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Biomedical subjects

M Chow

Publications and source records attributed to M Chow.

At least 91 records · Page 5Linked to original sources
PubMed1985

Three-dimensional structure of poliovirus at 2.9 A resolution.

The three-dimensional structure of poliovirus has been determined at 2.9 A resolution by x-ray crystallographic methods. Each of the three major capsid proteins (VP1, VP2, and VP3) contains a "core" consisting of an eight-stranded antiparallel beta barrel with two flanking helices. The arrangement of beta strands and helices is structurally similar and topologically identical to the folding pattern of the capsid proteins of several icosahedral plant viruses. In each of the major capsid proteins, the "connecting loops" and NH2- and COOH-terminal extensions are structurally dissimilar. The packing of the subunit "cores" to form the virion shell is reminiscent of the packing in the T = 3 plant viruses, but is significantly different in detail. Differences in the orientations of the subunits cause dissimilar contacts at protein-protein interfaces, and are also responsible for two major surface features of the poliovirion: prominent peaks at the fivefold and threefold axes of the particle. The positions and interactions of the NH2- and COOH-terminal strands of the capsid proteins have important implications for virion assembly. Several of the "connecting loops" and COOH-terminal strands form prominent radial projections which are the antigenic sites of the virion.

Amino Acid Sequence↗
PubMed1985

Purification and characterization of a protein-tyrosine kinase encoded by the Abelson murine leukemia virus.

Sequences termed v-abl, which encode the protein-tyrosine kinase activity of Abelson murine leukemia virus, have been expressed in Escherichia coli as a fusion product (ptabl50 kinase). This fusion protein contains 80 amino acids of SV40 small t and the 403 amino acid protein kinase domain of v-abl. We report here the purification and characterization of this kinase. The purified material contains two proteins (Mr = 59,800 and 57,200), both of which possess sequences derived from v-abl. Overall purification was 3,750-fold, with a 31% yield, such that 117 micrograms of kinase could be obtained from 40 g of E. coli within 6-7 days. The specific kinase activity is over 170 mumol of phosphate min-1 mumol-1, comparable to the most active protein-serine kinases. Kinase activity is insensitive to K+, Na+, Ca2+, Ca2+-calmodulin, cAMP, or cAMP-dependent protein kinase inhibitor. The Km for ATP is dependent on the concentration of the second substrate. GTP can also be used as a phosphate donor. The enzyme can phosphorylate peptides consisting of as few as two amino acids and, at a very low rate, free tyrosine. Incubation of the kinase with [gamma-32P]ATP results in incorporation of 1.0 mol of phosphate/mol of protein. This reaction, however, cannot be blocked by prior incubation with unlabeled ATP. Incubation of 32P-labeled kinase with either ADP or ATP results in the synthesis of [32P]ATP. This suggests the phosphotyrosine residue on the Abelson kinase contains a high energy phosphate bond.

Abelson murine leukemia virus↗
PubMed1985

Synthetic peptides from four separate regions of the poliovirus type 1 capsid protein VP1 induce neutralizing antibodies.

Peptides from different regions of the poliovirus type 1 capsid protein VP1 were synthesized. Antibodies raised against these peptides in rabbits and rats recognized the cognate peptides and denatured VP1. Peptides from four regions of VP1 generated antisera with neutralizing titers specifically against poliovirus type 1. Antisera against all other regions of VP1 failed to neutralize virus infectivity, although some of the antisera clearly bound to native virions. Thus, the neutralizing determinants on VP1 reside in specific noncontiguous regions of the protein and can be defined by specific peptides from these regions.

Amino Acid Sequence↗
PubMed1982

Synthesis of murine leukemia virus plus strong stop DNA initiates at a unique site.

The 5'-terminal segment of plus strong stop DNA has been isolated from an endogenous virion reverse transcription reaction and characterized. The plus strong stop DNA is shown to initiate with the sequence 5'AATGAAAGA.... The 5'-terminal nucleotide is a deoxyribonucleotide. No residual protein or RNA moiety was found attached to the plus strong stop DNA. Thus, the mechanism which primes plus strand synthesis is still unclear. No evidence for multiple initiation sites or heterogeneous starts is observed. This data indicates that the initiation of plus strong stop DNA synthesis by the virion RNA-dependent DNA polymerase is a precise event which occurs at a unique site on the retrovirus genome.

Base Sequence↗
PubMed1982

Isolated poliovirus capsid protein VP1 induces a neutralizing response in rats.

Antibodies were raised in rats against the poliovirus type 1 capsid proteins, VP1, VP2, and VP3. Antibodies directed against VP1 from type 1 poliovirus (Mahoney) neutralized type 1 but not type 2 poliovirus. Antibodies raised against VP2 and VP3 failed to neutralize type 1 virus. Thus, VP1 appears to be a neutralizing antigen for poliovirus and in its denatured form presents to the immune system its neutralizing determinants.

Animals↗
PubMed1979

Ticarcillin.

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Humans↗
PubMed1978

Prediction of gentamicin serum levels using a one-compartment open linear pharmacokinetic model.

The accuracy of predicting serum gentamicin levels based on a one-compartment open linear pharmacokinetic model was studied. Twenty-two patients accounted for 59 serum gentamicin levels which were measured by microbiologic assay and compared with predicted serum levels determined by pharmacokinetic calculation. Seventeen serum levels were collected at peak times, 15 at trough time and 27 at times between peak and trough. Forty-nine of the levels were obtained from patients with impaired renal function. Predicated gentamicin levels correlated well with measured serum levels (r = 0.85, p less than 0.001). Of the measured levels, 56% were within +/- 1 microgram/ml of the predicted levels. Of 49 levels collected from patients with impaired renal function, 59% were within +/- 1 microgram/ml of the predicted level. In 13 patients from whom multiple serum gentamicin levels were collected and predictions based on half-life or elimination rate obtained by fitting the first level, 83% of the measured levels were within +/- 1 microgram/ml of the predicted level. The one-compartment open linear pharmacokinetic calculations can be used to adequately predict serum gentamicin levels. In patients with changing or diminished renal function, pharmacokinetic predictions may not be accurate, and actual serum level determinations may be needed to monitor gentamicin therapy.

Adult↗
PubMed1977

Circulating immune complexes in patients with atopic allergy.

Sera from forty-nine patients with atopic allergy were tested for the presence of circulating immune complexes by the sensitive, quantitative Clq assay. Compared to twenty-five normal individuals the atopic patients had significantly higher mean values of Clq reactive material, expressed as Clq inhibition values. The highest mean values were seen in the group (twenty-one patients) who had been on long term maintenance immunotherapy for 5 or more years. When positive sera were fractionated by ultracentrifugation on sucrose density gradients, the Clq reactive material was found in intermediate (7S-19S) and heavy (greater than 19S) regions. The heavy material contained both IgM and IgG. It is suggested that the IgG antibodies known to be produced by chronic hyposensitization procedures in allergic individuals may circulate in the serum as antibody-allergen immune complexes, and could carry out their blocking action in this form.

Antigen-Antibody Complex↗
PubMed1975

Considerations of symmetry in the cortical integration of tetrahymena doublets.

Homopolar doublets of syngen 1, T. pyriformis, may be induced by treatment of conjugating pairs with immobilizing antiserum. These doublets have geometric properties and basal body populations generally indicative of separate autonomous integrative systems in the two halves. The duplex system, though metastable, is transformed through a process of "simplification" back to the simplex state. The transformation is not a single event, but a series involving changes at different times for different structures and processes; for the micronuclei and the macronuclei; for the capacity to generate two oral apparatuses through stomatogenesis and the capacity to develop them through oral replacement; for the structures at the anterior and posterior ends of the cell; for the numbers of ciliary rows and for the numbers of basal bodies which make up the rows. Although the two semicells composing a doublet are in important respects independent of each other, they are coordinated in significant ways. The positions of the contractile vacuole pores and their numbers depend not only on the number of ciliary rows in a semicell, but also on the number of ciliary rows in the opposing twin. Most notably, the probability for dual stomatogenesis, and hence the perpetuation of the doubled oral apparatus, depends on the symmetry of the semicells. The cell as a whole is maintained as an integrated unit over a prolonged interval as various aspects of duplex structure and function are progressively consolidated.

Cilia↗