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Biomedical subjects

C C Liu

Publications and source records attributed to C C Liu.

At least 307 records · Page 17Linked to original sources
PubMed1973

Amino acid activation in mammalian brain. Purification and characterization of tryptophan-activating enzyme from buffalo brain.

l-Tryptophan-activating enzyme [l-tryptophan-tRNA ligase (AMP), EC 6.1.1.2] of water-buffalo brain was purified to near homogeneity by heat and pH treatments, ammonium sulphate fractionation, column chromatography on DEAE-cellulose, hydroxyapatite and Amberlite CG-50, and gel filtration on Sephadex G-200. The purified enzyme catalyses tryptophanyl-tRNA formation with yeast tRNA, but not with Escherichia coli tRNA. The enzyme exhibits multiple peaks of activity in Sephadex gel filtration with molecular weights corresponding to 155000, 105000 and 50000. However, only one peak of activity with molecular weight of 155000 can be detected when the enzyme is subjected to gel filtration at high concentration. Disc gel electrophoresis in the presence of sodium dodecyl sulphate reveals a single band with molecular weight of 55000. The activity of the enzyme is concentration dependent. Different K(m) and V(max.) values are obtained at different enzyme concentrations. These data suggest that this enzyme may exist in different quaternary structures, each with its own kinetic constants. The enzyme activity is inhibited by p-chloromercuribenzoate, and is not protected by the presence of the substrates, l-tryptophan, Mg(2+), ATP, in any combination.

Adenosine Triphosphate↗
PubMedDate not supplied

Neutralizing antibody provided protection against enterovirus type 71 lethal challenge in neonatal mice.

Experimental infection with enterovirus type 71 (EV71) induced death in neonatal mice in an age- and dose-dependent manner. The mortality rate was 100% following intraperitoneal inoculation 1-day-old ICR mice and this gradually decreased as the age at the time of inoculation increased (60% in 3-day-old mice and no deaths occurred in mice older than 6 days of age). A lethal dose greater than 10(8) PFU was necessary. Lethargy, failure to gain weight, rear limb tremors and paralysis were observed in the infected mice before death. EV71 was isolated from various tissues of the dead mice. Using a reverse transcription polymerase chain reaction technique with a specific primer pair, a 332-bp product was detected in the tissues that produced a culture positive for EV71. Protection against EV71 challenge in neonatal mice was demonstrated following passive transfer of serum from actively immunized adult mice 1 day after inoculation with the virus. Pups from hyperimmune dams were resistant to EV71 challenge. Additionally, maternal immunization with a formalin-inactivated whole-virus vaccine prolonged the survival of pups after EV71 lethal challenge.

Animals↗
PubMedDate not supplied

Applications of microfabrication techniques in electrochemical sensor development.

Electrochemical sensors have been used either as a whole or as an integral part of a chemical and biological sensing device. Microfabrication technology has been used in the development of electrochemical sensors. The recent advancement of micromachining techniques adds new impetus to electrochemical sensor development. Most noticeable is the application of anisotropic chemical etching, plasma etching, sacrificial layer methods, and high aspect ratio X-ray lithography to enhance the opportunity to produce scientifically and commercially viable electrochemical sensors. Examples will be used to illustrate the potential of microfabrication and micromachining techniques in electrochemical sensor development.

Anisotropy↗
PubMedDate not supplied

Human high molecular weight-melanoma associated antigen mimicry by mouse anti-idiotypic monoclonal antibodies MK2-23. Experimental studies and clinical trials in patients with malignant melanoma.

Following a description of the characteristics of the human high molecular weight-melanoma associated antigen (HMW-MAA), the rationale to use anti-idiotypic (anti-id) monoclonal antibodies (mAb) as immunogens to implement active specific immunotherapy in patients with malignant diseases is discussed. Among the anti-id mAb developed in this laboratory the mAb MK2-23, which had been elicited with the syngeneic anti-HMW-MAA mAb 763.74, has been shown with serological and immunochemical assays to bear the mirror image of the determinant recognized by mAb 763.74 on HMW-MAA. The anti-id mAb elicited humoral anti-HMW-MAA immunity in about 60% of patients with malignant melanoma. The immunogenicity of mAb MK2-23 is markedly enhanced by conjugation to a carrier and administration with an adjuvant, but is not affected by the administration of low doses of cyclophosphamide. Development of anti-HMW-MAA immunity in patients with malignant melanoma is associated with survival prolongation. These results in conjunction with the lack of major side effects in spite of repeated administrations of mAb MK2-23 suggest that active specific immunotherapy with mAb MK2-23 represents a useful therapeutic approach to malignant melanoma.

Animals↗
PubMedDate not supplied

Initiation of translation at internal AUG codons in mammalian cells.

Initiation of translation of eukaryotic mRNAs typically occurs at the first AUG triplet from the 5' end of the message, although several notable exceptions have been described. Using vectors which efficiently express the gene encoding the surface antigen of hepatitis B virus in monkey cells, we have studied the consequences of inserting ATG triplets in all three reading frames upstream of the usual translational initiation codon of this gene. In agreement with the scanning model for eukaryotic translation initiation, these additional codons can severely depress the initiation of translation at the 'authentic' start codon, although the extent of inhibition depends on sequences flanking the upstream AUG. Such inhibition can, however, be at least partially suppressed by the presence of a translation termination codon in-frame with the upstream AUG. These results raise the possibility that mammalian ribosomes can reinitiate translation at an AUG codon after previously initiating, and terminating, at an upstream site.

Animals↗