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Biomedical subjects

K Tong

Publications and source records attributed to K Tong.

9 recordsLinked to original sources
PubMed1997

Validity of the McGill Quality of Life Questionnaire in the palliative care setting: a multi-centre Canadian study demonstrating the importance of the existential domain.

This study was carried out in eight palliative care services in four Canadian cities. A revised version of The McGill Quality of Life Questionnaire (MQOL) is compared to a single-item scale measuring overall quality of life (SIS), and the self-administered version of the Spitzer Quality of Life Index (SA-QLI), to obtain evidence of validity. MQOL total score predicts SIS better than does SA-QLI, although much of the variance remains to be explained. The results of principal components analysis of data using this revised version of MQOL are similar to those from previous MQOL studies with different patient populations. The MQOL subscales, constructed on the basis of principal components analysis, demonstrate acceptable internal consistency reliability. The MQOL measures reflecting physical well-being and existential well-being are important for predicting SIS.

Humans↗
PubMed1996

Steric constraints in the recognition of peptide substrates for the epidermal growth factor receptor kinase.

Epidermal growth factor (EGF) stimulates cellular mitogenesis by binding to and activating its membrane-associated receptor. An important component of signal transduction by the activated receptor is the stimulation of an intrinsic tyrosyl residue-specific protein kinase, which selectively phosphorylates tyrosyl residues in the cytoplasmic tail of the receptor and in other cytoplasmic substrates. A recent study utilizing tyrsub, a new high affinity synthetic peptide substrate for the EGF receptor kinase, provided evidence that in peptide substrate binding, the tyrosyl residue plays the central role in recognition, with residues surrounding the tyrosyl residue contributing to stabilization of docking [Guyer et al. (1994) Arch. Biochem. Biophys. 312, 573-578]. A large body of previous work had identified acidic residues near the site of phosphorylation as most important for binding; therefore, other residues in tyrsub appeared to be promising sites for locating spectroscopic reporter groups. Since tyrsub has neutral residues -4 and +4 residues from the site of phosphorylation, we prepared two analogs of tyrsub, in each of which one of those residues was substituted with Cys. These cystyrsubs were found to be effectively phosphorylated by EGF receptor prepared from A431 cells, on stimulation with EGF, with high affinities [Km(app) = 40-50 microM.] Modification of the cystyrsubs with iodoacetamide had no deleterious effect on the ability of the peptide to be phosphorylated by the EGF receptor kinase, while the labeling by 5-iodoacetimidofluorescein completely abolished the productive interaction between the peptide and the EGF receptor. This unexpected failure of the fluorescently labeled peptides to be phosphorylated does, however, provide information on steric limitations to recognition of substrates by the EGF receptor kinase.

Binding Sites↗
PubMed1995

Angiotensin II regulates the expression of plasminogen activator inhibitor-1 in cultured endothelial cells. A potential link between the renin-angiotensin system and thrombosis.

Plasminogen activator-inhibitor C-1 (PAI-1) plays a critical role in the regulation of fibrinolysis, serving as the primary inhibitor of tissue-type plasminogen activator. Elevated levels of PAI-1 are a risk factor for recurrent myocardial infarction, and locally increased PAI-1 expression has been described in atherosclerotic human arteries. Recent studies have shown that the administration of angiotensin converting enzyme inhibitors reduces the risk of recurrent myocardial infarction in selected patients. Since angiotensin II (Ang II) has been reported to induce PAI-1 production in cultured astrocytes, we have hypothesized that one mechanism that may contribute to the beneficial effect of angiotensin converting enzyme inhibitors is an effect on fibrinolytic balance. In the present study, we examined the interaction of Ang II with cultured bovine aortic endothelial cells (BAECs) and the effects of this peptide on the production of PAI-1. 125I-Ang II was found to bind to BAECs in a saturable and specific manner, with an apparent Kd of 1.4 nM and Bmax of 74 fmol per mg of protein. Exposure of BAECs to Ang II induced dose-dependent increases in PAI-1 antigen in the media and in PAI-1 mRNA levels. Induction of PAI-1 mRNA expression by Ang II was not inhibited by pretreating BAECs with either Dup 753 or [Sar1, Ile8]-Ang II, agents that are known to compete effectively for binding to the two major angiotensin receptor subtypes. These data indicate that Ang II regulates the expression of PAI-1 in cultured endothelial cells and that this response is mediated via a pharmacologically distinct form of the angiotensin receptor.

Angiotensin II↗
PubMed1994

[Construction of secretion vectors using signal sequence of Bacillus subtilis alkaline protease E gene].

Escherichia coli can be used to study the expression signal of the gene aprE (alkaline protease E) according to its promoter strength to express the promoterless cat-86 gene in a promoter-probe plasmid, pGKV210. We have constructed a signal-sequence-probe plasmid, pBLa, based on the E. coli-B. subtilis plasmid pHP13, using the M. bla as a reporter. Two secretion vectors pSP1 and pSP2 were constructed subsequently based on pHP13 using the promoter and the signal sequence of aprE. DB104 carrying pSP1 showed much higher secretion rate of M. bla than that carrying pSP2. Analysis of DNA sequences surrounding the fusion junctions of the signal sequences and the M. bla gene in the two plasmids indicated that the signal sequence in pSP1 had a 30bp deletion at its 3' end. A new signal peptidase recognition site has been found in the linker-encoded amino acid sequence. The change in length of the signal peptide might somehow increase the secretion efficiency or the synthesis of M. bla.

Amino Acid Sequence↗
PubMed1993

[Effect of ribosomal protein mutation on the expression of alkaline protease gene in Bacillus subtilis].

Altogether 19 strains belong to 13 species of ribosomal protein mutants of Bacillus subtilis were tested in vitro transcription--translation system for their influence on the translation of alkaline protease gene (apr). It was found that 10 species (13 strains) of ribosomal protein mutants did affect the translation of apr mRNA. Streptomycin-dependent (Str-D) ribosomes almost did not translate the apr mRNA. Str-D inhibited the expression of apr gene at the translational level, but had no influence on neutral protease gene. There is a secondary structure complex at the translation initiation region of apr mRNA. When one of the secondary structure was destroyed by site directed mutagenesis, the translation efficiency was enhanced by 7.3 to 9.1 folds. The higher order structure of Str-D and Str-R ribosome were different and so were the affinity of Str-D and Str-R 30S subunits to the 5' end of apr mRNA. These results suggest that Str-D ribosomes could not translate apr mRNA because of the secondary structure complex, low initiation strength of apr mRNA, and alteration of the higher order structure of the Str-D ribosomes.

Bacillus subtilis↗