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Biomedical subjects

P C Cheng

Publications and source records attributed to P C Cheng.

At least 37 records · Page 2Linked to original sources
PubMed1991

Fungicidal effect of amphotericin B in urine: in vitro study to assess feasibility of bladder washout for localization of site of candiduria.

An in vitro study was performed to determine the optimum amphotericin B concentration and exposure time required to kill various strains of Candida albicans in urine. This is a preliminary study to assess the feasibility of using amphotericin B bladder washout for localization of the site of candiduria. In broth kinetic killing studies, amphotericin B at a concentration of greater than 100 micrograms/ml produced almost complete killing of 5 x 10(5) CFU of C. albicans per ml within 1.5 to 2 h. In urine studies (with various pH values, osmolalities, and electrolyte concentrations), amphotericin B at a concentration of 200 micrograms/ml with a 2-h exposure time decreased fungal counts of 21 strains of C. albicans from 5 x 10(6) to less than 200 CFU/ml. Bladder washout with greater than or equal to 200 micrograms of amphotericin B per ml and a dwell time of 2 h can therefore sufficiently sterilize the bladder of yeasts and may be a useful localization test.

Amphotericin B↗
PubMed1990

[Results of vascular reconstruction in lower limbs ischemia: a six-year clinical experience].

During the period between Dec. 1982 to Nov. 1988, a total of 412 patients with 471 limbs at risk of peripheral arterial occlusive disease underwent vascular surgical treatment at the Veterans General Hospital. There were 382 men and 30 women, who ranged in age from 20 to 84 years (mean 63.17 +/- 11.85 years). 95 cases were isolated aortoiliac occlusive disease, 94 cases were combined aortoiliac and femoropopliteal disease, 169 cases were femoropopliteal occlusive disease and 54 cases were femorotibialperoneal occlusive disease. Various reconstructive procedures were performed in the these patients. The cumulative limb salvage rate (LSR) exceeded cumulative patency rate (CPR) in all categories and the result of LSR and CPR were 97.6% and 91% for aortoiliac reconstructive surgery in six years, 96% and 77% for above-knee femoropopliteal saphenous vein bypass (SVB) in six years, 79% and 74% for below-knee femoropopliteal SBV and 63% and 34% for femoro-distal SVB in five years. 88% and 76% for above-knee femoropopliteal human umbilical vein (HUV) bypass in four years. 67% and 45% for femoro-distal HUV bypass in three years follow-up period individually. The immediate good symptomatic results of the vascular reconstruction was 88% encountered in isolated aortoiliac disease, 63% in combined aortoiliac and femoropopliteal disease, 70.4% in isolated femoropopliteal disease and only 26% in femorotibial-peroneal disease (FTP). No change symptoms was still higher (33%) in FTP than the other vascular reconstruction due to poor distal runoff in this series. The early postoperative mortality rate was 1.6%, the late mortality rate was 2.7%, the incidence of postoperative complication rate was 13.6%. The major lower limb amputation rate was low as 7% in our series.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Monitor unit calculations for breast or chest wall treatments.

Tangential breast fields always "flash" beyond the surface of the patient. Since the portion of the beam that is in air does not contribute scatter, external beam treatment planning computers that utilize stored beam data can lead to dose errors of up to 10%. These errors can be reduced by using an irregular field calculation program to adjust the monitor units to account for the loss of scatter.

Breast Neoplasms↗
PubMed1989

[Preliminary report on the clinical application of anti-Jo-1 antibody].

Jo-1 antigen was purified from the rabbit thymus acetone powder. Using it as antigen, we found anti-Jo-1 antibody in 25% of polymyositis, 7.1% in dermatomyositis, none in other connective tissue diseases nor non-connective tissue diseases. Other antinuclear antibodies, eg anti-RNP, anti-SSA were also found in our polymyositis-dermatomyositis patients. Our study suggested, the positivity of anti-Jo 1 antibody not only confirmed the patient's diagnosis of polymyositis but also demonstrated the autoimmune pathogenesis of this disease.

Antibodies, Antinuclear↗
PubMed1982

Formation of postsynaptic specializations induced by latex beads in cultured muscle cells.

An early event in the formation of neuromuscular junctions is an accumulation of acetylcholine receptors (AChRs) in the postsynaptic membrane. This concentration of receptors is essential for the establishment of the synaptic transmission. Previously, we showed that latex beads coated with positively charged polypeptide molecules can induce the formation of AChR clusters at the bead-muscle contacts (Peng, H. B., P.-C. Cheng, and P. W. Luther (1981) Nature 292: 831-834). In this study, we demonstrate that, in addition to AChR clusters, a set of postsynaptic specializations normally present at the adult neuromuscular junction also develops at the bead-muscle contacts in the absence of nerve. These specializations include the membrane-associated cytoplasmic density and its associated thin (6- to 8-nm) filaments, clusters of intramembranous particles, membrane invaginations, the basal lamina, and 60- to 100-nm coated vesicles. Our results indicate that the mechanism for the formation of the postsynaptic specializations is preprogramed in the muscle and can be triggered by an interaction with polypeptide-coated latex beads. Thus, this bead-muscle system can be used as a simple model for understanding the postsynaptic development during synaptogenesis.

Animals↗
PubMedDate not supplied

Half-scan cone-beam x-ray microtomography formula.

An x-ray shadow projection microtomographic system using a scannable point source is under development at AMIL-ARTS, SUNY at Buffalo. To overcome the limitations of the commonly used Feldkamp's cone-beam reconstruction formula, we have developed a generalized Feldkamp-type cone-beam reconstruction formula. In the generalized Feldkamp-type cone-beam reconstruction, a scanning locus can be either planar or helix-like, and a transaxial slice is reconstructed using projection data collected from a 360 degrees angular range (full scan). In this paper, the full-scan cone-beam formula is modified to require only projection data of approximate 180 degrees plus two fan-angles (half scan). First, a half-scan derivative-free noncircular fan-beam reconstruction formula is formulated. Then, a half-scan cone-beam reconstruction formula is derived as an extension of the half-scan fan-beam reconstruction formula using Feldkamp's procedure. Typical numerical simulation results are given for both half-scan formulae. Compared with the full-scan cone-beam formula, the half-scan cone-beam formula reduces the involved angular range of projection data and allows better longitudinal/temporal resolution.

Image Processing, Computer-Assisted↗
PubMedDate not supplied

Multiphoton confocal microscopy using a femtosecond Cr:forsterite laser.

With its output wavelength covering the infrared penetrating window of most biological tissues at 1,200-1,250 nm, the femtosecond Cr:forsterite laser shows high potential to serve as an excellent excitation source for the multiphoton fluorescence microscope. Its high output power, short optical pulse width, high stability, and low dispersion in fibers make it a perfect replacement for the currently widely used Ti:sapphire laser. In this paper, we study the capability of using a femtosecond Cr:forsterite laser in multiphoton scanning microscopy. We have performed the multiphoton excited photoluminescence spectrum measurement on several commonly used bioprobes using the 1,230 nm femtosecond pulses from a Cr:forsterite laser. Efficient fluorescence can be easily observed in these bioprobes through two-photon or three-photon excitation processes. These results will assist in the selection of dichroic beam splitter and band pass filters in a multiphoton microscopic system. We have also performed the autofluorescence spectrum measurement from chlorophylls in live leaves of the plant Arabidopsis thaliana excited by 1,230 nm femtosecond pulses from the Cr:forsterite laser. Bright luminescence from chlorophyll, centered at 673 and 728 nm, respectively, can be easily observed. Taking advantage of the bright two-photon photoluminescence from chlorophyll, we demonstrated the two-photon scanning paradermal and cross-sectional images of palisade mesophyll cells in live leaves of Arabidopsis thaliana.

Arabidopsis↗
PubMedDate not supplied

Comparison of the efficacy of cilofungin, fluconazole and amphotericin B in the treatment of systemic Candida albicans infection in the neutropenic mouse.

The relative efficacies of cilofungin, amphotericin B and fluconazole were compared in the treatment of systemic Candida albicans infection in neutropenic mice. Thirty-one day survival rates were lowest for cilofungin (14.6%), intermediate for amphotericin B (37.6%) and highest for fluconazole (50.5%). Residual tissue infection in surviving animals was observed with all agents, but was heaviest with fluconazole, especially in the kidneys.

Amphotericin B↗
PubMedDate not supplied

Visualization and interactive exploration of multidimensional confocal images.

A confocal image analysis system is developed for automatic extraction of surface representation of biological structures. A visualization system is also developed to manipulate these surface representations and to obtain morphometrical parameters and provides a powerful tool for biomedical research such as microstructural characterization, morphogenesis, cell differentiation, tissue organization, and embryo development.

3T3 Cells↗
PubMedDate not supplied

Tirapazamine plus cisplatin in advanced or recurrent carcinoma of the uterine cervix: a Southwest Oncology Group study.

The objective of this study was to determine objective response and overall survival (OS) and progression-free survival (PFS) following cisplatin plus tirapazamine treatment in eligible consenting patients with metastatic or recurrent squamous or adenosquamous carcinoma of the cervix. Treatment consisted of intravenous tirapazamine, 260 mg/m(2), followed by cisplatin, 75 mg/m(2), every 21 days for six cycles. Of 56 registered cases, 52 were evaluable for toxicity. There were six grade 4 toxicities (anemia [three], dyspnea [one], neutropenia/granulocytopenia [one], and dehydration [one]). Fifty-three patients were evaluable for response, OS, and PFS. The 6-month OS rate was 56.6% (95% CI 43.3-69.9%). The objective response rate was 32.1% (4 complete [2 confirmed and 2 unconfirmed] and 13 partial [8 confirmed and 5 unconfirmed]). Higher response rates (16/34 [47.1%] vs 1/19 [5.3%], P= 0.0018) were observed in patients who had not previously received radiation-sensitizing chemotherapy, as were OS and PFS (13.9 vs 4.0 months, P < 0.0001; 5.3 vs 1.8 months, P= 0.01). The OS was considered too low to warrant further testing in this disease setting. Despite this, tirapazamine plus cisplatin was active in patients who had not received cisplatin previously. Prior use of radiosensitizing chemotherapy impacted response and survival significantly and should be considered in future clinical trials.

Adult↗
PubMedDate not supplied

Unexpectedly large dose rate dependent output from a linear accelerator.

During our routine calibration of a Varian Clinac-20 linear accelerator, the absorbed dose for a fixed monitor unit (mu) was found to decrease with increasing dose rate. Between dose rates of 100 and 500 mu/min, there was up to 20% difference in absorbed dose for a 20-MeV electron beam. The cause of this problem was a failure in the electronics circuit of an integrating board. This paper presents our analysis of the problem and suggests a possible means of isolating such a failure to warn technologists, physicists, and engineers.

Biophysical Phenomena↗