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Biomedical subjects

F Rieger

Publications and source records attributed to F Rieger.

At least 127 records · Page 7Linked to original sources
PubMed1981

Cellular localization of the multiple molecular forms of acetylcholinesterase in cultured neuronal cells.

The cellular localization of the molecular forms of acetylcholinesterase was explored in chick sympathetic neurons and in mouse T28 cells (neuroblastoma X sympathetic ganglion cell hybrids) using the reversible, poorly lipid-soluble inhibitor of acetylcholinesterase, BW284C51, to protect cell surface activity while inactivating cytoplasmic activity with DFP, an irreversible, lipid-soluble inhibitor. Our results show protection of over 80% of the chick 11 S form and over 90% of the corresponding mouse 10 S form under these conditions, while over 90% of the chick 6.5 S and mouse 4 S forms are inhibited. The results suggest that the avian 11 S and mouse 10 S forms are predominantly or exclusively ectoenzymes while the respective 6.5 S and 4 S forms are confined to the cytoplasm.

Acetylcholinesterase↗
PubMed1981

Biochemical stability of the AChE molecular forms after cytochemical staining: postnatal focalization of the 16S AChE in rat muscle.

A biochemical analysis of rat muscle acetylcholinesterase (AChE) is possible after a cytochemical staining at pH7 (Koelle and Friedenwald method). The solubilization properties, the physicochemical characteristics (sedimentation coefficients) of the multiple molecular forms of AChE are similar before and after the cytochemical procedure without fixation and without ammonium sulfide treatment. This is in contrast to the partial inactivation obtained after conventional pH 5 cytochemical staining, which selectively inactivates 16S AChE. We found that pH 7 cytochemical staining in these same conditions afford a satisfying morphological visualization of the motor end-plate AChE. The combined cytochemical-biochemical techniques allow a very precise dissection of motor end-plate containing (neural) and free (aneural) regions. In rat muscle (sternomastoid), high levels of 16S AChE are present in the aneural region in the first stages of postnatal development. At the end of the 1st month after birth, the 16S AChE becomes restricted to the neural (motor end-plate) region.

Acetylcholinesterase↗
PubMed1981

[Molecular forms of acetylcholinesterase in frog skeletal muscle: effects of denervation].

In the muscles of the frog, four main molecular forms of acetylcholinesterase are present, with sedimentation coefficients of 5.7, 10.4, 13 and 17.6 S. The heaviest forms, 13 S and 17.6 S are found in both nerve-free segments and endplates zones of sartorius muscle. They decrease in long-term denervation experiments. Consequently, these two forms are not specifically localized in endplates containing regions. However, they depend either on muscle activity or on neural influence or both.

Acetylcholinesterase↗
PubMed1980

Development of the multiple molecular forms of acetylcholinesterase in chick paravertebral sympathetic ganglia: an in vivo and in vitro study.

The development of acetylcholinesterase (AChE) activity and the distribution of this enzyme among its multiple forms was studied in both tissue extracts and dissociated cell cultures of chick paravertebral sympathetic ganglia. In agreement with previous findings, total AChE (expressed either per ganglion or per microgram protein) increased in vivo between the time of formation of the paravertebral chain (embryonic day 7; E7) to hatching (E20-E21). After this time, enzyme activity changed much more slowly. Sucrose gradient sedimentation analysis of AChE in ganglia of post-hatching chicks revealed multiple forms of AChE with S values of approximately 6.5, 11 and 19.5. Developmental studies showed that 6.5 S and 11 S forms are present as early as day E7. Much of the pre-hatching increase in total AChE is due to increased levels of the 6.5 S form of the enzyme. By hatching, this form comprised approximately 85-90% of the total AChE activity. In contrast, during the first week after hatching, the activity of the 11 S form increased several-fold while that of the 6.5 S remained approximately unchanged. The 19.5 S form, which is thought to be associated with the synaptic membrane, was not detected prior to day E17 and reached adult levels (2-3% of total AChE activity) by the first week after hatching. Development of AChE was also studied in dissociated cell cultures of embryonic ganglia. Essentially all the AChE activity in such cultures was found to be associated with the neurons. Total AChE activity of cultured E11 ganglia increased in a pattern which was both qualitatively and quantitatively similar to that which occurred in vivol. Furthermore, it was found that development of both the 6.5 and 11 S forms of AChE took place in vitro. In cultures of E8, E11, E15 and E19 ganglia, the distribution of activity between the two forms after various times in vitro was similar to that which was found for in vivo ganglia at an equivalent embryonic stage. Such changes were not affected by the elimination of nonneuronal cells from the cultures. Two aspects of in vitro development, however, differed from that which occurred in vivo. First, an increase in 11 S AChE did not occur at ages equivalent to the first week post-hatching. Second, the 19.5 S form did not develop (even after several weeks) in cultures of E8, E11 and E15 ganglia, nor was this form (which was removed during dissociation of the ganglia) regenerated in cultures of E19 ganglia. Such findings suggest that the pattern of development of AChE and its multiple forms in chick sympathetic neurons is in part intrinsically programmed into these cells at an early stage of development as well as in part regulated by extrinsic signals that these cells receive from their chemical and cellular environment.

Acetylcholinesterase↗
PubMed1976

Torpedo marmorata acetylcholinesterase; a comparison with the Electrophorus electricus enzyme. Molecular forms, subunits, electron microscopy, immunological relationship.

Electron microscopy, sequential degradation by hydrolytic enzymes and the physical-chemical properties of the molecular forms of Torpedo acetylcholinesterase indicate that these molecules are structurally related to each other in the same way as the molecular forms of Electrophorus acetylcholinesterase: all are derived from a complex structure in which three tetrameric groups of subunits are associated with a rod-like 'tail'. In aged preparations the catalytic subunits are split into fragments in a manner similar to those of Electrophorus acetylcholinesterase. Immunological cross-reaction between both enzymes demonstrates the occurrence of common antigenic sites. The enzymes from the two sources, however, are different in their molecular weights and susceptibility to hydrolytic enzymes. Also, Torpedo acetylcholinesterase does not precipitate with either isologous or heterologous antibodies.

Acetylcholinesterase↗
PubMed1976

Molecular forms of Electrophorus acetylcholinesterase. Molecular weight and composition.

Molecular weights for the series of six Electrophorus acetylcholinesterase forms have been determined either by the sedimentation-diffusion equilibrium method or, particularly in the case of the very scarce G' and G inches forms, from their Stokes radius and sedimentation coefficient values. Both methods are in excellent agreement. The results provide good evidence for the model previously proposed, G inches, G' and G containing one, two and four subunits, whereas A, C and D possess, in addition to respectively one, two and three tetrameric sets of such subunits, a structural element, the tail. Although the amino acid composition of 'tailed' and globular forms did not reveal any significant feature of this element, its mass, about 100 000 daltons, could be deduced from a comparison of molecular weights for the two classes of acetylcholinesterase forms. This value is in close agreement with electron microscopic data. The tail is thought to consist of three 30 000-dalton strands.

Acetylcholinesterase↗
PubMed1976

Molecular forms of acetylcholinesterase: their de novo synthesis in mouse neuroblastoma cells.

Rat mouse AChE molecular forms are indistinguishable with respect to their sedimentation coefficients and their evolutive proportions during brain maturation. Among rat or mouse erythrocytes, rat C6 glial cells, and mouse 2A and NS 20 neuroblastoma cells, only neuroblastoma cells showed both the ES and HS molecular forms with a 1:1 proportion for NS 20 cells. All these cells lack a third molecular form (16S), which is present in rat and mouse superior cervical ganglia. After irreversible inhibition of pre-existing NS 20 neuroblastoma AchE, the ES form is first synthesized (de novo synthesis). The HS form begins to appear after a lag time of several hours and represents, 24 h after inhibition, only 15% of the total recovered activity, which is near the initial level. The initial relative proportions return by 2 to 3 days after inhibition. The recovery of the HS form is, for the most part, blocked by actinomycin D, which does not block the recovery of activity itself, which remains as an ES form. It seems that integration of the ES form into the HS form more probably depends on the synthesis of a new messenger RNA, which is required for the synthesis of either new AChE polypeptide chain, polymerization initiating protein or activating enzyme.

Acetylcholinesterase↗