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Biomedical subjects

C H Chen

Publications and source records attributed to C H Chen.

At least 307 records · Page 17Linked to original sources
PubMed1998

A nonlinear spatially variant object-dependent system model for prediction of partial volume effects and scatter in PET.

Accurate quantitation of small lesions with positron emission tomography (PET) requires correction for the partial volume effect. Traditional methods that use Gaussian models of the PET system were found to be insufficient. A new approach that models the non-Gaussian object-dependent scatter was developed. The model consists of eight simple functions with a total of 24 parameters. Images of line and disk sources in circular and elliptical cylinders, and an anthropomorphic chest phantom were used to determine the parameter values. Empirical rules to determine these parameter values for various objects based on those for a reference object, a 21.5-cm circular cylinder, were also proposed. For seven spheroids and a 3.4-cm cylinder, pixel values predicted by the model were compared with the measured values. The model-to-measurement-ratio was 1.03+/-0.07 near the center of the spheroids and 0.99+/-0.03 near the center of the 3.4-cm cylinder. In comparison, the standard single Gaussian model had corresponding ratios of 1.27+/-0.09 and 1.24+/-0.03, respectively, and the corresponding ratios for a double Gaussian model were 1.13+/-0.09 and 1.05+/-0.01. Scatter fraction (28.5%) for a line source in the 21.5-cm cylinder was correctly estimated by our model. Because of scatter, we found that errors in the measurement of activity in spheroids with diameters from 0.6 to 3.4 cm were more significant than previously appreciated.

Algorithms↗
PubMed1998

Characteristics of hepatocellular carcinoma presenting with variceal bleeding.

Patients with hepatocellular carcinoma may present with variceal bleeding as the initial symptoms. The aims of this study is to investigate the characteristics of such patients. A total of 1046 hepatocellular carcinoma cases were retrospectively retrieved from our computer records between 1980 and 1993. The medical records and image studies were reviewed. The status of each patient was assessed at the time of presentation. A total of 14 (about 1 %) patients with hepatocellular carcinoma presented with variceal bleeding. Five (36%) did not have past history of liver disease. The tumour size ranged from 2.5 to 11.3 cm. Compared with hepatocellular carcinoma patients not presenting with variceal bleeding, these patients had a higher percentage of portal vein thrombosis (57.1 vs 19.4%). In two patients, the hepatic tumours were missed in the initial abdominal sonography. The average survival time was 71 days. Seven patients died within 2 months mainly due to variceal bleeding (41.6%). Variceal bleeding might be a clue to the presence of hepatocellular carcinoma with portal vein thrombosis even in patients without a previous history of liver disease. The tumours in such patients might be the infiltrative type, and thus the portal vein should be carefully worked-up. Overall, these patients have an extremely poor prognosis. In the management of patients with variceal bleeding, the possibility of hepatocellular carcinoma with portal vein thrombosis should not be overlooked, especially in areas where this cancer is prevalent.

Carcinoma, Hepatocellular↗
PubMed1998

New electrocardiographic criteria for the differentiation between counterclockwise and clockwise atrial flutter: correlation with electrophysiological study and radiofrequency catheter ablation.

OBJECTIVE: To develop new electrocardiographic (ECG) criteria for the differentiation between counterclockwise and clockwise atrial flutters. BACKGROUND: Traditionally, the ECG differentiation between counterclockwise and clockwise atrial flutters is based on the flutter wave polarity in the inferior leads. However, determination of flutter wave polarity is subjective and sometimes difficult, especially in flutter waves of undulating pattern. PATIENTS: The study comprised 37 consecutive patients with drug resistant atrial flutter; 30 had counterclockwise and 17 had clockwise atrial flutter (10 had both forms of atrial flutter). The isthmus dependence was confirmed by entrainment study and catheter ablation. The ECG patterns of both types of atrial flutter were compared and the flutter wave polarity in the inferior leads was determined by four independent cardiologists. RESULTS: The flutter wave polarity in the inferior leads appeared negative in 24, positive in one, and equivocal in five of the counterclockwise atrial flutters; polarity appeared negative in one, positive in 10, and equivocal in six of the clockwise atrial flutters. However, the aVF/lead I flutter wave amplitude ratio was > 2.5 in all counterclockwise but < 2.5 in all clockwise atrial flutters. The flutter wave nadirs in the inferior leads corresponded to the upstrokes in V1 in all counterclockwise atrial flutters, but corresponded to the downstrokes in V1 in all clockwise atrial flutters. CONCLUSIONS: The flutter wave polarity in the inferior leads does not correlate well with the flutter wave rotating direction. However, counterclockwise and clockwise atrial flutters can be differentiated by new ECG criteria with high accuracy.

Adult↗
PubMed1998

In vivo murine left ventricular pressure-volume relations by miniaturized conductance micromanometry.

The mouse is the species of choice for creating genetically engineered models of human disease. To study detailed systolic and diastolic left ventricular (LV) chamber mechanics in mice in vivo, we developed a miniaturized conductance-manometer system. alpha-Chloralose-urethan-anesthetized animals were instrumented with a two-electrode pressure-volume catheter advanced via the LV apex to the aortic root. Custom electronics provided time-varying conductances related to cavity volume. Baseline hemodynamics were similar to values in conscious animals: 634 +/- 14 beats/min, 112 +/- 4 mmHg, 5.3 +/- 0.8 mmHg, and 11,777 +/- 732 mmHg/s for heart rate, end-systolic and end-diastolic pressures, and maximum first derivative of ventricular pressure with respect to time (dP/dtmax), respectively. Catheter stroke volume during preload reduction by inferior vena caval occlusion correlated with that by ultrasound aortic flow probe (r2 = 0.98). This maneuver yielded end-systolic elastances of 79 +/- 21 mmHg/microliter, preload-recruitable stroke work of 82 +/- 5.6 mmHg, and slope of dP/dtmax-end-diastolic volume relation of 699 +/- 100 mmHg.s-1.microliter-1, and these relations varied predictably with acute inotropic interventions. The control normalized time-varying elastance curve was similar to human data, further supporting comparable chamber mechanics between species. This novel approach should greatly help assess cardiovascular function in the blood-perfused murine heart.

Animals↗
PubMed1998

Correlation between urinary epidermal growth factor excretion and serum thyroid hormone in premature and term neonates.

Eighty neonates, including 14 full-term, 31 premature, 27 twin or triplet, 6 small-for-gestational-age, and 2 infants with hyperthyroidism, were evaluated. The urinary epidermal growth factor/creatinine ratio (EGF/Cr) on the 1st postnatal day was not statistically different among full-term, premature, multiple-pregnancy, and small-for-gestational-age infants (F = 1.06, p = 0.6). There was no difference in urinary EGF/Cr between the 1st postnatal day and the 7th day (p = 0.4 by paired t test). The urinary EGF/Cr was not correlated with the serum thyroid-stimulating hormone level (r = -0.162, n = 60, p = 0.21), but showed a positive correlation with serum total T3 (r = 0.526, n = 60, p < 0.001) and with serum total T4 (r = 0.460, n = 60, p < 0.001). The correlation between urinary EGF/Cr and serum free T4 was even much better (r = 0.727, n = 25, p < 0.001). These results implicate that thyroid hormone may play a role in regulating urinary EGF excretion.

Creatinine↗
PubMed1998

Increased cesarean section rates and emerging patterns of health insurance in Shanghai, China.

OBJECTIVES: This study examined the trend in cesarean section deliveries and the factors associated with it in the Minhang District of Shanghai, China. METHODS: A representative sample of the members of 2716 households in the district were interviewed in the fall of 1993. This study analyzed the data from 1959 married women of reproductive age with at least one live birth. RESULTS: During the past 3 decades, the proportion of infants born by cesarean section increased from 4.7% to 22.5%. Logistic regression analysis revealed that the highest cesarean section rate, which occurred in the most recent period of 1988 through 1993, was associated with form of medical payment, self-reported complications during pregnancy, higher birthweight, and maternal age. Government insurance pays all costs of cesarean sections and accounted for the highest proportion of the cesarean section rate. CONCLUSIONS: The high rates of cesarean sections in China are surprising given the lack of the factors that usually lead to cesarean sections. The increasing cesarean section rates may be an early indication that emerging forms of health insurance and fee-for-service payments to physicians will lead to an excessive emphasis on costly, high-technology medical care in China.

Adolescent↗
PubMed1998

Torsion of a malignant undescended testis.

Cryptorchid testis have a greater risk of malignant change than do normally descended testis. The undescended testis would also be susceptible to torsion by the mechanism of increase in testicular size. A 36-year-old man of torsion of malignant undescended testis is presented. He was diagnosed as having incarcerated inguinal hernia on his first visit to general surgeon due to acute left lower abdominal pain. At laparotomy, a 7.5 x 5.5 x 3.0 cm3, greyish tan color mass was found. The pathological diagnosis is choricarcinoma and teratoma, mixed germ cell tumor. We would emphasise that in any patient presenting with acute abdominal symptoms and an absent scrotal testis, the possibility of a complication of torsion of undescended testis should be considered.

Adult↗
PubMed1998

Urinary endothelin-1 in children with acute renal failure of tubular origin.

To understand the changes of urinary endothelin-1 (ET-1) concentrations in acute renal failure (ARF) and to investigate the origin of human urinary ET-1, we studied urinary ET-1 excretion in 70 normal children and 12 children with ARF caused by tubular dysfunction. Urinary ET-1 excretion was expressed as a ratio of urinary ET-1 to urinary creatinine (ET-1/Cr). Among healthy children, the highest urinary ET-1/Cr values were found during infancy. In patients with ARF, there was a positive correlation between urinary ET-1/Cr values and daily total urinary ET-1 (r = 0.42, n = 26, p < 0.05). Plasma ET-1 concentrations were elevated in children with ARF during the period of peak serum creatinine concentration. During the course of ARF, the lowest urinary ET-1/Cr value occurred during the period of peak serum creatinine, whereas the plasma ET-1 concentration declined after the peak. These results provide insight into the developmental changes of urinary ET-1 values in normal children, and illustrate the pattern of changes in plasma and urinary ET-1 concentrations during the course of ARF in children. The results suggest that renal production, rather than clearance from the circulation by glomerular filtration, may be the source of urinary ET-1.

Acute Kidney Injury↗
PubMed1998

Outcome of Graves' disease after antithyroid drug treatment in Taiwan.

The outcome of Graves' disease after treatment with antithyroid drugs (ATDs) varies widely among countries, and large-scale studies in Asia are rare. We investigated the associations of various clinical and laboratory features with the outcome of ATD therapy for Graves' disease in Taiwan. A total of 210 patients (177 women, 33 men; mean +/- SD age, 41.7 +/- 15.1 yr) treated with ATD in Taiwan were included. ATD therapy started with methimazole 30 mg daily or propylthiouracil 300 mg daily and was continued until a euthyroid state was achieved. Afterwards, 154 patients received a maintenance dose of ATD alone, while 56 patients received a combination of an ATD and thyroxine (L-T4). Patients were considered to be in remission if they remained in a euthyroid state for more than 2 years after drug withdrawal. The mean follow-up periods were 45.0 +/- 20.9 months for patients with remission and 30.4 +/- 19.8 months for those with relapse. Relapse occurred in 126 (60%) patients during the follow-up period, within 3 months after drug withdrawal in 47 (37%), and within 6 months in 60 (46%). The relapse rate was 100% among patients with two or more previous relapses. Patients with a second occurrence had a higher relapse rate than those with a first occurrence (84% vs 43%). Past history of recurrence, goiter size, thyroid-stimulating hormone level and thyrotropin-binding inhibition immunoglobulin activity at the end of ATD treatment were independently associated with relapse. Prolonged duration of treatment did not yield better results in patients with larger goiters or a history of recurrence, or both. Combination therapy with L-T4 yielded similar results to those achieved with ATD treatment alone. In conclusion, the relapse rate of Graves' disease after ATD treatment in Taiwanese patients was high, especially in those with a history of recurrence. The treatment duration and drug regimen did not affect the outcome.

Adolescent↗
PubMed1998

Osseous choristoma of oral cavity--report of two cases and review of the literature.

Osseous choristoma of the oral cavity is an extremely rare lesion. Two cases of osseous choristomas of oral cavity, representing two different natures of such lesions are reported. One was situated on the dorsal surface of posterior tongue just anterior to the circumvallate papillae and the other on the right buccal mucosa just below the orifice of the Stensen's duct. To date, about 73 cases of oral osseous choristoma have been reported in the literature including the two present cases, of which, 61 and 8 cases occurred in the tongue and buccal mucosa, respectively. The clinical and microscopic characteristics, and their common sites of these peculiar lesions are presented. The origin and pathogenesis of the lesion are discussed and the literature on the subject is reviewed.

Adult↗
PubMed1997

Mediation of Sonic hedgehog-induced expression of COUP-TFII by a protein phosphatase.

A Sonic hedgehog (Shh) response element was identified in the chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) promoter that binds to a factor distinct from Gli, a gene known to mediate Shh signaling. Although this binding activity is specifically stimulated by Shh-N (amino-terminal signaling domain), it can also be unmasked with protein phosphatase treatment in the mouse cell line P19, and induction by Shh-N can be blocked by phosphatase inhibitors. Thus, Shh-N signaling may result in dephosphorylation of a target factor that is required for activation of COUP-TFII-, Islet1-, and Gli response element-dependent gene expression. This finding identifies another step in the Shh-N signaling pathway.

Animals↗
PubMed1997

The coatomer protein beta'-COP, a selective binding protein (RACK) for protein kinase Cepsilon.

Distinct subcellular localization of activated protein kinase C (PKC) isozymes is mediated by their binding to isozyme-specific RACKs (receptors for activated C-kinase). Our laboratory has previously isolated one such protein, RACK1, and demonstrated that this protein displays specificity for PKCbeta. We have recently shown that at least part of the PKCepsilon RACK-binding site on PKCepsilon lies within the unique V1 region of this isozyme (Johnson, J. A., Gray, M. O., Chen, C.-H., and Mochly-Rosen, D. (1996) J. Biol. Chem. 271, 24962-24966). Here, we have used the PKCepsilon V1 region to clone a PKCepsilon-selective RACK, which was identified as the COPI coatomer protein, beta'-COP. Similar to RACK1, beta'-COP contains seven repeats of the WD40 motif and fulfills the criteria previously established for RACKs. Activated PKCepsilon colocalizes with beta'-COP in cardiac myocytes and binds to Golgi membranes in a beta'-COP-dependent manner. A role for PKC in control of secretion has been previously suggested, but this is the first report of direct protein/protein interaction of PKCepsilon with a protein involved in vesicular trafficking.

Amino Acid Sequence↗
PubMed1997

Ontogeny of the immune system: gamma/delta and alpha/beta T cells migrate from thymus to the periphery in alternating waves.

The embryonic thymus is colonized by the influx of hemopoietic progenitors in waves. To characterize the T cell progeny of the initial colonization waves, we used intravenous adoptive transfer of bone marrow progenitors into congenic embryos. The experiments were performed in birds because intravenous cell infusions can be performed more efficiently in avian than in mammalian embryos. Progenitor cells, which entered the vascularized thymus via interlobular venules in the capsular region and capillaries located at the corticomedullary junction, homed to the outer cortex to begin thymocyte differentiation. The kinetics of differentiation and emigration of the T cell progeny were analyzed for the first three waves of progenitors. Each progenitor wave gave rise to gamma/delta T cells 3 d earlier than alpha/beta T cells. Although the flow of T cell migration from the thymus was uninterrupted, distinct colonization and differentiation kinetics defined three successive waves of gamma/delta and alpha/beta T cells that depart sequentially the thymus en route to the periphery. Each wave of precursors rearranged all three TCR Vgamma gene families, but displayed a variable repertoire. The data indicate a complex pattern of repertoire diversification by the progeny of founder thymocyte progenitors.

Adoptive Transfer↗
PubMed1997

B cells in the bursa of Fabricius express a novel C-type lectin gene.

The avian bursa of Fabricius provides an essential microenvironment for B cell development and Ab repertoire expansion by a gene conversion mechanism. To explore regulatory interactions between B lineage cells and the bursal microenvironment, we sought to identify genes encoding cell surface molecules selectively expressed on bursal B cells. We report in this work the identification of the chB1 gene that encodes a C-type lectin molecule that is a distant relative of the mammalian B cell differentiation Ag, CD72. The chB1 gene is expressed by intrabursal B cells and a B cell line, DT40, that also diversifies its Ig V region genes by gene conversion. Two forms of this type II membrane protein, differing in their cytoplasmic domains, are generated by the differential usage of two translational initiation sites. The longer chB1 isoform, which is the most abundant, contains a consensus immunoreceptor tyrosine-based inhibitory motif in its cytoplasmic domain. Cross-linkage of the chB1 molecules inhibits proliferation of bursal B cells and the DT40 cell line. The chB1 lectin-like molecule may thus modulate intrabursal B cell development.

Amino Acid Sequence↗
PubMed1997

Comparison of continuous left ventricular volumes by transthoracic two-dimensional digital echo quantification with simultaneous conductance catheter measurements in patients with cardiac diseases.

Automated border detection enables real-time tracking of left ventricular (LV) volume by 2-dimensional transthoracic echocardiography. This technique has not been previously compared with simultaneously measured continuous LV volumes at rest or during transients in humans. We performed 18 studies in 16 patients (age 50 +/- 15 years, range 22 to 70; ejection fraction 63 +/- 20%, range 15% to 85%) in which continuous LV volumes acquired by digital echo quantification (DEQ) were compared with simultaneous conductance catheter volume obtained by cardiac catheterization. Both volume signals were calibrated by thermodilution-derived cardiac output and ventriculogram-derived ejection fraction. Volume traces acquired at rest were averaged to generate a comparison cycle. The averaged volume waveforms acquired by DEQ and by conductance catheter were similar during all phases of the cardiac cycle and significantly correlated (conductance catheter = slope. DEQ + intercept, slope = 0.94 +/- 0.09, intercept = 5 +/- 8 ml, r2 = 0.86 +/- 0.12, all p <0.0001). Steady-state hemodynamic parameters calculated using either averaged volume signal were significantly correlated. Transient obstruction of the inferior vena cava yielded a 45 +/- 13% decrease in end-diastolic volume. Successful recordings of DEQ volume during preload reduction were obtained in only 50% of studies. End-diastolic volumes from the 2 methods were significantly correlated (mean slope 0.88 +/- 0.31, mean intercept 14 +/- 37 ml, average r2 = 0.89 +/- 0.11, all p <0.01), as were end-systolic volumes: mean slope 0.80 +/- 0.43, intercept = -20 +/- 26 ml, r2 = 0.67 +/- 0.18, all p <0.05). We conclude that automated border detection technique by DEQ is reliable for noninvasive, transthoracic, continuous tracking of LV volumes at steady state, but has limitations in use during preload reduction maneuvers in humans.

Adult↗
PubMed1997

Catfish thrombocytes express an integrin-like CD41/CD61 complex.

A thrombocyte-specific antigen was identified in two closely related catfish, Ictalurus punctatus and Ictalurus furcatus, by monoclonal antibodies 4-20 and 7-2. The antibodies immunoprecipitate two noncovalently associated glycoprotein chains of Mr 180,000 and Mr 95,000. Under reducing conditions the Mr 180,000 chain is resolved into Mr 150,000 and 32,000 subcomponents. Analysis of N-terminal amino acid sequences indicates homology of the Mr 95,000 chain with the beta3 integrin subunit and homology of the Mr 150,000 chain with the alphaIIb integrin subunit. These antibodies induce catfish thrombocyte aggregation and alteration of cell shape. The data indicate conservation of the megakaryocyte/platelet-restricted CD41/CD61 complex in bony fish.

Amino Acid Sequence↗
PubMed1997

The screening of 13 short tandem repeat loci in the Chinese population.

Population studies of 13 short tandem repeat (STR) loci were carried out on Chinese in Taiwan. The STR loci included HUMF13B, HUMF13A01, HUMFES/FPS, HUMFABP, HUMPLA2A1, HUMTPOX, HUMTH01, HUMVWFA31/A, HUMCSFIPO, HUMLPL, HUMGPP3A09, HUMCYAR04 and HUMCD4. DNA samples from 100 unrelated individuals were screened. The STR allele patterns were detected by the fluorescence detector of an automated DNA sequencer. Two PCR amplifications were performed for each STR locus in this study. The first PCR amplification strategy used 26 base pairs of the T7 sequence extension in the 5' end of the forward primer of each STR locus. The second PCR amplification used a dye-labeled T7 primer instead of the forward primer in the first PCR amplification, and the first PCR products as template to produce fluorescent dye-labeled PCR products. PCR products of different STR loci with overlapping allele sizes could be detected in the same lane of the polyacrylamide gel on an automated DNA sequencer using different colored dye-labeled T7 primers. There was no need to directly conjugate the fluorescent dye to individual STR primers. The PCR products were obtained using 2 ng of template DNA in 25 microliters of PCR reaction mixture. No deviations from the Hardy-Weinberg equilibrium were observed for the 13 STR loci. The distributions of these STR alleles were different from those of Caucasians or Blacks. The probability of matching from the combination of the 13 STR loci was 5.9 x 10(-10) for our Chinese population. However, HUMF13B, HUMLPL and HUMCD4 loci were not as highly polymorphic as observed in other populations.

Alleles↗