Biomedical subjects

S M Chen

Publications and source records attributed to S M Chen.

At least 37 records · Page 2Linked to original sources

PubMed2000

Brugada syndrome without mutation of the cardiac sodium channel gene in a Taiwanese patient.

We describe a 45-year-old Taiwanese man with specific features of Brugada syndrome but no clinical features of structural heart disease. He was successfully treated with an implantable cardioverter-defibrillator. His electrocardiogram (ECG) patterns changed intermittently. Alpha-adrenoceptor stimulation and beta-adrenoceptor blockade augmented the characteristic ST-segment elevation, whereas alpha-adrenoceptor blockade and beta-adrenoceptor stimulation mitigated the ST-segment elevation. Intravenous procainamide administration did not aggravate ST-segment elevation when ECG had shown coved ST elevation in the right precordial leads. Molecular study did not reveal the same mutations in the cardiac sodium channel gene (SCN5A) as previously reported in Brugada syndrome. This case demonstrates the genetic heterogeneity of SCN5A in Brugada syndrome.

Adrenergic beta-Agonists↗

PubMed1999

Purification, characterization and crystallization of ERA, an essential GTPase from Escherichia coli.

ERA is an essential GTPase widely conserved in bacteria. Homologues of ERA are also present in higher eukaryotic cells. ERA is involved in bacterial cell cycle control at a point preceding cell division. In order to aid the functional investigation of ERA and to facilitate structure-function studies, we have undertaken the X-ray crystallographic analysis of this protein. Here, we report the purification and crystallization procedures and results. The purified ERA exhibits nucleotide-binding activity and GTP-hydrolytic activity. ERA is one of the very few multi-domain GTPases crystallized to date.

Bacterial Proteins↗

PubMed1999

Influence of endoscopic variceal ligation on oesophageal motility.

BACKGROUND: To determine the change of oesophageal manometry in patients with oesophageal varices before and after oesophageal variceal ligation (EVL). METHODS: Forty-five patients who had liver cirrhosis and oesophageal varices with high risk of bleeding were managed by EVL. Oesophageal manometry was performed just prior to the ligation and 4-6 weeks after obliteration of varices. Another 45 age- and sex-matched patients without hepatic, oesophageal or systemic disease served as the control group. RESULTS: At 5 cm above the lower oesophageal sphincter (LES), the amplitude of the contractive wave was significantly lower in patients before EVL (56.9 +/- 31.8 vs 80.1 +/- 30.1, P< 1.05) and returned to the level of control subjects after EVL (76.5 +/- 37.0 vs 80.1 +/- 30.1, P> 0.05). At 10 cm above LES, the amplitude of the contractive wave was significantly lower in patients before and after EVL than the control group (54.3 +/- 29.2 vs 68.1 +/- 29.5, 54.2 +/- 26.0 vs 68.1 +/- 29.5, respectively, P< 0.05). The percentage of tertiary waves was significantly higher in patients before and after EVL than in the control group (31.4 +/- 36.6 vs 5.8 +/- 15.1, 26.9 +/- 32.9 vs 5.8 +/- 15.1, respectively, P< 0.05). However, no significant swallowing disturbance was noted in patients after EVL. There was significantly greater LES length in patients before EVL (4.0 +/- 0.9 vs 3.4 +/- 0.7, P<0.05) but there was no significant difference in the LES length after EVL as compared with the control group. Eighty-six per cent (39/45) of patients developed paraoesophageal varices and 31% (14/45) developed new varices 6 months after variceal obliteration. However, there was no significant difference in manometry at the time of variceal obliteration between patients with variceal recurrence and those without. CONCLUSIONS: The presence of varices affected oesophageal motility. However, such abnormality had little clinical significance. Endoscopic variceal ligation normalized oesophageal motility and may not induce abnormal oesophageal motility. The manometric change can not be used to predict the recurrence of varices in cirrhotic patients after variceal obliteration.

Esophageal and Gastric Varices↗

PubMed1999

The incidence of ehrlichial and rickettsial infection in patients with unexplained fever and recent history of tick bite in central North Carolina.

We examined the clinical and laboratory findings of a consecutive series of patients from central North Carolina presenting with fever and a history of tick bite within the preceding 14 days. Evidence of a tick-transmitted pathogen was detected in 16 of 35 patients enrolled over a 2-year period. Nine patients were infected with Ehrlichia chaffeensis, and 6 were infected with a spotted fever group rickettsia; 1 patient had evidence of coinfection with E. chaffeensis and a spotted fever group rickettsia. Four patients had detectable antibodies against the human granulocytic ehrlichiosis agent; however, only 2 had a 4-fold antibody titer rise without detectable antibodies against E. chaffeensis. The other 2 were thought to have cross-reacting antibodies to E. chaffeensis. We conclude that ehrlichial infections may be as common as spotted fever group rickettsial infections in febrile patients from central North Carolina with a recent history of tick bite.

Adult↗

PubMed1999

Balance and muscular strength in normal children aged 9-12 years.

The purposes of this study were two fold. The first was to determine the effects of several independent variables on balance, and also on two muscular strength (dynamic and static) measurements respectively. The second purpose was to examine the relationship among the balance and the muscular strengths. Ninety-nine healthy children (58 boys and 41 girls) ranging in age from 9.6 to 12.7 years participated in this study. The subjects were selected from the 4th, 5th and 6th grades of an elementary school in Kaohsiung City. To assess balance, children were administered subtest 2 of Bruininks Oseretsky Test of Motor Proficiency (BOTMP). Dynamic strength was measured with the subtest 4 of the BOTMP. Static strength was measured quantitatively by "semi-squat two-hand lift". The Force Evaluation and Testing System was used for this testing. Height and weight measurements were obtained on each subject. The independent effects of variables on balance score and the two muscular strengths were assessed by stepwise multiple-regression analysis. The results revealed weight and dynamic strength were the effective predictors on estimating balance score. Gender and weight were found as important variables contributing in static load, whereas gender, weight, height and balance score were selected for significantly predicting dynamic strength score. Spearman correlation analysis revealed significant positive correlations between balance and dynamic strength and also between dynamic strength and static strength. The correlation analysis also showed a significant negative correlation between balance and static strength. Detailed implications of the results in the present study are discussed.

Child↗

PubMed1999

Sputum induction to improve the diagnostic yield in patients with suspected pulmonary tuberculosis.

OBJECTIVE: To evaluate the utility of sputum induction in the large-scale tuberculosis control program. METHODS: Prospective study on sputum induction for improving the diagnostic yield of pulmonary tuberculosis, and estimation of the direct costs for sputum induction. RESULTS: Of 1,648 tuberculosis suspects with poor or absent sputum production, induced sputum was smear-positive in 558 patients (353 previously smear-negative, 97 inadequate sputum and 108 unproductive). The direct cost per induced sputum was US $0.37. CONCLUSION: Sputum induction is an effective, low-cost, and simple technique for improving the smear-positive case detection rate in a tuberculosis control program.

Adolescent↗

PubMed1998

Myofascial trigger points in intercostal muscles secondary to herpes zoster infection of the intercostal nerve.

Chronic pain in the chest wall is a major complication after herpes zoster infection of intercostal nerves. It is usually difficult to control pain of such origin. Two cases are reported of postherpetic neuralgia after herpes zoster infection involving the intercostal nerves. Both patients had shooting, burning, aching, and localized pain in the muscle supplied by the involved intercostal nerves 1 to 3 months after onset. Compression palpation of a tender spot in one of these muscles induced a referred pain that followed the corresponding interspace, usually in the distal anterior direction. Local twitch responses could be elicited during injection of 0.5% or 1% lidocaine into one of these tender spots; the pain in the interspace was consistently eliminated immediately after injection. One patient had complete pain relief after three series of injections. The effect of pain relief for the other patient lasted for 1 to 2 weeks after the initial injection and lasted progressively longer (up to 2 months) after repeated injections. It appears that many of the tender spots formed in intercostal muscles after herpes zoster are myofascial trigger points that respond to injection with referred pain, local twitch responses, and immediate pain relief.

Anesthetics, Local↗

PubMed1998

Phentolamine effect on the spontaneous electrical activity of active loci in a myofascial trigger spot of rabbit skeletal muscle.

OBJECTIVE: To investigate the effect of phentolamine, a sympathetic blocking agent, on the spontaneous electrical activity (SEA) recorded from a locus of a myofascial trigger spot (MTrS), equivalent to a human trigger point, in rabbit skeletal muscle. DESIGN: Randomized control trial. SETTING: A university medical laboratory. PATIENTS OR OTHER PARTICIPANTS: Nine adult New Zealand rabbits. INTERVENTION: In the experimental group phentolamine mesylate (1mg/kg) was injected into the external iliac artery, followed by flushing with normal saline. The control group was treated with normal saline instead of phentolamine using the same procedure. MAIN OUTCOME MEASURES: SEA was recorded from multiple active loci of MTrSs in the biceps femoris muscle: initially SEA in the same locus was recorded before and immediately after phentolamine (or normal saline) injection; then SEA was recorded from 25 different active loci. The mean of the average integrated signal (AIS) of SEA was analyzed, comparing the effects of phentolamine and normal saline on SEA. RESULTS: In the same active locus, the AIS of SEA showed statistically a linear decay with time after phentolamine injection, with a correlation coefficient of .56 at p < .05. However, no statistical relationship could be derived for the control group data with time by using regression analysis, probably because of large variations among the rabbits and movement artifacts during the experiment. In 25 different loci in the phentolamine group, the mean of the AIS of SEA (7.92 microV) was significantly lower than that of the control group (9.89 microV) at p < .05. CONCLUSIONS: The results support the hypothesis that the autonomic nervous system is involved in the pathogenesis of myofascial trigger points. The application of the AIS as an evaluation index seems to be feasible in the quantitative measurement of SEA.

Adrenergic alpha-Antagonists↗

PubMed1998

Effects of parathyroid hormone infusion on glucose tolerance and glucose-stimulated insulin secretion in normal and uremic rats.

We used thyroparathyroidectomized (TPTX) rats with hypocalcemia to evaluate the effects of parathyroid hormone (PTH) infusion on glucose tolerance and glucose-stimulated insulin secretion in normal and uremic rats. Animals were subjected to oral glucose tolerance test (OGTT) and glucose-stimulated insulin secretion before and after TPTX or after their plasma calcium level was normalized by PTH infusion, vitamin D injection or calcium load. In both normal and uremic groups, TPTX produced a significant increase in area under the cure (AUC) of plasma glucose from 0 to 6 h in response to an oral glucose challenge and decrease plasma insulin level in response to glucose-stimulated insulin secretion. Before TPTX, uremic animals have a normal basal plasma insulin level (29 +/- 3 versus 31 +/- 2 microU/ml) and a normal glucose-stimulated insulin secretion, but significantly increase plasma glucose AUC in response to OGTT as compared with normal rats. TPTX worsen the response of glucose intolerance in uremic rats. After PTH infusion, vitamin D injection or calcium load, all rats in the response of OGTT and glucose-stimulated insulin secretion are recovered to the level before TPTX including normal and uremic rats, but uremic rats still have an abnormal glucose tolerance in response to OGTT. Uremic rats have a low basal plasma glucose level as compared with normal rats. TPTX significantly increase basal plasma glucose level in normal and uremic rats, but the uremic rats with TPTX have been found to elevate basal plasma glucose level to the range of normal rats. The basal plasma glucose level of normal rats with TPTX was recovered to the range before TPTX by PTH infusion, vitamin D injection or calcium load, but PTH infusion, vitamin D injection or calcium load did not decrease the level of basal plasma glucose in uremic rats with TPTX. All TPTX rats, including intact kidney or five-sixths Nx rats, were treated three times weekly by subcutaneous injection of 8 micrograms/kg L-thyroxin. These results indicate that uremia may produce thyroid dysfunction and PTH infusion did not affect the glucose tolerance in OGTT and glucose-stimulated insulin secretion in normal and uremic rats. In addition to PTH, other uremic toxins may be responsible for the glucose intolerance of uremia.

Animals↗

PubMed1998

Ultrasound measurement of the fetal cavum septi pellucidi.

OBJECTIVES: To establish normative data for the width of the fetal cavum septi pellucidi at various gestational ages. SUBJECTS AND METHODS: A total of 608 consecutive fetuses between 19 and 42 gestational weeks were included in this prospective study. The largest width of the cavum septi pellucidi was measured by two-dimensional ultrasound. Piecewise regression analysis was used to study the relationships between the width of the fetal cavum septi pellucidi, gestational age and biparietal diameter. RESULTS: The fetal cavum septi pellucidi width increased gradually between 19 and 27 weeks of gestation and then plateaued between 28 weeks and term. Regression analysis revealed significant associations between cavum septi pellucidi width and gestational age, and cavum septi pellucidi width and biparietal diameter. CONCLUSIONS: The present study provides normative data for fetal cavum septi pellucidi width and useful information about the development of the midline brain structure in the fetus.

Anthropometry↗

PubMed1998

Ultrastructural differentiation of the genogroups in the genus Ehrlichia.

Ultrastructural characteristics of 15 strains and isolates of ehrlichiae belonging to three genogroups, or clades of genetically related organisms united in the genera Ehrlichia, Cowdria, Anaplasma, Neorickettsia and a strain of Wolbachia pipientis which represents a fourth genogroup in this cluster of species, were studied in continuous cell culture or in vivo: E. canis (Oklahoma strain and VHE isolate), E. muris (AS 145), E. chaffeensis (Arkansas, 91HE17 and Sapulpa), human granulocytic ehrlichiae (HGE)(BDS, 96HE27, 96HE37, #54, #55 and #72), E. equi (MRK), E. sennetsu (Miyayama), E. risticii (HRC-IL). Wolbachia pipientis was studied in the naturally infected Aedes albopictus mosquito cell line Aa23. All organisms were similar in the normal ultrastructure of individual cells and in the ability to form abnormal, pathological ehrlichial cells of the same type irrespective of the species. Normally all ehrlichiae studied in cell culture existed in two morphological forms - reticulate and dense-cored cells, both of which could divide by binary fission. Most alterations were related to their membranes, especially the cell wall. Differences in the structure of intravacuolar microcolonies (morulae) of ehrlichiae and their inter-relations with the host cells allowed differentiation of the genogroups: the E. canis-E. chaffeensis-E. muris genogroup formed large morulae, with many ehrlichiae, often suspended in a fibrillar matrix, and the host cell mitochondria and endoplasmic reticulum usually aggregated near the morulae and were in contact with the morula membrane; the E. phagocytophila-E. equi-HGE group morulae had no fibrillar matrix, no contacts with host cell mitochodria, and they did not aggregate around the morulae; E. sennetsu-E. risticii group usually developed in small individual vacuoles that did not fuse with each other and divided along with the ehrlichiae.

Animals↗

PubMed1998

Sequencing multimegabase-template DNA with BigDye terminator chemistry.

Using the recently introduced BigDye terminators, large-template DNA can be directly sequenced with custom primers on automated instruments. Cycle sequencing conditions are presented to sequence DNA samples isolated from a number of microbial genomes including 750-kb Ureaplasma urealyticum, 1.2-Mb Mycoplasma fermentans, 2.3-Mb Streptococcus pneumoniae, and 4.6-Mb Escherichia coli. Average read lengths of >700 bp from unique primer annealing sites are often sufficient to fill final gaps in microbial genome sequencing projects without additional manipulations of template DNA. The technique can also be applied to sequence-targeted regions, thereby bypassing tedious subcloning steps.

Base Sequence↗

PubMed1998

Haemodynamic effects of chronic octreotide and tetrandrine administration in portal hypertensive rats.

Octreotide is an effective portal hypotensive drug in the control of variceal bleeding. Tetrandrine is a type of calcium channel blocker recently reported to reduce portal hypertension. The present study was undertaken to investigate the haemodynamic effects of octreotide and tetrandrine, alone and in combination, in portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation. Portal hypertensive rats were allocated into one of the four groups: vehicle group (saline, 0.5 mL/day), octreotide group (100 microg/kg per 12 h), tetrandrine group (20 mg/kg per 12 h), and octreotide (100 microg/kg per 12 h) plus tetrandrine (20mg/kg per 12 h) group. Tetrandrine or saline was administered by gavage, and octreotide by subcutaneous injection. The drug was given for 8 consecutive days, starting 1 day before ligation and continuing onwards. Haemodynamic parameters were measured thereafter, using the radioactive microsphere method. The portal venous pressure and portal tributary blood flow were significantly reduced, while portal territory and renal vascular resistances were significantly enhanced, by octreotide, tetrandrine, or octreotide plus tetrandrine in portal hypertensive rats, compared with the vehicle group. Our results showed that long-term administration of octreotide, tetrandrine, or octreotide plus tetrandrine led to portal hypotensive effects in portal hypertensive rats, but octreotide alone exerted better anti-hyperdynamic effects compared with tetrandrine alone. A combination of octreotide and tetrandrine offered no major beneficial anti-hyperdynamic effects compared with octreotide alone.

Alkaloids↗

PubMed1998

Peak height pattern in dichloro-rhodamine and energy transfer dye terminator sequencing.

Establishing the pattern in peak heights within local sequence contexts improves the accuracy of base calling and the identification of DNA sequence variations in dye-terminator cycle sequencing. We have systematically examined pairs of sequence-tagged sites (STSs) that vary at only a single nucleotide to determine how base changes influence the peak heights of neighboring bases in sequencing traces generated by two recently commercialized dye-terminator chemistries, the dichloro-rhodamine (dRhodamine) and the energy transfer (BigDye) terminators. For sequencing traces generated with the dRhodamine terminators, the peak height of a particular base in 28 of 64 possible 3-base windows (44%) can be predicted by knowing just one or two bases 5' to the base in question. For those generated with the BigDye terminators, the peak height of a particular base in 23 of 64 possible 3-base windows (36%) can be predicted by knowing the local sequence context. When the peak heights are binned slightly differently, 75% (48 out of 64 cases) of the base peaks generated by both dRhodamine and BigDye terminators fall in the middle half, confirming that the peak patterns of these two new dye terminator chemistries are much more even than those found in the original rhodamine dye terminator sequences.

Base Sequence↗

PubMed1998

Relationship between structure and anti-oxidation of tocopherol with molecular orbit theory.

AIM: To explore the relationship between different structures of tocopherol (Toc) and some phenol compounds and their anti-oxidative activities. METHODS: Use the ab initio calculation of molecular mechanics and quantum chemistry. RESULTS: The anti-oxidation of Toc was related to the ability to release active hydrogen, i.e., related to the O-H electron populations, frontier orbital energy (au), and the decreased amount of energy at the reaction ending stage. The order of hydroxyl O-H electron populations in different Toc model molecules were alpha < gamma < or = beta < delta, which was consistent with their anti-oxidation reported. CONCLUSION: The molecular orbit (MO) theory and the quantum chemical parameters can be used to analyze the anti-oxidation of phenol compounds with different structures.

Antioxidants↗

PubMed1998

Effects of zinc deficiency on endogenous antioxidant enzymes and lipid peroxidation in glomerular cells of normal and five-sixths nephrectomized rats.

We evaluated the effects of zinc deficiency on the activities of endogenous antioxidant enzymes and lipid peroxidation in rat glomerular cells (GCs). Male Sprague-Dawley rats (n = 48) were fed a zinc-deficient diet and deionized distilled water for 1 week to induce zinc deficiency. Half of the rats (zinc-deficient group) continued on this diet for 4 weeks, and the other half (zinc-replete group) were maintained on the same diet but with zinc-supplemented water (150 mg/Lzinc sulfate solution). Half of each group underwent five-sixths nephrectomy, while the other half underwent a sham operation. Another 12 normal rats (controls) were fed standard rat chow (containing 23.4% protein and 70 ppm zinc) and drank deionized distilled water. The zinc-deficient rats, including sham and five-sixths nephrectomized rats, showed severe growth retardation and poor appetite. Their mean plasma zinc concentrations were half that of normal control rats, but their plasma copper concentration was significantly higher than that of the control rats. Zinc supplementation corrected the abnormality of plasma zinc and copper concentrations and the loss of body weight in zinc-deficient rats. Zinc-deficient rats exhibited lower renal creatinine clearance and higher GC-malondialdehyde (GC-MDA) than zinc-replete rats. The remnant kidney of all five-sixths nephrectomized rats, including zinc-deficient and zinc-replete rats, showed a compensatory elevation in renal creatinine clearance and increased GC-MDA concentrations. Zinc concentrations in the renal cortex were decreased in zinc-deficient rats and the activities of GC-superoxide dismutase and GC-glutathione peroxidase were increased, while zinc-replete rats exhibited normal activities of GC-superoxide dismutase and GC-glutathione peroxidase. We suggest that zinc deficiency enhances the formation of reactive oxygen species but does not affect the activities of endogenous antioxidant enzymes in glomerular cells.

Animals↗

PubMed1997

New dye-labeled terminators for improved DNA sequencing patterns.

We have used two new dye sets for automated dye-labeled terminator DNA sequencing. One set consists of four, 4,7-dichlororhodamine dyes (d-rhodamines). The second set consists of energy-transfer dyes that use the 5-carboxy-d-rhodamine dyes as acceptor dyes and the 5- or 6-carboxy isomers of 4'-aminomethylfluorescein as the donor dye. Both dye sets utilize a new linker between the dye and the nucleotide, and both provide more even peak heights in terminator sequencing than the dye-terminators consisting of unsubstituted rhodamine dyes. The unsubstituted rhodamine terminators produced electropherograms in which weak G peaks are observed after A peaks and occasionally C peaks. The number of weak G peaks has been reduced or eliminated with the new dye terminators. The general improvement in peak evenness improves accuracy for the automated base-calling software. The improved signal-to-noise ratio of the energy-transfer dye-labeled terminators combined with more even peak heights results in successful sequencing of high molecular weight DNA templates such as bacterial artificial chromosome DNA.

DNA, Bacterial↗

PubMed1997

Phosphorylation can modulate the association of different sets of RNA binding proteins with the Vg1 localization signal RNA.

As assayed by both in vivo and in vitro UV-crosslinking techniques, four RNA binding proteins, with apparent molecular weight of 56, 54, 42, and 40 kilodaltons, associated specifically with the Xenopus Vg1 mRNA localization signal (LS) RNA. The 56 and 54 kD proteins were assigned as the masking proteins described previously, on the basis of their thermal stability and the effect of phosphorylation on RNA binding activity. The 42 and 40 kD proteins associated with the LS RNA at a lower extract concentration than the masking proteins did in vitro. Dephosphorylation will eliminate the RNA binding activities of all four proteins. However, either raising the extract concentration or phosphorylating the extract by the catalytic domain of protein kinase A had opposite effects on the crosslinking efficiencies of these two sets of RNA binding proteins. Phosphorylation might regulate this protein exchange process in vitro.

Animals↗