Factors in standardizing automated cholinesterase assays

A scientific panel assembled by the U.S. Environmental Protection Agency (EPA) determined that variability in cholinesterase (ChE) activities in the agency's pesticide/animal study database likely was due to a lack of accepted guidelines for ChE methodology. A series of trials was held in which participating laboratories measured ChE activity in blood and brain samples from untreated and pesticide-treated rats using a colorimetric assay method. The degree of inhibition of ChE activity in plasma and brain samples compared to controls was consistent among most of the laboratories. The ChE activity in erythrocyte samples differed more between laboratories due to a high blank, low erythrocyte AChE activity and hemoglobin absorption at the wavelength of the assay. Strategies are suggested for minimizing the variability of ChE activity in hemoglobin-rich samples.

Validity of a velodrome test for competitive road cyclists

The aim of this study was to evaluate the validity of a velodrome field test consisting of repeated rides of 2,280 m, with an initial speed of 28 km.h-1 and increments of 1.5 km.h-1 interspersed with 1-min recovery periods until exhaustion. A group of 12 male competitive road cyclists performed maximal cycling tests under velodrome and laboratory conditions. Velodrome oxygen uptake (VO2) and power output were estimated using equations previously published. Physiological responses to the two tests were compared. Relationships between performance in the velodrome and physiological parameters measured in the laboratory were studied. Maximal power output, heart rate and VO2 were similar in the velodrome and the laboratory [372 (SD 50) vs 365 (SD 36) W, 195 (SD 8) vs 196 (SD 9) beats.min-1 and 4.49 (SD 0.56) vs 4.49 (SD 0.46) l.min-1, respectively], while maximal velodrome blood lactate concentration was significantly higher [13.5 (SD 2.1) vs 11.8 (SD 3.1) mmol.l-1]. Velodrome heart rate was higher at submaximal exercise intensities representing 40%, 50% and 60% of maximal aerobic power, and velodrome blood lactate concentration was also higher at 60%, 70% and 80% of maximal aerobic power. The laboratory parameter that showed the highest correlation with the maximal cycling speed in the velodrome was maximal oxygen uptake (VO2max) expressed per unit of body mass (r = 0.93). In addition, the accuracy of different methods of estimation of the metabolic cost of cycling, rolling resistance, air resistance coefficients and VO2max were compared. Significant differences were found. In conclusion, the present results indicated the validity of a velodrome test used to estimate maximal aerobic parameters of competitive road cyclists, as long as the estimation is made using established equations. When road cyclists are tested in the laboratory, physiological values should be expressed per unit of body surface area or body mass, to predict more accurately the cyclist's performance level under specific field conditions.

Inhibition of rat brain phosphatidylinositol-specific phospholipase C by aluminum: regional differences, interactions with aluminum salts, and mechanisms

We have shown previously that aluminum chloride (AlCl3, 10-500 microM) inhibits hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) by phosphatidylinositol-specific phospholipase C (PI-PLC) in a concentration-dependent manner. In the present study, we characterize further the effects of aluminum on PI-PLC. A comparison of different brain regions and liver revealed varying basal PI-PLC specific activities, as well as differential susceptibility to inhibition by 100 microM AlCl3. The hippocampus had the highest specific activity of PI-PLC, followed by striatum, frontal cortex, cerebellum, and liver. PI-PLC inhibition by 100 microM AlCl3 was greatest in the liver, followed by cerebellum, hippocampus, cortex, and striatum. Moreover, 100 microM AlCl3 or aluminum lactate (Al (lac)) were similarly effective at inhibiting PI-PLC activity in rat cortical tissue. Addition of AlCl3 (100 microM) decreased PI-PLC activity at CaCl2 concentrations ranging from 0 to 2 mM; however, AlCl3 did not affect the shape of the calcium concentration curve, suggesting that aluminum does not inhibit PI-PLC activity by interference with the cofactor, calcium. AlCl3 (100 microM) did inhibit rat cortical PI-PLC hydrolysis of PIP2 in a competitive manner. These results demonstrate some regional/tissue differences in PI-PLC activity and its sensitivity to aluminum, and effects of AlCl3 and Al(lac) consistent with the effects previously noted in PI turnover in brain slices. Furthermore, our results suggest that competitive inhibition of PLC-mediated PIP2 hydrolysis by aluminum is a potential mechanism by which aluminum may cause the disruptions phosphoinositide signaling which have been reported following in vivo and in vitro exposure.

Maturational differences in chlorpyrifos-oxonase activity may contribute to age-related sensitivity to chlorpyrifos

Chlorpyrifos (CPF), a commonly used cholinesterase-inhibiting insecticide, is lethal at much lower doses to young animals than adults. To explain this higher sensitivity in younger animals, we hypothesized that young rats have less chlorpyrifos-oxonase (CPFOase) activity than adults. To test this hypothesis, CPFOase activity was measured in the brain, plasma, and liver of male, postnatal day 4 (PND4) and adult (PND90) Long-Evans rats. CPFOase is biochemically defined as a Ca(2+)-dependent A-esterase that hydrolyzes chlorpyrifos-oxon (CPFO), the active metabolite of CPE. No brain CPFOase activity was detected at either age. Plasma and liver CPFOase activities were markedly lower at PND4 compared to adult: PND4 plasma and liver CPFOase activities were 1/11 and 1/2 the adult plasma and liver activities, respectively. Because the Km of CPFOase activity was high (i.e., 210-380 microM), it was important to determine if this CPFOase activity could hydrolyze physiologically relevant concentrations (i.e., nM to low microM) of CPFO. This was accomplished by comparing the shifts in the tissue acetylcholinesterase (AChE) IC50 for CPFO in the presence or absence of CPFOase activity. One would expect an increase in the "apparent" IC50 if CPFOase hydrolyzes substantial amounts of CPFO during the 30 minutes the tissue is preincubated with the CPFO. In the adult, both plasma and liver AChE apparent IC50 values were higher in the presence of CPFOase activity, suggesting that the CPFOase in those tissues was capable of hydrolyzing physiologically relevant concentrations of CPFO within 30 minutes. In young animals, however, there was less of a shift in the IC50 curves compared to the adult, confirming that the young animal has less capacity than the adult to detoxify physiologically relevant concentrations of CPFO via CPFOase.

A Mono-Percoll separation technique improves sperm recovery of normal and male factor specimens when compared with the swim-up technique

The purpose of this study was to determine the effects of a simplified 80% Mono-Percoll sperm separation procedure on both normal and male factor semen samples compared with the standard swim-up technique. The parameters examined include sperm concentration, motility and morphology, total motile functional spermatozoa and percentage recovery. Normal patients demonstrated enhanced sperm parameters with the Mono-Percoll compared with the swim-up technique for concentration (67 x 10(6) versus 42 x 10(6)/ml, P < 0.001), motility (66 versus 59%, P < 0.001), morphology (56 versus 49%, P < 0.005) and percentage recovery (60 versus 42%, P < 0.005). Male factor patients showed enhanced sperm parameters with the Mono-Percoll procedure compared with the swim-up technique for motility (53 versus 42%, P < 0.05) and percentage recovery (54 versus 29%, P < 0.005), with no significant difference in concentration and morphology. In summary, the Mono-Percoll sperm recovery procedure is significantly better than the swim-up technique for male factor patients and patients with normal sperm parameters.

Regulatory and research issues related to cholinesterase inhibition

Assessing the neurotoxic potential of organophosphate and carbamate pesticides should be greatly facilitated by the knowledge that the mechanism of action of these insecticides is presumed to be the inhibition of cholinesterase, the enzyme which controls the levels of neurotransmitter, acetycholine. Although the inhibition of cholinesterase activity is the recognized mechanism of action, many questions remain regarding the use of cholinesterase inhibition data as a critical effect for establishing risk of cholinesterase-inhibiting pesticides. Specifically, questions have arisen regarding whether blood cholinesterase inhibition correlates with inhibition in target tissues (e.g. brain or muscle) and whether cholinesterase inhibition in any tissue correlates with the adverse clinical and behavioral effects produced by exposure to cholinesterase-inhibiting pesticides. Studies in our laboratory indicate that blood cholinesterase inhibition in both acute and subchronic dosing regimens correlates with inhibition in other tissues, if measurements are taken at the appropriate times. Moreover, there is evidence in the literature and from our laboratory that cholinesterase inhibition correlates with the emergence and severity of clinical signs of poisoning by cholinesterase-inhibiting pesticides.

Association between severity of illness and mortality from nosocomial infection

BACKGROUND

For the years 1987 through 1992, a study was undertaken to analyze nosocomial infection mortality data and to stratify risk according to severity of underlying illness to compare with published data from the Centers for Disease Control and Prevention.

METHODS

Nosocomial infections that contributed to or caused death were identified. In addition, during 1990 through 1992, severity of illness was determined as the subjective estimate of the risk of death or lack of risk of death during the current hospital admission before the onset of the nosocomial infection. These groups were named +SIC and -SIC, respectively.

RESULTS

It was determined that the data from death certificates in cases of known nosocomial infection were not sufficient to determine whether nosocomial infection contributed to or caused death. There was a 24% increase in cases of nosocomial infection contributing to or causing death when a physician reviewed deaths in patients with nosocomial infections who did not have a diagnosis of nosocomial infection listed on the death certificate. The rates for nosocomial infections contributing to or causing death are as follows: nosocomial pneumonia, 20%; and bloodstream infections, 19%. In patients who died and had severity of illness determination, there was a statistically significant difference in the rates of nosocomial infections contributing to or causing death between -SIC and +SIC groups for both nosocomial pneumonia and bloodstream infections. The rates for bloodstream infections were as follows: -SIC, 5%; and +SIC, 21%. For nosocomial pneumonia, the rates were as follows: -SIC, 13%; and +SIC, 23%.

CONCLUSION

In published reports from the Centers for Disease Control and Prevention, a rate of 13% is given for nosocomial pneumonia and bloodstream infections contributing to or causing death; however, there is no stratification for severity of illness in these reports. The presence of life-threatening illness before the onset of nosocomial pneumonia or bloodstream infection accounts for most deaths among our patients. For valid comparisons, mortality outcome data for nosocomial infections should be stratified for risk according to severity of underlying illness.

Slow accumulation of acetylcholinesterase in rat brain during enzyme inhibition by repeated dosing with chlorpyrifos

When given to rats, O,O'-diethyl-O-[3,5,6-trichloro-2-pyridyl]- phosphorothionate (chlorpyrifos), a common insecticide, causes an unusually lengthy dose-dependent fall in the activity of brain acetylcholinesterase (AChE; EC 3.1.1.7). To determine whether the slow recovery involves impaired AChE synthesis, experiments were designed to measure AChE activity, immunoreactive AChE protein (AChE-IR) and AChE mRNA. Male, Long-Evans rats, maintained at 350 +/- 5 g, were dosed (s.c.) weekly for 4 weeks with 0, 15, 30, or 60 mg/kg chlorpyrifos in peanut oil. Brain tissue was harvested 1, 3, 5, 7 and 9 weeks after treatment began. AChE activity was measured by Ellman assay, and AChE-IR was estimated by two-site ELISA using monoclonal antibodies to rat brain AChE. While AChE activity fell significantly at all times and doses, AChE-IR increased at 3 and 5 weeks in the two higher dosage groups. Larger increases of AChE-IR were observed after chlorpyrifos was administered for 4 weeks by the oral route. Northern blots quantified with reference to cyclophilin were consistent with stable levels of AChE mRNA. Overall, it appears that chronically reduced brain AChE activity after chlorpyrifos reflects sustained enzyme inhibition, not loss of enzyme protein or suppression of AChE message.

Comparison of the relative inhibition of acetylcholinesterase and neuropathy target esterase in rats and hens given cholinesterase inhibitors

Inhibition of neuropathy target esterase (NTE, neurotoxic esterase) and acetylcholinesterase (AChE) activities was compared in brain and spinal cords of adult While Leghorn hens and adult male Long Evan rats 4-48 hr after administration of triortho-tolyl phosphate (TOTP po, 50-500 mg/kg to hens; 300-1000 mg/kg to rats), phenyl saligenin phosphate (PSP im 0.1-2.5 mg/kg to hens; 5-24 mg/kg to rats), mipafox (3-30 mg/kg ip to hens and rats), diisopropyl phosphorofluoridate (DFP sc, 0.25-1.0 mg/kg to hens; 1-3 mg/kg to rats), dichlorvos (5-60 mg/kg ip to hens; 600-2000 mg/kg to rats), and carbaryl (300-560 mg/kg ip to hens; 30-170 mg/kg to rats). Inhibitions of NTE and AChE were dose-related after administration of all compounds to both species. Hens and rats given TOTP, PSP, mipafox, and DFP demonstrated delayed neuropathy 3 weeks later, with spinal cord lesions and clinical signs more notable in hens. Ratios of NTE/AChE inhibition in hen spinal cord, averaged over the doses used, were 2.6 after TOTP, 5.2 after PSP, 1.3 after mipafox, and 0.9 after DFP, which contrast with 0.53 after dichlorvos, 1.0 after malathion, and 0.46 after carbaryl. Rat NTE/AChE inhibition ratios were 0.9 after TOTP, 2.6 after PSP, 1.0 after mipafox, 0.62 after DFP, 1.3 after dichlorvos, 2.2 after malathion, and 1.1 after carbaryl. The lower NTE/AChE ratios in rats given dosages of the four organophosphorus compounds that caused delayed neuropathy interferred with survival, an effect that was not a problem in hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on the correlation between blood cholinesterase inhibition and 'target tissue' inhibition in pesticide-treated rats

Inhibition of cholinesterase activity in the blood has been proposed as an index of ChE activity in tissues targeted by ChE-inhibiting pesticides, including the muscle end-plate region and the central nervous system (CNS). While opinions vary regarding the utility of blood ChE activity in predicting ChE activity in the target tissues, there appear to be no comprehensive studies designed to assess this possible correlation in a time- and dose-dependent manner. We undertook this type of study by administering a single dose of an organophosphate, chlorpyrifos (0, 30, 60 or 125 mg/kg in corn oil, s.c.) to rats and then sacrificing animals at 1, 4, 7, 21 or 35 days after dosing. Whole blood, plasma, erythrocytes, frontal cortex, hippocampus, striatum, hypothalamus and diaphragm tissue were collected and assayed for ChE activity. Collapsed across dosages, optimal correlations of blood ChE activity with brain or muscle activity occurred 7-21 days after dosing (when ChE inhibition was maximal and most stable). At all times after dosing, there was a high correlation among ChE activity in the hippocampus, striatum and frontal cortex. Generally, ChE activity in whole blood and erythrocytes correlated better with the activity in brain and muscle than did activity in the plasma (whole blood > or = erythrocytes >> plasma). Similar relationships were also observed in a more abbreviated study using a direct acting organophosphate, paraoxon. ChE activity was determined in blood components, brain and muscle at the time of maximal inhibition (4 h after injection) and during recovery (24 hrs after injection) using two dosage levels (0.17 or 0.34 mg/kg, s.c.). Taken together, these data indicate that the level of ChE activity in the blood may accurately reflect activity in other tissues, but that this correlation is tissue- and time-specific.

Fenthion produces a persistent decrease in muscarinic receptor function in the adult rat retina

Several reports have suggested that exposure to organophosphate pesticides damages the visual system. The prolonged effects of an acute dose of fenthion (dimethyl 3-methyl-4-methylthiophenyl phosphorothionate) were studied on the cholinergic system of the rat retina. Fenthion was administered in a single dose of 0 or 100 mg/kg (sc, in corn oil) to adult, male, Long-Evans rats. The animals were killed 4, 14, or 56 days after treatment and cholinesterase (ChE) activity as well as muscarinic receptor (mChR) function measured in the retina and frontal cortex. Fenthion produced 89% inhibition of ChE activity in both tissues at 4 days, and, although there was recovery, slight (15%) inhibition of the enzyme activity was still observed at 56 days in both tissues. A long-lasting decrease in carbachol-stimulated inositolphosphate (IP) release was observed following fenthion treatment in the retina: IP release was depressed at 4 days and this depression persisted up to 56 days after dosing. The density of mChR in the retina as well as in the cortex was decreased by 14-20% at 4 days and returned to control levels by 56 days. Fenthion had no effect on the metabolism of phospholipids in the retina following intraocular injections of labeled precursors [3H]myo-inositol, [methyl-14C]choline, or [2-3H]glycerol 4 days after fenthion treatment. These prolonged effects of fenthion on mChR function (signal transduction) appear to be specific to the retina as the cortex showed no change in receptor-stimulated IP release even in the presence of significant mChR down-regulation and ChE inhibition. This dose of fenthion did not produce overt morphological changes in the retina or in the cortex, as observed with light microscopy, although an increase in glial fibrillary acidic protein immunoreactivity (GFAP IR) extending from the internal limiting membrane to the external limiting membrane of the retina was noted. This increase in GFAP IR was observed at 14 days and persisted as long as 56 days post-treatment in the retina, but was not noted in the cortex at any of the time points studied. Thus, this long-lasting perturbation in the retinal cholinergic second messenger system induced by fenthion may occur independently of depressed ChE activity and down-regulation of mChR.

Effects of organophosphates on the visual system of rats

The possibility that exposure to organophosphate insecticides can lead to ocular damage is suggested by Japanese studies from the 1960s and 1970s indicating that exposed humans developed chronic ocular degeneration, in addition to showing more commonly accepted effects of cholinesterase-inhibiting compounds. Other papers reported ocular lesions in laboratory animals treated with organophosphates. More recently, retinal degeneration following chronic organophosphate treatment has been reported to the Environmental Protection Agency by pesticide manufacturers in studies conducted in compliance with good laboratory practice regulations. Several factors, however, have prompted scepticism regarding organophosphate-induced ocular toxicity, including the widespread use of organophosphate compounds for both agricultural and ophthalmological practices without numerous additional reports of comparable ocular toxicity. We are developing a research program to address these issues involving electrophysiological, biochemical and histological investigations of rats treated with organophosphate insecticides. The research program is young, but early results are available. Notably, retinas from rats treated with a single subcutaneous injection of 100 mg kg-1 fenthion showed decreases in carbachol-stimulated release of inositol phosphate, an indicator of cholinergically-mediated intracellular second messenger systems. These effects persisted at least 56 days after fenthion administration. This could indicate several different toxicological actions, which are currently under investigation. It is concluded that the possible association between exposure to organophosphates and ocular toxicity cannot be dismissed, and that several important research issues need to be resolved.

An effective continuous quality improvement approach to the prevention of ventilator-associated pneumonia

In 1989, our medical center used continuous quality improvement concepts in the creation of a Nosocomial Pneumonia Prevention Team whose aim was to significantly reduce nosocomial ventilator-associated pneumonia. The team included representatives from nursing, respiratory therapy, pulmonary medicine, internal medicine, anesthesiology, education and training, and infection control. Because the majority of mechanically ventilated patients were located in the intensive care unit, this unit became the focus of the prevention efforts. Team meetings were held regularly, with all representatives brainstorming barriers, possible interventions, methods of outcome measurement, and frequency of evaluation. Policies and procedures were reviewed, surveillance was increased, handwashing practices were surveyed, periodic feedback to staff was begun, and an educational program was developed and presented. During 1990, we observed a 57% reduction in ventilator-associated pneumonia from the baseline years, 1987 and 1988. Statistical comparison of proportions by z test indicated a p value less than 0.05. Fifteen cases of nosocomial ventilator-associated pneumonia were prevented and a cost saving of $105,000 was realized. Performance of traditional surveillance for outliers, coupled with literature-based thresholds, can lead to tolerance of inordinately high endemic rates. Infection control programs can significantly reduce endemic rates of nosocomial ventilator-associated pneumonia through continuous quality improvement methods and multidisciplinary interventions, with standard infection control procedures used for improvement.

Determination of acrylamide in rat serum and sciatic nerve by gas chromatography-electron-capture detection

A modified method for the derivatization and determination of acrylamide as 2-bromopropenamide by gas chromatography-electron-capture detection was developed and applied to serum and sciatic nerve from rats. The method was accurate and precise over the calibration range 2.24-7.47 micrograms/ml in serum diluted 1:125 and 4-122 micrograms/g in sciatic nerve homogenate (5 mg/ml). limits of detection were estimated to be 1200 ng/ml in undiluted serum and 3 micrograms/g in intact sciatic nerve. The use of less dilute samples to allow for lower limits of detection appears feasible. The time-course of acrylamide in serum and sciatic nerve was studied after acute dosing and indicated elimination half-lives of 1.8 and 2.0 h for serum and sciatic nerve, respectively. A dose-effect relationship was established for each matrix after acute dosing and the measured acrylamide concentrations in serum (microgram/ml) were approximately the same as in sciatic nerve (microgram/g).

A modified spectrophotometric method appropriate for measuring cholinesterase activity in tissue from carbaryl-treated animals

Inhibited cholinesterase in tissues of animals exposed to carbamate pesticides is known to reactivate readily, presenting considerable problems in the accurate assessment of cholinesterase activity in these tissues. Decarbamylation of cholinesterase is favored when the tissue samples are diluted and/or are incubated for an extended time. The present study was performed to identify modifications of the commonly used spectrophotometric assay for cholinesterase activity that would minimize spontaneous reactivation of enzyme activity. Those modifications included preincubation of concentrated tissue with concentrated chromogen (i.e., DTNB), dilution to final reaction volume immediately before measurement, and measurement of cholinesterase over a short period of time (5-10 min). The Ellman assay with and without modifications was performed using a microtiter plate reader on tissues from carbaryl-treated rats:undiluted plasma, diluted erythrocytes (1:25), minimally diluted erythrocytes (1:2), diluted brain (1:100), or minimally diluted brain (1:2). The results were compared to cholinesterase activities obtained using a radiometric method which employs minimally diluted tissue and short incubation times. The degree of cholinesterase inhibition for undiluted or minimally diluted tissue assayed by the modified method agreed with those obtained using the radiometric method. Even if the tissues were diluted immediately before assay, however, significant reactivation occurred by the time the first measurements were made by the conventional method. Furthermore, significant spontaneous reactivation may still occur using the modified method if the assay is run for more than 10 min. Use of this modified Ellman method will enable more accurate estimation of in vivo cholinesterase activity in animals treated with carbamates.

Direct measurement of fast axonal organelle transport in the sciatic nerve of rats treated with acrylamide

The effects of acrylamide on fast axonal transport have been measured primarily using the indirect methods of isotope or enzyme accumulation. We report the first direct evaluation of the effects of subchronic acrylamide dosing (150, 300, or 500 mg/kg total dose, i.e., 50 mg/kg, 2x/wk, for 1.5, 3, 5 wk, respectively) on the fast axonal transport motility machinery itself using video-enhanced differential interference contrast optics with digital image processing and computer analysis. Four principle observations were made: (1) Rapid anterograde transport was not affected at any dosage level within 1 wk after cessation of dosing. (2) A high cumulative dosage (500 mg/kg total) of acrylamide or bisacrylamide produced approximately 7-18% decrease in the rate of retrograde transport in both myelinated and unmyelinated axons. (3) Lower dosages of acrylamide (150 or 300 mg/kg total) produced an increase in retrograde transport rates in myelinated axons only. (4) During the "recovery" phase for the 500 mg/kg acrylamide animals (i.e., 3 or 5 wk after the last dosage of acrylamide) the rate of anterograde transport in the myelinated axons was decreased at 3 wk but not at 5 wk, and the rate of retrograde transport in the myelinated axons returned to control levels while the retrograde transport in the unmyelinated axons continued at abnormally slow speeds. The application of this new technique to evaluate the neurotoxic effects of acrylamide provides evidence of dynamic changes in the axonal transport motility machinery itself and differential effects on myelinated versus unmyelinated fibers.

Behavioral and neurochemical effects of acute chlorpyrifos in rats: tolerance to prolonged inhibition of cholinesterase

The preponderance of studies of tolerance to organophosphate (OP) cholinesterase (ChE) inhibitors indicates that functional recovery accompanies neurochemical compensations for the inhibited enzyme. Contrary to prediction, rats dosed with the OP diisopropylfluorophosphate (DFP) showed progressive and persistent impairment of cognitive and motor function over a 3-week period of daily exposure, despite neurochemical and pharmacological evidence of tolerance to its inhibition of ChE. To determine whether these functional effects of DFP resulted from inhibition of ChE and downregulation of muscarinic cholinergic receptors, rats were dosed with chlorpyrifos (CPF), an OP pesticide which inhibits blood and brain ChE of rats for weeks after a single injection. Long-Evans rats were trained to perform an appetitive test of memory and motor function and were then injected s.c. with 0, 60, 125 or 250 mg/kg of CPF in peanut oil and tested 5 days/week for 7 weeks. Unconditioned behavior was also rated for signs of cholinergic toxicity. CPF inhibited ChE activity in whole blood in a dose-related manner for more than 53 days. The degree and time course of ChE inhibition in blood and brain and the downregulation of muscarinic receptors in brain after 125 mg/kg of CPF closely paralleled the previously reported effects of 25 daily injections of 0.2 mg/kg of DFP. In addition, CPF-treated rats were subsensitive to oxotremorine-induced hypothermia for at least 32 days after CPF. However, functional deficits (in working memory and motor function) appeared within 2 days after injection of CPF and recovered within 3 weeks, long before ChE activity and receptor density returned to control levels. Thus, the effects of CPF were neither progressive nor as persistent as those seen during daily DFP injections. This difference suggests that the DFP-induced behavioral changes observed previously cannot be attributed entirely to its effects on ChE activity and changes in [3H]quinuclidinyl benzilate binding.

The role of neurotoxic esterase (NTE) in the prevention and potentiation of organophosphorus-induced delayed neurotoxicity (OPIDN)

The first step in the initiation of organophosphorus-induced delayed neuropathy (OPIDN) is proposed to be the phosphorylation of an enzyme found in the nervous system called neurotoxic esterase (neuropathy target esterase, NTE). It has been known for over twenty years that non-neuropathic inhibitors of NTE exist and can actually prevent OPIDN when given before a neuropathic organophosphate (OP). Within the last three years it has become evident that another outcome is possible following in vivo interaction between neuropathic and nonneuropathic NTE inhibitors. When administered after OP exposure, nonneuropathic inhibitors can intensify or potentiate signs of OPIDN in adult chickens. Additionally, whereas developing chickens are typically resistant to the effects of neuropathic OPs, resistant age groups will develop OPIDN when exposure to a neuropathic OP is followed by the non-neuropathic NTE inhibitor phenylmethylsulfonyl fluoride. As in the case of prevention, studies of the potentiation of OPIDN may yield insight into mechanisms involved in the pathogenesis of delayed neurotoxicity. A brief review of current knowledge regarding the role of NTE in both the prevention and potentiation of OPIDN is presented.

Relationship of neuropathy target esterase inhibition to neuropathology and ataxia in hens given organophosphorus esters

Adult White Leghorn hens were acutely exposed to 3 dosages of the following organophosphorus compounds: mipafox, tri-ortho-tolyl phosphate (TOTP), phenyl saligenin phosphate, and diisopropylphosphorofluoridate (DFP). Neuropathy target esterase (NTE) activity was measured in brain and spinal cord 4 or 48 h after exposure. Ataxia was assessed using an 8-point rating scale on days 9 through 21 after administration, and neuropathological examination was conducted on samples collected from perfusion-fixed animals on day 21. Morphological alterations were indicated by lesion scores between 0 (no lesions) and 4 (diffuse involvement of spinal cord tracts and > 25% degeneration of peripheral nerve fibers). Dosages of mipafox (30 mg/kg i.p.), TOTP (500 mg/kg p.o.), phenyl saligenin phosphate (2.5 mg/kg i.m.) and DFP (1 mg/kg s.c.) that were capable of inhibiting NTE > 80% in both brain and spinal cord preceded ataxia which reached maximal levels (scores of 7-8), and development of lesions scored as 4. Hens were notably impaired (ataxia scores of 3-4) 21 days after administration of dosages of mipafox (3 and 6 mg/kg), TOTP (90 mg/kg), phenyl saligenin phosphate (0.1 and 0.2 mg/kg), and DFP (0.4 mg/kg) when spinal cord NTE was inhibited 40-75%. Lesions were, however, only noted in spinal cord and peripheral nerves of hens given TOTP or DFP (scores 1-3). These data indicate that inhibition of spinal cord NTE > 80% was predictive of severe ataxia and extensive pathology in the hen and that less NTE inhibition was indicative of less severe ataxia and a lower score for neuropathological damage.

Locally synthesized phosphatidylcholine, but not protein, undergoes rapid retrograde axonal transport in the rat sciatic nerve

Retrograde axonal transport of phosphatidylcholine in the sciatic nerve has been demonstrated only after injection of lipid precursors into the cell body region. We now report, however, that after microinjection (1 microliter) of [methyl-3H]choline chloride into the rat sciatic nerve (35-40 mm distal to the L4 and L5 dorsal root ganglia), time-dependent accumulation of 3H-labeled material occurred in dorsal root ganglia ipsilateral, but not contralateral, to the injection site. The level of radioactivity in the ipsilateral dorsal root ganglia was minimal at 2 h after isotope injection but was significantly increased at 7, 24, 48, and 72 h after intraneural isotope injection (n = 3-8 per time point); at these time points, all of the radiolabel in the chloroform/methanol extract of the ipsilateral dorsal root ganglia was present in phosphatidylcholine. The radioactivity in the water-soluble fraction did not show a time-dependent accumulation in the ipsilateral dorsal root ganglia as compared with the contralateral DRGs, ruling out transport or diffusion of precursor molecules. In addition, colchicine injection into the sciatic nerve proximal to the isotope injection site prevented the accumulation of radiolabel in the ipsilateral dorsal root ganglia. Therefore, this time-dependent accumulation of radiolabeled phosphatidylcholine in the ipsilateral dorsal root ganglia is most likely due to retrograde axonal transport of locally synthesized phospholipid material. Moreover, 24 h after injection of both [3H]choline and [35S]-methionine into the sciatic nerve, the ipsilateral/contralateral ratio of radiolabel was 11.7 for 3H but only 1.1 for 35S, indicating that only locally synthesized choline phospholipids, but not protein, were retrogradely transported.

Developmental changes in carbachol-stimulated inositolphosphate release in pigmented rat retina

Carbachol-stimulated release of inositolphosphates (IP) was studied in the whole retina from Long-Evans rats of different ages (day 5, 10, 15, 20, adult) following in vitro incorporation of [3H]myo-inositol. Unlike the albino rat retina, the pigmented retina was highly light-sensitive, making it necessary to dark adapt the animals and perform retinal dissections under low illumination to prevent light-induced IP release. Retinae from postnatal day 10 rats showed the highest amount of carbachol-stimulated IP released. This response to carbachol decreased with age until postnatal day 20 when it reached adult levels. The pigmented rat retina showed a sharp fall in the degree of carbachol (1 mM)-stimulated IP released at the time of eye-opening (450% above basal in retinae from 10 day old animals, as compared to 230% above basal in 15 day old retinae). Basal release of IP was not altered in the retina during development. Muscarinic cholinergic receptor density was, however, found to increase 5 fold with age, reaching adult levels by PND 20. Retinal weight and protein per retina also increased (four fold) from day 5 to adult; however, the in vitro incorporation of [3H]myo-inositol into phosphoinositides (calculated as per mg protein) did not change during development. Thus, in animals prior to eye opening, a much higher proportion of phosphoinositides appears to be hydrolyzed upon muscarinic receptor stimulation. During retinal development a change in sensitivity to the agonist-sensitive pool(s) of phosphoinositides may occur and/or there may be alterations in the efficacy of receptor coupling to the second messenger system resulting in the disassociation observed between the drastic increase in receptor number and the apparent decrease in receptor-stimulated release of IP.

Paraoxon toxicity is not potentiated by prior reduction in blood acetylcholinesterase

The role of blood acetylcholinesterase in moderating the effects of organophosphate challenge in rats was tested. Adult male rats (n = 42) were injected (iv) either with monoclonal antibodies (MAb) to rat acetylcholinesterase (EC 3.1.1.7; AChE) or normal mouse IgG (controls). Two days later, the rats were injected (sc) with either a mild (0.17 mg/kg) or moderate dosage (0.34 mg/kg) of paraoxon or with vehicle. Neurological integrity was assessed by a functional observational battery followed by motor activity, 3 to 4 hr after dosing. Blood, brain, and diaphragm tissues were then collected for determination of AChE activity. MAb treatment reduced whole blood and plasma AChE activity by 32 and 90%, respectively, but did not affect neurobehavioral parameters or the AChE activity of brain or diaphragm. The paraoxon challenge produced dose-related neurobehavioral changes and inhibition of brain and diaphragm AChE activity to the same extent in IgG- and MAb-treated rats. Thus, significant loss in blood AChE alone produced no detectable neurobehavioral deficits and did not alter the subsequent responses to paraoxon challenge.

Subacute ethanol consumption reverses p-xylene-induced decreases in axonal transport

Human exposure to organic solvents is often complicated by ethanol ingestion and the literature is replete with demonstrations of metabolic interactions between ethanol and organic solvents at a pharmacokinetic level. Because of the possible modulation of xylene toxicity by ethanol consumption, the present group of studies characterizes the effect of ethanol on the p-xylene-induced decrease in axonal transport in the rat optic system previously reported by our laboratory. Long-Evans, hooded, male rats were divided randomly into two groups: those receiving 10% ethanol in their drinking water and those receiving water only. These two groups were further subdivided into two groups which were either exposed by inhalation to 1600 ppm p-xylene for 6 h/day, 5 days/week for 8 exposure-days or were treated identically except that they were exposed to air while in the inhalation chambers. The ethanol-drinking rats were given ethanol 6 days prior to and on the days of the inhalation exposure. Immediately after removal from the inhalation chambers on the last exposure day, the animals were injected intraocularly with [35S]methionine and [3H]fucose to measure the synthesis and rapid axonal transport of proteins and glycoproteins, respectively, in the retinal ganglion cells. The animals were sacrificed 20 h later, and the amount of radioactivity in different areas of the retinal ganglion cells was determined by liquid scintillation counting. As in previous experiments, the xylene exposure group showed a significant reduction in axonal transport of proteins and glycoproteins, whereas the ethanol exposure alone produced no significant reductions in the transport of either proteins or glycoproteins. In the animals receiving both ethanol and xylene, however, the ethanol treatment prevented the decreased transport characteristic of the xylene only animals, i.e. in all areas of the optic projections the level of transport were similar to the level present in the control groups. These data suggest that the xylene-induced reduction in rapid axonal transport was reversed (or prevented) by subacute ethanol consumption.

Physiological correlates of middle-distance running performance. A comparative study between men and women

To compare the relative contributions of their functional capacities to performance in relation to sex, two groups of middle-distance runners (24 men and 14 women) were selected on the basis of performances over 1500-m and 3000-m running races. To be selected for the study, the average running velocity (v) in relation to performances had to be superior to a percentage (90% for men and 88% for women) of the best French v achieved during the season by an athlete of the same sex. Maximal O2 consumption (VO2max) and energy cost of running (CR) were measured in the 2 months preceding the track season. This allowed us to calculate the maximal v that could be sustained under aerobic conditions, va,max. A v:va,max ratio derived from 1500-m to 3000-m races was used to calculate the maximal duration of a competitive race for which v = va,max (tva,max). In both groups va,max was correlated to v. The relationships calculated for each distance were similar in both sexes. The CR [0.179 (SD 0.010) ml.kg-1 x m-1 in the women versus 0.177 (SD 0.010) in the men] and tva,max [7.0 (SD 2.0) min versus 8.4 (SD 2.1)] also showed no difference. The relationships between VO2max and body mass (mb) calculated in the men and the women were different. At the same mb the women had a 10% lower CR than the men; their lower mb thus resulted in an identical CR.(ABSTRACT TRUNCATED AT 250 WORDS)

Retrograde axonal transport of locally synthesized phosphoinositides in the rat sciatic nerve

Although autoradiography has demonstrated local incorporation of [3H]inositol into axonal phospholipids after intraneural injection, retrograde axonal transport of phosphatidylinositol has only been demonstrated after injection of lipid precursor into the cell body regions (L4 and L5 dorsal root ganglia) of the sciatic nerve. We now report the retrograde axonal transport of inositol phospholipids synthesized locally in the axons. Following microinjection of myo-[3H]inositol into the rat sciatic nerve (50-55 mm distal to L4 and L5 dorsal root ganglia), a time-dependent accumulation of 3H label occurred in the dorsal root ganglia ipsilateral to the injection site. The ratio of dpm present in the ipsilateral dorsal root ganglia to that in the contralateral dorsal root ganglia was not significantly different from unity between 2 and 8 h following isotope injection but increased to 10-12-fold between 24 and 72 h following precursor injection. By 24 h following precursor injection, the ipsilateral/contralateral ratio of the water-soluble label in the dorsal root ganglia still remained approximately 1.0, whereas the corresponding ratio in the chloroform/methanol-soluble fraction was approximately 20. The time course of appearance of labeled lipids in the ipsilateral dorsal root ganglia after injection of precursor into the nerve at various distances from the dorsal root ganglia indicated a transport rate of at least 5 mm/h. Accumulation of label in the dorsal root ganglia could be prevented by intraneural injection of colchicine or ligation of the sciatic nerve between the dorsal root ganglia and the isotope injection site. These results demonstrate that inositol phospholipids synthesized locally in the sciatic nerve are retrogradely transported back to the nerve cell bodies located in the dorsal root ganglia.

Murine susceptibility to organophosphorus-induced delayed neuropathy (OPIDN)

This study reports that CD-1 strain mice are neuropathologically and biochemically responsive to acute doses of tri-ortho-cresyl phosphate (TOCP). Young (25-30 g) male and female animals were exposed (po) to a single dose of TOCP (580-3480 mg/kg) and sampled for neurotoxic esterase (NTE) activity at 24 and 44 hr postexposure and for neuropathic damage 14 days later. Biochemically, high intragroup variability existed at the lower doses, and at higher levels of TOCP exposure (i.e., greater than or equal to 1160 mg/kg), mean brain NTE inhibition never exceeded 68%. Hen and mouse brain NTE activity, assayed in vitro for sensitivity to inhibition by tolyl saligenin phosphate (TSP), the active neurotoxic metabolite of TOCP, showed similar IC50 values. Histologically, highly variable spinal cord damage was recorded throughout treatment groups and mean damage scores followed a dose-response pattern with no apparent correlation to threshold (i.e., greater than or equal to 65%) inhibition of brain NTE activity. Topographically, axonal degeneration in the mouse spinal cord predominated in the lateral and ventral columns of the upper cervical cord. Unlike the rat, which displays degeneration in the upper cervical cord's dorsal columns (i.e., gracilis fasciculus) in response to TOCP intoxication, treated mice showed minimal damage to this tract. To examine this discrepancy further, ultrastructural morphometric analysis of axon diameters in the cervical cord was performed in control mice and rats. These results indicated that in both species, the largest diameter (greater than or equal to 4 microns) axons are housed in the ventral columns of the cervical spinal cord, suggesting that axon length and diameter may not be the only criteria underlying fiber tract vulnerability in OPIDN.

Potentiation of organophosphorus-induced delayed neurotoxicity by phenylmethylsulfonyl fluoride

It is well known that pretreatment with the serine esterase inhibitor phenylmethylsulfonyl fluoride (PMSF) can protect experimental animals from organophosphorus-induced delayed neurotoxicity (OPIDN), presumably by blocking the active site of neurotoxic esterase (NTE) such that binding and "aging" of the neuropathic OP is thwarted. We report here that while PMSF (60 mg/kg, sc) given 4 h before the neuropathic organophosphate (OP) mipafox (50 mg/kg, im) completely prevented the clinical expression of OPIDN in hens, the identical PMSF treatment markedly amplified the delayed neurotoxicity (relative to hens treated with OP only) if administered 4 h after mipafox (5 or 50 mg/kg, im). Moreover, in a separate experiment using diisopropylphosphorofluoridate (DFP) as the neurotoxicant in place of mipafox, posttreatment with PMSF 4 h after DFP (0.5 mg/kg) also accentuated the severity of ataxia. These data indicate that PMSF only protects against OPIDN if given prior to exposure to the neurotoxicant; treatment with PMSF after OP exposure critically exacerbates the delayed neurotoxicity from exposure to organophosphorus compounds.

The aesthetic alliance: nurses and medical facials

This article introduces and explains methods for integrating services of dermatology nurses and cosmetic dermatologists. Basic aesthetic techniques can be incorporated into the dermatology practice; or a specialist, namely a licensed aesthetician, can perform the medical facial.

Kaposi's sarcoma in transfusion-associated acquired immunodeficiency syndrome. A case report and review of the literature

Kaposi's sarcoma in transfusion-associated acquired immunodeficiency syndrome is rare; to our knowledge, only four previous cases have been reported. We report a unique case of transfusion-associated acquired immunodeficiency syndrome in a 74-year-old woman. At autopsy, both lungs were extensively affected by Kaposi's sarcoma, Pneumocystis carinii, and cytomegalovirus infection. These three processes led to respiratory failure and accounted for her death.

Modulation of neurotoxic esterase activity in vitro by phospholipids

Neurotoxic esterase (NTE), the proposed molecular site for the initiation of organophosphorus-induced delayed neuropathy, is a membrane-associated enzyme. NTE activity was solubilized from chicken brain microsomal membranes with the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1- propanesulfonate and partially separated from other solubilized hen brain esterases by DEAE-Sephacel anion-exchange chromatography using stepwise increases in salt concentration; however, there was poor recovery of NTE activity and only a slight increase in NTE specific activity. NTE activity in the "high salt" fraction (i.e., the NTE-enriched fraction) was markedly activated by a heat-stable factor(s) present in other fractions eluted from the column. This activating factor was extracted with organic solvents, suggesting that it may be lipid. In a related study, purified phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine were also found to activate the partially separated NTE activity in a concentration-dependent manner while phosphatidyl-inositol was found to inhibit the same partially separated NTE fraction in a concentration-dependent manner. The results suggest that lipids may modulate NTE activity and that the loss of lipid cofactors during chromatographic separations may underlie some of the difficulties encountered in isolation of active NTE.

Biochemical and morphological validation of a rodent model of organophosphorus-induced delayed neuropathy

Exposure to certain organophosphates (OPs) produces a delayed degeneration of the longest and largest nerve fibers (OPIDN). Until recently, investigators have used the chicken as the primary experimental model of OPIDN. Although the chicken is extremely sensitive to the ataxia associated with this neuropathy, it lacks an extensive biochemical, electrophysiological and pathological data-base. Because of this we set out to develop a rodent model of OPIDN with morphological and biochemical correlates similar to those seen in the chicken. Historically the rat had been labeled insensitive to OPIDN because of its lack of demonstrable ataxia in response to the neuropathic OPs. This paper describes the validation of a rodent model with biochemical and morphological endpoints similar to those described in the clinical and experimental literature for other models of OPIDN.

Comparison of incremental and steady state tests of endurance training

To compare the results obtained by incremental or constant work load exercises in the evaluation of endurance conditioning, a 20-week training programme was performed by 9 healthy human subjects on the bicycle ergometer for 1 h a day, 4 days a week, at 70-80% VO2max. Before and at the end of the training programme, (1) the blood lactate response to a progressive incremental exercise (18 W increments every 2nd min until exhaustion) was used to determine the aerobic and anaerobic thresholds (AeT and AnT respectively). On a different day, (2) blood lactate concentrations were measured during two sessions of constant work load exercises of 20 min duration corresponding to the relative intensities of AeT (1st session) and AnT (2nd session) levels obtained before training. A muscle biopsy was obtained from vastus lateralis at the end of these sessions to determine muscle lactate. AeT and AnT, when expressed as % VO2max, increased with training by 17% (p less than 0.01) and 9% (p less than 0.05) respectively. Constant workload exercise performed at AeT intensity was linked before training (60% VO2max) to a blood lactate steady state (4.8 +/- 1.4 mmol.l-1) whereas, after training, AeT intensity (73% VO2max) led to a blood lactate accumulation of up to 6.6 +/- 1.7 mmol.l-1 without significant modification of muscle lactate (7.6 +/- 3.1 and 8.2 +/- 2.8 mmol.kg-1 wet weight respectively). It is concluded that increase in AeT with training may reflect transient changes linked to lower early blood lactate accumulation during incremental exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical and neuropathological assessment of triphenyl phosphite in rats

The putative neurotoxicity of the organophosphorus compound triphenyl phosphite (TPP) was examined in Long Evans, adult male rats. Animals were exposed to two 1.0 ml/kg (1184 mg/kg) injections (sc) of TPP spaced 1 week apart and sampled for biochemical and neuropathological examination. At the time of sampling, rats displayed dysfunctional changes including tail rigidity, circling, and hindlimb paralysis. Neuropathic damage was confined to the lateral and ventral columns of all spinal levels and consisted of myelin ellipsoids and giant axonal swellings filled with smooth endoplasmic reticulum. Wallerian-like degeneration was observed in the spinal roots, the sciatic nerve, and tibial branches. Biochemical assessment of brain acetylcholinesterase (AChE) and neurotoxic esterase (NTE) activity was determined 1, 4, 24, 48, and 72 hr after the second TPP treatment. Both enzyme activity concentrations were depressed maximally at 48 hr postexposure by 30 and 39%, respectively. Serum cholinesterase, sampled 48 hr after the second TPP exposure was depressed by 33%. Data from this study indicate that subchronic exposure to the organophosphite TPP results in severe neurotoxic consequences which differ from those previously described in rats with organophosphorus-induced delayed neuropathy.

Effects of hypothermia on the in vivo measurement of rapid axonal transport in the rat: a cautionary note

Rapid axonal transport of glycoproteins was examined in the retinofugal projections of hypothermic and normothermic adult male Long-Evans hooded rats previously receiving intraocular injections of [3H]fucose. The amount of retinal fucosylation appeared normal in the hypothermic animals 3.5 h after isotope injection, but glycoprotein transport was reduced relative to normothermic controls. This reduction was especially pronounced in the most distal structure of the retinofugal tract (superior colliculus). We conclude that rapid axonal transport decreases with reductions in mammalian body temperature. This finding emphasizes the importance of controlling body temperature in in vivo studies of mammalian axonal transport.

An in vitro comparison of rat and chicken brain neurotoxic esterase

A systematic comparison was undertaken to characterize neurotoxic esterase (NTE) from rat and chicken brain in terms of inhibitor sensitivities, pH optima, and molecular weights. Paraoxon titration of phenyl valerate (PV)-hydrolyzing carboxylesterases showed that rat esterases were more sensitive than chicken to paraoxon inhibition at concentrations less than or equal to microM and superimposable with chicken esterases at concentrations of 2.5-1000 microM. Mipafox titration of the paraoxon-resistant esterases at a fixed paraoxon concentration of 100 microM (mipafox concentration: 0-1000 microM) resulted in a mipafox I50 of 7.3 microM for chicken brain NTE and 11.6 microM for rat brain NTE. NTE (i.e., paraoxon-resistant, mipafox-sensitive esterase activity) comprised 80% of chicken and 60% of rat brain paraoxon-resistant activity with the specific activity of chicken brain NTE approximately twice that of rat brain NTE. The pH maxima for NTE from both species was similar showing broad, slightly alkaline optima from pH 7.9 to 8.6. [3H]Diisopropyl phosphorofluoridate (DFP)-labeled NTE from the brains of both species had an apparent mol wt of 160,000 measured by sodium dodecyl sulfate polyacrylamide gel electrophoresis. In conclusion, NTE from both species was very similar, with the mipafox I50 for rat NTE within the range of reported values for chicken and human NTE, and the inhibitor parameters of the chicken NTE assay were applicable for the rat NTE assay.

Phenylmethylsulfonyl fluoride protects rats from Mipafox-induced delayed neuropathy

Initiation of organophosphorus-induced delayed neuropathy (OPIDN) is thought to consist of two molecular events involving the phosphorylation of the target enzyme, neurotoxic esterase, or neuropathy target enzyme (NTE), and a subsequent "aging" reaction which transforms the inhibited NTE into a charged moiety critical to the neuropathic process. Compounds that inhibit NTE but cannot age because of their chemical structure abort this two-stage initiation process, and when administered before a neurotoxic organophosphorus compound (OP), protect against the neuropathy by blocking NTE's active site (Johnson, 1970). In support of this, we report that prior exposure to a nonaging NTE inhibitor, phenylmethylsulfonyl fluoride (PMSF), protects rats from neurological damage after subsequent exposure to a neurotoxic OP, Mipafox. Adult, male, Long Evans rats were exposed to either PMSF (250 mg/kg, sc) or to Mipafox (15 mg/kg, ip) and a time course of brain NTE inhibition and recovery was defined. A separate group of PMSF-treated rats was exposed to Mipafox when brain NTE inhibition was 87.7 +/- 2.3%. Conversely, another group of rats, pretreated with Mipafox, was dosed with PMSF when NTE inhibition was 90.2 +/- 0.8%. A third group of animals, treated with PMSF, was exposed to Mipafox 14 days later, when NTE activity had recovered to within 10 +/- 4.2% of control amounts. Histopathological survey (14 to 21 days post-exposure) indicated severe cervical cord damage (damage score greater than or equal to 3) in the following frequencies: PMSF, 0%; Mipafox, 85%; PMSF-4 hr-Mipafox, 0%; Mipafox-4 hr-PMSF, 100%; PMSF-14 days-Mipafox, 75%; controls, 0%. These data indicate that PMSF pretreatment protects rats against Mipafox-induced neurological damage and that the timing of administration and order of presentation are critical to this protection. These results support the hypothesis that the initiation of OPIDN is a multistage event involving inhibition and aging, and these stages are experimentally separable.

Body temperature-dependent and independent actions of chlordimeform on visual evoked potentials and axonal transport in optic system of rat

Pattern-reversal-evoked potentials (PREPs), flash-evoked potentials (FEPs), rapid axonal transport in the optic system and body temperature were measured in hooded rats, treated with either saline or the formamidine insecticide/acaricide, chlordimeform (CDM). Rats receiving chlordimeform had low body temperatures when housed at standard laboratory room temperature, 22 degrees C, but not at 30 degrees C. Peak latencies of flash-evoked potentials were prolonged by chlordimeform at 22 degrees C, but not at 30 degrees C. The rate of axonal transport was slowed in chlordimeform-treated hypothermic rats, but not in chlordimeform-treated warmed rats. These findings suggest that the flash-evoked potential and axonal transport changes produced by chlordimeform were an indirect consequence of hypothermia. In contrast, chlordimeform increased pattern-reversal evoked potential peak latencies and peak-to-peak amplitudes independent of body temperature. These findings confirm and extend previous reports of chlordimeform-induced hypothermia, emphasize the importance of changes in body temperature as a possible confounding factor in studies of neuroactive agents and demonstrate that chlordimeform has both body-temperature-dependent and independent actions in the visual system in the rat.

The relationship between neurological damage and neurotoxic esterase inhibition in rats acutely exposed to tri-ortho-cresyl phosphate

A rodent model of organophosphorus-induced delayed neuropathy (OPIDN) has been developed using Long-Evans adult male rats exposed to tri-ortho-cresyl phosphate (TOCP). In the present study an attempt was made to relate neurochemical with neuropathological changes in rats exposed to single dosages of TOCP ranging from 145 to 3480 mg/kg. The degree of neurotoxic esterase (NTE) inhibition, measured at 20 and 44 hr and at 14 days postexposure was correlated with the appearance of spinal cord pathology 14 days postexposure in a separate group of similarly dosed rats. Those dosages that inhibited mean NTE activity in spinal cord greater than or equal to 72% and brain greater than or equal to 66% of control values within 44 hr postexposure produced marked spinal cord pathology 14 days postexposure in greater than or equal to 90% of similarly dosed animals. In contrast, dosages of TOCP which inhibited mean NTE activity in the spinal cord less than or equal to 65% and in the brain less than or equal to 57% produced spinal cord pathology in less than or equal to 15% of the animals. These data indicate that NTE inhibition may be used as a biochemical predictor for TOCP-induced neurological damage in rats.

[Anatomo-vectorcardiographic correlation in ventricular growth in congenital heart diseases]

Anatomo-vectorcardiographic correlations were studied in 59 cases of congenital heart disease. In the group with interventricular septal defect and pulmonary hypertensión, a statistically significant correlation between the thickness of the free right ventricular wall, at its outflow tract, and the inscription time of the vertex of the S loop, was found. In the group of Fallot's tetralogy, the segmentary hypertrophy of the right ventricle, which is the most frequent, explains very well the terminal portion of frontal and sagittal vectorcardiograms located below the 0 point. In the group with interatrial septal defect and pulmonary hypertension, a statistically significant correlation between the thickness of the antero-lateral superior third of the free right ventricular wall and the inscription time of the vertex of the S loop, was shown. In the group of congenital malformations with repercussion on the left ventricle (interventricular septal defect, patent ductus arteriosus and coarctation of aorta), a statistically significant correlation between the anatomical findings of a hypertrophied superior third of this ventricle and the inscription time of the vertex of the R loop, was observed.