Biomedical subjects

S H Lee

Publications and source records attributed to S H Lee.

At least 19 recordsLinked to original sources

PubMed2000

Selenite negatively regulates caspase-3 through a redox mechanism.

Selenium, an essential biological trace element, exerts its modulatory effects in a variety of cellular events including cell survival and death. In our study we observed that selenite protects HEK293 cells from cell death induced by ultraviolet B radiation (UVB). Exposure of HEK293 cells to UVB radiation resulted in the activation of caspase-3-like protease activity, and pretreatment of the cells with z-DEVD-fmk (N-benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone), a caspase-3 inhibitor, prevented UVB-induced cell death. Interestingly, enzymatic activity of caspase-3-like protease in cell lysates of UVB-exposed cells was repressed in vitro by the presence of selenite. Selenite also inhibited the in vitro activity of purified recombinant caspase-3 in cleaving Ac-DEVD-pNA (N-acetyl-Asp-Glu-Asp-p-nitroanilide) or ICAD(L) (inhibitor of a caspase-activated deoxyribonuclease) and in the induction of DNA fragmentation. The inhibitory action of selenite on a recombinant active caspase-3 could be reversed by sulfhydryl reducing agents, such as dithiothreitol and beta-mercaptoethanol. Furthermore, pretreatment of cells with selenite suppressed the stimulation of the caspase-3-like protease activity in UVB-exposed cells, whereas dithiothreitol and beta-mercaptoethanol reversed this suppression of the enzymatic activity. Taken together, our data suggest that selenite inhibits caspase-3-like protease activity through a redox mechanism and that inhibition of caspase-3-like protease activity may be the mechanism by which selenite exerts its protective effect against UVB-induced cell death.

Caspase 3↗

PubMed2000

Stretch-activated and background non-selective cation channels in rat atrial myocytes.

1. Stretch-activated channels (SACs) were studied in isolated rat atrial myocytes using the whole-cell and single-channel patch clamp techniques. Longitudinal stretch was applied by using two patch electrodes. 2. In current clamp configuration, mechanical stretch of 20 % of resting cell length depolarised the resting membrane potential (RMP) from -63.6 +/- 0.58 mV (n = 19) to -54.6 +/- 2.4 mV (n = 13) and prolonged the action potential duration (APD) by 32.2 +/- 8.8 ms (n = 7). Depolarisation, if strong enough, triggered spontaneous APs. In the voltage clamp configuration, stretch increased membrane conductance in a progressive manner. The current-voltage (I-V ) relationship of the stretch-activated current (ISAC) was linear and reversed at -6.1 +/- 3.7 mV (n = 7). 3. The inward component of ISAC was abolished by the replacement of Na+ with NMDG+, but ISAC was hardly altered by the Cl- channel blocker DIDS or removal of external Cl-. The permeability ratio for various cations (PCs:PNa:PLi = 1.05:1:0.98) indicated that the SAC current was a non-selective cation current (ISAC,NC). The background current was also found to be non-selective to cations (INSC,b); the permeability ratio (PCs:PNa:PLi = 1.49:1:0.70) was different from that of ISAC,NC. 4. Gadolinium (Gd3+) acted on INSC,b and ISAC,NC differently. Gd3+ inhibited INSC,b in a concentration-dependent manner with an IC50 value of 46.2 +/- 0.8 microM (n = 5). Consistent with this effect, Gd3+ hyperpolarised the resting membrane potential (-71.1 +/- 0.26 mV, n = 9). In the presence of Gd3+ (0.1 mM), stretch still induced ISAC,NC and diastolic depolarisation. 5. Single-channel activities were recorded in isotonic Na+ and Cs+ solutions using the inside-out configuration. In NMDG+ solution, outward currents were abolished. Gd3+ (100 microM) strongly inhibited channel opening both from the inside and outside. In the presence of Gd3+ (100 microM) in the pipette solution, an increase in pipette pressure induced an increase in channel opening (21.27 +/- 0.24 pS; n = 7), which was distinct from background activity. 6. We concluded from the above results that longitudinal stret in rat atrial myocytes induces the activation of non-selective cation channels that can be distinguished from background channels by their different electrophysiology and pharmacology.

Action Potentials↗

PubMed2000

Cloning and characterization of cDNA encoding zebrafish Danio rerio NM23-B gene.

A full-length zebrafish NM23-B cDNA was cloned and sequenced. The zebrafish NM23-B cDNA consists of 624bp with an open reading frame of 153 amino acids. NM23-B mRNA of approximately 0.7kb is present in adult zebrafish tissues. Zebrafish NM23-B his-tagged protein (17kDa) was produced in E. coli and characterized by binding and UV-cross-linking to a single-stranded telomeric repeat (TTAGGG)(6). This is the first report to show that fish have a NM23-H2 homologue that is similar to that in humans.

Amino Acid Sequence↗

PubMed2000

Early expression of angiogenesis factors in acute myocardial ischemia and infarction.

BACKGROUND: When the myocardium is deprived of blood, a process of ischemia, infarction, and myocardial remodeling is initiated. Hypoxia-inducible factor 1 (HIF-1) is a transcriptional activator of vascular endothelial growth factor (VEGF) and is critical for initiating early cellular responses to hypoxia. We investigated the temporal and spatial patterns of expression of the alpha subunit of HIF-1 (HIF-1alpha) and VEGF in specimens of human heart tissue to elucidate the early molecular responses to myocardial hypoxia. METHODS: Ventricular-biopsy specimens from 37 patients undergoing coronary bypass surgery were collected. The specimens were examined by microscopy for evidence of ischemia, evolving infarction, or a normal histologic appearance. The specimens were also analyzed with the reverse-transcriptase polymerase chain reaction for HIF-1alpha and VEGF messenger RNA (mRNA) expression and by immunohistochemical analysis for the location of the HIF-1alpha and VEGF proteins. RESULTS: HIF-1alpha mRNA was detected in myocardial specimens with pathological evidence of acute ischemia (onset, <48 hours before surgery) or early infarction (onset, <24 hours before surgery). In contrast, VEGF transcripts were seen in specimens with evidence of acute ischemia or evolving infarction (onset, 24 to 120 hours before surgery). Patients with normal ventricles or evidence of infarction in the distant past had no detectable levels of either VEGF mRNA or HIF-1alpha mRNA. HIF-1alpha immunoreactivity was detected in the nuclei of myocytes and endothelial cells, whereas VEGF immunoreactivity was found in the cytoplasm of endothelial cells lining capillaries and arterioles. CONCLUSIONS: An increase in the level of HIF-1alpha is an early response to myocardial ischemia or infarction. This response defines, at a molecular level, one of the first adaptations of human myocardium to a deprivation of blood. HIF-1alpha is a useful temporal marker of acutely jeopardized myocardium.

Acute Disease↗

PubMed2000

Kainic acid-induced seizures cause neuronal death in infant rats pretreated with lipopolysaccharide.

A major controversy in human epilepsy is whether severe seizures in infants or young children cause brain damage and subsequent epilepsy. Kainic acid (KA) produces severe seizures in infant rats, but hippocampal neuronal death and mossy fibre sprouting have not been previously demonstrated. There are similarities between lipopolysaccharide (LPS) pretreatment and KA-induced seizures in rats and the febrile convulsion of young children, in that both processes are associated with an immune stimulus and seizures. Infant rats, co-treated with LPS and KA, showed hippocampal neuronal death and mossy fibre sprouting. Taken together, our results suggest that severe febrile convulsion of young children may cause hippocampal damage and synaptic reorganization.

Animals↗

PubMed2000

Production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by high-cell-density cultivation of Aeromonas hydrophila.

The newly screened Aeromonas hydrophila produces copolymer consisting of 3-hydroxybutyrate (3HB) and 3-hydroxyhexanoate (3HHx). The characteristics of cell growth and polymer accumulation were examined using various carbon sources. P(3HB-co-3HHx) was produced from lauric acid and oleic acid only. P(3HB-co-3HHx) content can be increased by limitation of phosphorus. A maximal P(3HB-co-3HHx) content of 28.8 wt% could be obtained in flask culture. By applying the optimally designed nutrient feeding strategy, cell dry weight, P(3HB-co-3HHx) content, and 3HHx fraction obtained over the course of 43 h were 95.7 g/L, 45.2 wt%, and 17 mol%, respectively, resulting in a productivity of 1.01 g polyhydroxyalkanoate (PHA)/L. h.

3-Hydroxybutyric Acid↗

PubMed2000

Effect of verapamil on long-term tachycardia-induced atrial electrical remodeling.

BACKGROUND: The effect of verapamil on long-term tachycardia-induced atrial electrical remodeling has not been reported. METHODS AND RESULTS: Forty-eight dogs were randomly divided into verapamil and control groups. The dogs in the verapamil group received verapamil 120 mg every day, those in the control group did not receive verapamil. Atrial effective refractory period (AERP), inducibility of atrial fibrillation (AF), and duration of AF were assessed before and after complete atrioventricular junction ablation with 1-day, 1-week, or 6-week rapid atrial pacing (780 bpm). AERP shortening, AERP dispersion, AERP maladaptation, and inducibility of AF after 1-day pacing was significantly attenuated by verapamil. However, verapamil did not have any significant effect on these parameters in the dogs with 1-week or 6-week pacing. Verapamil did not have any significant effect on the conduction velocity in the dogs with 1-day, 1-week, or 6-week pacing. Before rapid atrial pacing, verapamil significantly prolonged the duration of AF. In the dogs with 1-day pacing, the duration of AF measured immediately after termination of pacing was similar between the control and verapamil groups. However, in the dogs with 1-week or 6-week pacing, the duration of AF after pacing was significantly longer in the verapamil group. CONCLUSIONS: Verapamil cannot prevent long-term (1 and 6 weeks, respectively) tachycardia-induced changes of atrial electrophysiological properties. Furthermore, verapamil increases the duration of AF in the dogs either before or after long-term rapid atrial pacing.

Adaptation, Physiological↗

PubMed2000

Requirement of Rbp9 in the maintenance of Drosophila germline sexual identity.

Drosophila germline sex determination is controlled by a group of genes expressed at early stages of oogenesis (ovo, otu, bam, and Sxl, etc.). Mutations in these genes cause not only sex transformation of female germ cells, but also ovarian tumors. Although mutations at the Rbp9 locus also cause an ovarian tumor phenotype, Rbp9 has been shown to function during later developmental stages than do other ovarian tumor-causing genes. To test whether Rbp9 is also required for germline sex determination, we examined the sex transformation process of female germ cells in Rbp9 mutant flies. The detection of Sxl male transcripts and other male germline markers in Rbp9 mutant ovaries revealed that the Rbp9 mutation caused a partial germline sex transformation. Therefore, sex determination signals that persist throughout oogenesis appear to be required for proper maintenance of germline sexual identity.

Animals↗

PubMed2000

A distinct tumor suppressor gene locus on chromosome 15q21.1 in sporadic form of colorectal cancer.

The SM1311 family is an Ashkenazi family with dominantly inherited predisposition to colorectal adenomas and carcinomas and has a high-penetrance locus in chromosome 15q, with a multipoint logarithm of the odds score of 3.06 at marker D15S118. In the present study, we performed a high-density loss of heterozygosity study with 13 polymorphic microsatellite markers, including D15S118, spanning 15q15.3-q22.1, on 70 cases of the sporadic form of colorectal tumors. Our deletion mapping data showed a locus at D15S968 in chromosomal sub-band 15q21.1 may harbor a tumor suppressor gene in an area <0.521 Mb in physical map distance defined by markers D15S514 and D15S222. THBS1, 0.185 Mb proximal to D15S968, is the nearest known gene to this specific narrow loss of heterozygosity region. Thus, we speculate that THBS1 might be the most probable candidate gene involved in colorectal cancer carcinogenesis.

Adenocarcinoma↗

PubMed2000

In vitro blastocyst formation of human oocytes obtained from unstimulated and stimulated cycles after vitrification at various maturational stages.

OBJECTIVE: To evaluate the developmental competence and chromosomal normality of oocytes vitrified at various times after maturation culture. DESIGN: In vitro model study. SETTING: A university-affiliated hospital. PATIENT(S): Unstimulated women who underwent cesarean section or oophorectomy and infertile women who underwent a long protocol of GnRH stimulation. INTERVENTION(S): Retrieved oocytes were vitrified at 0 or 48 hours after culture in unstimulated cycles and at 0, 8-15, or 24-28 hours after culture in stimulated cycles. MAIN OUTCOME MEASURE(S): Postthaw morphologic normality, maturation, fertilization, cleavage, blastocyst formation, and chromosome number. RESULT(S): In the 53 oocytes that were obtained from unstimulated cycles, no statistically significant differences were found in rates of morphologic normality (range, 56%-63%) or fertilization (range, 31%-37%) according to the time of vitrification. In the 50 oocytes that were obtained from stimulated cycles, more of those that were vitrified at 24-28 hours were morphologically normal than those that were vitrified at 0 or 8-15 hours. Regardless of these differences, high cleavage rates (83%-100%) were obtained that did not differ significantly among the treatment groups. In both cycles, 20%-43% of cleaved oocytes developed to the blastocyst stage by 6 days after IVF. All the karyotyped blastocysts, three from unstimulated cycles and four from stimulated cycles, had a normal number of chromosomes. CONCLUSION(S): Vitrified and thawed oocytes from unstimulated or stimulated cycles developed to the blastocyst stage, regardless of when vitrification occurred; the number of chromosomes in the blastocysts was normal.

Adult↗

PubMed2000

Phenolic compounds from the leaves of Cornus controversa.

Two novel phenolic compounds from the leaves of Cornus controversa (Cornaceae) were characterized as (-)-2,3-digalloyl-4-(E)-caffeoyl-L-threonic acid and (-)-2-galloyl-4-(E)-caffeoyl-L-threonic acid, using spectroscopic methods.

Phenols↗

PubMed2000

Effects of soybean diet on the beta cells in the streptozotocin treated rats for induction of diabetes.

Certain dietary components have been reported to potentially suppress the initiation of experimental insulin-dependent diabetes mellitus (IDDM) in animal models. In the present study, we showed that dietary soybean prevents induction of experimental hyperglycemia by retaining beta cell activity. In rats fed raw soybean, expression of insulin mRNA in pancreatic beta cells was significantly increased compared to those fed with normal diet. In those rats and upon injection of streptozotocin, only few beta cells underwent cell death, most of them demonstrating active viability with enhanced mRNA expression and insulin content. This is consistent with the fact that blood glucose level was normalized (72.51 +/- 1.54 mg/dl) after a transitory hyperglycemic state (> 300 mg/dl). It implies the dietary soybean can prevent beta cell injury by streptozotocin. Moreover, a prolonged hyperglycemia was not observed in rats fed raw soybean even when this was substituted by the normal diet after streptozotocin injection. In contrast, in streptozotocin-treated rats fed normal diet, most beta cells were destroyed and severe hyperglycemia was observed. Although the protective effect was not recorded in the rats fed with heated soybean, some beta cells were found to retain their cell organelles for insulin secretion indicating that some heat-stable components of soybean might prevent the cytotoxic insult. Therefore, we suggest that dietary soybean protected the streptozotocin-induced beta cell damage and restrained the development of hyperglycemia in rats.

Animals↗

PubMed2000

Development of neuron-neuron synapses.

Our understanding of neuronal synapse development has advanced in recent years. The development of glycinergic synapses appears to depend on gephyrin and glycine receptor activity. Molecular characterization of the structure and development of glutamatergic synapses is in progress, but the underlying mechanisms remain unclear. Activity-dependent mechanisms and specific molecules that regulate the morphological development of dendritic spines have recently been identified.

Animals↗

PubMed2000

Novel approaches to monitor bacterial gene expression in infected tissue and host.

Elucidating the complex and dynamic host-microbe interactions during infection requires, among other things, detailed knowledge of microbial gene expression in vivo. Recently, advances in fluorescence and bioluminescence detection techniques, as well as recombinase-based in vivo expression technology, have rendered monitoring virulence gene expression in vivo a feasible task. These techniques have been adapted by several laboratories to study the spatial and temporal patterns of virulence gene expression by organisms such as Salmonella typhimurium, Listeria monocytogenes, Yersinia entercolitica and Vibrio cholerae during infection of tissue culture or animal models of infection.

Animals↗

PubMed2000

Establishment of a phagocytic cell line from Bombina orientalis.

Continuous serum-free culture of Bok-2 cells was generated from primary culture of the tail bud stage embryos of the toad, Bombina orientalis. Bok-2 cells can be maintained in modified L-15 serum-free medium prepared by mixing L-15 medium, lactalbumin enzymatic hydrolysate, sucrose and sodium bicarbonate. Bok-2 cells have an ameboid behavior and morphology. When Bok-2 and viable Candida albicans were co-cultured, Bok-2 cells showed an immune response characterized by chemotaxis, phagocytosis and partial clearing activity of Candida cells and colonies. And Bok-2 cells also showed phagocytosis of latex beads without serum treatment and displayed numerous pseudopodia, membrane evagination for phagocytosis and phagosome activity. On the basis of these results, Bok-2 cells were identified as professional phagocytes.

Animals↗

PubMed2000

The role of IL-12 in inflammatory activity of patients with rheumatoid arthritis (RA).

The aim of this study was to investigate the role of IL-12 in patients with RA. IL-12 (p70) and its associated cytokines were measured in sera and synovial fluid (SF) using an enzyme-linked immunosorbent method. Seven American College of Rheumatology (ACR) core set measures as well as IL-12 levels were sequentially monitored at the commencement and 4 months after treatment with a low-dose steroid and disease-modifying anti-rheumatic drugs (DMARDs). In sera, 64 (42.2%) of 152 RA patients had detectable concentrations of IL-12 (p70), whereas one (1.4%) of 69 osteoarthritis (OA) patients and five (10%) of 50 healthy controls had detectable IL-12 (P < 0.001). The median level of circulating IL-12 was also higher in RA patients (P < 0.001). In SF, the number of patients with detectable IL-12 and the median IL-12 levels were significantly higher in RA patients (n = 53) than in OA patients (n = 22). In paired samples (n = 53) of sera and SF from RA patients, IL-12 levels were higher in the SF than in sera (P < 0.001). Patients with detectable IL-12 (n = 51) in sera had higher tender joint scores (P = 0.003), swollen joint scores (P < 0.001) and C-reactive protein (CRP; P = 0.036), than those without (n = 55). Four months after treatment with DMARDs, the improved group showed a larger IL-12 decrease than the non-improved group (P = 0.017). The levels of IL-12 correlated positively with those of IL-2, interferon-gamma, IL-6, and tumour necrosis factor-alpha, but were correlated inversely with those of IL-10. Our results demonstrate that IL-12 levels reflect RA disease activity and that IL-12 is involved in the production of proinflammatory cytokines. An IL-12 blockade could be useful for the treatment of RA.

Adult↗

PubMed2000

Dehydroevodiamine.HCl prevents impairment of learning and memory and neuronal loss in rat models of cognitive disturbance.

We previously reported that dehydroevodiamine.HCl (DHED) has anticholinesterase and antiamnesic activities. To verify the effects of DHED on cognitive deficits further, we tested it on the scopolamine-induced amnesia model of the rat using the passive avoidance and eight-arm radial maze tests. A single (20 mg/kg p.o.) and repeated (10 mg/kg p.o.) administrations of DHED could significantly reverse the latency time shortened by scopolamine (1 mg/kg i.p.) to control level. The impaired spatial working memory induced by scopolamine (1 mg/kg i.p.) was also improved significantly by a single injection (6.25 mg/kg i.p.) and repeated administrations of DHED (10 mg/kg p.o.) in the eight-arm radial maze test. In addition, we examined the effects of DHED on the memory impairment and the histological changes of the brain after unilateral electrolytic lesion of the entorhinal cortex (EC) and middle cerebral artery occlusion in rats. The cognitive deficits caused by EC lesion and middle cerebral artery occlusion were improved significantly by repeated administrations of DHED (6.25 mg/kg i.p.) after EC lesion or ischemic insult once a day for 7 days in the passive avoidance test. Histological analysis showed that the neuronal loss in the DHED-treated group was notably reduced in the hippocampal area (CA1) of ischemic rats and in the dentate gyrus and hippocampal area (CA1 and CA3) of EC-lesioned rats compared with the nontreated group. The infarction area was decreased significantly by a single administration of DHED (6.25 mg/kg i.p.) 30 min before ischemic insult for 6 h. These results suggest that DHED might be an effective drug for not only the Alzheimer's disease type, but also the vascular type of dementia.

Alkaloids↗

PubMed2000

Somatic mutations of Fas (Apo-1/CD95) gene in cutaneous squamous cell carcinoma arising from a burn scar.

Fas (Apo-1/CD95) is a cell-surface receptor involved in cell death signaling, and recent reports have suggested that defects within the Fas receptor pathway such as Fas mutation play an important part in the development and progression of human tumors. Burn scar-related squamous cell carcinoma of skin is a unique subtype of cutaneous squamous cell carcinoma, and tends to be more aggressive in nature than conventional squamous cell carcinoma. The molecular mechanisms underlying the development and progression of burn scar-related squamous cell carcinoma, however, are not clear. In this study, we analyzed the entire coding region and all splice sites of the Fas gene for the detection of the somatic mutations in a series of 50 conventional squamous cell carcinomas and 21 burn scar-related squamous cell carcinomas by polymerase chain reaction, single strand conformation polymorphism, and DNA sequencing. We detected mis-sense mutations in three of 21 burn scar-related squamous cell carcinomas (14.3%), whereas no mutation was detected in 50 conventional squamous cell carcinomas. Of the three Fas mutations detected in the burn scar-related squamous cell carcinomas, one was found in Fas ligand-binding domain, another one was identified in the death domain known to be involved in the transduction of an apoptotic signal, and the other one was found in the transmembrane domain. Our data show that some burn scar-related squamous cell carcinomas have Fas gene mutations in important regions for the apoptosis function and suggest that these mutations might be involved in the pathogenesis of burn scar-related squamous cell carcinomas. In addition, our results provide an important clue to understanding the difference between burn scar-related squamous cell carcinoma and conventional squamous cell carcinoma at the molecular level.

Adolescent↗