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Biomedical subjects

C F Yang

Publications and source records attributed to C F Yang.

At least 37 records · Page 2Linked to original sources
PubMed2000

Resolution of the pathways of poliovirus type 1 transmission during an outbreak.

An outbreak of poliomyelitis with 20 cases occurred in Israel, Gaza, and the West Bank from October 1987 to October 1988. The wild type 1 poliovirus associated with the outbreak was most closely related to viruses found in the Nile Delta. The epidemiologic links among patients involved in the outbreak and patients with community-acquired infections during the outbreak were inferred from the evolutionary relationships among isolates of the outbreak virus. Complete VP1 sequences (906 nucleotides) were determined for 12 clinical and 4 sewage isolates. A total of 58 nucleotide differences were found among the 16 isolates; 74% of all substitutions were synonymous third-position transitions. An evolutionary tree, representing both the pathways of VP1 sequence evolution and the inferred chains of virus transmission during the outbreak, was constructed under the assumption that each substitution had occurred only once. The combined epidemiologic and molecular data suggest that a single founder strain was introduced into Israel from the vicinity of Gaza in the fall of 1987. Poliovirus circulation was apparently localized to southern communities during the winter and spread north by the following summer into the Hadera subdistrict of Israel, where it radiated via multiple chains of transmission into other communities in northern Israel and the West Bank. The close sequence matches (>99%) between clinical and sewage isolates from the same communities confirm the utility of environmental sampling as a tool for monitoring wild poliovirus circulation.

Base Sequence↗
PubMed2000

Small hepatocellular carcinoma: safety and efficacy of single high-dose percutaneous acetic acid injection for treatment.

PURPOSE: To evaluate the safety and efficacy of single high-dose percutaneous acetic acid injection (PAI) for treatment of small (<3-cm-diameter) hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Eighteen patients with HCC (22 nodules; diameter range, 1.5-3.0 cm) underwent single PAI. With ultrasonographic or computed tomographic (CT) guidance, 4-11 mL of 50% acetic acid was slowly injected into the center of the nodule through a skinny multiple-side-hole needle. Follow-up was performed with helical contrast material-enhanced CT. Complications of high-dose PAI were recorded. RESULTS: Seventeen nodules showed no local recurrence (follow-up, 6-29 months) after single PAI. At a mean follow-up of 15.6 months, mean tumor diameter was 2.1 cm and mean injected volume was 6.4 mL. Four nodules showed residual tumor (mean tumor diameter, 2.6 cm; mean injected volume, 5.8 mL). The mean ratio of injected to estimated volume of acetic acid was 1.21 in cases of successful single PAI and 0.72 in cases of local recurrence (P < .001). One patient with preexistent right portal venous thrombosis died of hepatic failure 37 days after PAI. Other complications included severe pain (11%), high fever (4%), and segmental wedge infarction (4%). CONCLUSION: Single high-dose PAI is safe and effective for treatment of small HCC.

Acetic Acid↗
PubMed2000

Carpal tunnel syndrome caused by tophaceous gout: CT and MR imaging features in 20 patients.

OBJECTIVE: The objective of this study is to describe the CT and MR imaging findings of gouty tophi in the wrist and present this entity as a cause of carpal tunnel syndrome. MATERIALS AND METHODS: Retrospective review of the CT (n = 18) and MR imaging (n = 20) studies of the wrist in patients with a documented diagnosis of gout who presented with gout-related carpal tunnel syndrome was performed; images of 24 wrists were collected over a 5-year period. Patient population included 20 men, who ranged in age from 35 to 76 years. All images were reviewed by two musculoskeletal radiologists who reached a consensus opinion. Surgical correlation was available in 12 patients. RESULTS: Tophi were found in the floor of the carpal tunnel (n = 18), carpal bones (n = 17), radiocarpal joint (n = 17), and extensor tendons or tendon sheaths (n = 16) of the wrist. All tophi showed similar signal characteristics (from low to intermediate signal intensity on T1-weighted images with heterogeneous signal intensity on T2-weighted images) with the exception of tophi in the floor of the carpal tunnel (low signal intensity on T2-weighted images). Varying degrees of calcification were noted on CT and MR imaging studies. Gadolinium-enhanced MR studies showed heterogeneous enhancement. CONCLUSION: Gouty tophi should be entertained as a cause of carpal tunnel syndrome in the appropriate patient population. Familiarity with this entity and its imaging characteristics may prove helpful in diagnosis and preoperative planning.

Adult↗
PubMed2000

Modulation transfer function and critical flicker frequency in high-myopia patients.

BACKGROUND AND PURPOSE: Critical flicker frequency (CFF) decreases due to optic nerve and retinal damage in patients with optic neuritis or glaucoma. Because retinal degeneration is also found in high myopia, we investigated whether the modulation transfer function (MTF) and CFF are altered in patients with high myopia. METHODS: Forty-six patients with high myopia (< -8 diopters, D) were recruited from our outpatient department. The control group comprised 21 young volunteers with myopia of 0 to -2 D. The myopic and control groups were similar in terms of age and sex. RESULTS: At all frequencies tested, the myopic group had lower CFF and higher modulation values than the control group. The mean CFF was significantly lower in myopic patients (46.8 +/- 9.0 Hz) than in control subjects (52.5 +/- 4.4 Hz). Patients with extremely high myopia (< -10 D) had significantly greater modulation values at 5, 10, 15, 55 and 60 Hz than those with moderately high myopia (-8 D to -10 D). The CFF did not differ significantly between those with extremely high (46.3 +/- 8.8 Hz) and those with moderately high (49.0 +/- 6.9 Hz) myopia. CONCLUSIONS: The findings of this study support that the CFF decreases and MTF increases in patients with high myopia, and that the alternation of MTF is related to the degree of myopia. CFF and MTF may, therefore, have potential as indexes to evaluate the severity of retinal degeneration in patients with high myopia.

Adolescent↗
PubMed2000

Unusual signs for dural arteriovenous fistulas with diffuse basal ganglia and cerebral calcification.

We present a case of multiple dural arteriovenous fistulas (AVFs) in a 60-year-old man with the chief complaint of worsening headache, altered mental status and progressively unsteady gait over the course of one year. Computerized tomography revealed diffuse, symmetric calcification in the bilateral basal ganglia and bilateral periventricular and subcortical white matter. Magnetic resonance imaging revealed multiple, enhanced, punctate and linear vessels. These images were due to reflux into the parenchymal veins in the dural AVF of the superior sagittal sinus within the basal ganglia and deep white matter of both cerebral hemispheres. Cerebral angiography disclosed multiple dural AVFs. The exact mechanism of basal ganglia and subcortical calcification is proposed to be an arterial steal phenomenon or persistent venous congestion, with calcification occurring in a chronic hypoperfused state or with dystrophic changes in the walls of congested veins.

Arteriovenous Fistula↗
PubMed2000

Effect of strenuous arm exercise on oxidized-LDL-potentiated platelet activation in individuals with spinal cord injury.

This study investigates how strenuous arm exercise affects oxidized-low density lipoprotein (O(X)-LDL) mediated-platelet activation in patients with SCI. Ten patients with SCI and ten age- and sex-matched healthy subjects exercised strenuously using an arm crank ergometer. The following measurements were taken both when the subjects were at rest, and immediately after exercise: plasma lipid profile, O(X)-LDL mediated platelet aggregability and [Ca(2+)]i, urinary 11-dehydro-thromboxane B2 (11-dehydro-TXB2) and 8-iso-prostaglandin F(2alpha), (8-iso-PG F(2alpha)) contents, and plasma NO metabolite (nitrite plus nitrate) level. Based on these measurements, the major findings of this study can be summarized as follows: 1) the SCI group had higher urinary 8-iso-PGF(2alpha) and 11-dehydro-TXB2 contents, but a lower plasma nitrite plus nitrate level than the control group; 2) at rest, the SCI group had a higher platelet aggregability and [Ca(2+)]i, and O(X)-LDL-potentiated platelet activation than the control group; 3) O(X)-LDL-potentiated platelet aggregation was enhanced by strenuous arm exercise in both groups, but the effect of exercise was more pronounced in the SCI group than in the control group; 4) treating the platelet with L-arginine inhibited O(X)-LDL-potentiated platelet activation in both groups. The study concludes that individuals with SCI had more extensive resting and exercise-enhanced O(X)-LDL-potentiated platelet activation and greater amounts of preformed lipid peroxides than those without SCI. Therefore, supplementation therapy with antioxidants may be needed for patients with SCI, especially in a strenuous arm exercise period.

Adult↗
PubMed1999

Sodium selenite-induced oxidative stress and apoptosis in human hepatoma HepG2 cells.

The mechanisms involved in the anti-carcinogenic activity of selenium remain to be elucidated. In the present study, we examined sodium selenite-induced oxidative stress and apoptosis in a human hepatoma cell line (HepG2). Sodium selenite (10 microM) exerted clear cytotoxic effect, as shown by the significant increase of lactate dehydrogenase leakage. Selenite-induced DNA alterations in apoptosis were studied by: 1. comet assay; 2. TdT-mediated dUTP nick end-labeling assay. In addition, characteristic apoptotic morphological alterations were also observed in selenite-treated cells. Our results clearly show that Se-induced cell death occurs predominantly in the form of apoptosis. Selenite-induced oxidative stress was evaluated by the measurement of reactive oxygen species production using lucigenin-dependent chemiluminescence. The involvement of glutathione in selenite-induced oxidative stress was further demonstrated by the concurrent decline of intracellular reduced glutathione and increase of oxidized glutathione contents in Se-treated cells. Moreover, the finding that selenite-induced oxidative stress and apoptosis was significantly attenuated by superoxide dismutase, catalase and deferoxamine provides additional evidence to suggest that Se-induced oxidative stress mediates the induction of apoptosis, a mechanism related to the anti-carcinogenic and chemopreventive effect of Se.

Apoptosis↗
PubMed1999

Protective effect of ebselen against hydrogen peroxide-induced cytotoxicity and DNA damage in HepG2 cells.

The protective effect of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a selenoorganic compound, against hydrogen peroxide (H2O2)-induced cytotoxicity and DNA damage was investigated in a human hepatoma cell line, HepG2. The inhibitory effect of H2O2 on cell growth was determined using the tetrazolium dye colorimetric test (MTT test), and the cytotoxicity and lipid peroxidation were estimated by lactate dehydrogenase (LDH) leakage and malondialdehyde (MDA) formation, respectively. DNA damage was detected using single cell gel electrophoresis (comet assay), and intracellular reactive oxygen species (ROS) formation was measured using a fluorescent probe 2',7'-dichlorofluorescein diacetate (DCFH-DA). The results showed that H2O2 suppressed the growth of HepG2 cells and the addition of ebselen significantly reduced the suppression. Furthermore, ebselen also displayed a dose-dependent reduction of LDH leakage and MDA formation in H2O2-treated cells. The results also demonstrate that ebselen was able to reduce the ROS formation and DNA damaging effect caused by H2O2 in a dose-dependent manner. These findings suggest that ebselen has a strong protective ability against the cytotoxicity and DNA damaging effect caused by reactive oxygen species.

Azoles↗
PubMed1999

In vivo newly translated polypeptides are sequestered in a protected folding environment.

Molecular chaperones play a fundamental role in cellular protein folding. Using intact mammalian cells we examined the contribution of cytosolic chaperones to de novo folding. A large fraction of newly translated polypeptides associate transiently with Hsc70 and the chaperonin TRiC/CCT during their biogenesis. The substrate repertoire observed for Hsc70 and TRiC is not identical: Hsc70 interacts with a wide spectrum of polypeptides larger than 20 kDa, while TRiC associates with a diverse set of proteins between 30 and 60 kDa. Overexpression of a bacterial chaperonin 'trap' that irreversibly captures unfolded polypeptides did not interrupt the productive folding pathway. The trap was unable to bind newly translated polypeptides, indicating that folding in mammalian cells occurs without the release of non-native folding intermediates into the bulk cytosol. We conclude that de novo protein folding occurs in a protected environment created by a highly processive chaperone machinery and is directly coupled to translation.

Animals↗
PubMed1999

Insertion/deletion mutations of type I oculocutaneous albinism in chinese patients from Taiwan.

Type I oculocutaneous albinism (OCA1) is an autosomal recessive disorder, which is caused by the reduction or the absence of tyrosinase activity in melanocytes of the skin, hair and eyes. Although tyrosinase mutations of OCA1 have been extensively analyzed in most populations worldwide, there is no systemic study of OCA1 mutation in Chinese patients. By use of single strand conformation polymorphism and direct sequencing, we had detected 21 mutant alleles out of 24 OCA1 chromosomes screened (87.5%). Detected mutant alleles include one splicing site, three insertion/deletion and five missense mutations, of which the splicing site nucleotide alteration (IVS 1-3C>G) and two each of the insertion/deletion (232-233 ins GGG and 861-862 del TT) and missense mutations (Cys 289 Gly and Trp 400 Leu) are novel. The ins/del mutations accounts for about 37.5% in Chinese OCA1 alleles. The 232-233 ins GGG, one of the novel mutations, was found to be most frequent (25%) among the OCA1 alleles in Chinese. Through this study, we found that while some of the OCA mutant alleles were identified in other populations, ethnic difference still exists. Hum Mutat 14:542, 1999.

Albinism, Oculocutaneous↗
PubMed1999

Intra-articular gouty tophi of the knee: CT and MR imaging in 12 patients.

OBJECTIVE: To define the imaging characteristics of intra-articular tophi of the knee. DESIGN AND PATIENTS: Twelve patients with intra-articular tophi in the knee were studied with routine MR imaging, gadolinium (Gd)-enhanced MR imaging, and CT over a 4-year period. There were 11 men and one woman, 25-82 years of age (mean age 48 years). Four patients did not have a documented history of gout at the time of the MR examination. The diagnosis of intra-articular tophi was provided by arthroscopy and histological examination (5 patients), by microscopic study of joint fluid (5 patients), or by characteristic clinical, laboratory and imaging findings (2 patients). RESULTS: In 15 MR examinations the tophi were located purely intra-articularly in 10 knees. In the remaining five MR studies, periarticular soft tissues or bone, or both, were involved. All the intra-articular tophi manifested low to intermediate signal intensity on both T1- and T2-weighted images. All five Gd-enhanced MR examinations demonstrated a heterogeneous peripheral enhancement. All 10 CT scans showed varying degrees of stippled calcifications within the tophi. The nature of the calcifications was confirmed on histological examination in three patients. CONCLUSION: Presenting clinical manifestations of gout may relate to intra-articular tophaceous deposits. Such deposits present as masses on MR images with low to intermediate signal intensity on both T1- and T2-weighted images and a characteristic enhancement pattern following intravenous Gd administration. These features relate primarily to internal calcifications, which are most evident on CT images. MR evaluation (including Gd administration) supplemented, in some cases, with CT scanning allows accurate diagnosis of intra-articular tophaceous deposits.

Adult↗
PubMed1999

Design of synthetic hexapeptide substrates for prostate-specific antigen using single-position minilibraries.

Prostate-specific antigen (PSA), a serine endoprotease with chymotrypsin-like substrate specificity, is a marker used widely for detection of prostate cancer and other prostate diseases, catalyzing hydrolysis of the gel-forming proteins semenogelins I and II, which are synthesized and secreted by the seminal vesicle. In this study we report the use of two single-position minilibraries and RP-HPLC selection to optimize a hexapeptide substrate for PSA, spanning substrate positions P3 to P3'. PSA has been shown previously to prefer tyrosine in position P1 [Denmeade et al. (1997) Cancer Research, 57, 4924-4930]. Here we demonstrate preference for serine in position P1' and strong preference for phenylalanine in position P2. Based on these results we have designed and demonstrated the utility of the optimized fluorogenic PSA substrate 7-methoxy-coumarin-4-acetylGlnPheTyrSerSerAsnLys(epsilon-2,4-dinit rophenyl)amide, 1, which permits continuous monitoring of PSA endopeptidase activity at high sensitivity.

Chromatography, High Pressure Liquid↗
PubMed1999

Suppression of experimental corneal angiogenesis by focal X-ray irradiation.

PURPOSE: To investigate the effect of focal X-ray irradiation on experimental corneal angiogenesis in the rabbit. METHODS: A gelatin hydrogel sheet impregnated with basic fibroblast growth factor was implanted into the corneal stroma of rabbits; this induced corneal angiogenesis. After the first sign of corneal angiogenesis was noted, the corneal region was irradiated with a dose of 10 Gy or 20 Gy. The control rabbits received no irradiation. The eyes were examined by slitlamp biomicroscopy and photographed, over a period of 28 days. The maximum length and total surface area of corneal angiogenesis were quantified by computerized image analysis. RESULTS: Corneal angiogenesis was noted on day 3 following implantation of the hydrogel sheet. In the rabbits irradiated with 10 Gy, the maximum length and total surface area of corneal angiogenesis were both significantly lower on day 4 and 7 following irradiation, compared to the respective measurement in the controls. In the rabbits irradiated with 20 Gy, the maximum length and total surface area of corneal angiogenesis were significantly lower between days 4 and 21, and between days 4 and 14, respectively, compared to the respective measurement in the controls. CONCLUSIONS: Focal X-ray irradiation to the corneal region suppressed corneal angiogenesis in a dose-dependent manner. Focal X-ray irradiation may be beneficial in treating ocular angiogenesis.

Animals↗
PubMed1999

Effect of Salvia miltiorrhiza on aflatoxin B1-induced oxidative stress in cultured rat hepatocytes.

Recent findings have suggested that oxidative damage might contribute to the cytotoxicity and carcinogenicity of aflatoxin B1 (AFB1). Salvia miltiorrhiza (Sm), a herbal plant that has been used extensively in traditional Chinese medicine for treating cardiovascular and liver diseases, is believed to have some antioxidative capabilities. In this study, the protective effect of Sm against AFB1-induced cytotoxicity was investigated in cultured primary rat hepatocytes. AFB1-induced cytotoxicity and lipid peroxidation (LPO) were estimated by determination of lactate dehydrogenase (LDH) leakage and thiobarbituric acid reactive substances (TBARS) formation, respectively. Intracellular reactive oxygen species (ROS) formation was measured using a fluorescent probe 2',7'-dichlorofluorescein diacetate (DCFH-DA). In addition, changes of intracellular glutathione (GSH) content were also studied. Results showed that Sm was able to suppress the LDH leakage induced by AFB1 in a dose-dependent manner. A dose-dependent inhibitory effect of Sm on AFB1-induced LPO was also found in hepatocytes treated with Sm. It was further observed that Sm produced an inhibitory effect on ROS formation caused by AFB1. Concomitantly, the GSH content in Sm-treated groups increased substantially compared to those without Sm treatment. These findings suggest that Sm can inhibit the cytotoxicity of AFB1 through decreasing ROS formation, inhibiting LPO and preventing GSH depletion. The major component of the aqueous extract of Sm was identified by using high performance liquid chromatography (HPLC), proton magnetic resonance (1H-NMR) and mass spectrum (MS). Analytical results suggested that D(+)beta3,4-dihydroxyphenol lactic acid (DA) is the main compound of the aqueous extract of Sm.

Aflatoxin B1↗
PubMed1999

Central nervous pathway for acupuncture stimulation: localization of processing with functional MR imaging of the brain--preliminary experience.

PURPOSE: To characterize the central nervous system (CNS) pathway for acupuncture stimulation in the human brain by using functional magnetic resonance (MR) imaging. MATERIALS AND METHODS: Functional MR imaging of the whole brain was performed in two groups of nine healthy subjects during four stimulation paradigms: real acupuncture at acupoints ST.36 (on the leg) and LI.4 (on the hand) and control stimulations (minimal acupuncture and superficial pricking on the leg). Stimulations were performed in semirandomized, balanced order nested within two experiments. Psychophysical responses (pain, De-Qi effect [characteristic acupuncture effect of needle-manipulation sensation], anxiety, and unpleasantness) and autonomic responses were assessed. Talairach coordinates-transformed imaging data were averaged for a group analysis. RESULTS: Acupuncture at LI.4 and ST.36 resulted in significantly higher scores for De-Qi and in substantial bradycardia. Acupuncture at both acupoints resulted in activation of the hypothalamus and nucleus accumbens and deactivation of the rostral part of the anterior cingulate cortex, amygdala formation, and hippocampal complex; control stimulations did not result in such activations and deactivations. CONCLUSION: Functional MR imaging can demonstrate the CNS pathway for acupuncture stimulation. Acupuncture at ST.36 and LI.4 activates structures of descending antinociceptive pathway and deactivates multiple limbic areas subserving pain association. These findings may shed light on the CNS mechanism of acupuncture analgesia and form a basis for future investigations of endogenous pain modulation circuits in the human brain.

Acupuncture Analgesia↗
PubMed1999

Small functional adrenal cortical adenoma: treatment with CT-guided percutaneous acetic acid injection--report of three cases.

Two patients with Conn syndrome and one patient with Cushing syndrome underwent computed tomography (CT)-guided tumor ablation with a total of 5-11 mL of 50% acetic acid injected into their adrenal nodule (1.3-3.3 cm in diameter). No major complications were encountered during or after the procedure. All patients were symptom free with normal laboratory test results for at least 1-year follow-up. CT images showed complete cystic change with tumor size regression. Our preliminary results suggest that percutaneous acetic acid injection is a safe and effective alternative for treatment of small functional adrenal cortical adenoma.

Acetic Acid↗
PubMed1999

Intracranial acute arterial ischemia of the anterior circulation: evaluation with three-dimensional time-of-flight magnetic resonance angiography.

BACKGROUND: Stroke has been the second most common cause of death, after cancer, in Taiwan since 1983. The cost of stroke to society in terms of morbidity, mortality and economics is profound. Heightened interest in the early diagnosis and treatment of acute stroke challenges neuroimagers to optimize available modalities and to develop new techniques for the evaluation of cerebrovascular disease. The aim of this study was to investigate the effectiveness of magnetic resonance angiography (MRA) in conjunction with spin-echo imaging in patients with acute brain infarction of the anterior circulation. METHODS: Magnetic resonance imaging and three-dimensional Fourier transformed time-of-flight MRA studies, performed on 50 patients within one week after the onset of cerebral ischemia, were retrospectively reviewed and correlated with clinical records. Five of the 50 MRAs were considered nondiagnostic and excluded because of poor patient cooperation. RESULTS: In 41 of the 45 cases, the area of infarct corresponding to the clinical deficit at the time of study was identified on T2-weighted spin-echo images. Arterial occlusions or severe stenoses that corresponded to ischemic manifestations were identified with MRA in 37 of the 45 patients. A focal discontinuity with decreased arterial caliber corresponded to stenosis and nonvisualization of distal branches represented arterial occlusion. MRA provided information for 23 cases not obtained from the MR images. CONCLUSIONS: Vascular lesions demonstrated on intracranial MRA show a high correlation with infarct distribution. MRA, which provides information adjunctive to conventional MR imaging in a majority of cases, is concluded to be an important component of the complete evaluation of brain infarction.

Acute Disease↗