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Biomedical subjects

R S Chen

Publications and source records attributed to R S Chen.

At least 37 records · Page 2Linked to original sources
PubMed1999

Anatomic basis of iliac crest flap pedicled on the iliolumbar artery.

This paper presents the anatomy and clinical applications of an iliac crest flap pedicled on the iliolumbar artery. 54 iliolumbar arteries were filled with pink plastic in 27 adult cadavers. Their origin, course and branches, and the surroundings were investigated, and the external diameter, length of segments and terminal distribution were measured. The iliolumbar artery was constant, but with a few variations. Its length was 7.0 +/- 3.9 cm, and the outer diameter 2.0 +/- 0.4 mm at the lateral edge of the psoas major muscle. Based on the anatomic findings, the surgical technique for a bone flap based on the iliolumbar artery was designed. Its clinical applications included both free bone grafting (in 2 patients) and pedicled bone transfer (in another 2 patients). The clinical results were satisfactory. The iliac crest flap pedicled on the iliolumbar artery is a reliable bone flap for clinical usage.

Adult↗
PubMed1999

Root deformation during root-end preparation.

Ultrasonic root-end preparation techniques have recently been introduced and revolutionized the field of endodontic surgery. However, several reports claimed that there was an increasing incidence of crack formation after ultrasonic root-end preparation. As yet, little work has focused on the root deformation during root-end preparation. Thus, the purpose of this investigation was to measure the amount of root deformation during root-end preparation with the use of microhandpiece and ultrasonic systems by using strain gauge methods, and simultaneously to detect any cracks with the aid of the stereomicroscope, stain, and an image processing system. The results demonstrated the ultrasonic instrumentation produced significantly greater strain on average than that generated with the microhandpiece system. From the viewpoint of fracture, any technique that could diminish the strain on the root would decrease the likelihood of fracture; however, no crack was observed on any resected surface of roots in this study.

Dental Instruments↗
PubMed1999

Random X chromosome methylation patterns in the carriers with clinical phenotypic expressions of X-linked recessive bulbospinal neuronopathy.

OBJECTIVES: We report the unusual phenotypic expression in 2 female carriers of a family with X-linked recessive bulbospinal neuronopathy (X-BSN). We analyze the methylation pattern of the androgen receptor (AR) gene to inspect the possibility of non-random X chromosome inactivation to be the underlying mechanism. MATERIAL AND METHODS: Twenty-three members in 3 generations of a Taiwanese family were examined and studied for genomic DNA analysis. We analyzed the sequence of the first exon of the AR gene to identify the numbers of CAG repeats, and to determine the methylation pattern by using the restriction enzymes HpaII and HhaI. RESULTS: There were 3 probands and 5 carriers and 2 of the carriers manifested clinical symptoms. Sequence analysis revealed that the numbers of trinucleotide repeats ranged from 42 to 45 in one allele of the X-chromosome in the 5 female carriers. The restriction pattern of the HpaII and HhaI recognizable sites of the X-chromosome indicated a random methylation. CONCLUSION: Our data suggest that molecular genetic studies are important in confirming the diagnosis of X-BSN and early detection of female carriers, and the random or non-random methylation pattern of the X-chromosome is not a determining factor for partial expression of the abnormal AR gene in some carriers.

Adult↗
PubMed1999

Path analysis shows that increasing ketogenic ratio, but not beta-hydroxybutyrate, elevates seizure threshold in the Rat.

Previous work has identified several criteria that may be important in determining the efficacy of the ketogenic diet as a treatment for intractable epilepsy in children. The present study was designed to investigate the influence of four major variables on seizure threshold, i.e. ketogenic ratio, body weight, age at diet onset and beta-hydroxybutyrate in rats. Path analysis was used to statistically model and quantify the causal relationships among variables. Results indicate that seizure threshold was significantly elevated with increasing ketogenic ratios (i.e. more fats vs. carbohydrates and proteins) and decreasing weight. Conversely, age at diet onset and plasma levels of beta-OHB showed no causal relation to seizure resistance. These results suggest that the efficacy of the ketogenic diet is independent of the level of ketonemia but is markedly influenced by diet and growth.

3-Hydroxybutyric Acid↗
PubMed1998

Protein folding simulation with genetic algorithm and supersecondary structure constraints.

We describe an algorithm to compute native structures of proteins from their primary sequences. The novel aspects of this method are: 1) The hydrophobic potential was set to be proportional to the nonpolar solvent accessible surface. To make computation feasible, we developed a new algorithm to compute the solvent accessible surface areas rapidly. 2) The supersecondary structures of each protein were predicted and used as restraints during the conformation searching processes. This algorithm was applied to five proteins. The overall fold of these proteins can be computed from their sequences, with deviations from crystal structures of 1.48-4.48 A for C(alpha) atoms.

Algorithms↗
PubMed1998

Electrophysiological studies of early stage corticobasal degeneration.

We conducted electrophysiological studies in two Asian patients with probable corticobasal degeneration (CBD). The duration of illness from onset was 16 and 20 months, respectively. The clinical manifestations were markedly asymmetric and characterized by cortical sensory loss, apraxia, action myoclonus, action tremor, and akinetic-rigid parkinsonism. Neither patient responded to levodopa therapy. Simple photon-emission computed tomography (SPECT) study showed significantly decreased regional cerebral blood flow in the frontoparietal areas and thalamus opposite to the predominantly affected limb. A series of electrophysiological studies failed to identify giant somatosensory evoked potentials (SEPs), enhanced long latency electromyography (EMG) reflex, and cortical spikes preceding myoclonic jerk. However, the earliest cortical component of the median nerve SEP was exclusively enlarged in one patient and preserved with depression of the subsequent components in the other patient. Significantly shorter postmotor-evoked potential (MEP) silent period was found after the transcranial magnetic stimulation of the motor cortex in both patients. CBD is a unique clinical entity characterized by action myoclonus probably the result of the pathologic hyperexcitability of the motor cortex, based on a loss of inhibitory input from the sensory cortex.

Aged↗
PubMed1998

Emotional symptoms are secondary to the voice disorder in patients with spasmodic dysphonia.

The aims of this study were to evaluate the emotional status and life quality of the patients with spasmodic dysphonia (SD) before and after botulinum toxin treatment, and to ascertain whether SD is a somatoform disorder. Ten patients with spasmodic dysphonia were injected unilaterally into the vocal cord with botulinum toxin. Before botulinum toxin treatment, two clinician's rating scales--Hamilton Depression Rating Scale (HDRS) and Hamilton Anxiety Rating Scale (HARS), and three self-rating psychometrics--Zung's Self-Rating Depression Scale (SDS), Life Quality Scale (GHQ/QL-12), and Symptom Distress Checklist (SCL-90) were applied. Self-rating scales were also administered in 20 matched normal controls. The patients were reevaluated 1 month after botulinum toxin treatment. The Clinical Global Impression Scale (CGI) was also rated by the patients themselves and a speech pathologist. The mean scores of SD patients were significantly higher than that of controls in SDS, and subscales of somatization, obsessive-compulsive symptoms, depression, anxiety, and psychoticism in SCL-90. The mean score of GHQ/QL-12 was significantly higher in the control group. The scores of HDRS, SDS, GHQ/QL-12 and subscales of somatization, depression, and anxiety in SCL-90 showed significant improvement after botulinum treatment. In CGI, seven patients were rated as improved by patients themselves and the speech pathologist. The patients with SD had more anxiety, depression and somatization symptoms, and poor life quality than normal controls. Their emotional status and life quality improved after botulinum toxin treatment. The results suggest that the emotional symptoms of patients with SD are mainly secondary to voice disorder.

Adult↗
PubMed1998

Molecular dynamic simulation of chaperonin-mediated protein folding.

We use molecular dynamics methods to simulate chaperonin-mediated refolding of barnase. A "chaperonin" term is added to the force field in order to simulate the hydrophobic environment in the central cavity of the chaperonins. Two aspects of our simulation results are consistent with experiments: (1) The hydrophobic environment of the central cavity of the chaperonin is an advantageous condition for the refolding of the misfolded intermediates. (2) One cycle of binding and release is not enough for the successful folding. Chaperonin-assisted protein folding maybe a procedure of multiple cycles of binding and release from the chaperonin.

Bacterial Proteins↗
PubMed1998

Implementation of an oral and maxillofacial radiology image management and communication system.

OBJECTIVES: To implement an oral and maxillofacial radiology image management and communication system (OMFR IMACS) in the School of Dentistry, National Taiwan University. METHODS: An OMFR IMACS has been implemented over 3 years in three phases: (1) Establishment of an OMFR image processing laboratory for research and graduate student training; (2) Installation of network infrastructure and (3) Total system integration. RESULTS AND CONCLUSIONS: Intraoral, panoramic, cephalometric, and TMJ radiographs are directly processed with digital image acquisition devices or are converted into a digital format for viewing via UTP cable through FastEthernet in the eleven different divisions of the school. The system archives about 400 Mb of imaging data daily, representing 80% of the workload of the OMFR Division. The system is now used parallel to the conventional film-library system and has been integrated as part of the oral health service.

Humans↗
PubMed1998

Torsional relaxation for biopolymers.

We describe a method for making natural, physical movements in a chained polymer by sequentially adjusting a few neighboring torsion angles in the polymer backbone. In addition to being very fast and easy to implement, the method is also very general. It applies equally well to proteins and nucleic acids. This method is then used to design a local refinement procedure. We test the refinement procedure on the minimization of a simple energy function for proteins. The energy function has a simplified potential for hydrophobic interaction, a hydrogen-bond term, and a term for van der Waals interaction. There is considerable current interest in such simple energy functions for protein folding. When applied to refine structures found by a global search method, the refinement is able to produce large reduction in the hydrogen-bond term and the van der Waal term of the energy. We conclude that the method is particularly effective in finding good "packing" of residues in an initially compact conformation.

Algorithms↗
PubMed1998

Long-term progression in chronic manganism: ten years of follow-up.

We studied the long-term clinical course of five patients with chronic manganese intoxication. The mean scores of the King's College Hospital Rating Scale for Parkinson's disease increased from 15.0 +/- 4.2 in 1987 to 28.3 +/- 6.70 in 1991 and then to 38.1 +/- 12.9 in 1995. The deterioration was most prominent in gait, rigidity, speed of foot tapping, and writing. Tissue concentrations of manganese in blood, urine, scalp hair, and pubic hair returned to normal. Follow-up MRIs did not show paramagnetic high-signal intensity on T1-weighted images. The data indicate that clinical progression in patients with manganese parkinsonism continues even 10 years after cessation of exposure.

Chronic Disease↗
PubMed1998

X-linked recessive bulbospinal neuronopathy: clinical and molecular studies in a Taiwanese family.

We describe clinical, biochemical, and molecular studies on a Taiwanese family with X-linked recessive bulbospinal neuronopathy. There were three probands and five female carriers among the 23 members examined. The clinical manifestations included progressive muscle weakness, diffuse fasciculation, postural tremor, muscle cramps, dysarthria, dysphagia, diabetes, and gynecomastia. Phenotypic expression varied among the affected subjects. Two carriers also had postural tremor and perioral fasciculation. Endocrine tests were normal except for a mild increase in serum testosterone and/or growth hormone in one patient and one carrier. Type IV hyperlipoproteinemia was observed in two patients, one carrier, and one healthy offspring. Molecular genetic studies confirmed elongation of the CAG triplet repeat in exon 1 of the gene for the androgen receptor. Sequence analysis showed that there were 42 to 43 CAG repeats in the three probands and 42 to 45 in the five carriers. The mutant allele had a tendency to increase by one or two repeats from one generation to the next. The length of CAG repeats at which the mutant allele became unstable was shorter in our family than in previous reports. The normal allele was also unstable and had a tendency to shrink by one of five repeats during transmission. These findings suggest that the number of CAG triplet repeats is variable in both the mutant and normal alleles.

Adolescent↗
PubMed1997

Reciprocal inhibition in Parkinson's disease.

We studied the inhibition of median H-reflex by conditioning stimuli on the radial nerve in 14 normal controls, 6 patients with unilateral and 1 patient with predominantly left-sided Parkinson's disease. In normal controls, the electrophysiological studies were performed on their right hands, yet both hands were examined in patient group. In the controls, we identified three inhibitory phases, with maximal inhibition at conditioning-test intervals of 0 ms (41.66 +/- 4.73%), 20 ms (45.19 +/- 4.33%), and 100 ms (44.55 +/- 6.84%), respectively. In the less- or a- symptomatic side of the patient group, the inhibitory patterns are similar to those of the controls. However, in the symptomatic arms, loss of inhibition, or even mild potentiation, was observed in the third inhibitory phase. When the symptomatic and asymptomatic sides of patients were compared, in contrast to the striking phenomenon found between symptomatic side and the controls, no difference was observed in the third phase. The current results imply that, although no obvious rigidity can be detected on the asymptomatic sides, subtle functional corruption may have occurred within the contralateral basal ganglia in patients with unilateral Parkinson's disease. The remarkable change of the third phase on the symptomatic sides of patients suggests the perturbation of the polysynaptic long latency reflex pathway may somehow play a role in the rigidity pathogenesis.

Adolescent↗
PubMed1997

Carbamazepine inhibition of neuronal Na+ currents: quantitative distinction from phenytoin and possible therapeutic implications.

Carbamazepine and phenytoin, two of the most commonly prescribed antiepileptic drugs, have been proposed to share a similar mechanism of action by use-dependent inhibition of Na+ channels. The proposed similar mechanism of action, however, cannot explain the common clinical experiences that the two drugs are different; in some patients, one drug may be more effective than the other. This may occur even when optimal therapeutic concentrations are reached with both medications in plasma or the cerebrospinal fluid. In this study, we show that the action of the two drugs on Na+ channels are quantitatively very different. The affinity between inactivated Na+ channels and carbamazepine (apparent dissociation constant approximately 25 microM) is approximately 3 times lower than that of phenytoin, yet the binding rate constant of carbamazepine onto the inactivated Na+ channels is approximately 38,000 M(-1)/sec(-1), or approximately 5 times faster than that of phenytoin. It is speculated that carbamazepine may be more effective than phenytoin in treating seizures whose ictal depolarization shift is relatively short, whereas a better response to phenytoin may imply abnormal discharges characterized by more prolonged depolarization.

Animals↗
PubMed1997

Coenzyme Q10 treatment in mitochondrial encephalomyopathies. Short-term double-blind, crossover study.

We report a short-term double-blind, crossover study of CoQ10 in 8 patients with mitochondrial encephalomyopathies. Four patients had myoclonus epilepsy with ragged-red fibers syndrome, 3 had mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes syndrome, and 1 had chronic progressive external ophthalmoplegia with myopathy. A trend of effectiveness of CoQ10 in several parameters was noted. Fatigability of daily activities was alleviated. The endurance to muscle exercise was augmented. Global muscle strength scored by Medical Research Council scale was increased. The extent of elevation in serum lactate and pyruvate levels after exercise was decreased. However, only the global MRC index score had a statistical significance (p < 0.05). There were no side effects during therapy. The serum CoQ10 levels were significantly lower in patients than in normal controls before CoQ10 treatment and increased significantly after treatment.

Activities of Daily Living↗
PubMed1997

Total failure energy of a composite resin bonded to human enamel.

Total failure energy is defined as the energy required to stress a bond to the point of fracture. This study was designed to assess and compare the total failure energy of a resin-enamel bond with conventional tensile and shear bond strengths. A commercially available composite resin was bonded to human enamel surface. During testing, the applied load versus displacement of the load fixture was recorded and analyzed by a data acquisition system. The tensile and shear bond strengths as well as the total failure energies were calculated. The mean tensile bond strength (21.2 MPa) was higher than the mean shear bond strength (11.6 MPa). The mean total energy applied for tensile failure of the bond (2.1 kg.mm) was also higher than that for the shear failure (1.5 kg.mm). There were statistically significant correlations between bond strength and total failure energy. The failure modes of the shear bond test revealed a higher frequency of adhesive failures compared to the tensile bond test. Further, a dramatic difference existed in the cohesive failure mode between tensile (cohesive composite failure) and shear (cohesive enamel failure) tests. The total failure energy, which represents the fracture strength as well as the failure process of a bond, may be considered an appropriate criterion for characterizing the failure of a bond.

Composite Resins↗