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Biomedical subjects

C N Chang

Publications and source records attributed to C N Chang.

At least 37 records · Page 2Linked to original sources
PubMed1999

The characteristic study of TSP, PM2.5-10 and PM2.5 in the rural site of central Taiwan.

The total suspended particle (TSP), PM2.5-10 (aerodynamic diameter less than 10 microns) and PM2.5 concentration (aerodynamic diameter less than 2.5 microns) concentrations were sampled by PS-1 and Universal sampler on the roof (25 m) of the Medical and Engineering Building in the campus of Hungkuang Institute of Technology (HKIT) which is located at a height of 500 m on Da Du Mountain. The results indicated that average TSP, PM2.5-10 and PM2.5 concentrations are 0.42, 0.34 and 0.019 mg/m3 in the day time, respectively and are 0.32, 0.26 and 0.017 mg/m3 in the night time, respectively. The ratios of PM2.5-10/TSP were from 76% to 85% and from 50% to 91% for day and night period, respectively. It indicated that the major composition in the total suspended particles was PM2.5-10 in the rural site. The relationship between TSP and PM2.5-10 is TSP = 1.16PM2.5-10 + 0.027 and TSP = 1.01 PM2.5-10 + 0.058 in the day and night time, respectively. The correlation coefficient (R2) is 0.98 and 0.97 for day and night period, respectively. The relationship between PM2.5-10 and PM2.5 is PM2.5 = 0.0005PM2.5-10 + 0.019 and PM2.5 = 0.037PM2.5-10 + 0.0076 in the day and night period, respectively. The correlation coefficient (R2) is 3E-5 and 0.67 for day and night period, respectively. The relationships between TSP, PM2.5-10, PM2.5 particle concentrations and wind speed (R2) in the day time are 0.71, 0.64, 0.43, respectively and are 0.83, 0.79, 0.57, respectively in the night time. The proposed reasons are that there are more activities caused by people (students) and natural living animals which absorbed some of the particles during the day time. Thus, the correlation coefficients for the night time are better than those of day time. The particle size distributions are both bimodel in the day and night time. The major peaks in the day time appear in the particle diameter between 0.031-0.056 micron and 3.16-5.62 microns in the day period and appear between 0.017-0.031 micron and 1.78-3.16 microns in the night period. The results indicate that the particle size distribution in the day time tends to be of larger particle size mode than the night time.

Air Pollutants↗
PubMed1999

Epitope mapping of CCR5 reveals multiple conformational states and distinct but overlapping structures involved in chemokine and coreceptor function.

The chemokine receptor CCR5 is the major coreceptor for R5 human immunodeficiency virus type-1 strains. We mapped the epitope specificities of 18 CCR5 monoclonal antibodies (mAbs) to identify domains of CCR5 required for chemokine binding, gp120 binding, and for inducing conformational changes in Env that lead to membrane fusion. We identified mAbs that bound to N-terminal epitopes, extracellular loop 2 (ECL2) epitopes, and multidomain (MD) epitopes composed of more than one single extracellular domain. N-terminal mAbs recognized specific residues that span the first 13 amino acids of CCR5, while nearly all ECL2 mAbs recognized residues Tyr-184 to Phe-189. In addition, all MD epitopes involved ECL2, including at least residues Lys-171 and Glu-172. We found that ECL2-specific mAbs were more efficient than NH2- or MD-antibodies in blocking RANTES or MIP-1beta binding. By contrast, N-terminal mAbs blocked gp120-CCR5 binding more effectively than ECL2 mAbs. Surprisingly, ECL2 mAbs were more potent inhibitors of viral infection than N-terminal mAbs. Thus, the ability to block virus infection did not correlate with the ability to block gp120 binding. Together, these results imply that chemokines and Env bind to distinct but overlapping sites in CCR5, and suggest that the N-terminal domain of CCR5 is more important for gp120 binding while the extracellular loops are more important for inducing conformational changes in Env that lead to membrane fusion and virus infection. Measurements of individual antibody affinities coupled with kinetic analysis of equilibrium binding states also suggested that there are multiple conformational states of CCR5. A previously described mAb, 2D7, was unique in its ability to effectively block both chemokine and Env binding as well as coreceptor activity. 2D7 bound to a unique antigenic determinant in the first half of ECL2 and recognized a far greater proportion of cell surface CCR5 molecules than the other mAbs examined. Thus, the epitope recognized by 2D7 may represent a particularly attractive target for CCR5 antagonists.

Amino Acid Sequence↗
PubMed1999

Proton MR spectroscopy in patients with complex partial seizures: single-voxel spectroscopy versus chemical-shift imaging.

BACKGROUND AND PURPOSE: Proton MR spectroscopy has recently been applied to the evaluation of seizures, but few comparisons have been made between different clinical spectroscopic techniques. Our goal was to determine whether there is a significant difference between hippocampal NAA/(Cho+Cr) ratios obtained by single-voxel spectroscopy (SVS) and by chemical-shift imaging (CSI). METHODS: Twelve healthy adults and eight patients with complex partial seizures were studied on a 1.5-T MR scanner using a proton SVS method. Another 12 healthy adults and 10 patients with complex partial seizures were recruited for a proton CSI study, which was performed on a different 1.5-T MR system. The NAA/(Cho+Cr) ratio was calculated from the integral peak areas by curve fitting. The two-tailed t-test was used for statistical analysis. RESULTS: The mean value +/- standard deviation of the hippocampal NAA/(Cho+Cr) ratio in healthy control subjects was 0.63 +/- 0.07 by SVS, with 0.62 +/- 0.15 for the anterior hippocampus and 0.65 +/- 0.11 for the posterior hippocampus by CSI. There was no significant difference between the control group data obtained by SVS and those by CSI, nor was there a regional difference in the CSI NAA/(Cho+Cr) ratio in the hippocampus. Relative to the control group, the patients with seizures had a significant decrease in the NAA/(Cho+Cr) ratio in the abnormal hippocampus: -28% by SVS, and -24% in the anterior hippocampus and -18% in the posterior hippocampus by CSI. Proton SVS and CSI detected hippocampal abnormalities, unilateral or bilateral, in all patients of each group. CONCLUSION: Under similar measurement conditions, proton SVS and CSI provide similar NAA/(Cho+Cr) ratios among healthy control subjects, and they possess comparable ability for detecting hippocampal abnormalities in patients with complex partial seizures.

Adolescent↗
PubMed1999

Proton chemical shift imaging of the hippocampus in patients with complex partial seizures.

BACKGROUND: Cerebral metabolites can be evaluated non-invasively using in vivo proton magnetic resonance spectroscopy (MRS). Decreased N-acetylaspartate (NAA) and increased choline-containing compounds (Cho) and creatine-phosphocreatine (Cr) have been found in the hippocampus of patients with complex partial seizures (CPS). METHODS: We prospectively studied hippocampal proton MRS of 10 patients with CPS and 12 control subjects by using the chemical shift imaging (CSI) technique. The spectral data were analyzed in terms of the ratio between the integral peak area of NAA and that of (Cho + Cr). RESULTS: Compared with the control group, patients with CPS showed a significantly lower NAA/(Cho + Cr) ratio, both in the anterior and posterior hippocampus (p value = 0.001 and 0.002, respectively). Metabolic abnormalities of the hippocampus were detected using proton CSI in all the patients with normal MRI results (4 patients) and those with normal EEG results (3 patients). Lateralizations using proton CSI were obtained in all the 10 patients in this study, including concordant lateralization in the 6 patients with MRI-detectable abnormalities. CONCLUSION: The hippocampal abnormalities in patients with CPS can be detected early using proton CSI than using MRI or surface EEG. Lateralization of the seizure focus using proton CSI is possible, but further correlation with the surgical outcome in a larger study group is necessary.

Adolescent↗
PubMed1998

Dexamethasone inhibits ischemia-induced transient reduction of neurotrophin-3 mRNA in rat hippocampal neurons.

Dexamethasone (DEX) increases the expression of neurotrophin-3 (NT-3) in normal rat hippocampal neurons, whereas transient forebrain ischemia reduces the NT-3 mRNA level. The effect of DEX on the expression of NT-3 mRNA in injured brain cells after ischemia has not been investigated, however. Using in situ hybridization and ribonuclease protection assay methods, we studied NT-3 mRNA expression in rats with and without DEX administration after transient forebrain ischemia. Without DEX treatment, NT-3 mRNA was down-regulated in the hippocampal neurons at 2, 4, 12 h and returned to basal levels 24 h following ischemia. With DEX treatment, however, NT-3 mRNA showed no change at 2, 4 and 12 h and increased 24 h after ischemia. The results indicate that DEX inhibits ischemia-induced NT-3 mRNA down-regulation during the first 12 h and up-regulates NT-3 mRNA 24 h after ischemia. DEX administration might be effective in influencing some of the pathophysiological effects of ischemia in the hippocampus.

Animals↗
PubMed1998

Nuclear multiparameter flow cytometric DNA analysis of human brain tumors: correlation of DNA content with tumor histology and clinical behavior.

BACKGROUND: Using fresh surgical specimens of brain tumors to investigate cellular DNA content is uncommon. The aim of this study is to elucidate the relationship among cellular nuclear DNA content, tumor histology, and tumor clinical behavior of various tumors of the central nervous system. METHODS: Multiparameter flow cytometry (FACStar, Becton-Dickinson, San Jose, CA) was randomly applied to analyze 40 fresh surgical specimens from brain tumors. Histologically, there were 19 cases of benign tumors and 21 cases of malignant tumors. RESULTS: DNA distribution profiles in the benign tumors revealed 15 cases of diploidy and four cases of aneuploidy, while the malignant tumors had eight cases of diploidy and 13 cases of aneuploidy (p < 0.01). The mean DNA index (DI) in benign tumors was 1.13 +/- 0.27 and in malignant tumors 1.43 +/- 0.48 (p < 0.05). The mean proliferative index (PI) in benign tumors was 10.27 +/- 5.46% and 18.44 +/- 8.98% in malignant tumors (p < 0.05). Clinically, 10 patients had postoperative recurrence. The PI in recurrent and nonrecurrent tumors was 17.83 +/- 11.13% and 13.20 +/- 7.19%, respectively (p < 0.05). The 1-year cumulative survival rate in benign tumors was 78.9%, and 57.1% in malignant tumors (p < 0.05). CONCLUSIONS: Malignant tumors had a significantly higher incidence of aneuploid DNA histograms, a higher DNA index, and a higher proliferative index. Tumors with a high PI had a higher incidence of recurrence and a lower survival rate. Multiparameter DNA analysis by flow cytometry provides a valuable diagnostic aid for the histopathologic differentiation of human brain tumors.

Adolescent↗
PubMed1997

The endocrine mechanism of sex reversal in the protandrous black porgy, Acanthopagrus schlegeli: a review.

Black porgy, Acanthopagrus schlegeli Bleeker, a marine protandrous hermaphrodite, is a functional male for the first 2 years of life but begin to sexually reverse to female after the third year. This sex pattern provides a very good model to study the mechanism of sex reversal in fish. The gonad at 5 month of age consisted of testicular tissue with few primary oocytes at 5 month of age. The ovarian tissue became dominant at 18 months of age during the non-spawning season. Testicular and ovarian tissues were separated by connective tissue. Plasma estradiol-17 beta(E2), vitellogenin and 11-ketotestosterone (11-KT) profiles in males were significantly different from those in the 3-year-old reversing females. Peak levels of plasma E2 in the reversing females occurred during the early prespawning season (in October). Lower levels of plasma E2 were, however, observed in the males. Plasma 11-KT levels significant decreased but no changes of plasma testosterone were detected in the reversing females. Exogenous E2 suppressed the testicular development but induced the gonadal aromatase activity, ovarian development and sex reversal in 2-year-old black porgy. Exogenous T and LHRH analog did not have effects on the sex reversal. Higher concentrations of pituitary GtH II and mRNA of GtH II-beta subunit were detected in the reversed females. These data suggested that E2 and gonadal aromatase closely associated to the occurrence of sex reversal. A working model of the sex reversal in black porgy is proposed.

Animals↗
PubMed1997

An antibody reactive with domain 4 of the platelet-derived growth factor beta receptor allows BB binding while inhibiting proliferation by impairing receptor dimerization.

A panel of murine monoclonal antibodies was generated against the extracellular domain of the human platelet-derived growth factor (PDGF) beta receptor (PDGFRbeta). These antibodies were assayed for both the ability to inhibit binding of PDGF BB to PDGFRbeta+ cells as well as the capacity to inhibit PDGF BB-mediated mitogenesis. As expected, all antibodies that could prevent PDGF BB binding also inhibited mitogenesis. However one antibody (M4TS.11), with no detectable ability to inhibit PDGF BB binding, was a potent inhibitor of proliferation induced by PDGF BB. Further characterization indicated that M4TS.11 impaired PDGFRbeta dimerization, revealing the mechanism by which it prevented PDGF BB-mediated mitogenesis. Using domain deletion mutants of the extracellular portion of PDGFRbeta, the determinant recognized by this antibody was localized to the fourth extracellular domain of PDGFRbeta, indicating that this domain, which is not involved in ligand binding, actively participates in receptor dimerization and signal transduction. The M4TS.11 antibody could also inhibit PDGF BB-mediated proliferation of responsive cells from both the baboon and the rabbit, indicating the determinant recognized by the antibody is not limited to humans and making it possible to use this antibody to evaluate the therapeutic benefit of interfering with PDGF in animal models of human disease.

Animals↗
PubMed1997

Reoperation for recurrent trigeminal neuralgia after microvascular decompression.

BACKGROUND: Microvascular decompression (MVD) is an effective technique for those who have trigeminal neuralgia (TN) but cannot tolerate, or show no response to medicine. Though the initial success rate is high, some patients may develop severe recurrent neuralgia, especially after a longer period of follow-up. The efficacy of reoperation needs to be evaluated. To know the possible risk factors of recurrence after initial MVD is mandatory to the management of recurrent TN. METHODS: Among the 80 cases of TN treated with MVD, five cases showed severe recurrent symptoms within a follow-up period from 9 months-4 years. The symptoms recurred on the same side of the face, and were unresponsive to medical treatment. Brain computed tomography (CT) and magnetic resonance imaging (MRI) may reveal the etiology of recurrence. Repeat decompression of the trigeminal nerve was the main goal of reoperation, which was done via a suboccipital approach. RESULTS: Over the past 17 years, 80 MVDs for TN have been performed at Chang Gung Memorial Hospital. There were five cases of serious postoperative recurrence, which could not be relieved by medicine. Recurrence occurred 1 day-12 months after the initial surgery. Three cases were due to vascular compression, while two were caused by the local effect of Teflon felt. Reoperation produced complete remission in four patients, and partial remission in one. CONCLUSIONS: An increasing number of patients may experience severe recurrent TN after initial MVD during a long period of follow-up. Reoperation is safe and beneficial for these patients, but the results are dependent on the etiology of the recurrence. Further vascular compression of the trigeminal nerve can be relieved by MVD. Otherwise, in cases of severe adhesion caused by Teflon, complete microneural lysis can achieve satisfactory results.

Adult↗
PubMed1997

Treatment of frontal sinus osteoma using a craniofacial approach.

Osteoma is one of most common benign tumors of the nose and paranasal sinuses, with the frontal sinus being its most frequent location. It may be locally destructive and aggressive with possible intracranial complications. Osteoma of the frontal sinus comprises 57% of all osteomas in the paranasal sinuses. In 1939, Childrey reviewed 3,510 consecutive sinus radiographs taken for any reason and found an incidence of 0.43% of paranasal sinus osteomas. There are many operative approaches for frontal sinus osteomas, such as external frontoethmoidal approach and osteoplastic frontal sinusectomy, both with high recurrence rates. Those traditional operative methods cannot radically eradiate the osteoma grown in the posterior table of the frontal sinus. From July 1991 to June 1992, three patients with symptomatic frontal sinus osteomas were operated by a craniofacial approach. One patient is presented here in detail. A coronal incision is used and is found to be beneficial both in surgical exposure and in reconstruction with a calvarial bone graft. The patient has been followed for 3.5 years without osteoma recurrence.

Bone Neoplasms↗
PubMed1997

Optic nerve decompression in fibrous dysplasia: indications, efficacy, and safety.

Optic nerve decompression is controversial in posttraumatic visual loss and as a prophylactic therapy in fibrous dysplasia involving the optic canal. It is less controversial for the treatment of optic nerve compression in fibrous dysplasia. Thirteen patients with craniomaxillofacial fibrous dysplasia who underwent 16 optic nerve decompressions at the Chang Gung Craniofacial Centre for both therapeutic (10) and prophylactic (6) indications are reported. One patient sustained a clinically useful improvement in vision in response to two therapeutic decompressions, and another demonstrated marked improvement after therapeutic decompression, with visual acuity improving from 0.4 to 1.0 in the affected eye. No patient underwent a permanent deterioration of vision as a result of either therapeutic or prophylactic decompression. One patient suffered extraocular muscle dysfunction that was corrected with strabismus surgery. A review of the literature clarifies the controversies and allows establishment of indications for optic nerve decompression.

Adolescent↗
PubMed1997

Neuroimaging in intractable complex partial seizures.

We retrospectively analyzed 19 patients with intractable complex partial seizures who underwent temporal lobectomy and compared the usefulness of various imaging techniques in diagnosis and localization. Pathologic findings consistent with mesial temporal sclerosis were found in 12 patients arteriovenous malformations in four, tumors in three, and coexistence of a tumor and mesial temporal sclerosis in one. Electroencephalography and single photon emission computed tomography detected lateralized functional abnormality in two patients when computed tomography (CT) and magnetic resonance imaging (MRI) showed equivocal results. Both CT and MRI showed all arteriovenous malformations and tumors. CT detected only four cases of mesial temporal sclerosis, while MRI showed nine cases. Detection, delineation and diagnosis of lesions responsible for complex partial seizures are essential for good surgical results. Thus, the importance of image studies, especially MRI, should be emphasized in patients with complex partial seizures.

Adolescent↗
PubMed1997

Proton magnetic resonance spectroscopy in patients with complex partial seizures.

We prospectively studied eight patients with complex partial seizures, using single-voxel proton magnetic resonance spectroscopy (MRS). Control data from 12 healthy volunteers were obtained with the same MRS protocol. The ratios between the peak areas of N-acetylaspartate, creatine and phosphocreatine (Cr), and choline-containing compounds (Cho) were analyzed. The results showed statistically significant lower N-acetylaspartate:Cr, N-acetylaspartate:Cho, and N-acetylaspartate: Cho + Cr ratios, and a higher Cho:Cr ratio in the mesial temporal lobes of the patient group than in healthy controls. Because N-acetylaspartate is located in the neurons and Cho and Cr in the glial cells, these observations represent the underlying neuronal loss and reactive astrocytosis in the epileptogenic foci. MRS can detect abnormal metabolic changes in most complex partial seizure patients with normal electroencephalography and magnetic resonance images. MRS can also identify bitemporal abnormalities which are a common feature in patients with complex partial seizures. Proton MRS could not confirm the specific location of seizure foci. Further investigation with quantitative spectral analysis and correlation with surgical outcome is needed to improve the contribution of MRS to the diagnosis and localization of seizure foci.

Adult↗
PubMed1996

Prolonged circulatory arrest in moderate hypothermia with retrograde cerebral perfusion. Is brain ischemic?

BACKGROUND: Circulatory arrest (CA), which provides a bloodless field and good visualization without the need of aortic cross-clamp, is commonly used to facilitate repair of aortic lesions. However, extended periods of CA may impair cerebral metabolism and cause ischemic injury. Studies were performed to evaluate the efficacy of retrograde cerebral perfusion (RCP) in protecting the brain from ischemic injury during a prolonged period of CA in moderate hypothermia. METHODS AND RESULTS: Twenty-three patients (18 men and 5 women) were operated on for aortic lesions (17 acute type A aortic dissection and 6 chronic type A aortic dissection with Marfan's syndrome). The aortic operations were performed with CA (58 to 104 minutes; mean +/- SD, 75 +/- 12 minutes) at a rectal temperature of 23.3 +/- 0.5 degrees C (21 degrees C to 25 degrees C). For RCP, cold (14 degrees C to 18 degrees C) oxygenated blood (300 mL/min) was pumped to the superior vena cava with internal jugular venous pressure of 15 +/- 5 mm Hg. The cardiopulmonary bypass time was 157 +/- 18 minutes. Cortical blood flow during RCP detected by subdural laser Doppler probe was 10 +/- 5% of baseline. Percent oxygen extraction and pyruvate and lactate levels (26 +/- 2% and 0.43 +/- 0.17 and 45 +/- 16 mg/dI) were insignificantly different from those before CA (28 +/- 3% and 0.71 +/- 0.08 and 62 +/- 20 mg/dL, P > .05). Creatine kinase-BB isoenzyme was undetectable. All but 1 patient survived the operation (95.5%) and woke up without neurological deficit. Follow-up (mean, 13 months) was complete in all survivors. There were no late deaths. Cerebral functional studies performed 3 months after discharge showed results insignificantly different from those of the normal control subjects. CONCLUSIONS: There is no evidence of ischemia of the brain during prolonged moderate hypothermic CA with the aid of RCP. Retrograde cerebral perfusion effectively extends the safe time of CA. Deep hypothermia during CA seems unnecessary.

Adult↗
PubMed1996

p53 gene mutation in cerebral primitive neuroectodermal tumor in Taiwan.

p53 mutation has been rarely reported in cerebral primitive neuroectodermal tumors (PNET). To determine the significance of p53 mutations in the development of cerebral PNET, we studied cerebral PNET samples from 14 patients, 8 females and 6 males with a mean age of 38 years (range 10 months to 77 years) who had total or subtotal surgical resection. Histological typing of PNET with neuronal (N) and non-neuronal (NN) differentiation groups revealed 8 and 6 cases, respectively. Six (43%) of the 14 patients had p53 mutation. The p53(+) and p53(-) groups had an age range of 19-77 with a mean of 49 years and 10 months to 57 years with a mean of 30 years, respectively. p53 expression between the PNET-N and PNET-NN groups was 5 of 8 (62.5%) and 1 of 6 (16.7%), respectively. The mutations contained 3 transitions, 2 transversions and 1 frameshift; none of them occurred at the site of 'hot-spot' residues (codons 175, 248, 273). The results suggest that: (1) p53 mutation in cerebral PNET tends to show a higher incidence of neuronal differentiation and occurs in the older age group in Taiwan, (2) there was no difference in survival time between the PNET-N and PNET-NN groups (7 months and 6 months) (P = 0.54), and between p53(+) and p53(-) groups (6 months and 7 months) (P = 0.57), and (3) PNET may be an entity of a heterogenous group of tumors with different genetic mechanisms controlling their trends of differential lineage. Further studies are needed to determine the significance of p53 mutations in PNET development, especially the role of carcinogens in the genesis of PNET in Taiwan.

Adolescent↗
PubMed1996

Myocardial perfusion and function in dogs with moderate coronary stenosis.

MRI studies of first-pass contrast enhancement with polylysine-Gd-DTPA and myocardial tagging using spatial modulation of magnetization (SPAMM) were performed to assess the feasibility of a combined regional myocardial blood flow and 2D deformation exam. Instrumented closed-chest dogs were imaged at a baseline control state (Cntl) followed by two interventions: moderate coronary stenosis (St) achieved by partial occlusion of the left anterior descending (LAD) and moderate coronary stenosis with dobutamine loading (StD). Hypoperfusion of the anterior region (ANT) of the myocardium (LAD distribution) relative to the posterior wall (POS) based on the upslope of the signal intensity time curve from the contrast-enhanced MR images was demonstrated only with dobutamine loading (ANT:POS Cntl = 1.077 +/- 0.15 versus ANT:POS StD = 0.477 +/- 0.11, P < 0.03) and was confirmed with radiolabeled microspheres measurements (ANT:POS Cntl = 1.18 +/- 0.2 ml/min/g versus ANT:POS StD = 0.44 +/- 0.1 ml/min/g; P < 0.002). Significant changes in regional myocardial shortening were only seen in the StD state (P < 0.02); the anterior region showed impaired myocardial shortening with dobutamine loading (P = NS), whereas the nonaffected POS region showed a marked increase in shortening when compared with Cntl (Cntl = 0.964 +/- 0.02 versus StD = 0.884 +/- 0.03; P < 0.001). These results demonstrate that an integrated quantitative assessment of regional myocardial function and semiquantitative assessment of myocardial blood flow can be performed noninvasively with ultrafast MRI.

Animals↗