Biomedical subjects

P C Tseng

Publications and source records attributed to P C Tseng.

11 recordsLinked to original sources

PubMed1998

A unique high-performance wide-range (10-1500 eV) spherical grating monochromator beamline.

A wide-spectral-range high-performance 6 m-spherical grating monochromator (6 m-SGM) beamline has been designed and is under construction at SRRC. Two different entrance slits, instead of additional mirrors, are used to optimize the overall performance. Six gratings are used to cover photon energies from 10 to 1500 eV. Movable entrance slits and bendable vertical focusing mirrors are used to enhance further the beamline performance. A bendable horizontal focusing mirror is used to improve the resolution and to focus the photon beam at the experimental station immediately after the exit slit. Several end-stations can be installed at the same time to utilize the beam time fully. The expected energy-resolving power, with both slit openings set at 10 micro m, is up to 15 000 and 40 000 for the high- and low-energy branches, respectively. A photon flux of 1 x 10(11) photons s(-1) can be obtained with an energy-resolving power of 20 000.

Journal Article↗

PubMed1998

A high-performance wide-range beamline for elliptically polarized undulator source.

A high-performance wide-range beamline has been designed for monochromatizing circularly polarized photons with energies from 10 to 1400 eV. A grazing SGM-based beamline with two entrance slits has been employed to optimize the performance. The degree of the circular polarization affected by the beamline optics has been analysed. The horizontal and vertical refocusing mirrors have been specially arranged to improve greatly the polarization degree in the low-energy region. By connecting this beamline to a high-efficiency elliptically polarized undulator, this beamline should be able to provide, in the entire energy range, intensive and high-resolution photons of a high degree of circular polarization.

Journal Article↗

PubMed1998

Design of a high-flux and high-resolution VUV bending-magnet beamline.

A high-flux and high-resolution VUV beamline (4-40 eV) has been designed and is under construction at SRRC. This beamline, which collects 50 mrad of horizontal radiation, uses a 6 m cylindrical-grating monochromator with an incident angle of 70 degrees instead of the conventional normal-incidence-monochromator (NIM) design. Special features, such as movable entrance slit, bendable vertical focusing mirror and movable curved exit slit, are employed to enhance greatly the beamline performance. With both slit openings set at 10 micro m, the energy-resolving power can reach as high as 70000. Photon fluxes of 1 x 10(13) and 1 x 10(10) photons s(-1) are calculated for energy-resolving powers of 1000 and 40000, respectively. The best image size at the sample position is smaller than 0.45 x 0.2 mm.

Journal Article↗

PubMed1994

Experience with the intravenous totally implanted port in patients with gynecologic malignancies.

The purpose of this paper was to assess the intraoperative and long-term complications associated with intravenous totally implanted devices in women with pelvic cancers. Retrospective review of medical records was performed for 67 consecutive women with pelvic cancers who underwent port insertion. Seventy catheters were successfully placed in 67 patients. Pneumothorax occurred in three cases (4.3%), none requiring chest tube placement. Malposition of the catheter occurred in four patients (5.7%). Two infected ports (2.9%) were removed after a failed trial of antibiotics. Venous thrombosis developed in one woman, requiring removal of the system. In conclusion, semipermanent central venous catheters facilitate delivery of chemotherapy, parenteral nutrition, blood products, antibiotics, and hydration in cancer patients. This is the first report detailing the experience with a totally implanted subcutaneous port in patients with gynecologic malignancies. We demonstrate that such devices may be inserted and utilized with a low incidence of complications in this patient population.

Adolescent↗

PubMed1992

Ovarian cancer staging: does it require a gynecologic oncologist?

Forty-seven patients with presumed Stages I-II invasive ovarian epithelial carcinoma were treated with intravenous 50 mg/m2 cis-platinum, for 2-18 cycles (median, 9), 50 mg/m2 doxorubicin for 2-14 cycles (median, 9), and/or 600 mg/m2 cyclophosphamide for 2-14 cycles (median, 6) after surgical staging by a gynecologic oncologist or a nononcologic surgeon. Mean follow-up is 6.8 years. Cumulative 5-year actuarial survival is 73 +/- 6%; 75 +/- 12% for Stage I and 71 +/- 8% for Stage II disease. When screened for poor prognosticators, only the specialty of the operating surgeon was identified (P < 0.05). Five-year actuarial survival and disease-free survival, respectively, for Stages I-II patients surgically staged by a gynecologic oncologist were 83 +/- 7% and 76 +/- 8%, compared to 59 +/- 11% (P < 0.05) and 39 +/- 11% (P < 0.03) for the group operated upon by a nononcologist.

Actuarial Analysis↗

PubMed1991

Adjuvant whole-abdominal radiation therapy in uterine papillary serous carcinoma.

Nine patients from 34 to 74 years of age (median, 67 years of age) with uterine papillary serous carcinoma (UPSC) were treated with whole-abdominal radiation therapy (WART) on an adjuvant basis after cytoreductive surgery. All patients were treated with megavoltage photons to an abdominopelvic field to a median dose of 2500 cGy, with continued treatment to a whole pelvic field to a median dose of 4500 cGy. Three patients received additional boost to the vaginal apex. Follow-up time ranged from 6 to 31 months (median, 25 months) after completion of WART. Six patients had recurrent disease at 5 to 20 months (median, 7.5 months). Four of these patients died of their disease during the follow-up period. Three of six patients in whom treatment failed had disease at the vaginal apex. None of these patients received boost radiation therapy to that site. In contrast, two of three patients remaining disease free were treated with additional vaginal apex irradiation. Based on these results, the authors do not routinely recommend WART for adjuvant treatment of UPSC. They do, however, recommend vaginal apex irradiation for these patients.

Adult↗

PubMed1989

CA 125, NB/70K, and lipid-associated sialic acid in monitoring uterine papillary serous carcinoma.

Ninety-four plasma samples from 18 women with uterine papillary serous carcinoma were analyzed for three circulating tumor markers: CA 125, NB/70K, and lipid-associated sialic acid. Tumor marker values were correlated with the patients' clinical status. Preoperatively, CA 125, NB/70K, and lipid-associated sialic acid were elevated in 62, 64, and 67%, respectively. The distribution of clinical stages was I -- 56%, II -- 28%, III -- 6%, and IV -- 11%. The distribution of surgical stages was I -- 28%, II -- 17%, III -- 0%, and IV -- 56%. Nine of ten patients with an elevated tumor marker had extrauterine disease confirmed surgically. Eight of nine patients with elevated levels of two markers had extrauterine disease. Four of four patients with three elevated markers had extrauterine disease. There were two false-positive elevations, both in patients who had occult surgical stage II disease. Rising and falling tumor marker levels correlated with progression and regression of disease, respectively. A doubling of CA 125 predicted clinical recurrence in four of six women an average of 17 weeks before clinical confirmation. Lipid-associated sialic acid levels that increased by 25% or by five units predicted recurrence or rapid progression in three of six patients in an average of 5 weeks, and a 50% elevation in NB/70K predicted recurrence in two of three patients by 5 and 3 weeks before clinical confirmation. Although the number of patients in this series is small, preoperative elevated tumor markers in patients known to have uterine papillary serous carcinoma correlate closely with the presence of extrauterine disease. This information should influence surgical management and may be useful in postsurgical treatment assessment.

Aged↗

PubMed1986

Characterization of alpha-actinin from Acanthamoeba.

Characterization of a protein from Acanthamoeba that was originally called gelation protein [T.D. Pollard, J. Biol. Chem. 256:7666-7670, 1981] has shown that it resembles the actin filament cross-linking protein, alpha-actinin, found in other cells. It comprises about 1.5% of the total amoeba protein and can be purified by chromatography with a yield of 13%. The native protein has a molecular weight of 180,000 and consists of two polypeptides of 90,000 Da. The Stokes' radius is 8.5 nm, the intrinsic viscosity is 0.35 dl/dm, and the extinction coefficient at 280 mm is 1.8 X 10(5)M-1 X cm-1. Electron micrographs of shadowed specimens show that the molecule is a rod 48 nm long and 7 nm wide with globular domains at both ends and in the middle of the shaft. On gel electrophoresis in sodium dodecylsulfate the pure protein can run as bands with apparent molecular weights of 60,000, 90,000, 95,000, or 134,000 depending on the method of sample preparation. Rabbit antibodies to electrophoretically purified Acanthamoeba alpha-actinin polypeptides react with all of these electrophoretic variants in samples of purified protein and cell extracts. By indirect fluorescent antibody staining of fixed amoebas, alpha-actinin is distributed throughout the cytoplasmic matrix and concentrated in the hyaline cytoplasm of the cortex. The protein cross-links actin filaments in the presence and absence of Ca++. It inhibits slightly the time course of the spontaneous polymerization of actin monomers but has no effect on the critical concentration for actin polymerization even though it increases the apparent rate of elongation to a small extent. Like some other cross-linking proteins, amoeba alpha-actinin inhibits the actin-activated ATPase of muscle myosin subfragment-1. Although Acanthamoeba alpha-actinin resembles the alpha-actinin from other cells in shape and ability to cross-link actin filaments, antibodies to amoeba and smooth muscle alpha-actinins do not cross react and there are substantial differences in the amino acid compositions and molecular dimensions.

Actinin↗

PubMed1984

Physical, immunochemical, and functional properties of Acanthamoeba profilin.

Acanthamoebe profilin has a native molecular weight of 11,700 as measured by sedimentation equilibrium ultracentrifugation and an extinction coefficient at 280 nm of 1.4 X 10(4) M-1cm-1. Rabbit antibodies against Acanthamoeba profilin react only with the 11,700 Mr polypeptide among all other ameba polypeptides separated by electrophoresis. These antibodies react with a 11,700 Mr polypeptide in Physarum but not with any proteins of Dictyostelium or Naeglaria. Antibody-binding assays indicate that approximately 2% of the ameba protein is profilin and that the concentration of profilin is approximately 100 mumol/liter cells. During ion exchange chromatography of soluble extracts of Acanthamoeba on DEAE-cellulose, the immunoreactive profilin splits into two fractions: an unbound fraction previously identified by Reichstein and Korn (1979, J. Biol. Chem., 254:6174-6179) and a tightly bound fraction. Purified profilin from the two fractions is identical by all criteria tested. The tightly bound fraction is likely to be attached indirectly to the DEAE, perhaps by association with actin. By fluorescent antibody staining, profilin is distributed uniformly throughout the cytoplasmic matrix of Acanthamoeba. In 50 mM KCl, high concentrations of Acanthamoeba profilin inhibit the elongation rate of muscle actin filaments measured directly by electron microscopy, but the effect is minimal in KCl with 2 MgCl2. By using the fluorescence change of pyrene-labeled Acanthamoeba actin to assay for polymerization, we confirmed our earlier observation (Tseng, P. C.-H., and T. D. Pollard, 1982, J. Cell Biol. 94:213-218) that Acanthamoeba profilin inhibits nucleation much more strongly than elongation under physiological conditions.

Actins↗

PubMed1982

Actin and myosin function in acanthamoeba.

We have studied the functions of contractile proteins in Acanthamoeba by a combination of structural, biochemical and physiological approaches. We used electron microscopy and image processing to determine the three-dimensional structure of actin and the orientation of the molecule in the actin filament. We measured the rate constants for actin filament elongation and re-evaluated the effect of MgCl2 on the filament nucleation process. In Acanthamoeba actin polymerization is regulated, at least in part, by profilin, which binds to actin monomers, and by capping protein, which both nucleates polymerization and blocks monomer addition at the 'barbed' end of the filament. To test for physiological functions of myosin-II, we produced a monoclonal antibody that inhibits the actin-activated ATPase. When microinjected into living cells, this active-site-specific antibody inhibits amoeboid locomotion. We expect that similar experiments can be used to test for the physiological functions of the other components of the Acanthamoeba contractile system.

Actins↗

PubMed1982

Mechanism of action of Acanthamoeba profilin: demonstration of actin species specificity and regulation by micromolar concentrations of MgCl2.

Acanthamoeba profilin strongly inhibits in a concentration-dependent fashion the rate and extent of Acanthamoeba actin polymerization in 50 mM KCl. The lag phase is prolonged indicating reduction in the rate of nucleus formation. The elongation rates at both the barbed and pointed ends of growing filaments are inhibited. At steady state, profilin increases the critical concentration for polymerization but has no effect on the reduced viscosity above the critical concentration. Addition of profilin to polymerized actin causes it to depolymerize until a new steady-state, dependent on profilin concentration, is achieved. These effects of profilin can be explained by the formation of a 1:1 complex with actin with a dissociation constant of 1 to 4 microM. MgCl2 strongly inhibits these effects of profilin, most likely by binding to the high-affinity divalent cation site on the actin. Acanthamoeba profilin has similar but weaker effects on muscle actin, requiring 5 to 10 times more profilin than with amoeba actin.

Actins↗