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Biomedical subjects

C K Sun

Publications and source records attributed to C K Sun.

At least 19 recordsLinked to original sources
PubMed2001

Effect of ischemia-reperfusion injury on the microcirculation of the steatotic liver of the Zucker rat.

BACKGROUND: Much discussion has been focused on the use of steatotic livers for transplantation due to the prevalence of steatosis in the potential donor liver pool (1). The aim of this study was to investigate the possibility that the microcirculation of steatotic liver is more sensitive to the ischemia-reperfusion (IR) injury than normal liver. METHODS: The left liver lobe of obese (n=9) and lean Zucker rats (n=9) were subjected to 40 min of warm ischemia followed by 60 min of reperfusion. Fluorescent probes rhodamine 123 (Rh123), bisbenzimide (Bis), and rhodamine 6G (Rh6G) were administered for the identification by intravital fluorescence microscopy (IVFM) of mitochondrial membrane potential, hepatocyte nuclei and leukocytes, respectively before hepatic ischemia and at 15, 30, 45, and 60 min after reperfusion. Blood samples were obtained before and after 60 min of reperfusion. Liver tissue was taken at the end of experiment for histological analysis. RESULTS: The liver of the obese rats showed prominent macro- and microvesicular fatty changes (MAFC and MIFC) and hepatocyte swelling. Under IVFM, the obese animals had significantly wider hepatic cords (23.1+/-0.8 microm) than the lean ones (15.9+/-0.5 microm) (P<0.01), whereas no significant difference in sinusoidal diameters was noted. The number of functional sinusoids significantly decreased after 30 min of reperfusion in both groups but no significant change was noted in the nucleus count throughout the experiment. Rh123 fluorescence intensity dropped significantly in the obese group after 60 min of reperfusion but not in the lean rats. Leukocyte adherence showed a significant rise after reperfusion in both groups. Plasma AST and ALT levels were 40- and 24-fold higher respectively for the obese animals after IR compared with their preischemic values, whereas the corresponding increase were 4.2- and 3.4-fold for the lean animals, respectively. CONCLUSIONS: Our results indicate that the liver of the obese Zucker rat is steatotic and presents with an abnormal microcirculation manifested by a reduced sinusoidal density. IR led to significantly greater hepatic injury in the steatotic than in the normal liver. This injury was accompanied by a significant reduction in the functional sinusoidal density and mitochondrial membrane potential as assessed by Rh123-associated fluorescence in the steatotic liver. In conclusion, the increased sensitivity of the steatotic liver to IR injury would appear to involve both alterations in blood flow in the microcirculation and to cellular changes.

Alanine Transaminase↗
PubMed2001

Combined carotid arteries-aortic arch transplantation in rats: development of a new microsurgical model.

A new microsurgical model of combined carotid arteries-aortic arch transplantation in the rat is described. In this model, the combined carotid arteries-aortic arch were harvested and end-to-end anastomosed to the recipient's right carotid artery using a sleeve anastomosis technique. The total graft ischemia time and in particular the time required to perform the arterial anastomoses was significantly reduced. No surgical failure was encountered. Ten-day graft patency was 100% (15/15). Our study results demonstrated that the sleeve anastomosis technique for combined carotid arteries-aortic arch transplantation in the rat is fast and easy to perform and has a high rate of success.

Anastomosis, Surgical↗
PubMed2000

A novel approach to the quantification of hepatic stellate cells in intravital fluorescence microscopy of the liver using a computerized image analysis system.

Hepatic stellate cells (HSC) are nonparenchymal liver cells which reside in the space of Disse within the hepatic microcirculatory unit. HSC can be distinguished using intravital fluorescent microscopy (IVFM) due to the autofluorescence from their intracellular vitamin A. Herein we report on a novel approach for the quantification of video-recorded rat HSC images acquired by IVFM (excitation 360 nm/emission 420 nm) by the combined use of the "Cell counting macro" and the "Measurement macros" in the NIH image software. The approach involved two major steps using (i) the "Cell counting macro" for automatic detection, threshold-setting, and generation of a binary image of the vitamin A autofluorescence in the HSC images and (ii) the "Compute percent black and white" command in the "Measurement macros" to automatically determine the HSC density (%), which was then expressed as percentage of the total area of vitamin A autofluorescence-associated sites per observation area. Comparing the vitamin A autofluorescence areas in the original and the binary fashion HSC images revealed that the "Cell counting macro" was an optimal option for the analysis of the low-magnification (x10 objective) HSC images, whereas this macro was not suitable for the analysis of the higher magnification (40x objective) HSC images unless modifications were made. Our analysis revealed that HSC represent approximately 4-5% of the total area of the liver surface. In analyzing the higher magnification HSC microfluorographs, the use of the original "Cell counting macro" resulted in a significant underestimation of HSC density (60% reduction, P < 0.01) when compared with those analyzed using our modified macro. This study represents the first report of an automatic and reliable approach to the intravital fluorescent microscopic quantification of HSC using a computer-NIH image analysis system.

Animals↗
PubMed1997

[Ceramide pathway].

Ceramide may be generated from many metabolism routes. As a novel second messenger, ceramide plays important roles in a variety of physiologic or pathologic events relating to cellular growth, proliferation, differentiation, apoptosis and injuries. It is expected that new insights into the ceramide pathway would promote our understanding of the complex mechanisms for signal transduction.

Animals↗
PubMed1996

[The effect of batroxobin on coronary segmental resistance and coronary blood flow in acute myocardial ischemic dogs].

To study the effects of batroxobin on coronary circulation and cardiac performance in acute myocardial ischemia, Batroxobin was given intravenously to dogs with experimental coronary stenosis. A dose-dependent increase of coronary blood flow (CBF) was observed. Forty minutes after batroxobin (2 BU.kg-1 at infusion rate 0.1 BU.kg-1.min-1) administration, CBF increased by 12% (P < 0.05), small coronary resistance(RS) decreased from 4.1 +/- 0.5 to 3.2 +/- 0.5 mmHg.min.ml-1 (P < 0.01), while large coronary resistance(RL) changed insignificantly from 3.9 +/- 0.8 to 3.8 +/- 0.7 mmHg.min.ml-1 (P > 0.05). Two hours following drug administration, the changes in CBF, RS and RL still remained and RT decreased by 13% (P < 0.05). The + LV(dp/dt)max and -LV(dp/dt)max increased by 14% and 16% (P < 0.05) respectively compared with those in control group. It is concluded that batroxobin improves the ischemic canine coronary circulation and cardiac performance by way of lowering the small coronary resistance and thus increasing CBF. The data also suggest the benificial effect of batroxobin in acute myocardial ischemia.

Animals↗
PubMed1989

Molecular and epidemiologic study of multiresistant Escherichia coli infections in Kaohsiung area.

Totally 70 Escherichia coli (E. coli) isolated strains from patients in Chang Gung Memorial Hospital, Kaohsiung Medical College affiliated Chung Ho Memorial Hospital and the Navy General Hospital of the Republic of China, all in Kaohsiung, were collected during the period of July 1986-August 1987 and examined for their susceptibility to several antimicrobial agents as well as for their plasmid contents. The isolates tested showed a high level of resistance to ampicillin (Ap) (90.4%), piperacillin (Pip) (89.0%), tetracycline (Tc) (88.7%), streptomycin (Sm) (87.7%), chloramphenicol (Cm) (78.4%), kanamycin (Km) (72.6%) and sulfamethoxazole/trimethoprim (Sxt) (54.2%). Observations of the resistance patterns revealed that the dominant type was Ap-Tc-Cm-Sm-Pip-Km. The results of plasmid curing and transfer experiments indicated that three plasmids with molecular weights 49.2-51.6 Mdal, 69.8-178 Mdal and a third one with molecular weight larger than 178 Mdal carried resistance determinants for Gm-Nn, Sm-Km-Tc and Tc-Cm-Km, respectively.

China↗
PubMedDate not supplied

Mapping piezoelectric-field distribution in gallium nitride with scanning second-harmonic generation microscopy.

Taking advantage of the electric field-enhanced second-harmonic generation effect in bulk gallium nitride (GaN) and indium gallium nitride (InGaN) quantum wells, we demonstrated the piezoelectric field distribution mapping in bulk GaN and InGaN multiple-quantum-well (MQW) samples using scanning second-harmonic generation (SHG) microscopy. Scanning SHG microscopy and the accompanying third-harmonic generation (THG) microscopy of the bulk GaN sample were demonstrated using a femtosecond Cr:forsterite laser at a wavelength of 1230 nm. Taking advantage of the off-resonant electric field-enhanced SHG effect and the bandtail state-resonance THG effect, the second- and third-harmonic generation microscopic images obtained revealed the piezoelectric field and bandtail state distributions in a GaN sample. Combined with 720 nm wavelength excited two-photon fluorescence microscopy in the same sample, the increased defect density around the defect area was found to suppress bandedge photoluminescence, to increase yellow luminescence, to increase bandtail state density, and to decrease residue piezoelectric field intensity. Scanning SHG microscopy of the InGaN MQW sample was resonant excited with 800 nm femtosecond pulses from a Ti:sapphire laser in order to suppress SHG contribution from the bulk GaN substrate. Taking advantage of the strong piezoelectric field inside the InGaN quantum well, the wavelength resonant effect, and the electric field-enhanced SHG effect of InGaN quantum wells, resonant scanning SHG microscopy revealed the piezoelectric field distribution inside the wells. Combined with accompanying three-photon fluorescence microscopy from the bulk GaN substrate underneath the quantum wells, the direct correspondence between the piezoelectric field strength inside the quantum well and the substrate quality can be obtained. According to our study, the GaN substrate area with bright bandedge luminescence corresponds to the area with strong SHG signals indicating a higher stained-induced piezoelectric field. These scanning harmonic generation microscopies exhibit superior images of the piezoelectric field and defect state distributions in GaN and InGaN MQWs not available before. Combining with scanning multiphoton fluorescence microscopy, these techniques open new ways for the physical property study of this important material system and can provide interesting details that are not readily available by other microscopic techniques.

Journal Article↗