Acute and subacute inhalation toxicity studies of a new broad spectrum insect repellent, N,N-diethylphenylacetamide

N,N-Diethylphenylacetamide (DEPA) is an inexpensive, long-acting and broad spectrum insect repellent. The acute LC50 for a 4-h exposure of DEPA aerosol was found to be 1.451 mg l-1 (1.290-1.633) in male and 1.375 mg l-1 (1.307-1.447) in female rats. DEPA did not cause delayed deaths. Acute exposure to 0.9 LC50 revealed that liver might be a target organ for DEPA toxicity. On subacute exposures to 0.2, 0.6 and 0.8 LC50 for 6 h per day, 5 days a week for 2 weeks, there was no significant change in the 0.2 LC50 group, as evaluated by the body weight gain and organ body weight ratio. The minimal changes observed in the 0.6 LC50 group were of reversible type as the animals recovered on cessation of exposure. A massive concentration of 0.8 LC50 produced lethal effects. The study shows that DEPA has a low mammalian toxicity by inhalation as was found earlier with cutaneous application of the insect repellent.

Spontaneous pneumothorax in metastatic choriocarcinoma

We report a case of spontaneous bilateral pneumothoraces due to metastatic choriocarcinoma. The patient was successfully treated with tube thoracostomy and chemotherapy. Pneumothorax as a complication of choriocarcinoma has not been reported previously.

Dermal intoxication of mice with bis(2-chloroethyl)sulphide and the protective effect of flavonoids

The influence of dermal application of sulphur mustard (SM) on hepatic lipid peroxidation and the protective effect of flavonoids in SM toxicity was investigated. SM applied on the skin of mice (0.25 or 0.5 LD50) depleted glutathione (GSH) in blood and liver. Malondialdehyde (MDA) levels in the liver showed an increase indicating lipid peroxidation. Administration of vitamin E or two flavonoids, gossypin (GN) and hydroxyethyl rutosides (HR) after dermal application of SM did not alter depletion of GSH but did reduce the MDA level significantly. Survival time of mice with 1 LD50 SM applied dermally was increased by GN and HR to a greater extent than by vitamin E or sodium thiosulphate probably due to one or more of the analgesic, anti-inflammatory, antihepatotoxic, antihistaminic, mast cell stabilization, lipid peroxidation inhibitory and free radical scavenging actions of the flavonoids. The present study indicates that dermally applied SM can induce lipid peroxidation and GSH depletion, and flavonoids may be beneficial in reducing the toxicity.

Sarcoidosis presenting as recurrent left laryngeal nerve palsy

A patient with sarcoidosis presented with hoarseness caused by mediastinal lymph nodes compressing the left recurrent laryngeal nerve. The response to corticosteroids was dramatic and complete.

The effect of pyridostigmine and physostigmine on acute toxicity of diisopropyl fluorophosphate in rats

Diisopropyl fluorophosphate (DFP) given to rats in lethal concentration (100 mg/m3, by inhalation for 40 min) significantly inhibited acetylcholinesterase activity in the blood, lung, liver and brain, and induced hyperglycaemia and glycogen mobilization in the liver, diaphragm and brain. Pretreatment (maximum sign-free dose) with carbamates, pyridostigmine (0.075 mg/kg, i.m.) or physostigmine (0.1 mg/kg, i.m.) 15 min before exposure to DFP, modified the inhibited acetylcholinesterase activity only in peripheral tissues. However, the hyperglycaemia and glycogen depletion induced by DFP inhalation were not modified by carbamate pretreatment. The time of survival of DFP exposed animals increased after pretreatment with carbamates, more after physostigmine (81 min) than after pyridostigmine (59 min). The animals exposed to DFP exhibited severe tremors and convulsions as compared to the animals pretreated with carbamates.

DFP induced changes in acetylcholinesterase activity and glycogen level in certain brain regions of mice

DFP in acute dose (2 mg/kg i. p.) in mice significantly inhibited acetylcholinesterase AChE) activity in five regions of brain i.e. cerebral cortex, corpus striatum, medulla, cerebellum and hypothalamus. The inhibition was accompanied by depletion of glycogen from these regions 1 hr after DFP administration. The inhibition of enzyme activity was more in corpus striatum and medulla and glycogen depletion was more in cerebral cortex in comparison to other regions of the brain. These changes may be due to stimulatory effect of DFP on these regions of brain in mice.

Non-specific cardiovascular depressant effect of methyl isocyanate (MIC) in rats

Methyl isocyanate (MIC) either inhaled (5, 10 mg/lit) or administered by intravenous (5, 10, 28 mg/kg) or subcutaneous (1300, 1500 mg/kg) routes produced a dose dependent fall in blood pressure (BP) and heart rate (HR) in anaesthetised rats. Higher doses (10 mg/lit inhalation, 10 & 28 mg/kg i.v., 1500 mg/kg s.c.) increased the lung body weight index (LBI) and tracheobronchial resistance (TBR) concomitant with gross pulmonary damage and edema. However, lower doses (5 mg/lit inhalation, 5 mg/kg i.v., 1300 mg/kg s.c.) produced the cardiovascular depressant effect without affecting LBI, lung morphology and TBR. The effects of MIC on BP, HR and TBR were not counteracted by muscarinic, histaminic and 5-HT receptor blockers and by vagotomy. Studies with hydrolysis products of MIC showed that relatively large doses of methylamine (MA) and dimethylurea (DMU) (i.v.) produced cardiovascular depressant effects, without affecting the LBI & TBR. The results indicate that the cardiovascular depressant effect of MIC may not be entirely a sequel to its effect on respiratory organs, release of vasoactive substances or its hydrolysis products. A non-specific cardiovascular depressant effect of MIC is suggested.

Effect of subacute exposure to methyl isocyanate on testicular histomorphology in mice

Mice exposed to methyl isocyanate (MIC; 134 mg.m-3 for 30 min = 4020 mg.min-1.m-3) showed a marked loss of body weight after 24 hr and the mean body weight of the exposed group was significantly less than the control, even 15 days after the exposure. No significant change was observed on relative testicular weight. Spermatozoa in the seminiferous tubules disappeared 3 days post exposure. Primary and secondary spermatocytes were hypertrophied. Normalization occurred after 15 days.

Gas chromatographic studies of the carbamylation of haemoglobin by methyl isocyanate in rats and rabbits

Carbamylation of the N-terminal valine of haemoglobin with methyl isocyanate in rats and rabbits has been demonstrated in vitro and in vivo by gas chromatography. N-Methylcarbamylated haemoglobin, converted by cyclization into 3-methyl-5-isopropylhydantoin, has been quantified by gas chromatography. Standard hydantoin was synthesized, chemically characterized and used for calibration. The method is simple and reliable in the concentration range 0.06-2 nmol. Carbamylation of haemoglobin by methyl isocyanate in vivo in rats can be identified only above a dose of 1.05 mg/l in inhalation exposures. It is inferred that methyl isocyanate in the "active" form crosses the alveolar and erythrocyte membranes and carbamylates the haemoglobin.