Biomedical subjects

H S Chang

Publications and source records attributed to H S Chang.

At least 37 records · Page 2Linked to original sources

PubMed2000

Orchestrated transcription of key pathways in Arabidopsis by the circadian clock.

Like most organisms, plants have endogenous biological clocks that coordinate internal events with the external environment. We used high-density oligonucleotide microarrays to examine gene expression in Arabidopsis and found that 6% of the more than 8000 genes on the array exhibited circadian changes in steady-state messenger RNA levels. Clusters of circadian-regulated genes were found in pathways involved in plant responses to light and other key metabolic pathways. Computational analysis of cycling genes allowed the identification of a highly conserved promoter motif that we found to be required for circadian control of gene expression. Our study presents a comprehensive view of the temporal compartmentalization of physiological pathways by the circadian clock in a eukaryote.

Arabidopsis↗

PubMed2000

The downregulation of Bcl-2 expression is necessary for theophylline-induced apoptosis of eosinophil.

Apoptosis of eosinophils is of increasingly important value in modulating allergic inflammatory airway diseases, such as asthma, and is suppressed by interleukin-5 (IL-5) in in vitro culture. In this study, we examined the effects of theophylline on survival/apoptosis, intracellular cAMP concentration, and Bcl-2 protein expression. Treatment with theophylline protected eosinophils against IL-5-mediated inhibition of apoptosis with a simultaneous suppression of survival in a dose-dependent manner. Theophylline caused an increase in the intracellular cAMP levels of IL-5-stimulated eosinophils. Enhancement of eosinophil apoptosis was consistent with an increase in DNA fragmentation in eosinophils treated with theophylline. On the other hand, the Bcl-2 protein appeared to be expressed constitutively in freshly isolated eosinophils. Bcl-2 expression was augmented by IL-5 stimulation, yet it was considerably inhibited by theophylline treatment. These data suggest that intracellular cAMP levels and Bcl-2 expression are involved in the suppression of eosinophil survival by theophylline.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗

PubMed2000

Role of cAMP-dependent pathway in eosinophil apoptosis and survival.

The survival and apoptosis of eosinophils is of pivotal importance for controlling allergic diseases such as asthma and rhinitis. In this study we have investigated the role for cAMP in regulating eosinophil survival and apoptosis in the absence of eosinophil-active cytokines. The treatment with dibutyryl cyclic AMP (dbcAMP) increased eosinophil survival with a concomitant decrease of apoptosis in a dose-dependent manner. The pretreatment with a protein kinase A (PKA) inhibitor blocked the effects of dbcAMP on survival and apoptosis of eosinophils. The catalytic subunit of PKA was translocated to nucleus in parallel with a robust increase of intracellular cAMP levels upon exposure to dbcAMP but not IL-5, suggesting the separation of PKA activation from the IL-5-induced suppression of eosinophil apoptosis. When eosinophils were treated with pharmacological inhibitors of protein kinases prior to exposure to dbcAMP or IL-5, only the mitogen-activating protein kinase (MAPK) inhibitor, PD098059, was partly able to block dbcAMP-induced augmentation of eosinophil viability, whereas both Janus kinase 2 and MAPK inhibitors effectively interrupted the IL-5-induced prolongation of eosinophil survival. The effects of dbcAMP and these protein kinase inhibitors on eosinophil apoptosis were confirmed by morphologic analysis. We propose that a cAMP-dependent pathway may constitute an important component for regulating eosinophil survival/apoptosisand that cAMP may inhibit eosinophil apoptosis through the activation of PKA and of subsequent MAPK in part.

Apoptosis↗

PubMed2000

Multiple oscillators provide metastability in rhythm generation.

Biological rhythms such as cardiac and circadian rhythms arise from activity of multiple oscillators with dispersed intrinsic frequencies. It has been proposed that a stable population rhythm, fundamental to normal physiological processes, can be achieved in these systems by synchronization, through mutual entrainment, of individual oscillators. Mutual entrainment, however, is unlikely to be the mechanism underlying the generation of a stable rhythm in a population of multiple weakly coupled or uncoupled oscillators. We have recently identified such a population that is involved in the sympathetic regulation of vascular tone in a thermoregulatory circulation. In this paper, we investigate the stability of the output rhythm of these sympathetic oscillators by subjecting the system to a periodic driving force (the lung inflation cycle-related activity). We show that a population rhythm coupled to the drive can remain stable over a much wider driving frequency range compared with that of any one of its constituent oscillators. This population rhythmicity still exists despite the fact that the dominant frequencies of individual oscillators are not necessarily 1:1 frequency-locked to the drive. We provide evidence to show that this population metastability is achieved through linear and nonlinear dynamic interactions between the driving force and single sympathetic oscillators. Our study suggests that the generation of a stable population rhythm can exist even in the absence of mutual entrainment of its constituents, and this allows the population to generate a stable and flexible patterned response.

Activity Cycles↗

PubMed2000

Identification of genes expressed in the epithelium of porcine oviduct containing early embryos at various stages of development.

As a first step toward elucidation of the action of factors secreted by the epithelium of oviduct, differential display reverse transcription-polymerase chain reaction (DDRT-PCR) was used in this study to identify transcripts of such oviductal factors in gilts carrying various stages of early embryo development post hormone-induced ovulation. A total of 13 differentially expressed transcripts were identified between 50 and 120 hr post-hCG injection (between 1- and 8-cell embryonic stages). Twelve of these transcripts were found to be initially expressed at 96 hr post-hCG injection (at 4-cell embryonic stage) and beyond. Three of such genes were shown by sequence analysis to be the porcine transforming growth factor-alpha, the porcine transforming growth factor-beta-binding protein II and a porcine astral natriuretic factor receptor-like transcript. Only one differentially expressed gene was detected between 50-60 and 85 hr post-hCG injection, and this gene turned out to be the porcine follicle-stimulating hormone receptor. The remaining eight transcripts detected by DDRT-PCR were novel. Moreover, most of these newly expressed genes were found to be turned on at a time coincidental with that of the 4-cell block of porcine embryos cultured in vitro. Our results demonstrate that DDRT-PCR is a feasible approach for rapid identification of genes that are differentially expressed in oviductal epithelium. Some of the genes thus identified may be important for unhindered development of embryos in the oviduct.

Animals↗

PubMed2000

Lumbar herniated disc presenting with cauda equina syndrome. Long-term follow-up of four cases.

BACKGROUND: Cauda equina syndrome is a relatively rare presenting symptom of lumbar herniated discs. Early operative decompression is advocated, but it may not always restore the bladder function. In such cases, knowing the long-term outcome of bladder or sphincter disturbances is quite useful in planning the management of these patients. METHODS: Hospital records of patients operated on for lumbar herniated discs were reviewed. Charts and imaging studies of those patients who presented with classic cauda equina syndrome were analyzed. RESULTS: There were 4 patients (2.8%) of 144 consecutive surgical series of lumbar disc herniation, whose presenting symptom was classic cauda equina syndrome. Postoperatively, the patients had been followed at the clinic for a mean period of 6.4 years. Certain characteristic findings were noted on patients' neurological and radiological examinations. Although the recovery process of bladder function was very slow, taking months to years, all four patients achieved almost normal voiding with no major impairment of daily activities. CONCLUSIONS: Even if short-term recovery of bladder function is poor after lumbar disc surgery for cauda equina syndrome, the long-term outcome is not necessarily so. We should follow up on these patients with such measures as intermittent self-catheterization and drug therapy, expecting slow but steady recovery of bladder and sphincter function.

Adult↗

PubMed2000

Multicenter surveillance study for nosocomial infections in major hospitals in Korea. Nosocomial Infection Surveillance Committee of the Korean Society for Nosocomial Infection Control.

BACKGROUND: The goals of a surveillance for nosocomial infections (NIs) are to observe the magnitude and characteristics of NIs and to plan and evaluate policies and guidelines of infection control. This study was designed to determine the rate and distribution of NIs and their causative pathogens in Korean hospitals. METHODS: Prospective surveillance was performed at 15 acute care hospitals with more than 500 beds during a 3-month period from June to August 1996. The case-finding methods were laboratory-based surveillance for patients in the general wards and a direct review of medical charts done regularly for all the patients in the intensive care units. RESULTS: A total of 3162 NIs were found among 85,547 discharged patients, with an overall nosocomial infection rate of 3.70 per 100 patients discharged. Urinary tract infections constituted 30.3% of all NIs. Other infections were pneumonias, 17.2%, surgical site infections, 15.5%, and primary bloodstream infections, 14.5%. The infection rate was the highest in neurosurgery (14.21), followed by neurology (8. 62) and ontology services (6.70). The infection rate in intensive care units was higher than it was in the general wards (10.74 vs 2. 57, P =.001). The commonly isolated organisms were Staphylococcus aureus (17.2%), Pseudomonas aeruginosa (13.8%), and Escherichia coli (12.3%). CONCLUSIONS: This first multicenter surveillance study provided extensive information on the current status and trends of NIs in major hospitals in Korea. The results may contribute to the evaluation of infection control programs and the development of effective strategies in these hospitals.

Contact Tracing↗

PubMed2000

Physiological, pharmacological and neurohormonal assessment of autonomic function in progressive supranuclear palsy.

The clinical features of progressive supranuclear palsy (PSP) overlap with other parkinsonian syndromes, including multiple system atrophy (MSA). Autonomic dysfunction is a characteristic of MSA, but has also been described in PSP. We therefore report results from a series of physiological studies of cardiovascular autonomic function in 35 PSP and 20 MSA subjects, and 26 age-matched healthy control subjects. The response to growth hormone-clonidine testing, a neuropharmacological assessment of central adrenoceptor function, was also assessed in 14 PSP and 10 MSA subjects, and compared with 10 controls. None was on medication which may have affected the results. Orthostatic hypotension did not occur in PSP subjects or controls, unlike MSA subjects. Overall there was no evidence of sympathetic vasoconstrictor failure in PSP subjects, unlike MSA subjects, although the pressor response to mental arithmetic was reduced. Cardiac parasympathetic function was affected in only a minority (three of 35) of PSP subjects and was abnormal in MSA subjects. After clonidine administration, growth hormone rose in PSP subjects (median increase 4.3; interquartile range 1.8-7.8 mU/l) and controls, unlike MSA subjects (0.9; 0.3-2.4 mU/l; P < 0.005, Mann-Whitney U-test). In conclusion, in PSP subjects, responses to both physiological and pharmacological tests provided evidence against widespread autonomic dysfunction; this differed markedly from MSA subjects. Thus, cardiovascular autonomic dysfunction should be an exclusionary feature in the diagnosis of PSP.

Adrenergic alpha-Agonists↗

PubMed2000

Adverse effects of limited hypotensive anesthesia on the outcome of patients with subarachnoid hemorrhage.

OBJECT: This study was aimed at clarifying the effect of intraoperative hypotensive anesthesia on the outcome of early surgery in patients with subarachnoid hemorrhage (SAH) caused by saccular cerebral aneurysms. Other factors were also screened for possible effects on the outcome. METHODS: Hospital charts in 84 consecutive patients with SAH who underwent aneurysm clipping by Day 4 were examined. Possible factors affecting the outcome were analyzed using multiple logistic regression with the dichotomous Glasgow Outcome Scale score as the outcome variable. The relationship between the intraoperative hypotension and the occurrence and severity of vasospasm was studied using both single- and multivariate analyses. CONCLUSIONS: Intraoperative hypotension had a significantly adverse effect on the outcome of SAH. Hypotension was also related to more frequent and severe manifestations of vasospasm. A long-lasting effect of brain retraction is possibly the cause of this phenomenon. The data contained in this study preclude the use of intraoperative hypotension even in a limited form.

Adult↗

PubMed1999

Potential biomarker of coal workers' pneumoconiosis.

It is well known that various cytokines and growth factors secreted from macrophages/monocytes play the key role in the pathogenesis of pneumoconiosis. These can act as biosensors for the prediction of pneumoconiosis. To evaluate which cytokines can be used as sensitive biomarkers in pneumoconiosis, we measured tumor necrosis factor-alpha (TNF-alpha), interleukin-8 (IL-8) and platelet-derived growth factor-AA (PDGF-AA) in supernatant of monocytes with or without coal dust (5 mg/ml) and serum in 42 coal miners with pneumoconiosis and ten healthy control. The coal-stimulated release of TNF-alpha and IL-8 from blood monocytes was significant increased in pneumoconiosis patients compared with controls. The level of TNF-alpha and IL-8 in blood serum was higher in subjects with pneumoconiosis than in controls.

Biomarkers↗

PubMed1999

Silica-induced apoptosis in vitro and in vivo.

Silica exposure results in an initially acute inflammatory response followed by chronic fibrotic change. The mechanism for the maintenance of silica-induced inflammation has not been understood yet. In silica-induced acute inflammation and chronic fibrosis, various mediators such as reactive oxygen species, cytokines and growth factors are released. And these substances are suggested to have the regulatory role for the inflammation and fibrosis by possessing the potential to influence apoptosis. To demonstrate the apoptosis as an underlying mechanism for the development of silicosis, in vitro and in vivo models were designed. In in vitro study, we evaluated that apoptotic cell fraction in silica (10, 50 microg/cm2)-treated A549 cells was significantly increased in comparison with control by FACS (fluorescein activated cell sorter). Also genomic DNA from silica (10, 50 microg/cm2)-treated A549 showed DNA ladder formation while control and 1 microg/cm2 groups didn't. In in vivo study, total cell numbers and apoptotic cell numbers of BAL (bronchoalveolar lavage) fluid from silica (10, 20, 40 mg/kg)-instilled rats were significantly higher than control group from 1 week. From these results, we concluded acute and chronic presence of apoptosis may contributes to silica-induced acute inflammation and chronic fibrosis.

Animals↗

PubMed1999

Sympathetic neuronal oscillators are capable of dynamic synchronization.

In this paper we show that the discharges of sympathetic neurons innervating an identified peripheral target are driven by multiple oscillators that undergo dynamic synchronization when an entraining force, central respiratory drive (CRD), is increased. Activity was recorded from postganglionic sympathetic neurons (PGNs) innervating the caudal ventral artery of the rat tail: (1) at the population level from the ventral collector nerve (VCN); and (2) from pairs of single PGNs recorded simultaneously using a focal recording technique. Autospectral analysis of VCN activity revealed a more prominent rhythmical component in the presence of CRD than in its absence, suggesting that (1) multiple oscillators drive the discharges of PGNs and (2) these oscillators can be entrained and therefore synchronized by CRD. This interpretation was supported by analysis of the firing behavior of PGN pairs. Autocorrelation and cross-correlation analysis showed that pairs were not synchronized in the absence of CRD but showed significant synchronization when CRD was enhanced. Time-evolving spectral analysis and raster plots demonstrated that the temporal stability of PGN-to-PGN and CRD-to-PGN interactions at a given level of CRD were also dynamic in nature, with stable constant phase relationships predominating as CRD was increased. This is the first reported example of dynamic synchronization in populations of single postganglionic sympathetic neurons, and we suggest that, as in sensory processing and motor control, temporal pattern coding may also be an important feature of neuronal discharges in sympathetic pathways.

Animals↗

PubMed1999

Cysteine carboxyl O-methylation of human placental 23 kDa protein.

C-Terminal carboxyl methylation of a human placental 23 kDa protein catalyzed by membrane-associated methyltransferase has been investigated. The 23 kDa protein substrate methylated was partially purified by DEAE-Sephacel, hydroxyapatite and Sephadex G-100 gel filtration chromatographies. The substrate protein was eluted on Sephadex G-100 gel filtration chromatography as a protein of about 29 kDa. In the absence of Mg2+, the methylation was stimulated by guanine nucleotides (GTP, GDP and GTPgammaS), but in the presence of Mg2+, only GTPgammaS stimulated the methylation which was similar to the effect on the G25K/rhoGDI complex. AFC, an inhibitor of C-terminal carboxyl methylation, inhibited the methylation of human placental 23 kDa protein. These results suggests that the substrate is a small G protein different from the G25K and is methylated on C-terminal isoprenylated cysteine residue. This was also confirmed by vapor phase analysis. The methylated substrate protein was redistributed to membrane after in vitro methylation, suggesting that the methylation of this protein is important for the redistribution of the 23 kDa small G protein for its putative role in intracellular signaling.

Cysteine↗

PubMed1999

Thoracic disc herniation mimicking acute lumbar disc disease.

STUDY DESIGN: Case report of a 49-year-old woman with a lower thoracic disc herniation mimicking acute lumbosacral radiculopathy. OBJECTIVE: To describe an unusual case of thoracic disc herniation mimicking acute lumbar disc disease. SUMMARY OF BACKGROUND DATA: Symptomatic thoracic disc herniation is rare and its clinical manifestations differ widely from those of cervical and lumbar disc herniations. Midline back pain and signs of spinal cord compression progressing over months or years are the predominant clinical features. Acute and subacute thoracic disc herniation occurs in less than 10% of patients, and isolated root pain is unusual. METHODS: A 49-year-old woman had acute low back pain radiation into the left buttock and the lateral aspect of the left leg and left foot. Magnetic resonance imaging study showed a bulging disc and posterior osteophytes at T11-T12. RESULTS: Surgical removal of the herniated disc and osteophytes rapidly relieved her symptoms and neurologic deficits. A follow-up neurologic examination 3 years later showed normal motor and sensory functions, although low back soreness was noted occasionally. CONCLUSION: A case of thoracic disc herniation mimicking an acute lumbosacral radiculopathy is presented. Compression of the lumbosacral spinal nerve roots at the lower thoracic level after exit from the lumbar enlargement may be the mechanism for this unusual presentation.

Acute Disease↗

PubMed1999

Current perception threshold testing in Fabry's disease.

We investigated 16 patients with Fabry's disease (eight hemizygous men and eight heterozygous women) in one family. We used constant current perception threshold (CPT) testing, which evaluated three major sensory nerve fiber populations, to assess subjective complaints of pain and paresthesias. We also examined clinical and biochemical features and compared the values of CPTs and nerve conduction studies (NCS) in detecting the sensory neuropathy. Our results showed that CPT testing at low frequencies (5 and 250 Hz) was significantly more sensitive than at a higher frequency (2 kHz) and NCS in detecting sensory neuropathy in patients with Fabry's disease. However, there was no correlation between CPT testing and clinical symptom scores, duration of disease, creatinine clearance (Ccr) values or alpha-galactosidase A (AGA) activities in either hemizygous or heterozygous patients. Hemizygous patients clinically demonstrated more severe symptom scores, poorer renal function, and higher prevalence of hypohidrosis and corpora angiokeratomas than did heterozygous patients, which indicates that detailed clinical examinations can differentiate the clinical status of hemizygous men from heterozygous women. There were no associations between the biochemical levels of serum AGA activity and renal function (Ccr values) or the symptom scores (grading of acroparesthesia), indicating that biochemical parameters do not predict clinical severity.

Adolescent↗

PubMed1999

Interleukin (IL)-5 downregulates tumor necrosis factor (TNF)-induced eotaxin messenger RNA (mRNA) expression in eosinophils. Induction of eotaxin mRNA by TNF and IL-5 in eosinophils.

An eotaxin is a chemoattractant specific for eosinophils that are known to play a role in helminth infection and allergic responses. Although several cellular sources have been reported to produce eotaxin, it would be interesting to know whether eosinophils are able to produce their own eotaxin and participate in recruitment of themselves in response to inflammation. To this end, a cloned eotaxin complementary DNA was transcribed in vitro to use as a probe for detecting eotaxin messenger RNA (mRNA), and eotaxin protein levels were determined by enzyme-linked immunosorbent assay. Eotaxin mRNA was, as analyzed by in situ hybridization, rarely detectable in unstimulated eosinophils, but was strongly induced in eosinophils when stimulated with tumor necrosis factor (TNF). Interleukin (IL)-5, which is known to be a major factor of eosinophil survival in vivo and in vitro, was also able to induce a modest level of eotaxin mRNA but inhibited TNF-induced eotaxin mRNA expression in a dose-response manner. Dexamethasone inhibited TNF-induced eotaxin mRNA expression. This result was consistent with that from reverse transcription/polymerase chain reaction followed by Southern blot analysis. Unlike the little expression of eotaxin mRNA in the absence of stimuli, the measurement of eotaxin protein revealed that a considerable amount of eotaxin protein was constitutively produced in unstimulated eosinophils. Its expression was upregulated by TNF and IL-5 as well. However, the inhibitory effect of IL-5 on TNF-mediated eotaxin protein production was not as pronounced as that on eotaxin mRNA induction. Collectively, these data reflect the complex physiology of eosinophils in the expression of eotaxin gene upon the exposure to their survival and/or death factors.

Chemokine CCL11↗

PubMed1999

Aplastic anemia in a petrochemical factory worker.

A petrochemical worker with aplastic anemia was referred to our hospital. He worked in a petroleum resin-producing factory and had been exposed to low-level benzene while packaging the powder resin and pouring lime into a deactivation tank. According to the yearly environmental survey of the working area, the airborne benzene level was approximately 0.28 ppm. Exposure to benzene, a common chemical used widely in industry, may progressively lead to pancytopenia, aplastic anemia, and leukemia. The hematotoxicity of benzene is related to the amount and duration of exposure. Most risk predictions for benzene exposures have been based on rubber workers who were exposed to high concentrations. In the petroleum industry, the concentration of benzene is relatively low, and there are disputes over the toxicity of low-level benzene because of a lack of evidence. In this paper we report the case of aplastic anemia induced by low-level benzene exposure.

Anemia, Aplastic↗

PubMed1999

Relation between erythrocyte reduced glutathione and glutamate concentrations in Korean Jindo dogs with erythrocytes possessing hereditary high activity of Na-K-ATPase and a high concentration of potassium.

The concentrations of sodium, potassium, reduced glutathione (GSH) and free amino acids and Na-K-ATPase activity in erythrocytes were examined in 35 purebred Jindo dogs in Korea. The incidence of Jindo dogs with a high potassium concentration and high activity of Na-K-ATPase in erythrocytes (HK phenotype) was 25.7%. The erythrocyte GSH concentration in HK Jindo dogs varied widely, from 2.45 to 12.38 mmol/l of RBCs, and was positively correlated with the erythrocyte glutamate concentration. These results indicate that HK Jindo dogs have normal to very high levels of erythrocyte GSH, which might result from the varying quantity of Na-dependent glutamate influx in the erythrocytes.

Animals↗