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Biomedical subjects

A Wu

Publications and source records attributed to A Wu.

At least 199 records · Page 11Linked to original sources
PubMed1985

Colorectal cancer in Chinese and Chinese-Americans.

Rationale and plans are described for a collaborative case-control study of large bowel cancer among Chinese-Americans in Los Angeles and the San Francisco Bay Area and among Chinese in Zhejiang Province, People's Republic of China. A common protocol and questionnaire will be used during personal interviews of approximately 400 Chinese and 300 Chinese-American patients with histologically confirmed adenocarcinoma of the colon or rectum and 2,100 Chinese and Chinese-American controls. Controls will be matched to patients on age, sex, and community of residence. The information requested from subjects will permit testing of hypotheses relating colorectal cancer risk to: dietary factors, including intake of fat (saturated and unsaturated), animal protein, fiber, and vitamins A and E and ascorbic acid; physical activity levels and body mass index; reproductive factors among women; history of bowel disease; and family history of cancer. The information requested of Chinese-American subjects will also permit testing of hypotheses relating cancer risk to such migrant factors as United States versus Chinese nativity, duration of residence in the United States, and Chinese province of ancestry. These factors will be tested for associations with cancers of the colon and rectum separately and with cancers of the large intestine as a whole. We will examine sex and geographic differences in relative risks for etiologic factors, location of tumors within the large bowel, histologic subtype of adenocarcinoma, and frequency of accompanying polyps.

Adult↗
PubMed1985

Cytotoxicity of cisplatin and cisdiammine-1,1-cyclobutane dicarboxylate in MGH-U1 cells grown as monolayers, spheroids, and xenografts.

The cytotoxicity of cisplatin and cisdiammine-1,1-cyclobutane dicarboxylate (CBDCA) was examined using the MGH-U1 human bladder carcinoma cell line, grown as monolayer cultures, multicellular tumor spheroid(s) (MTS), and xenografts in immune-deprived CBA/CaJ mice. The cell survival of exponentially growing monolayers and MTS treated with cisplatin declined in a monoexponential fashion with a concentration of drug resulting in 10% colony survival (D10) of 7.75 micrograms/ml and 9.5 micrograms/ml, respectively. MTS growth delay determination demonstrated a drug concentration-dependent increase in growth delay and a correlation between decreasing surviving fraction and increasing growth delay. In vivo treatment of MGH-U1 xenografts with cisplatin caused a modest decrease in surviving fraction although the xenografted cells treated in vitro demonstrated the same sensitivity to cisplatin as those cells maintained continuously in vitro. The D10 for CBDCA treatment was 246 micrograms/ml for exponentially growing monolayer cells and 196 micrograms/ml for MTS. Growth delay studies with CBDCA showed a concentration-dependent increase in spheroid growth delay and a correlation between decreasing surviving fraction and growth delay similar to cisplatin. The conclusions were that: 1) cisplatin and CBDCA did not have any difficulty penetrating into spheroids, 2) both agents appeared to be active against the noncycling poorly nourished cells found near the necrotic center of spheroids, 3) both cisplatin and CBDCA were cytotoxic toward MGH-U1 cells but cisplatin was 20-30 times more effective, and 4) the limited cytotoxic effect of cisplatin in vivo may be due to the low area under the concentration times the time curve achieved in vivo and not due to intrinsic cell resistance.

Animals↗
PubMed1984

Rationale for the use of hypnotic agents in a general hospital.

A survey at a teaching hospital found that 46% of medical patients had prescriptions written specifically for sleep and 31% received a hypnotic agent at least once during hospitalization. Physicians for 96% of surgical patients ordered hypnotic agents and 88% received such a drug. The rationale for prescribing hypnotic agents was not well documented. Administration did not correlate with requests by patients, with previous use of hypnotic agents, or with recorded indications of sleep disturbance; however, the chance of receiving a hypnotic agent was greater if the patient was on a private instead of a ward service and if nurses were more inclined to fill as-needed prescriptions. Patients who received a hypnotic agent did not rate the quality of their sleep as being any better than those who did not, and they complained of as many awakenings during the night. Further studies are necessary to ascertain the indications and efficacy of hypnotic agents for hospitalized patients.

Adult↗
PubMed1983

Generation time of leukaemic blast progenitor cells.

Previous studies have indicated that the generation time of human leukaemic cells is longer than that of normal haematopoietic cells. We have employed a modification of the thymidine (TdR)-suicide technique to measure directly the generation time of leukaemic progenitor cells capable of colony formation. The results obtained with two human leukaemic cell lines (KG-1 and HL-60) and with blast progenitor cells from two patients with acute myelogenous leukaemia indicate generation times ranging from 9 X 0-22 X 0 hr and S-phase durations ranging from 5 X 5-8 X 0 hr. Using the same technique, the generation time of normal bone marrow CFU-c was determined to be 9-11 hr. These findings suggest that the proliferation rate of human leukaemic blast progenitor cells is similar to that of normal haematopoietic stem cells.

Adolescent↗
PubMed1982

The effects of halothane on sympathetic ganglionic transmission.

The effects of halothane on ganglionic transmission were studied in the stellate ganglion of the guinea pig using intracellular recordings in vitro. Depression of synaptic transmission is one of the actions common to many general anesthetics. The aim of this study was to investigate which of the processes involved in synaptic transmission are affected by halothane in concentrations comparable to those used during surgical anesthesia. The neurons of the stellate ganglion were depolarized using preganglionic nerve stimulation, postganglionic nerve stimulation, and intracellular stimulation before ad after introduction of halothane (vaporizer settings of 0.75% and 1.5% produced bath concentrations of 8 and 18 mg/dl, respectively). Halothane at both concentrations depressed sympathetic ganglionic transmission which was induced by stimulation of preganglionic nerves. Axonal transmission and the excitability of the postganglionic neurons to direct intracellular stimulation was far less sensitive to halothane than synaptic transmission. The depression of ganglionic transmission seen in the present study was most likely due to a decrease in transmitter release although alterations in postsynaptic receptor properties could have been involved as well. The decrease in sympathetic activity resulting from depression of ganglionic transmission probably contributes to the arterial hypotension seen during halothane anesthesia, along with direct myocardial depression, inhibition of catecholamine release from the adrenal medulla, direct action on vascular smooth muscle, and central sympathetic depression.

Action Potentials↗
PubMed1982

Isolation of genome-enzyme complex from cytoplasmic polyhedrosis virus of silkworm Bombyx mori.

The genome-enzyme complex is isolated from the silkworm cytoplasmic polyhedrosis virus with DEAE-Sephadex column chromatography after ultraviolet irradiation. The genome-enzyme complex shows both RNA-polymerase and methyltransferase activities while using 3H-UTP and [3H-methyl]-S-adenosyle-L-methionine as substrates. Like the double-stranded RNA genome of CPV, the genome-enzyme complex could be separated into nine segments on polyacrylamide gel electrophoresis. It is demonstrated that the RNA polymerase and methyl-transferase are tightly bound to the double-stranded RNA genome and that the individual segments of the genome-enzyme complex all possess RNA-polymerase and methyltransferase activities. It appears that each segment of the double-stranded RNA genome is transcribed independently.

Bombyx↗
PubMed1980

Hemoglobin affinity for oxygen during short-term exhaustive exercise.

We assessed hemoglobin affinity for oxygen (standard P50: pH 7.40, PCO2 40 Torr, temperature 37 degrees C) in 3 series of studies of 16 male subjects who performed exhaustive treadmill exercise of 10 min duration. Standard P50 was significantly elevated (0.7--2.5 Torr) during the last minute of and for 30 min following exercise. Exercise while carboxyhemoglobin (HbCO) was acutely elevated to 5% did not affect std P50 any differently than exercise alone. 2,3-Diphosphoglycerate (2,3-DPG) was significantly elevated after exercise, but not during or 30 min postexercise, and it correlated significantly with P50 in 2 studies (r, 0.43--0.68). ATP (mumol/100 ml) was significantly elevated only 3 min postexercise. Serum [Na+], [K+], [Cl-], osmolarity, and hemoglobin (Hb) concentration were significantly elevated during exercise with [Na+] osmolarity, and [Hb] remaining significantly elevated postexercise. There was no significant correlation between std P50 and any of these variables. Multiple correlation regression analysis between P50 and 2,3-DPG, ATP, and [Na+] yields a coefficient of 0.86. We conclude this type of exercise is unique in causing a small change in std P50 that appears to be mediated by several factors.

Adult↗
PubMed1978

Stereoelectronic factors in the binding of substrate analogues and inhibitors to purine nucleoside phosphorylase isolated from human erythrocytes.

Several aspects of the stereoelectronic requirements of substrates of human erythrocytic purine nucleoside phosphorylase (E.C. 2.4.2.1) were elucidated providing the following information: (a) the N1 position cannot have a nonhydrogen substituent; (b) the 5'-OH group must be present for catalytic activity to be exhibited but is not an essential functional group for inhibitory action to be observed; (c) on the C8 position groups larger than -NH2 or -Br cannot be accommodated; (d) the syn-glycosyl conformation (i.e., 8-bromoguanosine) is acceptable but may not be an absolute requirement for phosphorolysis; (e) among nucleic base inhibitors methylation at N3, N7, or N9 vastly decreases the inhibitory properties as does a nitrogen in lieu of C-H in the 8 position. The results clearly indicate that this enzyme differs in its stereoelectronic requirements from the Escherichia coli enzyme.

Binding, Competitive↗
PubMed1978

Mass fragmentographic determination of pentachlorophenol in rainbow trout.

Pentachlorophenol (PCP) is extracted from selected tissues of rainbow trout and converted to pentachloroanisole (PCA) by means of alkylation in the presence of potassium carbonate as a condensing agent. Pentachlorophenetole (PPT) is used as an internal standard. The electron impact mass fragmentography is carried out by monitoring m/e 280 (PCA), 294 (PPT), and 237. A plot of peak height vs. concentration is linear from 0.03 to 4.0 ng. Accuracy and precision of the method is +/-2% (N - 36). The results are accurate enough to warrant the use of this method for determining PCP in fish, as well as for monitoring PCP from various environmental sources. In addition, this technique provides a simple and rapid method by which a mixture of PCA and PCP can be determined simultaneously.

Animals↗