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Biomedical subjects

H Chow

Publications and source records attributed to H Chow.

9 recordsLinked to original sources
PubMed1991

Microalgae as bioabsorbents for treating mixture of electroplating and sewage effluent.

The effectiveness of copper and nickel uptake by microalgae grown in the mixture of electroplating effluent and sewage was studied. The results showed that a high percentage of copper removal (68.1%-88.2%) was achieved by Chlorella pyrenoidosa (strain No. 26) reared in the mixture of 90% electroplating effluent and 10% raw sewage during the first 3 days despite the fact that cell growth was inhibited. Similar results were also obtained by using Chlorella HKBC-C3, another species collected from one of the heavy metal polluted sites in Hong Kong, isolated and cultured in the Biology Department. There was no significant difference (P greater than 0.05) in the removal of copper and nickel from the effluent between these 2 algal species. However, it was noted that removal of nickel from the mixture by the two species were comparatively lower (less than 20%) than the removal of copper (greater than 68%).

Absorption↗
PubMed1990

Uncertainty in dose estimation for gynecological implants.

One source of uncertainty in doses computed for intracavitary gynecological applications is the imprecision inherent in localizing the sources and the points of interest on radiographs of the implant and in transferring that data into the treatment planning computer. To quantify the effect of these activities on the accuracy of computed doses, five physicists and two dosimetrists performed computerized dose calculations on five applications chosen randomly from our patient files. For each of these applications, doses were computed at the traditional points A and B and at points in the bladder and rectum. Using identical sets of films, each planner located both the radioactive sources and points of interest, or only the sources, or only the points of interest. Another set of films was used to measure the accuracy of digitizing alone. Planners received no instructions on either the definition or the placement of the points of interest. Overall uncertainties in computed doses to points A and B and bladder were found to be about 7%. Uncertainty in dose to the rectum was on the order of 50%. Analysis of the results showed that about 1% of the error was due to digitization and about 2% to identification of source locations. Among the individual planners, almost all of the dose variation was from differences in placement of the points of interest on the implant radiographs. The results demonstrate the need for standard definitions and locations for points of calculation so that meaningful comparisons can be made among institutions.

Brachytherapy↗
PubMed1987

Colonoscopic therapy of acute pseudoobstruction of the colon.

All patients with the diagnosis of acute colonic pseudoobstruction at the University of California, Davis Medical Center from 1979-1985 were reviewed. These 25 patients were initially treated conservatively (nasogastric tube/rectal tube/enemas) and this was successful in eight of 25 patients (32%). The remaining 17 patients (68%) unresponsive to conservative therapy received endoscopic intervention, either colonoscopic suction decompression (CSD) or colonic suction decompression with proximal colonic tube placement (CDT) for continuous decompression. Of the endoscopic procedures performed, 13/17 (76%) resulted in successful acute decompression. Recurrences occurred in 6/13 (45%) (3/7 in the colonoscopic suction decompression group and three of six in the colonic tube placement group). In the 10 failures, six further procedures were attempted, but only one was successful. These patients were then treated conservatively. There were no instances of colonic perforation. Acute pseudoobstruction in our experience is a benign entity that can be safely and successfully treated nonsurgically. Colonoscopic suction decompression is often initially successful but has a high frequency of recurrence. Newer techniques to prevent recurrence, i.e., colonic tube placement, are of potential benefit but presently have technical problems.

Acute Disease↗
PubMed1985

Effect of pretreatment with cyclophosphamide on high-dose toxicity of melphalan in mice.

This study was undertaken to evaluate the effect of pretreatment (or priming) with cyclophosphamide (CY) on lethal toxicity of high-dose melphalan (MELPH) in mice. In C57BL/6 X DBA/2 F1 (hereafter called B6D2F1) mice given an injection of a single dose of CY, 50 mg/kg, 1-5 days before MELPH, 20 mg/kg, improved survival was noted in only one of five experiments. Reducing the challenge dose of MELPH to 17 mg/kg did not improve survival consistently. Priming with CY, 50 mg/kg, 3 days before a dose of MELPH, 20 mg/kg, did not improve survival in CBA/J or C57BL/6 mice. These results indicate that CY is an inconsistent priming agent for abrogating high-dose MELPH toxicity in mice. A slightly earlier recovery of regenerating hemopoietic and of jejunal crypt cells was noted in CY-primed B6D2F1 mice given injections of a low dose of MELPH, 15 mg/kg. The occasional improved animal survival noted in CY-primed B6D2F1 mice might be related to this earlier cell recovery.

Animals↗
PubMed1978

Photosynthetic pigments of green sulfur bacteria. The esterifying alcohols of bacteriochlorophylls c from Chlorobium limicola.

Bacteriochlorophyll c, the light-harvesting pigment from the green sulfur bacteria Chlorobium limicola, has been resolved into over a dozen chemically similar components by a new high pressure reversed-phase chromatographic procedure based on a stationary phase of polyethylene power. Detailed spectroscopic characterization of the resolved components has resulted in the identification of four different chlorins and six different esterifying alcohols. The major esterifying alcohol is trans, trans-farnesol, but smaller amounts of geranylgeraniol, tetrahydrogeranylgeraniol, phytol, cis-9-hexadecen-1-ol and 4-undecyl-2-furanmethanol are also observed. The high information content intrinsic in the compositional analyses of the complex pigment mixtures found in green sulfur bacteria appears to provide a new probe of the mechanisms of pigment biosynthesis in these organisms.

Alcohols↗
PubMedDate not supplied

Bacterial peritonitis following esophageal injection sclerotherapy for variceal hemorrhage.

Patients presenting with ascites and upper gastrointestinal hemorrhage were studied prospectively. Five patients presenting with acute variceal hemorrhage were found not to have pre-existing spontaneous bacterial peritonitis on initial paracentesis. However, three of these five developed findings compatible with bacterial peritonitis after sclerotherapy. Although the number of cases is small, our results support the monitoring of ascitic fluid after sclerotherapy.

Adult↗
PubMedDate not supplied

Dose delivery error detection by a computer-controlled linear accelerator.

A commercial dual photon energy, computer-controlled linear accelerator has a complex collimation and beam delivery system. For accurate dose delivery, six separate motorized elements must be properly positioned for a given beam selection. Experimentally instituted misalignments of the primary electron scattering foils, the primary collimator, the flattening filter, the scattering foil carousel, and the backscatter shield or shutter produced significant dose delivery errors. The ability of the Mylar window monitor chamber to detect these errors was examined for x-ray beams. The fault detection system failed to interrupt dose delivery in a number of situations where the error in dose per monitor unit delivered ranged from -6% to +270% of the calibrated value.

Computers↗
PubMedDate not supplied

Phosphorus in wine: comparison of atomic absorption spectrometry methods.

Phosphorus in wine may be determined directly or indirectly by atomic absorption spectrometry. The direct method uses the carbon rod atomizer as the excitation source and a phosphorus hollow cathode lamp. In the indirect determination, one measures the amount of molybdenum that will complex with phosphorus in the wine. Both nitrous oxide-acetylene and air-acetylene flames are suitable as atomization sources in this indirect method. The resultant data have been compared with those from the AOAC colorimetric method (11.032-11.034). A 2-sample comparison test showed the results to be insignificantly different at the 95% confidence limits.

Indicators and Reagents↗