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Biomedical subjects

T C Lee

Publications and source records attributed to T C Lee.

At least 55 records · Page 3Linked to original sources
PubMed2000

Tin-protoporphyrin potentiates arsenite-induced DNA strand breaks, chromatid breaks and kinetochore-negative micronuclei in human fibroblasts.

Numerous reports have shown that oxidative stress is involved in arsenite-induced genetic damage. Arsenite is also a potent inducer of heme oxygenase (HO)-1. To understand whether HO-1 could function as a cellular antioxidant and protect cells from arsenite injury, the effects of tin-protoporphyrin (SnPP), a competitive inhibitor of HO-1, on arsenite-induced genetic damage were examined in human skin fibroblasts (HFW). In the present study, we found that SnPP at 100 microM significantly potentiated arsenite-induced cytotoxicity, DNA strand breaks (assayed by alkaline single cell gel electrophoresis(SCGE)), and chromatid breaks. Although arsenite alone mainly induced kinetochore-plus micronuclei (K(+)-MN), SnPP only synergistically enhanced kinetochore-negative micronuclei (K(-)-MN). The increase in K(-)-MN by SnPP cotreatment was consistent with the increase in DNA strand breaks and chromatid breaks caused by SnPP. However, at higher arsenite doses, K(+)-MN was significantly reduced by SnPP. Pretreatment of HFW cells with hemin, an inducer of HO-1, significantly attenuated the cytotoxicity of arsenite. Therefore, the present results suggest that HO-1 induction by arsenite plays certain roles in protecting cells from arsenite-induced injury.

Arsenites↗
PubMed2000

Determination of 14 elements in Taiwanese bones.

The objective of this study was to measure the concentration of 14 elements in human bone and investigate the affecting factors. This study aims to establish a database of elements in Taiwanese bone. Seventy-seven bone samples were taken from 70 subjects who were undertaking various bone surgeries from a medical center in central Taiwan. Bone samples were pretreated using microwave digestion and then, after determining the optimal conditions for analysis, fourteen elements were analyzed using Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). Results showed that Ca had the highest concentration, followed by Mg and Zn. The lowest concentrations were of Mn, followed by Cd and Co. There was a positive correlation between the frequency of seafood intake and presence of all the 14 elements in human bone. There were several elements that had positive inter-correlation: As with Co; Al, Ag and Ca; Ni with Co, Mn and Al; Co with Al, Ag and Ca; Mn with Cr and Cu; Cr with Cu; Mg with Ca; Al with Ag and Ca; Ag with Ca; and also Zn with Mg. There were no significant differences found between concentrations of elements and etiology of bone disease and age. The authors suggest that further studies be conducted to establish a normal value of elements in human bone in Taiwan. This will greatly benefit the understanding of the relationship between disease pattern and elements in human bone.

Adult↗
PubMed2000

Delayed apnea in patients with mid- to lower cervical spinal cord injury.

STUDY DESIGN: A retrospective study of 36 patients with mid- to lower cervical spinal cord injury (CSCI) divided into two groups based on whether delayed apnea developed. OBJECTIVES: To determine nonpulmonary risk factors associated with the development of delayed apnea in mid- to lower cervical spinal cord injury. SUMMARY OF BACKGROUND DATA: Patients with mid- to lower cervical spinal cord injury are generally at lower risk of developing respiratory failure than those with high cervical spinal cord injury. Respiratory failure manifesting as sudden apnea may occur days or even weeks after injury without any pulmonary complications in such patients. METHODS: An index group of eight patients with complete mid- to lower cervical spinal cord injury in whom delayed catastrophic apnea occurred were reviewed. Another group of 28 patients with cervical spinal cord injury of identical magnitude and presentation but without respiratory failure served as the control group. Six parameters presumed to be related to the delayed apnea were analyzed. RESULTS: The extent of cord lesions was significantly different, being diffuse in most of the index patients, but focal in the majority of the control patients (P<0.001). Involvement of the C4 segment of cord appeared to be more frequent in the index group; however, the difference was not statistically significant (P = 0.091). The incidence of transient bradycardia (P<0.01) and dyspnea (P<0.001) in the index group was significantly higher than in the control group. Paralytic ileus was a much rarer event and found to be unrelated to the occurrence of apnea. In five of the eight index patients, the apnea occurred during sleep. Six of the eight index patients died of it. CONCLUSIONS: Delayed but devastating apnea may develop in patients with mid- to lower cervical cervical spinal cord injury, even when they are clinically stable and free from any pulmonary complications. The presence of diffuse, extensive cord lesions, respiratory distress, or bradycardia with or without associated hypotension, however transient and self-limited, should be regarded as warning signs. Sleep was found to be a risky period of time.

Adult↗
PubMed2000

Abnormal aortic valve development in mice lacking endothelial nitric oxide synthase.

BACKGROUND: Endothelium-derived nitric oxide (NO) is produced by an oxidative reaction catalyzed by endothelial NO synthase (eNOS). NO plays a crucial role in controlling cell growth and apoptosis, as well as having well-characterized vasodilator and antithrombotic actions. More recently, endothelium-derived NO was shown to be involved in postdevelopmental vascular remodeling and angiogenesis, as well as in the formation of limb vasculature during embryogenesis. Therefore, we investigated the role of endothelium-derived NO during cardiovascular development using mice deficient in eNOS. METHODS AND RESULTS: We examined the hearts of 12 mature eNOS-deficient and 26 mature wild-type mice. Five of the mature eNOS-deficient mice had a bicuspid aortic valve; none of the 26 wild-type animals exhibited identifiable valvular or cardiac abnormalities. Immunohistochemical analysis revealed prominent eNOS expression localized to the endothelium lining the valve cusps of the aorta in mature wild-type mice; expression was localized to the myocardium and endothelial cell monolayer lining the valve leaflets in the developing embryo. CONCLUSIONS: These results show a strong association between eNOS deficiency and the presence of a bicuspid aortic valve; they provide the first molecular insight into one of the most common types of congenital cardiac abnormality.

Animals↗
PubMed2000

Arsanilic acid-Sepharose chromatography of pyruvate kinase from KB cells.

In the present study, arsanical-based affinity chromatography for pyruvate kinase (PK) isolation was explored. p-Arsanilic acid (4-aminophenyl arsonic acid), which contains an arsonic acid moiety structurally similar to inorganic pentavalent arsenate, was conjugated to Sepharose 4B via its para-amino group to form an As(V)-Sepharose matrix. The cellular proteins from KB cells bound to arsonic acid moieties were eluted by 50 mM sodium arsenate in Tris-HCl buffer (50 mM, pH 7.6). A single protein band with a molecular mass of 58 kDa was shown on a sodium dodecyl sulfate-polyacrylamide gel. By immunoblotting, amino acid sequencing and enzymatic analysis, the sodium arsenate-eluted 58-kDa protein was demonstrated to be a human PK (type M2). By using this one-step As(V)-Sepharose chromatography, PK from KB cells was purified 35.4-fold with a specific activity of 153.15 U/mg protein in the presence of 6 mM fructose-1,6-biphosphate. Although PK was eluted from an As(V)-Sepharose column with sodium arsenate, PK activity was apparently inhibited by the used eluent system, but not by p-arsanilic acid, indicating a specific interaction of As(V) to PK. In summary, our results indicate that As(V)-Sepharose can serve as a simple and efficient chromatographic support for PK purification from KB cells.

Arsanilic Acid↗
PubMed2000

Sequential labelling of microdamage in bone using chelating agents.

Basic fuchsin labels microcracks, but a series of stains is required to differentiate between preexisting and test-induced microcracks and to label their growth in vitro. Basic fuchsin and five chelating agents-alizarin complexone, calcein, calcein blue, oxytetracycline, and xylenol orange-were randomly assigned to label microcracks in sequential rib sections from 10 donors. The density, length, and location of the microcracks did not differ significantly between the six stains, suggesting that each was equally effective in detecting microcracks. Paired specimens of trabecular bone were machined from bovine tibiae, stained with oxytetracycline, and fatigued in compression. One specimen from each pair was then stained with xylenol orange. Preexisting microdamage was stained with oxytetracycline, propagating microcracks with both stains and new, test-initiated damage with xylenol orange. Chelating agents are site-specific markers of the initiation and growth of microcracks.

Bone and Bones↗
PubMed2000

Disgust sensitivity and contamination fears in spider and blood-injection-injury phobias.

Disgust has been implicated in the onset and maintenance of blood-injection-injury (BII) and animal phobias. Research suggests that people with these phobias are characterized by an elevated sensitivity to disgust-evoking stimuli separate from their phobic concerns. The disgust response has been described as the rejection of potential contaminants. Disgust-motivated avoidance of phobic stimuli may therefore be related to fears of contamination or infection. The present study compared BII phobics, spider phobics and nonphobics on two measures of disgust sensitivity and two measures of contamination fears. Positive correlations were found between disgust sensitivity and contamination fear. Specific phobics scored higher than nonphobics on all scales and BII phobics scored higher than spider phobics on contamination fear measures. Furthermore, the contamination fear scales were correlated with the blood phobia measure, but not correlated with the spider phobia measure. The results suggest that while both phobias are characterized by elevated disgust sensitivity, contamination fear is more prominent in BII than spider phobia.

Adolescent↗
PubMed2000

Blockade of endothelin receptors markedly reduces atherosclerosis in LDL receptor deficient mice: role of endothelin in macrophage foam cell formation.

OBJECTIVE: We evaluated the direct effects of long-term blockade of ET(A) and ET(B) receptors using a mixed endothelin (ET) receptor antagonist, LU224332, in the low density lipoprotein receptor (LDL-R) knockout mouse model of atherosclerosis. METHODS: Four groups of LDL-R deficient mice were studied: control mice fed normal chow (group I); mice fed a high cholesterol (HC, 1.25%) diet alone (group II), HC fed animals treated with LU224332 (group III); and mice fed normal chow treated with the LU compound (group IV). All treatments were continued for 8 weeks at which time the animals were sacrificed and the aortae were removed and stained with oil red O. Atherosclerotic area (AA) was determined by quantitative morphometry and normalized relative to total aortic area (TA). RESULTS: Cholesterol feeding resulted in a marked increased in total plasma cholesterol ( approximately 15 fold) and widespread aortic atherosclerosis (AA/TA: group I: 0.013+/-0.007; group II: 0.33+/-0. 11; P<0.001). Atherosclerotic lesions were characterized by immunohistochemistry as consisting mainly of macrophages which also showed high levels of ET-1 expression. Treatment with ET antagonist significantly reduced the development of atherosclerosis (AA/TA: group III: 0.19+/-0.07, P<0.01 vs. group II), without altering plasma cholesterol levels and blood pressure. The direct effect of LU224332 on macrophage activation and foam-cell formation was determined in vitro using a human macrophage cell line, THP-1. Treatment of the THP-1 cells with LU224332 significantly reduced cholesterol ester and triacylglycerol accumulation and foam-cell formation on exposure to oxidized LDL (P<0.01 and P<0.05, respectively). CONCLUSION: We conclude that a nonselective ET receptor antagonist substantially inhibited the development of atherosclerosis in a genetic model of hyperlipidemia, possibly by inhibiting macrophage foam-cell formation, suggesting a role for these agents in the treatment and prevention of atherosclerotic vascular disease.

Animals↗
PubMed2000

K-wire position in tension band wiring of the olecranon - a comparison of two techniques.

Tension band wiring is a recognised standard treatment for olecranon fractures. We studied the effect of K-wire position on backing out of the wire in a group of 80 patients with closed transverse olecranon fractures with a minimum follow-up time of 9 months. The rate of wires backing out as seen on X-ray was three times greater in patients who had K-wires passed down the long axis of the ulna rather than across the anterior cortex as recommended by the AO group. There was a corresponding higher rate of local complications in these patients. 42% of this group had to have the metal removed compared with 11.4% of the transcortical group. We compared the biomechanical properties of both K-wires positions in a human cadaveric model. The maximum pull-out strength for each configuration was recorded in 20 elbow joints. The average maximum pullout strength for the intramedullary wires was 56.3 N (range 27. 7-95.6 N) and 122.7 N for the transcortical wires (range 56.7-201.2). The results of both the clinical study and biomechanical data support the routine use of transcortical placement of K-wires in tension-band wiring of transverse olecranon fractures.

Adolescent↗
PubMed2000

Effect of extrusion temperature on the solubility and molecular weight of lentil bean flour proteins containing low cysteine residues.

Lentil flour was extruded at die temperatures of 135, 160, and 175 degrees C. The soluble protein content in the extrudates decreased by 40.1% in the extracting buffer (1% sodium dodecyl sulfate in 50 mM sodium phosphate buffer, pH 6.9) as the extrusion die temperature was increased to 175 degrees C. The most insoluble proteins in the extrudates extruded at die temperatures of up to 175 degrees C could be resolubilized by using sonication. The total disulfide content and sulfhydryl content in the extrudates decreased. The SDS-PAGEs showed that the molecular weight distribution of proteins in the lentil flour changed little before and after extrusion as well as during reduction. The results from this study show that the extrusion temperature had less effect on the solubility and molecular weight of the lentil proteins, which contain a lower level of cysteine residues than wheat proteins.

Cysteine↗
PubMed2000

Correlation of lycopene measured by HPLC with the L, a, b color readings of a hydroponic tomato and the relationship of maturity with color and lycopene content.

Tomatoes (Lycopersicon esculentum cv. Laura) were separated, according to the ripening stage, by a sensory panel into seven groups, and color was measured on the tomato surface with a Minolta Chroma meter. The L, a, b, hue, chroma, and lycopene content were plotted against the maturity stages of the tomatoes, and several good correlations were found. The a/b ratio and the lycopene content were the parameters that allowed six of seven maturity groups in the tomato to be statistically distinguished. The lycopene content, measured by HPLC, was also correlated with the color measurements, and the a, a/b, and (a/b)(2) color factors produced the best regressions. An estimation of the lycopene content in tomatoes can be achieved by using a portable chroma meter, with a possible field usage application. Equations to calculate the lycopene content of tomatoes based on the color readings are reported.

Carotenoids↗
PubMed2000

Calpain-mediated proteolytic cleavage of troponin I induced by hypoxia or metabolic inhibition in cultured neonatal cardiomyocytes.

While ischemic damage to myofibrillar proteins is thought to be responsible in part for depressed cardiac function, the relation between myofilament protein breakdown and chronic hypoxia has not been defined. We previously characterized a chemical hypoxia model of neonatal cardiomyocytes mediated by 1 mM azide that exhibits features of calpain activation (Mol Cell Biochem 178:141-149, 1998). We here show that both hypoxia and azide-mediated metabolic inhibition induced heme oxygenase-1 expression, and caused cell death associated with lipid peroxidation. While blocking calcium influx or inhibiting calpain activity efficiently attenuated hypoxia-induced cell injury, it failed to prevent cell injury caused by adenoviral overexpression of the tumor suppressor protein p53. Inhibitors of caspases, on the other hand, suppressed cell injury caused by p53 overexpression. Hypoxia caused selective cleavage of troponin I (TnI), which could be suppressed by either nifedipine or calpeptin. Other myofilament proteins such as troponin T, myosin heavy chain, and actin appeared to remain largely intact. p53-mediated cell injury exhibited proteolysis of the caspase protein substrate lamin B without appreciable breakdown of TnI. We suggest that calpain-induced TnI breakdown may constitute a unique biochemical marker associated with chronically hypoxic cardiomyocytes.

Animals↗
PubMed2000

Visualisation of three-dimensional microcracks in compact bone.

Microdamage in bone contributes to the loss of bone quality in osteoporosis and is thought to play a major role in both fragility and stress fractures (Schaffler et al. 1995). In this study, in vivo microcracks in human ribs were bulk-stained in basic fuchsin and viewed in longitudinal section and in 3 dimensions using 2 different computer-based methods of reconstruction: (1) serial sectioning of methylmethacrylate embedded sections using a sledge macrotome and identification of microcracks using UV epifluorescence followed by computerised reconstruction of microcracks using software and (2) laser scanning confocal microscopy of thick sections followed by reconstruction of microcracks into a 3-D image. The size and shape of microcracks were found to be similar using both techniques. Both techniques of reconstruction showed microcracks to be approximately elliptical in shape. From the serial sectioning reconstructions (n = 9), microcracks were found to have a mean length of 404 +/- 145 microm (mean +/- S.D.) (in the longitudinal direction) and mean width of 97 +/- 38 microm (in the transverse direction). Using epifluorescence microscopy, 92 microcracks were identified; mean microcrack length was 349 +/- 100 microm in the longitudinal direction. This was consistent with other results (Burr & Martin, 1993) and with the theoretical prediction of an elliptical crack shape with aspect ratio (longitudinal: transverse) of 5:1 deduced from analysis of random 2-D sections (Taylor & Lee, 1998). The results obtained provide new data on the nature of microcracks in bone and the method has the potential to become a useful tool in the calculation of stress intensity values which indicate the probability of an individual microcrack propagating to cause a stress or fragility fracture.

Aged↗
PubMed2000

Interobserver agreement in the electrocardiographic diagnosis of acute myocardial infarction in patients with left bundle branch block.

STUDY OBJECTIVE: To determine the interobserver agreement between cardiologists and emergency physicians in the ECG diagnosis of acute myocardial infarction (AMI) in patients with left bundle branch block (LBBB) using the ECG algorithm previously described by Sgarbossa et al. METHODS: Using the Sgarbossa ECG algorithm, 4 cardiologists and 4 emergency physicians independently interpreted a test set of 224 ECGs with LBBB, of which 100 ECGs were from patients with an evolving AMI. A subset of 25 ECGs was reinterpreted by each reader to test intraobserver agreement for AMI as well as interobserver agreement for the degree of ST-segment deviation. Agreement rates for AMI were estimated using the kappa statistic. In addition, the sensitivity and specificity for diagnosing AMI were determined for each reader, using the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO I) enzyme criteria for AMI as the gold standard. The study was conducted at 3 university-affiliated medical centers. The test set contained ECGs from 100 patients enrolled in the GUSTO I trial with LBBB on their initial ECG and an evolving AMI confirmed by serum cardiac enzyme changes, and 124 control patients from the Duke Databank for Cardiovascular Disease who had stable, angiographically documented coronary artery disease and LBBB. RESULTS: There was excellent interobserver agreement (kappa=0.81, 95% confidence interval [CI] 0.80 to 0.83) between cardiologists and emergency physicians for diagnosing AMI. Intraobserver agreement kappa values for AMI diagnosis by cardiologists and emergency physicians were 0.81 (95% CI 0.67 to 0.94) and 0.71 (95% CI 0.54 to 0.89). The median sensitivity for diagnosing AMI by cardiologists and emergency physicians was 73% (range 66% to 80%) versus 67% (range 61% to 75%); median specificity was 98% (range 97% to 99%) versus 99% (range 98% to 99%). Spearman rank correlation coefficients for the degree of ST-segment deviation in all 12 leads was 0.86 (95% CI 0.85 to 0.87) among all readers. CONCLUSION: There is excellent interobserver agreement between cardiologists and emergency physicians for diagnosing AMI when applying the Sgarbossa ECG algorithm to patients with LBBB. Emergency physicians should be able to reliably use this algorithm when evaluating patients.

Adult↗
PubMed2000

Quality comparison of hydroponic tomatoes (Lycopersicon esculentum) ripened on and off vine.

There is a general belief that the quality of tomatoes ripened on vine is better than tomatoes ripened off the vine, influencing among other parameters, the price of this commodity. We compared the quality of hydroponic tomatoes ripened on and off vine by chemical, physical, and sensory evaluation to find what attributes are affected and to what extent. Lycopene, beta-carotene, total and soluble solids, moisture content, ascorbic acid, acidity, pH, texture, and color were analyzed. Tomatoes ripened on vine had significantly more lycopene, beta-carotene, soluble and total solids, higher a* and lower L*, and were firmer. However, a 100-judge panel rated only the color and overall liking of the vine-ripened tomatoes as more intense than the fruit ripened off vine. Therefore, the chemical and physical differences were mostly not large enough to influence the panelist's perception. The characterization of tomatoes ripened on and off vine may help to guide post-harvest handling and treatment and to improve the quality of tomatoes ripened off vine.

Ascorbic Acid↗
PubMed2000

Changes of bilateral palmar skin temperature in transthoracic endoscopic T-2 sympathectomy.

OBJECT: Transthoracic endoscopic T-2 sympathectomy is currently the treatment of choice for palmar hyperhidrosis (PH). Intraoperative monitoring of palmar skin temperature (PST) is often used to assess the adequacy of sympathetic ablation. The aim of this study was to investigate the time course of PST changes during the operation and to determine factors involved in the sympathetic modulation of the palmar skin blood flow. METHODS: Eighty-one patients with PH underwent bilateral transthoracic endoscopic sympathectomy of T-2 in which continuous intraoperative PST monitoring was used. Palmar skin temperature data, recorded every 30 seconds throughout the operation, were plotted against time, and a graph of two PST curves was obtained in each case. A multiphasic curve pattern of great similarity was observed in nearly 70% of cases. Specific PST readings at different operative stages were collected and averaged for all cases. The trend of PST changes in response to different procedures during the operation was analyzed. It was found that unilateral procedures caused simultaneous bilateral PST alterations. In almost all cases, bilateral PST was dramatically lowered when unilateral skin incision and intercostal muscle dissection were performed. The temperature remained low until the T-2 sympathectomy was finished on one side. In addition, unilateral T-2 sympathectomy induced synchronous elevation of bilateral PST. However, the ipsilateral response was significantly stronger than that on the contralateral side. CONCLUSIONS: Although intraoperative monitoring of PST is a reliable guide for surgeons performing endoscopic transthoracic sympathectomy, it is important to realize that PST fluctuates at different stages during the operation and that surgical procedures themselves can significantly influence PST readings. The PST data recorded at specific time points, therefore, can be misleading in terms of accuracy and the completeness of ablation of the target sympathetic ganglia, especially when the sympathetic trunk or ganglia are anatomically aberrant.

Adolescent↗