Biomedical subjects

S Hu

Publications and source records attributed to S Hu.

At least 19 recordsLinked to original sources

PubMed1999

A genetic association for cigarette smoking behavior.

Dopaminergic genes are likely candidates for heritable influences on cigarette smoking. In an accompanying article, Lerman et al. (1999) report associations between allele 9 of a dopamine transporter gene polymorphism (SLC6A3-9) and lack of smoking, late initiation of smoking, and length of quitting attempts. The present investigation extended their study by examining both smoking behavior and personality traits in a diverse population of nonsmokers, current smokers, and former smokers (N = 1,107). A significant association between SLC6A3-9 and smoking status was confirmed and was due to an effect on cessation rather than initiation. The SLC6A3-9 polymorphism was also associated with low scores for novelty seeking, which was the most significant personality correlate of smoking cessation. It is hypothesized that individuals carrying the SLC6A3-9 polymorphism have altered dopamine transmission, which reduces their need for novelty and reward by external stimuli, including cigarettes.

Adult↗

PubMed1998

Unusual propargylic oxidations catalyzed by chloroperoxidase.

This paper describes a new chloroperoxidase oxidative activity, namely, propargylic oxidations. Under appropriate conditions, chloroperoxidase catalyzes the oxidation of a variety of 2-alkynes to aldehydes via alcohol intermediates. Both hydrogen peroxide and t-butyl hydroperoxide can serve as terminal oxidants. The triple bond in the substrate is usually untouched. A free radical mechanism is proposed for the initial hydroxylation step in the overall reaction.

Alkynes↗

PubMed1998

Caspase-14 is a novel developmentally regulated protease.

Caspases are a family of cysteine proteases related to interleukin-1 converting enzyme (ICE) and represent the effector arm of the cell death pathway. The zymogen form of all caspases is composed of a prodomain plus large and small catalytic subunits. Herein we report the characterization of a novel caspase, MICE (for mini-ICE), also designated caspase-14, that possesses an unusually short prodomain and is highly expressed in embryonic tissues but absent from all adult tissues examined. In contrast to the other short prodomain caspases (caspase-3, caspase-6, and caspase-7), MICE preferentially associates with large prodomain caspases, including caspase-1, caspase-2, caspase-4, caspase-8, and caspase-10. Also unlike the other short prodomain caspases, MICE was not processed by multiple death stimuli including activation of members of the tumor necrosis factor receptor family and expression of proapoptotic members of the bcl-2 family. Surprisingly, however, overexpression of MICE itself induced apoptosis in MCF7 human breast cancer cells, which was attenuated by traditional caspase inhibitors.

Amino Acid Sequence↗

PubMed1998

Macaques infected with cloned simian immunodeficiency virus show recurring nef gene alterations.

We compared nef gene sequences isolated by polymerase chain reaction from peripheral blood lymphocyte DNA of macaques that had been inoculated with either biologically (E11S) or molecularly (clone 8) cloned SIV/Mne. Two samples from each animal obtained either early (weeks 2-8) or late (weeks 21-137) after infection were analyzed. Three substitutions in the predicted Nef amino acid sequence were seen in all animals at the late time point, and two other substitutions were seen in all except one. Two of the common exchanges are located approximately 40 residues apart in the Nef core sequence but are juxtaposed on the tertiary structure as judged by computer modeling using the structure of the HIV Nef core protein as a guide. Most recurrent in vivo changes replaced a residue found in the cloned Nef sequence with one present in a consensus derived by aligning the Nef sequences of the SIV/Sm clade. Recombinant virus containing a macaque-adapted (MA nef) nef on the clone 8 backbone was 3-fold more infectious on SMAGI cells than the original virus. A lymphocyte line infected with SIV-clone 8-MAnef contained a large proportion of cells carrying provirus with defective nef genes. These findings suggest that the nef gene of the cloned SIV/Mne had undergone attenuating mutations during propagation in tissue culture that were "corrected" in vivo.

Amino Acid Sequence↗

PubMed1998

Kappa-opioid potentiation of tumor necrosis factor-alpha-induced anti-HIV-1 activity in acutely infected human brain cell cultures.

Opioids have been postulated to play an immunomodulatory role in the pathogenesis of HIV-1. Synthetic kappa-opioid receptor (KOR) ligands have been found to inhibit HIV-1 expression in acutely infected microglial cell cultures. We recently found that interleukin(IL)-1beta and tumor necrosis factor(TNF)-alpha have antiviral effects in acutely infected mixed glial/neuronal cell cultures. In the present study, we investigated whether selective KOR ligands would exert antiviral effects in acutely infected brain cell cultures. While the KOR ligand trans-3,4-dichloro-N-methyl-N[2-(1-pyrolidinyl)cyclohexyl]benze neaceamide methanesulfonate (U50,488) alone had little anti-HIV-1 activity, this opioid potentiated in a concentration-dependent manner the antiviral activity of TNF-alpha, but not of IL-1beta. The potentiating effect of U50,488 was detected after a 6-hr pretreatment and peaked at 24 hr. The KOR antagonist nor-binaltorphimine completely blocked the potentiating effect of U50,488, suggesting the involvement of a KOR-mediated mechanism. Antibodies to TNF-alpha completely blocked the potentiating effect of U50,488, suggesting a critical role for TNF-alpha. Antibodies to IL-1beta blocked the potentiating effect of U50,488, suggesting that IL-1beta was released following U50,488 treatment, which might contribute to the potentiating effect of U50,488. These in vitro findings support the notion that synthetic kappa-opioids could be considered as potential adjunctive therapeutic agents in HIV-1-related brain disease.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1998

Kappa-opioid modulation of human microglial cell superoxide anion generation.

Opioids have been postulated to play an immunomodulatory role in the CNS. Recently, we found that priming microglia with interferon (IFN)-gamma or tumor necrosis factor (TNF)-alpha resulted in an enhanced production of superoxide anion, a reactive oxygen intermediate that may be pathogenic during brain inflammation. In the present study, we investigated the effects of trans-3,4-dichloro-N-methyl-N[2-(1-pyrolidinyl)cyclohexyl]benze neaceamide methanesulfonate (U50,488), a selective kappa-opioid ligand, on microglial cell superoxide production when cells were primed with cytokines or stimulated with phorbol myristate acetate. While treatment of microglial cells with U50,488 had little effect on nonstimulated or stimulated superoxide production, this opioid inhibited (by >70%) the priming effects of cytokines. Maximal inhibition of microglial cell superoxide generation by U50,488 was observed at 10 nM for the priming effect of interferon-gamma and at 1 microM for tumor necrosis factor-alpha. Pretreatment of microglial cell cultures for 30 min with an equal concentration of the selective kappa-opioid receptor antagonist nor-binaltorphimine (nor-BNI) completely blocked the inhibitory effect of U50,488. The results of this study suggest that kappa-opioids may have therapeutic potential in inflammatory diseases of the CNS involving reactive oxygen intermediates produced by activated microglia.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1998

Amyloid precursor protein processing in sterol regulatory element-binding protein site 2 protease-deficient Chinese hamster ovary cells.

Amyloid peptides of 39-43 amino acids (Abeta) are the major constituents of amyloid plaques present in the brains of Alzheimer's (AD) patients. Proteolytic processing of the amyloid precursor protein (APP) by the yet unidentified beta- and gamma-secretases leads to the generation of the amyloidogenic Abeta peptides. Recent data suggest that all of the known mutations leading to early onset familial AD alter the processing of APP such that increased amounts of the 42-amino acid form of Abeta are generated by a gamma-secretase activity. Identification of the beta- and/or gamma-secretases is a major goal of current AD research, as they are prime targets for therapeutic intervention in AD. It has been suggested that the sterol regulatory element-binding protein site 2 protease (S2P) may be identical to the long sought gamma-secretase. We have directly tested this hypothesis using over-expression of the S2P cDNA in cells expressing APP and by characterizing APP processing in mutant Chinese hamster ovary cells that are deficient in S2P activity and expression. The data demonstrate that S2P does not play an essential role in the generation or secretion of Abeta peptides from cells, thus it is unlikely to be a gamma-secretase.

Amyloid Precursor Protein Secretases↗

PubMed1998

IL-10 down-regulates human microglial IL-8 by inhibition of NF-kappaB activation.

In the present study, we tested the hypothesis that interleukin (IL)-10 down-regulates human microglial cell IL-8 release by inhibiting activation of nuclear factor kappa B (NF-kappaB). Immunohistochemical staining demonstrated that IL-10 markedly suppressed lipopolysaccharide (LPS)- and IL-1beta-stimulated IL-8 expression. NF-kappaB involvement was suggested by the finding that pyrrolidinedithiocarbamate, a known inhibitor of NF-kappaB activation, blocked LPS- and IL-1beta-induced IL-8 production. Consistent with our hypothesis, IL-10 treatment of LPS- and IL-1beta-stimulated microglia was associated with a marked decrease in NF-kappaB translocation from the cytoplasm to the nucleus.

Down-Regulation↗

PubMed1998

Determination of the amino acid neurotransmitters in the dorsal root ganglion of the rat by capillary electrophoresis with a laser-induced fluorescence-charge coupled device.

A sensitive, rapid and accurate analysis of the amino acid neurotransmitters in dorsal root ganglion (DRG) of rat was accomplished by capillary electrophoresis with a laser-induced fluorescence-charged coupled device (LIF-CCD) and fluorescein isothiocyanate (FITC) derivatization. Since the CCD is an image detector with a matrix array of photoelements, the photogenerated charge generated from single photoelements was summed up by on-chip charge binning, and used to improve the detection sensitivity. A self-compiled data processing program was used to calculate digitally the summation of the multiwavelength data and transform three-dimensional electropherograms into two-dimensional electropherograms. Use of this program improved the detection sensitivity, the extraction of useful statistical data and the performance of the quantitative analysis. Owing to its excellent detectability and the unique characteristic of its two-dimensional format, which allows to perform analog and digital summation, high detection sensitivity with detection limits ranging from 1.2 to 17.2 nM was obtained for the amino acid neurotransmitters by LIF-CCD. This method was demonstrated to be a powerful tool for analyzing the complex biological samples through quantitative determination of the six amino acid neurotransmitters in the DRG of rat.

Animals↗

PubMed1998

Cytokine regulation of human microglial cell IL-8 production.

IL-8 involvement in neutrophil activation and chemotaxis may be important in inflammatory responses within the central nervous system, secondary to meningitis, encephalitis, and traumatic injury. The source of IL-8 within the brain during these inflammatory processes, however, is unknown. To explore the role of microglia in the production of IL-8, human fetal microglia, which are the resident macrophages of the brain, were treated with LPS and pro- and anti-inflammatory cytokines to determine their effects on IL-8 production. We found that IL-8 protein levels increased in response to LPS or IL-1 beta, or to TNF-alpha, which also corresponded to elevated IL-8 mRNA levels by RT-PCR. Pretreatment with IL-4, IL-10, or TGF-beta 1 potently inhibited the stimulatory effects of these proinflammatory agents. These findings indicate that human microglia synthesize IL-8 in response to proinflammatory stimuli, and that anti-inflammatory cytokines down-regulate the production of this chemokine. These results may have important therapeutic implications for certain central nervous system insults involving inflammation.

Age Factors↗

PubMed1998

Midline Fasciclin: a Drosophila Fasciclin-I-related membrane protein localized to the CNS midline cells and trachea.

Drosophila Fasciclin I is the prototype of a family of vertebrate and invertebrate proteins that mediate cell adhesion and signaling. The midline fasciclin gene encodes a second Drosophila member of the Fasciclin I family. Midline Fasciclin largely consists of four 150 amino acid repeats characteristic of the Fasciclin I family of proteins. Immunostaining and biochemical analysis using Midline Fasciclin antibodies indicates that it is a membrane-associated protein, although the sequence does not reveal a transmembrane domain. The gene is expressed in a dynamic fashion during embryogenesis in the blastoderm, central nervous system midline cells, and trachea, suggesting it plays multiple developmental roles. Protein localization studies indicate that Midline Fasciclin is found within cell bodies of midline neurons and glia, and on midline axons. Initial cellular analysis of a midline fasciclin loss-of-function mutation reveals only weak defects in axonogenesis. However, embryos mutant for both midline fasciclin and the abelson nonreceptor tyrosine kinase, show more severe defects in axonogenesis that resemble fasciclin I abelson double mutant phenotypes.

Amino Acid Sequence↗

PubMed1998

Morphine enhances complement receptor-mediated phagocytosis of Cryptococcus neoformans by human microglia.

Recent studies have shown that opiates modulate the function of microglia, the resident macrophages of the brain. In this study, the effect of morphine on phagocytosis by human fetal microglial cells of the opportunistic fungus Cryptococcus neoformans was studied. Contrary to earlier findings with swine microglia, opsonization was required for the phagocytosis of C. neoformans by human microglia. Moreover, morphine (10(-8)M) was shown to augment uptake of opsonized C. neoformans by over 50%. This contrasts with the earlier finding of morphine-induced inhibition of phagocytosis of nonopsonized cryptococci by swine microglia. The effect of morphine on cryptococcal phagocytosis by human microglia was reversed by treatment of microglial cells with mu opiate receptor antagonists as well as by addition of anti-complement receptor antibodies to the cell cultures, indicating that both the mu opiate receptor and the complement receptor are involved in morphine-enhanced phagocytosis. These findings support the concept of opiates as neuroimmunomodulatory agents and demonstrate that the effects of opiates on microglial cells may be influenced by the animal species from which the cells are derived.

Analgesics, Opioid↗

PubMed1998

Human keratinocyte growth factor recombinantly expressed in Chinese hamster ovary cells: isolation of isoforms and characterization of post-translational modifications.

Keratinocyte growth factor (KGF) is a member of the fibroblast growth factor family that acts specifically on epithelial cells in a paracrine mode. We employed a mammalian expression system to synthesize recombinant human KGF and isolated two preparations, KGF-a and KGF-b, from medium conditioned by Chinese hamster ovary cells. On an SDS-PAGE gel, KGF-a migrates as two bands near 25-29 kDa and contains both N- and O-linked sugar moieties attached near the N-terminus. Detailed structural characterization confirms that KGF-a contains a single amino acid sequence predicted from cDNA sequence and the molecule has two intramolecular disulfide bridges, Cys1-Cys15 and Cys102-Cys106. An additional Cys at position 40 is free and resides in a solvent-inaccessible environment. Mass spectrometric analyses of KGF-a peptides verify the occurrence of several post-translational modifications in the molecule, including partial oxidation at Met28, partial sulfation at Tyr27, and glycosylation at Asn14 and Thr22. The Asn-linked carbohydrate structures are heterogeneous, which include biantennary, triantennary, and tetraantennary structures with none or up to four sialic acids attached to various structures, while the Thr-linked carbohydrates contain typical mucin-type structures. KGF-b is an N-terminally truncated form of KGF-a posttranslationally processed at Arg23 and is not glycosylated. Both KGF-a and KGF-b forms are capable of stimulating DNA synthesis in quiescent Balb/MK mouse epidermal keratinocytes.

Amidohydrolases↗

PubMed1998

Orphan opioid receptor oligonucleotides inhibit HIV-1 expression in human brain cells.

We found that orphan opioid receptor (OR) mRNA was constitutively expressed in human fetal microglia, astrocytes, and cerebral cortical neurons. An OR antisense oligonucleotide markedly inhibited HIV-1 expression in enriched microglial cell and the mixed glial/neuronal cell cultures but not in the chronically infected promonocytic U1 cells. The sense oligonucleotide also inhibited HIV-1 expression in brain cell cultures. These findings indicate that while human brain cells constitutively express mRNA for OR, antisense oligonucleotides to OR non-specifically inhibit acute HIV-1 infection.

Anti-HIV Agents↗

PubMed1998

Benzodiazepines, glia, and HIV-1 neuropathogenesis.

Although the precise mechanisms whereby HIV-1 infection induces neurodegeneration have yet to be determined, a great deal of evidence has incriminated glial cells and the production of proinflammatory mediators in this pathologic process. For this reason, ideal therapeutic agents for the treatment of AIDS dementia would attenuate HIV-1 neuropathogenesis through both direct inhibition of viral expression and suppression of brain cell-produced immune mediators. Benzodiazepines (BDZs), such as Valium, are extensively prescribed drugs for anxiety disorders, which readily cross the blood-brain barrier and have demonstrated immunomodulatory properties. BDZs bind to primary human microglial cells, the principal site of HIV-1 replication in the brain, and inhibit lipopolysaccharide (LPS) induced tumour necrosis factor (TNF-alpha) production by these cells in a concentration-dependent manner. Treatment of HIV-1-infected primary human microglial, as well as mixed glial/neuronal, cell cultures with BDZs inhibits the expression of HIV-1 p24 antigen. BDZ-induced inhibition of HIV-1 expression in chronically infected promonocytic (U1) cells has been found to be associated with decreased activation of the nuclear transcription factor kappa B (NF-kappa B). Because HIV-1 expression is critically dependent on the cellular transcription machinery, inhibition of the activation of transcription factors, which participate in both HIV-1 expression and the production of neurotoxic immune mediators, by BDZ analogs may provide new therapeutic options for AIDS dementia.

AIDS Dementia Complex↗

PubMed1998

Determining the degree of chaos from analysis of ISI time series in the nervous system: a comparison between correlation dimension and nonlinear forecasting methods.

Two different chaotic time series analysis methods--the correlation dimension and nonlinear forecasting--are introduced and then used to process the interspike intervals (ISI) of the action potential trains propagated along a single nerve fiber of the anesthetized rat. From the results, the conclusion is drawn that compared with the correlation dimension, nonlinear forecasting is more efficient and robust for chaotic ISI time series analysis in a noisy environment. Moreover, the evolution of the correlation coefficient curves calculated from nonlinear forecasting can qualitatively give a better reflection of the unpredictability of the system's future behavior and is in good agreement with the values of the largest Lyapunov exponent that quantitatively measures the degree of chaos.

Animals↗

PubMed1998

A functional polymorphism in the monoamine oxidase A gene promoter.

We describe a new polymorphism upstream of the gene for monoamine oxidase A (MAOA), an important enzyme in human physiology and behavior. The polymorphism, which is located 1.2 kb upstream of the MAOA coding sequences, consists of a 30-bp repeated sequence present in 3, 3.5, 4, or 5 copies. The polymorphism is in linkage disequilibrium with other MAOA and MAOB gene markers and displays significant variations in allele frequencies across ethnic groups. The polymorphism has been shown to affect the transcriptional activity of the MAOA gene promoter by gene fusion and transfection experiments involving three different cell types. Alleles with 3.5 or 4 copies of the repeat sequence are transcribed 2-10 times more efficiently than those with 3 or 5 copies of the repeat, suggesting an optimal length for the regulatory region. This promoter region polymorphism may be useful as both a functional and an anonymous genetic marker for MAOA.

Adult↗

PubMed1998

Testosterone and its metabolites modulate 5HT1A and 5HT1B agonist effects on intermale aggression.

Our understanding of the neurochemical and neuroendocrine systems' regulating the display of offensive intermale aggression has progressed substantially over the past twenty years. Pharmacological studies have shown that serotonin, via its action at 5HT1A and/or 5HT1B receptor sites, modulates the display of intermale aggressive behavior and that its effects serve to decrease behavioral expression. Neuroendocrine investigations, in turn, have demonstrated that male-typical aggression is testosterone-dependent and studies of genetic effects, metabolic function and steroid receptor binding have shown that facilitation of behavioral displays can occur via independent androgen-sensitive or estrogen-sensitive pathways. Remarkably, there have been virtually no studies that examined the interrelationship between these facilitative and inhibitory systems. As an initial step toward characterizing the interaction between the systems, studies were conducted that assessed hormonal modulation of serotonin function at 5HT1A and 5HT1B receptor sites. They demonstrated: (1) that the androgenic and estrogenic metabolites of testosterone differentially modulate the ability of systemically administered 8-OH-DPAT (a 5HT1A agonist) and CGS12066B (a 5HT1B agonist) to decrease offensive aggression; and (2) when microinjected into the lateral septum (LS) or medial preoptic area (MPO), the aggression-attenuating effects of 1A and 1B agonists differ regionally and vary with the steroidal milieu. In general, the results suggest that estrogens establish a restrictive environment for attenuation of T-dependent aggression by 8-OH-DPAT and CGS 12066B, while androgens either do not inhibit, or perhaps even facilitate, the ability of 5HT1A and 5HT1B agonists to reduce aggression. Potential mechanisms involved in the production of these steroidal effects are discussed and emerging issues that may impact on efforts to develop an integrative neurobiological model of offensive, intermale aggression are considered.

Aggression↗