PubMed Health⌕ Search

Biomedical subjects

P C Zhang

Publications and source records attributed to P C Zhang.

15 recordsLinked to original sources
PubMed2003

Comparison of histology between recurrent tonsillitis and tonsillar hypertrophy.

To elucidate the aetiology of tonsillar hypertrophy and recurrent tonsillitis, it is important to determine whether a difference exists between these two conditions in microanatomical architecture. The aim of this study was to investigate the difference in follicle size and numbers in tonsils for patients with tonsillar hypertrophy and recurrent tonsillitis using an image analysis method. Our results showed that there was no significant difference in the mean follicle numbers per counting field (40x magnification) between recurrent tonsillitis (4.5 +/- 2.1) and tonsillar hypertrophy (3.8 +/- 0.5). However, the mean follicle area in the tonsillar hypertrophy group (0.23 +/- 0.02 mm2) is significantly (P < 0.01) larger than in the recurrent tonsillitis group (0.15 +/- 0.02 mm2). Our study demonstrates that tonsillar hypertrophy is characterized histologically by an enlargement of follicles compared with chronic tonsillitis, indicating a hyperplastic condition of lymphoid cells in the germinal centres. It may also explain the difference in aetiology and/or immune defence mechanism underlying these two conditions.

Adolescent↗
PubMed2003

Adapting the Quesant Nomad atomic force microscope for biology and patch-clamp atomic force microscopy.

The Quesant Nomad atomic force microscope (AFM) was modified to produce a reliable patch-clamp AFM for demanding biologic applications. The AFM's laser optics forms the basis of a condenser that allows simultaneous Köhler illumination and AFM imaging on an inverted optical microscope. The original AFM scan head was replaced with plastic and glass to make it biologically inert. A bevel cut in the new scan head permits clearance for patch clamp pipets. Cantilevers are attached to the scan head with a quick setting silicone rubber that is readily removable. Software was developed to (a) automate a gentle approach and set a specific feedback force, (b) provide a mouse-driven control of the X-Y position of the probe tip and recall of saved locations, and (c) measure force-distance curves over user defined paths. Additional modifications were made to minimize mechanical noise. The patch-clamp AFM achieves 600 fA (3 kHz bandwidth) and 1 A RMS noise levels (10 kHz bandwidth). The correlation of electrical and mechanical information allows signal averaging and measures sub-Angstrom, sub-millisecond electromotile responses from cells.

Cell Membrane↗
PubMed2001

Voltage-induced membrane movement.

Thermodynamics predicts that transmembrane voltage modulates membrane tension and that this will cause movement. The magnitude and polarity of movement is governed by cell stiffness and surface potentials. Here we confirm these predictions using the atomic force microscope to dynamically follow the movement of voltage-clamped HEK293 cells in different ionic-strength solutions. In normal saline, depolarization caused an outward movement, and at low ionic strength an inward movement. The amplitude was proportional to voltage (about 1 nm per 100 mV) and increased with indentation depth. A simple physical model of the membrane and tip provided an estimate of the external and internal surface charge densities (-5 x 10(-3) C x m(-2) and -18 x 10(-3) C x m(-2), respectively). Salicylate (a negative amphiphile) inhibited electromotility by increasing the external charge density by -15 x 10(-3) C x m(-2). As salicylate blocks electromotility in cochlear outer hair cells at the same concentration, the role of prestin as a motor protein may need to be reassessed.

Cell Line↗
PubMed2001

Five new diprenylated flavonols from the leaves of Broussonetia kazinoki.

Five new diprenylated flavonols, broussonol A (1), broussonol B (2), broussonol C (3), broussonol D (4), and broussonol E (5), along with two known compounds, were isolated from an ethanolic extract of the leaves of Broussonetia kazinoki. Their structures were elucidated by chemical and spectral methods. Cytotoxic activities were evaluated against several different cell lines.

Dose-Response Relationship, Drug↗
PubMed2001

Evaluation of nasal cavity by acoustic rhinometry in Chinese, Malay and Indian ethnic groups.

Acoustic rhinometry (AR) evaluates the geometry of the nasal cavity by measuring the minimum cross-sectional area (MCA) and nasal volume (V) by means of acoustic reflection. Understanding the normal and pathologic conditions of the internal nasal cavity using AR is important in the diagnosis of structural abnormalities in patients. The aim of this study was to investigate the normal range of AR parameters in healthy volunteers from three ethnic groups in Singapore: Chinese, Malay and Indian. We also attempted to evaluate the role of these measurements in the documentation of structural abnormalities in the nose. A total of 189 Singaporeans, aged > or = 18 years, were recruited from a nationwide survey study. They comprised 83 Chinese, 35 Malays and 71 Indians. Eighty-nine subjects had a rhinoscopically normal nose (Group 1), 77 had significant septal deviation (Group 2) and 23 had inferior turbinate hypertrophy (Group 3). AR was performed to measure the MCA at the anterior 1-5 cm from the nostril and the volume (V) between points at the nostril and 5 cm into the nose. A mean MCA (mMCA; equal to (L + R)/2) and a total volume (Vt; equal to L + R) were then calculated for each subject, where L and R refer to the measurements made for the left and right nostrils, respectively. The results showed that there was no statistically significant difference in mMCA (p = 0.80) and Vt (p = 0.60) among the three ethnic subgroups of Group 1. Statistically significant differences were found only between Groups 1 and 3 (p < 0.001 for both mMCA and Vt) and between Groups 2 and 3 (p = 0.001 for mMCA and p = 0.013 for Vt). Although there was no significant difference between Groups 1 and 2, significant differences in MCA (p = 0.001) and V (p = 0.040) were found between the narrower sides (smaller volume) and the wider sides in Group 2, indicating volume compensation between the nasal cavities. In conclusion, our study demonstrates that there is no significant difference in the normal range of AR measurements among Chinese, Malay and Indian ethnic groups. AR is able to determine the structural abnormality of the internal nasal cavity caused by septal deviation and inferior turbinate hypertrophy.

Acoustics↗
PubMed2001

[Chemical constituents from the leaves of crataegus pinnatifida Bge. var. major N.E.Br].

AIM: To study the chemical constituents in the leaves of Crataegus pinnatifida Bge. var. major N.E.Br.. METHODS: Compounds were isolated by using porous resin, silica gel, polyamide chromatographic techniques etc. Their structures were elucidated by chemical and spectroscopic methods. RESULTS: Eight compounds were identified as pinnatifin I (1), quercetin (2), 3-O-beta-D-glucopyranosyl quercetin (3), 3-O-beta-D-galacopyranosyl quercetin (4), 3-O-beta-D-glucopyranosyl (6-->1)-alpha-L-rhamnosyl quercetin (5), 3-O-beta-D-galacopyranosyl (6-->1)-alpha-L-rhamnosyl quercetin (6), kaempferol (7), 7-O-alpha-L-rhamnosyl-3-O-beta-D- glucopyranosyl kaempferol (8). CONCLUSION: Compound 1 is a new compound. Compound 8 was isolated from this plant for the first time.

Crataegus↗
PubMed1995

Atomic force microscopy study of fine structures of the entire surface of red blood cells.

Glutaraldehyde-fixed red blood cells were imaged by tapping mode atomic force microscopy (TMAFM) in air at room temperature. The results show that TMAFM can visualize the morphology of the red blood cell at both cellular and nanometer scales. The scan size covers the range from several hundred nanometers to more than one hundred micrometers. TMAFM not only has a higher resolution than the optical microscope, but also can observe biological samples without precoating as required for scanning electron microscopy (SEM). The AFM images of the entire surface of an uncoated red blood cell with nanometer resolution are successfully reconstructed by 28 AFM images of the preselected subareas on the surface of the red blood cell. These images reveal directly the fine structures of the external surface of uncoated red blood cells in air. The surface exhibits a characteristic structure composed of a large number of closely-packed nanometer particles with a size ranging from a few nanometers to tens of nanometers. These "particulate" components are evenly distributed, and no jumping protrusion or depression structures were found. These particles give rise to a very smooth surface of the red blood cell as shown in a large-scan AFM image. In addition, the 28 AFM images obtained by the continuous scanning over 3 hours indicate that TMAFM can image soft biological samples such as red blood cells stably and reproducibly.

Erythrocytes↗
PubMed1990

[The determination of DNA adducts in liver and lung of mice exposed to dimethylnitrosamine].

The purpose of this study was to assess the role of dimethylnitrosamine (DMN) in DNA lesions and to determine the levels of O6-methyl-guanine (O6-mGua) and N-7-methyl-guanine (m7-Gua). Mice were treated with 10 ppm DMN in drinking water for 1, 2, 4, 8, 16 and 32 days. The average dosage of DMN was 2 mg/kg/day, DNA was isolated from liver and lung specimens, and its purine bases separated by high-performance liquid chromatography with fluorescence detection. The results showed the presence of O6-mGua and m7-Gua in the DNA following administration of DMN. The m7-Gua was found to be unsteady. O6-mGua decreased rapidly after 1 and 2 days treatment with DMN, but was raised after 32 days with continuous exposure. These findings suggest that damaged DNA would be repaired in vivo, but with continuous exposure to DMN, O6-mGua would accumulate in the DNA and this might be the cause of tumor induction.

Animals↗
PubMed1987

Modified alkali digestion method for pulmonary asbestos fibre counts.

In using the standard alkali digestion method for pulmonary asbestos fibre count, it was found that carbonaceous particles often obscured the presence of asbestos bodies (coated fibres) rendering their quantification inaccurate, particularly in lungs with a high soot particle content and a low fibre count. We applied the chloroform-ethanol separation technique from the bleaching agent digestion method to the alkali digestion method to remove the carbonaceous particles. It was found that coated fibres are much easier to visualize and count. The uncoated fibre count was nevertheless more accurate with the original method. The coated and uncoated fibre counts from 21 lung specimens were compared using both methods. The total fibre count was considered better derived from using both techniques.

Alkalies↗