PubMed Health⌕ Search

Biomedical subjects

K H Chang

Publications and source records attributed to K H Chang.

At least 127 records · Page 7Linked to original sources
PubMed1994

Contrast enhancement of brain tumors at different MR field strengths: comparison of 0.5 T and 2.0 T.

PURPOSE: To compare the degree of MR contrast enhancement of 0.5 T and 2.0 T in various brain tumors. METHODS: MR images were studied prospectively in each of 31 patients with brain tumors (11 gliomas, 6 meningiomas, 6 neurinomas, and 8 others) before and after intravenous injection of gadopentetate dimeglumine. In every patient, both 0.5-T and 2.0-T MR studies were done within 1 week. Each patient received an initial standard dose (0.1 mmol/kg) of gadopentetate dimeglumine, followed by a subsequent 0.1-mmol/kg dose (total, double dose) in MR of each field strength. MR was done before and after each injection of the contrast agent. Degree of contrast enhancement in the lesions was assessed both visually and quantitatively. RESULTS: With standard-dose study, the tumor enhancement was visually stronger at 2.0 T than at 0.5 T in 9 gliomas. In extraaxial tumors there was visually no or minimal difference between 0.5 T and 2.0 T. Overall mean contrast-enhancement ratio and tumor and brain contrast-to-noise ratio were higher at 2.0 T than at 0.5 T by 53% and 108%, respectively. The double-dose study showed higher contrast-enhancement ratio and contrast-to-noise ratio than the standard-dose study at both field strengths, and the differences between 0.5 T and 2.0 T were almost similar to those of the standard-dose study. The degree of contrast enhancement with the standard dose at 2.0 T was comparable to that of the double dose at 0.5 T in most intraaxial tumors. CONCLUSION: The results suggest that effect of contrast enhancement increases with the field strength. Therefore, reevaluation of optimal doses of contrast media may be needed in a variety of brain lesions at each field strength.

Adolescent↗
PubMed1994

Preembolization functional evaluation in supratentorial cerebral arteriovenous malformations with superselective intraarterial injection of thiopental sodium solution.

Superselective intraarterial injections of thiopental sodium solution for evaluation of local brain function were performed before embolization in 38 consecutive patients with supratentorial arteriovenous malformations to evaluate the role of the test using thiopental sodium solution. Thiopental sodium (30-50 mg) was injected in 68 arteries (44 middle cerebral arteries, 13 anterior cerebral arteries, 7 posterior cerebral arteries, 3 external carotid arteries, and 1 thalamo-perforating artery) through superselective microcatheters just before the injection of cyanoacrylate mixture for the embolization. The test was negative in 57 arteries and there were neurologic dysfunctions in 3 of them after embolization. The neurologic deficits in these cases were caused by reflux of embolic material, spasm of the main arterial trunk, or neglected mild sensory change, respectively, and there was no real false-negative test. The embolization could not be performed due to positive test in 9 arteries. Two arteries with positive tests but acceptable symptoms were embolized and the same neurologic deficits developed immediately after embolization. There was no local arterial complication by an injection of the thiopental sodium solution. All neurologic deficits caused by positive tests developed immediately and were completely relieved within 5 min without specific management. Superselective intraarterial injection of thiopental sodium solution is a safe and reliable test for the evaluation of local brain function before embolization of supratentorial arteriovenous malformations.

Adolescent↗
PubMed1993

Intracranial mesenchymal chondrosarcoma: a case report and literature review.

Intracranial mesenchymal chondrosarcoma is a rare entity. The case of a 13-year-old girl with mesenchymal chondrosarcoma which seemed to arise from the dura mater is presented here together with a review of the literature. In the present case, the tumor involved the superior sagittal sinus. It recurred 21 months after gross total removal of the mass and coagulation of the involved wall of the superior sagittal sinus. Reoperation was performed followed by radiation therapy.

Adolescent↗
PubMed1993

Traumatic spinal cord injuries in the rural region of Taiwan: an epidemiological study in Hualien county, 1986-1990.

In order to survey the epidemiological characteristics of traumatic spinal cord injuries (SCI) in Hualien county, a retrospective study was conducted from January 1986 to December 1990 in four local general hospitals. During this period, 135 traumatic SCI patients were identified and 99 of them were residents of Hualien county. The estimated annual incidence of traumatic SCI in Hualien county was 56.1 per million population. As a result of injury 36 patients were tetraparetic, 33 tetraplegic, 12 paraparetic and 18 paraplegic. The male/female ratio was 4:1. The mean age of onset for male patients was 44 years, and that for female patients was 46 years. The major causes of SCI were traffic accident (61.6%) followed by accidental falls (23.3%). The average duration of hospitalisation ranged from 62 days in paraparetics to 132 days in tetraplegics. Ten patients died of respiratory failure or sepsis, and the mortality rate was 10.1%. Our data revealed that traumatic SCI was prevalent in Hualien county in comparison with epidemiological studies elsewhere. The special population composition of Hualien county and the preponderance of the motorcycle as a transportation vehicle in this area might result in its unique epidemiological characteristics.

Accidental Falls↗
PubMed1993

Cell type-specific proteins which interact with the 5' nontranslated region of hepatitis A virus RNA.

The 5' nontranslated region (5'NTR) of hepatitis A virus (HAV) RNA contains structural elements which facilitate 5' cap-independent initiation of virus translation and are likely to interact with cellular proteins functioning as translation initiation factors. To define these interactions, we characterized the binding of ribosome-associated proteins from several cell types to synthetic RNAs representing segments of the 5'NTR by using a UV cross-linking/label transfer assay. Four major proteins (p30, p39, p57, and p110) were identified. p30 and p39 were present in ribosomal salt washes prepared only from HAV-permissive BS-C-1 and FRhK-4 cells, while p57 was found only in HeLa cells and rabbit reticulocyte lysates. p110 was present in all cell types. Both p30 and p39 bound to multiple sites within the 5'NTR. Efficient transfer of label to p30 occurred with minimal RNA probes representing nucleotides (nt) 96 to 155, 151 to 354, and, to a much lesser extent, 634 to 744, while label transfer to p39 occurred with probes representing nt 96 to 155 and 634 to 744. All of these probes represent regions of the 5'NTR which are rich in pyrimidines. Competitive inhibition studies indicated that both p30 and p39 bound with greater affinity to sites in the 5' half of the NTR (a probe representing nt 1 to 354) than to the more 3' site (nt 634 to 744). Binding of p39 to the probe representing nt 96 to 155 was inhibited in the presence of an equal amount of proteins derived from HeLa cells, suggesting that p39 shares binding site specificity with one or more HeLa cell proteins. A 57-kDa protein in HeLa cell protein extracts reacted with antibody to polypyrimidine tract-binding protein in immunoblots, but no immunoreactive protein was identified in a similar BS-C-1 protein fraction. These results demonstrate that ribosome-associated proteins which bind to the 5'NTR of HAV vary substantially among different mammalian cell types, possibly accounting for differences in the extent to which individual cell types support growth of the virus. Mutations in the 5'NTR which enhance the growth of HAV in certain cell types may reflect specific adaptive responses to these or other proteins.

Animals↗
PubMed1993

Cerebral sparganosis: MR imaging versus CT features.

Fourteen magnetic resonance (MR) images of 11 patients with cerebral sparganosis were reviewed retrospectively and compared with 13 computed tomographic (CT) scans of 10 of the patients. All patients underwent both nonenhanced and contrast material-enhanced MR imaging. All white matter degenerations, which were slightly hypointense on T1-weighted images and were hyperintense on T2-weighted images, were seen as areas of low attenuation on CT scans. Better contrast between normal and degenerated brain tissues was seen at MR, and two lesions were seen that were missed at CT. The parasitic granuloma was isointense to brain parenchyma on images obtained with all pulse sequences. On two follow-up MR images, location or shape of the enhancing lesions changed, suggesting migration of the worm. A new finding of hyperintensity on T1-weighted images and hypointensity on T2-weighted images in subcortical areas probably due to petechial hemorrhages was demonstrated in eight patients only at MR. Small calcific foci, which were important diagnostic clues of cerebral sparganosis, were detected in four patients only at MR, while they were seen in eight patients at CT.

Adolescent↗
PubMed1993

Gliomatosis cerebri: comparison of MR and CT features.

OBJECTIVE: Gliomatosis cerebri is a diffuse infiltrative glial neoplasm frequently involving both cerebral hemispheres. Diagnosis and evaluation of its extent with CT are known to be difficult. The purpose of this study was to compare the MR and CT findings in gliomatosis cerebri. MATERIALS AND METHODS: MR images of nine patients were reviewed retrospectively and compared with CT scans. Pathology was determined by open or stereotaxic biopsy. The MR images included sagittal T1-weighted, axial proton density-weighted, and T2-weighted images. Contrast material was administered in seven patients. Unenhanced and enhanced CT scans were obtained in eight patients. RESULTS: On proton density-weighted and T2-weighted MR images, the most common findings were poorly defined bilateral areas of diffuse high signal intensity in the cerebral hemisphere. On T1-weighted images, the lesions were isointense to hypointense compared with normal brain. Enhanced T1-weighted images showed focal parenchymal enhancement in three patients and meningeal enhancement in one. On CT scans, the lesions showed poorly defined areas of subtle low density or isodensity, and appeared much smaller than those on T2-weighted MR images. Enhancement was seen in only one case. The extent of disease was evaluated much better on T2-weighted MR images than on T1-weighted MR images and CT scans. CONCLUSION: In gliomatosis cerebri, MR imaging is more sensitive than CT for detecting lesions and shows the extent of disease better than CT does. Accordingly, MR imaging should be used as a primary imaging study in the evaluation of gliomatosis cerebri.

Adult↗
PubMed1993

High-dose-rate afterloading brachytherapy in carcinoma of the uterine cervix.

High-dose-rate (HDR) afterloading brachytherapy has been used at Mackay Memorial Hospital since 1984 for the treatment of gynecological malignancies. From October 1984 to October 1990, a total of 321 previously untreated patients with biopsy proven uterine cervical cancer were treated with radiation therapy with curative intent. According to FIGO staging, the patients were grouped into stage I (19 patients), stage IIA (13 patients), stage IIB (96 patients), stage III (158 patients) and stage IVA (35 patients). All patients received a combination of external beam irradiation plus intracavitary brachytherapy using the Buchler Remote Afterloading (RAL) system. For most cases, external beam irradiation using a Co-60 or Clinac 1800 photon beam (6 MV or 15 MV) of 3,060 cGy to 3,960 cGy was given to the whole pelvis (180 cGy/day, five days/week), followed by a midline shield after RAL. The total dose to the pelvic sidewall was 5,040 cGy to 5,400 cGy. The overall actuarial five-year survival rate was 55%. The total complication rate in a follow-up of two to eight years was 1% to 4%, and a good correlation existed between rectal complications and the calculated rectal dose. We conclude that fractionated HDR intracavitary therapy concurrent with teletherapy can achieve a high regional control rate with few complications, and can reduce the cost of hospitalization and the risk of anesthesia.

Adult↗
PubMed1993

Radiotherapy following simple hysterectomy in patients with invasive carcinoma of the uterine cervix.

From January 1980 to December 1988, a total of 73 cases of invasive cervical cancer after simple hysterectomy were treated with radiotherapy. Seven patients were excluded due to incomplete treatment or loss of follow-up. Among the 66 patients, 52 had squamous cell carcinoma and 14 had adenocarcinoma or adenosquamous cell carcinoma. The patients were grouped as follows: group A, patients without gross residual tumor (n = 32); group B, patients with gross residual tumor (n = 23); and group C, patients with gross recurrent tumor (n = 11). All patients in groups A and B received radiotherapy immediately (within 4 months) following their simple hysterectomy. Patients in group C were treated six months to five years later. Different methods of radiotherapy were delivered during the two consecutive time periods. Before 1985, patients (n = 30) were irradiated with a dose of 45-50 Gy in the midpelvic plane, followed by a transvaginal boost of 30 Gy. After 1985, patients (n = 36) were treated with the same midpelvic dose, and boosted with 30 Gy by high-dose-rate brachytherapy. The overall five-year survival rate was 67%. The five-year survival rates were 81% in group A, 56% in group B, and 45% in group C. A low complication rate (10%) was obtained in our series.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1993

MR appearance of central neurocytoma.

To provide a detailed description of the MR appearances of central neurocytoma, MR images of 13 patients with central neurocytoma were retrospectively reviewed and compared with CT examinations. The histology was confirmed by ultrastructural and immunohistochemical studies. In 12 patients the tumors were histologically benign and located in the anterior part of the lateral ventricle, 6 of which extended to the 3rd ventricle. There was one case of a histologically malignant variant involving the thalamus and lateral ventricle. The tumors were primarily solid, but contained cysts (85%, 11/13), calcifications (69%, 9/13), and signal void from tumor vessels (62%, 8/13), frequently producing heterogeneous signal intensity on both T1- and T2-weighted images. Most of the solid portion appeared isointense or slightly hyperintense relative to the cerebral cortex on all MR pulse sequences. Calcifications were iso- or hypointense on MR, making them difficult to characterize with MR alone. Intratumoral hemorrhage was seen in 2 patients on MR but not on CT. Contrast enhancement was variable in degree and pattern. Coronal and sagittal MR images were valuable in evaluating the tumor extent and origin site, and in planning the surgical approach. It is concluded that MR imaging appears to be more useful than CT in the overall evaluation of central neurocytoma, even though calcification is better characterized with CT.

Adult↗
PubMed1992

Why do human hepatitis viruses replicate so poorly in cell cultures?

The five viruses which classically cause hepatitis in man represent diverse families of viruses and share in common only a striking hepatotropism and substantial restrictions to replication in conventional cell cultures. Hepatitis A virus is unique among these viruses in that it is amenable to propagation in cell culture, but replication of this virus is much slower and less efficient than replication of other picornaviruses. This probably reflects less efficient cap-independent viral translation, as well as restrictions at other points in the replication cycle. We speculate that the significantly restricted replication of hepatitis viruses in cell culture reflects evolutionary forces controlling their transmission and propagation through human populations.

Base Sequence↗
PubMed1992

Ancestry of the 4-chlorobenzoate dehalogenase: analysis of amino acid sequence identities among families of acyl:adenyl ligases, enoyl-CoA hydratases/isomerases, and acyl-CoA thioesterases.

We have deduced the nucleotide sequence of the genes encoding the three components of 4-chlorobenzoate (4-CBA) dehalogenase from Pseudomonas sp. CBS-3 and examined the origin of these proteins by homology analysis. Open reading frame 1 (ORF1) encodes a 30-kDa 4-CBA-coenzyme A dehalogenase related to enoyl-coenzyme A hydratases functioning in fatty acid beta-oxidation. ORF2 encodes a 57-kDa protein which activates 4-CBA by acyl adenylation/thioesterification. This 4-CBA:coenzyme A ligase shares significant sequence similarity with a large group of proteins, many of which catalyze similar chemistry in beta-oxidation pathways or in siderophore and antibiotic synthetic pathways. These proteins have in common a short stretch of sequence, (T,S)(S,G)G(T,S)(T,E)G(L,X)PK(G,-), which is particularly highly conserved and which may represent an important new class of "signature" sequence. We were unable to find any proteins homologous in sequence to the 16-kDa 4-hydroxybenzoate-coenzyme A thioesterase encoded by ORF3. Analysis of the chemistry and function of the proteins found to be structurally related to the 4-CBA:coenzyme A ligase and the 4-CBA-coenzyme A dehalogenase supports the proposal that they evolved from a beta-oxidation pathway.

Amino Acid Sequence↗
PubMed1992

Isolation and characterization of the three polypeptide components of 4-chlorobenzoate dehalogenase from Pseudomonas sp. strain CBS-3.

The three genes encoding the 4-chlorobenzene dehalogenase polypeptides were excised from a Pseudomonas sp. CBS-3 DNA fragment and separately cloned and expressed in Escherichia coli. The three enzymes were purified from the respective subclones by using an ammonium sulfate precipitation step followed by one or two column chromatographic steps. The 4-chlorobenzoate:coenzyme A ligase was found to be a homodimer (57-kDa subunit size), to require Mg2+ (Co2+ and Mn2+ are also activators) for activity, and to turn over MgATP (Km = 100 microM), coenzyme A (Km = 80 microM), and 4-chlorobenzoate (Km = 9 microM) at a rate of 30 s-1 at pH 7.5 and 25 degrees C. Benzoate, 4-bromobenzoate, 4-iodobenzoate, and 4-methylbenzoate were shown to be alternate substrates while 4-hydroxybenzoate, 4-aminobenzoate, 2-aminobenzoate, 2,3-dihydroxybenzoate, 4-coumarate, palmate, laurate, caproate, butyrate, and phenylacetate were not substrate active. The 4-chlorobenzoate-coenzyme A dehalogenase was found to be a homotetramer (30 kDa subunit size) to have a Km = 15 microM and kcat = 0.3 s-1 at pH 7.5 and 25 degrees C and to be catalytically inactive toward hydration of crotonyl-CoA, alpha-methylcrotonyl-CoA, and beta-methylcrotonyl-CoA. The 4-hydroxybenzoate-coenzyme A thioesterase was shown to be a homotetramer (16 kDa subunit size), to have a Km = 5 microM and kcat = 7 s-1 at pH 7.5 and 25 degrees C, and to also catalyze the hydrolyses of benzoyl-coenzyme A and 4-chlorobenzoate-coenzyme A. Acetyl-coenzyme A, hexanoyl-coenzyme A, and palmitoyl-coenzyme A were not hydrolyzed by the thioesterase.

Bacterial Proteins↗
PubMed1992

Cerebral sparganosis: analysis of 34 cases with emphasis on CT features.

Cerebral sparganosis is a rare parasitic CNS disease, producing chronic active granulomatous inflammation. We retrospectively reviewed the clinical data, CT scans and histopathologic specimens in 34 patients with cerebral sparganosis. The majority of the patients (89%) were rural inhabitants; 75% had a history of ingestion of frogs and/or snakes. The major presenting symptoms were seizure (84%), hemiparesis (59%) and headache (56%) of chronic course. On CT scans, the disease most frequently involved the cerebral hemispheres, particularly frontoparietal lobes, with occasional extension to the external and internal capsules and basal ganglia. The cerebellum was rarely involved. Bilateral involvement was seen in 26%. The main CT findings consisted of white matter hypodensity with adjacent ventricular dilatation (88%), irregular or nodular enhancing lesion (88%), and small punctate calcifications (76%). In combination, the CT triad above appears to be specific for this disease, and was noted in 62% of cases. Of 16 follow-up CT scans, 5 (38%) showed a change in the location of the enhancing nodule. With a single CT scan, it does not appear to be possible to determine whether the worm is alive or dead, information important for deciding whether to intervene surgically. Change in the location of the enhancing nodule and/or worsening of the other CT findings on sequential CT scans would suggest that the worm is alive and that the patient is a candidate for surgery.

Adult↗
PubMed1992

Marchiafava-Bignami disease: serial changes in corpus callosum on MRI.

Serial MRI findings of changes in corpus callosum lesions in two cases of Marchiafava-Bignami disease are presented. In both, MRI displayed diffuse swelling of the corpus callosum in the acute stage, thought to represent oedema and demyelination. In the chronic stage, in addition to atrophy of the corpus callosum with presumed focal necrosis, previously undescribed focal hypointensity on T2-weighted images, of unknown cause, was observed in the corpus callosum.

Alcoholism↗
PubMed1992

The nucleotide sequences of wild-type coxsackievirus A9 strains imply that an RGD motif in VP1 is functionally significant.

We have shown previously that, compared to other enteroviruses, the coxsackievirus A9 (CAV-9) prototype strain, Griggs, contains a C-terminal extension to the capsid protein VP1 and that within this extension there is an RGD (arginine-glycine-aspartic acid) motif. To determine whether these features are found in other CAV-9 strains and therefore analyse whether they are likely to be functionally important, we have determined the nucleotide sequence of the appropriate region from five strains, isolated over a 25 year period. The results indicate that there is considerable diversity between the strains and there is little correlation between nucleotide sequence identity and date of isolation. All isolates exhibit the VP1 extension and although its amino acid sequence is otherwise variable, the RGD motif is common to all. This conservation of sequence, within a region which can otherwise vary, implies that the RGD sequence must be functionally significant. The VP1 extension shows similarity to sequences found in foot-and-mouth-disease virus strains and to part of the precursor of the cellular protein, human transforming growth factor beta, and the possible significance of these observations is discussed.

Amino Acid Sequence↗
PubMed1992

Delayed encephalopathy after acute carbon monoxide intoxication: MR imaging features and distribution of cerebral white matter lesions.

Magnetic resonance (MR) images obtained in 15 patients with delayed encephalopathy after acute carbon monoxide (CO) intoxication were reviewed. Images had been obtained 4-9 weeks after exposure to CO, during the relapse of neuropsychiatric symptoms after initial recovery. Bilateral symmetric confluent high signal intensity in the periventricular white matter and centrum semiovale was seen on long-repetition-time images (n = 15). The high intensity extended into the corpus callosum (n = 11), subcortical U fibers (n = 12), and external (n = 9) and internal (n = 7) capsules. Bilateral diffuse low-intensity signal in the thalamus and putamen on T2-weighted images, suggesting iron deposition, was demonstrated in 10 patients. Bilateral ischemia or necrosis of the globus pallidus was seen in nine patients. In three of four patients with follow-up MR imaging studies, a decrease in extent and signal intensity of white matter lesions accompanied lessening of clinical symptoms. These results suggest that the main pathologic feature of delayed encephalopathy associated with CO intoxication is a reversible demyelinating process of the cerebral white matter.

Adult↗