Biomedical subjects

C Y Chang

Publications and source records attributed to C Y Chang.

At least 109 records · Page 6Linked to original sources

PubMed2000

Fat in the cerebral falx.

BACKGROUND: Fat within the cerebral falx is commonly encountered in our daily practice but has never been characterized and reported. The purpose of this study was to determine the incidence of fat within the cerebral falx and to identify its clinical features. METHODS: The cerebral falx was prospectively imaged in 1,570 consecutive brain computed tomographic scans and its features characterized. Cerebral magnetic resonance imaging was done in some patients. RESULTS: Of the 1,570 cases studied, 115 revealed a small amount of fat in the cerebral falx. This fat had a purely negative Hounsfield value. It produced a high signal on both T1- and T2-weighted magnetic resonance images. There was no calcified component. The fat was seen most commonly in aged patients. No related symptoms were noted. CONCLUSIONS: Among the patients studied, fat in the cerebral falx had an incidence of 7.3%. It is an incidental finding in adults and requires no further evaluation or treatment.

Adolescent↗

PubMed2000

Computed tomography and magnetic resonance imaging characteristics of giant pituitary adenomas.

PURPOSE: The purpose of this study was to characterize the computed tomography (CT) and magnetic resonance (MR) imaging features of giant pituitary adenoma (GPA) and to demonstrate the pathways of the spread of GPA. METHODS: CT and/or MR imaging scans of 356 patients evaluated preoperatively for single pituitary tumor were reviewed. Fourteen tumors (4%) fulfilled the radiologic criteria for GPA. There were 10 male and four female patients, ranging in age from 22 to 71 years (mean, 52 yr). We retrospectively reviewed the CT and MR imaging scans of these patients to characterize tumor appearances and identify the pathways of tumor extension. RESULTS: Thirteen tumors (93%) extended upward to the suprasellar cistern, and/or hypothalamus and third ventricle. Infrasellar extension through the sellar floor and sphenoid sinus to the skull base, or to the ethmoid sinus or the nasopharynx, was identified in seven patients (50%). Eight patients (57%) had lateral invasion to the cavernous sinus. Temporal and frontal extension was apparent in seven patients (50%) and six patients (43%), respectively. Five patients (36%) had posterior subtentorial extension to the posterior fossa. Histologically, only two GPAs showed invasive features. There was no correlation among histologic features, pituitary hormone concentrations, and evidence of tumor aggressiveness on CT and MRI scans. CONCLUSIONS: GPA has the potential for widespread, multi-directional extension. Our results indicate that any type of pituitary adenoma, regardless of its endocrinologic activity, may invade surrounding structures. Suprasellar invasion is the most common pathway of tumor spread, followed by infrasellar, lateral, anterior, and posterior routes.

Adenoma↗

PubMed2000

Struma ovarii mimicking a benign multicystic ovarian tumor: MR imaging in one case.

Struma ovarii is a rare form of mature teratoma of the ovary. A case of struma ovarii is presented with magnetic resonance (MR) imaging and pathologic findings. MR imaging showed a multiloculated cystic adnexal mass with well-defined margin and septum. Internal cystic spaces presented homogeneous signal intensity of fluid content in both T1-weighted and T2-weighted images. Subtle contrast enhancement was depicted in internal septi. Imaging features were indistinguishable from benign multicystic ovarian tumor, and different from the reported cases in the literature.

Adolescent↗

PubMed1999

Peptide antagonists of the human estrogen receptor.

Estrogen receptor alpha transcriptional activity is regulated by distinct conformational states that are the result of ligand binding. Phage display was used to identify peptides that interact specifically with either estradiol- or tamoxifen-activated estrogen receptor alpha. When these peptides were coexpressed with estrogen receptor alpha in cells, they functioned as ligand-specific antagonists, indicating that estradiol-agonist and tamoxifen-partial agonist activities do not occur by the same mechanism. The ability to regulate estrogen receptor alpha transcriptional activity by targeting sites outside of the ligand-binding pocket has implications for the development of estrogen receptor alpha antagonists for the treatment of tamoxifen-refractory breast cancers.

Amino Acid Sequence↗

PubMed1999

Estrogen receptor (ER) modulators each induce distinct conformational changes in ER alpha and ER beta.

Estrogen receptor (ER) modulators produce distinct tissue-specific biological effects, but within the confines of the established models of ER action it is difficult to understand why. Previous studies have suggested that there might be a relationship between ER structure and activity. Different ER modulators may induce conformational changes in the receptor that result in a specific biological activity. To investigate the possibility of modulator-specific conformational changes, we have applied affinity selection of peptides to identify binding surfaces that are exposed on the apo-ERs alpha and beta and on each receptor complexed with estradiol or 4-OH tamoxifen. These peptides are sensitive probes of receptor conformation. We show here that ER ligands, known to produce distinct biological effects, induce distinct conformational changes in the receptors, providing a strong correlation between ER conformation and biological activity. Furthermore, the ability of some of the peptides to discriminate between different ER alpha and ER beta ligand complexes suggests that the biological effects of ER agonists and antagonists acting through these receptors are likely to be different.

Amino Acid Sequence↗

PubMed1999

Singlet oxygen is the major species participating in the induction of DNA strand breakage and 8-hydroxydeoxyguanosine adduct by lead acetate.

To investigate DNA damage induced by Pb2+ and its prevention by scavengers, we determined DNA strand breakage and the formation of 8-hydroxydeoxyguanosine (8-OHdG) in DNA using plasmid relaxation assay and HPLC with electrochemical detection, respectively. Lead acetate induced DNA strand breakage in 10 mM of Hepes buffer, pH 6.8, in a time- and dose-dependent manner. Compared with lead, zinc acetate did not significantly induce DNA breakage. The singlet oxygen scavengers NaN3 and 2,2,6,6-tetramethyl-4-piperidone (TEMP) inhibited lead-induced DNA breakage more efficiently than the hydroxyl radical scavengers mannitol and DMPO. Deuterium oxide (D2O), a singlet oxygen enhancer, potentiated lead-induced DNA breakage. At low ratios to Pb2+, NADPH, glutathione, and 2-mercaptoethanol enhanced lead-induced DNA breakage, whereas high ratios of these agents protected it. Catalase and superoxide dismutase (SOD) did not protect DNA breaks induced by Pb2+. Lead-induced DNA breakage was markedly enhanced by H2O2, and this induction was inhibited by NaN3, TEMP, EDTA, catalase, BSA, and glutathione. In contrast, mannitol and SOD potentiated Pb2+/H2O2-induced DNA breaks. The results indicate that singlet oxygen, lead, and H2O2 are all involved in the reaction system, whereas hydroxyl radical and superoxide did not. Lead could cause a small amount of 8-OHdG formation in calf thymus DNA and dose-dependently induced the formation of this adduct in the presence of H2O2. Singlet oxygen scavengers were more effective than hydroxyl radical scavengers in protection from lead/H2O2-induced 8-OHdG adducts. Taken together, these results suggest that lead may induce DNA damage through a Fenton-like reaction and that singlet oxygen is the principal species involved.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1999

Aberrant left brachiocephalic vein: CT imaging findings and embryologic correlation.

Computed tomography was utilized to evaluate aberrant left brachiocephalic vein (ALBCV), an infrequently discussed congenital vascular anomaly among Chinese people. Associated vascular variation and possible embryonic correlation are discussed. Since 1990, a total of 14 cases of ALBCV have been reported in patients receiving CT scan of chest, and was mainly an incidental diagnosis. One case was confirmed angiographically and two others were confirmed by magnetic resonance imaging. Emphasis was placed on the entry of the azygos vein into the superior vena cava (SVC), the length of the SVC, and the presence of other cardiovascular abnormalities. Of the 14 cases of ALBCV, the level of azygos vein entry was higher than the origin of the SVC in 7 cases: 4 were approximately the same level and 3 were lower. The average length of the SVC was approximately 5. 6 cm shorter than that of the general population, which is approximately 7.0 cm. Three cases had associated vascular anomaly. Most cases of ALBCV had azygos vein drainage level higher than or equal to the origin of the SVC. Right-sided aorta is one of the causes giving rise to the ALBCV during embryonic development. The CT scan remains a definitive diagnostic modality for ALBCV.

Adolescent↗

PubMed1999

Characterization of the dual start motif of a class II holin gene.

Holins are small membrane proteins that, at a genetically programmed time in a bacteriophage infective cycle, allow bacteriolytic enzymes, or endolysins, to escape to the periplasm and to attack the cell wall. Most holins fall into two sequence classes, I and II, based on the number of potential transmembrane domains (three for class I and two for class II). The prototype class I holin gene, S lambda, has a dual start motif and encodes not only the effector holin, Slambda105, but also an inhibitor, Slambda107, with a Met-Lys ...extension at the terminus. The prototype class II holin gene of phage 21, S 21, begins with the motif Met-Lys-Ser-Met ..., and a potential RNA secondary structure overlaps the Shine-Dalgarno sequence. Here, we demonstrate that (i) two protein products are elaborated from S 21, S2171 and S2168; (ii) the shorter product is required for lysis; (iii) the longer product, S2171, inhibits S 21 function; and (iv) the Lys-2 residue is important for the inhibitor function. Moreover, the RNA stem-loop structure is involved in the downregulation of S2171 synthesis. However, our results suggest that, in S 21, different segments of the single consensus Shine-Dalgarno sequence serve the two translational starts. These results show that the dual start motifs of class II holin genes are functionally homologous to those of class I holin genes.

Alleles↗

PubMed1999

Identification of five spinocerebellar ataxia type 2 pedigrees in patients with autosomal dominant cerebellar ataxia in Taiwan.

OBJECTIVES: The autosomal dominant cerebellar ataxias (ADCAs) are a group of genetically diverse neurological conditions linked by progressive deterioration in balance and coordination. Spinocerebellar Ataxia Type 2 (SCA2) is one of the ADCAs and also belongs to a special group caused by the expansion of an unstable CAG repeat encoding a polyglutamine tract. We aimed to investigate the frequency of SCA2 mutation in the ataxia patients referred to the clinic. MATERIALS AND METHODS: We screened 58 families with inherent cerebellar ataxia and 57 normal individuals by the use of radioactive genomic polymerase chain reaction (PCR) method. A simple non-radioactive PCR for rapid detection of the expanded SCA2 alleles via agarose gel electrophoresis was also employed. RESULTS: Eight SCA2 affected patients and 1 at-risk individual in 5 unrelated SCA2 families were identified. The CAG repeats of normal alleles in the sample studied range in size from 16 to 30 repeat units, while those of SCA2 chromosomes are expanded to 34 to 49 repeat units. Our results also showed that unlike SCA 1 and SCA3/MJD, the size distribution of the normal alleles showed few polymorphisms, with the 22 repeat allele accounting for 90.1%. Homozygosity in normal individuals was 80.2%. No overlap in ataxin-2 allele size between normal and expanded chromosomes was observed. CONCLUSION: This is the first report of the SCA2 gene distributions in the population of Taiwan. The SCA2 mutation accounts for 8.6% of ADCA type I families referred to us, intermediate between SCA1(1.7%) and SCA3/MJD (24%) of the ADCA type I families in our collection.

Adolescent↗

PubMed1999

The C-terminal sequence of the lambda holin constitutes a cytoplasmic regulatory domain.

The C-terminal domains of holins are highly hydrophilic and contain clusters of consecutive basic and acidic residues, with the overall net charge predicted to be positive. The C-terminal domain of lambda S was found to be cytoplasmic, as defined by protease accessibility in spheroplasts and inverted membrane vesicles. C-terminal nonsense mutations were constructed in S and found to be lysis proficient, as long as at least one basic residue is retained at the C terminus. In general, the normal intrinsic scheduling of S function is deranged, resulting in early lysis. However, the capacity of each truncated lytic allele for inhibition by the S107 inhibitor product of S is retained. The K97am allele, when incorporated into the phage context, confers a plaque-forming defect because its early lysis significantly reduces the burst size. Finally, a C-terminal frameshift mutation was isolated as a suppressor of the even more severe early lysis defect of the mutant SA52G, which causes lysis at or before the time when the first phage particle is assembled in the cell. This mutation scrambles the C-terminal sequence of S, resulting in a predicted net charge increase of +4, and retards lysis by about 30 min, thus permitting a viable quantity of progeny to accumulate. Thus, the C-terminal domain is not involved in the formation of the lethal membrane lesion nor in the "dual-start" regulation conserved in lambdoid holins. Instead, the C-terminal sequence defines a cytoplasmic regulatory domain which affects the timing of lysis. Comparison of the C-terminal sequences of within holin families suggests that these domains have little or no structure but act as reservoirs of charged residues that interact with the membrane to effect proper lysis timing.

Amino Acid Sequence↗

PubMed1999

Clinical impact of upper gastrointestinal tract injuries in glyphosate-surfactant oral intoxication.

Fifty patients with glyphosate-surfactant oral ingestion were studied with upper gastrointestinal (UGI) endoscopic grading using Zargar's modified grading system for mucosal corrosive injury. Esophageal injury was seen in 68% of the patients, gastric injury in 72%, and duodenal injury in 16%. There were no grade 3 injuries. The upper gastrointestinal tract injuries caused by glyphosate-surfactant were minor in comparison with those by other strong acids. The WBC count, amount of glyphosate-surfactant ingested, length of hospital stay and the occurrence of serious complications increased markedly in the group which had grade 2 esophageal injuries. Thus, the severity of the esophageal injuries may be a prognostic factor for the patient with glyphosate-surfactant ingestion. The UGI endoscopy may be indicated for grading esophageal injury in patients who have ingested glyphosate-surfactant in amounts greater than 100 ml. Physicians should pay more attention to the patients with grade 2 or 3 esophageal injuries to prevent serious complications and to provide aggressive supportive care.

Administration, Oral↗

PubMed1999

Evaluation of ocular arterial changes in glaucoma with color Doppler ultrasonography.

The purpose of this study was to evaluate hemodynamic changes of the retrobulbar vasculature caused by different intraocular pressures with color Doppler ultrasonography. Fifty normal eyes in 25 patients, 13 patients with normal tension glaucoma, and 19 patients with acute glaucoma and increased intraocular pressure (greater than 30 mm Hg) were enrolled in this study. In 15 of 19 patients with acute glaucoma patients, follow-up color Doppler ultrasonography was also undertaken after laser peripheral iridectomy when the intraocular pressure had returned to normal. The peak systolic velocity, end diastolic velocity, resistive index, time average maximum velocity, and pulsatility index were compared in different vessels, including the central retinal artery, lateral posterior ciliary artery, medial posterior ciliary artery, and ophthalmic artery in each orbit. The peak systolic velocity, end diastolic velocity, and time average maximum velocity of the central retinal artery were significantly lower (P<0.01) in acute glaucoma patients than in the control group. The resistive index and pulsatility index of the central retinal artery were significantly higher (P<0.01) in acute glaucoma patients than in the control group. The end diastolic velocity of the lateral and medial posterior ciliary arteries was significantly lower in patients with acute glaucoma than in the control group, and the resistive index and pulsatility index of both of these arteries were significantly higher (P<0.001) in patients with acute glaucoma than in the control group. However, no statistical significantly differences were found in the peak systolic velocity or time average maximum velocity in either of the posterior ciliary arteries; similarly, no statistically significant differences were noted in any of the parameters in the ophthalmic artery between the control group and the group with acute glaucoma. The pulsatility index of the central retinal artery and of the lateral and medial posterior ciliary arteries was significantly lower (P<0.01) in acute glaucoma patients after laser therapy than in acute glaucoma patients before laser therapy. The resistive index of both posterior ciliary arteries was also significantly lower (P<0.004) in acute glaucoma patients after laser therapy than before laser therapy. All parameters for all vessels examined among the normal subjects, the patients with normal tension glaucoma, and the patients with acute glaucoma after laser therapy when the intraocular pressure had returned to normal showed no statistically significant differences. Color Doppler ultrasonography is a good modality for both imaging and studying the hemodynamics of the perioptic nerve vessels.

Aged↗

PubMed1999

Alternative and effective treatment of shoulder ganglion cyst: ultrasonographically guided aspiration.

The therapeutic effect of ultrasonographically guided aspiration of a ganglion cyst of the shoulder is evaluated. Fifteen patients (nine male, six female) with chronic shoulder pain were enrolled in this study. Each patient was referred to rule out rotator cuff lesion. The ultrasonographic examination showed an anechoic cystic lesion in the shoulder region in every patient and abnormality of the rotator cuff in only four patients. Under ultrasonographic guidance, an 18 gauge needle was inserted into the cyst to aspirate the fluid. Initial sonographic imaging showed the cyst, which appeared as a localized fluid accumulation and was located between the deltoid muscle and the subscapularis tendon in seven patients, between the deltoid muscle and the biceps tendon in one patient, below the coracoacromial ligament in five patients, and over suprascapular notch area in one patient. The ganglion cysts ranged in size from 3.5 to 30 mm. The amount of aspirated fluid in each cyst varied from 0.4 to 12 ml (mean, 2.6 ml +/- 3.1) with a clear or light yellowish color and a jelly-like appearance. No major complications occurred during or after this procedure. The symptom (pain) was improved after sonographically guided aspiration in each patient. Follow-up study showed complete relief of pain in four patients, marked improvement in nine patients, and mild improvement but still persistent shoulder pain in two patients. Duration of follow-up study ranged from 2 to 24 months (mean, 6.4 months +/- 6.9). The success rate for sonographically guided aspiration was 86% on the basis of marked symptom improvement or relief. Ultrasonographically guided aspiration of shoulder ganglion cysts is an effective procedure in the management of shoulder pain caused by ganglion cysts.

Adult↗

PubMed1999

Arachnoid granulations--computerized tomography and magnetic resonance imaging features: a case report.

A 71-year-old woman had arachnoid granulations found in the straight and transverse sinuses on computerized tomography (CT) and magnetic resonance imaging (MRI). The arachnoid granulations appeared as low-density masses on CT. They gave low signals on T1-weighted MR images and high signals on T2-weighted images. Arachnoid granulations are usually of no clinical significance. They have characteristic CT and MRI manifestations and should not be mistaken for sinus thrombosis or intrasinus tumors.

Aged↗

PubMed1999

Vascular lesion of the masseter presenting with phlebolith.

When evaluating an intramuscular soft tissue mass, a large differential diagnosis including both benign and malignant lesions must be considered. Because the treatment of these masses can range from simple observation to radical surgical excision, a minimally invasive but accurate method of diagnosis is desired. The workup should include radiographic imaging. MRI is the modality of choice for differentiating soft tissue lesions, although CT may be helpful in identifying calcifications such as a phlebolith. Although usually unnecessary, a sialogram can verify that a calcification lies within or outside the salivary ductal system. In most cases a biopsy specimen is required to confirm the diagnosis. However, if the imaging studies show characteristics consistent with a vascular soft tissue mass, the finding of a phlebolith is pathognomonic for a benign vascular lesion. If such a lesion is not causing significant cosmetic or functional disability, it can be observed without the need for invasive biopsy or treatment.

Adult↗

PubMed1999

Intracranial pathology: comparison of intraoperative ultrasonography with computerized tomography and magnetic resonance imaging.

BACKGROUND: High-resolution, real time, intraoperative ultrasonography (IOUS) has been used in a number of cases in our neurosurgical department to identify, localize and characterize intracranial abnormalities. We compare the images of IOUS with those of computerized tomography (CT) and magnetic resonance imaging (MRI) in order to enhance our experience and confidence. METHODS: IOUS images were compared with preoperative CT scans and/or MRIs in 30 intracranial masses. Tumor size and margin, echogenicity and edema were the features compared. RESULTS: The images of IOUS, CT and MRI correlated closely except for images of primary gliomas. IOUS was more effective than CT and MRI in delineating the extent of a glioma, determining whether a lesion was cystic, with or without septation, or solid and in guiding surgical procedures. The contrast enhancement available with CT and MRI could not be demonstrated with IOUS. CONCLUSIONS: IOUS provides exquisite detail of intracranial pathology as well as, or even better than, CT and MRI. Its application should be emphasized to minimize damage of normal brain tissue and increase the completeness of tumor resection.

Adult↗

PubMed1999

Magnetic resonance imaging of unilateral olivary hypertrophy due to pontine tegmental hemorrhage: a case report.

Olivary hypertrophy (OH) is not a primary lesion but, rather, develops as a lesion of the Guillain-Morraret triangle, which is composed of the contralateral dentate nucleus, the ipsilateral red nucleus and the ipsilateral inferior olivary nucleus. OH is usually accompanied by palatal myoclonus or other involuntary movements such as extremity myorhythmia. One case of unilateral OH following ipsilateral pontine tegmental hemorrhage is presented. Magnetic resonance imaging (MRI) showed high signal intensity in the inferior olivary nuclei on T2- and proton-density-weighted images. Enlargement of the inferior olivary nuclei was also noted. MRI may currently be the only procedure capable of confirming the diagnosis.

Cerebral Hemorrhage↗

PubMed1999

Giant cell reparative granuloma: a case report.

Giant cell reparative granuloma (GCRG) is an infrequent benign lesion with undetermined etiopathogenesis affecting the maxillary and mandibular bone and, rarely, the skull. It is also extremely rare in the sphenoid bone. GCRG is usually diagnosed by histologic examination of bone lesions. We report a case of GCRG originating from the sphenoid bone. Computerized tomography revealed an expansile lesion with thinning or destruction of the cortical bone. The lesion itself was slightly hyperdense with good but inhomogeneous contrast enhancement. Reported magnetic resonance image findings showed hyperintensity on both T1-weighted and T2-weighted images and variable contrast enhancement. Plain skull radiographs usually reveal a lytic lesion within the bone.

Child↗