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Biomedical subjects

K H Chang

Publications and source records attributed to K H Chang.

At least 37 records · Page 2Linked to original sources
PubMed2001

G561 site-directed deletion mutant chitinase from Aeromonas caviae is active without its 304 C-terminal amino acid residues.

A G561 mutant of the Aeromonas caviae chitinase ChiA was made by PCR site-directed deletion mutagenesis in order to study the role of the 304 C-terminal amino acid residues of ChiA in the enzymatic hydrolysis of chitin. The recombinant ChiAG561 encoded on a 1.6-kb DNA fragment of A. caviae chiA was expressed in a heterologous Escherichia coli host using the pET20b(+) expression system. The His-Tag-affinity-purified recombinant ChiAG561 had a calculated molecular mass of 63,595 Da, which was consistent with the 67,000 Da estimated by SDS-PAGE. The G561 deletion mutant enzyme had the same optimum pH (6.5) as the full-length ChiA and a lower optimum temperature (37 degrees C instead of 42.5 degrees C). Biochemical properties of the recombinant ChiAG561 suggested that deletion of the 304 C-terminal amino acid residues of ChiA did not significantly affect ChiA enzyme activity. However, compared to the full-length ChiA, the mutant chitinase had a ten-fold higher relative activity with 4-methylumbelliferyl-N-N'-N"-triacetylchitotriose [4-MU-(GlcNAc)3] as a substrate, and higher rates of hydrolysis with both chitin and colloidal chitin substrates. Results obtained from this study suggest that the active region of A. caviae ChiA is located in the region before G561 of the protein molecule.

Aeromonas↗
PubMed2001

Neuroimaging findings of cortical dyslamination with cytomegaly.

PURPOSE: Our aims were to identify (a) the characteristic magnetic resonance imaging (MRI) findings of cortical dyslamination with cytomegaly, including dysplastic and destructive lesions; (b) the relationship between MRI findings and pathologic characteristics; (c) the diagnostic role of functional neuroimaging studies in patients with these pathologies. METHODS: The series consisted of 23 adult patients who had proven cortical dyslamination with cytomegaly. The abnormalities found on MRI were subdivided according to the patterns of involvement. They also were compared with the patients' pathologic characteristics. With visual qualitative analysis, [18F]fluorodeoxyglucose with positron emission tomography (FDG-PET), and ictal single-photon emission computed tomography (SPECT), observations were classified as localizing, lateralizing, nonlateralizing, false-localizing, and false-lateralizing. The standard for correct localization of neuroimages was defined to be the resected lobe. RESULTS: Focal abnormalities were found in 14 cases by MRI. Six cases showed typical MRI findings of focal cortical dysplasia, with focal areas of cortical thickening with or without poor grey-white matter differentiation. Focal subcortical high signal intensities on T2-weighted images occurred in two cases. Six patients had the focal destructive pattern. Three of eight cases with normal MRI and four of eight cases with the nondestructive cortical dysplasia pattern had balloon cells. However, these were not found in six patients with the destructive MRI pattern. FDG-PET localized the pathologic lobe in 13 (65%) of 20 cases, and ictal SPECT achieved this in 11 (61.1%) of 18 cases. FDG-PET and ictal SPECT also correctly localized the pathologic lobe in four and two cases with normal MRI, respectively. CONCLUSIONS: Two distinct patterns of abnormal MRI were found in the pathology of cortical dyslamination with cytomegaly. These dysplastic and destructive patterns might reflect different pathogeneses, such as the time of insult. FDG-PET and ictal SPECT have confirmatory and independent diagnostic roles in localizing epileptogenic foci.

Adult↗
PubMed2001

alpha-MSH decreases apoptosis in ischaemic acute renal failure in rats: possible mechanism of this beneficial effect.

BACKGROUND: Apoptosis frequently occurs in acute renal injury but the molecular mechanisms responsible for this distinct form of cell death are largely unknown. Fas belongs to the tumour necrosis factor (TNF)/nerve growth factor superfamily and engagement by Fas ligand induces apoptosis in various epithelial cells. To investigate the role of apoptosis and associated mechanisms, we examined the occurrence of apoptosis and Fas and Fas ligand expression, and the therapeutic effect of alpha-melanocyte-stimulating hormone (alpha-MSH), a potent anti-inflammatory cytokine in an ischaemic acute renal failure (ARF) rat model. We also examined neutrophil infiltration together with intercellular adhesion molecule-1 (ICAM-1) expression because of their possible involvement in apoptosis due to their ability to release various inflammatory cytokines and reactive oxygen species. METHODS: After unilateral nephrectomy in female Sprague-Dawley rats, the renal artery of the contralateral kidney was clamped for 40 min and reperfused. alpha-MSH or vehicle was injected intraperitoneally immediately after reperfusion and at 1, 6, or 24 h after reperfusion. The expression of Fas and Fas ligand was studied by western blot analysis and semiquantitative reverse transcription polymerase chain reaction (RT-PCR). Apoptosis was assessed by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) method, and neutrophil infiltration by naphthol AS-D chloracetate staining. The degree of apoptosis, neutrophil infiltration, and Fas and Fas ligand, and ICAM-1 expression, as well as biochemical and histological data were compared between the alpha-MSH and the vehicle-treated groups. RESULTS: Intraperitoneally administered alpha-MSH significantly reduced renal injury, measured by blood urea nitrogen (BUN) and creatinine and by the degree of tubular necrosis (109.6+/-7.1/54.7+/-3.1 mg/dl for BUN, and 1.6+/-0.2/1.03+/-0.06 mg/dl for creatinine 24 h after ischaemia) (5.4+/-0.8/2.6+/-0.3 for injury score 24 h after ischaemia). Ischaemia caused an increase in Fas and Fas ligand expression and was accompanied by morphological evidence of apoptosis. alpha-MSH significantly reduced the degree of apoptosis, as well as Fas and Fas ligand expression (mean apoptotic cell number, 41.7+/-3.5/14.2+/-2.2 per x200 field at 24 h after ischaemia. Fas protein expression: sham, 1409+/-159 DI (densitometric index); vehicle/alpha-MSH, 2818+/-635/1306+/-321 DI at 24 h and 5542+/-799/2867+/-455 DI at 72 h after ischaemia. Fas ligand protein expression: sham, 1221+/-181 DI; vehicle/alpha-MSH, 2590+/-85/1279+/-169 DI at 4 h, 4376+/-268/2432+/-369 DI at 24 h and 5200+/-648/2253.7+/-1104 DI at 72 h after ischaemia). Neutrophil infiltration and ICAM-1 expression were also significantly reduced in alpha-MSH group (neutrophil infiltration: vehicle/ alpha-MSH, 5.05+/-1.8/1.59+/-0.4) (ICAM-1 expression, vehicle/alpha-MSH 0.46+/-0.21/0.29+/-0.19). CONCLUSION: These results suggest that apoptosis clearly contributes to tubular cell loss in ischaemia/reperfusion (I/R) injury possibly by neutrophil-mediated pathways or an increase in Fas-Fas ligand expression. The observed beneficial effect of alpha-MSH could be related to these mechanisms.

Acute Kidney Injury↗
PubMed2001

Early development of vasogenic edema in experimental cerebral fat embolism in cats: correlation with MRI and electron microscopic findings.

RATIONALE AND OBJECTIVES: To evaluate the magnetic resonance imaging and electron microscopic findings of the hyperacute stage of cerebral fat embolism in cats and the time needed for the development of vasogenic edema. METHODS: Magnetic resonance imaging was performed at 30 minutes (group 1, n = 9) and at 30 minutes and 1, 2, 4, and 6 hours after embolization with triolein (group 2, n = 10). As a control for group 2, the same acquisition was obtained after embolization with polyvinyl alcohol particles (group 3, n = 5). Magnetic resonance images were analyzed qualitatively and quantitatively. Electron microscopic examination was done in all cats. RESULTS: In group 1, the lesions were iso- or slightly hyperintense on T2-weighted (T2W) and diffusion-weighted (DWIs) images, hypointense on the apparent diffusion coefficient (ADC) map image, and markedly enhanced on the gadolinium-enhanced T1-weighted images (Gd-T1WIs). In group 2 at 30 minutes, the lesions were similar to those in group 1. Thereafter, the lesions became more hyperintense on T2WIs and DWIs and more hypointense on the ADC map image. The lesions were enhanced on Gd-T1WIs at all acquisition times. In group 3, the lesions showed mild hyperintensity on T2WIs at 6 hours but hypointensity on the ADC map image from 30 minutes, with a tendency toward a greater decrease over time. The lesions were not enhanced on Gd-T1WIs at any time point. Electron microscopic findings revealed discontinuity of the capillary endothelial wall, perivascular and interstitial edema, and swelling of glial and neuronal cells in groups 1 and 2. Cellular swelling and interstitial edema were more prominent in group 2. In group 3, interstitial edema was seen; however, discontinuity of the endothelial wall was absent. CONCLUSIONS: The lesions were hyperintense on T2WIs and DWIs, hypointense on the ADC map image, and enhanced on Gd-T1WIs. On electron microscopy, the lesions showed cytotoxic and vasogenic edema with disruption of the blood-brain barrier. Vasogenic edema seems to develop within 30 minutes in cerebral fat embolism in cats.

Animals↗
PubMed2001

Grey matter abnormalities in obsessive-compulsive disorder: statistical parametric mapping of segmented magnetic resonance images.

BACKGROUND: Although a number of functional imaging studies are in agreement in suggesting orbitofrontal and subcortical hyperfunction in the pathophysiology of obsessive-compulsive disorder (OCD), the structural findings have been contradictory. AIMS: To investigate grey matter abnormalities in patients with OCD by employing a novel voxel-based analysis of magnetic resonance images. METHOD: Statistical parametric mapping was utilised to compare segmented grey matter images from 25 patients with OCD with those from 25 matched controls. RESULTS: Increased regional grey matter density was found in multiple cortical areas, including the left orbitofrontal cortex, and in subcortical areas, including the thalamus. On the other hand, regions of reduction were confined to posterior parts of the brain, such as the left cuneus and the left cerebellum. CONCLUSIONS: Increased grey matter density of frontal-subcortical circuits, consonant with the hypermetabolic findings from functional imaging studies, seems to exist in patients with OCD, and cerebellar dysfunction may be involved in the pathophysiology of OCD.

Adult↗
PubMed2001

Optimal production and in vitro activity of recombinant endostatin from stably transformed Drosophila melanogaster S2 cells.

Recombinant plasmids containing a complementary deoxyribonucleic acid coding mouse endostatin were transfected and stably expressed in Drosophila melanogaster Schneider 2 (S2) cells. Stably transformed polyclonal cell populations expressing recombinant endostatin were isolated after 4 wk of selection with hygromycin B. Recombinant endostatin expressed in the stably transformed S2 cells under the influence of the Drosophila BiP protein signal sequence was secreted into the medium. Recombinant endostatin was also purified to homogeneity using a simple one-step Ni2+ affinity fractionation method. Purified recombinant endostatin inhibited endothelial cell proliferation in a dose-dependent manner. The concentration at maximum inhibition for recombinant endostatin was approximately 1.8 microg/ml. The stably transformed S2 cells produced 18 mg recombinant endostatin/L 7 d after induction with 5 microM CdCl2. Sodium butyrate supplementation (2.5 mM) increased recombinant endostatin production by 17%. These findings demonstrate optimal production and in vitro activity of recombinant endostatin from stably transformed D. melanogaster S2 cells.

Angiogenesis Inhibitors↗
PubMed2001

Incidence and clinical profile of extra-medial-temporal epilepsy with hippocampal atrophy.

We tried to investigate the incidence and the clinical profile of intractable epilepsy with hippocampal atrophy and ictal onset zones located in areas other than the hippocampus (extra-medial-temporal epilepsy; EMTE). We included patients who had hippocampal atrophy confirmed by MRI but with extra-medial-temporal ictal onset zones as verified by invasive intracranial electrodes or video-EEG monitoring. The case histories, interictal EEG, ictal semiology, other MRI findings in addition to hippocampal atrophy, and results of ictal SPECT and PET scans were evaluated. Results were compared with those of surgically proven medial temporal lobe epilepsy with hippocampal atrophy recruited during the same period. 8.5% of the intractable epilepsy patients with hippocampal atrophy had extra-medial temporal epileptogenic zones. A history of encephalitis and hemiconvulsion-hemiparesis were significantly common in the EMTE group. Most of the interictal EEGs of EMTE patients showed extratemporal irritative zones. MRI, ictal SPECT, and FDG-PET seemed to be helpful at localizing the true epileptogenic zones. The predominant EMTE seizure type was focal motor seizure with secondary generalization. Some portion of intractable epilepsy patients with hippocampal atrophy had extra-medial-temporal epileptogenic foci and careful analysis of semiology and neuroimagings could yield clues to correct diagnosis.

Adult↗
PubMed2001

The value of cystoscopy and intravenous urography after magnetic resonance imaging or computed tomography in the staging of cervical carcinoma.

The clinical staging system for cervical carcinoma presently recommended by the International Federation of Gynecology and Obstetrics (FIGO) does not include MRI or CT findings and thus suffers limited accuracy. Recently however, the positive contributions of MRI and CT to preoperative staging have been reported. This study involves a determination of the value of routine cystoscopy and intravenous urography, in the detection of bladder invasion or hydronephrosis resulting from cervical carcinoma, among patients who had undergone MRI or CT. Among a total 296 patients with cervical carcinoma, 271 patients (92%) had undergone MRI and 25 (8%) CT. Bladder invasion was identified pathologically by cystoscopic biopsy in 8 (57%) of the 14 patients with suspected bladder invasion on MRI or CT. There was no bladder invasion in any of the other cases lacking in bladder invasion evidence on MRI or CT. Hydronephrosis was identified by intravenous urography in 18 patients, as it also was in all of these cases on MRI or CT, confirming a negative predictive value for MRI or CT, in detecting bladder invasion or hydronephrosis from cervical carcinoma, of 100%. Therefore, although MRI or CT cannot totally replace cystoscopy, the latter is unnecessary in the absence of bladder invasion evidence on MRI or CT. Intravenous urography, however, can be safely omitted whenever MRI or CT is performed.

Adult↗
PubMed2001

Urethral diverticulo-rectal fistula in AIDS.

A 41-year-old heterosexual African man was evaluated for persistent urethral discharge, pneumaturia and watery diarrhea. Radiographic and endoscopic procedures established the diagnosis of a rectourethral fistula. The differential diagnosis of an acquired rectourethral fistula and the significance of AIDS are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Lateralizing ability of single-voxel proton mr spectroscopy in hippocampal sclerosis: comparison with mr imaging and positron emission tomography.

BACKGROUND AND PURPOSE: Proton MR spectroscopy (MRS) is still in the early stages in the evaluation of epilepsy, and comparisons with MR imaging and positron emission tomography (PET) in the same patients have rarely been documented. The purpose of this study was to evaluate the lateralizing ability of single-voxel MRS in comparison with MR imaging and PET in patients with hippocampal sclerosis. METHODS: Thirty-three patients with intractable temporal lobe epilepsy whose MR imaging diagnosis was unilateral hippocampal sclerosis and who underwent anterior temporal lobectomy and had good postsurgical outcome over 1-year follow-up were included in the study. MR spectra were obtained from the hippocampus bilaterally, using the point-resolved spectroscopy sequence. Metabolite ratios of NAA/Cho and NAA/Cr were calculated from the relative peak height measurements. An NAA/Cho ratio of 0.8 or less and an NAA/Cr ratio of 1.0 or less were regarded as abnormal. The MRS results were compared retrospectively with those of MR imaging and PET as to the ability to lateralize the epileptogenic focus. RESULTS: The sensitivity of MRS and PET (concordance with MR imaging) was 85% each in the lateralization of the ipsilateral lesion side. Bilateral abnormalities were seen in 30% of the patients. False-lateralization rates for MRS and PET were 3% and 6%, respectively. The concordance rate of MRS and PET was 73%, when comparing the results of the ipsilateral lesion side. CONCLUSION: MRS may be used as an adjunct tool in the evaluation of hippocampal sclerosis, like PET, although its sensitivity has to be improved and the clinical significance of bilateral abnormality is still to be determined.

Adolescent↗
PubMed2001

Spinal intradural extramedullary capillary hemangioma: MR imaging findings.

SUMMARY: Spinal intradural extramedullary capillary hemangiomas are extremely rare. We present the MR imaging and histologic findings in three patients with this abnormality. The three patients were men who had symptoms of either myelopathy (n = 2) or radiculopathy (n = 1). The tumors were well demarcated, 1.5-2.0 cm in diameter, and were located at the posterior or posterolateral portion of the thecal sac (one at the L1 level and the other two at the midthoracic level). On MR images, the tumor showed isointensity relative to the spinal cord on T1-weighted images, hyperintensity on T2-weighted images, and strong homogeneous enhancement on contrast-enhanced T1-weighted images in all three patients. In two patients, the dural tail sign was observed. Capillary hemangioma should be included in the differential diagnosis of a spinal intradural extramedullary tumor.

Adult↗
PubMed2001

Comparative analysis of MR imaging, positron emission tomography, and ictal single-photon emission CT in patients with neocortical epilepsy.

BACKGROUND AND PURPOSE: MR imaging, positron emission tomography (PET), and single-photon emission CT (SPECT) play important roles in presurgical localization of epileptic foci. However, comparative study of these imaging methods for cases of neocortical epilepsy has been limited. The purpose of this study was to compare the sensitivities of these three imaging methods for presurgical localization of neocortical epileptogenic foci. METHODS: We studied 117 consecutive patients who underwent surgery for intractable neocortical epilepsy. The pathologic substrates were neuronal migration disorder (n = 77), tumor (n = 15), and others (n = 25). MR imaging was compared retrospectively with (18)F-fluorodeoxyglucose PET and ictal technetium-99m hexamethylpropyleneamine oxime SPECT regarding their capability to correctly localize the epileptogenic foci. The pathologic findings were used as the standard of reference. RESULTS: Overall, MR imaging, PET, and ictal SPECT correctly localized the lesions for 59.8%, 77.7%, and 70.3% of the patients, respectively, with a 38% concordance rate among the three methods. PET was most sensitive (71-100%) in detecting all substrates. MR imaging was as sensitive (100%) as PET in detecting tumor but was least sensitive (48.1%) in detecting neuronal migration disorder. Ictal SPECT was more sensitive (75.8%) than MR imaging in detecting neuronal migration disorder. Patients with imaging abnormalities achieved good outcomes in 81.4% of the cases, in contrast to 59.5% for those without imaging abnormalities (P <.05). CONCLUSION: PET and ictal SPECT were overall more sensitive than was MR imaging, despite the low concordance rate and variable sensitivity depending on substrates. The detection of abnormalities by MR imaging was associated with good outcome. PET or ictal SPECT can be well used as complementary tools, particularly in cases of negative MR imaging findings.

Brain Diseases↗
PubMed2000

Cell biology of tubotympanum in relation to pathogenesis of otitis media - a review.

The sterility of the eustachian tube and tympanic cavity of normal individuals is maintained not only by the adaptive immune system, but also by the mucociliary system and the antimicrobial molecules of innate immunity. Mucin production and periciliary fluid homeostasis are essential for normal mucociliary function and dysfunction of this system is an important risk factor for otitis media. The secreted antimicrobial molecules of the tubotympanum include lysozyme, lactoferrin, beta defensins, and the surfactant proteins A and D (SP-A, SP-D). Defects in the expression or regulation of these molecules may also be the major risk factor for otitis media.

Animals↗
PubMed2000

Diffusion-weighted imaging in Wallerian degeneration.

We report two patients displaying hyperintensities on diffusion-weighted imaging (DWI) in the area of Wallerian degeneration (WD) at 12 days after stroke. High signal intensities were more conspicuous on DWI than on T2-weighted images. Both patients showed decreased diffusion anisotropy resulting in elevated apparent diffusion coefficient in the area of WD. These patients illustrate that DWI may be useful in the detection of the early stage of WD.

Aged↗
PubMed2000

Scrub typhus encephalomyelitis with prominent focal neurologic signs.

BACKGROUND: Encephalomyelitis with prominent focal neurologic signs and associated neuroradiologic abnormalities has not been previously described in scrub typhus. CASE DESCRIPTION: A 22-year-old woman was admitted because of fever and an altered mental state. Neurologic examination revealed bilateral sixth and seventh nerve palsies, bilateral gaze evoked nystagmus, anarthria, dysphagia, quadriparesis, and sensory level at T1. Serum and cerebrospinal fluid samples were positive for tsutsugamushi antibody. The patient's magnetic resonance images demonstrated the lesions responsible for the neurologic dysfunctions: in the lower brainstem, cerebellar peduncles, and spinal cord. It was interesting that the gray matter of the spinal cord was predominantly involved. CONCLUSIONS: The recognition of unusual manifestations and the clinical suspicion of this treatment-responsive disease may be important, particularly in the face of increasing international and intranational travel.

Adult↗
PubMed2000

High cyclooxygenase-2 expression in stage IB cervical cancer with lymph node metastasis or parametrial invasion.

OBJECTIVE: The enzymes cyclooxygenase (COX)-1 and -2 are necessary for the synthesis of prostaglandins. COX-2 is usually absent in normal cells and is upregulated and expressed as a product of the "immediate early" gene during inflammatory processes. In previous studies, the expression of COX-2 has been shown to be induced by proinflammatory cytokines, and suggestions have been made that overexpression of COX-2 suppresses apoptosis and is directly related to tumor growth. We have attempted to determine a relationship between tumor invasion and metastasis of uterine cervical cancer and COX and apoptosis by comparing the protein expression of apoptosis, COX-1, and COX-2 in tumor tissues. METHODS: The subjects were 36 patients who were FIGO stage IB uterine cervical cancer patients who underwent surgery at Ajou University Hospital. There were 12 cases with lymph node or parametrial involvement. All tissues were subjected to immunohistochemical staining for COX-1, -2, and TUNEL method for apoptosis detection, and the following results were obtained. RESULTS: Tumor tissues confirmed by cytokeratin were separated into tumor surface, tumor stroma, and invasion site portions, in which decreased apoptosis was observed in the invasion sites. COX-2 expression was observed in all tumor tissues and was especially strong in the tumor invasion site. Therefore, it is suggested that COX-2 expression may suppress cell apoptosis at the tumor invasion site. When COX-2 expression was investigated according to the groups with regard to the presence of lymph node or parametrial involvement, there was a statistically significant (Mann-Whitney U test) COX-2 expression difference in the tumor invasion site (P value = 0.040) and the tumor stroma (P value = 0. 028). CONCLUSIONS: In surgically treated stage IB cervical cancer patients, COX-2 was significantly expressed when lymph node or parametrial involvement was present. These results suggest that the expression of COX-2 in stage IB cervical cancer may downregulate apoptotic processes and thus enhance tumor invasion and metastasis.

Apoptosis↗