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Biomedical subjects

T Chang

Publications and source records attributed to T Chang.

At least 55 records · Page 3Linked to original sources
PubMed1999

Effects of microwave heating on systemic and local infiltrating lymphocytes in patients with chronic limb lymphedema.

OBJECTIVES: To observe the characteristics of lymphocyte phenotypes in systemic and local skin and to evaluate the effects of microwave heating and bandaging treatment on chronic limb lymphedema. METHODS: Totally 27 patients with lymphedema and 10 normal subjects were examined with alkaline phosphatase-anti-alkaline phosphatase (APAAP) and avidin-biotin-peroxidase (ABC) immunohistochemistry for the observation of systemic lymphocyte phenotypes and inflammatory cell infiltration of skin tissues. RESULTS: In the peripheral blood of patients with chronic limb lymphedema, the number of CD4 T lymphocytes and the ratio of CD4/CD8 decreased, while the number of CD8 T lymphocytes increased. Obvious dermal perivascular infiltration of T lymphocytes was also observed. After two courses of microwave heating and bandaging treatment, the number of CD4 T lymphocytes augmented and the decreased CD4/CD8 ratio returned to normal, and the number of CD8 T lymphocytes reduced. The perivascular T lymphocyte infiltration in the dermis resolved and the number of macrophages elevated. CONCLUSION: Microwave heating and bandaging treatment can regulate the imbalance of systemic and local immunity in patients with chronic lymphedema.

Adolescent↗
PubMed1998

Identification of free deaminated sialic acid (2-keto-3-deoxy-D-glycero-D-galacto-nononic acid) in human red blood cells and its elevated expression in fetal cord red blood cells and ovarian cancer cells.

Chemical studies have shown the occurrence of the deaminated sialic acid 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN) in paired samples of blood obtained from mothers and newborns of healthy human individuals. Most of the KDN was found in red blood cells, although low levels were detected in mononuclear cells. No N-glycolylneuraminic acid was detected. Unexpectedly, nearly all of the KDN in fetal cord and matched maternal red blood cells was present as the free sugar and comparatively little occurred conjugated or as cytidine 5'-KDN phosphate. The amount of free KDN in fetal newborn red blood cells was 2.4-fold higher than in red blood cells from the mothers or from healthy nonpregnant women. Free KDN was also identified in normal human ovaries, in ovarian tumors, and in ascites cells obtained from ovarian cancer patients. Importantly, as in fetal cord red blood cells, a distinguishing feature of KDN expression in ovarian tumor cells was an elevated level of free KDN compared with normal controls. A positive correlation was found between an increase in the ratio of free KDN/N-acetylneuraminic acid in ovarian adenocarcinomas and the stage of malignancy. This was particularly evident in tumor cells isolated from the ascites fluid. The central importance of these new findings is 2-fold. First, they show that free KDN is a minor but ubiquitous sialic acid in human red blood cells and that its elevated expression in red blood cells from fetal cord blood compared with maternal red blood cells may be developmentally related to blood cell formation during embryogenesis. Second, the enhanced expression of KDN in ovarian cancer cells suggests that this sialic acid, like the alpha2,8-linked polysialic acid glycotope, may be an oncofetal antigen in these tumors and thus could be an "early warning" signal for onset of disease and/or a marker for detection of recurrence of disease. These new findings highlight the importance of elucidating the role that KDN and KDN-containing glycoconjugates may play in normal development and malignancy.

Adenocarcinoma↗
PubMed1998

The C-terminal segment is essential for maintaining the quaternary structure and enzyme activity of the nitric oxide forming nitrite reductase from Achromobacter cycloclastes.

We have constructed and expressed a series of mutated nitrite reductase (NIR) mutants based on the sequence of NIR from Achromobacter cycloclastes. Deleting a pentapeptide, an undecapeptide, or a heptadecapeptide from the C-terminus of NIR resulted in a series of C-terminal deletion mutated proteins designated as NIR-5, NIR-11, and NIR-17, respectively. A C-terminally extended mutated protein, NIR+8, was also produced, which contains an extra octapeptide attached to the C-terminus of the wild-type NIR. An SDS-PAGE system using tris-tricine buffer could retain the native NIR in its trimeric form, thus offering a convenient method to check the quaternary structure of NIR analogs. By using this system it was found that NIR-5 was maintained as trimer and retained 72% of wild-type enzyme activity. However, both NIR-11 and NIR-17 behaved as monomers in the SDS-PAGE and lost all their enzyme activity. Although NIR+8 maintained its trimeric structure it was enzymatically inactive. These results clearly indicate that the C-terminal undecapeptide is essential for maintaining the quaternary structure as well as the full enzymatic activity, as expected from the X-ray crystallography studies.

Alcaligenes↗
PubMed1998

Mouse brain potassium channel beta1 subunit mRNA: cloning and distribution during development.

The pore-forming alpha subunits of voltage-gated potassium channels in neurons and other excitable cells are expressed in association with accessory beta subunits. These subunits both promote insertion of channel complexes into surface membranes and influence their electrophysiological properties. As part of an effort to understand the regulation of voltage-gated potassium channels during development, we cloned the mouse homolog of the rat Kvbeta1 potassium channel subunit. Kvbeta1 subunits are known to associate preferentially with Shaker (Kv1)-related alpha subunits. We then used a digoxigenin-tagged cRNA probe and in situ hybridization techniques to visualize the appearance of Kvbeta1 mRNA transcripts during late embryonic and early neonatal development of the mouse brain. We detected Kvbeta1-specific labeling of cells in hippocampus, cerebral cortex, caudate putamen, colliculus, and cerebellum. In hippocampus, we observed Kvbeta1 mRNA in CA3 pyramidal neurons at the earliest time examined, embryonic day 16 (E16). Between E16 and postnatal day 7 (P7), cell labeling increased uniformly across the pyramidal neurons of Ammon's horn (CA1, CA2, and CA3). Subsequently, between P7 and P22, regional differences characteristic of mature hippocampus appeared-intense labeling of neurons in CA3 and CA1, and less in CA2. In cortex, labeling of cells in the subplate and cortical plate layers was observed at E16. During development, the intensity of this labeling increased, and labeled cells persisted into the adult stage in the deep cortical layer (VIb) formed from subplate neurons. Additional labeling of scattered solitary cells in cortical layers II-VIa emerged between P3 and P7 and was prominent in mature cortex. In caudate putamen, Kvbeta1-labeled cells were observed at P1 and were restricted to the lateral and rostral half of the caudate. During development, labeling expanded caudally and medially and eventually filled the mature caudate putamen. In colliculus, a small population of inferior colliculus cells showed labeling at P7, and additional labeling of scattered cells appeared during development. In superior colliculus, labeling was observed only in the adult deep gray layer. In cerebellum, intense labeling was observed in Purkinje cells at all stages between P1 and adult. Labeling was also seen in granule neurons in the external granule layer at early postnatal stages and in the inner granule layer beginning at P7.

Amino Acid Sequence↗
PubMed1998

Smokeless tobacco extracts activate complement in vitro: a potential pathogenic mechanism for initiating inflammation of the oral mucosa.

The use of smokeless tobacco has been linked to an increased incidence of inflammation of the buccal and gingival mucosa. However, the mechanisms by which smokeless tobacco initiates inflammation are not well understood. The complement cascade is a ubiquitous source of proinflammatory molecules and can be activated rapidly by a wide variety of agents. Therefore, the effect of smokeless tobacco on complement was investigated as a potential pathogenic mechanism for triggering inflammation of the oral mucosa. Aqueous extracts of loose leaf chewing tobacco (1S1), dry snuff (1S2), and moist snuff (1S3), added to normal human serum, depleted complement hemolytic activity in a dose-dependent manner. Experiments utilizing sera deficient in one specific complement component indicated that the smokeless tobacco-induced depletion of hemolytic activity was due largely to consumption of C3. Furthermore, assays designed to test the activity of the alternative pathway of complement clearly showed that all three extracts depleted the hemolytic activity of this pathway. Finally, all three smokeless tobacco extracts activated the alternative pathway since significantly elevated levels of the cleavage fragments iC3b and Bb were detected in extract-treated serum. High quantities of the classical pathway cleavage fragment C4d also were detected in serum treated with moist snuff (1S3). The results clearly demonstrate that smokeless tobacco extracts activate the alternative pathway and also suggest some measure of classical pathway activation. Activation of complement by smokeless tobacco may be a mechanism for initiating inflammation of the oral mucosa.

Complement Activation↗
PubMed1998

A prospective study of bone mineral density change in Taiwan.

In 1989, a cross-sectional study was carried out in Lin-Kou Township, Taiwan, to determine the distribution of bone mineral density (BMD) in the lumbar spine of Chinese people. Lumbar spine BMD was measured using dual-photon absorptiometry in 404 healthy volunteers (266 women and 138 men, aged 15 to 83 years). In 1994-1995, 318 of the same volunteers were reexamined for the present study. Except for there being fewer males and smokers present, there were no significant differences between the second survey respondents and nonrespondents. Spine BMD decreased at over 1% per year in Chinese women over age 50, which was somewhat higher than reported for caucasian women. Since there was a loss of BMD in Chinese women after their 20s, a case can be made for starting preventive activities for female adolescents. There were no differences in the mean BMD change rates among the different age groups of Chinese men. Baseline BMD, menopause, and weight change were associated with the lumbar spine BMD change rates in Chinese women. Body mass index was the only variable significantly associated with BMD change in Chinese men. The rate of BMD change was not associated with diet.

Absorptiometry, Photon↗
PubMed1998

Telomerase activity in benign and malignant human thyroid tissues.

Telomerase is a specialized ribonucleoprotein polymerase that directs the synthesis of telomerase repeats at chromosome ends. Accumulating evidence has indicated that telomerase is stringently repressed in normal human somatic tissues but reactivated in cancers and immortal cells, suggesting that activation of telomerase activity plays a role in carcinogenesis and immortalization. In this work, the status of telomerase activity during the development of human thyroid cancer was determined using telomeric repeat amplification protocol (TRAP) in 14 nodular hyperplasia, 14 adenomas, 23 papillary carcinomas and 11 follicular carcinomas. Positive telomerase activity was detected in 2 of 14 nodular hyperplasias (14%), 4 of 14 adenomas (29%), 12 of 23 papillary carcinomas (52%) and 10 of 11 follicular carcinomas (91%). The cancers that are negative for telomerase activity are mostly in early stage (stage I or II). These results suggest that telomerase reactivation plays a role during the development of thyroid cancer.

Adenocarcinoma, Follicular↗
PubMed1998

The influence of electric fields on the epileptiform bursts induced by high potassium in CA3 region of rat hippocampal slice.

The effects of pulsed direct current (dc) electric fields on the frequency of spontaneous bursting in a model epileptic focus were studied. The high potassium hippocampal slice model was used to generate spontaneous burst firing activity similar to interictal spikes in the pyramidal cell layer of CA3. Electric fields were generated from platinum subdural electrodes placed in the perfusion bath. Three hundred and seventy-eight experimental trials were performed on 10 hippocampal slices from 10 rats and the effects of field polarity, field strength and duration of stimuli on firing frequency was examined. Hippocampal slices were oriented horizontally with the CA3 layer towards the positive electrode, the average interburst interval did not correlate significantly with polarity of the delivering pulses (one-way ANOVA, p = 0.96). Average interburst interval showed a significant correlation with pulse duration of 200 and 400 msec (p = 0.030 and p = 0.004, respectively). As a function of field strength, there were significant average interval changes for fields of 33, 46, and 73 mV/mm (p = 0.024, p = 0.001 and p = 0.001, respectively). In conclusion, CA3 burst firing activity in high potassium concentration can therefore be altered by electric fields.

Action Potentials↗
PubMed1998

Development, validation, and interlaboratory comparison of an HMG-CoA reductase inhibition assay for quantitation of atorvastatin in plasma matrices.

An HMG-CoA reductase inhibition assay was developed and validated for quantitation of atorvastatin in human, dog, rat, and mouse plasma. Atorvastatin was isolated from plasma by protein precipitation. Rat-liver microsomes were used to provide the reductase enzyme. The method was validated by assaying calibration standards and quality controls in triplicate on each of the 3 days. A customized computer program was used for data calculation. Quantitation of the assay ranged from 0.36 to 16 ng/ml of atorvastatin in different plasma matrices. Assay precision and accuracy, based on the coefficient of variation and percent relative error, respectively, of quality controls were 10.4% to 14.5% and within +/- 6.25% in human; 4.89% to 10.6% (+/- 8.13%) in dog; 2.68% to 8.62% (+/- 5.00%) in rat; and 3.68% to 8.96% (+/- 5.38%) in mouse plasma. The method has been applied to pharmacokinetic studies of atorvastatin in human and toxicokinetic studies in dog, rat, and mouse after atorvastatin administration. Atorvastatin equivalent concentrations in a set of plasma samples from subjects receiving single and multiple doses of atorvastatin were determined by validated HMG-CoA reductase inhibition assays at four different laboratories. Results were compared using linear regression and concordance correlation statistical procedures. Good agreements among these data indicated that results from different laboratories with the same validated method can be used interchangeably.

Animals↗
PubMed1998

Effects of elution [correction of eution] conditions on the separation of calpastatin, mu- and m-calpain on DEAE-Sephacel chromatography.

A rapid stepwise measurement for the activities of calpastatin and mu- and m-calpains was developed by using 2-stage elution at pH 8.5 and then 7.0. The activities of calpastatin, mu-calpain and m-calpain can be rapidly assayed following the separation on DEAE-Sephacel chromatography by a 2 stage elution with 90 mM NaCl (pH 8.5), and then by 200 and 300 mM NaCl in elution buffer (pH 7.0). No significant differences in the recovery of these proteinases and inhibitor was observed between stepwise gradient and linear gradient methods.

Buffers↗
PubMed1998

High resolution computed tomography of temporal bone fracture.

BACKGROUND: High resolution computed tomography (HRCT) is highly efficient in demonstrating the anatomy of the temporal bone. This study evaluates its application to temporal bone fractures (TBF). METHODS: We collected data from 26 cases of TBF in the past two years. All cases underwent HRCT examination. The clinical information was reviewed and correlated with the imaging findings. RESULTS: Eighty-six percent of the cases had longitudinal fractures. Axial scans were the most useful in identifying the fracture line. Mastoid opacification on routine head computed tomography (CT) was also useful in indicating possible TBFs. Complications of TBF, such as ossicular chain disruption, facial nerve damage or otorhino-liquorrhea, were identified clearly using HRCT. CONCLUSIONS: To minimize or prevent the sequelae of TBF, accurate radiologic evaluation is necessary as soon as possible after injury. HRCT of the temporal bone delineates the bony and soft tissue anatomy with high accuracy and we recommend it as the diagnostic modality of choice.

Adolescent↗
PubMed1998

Endovascular embolization of arteriovenous fistulas of the external carotid artery.

BACKGROUND: External carotid arteriovenous fistulas (AVFs) are rare and most hospitals have limited experience with their management. This study was designed to evaluate the effectiveness and safety of endovascular embolization of AVFs of the external carotid artery under angiographic control. METHODS: A series of 13 patients with AVFs involving the branches of the external carotid artery, all treated with endovascular embolization, were reviewed. There were 10 males and three females ranging in age from nine to 46 years, with a mean of 27 years. The most frequent presenting symptoms were pulsatile tinnitus, followed by bruit and/or thrill, ocular problems, headache and a pulsatile mass in the neck. The middle meningeal artery was most often involved, followed by the internal maxillary artery and the occipital artery. The AVFs were caused by trauma in 10 patients and occurred spontaneously in three. N-butyl-2-cyanoacrylate was used to embolize the fistula in 11 patients and a detachable balloon was used in two. RESULTS: All the patients were cured and no significant complications were observed. No recurrence was noted after a clinical follow-up of three months to seven years (mean, 37 months). CONCLUSIONS: Endovascular embolization proved to be a safe and effective procedure. It should be the treatment of choice for repair of external carotid AVFs.

Adolescent↗
PubMed1998

Orbital invasion in nasopharyngeal carcinoma: evaluation with computed tomography and magnetic resonance imaging.

BACKGROUND: Ocular symptoms and tumor cranial nerve involvement are commonly observed in patients with nasopharyngeal carcinoma (NPC). These are primarily due to tumor invasion of the cavernous sinus and/or skull base, as direct tumor invasion of the orbit is very rare. This study was designed to assess computed tomography (CT) and magnetic resonance imaging (MRI) in documenting orbital invasion caused by NPC, with a special emphasis on the route of orbital extension. METHODS: A total of 562 patients with histopathologically prove NPC were examined using CT and/or MRI for tumor staging or post-treatment follow-up. We retrospectively reviewed CT and MRI findings to identify tumor invasion to orbital cavities and to evaluate the pathway of tumor spread. RESULTS: Eighteen patients had tumor extension into the orbital cavities. Seventeen patients had ocular complaints. Fourteen of 18 showed unilateral orbital involvement and four patients showed bilateral orbital involvement. The route from the pterygopalatine fossa and inferior orbital fissure into the orbital cavities was the most common pathway of NPC invasion (n = 13), followed by ethmoid sinus and/or sphenoid sinus into the orbits (n = 4). In one patient, the route of orbital invasion was difficult to determine due to massive tumor extension. CONCLUSION: Direct orbital invasion is rare in NPC. The pterygopalatine fossa and inferior orbital fissure are the most common routes of invasion, followed by invasion via the ethmoid and/or sphenoid sinuses. Coronal sections best show these findings on CT or MRI. Our study also shows that either CT or MRI provide essential information in documenting orbital invasion and determining the pathway of tumor spread.

Adult↗
PubMed1998

Steroid sulphatase deficiency is the major cause of extremely low oestriol production at mid-pregnancy: a urinary steroid assay for the discrimination of steroid sulphatase deficiency from other causes.

A method for determining whether a pregnant woman with an extremely low serum oestriol (ELSE) measurement of mid-trimester is carrying a fetus with steroid sulphatase deficiency or another more serious disorder is described. We undertook GC/MS analysis of steroids in random maternal urine samples and quantified oestriol, oestriol precursors (dehydroepiandrosterone (DHEA), 5-androstene-3 beta, 17 beta-diol, 16 alpha-hydroxy-dehydroepiandrosterone and 5-androstene-3 beta, 16 alpha, 17 beta-triol), pregnanediol, and five other steroids largely unaffected by pregnancy (androsterone, etiocholanolone, tetrahydrocortisol, 5 alpha-tetrahydrocortisol and tetrahydrocortisone). Thirty-two samples collected from seven normal pregnant women between the 7th and 27th week of pregnancy and 22 from individuals with ELSE were analysed. Diagnostic ratios of excreted products were developed. These included ratios of oestriol and oestriol precursors to the cumulative value for the five non-pregnancy-related steroids and ratios of oestriol and oestriol precursors to pregnanediol and to each other. Our data demonstrated high 3 beta-hydroxy-5-ene steroid excretion in all ELSE patients together with low urinary oestriol excretion, a situation only consistent with deficiency of steroid sulphatase. The normal individuals had high oestriol and low excretion of oestriol precursors. No patient in our series showed the low oestriol levels and low oestriol precursor values that would indicate a fetal adrenal abnormality as the underlying defect.

Androstenediol↗
PubMed1997

A continuous method for measuring calpain activity.

A simplified methodology for assaying the caseinolysis by calpains was developed. This methodology, including the incubation of calpain with casein and direct measurement of the absorbance at 500 nm, is based on the turbidity of the reaction mixture caused by the aggregation of hydrolysates during the reaction. Unlike the typical caseinolysis assay, this novel assay does not need to separate the substrate from hydrolysates and can be continuously monitored in visible wavelength range. The activity of calpain is expressed by the maximum reaction velocity (delta A500/min) at 25 degrees C).

Animals↗
PubMed1997

Pharmacokinetics of pirmenol enantiomers and pharmacodynamics of pirmenol racemate in patients with premature ventricular contractions.

The pharmacokinetics and pharmacodynamics of pirmenol were investigated in 12 patients with premature ventricular contractions (PVCs) after oral administration of racemic pirmenol, 100 mg and 200 mg every 12 hours. Holter monitoring was performed and serial blood samples were collected after the seventh doses. Plasma concentrations of pirmenol enantiomer were determined using a stereospecific liquid chromatographic assay. Clearance of total (-)-pirmenol was 20% higher than that of total (+)-pirmenol, and the difference in unbound clearance was 45% between enantiomers. Total pirmenol showed a smaller difference because of stereoselective protein binding, with 25% (100-mg dose) or 27% (200-mg dose) higher fraction unbound for (+)-pirmenol than for (-)-pirmenol. Distribution volume was similar for both enantiomers. Dose-dependent clearance was observed for unbound pirmenol enantiomers, as both enantiomers showed 20% lower unbound clearance at the higher dose. Antiarrhythmic effect (% reduction in PVCs from baseline) was correlated with plasma concentrations of pirmenol using a sigmoid maximum drug effect model, and patients showed a large variability in their antiarrhythmic response to plasma concentrations of pirmenol. The median value for minimum effective plasma concentration of racemic pirmenol was 1.5 micrograms/mL.

Adult↗