Biomedical subjects

S C Lee

Publications and source records attributed to S C Lee.

At least 145 records · Page 8Linked to original sources

PubMed2000

Role of MIP-1beta and RANTES in HIV-1 infection of microglia: inhibition of infection and induction by IFNbeta.

Microglia are the major target of HIV-1 infection in the brain. Microglial infection is CD4-dependent, but the role of chemokine receptors CCR5 and CCR3 and their natural ligands in modulating HIV-1 infection in microglia has been questioned. In primary human fetal microglial cultures, we demonstrate that HIV-1 infection of these cells is dependent on CCR5, since an antibody to CCR5 completely blocked productive infection. Anti-CCR3, in contrast, had a smaller inhibitory effect which was not statistically significant. The chemokine ligands for CCR5, RANTES and MIP-1beta, also potently inhibited HIV-1 infection in microglia, but the third ligand MIP-1alpha failed to show inhibition. Interestingly, when microglial cultures were treated with antibodies specific to each of these chemokines, HIV-1 infection was enhanced by anti-RANTES and anti-MIP-1beta, but not by anti-MIP-1alpha. These results demonstrate the presence of endogenous chemokines that act as endogenous inhibitors of HIV-1 infection in microglia. Additionally, IFNbeta, a known anti-viral cytokine, also provided potent inhibition of viral infection as well as induction of all three chemokines in microglia. These results suggest the possibility that type I interferon can down-modulate microglial HIV-1 infection in vivo by multiple mechanisms.

AIDS Dementia Complex↗

PubMed2000

Modulation of interleukin-1beta and tumor necrosis factor alpha signaling by P2 purinergic receptors in human fetal astrocytes.

In human astrocytes, interleukin-1beta (IL-1beta) is a potent inducer of genes associated with inflammation. In this study, we tested the hypothesis that in primary cultures of human fetal astrocytes signaling by the P2 purinergic nucleotide receptor pathway contributes to, or modulates, cytokine-mediated signal transduction. Calcium imaging studies indicated that most cells in culture responded to ATP, whereas only a subpopulation responded to UTP. Pretreatment of astrocytes with P2 receptor antagonists, including suramin and periodate oxidized ATP (oATP), resulted in a significant downregulation of IL-1beta-stimulated expression of nitric oxide, tumor necrosis factor (TNFalpha), and IL-6 at both the protein and mRNA levels, without affecting cell viability. In cells transiently transfected with reporter constructs, IL-1beta demonstrated more potent activation of the transcription factors nuclear factor -kappaB (NF-kappaB) and activator protein-1 (AP-1) than TNFalpha. However, pretreatment with oATP downregulated activation of NF-kappaB and AP-1 by IL-1beta or TNFalpha. Electromobility shift assays using oligonucleotides containing specific NF-kappaB binding sequences confirmed that pretreatment with oATP or apyrase attenuated cytokine-mediated induction of this transcription factor. From these data, we conclude that P2 receptor-mediated signaling intersects with that of IL-1beta and TNFalpha to regulate responses to cytokines in the CNS. Because inflammation, trauma, and stress all lead to the release of high levels of extracellular nucleotides, such as ATP and UTP, signaling via P2 receptors may provide a mechanism whereby cells can sense and respond to events occurring in the extracellular environment and can fine tune the transcription of genes involved in the inflammatory response.

Adenosine Triphosphate↗

PubMed2000

Melanisation of Cryptococcus neoformans in human brain tissue.

Melanin-specific reagents revealed melanin in cryptococcal cell walls from human brain tissue, and fungal-cell melanin "ghosts" were recovered from infected tissue. The results indicate that Cryptococcus neoformans melanises during human infection.

Amphotericin B↗

PubMed2000

A 5-year study of the seroepidemiology of Klebsiella pneumoniae: high prevalence of capsular serotype K1 in Taiwan and implication for vaccine efficacy.

Seroepidemiology of Klebsiella pneumoniae was determined for 1000 nonrepetitive K. pneumoniae isolates collected by a medical center in Taiwan during 1993-1997. Of these, 630 isolates (63%) were from community-acquired infections; the rest were from hospital-acquired infections. The isolates were serotyped according to capsular antigen by countercurrent immunoelectrophoresis. About 77% were typeable. Serotypes K1 and K2 accounted for 21.7% and 9.3% of the isolates, respectively, followed by K57 (5.1%), K54 (4.2%), K21 (3. 3%), and K16 (3%). The frequency of serotype K1 among bacteremic isolates (30.8%) far exceeded that reported by other investigators worldwide. Molecular typing of random K1 isolates by pulsed-field gel electrophoresis revealed several different pulsotypes, suggesting a nonclonal spread. This study indicates that a Klebsiella vaccine developed in Europe is not optimal for use in Taiwan because it does not contain the most predominant serotypes-K1, K54, and K57.

Antibodies, Bacterial↗

PubMed2000

Production of medium-chain-length polyhydroxyalkanoates by high-cell-density cultivation of Pseudomonas putida under phosphorus limitation.

High-cell-density fed-batch cultures of Pseudomonas putida were carried out for the production of medium-chain-length polyhydroxyalkanoates (PHAs) using oleic acid as a carbon source. By employing an optimal feeding strategy without the limitation of any nutrient, a high cell concentration of 173 g/L was achieved, but the PHA concentration and PHA content were only 32.3 g/L and 18.7 wt%, respectively. To increase the PHA concentration and content, phosphorus limitation was applied during fed-bath culture by reducing the initial KH(2)PO(4) concentration. When the initial KH(2)PO(4) concentration was reduced to 4 g/L, cell concentration, PHA concentration, and PHA content obtained in 38 h were 141 g/L, 72. 6 g/L, and 51.4 wt%, respectively, resulting in a high productivity of 1.91 g PHA/L per hour.

Bioreactors↗

PubMed2000

Heparin reduces the alpha-helical content of cobra basic phospholipase A(2) and promotes its complex formation.

The interaction of phospholipase A(2) (PLA(2)) with glycosaminoglycans (GAGs) has recently attracted attention in view of its implication on inflammation and cell proliferation. By using Fourier Transformed Infrared (FTIR) spectroscopic measurements, we demonstrate here that binding of cobra basic phospholipase A(2) from Naja nigricollis (N-PLA(2)) to heparin may induce a significant conformational change observed in the amide I region of the enzyme's alpha-helical and beta-sheet structure. It is observed that notable conformational change of N-PLA(2) due to heparin binding occurs only when heparin's chain length is at least an octasaccharide as evidenced by circular dichroism and optical density measurements. This correlation may be an important factor in the aggregation of N-PLA(2) and N-PLA(2)-heparin complexes. Heparin induced change in conformation of PLA(2) is suggested to be a notable link in understanding the diversity in PLA(2) activity when rendered to the extracellular matrix of cell membranes that is full of GAG molecules.

Animals↗

PubMed2000

Cutaneous injection of human subjects with macrophage inflammatory protein-1 alpha induces significant recruitment of neutrophils and monocytes.

Macrophage inflammatory protein (MIP-1 alpha), a member of the CC chemokine subfamily, has been shown to attract T cells and monocytes in vitro and to be expressed at sites of inflammation. Although the in vitro activities of MIP-1 alpha have been well documented, the in vivo biological activities of MIP-1 alpha in humans have not been studied. To address this, we challenged human subjects by intradermal injection with up to 1000 pmol of MIP-1 alpha and performed biopsies 2, 10, and 24 h later. Although no acute cutaneous or systemic reactions were noted, endothelial cell activation, as indicated by the expression of E-selectin, was observed. In agreement with its in vitro activity, monocyte, lymphocyte, and, to a lesser degree, eosinophil infiltration was observed, peaking at 10-24 h. Surprisingly, in contrast to its reported lack of in vitro neutrophil-stimulating activity, a rapid infiltration of neutrophils was observed in vivo. This neutrophil infiltration occurred as early as 2 h, preceding the appearance of other cells, and peaked at 10 h. Interestingly, we found that neutrophils in whole blood, but not after isolation, expressed CCR1 on their cell surface. This CCR1 was thought to be functional as assessed by neutrophil CD11b up-regulation following whole-blood MIP-1 alpha stimulation. These studies substantiate the biological effects of MIP-1 alpha on monocytes and lymphocytes and uncover the previously unrecognized activity of MIP-1 alpha to induce neutrophil infiltration and endothelial cell activation, underscoring the need to evaluate chemokines in vivo in humans.

Adolescent↗

PubMed2000

Systemic administration of 4-chlorokynurenine prevents quinolinate neurotoxicity in the rat hippocampus.

The synthetic compound 4-chlorokynurenine has been shown to be enzymatically transaminated to the selective glycine(B) receptor antagonist 7-chlorokynurenate. Since 4-chlorokynurenine, in contrast to 7-chlorokynurenate, readily penetrates the blood-brain barrier, the present study evaluated its neuroprotective properties after systemic administration in rats. Intrahippocampal injection of the NMDA receptor agonist quinolinate (15 nmol/l microl) was used as the neurotoxic paradigm. Serum and hippocampal tissue measurements confirmed that 4-chlorokynurenine serves as an effective pro-drug of 7-chlorokynurenate both in the periphery and in the brain. These studies and complementary hippocampal microdialysis experiments compared the effects of single and repeated injections of 4-chlorokynurenine (50 or 200 mg/kg, intraperitoneal (i.p.), 10 min prior to an intrahippocampal quinolinate injection; or 50 mg/kg, i.p., 10 min before and 30, 120 and 360 min after quinolinate). With the multiple-dosing regimen, extracellular 7-chlorokynurenate levels in the hippocampus reached a maximum of approximately 750 nM 7 h after quinolinate and gradually decreased with a half-life of about 3 h. In contrast, a single injection of 200 mg/kg 4-chlorokynurenine resulted in a considerably shorter rise in extracellular 7-chlorokynurenate without yielding higher peak levels. In separate animals, repeated treatment with 50 mg/kg 4-chlorokynurenine, but not a single injection of 200 mg/kg of the pro-drug, provided total protection against quinolinate-induced excitotoxicity. These data suggest that a prolonged and functionally relevant blockade of hippocampal glycine(B) receptors can be achieved after the systemic administration of 4-chlorokynurenine.

Animals↗

PubMed2000

Novel microtubule-associated protein-2 isoform is expressed early in human oligodendrocyte maturation.

We have identified a developmentally regulated, oligodendrocyte-specific protein, designated microtubule-associated protein-2 expressing exon 13 (MAP-2+13), in the human central nervous system (CNS). Monoclonal antibodies directed against MAP-2+13 labeled oligodendrocytes in the white matter of human fetal spinal cord. Double-label immunofluorescence and confocal microscopy, and immunoelectron microscopy localized MAP-2+13 to the soma and extending processes of fetal oligodendrocytes, but not to the myelin sheath. The immunoreactivity was throughout the perikarya. Ultrastructural examination of the fetal myelin sheaths showed them to be thin and not fully compacted, indicating that myelination was in progress. There was no overlap in staining of GFAP+ astrocytes and MAP-2+13+ oligodendrocytes. MAP-2+13 was also expressed in intermediate filament-negative "radial glia" extending from the central canal to the subpial surface. In the mature CNS, MAP-2+13 also marked cells of oligodendroglial morphology, but these cells were rare. These finding demonstrate that in the human CNS, MAP-2+13 is a novel protein transiently expressed in cells of oligodendroglial lineage.

Antibodies, Monoclonal↗

PubMed2000

Differential induction of chemokines in human microglia by type I and II interferons.

Chemokines are secreted proteins that function as chemoattractants, mediating the recruitment of specific subsets of leukocytes to sites of tissue damage and immunological reactions. Chemokines may also function as antiviral agents, since viruses such as human immunodeficiency virus type 1 (HIV-1) use chemokine receptors as co-receptors for viral entry. This study examines whether virus-induced interferon, IFNbeta, or immune-related interferon, IFNgamma, affects the production of beta-chemokines by CNS microglia and peripheral monocytes. When IFNbeta was used as the stimulus, induction of MIP-1alpha, MIP-1beta, MCP-1, and RANTES mRNA and protein was observed within 12 h of stimulation in microglia. By contrast, when IFNgamma was used as the stimulus, only MCP-1 was induced. IFNbeta stimulation of blood monocytes resulted in upregulation of MIP-1alpha, MIP-1beta, and MCP-1. Thus, type I and II interferons differentially regulate beta-chemokines in human fetal microglia and peripheral blood monocytes. These observations may have relevance for the therapeutic activity of IFNbeta in multiple sclerosis and for the antiviral effects of IFNbeta for HIV-1 infection of monocytes and microglia.

Cells, Cultured↗

PubMed2000

Myoclonus from selective dentate nucleus degeneration in type 3 Gaucher disease.

OBJECTIVE: To describe a case with a new genetic variant of type 3 Gaucher disease presenting with stimulus-sensitive and action myoclonus in the presence of selective dentate abnormalities. DESIGN: Clinical, pathologic, and molecular genetic studies. SETTING: Medical school departments. PATIENT: A 6-year-old girl with type 3 Gaucher disease experienced progressively crippling generalized stimulus-sensitive and action myoclonus. Repeated electroencephalographic examination did not show cortical activity associated with the myoclonus, suggesting its subcortical origin. Neuropathological examination revealed selective degeneration of the cerebellar dentate nucleus and dentatorubrothalamic pathway in the face of essentially complete lack of storage in the brain. Mutation analysis identified the following 2 mutant alleles: one with a V394L mutation and the other with the lesion RecTL (D409H + L444P + A456P + V460V), which resulted from a recombination event, with the pseudogene located 16 kilobases downstream from the structural gene. CONCLUSION: Given the restricted abnormalities, this genetically unique case provides insight into the pathogenesis of myoclonus and suggests a prominent role for the cerebellar dentate nucleus in its genesis.

Cerebellar Nuclei↗

PubMed2000

Distinct patterns of stimulus-inducible chemokine mRNA accumulation in human fetal astrocytes and microglia.

Interferon-gamma-inducible 10 kd protein (IP-10) is an ELR (Glu-Leu-Arg)(-) alpha chemokine with known chemotactic effects on T cells and monocytes, as well as anti-viral, anti-angiogenic, and anti-tumor effects. Previous studies have demonstrated that in cultured rat astrocytes and microglia, stimulation with LPS or virus can induce the expression of IP-10. In this study, we determined the pattern of IP-10 gene induction in primary human microglia and astrocytes by cytokines and LPS using ribonuclease protection assay. The expression of IP-10 mRNA was compared with that of other alpha (IL-8) and beta chemokines. The results showed that in human microglia, IP-10 expression was induced equally potently by LPS, IFNbeta or IFNgamma. "Proinflammatory" cytokines IL-1beta or TNFalpha also induced small amounts of IP-10 mRNA. "Anti-inflammatory" cytokines IL-4, IL-10 and TGFbeta were ineffective in inducing IP-10 in microglia. In human astrocytes, induction of IP-10 mRNA by cytokines was similar to that in microglia. LPS, however, was ineffective in inducing IP-10 in human astrocytes. The monocyte chemoattractant beta-chemokine I-309 mRNA was induced in human astrocytes and microglia by IFNbeta or IFNgamma, or by LPS in microglia, showing a tight co-regulation with IP-10 mRNA expression. In contrast to the potent induction of IP-10 and I-309 by IFNs in human glia, the ELR(+) alpha chemokine IL-8 mRNA was induced by IL-1beta and TNFalpha, and to a lesser extent by IFNbeta in microglia. IFNbeta but not IFNgamma was effective in inducing the expression of beta chemokines MIP-1alpha and MIP-1beta in human microglia, with the levels of mRNA similar to those induced by IL-1beta or TNFalpha. Neither MIP-1alpha nor MIP-1beta mRNAs were induced by any stimulation in human astrocytes. The induction of RANTES mRNA in microglia by IFNbeta, IL-1beta or TNFalpha was variable, showing no to low level expression depending on the case, whereas LPS provided a consistent inducing signal. In astrocytes, only cytokine combinations (IFN + IL-1beta) effectively induced the RANTES mRNA. These results demonstrate that distinct sets of chemokine genes are induced in human glial cells by cytokines and interferons. These results may have wide implications for inflammatory, vascular and neoplastic diseases of the CNS.

Astrocytes↗

PubMed2000

Measurement of central activation failure of the quadriceps femoris in healthy adults.

The purpose of this investigation was to describe the relationship between the central activation ratio (CAR) and the percent maximum voluntary effort (% MVE) during isometric quadriceps femoris contractions. Twenty-one healthy, young adults participated in three test sessions. During each session, one of three train types was tested: a 100-HZ 120-ms train, a 100-HZ 250-ms train, or a 50-HZ 500-ms train. Subjects were seated on a force dynamometer and stabilized to perform a 3-5-s isometric knee extension at MVE. Force targets were set at 25, 50, 75, and 100% of the MVE. With 5 min rest between efforts, subjects produced forces at the specified target levels. When each target was reached, the test train was delivered to quantify the amount of central activation. There were no significant differences in CARs across train types during maximal efforts, but during submaximal efforts at 25 and 50%, the 100-HZ 250-ms and 50-HZ 500-ms trains produced significantly lower CARs than the 100-HZ 120-ms train. The relationship between the CAR and the %MVE was curvilinear and best described by a second-order polynomial for all three train types. If tests of central activation are going to be used clinically, it is important to know the relationship between the CAR and voluntary effort; however, further study will be required to extend these results to specific patient populations.

Adult↗

PubMed2000

Chiral separation of the enantiomers of metoprolol and its metabolites by high performance liquid chromatography.

(1'R, 2R)-, (1'R, 2S)-, (1'S, 2R)- and (1'S, 2S)-alpha-hydroxymetoprolol; (2R)- and (2S)-O-desmethylmetoprolol; and (2R)- and (2S)-metoprolol acid are major metabolites of (2R)-and (2S)-metoprolol, beta-adrenergic antagonist. The focus of most chiral separation methods until now has been on determination of the enantiomeric parent drug. However, it is just as important to be able to follow the metabolism of the enantiomers and their possible chiral metabolites. Therefore, for the study of stereoselective metabolism and pharmacokinetics of metoprolol, the chiral separation of the enantiomers of metoprolol and its metabolites has been investigated using four chiral stationary phases, i.e., Chiralcel OD, Chiral-AGP, Cyclobond I and Sumichiral OA-4900 columns. Metoprolol acid was resolved only by Sumichiral OA-4900. Chiralcel OD provided the highest separation factor and resolution value for metoprolol and O-desmethylmetoprolol and partially resolved the four stereoisomers of alpha-hydroxymetoprolol. Diastereomeric alpha-hydroxymetoprolols were resolved using the coupled column chromatographic system of two chiral stationary phases, Sumichiral OA-4900 column and Chiralcel OD column.

Adrenergic beta-Antagonists↗

PubMed2000

In vitro maturation, fertilization, and development of human germinal vesicle oocytes collected from stimulated cycles.

OBJECTIVE: To evaluate whether germinal vesicle (GV) oocytes from stimulated cycles can be a source of embryos. DESIGN: In vitro model study. SETTING: Specialized laboratory of women's clinic. PATIENT(S): Women in whom oocytes were retrieved at the GV stage. INTERVENTION(S): After culture of GV oocytes in the modified TLP medium with human follicular fluid, oocytes that reached the metaphase II stage underwent ICSI. Potential of fertilization and subsequent cleavage of in vitro-matured oocytes was compared with that of an in vivo-matured control. MAIN OUTCOME MEASURE(S): Maturation rate, rate of pronuclei formation, and developmental activity. RESULT(S): The maturation rate of GV oocytes from follicles primed with gonadotropin was not affected by the presence or absence of cumulus. However, the maturation was more synchronous in oocytes with cumulus than in those without cumulus. Proportions of oocytes with two pronuclei and embryos cleaved to the 16-cell stage after ICSI were significantly lower in the oocytes matured in vitro than in the oocytes matured in vivo. CONCLUSION(S): Human GV oocytes from stimulated ovaries can be matured, fertilized, and developed in vitro. Production of embryos from GV oocytes will increase the opportunity for achieving pregnancy.

Cell Nucleus↗

PubMed2000

Indoor and outdoor air quality investigation at schools in Hong Kong.

Five classrooms in Hong Kong (HK), air-conditioned or ceiling fans ventilated, were chosen for investigation of indoor and outdoor air quality. Parameters such as temperature, relative humidity (RH), carbon dioxide (CO2), sulphur dioxide (SO2), nitric oxide (NO), nitrogen dioxide (NO2), respirable particulate matter (PM10), formaldehyde (HCHO), and total bacteria counts were monitored indoors and outdoors simultaneously. The average respirable particulate matter concentrations were higher than the HK Objective, and the maximum indoor PM10 level exceeded 1000 microg/m3. Indoor CO2 concentrations often exceeded 1000 microl/l in air-conditioning and ceiling fan classrooms, indicating inadequate ventilation. Maximum indoor CO2 level reached 5900 microl/l during class at the classroom with cooling tower ventilation. Increasing the rate of ventilation or implementation of breaks between classes is recommended to alleviate the high CO2 level. Other pollution parameters measured in this study complied with the standards. The two most important classroom air quality problems in Hong Kong were PM10 and CO2 levels.

Air Pollution↗

PubMed2000

The effect of nimodipine on opioid antagonist-induced upregulation and supersensitivity.

Regulation of calcium flux has been suggested to play a role in acute and chronic effects of opioids. Previous studies have shown calcium channel blockers can inhibit opioid agonist-induced downregulation of mu-opioid receptors and may reduce the magnitude of tolerance. In the present study, we determined if calcium channel blockade would affect increases in opioid receptor density and functional supersensitivity produced by chronic opioid antagonist treatment in the mouse. Mice were implanted subcutaneously with a 15-mg naltrexone (NTX) or placebo pellet. Mice also were implanted with an osmotic minipump that infused nimodipine (100 microg/kg/day) or a second placebo pellet. This protocol yielded four groups: nimodipine-NTX; nimodipine-placebo; placebo-NTX; placebo-placebo. On the seventh day, pumps and pellets were removed. Twenty-four hours later, a morphine dose-response study was conducted (tail flick); or mice were sacrificed and saturation binding studies ([3H]DAMGO) were performed in whole brain. NTX treatment significantly increased the analgesic potency of morphine by approximately 60%. Nimodipine increased the potency of morphine by approximately 50%. For mice treated with both nimodipine and NTX, there was an additive effect on morphine potency ( approximately 120% increase). In binding studies, NTX increased the density of mu-opioid receptors similarly ( approximately 60-70%) in the presence and absence of nimodipine treatment, with no change in affinity. No effect of chronic nimodipine alone on mu-opioid receptor binding was observed. These data indicate that NTX-induced upregulation and supersensitivity are independent of calcium channel blockade by nimodipine. These results contrast with those from tolerance and downregulation studies, and confirm suggestions that different substrates mediate chronic opioid agonist and antagonist-induced effects in vivo. Finally, in a separate study, morphine potency was unaffected by acute nimodiopine (100 microg/kg; SC), suggesting that prolonged exposure to this calcium channel blocker is required to increase morphine potency.

Animals↗

PubMed2000

Effects of red ginseng saponins and nootropic drugs on impaired acquisition of ethanol-treated rats in passive avoidance performance.

Effects of single and repeated administration of red ginseng total saponins (ROTS) and nootropic drugs were examined on impairment of acquisition induced by single oral administration of 3 g/kg ethanol (EtOH) in a step through test. The inhibitory effect of EtOH on acquisition was significantly reduced following single or repeated RGTS administration. The nootropic drugs, piracetam and N-methyl-D-glucamine, given orally significantly reduced impairment of acquisition induced by EtOH. On the other hand, the inhibitory effect of repeated RGTS on the EtOH-induced amnesia was blocked by the pretreatment of alpha-methyl-p-tyrosine (alpha-MT), an inhibitor of catecholamine synthesis, in a dose-dependent manner but not p-chlorophenylalanine (PCPA), an inhibitor of serotonin synthesis, whereas the inhibitory effect of repeated N-methyl-D-glucamine on the EtOH-induced amnesia was blocked neither by alpha-MT nor PCPA. These results suggest that repeated RGTS and N-methyl-D-glucamine ameliorate the impairing effect of EtOH on acquisition, and the effect of RGTS on EtOH-induced amnesia is dependent on the catecholaminergic but not serotonergic neuronal activity, while RGTS and N-methyl-D-glucamine seem to have a different mechanism on EtOH-induced amnesia.

Amnesia↗