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Biomedical subjects

M W Yu

Publications and source records attributed to M W Yu.

70 records · Page 4Linked to original sources
PubMed1985

Interaction between various polymerized human albumins and hepatitis B surface antigen.

A variety of albumin polymers were prepared and tested for binding with hepatitis B surface antigen (HBsAg): synthetic polymers cross-linked by either glutaraldehyde or carbodiimide; heat-aggregated polymers made by heating albumin solutions at 60 degrees C for 10 h with or without albumin stabilizer; and polymers isolated from fresh or long-stored commercial therapeutic albumin solutions. A sensitive solid-phase, competitive-inhibition radioimmunoassay, which can detect as little as 10 ng of glutaraldehyde-cross-linked human albumin polymer (PHALB-G), was developed and used to measure binding. The binding of PHALB-G with HBsAg was 150- to 1,000-fold greater than that of any other albumin polymer. Glutaraldehyde-cross-linked bovine albumin polymer showed no binding. Albumin monomer and dimer fractions produced by glutaraldehyde treatment exhibited some binding, albeit much weaker than PHALB-G. As measured by a direct-binding assay with solid-phase PHALB-G, the attachment of HBsAg particles from sera positive for antibody to the e antigen was less efficient than that from sera positive for e antigen, even when all sera were tested at equal HBsAg concentrations. In protein blot experiments with radiolabeled albumin preparations, PHALB-G bound almost exclusively to HBsAg polypeptide P31 and showed no binding with the major polypeptides P23 and P26. None of the other radiolabeled albumin polymers was reactive. These results indicate that the interaction between PHALB-G and HBsAg is not due to polymerization of albumin per se, but rather is unique and site specific.

Binding, Competitive↗
PubMed1984

Quantitative determination of the stabilizers octanoic acid and N-acetyl-DL-tryptophan in human albumin products.

Methods were developed for the determination of octanoic acid and N-acetyl-DL-tryptophan, which are used as stabilizers in the human blood-derived therapeutic products normal serum albumin and plasma protein fraction. The method for octanoic acid uses GC; quantitation is achieved using heptanoic acid as the internal standard. The method for N-acetyl-DL-tryptophan is based on UV spectrophotometry of the acid-soluble fraction remaining after precipitation of the protein (epsilon 280 for N-acetyl-DL-tryptophan, 5250). The coefficient of variation for replicate determinations of octanoic acid averaged 3.9% (range 2.1-5.5%); that of N-acetyl-DL-tryptophan averaged 1.9% (range 0.5-4.0%). Use of these methods for the analysis of 138 lots of commercial products for octanoic acid and 159 lots for N-acetyl-DL-tryptophan showed that the stabilizer contents of 132 and 158 of these lots, respectively, were within 20% of the value indicated on the product label.

Albumins↗
PubMed1984

Stabilization of human albumin by caprylate and acetyltryptophanate.

The thermal stabilization of human albumin by caprylate (CA) and acetyltryptophanate (AT) was studied by monitoring the formation of albumin polymer (defined as species larger than dimer) on the basis of its molecular size as well as its characteristic migration as alpha-globulin. Heating 5% protein solutions of purified albumin monomer, cohn fraction V, and fraction IV-4 + V at 60 degrees C in 0.1 M sodium phosphate or 145 mM sodium chloride, pH 7.0, established the following order of stabilizer effectiveness: 4 mM CA + 4 mM AT approximately 4 mM CA greater than 8 mM AT greater than or equal to 2 mM CA greater than 4 mM AT. However, albumin was more thermally stable in the chloride medium. Raising the CA concentration above 4 mM provided little additional stabilization. The D- and L-enantiomers of AT were equally effective, but 16 mM AT was needed to equal the effect of 4 mM CA. L-Tryptophanate exerted only slight stabilization, even at 32 mM; D-tryptophanate was even less effective. The albumin polymer level increased progressively with time at 60 degrees C in 2 mM CA or 4 mM AT, whereas in 4 mM CA it reached a plateau in 4-6 h. Acetone drying of albumin-rich fractions was shown to remove nearly all endogenous fatty acid, rendering the protein thermally labile unless sufficient exogenous stabilizer(s) was added. Even in the presence of 145 mM sodium chloride and 4 mM CA + 4 mM AT or 4 mM CA, the stabilizing effect of endogenous fatty acid was still detectable.

Anions↗
PubMed1980

Increased phosphorylation of specific nuclear proteins in superior cervical ganglia and PC12 cells in response to nerve growth factor.

Treatment of rat superior cervical ganglia in culture with nerve growth factor (NGF) increases the amount of radioactive phosphate incorporated into a nuclear protein band. This band migrates coincidentally with H1 histone on 10% sodium dodecyl sulfate/polyacrylamide gels. The increase in phosphate incorporation is at least 70% and occurs only in tissues known to be responsive to NGF. It is not produced by treatment with related peptides, but is observed after the addition of dibutyryl cyclic AMP. An increase in phosphorylation can be detected after 1 h, and can be seen with as little as 10 ng/ml of NGF in the medium. Neither actinomycin D nor cycloheximide inhibits the effect. When the nuclei are extracted with 0.2 M H2SO4 and the extract analyzed on acid-urea/polyacrylamide gels, two NGF-responsive proteins can be detected. One protein again migrates with the H1 histone marker; the other migrates more slowly than H1. These two NGF-responsive proteins have molecular weights of approximately 30,000 and are chromatin-bound. They are not soluble in 5% perchloric acid, but can be extracted from the nuclei with 0.35 M NaCl. No increase in the phosphorylation of these proteins was seen in ganglia from 6-hydroxydopamine-treated rats. The phosphorylation of the proteins in both control and NGF-treated ganglia occurs almost exclusively on serine residues. The amino acid compositions of the two nuclear proteins show that they are different from the H1 histone and different from each other. Both nerve growth factor (NGF) and epidermal growth factor (EGF) increase the incorporation of radioactive phosphate into a specific nuclear protein in cultures of PC12, a clone of rat pheochromocytoma. Purified NGF antibody blocks the effect of NGF, but not that of EGF; EGF antiserum neutralizes the effect of EGF, but not that of NGF. Insulin, glucagon, and dexamethasone are without effect. The increase in phosphorylation due to NGF can be detected within 1 h. Dibutyryl cyclic AMP increases the phosphorylation of this protein, but dibutyryl cyclic GMP does not. Neither the uptake nor the overall incorporation of [32P]orthophosphate is altered by NGF, EGF, or dibutyryl cAMP under the present experimental conditions. The nuclear protein exhibiting increased radioactivity is similar in solubility, size, and amino acid composition to one of the NGF-responsive nuclear proteins from sympathetic ganglia.

Adrenal Gland Neoplasms↗
PubMed1975

Interaction of flavins with electron-rich metals.

A complex of the electron-rich ion Cu(I) with the flavoquinone analogue 10-methylisoalloxazine has been synthesized and characterized by x-ray methods. The complex is unstable to oxygen. It is black-green in color, in contrast with the bright yellow, orange, or orange-brown crystalline complexes of 10-methylisoalloxazine or riboflavin with Cu(II), Ag(I), and Pb(II). These results are indicative of strong perturbation of the flavin electronic structure by the Cu(I) ion and suggest that this complex is a reasonable model for incipient transfer of an electron from a reduced metal to flavoquinone. the crystal structure is orthorhombic, Pna2-1, with unit cell constants a = 31.24(1) (figures in parentheses are estimated standard deviations), b = 12.862(4), c = 6.239(2) A, Pobs = 1.76 g per cm-3 and Pcalc = 1.77 g per cm-3 for Z = 4 and asymmetric formula CuClO4-2(C11H8N4O2). HCOOH. The final R factor based on 1250 counter-measured data is 8.8%. The 2 independent 10-methylisoalloxazine molecules, A and B, bind strongly to the cuprous ion throug N(5) of each flavin. The copper is approximately linearly coordinated with an N-Cu-N angle of 153(1) degrees, and Cu-N(5) distances of 1.94(2) A and 1.92(2) A. The next nearest atoms to Cu are the O(4) oxygens of each flavin, forming weak bonds with distances Cu-O(4) = 2.27(2) A and 2.21(2) A for molecules A and B. The dihedral angle between the 2 10-methylisoalloxazine molecules is 65.4 degrees.

Binding Sites↗
PubMedDate not supplied

Partitioning of hepatitis C virus during Cohn-Oncley fractionation of plasma.

Because of concern about the safety of immune globulins with respect to transmission of hepatitis C, the partitioning of hepatitis C virus (HCV) during alcohol fractionation of a plasma pool prepared exclusively from anti-HCV-reactive donations was examined. Quantitation of HCV RNA was accomplished by nested polymerase chain reaction (PCR) at limiting dilutions. One PCR unit was arbitrarily defined as the minimum amount of HCV RNA from which an amplified product could be detected. The starting plasma pool contained 1.4 x 10(5) PCR units per mL. Most of the HCV RNA was found in cryoprecipitate and in Cohn fractions I and III, but it was also detected in fraction II, which is used for immunoglobulin G preparations. A 3.4-percent solution of IgG prepared from this fraction II contained 30 PCR units per mL. The fractionation process leading to immune globulin resulted in overall reduction in HCV RNA by a factor of 4.7 x 10(4). Although the presence of HCV RNA in the final product does not necessarily imply the presence of infectious virus, this work suggests that the safety of immune globulins with respect to HCV transmission is not due solely to the partitioning of HCV away from the immunoglobulin fraction.

Base Sequence↗