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PubMed1983

Cytochemical demonstrations of protease in human peripheral blood cells by use of new alpha-naphthyl ester substrates.

The proteases of human leukocytes were cytochemically studied by use of new alpha-naphthyl esters, tosyl-L-lysine-alpha-naphthyl ester (TLNE) and acetyl-L-tyrosine-alpha-naphthyl ester (ATNE). The hydrolytic activities were strong only in neutrophils, with both substrates. They were inhibited completely by DFP and chymostatin, but not by leupeptin and iodoacetate. These results indicate that chymotrypsin-like enzyme(s), capable of hydrolyzing both substrates, exist in neutrophils.

Chymotrypsin↗
PubMed1982

Histochemical localization of kallikrein-like Pro-Phe-Arg-naphthylester esterase activity in the rat kidney.

In the rat kidney the presence of the kallikrein-like pro-phe-argnaphthylester esterase activity was demonstrated by a simultaneous coupling azo dye method. The enzyme was identified as a serine-protease because it was inhibited by preincubation with diisopropyl-fluorophosphate and unaffected by sodium iodoacetate. Since kallikrein is a serine-protease and prophe-arg-naphthylester is a synthetic and sensitive substrate for kallikrein, the enzyme activity revealed by this method was considered to represent kallikrein, although non-kallikrein esterase activity is not totally excluded. The enzyme activity was localized mainly in the outer stripe of the outer medulla, with focal extensions primarily only in the lower half of the cortex corresponding to the medullary rays.

Animals↗
PubMed1975

Studies about the specificity of the histochemical localization of choline acetyltransferase.

1. Tissues examined for the histochemical localization of choline acetyltransferase are best fixed by acetone. 2. Topographical identification of choline acetyltransferase by its reaction products is not only substrate-dependent because a slight staining also occurred in the absence of the substrates choline and acetyl-coenzyme in the incubation medium. 3. Histochemical localization of choline acetyltransferase was inhibited by sarin but not by DFP or eserine. 4. According to Burt and Silver's method cells and cell organelles, of which the enzymatic content is doubtful, where stained. 5. Chloroacetylcholine-perchlorate did not inhibit the histochemical localization of choline acetyltransferase. 6. The staining of acetylcholinesterase showed a different topographical distribution although both methods were inhibited by sarin.

Acetone↗
PubMed1978

The multiple forms of brain acetylcholinesterase. II. A suggestion of their functional importance.

The pattern of the multiple forms of the acetylocholinesterase (AChE, E.C. 3.1.1.7) of the rat brain is investigated using polyacrylamide gradient micro-gel electrophoresis with regard to a possible functional importance of this individual forms. The patterns of the AChE-forms of selected regions of the CNS are compared and certain differences could be shown. After increased cholinergic input (into the hippocampus by electrical stimulation of the nc. septi medialis) an aggregation of AChE subunits is detectable. Subletal intoxication with an irreversible inhibitor of AChE is followed by a faster recovery of the smaller forms. A suggestion of a possible functional role of the multiple forms of AChE is discussed.

Acetylcholinesterase↗
PubMed1984

Protection against diisopropylfluorophosphate intoxication by pyridostigmine and physostigmine in combination with atropine and mecamylamine.

Atropine (A), mecamylamine (M), pyridostigmine (Py) and physostigmine (Ph) are pretreatment components of Mix I (A = 0.79, M = 0.79, Py = 0.056 mg/kg) and Mix II (A = 0.79, M = 0.79, Ph = 0.026 mg/kg). They have been successfully used in antagonizing Soman intoxication in experimental animals. Rats were pretreated with either Mix I or Mix II and subsequently exposed to diisopropylfluorphosphate (DFP). Pretreatment with Mix I or Mix II (i.m.) 30 min before DFP (i.v.) protected rats from the lethal effects of DFP. The protective ratios were 2.8 (Mix I) and 6.9 (Mix II). Changes in brain levels of acetylcholine (ACh) were measured to help understand the basis for effectiveness of these pretreatments. In the absence of DFP, pretreatments had no significant (P greater than 0.05) effect on bound or free ACh. Pretreatment did not prevent the DFP-induced rise in bound and free ACh nor the agent-induced physical incapacitation at 30 min post exposure. At 2 h after DFP exposure, rats pretreated with Mix II, but not Mix I, showed significant recovery from signs of physical incapacitation. At 30 min after the administration of 3.3 mg/kg of DFP (i.v.), the levels of free and bound ACh in rats given Mix I or Mix II pretreatment increased above control levels by 705% and 116% and 120% and 43%, respectively. By 2 h after DFP, cerebral ACh levels had changed to 437% and 91% with Mix I pretreatment and 26% and 50% with Mix II pretreatment. These data suggest a correlation between DFP-induced increases in the levels of cerebral ACh, possibly free, and physical incapacitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1979

The multiple forms of brain acetycholinesterase. III. Implications for the histochemical demonstration of acetylcholinesterase.

The multiple forms of acetylcholinesterase (AChE, E.C. 3.1.1.7) have been investigated with regard to their histochemical demonstrability. Their pattern is influenced by buffer treatment, fixation, and by incubation conditions causing aggregation and disaggregation as well as loss or inactivation of individual forms. The standard histochemical method for AChE preferentially demonstrates the high molecular forms. Most of the oligomer forms are washed out or inactivated. A selective demonstration of the highly aggregated forms is possible either by inhibition of the oligomers with diisopropylfluoridate (DFP) or by specifically dissolving them out. No reason could be found for the selective demonstration of the low molecular weight forms.

Acetylcholinesterase↗
PubMed1994

Insecticide resistance and malathion carboxylesterase in the sheep blowfly, Lucilia cuprina.

Resistance to the organophosphorus insecticide malathion in genetically related strains of the Australian sheep blowfly Lucilia cuprina was examined. Separate lines of blowflies were established by homozygosis of the fourth chromosome of the parental RM strain. Both the RM and the derived resistant (der-R) strains are approximately 100 times more resistant to malathion than the related susceptible der-S strain, resistance being correlated with a 45- to 50-fold increase in a malathion carboxylesterase (MCE) activity. MCE has a pH optimum ranging between 6.6 and 8.0 and is strongly inhibited by the carboxylesterase inhibitors triphenyl phosphate, paraoxon, and diisopropylfluorophosphate. Subcellular fractionation revealed that MCE was localized predominantly to the cytosol and mitochondria in both resistant and susceptible blowflies. A single MCE was purified to homogeneity from RM blowflies. It has a pI of 5.5, is a monomer of 60.5 kDa, and hydrolyzes malathion with a Vmax of 755 nmol/min/mg protein and a Km of 11.0 microM. L. cuprina have thus evolved a remarkable MCE which is faster and more efficient at hydrolyzing a specific insecticide than any other insect esterase vet described.

Amino Acid Sequence↗
PubMed1996

Biochemical characterization of juvenile hormone esterases from lines selected for high or low enzyme activity in Gryllus assimilis.

In a previous study, activity of the insect endocrine regulator juvenile hormone esterase (JHE), in the cricket Gryllus assimilis, was subjected to bidirectional selection. This resulted in three pairs of high- and low-selected lines, each of which differed by 3.5-fold in JHE activity. In the present study, juvenile hormone esterases from these lines were characterized with respect to the Michaelis constant (K(m)), thermostability, and inhibition. None of three high-selected JHEs differed from its respective low-selected JHE in the Michaelis constant (K(m)) for juvenile hormone. Similarly, the high-selected JHEs did not differ from the low selected JHEs in thermostability or inhibition by either of two general esterase inhibitors (DFP, eserine) or a "JHE-specific" inhibitor (OTFP). Thus no evidence was obtained to suggest that the response to selection was due to allozymes or isozymes with altered kinetic or stability properties. Kinetic and stability properties were also very similar for the JHEs from the three high-selected or the three low-selected lines. Finally, none of the thermostability or inhibition profiles for any of the six JHEs exhibited sharp discontinuities, thus providing no evidence for the existence of multiple isozymes. The available evidence points to genetically variable regulators which affect the synthesis, degradation, or tissue distribution of JHE as being responsible for the divergence in JHE activity between the selected lines.

Acetone↗
PubMed1976

Efficacy of repeated pharmacotherapy in experimental acute poisonings with fluostigmine.

The effectiveness of repeated pharamacotherapy in acute poisonings with fluostigmine was studied in rats. It was demonstrated, that the second i.p. administration of obidoxime (40 mg/kg) was without effect. Repeated i.p. administration of atropine (10 mg/kg) shown marked efficacy only in animals treated previously with atropine (10 mg/kg) and diazepam (2.5 mg/kg). This procedure was without effect in animals treated just after intoxication with atropine (10 mg/kg) or atropine (10 mg/kg) and obidoxime (40 mg/kg). Subsequent administration of diazepam (2.5 mg/kg) or caramiphen (10 mg/kg) was without effect.

Animals↗