Biomedical subjects

K H Chang

Publications and source records attributed to K H Chang.

At least 145 records · Page 8Linked to original sources

PubMed1992

Intraventricular neurocytoma: clinicopathological analysis of seven cases.

A retrospective analysis of seven patients with intraventricular neurocytoma is presented. Patient age at diagnosis ranged from 15 to 38 years (mean 24.6 years) and the male:female ratio was 6:1. Raised intracranial pressure due to hydrocephalus was the main cause of the clinical manifestations. An isodense mass with multiple intratumoral cysts and homogeneous contrast enhancement was the characteristic computerized tomography finding. The lesions commonly involved the lateral ventricle with or without extension to the third ventricle. Cerebral angiography showed homogeneous vascular staining in five patients. Magnetic resonance images revealed a mass isointense with the cerebral cortex on both T1- and T2-weighted images. Gadolinium-diethylenetriaminepenta-acetic acid-enhanced images showed homogeneous enhancement. Total removal of the tumor was possible in four patients. Pathologically, six cases were initially diagnosed as oligodendroglioma and the remaining case as ependymoma. However, immunohistochemical studies demonstrated strong positivity for neuron-specific enolase in all seven cases and for synaptophysin in five cases. On electron microscopy, three cases showed well-defined neurosecretory granules and 10-nm microtubules in their cytoplasm and cytoplasmic processes. One patient developed a recurrent tumor 18 months after surgery. The remaining six patients are free of recurrent tumors at 2 to 62 months after surgery. It is suggested that neurocytoma must be included in the differential diagnosis of intraventricular lesions, and that electron microscopic and immunohistochemical studies should be undertaken.

Adolescent↗

PubMed1992

MR imaging of the internal carotid artery in ischemic cerebrovascular disorders--clinical and angiographic correlation.

This study was intended to correlate the appearance of the cavernous segment of the carotid artery on MR images with the presence of significant stenosis or occlusion of the cervical carotid artery as seen on angiograms in 37 patients with cerebrovascular disorders who had brain MRI and arteriography. Three patients demonstrated an isointense signal within the carotid artery's cavernous segment, correlating with complete carotid occlusion as seen angiographically. Ten patients had variable signal intensity and/or luminal narrowing in the carotid siphon; seven of these findings correlated with angiographic evidence of carotid occlusion, while carotid branch occlusion was seen angiographically in the other three. The demonstration of normal signal void within a normal-appearing cavernous segment of the internal carotid artery in the remaining 24 patients correlated with an absence of significant stenosis within the cervical segment in 21 patients. In the remaining three, significant disease of the internal carotid artery was found. Isointensity or luminal irregularity within the intracranial carotid artery can indicate complete occlusion or slow flow. The presence of normal flow void in the intracranial segment does not exclude significant abnormality of the cervical segment of the carotid artery.

Adolescent↗

PubMed1992

Seventy-two patients' experience with an implantable drug delivery system for chemotherapy or total parenteral nutrition.

An implantable drug delivery system will play an important role for patients who need chemotherapy or prolonged total parenteral nutrition in the future. We implanted 72 injection capsules in 74 patients who were undergoing aggressive chemotherapy or total parenteral nutrition programs. These capsules were implanted in different positions, including central access in 67 cases, peritoneal cavity in 1, hepatic artery in 2, portal vein in 1 and intrathecal space in 1. The actual median functional survival of the injection capsules was 12.3 months (range, 2 months to 4 years). The total cumulative puncture numbers were 1651 (range, 5 to 153; median 23). There was no unsuccessful instance in infusion or injection. To date, 27 patients still survive. The complication rate was about 7% including 1 sepsis, 1 skin infection, 1 catheter thrombosis, 1 dislodgement of reservoir and 1 catheter-reservoir disengagement, which were all corrected by a secondary operation without mortality. Patency of the Port-A-Cath system was maintained using a regular flushing schedule once every 30 days. The results of this study suggest that the implantable drug delivery system can provide a safe and reliable method for venous access or even arterious access in patients requiring intermittent or prolonged intravenous therapy.

Adolescent↗

PubMed1991

Novel enzymic hydrolytic dehalogenation of a chlorinated aromatic.

Microbial enzyme systems may be used in the biodegradation of persistent environmental pollutants. The three polypeptide components of one such system, the 4-chlorobenzoate dehalogenase system, have been isolated, and the chemical steps of the 4-hydroxybenzoate-forming reaction that they catalyze have been identified. The genes contained within a 4.5-kilobase Pseudomonas sp. strain CBS3 chromosomal DNA fragment that encode dehalogenase activity were selectively expressed in transformed Escherichia coli. Oligonucleotide sequencing revealed a stretch of homology between the 57-kilodalton (kD) polypeptide and several magnesium adenosine triphosphate (MgATP)-cleaving enzymes that allowed MgATP and coenzyme A (CoA) to be identified as the dehalogenase cosubstrate and cofactor, respectively. The dehalogenase activity arises from two components, a 4-chlorobenzoate:CoA ligase-dehalogenase (an alpha beta dimer of the 57- and 30-kD polypeptides) and a thioesterase (the 16-kD polypeptide).

Adenosine Triphosphate↗

PubMed1991

Stresses at the dentinoenamel junction of human teeth--a finite element investigation.

A three-dimensional, linear, elastic finite element model of a maxillary first premolar from longitudinal ground sections was developed to investigate stress variation in the enamel and dentin adjacent to the dentinoenamel junction (DEJ). The effect of regional variation in the contour of the DEJ on the stress patterns for enamel and dentin was also analyzed. The normal (compressive or tensile) and shear stresses in the dentin and enamel surfaces of the DEJ were computed for a vertical load of 170 N acting on the entire occlusal surface of the model. The normal stresses in dentin and enamel were maximum on the occlusal surface of the model and diminished along the buccal and lingual surfaces of the DEJ. However, the magnitude of the normal stresses increased at the cervical enamel, which also showed increased values for shear stress distribution. The normal and shear stresses were markedly affected by the contour of the DEJ and the thickness of enamel in the occlusal third on the buccal and lingual surfaces. The results suggested that because the mechanical interlocking between enamel and dentin in the cervical region is weaker than in other regions of the DEJ, enamel in this region may be susceptible to belated cracking that could eventually contribute to the development of cervical caries.

Bicuspid↗

PubMed1991

Radiotherapy for postoperative recurrent uterine cervical carcinoma.

From January 1980 to December 1985, a total of 110 patients with postoperative recurrent uterine cervical carcinoma were treated with radiotherapy. The mean age was 53 years. Ten patients were excluded due to incomplete treatment. The population was grouped according to the classification by Ciatto et al. into patients with central recurrence (n = 48), with peripheral limited recurrence (n = 43), and with peripheral massive recurrence (n = 9). The midpelvic dose given to patients with central recurrence was 40 to 45 Gy, followed by a boost given either by perineal teletherapy with 30 Gy or brachytherapy with 30 Gy at 0.5 cm. beneath the vaginal mucosa. For the peripheral group, the midpelvic dose was 50 Gy followed by a boost of 10 Gy through reduced portals. Further boost to the vaginal mucosa was given by either of the two methods mentioned above. The overall 5-year survival rate was 28%. In the group with central recurrence, it was 42% and in the group with peripheral recurrence 15%. Sixteen patients had persistent local tumor and 15 patients developed distant metastasis. Complications noted were proctitis (5%), cystitis (2%), vesicovaginal fistula (2%) and rectovaginal fistula (2%). Our data clearly indicate that radiotherapy was effective in controlling central recurrence, but for peripheral recurrence, control rate and prognosis were less favorable.

Adult↗

PubMed1991

Magnetic resonance imaging in brainstem ischemic stroke.

To evaluate the efficacy of magnetic resonance imaging in brainstem stroke, we studied 21 cases of clinically definite brainstem ischemic stroke with brain magnetic resonance imaging (MRI) and conventional computed tomography (CT). MRI demonstrated brainstem lesions in 79% of the cases (16.5 out of 21), while CT revealed 33% (7 out of 21) when cases with suspicious lesions counted as 0.5. Although MRI was done a few days later than CT in most cases, MRI was superior to CT in detecting the number and the size of ischemic lesions, with clear delineation of anatomy and visualization of the status of the blood flow in the vertebral-basilar artery. Disappearance of the flow signal void in the basilar artery can be an important clue in diagnosing occlusion or thrombus of the basilar artery. By delineating the extent and the location of the infarction, MRI findings allowed an interpretation of whether the ischemic vessel is a small basilar branch or a large vessel vertebral or basilar artery.

Adult↗

PubMed1991

Results of postoperative radiotherapy for clinical stage Ib uterine cervical carcinoma with evidence of microscopic involvement of surgical margin, parametrium and/or lymph node metastasis.

From January 1979 to September 1985, a total of 125 patients preoperatively staged as International Federation of Gynecology and Obstetrics (FIGO) Ib uterine cervical carcinoma were proven to have either microscopic involvement of the surgical margin, parametrium and/or regional lymph node metastasis histopathologically after radical hysterectomy and pelvic lymphadenectomy. All of these patients were treated postoperatively with radiotherapy because of the above indications. Based on indications of postoperative radiotherapy, patients were divided into 3 major subgroups according to the microscopic involvement: group A patients (50) with microscopic evidence of regional lymph node metastasis only; group B patients (59) with microscopic evidence of parametrial involvement; and group C patients (16) with microscopic infiltration of the surgical margin involving the vaginal cuff. All patients were treated with external irradiation using a Cobalt-60 teletherapy machine. The overall actuarial 5-year survival rate was 62% with a 77% 5-year survival rate for group A, a 50% rate for group B and a 75% rate for group C. Further analysis of the prognostic factors revealed that those with regional lymph node involvement of 4 or less had a better chance of survival than those with lymph node involvement of more than 4. Also those with poorly differentiated squamous cell carcinoma had a lower 5-year survival rate than those with moderately or well-differentiated squamous cell carcinoma. Univariate analysis revealed that hemoglobin values, age, and the time interval from surgery to radiotherapy were not significant prognostic factors.

Adenocarcinoma↗

PubMed1990

Clinical utility of partial flip angle T2-weighted spin-echo imaging of the brain.

To assess the clinical usefulness of partial flip angle (PFA) spin-echo (SE) brain imaging, a total of eighty patients were examined with both conventional double echo T2-weighted SE (2500/30, 80/90 degrees/one excitation) and PFA double echo SE (1200/30, 70/45 degrees/two excitations) on 2.0T system. Two comparative studies were performed: (1) in 65 patients PFA SE technique was compared with conventional SE without flow compensating gradients, and (2) in 15 patients the former was compared with the latter with flow compensating gradients. Imaging time was nearly identical in each sequence. In both studies we found that PFA T2-weighted SE images were almost identical to those obtained with the conventional SE technique in the contrast characteristics and the detection rate of the abnormalities (100%, 85/85 lesions), and more importantly, PFA SE revealed few flow artifacts in the brain stem, temporal lobes and basal ganglia which were frequently seen on conventional SE without flow compensating gradients. Additionally, PFA SE images demonstrated no suppression of CSF flow void in the aqueduct which was commonly seen on conventional SE with flow compensating gradients. In overall image quality, the PFA SE images, particularly the second echo images, were almost comparable with those of conventional SE with flow compensating gradients. A flip angle of 45 degrees seems to be close to Ernst angle, the angle at which maximum signal occurs, for a given TR of 1200 msec for CSF and most of the abnormalities containing higher water content.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Gd-DTPA enhanced MR imaging in intracranial tuberculosis.

Twenty-six patients with intracranial tuberculosis (Tb) (10 with acute meningitis, 5 with chronic meningitis, 5 with meningitic sequelae and 6 with localized tuberculoma(s)) were examined with MR before and after Gd-DTPA enhancement (0.1 mmol/kg), using 2.0T superconducting unit, and the images were retrospectively analyzed and compared with CT scans. Without Gd-DTPA enhancement, the MR images were generally insensitive to detection of active meningeal inflammation and granulomas. The signal intensity of granulomas was usually isointense to gray matter on both T1- and T2-weighted images, whether they were associated with diffuse meningitis or presented as localized tuberculoma(s). A few granulomas showed focal hypointensity on T2-weighted images. Calcifications seen on CT of the meningitic sequelae group usually appeared markedly hypointense on all spin-echo sequences. On Gd-DTPA enhanced T1-weighted images, abnormal meningeal enhancement indicating active inflammation was conspicuous, and the granulomas often appeared as conglomerated ring-enhancing nodules, which seems to be characteristic of granulomas. Thin rim enhancement around the suprasellar calcifications were observed in two out of 5 patients with meningitic sequelae. Compared with CT, MR detected a few more ischemic infarcts, hemorrhagic infarcts, meningeal enhancement and granulomas in the acute meningitis group, but missed small calcifications in the basal cisterns well shown on CT in the sequelae group. Otherwise, MR generally matched CT scans. MR imaging appears to be superior to CT in evaluation of active intracranial Tb only if Gd-DTPA is used, while CT is better than MR in evaluating meningitic sequelae with calcification.

Adolescent↗

PubMed1990

Deep sylvian meningioma in a child.

Meningioma is a rare brain tumor in childhood, but one located deep in the sylvian fissure without any connection to the dura or ventricular system is even more unusual. A 2-year-old boy with a deep sylvian meningioma is presented. This is the youngest case as well as the third intrasylvian meningioma reported in the pediatric age group (up to age 15).

Child, Preschool↗

PubMed1990

Gd-DTPA-enhanced MR imaging of the brain in patients with meningitis: comparison with CT.

Plain and Gd-DTPA-enhanced MR images of the brain were obtained in 18 consecutive patients with meningitis (eight with tuberculous, five with bacterial, three with viral, and two with fungal infections); the MR images were compared with CT scans. MR images were obtained on a 2.0-T superconducting unit with both T1- and T2-weighted pulse sequences before injection and with a T1-weighted sequence after injection of Gd-DTPA (0.1 mmol/kg) in all patients. In tuberculous meningitis, MR imaging depicted ischemia/infarct, hemorrhagic infarct of basal ganglia, meningeal enhancement at either basal cistern or convexity surface of brain, and associated small granulomas in a few more patients than CT did. In bacterial meningitis, primary foci of extracranial inflammation (i.e., mastoid, paranasal sinuses) and adjacent intracranial lesions including localized dural inflammation, subdural fluid collection, and/or brain parenchymal lesions were demonstrated much better on MR than on CT. Otherwise, MR images generally matched the CT scan. Although the plain MR images, both T1- and T2-weighted, were the most sensitive in delineating ischemia/infarct, hemorrhage, and edema, they were not as specific as Gd-DTPA-enhanced T1-weighted images and postcontrast CT scans in defining the active inflammatory process of the meninges and focal lesions precisely. We conclude that if Gd-DTPA is used, MR imaging appears to be superior to CT in the evaluation of patients with suspected meningitis. Precontrast MR is needed to delineate ischemia/infarct, edema, and subacute hemorrhage.

Adolescent↗

PubMed1990

MR imaging findings of moyamoya disease.

The brain MR images of 23 patients with angiographically proved moyamoya disease were reviewed to evaluate the capability of MR to demonstrate vascular and parenchymal abnormalities. All the MR images were obtained on a 2.0 T superconducting system and included T1-weighted sagittal and T2-weighted axial images without implementation of flow compensation (FC). The vascular abnormalities demonstrated on MR images were narrowing of the cavernous internal carotid artery (ICA) (73%), narrowing or occlusion of the supraclinoid ICA (87%) and proximal middle cerebral artery (MCA) (91%), and multiple collateral vessels in the basal ganglia and/or thalamus (96%). The parenchymal abnormalities included ischemic infarctions (74%), predominantly located in watershed areas, hemorrhagic infarctions (26%), intracerebral hematomas (13%), and intraventricular hemorrhage (13%). In conclusion, MR imaging was a useful diagnostic modality for detecting both vascular and parenchymal abnormalities associated with moyamoya disease. This may obviate the need for invasive angiography as far as the diagnosis is wanted at the non-quantitative level.

Adolescent↗

PubMed1990

Palliative radiotherapy of cerebral metastasis from lung cancer.

Cerebral metastasis is a common manifestation of lung cancer. Presenting signs and symptoms are often grave, and consequently often result in patients being debilitated for the rest of their lives. Radiotherapy has been used to treat a majority of these cases, and is considered as the treatment of choice. At Mackay Memorial Hospital, we collected from 1982 to 1985, the records of 42 lung cancer patients with brain metastasis. All the cases had a histological diagnosis of primary lung cancer; most of them were squamous cell carcinoma and adenocarcinoma; only two cases were small cell carcinoma. The diagnosis of brain metastasis was established by computed tomographic scans of the brain and radioisotopic brain scans. Of the 42 cases, 22 received palliative radiotherapy from a cobalt-60 teletherapy machine to the whole brain for a total dose of 30 Gray (Gy) in 10-15 fractions over a time span of 2 to 3 weeks, while the remaining patients only received medical treatment (e.g. cranial decompression with mannitol, steroids, etc.). Most of the patients have already died. In our study, those who received radiotherapy attained considerable palliation of their symptoms and signs, including improvement of their general performance status and neurological function. Although the treatment did not prolong the patient's survival, it did decrease considerably the disability caused by the metastatic disease.

Adenocarcinoma↗

PubMed1990

Selective cytotoxic effects of immunotoxin--monoclonal anti-AFP-abrin-A chain conjugate on several human hepatoma cell lines.

A highly specific monoclonal antibody (anti-AFP) against alpha-fetoprotein (AFP) was linked to N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) to form conjugates which were purified with a protein A-sepharose CL-4B affinity column. The conjugate, PDP-Anti-AFP was then covalently coupled to the toxic abrin-A chain to synthesize immunotoxins. The immunotoxin, anti-AFP-abrin-A conjugate, which was also purified with a protein A-sepharose CL-4B affinity column, had a molecular weight of 180,000 and had 80% antigen-binding activity that of anti-AFP activity and 92% toxicity of abrin-A chain. The immunotoxin showed selective cytotoxicities toward the AFP secreting human hepatoma cell lines, such HepG2 and Hep3B, but not toward AFP non-secreting human hepatoma cell line, PLC/PRF/5.

Abrin↗

PubMed1989

Unusual MR manifestations of neurocysticercosis.

MR and CT features of neurocysticercosis are variable and depend fundametally on the stage in evolution of the infection, location, number and size of the worm. The authors retrospectively evaluated MR images obtained on a 2.0T superconducting unit in 22 neurocysticercosis patients and observed various MR features including some new findings. A variety of MR findings are presented with special reference to six case reports. The features include: (1) a large simple cyst containing both internal septations and a scolex; (2) suprasellar racemose cysts mimicking other cysts, (3) a fourth ventricular cyst readily depicted by aid of CSF flow-void in the sagittal plane; (4) degenerating cysts showing "white target" appearance; (5) granulomatous lesions having a "black target" appearance; and (6) a meningitic form showing Gd-DTPA enhancement of basal cisterns and of a subacute infarct.

Adolescent↗

PubMed1989

The nucleotide sequence of coxsackievirus A9; implications for receptor binding and enterovirus classification.

The complete nucleotide sequence of the genome of coxsackievirus A9 (CAV-9) has been determined from cDNA cloned in Escherichia coli. Excluding the 3' poly(A) stretch, the RNA genome is 7452 nucleotides long and encodes a single polyprotein of 2201 amino acids. Comparison of the nucleotide and predicted amino acid sequences with those of the coxsackieviruses B1, B3 and B4 reveals a surprising degree of homology, with overall amino acid homologies of 86.9%, 86.2% and 87.0%, respectively. In contrast, there is much less homology to another coxsackie A virus, CAV-21, 60.4% overall amino acid homology. This demonstrates the high degree of diversity within the CAV group and indicates that the current classification does not directly correlate with molecular genetic properties. One major feature of CAV-9 is an insertion, relative to all other enteroviruses sequenced to date, which is located at the C terminus of VP1, and includes an arginine-glycine-aspartic acid tripeptide. Such sequences in a number of other proteins are known to have activity in promoting attachment to cell receptors and the implications for CAV-9 receptor binding are discussed.

Amino Acid Sequence↗

PubMed1989

The use of lithium carbonate to correct leukopenia during cancer treatment.

Leukopenia is a common complication noted in patients receiving radiotherapy and/or chemotherapy but no effective method has been reported so far to correct this complication. In the field of psychiatry, lithium carbonate used in treating depression has been noted to have induced leukocytosis as a side effect. From July 1985 to December 1987, a total of 111 patients receiving radiotherapy and/or chemotherapy with leukopenia were included in this study. There were sixty nine patients who received lithium carbonate and the remaining forty two patients served as control group were allowed to stop their primary treatment temporarily without medication during their period of leukopenia. For the group given lithium carbonate, 79% of the patients were able to recover their white blood count (WBC) above 3,000/cu.mm. within 5 days and finished their primary treatment smoothly. For the control group, it took them on the average about 11.8 days of rest in order to recover their WBC level to 3,000/cu.mm. and above. Reports in the recent literature indicates that the average toxic level is around 1.5 mEq/l to 2.0 mEq/l. In our study, the average serum lithium level before administration is 0.44 mEq/l, it reached 0.59 mEq/l and 1.08 mEq/l after the fifth and the 10th day of intake respectively. From this laboratory data, obviously no patient reached the toxic level and no side effects were noted clinically. Based on these figures, we can see clearly that lithium carbonate can shorten the period of leukopenia in comparison to the control group which was not given any medication.

Adolescent↗