Immediate post-dosing paralysis following severe soman and VX toxicosis in guinea pigs.

There have been numerous studies of the central nervous system (CNS) involvement in organophosphate (OP) poisoning showing status epilepticus and/or 'electrographic seizures'. Brain damage has been demonstrated as 'neuronal necrosis' primarily in the cortex, thalamus and hippocampus. To the authors' knowledge there have been no reports of partial/total paralysis following close upon OP exposure although delayed paralysis has been reported. This report summarizes the immediate, OP induced paralytic events recorded in guinea pigs during development of the Canadian reactive skin decontaminant lotion (RSDL). As part of the development work, supra-lethal cutaneous doses of OP were applied to large numbers of guinea pigs followed by decontamination with the RSDL or predecessor lotions and solvents. Soman (pinacolyl methylphosphonofluoridate; GD) challenges were applied to 1277 animals and S-(2-diisopropyl-aminoethyl) methylphosphorothiolate (VX) challenges to 108. The classic sequence of clinical signs--ptyalism, tremors, fasciculations, convulsions, apnea and flaccid paralysis before death--was seen in the 658 animals that died and in many of the survivors. Eighty-four of 688 survivors of GD and 4 of 39 survivors of VX showed random paralysis of various distal regions following recovery from an insult which produced convulsions and/or flaccid paralysis. Because the experiments were designed to assess the decontamination procedures, there were no apparent relationships between the amounts of OP applied and the sequellae recorded. The observations of paralysis were also incidental to the prime focus of the experiments. Because of this, only ten animals paralysed following GD exposure were examined for histological effects. The pathologist diagnosed 'encephalomalacia' and 'focal necrotic lesions' in the cerebral cortex and 'focal necrotic lesions' in one spinal cord. Of the 84 guinea pigs paralysed after GD challenge, one was not decontaminated and the decontaminants used on the remainder were sufficiently varied that there appeared to be no relationship between the type of decontaminant and the resulting paralysis.

GB toxicity reassessed using newer techniques for estimation of human toxicity from animal inhalation toxicity data: new method for estimating acute human toxicity (GB).

Estimated human inhalation toxicity values for Sarin (GB) were calculated using a new two independent (concentration, exposure time), one dependent (toxic response), non-linear dose response (toxicity) model combined with re-evaluated allometric equations relating to animal and human respiration. Historical animal studies of GB toxicity containing both exposure and fractional animal response data were used to test the new process. The final data set contained 6621 animals, 762 groups, 37 studies and 7 species. The toxicity of GB for each species was empirically related to exposure concentration (C; mg m(-3)) and exposure time (T; min) through the surface function Y = b0 + b1 Log10C + b2 Log10T or Y = b0 + b2 Log10C(n)T where Y is the Normit, b0, b1 and b2 are constants and n is the 'toxic load exponent' (Normit is PROBIT - 5). Between exposure times of 0.17 and 30 min, the average value for n in seven species was 1.35 +/- 0.15. The near parallel toxic load equations for each species and the linear relationship between minute volume/body weight ratio and the inhalation toxicity (LCt50) for GB were used to create a pseudo-human data set and then an exposure time/toxicity surface for the human. The calculated n for the human was 1.40. The pseudo-human data had much more variability at low exposure times. Raising the lower exposure limit to 1 min, did not change the LCt50 but did result in lower variability. Raising the lower value to 2 min was counterproductive. Based on the toxic load model for 1-30 min exposures, the human GB toxicities (LCt01, LCt05, LCt50 and LCt95) for 70 kg humans breathing 15 l min(-1) were estimated to be 11, 16, 36 and 83; 18, 25, 57 and 132 and 24, 34, 79 and 182 mg x min m(-3) for 2, 10 and 30 min exposures, respectively. These values are recommended for general use for the total human population. The empirical relationships employed in the calculations may not be valid for exposure times >30 min.

Inhalation toxicity in mice exposed to sarin (GB) for 20-720 min.

Most of the historical data for the toxicity of sarin (GB) was collected for exposure times of <10 min in attempts to establish the utility of and defence against this agent in offensive military use. However, information concerning the toxicity of GB (and other nerve agents) from longer exposures of 1-12 h is critical for all personnel who must work in or close to low-level concentrations of chemical for extended periods and for all personnel, dressed in Individual Protective Equipment, who need to know when, and if, it is safe to take off these cumbersome garments.The data presented for the toxicity of GB to mice for whole-body exposures of 20 min to 12 h are intended to form part of an ongoing, multi-species effort aimed at establishing toxicity estimates for humans for these longer exposure times: LCT50 values of 430, 540, 900, 1210 and 2210 mg.min m(-3) or LC50 values of 21.5, 9.0, 5.0, 3.4 and 3.1 mg m(-3) were obtained for mice for 20-, 60-, 180-, 360- and 720-min exposures to GB, respectively. The data for longer exposures do not follow Haber's rule (LCT50=CT). The 20- and 60-min data fit the 'toxic load model' involving CnT that was established previously from historical data for 0.17-30 min GB exposures to mice. The LCT(50) and LC50 values for 3, 6 and 12 h are progressively higher (toxicity lower) than predicted by either Haber's rule or the toxic load model.

Allometric respiration/body mass data for animals to be used for estimates of inhalation toxicity to young adult humans.

The relationship between body weight (BW) and respiratory minute volume (V(m)) was reviewed by collecting a database from the literature. The data were separated into anaesthetized and non-anaesthetized groups. Only young adult terrestrial mammals were included in the final data set. This database is the largest to be reported to date, is the first to separate the anaesthetized and non-anaesthetized groups and is matched to the target population of young, fit adult humans. The data set of non-anaesthetized animals contained 142 studies representing 2616 animals and 18 species from mice at 12 g body weight to horses and a giraffe at ca. 500 kg body weight. Analysis of the data indicated a power law (allometric) relationship between the minute volume and body weight. The resulting allometric equations for the empirical relationship between minute volume and body weight are: log(10)V()(m)= -0.302 + 0.809 log(10)BW and V(m) = 0.499 BW(0.809)where V(m) is the minute volume (l min(-1)) and BW is the body weight (kg). From these equations, a minute volume of 15.5 lmin(-1)was obtained for a 70 kg human in the same physiological and/or emotional state as the animals. The results of the analyses were compared to other empirical studies in the literature, the more recent of which also indicated a scaling factor of 0.8. The relationship between minute volume and body weight is recommended for use in estimating the inhalation toxicity to young adult humans (military personnel), because this is the first study to use a large database focused exclusively upon non-anaesthetized young adult terrestrial mammals.

Efficacy of an oximate-based skin decontaminant against organophosphate nerve agents determined in vivo and in vitro.

Recent Canadian research efforts have been directed towards the development of a reactive skin decontaminant (RSD) lotion active against classical nerve agents and mustard. The formulation presently under study consists of a 1.25 molal solution of potassium 2,3-butanedione monoximate (KBDO) in polyethylene glycol methylether 550. Although this formulation has shown good efficacy, concern has been expressed as to the potential toxicity of the reaction products of KBDO and organophosphate (OP) nerve agents. This report details the high efficacy of this lotion in inactivating OPs as measured by the systemic toxicity of the OP/RSD mixtures in rats. In addition, primary cultures of chick embryo neurons were also used to test the efficacy of the RSD. By relating the anticholinesterase activity in these cultures of the OP/RSD mixture to that of pure OP standards, a sensitive measure of the value of the RSD in inactivating tabun, sarin, soman and VX was obtained. Experiments with all four nerve agents in this in vitro system provided a good correlation with the in vivo data, and also indicated that the inactivation process was time- and agent-dependent and also related to the ratio of OP to RSD.

Seasonal changes in the plasma isoenzymes of lactate: NADH oxidoreductase in Hereford cows under range conditions.

Plasma levels of lactate: NADH oxidoreductase (LD) and the proportions of five major isoenzymes were estimated in samples taken in January, March, June, July and November from Hereford cows kept under range conditions. Seasonal changes were observed in both total LD and the proportions of the isoenzymes. Levels of total LD and all isoenzymes were low in winter and high in summer. Proportions of LD4 and LD5, the electrophoretically slow isoenzymes which predominate in muscle, increased in summer at the expense of LD1, the fast isoenzyme which predominates in liver and erythrocytes. LD1 was increased in November, at the time when other isoenzyme levels were decreasing from summer high levels. The seasonal changes observed in plasma LD were attributed to changes in diet and/or water supply and activity of the range cows.

Excess rumen product anions in cattle. I. Blood clearance rates and reduced liver function from sublethal doses of volatile fatty acids, lactate and succinate.

Blood clearance rates of volatile fatty acids, lactate and succinate were estimated in cattle following a single rapid intravenous injection of a Na-anion solution. Bromosulfophthalein was administered immediately before the anion to monitor the effects upon liver function, blood circulation, and dose equilibrium. Acetate, propionate, and valerate at doses up to 5 mmole/kg were cleared quickly from the blood by a first-order process without effects either upon the animal or bromosulfophthalein clearance. Injection of acetic acid solutions produced no effects. Butyrate was toxic at doses above 1 mmole/kg and progressively affected both the rate and progress of bromosulfophthalein clearance as the dose increased. Lactate and succinate were toxic and lethal at doses around 0.25 mmole/kg, and caused both reduced rates and altered progress of bromosulfophthalein clearance. The toxic reactions resulted in total collapse from loss of muscle tone. The butyrate and lactate effects were accentuated when the anion solutions were injected at low pH where a large portion of the anion would be unionized. Levels of butyrate, lactate and succinate in the rumens of feedlot cattle were high enough to provide toxic doses of these anions. The results are discussed in terms of the effects of excess rumen production of these anions upon the liver function and health of feedlot cattle.

Excess rumen product anions in cattle. II. Toxic and lethal effects with butyrate.

Toxicity to butyrate was observed in 100-250 kg male Holstein calves following intravenous injection of 0.7-3.6 mmole/kg body weight, intravenous infusion with 0.12-0.53 mmole/min/kg body weight and intraruminal dosage with 19.4 mmole/kg body weight butyrate. Lower doses produced ataxia and serous nasal discharge. Higher doses produced sudden flaccid paralysis and death from asphyxia. No postmortem lesions, gross or histological, were observed. Plasma K+ was reduced to 2.2-2.5 mEq/L. When infusions were stopped, rapid recovery preceded clearance of butyrate and low K+ remained. Nerve depolarization in the central nervous system may be the cause of the toxic effects. Butyrate acidosis is suggested as a factor in unexplained sudden deaths in ruminants.

Sources of normal variation of plasma l-aspartate:2-oxoglutarate aminotransferase in Hereford range cattle.

1. Plasma levels of L-aspartate:2-oxoglutarate aminotransferase (AST) were estimated in Hereford cattle, 1 month to 12 years of age, kept under range conditions and in a group of Hereford x Angus cows kept on the same range. 2. Plasma levels of AST were estimated in a group of Crossbred cows and their calves fed a constant diet and kept in individual pens in the same geographic area as the Herefords. 3. Seasonal changes in mean plasma AST were observed in the Herefords corresponding with the change from dry winter grasses/hay and well water to fresh spring and summer grasses and slough water. No seasonal changes were observed in the Crossbreds given a constant dry diet and city water. 4. Plasma AST increased with age in calves 1 to 12 months of age in the Herefords but not in the Crossbreds. Mean plasma AST did not change with age in any of the adult cattle studied. 5. Small increases in plasma AST corresponding to increases in ambient temperature above - 12 degrees C were observed in the Crossbreds. 6. An increase in plasma AST was observed near the time of first ovulation in the confined cows. 7. No relationship could be demonstrated between plasma AST and sex, breed or time to parturition in the range cattle. Breed differences were observed in the Crossbred cows.

Sources of normal variation of plasma lactate dehydrogenase in range cattle.

1. Plasma levels of lactate dehydrogenase (LD) were estimated in Hereford cattle of 1 month to 12 yr of age kept under range conditions. 2. Plasma levels of LD were estimated in a group of confined cows and their calves fed a constant diet and kept in individual pens in the same geographic area as the range Herefords. 3. Large seasonal changes in mean plasma LD were observed in the range cattle but not in the confined, constant diet group. The seasonal changes corresponded with the appearance of new growth on the range. 4. Changes in plasma LD were observed at weaning time in the range cattle but not in the confined group. 5. Sex had no effect upon plasma LD levels in the juvenile animals of either group. No comparison of adult animals could be made. 6. Mean plasma LD levels did not change with age but the seasonal effect decreased in magnitude as the animals matured. 7. An increase in plasma LD was observed around the first ovulation in the confined animals. 8. A decrease in plasma LD was observed during parturition in the confined group.

Anorexia as the probable cause of plasma alpha-lipoprotein changes seen in avian erythroblastosis.

The plasma alpha-lipoprotein bands seen on starch-gel electrophoresis are progressively split and retarded as avian erythroblastosis progresses. Similar changes may be produced in normal birds by starvation, and by pair-feeding methods. Anorexia appears to be a major cause, if not the total cause, of the plasma alpha-lipoprotein changes seen in erythroblastosis.