Biomedical subjects

C K Chou

Publications and source records attributed to C K Chou.

At least 19 recordsLinked to original sources

PubMed2004

Ultrasound diagnosis of paratesticular rhabdomyosarcoma.

Rhabdomyosarcoma is the most common tumour of the lower genitourinary tract in children in the first two decades. Paratesticular rhabdomyosarcoma is associated with a significantly better outcome than lesions elsewhere in the genitourinary tract. Although ultrasound is considered the imaging modality of choice for evaluating intrascrotal pathology, the ultrasound appearance of paratesticular rhabdomyosarcoma has rarely been reported and may be confused with other disease entities such as epididymitis, adenomatoid tumour and leiomyoma. We present the ultrasound features of a paratesticular rhabdomyosarcoma, discussing the clinical features and differential diagnosis.

Adolescent↗

PubMed2004

Malignant mesothelioma of the tunica vaginalis testis.

Malignant mesothelioma of the tunica vaginalis is rare, and is usually not diagnosed until surgery is undertaken. Reports on the ultrasound features of this tumour are limited. We present an unusual case with ultrasound features mimicking an adenomatoid tumour.

Adenomatoid Tumor↗

PubMed2003

Testing the effectiveness of small radiation shields for mobile phones.

Nine small radiation shields made to adhere to the case of mobile phones were tested at 914 and 1880 MHz. Five popular products were tested because advertisements typically claim they are up to 99% effective in blocking radio frequency (RF) radiation emitted from mobile phones. Also, four other conceptually unusual products were tested because advertisements typically claim they emit oscillations that counteract the RF radiation from mobile phones. Each shield was tested on the same mobile phone, and measurements were made to compare the absorption of RF energy in the head with and without each shield attached to the phone. The phone was positioned against a head model, and an automated measurement process was used to determine specific absorption rate (SAR) in the same way it is used at Motorola to test the compliance of mobile phones with respect to human exposure limits. The location of the peak SAR was not observed to change with any of the shields attached to the phone, and the 1 g, peak spatial average SAR did not change by any statistically significant amount. These results indicate the small shields are ineffective in reducing the exposure of the head to RF energy emitted by a mobile phone.

Electromagnetic Fields↗

PubMed2003

Auditory response to pulsed radiofrequency energy.

The human auditory response to pulses of radiofrequency (RF) energy, commonly called RF hearing, is a well established phenomenon. RF induced sounds can be characterized as low intensity sounds because, in general, a quiet environment is required for the auditory response. The sound is similar to other common sounds such as a click, buzz, hiss, knock, or chirp. Effective radiofrequencies range from 2.4 to 10000 MHz, but an individual's ability to hear RF induced sounds is dependent upon high frequency acoustic hearing in the kHz range above about 5 kHz. The site of conversion of RF energy to acoustic energy is within or peripheral to the cochlea, and once the cochlea is stimulated, the detection of RF induced sounds in humans and RF induced auditory responses in animals is similar to acoustic sound detection. The fundamental frequency of RF induced sounds is independent of the frequency of the radiowaves but dependent upon head dimensions. The auditory response has been shown to be dependent upon the energy in a single pulse and not on average power density. The weight of evidence of the results of human, animal, and modeling studies supports the thermoelastic expansion theory as the explanation for the RF hearing phenomenon. RF induced sounds involve the perception via bone conduction of thermally generated sound transients, that is, audible sounds are produced by rapid thermal expansion resulting from a calculated temperature rise of only 5 x 10(-6) degrees C in tissue at the threshold level due to absorption of the energy in the RF pulse. The hearing of RF induced sounds at exposure levels many orders of magnitude greater than the hearing threshold is considered to be a biological effect without an accompanying health effect. This conclusion is supported by a comparison of pressure induced in the body by RF pulses to pressure associated with hazardous acoustic energy and clinical ultrasound procedures.

Animals↗

PubMed2003

Microwave effects on the nervous system.

Studies have evaluated the electroencephalography (EEG) of humans and laboratory animals during and after Radiofrequency (RF) exposures. Effects of RF exposure on the blood-brain barrier (BBB) have been generally accepted for exposures that are thermalizing. Low level exposures that report alterations of the BBB remain controversial. Exposure to high levels of RF energy can damage the structure and function of the nervous system. Much research has focused on the neurochemistry of the brain and the reported effects of RF exposure. Research with isolated brain tissue has provided new results that do not seem to rely on thermal mechanisms. Studies of individuals who are reported to be sensitive to electric and magnetic fields are discussed. In this review of the literature, it is difficult to draw conclusions concerning hazards to human health. The many exposure parameters such as frequency, orientation, modulation, power density, and duration of exposure make direct comparison of many experiments difficult. At high exposure power densities, thermal effects are prevalent and can lead to adverse consequences. At lower levels of exposure biological effects may still occur but thermal mechanisms are not ruled out. It is concluded that the diverse methods and experimental designs as well as lack of replication of many seemingly important studies prevents formation of definite conclusions concerning hazardous nervous system health effects from RF exposure. The only firm conclusion that may be drawn is the potential for hazardous thermal consequences of high power RF exposure.

Animals↗

PubMed2003

Effects of glucose concentration on in vitro fertilization in BALB/c mice.

BALB/c mice are widely used in genetic, tumour and immunological studies. However, the mice demonstrate a lower reproduction rate, low fertility and small litters, because of their highly genetic homozygoisty. Based on in vitro fertilization (IVF), a routine technique for biomedical studies, it is worth to evaluate the effects to BALB/c mice on IVF efficiency. In order to test the genetic factor affecting the IVF efficiency of BALB/c, four reciprocal IVF tests of BALB/cByJ and FVB/NCrl mice were performed. The results showed that the average fertility of IVF sponsored by FVB/NCrl spermatozoa was 69.6%, but only 12.1% was obtained from BALB/cByJ strain. Effect of glucose contained in the culture medium to the IVF efficiency of BALB/cByJ was also evaluated. The results showed that the fertility of BALB/cByJ spermatozoa incubated with 0, 2.7, 5.5, 11.1 and 22.2 mm of glucose in the TYH medium were 6.8, 9.9, 13.9, 32.7 and 22.2%, respectively. It is showed that IVF efficiency of BALB/cByJ spermatozoa could be improved depending on the concentration of glucose in the IVF medium. According to the results, it is beleived that lower IVF of BALB/cByJ mice might be due to the genetic defect in spermatozoa and increasing glucose in the IVF medium which significantly affect the IVF efficiency of BALB/cByl via activating the spermatozoa.

Animals↗

PubMed2003

Case report: diabetic mastopathy.

Diabetic mastopathy is a source of confusion with breast carcinoma. The association between mastopathy and Type I diabetes of long duration has been reported, but this clinical condition is poorly recognized since breast examination is not routinely performed in young diabetic patients. Radiologists' awareness of the constellation of findings in diabetic mastopathy may spare patients from undergoing unwarranted surgical biopsies.

Adult↗

PubMed2003

Estimation of the SAR in the human head and body due to radiofrequency radiation exposure from handheld mobile phones with hands-free accessories.

It was reported by others that hands-free accessories increase the absorption of RF energy in a human head compared to a handset alone. The results of this study show that the opposite is observed when proper dosimetric methods are employed. It is pointed out that for correct estimation of the exposure level it is necessary to use appropriate physical and experimental models and measurement instrumentation, following internationally recommended standards. The human phantoms used for measurements involving the hands-free accessories should include the torso; i.e., measurements should not be performed on the head phantom alone. This has a significant impact on the results because the RF energy coupled into the leads of hands-free accessories is strongly attenuated by the body. Numerical simulations using the Finite-Difference Time-Domain (FDTD) method and experimental measurements with a miniature electric-field probe are in good agreement and show a decrease, not an increase, in RF energy exposure in the human head from hands-free accessories.

Cell Phone↗

PubMed2001

Variations of dose and electrode spacing for rat breast cancer electrochemical treatment.

Electrochemical treatment (EChT) with direct current delivered through implanted electrodes has been used for local control of solid tumors in humans. This study tested the hypothesis that rat breast cancer responses to EChT are dependent on electrode spacing and dose, and explored suitable parameters for treating breast cancers with EChT. Rat breast cancers were initiated by injecting 1 x 10(6) MTF-7 cells to the right mammary gland fat pad of Fisher 344 female rats. The rats were randomly divided into designated experimental groups when the tumors grew to approximately 2 x 2 x 2 cm. One hundred and thirty rats were used for a survival study and 129 for a pathology study. A 4-channel EChT machine was used to administer coulometric doses. The survival study indicated that local tumor control rate is less than 40% in the 40 coulomb (C) and 60 C groups and more than 70% in the 80 and 100 C groups. Sixty six rats died of primary tumors, including all 10 rats in the control group. Once a rat's primary tumor was controlled, no recurrence was found. The main reason for terminating the primary tumor-free rats (51) was lymph node metastasis. Thirteen tumor-free rats survived for more than 6 months. The pathology study showed a significant dose effect on EChT induced tumor necrosis. At 10, 20, 40, and 80 C, the fraction showing necrosis were 39.7, 52.3, 62, and 77.7%, respectively (P </= 0.001). Electrodes spacing was not an important factor within a given range. At 5, 10, and 15 mm spacing, the fraction showing the necrosis were 54.1, 60.4, and 59.2%, respectively (P = 0.552). The overlap rate of necroses was similar in the 5 and 10 mm groups (82.5 and 85%) and lower in the 15 mm group (65%). We conclude that the tumor responses to EChT, local control, survival rates, and necrosis percentages were significantly increased with increasing dose. The changes in electrode spacing (3, 5, and 10 mm) did not significantly affect the tumor responses to EChT within the same dose. For a diameter of 2.0-2.5 cm rat breast cancer, EChT should be applied with 5-10 mm spacing and a minimum dosage of 80 C.

Animals↗

PubMed2001

Inhibition of group A streptococcus infection by carboxyfullerene.

The effect of a water-soluble trimalonic acid derivative of fullerene, carboxyfullerene, against Streptococcus pyogenes infection was tested. Pretreatment with carboxyfullerene was able to protect mice from S. pyogenes infection in an air pouch model. S. pyogenes-induced death and skin injury were inhibited dose dependently by carboxyfullerene. Administration of carboxyfullerene via the peritoneum and air pouch at 3 h post-S. pyogenes infection was able to protect 33% of mice from death. Surveys of exudates of the air pouch of carboxyfullerene-treated mice revealed that survival of infiltrating neutrophils was prolonged and that the bacteria were eliminated as a result of enhanced bactericidal activity of the neutrophils. Furthermore, carboxyfullerene was able to directly inhibit in vitro growth of S. pyogenes. These data suggest that carboxyfullerene can be considered an antimicrobial agent for group A streptococcus infection.

Animals↗

PubMed2000

Light-independent inactivation of dengue-2 virus by carboxyfullerene C3 isomer.

Carboxyfullerene (C60) is known as a photosensitizer for virus inactivation. Its regioisomer with C3 symmetry, named the C3 isomer, could also inactivate the dengue-2 virus without light when the dose of C3 isomer was increased to 40 microM, indicating the possible involvement of a light-independent mechanism. Further analysis showed that the C3 isomer blocked viral replication at the attachment and penetration stages, suggesting that a direct interaction between the C3 isomer and the virion is required for inactivation. The C3 isomer with a bipolar structure showed better lipid interaction and dengue-2 virus suppression than D3, another isomer that contains evenly distributed hydrophilic side chains. Moreover, the C3 isomer selectively inactivated enveloped viruses (viz., dengue-2 virus and Japanese encephalitis virus) instead of nonenveloped viruses (viz., enterovirus 71 and coxsackievirus B3). Collectively, these findings support the hypothesis that C3 isomer suppression of enveloped viruses is effected through its hydrophobic interaction with the viral lipid envelope. Our report, which demonstrates the light-dependent and -independent mechanisms of C60 on viral inactivation, will aid in the development of novel anti-viral agents for use against enveloped viruses.

Animals↗

PubMed2000

Cloning and expression of ZAK, a mixed lineage kinase-like protein containing a leucine-zipper and a sterile-alpha motif.

A novel mixed lineage kinase-like protein ZAK, containing a leucine-zipper (LZ) and a sterile-alpha motif (SAM), was cloned. This cDNA has 2456 bp and encodes a protein of 800 amino acids that contains a kinase catalytic domain, a leucine-zipper and a SAM. The molecular weight of this protein is 91kDa. Northern blot analysis revealed that the expression of this ZAK gene is found in various parts of human tissues. We also found that ZAK proteins might form homodimers or oligomers in mammalian cells. MLKs have been proposed to function as mitogen-activated protein kinase kinase kinase in pathways leading to MAPK cascade. The expression of ZAK in mammalian cells specifically leads to the activation of the JNK/SAPK pathway as well as the activation of transcription factor, NF-kappaB. Overexpression of the ZAK gene induces the apoptosis of a hepatoma cell line.

Amino Acid Sequence↗

PubMed2000

Cloning and characterization of a novel human ninein protein that interacts with the glycogen synthase kinase 3beta.

Using human glycogen synthase kinase 3beta (GSK-3beta) as bait in the yeast two-hybrid system, we identified a novel human centrosome associated protein, hNinein. When the full length cDNA of hNinein was sequenced, it showed that an open reading frame encoded a protein consisting of 2047 amino acids with a predicted molecular mass of 239 kDa. The features of this protein include a potential GTP binding site, a large coiled-coil domain together with four leucine zipper domains and a GSK-3beta binding site. Fluorescence microscopy experiment showed that hNinein is localized in the pericentriolar matrix of the centrosome. In addition, hNinein also showed to react with centrosomal autoantibody sera. Our findings suggest that hNinein may be involved in the formation of centrosome matrix and interacts with the GSK-3beta, implying that it may also be regulated by GSK-3beta phosphorylation signaling.

Amino Acid Sequence↗

PubMed2000

Three rat brain alternative splicing dynamin-like protein variants: interaction with the glycogen synthase kinase 3beta and action as a substrate.

Dynamin-like protein, a large GTP-binding protein, has recently been cloned, and studies have shown that it may be involved in the formation of coated vesicles. In this report, three different alternatively spliced dynamin-like protein variants (DLP1-WT, -11, and -37) from rat brain were identified by reverse transcription/polymerase chain reaction (RT-PCR). One novel rat alternatively spliced variant (DLP1-37), not described previously, was identified. We examined the interaction of these three rat brain dynamin-like protein variants with glycogen synthase kinase 3beta (Gsk-3beta) using the yeast two-hybrid screening, in vitro binding assay, and immunoprecipitation analysis. It was found that all three examined rat brain dynamin-like protein variants can bind to Gsk-3beta. Moreover, in vitro kinase (phosphorylation) assay showed that mammalian dynamin-like protein acts as a substrate for glycogen synthase kinase 3beta. These data suggest that Gsk-3beta may participate in a functional role in dynamin-like proteins in vesicle trafficking.

Alternative Splicing↗

PubMed2000

Complexes formation between insulin receptor and extracellular signal-regulated kinases ERKs.

A property of signal transduction pathways that might explain their efficiency and specificity is the formation of signaling complexes. The recent demonstration that adaptor proteins can interact with many components of the extracellular signal-regulated kinases (ERKs) signaling cascade leads us to investigate whether such complexes may include the transmembrane receptor. The present work shows that in human hepatoma Hep3B cells, insulin receptor (IR) can be coimmunoprecipitated with other components of the ERKs cascade: insulin receptor substrate (IRS), Raf-1, and ERKs. Furthermore, these complexes formed near the cytoplasmic membrane even prior to insulin stimulation.

Blotting, Western↗

PubMed2000

Characterization of a strain-specific monoclonal antibody to hepatitis delta virus antigen.

Sequences of the hepatitis delta virus (HDV) vary to different degrees among isolates. A monoclonal antibody, designated as HP6A1, against the antigen of HDV (HDAg) has been characterized for its specificity. HP6A1 bound to HDAg of isolate 25 (genotype I) that was used for immunization, but not to others of both genotypes I and II. The epitope recognized by HP6A1 was then determined by a phage library displaying various heptapeptides. A consensus peptide deduced has the best match with that of residues 4-10 of HDAg (isolate 25). To confirm the phage mapping result, Escherichia coli recombinant proteins containing different lengths and various segments of HDAg (isolate 25) were constructed. The shortest HDAg segment contained in the fusion protein that reacted with HP6A1 was residues 1-10. When this peptide was added to the N-terminus of a heterologous protein engineered for eucaryotic expression, the fusion protein was detected by HP6A1. It is concluded that HP6A1 recognizes an epitope located at the N-terminus of HDAg (isolate 25). Since viruses of quasi-species exist in natural infections, a question of how different viral strains interact in vivo remains to be explored. The highly specific MAb opens a possibility to examine the fate of one strain in the presence of other related species in a cell transfection system.

Amino Acid Sequence↗

PubMed2000

Differentiation of obstructive from non-obstructive small bowel dilatation on CT.

PURPOSE: to find a useful decision procedure for the differentiation of obstructive from non-obstructive small bowel (SB) dilatation on the computed tomography (CT). MATERIALS AND METHODS: four criteria were divided into different degrees and evaluated. These include: (A): continuity (non-continuous, continuous); (B): transition zone (absent, gradual, abrupt); (C): prestenotic SB fluid (minimal, about one-fourth, one-half, and three-fourths, nearly complete); and (D): colonic contents (minimal, moderate, considerable). One hundred fifty-three examinations, 86 obstructive and 67 non-obstructive, were analyzed using chi(2)-square tests to determine the relationship of each criterion to the presence of small bowel obstruction (SBO), whether the proportions of various degrees of these criteria differed significantly among the obstructive and non-obstructive subgroups, and to classify the criteria with a tree-based model (calculated by the computer) for the development of a useful decision procedure. RESULTS: in each of the four criteria, the trend of probability of obstruction was statistically significant (P=0.0000). The proportions of most, except two, of the various degrees of different criteria in the obstructive and non-obstructive subgroups differed significantly (P<0.01). The obstruction tends to have a continuou dilatation, an abrupt transition, more prestenotic SB fluids, and less colonic contents. The results of classification by a tree-based model were 76 true-positive, ten false-negative, six false-positive, and 61 true-negative. The sensitivity was 88%; specificity was 91%; positive predictive value was 93%; negative predictive value was 86%; and the overall accuracy was 90%. CONCLUSION: by analyzing the above four criteria together, a useful tree-based model can be developed and utilized as a supplemental decision procedure for the differentiation of obstructive from non-obstructive SB dilatation. The accuracy can be further promoted if the factor of a recognized pathologic condition is taken into consideration.

Decision Trees↗

PubMed2000

Gait analysis after ankle arthrodesis.

The purpose of this study was to employ a computerized motion analysis system to identify the effect of ankle arthrodesis on the three-dimensional kinematic behavior of the rear and fore foot during level walking. A three-segment rigid body model was used to describe the motion of the foot and ankle. The results demonstrated that sagittal plane motion of the hindfoot was significantly decreased in the foot of patients having had ankle arthrodesis compared to normal subjects. The kinematic data indicated a generalized stiffness of the hindfoot on the involved foot in the sagittal plane. Sagittal plane movement in the forefoot and transverse plane movements in the hindfoot and forefoot increased in patients compared to controls.

Adolescent↗