Biomedical subjects

S Hu

Publications and source records attributed to S Hu.

At least 181 records · Page 10Linked to original sources

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↗

PubMed1998

In vitro and in vivo evidence for actin association of the naphthylphthalamic acid-binding protein from zucchini hypocotyls.

The N-1-naphthylphthalamic acid (NPA)-binding protein is part of the auxin efflux carrier, the protein complex that controls polar auxin transport in plant tissues. This study tested the hypothesis that the NPA-binding protein (NBP) is associated with the actin cytoskeleton in vitro and that an intact actin cytoskeleton is required for polar auxin transport in vivo. Cytoskeletal polymerization was altered in extracts of zucchini hypocotyls with reagents that stabilized either the polymeric or monomeric forms of actin or tubulin. Phalloidin treatment altered actin polymerization, as demonstrated by immunoblot analyses following native and denaturing electrophoresis. Phalloidin increased both filamentous actin (F-actin) and NPA-binding activity, while cytochalasin D and Tris decreased both F-actin and NPA-binding activity in cytoskeletal pellets. The microtubule stabilizing drug taxol increased pelletable tubulin, but did not alter either the amount of pelletable actin or NPA-binding activity. Treatment of etiolated zucchini hypocotyls with cytochalasin D decreased the amount of auxin transport and its regulation by NPA. These experimental results are consistent with an in vitro actin cytoskeletal association of the NPA-binding protein and with the requirement of an intact actin cytoskeleton for maximal polar auxin transport in vivo.

Actins↗

PubMed1998

Cryptococcal glucuronoxylomannan induces interleukin (IL)-8 production by human microglia but inhibits neutrophil migration toward IL-8.

On the basis of the clinical observation that the cerebrospinal fluid (CSF) of patients with cryptococcal meningitis contains high levels of the chemokine interleukin (IL)-8 but few polymorphonuclear leukocytes (PMNL), the production of IL-8 by cultured brain glial cells after stimulation with two serotypes of cryptococcal capsular polysaccharide glucuronoxylomannan (GXM) was studied, followed by an assessment of the effect of GXM on PMNL migration toward IL-8. GXM serotype A but not D was capable of inducing IL-8 production in human fetal microglial cell but not in astrocyte cultures. When added directly to the PMNL, GXM (both serotypes) potently blocked PMNL migration toward IL-8. The mechanism of GXM's inhibitory effect appeared to involve cross-desensitization. These findings suggest that GXM can induce IL-8 production in the brain but that GXM in the systemic circulation inhibits migration of PMNL toward IL-8.

Astrocytes↗

PubMed1998

Comparative effectiveness and molecular pharmacological mechanisms of antiallergic agents on experimental conjunctivitis in mice.

The purpose of this study was to determine the effectiveness of antiallergic agents in the treatment of experimental murine ragweed conjunctivitis. SWR/J mice were divided into eight groups: 1; normal controls (unmanipulated); 2, untreated; 3, lodoxamide; 4, cromolyn; 5, livocarbastine; 6, nedocromil; 7, buffer solution (BS); and 8, tetrandine (TDR). Groups 2-8 were exposed to ragweed pollen through topical application to conjunctival and nasal mucosa, followed by conjunctival challenge with the allergen. Allergic conjunctivitis was evaluated by scoring of the clinical signs and histopathology. mRNA gene expression of interleukin 1beta (IL-1beta), IL-6 and tumor necrosis factor alpha (TNF-alpha) in conjunctiva was analyzed by reverse transcription polymerase chain reaction techniques. Exposed mice developed allergic conjunctivitis clinically and histologically that was modulated by topical lodoxamide, cromolyn, livocarbastine, or nedocromil eye drops or TDR intraperitoneally injected. Histopathologic analysis demonstrated that the drugs and TDR significantly reduced conjunctival eosinophil infiltration and the number of intact and degranulating mast cells. IL-1beta and TNF-alpha mRNA gene expression in conjunctiva of treated mice was inhibited compared with untreated and BS-treated controls. No IL-6 mRNA expression was observed even on the conjunctiva of the untreated mice. The antiallergic drugs and TDR exerted a similar action on the murine model of allergic conjunctivitis and demonstrated pharmacologic effectiveness on the conjunctival mRNA expression of cytokines IL-1beta and TNF-alpha.

Alkaloids↗

PubMed1998

Keloidal dermatofibroma: report of 10 cases of a new variant.

Dermatofibroma is a common cutaneous tumor. Unusual variants of dermatofibroma that exhibit various epidermal changes or different cellular composition have been described. We observed 10 cases of a novel variant of dermatofibroma characterized by keloidal change within the tumor. Formalin-fixed, paraffin-embedded tissues were used for histochemical and immunohistochemical studies. The patients consisted of six women and four men; median age was 34 years (17 to 59 years). All tumors occurred on the extremities, and six were present for at least 2 years. Tenderness was mentioned in four cases. They were described as erythematous or brown papules 1 cm or smaller. Clinical appearance did not deviate from that of ordinary dermatofibromas. Microscopically, the excised tumors showed a superficial circumscribed area of keloidal change under an atrophic epidermis in an otherwise ordinary dermatofibroma. In the keloidlike area, multinucleated giant cells, hemorrhage, hemosiderin deposits, and scattered KiM1P-positive histiocytes, but not factor XIIIa-positive or CD34-positive cells were present among the thick collagen fibers. There were no known recurrences. This variant dermatofibroma should not be overlooked as a simple keloidal scar. The observation of keloidal change in dermatofibromas may support the connotation that trauma is a possible cause of dermatofibroma. The fact that Asian people are more prone to develop keloid may have led us to find this new variant.

Adolescent↗

PubMed1998

Effect of cytokines on anticryptococcal activity of human microglial cells.

The effect of selected cytokines on the antifungal activity of human microglia was studied with encapsulated and acapsular strains of Cryptococcus neoformans. None of the cytokines tested increased the fungistatic activity of microglia, suggesting that killing of cryptococci within the central nervous system is dependent on other host defense mechanisms.

Cryptococcus neoformans↗

PubMed1998

Study on delay two-phase multiple organ dysfunction syndrome.

OBJECTIVE: To study the injury factors, pathogenic process and clinical features of delay two-phase multiple organ dysfunction syndrome (MODS) in severe burned patients and to replicate a standardized animal model that would accurately imitate the clinical features of MODS. METHODS: Forty-five human patients with burn size larger than 30% total body surface area (TBSA) were analyzed. All of them underwent severe burn shock in early stage and sepsis in late stage. Thirty-two goats were randomly divided into three groups: 1) hemorrhagic shock (group H, n = 6); 2) endotoxemia (group E, n = 6); and 3) hemorrhagic shock plus endotoxemia (group M, n = 20). Hemorrhagic shock was produced according to the method of Wigger (6.7 kPa for an hour, 1 kPa = 7.5 mmHg). Endotoxin (E. coli O111 B4) was given via the portal vein 24 hours after the resuscitation of hemorrhagic shock, in a dose of 30 ng/kg/min for 5 consecutive days. During the observation period of 10 days, all animals were hemodynamically monitored, given standard metabolic support and due cardiac and pulmonary support according to human intensive care. RESULTS: All the patients showed burn shock at 1-3 days and hyperdynamic circulation, hypermetabolism and systemic inflammatory responses over two weeks post-injury. Thirteen cases were found to develop MODS according to the prevailing diagnostic criteria, and 10 of them died with a mortality of 77%. Eighteen animals died in group M with a mortality of 90%, 12 of the 18 developed MODS, with overall incidence of 60%. Most animals in group M showed changes similar to that observed in human cases. The experimentation proved that in the pathogenic process of MODS, there was a two-hit phenomenon in the dvelopment of the syndrome. To prevent the development of MODS, it therefore was imperative to blunt the first hit or the second hit, so that an excessive inflammatory response was alleviated. This postulation has been verified in the treatment of extensive burns. Two patients with burn extent reaching 100% TBSA survived with only mild acute respiratory distress syndrome (ARDS) and renal dysfunction after comprehensive treatment of burn shock, including adequate fluid resuscitation, drugs to remove oxygen free radicals, rapid restoration of pHi, and early extensive excision of burn eschars. CONCLUSION: Both in human patients or animal experimentation, the typical delay two-phase MODS is shown to be produced by two successive insults in the forms of hypovolemic shock and sepsis. This postulation is helpful in formulating the prevention and treatment modality of MODS.

Adult↗