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At least 433 records · Page 24Linked to original sources

PubMed2006

Effects of carvedilol on M2 receptors and cholinesterase-positive nerves in adriamycin-induced rat failing heart.

Heart failure is correlated with attenuation of parasympathetic nervous function and enhanced sympathetic activity. Carvedilol, a third-generation beta-blocker, may improve the prognosis of heart failure better than selective beta(1)-blockers. Not all of its effects, however, can be explained by direct actions on the sympathetic nervous system. This study was therefore performed to investigate the possible alterations of muscarinic cholinergic (M)(2) receptors and cholinesterase-positive nerves in different regions of the adriamycin-induced failing rat heart, and the potential effects of carvedilol on these M(2) receptors and cholinesterase-positive nerves. Karnovsky-Roots histochemical staining combined with point counting methods, and immunochemical streptavidin-biotin complex staining and image analysis were used to test the distribution of cholinesterase-positive nerves and the expression of M(2) receptors, respectively. Our results show that the cholinesterase-positive nerve system was downregulated in the adriamycin-induced failing heart group, while the density of M(2) receptors was increased in the carvedilol 3- and 10-mg/kg body weight groups, especially in the endocardial tissues of the left-ventricular free wall. It is concluded that upregulation of M(2) receptors may be one of the potential mechanisms by which carvedilol exert its action on heart failure.

Adrenergic alpha-Antagonists↗

PubMed2005

Electrochemical sensor based on Arthrobacter globiformis for cholinesterase activity determination.

The sensors applied recently for determination of cholinesterase activity are mostly enzymatic amperometric sensors, in spite of their disadvantages: short life-time at ambient temperature, instability of the response, interferences, as well as passivation of the electrode surface. In the present paper a new approach for determination of cholinesterase activity was proposed, overcoming the main drawbacks of the analysis performed with amperometric enzymatic sensors. Instead of the immobilization of enzymes on a conducting electrode surface, whole cells of Arthrobacter globiformis, containing choline oxidase were fixed on a Clark type oxygen probe. Current proportional to bacteria respiration is registered as a sensor response. The application of whole cells of bacteria as a sensing element permits to achieve high stability of the response and long life-time of the sensor at ambient temperature, due to the conservation of the enzyme in its natural micro-environment inside the immobilized cells. The proposed sensor keeps its functionality more than 7 weeks stored in deionized water at ambient temperature. For the first 2 weeks the amplitude of the response decreases with only 10% and at the end of the studied 7 weeks period the response was 50% of the initial. The other advantages of the proposed sensor are: the dissolved oxygen is used as a mediator which concentration can be reliably and interferences free measured by the aim of a Clark type oxygen probe applied as a transducer; reproducible bacterial membranes can be elaborated by filtration of resuspended bacterial culture after preliminary determination of its activity; application of membranes containing lyophilized bacteria capable to be conserved infinitely long time and activated just before their application; negligible cost compared with the sensors based on immobilized enzymes. The steady-state response of the proposed bacterial sensor to choline obtained in 200 s is linear in the investigated concentration range up to 2 x 10(-4) moldm(-3), with detection limit of 8 x 10(-8) moldm(-3) and sensitivity of 4 x 10(-1) microAcm(3)mol(-1), at pH 6, temperature of 25 degrees C and stirring rate of 300 rpm. Choline is formed as a result of the catalytic hydrolysis (depending on the cholinesterase activity) of the substrate acetylcholine. Linear calibration graph for cholinesterase activity determination was obtained in the range up to 11 mUcm(-3), with a slope of 1.97 x 10(-2) microAcm(3)mU(-1), at pH 6, temperature of 25 degrees C and stirring rate of 300 rpm. The tests with reconstituted lyophilized serum with known activity used as a control sample confirm the accuracy of the proposed method. The relative error of the determination was only 2.82%.

Arthrobacter↗

PubMed2005

Humans appear no more sensitive than laboratory animals to the inhibition of red blood cell cholinesterase by dichlorvos.

Inhibition of red blood cell (RBC) cholinesterase is a consistent and sensitive indicator of exposure to dichlorvos (DDVP). Absent human data, default 10-fold adjustment factors for potential interspecies and intraspecies sensitivity differences would be used in developing a reference dose from the no observed effect levels for this endpoint obtained in toxicological assessments of laboratory animals. However, many studies of the cholinesterase-inhibiting effects associated with DDVP exposure have been conducted in humans, including healthy male volunteers, other healthy subpopulations, and diverse clinical subpopulations. Indeed, ample human data exist to permit a data-based assessment of potential interspecies sensitivity differences in RBC cholinesterase inhibition associated with DDVP exposure. In aggregate, these data demonstrate that the DDVP doses producing inhibition in humans are virtually identical to those eliciting the same levels of inhibition in laboratory rats, mice, monkeys, and dogs. Thus, healthy humans appear to be no more sensitive than laboratory animals to DDVP's effects on RBC cholinesterase, and an interspecies uncertainty factor of 1 is appropriate and scientifically warranted for use in DDVP risk assessments.

Algorithms↗

PubMed2001

Testosterone mediates sex difference in hypothermia and cholinesterase inhibition by rivastigmine.

The fall in body temperature and inhibition of hypothalamic cholinesterase induced by rivastigmine (a pseudo-reversible carbamate inhibitor) were compared in male and female rats. In males, 1.5 mg/kg lowered body temperature by 1 degrees C and in females by 3.2 degrees C (P<0.001) and inhibited cholinesterase by 65% and 74%, respectively (P<0.05). Pilocarpine (20 mg/kg) decreased body temperature by 1.1 degrees C in males and 1.9 degrees C in females (P<0.05). Orchidectomy, but not ovariectomy, abolished the sex difference in the hypothermic effect of pilocarpine and the enzyme inhibition induced by rivastigmine, but not in its effect on body temperature. Testosterone (10 mg/rat) decreased the cholinesterase inhibition and the temperature reduction induced by rivastigmine in gonadectomised males and females, but that induced by pilocarpine in males only. In conclusion, rivastigmine causes less inhibition of cholinesterase because testosterone may interfere with its entry into the brain. Testosterone may further decrease the temperature-lowering effect of rivastigmine and acetylcholine receptor agonists in males by an action at a receptor level.

Animals↗

PubMed1992

Association between life-threatening cocaine toxicity and plasma cholinesterase activity.

STUDY OBJECTIVE: To determine whether plasma cholinesterase (pseudocholinesterase) activity is a marker for severe cocaine toxicity. DESIGN: A prevalence study in a cohort of cocaine users. SETTING: A large urban emergency department. PARTICIPANTS: During a three-month period in 1989, 187 patients who presented to the ED on 191 consecutive occasions with signs and symptoms consistent with cocaine intoxication were prospectively enrolled in the study protocol. METHODS AND MEASUREMENTS: All patients had plasma cholinesterase activity determined by the electrometric method. The patients who were cocaine positive were stratified into one of two groups: life-threatening toxicity (LT) and non-life-threatening toxicity (NLT), based on a predetermined set of criteria. Cocaine-negative patients served as controls for the LT group if criteria were otherwise met. RESULTS: Mean (+/- SD) plasma cholinesterase activities for the LT, NLT, and control groups were 682 +/- 277, 904 +/- 279, and 1,058 +/- 385 Michel units/L, respectively. All three groups were significantly different from each other (P less than .05 by analysis of variance). CONCLUSION: The data suggest that decreased plasma cholinesterase activity is associated with increased risk of life-threatening cocaine toxicity.

Adult↗

PubMed2002

Serum cholinesterase activity reflects morbidity in burned patients.

Blood samples of 200 patients with thermal injuries were drawn apparently to determine the trend of the cholinesterase activity. In relation to the severity of the injury, a characteristic decrease was noted during the first days after admission. A recovery to normal values was achieved in all survivors (150 patients) after a proportionate period of time, but in the group of non-survivors (50 patients), no complete recovery to normal levels was found. Furthermore, a significant relationship between serum cholinesterase activity and the severity of morbidity was detected, the fall of the cholinesterase activity at the very beginning was significantly higher (P<0.004) in patients who died (1.3kU/l) than in patients who survived (0.7kU/l). Already 24h after admission, the mean activity was significantly lower (P<0.003) in non-survivors (2.5kU/l) than in survivors (3.2kU/l). It seems that the serum cholinesterase is a sensitive indicator for the morbidity of patients with severe burn injuries.

Analysis of Variance↗

PubMed1996

The significance of the activity of CSF cholinesterases in dementias.

This article reviews the significance of changes in the level of cerebrospinal fluid acetylcholinesterase or cholinesterase in patients with Alzheimer's disease or other dementias. Evidence has shown that the methodology of assaying cerebrospinal fluid acetylcholinesterase or cholinesterase is reliable and the activity of the enzyme is stable. Low acetylcholinesterase or cholinesterase levels presenting in cerebrospinal fluid of a demented individual may confirm the clinical diagnosis of Alzheimer's disease or other organic dementia. A low activity of acetylcholinesterase or cholinesterase existing in cerebrospinal fluid of a non-demented individual may indicate a brain at risk, or that the person is in the preclinical stage of dementia. Recognition of the presence of the preclinical stage may be very beneficial for explaining the real meaning of the 'overlap' in the biochemistry and pathology between dementia and non-dementia, and also very important for prevention and treatment. Therefore, the strategy of prevention and of treatment should no longer be designed to inhibit acetylcholinesterase activity. In contrast, it should be designed to enhance the neuronal acetylcholinesterase activity or to delay the degeneration of brain acetylcholinesterase system.

Acetylcholinesterase↗

PubMed1999

Cholinesterases from the marine mussels Mytilus galloprovincialis Lmk. and M. edulis L. from the freshwater bivalve Corbicula fluminea Müller.

In order to improve the molecular basis for the use of bivalve cholinesterases as a reliable biomarker for aquatic pollution, the polymorphism and characterization of these enzymes in Mytilus edulis, Mytilus galloprovincialis and Corbicula fluminea were investigated. All results are consistent with the presence of only one pharmacological form of cholinesterase in each species. The molecular masses were 180 kDa for the two marine mussels and 240 kDa for C. fluminea. The cholinesterases are anchored to the membrane by a glycosyl inositol phosphate like the Ga form (type I) described in vertebrates. Surprisingly, these cholinesterases were poorly inhibited by organophosphorous compounds compared to enzymes from other sources. This suggests that these bivalves could be used as a biomarker for acute rather than chronic contaminations by anticholinesterase insecticides.

Animals↗

PubMed1970

Purification and properties of human serum cholinesterase.

Cholinesterase was purified from human serum by a three-stage procedure involving chromatography on DEAE-cellulose at pH4.0, an electrofocusing technique and gel filtration on Sephadex G-200. The final product was purified 13000-fold with a yield of 54%, and only one protein and one cholinesterase band could be demonstrated by polyacrylamide-disc electrophoresis. The catalytic properties appeared to be unchanged by the purification procedure. The molecular weight was determined by both ultracentrifugation in a density gradient and gel filtration, and values close to 366000 were obtained. The isoelectric point of cholinesterase was estimated to be pH3.99. The method appears suitable for the preliminary purification of the rare genetic variants of human cholinesterase.

Blood Protein Electrophoresis↗

PubMed2002

Does sevoflurane inhibit serum cholinesterase in children?

Serum cholinesterase activity was measured at induction, and following anaesthesia in 41 children aged between 4 and 30 months. The median exposure to sevoflurane was 273%.min. The results did not demonstrate any significant difference in cholinesterase activity, when expressed by gram of serum proteins following inhalation anaesthesia using sevoflurane or intravenous anaesthesia using propofol. The values (SD) obtained were 175 (42) UI.g(-1) before anaesthesia and 177 (43) UI.g(-1) following anaesthesia. The only change in cholinesterase activity detected was related to heamodilution. We conclude that plasma fluoride concentration following sevoflurane administration [13.8 (4.2) microm x l(-1)] is too low to exert an inhibiting effect on in vivo cholinesterase activity and that the previously reported decrease in mivacurium requirements during sevoflurane anaesthesia is unlikely to be due to inhibition by fluoride ions.

Anesthetics, Inhalation↗

PubMed2000

Increased levels of tau protein in SH-SY5Y cells after treatment with cholinesterase inhibitors and nicotinic agonists.

Several cholinesterase inhibitors used in the treatment of Alzheimer's disease (AD) have been shown to interact with an allosteric site on the nicotinic acetylcholine receptor (nAChR). A possible linkage between the phosphorylation state of tau, the major component of paired helical filaments found in AD brain, and stimulation of nAChRs by cholinesterase inhibitors and nicotinic agonists was investigated. Western blot analysis showed that treatment of SH-SY5Y cells for 72 h with the cholinesterase inhibitors tacrine (10(-5) M), donepezil (10(-5) M), and galanthamine (10(-5) M), nicotine (10(-5) M), and epibatidine (10(-7) M) increased tau levels as detected with Tau-1, AT 8, and AT 270 monoclonal antibodies and binding of [3H]epibatidine. The increase in tau immunoreactivity induced by nicotine, epibatidine, and tacrine, but not the up-regulation of nAChRs, was prevented by the antagonists d-tubocurarine and mecamylamine. Both antagonists were synergistic with the nicotinic agonists in causing up-regulation, but only d-tubocurarine showed a synergistic effect with tacrine. The increased tau immunoreactivity induced by tacrine was not prevented by atropine, indicating that in terms of cholinergic receptors, tacrine modulates tau levels mainly through interactions with nAChRs and not with muscarinic receptors. Additional work is needed to determine the exact mechanism by which cholinesterase inhibitors and nicotinic agonists modulate phosphorylation and levels of tau protein.

Alkaline Phosphatase↗

PubMed1987

Isolation and characterization of full-length cDNA clones coding for cholinesterase from fetal human tissues.

To study the primary structure and regulation of human cholinesterases, oligodeoxynucleotide probes were prepared according to a consensus peptide sequence present in the active site of both human serum pseudocholinesterase (BtChoEase; EC 3.1.1.8) and Torpedo electric organ "true" acetylcholinesterase (AcChoEase; EC 3.1.1.7). Using these probes, we isolated several cDNA clones from lambda gt10 libraries of fetal brain and liver origins. These include 2.4-kilobase cDNA clones that code for a polypeptide containing a putative signal peptide and the N-terminal, active site, and C-terminal peptides of human BtChoEase, suggesting that they code either for BtChoEase itself or for a very similar but distinct fetal form of cholinesterase. In RNA blots of poly(A)+ RNA from the cholinesterase-producing fetal brain and liver, these cDNAs hybridized with a single 2.5-kilobase band. Blot hybridization to human genomic DNA revealed that these fetal BtChoEase cDNA clones hybridize with DNA fragments of the total length of 17.5 kilobases, and signal intensities indicated that these sequences are not present in many copies. Both the cDNA-encoded protein and its nucleotide sequence display striking homology to parallel sequences published for Torpedo AcChoEase. These findings demonstrate extensive homologies between the fetal BtChoEase encoded by these clones and other cholinesterases of various forms and species.

Acetylcholinesterase↗

PubMedDate not supplied

Weak inhibitors protect cholinesterases from stronger inhibitors (dichlorvos): in vitro effect of tiapride.

Metoclopramide is a benzamide dopamine receptor antagonist and serotonine receptor agonist widely used as an antiemetic and gastric prokinetic drug. In addition, metoclopramide is a weak and reversible inhibitor of cholinesterases. The authors have previously shown that metoclopramide has a cholinesterase protective effect against inhibition by organophosphates (OPs). The putative mode of protective action of metoclopramide is, when administered in excess, competion for the active site of the enzyme with the more potent OP. In the present paper the authors present their results using another benzamide with weak cholinesterase inhibitory properties, tiapride (TIA). The purpose of the study was to quantify in vitro the extent of TIA-conferred protection, using dichlorvos (dichlorovinyl dimethyl phosphate; DDVP) as an inhibitor. DDVP is a moderately toxic (LD50 in rats in the milligram range), non-neuropathic OP. The substance is responsible for a large number of accidental or suicidal exposures. Red blood cell (RBC) acetylcholinesterase (AChE) activities in whole blood and butyrylcholinesterase (BChE) activities in human plasma were measured photometrically in the presence of different DDVP and TIA concentrations and IC50 was calculated. Determinations were repeated in the presence of increasing TIA concentrations. The IC50 of DDVP increases with the TIA concentration in a linear manner. The protective effect of TIA on cholinesterase could be of practical relevance in the treatment of OP poisoning. The authors conclude that in vivo testing of TIA as an OP protective agent is warranted.

Acetylcholinesterase↗

PubMed2006

Measuring cholinesterase activity in human saliva.

To assess the potential for using saliva in pesticide biomonitoring, the consistency of cholinesterase activity in human saliva collected over time was examined. In this pilot study, saliva was collected from 20 healthy adults once per week for 5 consecutive weeks using 2 different collection methods: a disposable plastic pipette, and a cotton-wool roll. A brief questionnaire was conducted each week to document changes in exposure to cholinesterase inhibitors for the duration of the sampling. To measure cholinesterase activity, an existing radiometric method was modified to make it suitable for human saliva. Using this method, cholinesterase activity was measurable in saliva, and duplicate samples showed reliable repeatability. Activity in both collection methods ranged from 3 to 265 nmol/h/ml saliva (mean = 52 +/- 37 [SD] nmol/h/ml saliva). For some individuals, enzyme activity was consistent over the five sampling weeks; for others, activity was highly variable. Coefficients of variation (CVs) were calculated to assess variability, and mean CVs were the same for both collection methods (about 35%). Adjusting for protein concentration in the pipette-collected samples did not change results. Both collection methods worked well for collecting between 1 and 3 ml saliva, but at the majority of visits (86%), participants preferred the cotton-wool roll. Results from this study suggest that saliva may be a useful indicator of potential neurotoxic effects from exposure to organophosphorus and carbamate pesticides, but that factors affecting variability should be explored further.

Adult↗

PubMed1978

Plasmapheresis and plasma cholinesterase.

Plasma cholinesterase (E.C. 3.1.1.8) concentrations were measured in nine outpatients who were undergoing regular plasmapheresis. A single plasmapheresis produced a 64% reduction in cholinesterase concentration compared with the value before plasmaphersis. Another patient who received four plasma exchanges in 6 days showed a progressive reduction in cholinesterase concentration to only 8% of the initial value. It is suggested that drugs metabolized by cholinesterase should be used with caution in patients undergoing plasmapheresis, particularly when frequent plasma exchanges are undertaken.

Adolescent↗

PubMed1989

Intra-individual variation in plasma and erythrocyte cholinesterase activities and the monitoring of uptake of organo-phosphate pesticides.

The measurement of plasma and erythrocyte cholinesterase activities is used to monitor absorption of anti-cholinesterase organo-phosphorus compounds. A fall in an individual's enzyme activity signifies excessive exposure if it is clearly greater than the normal intra-individual variation found in unexposed subjects. The extent of normal variation in enzyme activity as measured is dependent on both the true intra-individual biological variation and the precision of the method used. This report defines normal variation in plasma and erythrocyte cholinesterase activity using the assay developed and used routinely in our laboratory. We have also defined the relation between the precision of the assay used by a laboratory and the sensitivity with which a significant depression in successive enzyme measurements can be detected. This allows occupational physicians, who use cholinesterase measurements to monitor organo-phosphate exposure, to establish percentage depressions from their method precision data that may possibly indicate organo-phosphate uptake between successive enzyme measurements. We have calculated that, with our analytical precision, percentage drops between two successive measurements that are greater than 15 and 7.5 per cent for the plasma and erythrocyte enzymes respectively suggest significant organo-phosphorus absorption in pesticide workers.

Cholinesterase Inhibitors↗

PubMed1993

Cholinesterase assessment as a result of fenitrothion exposure: a survey in a group of public health workers exposed to an organophosphorus pesticide.

Antimalarial spraying activities are very important for the malaria control programme in Central Region, Sudan. Fenitrothion, an organophosphorus pesticide, is used for that purpose. A survey of 17 spraying group workers plus three controls was carried out. Whole blood cholinesterase determination was done using the Tintometric method. The maximum and minimum temperatures recorded on the days of the survey were 99 and 78 degrees F respectively. The relative humidity ranged between 82 and 40 per cent in the morning and afternoon respectively. Cholinesterase levels were measured on two pre-start days and then pre- and post-exposure levels were determined on 13 days of a 42 day spraying campaign. On 11 out of the 13 days, cholinesterase levels showed a significant drop. The cholinesterase levels of some members of the spraying team decreased by 25 per cent, 37.5 per cent or 50 per cent which were considered as slight-moderate, moderate-pronounced and pronounced inhibition, respectively.

Adult↗

PubMed2005

Plasma cholinesterase level of Ethiopian farm workers exposed to chemical pesticide.

BACKGROUND: Pesticide applications can have unwanted health consequences. AIM: To study cholinesterase levels in farm workers with varying exposure to chemical pesticide. METHODS: Plasma cholinesterase (PChE) was measured in workers at two Ethiopian farms. A standard questionnaire adopted from the British Medical Research Council was used to determine the health status of the subjects. RESULTS: A total of 82 farm workers and 47 controls participated in the study. While the mean values of plasma cholinesterase were generally lower in those exposed, this difference was only significant in the sprayers at Birr farm (P<0.05). In this group, four sprayers had cholinesterase activity lower than 50%. CONCLUSION: The sprayers in both farms were the most affected groups, suggesting that improved controls on workplace exposure to pesticide is required in these groups of workers.

Adult↗