Effect of interaction of volatile anesthetics and high hydrostatic pressure on central neurons

Autoactive neurons in the central nervous system of Helix and Aplysia were studied after exposure to several volatile anesthetics and under compression by mineral oil. Voltage clamp studies reveal that halothane will eliminate the slow inward current that underlies oscillatory activity in burster neurons, while high pressure shifts the negative resistance region of the current without causing its elimination. Simultaneous application of the anesthetic and pressure results in the loss of inward current over a time course similar to that of halothane application alone. It is concluded that in this system, pressure and anesthetics are not acting antagonistically at the site in the membrane that controls slow wave conductances.

Effect of trichloroethylene on cilia activity in rabbit trachea

The ciliotoxicity of trichloroethylene was studied in terms of the time required for ciliostasis in specimens of trachea from 35 male rabbits following exposure of the specimens to different vapour concentrations. The highest vapour concentration was linked with the most rapid ciliostasis but even in the lowest concentration tested, 5.000 p.p.m. (26 g/m3), hastened ciliostasis. Specimens from the upper region of the trachea underwent ciliostasis more slowly than did those from the lower region. The absolute uptake of trichloroethylene was lower in the former than in the latter specimen. The difference in uptake could not be explained by a difference in weight or in lipid content. That ciliostasis occurred at different times depending upon the region of the trachea, favours the theory of a critical tissue concentration for trichloroethylene.

Acetaldehyde level in the blood and liver aldehyde dehydrogenase activities in trichloroethylene-treated rats

The liver NAD+-dependent aldehyde dehydrogenase (AldDH) activity and the acetaldehyde level in the blood during ethanol metabolism after trichloroethylene (trichlene) exposure were studied in rats. Trichlene inhalation caused large elevations in acetaldehyde levels during ethanol metabolism and caused decreases in the activity of the AldDH with a low Km value in mitochondrial and soluble fractions of liver cells. No significant effects were found in the activity of the high Km-enzyme in mitochondrial, soluble and microsomal fractions. Time course of inhibition of the mitochondrial low Km-enzyme and that of elevations in acetaldehyde levels during ethanol metabolism after trichlene exposure were similar. These findings suggest that acetaldehyde formed from ethanol in vivo is oxidized primarily by the mitochondrial low Km-enzyme.

Suggested procedures for reducing the pathology workload in a carcinogen bioassay program, Part I

Large test programs have been set up to help assess the carcinogenic potential of chemicals introduced into the environment. Most test protocols used in these programs require large numbers of animals and extensive pathologic evaluation of all test and control animals. In this paper we describe modifications to the present pathology protocol which will reduce the pathology workload of the program and make only small changes in the operational character of the screen. The first modification derives from the fact that a tumorigenic effect may be ruled out by looking at the treated animals only. The second procedure suggested uses simple random samples to provide information about the treated groups with still less pathology work. It is emphasized that these proposed modifications should be regarded as a starting point for further discussion and that we encourage comments from all interested scientists.

Effects of analgesics during labor

Four analgesic agents were studied during labour: pethidinesparine, ketamine hydrochloride, nitrous oxide-oxygen, and trichloroethylene in air (Trilene). Excellent analgesia was achieved with ketamine, however hallucinations were troublesome. Trichloroethylene analgesia was good without side-effects. Pethidine-sparine produced moderate analgesia but with nausea and/or vomiting. Nitrous oxide 50% presented poor analgesia. Uterine activity was insignificantly diminished in the late first stage after administration of all analgesic agents except with ketamine. There were no untoward effects on fetuses.

Choice reaction time in workers using trichloroethylene

Eight-choice reaction time studies were carried out on women using trichloroethylene (TCE) as an industrial solvent, and simultaneous tests were performed on control subjects. The women exposed to TCE showed an increase in choice reaction time compared with the control subjects. This divergent trend was substantial at a factory where TCE levels exceeded the recommended threshold limit value (TLV). The divergence was less pronounced, but still clearly evident at another factory where TLV was not exceeded.

Transforming activities of trichloroethylene and proposed industrial alternatives

Three chlorinated hydrocarbons, proposed or already in use as industrial substitutes for the hydrocarbon trichloroethylene, were tested for in vitro transforming potential in a Fischer rat embryo cell system (F1706), which previously has been shown to be sensitive to transformation by chemical carcinogens. Trichloroethylene and the three substitutes (1, 1, 1 trichloroethane, tetrachloroethylene and methylene chloride) all were found to induce transformation, the three substitutes being equal or more efficient transforming agents.

Genetic activity of trichloroethylene in yeast

Trichloroethylene (TCE) was tested for its ability to induce both point mutation and mitotic gene conversion in diploid strain of yeast. Saccharomyces cerevisiae (strain D7) was tested for both activities in culture with and without a mammalian microsomal activation system and in the intrasanguineous host-mediated assay in mice. Strain D4 (gene conversion) was tested only in the host-mediated assay. In suspension tests with D7, TCE was toxic but not genetically active without microsomal activation. When a mouse liver 10,000 xg supernatant was included in the suspension tests, dose related increases in both mutation and gene conversion were seen at survival levels of greater than 50 percent. In the host-mediated assay, TCE induced both point mutation and gene conversion in D7 and gene conversion in D4 when recovered from the liver and kidneys after both acute and subacute dosing. Yeasts recovered from the lungs showed little, if any, increase in either point mutation or gene conversion.

Labilization of brain lysosomes by trichloroethylene metabolites and peroxide anion in vitro

Lysosomes were isolated from adult male Wistar rat brain and incubated in vitro with 10 micron trichloroethylene and microsomes or postmicrosomal supernatant with added NADPH. Freezing and incubation with the solvent alone served as controls. The results were compared with the effect of peroxide anion from the xanthine-xanthine oxidase reaction. Mere solvent did not cause an appearance of acid proteinase activity in the incubation medium whereas other treatments induced lysosomal labilization.

Biochemical and toxicological effects of combined exposure to 1,1,1-trichloroethane and trichloroethylene on rat liver and brain

1. Inhalation exposure of adult male rats to a mixture of 1,1,1-trichloroethane (500 p.p.m.) and trichloroethylene (200 p.p.m.) for four days 6 h daily resulted in an accumulation of 1,1,1-trichloroethane in perirenal fat. Further exposure on the fifth day caused a rapid increase in various organ contents of both solvents with secondary depression of brain RNA. 2. The four-day exposure doubled the RNA content of liver and caused a slight decline in the concentrations of glutathione in liver. 3. The amount of cytochrome P-450 in liver was increased, as well as the overall mono-oxygenase activity, measured with styrene as substrate. During continuing treatment on the fifth day, styrene mono-oxygenase activity decreased, the activity after 6 h being only about 50% of that at the beginning of the fifth day of exposure. 4. UDP-glucuronosyl transferase activity (measured in digitonin-activated microsomes) was doubled by the four-day combined exposure to 1,1,1-trichloroethane and trichloroethylene. 5. The changes during the fifth day of exposure, e.g. rapid increase in the concentrations of solvents in organs, the detection of trichloroethylene in tissues and depression of mono-oxygenase activity, obviously also occurred during the exposures on days 1 to 4 and reverted during each post-exposure period.

Suggested procedures for reducing the pathology workload in a carcinogen bioassay program, Part II: Incorporating blind pathology techniques and analysis for animals with tumors

Large testing programs have been set up to help assess the carcinogenic potential of chemicals introduced into the environment. Most test protocols used in these programs require extensive pathologic evaluations of all test and control animals. In Part I we proposed modifications to such complete pathology protocols which would allow substantial reduction in pathology workload while making only small changes in the operational character of the screen. The modifications suggested did require that slides from controls and treatment animals be handled differently and they did not call for a total tumor analysis (i.e. they do not allow blind pathology). In this paper we discuss how blind pathology can be incorporated and suggest a procedure to recover the "total tumor" aspect. It is emphasized that these modifications should be regarded as a starting point for further discussion and that we encourage comments from all interested scientists.

[Metabolism of m-xylene in rats after administration of chlorinated hydrocarbons (author's transl)]

Male albino rats of the Donryu strain were divided into 4 groups: the normal control group, tetrachloromethane (CCl4, TCM) group, tetrachloroethylene (CCl2 = CCl2, PCE) group and trichloroethylene (CHCl = CCl2, TCE) group. Each group was consisted of 6 animals. TCM, PCE and TCE were administered orally at a dosage of 13 mmoles/kg as a 50% v/v olive oil solution to rats 24 hours prior to an oral administration of m-xylene (8.2 mmoles/kg as a 50% v/v olive oil solution). The normal control group was administered only olive oil (2.5 ml/kg) 24 hours prior to m-xylene dose. Urine was collected 24, 48, 72 and 96 hours after administration of m-xylene. The urine was analysed for m-methylhippuric acid (m-MHA) by the paper chromatographic method of Ogata et al. The results obtained were as follows: 1) Total urinary excretion of m-MHA in the normal control group was equivalent on a molar basis to about 58% of m-xylene received, and the major portions of the metabolites were excreted on the 1st day. 2) In TCM group, total urinary excretion of m-MHA was about a half of that in the normal control group. It was equivalent on a molar basis to about 30% of m-xylene received (p less than 0.01), and the urinary excretion of m-MHA on the 1st day was significantly less than those of the normal control group (p less than 0.001) and TCE group (p less than 0.05). 3) In PCE group, urinary excretion of m-MHA on the 1st day was significantly less than that of the normal control group (p less than 0.01) and the excretion was delayed. 4) In TCE group, total urinary excretion of m-MHA was slightly but not significantly less than that of the normal control group (p less than 0.05). 5) In TCM-ip group of rats which were given TCM orally 24 hours prior to the administration of m-xylene by intraperitoneal injection, urinary excretion of m-MHA on the 1st day and in 4 days after administration of m-xylene was less than that of the control-ip group.

Trichloroethylene and 1,1,1-trichloroethane: effects on brain and liver after five days intermittent inhalation

The inhalation exposure of adult male rats to 7.9 mumol/l (200 ppm) of trichloroethylene for 4 days 6 h each day led to an accumulation of the solvent in the perirenal fat 17 h after the last exposure. Exposures to 20 mumol/l (500 ppm) of 1,1,1-trichloroethane caused similar accumulation. The latter rats presented no changes in their behaviour in an open-field test whereas the motor behaviour of the animals exposed to trichloroethylene was more active in comparison to controls 1 h after the exposure on the 4th day. Trace effects of trichloroethylene on emotional behaviour of the same rats could be seen 17 h after the last exposure. Further exposures on the 5th day increased brain, liver, lung and blood contents of trichlorethylene and 1,1,1-trichloroethane. A slight decrease in brain RNA content was found in the 1,1,1-trichloroethane exposed rats while RNA decreased significantly after the fifth day of trichloroethylene inhalation. The exposure to 1,1,1-trichloroethane on the 5th day depressed also the microsomal cytochrome P-450 content in liver of rats whereas trichloroethylene increased the hemochrome content slightly at the same time.

Carcinogenicity of trichloroethylene: fact or artifact?

Technical trichloroethylene has been found carcinogenic in mice after high daily doses per os. A GC-MS analysis of this technical sample revealed the presence of considerable amounts of epichlorohydrin and 1.2-epoxibutane as stabilizers. These epoxides are highly mutagenic in the Ames test and are, most probably, responsible for the carcinogenic effect found in mice. The question whether trichloroethylene is carcinogenic or not remains open.

Proposed biological threshold limit values for industrial exposure to trichloroethylene vapor

A model was used for the simulation of the pharmacokinetics of inhaled trichloroethylene (TRI) vapor. Computed data of TRI in alveolar air and of trichloroacetic acid (TCA) and trichloroethanol (TCE) in blood and urine agreed satisfactorily with experimental results obtained by various authors. Biological threshold limit values were calculated for subjects exposed at rest to a steady concentration of 100 ppm of TRI in ambient air, between 0800 and 1200 and between 1300 and 1700, five days week during the whole year. The Monday to Friday range of values for urinary excretion (243--322 mg of TCA/24 h and 288--429 mg of TCE/24 h) roughly corresponded to the findings of several surveys among TRI workers in industry. The hypnotic effect of TCE and/or TRI during steady or fluctuating industrial TRI exposure was discussed with the aid of the model.

Mechanisms of chronotropic effects of volatile inhalation anesthetics

The chronotropic effects of all currently available volatile anesthetics were investigated in isolated rat atrial preparations. Anesthetic ethers, diethyl ether, methoxyflurane, and enflurane elicited a dose-dependent positive chronotropic effect. Fluroxene produced a slight depression at low concentrations. The halogenated hydrocarbon anesthetics, halothane, chloroform, and trichloroethylene, did not show a uniform pattern. Halothane's effect was small and biphasic. Chloroform caused a dose-dependent decrease in heart rate, and trichloroethylene caused a marked positive chronotropic effect. The dose-response curves in all anesthetics remained unaltered in the presence of either 3 x 10(-7) M dl-propranolol or 1 x 10(-6) M atropine. It is concluded that volatile anesthetics elicit significant direct chronotropic actions on rat atrial preparations. The mechanism of their actions does not involve stimulation of beta-adrenergic or cholinergic receptors.

Trichloroethylene-induced deactivation of cytochrome P-450 and loss of liver glutathione in vivo

Liver microsomal enzyme activities and glutathione (GSH) contents of fasted male rats pretreated with phenobarbital (PBT) or vehicle controls were measured during and after exposure to trichloroethylene (TRI) (1% x 2 hr). TRI caused morphologic liver injury only in the pbt animals. Cytochrome P-450 and b5 contents were diminished by the end of the first hr of TRI exposure and NADH-cytochrome c reduction increased three-fold by eight hr in the PBT animals. The only change in vehicle animals exposed to TRI was a decrease in NADPH-cytochrome c reductase activity by eight hr. Hepatic GSH contents of vehicle animals, constant during TRI exposure, rose with time. In contrast, in PBT animals, hepatic GSH contents decreased during TRI exposure and then rebounded. Decreases in GSH were most profound in the microsomal fraction. When fed animals with approximately two-fold higher hepatic GSH levels than fasted animals were exposed to TRI, they had shorter anesthesia recovery times and less liver injury, although excreting similar or slightly more trichlorinated metabolite into their urine in 24 hr than their fasted counterparts. We suggest that the hepatoxic effects of trichloroethylene are caused by inadequate detoxification of its reactive intermediates.

Cardiorespiratory effects of outpatient anesthesia for oral surgery: trichloroethylene-halothane

The cardiorespiratory effects of trichloroethylene supplementation of nitrous oxide-oxygen anesthesia, with simultaneous use of halothane at induction as needed, were studied in outpatient oral surgery patients undergoing dental extractions under general anesthesia. The technique produced no deleterious cardiovascular effects that could be attributed to the combined use of these agents. Elevations of blood pressure, stroke volume, and peripheral resistance indicated light anesthesia. The versatility of halothane combined with the absence of nephrotoxic and hepatotoxic breakdown products of trichloroethylene provides a satisfactory technique for outpatient oral surgery. The agents appear pharmacologically complimentary in that halothane lacks analgesic properties and postoperative shivering occurs, while induction with trichloroethylene is slow and tachypnea is a problem.

General anaesthetics and the acetylcholine-sensitivity of cortical neurons

1The effects of general anaesthetics on neuronal responses to iontophoretically-applied acetylcholine have been examined in slices of guinea-pig olfactory cortex maintained in vitro. 2 Acetylcholine excited 61% of the prepiriform neurones tested. The excitation was blocked by atropine, but not by dihydro-beta-erythroidine or gallamine. 3 Alphaxalone reversibly depressed the acetylcholine-sensitivity of prepiriform neurones. Pentobarbitone did not consistently depress the acetylcholine sensitivity of these cells. 4 Ether, methoxyflurane, trichloroethylene and halothane caused a dose-related augmentation of acetylcholine-induced firing. 5 These results show that general anaesthetics do not necessarily depress the sensitivity of nerve cells to all excitatory substances and that different anaesthetics may affect a particular excitatory process in various ways.