Biomedical subjects

S M Chen

Publications and source records attributed to S M Chen.

At least 19 recordsLinked to original sources

PubMed2006

Improved search for nu(mu) --> nu(e) oscillation in a long-baseline accelerator experiment.

We performed an improved search for nu(mu) --> nu(e) oscillation with the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment, using the full data sample of 9.2 x 10(19) protons on target. No evidence for a nu(e) appearance signal was found, and we set bounds on the nu(mu) --> nu(e) oscillation parameters. At Deltam(2)=2.8 x 10(-3) eV(2), the best-fit value of the K2Knu(mu) disappearance analysis, we set an upper limit of sin(2)2theta(mue) < 0.13 at a 90% confidence level.

Journal Article↗

PubMed2006

Involvement of norepinephrine in the hyperglycemic responses of the freshwater giant prawn, Macrobrachium rosenbergii, under cold shock.

Hyperglycemic response of freshwater giant prawn, Macrobrachium rosenbergii, under acute cold shock was investigated, and the involvement and stimulatory pathways of norepinephrine (NE) on induced-glycemia were further examined. Remarkable elevations in hemolymph glucose at comparable magnitude were observed in both intact and eyestalkless prawn under cold treatments, suggesting that hyperglycemic response of this species is not solely mediated through the actions of crustacean hyperglycemic hormone released from X-organ sinus gland complex on the target tissues, but NE is involved. Positive and significant correlations were noted between the hemolymph glucose titers and NE contents in both thoracic ganglia and the hemolymph, suggesting that NE plays a significant role in the hyperglycemic responses of this species under cold. Depressive effects of various adrenoceptor antagonists monitored in vivo and in vitro further suggest that the action of NE is primarily mediated through both alpha1- and beta1-adrenoceptors.

Amines↗

PubMed2005

Search for coherent charged pion production in neutrino-carbon interactions.

We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed, and an upper limit of is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.

Journal Article↗

PubMed2005

Study on changes of heme oxygenase-1 expression in patients with coronary heart disease.

BACKGROUND: Heme oxygenase (HO) is a rate-limiting enzyme of endogenetic carbon monoxide (CO) that degrades heme into carbon monoxide, bilirubin, and iron. These products have important physiologic effects: bilirubin is a potent antioxidant that can act against ischemia/reperfusion injury; there is a negative correlation between the content of HO-1 and the incidence of coronary heart disease (CHD). HYPOTHESIS: This study was undertaken to investigate the changes of HO-1 in patients with CHD. METHODS: Thirty-five patients with acute myocardial infarction (AMI), 40 patients with unstable angina pectoris (UAP, diagnosed by coronary angiography), and 30 patients with stable angina pectoris (AP, diagnosed by coronary angiography) were selected for the study; another 30 patients with normal coronary artery (diagnosed by coronary angiography) were selected as controls. The levels of HO-1 protein expression in monocyte and lymphocyte in the subjects were tested by immunohistochemistry and western blot. Computer picture analyzing systems were also used to measure the levels of HO-1 protein expression. RESULTS: Heme oxygenase-1 protein is located in cell plasma. The levels of HO-1 protein expression in patients with CHD were significantly higher than in those without CHD (p < 0.01). There were significant differences of HO-1 expression among the three groups of patients with CHD. The group with AMI was the highest, followed by the group with UAP and finally by the group with AP. CONCLUSIONS: There is a higher expression of HO-1 in patients with CHD. The levels of HO-1 protein are associated with the severity of CHD.

Biomarkers↗

PubMed2001

Gastric emptying and intestinal transit of liquid and solid markers in rats with chronic uremia.

Gastrointestinal motor abnormalities may account for dyspeptic symptoms of chronic uremia patients. However, the data on gastric emptying are conflicting in human studies. We, therefore, assessed gastric emptying and gastrointestinal transit in a rat uremia model. Chronic uremia was induced by five-sixths nephrectomy in the rats. After 20-hour fasting, the rats were loaded with 70 glass beads as solid markers through a gastric catheter. Two hours later, the stomach was exposed and the small intestine was equally divided into 10 segments. The glass beads in the stomach and in each intestinal segment were counted. The gastric emptying was expressed as the ratio of the number of glass beads in the small intestine to that counted from the entire gastrointestinal tract. The intestinal transit was assessed by analyzing the geometric center of the distribution of glass beads in the intestinal segments. Two conventional nonabsorbable markers, radioactive chromate and charcoal, were also used to evaluate gastric emptying and intestinal transit in the fasted state. Additionally, similar experiments of glass beads were performed in the fed state. It was found that, in the fasted state, the gastric emptying and the intestinal transit of liquid or solid markers were little affected by uremia. In the fed state, however, chronic uremia significantly decreased the intestinal transit but hardly affected the gastric emptying. We conclude that the postprandial intestinal transit, but not the gastric emptying, of solid markers may be decreased in the fed state by chronic uremia in a severity-dependent manner of a rat model, which resembles the findings in uremic patients.

Animals↗

PubMed2001

ATR/ATM-mediated phosphorylation of human Rad17 is required for genotoxic stress responses.

Genotoxic stress triggers the activation of checkpoints that delay cell-cycle progression to allow for DNA repair. Studies in fission yeast implicate members of the Rad family of checkpoint proteins, which includes Rad17, Rad1, Rad9 and Hus1, as key early-response elements during the activation of both the DNA damage and replication checkpoints. Here we demonstrate a direct regulatory linkage between the human Rad17 homologue (hRad17) and the checkpoint kinases, ATM and ATR. Treatment of human cells with genotoxic agents induced ATM/ATR-dependent phosphorylation of hRad17 at Ser 635 and Ser 645. Overexpression of a hRad17 mutant (hRad17AA) bearing Ala substitutions at both phosphorylation sites abrogated the DNA-damage-induced G2 checkpoint, and sensitized human fibroblasts to genotoxic stress. In contrast to wild-type hRad17, the hRad17AA mutant showed no ionizing-radiation-inducible association with hRad1, a component of the hRad1-hRad9-hHus1 checkpoint complex. These findings demonstrate that ATR/ATM-dependent phosphorylation of hRad17 is a critical early event during checkpoint signalling in DNA-damaged cells.

Animals↗

PubMed2001

Dystonia following administration of intravenous radiographic contrast material.

We describe a patient who experienced dystonia coincident with the administration of an i.v. contrast agent. Dystonic reactions are not well known outside of the fields of Emergency Medicine, Neurology, and Psychiatry. They have not been previously reported as a reaction to i.v. contrast material. Prompt consideration and treatment of this condition may prevent unnecessary patient discomfort and interventions.

Adult↗

PubMed2001

Inhibitory effect of dry needling on the spontaneous electrical activity recorded from myofascial trigger spots of rabbit skeletal muscle.

OBJECTIVE: Dry needling of myofascial trigger points can relieve myofascial pain if local twitch responses are elicited during needling. Spontaneous electrical activity (SEA) recorded from an active locus in a myofascial trigger point region has been used to assess the myofascial trigger point sensitivity. This study was to investigate the effect of dry needling on SEA. DESIGN: Nine adult New Zealand rabbits were studied. Dry needling with rapid insertion into multiple sites within the myofascial trigger spot region was performed to the biceps femoris muscle to elicit sufficient local twitch responses. Very slow needle insertion with minimal local twitch response elicitation was conducted to the other biceps femoris muscle for the control study. SEA was recorded from 15 different active loci of the myofascial trigger spot before and immediately after treatment for both sides. The raw data of 1-sec SEA were rectified and integrated to calculate the average integrated value of SEA. RESULTS: Seven of nine rabbits demonstrated significantly lower normalized average integrated value of SEA in the treatment side compared with the control side (P < 0.05). The results of two-way analysis of variance show that the mean of the normalized average integrated value of SEA in the treatment group (0.565 +/- 0.113) is significantly (P < 0.05) lower than that of the control (0.983 +/- 0.121). CONCLUSIONS: Dry needling of the myofascial trigger spot is effective in diminishing SEA if local twitch responses are elicited. The local twitch response elicitation, other than trauma effects of needling, seems to be the primary inhibitory factor on SEA during dry needling.

Animals↗

PubMed2001

"Burnout" in intensive care nurses.

The purpose of this research was to examine the relationship between burnout components and selected demographic variables in a group of intensive care unit nurses. This research hopes to heighten awareness of both intensive care nurses and hospital administrators of the importance of burnout in their work setting. A descriptive correlational study design was used to examine the extent of burnout according to selected demographic variables. Sixty-eight intensive care nurses from two hospitals and critical care courses at one university completed a demographic data form and the research questionnaire of the Maslach Burnout Inventory (MBI). Statistical analysis included non-parametric tests. Study results indicated low to moderate levels of total component scores in all intensive care nurses and on all three subscales of the assessment instrument. Results also indicated that, in this sample, younger nurses (20-29 years of age), separated and divorced nurses, and staff who work full time in ICUs were the most prone to emotional exhaustion. These research findings recommend support for ICU nurses to prevent burnout in their work setting. Further research is necessary to examine what kinds of working environments (job related stress) are effective in mitigating burnout amongst staff in the intensive care field.

Adaptation, Psychological↗

PubMed2001

Possible site of decreased intestinal zinc absorption in chronic uremic rats.

BACKGROUND/AIMS: Previous zinc tolerance tests in uremic patients indicated decreased intestinal zinc absorption. In the present study, a zinc tolerance test was initially applied to a uremic rat model and subsequently the possible site of malabsorption investigated. METHODS: Chronic uremia was induced by five-sixths nephrectomy. Both control and nephrectomized rats were divided into three groups including animals with intact intestine, removal of the jejunum, and removal of the ileum. Each rat was orally loaded with zinc sulfate (80 mg/kg) in conscious state. Blood samples were drawn before and after zinc load at different intervals during 6 h for zinc analysis. The area under the plasma zinc curve (AUC) and the maximal increase of plasma zinc level (C(max)) were calculated. RESULTS: Jejunectomy decreased both AUC and C(max) in control and nephrectomized rats, whereas ilectomized animals remained, interestingly, unchanged with regard to these two parameters. Significant decreases in both AUC and C(max) were observed in nephrectomized rats as compared with the control rats. CONCLUSIONS: The jejunum is the main site of zinc absorption in response to a large oral load of zinc sulfate in both normal and uremic rats. The data further suggest that five-sixths nephrectomy reduces gastrointestinal zinc absorption in rats predominantly by the ileum.

Animals↗

PubMed2001

[Influence of gravity change on EGF-induced signal transduction].

With the development of aerospace technology, biological effects induced by alteration of gravitation are drawing more and more attention. Among them the influence of alteration of gravitation on cytokine-induced signal transduction has been well studied recently. Epidermal growth factor (EGF)-induced signal transduction can activate increase of cell proliferation in most cell types, so it is always a hotspot in these years. Among the early effects evoked by EGF are receptor clustering, cell rounding, and early gene expression. After the study about the induction of EGF on human A431 cell line, it was observed that EGF-induced c-fos and c-jun expression decreased in microgravity. This was caused by alteration of the EGF receptor and protein kinase C-mediated signal transduction pathways. Meanwhile the key component of cytoskeleton, the actin microfilament system, was found to be linked to the EGF-induced signal transduction cascades either. So it seems reasonable to suggest that the cytoskeleton constitutes the gravity-sensitive cell component.

Actin Cytoskeleton↗

PubMed2001

[Bone-inducing activity of human bone morphogenetic protein-2 102 peptide].

To analyze the bone-inducing activity of C terminal of hBMP-2 and get a new recombinant product of hBMP-2, the gene encoding 102 aa of hBMP-2 mature peptide C terminal was cloned and expressed in E. coli and the first Cys was mutated with Ser. The fragments encoding the target peptide were amplified and cloned into heat-inducible expression vector pDH and transformed into E. coli DH5 alpha. After induction, a new protein bond appeared on the SDS-PAGE. The expressed products amounted to 30% of the total bacterial protein, which existed in the form of inclusion body. The products of bacterial lysates were purified through the ion-exchange chromatography. The denatured proteins were dialysed and diluted directly into the refolding buffer. The renatured products were implanted into mouse thigh muscles to analyze their bone-inducing activity respectively. The results of histological assay showed that the 102 peptide of hBMP-2 could ectopically induce formation of bone, while the mutated 102 peptide of hBMP-2 could not. It suggested hBMP-2 102 peptide still had bone-inducing activity. The first Cys of hBMP-2 mature peptide might be necessary for integrity of three pairs of disulfide bond, and also essential for bone-inducing activity of hBMP-2.

Animals↗

PubMed2000

Contributions of protein disulfide isomerase domains to its chaperone activity.

Protein disulfide isomerase (PDI), a member of the thioredoxin (Trx) superfamily, consists of five consecutive domains, a-b-b'-a'-c. Domain combinations, AB, A'C, B'A'C and AB-C, and hybrids of PDI domains with Trx, Trx-C and Trx-B'A'C, have been constructed and expressed in Escherichia coli to examine the contributions of PDI domains to its enzyme and chaperone activities. All the combination and hybrid products are considerably less active than intact PDI in their enzyme activities. Recombinant products containing C, at low concentrations, inhibit the reactivation of lysozyme in HEPES buffer, while those without C do not. Only the intact PDI molecule and the hybrid molecule, Trx-B'A'C, but to a much lower level, show general chaperone activity in assisting the reactivation of denatured D-glyceraldehyde-3-phosphate dehydrogenase. It is suggested that all domains of PDI contribute to the binding of target protein for its chaperone activity.

Buffers↗

PubMed2000

Isolation and preliminary characterization of the human and mouse homologues of the bacterial cell cycle gene era.

Era is an essential GTPase that is required for proper cell cycle progression and cell division in Escherichia coli and is found in nearly all bacteria sequenced to date. To determine whether Era is also present in eukaryotic organisms, we searched the dbEST database and found EST clones coding for proteins that were similar to Era. Full sequencing of these ESTs from human and mouse identified a conserved homologue, ERAL1 (Era-like 1). ERAL1 maps to 17q11.2 in human and is located in the syntenic region of mouse chromosome 11. ERAL1 may be an attractive candidate for a tumor suppressor gene since ERAL1 is located in a chromosomal region where loss of heterozygosity is often associated with various types of cancer.

Amino Acid Sequence↗

PubMed2000

Increased immunoreactive labeling of the spinal N-methyl-D-aspartate R1 receptors after dorsal root ganglionectomy in the rats.

The N-methyl-D-aspartate (NMDA) receptor plays an important role in the development of the autotomy after dorsal root ganglionectomy (DRGn). In this study, we further investigated the expression of the NMDAR1 in the spinal cord of the rats after right DRGn by immunohistochemical analyses. Computerized densitometric analysis of the NMDAR1 immunoreactivity was done and the integrated optical density (IOD) of the superficial laminae of the dorsal horn of the spinal cord was measured. The immunoreactive labeling of the NMDAR1 was increased in the cervical spinal cord ipsilateral to the DRGn from day 5 to 14 after DRGn. The ratio of the right/left IOD of the rats receiving DRGn was significantly higher than the rats in the sham-operated group and the control group (P<0.05). The expression of the NMDAR1 increased gradually to reach the peak at day 7 after DRGn (mean right/left IOD ratio=1.52), then decreased thereafter. The increased expression of the NMDAR1 at day 7 was suppressed by MK-801 (NMDA receptor antagonist) administered immediately after DRGn, but not by normal saline or 1,2,3,4-tetrahydro-6-nitro-2, 3-dioxo-benzo[f] quinoxaline-7-sulfonamide (NBQX, non-NMDA receptor antagonist). The results indicated that the expression of the NMDAR1 in the superficial laminae of the dorsal horn of the spinal cord was increased after DRGn and the time course was compatible with the onset and development of the autotomy induced by DRGn.

Animals↗

PubMed2000

Sinoatrial nodal artery aneurysm with right ventricular outflow tract compression: report of a case.

We described a 16-year-old boy with sinoatrial nodal (SAN) artery aneurysm that drained into right atrium and compressed right ventricular outflow tract. The patient was clinically asymptomatic. Hemodynamic study revealed a 15 mm Hg peak systolic pressure gradient at right ventricular outflow tract. The fistula was successfully excised without sequalae. Cathet. Cardiovasc. Intervent. 51:328-331, 2000.

Adolescent↗

PubMed2000

Lead induced alterations in nitrite and nitrate levels in different regions of the rat brain.

Nitric oxide (NO) is a free radical synthesized by nitric oxide synthase (NOS) during the conversion of L-arginine to citrulline. Lead (Pb) affects neuronal functioning in the rat brain. Nitric oxide, a neuronal messenger has a short half life and converts immediately into nitrite and nitrate. The present study is designed to determine lead-induced alterations in NO production by measuring nitrite and nitrate in the cerebellum, the hippocampus, the frontal cortex and the brain stem of the rat brain. Male Sprague-Dawley rats were treated with lead acetate (5 and 15 mg/kg body wt.) by intraperitoneal injection. The control and experimental rats were sacrificed at the end of 7 and 14 days after treatment and different regions of the brain were isolated. Nitrite and nitrate (NOx) levels were estimated by the chemiluminescent method using the NOA 280 (Sievers). The data suggested dose-dependent and region-specific responses to lead. Both treatments of lead reduced NOx levels in the cerebellum and the hippocampus. However, the frontal cortex and the brain stem responded differently to Pb exposure. NOx levels in the frontal cortex were significantly increased in rats treated with low and high doses of Pb for 7 days but not in rats treated for 14 days, whereas in the brain stem, NOx levels were increased in a dose- and time-dependent manner. Although, the response was time-dependent, the variation between 7- and 14-day treatment was not clearly delineated. These results provide additional evidence that Pb exposure alters NO-production in rat brain leading to neuronal dysfunction.

Animals↗

PubMed2000

Ouabain resistance of a human trophoblast cell line is not related to its reactivity to ouabain.

Ouabain is a specific inhibitor of sodium, potassium-dependent adenosine triphosphatase (Na,K-ATPase), a P-type ion-transporting ATPase which is essential for the maintenance of adequate concentrations of intracellular Na+ and K+ ions. The present study describes the establishment of a ouabain-resistant mutant, TLouaR, from a human trophoblast cell line TL. Morphologically TL and TLouaR are indistinguishable, but, TLouaR is about 1000 times more resistant to the cytotoxic effect of ouabain and > 2000 times to that of bufalin and yet ouabain can retard the growth of the TLouaR cells and in parallel reduce its cloning efficiency in a time- and dose-dependent manner. Furthermore, Na,K-ATPase activity from TLouaR cells is inhibitable by ouabain albeit with lower efficiency. [3H]ouabain binding studies reveal that TLouaR cells have less (P < 0.05) ouabain binding sites (1.7 +/- 0.15 x 10(4)/cell vs. 2.3 +/- 0.115 x 10(4)/cell in the control). However, affinities (dissociation constants Kd) to ouabain for TL and TLouaR cells are not significantly different. Lastly, Na,K-ATPase activity (1.375 +/- 0.25 micromole ATP/min mg protein) of TLouaR cells is significantly higher (P < 0.05) than that of the TL cells (0.895 +/- 0.12 micromole ATP/min x mg protein). These studies show that the interactions between ouabain and Na,K-ATPase can be mediated through different pathways resulting in diverse phenotypic characteristics. In addition, ouabain resistance does not necessarily reflect the lack of response to the digitalis drug. The exact mechanisms of ouabain resistance observed in the present study remain to be determined but the TLouaR cells may be the best tool to uncover the many functional characteristics of Na,K-ATPase.

Adenosine Triphosphatases↗