PubMed Health⌕ Search

Biomedical subjects

Y Ho

Publications and source records attributed to Y Ho.

50 records · Page 3Linked to original sources
PubMed1993

Comparison of the major outer-membrane protein (MOMP) gene of mouse pneumonitis (MoPn) and hamster SFPD strains of Chlamydia trachomatis with other Chlamydia strains.

Restriction fragments containing the major outer-membrane protein (MOMP) gene from two nonhuman (rodent) strains of Chlamydia trachomatis, the mouse pneumonitis (MoPn) strain and the SFPD strain isolated from hamsters with transmissible proliferative ileitis, were cloned and sequenced. The MOMP genes of both MoPn and SFPD encode an identical 22-amino acid leader peptide and mature polypeptides of 365 and 382 amino acids, respectively. Alignment of the MOMP genes of the two rodent strains revealed 91% identity. By comparison with other known chlamydial MOMP gene sequences, there was 80%-83% identity with human biovars strains of C. trachomatis, and there was 69%-70% identity with C. psittaci and C. pneumoniae strains. The main differences in these sequences were clustered into four variable domains. A minimum-length evolutionary tree was constructed on the basis of the MOMP gene variable positions by using PIMA package software. The minimum mutation distances indicated that (i) the MOMP genes of all chlamydial strains may have evolved from a common ancestor; (ii) all the strains of C. trachomatis compose one of the subtrees, and strains of C. psittaci and C. pneumoniae compose the other subtree; and (iii) in the C. trachomatis subtree, the human and the rodent strains are divided into two clusters. The branching pattern of this evolutionary tree is generally consistent with current classification based on serological, morphological, and other biological characteristics.

Amino Acid Sequence↗
PubMed1992

Early complement components enhance neutralization of Chlamydia trachomatis infectivity by human sera.

Immunoglobulin G in human serum neutralizes chlamydial infectivity in vitro. Complement-intact, C5-depleted, and C8-depleted human serum all have significantly more neutralizing activity than serum heated to inactivate early components of complement. Cobra venom factor, an analog of human C3b, enhances neutralization of antichlamydial immunoglobulin G in the absence of early complement components.

Blood Bactericidal Activity↗
PubMed1989

Determination of isoniazid methanesulphonate and its metabolites in rabbit blood by high-performance liquid chromatography.

A rapid and sensitive high-performance liquid chromatographic method is described for simultaneous determination of isoniazid methanesulphonate (IHMS) and its metabolites, such as isoniazid (INH) and acetylisoniazid (AcINH) in rabbit blood. According to stability studies, IHMS was most stable at pH 3-5. After acidifying the blood to pH 5.0, a suitable amount of acetonitrile was added to the supernatant for extraction and niacinamide served as an internal standard. After evaporation, the residue was reconstituted with phosphate buffer and aliquots of this solution were separated on a reversed-phase phenyl column by a mobile phase consisting of 0.25 mM tetrabutylammonium phosphate as a paired-ion reagent. UV detection was performed at 280 nm. Under these conditions, the between-run coefficients of variation of IHMS, INH and AcINH from 1 to 25 microns/ml were 4.7 +/- 2.5, 5.4 +/- 1.0 and 5.1 +/- 3.1%, respectively. Hence this sensitive, reproducible and accurate method was suitable for pharmacokinetic studies of IHMS.

Animals↗
PubMed1987

Chemical modification of bovine transducin: effect of fluorescein 5'-isothiocyanate labeling on activities of the transducin alpha subunit.

Fluorescein 5'-isothiocyanate (FITC) was used to modify the lysine residues of bovine transducin (T), a GTP-binding protein involved in phototransduction of rod photoreceptor cells. The incorporation of FITC showed a stoichiometry of approximately 1 mol of FITC/mol of transducin. The labeling was specific for the T alpha subunit. There was no significant incorporation on the T beta gamma subunit. The modification had no effect on the transducin-rhodopsin interaction or on the binding of guanosine 5'-(beta, gamma-imidotriphosphate) [Gpp(NH)p] to transducin in the presence of photolyzed rhodopsin. The dissociation of the FITC-transducin-Gpp(NH)p complex from rhodopsin membrane remained unchanged. However, the intrinsic GTPase activity of T alpha and its ability to activate the cGMP phosphodiesterase were diminished by FITC modification. The rate of FITC labeling of the transducin-Gpp(NH)p complex was about 3-fold slower than that of transducin. Limited tryptic digestion and peptide mapping were used to localize the FITC labeling site. The majority of the FITC label was on the 23-kilodalton fragment, and a minor amount was on the 9-kilodalton fragment of the T alpha subunit. These results indicate that FITC labeling does not alter the activation of transducin by photolyzed rhodopsin but does affect the GTP hydrolytic activity as well as the GTP-induced conformational change of T alpha, which ultimately leads to the activation of cGMP phosphodiesterase.

Animals↗
PubMed1982

Purification and properties of a transcriptional activator. The cII protein of phage lambda.

We have purified the phage lambda transcriptional activator protein cII. The procedure described allows cII to be obtained in both high purity and yield, and thus allows detailed physical and chemical analysis. We demonstrate that cII in solution is a tetrameric protein and that it undergoes specific processing at its NH2-terminal end. In addition, the protein is characterized as to its molar extinction coefficient, molecular weight, amino acid composition, isoelectric point, alpha-helical content, and antigenic capability.

Amino Acids↗
PubMed1981

Effect of pyridine homologues on respiratory control and H+/O ratio in mitochondria.

The effect of pyridine homologues on proton leakage, respiratory control, oxidative phosphorylation, and H+/O ratio in mitochondria have been examined. Up to a concentration of 1 mM, hydrophobic pyridine homologues diminish respiratory control in bovine heart mitochondria by increasing the State 4 respiration rate but have relatively minor effects on the State 3 and the 2,4-dinitrophenol-uncoupled respiration rates. Neither the proton gradient generated by electron transport in mitochondria in the presence of potassium ion and valinomycin, nor the rate of its anaerobic decay was affected by pyridine homologues. These observations suggest that the basal rate of electron transport is governed not directly by proton gradient, but by molecular processes in the energy-transducing membrane which can be affected by the proton gradient. By assuming that pyridine homologues are bound at low concentrations to specific functional groups in the inner membrane, the observed rates of State 4 respiration can be related quantitatively to the concentration of the organic base in solution. The observation that low concentrations of pyridine homologues decrease the H+/O ratio of mitochondria seems difficult to reconcile with the assumption that proton extrusion is driven directly by electron transport.

Anaerobiosis↗
PubMed1977

Criss-cross heart with congenitally corrected transposition: report of a case with d-transposed aorta and ventricular preexcitation.

A case is described of corrected transposition in a situs solitus individual, in which, despite the presence of atrioventricular discordance (1-bulboventricular looping), the aorta was right-sided. A ventricular septal defect and pulmonary stenosis were also present, and the case had been erroneously diagnosed during life as complete transposition. The true diagnosis was not appreciated at surgery, and correction of the anomaly was attempted using a modification of Fontan's operation. The criss-cross atrioventricular connections were only fully appreciated at autopsy. The patient also exhibited ventricular preexcitation of Wolff-Parkinson-White variety type A. Histopathological examination revealed the presence of two atrioventricular nodes in the right atrium, each contacting the ventricular conduction tissue which was distributed to the morphologically appropriate ventricles. In addition, a left-sided accessory atrioventricular connection perforated the anulus of the left-sided, morphologically tricuspid, valve.

Aorta↗
PubMed1976

Uptake of partially thiolated DNA by ascites tumor cells.

The uptake and intracellular localization by Ehrlich ascites cells of partially [35S]thiolated homologous DNA ("antitemplate") were studied in comparison with that of the corresponding unmodified [3H]DNA, at 37 degrees and 0 degrees, under standardized conditions. For the unmodified DNA, washing the cells after incubation with 0.08 M iodoacetate (in 0.15 M NaCl) alone gave high but reproducible uptake values (23%); washing with 1 M NaCl reduced the cell-associated DNA to 12% (less than 1% at 0 degrees). It appears that 1 M NaCl is able to remove DNA reversibly bound to the cells, similarly to DNase treatment. Approximately 5% of the input [3H]DNA was taken up into the cell nuclei. Diethylaminoethyl dextran (1:1, by weight) greatly enhanced the cellular uptake of [3H]DNA. In the case of [35S]thiolated DNA, the rate as well as the extent of uptake was significantly higher (33%). Washing the cells with 1 M NaCl or treatment with DNase caused relatively small decrease in the total cell-associated [35S]thiolated DNA, the bulk of which (22% of input) was recovered in the isolated nuclei. Stimulation by diethylaminoethyl dextran of the uptake of [35S]thiolated DNA could not be established because of the insolubility of the 1:1 complex in 1 M NaCl. Excess calcium ions during incubation dramatically increased the uptake of the thiolated DNA at 37 degrees (but not at 0 degrees) by the cells (to 90 to 100%) and into the nuclear fraction (to 70% of the total [35S]DNA input). The calcium salt procedure appears to be applicable to the in vivo testing of thiolated DNA's as potential chemotherapeutic agents.

Animals↗
PubMed1974

On the methylated purine content of tRNA present in tumours.

The methylated purine content of tRNA bulk extracted from human hepatomata has been compared with that in normal human liver. The analyses were carried out with the aid of ion-exchange chromatography. The molar proportions of 5 bases detected in acid hydrolysates of tumour tRNA (N(2)-methylguanine, 1-methylguanine, 7-methylguanine, N(2)-dimethylguanine and 1-methyladenine) were not abnormally elevated.

Chromatography, Ion Exchange↗
PubMedDate not supplied

A response of Panc-1 cells to cis-platinum, assessed with a cDNA array.

BACKGROUND: The problem posed by the lack of response of cells in most solid cancers to current chemotherapy generally remains intractable. MATERIALS AND METHODS: The use of cDNA arrays represents one global approach to identifying reasons for this failure. A messenger RNA response of pancreatic cancer (Panc-1) cells after culture for 24 hours with 12 microM cis-platinum was analyzed with a commercial cDNA array. RESULTS: Major drug-induced events included inhibition of messenger RNAs associated with cell proliferation and up-regulation of generally countervailing DNA repair, cellular stress, heat shock protein, glutathione stress-related and multiple drug resistance enzyme messenger RNAs, accompanied by a limited programmed cell death response. CONCLUSION: Induction of widespread normal stress-induced countervailing mRNAs by comparatively non-selective agents such as cis-platinum strongly biases against a successful therapeutic outcome. This paradoxical result of a therapeutic intent provides a further compelling argument for the use of specifically-targeted therapy such as growth factor receptor, tyrosine kinase and other discretely focused agents, probably employed in combinations based on expression of their targets in an individual patient's cancer, as identified by cDNA or proteonomic arrays.

Antineoplastic Agents↗