Browsing by Author "PERELMAN, A"

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    A SIMPLE ASSAY TO ESTIMATE THE ACETYLCHOLINESTERASE MOLECULAR-FORMS IN CRUDE EXTRACTS OF RAT SKELETAL-MUSCLE
    (1989) PERELMAN, A; INESTROSA, NC
    All the current methods available for analyzing the acetylcholinesterase (AChE) molecular forms are time consuming and require the use of expensive equipment. We have found that by using the differential inactivation of globular (G4 + G1) and asymmetric AChE forms by high Mg2+ concentration, we can set up a very easy and quick assay that allows us to determine the relative proportions of AChE molecular forms present in rat skeletal muscles. This assay will be of great help in estimating changes in the muscle AChE forms under experimental conditions that require several simultaneous determinations.
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    DIFFERENT MEMBRANE-BOUND FORMS OF ACETYLCHOLINESTERASE ARE PRESENT AT THE CELL-SURFACE OF HEPATOCYTES
    (1989) PERELMAN, A; BRANDAN, E
    In the present study we have determinated the acetylcholinesterase molecular forms present in rat liver hepatocytes; we have also studied the association of acetylcholinesterase with the cell surface of the hepatocytes. Subcellular fractionation indicated that rough endoplasmic reticulum and plasma-membrane-enriched fractions contains G4 and G2 acetylcholinesterase forms bound to membranes. Hepatocytes incubated with phosphatidylinositol-specific phospholipase C released about 70% of the surface acetylcholinesterase. Sedimentation analysis showed that all the solubilized acetylcholinesterase activity comes exclusively from a G2 dimer. The G4 hydrophobic form of acetylcholinesterase accounts for the additional cell-surface activity. The existence of these two forms of acetylcholinesterase on the surface of hepatocytes was further established by analyzing the phosphatidylinositol-specific phospholipase C sensitivity of the acetylcholinesterase molecular forms present in isolated rat liver plasma membranes.
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    DIFFERENTIAL ASSOCIATION AND DISTRIBUTION OF ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE WITHIN RAT-LIVER SUBCELLULAR ORGANELLES
    (1990) PERELMAN, A; ABEIJON, C; HIRSCHBERG, CB; INESTROSA, NC; BRANDAN, E
    Rat liver cholinesterases were found to share properties and characteristics with those expressed in cholinergic tissues. The distribution and presence of different molecular forms of cholinesterases in different subcellular organelles of rat liver were studied. The rough and smooth endoplasmic reticulum and Golgi apparatus were enriched in the G4 molecular form of acetylcholinesterase (AChE) (relative to the G2 molecular form), while the inverse was found in the plasma membrane. The interaction of these molecular forms of AChE with the Golgi membrane was studied in detail. Approximately one-half of the G4 form was free within the lumen while the remainder was an intrinsic membrane protein; all the G2 molecular form was anchored to the membrane via phosphatidylinositol. Only the G1 and G2 molecular forms of butyrylcholinesterase (BuChE) were found in the above subcellular organelles; both molecular forms were soluble within the lumen of Golgi vesicles. These results indicate that rat liver expresses several molecular forms of AChE which have multiple interactions with membranes and that liver is unlikely to be the source of the G4 form of BuChE present in high concentration in the plasma.
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    NEUROTRANSMITTER-RELATED ENZYME ACETYLCHOLINESTERASE IN JUVENILES OF CONCHOLEPAS-CONCHOLEPAS (MOLLUSCA, GASTROPODA, MURICIDAE)
    (1990) GONZALEZ, M; PERELMAN, A; FUENTES, ME; CASTILLA, JC; LABARCA, R; BRANDAN, E; GONZALEZPLAZA, R; INESTROSA, NC
    With the aim of understanding the organization of the nervous systemn in the Prosobranchia gastropod Concholepas concholepas, we studied the properties, specificity, sedimentation coefficient, and solubility of the cholinergic enzyme, acetylcholinesterase (AChE). It was found that 95% of the esterase was inhibited by BW284c51 dibromide but not by iso-OMPA, which is consistent with the specificity of AChE. The calculated Km 0.22 mM is eight to ten times higher than are the Kms for AChE of other invertebrates and similar to the values reported for fish and vertebrates. The AChE shows a maximal activity around 22.degree. C, has a glycoprotein character and presents sedimentation coefficients of 6.5 S and 10.5 S. Most of this AChE activity is soluble under low ionic strength conditions; however, the enzyme aggregates in the absence of detergents. In conclusion, our evidence indicates the presence of a well-recognized molecular marker that could be useful for the study of the development of Concholepas concholepas.