PubMed Health⌕ Search

Biomedical subjects

Y T Chiu

Publications and source records attributed to Y T Chiu.

15 recordsLinked to original sources
PubMed2006

Effect of pH on binding of mutagenic heterocyclic amines by the natural biopolymer poly(gamma-glutamic acid).

Poly(gamma-glutamic acid) (gamma-PGA), a nontoxic and biodegradable macropolymer, was evaluated for its efficiency in binding three mutagenic heterocyclic amines (HAs), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-p-2), as affected by pH in a batch mode. The maximum HA sorption was attained for pH 3-7 and decreased sharply for pH less than 3. Binding isotherms obtained at pH 2.5 and 5.5 showed different isotherm shapes that belong to S and L types, respectively. The isotherm data at pH 2.5 were well described by a linear form of the Langmuir equation, while at pH 5.5 it showed two distinct curves, which were precisely fitted as multiple Langmuir curves. The deviation of linearity in Scatchard plot proved the multisite HA sorption. The Brunauer-Emmett-Teller equation also fitted better to isotherm data at pH 5.5, suggesting a multisite sorption caused by multimolecular HA layers on gamma-PGA. High HA sorption levels of 1250, 667, and 1429 mg/g at pH 2.5 and 1429, 909, and 1667 mg/g at pH 5.5 were observed for MeIQ, 4,8-DiMeIQx, and Trp-p-2, respectively. Among the HAs studied, the sorption capacity correlated directly with hydrophobicity of HAs and inversely with the number of methyl groups in HA molecules. The plausible binding mechanism of HAs on gamma-PGA may include a combination of hydrophobic, hydrogen-bonding, ionic, and dipole-dipole interactions.

Adsorption↗
PubMed2004

Cardiac complications of enterovirus rhombencephalitis.

BACKGROUND: Epidemics of enterovirus 71 infection have caused the death of many children throughout the world. Rhombencephalitis, brain stem encephalitis, and heart failure were present in all of the fatal cases. However, no evidence of myocarditis was noted in the heart specimens, and the mechanism of heart failure remains unknown. AIMS: To characterise the presentation of cardiac complications in children with enterovirus rhombencephalitis and discuss its pathogenesis. METHODS: Ninety one consecutive patients with enterovirus rhombencephalitis underwent echocardiography. Of these, 17 patients (nine male, eight female; median age 14 months, range 4-57 months) with left ventricular dysfunction were studied. RESULTS: Tachycardia was noted in all patients and systemic hypertension in 12. Muscle-brain fraction of creatine kinase was >5% in 14 patients. Plasma norepinephrine and epinephrine levels were significantly raised in the three patients in whom these were analysed. Electrocardiographic abnormalities were noted in eight patients. Pulmonary oedema was complicated in 15 patients. The initial ejection fraction of the left ventricle was 22-58% (mean 37%, SD 11%). All patients deteriorated to hypotensive shock within 12 hours and 13 died. Heart specimens from seven patients showed no evidence of myocarditis, but significant coagulative myocytolysis, myofibrillar degeneration, and cardiomyocyte apoptosis were observed. CONCLUSIONS: Acute heart failure was noted in 19% of patients with enterovirus rhombencephalitis, which had a fatality rate of 77%. It was not caused by myocarditis but possibly by neurogenic cardiac damage.

Blood Pressure↗
PubMed1999

Statistical method for characterization of hypertrophic cardiomyopathy by use of morphologic and pathologic measurements in pigs (Sus scrofa domestica).

BACKGROUND AND PURPOSE: Hypertrophic cardiomyopathy (HCM) is characterized by symmetric or asymmetric hypertrophy of the left and/or right ventricle. Morphologic and pathologic indices (MI and PI) of hearts were established for classification of HCM in pigs. METHODS: Fifty on-farm-performance-tested pigs (average body weight, 104.3 kg; age, 224.5 days) were randomly selected. Heart weight, length, width, heart-to-body weight ratio, and thickness of the cranial and middle portions of ventricular septum and left ventricular free wall were measured. Myocyte disorganization and necrosis, myocardial and endocardial fibrosis, and intramural coronary arterial occlusion were scored. Principal component analysis and stepwise regression analysis were used to establish MI and PI. RESULTS: MI was established by using the first principal component as the dependent variable and applying stepwise regression analysis. Hearts were classified as morphologically normal, suspicious, and hypertrophic according to the range of MI. The same statistical method was used to find PI. Hearts were classified as pathologically normal, moderately affected, or seriously affected according to the range of PI. Combining MI and PI, hearts could be classified into five groups: no hypertrophy with minor lesion (normal); hypertrophy but with rare lesion; no hypertrophy but seriously affected; suspicious; and hypertrophy and seriously affected (heart with HCM). Another 119 hearts were collected and classified. The variation of heart measurements was consistent with the original purpose of classification. CONCLUSIONS: Using fewer measurements for identification of HCM objectively in pigs seems to have practical application.

Animals↗
PubMed1998

Heparinization on pericardial substitutes can reduce adhesion and epicardial inflammation in the dog.

OBJECTIVE: Primary concerns about currently available pericardial substitutes include adhesion and epicardial reaction. The purpose of this study is to evaluate host reaction to pericardial substitutes with and without incorporating slow heparin release. METHODS: To avoid biologic variation among these pericardial patches, we made a composite of six membranes. The composite membrane consisted of epoxy-fixed patches with (1) or without (2) ionically bound heparin, a glutaraldehyde-fixed patch with (3) or without (4) ionically bound heparin, an expanded polytetrafluoroethylene patch (5), and a polyester polymeric patch (6). Ten recipient dogs weighing from 12 to 19 kg (mean 13.6 kg) were used to assess the composite membranes as pericardial substitutes. The implanted composite membranes were retrieved 1 week (one dog), 2 weeks (one dog), 4 weeks (one dog), 8 weeks (one dog), and 12 weeks (six dogs) after implantation. RESULTS: Overall, the synthetic patches had a more notable inflammatory reaction than the biologic patches with or without ionically bound heparin. The heparin-bound patches caused significantly less inflammation than their nonheparinized counterparts. The heparinized porcine patches cross-linked with different compounds were found to have less fibrous formation than the nonheparinized patches and the synthetic patches. CONCLUSIONS: Heparinized pericardial substitutes may cause less adhesion and inflammatory reaction than nonheparinized material.

Animals↗
PubMed1997

XTT-colorimetric assay as a marker of viability in cryoprocessed cardiac valve.

This study sought to evaluate the use of tetrazolium salt XTT reduction as an indicator of valvular viability in a cryoprocessed porcine cardiac homograft model. The XTT tetrazolium assays was based on the metabolic reduction of Sodium 3'-[1-(phenylamino-carbonyl)-3,4-Tetrazolium]-bis(4-methoxy-6-nitro) benzene sulfonic acid hydrate. The relationship between XTT reduction and: (1) leaflet tissue with various weight (n = 24); (2) morphometric evaluation (n = 30); (3) cadaveric ischemic intervals (n = 30); (4) freeze-thawing (n = 30) has been studied. The measurement of XTT reduction were significantly correlated with the weight of cardiac leaflets, in the range of 30 to 180mg (y=0.015x-0.063; r=0.99). Compared to morphometry of valvular damage, the reduction of mitochondrial enzymatic activity in cardiac leaflets was correlated with matrix cells without irreversible damage (r=0.89, P<0.005). The depletion of XTT reduction occurred dependent of ischemic time intervals. In general, freeze-thawing reduced more than 20% activity of mitochondrial dehydrogenase. We concluded that XTT tetrazolium assay is highly sensitive to determine valvular injury. The study demonstrated its potential for testing of cryopreserved cardiac valve.

Animals↗
PubMed1997

Alteration of endogenous antioxidant enzymes in naturally occurring hypertrophic cardiomyopathy.

We have recently developed a porcine model with naturally occurring hypertrophic cardiomyopathy (HCM). Similar to humans, occluded intramural coronary artery and damaged mitochondria are frequently observed in these animals in which the disease is thought to be associated with the local ischemia of myocardium. In view of antioxidant functions involved in the ischemic injury, we measured the expression of endogenous antioxidant enzymes in the tissues with and without HCM. The results showed a significant increase of Cu,Zn-superoxide dismutase (SOD), but not Mn-SOD, and decrease of catalase (CAT) activities in the various areas of HCM hearts. It was demonstrated that SOD/CAT ratios in the HCM hearts were significantly higher than those in normals and were found to be dramatically correlated with the severity of cardiac hypertrophy. The altered SOD/CAT ratio was also consistent with increase in lipid damage. We hypothesize that the elevated SOD combined with an inadequate amount of H2O2 scavenging enzyme may lead HCM heart at oxidative stress risk. However, the pathogenic role of imbalanced antioxidant enzyme needs to be further explored.

Animals↗
PubMed1997

Intramural coronary artery disease in swine with naturally occurring hypertrophic cardiomyopathy.

Intramural coronary artery disease (ICAD) has been reported in myocardium affected with hypertrophic cardiomyopathy (HCM), but has never been studied in detail with respect to the cell type or lipid infiltration involved in the wall-thickening. The lack of heart samples may be one of the rationales to hamper the progress in investigating this disease. Recently, the discovery of naturally occurring HCM in swine has provided an excellent opportunity for the study of ICAD because of the high prevalence of ICAD in this animal. The present study provides a detailed structure feature in the thickened arterial wall of ICAD by both histologic and electron microscopic means. Morphologically, the feature of ICAD is due primarily to the neointimal thickening. Smooth muscle cells (SMC) and extracellular matrix (collagen and elastic fibers) are the major components responsible for the thickened neointima. Fragmentation of the internal elastic membrane is associated with the migration and proliferation of SMC from the media to the intima. Therefore, pigs with HCM may be a potential animal model not only for the study of the mechanism by which SMC migrate and proliferate into intima, but also for the future investigation of interventions in coronary artery occlusion.

Animals↗
PubMed1996

Evaluation of an epoxy-fixed biological patch with ionically bound heparin as a pericardial substitute.

In an attempt to develop an improved pericardial substitute, we undertook the development of an epoxy-fixed biological patch with ionically bound heparin. The study was to evaluate the cross-linking characteristics of this newly developed biological patch using its glutaraldehyde-fixed counterpart as a control. In addition, the feasibility of using this newly developed biological patch as a pericardial substitute was assessed in a canine model. In the study, it was observed that the epoxy-fixed biological patch appeared more similar to the native pericardium in colour and was more pliable than its glutaraldehyde-fixed counterpart. Also, both the epoxy- and glutaraldehyde-fixed biological patches had significant increases in fixation index and denaturation temperature as compared to the fresh one (p < 0.05). In the canine study, the epoxy-fixed biological patch with ionically bound heparin was found to have significantly less adhesion formation than those currently used clinically (p < 0.05).

Analysis of Variance↗
PubMed1996

Adipofascial flap of the lower leg based on the saphenous artery.

The adipofascial flap of the lower leg based on the saphenous artery is a modification of the saphenous artery flap. It has been used successfully in 5 patients for reconstruction of soft tissue defects around the knee and superior third of the tibia. The size of these flaps ranged from 5 x 12 cm to 5 x 18 cm. All flaps survived completely. These cases had minimal donor site morbidity because their donor sites were closed primarily with the preserved overlying skin.

Adolescent↗
PubMed1996

The lateral calcaneal artery adipofascial flap.

The lateral calcaneal artery adipofascial flap is a modification of the lateral calcaneal artery skin flap. It has been used successfully in five patients. In comparison to the skin flap, it has the advantages of more versatile clinical applications, better aesthetic result of the donor site and sural nerve preservation.

Adipose Tissue↗
PubMed1996

Substantial decrease of heat shock protein 90 in ventricular tissues of two sudden-death pigs with hypertrophic cardiomyopathy.

We recently developed a pig model with naturally occurring hypertrophic cardiomyopathy (HCM). To further characterize the biochemical features of high frequency of sudden death affected by this disease, the protein profiles of ventricular tissues were analyzed on normal, HCM, and HCM with sudden-death pigs. By sodium dodecylsulfate-polyacrylamide gel electrophoresis, a protein corresponding to an apparent molecular mass of 90 kDa (p90) was found to be markedly decreased in the HCM-affected tissues of sudden-death pigs, but not in HCM or normal pigs. Further study showed that the primary decrease of p90 in HCM pigs with sudden death was located mainly in the interventricular septum. As determined by the molecular mass and isoelectric point on 2-dimensional gels and Western immunoblot with a specific 90 kDa heat shock protein (HSP90) monoclonal antibody, the unknown protein was identified as HSP90. Our findings indicate for the first time that substantially decreased heart HSP90 is associated with HCM pigs with sudden death. Although the role that HSP90 may play in protecting pigs with HCM from sudden death is still nuclear, the model itself may provide further insight into understanding the role of heat shock proteins in cardiac sudden death.-Lee, W.-C., Lin, K.-Y., Chiu, Y.-T., Lin, J.-H., Cheng, H.-C., Huang, H.-C., Yang, P.-C., Liu, S.-K., Mao, S. J. T. Substantial decrease of heat shock protein 90 in ventricular tissues of two sudden-death pigs with hypertrophic cardiomyopathy.

Animals↗
PubMed1996

Heritability estimate of hypertrophic cardiomyopathy in pigs (Sus scrofa domestica).

The purpose of this study was to evaluate the heritability of hypertrophic cardiomyopathy (HCM) in pigs and the relation between HCM and heart measurements, pathologic features, and growth to provide references for HCM line development. A total of 353 on-farm tested gilts (females) and boars (males) from 74 sire families were randomly selected from a single breeding farm where HCM was prevalent. Hearts were collected after animals were slaughtered. Heart length, width, and weight, heart-to-body weight ratio, and thickness of the cranial, middle, and caudal portions of the ventricular septum, left and right ventricles, and apex were measured. Cardiac hypertrophy and myocyte disorganization, myocardial and endocardial fibrosis, and intramural coronary arterial occlusion were used as criteria for HCM. Growth traits were evaluated from average daily body weight gain, ultrasonically determined backfat thickness, loin-eye area, and performance selection index. Heritability of the disease was estimated by treating it as a threshold trait. The prevalence of HCM in three studied breeds was 5.26 in Duroc, 22.98 in Landrace, and 5.56% in Yorkshire pigs. The value in Landrace pigs was significantly (P < 0.001) higher than that in the other pigs. There was no significant difference between sexes. In general the heart of pigs with HCM was heavier, wider, longer, and thicker than that of clinically normal pigs. Backfat was the only growth trait with a difference (P < 0.05) among pig breeds. The HCM pigs were leaner than normal pigs. Leaner pigs may have a higher risk of HCM. Heritability of HCM was > 0.30 for all three breeds, but the standard errors of these estimates were high because of limited sample size, in particular for the Yorkshire and Duroc breeds. The preliminary results of this study indicate that HCM in pigs is moderately heritable; thus development of a high-HCM incidence line by selection is possible.

Animals↗
PubMed1979

Aneurysmal bone cyst of the temporal bone.

Aneurysmal bone cysts occurring within the calvarium are uncommon. The following case report describes the radiological and pathological findings of a temporal bone aneurysmal bone cyst with intra- and extracranial manifestations. The pertinent literature is reviewed.

Adolescent↗
PubMedDate not supplied

Characterization and quantitation of extracellular collagen matrix in myocardium of pigs with spontaneously occurring hypertrophic cardiomyopathy.

The extracellular matrix between cardiocytes has been suggested to play an important role in maintaining the structure and function of the heart. The purpose of this study was to elucidate the morphological changes in the collagen of the extracellular matrix (ECM) in the hearts of pigs with hypertrophic cardiomyopathy. Sixty pigs diagnosed with hypertrophic cardiomyopathy from 605 purebred Landrace pigs ages 6 to 9 months were used in this study. Morphologically, these pigs with hypertrophic cardiomyopathy had increased heart weight and heart-to-body weight ratio, thickening of the left ventricular (LV) and right ventricular (RV) free walls and septum, disorientation of cardiocytes, myocardial fibrosis, and intramural coronary arteriosclerosis. Similar observations have been described in our preliminary report (Cardiovasc Pathol 3:261, 1994). In the present study, we have modified the silver impregnation technique to stain paraffin-embedded sections to demonstrate three types of ECM. There were endomysial struts, perimysial weaves, and epimysial coils in the myocardium. The light microscopic findings of the struts, weaves, and coils were also confirmed by scanning electromicroscopic examination. The numbers of these fine structures were increased significantly in the pigs with hypertrophic cardiomyopathy. In addition, the amounts of collagen in the LVs, RVs, and septum (Sep) in pigs with hypertrophic cardiomyopathy (LV = 19.37+/-0.79, RV = 23.72+/-0.72, Sep = 20.38+/-0.94 microg/mg, n = 60) were significantly higher (p < 0.01) than that in similar areas of normal pigs (LV = 14.56+/-1.11, RV = 18.90+/-1.02, Sep = 14.99+/-1.33 microg/mg, n = 30, respectively). Our findings of an overall increase of collagen content suggested that the accumulation of collagen matrix might be another factor responsible for the diastolic dysfunction of hypertrophic cardiomyopathy. These results might also infer that the increased collagen matrix could contribute to the stiffness of the cardiac chambers, thereby markedly affecting systolic and diastolic function of the heart. These observations provide further support that the pig may be an animal model for human cardiovascular disease.

Animals↗