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S H Yen

Publications and source records attributed to S H Yen.

10 recordsLinked to original sources
PubMed1979

Biochemical and immunological characterization of neurofilaments in experimental neurofibrillary degeneration induced by aluminum.

In order to identify the protein composition of 10 nm neuronal filaments, we prepared enriched fractions of rabbit spinal neurons undergoing experimental neurofilamentous degeneration induced by aluminum. Electron microscopy of the isolated perikarya showed well-preserved, large perinuclear masses of neurofilaments, which were not found in similarly isolated control perikarya. Comparison of these glial-free fractions by SDS-polyacrylamide gel electrophoresis revealed several-fold augmentation in the filament-enriched neurons of proteins migrating at 68,000 and 160,000 daltons, with an additional component at 200,000 daltons. Otherwise, the protein patterns were identical; no band was found at 51,000 daltons, the molecular weight assigned to the major proteins both of glial filaments and of a previously reported bovine brain filament preparation. An antiserum raised against the 160,000 dalton component of a modified bovine brain filament fraction produced specific and intense fluorescent staining of the aluminum-induced neurofilament bundles. Antibodies to the 51,000 dalton protein of brain filaments and to tubulin failed to stain the induced filaments. The results strongly support the hypothesis that both normal and aluminum-induced neuronal filaments are composed of 68,000, 160,000 and 200,000 dalton polypeptides and do not contain significant amounts of the 51,000 dalton filament protein. The likelihood of biochemical heterogeneity among organelles with similar morphology, namely the glial and neuronal filaments, is raised.

Aluminum↗
PubMed1979

Dopamine beta-hydroxylase distribution in density gradients: physiological and artefactual implications.

Knowledge of the vesicular origin of circulating dopamine beta-hydroxylase (DbetaH) is indispensable for any attempts to explain the parallelism or lack of it between circulating enzyme and catecholamines as they may relate to physiological stress, forms of hypertension, neurological disorders, and the response to pharmacological agents. The present study represents an effort to evaluate and to place in proper perspective data based on the DbetaH activity found in the region of the light vesicle peak of noradrenaline (NA), which is used as a quantitative measure of a population of small terminal vesicles. Distributions of vesicles and subvesicular components are compared with DbetaH and NA in sucrose-D2O density gradients used to prepare relatively pure fractions of large dense cored vesicles (LDV) from bovine splenic nerve. Although NA in sedimentable particles of the light vesicle peak is likely to be a valid measure of a small vesicle population, the following is demonstrated: (1) A substantial fraction (25%-37%) of the total sedimentable DbetaH activity can be proven to distribute in the region of the light vesicle peak from a tissue with an insignificant small vesicle population. Based on studies of vesicles from sequential nerve segments, this enzyme activity probably corresponds to a population of "immature" LDV which are undergoing axoplasmic transport and have not synthesized their full complement of transmitter. (2) Physical lysis which depletes the matrix of LDV causes redistribution of DbetaH activity from the heavy vesicle peak into the region of the light vesicle peak. Analogously, DbetaH associated with exocytosed LDV and retrograde transport particles is also likely to contaminate the region of the light vesicle peak. (3) Based on available data, it can be calculated that each small dense cored vesicle could contain only 0.1-0.5 molecules of DbetaH and that a contamination of only 0.016% LDV can account for all of the DbetaH reported to occur in the light vesicle peak of normal rat vas deferens preparations.

Animals↗
PubMed1978

Intermediate filaments in nervous tissues.

Intermediate filaments have been isolated from rabbit intradural spinal nerve roots by the axonal flotation method. This method was modified to avoid exposure of axons to low ionic strength medium. The purified filaments are morphologically 75-80 percent pure. The gel electrophoretogram shows four major bands migrating at 200,000, 145,000, 68,000, and 60,000 daltons, respectively. A similar preparation from rabbit brain shows four major polypeptides with mol wt of 200,000 145,000, 68,000, and 51,000 daltons. These results indicate that the neurofilament is composed of a triplet of polypepetides with mol wt of 200,000, 145,000, and 68,000 daltons. The 51,000-dalton band that appears in brain filament preparations as the major polypeptide seems to be of glial origin. The significance of the 60,000- dalton band in the nerve root filament preparation is unclear at this time. Antibodies raised against two of the triplet proteins isolated from calf brain localize by immunofluorescence to neurons in central and peripheral nerve. On the other hand, an antibody to the 51,000-dalton polypeptide gives only glial staining in the brain, and very weak peripheral nerve staining. Prolonged exposure of axons to low ionic strength medium solubilizes almost all of the triplet polypeptides, leaving behind only the 51,000- dalton component. This would indicate that the neurofilament is soluble at low ionic strength, whereas the glial filament is not. These results indicate that neurofilaments and glial filaments are composed of different polypeptides and have different solubility characteristics.

Animals↗
PubMed1976

Biochemistry of the filaments of brain.

Intermediate filaments-cytoplasmic filaments with a diameter of 8-9 nm-have been described in a large variety of cell types. In this study, the subunit protein of the neurofilament and the presumptive subunit of the astroglial filament are compared by immunological and biochemical methods and are found to be very similar. Strong crossreactions are also found between these proteins in a variety of mammalian species. These results suggest that the intermediate filaments may, like microtubules and microfilaments, represent a highly conserved and widely distributed fibrous protein system.

Animals↗