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Biomedical subjects

C K Chou

Publications and source records attributed to C K Chou.

At least 199 records · Page 11Linked to original sources
PubMed1979

Carbon-loaded Teflon electrodes for chronic EEG recordings in microwave research.

Conventional metal electrodes can cause serious modification and intensification of the rate of energy absorption in tissues during exposure of animals to microwaves. Carbon-loaded Teflon with a conductivity close to that of tissue has been implanted and maintained for four to six months at cortical and subcortical locations in rabbits. The EEG and its spectrum as recorded from the carbon-loaded Teflon electrodes are comparable to those recorded from conventional metal electrodes. Histological examination showed good tissue compatibility. Recordings made during acute exposure of rabbits to microwave radiation (2450-MHz) at 100 mW/cm2 showed no electromagnetic interference. The results indicate that carbon-loaded Teflon electrodes can be implanted chronically to record the EEG in animals during the course of microwave radiation.

Animals↗
PubMed1977

Purification of phosphoprotein phosphatase from bovine cardiac muscle that catalyzes dephosphorylation of cyclic AMP-binding protein component of protein kinase.

A phosphoprotein phosphatase that catalyzes the dephosphorylation of cyclic adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase from bovine cardiac muscle has been purified to homogeneity by a modification of the procedure of Brandt et al. (Brandt, H., Capulong, Z.L., and Lee, E. Y. C. (1975) J. Biol. Chem. 250, 8038-8044). Treatment of the enzyme preparation with ethanol during the early stages of purification results in activation concomitant with reduction in molecular weight to 30,000. The purified activated enzyme has a Km for phospho-protein kinase in the presence or absence of 1.2 mM Mn2+ of 5 and 22 micronM, respectively. Phosphatase activity on phospho-protein kinase but not on other phosphoprotein substrates was cAMP-dependent. This selective activation by cAMP reflects the preference of the phosphatase for the free, phosphorylated cAMP-binding protein rather than the phosphoholoenzyme.

Animals↗
PubMedDate not supplied

MRI manifestations of gastrointestinal lymphoma.

The magnetic resonance (MR) images of 11 cases of gastrointestinal lymphoma are presented. The findings include irregularly thickened mucosal folds, irregular submucosal infiltration, annular constricting lesion, exophytic tumor growth, mesenteric masses, and mesenteric/retroperitoneal lymphadenopathy. The tumors were homogeneous and intermediate in signal intensity on T1-weighted images. Heterogeneously increased signal intensities were noted on T2-weighted images. There was mild to moderate enhancement after intravenous administration of gadolinium dimeglumine (Gd-DTPA). The submucosal tumor infiltration might be outlined between the strongly GD-DTPA-enhanced mucosa and the low-intensity muscular layer. In one case that received tumor resection, the pathological examination showed destruction of most parts of the muscular layer, and the MR images did not disclose the low-intensity muscular zone.

Adolescent↗
PubMedDate not supplied

Abdominal pseudotumors and simulated lymphadenopathy in MRI: differential features with the use of retrograde air insufflation.

In order to evaluate the contribution of retrograde air insufflation in decreasing the occurrence of pseudotumor appearance and mimicked lymphadenopathy due to nonair-distended bowel loops, we retrospectively compared two groups of magnetic resonance (MR) examinations. In the group receiving retrograde air insufflation, 10.8% (67 of 619) of images showed a tumor-like lesion due to nonair-distended bowel loop(s), whereas in the group not receiving air introduction, a tumor-like lesion was simulated in 45.6% (140 of 307) of images. Furthermore, a collapsed bowel loop(s) mimicking an enlarged lymph node close to the aorta, inferior vena cava, or bilateral iliac vessels was found in 9.5% (24 of 252) of images of the latter group, in contrast to only 1.8% (9 of 505) of images of the former group. This study shows that retrograde air insufflation greatly reduces the occurrence of pseudotumor appearance and false impression of paraaortic, paracaval, or parailiac lymphadenopathy secondary to nonair-distended bowel loop(s).

Abdomen↗
PubMedDate not supplied

MRI demonstration of peritoneal implants.

The magnetic resonance imaging (MRI) findings of 12 proven cases of peritoneal implants, mainly carcinomatosis, were reviewed for evidence of peritoneal seedings. The seeded sites include the pouch of Douglas, the ileocecal and retrocecal regions, the right and left paracolic gutters, Morison's pouch, the right subdiaphragmatic parietal peritoneum, the greater and lesser omentum, the gastrocolic, gastrosplenic, and phrenicocolic ligaments, the small bowel mesentery, the sigmoid and transverse mesocolons, and the small and large bowel walls. Sizes varied from less than 1 cm to omental cake and bulky tumors. The findings include linear or tiny nodular infiltrations of the omentum and subperitoneal fat (ligamentous, mesenteric, and mesocolic), focal or segmental wall thickenings, loss of unilateral colonic haustration with sacculation on the contralateral side, and nodular soft tissue masses along different locations of the peritoneal surfaces. Air was introduced via an antegrade or retrograde method to act as a gastrointestinal contrast agent and was found to be useful for delineating the seedings. As is true with computed tomography scan, miliary implants are also not detectable with MRI. The sensitivity and specificity of MRI in detecting peritoneal implants remain to be determined.

Abdominal Neoplasms↗
PubMedDate not supplied

MRI manifestations of gastrointestinal wall thickening.

The appearance of gastrointestinal wall thickening of various entities is demonstrated on magnetic resonance imaging (MRI). The entities include benign gastric ulcer, gastric carcinoma, pancreatic carcinoma with direct invasion of stomach, duodenal leiomyoma, radiation enteritis, peritonitis, colonic carcinoma, recurrent carcinoma at the gastrojejunal anastomosis with direct extension to the transverse colon, colocolic intussusception, sigmoid diverticulitis with pericolonic abscess and fistula into the urinary bladder, and lymphoma of the stomach, duodenum, small bowel, and colon. Air was introduced antegradedly or retrogradedly into the alimentary tract to act as a contrast agent. When the bowel was distended by air, the normal bowel wall was barely visible or even invisible. Abnormal focal or segmental wall thickening was outlined between the intraluminal air and extraluminal fat. In some instances, the thickenings were better demonstrated on coronal or sagittal sections. The proper muscular layer of the bowel has a low-signal intensity and was delineated between the thickened mucosa-submucosa and extramural fat. Interruption of this low-intensity zone might represent tumor invasion through the muscular layer.

Digestive System↗
PubMedDate not supplied

CT of the duodenojejunal junction.

To determine the location of the duodenojejunal junction (DJJ) at computed tomography (CT), we retrospectively reviewed 309 consecutive CT examinations. These included 162 men and 127 women (mean age = 57 years old, range = 11-85 years old). Some people received more than one examination. The clinical indications included various kinds of neoplasms, inflammations, congenital lesions, trauma, and other conditions. The DJJ was defined as the first sectioned ascending duodenum whose major part lies to the right side of the crossing part of the inferior mesenteric vein over the immediate beginning of the jejunum. Forty-nine examinations were excluded due to distortion of the DJJ by contiguous pathologic processes or nonadministration of intravenous contrast medium. In 36 examinations, the junctions were not identified. In the successfully identified 224 examinations, the DJJ was located to the left in 75 (33.5%), in the left half in 87 (38.8%), and in the right half or to the right of the vertebral body in 4 (1.8%) examinations. The midline of the DJJ was along the left margin and in the midline of the vertebral body in 53 (23.7%) and 5 (2.2%) examinations. In the anteroposterior direction, it was totally in front of the aorta in 189 (84.4%) and within the projected contour of the aorta in 11 (4.9%) examinations. The midline of the DJJ was along the anterior margin of the aorta in 24 (10.7%) examinations. Its cephalocaudal position was at the upper L1 in 36 (16.1%), lower L1 in 70 (31.3%), upper L2 in 75 (33.5%), and lower L2 in 21 (9.4%) examinations even though it ranged from upper T12 to upper L3.(ABSTRACT TRUNCATED AT 250 WORDS)

Contrast Media↗
PubMedDate not supplied

Small bowel volvulus.

Two cases of small bowel volvulus with mild clinical symptoms in which upper gastrointestinal series, computed tomography, and magnetic resonance imaging were performed are reported. Angiography was also performed in one case. Neither patient received laparotomy and the diagnosis was based on imaging findings.

Female↗
PubMedDate not supplied

Functional implication of human serine/threonine kinase, hAIK, in cell cycle progression.

Protein phosphorylation is involved in many biological activities and plays important roles in cell cycle progression. In the present study, we identified a serine/threonine kinase, hAIK, from human hepatic cells using degenerated polymerase chain reactions with a pair of primers derived from the highly conserved sequence in the catalytic domain of kinases. The full-length hAIK cDNA was then obtained, which contained 403 amino acids and was homologous to Drosophila Aurora2 and yeast Ipl1 proteins. Northern blotting analysis revealed that hAIK was highly expressed in the testis but not in other tissues. Expressions of hAIK drastically increased in cancer tissues/cell lines but not in fibroblasts or nontumorigenic cell lines. The recombinant hAIK protein phosphorylated itself and histone H1; this phosphorylation activity was totally abolished after a point mutation at the catalytic domain (hAIKm). During the interphase cell, hAIK was found mainly in the cytoplasm; during mitosis hAIK accumulated at the centrosomes. In addition, overexpression of hAIK in cancer cell lines (HEK293T and HeLa) appeared to inhibit cell cycle progression. None of these phenomena were observed in hAIKm whose kinase activity was rendered inactive. Our results suggest that hAIK protein/activity might modulate cell cycle progression by interacting with the centrosomes and/or proteins associated with these structures.

Amino Acid Sequence↗
PubMedDate not supplied

Protein kinase C-mediated tyrosine phosphorylation of paxillin and focal adhesion kinase requires cytoskeletal integrity and is uncoupled to mitogen-activated protein kinase activation in human hepatoma cells.

Treatment of cultured human hepatoma HepG2 cells with the protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), results in an increase in tyrosine phosphorylation of several proteins, including the focal adhesion kinase (FAK) and paxillin using anti-phosphotyrosine Western blotting and immunoprecipitation. However, when cells are in suspension or in the presence of cytochalasin D which disrupts the intracellular network of actin microfilaments, TPA loses its ability to stimulate tyrosine phosphorylation of FAK and paxillin but it still activates mitogen-activated protein kinase (MAPK) and induces PKC translocation from cytosol to the membrane in HepG2 cells. On the other hand, PD98059, a specific inhibitor of mitogen-activated protein kinase kinase, blocks TPA-induced MAPK activation but has no effect on TPA-induced tyrosine phosphorylation. Our findings suggest that TPA-induced tyrosine phosphorylation of FAK and paxillin in human hepatoma cells is PKC dependent and requires the integrity of the cell cytoskeleton but is uncoupled to the signal transduction pathway of PKC leading to the translocation of PKC and MAPK activation.

Blotting, Western↗
PubMedDate not supplied

Utilization of Drosophila eye to probe the functions of two mammalian serine/threonine kinases, Snk and HsHPK.

Here we report a quick functional analysis of two mammalian serine/threonine kinases, a serum inducible kinase (Snk) and Homo sapiens hepatoma protein kinase (HsHPK), using Drosophila eye as a model system. We generated transgenic fly lines carrying constructs of both kinases under control of the GAL upstream activating sequence (UAS). Each UAS line was then crossed to a line in which GAL4 expression was driven by one of the following promoters, eyeless (ey), glass or decapentaplegic. Thus, different kinase mutants can be ectopically expressed in a promoter-dependent manner. We observed that the ectopic expression of either the wild-type or active form of Snk driven by the glass promoter resulted in a rough-eye phenotype. Nevertheless, the ectopic expression of HsHPK under the control of the ey promoter resulted in a small-eye phenotype. The results of this study demonstrated that ectopic expression of these two mammalian genes could be achieved by the regulation of Drosophila promoters. In addition, the effects of these ectopically expressed genes on eye development could be an implication of their functions with respect to cell proliferation and differentiation. Thus, Drosophila eye, with the powerful genetic tools and vast information on eye development available, can be a useful system to probe the functions of mammalian genes in the postgenome era.

Animals↗
PubMedDate not supplied

CT of small bowel ischemia.

We evaluated the computed tomographic (CT) features of small bowel (SB) ischemia and necrosis and correlated the findings with clinical outcome or patient prognosis. Sixty-eight surgically or angiographically proved cases of SB ischemia were retrospectively reviewed. The CT features of intestinal ischemia were divided into three groups: (A) thinned bowel wall with poor enhancement, intramural gas, or portal venous gas; (B) thickened SB wall without superior mesenteric vein thrombosis; and (C) thickened SB wall with superior mesenteric vein thrombosis or intussusception. The evaluated factors included bowel wall or mucosal enhancement pattern, SB dilatation, mesenteric edema, and CT evidence of narrowing or occlusion of the superior mesenteric artery or vein. The bowel necrosis rates and mortalities were compared with chi-square test. Oral contrast material was not administered. Intramural gas and SB dilatation were associated with a higher bowel necrosis rate (eight of eight, 100%, and 17 of 21, 81%, respectively) in group A. Poor mucosal enhancement of the thickened bowel wall indicated a higher bowel necrosis rate in groups B (six of seven, 86%) and C (12 of 12, 100%) than did normal mucosal enhancement. Only intramural gas was accompanied with a higher mortality (six of eight, 75%). Intramural gas of a thinned bowel wall and poor mucosal enhancement of a thickened small bowel wall are useful signs of bowel necrosis. Intramural gas would indicate poor patient prognosis.

Aged↗
PubMedDate not supplied

CT of the mesenteric vascular anatomy.

BACKGROUND: To evaluate the appearance of the arrangement of the superior mesenteric artery (SMA) and superior mesenteric vein (SMV) on computed tomography (CT) in normal patients and in patients with abdominal masses. METHODS: One hundred seventy-seven consecutive abdominal CT examinations of 143 adults and two children were reviewed. The relationship of the SMV to the SMA was recorded at four locations: the beginning of the mesenteric vessels and levels 3 cm, 6 cm, and 9 cm caudad to the beginning. The relationship of the SMV to the SMA was divided into four quadrants in relation to the SMA: I, ventral right or directly ventral; II, dorsal right or directly right; III, dorsal left or directly dorsal; and IV, ventral left or directly left. RESULTS: In the beginning of the SMV-SMA complex and levels 3 cm, 6 cm, and 9 cm caudal to the beginning, the SMV was located in quadrant I in 146, 84, 69, and 43 examinations, in quadrant II in 31, 93, 71, and 27 examinations, in quadrant III in zero, zero, five, and three examinations, and in quadrant IV in zero, zero, nine, and 15 examinations, respectively. The cases with SMV inversion had neither malrotation nor adjacent tumor compression. All the cases with an adjacent tumor-induced compression of the SMV-SMA complex had a normal SMV-SMA relationship. CONCLUSION: In the first 3 cm, the SMV is always to the right of the SMA. Caudal to the level of 6 cm, the SMV may be located to the left of the SMA without evidence of malrotation. A midgut nonrotation is more likely to be present when a proximal SMV inversion is coexistent with a rightward direction of the proximal jejunal vessels. A hypothetical depiction of the step-by-step change of the SMV-SMA relationship during embryologic development may explain the arrangement patterns of the mesenteric vessels in normal rotation and midgut nonrotation.

Abdominal Neoplasms↗
PubMedDate not supplied

CT of large small-bowel diverticulum.

The previous reports concerning the computed tomographic (CT) appearances of small bowel diverticulum are usually limited to those of diverticulitis. We present the CT findings of uncomplicated, large small bowel diverticulum in five patients. An interesting coexistence of large small bowel diverticulum and small bowel volvulus will be mentioned. Four patients had recurrent abdominal pain in the past 2 years.

Aged↗
PubMedDate not supplied

CT of agenesis and atrophy of the right hepatic lobe.

BACKGROUND: To identify and differentiate agenesis and severe atrophy of the right hepatic lobe on computed tomography (CT). METHODS: The CT examinations of three cases of agenesis and 11 cases of severe atrophy of the right hepatic lobe were reviewed. We evaluated visibility of the three hepatic veins, the two main portal veins (including their branches if necessary), the dilated intrahepatic ducts, enlargement of the medial and lateral segments of the left lobe and caudate lobe of the liver, presence of a retrohepatic gallbladder, hyperattenuation of the atrophic liver parenchyma, posterolateral interposition of the hepatic flexure of the colon, and upward migration of the right kidney. RESULTS: In the three cases of agenesis, no structure can be recognized as the right hepatic vein, right portal vein, or dilated right intrahepatic ducts. In the 11 cases of severe lobar atrophy, the right portal vein (or its branches) was recognized in eight cases, the right hepatic vein in four cases, and the dilated right intrahepatic ducts in 11 cases. The degree of enlargement of the lateral segment does not necessarily change inversely with the size of the medial segment and the caudate lobe. The retrohepatic gallbladder is present in eight cases (two in agenesis and six in atrophy). The phenomenon of hyperattenuation of the atrophic liver parenchyma was noted in six cases. CONCLUSION: Even though a retrohepatic gallbladder and a severely distorted hepatic morphology due to compensatory hypertrophy of the left and caudate lobes may raise a suspicion of agenesis of the right lobe of the liver, absence of visualization of all of the right hepatic vein, right portal vein and its branches, and dilated right intrahepatic ducts is a prerequisite of the diagnosis of agenesis of the right hepatic lobe on CT. In severe lobar atrophy, at least one of these structures is recognizable.

Adult↗
PubMedDate not supplied

Reconstruction of plantar heel defect using reinnervated, skin-grafted flexor digitorum brevis flap.

Two cases with extensive plantar avulsion injuries had their heel defects resurfaced initially with full thickness skin grafts. Two months later, reinnervation presented in areas of grafted skin innervated by medial and lateral plantar nerves. No reinnervation was found in the plantar heel region originally innervated by the medial calcaneal nerve. Heel ulceration in the non-sensate, grafted skin occurred in the first case. Reinnervated, skin-grafted flexor digitorum brevis muscle flaps were then used for reconstructing the non-sensate plantar heels. There was no breakdown of skin during the follow-up period of 8 months and 6 months respectively. This method provides sensate and durable cover for extensive plantar heel defects.

Adolescent↗