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C K Chou

Publications and source records attributed to C K Chou.

At least 181 records · Page 10Linked to original sources
PubMed1984

Effect of microwave radiation on the beating rate of isolated frog hearts.

One hundred and two isolated frog hearts were divided into ten groups and placed individually in a waveguide filled with Ringer's solution and exposed to 2,450-MHz CW radiation at 2 and 8.55 W/kg. Heart rate was recorded using one of the following methods: 3-M KCl glass electrode, ultrasound probe, tension transducer, Ringer's solution glass electrode, and a metal wire inserted in the Ringer's solution electrode. An accelerated decrease of heart rate was observed only in those groups recorded using the 3-M KCl electrode and the metal wire Ringer's solution electrode. No effect was found in the other groups. These results indicate that bradycardia in isolated hearts could be caused by electrode artifacts resulting from the intensification of electromagnetic fields.

Animals↗
PubMed1984

SAR in rats exposed in 2,450-MHz circularly polarized waveguides.

Average specific absorption rates (SARs) for live rats exposed in 2,450-MHz circularly polarized waveguides were estimated from the total system loss determined from measurements using five power meters, and a correction factor representing actual SAR/apparent SAR. The actual SAR was measured by twin-well calorimetry and the apparent SAR by power meters. Values were obtained for carcasses of various body masses for five orientations. The average SAR with free movement in the cages changed less than threefold as the rats grew from 200 to 700 g. The ratio of peak to average SAR in the body was less than 3. These results indicate relatively constant energy disposition in rats exposed in the circularly polarized waveguide.

Animals↗
PubMed1984

Formulas for preparing phantom muscle tissue at various radiofrequencies.

The dielectric properties of various test samples of phantom tissue were measured using an automated and temperature-controlled slotted line. The ingredients for phantom materials were determined for simulating high-water content tissue at 13.56, 27.12, 40.68, 70, 100, 200, 300, 433, 750, 915, and 2,450 MHz. The ingredients consisted of water, TX-150 (a gelling agent), sodium chloride, and polyethylene powder (200-2,450 MHz) or aluminum powder (13.56-100 MHz). The dielectric constant and conductivity of these materials at different temperatures (15, 22, 30 degrees C) were characterized.

Hot Temperature↗
PubMed1984

Design and thermometry of an intracavitary microwave applicator suitable for treatment of some vaginal and rectal cancers.

The construction of a modified coaxial cable as an intracavitary microwave applicator suitable for use in some vaginal and rectal cancers is presented. Thermometry was performed for microwave frequencies of 300, 400, 650, and 915 MHz. Temperature profiles in tissue phantoms were obtained with non-perturbing temperature probes and thermography, and the data were compared with those obtained in dogs. The temperature profiles were dependent on the frequency of the microwaves and the insertion depth of the applicator. In addition, an acrylic cylindrical spacer external to the applicator also altered the heating pattern. Therefore, with proper combinations of frequency, insertion depth and spacer, the applicator can be used for heating tumors in some clinical situations.

Animals↗
PubMed1984

Characterization of human growth hormone from acromegalic pituitary tumors.

Human growth hormone (HGH) was extracted from acromegalic pituitary tumors at pH 10.5 and precipitated with ammonium sulfate at 20-40% saturation. It was purified on a Sephadex G-100 column to yield monomeric HGH. The tumor-HGH was indistinguishable from the authentic one in polyacrylamide gel electrophoresis at pH 8.3 or in the presence of sodium dodecyl sulfate, high-performance liquid chromatography, radioimmunoassay, peptide map, amino acid composition and N-terminal partial amino acid sequence. The tumor-HGH is active in the tibia assay and bodyweight gain test in hypophysectomized rats with comparable potency to that of the authentic sample.

Acromegaly↗
PubMed1983

Polyamide thin-layer chromatography of phosphorylated tyrosine, threonine, and serine.

One-dimensional thin-layer chromatography on polyamide plates offers an easy and rapid identification of O-phosphotyrosine. The thin-layer plate is developed for 30 min in 5% propionic acid containing 0.013%-0.025% sodium dodecyl sulfate. O-Phosphotyrosine, with Rf = 0.54, can be well separated from O-phosphothreonine and O-phosphoserine, which comigrate at Rf = 0.72.

Chromatography, Thin Layer↗
PubMed1983

Chronic exposure of rabbits to 0.5 and 5 mW/cm2 2450-MHz CW microwave radiation.

Two groups of 16 male New Zealand rabbits were exposed to 2450-MHz continuous wave microwave fields in two experiments of 90 days each. The incident power densities of the first and second experiment were 0.5 and 5 mW/cm2, respectively. During each study, 16 animals were adapted to a miniature anechoic chamber exposure system for at least 2 weeks, then 8 of them were exposed for 7 h daily, 5 days a week for 13 weeks, and the other 8 animals were sham exposed. The rabbits were placed in acrylic cages, and each was exposed from the top in an individual miniature anechoic chamber. Thermography showed a maximum specific absorption rate of 5.5 W/kg in the head and 7 W/kg in the back at 5-mW/cm2 incident power density. After each 7-h exposure session, the animals were returned to their home cages. Food consumption in the exposure chamber and body mass were measured daily. Blood samples were taken before exposure and monthly thereafter for hematological, morphological, chemical, protein electrophoresis, and lymphocyte blast transformation studies. Eyes were examined for cataract formation. Finally, pathological examinations of 28 specimens of organs and tissues of each rabbit were performed. Statistically, there was a significant (P less than .01) decrease only of food consumption during the 5-mW/cm2 exposure; other variables were not significantly different between exposed and control groups.

Animals↗
PubMed1983

Psychoactive-drug response is affected by acute low-level microwave irradiation.

The effects of various psychoactive drugs were studied in rats exposed for 45 min in a circularly polarized, pulsed microwave field (2450 MHz; SAR 0.6 W/kg; 2-microseconds pulses, 500 pps). Apomorphine-induced hypothermia and stereotypy were enhanced by irradiation. Amphetamine-induced hyperthermia was attenuated while stereotypy was unaffected. Morphine-induced catalepsy and lethality were enhanced by irradiation at certain dosages of the drug. Since these drugs have different modes of action on central neural mechanisms and the effects of microwaves depend on the particular drug studied, these results show the complex nature of the effect of microwave irradiation on brain functions.

Amphetamines↗
PubMed1983

Electrical discontinuity of tissue substitute models at 27.12 MHz.

Tissue-substitute models consisting of layers of synthetic, electrically equivalent subcutaneous fat, muscle, and bone shaped in conformation with the normal anatomy are used for rapid determination of distribution of temperature and specific absorption rate throughout the tissues when exposed to electromagnetic radiation. The surfaces of the bisected models are approximated during a short exposure period, then separated and scanned with a thermograph. A method was developed to eliminate the electrical discontinuity at the bisected surfaces while allowing separation and subsequent thermographic scanning. A thin layer of silk screen wetted with propylene glycol saturated with sodium chloride was used at the fat interface and a 0.9% sodium chloride solution was used to wet the screen at the muscle interface to eliminate electrical discontinuity during exposure to 27.12-MHz diathermy. Tests showed that in the presence of an electrical discontinuity the heating pattern was grossly distorted. With the method used, the electrical discontinuity is minimized and the subsequent thermographic scanning reveals that the heating pattern is equivalent to that of an intact model.

Adipose Tissue↗
PubMed1983

Immunological classification of T-cell acute lymphoblastic leukaemia using monoclonal antibodies.

We had been able to classify 70 cases of acute lymphoblastic leukemia (ALL) into different immunological subtypes based on surface marker analysis with the aid of a panel of monoclonal antibodies. The relative proportions of different ALL subclasses appears to be similar to those reported from Europe and the U.S.A. Our results also indicated that monoclonal antibodies OKT11, UCHT-2 and WT1 were very useful in defining pre-T or early T subtypes of ALL. The latter leukaemias lack most maturation-linked T-cell markers but share with the other T-ALL the characteristic of low density or undetectable insulin receptors.

Antibodies, Monoclonal↗
PubMed1983

Induction of plasma protein secretion in a newly established human hepatoma cell line.

To study the expression and the regulation of hepatocyte markers, we have undertaken to establish human hepatoma cell lines of various phenotypes. We now report the establishment of a new human hepatoma cell line, HA22T/VGH. This cell line has many of the properties of human hepatocellular carcinoma. Only 5 of 15 plasma proteins investigated were detected in the medium of a 10-day-old HA22T/VGH culture. However, when the HA22T/VGH cells and a clonal derivative, C5, were cultured in an aggregated form, all 15 plasma proteins were found in the culture medium. These results indicate that hepatoma cell lines with different phenotypes can be established, and they provide a good experimental framework to investigate differentiation of human hepatocytes.

Animals↗
PubMed1983

Insulin receptors on leukemia and lymphoma cells.

Tumor cells obtained from leukemia and lymphoma patients were investigated for specific insulin receptors. Using radioactive 125I-labeled insulin, specific insulin binding sites were demonstrated on most acute lymphocytic leukemia (ALL) and acute myelocytic leukemia (AML) cells, including acute promyelocytic leukemia (APL), chronic myelocytic leukemia (CML), and acute monocytic leukemia (AMoL) cells. Insulin receptors were not found on chronic lymphocytic leukemia (CLL) and malignant lymphoma (ML) cells. Specific insulin binding sites were also found on monocytes and thymocytes after treatment with phytohemagglutinin (PHA-P), but not on inactivated tonsil cells, peripheral blood lymphocytes, or thymocytes. There was no inverse correlation between the content of insulin receptors and the basal level of circulating insulin. These data suggest that the insulin receptor may be a new marker of acute leukemia and chronic myelocytic leukemia.

Adolescent↗
PubMed1982

Determination of electric current distributions in animals and humans exposed to a uniform 60-Hz high-intensity electric field.

The thermographic method for determining specific absorption rate (SAR) in animals and models of tissues or bodies exposed to electromagnetic fields was applied to the problem of quantifying the current distribution in homogeneous bodies of arbitrary shape exposed to 60-Hz electric fields. The 60-Hz field exposures were simulated by exposing scale models of high electrical conductivity to 57.3-MHz VHF fields of high strength in a large 3.66 X 3.66 X 2.44-m TE101 mode resonant cavity. After exposure periods of 2-30 s, the models were quickly disassembled so that the temperature distribution (maximum value up to 7 degrees C) along internal cross-sectional planes of the model could be recorded thermographically. The SAR, W', calculated from the temperature changes at any point in the scale model was used to determine the SAR, W, for a full-scale model exposed to a 60-Hz electric field of the same strength by the relation W = (60/f')2 . (sigma'/sigma) . W' where f' is the model exposure frequency, sigma' is the conductivity of the scale model at the VHF exposure frequency, and sigma is the conductivity of the full-scale subject at 60 Hz. The SAR was used to calculate either the electric field strength or the current density for the full-scale subject. The models were used to simulate the exposure of the full-scale subject located either in free space or in contact with a conducting ground plane. Measurements made on a number of spheroidal models with axial ratios from 1 to 10 and conductivity from 1 to 10 s/m agreed well with theoretical predictions. Maximum current densities of 200nA/cm2 predicted in the ankles of man models and 50 nA/cm2 predicted in the legs of pig models exposed to 60-Hz fields at 1kV/m agreed well with independent measurements on full-scale models.

Animals↗
PubMed1982

Systems for exposing mice to 2,450-MHz electromagnetic fields.

Two systems for exposing mice to 2,450-MHz electromagnetic fields are described. In a waveguide system, four mice were placed in a Styrofoam cage and exposed dorsally to circularly polarized electromagnetic fields. The temperature and humidity in the mouse holder were kept constant by forced-air ventilation. For 1-W input power to the waveguide, the average specific absorption rate (SAR) was determined by twin-well calorimetry to be 3.60 +/- 0.11 (SE) W/kg in 27-g mice. The maximum SAR at the skin surface determined thermographically was 8.36 W/kg in the head of the mouse. The second system was a miniature anechoic chamber. Six mice were irradiated dorsally to far field plane waves. Copper shielding and high-temperature absorbing material were lined inside the chamber to accommodate the high input power. The air ventilation at the location of the mice was separately controlled so that any heating in the absorber would not affect the animals. For 1-W input power, the average SAR was 0.17 +/- 0.01 W/kg and the maximum SAR at the skin surface was 0.41 W/kg in the animal when irradiated with body axis parallel to the E field; the SARs were 0.11 +/- 0.01 W/kg and 0.64 W/kg, respectively, when irradiated perpendicular to the E field.

Animals↗
PubMed1982

[A new human hepatoma cell line: establishment and characterization].

We have grown a human hepatoma cell line, designated as HA22T/VGH, from a 52-yr-old male hepatoma patient since July 1, 1980. This cell line has been subcultured more than 100 passages. The chromosome analysis of HA22T/VGH indicated that the chromosome numbers varied from 70 to 146, with the mode of 73. Methylcellulose soft agar assay showed that approximately 40% of the HA22T/VGH cells formed colonies. The HA22T/VGH produced tumors in nude mice. Histopathological studies of the tumor revealed the arrangement of hepatoma. Detected by the complement fixation method HA22T/VGH cells secreted ceruloplasmin, Factor B, C3, C4, Gc-globulin and alpha 1-acid-glycoprotein. These cells contained the liver associated enzymes: alanine amino transferase, tyrosine amino transferase and gamma-glutamyl transferase. HBsAg and alpha-fetoprotein were not detectable in the HA22T/VGH culture media or cell lysates by the radioimmunoassay.

Animals↗
PubMed1980

Microwave radiation and heart-beat rate of rabbits.

Each of three adult New Zealand rabbits, 2 male and 1 female albinos, was exposed dorsally or ventrally, to 2450-MHz plane waves for 20 min under each of several field conditions: 1) to continuous waves (CW) at 5 mW/cm2; 2) to pulsed waves (PW) of 1-microsecond width that recurred 700 pps at an average of 5 mW/cm2 and at a peak of 7.1 W/cm2; 3) to PW of 10-microseconds width at a peak of 13.7 W/cm2 that were synchronized with and triggered by the R wave of the electrocardiogram (EKG) at various delay times (0, 100, and 200 ms; and 4) to CW at 80 mW/cm2. Carbon-loaded Teflon electrodes were used to record the EKG from forelimbs of an animal before, during, and after irradiation whilst it was maintained in a constant exposure geometry in a wooden squeeze box. Field induced changes in the heart-beat rate were observed at 80 mW/cm2 but not a lower average power densities, although a peak positive chronotropic effect might have been occasioned by PM introduced at 100 and 200 ms after the R wave peak. No cumulative effect was observed over a period of four months. Thermographic analysis revealed relatively little absorption of microwave energy by the myocardium irrespective of anatomical aspect of exposure.

Animals↗
PubMed1979

Middle-ear structures contribute little to auditory perception of microwaves.

The contribution of the ossicles (middle-ear bones) to auditory perception of microwaves was evaluated by the brain-stem evoked response (BER). Amplitude and latency of BERs were recorded from guinea pigs that were stimulated at various intensities by acoustic pulses coupled to the auditory canal or via bone conduction, and by microwave pulses. Blocking of the external ear, middle-ear damping, and middle-ear destruction produced little change in the BERs that were elicited by microwave pulses. Results indicate that activity in the central auditory pathway as induced by pulsed microwaves only requires stimulation of the cochlea. Conduction of pressure waves through the bones of the calvarium appears to be the mechanism responsible in perception of pulsed microwaves.

Animals↗