpha-MSH) were measured by radioimmunoassay. The basal concentration of beta-EI was similar in WKY and SHR, whereas WKY had higher levels of ACTH and lower levels of alpha-MSH than SHR. In both strains acute stress enhanced the plasma concentration of beta-EI to the same extent and with a similar time-course. The increase of plasma beta-EI coincided with a rise in ACTH but not alpha-MSH. Gel chromatography of beta-EI revealed that plasma extracts contain similar amounts of beta-lipotropin- (beta-LPH) and beta-E-sized immunoreactive components, and that acute stress elevated both forms of beta-EI. Secondly, isolated tail arteries of SHR and WKY were perfused and field stimulated with two pulses at 1 Hz. beta-E depressed stimulation-evoked vasoconstriction with the same potency in both strains. Thus, basal and stress-induced levels of beta-EI did not differ in SHR and WKY. Moreover, in the tail artery of both strains the sensitivity of presynaptic opioid receptors towards beta-E was almost identical. If the beta-E sensitivity of these receptors in other arteries of WKY and SHR is also similar a major role of the circulating peptide in the development of hypertension is rather unlikely.

Biochemical changes associated with the potentiation of acetaminophen hepatotoxicity by brief anesthesia with diethyl ether

Acetaminophen hepatotoxicity in male CD-1 mice was enhanced markedly by brief anesthesia with diethyl ether (ether), and particularly so if acetaminophen was given several hours after ether. The present study was conducted to examine the possible biochemical mechanisms behind this delayed toxicologic synergism. In vitro biochemical studies indicated that ether anesthesia produced a delayed reduction in the activities of glucuronyl transferase and glutathione (GSH) S-transferase, and in the hepatic content of GSH. The hepatic content but not activity of the cytochromes P-450 was initially reduced by ether but recovered by the time of maximal toxicologic enhancement. In vivo studies showed that ether produced a small decrease in the plasma concentrations of glucuronide and sulfate conjugates of acetaminophen, with a concomitant, minor increase in the half-life of acetaminophen, and a major increase in the bioactivation of acetaminophen, as determined by an early, 2-fold increase in the plasma GSH and cysteine conjugates of acetaminophen, and a 3-fold increase in the covalent binding of acetaminophen to hepatocellular protein. Decreases produced by ether in the in vivo production of acetaminophen glucuronide correlated with increasing plasma concentrations of unmetabolised acetaminophen, decreasing hepatic GSH content and increasing covalent binding of acetaminophen to hepatocellular protein when these measurements were performed in the same animals. The biochemical mechanisms underlying the potentiation of acetaminophen hepatoxicity as measured by plasma glutamic pyruvic transaminase concentrations appeared to be due to delayed, complex effects of ether upon multiple enzymatic pathways of acetaminophen elimination and detoxification.

Investigations on metabolism, genotoxic effects and carcinogenicity of 2,2'-dichlorodiethylether

Either 40 mumole or 160 mumole 2,2'-DDE was injected into male Wistar rats and the metabolites, TdGA and HEMA, were determined in the 24-h urine specimens. Comparative investigations were carried out giving equimolar amounts of chloroethanol and 2-chloroacetaldehyde diethyl acetal. In a further step, inhalation experiments were performed to determine urinary excretion of the two metabolites after an 8-h exposure of male Wistar rats to 10, 50, 100, and 500 ppm 2,2'-DDE and to 50, 200, und 1,000 ppm vinyl chloride. A long-term study was conducted to investigate the possible carcinogenicity of 2,2'-DDE in male and female Sprague-Dawley rats following s.c. injections of 4.36 mumole and 13.1 mumole 2,2'-DDE in DMSO per week. The evaluation of tumor development in treated groups and controls were based on macroscopic inspection and histological examinations of the suspect organs and tissues. Analysis of the metabolites showed that HEMA excretion was much lower than the excretion of TdGA following the uptake of 2,2'-DDE, 2-chloroethanol and 2-chloroacetaldehyde diethyl acetal. Contrary to these, vinyl chloride uptake resulted in a higher urinary excretion of HEMA than TdGA. There was no appreciable increase in the number of tumors detected in 2,2'-DDE-treated animals when compared with untreated or DMSO-treated groups. Since irradiation of 2,2'-DDE with UV did not elevate mutagenic activity of the compound against Salmonella typhimurium TA100, the high mutagenicity of the compound found in a desiccator cannot be due to the liberation of mutagenic compounds produced under the influence of UV light.

Delayed enhancement of acetaminophen hepatotoxicity by general anesthesia using diethyl ether or halothane

Acetaminophen (Tylenol) is a widely used analgesic/antipyretic drug which is enzymatically bioactivated, or toxified, by the cytochromes P-450 to a hepatotoxic reactive intermediary metabolite. Brief general anesthesia with diethyl ether has been shown to inhibit both the toxifying cytochromes P-450 and enzymatic glucuronidation, the latter constituting up to 60% of acetaminophen elimination via a nontoxifying pathway. Thus ether potentially could produce a temporally differentiated inhibition of bioactivating and "detoxifying" pathways, resulting in an enhancement of acetaminophen hepatotoxicity if the balance favored bioactivation. To evaluate this possibility, separate groups of male NIH strain mice were treated with acetaminophen at different times after 5 min of anesthesia with ether. Ether produced a 40-fold enhancement in acetaminophen hepatotoxicity as determined by plasma glutamic-pyruvic transaminase (GPT) concentrations. This toxicologic enhancement was observed only if acetaminophen administration was delayed, with a maximal enhancement when acetaminophen was given 6 hr after ether, and no effect with a delay of 16 hr. Similar studies in male CD-1 mice were carried out using halothane (Fluothane) as the general anesthetic given either over 5 min or over 1 hr. While halothane given over 5 min had no effect, a 1 hr anesthetic duration produced a 10-fold increase in acetaminophen hepatotoxicity as determined by peak GPT concentration, with no observed hepatotoxicity in the halothane controls. Toxicologic enhancement occurred only with delayed administration of acetaminophen; however, the maximal enhancement observed with a 6-hr delay was still evident with a 12-hr delay. Conversely, inhibition of acetaminophen hepatotoxicity was observed if acetaminophen was given either 2 hr or 18 hr after halothane.(ABSTRACT TRUNCATED AT 250 WORDS)

Strain differences of ether susceptibility in mice

The susceptibility to ether in the following six strains of mice was tested: C57BL/6, DBA/2, BALB/c, C3H/He, ICR and ddY. Mice of 4 weeks old were exposed to a flow of air containing various concentrations of ether for 90 min and the mortalities were assessed. The C57BL/6 strain was the most resistant and the C3H/He strain was the most sensitive to the lethal effect of ether. The susceptibilities of the closed colony mice, ICR and ddY, were intermediate between those of C57BL/6 and C3H/He mice. The DBA/2 and BALB/c strains were more sensitive than these closed colony mice and made up a sensitive group with the C3H/He strain. The LD50 values for ether in male mice of C57BL/6 and C3H/He were 6.0 and 3.1% atm, and in female mice of these strains were 6.6 and 3.2% atm, respectively. The ED50 value of ether which was accompanied by loss of righting reflex after exposure for 10 min was also higher in male C57BL/6 mice than in male C3H/He mice.

Acute doxorubicin-induced cardiac arrhythmias during ether anesthesia

Acute intravenous administration of doxorubicin (30 and 50 mg/kg) elicited cardiac arrhythmias in the mouse, the severity and extent of which were dependent upon dose of doxorubicin and the anesthetic agent utilized. Fatal arrhythmias occurred in all mice given 50 mg/kg doxorubicin under ether anesthesia. Vasoactive amines may mediate the arrhythmogenicity of acute doxorubicin administration.

Sex difference of barbiturate-protection in experimental cerebral ischemia in spontaneously hypertensive rats (SHR)

Survival time following bilateral carotid occlusion was significantly longer in spontaneously hypertensive rats (SHR) anesthetized with barbiturate than in those with ether. Under barbiturate anesthesia, female SHR survived longer (16.6 h) than did males (10.9 h), whereas such sex difference was not found in those with ether anesthesia. The present results indicate sex difference of barbiturate-protection in cerebral ischemia.

Hypothalamic GABA system and plasma corticosterone in ether stressed rats

Exposure of rats to the ether stress (2 X 2 min within 15 min) activated the hypothalamo-hypophyseal-adrenal (HHA) axis, as evidenced by the increased plasma corticosterone concentration, and affected the hypothalamic GABA system. The aminooxyacetic acid (AOAA) or L-cycloserine-induced accumulation of GABA was decreased, and the activity of glutamate decarboxylase (GAD), the enzyme responsible for GABA synthesis, was increased following ether stress. The concentration of GABA and the activity of GABA: 2-oxoglutarate aminotransferase (GABA-T), the enzyme responsible for GABA catabolism, remained unchanged under given conditions. Diazepam, a drug known to potentiate GABA-ergic transmission, elevated the concentration of plasma corticosterone, but prevented its further increase by ether stress. In spite of the diminished accumulation of GABA, the results might suggest that ether stress activates the hypothalamic GABA system, which is then able to prevent a further response of the HHA axis to stress.

Carcinogenicity tests of certain environmental and industrial chemicals

Fourteen chemicals of varied uses were tested for carcinogenicity by oral administration in male and female Charles River CD rats. Under the conditions of the tests, propane sultone, propylene imine, and ethylenethiourea, in addition to the positive control N-2-fluorenylacetamide, were carcinogenic. Avadex, bis(2-chloroethyl) ether, the potassium salt of bis(2-hydroxyethyl) dithiocarbamic acid, ethylene carbonate, and semicarbazide hydrochloride were not carcinogenic under the test conditions. Dithiooxamide, glycerol alpha-monochlorohydrin, and thiosemicarbazide gave somewhat ambiguous results, though administered at high enough dose levels to be toxic. An inadequate number of animals survived treatments with sodium azide, sodium bisulfide, and vinylene carbonate, or the animals may not have received sufficiently high doses of the test chemicals to provide maximum test sensitivity. However, there were no indications that these three chemicals were carcinogenic under the test conditions.

Morphologic changes in mouse spermatozoa after exposure to inhalational anesthetics during early spermatogenesis

The authors studied anesthetic mutagenesis following exposure in vivo by use of an adaptation of the mouse spermatozoa morphology assay of Wyrobek and Bruce. The epididymal spermatozoa of (C57B1/C3H)F1 mice were examined for morphologic abnormalities following exposure to near-0.1 MAC and greater concentrations of general anesthetics. Twenty exposure hours (4 hr/day x 5 days) were conducted for nitrous oxide, diethyl ether, chloroform, trichlorethylene, halothane, methoxyflurane, enflurane, and isoflurane, each at two concentrations. Twenty-eight days after exposure, epididymal spermatozoa were examined. Statistically significant increases in the percentages of abnormal spermatozoa were found for chloroform, trichloroethylene, and enflurane, compared with controls. These data suggest that direct examination of reproductive cells following exposure to general anesthetics in vivo may be useful in the investigation of the genetic toxicities of these compounds.

Identification of S-(carboxymethyl)-L-cysteine and thiodiglycolic acid, urinary metabolites of 2,2'-bis-(chloroethyl)-ether in the rat

S-(carboxymethyl)-L-cysteine (CMC) and thiodiglycollic acid (TGA) were identified by gas chromatographic-mass spectrometric measurements in the urine of rats after intraperitoneal injections of 2,2'-bis-(chloroethyl)-ether (BCEE). It is therefore probable that BCEE is O-dealkylated by a mixed-function oxidation. The hepatocarcinogenic effect of BCEE may be explained by the liberation of chloroacetaldehyde in vivo.