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Biomedical subjects

I C Chen

Publications and source records attributed to I C Chen.

At least 19 recordsLinked to original sources
PubMed2006

Electrochemical modification of vertically aligned carbon nanotube arrays.

Electrochemical oxidation and reduction were utilized to modify vertically aligned carbon nanotube (CNT) arrays grown on a porous network of conductive carbon microfibers. Ultrafast and complete CNT opening and purification were achieved through electrochemical oxidation. Highly dispersed platinum nanoparticles were then uniformly and densely deposited as electrocatalysts onto the surface of these CNTs through electrochemical reduction. Using supercritical drying techniques, we demonstrate that the unidirectionally aligned and laterally spaced geometry of the CNT arrays can be fully retained after being subjected to each step of electrochemical modification. The open-tipped CNTs can also be electrochemically detached in full lengths from the supporting substrates and harvested if needed.

Journal Article↗
PubMed2006

alpha-Synuclein promoter RsaI T-to-C polymorphism and the risk of Parkinson's disease.

Increased alpha-synuclein expression may be involved in the pathogenesis of Parkinson's disease (PD). We investigated the association of Rep1 microsatellite and RsaI T-to-C substitution in the alpha-synuclein promoter region with the risk of PD by a case-control study. The RsaI C/C genotype and C allele were found less frequently in PD patients than in controls. A reduced risk of the Rep1-RsaI 0-C haplotype (OR = 0.57, 95% CI = 0.36-0.90) with PD was evident. The quantitative real-time PCR study showed that the alpha-synuclein mRNA expression was increased (although not significantly) in PD patients with RsaI T/T genotype or Rep1-RsaI 0-T haplotype as compared to T/C genotype or 0-C haplotype. Reporter constructs containing the RsaI C allele drove significantly lower transcriptional activity compared with the RsaI T allele in both IMR32 and 293 cells. The findings suggest that the RsaI T-to-C substitution may have a functional relevance to the susceptibility to PD.

Adult↗
PubMed2006

Genetic association of blaSHV-5 with transposable elements IS26 and IS5 in Klebsiella pneumoniae from Taiwan.

A cloned 5,248-bp EcoRI fragment from the Klebsiella pneumoniae transferable plasmid pKP53 (> 70 kb) containing bla(SHV-5) was sequenced. Insertion sequences IS26 and IS5 were found downstream from bla(SHV-5). The DNA sequences of the genetic environment surrounding bla(SHV-5) were homologous to plasmid p1658/97 from Escherichia coli, containing a truncated recF gene and a truncated deoR gene upstream and downstream from bla(SHV-5), respectively. RecF may be involved in bla(SHV-5) translocation to the plasmid by RecF-dependent recombination. This novel genetic environment may be associated with the successful proliferation and/or expression of SHV-5 in K. pneumoniae strains from Taiwan.

Base Sequence↗
PubMed2004

Non-adiabatic intramolecular and photodissociation dynamics studied by femtosecond time-resolved photoelectron and coincidence imaging spectroscopy.

Time-resolved photoelectron spectroscopy (TRPES) is emerging as a useful tool for the study of non-adiabatic dynamics in isolated polyatomic molecules and clusters due to its sensitivity to both electronic and vibrational dynamics. A powerful extension of TRPES, coincidence imaging spectroscopy (CIS), based upon femtosecond time-resolved 3D momentum vector imaging of both photoions and photoelectrons in coincidence, is a new technique for the study of complex dissociative processes. Here we show how these spectroscopies can be used to study both non-adiabatic intramolecular and photodissociation dynamics in polyatomic molecules. Intramolecular dynamics in the alpha, beta-enones acrolein, crotonaldehyde and methyl vinyl ketone are studied using both TRPES and laser-induced fluorescence of HCO(X) product yields. The location of the methyl group is seen to have very dramatic effects on the relative electronic relaxation rates and the HCO(X) yield. Applying both TRPES and CIS to the 200 nm and 209 nm photodissociation of the nitric oxide dimer, (NO)2, we observe the fs time-scale evolution of the excited parent neutral via its photoelectron spectrum and the emergence of the NO(A) photofragment including its energy and angular distributions.

Journal Article↗
PubMed2001

Self-sensitized photooxygenation of 3,4-dialkoxyfurans to vitamin C or its derivatives.

Self-sensitized photooxygenation of 3,4-dialkoxyfurans 3a-d with molecular oxygen and UV- or sunlight at room temperature gave vitamin C derivatives 2a-d in good to excellent yields. Furan 3c, having photodegradable protecting groups, was also photooxygenated to give L-ascorbic acid (1) in a "one-pot" reaction. Furthermore, a novel photolytic transformation was developed for deuteration of furan 3b at the C-2 position with D(2)O to give furan 3d in 95% yield. Toxicity of furans 3a-c and butenolides 2a-c against human embryonic cell, murine embryo fibroblasts, normal fibroblasts, HeLa, and Vero cell lines in the presence of oxygen and indirect solar light was found to be much less than those of the antipsoriasis drugs anthralin and 8-methoxypsoralen.

Animals↗
PubMed2001

Expression and characterization of monocot rice cytosolic CuZnSOD protein in dicot Arabidopsis.

Cytosolic CuZnSOD removes deleterious superoxides from plant cells. In order to understand its function better, we sought to express a monocot CuZnSOD gene in transgenic Arabidopsis. We constructed a transgene using the CaMV 35S promoter to express a rice cytosolic CuZnSOD gene in Arabidopsis and generated over 200 transformants. A 16 kD polypeptide, the same size as the native rice CuZnSOD polypeptide, was detected in the transgenic Arabidopsis. Interestingly, two forms of rice CuZnSOD, rSODI and rSODII, having the same dimeric size, were detected in the transgenic plants. rSODII protein was relatively abundant but had low specific activity. In contrast, rSODI protein was relatively rare and had high specific activity. Inter-conversion of rSODI and rSODII could be achieved by the addition and removal of copper ions into the purified recombinant SOD and to the leaf extract of transgenic plants. Our analysis indicates that rSODI most likely corresponds to native rice CuZnSOD that has incorporated the Cu and Zn ions required for full activity, whereas the less active rSODII form may not have properly incorporated the necessary copper ions.

Arabidopsis↗
PubMed2000

Balance evaluation in hemiplegic stroke patients.

BACKGROUND: Decreased equilibrium in standing and walking is a common problem associated with hemiplegic stroke patients. Stroke patients with balance problems are prone to falls. In addition to spatial recognition, the appropriate pattern of muscle activity to preserve balance depends on sensory and motor processes. Previous reports have mentioned that the right posterior parietal cortex seems to be predominantly involved in spatial integration. We therefore wanted to conduct a study to quantify and compare the balance control between right hemispheric stroke and left hemispheric stroke patients. METHODS: Thirty hemiplegic stroke patients (14 right, 16 left) and 15 age-matched healthy subjects were included in this study. The objective measurement of the basic components of balance control was performed using the SMART Balance Master. The motor status of the hemiplegic limbs was evaluated by Brunnstrom staging. The functional outcome of the stroke patients was evaluated by the functional independence measure (FIM). RESULTS: The balance function of stroke patients was significantly worse as compared to that of the healthy subjects especially in dynamic stability. However, different from the other reports, our right hemispheric stroke patients had better balance function than our left hemispheric patients. The locomotion and mobility scores of the FIM were also better in the right hemispheric stroke patients. CONCLUSION: This result suggested that the motor function of the healthy limbs of stroke patients may play an important role in their balance function. The results of this study may provide a guide for prescribing a more efficient rehabilitation program for stroke patients.

Adult↗
PubMed2000

Unexpected recurrent seizures following repeated spinal injections of tetracaine--a case report.

A 36-year-old male patient was scheduled to undergo ureteroscopic lithotomy because of left ureteral stone under spinal anesthesia. After receiving a renewed spinal anesthesia with 8 mg tetracaine to compensate for the first attempt (with 10 mg tetracaine), which proved to be a failure, he was soon seized with episodic seizure attacks. Central nervous system toxicity of the local anesthetic might be the cause of the seizure. We brought forward this case for discussion for warning that the possibility of systemic toxicity of local anesthetic might exist despite a seemingly undisputable spinal anesthesia.

Adult↗
PubMed1999

Cubital tunnel release with endoscopic assistance: results of a new technique.

We evaluated the results of cubital tunnel release with endoscopic assistance. The study included 76 patients (85 elbows); 47 women and 29 men. Nine patients had bilateral procedures. Patients were excluded if they had less than 1 year of follow-up, associated pathology at the elbow to account for the nerve compression, or recurrent cubital tunnel syndrome. Before surgery, cases were categorized by stage of cubital tunnel syndrome according to Dellon's classification: 33 (39%) elbows were classified as mild, 35 (41%) moderate, and 17 (20%) severe. Surgical results were assessed according to a modified Bishop rating system. The mean follow-up period was 32 months (range, 12-52 months). Results were excellent in 42% of the elbows, good in 45%, fair in 11%, and poor in 2%. Recurrence occurred in 3 elbows. There were no serious complications. The results of this study support our recommendation of cubital tunnel release with endoscopic assistance as a safe and reliable technique for the treatment of cubital tunnel syndrome, especially in patients with mild to moderate symptoms.

Adult↗
PubMed1998

Single pedicle vascularized double joint transfer: anatomic study of two models.

This study examined the anatomic structures that communicate between the tibial and fibular digital arteries of the second toe at the distal phalanx to identify a channel for retrograde blood flow from the dominant pedicle to the distal joint flap. We also assessed the feasibility of two models designed to mobilize toe joints to perform single pedicle vascularized double-joint transfer. The continuity of the vascular pathway in both models was demonstrated by microfil injection and angiographic study. The average mobile distance between the PIP joint and the MTP joint was 5.6 +/- 0.6 cm in model I and 5.1 +/- 0.4 cm in model II. The dissection and mobilizing procedures of the neurovascular pedicle are more complicated and extensive in model II than in model I, and the risk of jeopardizing vascularity of the distal joint flap is higher. Both models may be suitable to replace two adjacent metacarpophalangeal (MCP) joints in the hand or two nonadjacent MCP joints (excluding the thumb) separated by no more than one normal metacarpal.

Arteries↗
PubMed1998

Treatment of axillary bromhidrosis with superficial liposuction.

Axillary bromhidrosis or osmidrosis is a distressing problem that causes a serious personal and social handicap, especially in an Asian society. Surgical excision of the subcutaneous tissue, with or without skin excision in the axillary hair-bearing area, has been the treatment of choice for several decades. However, the complications of partial necrosis of wound edges or hematoma, and the possibility of the obvious unsightly scars, are always problems. We report our method of treatment of modified superficial liposuction with subdermal scraping under local anesthesia with tumescent infiltration. By using two tiny stab wounds, these two steps of liposuction can be done in the two-directional crisscross pattern. From August of 1995 to May of 1997, 20 patients (16 women and 4 men) received this surgery for bilateral axillas on an outpatient basis. The follow-up period ranged from 6 months to 27 months, and the mean follow-up period was 14 months. Eighteen patients (90 percent) had excellent to good results. Complication included only one minor wound infection that was cured easily. Two patients experienced transient subdermal fibrotic bands in one side of the axilla, and one patient experienced axillary skin with marked induration and retraction. All of these symptoms disappeared after 1 month or so. This minimal incision operation has the advantages of a high success rate, low complication rate, tiny to invisible scars, no change of hair distribution pattern, minimal postoperative care with a short term of compressive dressing (less than 2 days), and rapid recovery for daily activity and exercise.

Adolescent↗
PubMed1998

The influence of intra-graft heparin injection on the survival of composite grafts.

BACKGROUND: Intra-replant subcutaneous heparin injection has been reported to be an alternative to venous anastomoses in finger replantations. It has also been recommended for composite graft type replants. In this study, we investigated three different regimens of intra-graft heparin injection in a rabbit ear model. Our aim was to determine whether or not continuous oozing from an incision wound on a composite graft made by an intra-graft heparin injection would increase the survival of a larger composite graft. METHODS: A 25-mm-diameter circular composite graft (including dorsal skin and auricular cartilage) was harvested from the mid-portion of a rabbit ear. This size of graft was selected as the study model due to a significantly lower percent graft survival when compared to smaller-sized grafts (17.0 +/- 5.6%, p < 0.05). Three different regimens of intra-graft heparin injection were performed in the study group and the results of percent graft survival were compared. RESULTS: Intra-graft injection of heparin calcium 250 IU/0.1 ml qd for seven days resulted in a significantly higher percent graft survival than the other two regimens and a control group (64.0 +/- 9.7%, p < 0.05). The "flow-through" phenomenon was observed in this study. CONCLUSIONS: Intra-graft heparin injection resulted in a higher percent graft survival than the control group for the 25-mm-diameter circular composite graft. However, the mechanism of graft survival enhancement could not be clearly explained by this study. It is recommended that the clinical application of intra-graft heparin injection should only be used when subgraft hematoma can be avoided and systemic bleeding tendency is being closely monitored.

Animals↗
PubMed1997

Estrogenic activity of a dieldrin/toxaphene mixture in the mouse uterus, MCF-7 human breast cancer cells, and yeast-based estrogen receptor assays: no apparent synergism.

The estrogenic activity of dieldrin, toxaphene, and an equimolar mixture of both compounds (dieldrin/toxaphene) was investigated in the 21-day-old B6C3F1 mouse uterus, MCF-7 human breast cancer cells, and in yeast-based reporter gene assays. Treatment of the animals with 17beta-estradiol (E2) (0.0053 kg/day x3) resulted in a 3.1-, 4.8-, and 7.8-fold increase in uterine wet weight, peroxidase activity, and progesterone receptor binding, respectively. In contrast, treatment with 2.5, 15 and 60 micromol/kg (x3) doses of toxaphene, dieldrin, or dieldrin/toxaphene (equimolar) did not significantly induce a dose-dependent increase in any of the E2-induced responses. The organochlorine pesticides alone and the binary mixture did not bind to the mouse uterine estrogen receptor (ER) in a competitive binding assay using [3H]E2 as the radioligand. In parallel studies, estrogenic activities were determined in MCF-7 cells by using a cell proliferation assay and by determining induction of chloramphenicol acetyl transferase (CAT) activity in MCF-7 cells transiently transfected with plasmids containing estrogen-responsive 5'-promoter regions from the rat creatine kinase B and human cathepsin D genes. E2 caused a 24-fold increase in CAT activity in MCF-7 cells transiently transfected with creatine kinase B and a 3.8-fold increase in cells transiently transfected with the human cathepsin D construct. Treatment of MCF-7 cells with dieldrin, toxaphene, or an equimolar mixture of dieldrin plus toxaphene (10(-8)-10(-5) M) did not significantly induce cell proliferation or CAT activity in the transient transfection experiment with both plasmids. The relative competitive binding of the organochlorine pesticides was determined by incubating MCF-7 cells with 10(-9) M [3H]E2 in the presence or absence of 2 x 10(-7) M unlabeled E2 (to determine nonspecific binding), toxaphene (10(-5) M), dieldrin (10(-5) M), and equimolar concentrations of the dieldrin plus toxaphene mixture (10(-5) M). The binding observed for [3H]E2 in the whole cell extracts was displaced by unlabeled E2, whereas the organochlorine pesticides and binary mixture exhibited minimal to nondetectable competitive binding activity. E2 caused a 5000-fold induction of beta-galactosidase (beta-gal) activity in yeast transformed with the human ER and a double estrogen responsive element upstream of the beta-gal reporter gene. Treatment with 10(-6)-10(-4) M chlordane, dieldrin, toxaphene, or an equimolar mixture of dieldrin/toxaphene did not induce activity, whereas 10(-4) M endosulfan caused a 2000-fold increase in beta-gal activity. Diethylstilbestrol caused a 20-fold increase in activity in yeast transformed with the mouse ER and a single estrogen responsive element upstream of the beta-gal reporter gene. Dieldrin, chlordane, toxaphene, and endosulfan induced a 1.5- to 4-fold increase in activity at a concentration of 2.5 x 10(-5) M. Synergistic transactivation was not observed for any equimolar binary mixture of the pesticides at concentrations of either 2.5 x 10(-5) M or 2.5 x 10(-4) M. The results of this study demonstrate that for several estrogen-responsive assays in the mouse uterus, MCF-7 human breast cancer cells, and yeast-based reporter gene assays, the activities of both dieldrin and toxaphene were minimal, and no synergistic interactions were observed with a binary mixture of the two compounds.

Animals↗
PubMed1996

Microsurgical replantation of avulsed scalps.

Four cases of extensive scalp avulsion were successfully replanted in this reported series. All patients were female, with the youngest 3 years of age. All replanted scalps survived, with some marginal necrosis due to tissue destruction. Postoperative venous congestion of the involved ear in one patient was managed with anticoagulant therapy. Another patient underwent severe congestion of the whole replanted scalp and was treated with thin skin-graft shaving in the parietal area. In the follow-up period, all patients obtained hair growth in the scalp with light touch sensation.

Adult↗
PubMed1995

Progression to complete atrioventricular block in a patient with bundle branch re-entry tachycardia.

A 38-year-old man with no significant structural heart disease suffered from one episode of wide QRS tachycardia. The electrocardiogram showed a PR interval of 0.20 second and a QRS duration of 0.10 second. His bundle recording revealed an HV interval of 90-100 ms. The tachycardia was inducible with programmed stimulation and displayed a QRS morphology of complete left bundle branch block. It was characterized by an atrioventricular dissociation, a cycle length of 280 ms, and an H deflection preceding each QRS complex. Pacing from the right ventricular apex at a cycle length of 270 ms entrained the tachycardia, while at a cycle length of 260 ms, the tachycardia was terminated. Four years later, the patient presented with complete atrioventricular block with a wide QRS escape rhythm. An electrophysiologic study conducted while he was in 1:1 atrioventricular conduction showed an HV interval of 100 ms. Second-degree infrahisian block developed at an atrial paced cycle length of 700 ms. There was no induction of tachycardia with programmed stimulation before or after isoproterenol. The patient was treated with an implantation of a permanent pacemaker.

Adult↗
PubMed1995

Radiofrequency ablation therapy in concealed left free wall accessory pathway with decremental conduction.

An electrophysiologic study followed by transcatheter radiofrequency ablation therapy was performed in two adult patients with a permanent form of junctional tachycardia. Both patients had no structural heart disease and exhibited a normal resting ECG. The P wave during tachycardia was negative in leads 1, 3, and aVF, biphasic over V6, and positive in V1 and aVL in both patients, while the P-R/R-P interval ratio during tachycardia was 0.82 and 0.36, respectively, in both patients. Both patients displayed an eccentric atrial activation sequence with the earliest atrial activation occurring at the distal coronary sinus and a decremental retrograde conduction property during incremental ventricular pacing, suggesting the presence of a concealed slowly conducting left free wall accessory pathway. The tachycardia used the normal atrioventricular pathway for anterograde conduction and the concealed show left accessory pathway for retrograde conduction. It was terminated following adenosine administration in both patients; termination of tachycardia was due to a block in the retrograde accessory pathway in one patient and due to a block in the atrioventricular node in the other patient. Radiofrequency ablation was performed by the retrograde transaortic approach. The radiofrequency f4p4ent was delivered to the site of the earliest atrial activation during tachycardia at the ventricular aspect of the mitral annulus. The successful ablation site had a ventriculoatrial (VA) interval of 120 and 130 ms, respectively, and was located at the posterolateral and lateral aspects of the mitral annulus. Following ablation, there was no VA conduction; however, conduction through the normal atrioventricular pathway was noted during isoproterenol infusion in both patients. There was no induction of tachycardia. This study demonstrates that the permanent form of junctional tachycardia in adults can incorporate a concealed left free wall accessory pathway with a decremental property. Radiofrequency ablation therapy is effective and safe in this form of arrhythmia.

Adult↗