Biomedical subjects

C K Chou

Publications and source records attributed to C K Chou.

At least 73 records · Page 4Linked to original sources

PubMed1997

A mixture of allogeneic dermal tissue and autologous microskin grafting of rabbit skin wound.

In a rabbit model, transplantation of largely expanded microskin grafts (expansion ratio 25 X) were studied. In Group I, the autologous microskin grafts were transplanted onto the full-thickness skin defect on the back of a rabbit and were overlaid with Biobrane. In Group II, the autologous microskin grafts were mixed with allogeneic microdermal substance (expansion ratio 25 X) before the transplantation. The percentage of re-epithelialized area to the total grafted wound was analyzed by means of computerized planimetric analyses of photographs of the grafted wounds on days 11 and 13. Biopsies of the grafted wounds were done. On day 11, the mean percentage of Group I was 72.4% and that of Group II was 82.7%. On day 13, they were 82.3% in Group I and 92.3% in Group II. In Group II, the allogeneic dermal tissue did not cause obvious rejection in the neoepithelium. Histological features showed the existence of allogeneic dermal tissue in the grafted wound. The adding of largely expanded allogeneic dermal substance to autologous microskin grafts in Group II provided better circumstances than that in Group I for re-epithelialization of autologous mciroskin grafts.

Animals↗

PubMed1997

MRI-guided stereotatic aspiration for the treatment of deep-seated tentorial empyema: a case report.

Tentorial empyema is a rare intracranial infection. In the past, most authors treated the subdural empyema by craniotomy, craniectomy or burr hole drainage. In the case presented, magnetic resonance imaging (MRI)-guided stereotatic aspiration was used to treat deep-seated extensive tentorial empyema successfully, via a simple burr hole to avoid any brain resection and retraction. This operation method is relative simple and effective for treating deep-seated intracranial empyema, significantly reduces the risk of injury to the lateral temporal lobe cortex or transection of optic radiations. On the other hand, it must be emphasized that contrast-enhanced MRI scan may offer a more sensitive and better diagnostic procedure than contrast enhanced computed tomography (CT) scan.

Adult↗

PubMed1996

Identification of a protein kinase C (PKC) activator, daphnoretin, that suppresses hepatitis B virus gene expression in human hepatoma cells.

We examined the antiviral activity of a crude extract prepared from a Chinese medicinal herb Wikstroemia indica C.A. Mey. One active component, daphnoretin (7-hydroxyl-6-methoxy-3,7'-dicoumarylether), was identified, which showed strong suppressive effects on the expression of the hepatitis B surface antigen (HBsAg) in human hepatoma Hep3B cells. To examine the signaling pathway of daphnoretin on the Hep3B cells, we pretreated Hep3B cells with 12-O-tetradecanoylphorbol-13-O-acetate (200 nM) for 24 hr to down-regulate intracellular protein kinase C (PKC) levels and found that the PKC-down-regulated Hep3B cells did not respond at all to daphnoretin. Furthermore, daphnoretin induced translocation of PKC from the cytosol to the membrane and down-regulated intracellular PKC levels in the Hep3B cells, indicating that it may directly activate PKC. This hypothesis was supported by the observation that daphnoretin directly competed with [3H]phorbol dibutyrate for the binding of PKC in the whole cell and activated purified PKC activity in vitro. Our results demonstrated that daphnoretin, with a structure distinct from phorbol ester, is a PKC activator and has suppressive effects on HBsAg gene expression in human hepatoma cells.

Antineoplastic Agents, Phytogenic↗

PubMed1996

Suppression of the tumorigenicity of human hepatoma hep3B cells by long-term retinoic acid treatment.

We cultured human hepatoma Hep3B cells in the presence of RA (10(-5) M) for 30 days; the expression of both alpha-fetoprotein and hepatitis B virus surface antigen were suppressed over 70% at the transcriptional level by RA treatment. The doubling time of RA treated Hep3B cells was slightly different from the control cells when they were cultured in 5% fetal calf serum/DMEM medium. However, cultured under serum-free conditions, the control Hep3B cells still grow, but the RA treated cells could not attach to the substratum of the culture plate and stopped growing. In vivo assay indicated that RA treatment completely suppressed the tumorigenicity of Hep3B cells in nude mice.

Animals↗

PubMed1996

Radio frequency electromagnetic exposure: tutorial review on experimental dosimetry.

Radio frequency (RF) dosimetry is the quantification of the magnitude and distribution of absorbed electromagnetic energy within biological objects that are exposed to RF fields. At RF, the dosimetric quantity, which is called the specific absorption rate (SAR), is defined as the rate at which energy is absorbed per unit mass. The SAR is determined not only by the incident electromagnetic waves but also by the electrical and geometric characteristics of the irradiated subject and nearby objects. It is related to the internal electric field strength (E) as well as to the electric conductivity and the density of tissues; therefore, it is a suitable dosimetric parameter, even when a mechanism is determined to be "athermal." SAR distributions are usually determined from measurements in human models, in animal tissues, or from calculations. This tutorial describes experimental techniques that are used commonly to determine SAR distributions along with the SAR limitations and unresolved problems. The methods discussed to obtain point, planar, or whole-body averaged SARs include the use of small E-field probes or measurement of initial rate of temperature rise in an irradiated object.

Animals↗

PubMed1996

Adipofascial flap of the lower leg based on the saphenous artery.

The adipofascial flap of the lower leg based on the saphenous artery is a modification of the saphenous artery flap. It has been used successfully in 5 patients for reconstruction of soft tissue defects around the knee and superior third of the tibia. The size of these flaps ranged from 5 x 12 cm to 5 x 18 cm. All flaps survived completely. These cases had minimal donor site morbidity because their donor sites were closed primarily with the preserved overlying skin.

Adolescent↗

PubMed1996

Expression, characterization, and genomic structure of carp JAK1 kinase gene.

A 3.7-kb cDNA encodes the carp JAK1 kinase of 1,156 amino acid residues. The overall amino acid sequence identity between carp JAK1 and murine JAK1, JAK2, JAK3, and human TYK2 is 57%, 35.5%, 31.3%, and 42.4%, respectively. In addition, carp JAK1 shows higher sequence homology to mammalian JAK1 in both the kinase-like (JH2) and kinase (JH1) domains (approximately 70% identity). Therefore, carp JAK1 is a homolog of mammalian JAK1. To investigate the possible function of JH2 domain, full-length, and various truncated forms of carp JAK1 were produced in the baculovirus system. Our results demonstrate that c-JH1 and c-JH2 associate with each other and c-JH2 can be tyrosine-phosphorylated by c-JAK1 and by c-JH(1 + 2). The JAK1 gene was also isolated from a carp genomic library and characterized. This gene is divided into 24 exons spanning at least 31 kb of genomic DNA. Exon 1 contains the 5'-untranslated region and exon 2 contains the putative translation initiation site. The 2.5-kb DNA region upstream of the transcription initiation site contains numerous potential binding sites for transcription factors including NF-IL6, HNF-5, AP1, GHF-5, and E2A. When this DNA fragment was placed upstream of the chloramphenicol acetyltransferase (CAT) reporter gene and transfected into a carp CF cell line, it could drive the synthesis of CAT enzyme 16 times more efficiently than the promoterless pCAT-Basic. Deletion analysis defined a positive regulatory region between -1,023 and -528. A smaller region (-181 to +59) without any typical TATA-box sequences, G + C-rich sequences, or other binding sequences for known transcription factors still had promoter activity. Constructs without this region did not have detectable promoter activity. This suggests that this region of DNA may play an important role in the expression of carp JAK1 gene.

Amino Acid Sequence↗

PubMed1996

Continuous thoracic epidural anesthesia for breast augmentation.

Thirty consecutive cases were scheduled for submuscular breast augmentation under continuous thoracic epidural anesthesia. The epidural tube was placed into the intervertebral space between the third and fourth thoracic vertebrae. An average of 15 ml of 2% lidocaine with 1:80,000 epinephrine was used as a primary anesthetic agent. There were no significant changes in respiratory function; only a transient elevation of blood pressure and increased heart rate were noted. All cases were successfully anesthetized, except one case (3%) who had a partial analgesic effect and needed to combine general anesthesia. One patient needed a single dose of ephedrine, 20 mg, to treat hypotension. Perioperative complications included transient shivering (33%), stuffy nose (20%), nausea (7%), and shortness of breath (13%). These symptoms were alleviated after reassurance or light sedation and oxygen inhalation. Immediate postoperative pain of the operative site was effectively controlled by injection of local anesthetics through the epidural tube. This study revealed that thoracic epidural anesthesia was feasible, effective, and even better than conventional alternative anesthetic techniques for breast augmentation.

Adult↗

PubMed1996

Assessment of cellular telephone and other radio frequency exposure for epidemiologic research.

Epidemiologists are now embarking on the evaluation of the hypothesis that exposure to radio frequency energy from low-power wireless communication devices, such as portable cellular telephones, causes brain cancer and other adverse health outcomes. Even in the laboratory, exposures from radio frequency sources are difficult to quantify; their measurement in large populations for epidemiologic study is challenging. In this paper, we outline the nature and magnitude of these exposures and discuss the prospects for obtaining useful measures of exposure for epidemiologic research.

Brain Neoplasms↗

PubMed1996

Early diagnosis of necrotizing fasciitis by utilization of ultrasonography.

Necrotizing fasciitis is a rare and rapid progression soft tissue infection. The only identifiable feature is tissue necrosis along a single fascia plane. Because the skin is initially spared, it is difficult for early recognition prior to extensive tissue destruction. Ultrasonography was used for early diagnosis of this infection in five cases. All 5 patients presented with severe cellulitis. Under the suspicion of necrotizing fasciitis, ultrasonography was performed before surgical debridement. Tissue biopsy was done for histological confirmation of the diagnosis. Three patients were proven to have necrotizing fasciitis and two cellulitis only. The ultrasonographic findings of necrotizing fasciitis included: 1) irregularity of the fascia; 2) abnormal fluid collections along the fascia plane; and 3) diffuse thickening of the fascia when compared with the control site in the normal limb. However, in severe infectious cellulitis, the above mentioned findings were not observed. Our results indicate the usefulness of the ultrasonography for early diagnosis of necrotizing fasciitis.

Adult↗

PubMed1996

Squamous cell carcinoma of the nail bed.

Squamous cell carcinoma of the nail bed is a rare disorder. Metastasis is extremely unusual. A case of primary squamous cell carcinoma of the nail bed with metastasis to the regional lymph nodes is reported. The tumor was successfully treated by amputation of the involved finger, block dissection of the regional lymph nodes, postoperative irradiation of the involved axilla, and systemic chemotherapy. Early diagnosis by biopsy, especially in patients with recurrent and persistent disease of the nail bed, is recommended, so that treatment can be instituted early while the tumor is confined to its primary site.

Adult↗

PubMed1996

Zigzag V-Y advancement flap for medial canthal defect after tumor excision.

A zigzag V-Y advancement flap based on the angular artery is used to repair the medial canthal defect after tumor excision. Only the middle-third subcutaneous attachments to the flap are left intact, which contain the vascular pedicle. The advancing zigzag edges of the flap can be naturally inserted around both limbs of the medial canthus, and this disperses the tendency to linear contracture and "trap-door" scarring. The described technique is an excellent choice for medial canthal defect, providing a well-contoured and aesthetically pleasing reconstruction.

Basal Cell Carcinoma↗

PubMed1996

Evaluation of MRI compatibility of the modified nucleus multichannel auditory brainstem and cochlear implants.

Magnetic resonance imaging (MRI) has been contraindicated for users of cochlear implants because of the internal magnet and other possible interactions. Users of the Nucleus Mini-22 Cochlear Implant (CI) or the experimental Multichannel Auditory Brainstem Implant (ABI) may have other disorders that are best diagnosed by MRI. The CI and ABI were modified by replacing the internal magnet and integrated circuit lid with nonmagnetic material. Tests were conducted in a 1.5-T MRI machine. Safety tests for force, heating, induced current, unintentional implant output, and implant damage were conducted by using various phantom models. Image distortion was evaluated in two subjects with implants. The maximum force measured was 2,818 dynes. There was < 0.1 degree C temperature increase in the vicinity of the implant. The maximum induced charge was > or = 667 times less than the minimum charge for auditory stimulation. There was no unintentional output during MRI scans and no change in implant function after 10 repeated scans. Image distortion consisted primarily of darkening and was worst in the axial plane, where it extended 1-2 cm medially and inferiorly from the receiver/stimulator. Compatibility-test results were acceptable, with a large margin of safety. Image distortion is limited to darkening in the immediate vicinity of the implant.

Adult↗

PubMed1995

Oral administration of dihydroartemisinin and ferrous sulfate retarded implanted fibrosarcoma growth in the rat.

In the presence of iron, dihydroartemisinin forms free radicals and causes cell death. Since most cancer cells have high rates of iron intake, dihydroartemisinin would have selective cytotoxic effect on cancer cells. The present experiment was designed to study the effect of dihydroartemisinin and ferrous sulfate on the growth of implanted fibrosarcoma in the rat. We found that the growth rate of the tumor was significantly retarded by daily oral administration of ferrous sulfate followed by dihydroartemisinin. No significant tumor growth retardation effect was observed in rats treated with either dihydroartemisinin or ferrous sulfate alone. The drug treatment did not significantly affect body weight compared with untreated tumor-implanted animals and no apparent toxic effect was observed after drug treatment. An artemisinin analog-ferrous salt combination may provide a novel approach for cancer therapy.

Administration, Oral↗

PubMed1995

Absence of radiofrequency heating from auditory implants during magnetic resonance imaging.

The possibility of tissue heating due to an auditory brainstem implant (ABI) or a modified cochlear implant (CI) during magnetic resonance imaging (MRI) of the head was tested on a full-sized human phantom using a realistic phantom head consisting of simulated skull, brain, and muscle. Dielectric properties of the brain, muscle, and bone materials were similar to those of human tissues at 64 MHz. The body consisted of homogeneous phantom muscle enclosed in a human-shaped fiberglass shell. Thermographic and fiber-optic temperature measurements were conducted to reveal any heating. Thermograms of sagittal, frontal, and horizontal planes of the head with the ABI and CI electrodes were taken immediately before and after a 26 min MRI scan. The MRI sequence was set at 94 excitations and 25 ms echo time to induce maximum radiofrequency heating, as suggested by the General Electric Company. The difference of these two thermograms gives the heating results. In two uncut phantom heads. Teflon tubes were placed along the implanted ABI and CI, and temperature data were recorded via fiber-optic probes before, during, and after the MRI. Results showed no observable heating associated with the ABI and the modified CI during worst-case MRI of the head.

Brain↗

PubMed1995

Active compounds from Saussurea lappa Clarks that suppress hepatitis B virus surface antigen gene expression in human hepatoma cells.

We have examined the antiviral activity of the crude extract prepared from the root of Saussurea lappa Clarks, a Chinese medicinal herb which is widely used for many illnesses including cancer. Two active components, costunolide and dehydrocostus lactone, were identified which show strong suppressive effect on the expression of the hepatitis B surface antigen (HBsAg) in human hepatoma Hep3B cells, but have little effect on the viability of the cells. Both costunolide and dehydrocostus lactone suppress the HBsAg production by Hep3B cells in a dose-dependent manner with IC50s of 1.0 and 2.0 microM, respectively. Northern blotting analysis shows that the suppression of HBsAg gene expression by both costunolide and dehydrocostus lactone were mainly at the mRNA level. Furthermore, the suppressive effect of costunolide and dehydrocostus lactone on HBsAg and hepatitis B e antigen (HBeAg), a marker for hepatitis B viral genome replication in human liver cells, was also observed in another human hepatoma cell line HepA2 which was derived from HepG2 cells by transfecting a tandemly repeat hepatitis B virus (HBV) DNA. Similarly, the mRNA of HBsAg in HepA2 cells was also suppressed by these two compounds. Our findings suggest that costunolide and dehydrocostus lactone may have potential to develop as specific anti-HBV drugs in the future.

Antiviral Agents↗

PubMed1995

The novel desmethyldestruxin B2, from Metarhizium anisopliae, that suppresses hepatitis B virus surface antigen production in human hepatoma cells.

We have examined the antiviral activity of a crude extract prepared from the culture medium of the fungus Metarhizium anisopliae. Eight active destruxins were identified which showed strong suppressive effect on the production of the hepatitis B surface antigen (HBsAg) in human hepatoma Hep3B cells. One new compound, desmethyldestruxin B2 [1], was isolated from M. anisopliae. This structure was determined based on its nmr and mass spectral data.

Animals↗

PubMed1995

Reconstruction of the upper leg and knee with a reversed flow saphenous island flap based on the medial inferior genicular artery.

Soft-tissue defects around the knees and below-the-knee amputation stumps are difficult to reconstruct. We present an option for reconstruction of these defects. Reversed flow saphenous island flaps, based on the medial inferior genicular artery, were successfully transferred in 6 patients. All wounds healed well postoperatively. The donor defect can be closed directly when the width is less than 7 cm. This is a thin and reliable fasciocutaneous flap that is useful in covering defects around the knee joint, popliteal fossa, upper half of the leg, and below-the-knee amputation stump.

Adult↗