Vestibulo-oculomotor disturbances caused by industrial solvents

Animal experiments show that intoxication with hydrocarbon solvents influences the vestibulo-oculomotor reflex arc and indicate that the solvents block the inhibition of the vestibulo-oculomotor reflex presumably exerted by the cerebellum. The blood concentrations necessary to elicit oculomotor disturbances in animals were smaller than those that disturbed the vestibular function. Accordingly, in human experiments styrene and toluene exposure did not elicit any positional nystagmus but caused an increased saccade speed and a diminished visual suppression of vestibular nystagmus. Some cerebellar clinical pathologic process in patients who suffer from a psycho-organic syndrome caused by solvents leads us to believe that the cerebellum might be the most vulnerable part of the brain. Some patients had a positional nystagmus, but the most prominent pathologic signs were elicited by the visual suppression test. Our findings compare well with the increased saccade speed and diminished visual suppression in patients with cerebellar tumors and infarctions.

In vivo and in vitro mutagenicity studies of a possible carcinogen, trichloroethylene, and its two stabilizers, epichlorohydrin and 1,2-epoxybutane

In vivo and in vitro methodologies that have employed the yeast Schizosaccharomyces pombe as genetic indicator have been utilized to investigate the mutagenicity of two trichloroethylene (TCE) samples of pure and technical grade. Mutagenicity assays were also performed on two stabilizers contained in the technical grade sample: epichlorohydrin and 1,2-epoxybutane. In the in vitro studies a metabolic conversion system was supplied by liver homogenate (S-9) from mice and rats untreated and pretreated with phenobarbital and/or beta-naphthoflavone. Up to highly toxic doses of TCE were applied to growing and stationary-phase yeast cells. In the in vivo studies two different host-mediated assays, intrasanguineous and intraperitoneal methodologies, were performed on different mice breeds treated by oral administration. Epichlorohydrin and epoxybutane were tested singly or combined in a mixture of the same ratio as in the technical grade TCE sample. Both TCE samples gave negative results for in vivo and in vitro assays, whereas the two contaminants were found mutagenic only in vitro. The high toxicity of the technical TCE sample did not allow us to reach concentrations containing effective levels of its two additives.

Antibody elution from red blood cells by chloroform and trichloroethylene

Antibody elution by chloroform and trichloroethylene was compared with the Rubin ether method modified by Hughes-Jones for IgG antibodies and the Landsteiner and Miller heat method for IgM antibodies. After washing the cells, the chloroform and trichloroethylene method was done at 37 degrees C for 10 minutes. With this technique the eluate remained on the upper layer above the red blood cell stroma layer, while with Rubin's method the eluate remained below the cell stroma. The reported technique was as effective as the Landsteiner and Miller heat method for IgM antibodies, and a double volume of eluate was obtained.

Epinephrine-induced cardiac arrhythmias in rabbits exposed to trichloroethylene: potentiation by caffeine

Approximately 200 000 industrial workers are exposed to trichloroethylene in the United States. Individuals intoxicated with trichloroethylene are known to develop cardiac arrhythmias. Caffeine is known to be a cardiac stimulant and is one of the drugs most widely used by the American population. Therefore, it was of interest to study the effect of caffeine on the arrhythmogenicity of trichloroethylene. Rabbits were treated with a vehicle control (1 mL/kg, ip) or caffeine (10 mg/kg, ip, 30 minutes prior to exposure) and exposed for one hour to 6000 ppm trichlorethylene under dynamic airflow conditions. Epinephrine was infused until arrhythmias occurred after 7.5, 15, 30, 45 and 60 minutes of exposure and also 15 and 30 minutes post-exposure. Serial blood samples were collected at these time points and analyzed for trichloroethylene and the two major metabolites, trichloroethanol and trichloroacetic acid. Rabbits treated with caffeine and exposed to trichloroethylene developed more arrhythmias in response to epinephrine than rabbits exposed to trichloroethylene alone, and the arrhythmias occurred sooner and in response to lower doses of epinephrine. Caffeine treatment had no effect on trichloroethylene blood concentration, but significantly decreased trichloroethanol blood levels after 45 and 60 minutes of exposure to trichloroethylene. Caffeine also reduced blood levels of trichloroacetic acid. The data indicate that caffeine can potentiate the arrhythmogenicity of trichloroethylene in rabbits.

The fibrinolytic effects of anaesthesia

The fibrinolytic effects of six different anaesthetic agents were studied in 36 patients undergoing abdominal hysterectomy. Fibrinolytic activity was measured by dilute whole blood and euglobulin clot lysis times. Concentrations of plasminogen, fibrinogen and fibrin degradation products were also determined. Significant enhancement of fibrinolytic activity, measured as a decrease in clot lysis time, was seen during anaesthesia and surgery with all agents studied. Halothane produced the least effect and the greatest increase in fibrinolytic activity was seen during trichloroethylene anaesthesia. Lumbar extradural anaesthesia also consistently produced enhancement of fibrinolysis. The reasons for these results and their clinical implications are discussed.

Bordetella pertussis-induced hyperinsulinaemia without marked hypoglycaemia: a paradox explained

B. pertussis vaccine or pulmonary infection produced marked hyperinsulinaemia in mice relative to controls (e.g. control 32 mU/1; B. pertussis infected 113 mU/1). This was associated with a modest relative hypoglycaemia (15-25%). The hyperinsulinaemia was observed only when blood was collected from mice anaesthetized with ether, pentobarbitone, or trichloroethylene but not from unanaesthetized animals. Ether-induced hyperinsulinaemia in B. pertussis was transient. Adrenaline produced marked hyperinsulinaemia in B. pertussis-infected mice whereas it tended to produce hypoinsulinaemia in control animals. The hyperinsulinaemic effect of ether anaesthesia in B. pertussis-infected mice was significantly reduced by beta-adrenoceptor blockade using propranolol. It is suggested (a) that pertussis-infected or vaccinated mice are not chronically hyperinsulinaemic but show elevated insulin concentrations only when subjected to an additional stimulus; (b) that hyperinsulinaemia produced by anaesthesia in pertussis-treated mice is secondary to an altered responsiveness of the insulin-secreting cells to this stimulus; (c) that part of this stimulus may be due to catecholamines released during anaesthesia.

DNA damage by haloalkanes in human lymphocytes cultured in vitro

The DNA damaging activity of 7 haloalkanes was studied in a short-term in vitro system which utilized human lymphocytes. The parameters studied were the inhibition of scheduled (duplicative) and unscheduled (reparative) DNA syntheses seen as tritiated thymidine uptake. The results obtained suggested that chloromethyl methyl ether (CMME), 1,2-dibromoethane (DBE), trichloroethylene (TCE) and 1,2-dichloroethane (DCE) gave positive results such as DNA damaging agents, while carbon tetrachloride (CTC), chloroform (TCM) and dichloromethane (DCM) gave low or negative results.

Trichloroethylene: effects on body and organ weights in mice, rats and gerbils

The influence of continuous inhalation of 150 ppm trichloroethylene (TCE) on body, liver, spleen, and kidney weights in rats, mice, and mongolian gerbils was tested. An age dependent decrease in body weight gain was observed in female rats exposed to TCE. All 3 species showed liver enlargement caused by the exposure. The effect was much more pronounced in mice, in which the increase was 60--80%, than in rats and gerbils where it was only 20--30%. After the end of the TCE-exposure the liver weights of the mice decreased rapidly. After 5 days of rehabilitation the weight was only 10--20% higher than that of the controls. This difference persisted for at least 25 days. The spleen weight appeared unaffected or somewhat smaller in TCE-exposed animals of all species. An increased kidney weight (15%) was observe din TCE-exposed gerbils. This effect was less pronounced in mice and rats. Effects on the liver have earlier been seen only after exposure to concentrations much higher than that used in the present study. This difference in results is proposed to be due to the different schedules used for the exposure.

Mutagenic activity of vinyl compounds and derived epoxides

Many vinyl compounds, such as vinyl chloride and some inhalational anesthetics, are known to be mutagens. In the present study, 10 vinyl compounds or derived epoxides, widely used in industry, were assayed in the Salmonella typhimurium/mammalian microsome system. 3 strains of histidine-dependent S. typhimurium, TA1535, TA98 and TA100 were used. Of the 10 compounds, 4 were mutagens. They were 9-vinylanthracene, vinylcarbazole, 3-vinyl-7-oxabicyclo[4.1.0]heptane and 3-epoxyethyl-7-oxabicyclo[4.1.0]-heptane. The study confirmed the overall genotoxicity of vinyl compounds and epoxides and the need to carefully screen them for mutagenic/carcinogenic effects.

[Use of the D7 strain of S. cerevisiae in the determination of environmental risk. 1. Genetic effects of trichloroethylene]

Trichloroethylene (TCE) was tested for its ability to induce both point mutation and mitotic gene conversion in diploid strain of yeast. S. cerevisiae (strain D7) was tested for both activities in culture with and without a mammalian microsomal activation system and intrasanguinous host-mediated assay in mice. In suspension test with D7, TCE was genetically active only with microsomal activation. In vivo 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 genetic effects.

Day case anaesthesia and memory

Two simple anaesthetic techniques were administered to forty healthy women undergoing minor gynaecological surgery. There was a significantly shorter immediate recovery period following the use of a fentanyl and methohexitone technique. Memory function testing revealed an impairment of the ability to retain new information following anaesthesia. This returned to normal within 3 hr.

Normocapnic anaesthesia with trichloroethylene for intraocular surgery

Measurements of intraocular pressure (IOP) by applanation tonometry in twelve patients undergoing lens extraction showed that a normocapnic anaesthetic technique using 0.4% trichloroethylene with controlled ventilation of the lungs (IPPV) with large tidal volumes (14 ml/kg) reduced IOP by 13--20%. There was only a small reduction in arterial pressure. Normocapnia was easy to achieve by use of the single-limb co-axial Penlon (Bain type) anaesthetic breathing circuit in conjunction with an electrically-driven, small and inexpensive lung ventilator. The anaesthetic technique described using trichloroethylene is suitable for lens extraction surgery when it is desired to avoid a halothane anaesthetic for any reason.

Pattern of respiration and responses to carbon dioxide during trichloroethylene anaesthesia in the cat

Tidal volume (VT), minute ventilation (VE), the duration of inspiratats anaesthetized with 0.7%, 1% and 1.5% (inspired) trichloroethylene (TCE). The tracheal cannula was occluded at intervals at the start of inspiration and the tracheal pressure was measured to assess the force of contraction of the respiratory muscles. Anaesthesia with TCE 0.7% was associated with an increase in VE, a reduction in VT, and a marked increase in respiratory frequency and mean inspiratory flow rate, but PaCO2 values did not differ significantly from those in conscious animals. Ventilation was also greater than in conscious animals during anaesthesia with TCE 1%. TCE 1.5% caused a significantly greater PaCO2 than in conscious animals. All concentrations of TCE caused a reduction in the ventilatory response to carbon dioxide, measured by the steady-state method. Cervical vagal section did not abolish the tachypnoea caused by TCE.

Mutagenicity of inhalation anaesthetics: trichloroethylene, divinyl ether, nitrous oxide and cyclopropane

The mutagenic potential of trichloroethylene, divinyl ether, nitrous oxide and cyclopropane was assessed in vitro by microbial assay employing two histidine-dependent strains of Salmonella typhimurium, TA1535 and TA100. Anaesthetic agents in various concentrations were incubated with bacteria in the presence or absence of an enzyme system prepared from enzyme-induced rat liver. Nitrous oxide and cyclopropane were not mutagenic, whereas divinyl ether gave a strongly positive response. Results for trichloroethylene were equivocal. These and previous studies with the salmonella system, together with mutagenicity studies using different test systems, indicate that modern inhalation anaesthetic agents are unlikely to be mutagenic.

The influence of trichloroethylene and related drugs on the vestibular system

A previously described experimental model for studying the effect of industrial solvents on the vestibular system of rabbits has been applied to trichloroethylene. Estimation of trichloroethylene and its metabolites in blood and cerebrospinal fluid was performed by gas chromatography. Vestibular function was studied by recording nystagmus, induced by positional changes or accelerated rotation. At blood levels of trichloroethylene above 30 p.p.m. "positional nystagmus" develops. Two metabolites of trichloroethylene, chloral hydrate and trichloroethanol, which are known as central nervous system (CNS) depressants, did not induce this abnormal nystagmus. However, alpha-chloralose, a derivative of chloral hydrate, induced positional nystagmus and also a markedly exaggerated nystagmus developed during rotatory acceleration. It is suggested that solvents like trichloroethylene elicit vestibular disturbances by stimulation of central subcortical vestibulo-oculomotor connections. The stimulation may be caused by a blockage of inhibitory systems.