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Biomedical subjects

J W Chan

Publications and source records attributed to J W Chan.

18 recordsLinked to original sources
PubMed2005

Raman spectroscopic analysis of biochemical changes in individual triglyceride-rich lipoproteins in the pre- and postprandial state.

Individual triglyceride-rich lipoprotein (TGRL) particles derived from human volunteers are nondestructively analyzed by laser tweezers Raman microspectroscopy, and information on their composition and distribution is obtained. The Raman signature of single optically trapped very low-density lipoproteins (VLDL), a subclass of TGRL, which play an important role in cardiovascular disease, exhibits distinct peaks associated with molecular vibrations of fatty acids, proteins, lipids, and structural rearrangements of lipids. Our analysis of pre- and postprandial VLDL exhibits the signature of biochemical changes in individual lipoprotein particles following the consumption of meals. Interaction of VLDL with endothelium leads to the breakdown of complex triacylglycerols and the formation of a highly ordered core of free saturated fatty acids in the particle. A particle distribution analysis reveals trends in the degree to which this process has occurred in particles at different times during the postprandial period. Differences in particle distributions based on the different ratios of polyunsaturated to saturated fats in the consumed meals are also easily discerned. Individual lipoprotein particles hydrolyzed in vitro through addition of lipoprotein lipase (LpL) exhibit strikingly similar changes in their Raman spectra. These results demonstrate the feasibility of monitoring the dynamics of lipid metabolism of individual TGRL particles as they interact with LpL in the endothelial cell wall using Raman spectroscopy.

Adult↗
PubMed2004

Reagentless identification of single bacterial spores in aqueous solution by confocal laser tweezers Raman spectroscopy.

We demonstrate that optical trapping combined with confocal Raman spectroscopy using a single laser source is a powerful tool for the rapid identification of micrometer-sized particles in an aqueous environment. Optical trapping immobilizes the particle while maintaining it in the center of the laser beam path and within the laser focus, thus maximizing the collection of its Raman signals. The single particle is completely isolated from other particles and substrate surfaces, therefore eliminating any unwanted background signals and ensuring that information is collected only from the selected, individual particle. In this work, an inverted confocal Raman microscope is combined with optical trapping to probe and analyze bacterial spores in solution. Rapid, reagentless detection and identification of bacterial spores with no false positives from a complex mixed sample containing polystyrene and silica beads in aqueous suspension is demonstrated. In addition, the technique is used to analyze the relative concentration of each type of particle in the mixture. Our results show the feasibility for incorporating this technique in combination with a flow cytometric-type scheme in which the intrinsic Raman signatures of the particles are used instead of or in addition to fluorescent labels to identify cells, bacteria, and particles in a wide range of applications.

Bacillus cereus↗
PubMed2001

Isolated unilateral post-traumatic internuclear ophthalmoplegia.

A patient developed an isolated unilateral internuclear ophthalmoplegia (INO) after head trauma. An uncommon complication of closed head trauma, INO usually occurs bilaterally and is often associated with other neurologic deficits. The mechanism may be shear injury caused by angular acceleration leading to downward displacement of the posterior brainstem downward, stretching of the nerve fibers of the medial longitudinal fasciculus, or compression and tearing of its arterial supply.

Adult↗
PubMed2000

Clinical manifestations of tuberculosis in HIV-infected patients.

OBJECTIVE: The purpose of the present study was to evaluate the impact of HIV infection on the clinical presentation of tuberculosis. METHODOLOGY: We retrospectively studied the impact of HIV infection on the clinical presentation of tuberculosis. A total of 60 consecutive patients co-infected with HIV and tuberculosis were identified. RESULTS: Majority were male (88.3%) and the most common transmission category was heterosexual contact (80%). Most were in the advanced stage of HIV infection; 93% had CD4 cell count less than 200/mm3. Concerning the site of tuberculosis involvement, 37% had pulmonary involvement alone, 13% had extrapulmonary disease involving one single site, 50% had both pulmonary and extrapulmonary involvement. Fifteen (25%) patients also met the criteria of disseminated tuberculosis, who had a significantly lower mean CD4 cell count than those with pulmonary involvement alone (mean 40 vs 102; P = 0.048). Chest radiographs comprised a wide spectrum of manifestations. A considerable proportion had primary pulmonary tuberculosis pattern (38%) and normal radiographs (8.5%). CONCLUSIONS: Our patients generally had advanced HIV infection; 93% of those had CD4 lymphocyte count < 200/mm3. Extrapulmonary involvement and disseminated disease were common. Radiographic manifestations of pulmonary tuberculosis were often 'atypical' due to the greater proportion of primary tuberculosis among our patients.

AIDS-Related Opportunistic Infections↗
PubMed1999

A physical map of the chromosome of Xanthomonas campestris pv. phaseoli var. fuscans BXPF65.

A physical map of the Xanthomonas campestris pv. phaseoli var. fuscans BXPF65 chromosome was constructed by PFGE and Southern hybridization. The chromosome was 3938 kb and was composed of 39 XbaI restriction fragments. The size is close to that estimated for X. campestris pv. campestris based on DNA renaturation kinetics. Macrorestriction fragments containing genes for a 16S rRNA, pectate lyase, two-component regulatory system and hrp cluster were located on the physical map. Each of these probes hybridized to single macrorestriction fragments except the 16S rRNA probe, which hybridized to five fragments located in different areas on the chromosome map.

Blotting, Southern↗
PubMed1999

The molecular genetics of virulence of Xanthomonas campestris.

Bacteria belonging to the genus Xanthomonas are important pathogens of many plants, and their virulence appears to be due primarily to secreted and surface compounds that could increase host nutrient loss, or avoid or suppress unfavorable conditions in the host. Type II and III secretory pathways are essential for virulence. Some individual extracellular enzymes (type II-secretion dependent) affect final bacterial population levels, whereas some avirulence gene products (type III-secretion dependent) affect virulence by altering host metabolism. Avr proteins, probably secreted via a pilus, can also be recognized by host resistance gene products. Virulence is also associated with bacterial surface polysaccharides, which may help to avoid host defense responses, and regulatory gene systems, which can control virulence gene expression.

Journal Article↗
PubMed1997

Role of antiribosomal P protein antibodies in the diagnosis of lupus isolated to the central nervous system.

BACKGROUND: When lupus presents with isolated central nervous system findings, the usual serologic markers are often absent and diagnostic difficulty with a delay in treatment is common. OBJECTIVE: To report the usefulness of antiribosomal P protein antibodies in the diagnosis of lupus isolated to the central nervous system when results of tests for anti-double-stranded DNA antibodies are negative. DESIGN: Case report. SETTING: University medical center. PATIENT: The patient was evaluated and treated on referral and follow up for 1 year. RESULTS: We describe a patient with acute onset of psychosis followed by coma and focal clonic movements with undetectable DNA antibodies. Serum antiribosomal P protein antibody levels were elevated. Steroid therapy was followed by marked clinical improvement and a decrease in antibody titer. CONCLUSION: Antiribosomal P protein antibodies provide an important confirmatory test for the diagnosis of lupus isolated to the central nervous system when results of tests for anti-double-stranded DNA antibodies are negative.

Adult↗
PubMed1997

Pathogenesis of acute monocular blindness from leaking anterior communicating artery aneurysms: report of six cases.

This report describes six cases of leaking anterior communicating aneurysms, collected over 37 years, that caused acute monocular blindness. In two cases, surgical and pathologic evidence demonstrated the pathogenic mechanism: As the aneurysm enlarges, the down-pointing dome compresses the optic nerve from above and adheres to it. When the aneurysm ruptures through the adherent dome, it bleeds directly into the optic nerve, resulting in severe headache and monocular blindness. The other cases also suggest an alternative mechanism, namely, direct optic nerve compression by the aneurysm.

Adult↗
PubMed1990

Potential of Agrobacterium tumefaciens and Octopine-Utilizing Fluorescent Pseudomonas Strains To Attach to Susceptible Potato Tissues.

The binding characteristics of two octopine-catabolizing pseudomonads, Pseudomonas fluorescens B99A and E175D, which were isolated from crown galls, have been examined. The binding of strain B99A to potato disks was very weak, followed a Freundlich isotherm, and was temperature and pH independent. Strain E175D displayed strong attachment and followed a Langmuir isotherm. Despite these fundamental differences in binding characteristics, when each strain was placed in competitive binding assays with either Agrobacterium tumefaciens B6 or A. tumefaciens ATCC 15955, the number of bound pseudomonad cells decreased compared with those obtained in independent trials. Furthermore, the binding of A. tumefaciens cells was increased. In prebinding experiments, in which the potato disks were bound with the pseudomonads before exposure to the agrobacteria, the number of bound pseudomonad cells again decreased. This implies that increased desorption was occurring. In these prebinding studies, the numbers of bound A. tumefaciens ATCC 15955 increased, but the number of bound A. tumefaciens B6 remained the same. The mechanism for this observed synergism on the binding of agrobacterial cells and the depression in bound pseudomonad cells is believed to be alterations in the electrostatic or ionic charges on the plant and bacterial cell surfaces. The synergistic effect on A. tumefaciens undermines the use of these pseudomonads as potential biocontrol agents for crown gall.

Journal Article↗
PubMed1986

Correlation between auditory reaction time and intelligence.

Discriminative reaction times to auditory stimuli were measured for 150 students of the local Chinese population. Pearson's correlation with scores on the Standard Progressive Matrices and RTs was negative, becoming -0.30 when slower trials were eliminated. The possible basis for improvement was discussed in relation to cognitive processes and the general theory of assessing intelligence.

Adolescent↗
PubMedDate not supplied

The effect of surgery on the iliac apophysis: an experimental study.

The effect of surgery on the subsequent growth of the iliac apophysis was studied in 30 immature New Zealand White rabbits. Groups of animals were subjected to splitting of the iliac apophysis or excision of part of or the whole apophysis. These animals were compared to a group with a sham operation. Results showed that splitting with subsequent resuturing of the iliac apophysis resulted in normal growth in height but increased growth in width and thickness of the iliac bone. Excision of one third of the iliac apophysis did not interfere with subsequent growth, but excision of two thirds or more of the iliac apophysis resulted in retarded growth of the iliac bone. These experimental studies suggest that the iliac apophysis can be safely split in the surgical approach to a child's hip. Also one third of the iliac apophysis can be safely sacrificed for use as a physeal graft or for chondrocyte cultures.

Animals↗