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Biomedical subjects

M H Ho

Publications and source records attributed to M H Ho.

14 recordsLinked to original sources
PubMed1998

HIV-associated eosinophilic folliculitis in a Chinese woman: a case report and a survey in Hong Kong.

This is the first survey of eosinophilic folliculitis (EF) in patients infected with the human immunodeficiency virus (HIV) in Hong Kong. The present report provides the local data on HIV-associated eosinophilic folliculitis (HIV-EF) and includes the first Chinese, heterosexual female patient with this condition. This is a retrospective study on all HIV-positive patients (n = 451) attending the outpatient clinic of the AIDS Unit in Hong Kong. Patients diagnosed as having EF with histological support were included for analysis. The data were presented by descriptive method. Three patients were identified, all of them had skin biopsies done which confirmed the diagnosis; including the female case. Recognition of HIV-EF is important because it is indicative of significant immunosuppression with risk of opportunistic infection. We concluded that HIV-EF is no longer an exclusive male disease in homosexual patients only. We expect more female patients or heterosexual subjects who are HIV positive developing this disease in the future.

Adult↗
PubMed1997

Genome-wide expression monitoring in Saccharomyces cerevisiae.

The genomic sequence of the budding yeast Saccharomyces cerevisiae has been used to design and synthesize high-density oligonucleotide arrays for monitoring the expression levels of nearly all yeast genes. This direct and highly parallel approach involves the hybridization of total mRNA populations to a set of four arrays that contain a total of more than 260,000 specifically chosen oligonucleotides synthesized in situ using light-directed combinatorial chemistry. The measurements are quantitative, sensitive, specific, and reproducible. Expression levels ranging from less than 0.1 copies to several hundred copies per cell have been measured for cells grown in rich and minimal media. Nearly 90% of all yeast mRNAs are observed to be present under both conditions, with approximately 50% present at levels between 0.1 and 1 copy per cell. Many of the genes observed to be differentially expressed under these conditions are expected, but large differences are also observed for many previously uncharacterized genes.

Cell Division↗
PubMed1994

Three-dimensional finite element analysis of the effects of posts on stress distribution in dentin.

A finite element analysis was conducted to study the influence of posts on dentinal stress in pulpless teeth. Three-dimensional models of an intact Chinese maxillary central incisor with and without post restoration were analyzed. When the tooth was subjected to masticatory and traumatic loads, stress distributions in dentin were similar whether or not the post was present. Maximal dentinal stresses were reduced by only 7% to 10% and 10% to 14.5%, respectively, with gold alloy and stainless steel posts. Thus the reinforcement effects from posts appeared limited in pulpless incisors.

Alveolar Process↗
PubMed1992

Analysis of cholesterol in all lipoprotein classes by single vertical ultracentrifugation of fingerstick blood and controlled-dispersion flow analysis.

This new, highly sensitive analytical system, based on controlled dispersion of the flowing sample, gives a rapid, continuous, and direct analysis for cholesterol in all lipoprotein classes, separated by single vertical-spin density-gradient ultracentrifugation. In this Vertical Auto Profile-II fingerstick system, designated VAP-IIfs, a narrow-bore Teflon coil serves as the reactor with no segmentation of the analytical stream by air bubbles, in contrast to the Technicon AutoAnalyzer used in the VAP-I method. Concentrations of high-, low-, intermediate-, and very-low-density lipoprotein cholesterol and lipoprotein(a) cholesterol are determined by decomposing the spectrophotometric absorbance curve for the continuous analysis of the centrifuged sample, with use of software developed in this laboratory. Total cholesterol is determined from the total area under the absorbance curve. For assaying total cholesterol, the CV between aliquots within a rotor ranged from 1.35% to 3.15%; the CV between rotors was 2.45%. Because only 18 microL of sample is required, VAP-IIfs can be readily adapted to analysis for lipoprotein cholesterol profiles in capillary blood samples. Total cholesterol values by VAP-IIfs for fingerstick and venous samples from 23 subjects agreed well: slope = 1.01 (SD 0.03), intercept = -21 (SD 51) mg/L, Sy/x = 50 mg/L, and r = 0.992. Results by VAP-IIfs also correlated highly with results for duplicate samples analyzed at the Northwest Lipid Research Laboratories.

Cholesterol↗
PubMed1990

Flow injection analysis of L-lactate with enzyme amplification and amperometric detection.

A flow injection analysis method for the determination of the lactate anion with enzyme amplification and amperometric detection is described. The system utilizes an oxygen electrode for measurement of changes in the oxygen concentration in the flow stream. Two enzymes, lactate oxidase and lactate dehydrogenase, were randomly coimmobilized on aminopropyl controlled-pore glass (AMP-CPG) and packed into a reactor. beta-NADH was used as a coenzyme for the regeneration of lactate from pyruvate. The experimental conditions for the determination of the lactate anion were studied for this system by the simplex and the univariant methods. The results obtained under these two conditions were compared. The simplex experimental condition yielded a calibration curve whose linear portion had a slope that was 1.2 times greater than that of the linear portion of the curve obtained under univariant conditions. The limit of detection under simplex condition was 1.19 x 10(-7) M vs 3.29 x 10(-7) M lactate under univariant conditions. The relative standard deviation obtained for this system at 6 x 10(-6) M lactate (n = 10) was about 2.5% under simplex conditions and 3.6% under univariant maximization conditions.

Anions↗
PubMed1989

In vitro propagation of human hepatitis B virus in a rat hepatoma cell line.

A rat hepatoma cell line (Q7) of Morris hepatoma origin was transfected with a construct containing the tandem dimer genome of human hepatitis B virus (HBV) and the neomycin-resistant selection marker. The culture medium of several neomycin-resistant single-cell clones was found to accumulate high levels of secreted HBV surface antigen and core-related e antigen. HBV-specific replication intermediates, including relaxed circular and single-stranded DNA with a minus-strand polarity, could be found in both the intracellular fraction and the extracellular culture medium by the Southern blot procedure. One of these clones, designated Q7 HBV-21, was characterized in further detail. DNA polymerase activity was present in the virus particles produced by Q7 HBV-21 cells. Characteristic transcripts of HBV, including the 3.5-, 2.5-, and 2.1-kilobase mRNA as well as a core-gene-related transcript of 2.2 kilobases could be detected. Electron microscopic examination of the conditioned medium from Q7 HBV-21 cells identified 42-nm Dane-like particles as well as 22-nm subviral particles with a spherical or filamentous shape. This Q7 HBV-21 cell line has been maintained in the absence of neomycin for 1 year without losing the properties of HBV DNA replication and Dane-like particle production. Our results strongly suggest that the species barrier of HBV infection is at an early step of viral absorption onto or penetration into the target hepatocytes. This nonhuman system for HBV production in culture could be used to complement the human HepG2 system.

Animals↗
PubMed1988

Validity domain of the weak-phase-object approximation for electron diffraction of thin protein crystals.

The domain of validity of the weak-phase-object (WPO) approximation is evaluated for high-energy electrons (100 keV, 500 keV and 1 MeV) scattered by crystalline biological macromolecules. Cytochrome b5 is used as an example in which calculated dynamical diffraction intensities are used to simulate observed diffraction intensities which are then compared with intensities calculated by the weak-phase-object approximation. Three criteria of validity are used, namely the crystallographic residual (R value), the interpretability of difference Patterson maps, and the results of phasing by the heavy-atom isomorphous replacement method. The present calculations indicate that the error associated with the WPO approximation is quite acceptable up to a specimen thickness of 200 A for 100 keV electrons, which is two to four times the thickness limit for crystalline organic structures with much smaller unit-cell dimensions. An equally acceptable thickness limit at 500 keV and 1MeV is about 300-350 A.

Crystallography↗
PubMed1987

Enantiomeric composition analysis of amphetamine and methamphetamine by chiral phase high-performance liquid chromatography-mass spectrometry.

N-(Trifluoroacetyl)-l-prolyl- (N-TFA-l-prolyl-) d- and l-amphetamine diastereoisomers were separated by high-performance liquid chromatography and confirmed by an interfaced mass spectrometer system, using the commercially available N-3,5-(dinitrobenzoyl)phenylglycine chiral column. A separation factor of 1.52 and resolution of 3.8 were observed. N-TFA-l-prolyl-d- and -l-methamphetamine diastereoisomers were only partially resolved. The chiral stationary phase-solute interactions were studied by varying the mobile phase (2-propanol in hexane). Results indicate the separation mechanism proceeds via dipolar and hydrogen-bond interactions between the chiral stationary phase and the solute. A modified "dipole-stacking" model takes into account these interactions and explains the difference in separability observed for N-TFA-l-prolyl-d- and -l-amphetamine and N-TFA-l-prolyl-d- and -l-methamphetamine.

Amphetamine↗
PubMed1975

Daily rhythm in human urinary melatonin.

The melatonin in urine samples from six healthy adult volunteers was concentrated on Amberlite XAD-2 resin, eluted with organic solvents, and quantitated by use of a bioassay technique (the dermal melanaphore response of larval anurans to melatonin in their bathing medium). The melatonin content of samples collected between 11 p.m. and 7 a.m. was, in each case, several times higher than that of samples collected between 7 a.m. and 3 p.m. or between 3 p.m. and 11 p.m.

Adult↗