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Biomedical subjects

C M Chen

Publications and source records attributed to C M Chen.

At least 73 records · Page 4Linked to original sources
PubMed2000

Monte Carlo simulations of polymer brushes.

Three-dimensional Monte Carlo simulations of flexible and semiflexible polymer brushes at various grafting densities are carried out to study their equilibrium structure and attendant properties by using the bond fluctuation model. Our simulation results of long flexible polymer brushes are, in general, consistent with predictions of the self-consistent field theory. However, a depletion layer near the substrate is only observed at small grafting densities but not at medium densities. We have also measured the brush height and end-to-end distance of various polymer brushes, and their dependence on grafting density, chain length, and chain stiffness are obtained. The distribution of bending angles at various temperatures are calculated for four different forms of bending energy and our simulation results agree with theoretical predictions very well. Moreover, we study the isotropic-to-nematic transition of polymer brushes, which is found to be a continuous phase transition from our simulation results. Finally, we discuss the effects of local grafting density fluctuation on the monomer and end density distributions.

Journal Article↗
PubMed2000

Dilution wave and negative-order crystallization kinetics of chain molecules.

We show that the crystal growth rate of a very long-chain n-alkane C C(198)H(398) from solution can decrease with increasing supersaturation and follow strongly negative order kinetics. The experimental behavior can be well represented by a theoretical model which allows the molecule to attach and detach as either extended or folded in two. The obstruction of extended-chain growth by unstable folded depositions increases disproportionately with increasing concentration. As a consequence of this abnormal kinetics, a "dilution wave" can propagate and trigger a folded-to-extended-chain transformation on its way.

Crystallization↗
PubMed2000

Growth hormone gene polymorphisms and growth performance traits in Duroc, Landrace and Tao-Yuan pigs.

This study investigated the restriction fragment length polymorphism (RFLP) of the porcine growth hormone (pGH) gene in Duroc, Landrace, and Tao-Yuan pigs and its effects on growth performance and levels of plasma growth hormone in peripheral circulation. Genomic DNA extracted from 81 Tao-Yuan, 60 Landrace and 48 Duroc pigs were subjected to Southern blot hybridization with a pGH cDNA probe. Polymorphism was detected with the restriction enzymes TaqI and DraI. A comparison of these three breeds showed significant differences in allelic frequencies. Blood samples for radioimmunoassay (RIA) of GH were collected biweekly during the experimental period from pigs 12 to 40 weeks of age. Tao-Yuan pigs showed a mean plasma GH level (2.51 +/- 1.23 ng/mL) that was much lower than that of the Landrace (3.80 +/- 1.52 ng/mL) and Duroc (4.20 +/- 1.03 ng/mL) pigs (P < 0.05). Moreover, the Tao-Yuan pigs also showed poorer growth performance than the Landrace and the Duroc pigs both in the daily weight gain (0.37 +/- 0.06 vs. 0.67 +/- 0.05 and 0.70 +/- 0.05 kg/day, P < 0.01) and feed efficiency (3.12 +/- 0.28 vs. 2.60 +/- 0.14 and 2.52 +/- 0.12, P < 0.05). These results suggest that the growth performance trait in these pigs is highly correlated with their growth hormone genotype.

Animals↗
PubMed2000

Growth enhancement of fowls by dietary administration of recombinant yeast cultures containing enriched growth hormone.

In present study the methylotrophic yeast, Pichia pastoris, was used to express a recombinant growth hormone (rGH) gene of swine. A synthetic secretion cassette was constructed using the promoter of the alcohol oxidase1 gene (AOX1), and a alpha-factor signal peptide. After electroporatic transformation and zeocin selection, several clones exhibited high levels of rGH protein expression constituting more than 20% of total yeast protein. Over 95% of rGH was shown to be export into the culture supernatant. Yeast transformant containing the highest recombinant growth hormone level (rGH yeast) and native GS115 Pichia pastoris (non-rGH yeast, as a control) were separately cultured, harvested and adsorbed by wheat bran. Yeast cultures of four dosages (0.05, 0.1, 0.2, and 0.4%) were mixed respectively with chick basal diet and fed to simulated country chickens for 9 weeks. The results showed that, when compared to control chicks, the percentage of body weight gain was improved significantly (P<0.05) in chicks fed with diets containing 0.1 or 0.2% rGH-rich yeast culture at brooding stage, and in chicks fed with 0.4% rGH-rich yeast culture at growing stage. The average weight gain in rGH yeast treated groups for the full-term (0 to 63d) and short term (43 to 63d) of growth were 10.6 and 9.4%, respectively, better than the non-rGH yeast control group. These experimental data suggest that the use of rGH-containing yeast as a supplement in fed provided an alternative approach for growth improvement in simulated country chickens.

Alcohol Oxidoreductases↗
PubMed2000

Lung toxicity of paraquat in the rat.

In a rat model of paraquat-induced lung injury, pulmonary alveolar lavage fluid metabolic parameters were assessed to establish damage, and the use of surfactant was employed as a protective agent. Three groups of adult male Sprague-Dawley rats received intraperitoneal injection of paraquat (35 mg/kg body weight) in 1 ml saline, or received 1 ml saline, or no material. On d 3, 7, 14, and 21 after injection, pressure-volume curves and pulmonary alveolar lavage fluids were obtained. On d 3 paraquat significantly increased the lung wet/dry weight ratio and protein content but lowered phosphatidylcholine levels. There were no marked changes at other time points in the parameters examined. The pressure-volume curves initially moved downward and to the right on d 3 and 7 and then returned to control levels in the paraquat-treated rats. Immediate intratracheal administration of Survanta after paraquat injection (70 mg/kg body weight) tended to increase the survival rate on d 1 compared to rats without Survanta administration. Our results suggest that administration of exogenous surfactant may play a role in the treatment of patients poisoned with paraquat.

Animals↗
PubMed2000

Molecular epidemiological studies on foot-and-mouth disease type O Taiwan viruses from the 1997 epidemic.

Sequence diversity was assessed of the complete VP1 gene directly amplified from 49 clinical specimens during an explosive foot-and-mouth disease (FMD) outbreak in Taiwan. Type O Taiwan FMD viruses are genetically highly homogenous, as seen by the minute divergence of 0.2-0.9% revealed in 20 variants. The O/HCP-0314/TW/97 and O/TCP-022/TW/97 viral variants dominated FMD outbreaks and were prevalent in most affected pig-raising areas. Comparison of deduced amino acid sequences around the main neutralizable antigenic sites on the VP1 polypeptide showed no significant antigenic variation. However, the O/CHP-158/TW/97 variant had an alternative critical residue at position 43 in antigenic site 3, which may be due to selective pressure in the field. Two vaccine production strains (O1/Manisa/Turkey/69 and O1/Campos/Brazil/71) probably provide partial heterologous protection of swine against O Taiwan viruses. The type O Taiwan variants clustered in sublineage A1 of four main lineages in the phylogenetic tree. The O/Hong Kong/9/94 and O/1685/Moscow/Russia/95 viruses in sublineage A2 are closely related to the O Taiwan variants. The causative agent for the 1997 epidemic presumably originated from a single common source of type O FMD viruses prevalent in neighboring areas.

Amino Acid Sequence↗
PubMed2000

CD34, CD117, and actin expression in phyllodes tumor of the breast.

BACKGROUND: This study investigated the immunophenotypic patterns of CD34, CD117 (a product of the c-kit proto-oncogene), and actin (HHF35) in benign and malignant phyllodes tumors (PTs). We correlated the expression of CD34, CD117, and actin with histopathological grade. MATERIALS AND RESULTS: We analyzed 19 cases (7 benign and 12 malignant cases) of PTs using immunohistochemical analysis. Six of 7 benign PT stromal lesions stained positively for CD34, while only 3 of 12 cases of malignant PT were focally CD34 positive (P = 0.0106). Only 1 of the 7 benign PTs stromal lesions expressed CD117. Nine of the malignant PTs were composed CD117-positive fibroblasts. This result demonstrated that CD117 expression is associated with the malignant potential of PTs (P = 0. 0106). Actin (HHF-35) expression was found in 8 of 12 cases of malignant PTs (P = 0.027), but in only 1 of 7 cases of benign PTs. Actin expression was significantly (P = 0.04) correlated to frequent mitotic activity (>5 mitoses per 10 high-power fields). The immunophenotypic markers were not related to tumor size. Additionally, we sequenced part of the juxtamembrane region of the c-kit proto-oncogene and found point mutations in two malignant PTs. CONCLUSION: Our results demonstrated that expression of CD34 was associated with benign PTs, while CD117 and actin were preferentially expressed in malignant PTs. Our results implied that these immunohistological markers might be used for the histopathological grading of PTs.

Actins↗
PubMed2000

Treatment of acute closed humeral shaft fractures with Ender nails.

The effect of semirigid Ender nails (EN) in the treatment of closed humeral shaft fractures was reviewed and analyzed. Clinical study was set retrospectively with detailed parameters. One hundred and eighteen closed humeral shaft fractures, treated with closed reduction and internal fixation with ENs, were collected. The follow-up period was 78 (24-175) months. The average operation blood loss was 105 cc, operation time was 57 min, hospital stay was 6.5 days, and union time was 10.5 weeks. The postoperative complications included three superficial infections, one iatrogenic radial nerve palsy, eight nail backouts, and eight nonunions. In our experience, for closed humeral shaft fractures fixed surgically, EN is a good choice for its simplicity and efficacy, but the fracture gap should be minimized after fixation and postoperative care should be closely observed.

Adolescent↗
PubMed2000

Ipsilateral hip and distal femoral fractures.

We tried to find the trauma mechanism and treatment rationale of ipsilateral concomitant hip and distal femoral fractures involving the articular surface. Between 1988 and 1995, 15 cases of ipsilateral hip (confined to neck or trochanteric areas of the femur) and distal (confined to supra- and intercondylar area of the femur) femoral articular fractures were collected. The hip fractures consisted of 10 trochanteric fractures and five neck fractures, which were managed with reduction and fixation in 14 (Knowles' pin in eight, DHS in four and standard Gamma nail in two), and primary bipolar hemiarthroplastry in one. The distal femoral articular fractures were open in 11; these were managed with radical debridement, implantation of Septopal chains and immediate internal fixation, followed by prophylactic autogenous bone grafting 6 weeks later in the recent six cases (five Judet plates, four dynamic condylar screws and two condylar plates). The other four closed distal femoral fractures were managed with early reduction and internal fixation (two Judet plate, one dynamic condylar screw and one condylar plate). The union time was 20.3 (12-48) weeks for proximal fractures and 23.7 (12-36) weeks for distal fractures. Early infection developed in three cases. Nonunion of a femoral neck fracture developed in one case. The other complications were implant failure in one, coxa vara in one, refracture in one, delayed union in one and knee stiffness in one.

Adult↗
PubMed2000

Surgical treatment of displaced acetabular fractures - 72 cases followed for 10 (6-14) years.

Seventy-two displaced acetabular fractures managed surgically were evaluated retrospectively. The follow-up period was 10 (6-14) yr. The commonest fractures were posterior wall (28) and both columns (10). The surgical approaches were Kocher-Langenbeck (47), ilioinguinal (19) and extended iliofemoral (6). No neural monitoring was used in operations and no preventive agents for heterotopic ossification or thromboembolism were used perioperatively. Reduction was rated congruent in 59 (81.9%) and noncongruent in 13 (18.1%). The early postoperative complications were 1 vascular injury, 1 iatrogenic sciatic nerve injury, 1 deep vein thrombosis and 2 wound infections. The late complications were heterotopic ossification in 20 patients, avascular necrosis of the femoral head in 4 and symptomatic arthritis in 10. Functional outcomes were rated as excellent in 31, good in 23, fair in 7 and poor in 11. Our results show that traditional management is effective enough for displaced acetabular fractures.

Acetabulum↗
PubMed2000

Metal contents of fish from cultureponds near scrap metal reclamation facilities.

Milkfish (Chanos chanos) from four fish-culture ponds adjacent to different metal recovery facilities along the Er-Jen River area, Tainan, Taiwan, were sampled to determine their metal contents. Chemical analysis showed that fish tissue contained different concentrations of Cu: 0.71-6.37 micrograms/g, Pb: ND (not detectable) approximately 41.04 micrograms/g, Cd: ND approximately 0.41 microgram/g, Al: 6.75-64.11 micrograms/g, Ni: 0.062-0.504 microgram/g and Zn: 16.11-41.86 micrograms/g. The average concentrations of Cu, Al, Zn, Cd and Pb in fish samples from some of the ponds were significantly higher than those from the reference pond. In addition, there were variations in metal concentrations of fish collected from different ponds. Pond D had the highest mean values of Cu, Cd and Zn, and Pond B of Al and Pb. Further investigations are needed to determine the source of metal contamination in the fish.

Aluminum↗
PubMed2000

An early vision-based snake model for ultrasound image segmentation.

Due to the speckles and the ill-defined edges of the object of interest, the classic image-segmentation techniques are usually ineffective in segmenting ultrasound (US) images. In this paper, we present a new algorithm for segmenting general US images that is composed of two major techniques; namely, the early-vision model and the discrete-snake model. By simulating human early vision, the early-vision model can capture both grey-scale and textural edges while the speckle noise is suppressed. By performing deformation only on the peaks of the distance map, the discrete-snake model promises better noise immunity and more accurate convergence. Moreover, the constraint for most conventional snake models that the initial contour needs to be located very close to the actual boundary has been relaxed substantially. The performance of the proposed snake model has been shown to be comparable to manual delineation and superior to that of the gradient vector flow (GVF) snake model.

Algorithms↗
PubMed2000

The effect of posterior capsulorrhaphy in primary total hip arthroplasty: a prospective randomized study.

Between 1994 and 1997, 180 cases of primary total hip arthroplasty (THA) were performed with the posterior (Moore) approach for a variety of indications and studies prospectively. The cases were separated randomly into 2 groups to evaluate the effect of posterior capsulorrhaphy in the prevention of postoperative dislocation. In group 1 (96 cases), closure of the arthroplasty was performed with a posterior capsulorrhaphy; in group 2 (84 cases), closure was performed without capsulorrhaphy. The follow-up period was 38 months (range, 12-60 months). No dislocations occurred in group 1, whereas 2 dislocations (2.3%) occurred in group 2. Although the factors affecting dislocation in primary THA are many, a posterior capsulorrhaphy may be helpful in the prevention of posterior dislocation of primary THA performed with a posterior approach.

Arthroplasty, Replacement, Hip↗
PubMed2000

Expression of Chx10 and Chx10-1 in the developing chicken retina.

We have isolated full-length cDNAs of chick Chx10 and Chx10-1, two members of the paired type homeobox/CVC gene family. A comparison of sequences suggests that Chx10 is closely related to Alx/Vsx-2 and Vsx-2 of zebrafish and goldfish, respectively; while Chx10-1 is closely related to Vsx-1 of zebrafish and goldfish. Chx10 and Chx10-1 are expressed in the early retinal neuroepithelium, but not in the pigment epithelium and lens. The expression of Chx10 is present in most retinal neuroblasts, while Chx10-1 exhibits a novel pattern along the nasotemporal border. In the differentiating retina, both Chx10 and Chx10-1 are restricted to bipolar cells and are maintained at a low level in bipolar cells of the mature retina.

Amino Acid Sequence↗
PubMed2000

Bioequivalence study of tramadol by intramuscular administration in healthy volunteers.

Tramadol hydrochloride (CAS 36282-47-0) is a centrally acting analgesic agent binding to mu opiate receptors. The bioavailability of a new tramadol hydrochloride injection (Limadol) was compared with a commercially available reference product by intramuscular administration in twelve healthy Chinese male volunteers by a standard two-way cross-over trial. Each volunteer received a single 100 mg injection of tramadol HCl in each phase. The bioavailability was compared using the area under the plasma concentration-time curve from time 0 to 30 h (AUC0-30), the area under the plasma concentration-time curve from time 0 to infinity (AUC0-infinity), peak plasma concentration (Cmax), and time to reach peak plasma concentration (Tmax). No statistically significant difference was observed between the Tmax, Cmax, AUC0-30 and AUC0-infinity of the two preparations. It is concluded that test and reference formulations of tramadol hydrochloride are bioequivalent for both the extent and rate of absorption after a single intramuscular injection.

Absorption↗
PubMed2000

Thymus size and its relationship to perinatal events.

A retrospective study was conducted to assess radiographically the thymus size in well and sick neonates and to search for a possible relationship to perinatal events. Thymus size was expressed as cardiothymic:thoracic ratio (CT/T) by measuring the width of the cardiothymic shadow at the level of carina and dividing it by the width of the thorax at the costophrenic angles. The CT/T was measured on chest radiographs obtained on day 1 in well term neonates consecutively born in our nursery and sick neonates with meconium staining of the amniotic fluid, meconium aspiration syndrome or respiratory distress syndrome (RDS). Neonates with congenital anomalies, congenital heart disease or intrauterine growth retardation were excluded. There were no significant relationships between CT/T and sex, birth route, birthweight or gestational age in well and sick term neonates. The CT/T were comparable among well and sick term neonates and were significantly greater in the preterm neonates with RDS than in the preterm neonates without RDS. The CT/T was correlated to the birth route only in the preterm neonates. We conclude that thymus involution in the perinatal period is a complex process and the response is different between term and preterm neonates.

Birth Weight↗
PubMed2000

Adjuvant sequential chemotherapy with doxorubicin plus cyclophosphamide, methotrexate, and fluorouracil (ACMF) with concurrent radiotherapy in resectable advanced breast cancer.

Doxorubicin (Adriamycin) is an anthracycline effective in breast cancer. Despite a worldwide acceptance of Adriamycin in the adjuvant chemotherapy to maximize the survival benefit in the higher risk patients with breast cancer with promising results, oncologists in general do not favorably consider anthracyclines in the adjuvant treatment setting because of concern about the acute and chronic drug-related toxicity. For high-risk patients with breast cancer with more than three positive axillary lymph nodes, this series adopted a modified sequential regimen of ACMF first with Adriamycin (A) as a single agent in 3-weekly administration for three courses, and then a combination of cyclophosphamide, methotrexate, fluorouracil (CMF) every 3 to 4 weeks for six courses given in an outpatient setting concurrent with radiation therapy as an adjuvant treatment. A total of 56 patients underwent modified radical mastectomy and 3 others breast conservation surgery for their invasive breast cancer. Forty-seven (84%) patients completed the intended adjuvant treatment and 1 patient died of infection from treatment-related neutropenia. As a whole, the 3-year overall survival and disease-free survival rates of 56 patients analyzed were 82.3% and 64.4%, respectively. In this high-risk group, patients with four to nine positive nodes showed a slightly better trend of survival than those with 10 or more positive nodes without reaching statistically significant difference (36-month overall survival: 90.9% vs. 72.5%, p = 0.06; disease-free survival: 78.7% vs. 47.8%, p = 0.38). In this entire group of patients, locoregional recurrence was absent. A total of 55 episodes of grade III and IV hematologic toxicity were observed, with only one death from neutropenic sepsis. This modified ACMF regimen offers a good survival rate in breast cancer patients with more than three positive axillary lymph nodes. When these patients are carefully managed, the morbidity and mortality related to the treatment are low.

Adult↗