Hepatic injury and disturbed amino acid metabolism in mice following prolonged exposure to organophosphorus pesticides

Chronic occupational exposure to organophosphorus and carbamate-type pesticides significantly inhibits acetylcholinesterase activity and causes morbidity. This study on mice was designed to evaluate their amino profile and to identify signs of hepatic dysfunction following their chronic exposure to mixtures of organophosphorus pesticides. Laboratory mice were exposed to a formulated mixture of the six organophosphorus pesticides (Dimethoate, Chlorpyrifos, Profenofos, Pirimiphos methyl, Triazophos and Dimethoate) most commonly used in agriculture in this region of the Middle East. Doses (10% of LD50 of the mixture) were given once a week by gavage in corn oil for 7 weeks; the control group was given only corn oil. At the end of the exposure period, mice were culled and blood samples were collected to determine erythrocyte acetylcholinesterase activity, biochemical markers of liver function and concentrations of serum amino acids. Erythrocyte acetylcholinesterase activity and total serum proteins decreased significantly in the exposed group. Serum concentrations of alanine aminotransferase and aspartate aminotransferase, alanine, glutamic acid, glycine, isoleucine, leucine, methionine, ornithine, proline, serine, threonine and valine were significantly increased in the exposed mice, while serum levels of cystine were decreased significantly. There were also non-significant increases in serum alkaline phosphatase, gama-glutamyl transpeptidase and some of the other amino acids. Chronic exposure to mixtures of organophosphorus pesticides is associated with decreased acetylcholinesterase activity, hepatic dysfunction and disturbance of amino acids profile. Biochemical indices of hepatocellular injury and disturbed amino acid metabolism may be of value as markers of chronic exposure to such pesticides.     

Blood and brain n-pentanol in inhalation exposure

Male Wistar rats exposed to 100, 300 or 600 p.p.m. n-pentanol vapour for 7 to 14 weeks during five days weekly and 6 hrs daily showed a dose-dependent blood n-pentanol concentration. The brain n-pentanol content was linearly related to the blood pentanol concentrations although this relationship changed after 14 weeks because the brain n-pentanol was significantly smaller than the respective values at 7 weeks. Valeraldehyde, the primary metabolite of n-pentanol, was only found in the brain at the highest vapour dose level. The liver n-pentanol dehydrogenase and 7-ethoxycoumarin O-deethylase activities remained unchanged while kidney ethoxycoumarin deethylase activity was enhanced in a dose-dependent manner at both time points. Brain and muscle acetylcholinesterase activities were increased by the exposure dose-dependently after 7 weeks although this effect ameliorated after 14 weeks. Moderate n-pentanol vapour exposure seems to cause metabolic and functional adaptation in its target organs.     

Cadmium-induced hepatic and renal injury in chronically exposed rats: likely role of hepatic cadmium-metallothionein in nephrotoxicity

Rats were injected sc with 0.5 mg Cd/kg, 6 days/week, for up to 26 weeks. Hepatic and renal function and tissue Cd and metallothionein (MT) content were determined in tissues and plasma at various times after Cd injection. Cd in liver and kidney increased linearly for the first 10 weeks of treatment, but thereafter hepatic concentrations of Cd decreased by 33% whereas the content of Cd in kidney remained constant. MT in liver and kidney increased linearly during the first 12 weeks of Cd treatment to 4400 and 2300 micrograms MT/g, respectively, but rose only slightly thereafter. Circulating concentrations of MT progressively increased beginning 2 weeks after Cd treatment and were approximately 10 times control values in rats dosed with Cd for 12 or more weeks. Plasma activities of alanine and aspartate aminotransferase exhibited a time course similar to that observed with MT, and were elevated as early as the sixth week of Cd exposure. Sharp increases in activities of these enzymes also occurred after 10 to 12 weeks of dosing. Hepatic microsomal metabolism of benzo[a]pyrene and ethylmorphine was severely attenuated beginning 4 weeks after Cd. Renal injury occurred after hepatic damage, as evidenced by decreased in vitro p-aminohippuric acid uptake beginning 8 weeks after exposure. Urine outflow increased threefold 11 weeks after Cd exposure began, while urinary protein and Cd excretion increased beginning at Week 9. These data indicate the liver is a major target organ of chronic Cd poisoning, and suggest that Cd-induced hepatic injury, via release of Cd-MT, may play an important role in the nephrotoxicity observed in response to long-term exposure to Cd.     

Subacute nicotine exposure in cultured cerebellar cells increased the release and uptake of glutamate

Cerebellar granule and glial cells prepared from 7 day-old rat pups were used to investigate the effects of sub-acute nicotine exposure on the glutamatergic nervous system. These cells were exposed to nicotine in various concentrations for 2 to 10 days in situ. Nicotine-exposure did not result in any changes in cerebellar granule and glial cell viability at concentrations of up to 500 microM. In cerebellar granule cells, the basal extracellular levels of glutamate, aspartate and glycine were enhanced in the nicotine-exposed granule cells. In addition, the responses of N-methyl-D-aspartate (NMDA)-induced glutamate release were enhanced at low NMDA concentrations in the nicotine-exposed granule cells. However, this decreased at higher NMDA concentrations. The glutaminase activity was increased after nicotine exposure. In cerebellar glial cells, glutamate uptake in the nicotine-exposed glial cells were either increased at low nicotine exposure levels or decreased at higher levels. The inhibition of glutamate uptake by L-trans-pyrollidine-2,4-dicarboxylic acid (PDC) was lower in glial cells exposed to 50 microM nicotine. Glutamine synthetase activity was lower in glial cells exposed to 100 or 500 microM of nicotine. These results indicate that the properties of cerebellar granule and glial cells may alter after subacute nicotine exposure. Furthermore, they suggest that nicotine exposure during development may modulate glutamatergic nervous activity.     

Effects of perinatal treatment with lead and disulfiram on ALAD activity in blood, liver and kidney and urinary ALA excretion in rats

Disulfiram, which is metabolized to diethyldithiocarbamate, is known to greatly influence the tissue distribution of lead (Pb) and potentiate the toxic effect of lead in the central nervous system. Effects on delta-aminolevulinic acid dehydratase (ALAD) activity and urinary delta-aminolevulinic acid (ALA) excretion were studied in rats pre- and postnatally exposed to lead and disulfiram, singly or in combination. Pregnant rats were treated with lead (0.25% Pb in the drinking water), with disulfiram (0.1 mmol/kg orally twice a week) or with both lead and disulfiram from day 1 of pregnancy until weaning. After parturition the disulfiram was given subcutaneously directly to the offspring. ALAD activity in blood was inhibited to a similar extent in the group treated with lead alone and in the group treated with lead and disulfiram (7 and 10% of control activity, respectively). Liver and kidney ALAD activities were not affected by the combined treatment with lead and disulfiram. However, urinary excretion of ALA was increased twice as much in the group treated with lead and disulfiram as in the group treated with only lead. The haematocrits were also significantly more depressed after combined exposure to lead and disulfiram. Two weeks after cessation of exposure ALAD activity in blood was inhibited to 47% of control activity in both the lead- and the lead plus disulfiram-treated groups. At this time there was no effect due to treatment on urinary ALA excretion of haematocrit. The results indicate that disulfiram probably influences the effects of lead on ALAD activity at the site of haem synthesis in the bone marrow.2+t is     

Evidence for diazinon-mediated inhibition of cis-permethrin metabolism and its effects on reproductive toxicity in adult male mice

The potential toxicity resulting from combinatorial effects of organophosphorus and pyrethroid insecticides are not completely known. We evaluated male reproductive toxicity in mice co-exposed to diazinon and cis-permethrin. Nine-week-old male Sv/129 mice were exposed to diazinon (10μmol/kg/day) or cis-permethrin (90μmol/kg/day) alone or in combination (100μmol/kg/day), or vehicle (corn oil), for 6 weeks. Diazinon and the diazinon-permethrin mixture inhibited plasma and liver carboxylesterase activities. In the mixture group, urinary excretion of cis-permethrin metabolite 3-phenoxybenzoic acid decreased along with increased plasma and testicular concentrations of cis-permethrin, while excretion of diazinon metabolites, diethylphosphate and diethylthiophosphate, did not change, versus mice exposed to each chemical alone, which suggested that inhibition of carboxylesterase decreased the metabolic capacity to cis-permethrin. Though the co-exposure decreased testosterone biosynthesis, increased degenerate germ cells in seminiferous tubule and sperm morphological abnormalities versus controls more clearly than exposure to cis-permethrin alone, the expected potentiation of toxicity was not evident.     

Electrophysiological estimation of the actions of acetylcholinesterase inhibitors on acetylcholine receptor and cholinesterase in physically isolated Aplysia neurones.

1. The actions of representative cholinesterase inhibitors on the acetylcholine responses of physically isolated single neurones from the pedal ganglion of Aplysia californica were studied, using electrophysiological techniques and rapid agonist application to analyse both the inhibitory actions on the acetylcholine receptor-channel complex and the degree of inhibition of acetylcholinesterase activity on the same neurone. The inhibitors used were physostigmine, edrophonium and diisopropylfluorophosphate (DFP). 2. When selected neurones were suddenly exposed to 50 microM acetylcholine by a 'concentration clamp' technique a large Na-dependent inward current was initiated, and decayed in the continued presence of acetylcholine without external perfusion. However, if perfusion of the acetylcholine solution was reinitiated the current increased somewhat, indicating that the decay of current was due to some combination of receptor desensitization and local depletion of acetylcholine at the membrane by acetylcholinesterase. 3. With simultaneous application of acetylcholine (50 microM) and physostigmine (0.1 to 100 microM) there was a dose-dependent reduction of peak amplitude of the acetylcholine response. However, physostigmine at low concentrations (0.1 to 10 microM) caused a time-dependent increase in the current amplitude alone with a time- and dose-dependent inhibition of acetylcholinesterase activity. At the highest concentration of physostigmine (100 microM) acetylcholinesterase activity was abolished but the current peak was very depressed. After removal of physostigmine from the bathing solution, the current amplitude decreased toward the control at the two lower concentrations as the inhibitory actions on acetylcholinesterase activity were almost reversible, while at the two higher concentrations (10 and 100 microM) the current increased and the inhibition of acethylcholinesterase remained. 4. When acetylcholine (50 microM) and edrophonium (0.1 to 10 microM) were applied simultaneously, edrophonium caused a dose-dependent increase in the peak amplitude that was correlated with a dose-dependent inhibition of acetylcholinesterase activity. Prolonged exposure to edrophonium did not change the peak amplitude and there was no time-dependent change in the inhibition of acetylcholinesterase activity. At the highest concentration of edrophonium used (100 microM), simultaneous application with acetylcholine augmented the peak amplitude relative to control, but to a lesser extent than 10 microM. Prolonged exposure to the highest concentration of edrophonium caused a time-dependent reduction in the peak amplitude.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of the water-soluble fraction of petroleum on microsomal lipid metabolism of Macrobrachium borellii (Arthropoda: Crustacea)

The effect of the water-soluble fraction of crude oil (WSF) on lipid metabolism was studied at critical metabolic points, namely fatty acid activation, enzymes of triacylglycerol and phospholipid synthesis, and membrane (lipid packing) properties in the freshwater prawn Macrobrachium borellii. To determine the effect of the contaminant, adults and embryos at different stages of development were exposed to a sublethal concentration of WSF for 7 days. After exposure, microsomal palmitoyl-CoA synthetase (ACS) showed a two-fold increase in adult midgut gland. Embryo's ACS activity was also affected, the increment being correlated with the developing stage. Endoplasmic reticulum acylglycerol synthesis was also increased by WSF exposure in adults and stage 5 embryos, but not at earlier stages of development. Triacylglycerol synthesis was particularly increased (18.5%) in adult midgut gland. The microsomal membrane properties were studied by fluorescent steady-state anisotropy, using the rotational behavior of the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH). Microsomes from midgut gland of WSF-exposed prawn showed no differences in fluidity. Nevertheless, microsomes incubated with WSF in vitro increased their fluidity in a temperature- and WSF concentration-dependent fashion. Both, aliphatic and aromatic hydrocarbons individually tested elicited an increase in membrane fluidity at 10 mg/l, but at 4 mg/l only nC10-C16 aliphatics did. In vivo results indicate that WSF increased the activity of microsomal enzymes that are critical in lipid metabolism, though this change was not due to direct alterations in membrane fluidity, suggesting a synthesis induction, or an enzyme-regulatory mechanism. Nevertheless, hydrocarbons elicited membrane fluidity alterations in in vitro experiments at concentrations that could be found in the environment after an oil spill.     

Behavioural and Glial Cell Effects of Inhalation Exposure to Styrene Vapour with Special Reference to Interactions of Simultaneous Peroral Ethanol Intake

Abstract Male Wistar rats were exposed to 300 p.p.m. of styrene vapour with simultaneous ethanol ingestion for 4 to 17 weeks. The effects on behaviour were analyzed after 4, 9 and 13 weeks of the experiment. The most manifest behavioural effects were found in rats exposed to the combination, and the changes included increased preening time at the 4th week and increased ambulation and rearing at the end of the exposure. The ethanol ingestion affected also the accumulation of the solvent burden by delaying the peak solvent concentration in the perirenal fat to the 8th week of exposure. The fat solvent concentration did not differ from each other in the two groups at the end of the experiment, and they were similar as compared the concentration found in phenobarbital-pretreated rats exposed for reference. The styrene exposure had almost no effects on cerebral glial cells whereas ethanol induced unexpectedly increased protein destruction in them throughout the experiment. Co-exposure to ethanol and styrene decreased the magnitude of protein destruction in the glial cells. Withdrawal of the rats after an 8-week exposure showed that the styrene effects were largely abolished in two weeks of exposure-free period as analyzed by the determination of brain RNA and acid proteinase activity. Brain RNA was lower than control after two weeks of ethanol deprivation. The present data indicate that marked metabolic interactions between ethanol and styrene take place in agreement with experience on other similar solvent combinations.     

The effects on new-born rats of repeated carbaryl administration during gestation

Pregnant rats orally received 1 or 5 mg/kg of carbaryl from the 11th to the last day of gestation. The new-born were separated from their treated dams and killed the day they were born or 6 days afterwards. The acetylcholinesterase (AchE) activities of the tissues (blood, brain and liver) of the mother and of the new-born were compared with those of the control animals.No significant decrease in the enzyme activity was noted in the investigated tissues, an increase was even seen in the maternal blood and liver.After receiving 50 mg/kg of carbaryl from the 19th to the last day of gestation, the AchE activity is increased in the blood and reduced in the brain of both mothers and new-borns.The weight analysis of the dams and the new borns only shows a significant decrease at the dose of 50 mg/kg. The observed increase of the AchE activity could represent adaptation by the animal to exposure to low doses of carbaryl.     

Involvement of breast cancer resistance protein (ABCG2) in the biliary excretion mechanism of fluoroquinolones.

Fluoroquinolones are effective antibiotics for the treatment of bile duct infections. It has been shown that the biliary excretion of grepafloxacin is partly accounted for by multidrug resistance-associated protein 2 (MRP2/ABCC2), whereas neither MRP2 nor P-glycoprotein is involved in the biliary excretion of ulifloxacin. In the present study, we examined the involvement of breast cancer resistance protein (BCRP/ABCG2) in the biliary excretion of fluoroquinolones (grepafloxacin, ulifloxacin, ciprofloxacin, and ofloxacin). In Madin-Darby canine kidney II cells expressing human BCRP or mouse Bcrp, the basal-to-apical transport of grepafloxacin and ulifloxacin was greater than that of the mock control, which was inhibited by a BCRP inhibitor, 3-(6-isobutyl-9-methoxy-1,4-dioxo-1,2,3,4,6,7,12,12a-octahydropyrazino[1',2':1,6]pyrido[3,4-b]indol-3-yl)-propionic acid tert-butyl ester (Ko143). Plasma and bile concentrations of fluoroquinolones were determined in wild-type and Bcrp(-/-) mice after i.v. bolus injection. The cumulative biliary excretion of fluoroquinolones was significantly reduced in Bcrp(-/-) mice, resulting in a reduction of the biliary excretion clearances to 86, 50, 40, and 16 of the control values, for ciprofloxacin, grepafloxacin, ofloxacin, and ulifloxacin, respectively. Preinfusion of sulfobromophthalein significantly inhibited the biliary excretion of grepafloxacin in Bcrp(-/-) mice. There was no change in the tissue/plasma concentration ratios of fluoroquinolones in the liver or brain, whereas those in the kidney were increased 3.6- and 1.5-fold for ciprofloxacin and grepafloxacin, respectively, in Bcrp(-/-) mice but were unchanged for ofloxacin and ulifloxacin. The present study shows that BCRP mediates the biliary excretion of fluoroquinolones and suggests that it is also involved in the tubular secretion of ciprofloxacin and grepafloxacin.     

Pharmacokinetics and pharmacodynamics of the acetylcholinesterase inhibitor metrifonate in patients with renal impairment.

The aim of this study was to assess the influence of renal function on the pharmacokinetics, pharmacodynamics, safety, and tolerability of the acetylcholinesterase inhibitor metrifonate. Four groups of six age- and gender-matched subjects with varying degrees of renal function (creatinine clearances more than 90, 60-90, 30-60, and less than 30 mL/min/ 1.73 m2, respectively) were administered a single 50-mg oral dose of metrifonate. Blood and urine samples were collected for 24 hours and concentrations of metrifonate and its metabolites dichlorvos, dichloroacetic acid, and M3 were determined. Inhibition of acetylcholinesterase activity in erythrocytes and butyrylcholinesterase in plasma were also measured. Metrifonate was well tolerated in all treatment groups. The urinary excretion of metrifonate and dichlorvos decreased with decreasing renal function but accounted for less than 2% of the elimination. There were no statistically significant differences in primary pharmacokinetic parameters--Cmax, t(max), area under the concentration-time curve (AUC), and t1/2--of metrifonate and dichlorvos among the different groups. The excretion of dichloroacetic acid and M3 was not influenced by renal impairment. Acetylcholinesterase was not inhibited, whereas butyrylcholinesterase was inhibited markedly but independently of renal function. No metrifonate dose adjustments are needed when treating subjects with renal impairment.     

The effect of acetylcholinesterase-inhibition on the tonus of guinea-pig bronchial smooth muscle

The irreversible acetylcholinesterase inhibitor soman (O-[1,2,2-trimethylpropyl]-methyl-phosphonofluoridate) induced contraction of guinea-pig primary bronchial smooth muscle. The apparent affinity (ED50) of acetylcholine (ACh) was altered from control value of 12 microM to 0.3 microM following exposure of the bronchial smooth muscle to 14 microM soman for 15 min in vitro. The ED50 of the cholinergic agonist carbachol was not changed even when the acetylcholinesterase (AChE) activity was inhibited completely. The intrinsic activity (alpha) of ACh and carbachol was not significantly changed after exposure to soman for 15 min. The results demonstrate that the effect of soman is only due to its anticholinesterase activity. Furthermore, the contraction induced by histamine was not altered by concentrations of soman which increase the cholinergic stimulation. This indicates that histamine does not induce contraction of bronchial smooth muscle in guinea pig through the release of ACh or by modulation of muscarinic receptors. Furthermore, soman also inhibited the carboxylesterase activity in the primary bronchi. In respiratory tissue this group of enzymes may have a major protective function, due to their ability to bind several organophosphorus compounds. Compared to studies performed on other species, this study shows that guinea-pig bronchi are very sensitive to the AChE-inhibitor soman. Therefore, exposure to very low concentrations of AChE-inhibitors may induce contraction of bronchial smooth muscle.     

Opposite modulation of glutamate uptake by nicotine in cultured astrocytes with/without cAMP treatment

Cultured cerebellar astrocytes were exposed to nicotine with or without dibutyryl cAMP (dBcAMP) for 2 to 10 days in situ in order to determine the effects of nicotine exposure on glutamate uptake in differently conditioned astrocytes. After acute nicotine exposure, glutamate uptake was lower and higher in the naive and the preconditioned astrocytes, respectively. After subacute nicotine exposure, the inhibitory effect of L-trans-pyrollidine-2,4-dicarboxylic acid (PDC) on the glutamate uptake in the naive and the conditioned cells was decreased and increased, and the IC50's for PDC were higher and lower, respectively. In addition, glutamine synthetase activity after subacute nicotine exposure was lower in the naive and higher in the conditioned astrocytes; the change in Na+/K+ ATPase activity was the opposite to that in glutamine synthetase activity. These results suggest that nicotine modulates the characteristics of glial glutamate transporters and glutamine synthetase activity in astrocytes. Furthermore, nicotine might differently affect the state of glial cells during development.     

Eicosapentaenoic acid stimulates nitric oxide production and decreases cardiac noradrenaline in diabetic rats

1. The aim of the present study was to investigate whether long-term oral administration of eicosapentaenoic acid increases nitric oxide (NO) production and affects cardiac sympathetic activity in rats with diabetes mellitus. 2. We measured changes in urinary excretion of NO3-, a stable NO metabolite, and cardiac noradrenaline (NA) concentrations in non-diabetic rats and streptozotocin-induced diabetic rats treated with either ethyl icosapentate (EPA-E; 100 mg/kg per day; n = 10), a purified ethyl esterification product of eicosapentaenoic acid, or vehicle (distilled water; n = 10) for 6 weeks. The effects of N(G)-nitro-L-arginine (L-NNA), a NO synthase inhibitor, on urinary NO3- excretion and cardiac NA concentrations were also investigated in diabetic rats treated with EPA-E. 3. Urinary NO3- excretion was higher at weeks 5 and 6 in diabetic rats treated with EPA-E than in diabetic rats treated with vehicle (week 5: 120+/-8 vs 51+/-11 micromol/g per day, respectively (P<0.01); week 6: 279+/-83 vs 73+/-9 micromol/g per day, respectively (P<0.01)). Cardiac NA concentrations were higher in diabetic rats than in non-diabetic rats and were decreased in the left atrium and both ventricles in diabetic rats treated with EPA-E compared with control. Systemic administration of L-NNA abolished the increase in urinary excretion of NO3- and the decrease in cardiac NA concentrations in diabetic rats treated with EPA-E. 4. Long-term oral administration of EPA-E may stimulate NO production and increased NO is likely to play a role in inhibiting enhanced cardiac sympathetic activity in diabetic rats.     

Effect of caffeic acid phenethyl ester on gastric acid secretion in vitro

Caffeic acid phenethyl ester (CAPE), one of the major components of propolis (honeybee resin), has demonstrated a wide spectrum of activities including suppression of eicosanoids by inhibition of cyclooxygenase-1 and cyclooxygenase-2 enzyme activities. The aim of this study was to investigate the effect of CAPE on basal and secretagogues-stimulated gastric acid secretion in vitro. In the isolated, lumen-perfused, stomach preparation of mouse, CAPE (10-100 microM) did not affect the basal gastric acid secretion nor the secretion stimulated by histamine, pentagastrin, isobutyl methylxanthine and high levels of K+. By contrast, CAPE increased the gastric acid secretion induced by the muscarinic receptor agonist, 5-methylfurmethide (5-MEF). CAPE also inhibited the acetylcholinesterase activity in an in vitro colorimetric assay. Eserine (10 microM), a well known acetylcholinesterase inhibitor, also increased 5-MEF-stimulated acid secretion. Our results show that CAPE increases gastric acid secretion stimulated by an acetylcholine agonist receptor likely through inhibition of acetylcholinesterase activity.     

Effects of sodium fluoride on locomotor behavior and a few biochemical parameters in rats

Spontaneous motor activity and motor coordination were tested in adult female rats after treating with sodium fluoride at 20 or 40 mg/kg dose level daily for 60 days, using an activity chamber and a rota-rod apparatus, respectively. Total protein concentrations were determined in skeletal muscle, liver and serum of similarly treated animals. The activities of total cholinesterase and acetylcholinesterase were determined in blood and brain regions, respectively. Sodium fluoride treatment suppressed spontaneous motor activity. But no change was observed in the motor coordination of these animals. Tissue and serum protein concentrations were decreased. Cholinesterase activity was decreased in the blood and not in brain regions. A failure of sodium fluoride to impair motor coordination indicated that neuromuscular function required for a forced task was not deteriorated in these animals, although skeletal muscles were deprived of protein and blood cholinesterase activity was suppressed. A suppression of spontaneous motor activity suggests that fluoride has, by a central action, inhibited motivation of these animals to exhibit locomotor behavior. A cholinergic mechanism through a change in the activity of acetylcholinesterase may not account for this effect, since sodium fluoride treatment did not alter the activity this enzyme in brain regions. However, an involvement of monoamines may be proposed in view of previously reported finding that excessive fluoride intake has decreased the concentrations of 5-hydroxyindoleacetic acid and increased that of norepinephrine in rat brain.     

Interactions of calcium with purified and intact cell acetylcholinesterase of Electrophorus electricus

The effects of calcium on the activity of purified preparations of acetylcholinesterase (AChE) from the electric organ of Electrophorus electricus and the activity of the AChE in intact electroplaques from the same species were studied. The activity of the purified AChE was measured using an automatic pH-stat. The AChE activity of a single intact electroplaque was measured by a radiometric assay technique in which ¹⁴C-labeled acetylcholine (ACh) was applied to the innervated membrane only. The activity of purified AChE was markedly increased by 10 and 20 mM Ca²⁺ at all substrate concentrations tested. These same concentrations of Ca²⁺ increased the AChE activity of intact electroplaques at low substrate concentrations and inhibited the enzyme at ACh concentrations greater than 10^?3 M. The differences observed between the purified and intact cell enzyme are discussed in terms of electrostatic neighboring-group interactions.     

唑来膦酸对大鼠成骨细胞增殖、分化和矿化功能的影响

目的:观察唑来膦酸对大鼠成骨细胞生物学功能的影响。方法:体外培养的新生大鼠颅盖骨来源的成骨细胞,观察不同浓度(10-4M~10-11M)唑来膦酸对细胞增殖、碱性磷酸酶(ALP)活性和矿化结节形成的影响。结果:唑来磷酸浓度≥10-5M时抑制细胞增殖,10-6M~10-11M则不影响细胞增殖;10-7M~10-11M对ALP活性没有影响,10-7M对矿化小结形成有抑制作用,10-11M则促进矿化功能。结论:唑来磷酸在低浓度时不影响骨形成,选择恰当的剂量和给药方案可助于发挥双磷酸盐抑制破骨作用的同时促进骨形成。     

Effect of N-benzyl-D-glucamine dithiocarbamate on the renal toxicity produced by subacute exposure to cadmium in rats

The effect of N-benzyl-D-glucamine dithiocarbamate (BGD) on the renal toxicity produced by subacute exposure to cadmium in rats was studied. Rats were injected sc with CdCl2 (1.5 mg Cd/kg) daily for 26 days and thereafter they received 13 injections of BGD (400 mumol/kg) every other day. Urinary protein concentration and AST activity significantly increased after 20 days of cadmium treatment. The pattern of the increase in the urinary excretion of cadmium after cadmium treatment was consistent with that in the urinary excretion of protein and AST. Urinary excretion of amino acid increased gradually after the cessation of cadmium treatment. BGD treatment significantly decreased the urinary excretion of protein, aspartate aminotransferase (AST), and amino acid. Plasma AST activity was elevated 8 days after the beginning of cadmium treatment, indicating that the hepatic damage occurred prior to the renal damage. In addition, the microscopic examination of renal tissue from cadmium-treated rats revealed the necrosis of the proximal tubular cells. The cadmium concentrations in liver and kidney were significantly decreased by BGD treatment. The results of this study indicate that BGD treatment is effective in decreasing the cadmium concentrations in liver and kidney, resulting in the therapeutic effect on the cadmium-induced renal damage.