PubMed Health⌕ Search

Biomedical subjects

W Liu

Publications and source records attributed to W Liu.

At least 919 records · Page 51Linked to original sources
PubMed1993

Induction of nitric oxide synthase activity in human astrocytes by interleukin-1 beta and interferon-gamma.

Nitric oxide (NO) is a short-lived, diffusible molecule that has a variety of biological activities including vasorelaxation, neurotransmission, and cytotoxicity. In the central nervous system, a constitutive form of nitric oxide synthase (NOS) has been localized in a subset of neurons and in endothelial cells. In addition, both constitutive and LPS-inducible NOS has been demonstrated in rat astrocytes and microglia in vitro. In this report, we present evidence for the production of NO, as measured by the production of nitrite, in highly enriched human fetal astrocyte cultures stimulated with IL-1 beta. The production of nitrite paralleled the induction of NADPH diaphorase enzyme activity in the perikarya of the majority of stimulated astrocytes. The IL-1 beta-induced nitrite production by astrocytes was markedly enhanced when cells were co-stimulated with IFN-gamma or TNF-alpha (IFN-gamma > TNF-alpha); LPS had no effect used as a single agent or in combination with other cytokines. NGMMA and NG-nitro-arginine, competitive inhibitors of NOS, diminished the accumulation of nitrite, but calmodulin antagonists (trifluoperazine, W-5 and W-7) had little or no inhibitory effect. Human fetal microglia, in contrast to astrocytes, failed to secrete significant amounts of nitrite in response to various stimuli. The results demonstrate the presence of an inducible form of NOS in human fetal astrocytes; human microglia, in turn, may control astrocyte NO production by providing IL-1 beta as an activating signal.

Amino Acid Oxidoreductases↗
PubMed1993

The isolation of a yeast artificial chromosome (YAC) contig extending for 2 megabases in the vicinity of the von Hippel Lindau disease gene.

Von Hippel Lindau disease (VHL) is a rare autosomal dominant disease associated with tumors and cysts in multiple organ systems. The VHL disease gene is tightly linked to the polymorphic DNA marker 233E2 (D3S720) and flanked by 479H4 (D3S719) on its telomeric and RAF1 on its centromeric side. Two additional markers, D3S1038 and D3S601, have also been identified, and these markers, like D3S720, are very tightly linked to VHL. Previously 93 cosmid clones were mapped to the larger region, 3p24.2-pter, surrounding the VHL disease gene. Using a Southern-based screening strategy on pools of YAC clones we have isolated a contig of overlapping YAC clones that extends about 0.7 megabase centromeric, and about 1.3 megabases telomeric of D3S720 and contains all three tightly linked VHL markers. Individual YACs in this contig were hybridized to grids containing cosmids localized between 3p24.2-pter and to several cosmids localized by fluorescent in situ hybridization (FISH) to 3p25. A total of 28 cosmids were positioned on this contig of overlapping YAC clones. We have also identified homologous YAC clones to many additional cosmid clones localized between 3p24.2-p25, although these have not yet been precisely localized relative to the contig of YAC clones. This contig of YAC clones probably contains the VHL disease gene and should facilitate the isolation and characterization of this gene.

Base Sequence↗
PubMed1993

Distribution of pancreatic macrophages preceding and during early insulitis in young NOD mice.

Indirect evidence suggests there may be early influx of beta-cell-directed macrophages into the islets of NOD mice, and before the onset of T-cell insulitis. We have therefore examined immunohistochemically the pancreas of young female NOD mice with monoclonal antibody F4/80 for the presence of macrophages in intraislet, peri-islet, exocrine, and perivascular regions preceding insulitis (days 18 and 22) and during early insulitis (days 30 and 40) and compared their distribution in age-matched normal Swiss mouse pancreas. In the absence of insulitis (day 18 and day 22) and during very early insulitis (day 30) macrophage-positive cells had a predominantly exocrine and perivascular distribution with reduced numbers in the peri-islet area. Intraislet macrophages usually occurred singly and were sparse. At day 40, an enhanced influx of the immune cells was observed in intra- and peri-islet locations and in parallel with increased numbers in the exocrine areas. At this age, higher numbers of macrophages were observed within the islet, distributed among the T-cell infiltrate and also scattered among the endocrine cells. During the study period, the number of macrophages in the peri-, intraislet, and exocrine regions was significantly higher among NOD mice than in the Swiss mouse group (p = 0.003, p = 0.005, and p = 0.0009, respectively). In the absence of insulitis (days 18 and 22), although the number of positive cells tended to be higher in NOD mice, this difference reached statistical significance in the peri-islet area (p = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A soluble Bacillus cereus cytochrome P-450cin system catalyzes 1,4-cineole hydroxylations.

A cytochrome P-450-dependent monooxygenase system that catalyzes the stereospecific hydroxylation of the monoterpene substrate 1,4-cineole was demonstrated in cell-free preparations of Bacillus cereus UI-1477. 1,4-Cineole hydroxylations were catalyzed by a 100,000 x g (1-h)-centrifuging soluble, hexane-inducible enzyme that activated and incorporated molecular oxygen into hydroxylated products; required NADH; was inhibited by SKF-525A, imidazole, metyrapone, and octylamine; and displayed a 452-nm peak in the carbon monoxide difference absorption spectrum. The constant 7:1 ratio of endo/exo alcohol products formed when 1,4-cineole was hydroxylated by normal cells, hexane-induced cells, and cell extracts suggested that a single enzyme designated cytochrome P-450cin was responsible for both reactions.

Amines↗
PubMed1993

The antimicrobial effect of a structural variant of subtilin against outgrowing Bacillus cereus T spores and vegetative cells occurs by different mechanisms.

Subtilin is a ribosomally synthesized antimicrobial peptide that contains several unusual amino acids as a result of posttranslational modifications. Site-directed mutagenesis was employed to construct a structural variant of subtilin in which the unusual dehydroalanine (Dha) residue at position 5 was changed to alanine. Proton nuclear magnetic resonance spectroscopy, amino acid composition, and N-terminal sequence analysis established that the mutation did not disrupt posttranslational processing of the precursor peptide. This mutant subtilin was devoid of antimicrobial activity as assessed by its lack of inhibitory effects on outgrowth of Bacillus cereus T spores. However, this same mutant subtilin was fully active with respect to its ability to induce lysis of vegetative B. cereus T cells. Because an intact Dha-5 residue is required in the one instance but not in the other, it was concluded that the molecular mechanism by which subtilin inhibits (without lysis) spore outgrowth is not the same as the mechanism by which it inhibits (with lysis) vegetative cells.

Amino Acid Sequence↗
PubMed1993

Insertion and deletion mutations in the repA4 region of the IncFII plasmid NR1 cause unstable inheritance.

Mutants of IncFII plasmid NR1 that have transposons inserted in the repA4 open reading frame (ORF) are not inherited stably. The repA4 ORF is located immediately downstream from the replication origin (ori). The repA4 coding region contains inverted-repeat sequences that are homologous to the terC inverted repeats located in the replication terminus of the Escherichia coli chromosome. The site of initiation of leading-strand synthesis for replication of NR1 is also located in repA4 near its 3' end. Transposon insertions between ori and the right-hand terC repeat resulted in plasmid instability, whereas transposon insertions farther downstream did not. Derivatives that contained a 35-bp frameshift insertion in the repA4 ORF were all stable, even when the frameshift was located very near the 5' end of the coding region. This finding indicates that repA4 does not specify a protein product that is essential for plasmid stability. Examination of mutants having a nest of deletions with endpoints in or near repA4 indicated that the 3' end of the repA4 coding region and the site of leading-strand initiation could be deleted without appreciable effect on plasmid stability. Deletion of the pemI and pemK genes, located farther downstream from repA4 and reported to affect plasmid stability, also had no detectable effect. In contrast, mutants from which the right-hand terC repeat, or both right- and left-hand repeats, had been deleted were unstable. None of the insertion or deletion mutations in or near repA4 affected plasmid copy number. Alteration of the terC repeats by site-directed mutagenesis had little effect on plasmid stability. Plasmid stability was not affected by a fus mutation known to inactivate the termination function. Therefore, it appears that the overall integrity of the repA4 region is more important for stable maintenance of plasmid NR1 than are any of the individual known features found in this region.

Amino Acid Sequence↗
PubMed1993

Time-dependent changes in the chronotropic response to vagal stimulation in the newborn canine.

We characterized changes in the vagal chronotropic response during 3-min trains of vagal stimulation at 3, 5, and 8 Hz in anesthetized, chemically sympathectomized (6-hydroxydopamine) newborn canines (< 15 d of age). In response to vagal stimulation, the sinus cycle length gradually increased (within 30 s) to a maximum value that was dependent upon the stimulation frequency (p < 0.001). The chronotropic response then attenuated over the remainder of the vagal train. However, unlike in adult dogs, the degree of attenuation of the vagal chronotropic response (fade) was also highly dependent upon the frequency of vagal stimulation in the range 3-8 Hz (p < 0.002). We then compared the maximum change in sinus cycle length and fade in a group of neonates while stimulating the vagus at 3 Hz before and after the administration of physostigmine (0.2 mg/kg i.v.). Physostigmine resulted in a significant increase not only in the maximum percent change in sinus cycle length but in the magnitude of attenuation of the vagal response as well. Therefore, unlike the adult, in the newborn the magnitude of both the vagal response and fade are dependent upon concentrations of acetylcholine released in response to modest levels of vagal stimulation (< or = 8 Hz). This may be the result of differences between the newborn and the adult in the prestreceptor mechanisms of fade or in the susceptibility of the muscarinic receptor to desensitization by the neurotransmitter acetylcholine.

Acetylcholine↗
PubMed1993

Productive infection of human fetal microglia by HIV-1.

Central nervous system disease is a frequent finding in both pediatric and adult AIDS. Microglia have been shown to be the major target of HIV-1 infection in the central nervous system. However, studies in vitro concerning susceptibility of human microglia to HIV-1 infection reported conflicting results; microglia from adult brain showed productive infection by HIV-1, whereas microglia from fetal brain did not. To investigate this further and to define the possible mechanisms responsible for this difference, we prepared highly purified human microglial cell cultures from fetuses of 16 to 24 weeks' gestation and exposed them to monocytotropic (HIV-1 JR-FL and HIV-1 JR-CSF) isolates of HIV-1. Culture supernatants were examined for the presence of p24 antigen for a 4-week period after viral exposure. Concurrently, potential cytopathic effects and cellular viral antigen expression (gp41 and p24) were examined by light microscopy in combination with immunocytochemistry. The results showed that human fetal microglia can be productively infected by HIV-1 as judged by p24 antigen capture assay, syncytia formation, and gp41 and p24 immunoreactivity of infected microglia. In addition, by electron microscopy, numerous viral particles characteristic of HIV-1 were present both in the intracellular and extracellular compartments. Uninfected cultures or astrocytes overgrown in the microglial cultures did not show evidence of infection under identical experimental conditions. These data demonstrate that human fetal microglia, like their adult counterparts, are susceptible to HIV-1 infection in vitro and can support the production of virus.

Acquired Immunodeficiency Syndrome↗
PubMed1993

[Study on the induction of active immunity in human by injecting human anti-HBs antibodies].

One hundred and three health volunteers were injected with various doses of human anti-HBs (Ab1). The anti-idotypic antibodies (Ab2) and anti-antiidiotypic antibodies (Ab)3 in sera were tested at intervals of 30 days with ELISA. We found that the dynamic changes between Ab2 and Ab3 of immune sera were cyclical by way of their interaction and the Ag-specific Ab3 were the same as Ab1 in specificity. The results reconfirmed that exogenous human anti-HBs could induce active immunity by activation of idiotypic network and regulation in human body suggesting that injection of Ig into body could bring about not only passive immunity but also active immunity.

Adolescent↗
PubMed1993

[The number, distribution and effects of interleukin-2 receptor and CD4 antigens in benign and malignant lymphoproliferative diseases].

An analysis of immunophenotypes was made in benign and malignant lymphoproliferative diseases (35 cases) and short cultured lymphocytes of chronic tonsillitis (15 cases). The number, distribution and variation of interleukin-2 receptor (IL-2R, CD25) and CD4 positive cells in the above lesions were studied. The results showed that (1) there were more or less IL-2R+ and CD4+ cells presented in the tissues of benign lymphoproliferative lesions; (2) IL-2R antigen was also presented in some tumor and non-tumor cells with CD4+ reaction but it was not found in the cells with CD1+ or/and CD8+ reactions; (3) IL-2R and CD4 antigens were expressed in the proliferated lymphocytes stimulated by PHA. Although IL-2R antigen is not a specific marker to certain types of lymphocytes, it has some relations with immunophenotypes of lymphocytes. The functions and effects of IL-2, IL-2R and helper T lymphocytes were also discussed.

CD4 Antigens↗
PubMed1993

[A clinicopathological and immunohistochemical study of 49 cases of necrotizing lymphadenitis].

A clinicopathological and immunohistiochemical study of 49 cases of necrotizing lymphadenitis was made. Twenty-four patients were male and twenty-five female with the M:F ratio of 0.96:1. The patients ranged in age from 9 to 62 years with a mean of 26. Forty-nine patients had superficial lymphadenopathy, and twenty-two were accompanied by fever. The results also showed that there was multifoci necrosis present in the involved lymph nodes, particularly in the cortex or/and paracortex, with variable numbers of small lymphocytes, immunoblasts, histocytes and phagocytes, the latter with phagocytized nuclear debris derived from necrotizing T lymphocytes. However, granulocytes and plasmacytes were generally absent, and B lymphocytes rare. The pathogenesis of this disease remains unknown and the pathogen has not been found by Gram, Giemsa, PAS, Ziehl-Neelsen and Warthin-Starry stain. The diagnosis, differential diagnosis and etiology of this disease are discussed. We support the suggestion that this entity be called "Kikuchi-Fujimoto's disease" rather than "Histiocytic necrotizing lymphadenitis".

Adolescent↗
PubMed1993

Effects of exposure to trinitrotoluene on male reproduction.

A cross-sectional study was performed in 2 plants located in Henan Province in 1990 for observing the reproductive and sexual functions of male workers exposed to trinitrotoluene (TNT). The TNT concentrations in the workplace air, except the packing site, were found to have exceeded MAC (1 mg/m3). TNT exposed male workers complained of more sexual disorders such as impotence, the loss of libido and sexual hypoesthesia than the control group. Compared with the control group, the volume of semen and percentage of motile spermatozoa were found to have significantly decreased, and the sperm malformation incidence increased significantly in TNT exposed workers. The serum testosterone content in TNT exposed male workers was significantly decreased too.

Adult↗
PubMed1993

Acetaldehyde-collagen adducts in N-nitrosodimethylamine-induced liver cirrhosis in rats.

Increased acetaldehyde levels have been found in non-alcoholic liver diseases and an acetaldehyde-collagen adduct has been reported in rats with CCl4-induced cirrhosis. In cytosol and microsomes of rats with cirrhosis produced by N-nitrosodimethylamine, a similar acetaldehyde-protein adduct of approximately 200 kD was recognized by rabbit IgG raised against either an in vitro produced hemocyanin-acetaldehyde adduct or an in vivo occurring P4502E1-acetaldehyde adduct isolated from alcohol-fed rats, as well as by anti-rat collagen (I) IgG. Its immune complexes contained 3 proteins that reacted with the anti-collagen IgG and were digested by collagenase: 2 proteins with molecular weights similar to procollagens alpha 1 and alpha 2, and a beta 1,2(I)-like protein which was readily produced by in vitro modification of cytosol with acetaldehyde.

Acetaldehyde↗