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Biomedical subjects

T M Chen

Publications and source records attributed to T M Chen.

At least 73 records · Page 4Linked to original sources
PubMed1996

Metabolic fate of glucose in reversible low-flow ischemia of the isolated working rat heart.

The acute adaptation of myocardial glucose metabolism in response to low-flow ischemia and reperfusion was investigated in isolated working rat hearts perfused with bicarbonate saline containing glucose (10 mM) and insulin (40 microU/ml). Reversible low-flow ischemia was induced by reducing coronary perfusion pressure from 100 to 35 cmH2O. Tritiated glucose was used to assess rates of glucose transport and phosphorylation, flux from glucose to pyruvate, and oxidation of exogenous glucose. Rates of glycogen synthesis and glycolysis were also assessed. With ischemia, cardiac power decreased by more than two-thirds. Rates of glucose uptake and flux from glucose to pyruvate remained unchanged, while glucose oxidation declined by 61%. Rates of lactate release more than doubled, and fractional enrichment of glycogen remained the same. During reperfusion, glucose oxidation returned to the preischemic values. When isoproterenol was added during ischemia, glucose uptake increased, glycogen decreased, and lactate release increased. No effect was seen with pacing. We conclude that during low-flow ischemia and with glucose as the only exogenous substrate, net glucose uptake remains unchanged. There is a reversible redirection between glycolysis and glucose oxidation, while glycogen synthesis continues during ischemia and is enhanced with reperfusion.

Animals↗
PubMed1996

A new haemocompatible phospholipid polyurethane based on hydrogenated poly(isoprene) soft segment.

A new haemocompatible phospholipid polyurethane based on hydrogenated poly(isoprene) glycol (HPIP) and 4,4'-methylendiphenyl diisocyanate (MDI) was synthesized using 2-[bis(2-hydroxyethyl)methyl-ammonio]ethylstearylphosphate (BESP) and 1,4-butanediol (BD) as chain extender. The bulk and surface characteristics of this material was investigated by differential scanning calorimetry (DSC), dynamic viscoelasticity and tensile property measurements, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and contact angle measurement. This polymer possessed a hydrophobic surface revealed by contact angle measurement. The haemocompatibility of this polyurethane was evaluated by platelet rich plasma (PRP) contacting studies and scanning electron microscopy (SEM) observation using medical grade poly(vinyl chloride) (PVC) as the reference. The results show that this new polyurethane had relatively lower platelet adhesion and limited shape change for the attached platelets compared to PVC. The clotting time of the materials in contact with platelet poor plasma (PPP) was 99, 75, and 62 s and in contact with PRP was more than 240, 100, and 86 s for new polyurethane, PVC, and glass, respectively. This new phospholipid polyurethane is expected to have wide applications as coating or structural material for blood-contacting medical equipment due to its outstanding haemocompatibility and excellent mechanical strength.

Biocompatible Materials↗
PubMed1996

Endometrial stromal sarcoma of twenty cases.

BACKGROUND: Endometrial stromal sarcoma is a rare neoplasm. We reviewed twenty cases to study the characteristics of this disease. METHODS: Twenty cases of endometrial stromal sarcoma were treated at our hospital. The clinical stage, treatment and outcome were retrospectively analyzed. RESULTS: Endometrial stromal sarcoma comprised 4.3% of corpus cancers and 46.4% of uterine sarcomas at our hospital. Seven cases were stage I, one was stage II, ten were stage III, and two were stage IV at the time of diagnosis. Histopathologically, seventeen cases were classified as low-grade sarcoma and three were high-grade sarcoma. Seven patients had recurrence and five of them had already died of disease. Among these recurrent patients, one was stage II and six were stage III. All three patients with high-grade sarcoma and four with low-grade sarcoma had recurrence. CONCLUSIONS: We think mitotic count is an important prognostic factor in low-grade endometrial stromal sarcoma and high-grade endometrial stromal sarcoma has a poor prognosis even with post-operative adjuvant treatment.

Adjuvants, Pharmaceutic↗
PubMed1995

Clinical significance of intratumoral blood flow in cervical carcinoma assessed by color Doppler ultrasound.

BACKGROUND: Much evidence has suggested that vascular density reflects the clinical behavior of cancer. In this study, the intratumoral blood flow in cervical carcinomas was assessed by transvaginal color Doppler ultrasound, and its clinical significance was evaluated. METHODS: Sixty-five patients with Stage Ib-IIb cervical carcinoma exhibiting visible cervical tumor by transvaginal ultrasound were enrolled. All patients were scheduled for radical hysterectomy and pelvic lymph node dissection. Transvaginal color Doppler ultrasound was performed before surgery to search for blood flow signals from the tumor and the main uterine artery. The corresponding arterial resistance index (RI) was calculated. Clinical and pathologic data were recorded. A cytokinetic study was performed by propidium iodide staining and flow cytometry. The human papillomavirus (HPV) status was assessed by polymerase chain reaction. RESULTS: Intratumoral blood flow was detected by color Doppler ultrasound in 46.2% (30/65) of the tumors. Patients with detectable intratumoral blood flow exhibited significantly more pelvic lymph node metastasis (10/30 vs. 2/35, P = 0.005), a higher percentage of cancer cells in the S- + G2M-phase (30.02 +/- 18.54% vs. 19.35 +/- 11.21%, P < 0.005), and a higher prevalence of HPV infection (30/30 vs. 25/35, P = 0.001) when compared with those without intratumoral blood flow. No significant difference was observed concerning the patient's age, tumor size, clinical staging, histologic type, and DNA ploidy status between these two groups. Regression analysis of the intratumoral RI value on the S- + G2M-phase fraction showed linear regression (n = 30, r2 = 0.501, P < 0.01). The RI values of the main uterine artery showed no significant difference between these two groups. CONCLUSION: The intratumoral blood flow by transvaginal color Doppler ultrasound correlated well with a higher proliferation index, higher incidence of HPV infection, and pelvic lymph node metastasis in cervical carcinoma.

Adult↗
PubMed1995

Regional skin blood flow in deep burn wounds: a preliminary report.

Local skin blood flow (LSBF) using the Walker's deep burn rat model was studied on the first three postburn days using the carbon-14 iodoantipyrine ([14C]IAP) perfusion method. The radioactive [14C]IAP (12.5 microCi) was infused through the femoral vein over a period of 30 seconds and the blood samples were collected by a free flow from the femoral artery at 5-s intervals to evaluate the concentration of the isotope, in the blood. At the conclusion of the infusion, the rats were guillotined and biopsies were obtained from the burned skin, unburned skin from burned rats and skin from sham control rats to assay the isotope in the skin. The LSBF was calculated from the skin tissue and plasma radioactivity data using Jay's equation. The results showed significant decreases of the skin blood flow in the deep burn wound with 4.05 +/- 1.16, 5.31 +/- 1.32 and 4.77 +/- 2.48 ml/100 g/min as compared to the LSBF of unburned skin 10.27 +/- 1.49, 12.39 +/- 2.05, 14.79 +/- 1.85 ml/100 g/min on postburn days 1, 2 and 3 (P < 0.05). The blood flow of the control group skin was 11.5 +/- 1.97 ml/100 g/min (P < 0.05). There were also significant differences of LSBF among burn wounds on postburn days 1, 2 and 3 (P < 0.05). Pathological study of the deep burn wound showed that more of the blood flow was in the subcutaneous adjacent areolar tissue, than in the deep reticular dermis, and only a little occurred in the upper reticular dermis occasionally.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Human keratinocyte culture using porcine pituitary extract in serum-free medium.

Extensive burn wound coverage remains a major problem in acute and reconstructive stages due to shortage of autologous skin donor sites. Many reports have described successful coverage of extensive burn wounds by using cultured keratinocytes sheet graft alone or overlaying a glycosaminoglycan substrate, allodermis or xenodermis. In our experience, the use of Boyce and Ham's serum-free medium made the preparation of keratinocyte cultures simple and the cell growth was prompt. In this study, one of the supplements in Boyce's culture medium, the bovine pituitary extract (BPE at concentration of 140 micrograms/ml), was replaced by different concentrations of fresh frozen porcine pituitary extract (PPE). The protein concentration of the original preparation of PPE was also 140 micrograms/ml but in which 375 +/- 21 pg/ml (1/10 dilution) of platelet-derived growth factor (PDGF) was detected by immunoassay (PDGF ELISA). Our results proved that PPE is an ideal supplement for the in vitro growth of keratinocytes, and when its protein concentration is 350 micrograms/ml will induce a significant keratinocyte growth by day 9 when compared to the regular BPE and also to the other concentrations of PPE (P < 0.05).

Animals↗
PubMed1995

Analysis of (R)-4-oxo-5-phosphononorvaline (MDL 100,453) in rat plasma and brain dialysate using liquid chromatography after derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate.

A liquid chromatographic (LC) method with precolumn derivatization and fluorescence detection has been developed for the quantitation of (R)-4-oxo-5-phosphononorvaline (MDL 100,453), which is a selective antagonist of N-methyl-D-aspartate receptor, in rat plasma and brain dialysate. The plasma samples were deproteinized with acetonitrile and then derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC). The brain dialysis samples were dried in vacuum, reconstituted with borate buffer, and derivatized with AQC. The derivatized MDL 100,453 was analyzed by LC with a Nova-Pak C18 column at 32 degrees C using a gradient mobile phase. Detection was accomplished by fluorescence with excitation at 250 nm and emission at 395 nm. This analytical method was used to follow the time course of drug concentrations in rat plasma and brain dialysate after intravenous (i.v.) bolus injection of MDL 100,453 or a combination of i.v. bolus injection and i.v. infusion.

Aminoquinolines↗
PubMed1994

Inhibition of human neutrophil elastase with peptidyl electrophilic ketones. 2. Orally active PG-Val-Pro-Val pentafluoroethyl ketones.

Valylprolyvalyl pentafluoroethyl ketones with different N-protecting groups were evaluated in vitro and in vivo as inhibitors of human neutrophil elastase (HNE). Several of these compounds were found to be orally active in HNE-induced rat and hamster lung hemorrhage models. The compound with 4-(4-morpholinylcarbonyl)benzoyl as the protecting group, 71 (MDL 101,146), was studied in greater detail. Hydration and epimerization studies were performed on 71 and related compounds in various media, including human blood serum. High-performance liquid chromatography studies on a reversed-phase system as a measure of the lipophilicity of 71 and related compounds revealed a small range of relative retention times wherein the orally active compounds fell. The Ki value determined for 71 vs HNE was 25 nM.

Administration, Oral↗
PubMed1994

Vascular patterns of gestational trophoblastic tumors by color Doppler ultrasound.

BACKGROUND: Destruction of uterine vasculature is a common phenomenon in gestational trophoblastic tumors. The authors categorized such uterine vasculature by color Doppler ultrasound and studied its clinical significance. METHODS: Color Doppler ultrasound was performed in 28 patients with gestational trophoblastic tumors. The vascular morphologic manifestations were recorded, and the peak systolic velocity and resistance index of uterine artery were calculated. Serum beta-human chorionic gonadotropin (hCG) levels were measured periodically to monitor chemotherapy response. Seventeen uneventful postmole uteri were used as controls. Two-tailed Student's t-test and Fisher's exact test were used for statistical analysis. RESULTS: The gestational trophoblastic tumors were categorized as diffuse type (N = 7), lacunar type (N = 16), and compact type (n = 5) according to their vascular patterns. The mean serum beta-hCG level at diagnosis in diffuse type lesions (6608 +/- 6320 mIU/mL) was significantly lower than in the lacunar type (40462 +/- 39735 mIU/mL; P = 0.04) and compact type (212114 +/- 205126 mIU/mL; P = 0.02), whereas the level in compact type lesions was significantly higher than in the lacunar type (P = 0.003). Lacunar type lesions exhibited a significantly lower uterine artery resistance index (0.51 +/- 0.13) than diffuse type (0.66 +/- 0.10; P = 0.03) or compact type lesions (0.70 +/- 0.06; P = 0.02). All lesions exhibited significantly higher peak systolic velocity than control subjects (P < 0.001); however, no significant difference was observed among them. Brief courses (< 5 cycles) of chemotherapy cured more diffuse type (6 of 7) than lacunar type (3 of 15, P = 0.006) or compact type lesions (0 of 5, P = 0.008). Histopathologic diagnosis was available for 11 lesions. They were invasive mole in seven lacunar type lesions and choriocarcinoma in four compact type lesions. CONCLUSION: Vascular morphologic patterns of gestational trophoblastic tumors by color Doppler ultrasound correlated well with beta-hCG levels, uterine hemodynamics, chemotherapy response, and possibly the histopathologic diagnosis.

Arteries↗
PubMed1994

Cell kinetics and radiosensitivity of cervical squamous cell carcinoma.

Flow cytometry analyses of tumors from 12 patients with cervical squamous cell carcinoma under radiotherapy were performed in this preliminary study. Six patients with a high (> 10%) G2/M fraction before treatment showed greater than 50% tumor reduction after initial 2000 cGy radiotherapy. Only two out of six patients with a low (< 10%) G2/M fraction before treatment responded favorably and three of them already had recurrence during the follow-up period of 33-40 months. Hyperploidy (DNA index > 1.1) was observed in 5 patients; all of them responded well to radiotherapy in contrast to three out of seven diploid tumors.

Carcinoma, Squamous Cell↗
PubMed1994

Determination of MDL 74,405, a synthetic analogue of alpha-tocopherol, in dog plasma and heart tissue by high-performance liquid chromatography with electrochemical detection.

A high-performance liquid chromatographic (HPLC) procedure with electrochemical detection was developed to analyze MDL 74,405 (I), the (-)-(S)-enantiomer of an alpha-tocopherol analogue, in dog plasma and heart tissue after infusion (0.3 mg/kg/h). The sample preparation involved the addition of an internal standard to either the dog plasma and heart tissue prior to protein precipitation. After centrifugation, the resulting supernatant was directly analyzed by HPLC with a Zorbax Rx C8 column and a mobile phase of acetonitrile-0.04 M potassium phosphate, pH 7.0 (70:30, v/v). The concentration of I found was ca. 100 ng/ml in plasma and ca. 3 micrograms/g in heart tissue. A chiral separation with an Ultron ES-OVM column and a mobile phase of methanol-0.025 M potassium phosphate, pH 6.5 (17:83, v/v) was also used to investigate the enantiomeric conversion of I. Preliminary results of a probe study indicated that I is not inverted to the (+)-(R)-enantiomer in vivo.

Animals↗
PubMed1994

The genotypes and prognostic significance of human papillomaviruses in cervical cancer.

An integrated study on the role of human papillomaviruses (HPV) in cervical cancer has been conducted. Out of a total of 433 cases of cervical cancer, HPV-DNA was detected in 342 (79%) using the polymerase chain reaction (PCR). The incidence of HPV infection was not significantly related to histological types, although a lower incidence was noted in adenocarcinoma cases. The incidence of lymph node (LN) metastasis in adenosquamous carcinoma (55.6%) was significantly higher than in squamous cell carcinoma (SCC) and adenocarcinoma. HPV 16 was detected significantly more often in SCC than in adenocarcinoma. In contrast, HPV 18 was detected more often in adenocarcinoma than in SCC. As a whole, pelvic LN metastases were found in 24.3% of HPV+ cases, significantly higher than 11% of HPV- cases. However, the significant association of HPV-DNA with LN metastasis was only noted in stage I but not stage II. As far as histological types were concerned, the incidence of positive LN was: HPV+ SCC > HPV- SCC (p < 0.01), whereas HPV- adenocarcinoma > HPV+ adenocarcinoma (p = 0.12). Genotypes of HPV did not have any effect on nodal status. The presence of types of HPV were not associated with tumor size and distribution of clinical stage. Our results suggest that the prognostic significance of HPV-DNA on nodal status is dependent on histological types while the genotypes of HPV cannot account for prognostic significance in cervical cancer.

Adult↗
PubMed1994

Incremental angiogenesis assessed by color Doppler ultrasound in the tumorigenesis of ovarian neoplasms.

BACKGROUND: The crucial role of angiogenesis in tumor behaviour has been studied extensively in vitro. The authors assessed the in vivo angiogenesis in ovarian neoplasms by color Doppler ultrasound and waveform analysis. METHODS: The intratumor artery resistance index (RI) of 222 ovarian neoplasms referred for color Doppler ultrasound evaluation was measured, and the corresponding histopathologic diagnosis was recorded. RESULTS: Satisfactory intratumor artery waveforms were obtained at an average of 1.12 sites in 44.7% (68 of 152) of benign tumors and at 6.28 sites in 97.1% (68 of 70) of the malignant group. Great heterogeneity in RI values existed. The RI of the intratumor artery in the benign group during the follicular phase (mean, 0.678) was significantly higher (P < 0.001) than that of the luteal phase (mean, 0.414), epithelial ovarian carcinoma (n = 34; mean, 0.402), malignant germ cell tumor (n = 6; mean, 0.413), malignancy metastasized to the ovary (n = 18; mean, 0.357), and other rare malignancies (n = 4; mean, 0.435). The RI of primary ovarian malignancy (n = 41; mean, 0.411) was significantly higher than that of malignancy metastasized to the ovary (P < 0.05). The RI values of epithelium-originated neoplasms showed a significant incremental decrease from benign tumors (n = 48; mean, 0.695) toward borderline malignancy (n = 6; mean, 0.535; P < 0.01), early-stage ovarian carcinoma (n = 10; mean, 0.485; P < 0.01), and, finally, to advanced-stage ovarian malignancies (n = 29; mean, 0.398; P < 0.05). CONCLUSIONS: Angiogenesis is a common phenomenon in malignant ovarian neoplasms, but the intensity of neovascularization may depend on individual tumor characteristics. The authors documented the incremental decrease of the resistance index in ovarian neoplasms, which may reflect the increase in angiogenesis intensity as an indication of malignant potential.

Adolescent↗
PubMed1994

Human papillomavirus DNA and p53 status in stage IB bulky cervical cancer.

We used the polymerase chain reaction (PCR) to study the presence and typing of human papillomavirus (HPV) DNA, and PCR/single-strand confirmation polymorphism to survey the mutations of the p53 gene in exons 5-9 in 26 bulky stage IB cervical cancers. The HPV DNA was present in 20 out of the 21 (95%) squamous-cell carcinoma tissues, including 13 cases of HPV-16, 0 case of HPV-18, and 7 cases of other HPV types. In the other 5 adenocarcinoma tissues, 3 had HPV type-18 DNA and 2 had no detectable HPV DNA. The distribution of HPV DNA in bulky tumors was not statistically different from that in the other 228 squamous-cell carcinomas and 23 adenocarcinomas of smaller size operated upon during the same period. Out of the 26 patients, 9 (35%) had lymph node metastasis at the time of operation. During the follow-up period ranging from 19 to 48 months, 9 patients had recurrence and 7 of them died of disease. The distribution of HPV types was not related to the prognosis in these patients. There were no p53 mutations detected in all the 26 samples. Thus, HPV type and the status of p53 could not serve as additional prognostic factors in stage IB bulky cervical cancers.

Adenocarcinoma↗
PubMed1994

Effects of E5a and E7 genes of human papillomavirus type 11 on immortalized human epidermal keratinocytes and NIH 3T3 cells.

The E5a gene of HPV-11 expressed in NIH 3T3 cells led to tumorigenesis in nude mice; whereas when expressed in keratinocytes, E5a induced anchorage independent growth, but was nontumorigenic in nude mice. The E7 gene of HPV-11 expressed NIH 3T3 cells led to tumors in nude mice and morphological transformation, but not anchorage independent growth. Keratinocytes expressing the E7 gene induced colony formation in soft agarose, but not tumorigenesis in nude mice. Comparison of transforming activities of HPV-11 E5a and E7 genes of HPV-11 showed that the efficiency of cell transformation by E7 was weaker than that of E5a.

3T3 Cells↗
PubMed1994

Aqueous stability of human epidermal growth factor 1-48.

Human epidermal growth factor 1-48 (hEGF 1-48, Des(49-53)hEGF) is a single chain polypeptide (48 amino acids; 3 disulfide bonds; 5445 Da) possessing a broad spectrum of biologic activity including the stimulation of cell proliferation and tissue growth. In this study, three primary aqueous degradation products of hEGF 1-48 were isolated using isocratic, reverse phase/ion-pair HPLC. The degradation products were characterized using amino acid sequencing, electrospray ionization mass spectrometry, isoelectric focusing, and degradation kinetics. Results indicate that hEGF 1-48 degrades via oxidation (Met21), deamidation (Asn1), and succinimide formation (Asp11). The relative contribution of each degradation pathway to the overall stability of hEGF 1-48 changes as a function of solution pH and storage condition. Succinimide formation at Asp11 is favored at pH < 6 in which aspartic acid is present mostly in its protonated form. Deamidation of Asn1 is favored at pH > 6. The relative contribution of Met21 oxidation is increased with decreasing temperature, storage as a frozen solution (-20 degrees C), and exposure to fluorescent light.

Amino Acid Sequence↗
PubMed1994

Infrequent mutation in tumor suppressor gene p53 in gestational trophoblastic neoplasia.

In order to determine the p53 status of gestational trophoblastic neoplasia, 24 cases of molar pregnancies and two choriocarcinoma cell lines (JAR and JEG-3) were evaluated for the presence of mutations. The evaluation involved the whole coding sequence (i.e. exons 2-11) of the p53 gene with polymerase chain reaction (PCR) amplification of genomic DNA, followed by single strand conformation polymorphism (SSCP) and sequencing. Only one case of hydatidiform mole was found to have a missense point mutation (codon 295, CCT-->CTT, i.e. proline to leucine) of the p53 gene. The results suggest that p53 mutation is rarely involved in the pathogenesis of gestational trophoblastic neoplasia.

Base Sequence↗