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J Zheng

Publications and source records attributed to J Zheng.

At least 127 records · Page 7Linked to original sources
PubMed2000

Nitrogen Adsorption Studies of PAN-Based Activated Carbon Fibers Prepared by Different Activation Methods.

Polyacrylonitrile (PAN)-based activated carbon fibers (ACFs) prepared by various activation methods were characterized using low-temperature nitrogen adsorption over a wide relative pressure from 10(-6) to 1. Nitrogen adsorption is a standard tool for determination of porous structure parameters. In the present work, we carried out extensive adsorption studies of a series of PAN-ACFs activated by different methods. It was shown that the high-resolution alpha(S) plot provided valuable information about structural properties of samples under study. The pore size distributions of samples under study were calculated by employing the regularization method according to density functional theory. By these analyses, the pore development and the dominant pores of samples prepared by different methods can be clearly observed. Moreover, the adsorption measurement could provide profound insight into the structural heterogeneity of the ACFs. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Neuropeptide Y secretion from bovine chromaffin cells inhibits cyclic AMP accumulation.

Neuropeptide Y (NPY) is secreted from bovine chromaffin cells in response to nicotinic receptor stimulation and may exhibit autocrine, paracrine or endocrine effects. Stimulation of bovine chromaffin cells with nicotine followed by the addition of forskolin (FSK) to the media results in a decrease in cyclic AMP accumulation compared to that seen in the absence of nicotine. Pertussis toxin (PTX) treatment or the addition of BIBP 3226, a selective NPY Y1 receptor antagonist prevents the inhibitory effect of nicotine. Fractionation of media obtained from cells stimulated with nicotine reveals an NPY-like substance that inhibits FSK-stimulated cAMP accumulation. Thus, an NPY-like substance can be secreted from bovine chromaffin cells in quantities sufficient to inhibit FSK-stimulated cAMP accumulation. These results suggest that NPY can act in an autocrine fashion to regulate chromaffin cell function.

Animals↗
PubMed2000

Glc7p protein phosphatase inhibits expression of glutamine-fructose-6-phosphate transaminase from GFA1.

Inhibitor-1 (I-1) is a specific inhibitor of protein phosphatase-1 (PP1). We assayed the ability of I-1 to inhibit Saccharomyces cerevisiae PP1, Glc7p, in vivo. Glc7p like other PP1 catalytic subunits associates with a variety of noncatalytic subunits, and Glc7p holoenzymes perform distinct physiological roles. Our results show that I-1 inhibits Glc7p holoenzymes that regulate transcription and mitosis, but holoenzymes responsible for meiosis and glycogen metabolism were unaffected. Additionally, we exploited a genetic screen for mutants that were dependent on I-1 to grow. This scheme can identify processes that are negatively regulated by Glc7p-catalyzed dephosphorylation. In this paper I-1-dependent gfa1 mutations were analyzed in detail. GFA1 encodes glutamine-fructose-6-phosphate transaminase. One or more phosphorylated proteins activate GFA1 transcription because the pheromone response and Pkc1p/mitogen-activated protein kinase pathways positively regulate GFA1 transcription. Our findings show that an I-1-sensitive Glc7p holoenzyme reduces GFA1 transcription. Therefore, GFA1 is a member of a growing list of genes that are negatively regulated by Glc7p dephosphorylation.

Catalysis↗
PubMed2000

Five missense variants in the amino-terminal domain of the glucocorticoid receptor: no association with puerperal psychosis or schizophrenia.

Steroid hormone administration causes behavior changes in many and psychosis in a few. The clinical features suggest that genetic variants of the glucocorticoid receptor or cofactors could produce susceptible subpopulations who react adversely to hormonal cascades. To investigate this possibility, coding and splice site sequences of the glucocorticoid receptor were scanned for single nucleotide polymorphisms in genomic DNA samples from 100 schizophrenics (86 Caucasians and 14 African-Americans) and 40 Caucasians with puerperal psychosis. Five amino acid substitutions were found in the amino-terminal domain at frequencies of 0.6 to 3.8% in Caucasians: R23K, F29L, L112F, D233N, and N363S. In addition, four silent nucleotide changes were found: E22E, K293K, D677D, and N766N; a transversion in intron 4 occurred beyond the splice junction. None of these variants can be linked to these disorders at present. However, the N363S variant contributes a new potential phosphorylation site and has been associated with increased body mass and reduced bone mineral density [Huizenga et al., 1998], so it is possible that the other missense variants confer traits that currently are unrecognized. Comparisons to natural glucocorticoid receptor mutants in the familial glucocorticoid resistance syndrome and steroid resistant leukemias suggest that amino acid substitutions at highly conserved residues may cause severe functional defects and serious illness, while changes at less conserved sites produce lesser alterations and milder disease.

Amino Acid Sequence↗
PubMed2000

Prestin is the motor protein of cochlear outer hair cells.

The outer and inner hair cells of the mammalian cochlea perform different functions. In response to changes in membrane potential, the cylindrical outer hair cell rapidly alters its length and stiffness. These mechanical changes, driven by putative molecular motors, are assumed to produce amplification of vibrations in the cochlea that are transduced by inner hair cells. Here we have identified an abundant complementary DNA from a gene, designated Prestin, which is specifically expressed in outer hair cells. Regions of the encoded protein show moderate sequence similarity to pendrin and related sulphate/anion transport proteins. Voltage-induced shape changes can be elicited in cultured human kidney cells that express prestin. The mechanical response of outer hair cells to voltage change is accompanied by a 'gating current', which is manifested as nonlinear capacitance. We also demonstrate this nonlinear capacitance in transfected kidney cells. We conclude that prestin is the motor protein of the cochlear outer hair cell.

Amino Acid Sequence↗
PubMed2000

Cytokine-stimulated, but not HIV-infected, human monocyte-derived macrophages produce neurotoxic levels of l -cysteine.

Approximately one-quarter of individuals with AIDS develop neuropathological symptoms that are attributable to infection of the brain with HIV. The cognitive manifestations have been termed HIV-associated dementia. The mechanisms underlying HIV-associated neuronal injury are incompletely understood, but various studies have confirmed the release of neurotoxins by macrophages/microglia infected with HIV-1 or stimulated by viral proteins, including the envelope glycoprotein gp120. In the present study, we investigated the possibility that l -cysteine, a neurotoxin acting at the N-methyl-d -aspartate subtype of glutamate receptor, could contribute to HIV-associated neuronal injury. Picomolar concentrations of gp120 were found to stimulate cysteine release from human monocyte-derived macrophages (hMDM) in amounts sufficient to injure cultured rat cerebrocortical neurons. TNF-alpha and IL-1beta, known to be increased in HIV-encephalitic brains, as well as a cellular product of cytokine stimulation, ceramide, were also shown to induce release of cysteine from hMDM in a dose-dependent manner. A TNF-alpha-neutralizing Ab and an IL-1betaR antagonist partially blocked gp120-induced cysteine release, suggesting that these cytokines may mediate the actions of gp120. Interestingly, hMDM infected with HIV-1 produced significantly less cysteine than uninfected cells following stimulation with TNF-alpha. Our findings imply that cysteine may play a role in the pathogenesis of neuronal injury in HIV-associated dementia due to its release from immune-activated macrophages but not virus-infected macrophages. Such uninfected cells comprise the vast majority of mononuclear phagocytes (macrophages and microglia) found in HIV-encephalitic brains.

Animals↗
PubMed2000

Speciation of selenium compounds with ion-pair reversed-phase liquid chromatography using inductively coupled plasma mass spectrometry as element-specific detection.

For selenium speciation analysis, the hyphenation of chromatographic separation with element-specific detection has proved a useful technique. A powerful separation system, which is capable of resolving several biologically and environmentally important selenium compounds in a single column, is greatly needed. However, that has been difficult to achieve. In this paper eight selenium compounds, namely, selenite [Se(IV)], selenate [Se(VI)], selenocystine (SeCys), selenourea (SeUr), selenomethionine (SeMet), selenoethionine (SeEt), selenocystamine (SeCM) and trimethylselenonium ion (TMSe+), were separated by using mixed ion-pair reagents containing 2.5 mM sodium 1-butanesulfonate and 8 mM tetramethylammonium hydroxide as a mobile phase. The separation of these anionic, cationic and neutral organic selenium compounds on a LiChrosorb RP18 reversed-phase column took only 18 min at a flow-rate of 1.0 ml/min with isocratic elution, and baseline separation among the six organic Se compounds was achieved. Inductively coupled plasma mass spectrometry (ICP-MS) was employed as element-specific detection. A comparison of ICP-MS signal intensity obtained with a Barbington-type nebulizer and with an ultrasonic nebulizer (USN) was made. Different signal enhancement factors were observed for the various selenium compounds when a USN was used. The speciation technique was successfully applied to the study on chemical forms of selenium in a selenium nutritional supplement. Selenomethionine was found to be the predominant constituent of selenium in the supplement.

Chromatography, High Pressure Liquid↗
PubMed2000

Autocrine expression and ontogenetic functions of the PACAP ligand/receptor system during sympathetic development.

The superior cervical ganglion (SCG) is a well-characterized model of neural development, in which several regulatory signals have been identified. Vasoactive intestinal peptide (VIP) has been found to regulate diverse ontogenetic processes in sympathetics, though functional requirements for high peptide concentrations suggest that other ligands are involved. We now describe expression and functions of pituitary adenylate cyclase-activating polypeptide (PACAP) during SCG ontogeny, suggesting that the peptide plays critical roles in neurogenesis. PACAP and PACAP receptor (PAC(1)) mRNA's were detected at embryonic days 14.5 (E14.5) through E17.5 in vivo and virtually all precursors exhibited ligand and receptor, indicating that the system is expressed as neuroblasts proliferate. Exposure of cultured precursors to PACAP peptides, containing 27 or 38 residues, increased mitogenic activity 4-fold. Significantly, PACAP was 1000-fold more potent than VIP and a highly potent and selective antagonist entirely blocked effects of micromolar VIP, consistent with both peptides acting via PAC(1) receptors. Moreover, PACAP potently enhanced precursor survival more than 2-fold, suggesting that previously defined VIP effects were mediated via PAC(1) receptors and that PACAP is the more significant developmental signal. In addition to neurogenesis, PACAP promoted neuronal differentiation, increasing neurite outgrowth 4-fold and enhancing expression of neurotrophin receptors trkC and trkA. Since PACAP potently activated cAMP and PI pathways and increased intracellular Ca(2+), the peptide may interact with other developmental signals. PACAP stimulation of precursor mitosis, survival, and trk receptor expression suggests that the signaling system plays a critical autocrine role during sympathetic neurogenesis.

Animals↗
PubMed2000

Identification of an NPY-Y1 receptor subtype in bovine chromaffin cells.

Bovine chromaffin cells have been used in a variety of studies designed to reveal different aspects of neuropeptide Y (NPY) action. Pharmacological data have defined five NPY receptor subtypes, only one of which (Y3) has not been cloned. Some studies with bovine chromaffin cells have concluded that the effects of NPY on this cell type are mediated by the Y3 subtype. Previous work from our laboratory demonstrates that a Y1 subtype mediates the effect of NPY in this tissue. In the current studies we provide further evidence for the existence of the Y1 subtype in bovine chromaffin cells. BIBP3226, the selective Y1 antagonist, potently displaces [125I]NPY from its binding site IC50 = 1.91 x 10(-9) M. Moreover, [125I]BIBP3226 binds to bovine chromaffin cell membranes with high affinity (IC50 = 5.9 x 10(-8) M). Examination of BIBP3226 antagonism of NPY inhibition of forskolin stimulated cyclic AMP accumulation reveals that it is a competitive antagonist with a K(B) similar to the IC50 for [125I]BIBP3226 binding. Northern blot analysis using a porcine cDNA clone for the Y1 subtype demonstrates a 3.5-kb mRNA species in chromaffin cells. These data identify the bovine chromaffin cell NPY receptor as a Y1 subtype.

Animals↗
PubMed2000

Induction of apoptotic cell death and in vivo growth inhibition of human cancer cells by a saturated branched-chain fatty acid, 13-methyltetradecanoic acid.

A saturated branched-chain fatty acid, 13-methyltetradecanoic acid (13-MTD), was purified from a soy fermentation product, which was used by many cancer patients as a treatment supplement. Our preliminary study indicated that 13-MTD could induce cell death in human cancer cell lines K-562, MCF7, DU 145, NCI-SNU-1, SNU-423, NCI-H1688, BxPC3, and HCT 116. The ID50 dosage of 13-MTD for these tumor cells ranged from 10 to 25 microg/ml. Further investigation revealed that 13-MTD caused tumor cell death through rapid induction of apoptosis, which could be detected 2 h after the treatment of tumor cells with 13-MTD. Xenograft tumors of prostate carcinoma cell line DU 145 and hepatocarcinoma LCI-D35 were orthotopically implanted into nude mouse prostate and liver, respectively. 13-MTD was administered p.o. once daily to the implanted mice for approximately 40 days. Our results showed that 13-MTD could effectively inhibit the growth of orthotopic tumor implants of both cell lines compared with control groups. The average inhibition rate was 84.6% for DU 145 and 65.2% for LCI-D35 (P < 0.01). LD50 test results showed that mice could well sustain the oral feeding of 5 g/kg/day without observable anomaly. Our preliminary data demonstrated that 13-MTD could effectively inhibit in vitro and in vivo growth of various cancer cell lines by inducing apoptosis without significant toxic side effects, suggesting 13-MTD as a potential candidate for chemotherapy of human cancers.

Animals↗
PubMed2000

Circular dichroism and resonance raman comparative studies of wild type cytochrome c and F82H mutant.

The UV-visible, circular dichroism (CD), and resonance Raman (RR) spectra of the wild type yeast iso-1-cytochrome c (WT) and its mutant F82H in which phenylalanine-82 (Phe-82) is substituted with His are measured and compared for oxidized and reduced forms. The CD spectra in the intrinsic and Soret spectral region, as well as RR spectra in high, middle, and low frequency regions, are discussed. From the analysis of the spectra, it is determined that in the oxidized F82H the two axial ligands to the heme iron are His-18 and His-82 whereas in the reduced form the sixth ligand switches from His-82 to Met-80 providing the coordination geometry similar to that of WT. Based on the spectroscopic data, the conclusion is that the porphyrin macrocycle is less distorted in the oxidized F82H compared to the oxidized WT. Similar distortions are present in the reduced form of the proteins. Frequency shifts of Raman bands, as well as the decrease of the alpha-helix content in the CD spectra, indicate more open conformation of the protein around the heme.

Amino Acid Substitution↗
PubMed2000

Microdialysis sampling coupled to HPLC for transdermal delivery study of ondansetron hydrochloride in rats.

The transdermal delivery of ondansetron hydrochloride (ON) solution in propylene glycol (PG) with a widely used penetration enhancer, oleic acid (OA), was studied in rats by a microdialysis sampling technique. Dialysate samples collected from the probe were directly injected into the HPLC system without any pre-treatment and no interference occurred in the blank sample. A good linearity between the standard concentrations and peak areas within the calibration range was achieved. In vivo recovery (32.52 +/- 1.8%) of the probe was assessed with the retrodialysis method, which was used to calculate the ON concentration in the dermis. Oleic acid at the concentrations of 2% and 5% (w/v) increased the steady-state delivery rate from 0.001 to 0.030 and 0.058 microg/h, respectively. OA proved to be an effective enhancer for transdermal delivery of ON in rats.

Administration, Cutaneous↗
PubMed2000

Comparison of 3-D stereoscopic MR imaging with pre and post lesion recording in pallidotomy.

OBJECTIVES: A quantitative on-line analysis of electrical activity in the pallidum of Parkinsonian patients has been developed to determine the focal point of lesioning. Additional recordings are made after the lesioning, to assess residual neural activity. A 3-D volume stereoscopic image system is proposed to display the complex anatomy and to superimpose the electrophysiological data into this system. The purpose of this study is to understand the complex pathophysiology in real-time anatomic/image space and determine the location and effect of lesioning residual energy sites. MATERIAL AND METHODS: Thirty patients undergoing 41 pallidotomies are presented. Neuronal activity from the pallidum is recorded using a semi-microelectrode. Based on this activity, lesioning is performed. Post-lesion recordings are made to determine the necessity of additional lesioning. 3-D volume MR images are acquired pre and postoperatively and compared for accuracy of lesion sites. A 3-D stereoscopic image system has been developed to depict basal ganglia geometry in the last 5 patients. Electrophysiological data are superimposed on this image system to show the surgeon the virtual position of the electrode tip. RESULTS: A stereoscopic 3-D volume MR image system has been developed. This system more efficiently and accurately visualizes and records the coordinates of high neural activity in the pallidum and post lesion residual activity. Post-lesion power analysis was carried out in 30 patients. Additional lesions were indicated in 8 and different trajectories in 6. CONCLUSION: Real-time visualization of neural recording, both pre and post-lesioning during pallidotomy, facilitates the surgeon's understanding of the spatiotemporal relationships of pathophysiological properties within the globus pallidus.

Adult↗
PubMed2000

A novel association between the human heat shock transcription factor 1 (HSF1) and prostate adenocarcinoma.

A search for differentially expressed genes in a pair of nonmetastatic (PC-3) versus metastatic variant (PC-3M) human prostate carcinoma cell lines led to identification of the human heat shock factor (HSF1) as an overexpressed gene product in PC-3M cells. Analysis of primary prostate cancer specimens indicated that HSF1 is generally up-regulated in most of the malignant prostate epithelial cells relative to the normal prostate cells. Among the known effectors of HSF1 action, constitutive levels of HSP70 and HSP90 are not significantly altered by the naturally elevated expression of HSF1 as in PC-3M cells or by transduced overexpression of HSF1 in PC-3 cells. The basal levels of HSP27 in both cases are, however, consistently increased by two- to threefold. With respect to response to heat shock, high basal concentration of HSP90 is not further enhanced in these cells, and HSP70 is up-regulated irrespective of HSF1 level. Heat shock, however, causes an increase in HSP27 when HSF1 is up-regulated, except when the expression of HSF1 is already too high. These results document for the first time that HSF1 is overexpressed in human prostate cancer cells, at least one consequence of which in the prostate cancer cell lines tested is stimulation of both basal and stress-induced expression of HSP27, an important factor in cell growth, differentiation, or apoptosis.

Adenocarcinoma↗
PubMed2000

Aortic root replacement by ministernotomy: technique and potential benefit.

BACKGROUND: Although minimally invasive surgical procedures have aroused much interest in cardiac surgery, difficulty still exists with its application in most of the operations on great arteries. This report summarizes our initial experience of aortic root replacement by a superior ministernotomy in terms of operative indications, operative techniques, and potential benefits. METHODS: Between July 1999 and September 1999, 8 patients who were diagnosed with Marfan syndrome with aortic valve regurgitation underwent aortic root replacements with composite grafts. Clinical characteristics, in-hospital outcomes, and postoperative stay of these patients were compared with data of patients who had undergone Bentall procedure by standard median sternotomy from January to September 1999. RESULTS: There was no death in either group of patients. Demographics were similar between the two groups of patients. In the mini-incision group, the mediastinal drainage was significantly less than the standard incision group. The mean operating time was significantly longer than that in the standard incision group. The cardiopulmonary bypass time and aortic cross-clamping time were similar in both groups of patients. The mean intubation time, postoperative blood transfusion amount, duration of intensive care unit stay and postoperative hospital stay were less than that of the standard incision group; however, they all showed no statistical significant difference. CONCLUSIONS: Aortic root replacement by a superior ministernotomy in cardiopulmonary bypass with cannulas through the femoral artery and femoral vein or right atrium is a safe, reliable procedure with excellent exposure. The procedure provides a potential benefit of less trauma, quick recovery, and reduction of mediastinal drainage and reduction of blood transfusion.

Adult↗
PubMed2000

Isolation of cochlear inner hair cells.

In order to identify hair cell specific genes, it is essential to obtain isolated hair cells in quantity. While whole-cell recordings have been made from isolated inner hair cells (IHCs) from guinea pigs, detailed methods for obtaining a fairly large amount of isolated inner hair cells have not been published. Here we describe a protocol that can yield a fairly large amount of isolated gerbil IHCs. This technique can provide sufficient numbers of solitary IHCs for either electrophysiological studies of the cell's membrane properties or identifying genes related to IHC functions using techniques of molecular biology.

Animals↗
PubMed2000

Gating rearrangements in cyclic nucleotide-gated channels revealed by patch-clamp fluorometry.

Site-specific fluorescence recordings have shown great promise in understanding conformational changes in signaling proteins. The reported applications on ion channels have been limited to extracellular sites in whole oocyte preparations. We are now able to directly monitor gating movements of the intracellular domains of cyclic nucleotide-gated channels using simultaneous site-specific fluorescence recording and patchclamp current recording from inside-out patches. Fluorescence signals were reliably observed when fluorophore was covalently attached to a site between the cyclic nucleotide-binding domain and the pore. While iodide, an anionic quencher, has a higher quenching efficiency in the channel's closed state, thallium ion, a cationic quencher, has a higher quenching efficiency in the open state. The state and charge dependence of quenching suggests movements of charged or dipolar residues near the fluorophore during CNG channel activation.

Animals↗