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Biomedical subjects

P Feng

Publications and source records attributed to P Feng.

At least 73 records · Page 4Linked to original sources
PubMed1999

Elevated blood levels of soluble tumor necrosis factor receptors in nasopharyngeal carcinoma: correlation with humoral immune response to lytic replication of Epstein-Barr virus.

Nasopharyngeal carcinoma (NPC) is tightly associated with Epstein-Barr virus (EBV) infection and a heavy infiltration of lymphoid cells in the tumor tissue. Although various lines of evidence have shown that the immune systems of NPC patients have the potential to attack the tumor cells, it is not yet understood how this potential is blocked. In this study we determined the circulatory soluble tumor necrosis factor receptors (sTNFRI and sTNFRII), which are proven to be inhibitory to the anti-tumor effects of tumor necrosis factor-alpha (TNF-alpha), in NPC patients. The serum concentration of both sTNFRI and sTNFRII was determined with an ELISA method, and shown to be significantly higher in 28 NPC patients than in matched healthy controls. This elevation was found to be positively correlated with the serum titers of IgA against EBV early antigens and viral capsid antigens in NPC patients, suggesting that the increased serum concentration of sTNFRI and sTNFRII is possibly due to the EBV infection in NPC tumor cells. This is partly supported by FACS analysis of the circulatory T cells. Phenotypical expression of activation markers such as CD25, CD38, CD69 and CD71 in blood T cells was not significantly different between the NPC and control individuals, indicating the elevation of the sTNFRs is indeed derived from the local immune response in the tumor area. Based on these results, it seems that the increased sTNFRs may act as an inhibitor to decrease the host immune response towards tumor cells in NPC patients.

Adult↗
PubMed1999

[Effect of composite salviae dropping pill on endothelin gene expression in circulating endothelial cells of patients with coronary heart disease].

OBJECTIVE: To explore the effect of composite salviae dropping pill (CSDP) on endothelin (ET-1) gene expression in circulating endothelial cells. METHODS: Seventy cases of stable angina pectoris were randomly divided into 2 groups, the CSDP group and the isosorbide dinitrate (ID) group. They were treated with CSDP and ID respectively, their ET-1 gene expression in endothelial cells of peripheral circulation was measured before and after treatment by reverse transcriptase-Polymerase Chain Reaction and compared between the two groups as well as with that of 30 healthy subjects. RESULTS: Electrophoresis banding of 546 bp cDNA procured from 69 cases of 70 patients was positive, while no positive banding was obtained from healthy subjects. Six cases from the 29 patients treated with CSDP had their banding turned to negative, while in the ID group, no one had turned to negative after treatment. And ET-1 PCR product (absorbed optic density) in the CSDP group was markedly lower than that in the ID group, P < 0.05. CONCLUSION: DSP could inhibit ET-1 gene expression in endothelial cells of peripheral circulation directly.

Aged↗
PubMed1998

Hierarchically ordered oxides

Porous silica, niobia, and titania with three-dimensional structures patterned over multiple length scales were prepared by combining micromolding, polystyrene sphere templating, and cooperative assembly of inorganic sol-gel species with amphiphilic triblock copolymers. The resulting materials show hierarchical ordering over several discrete and tunable length scales ranging from 10 nanometers to several micrometers. The respective ordered structures can be independently modified by choosing different mold patterns, latex spheres, and block copolymers. The examples presented demonstrate the compositional and structural diversities that are possible with this simple approach.

Journal Article↗
PubMed1998

Brainstem carbachol injections in the urethane anesthetized rat produce hippocampal theta rhythm and cortical desynchronization: a comparison of pedunculopontine tegmental versus nucleus pontis oralis injections.

Previous research has demonstrated that brainstem injections of acetylcholine agonists (e.g., carbachol) produced electrophysiological indicators of rapid-eye-movement (REM) sleep in the cat. Recent reports now indicate that this phenomenon may hold true for rats as well. Relatively few reports, however, have examined the effect of these injections on REM indicators in the anesthetized rat, a preparation useful for elucidating underlying neurobiological mechanisms controlling REM sleep processes. The present study compared the effect of injections of carbachol (5 micrograms in 250 nl) into the pedunculopontine tegmental nucleus (PPTg) or the nucleus pontis oralis (NPO) on two tonic indicators of REM sleep in the urethane-anesthetized rat. Namely, changes in the hippocampal EEG and in the cortical EEG. Carbachol injections into either site produced a change in both the hippocampal EEG and cortical EEG to a REM-like state at short latencies. The length of these changes (duration of effect), however, was site-dependent. Thus, PPTg carbachol injections induced significantly longer lasting effects in both the hippocampal and cortical EEG than did NPO injections. The results that brainstem carbachol injections in rats, as in cats, may provide a useful model for investigating tonic REM sleep processes.

Anesthetics, Intravenous↗
PubMed1998

Genotypic and phenotypic changes in the emergence of Escherichia coli O157:H7.

Escherichia coli O157:H7 is a foodborne pathogen distinguished from typical E. coli by the production of Shiga toxins (Stx) and the inability to ferment sorbitol (SOR) and to express beta-glucuronidase (GUD) activity. An allele-specific probe for the GUD gene (uidA) and multilocus enzyme electrophoresis were used to elucidate stages in the evolutionary emergence of E. coli O157: H7. A point mutation at +92 in uidA was found only in O157:H7 and its nonmotile relatives, including a SOR+ O157:H clone implicated in outbreaks of hemolytic-uremic syndrome in Germany. The results support a model in which O157:H7 evolved sequentially from an O55:H7 ancestor, first by acquiring the Stx2 gene and then by diverging into two branches; one became GUD- SOR- , resulting in the O157:H7 clone that spread worldwide, and the other lost motility, leading to the O157:H clone that is an increasing public health problem in Europe.

Escherichia coli Infections↗
PubMed1998

Oxygen transfer characteristics in the compact callus aggregates of Rhodiola sachalinensis.

The effective diffusivity of oxygen in compact callus aggregates (CCA) of Rhodiola sachalinensis was extremely small, varying from 0.34 x 10(-11) to 5.4 x 10(-9) m2/s and increasing with particle diameter. The calculated results indicated that severe oxygen limitations occurred in the CCA aggregates. However, the direct determination of the viability of the cells demonstrated that the CCA aggregates contained a high fraction of viable cells. It was suggested that the tissue differentiation or plasmodesmata within the CCA aggregates may provide capillaries for improving transport of oxygen and other nutrients.

Drugs, Chinese Herbal↗
PubMed1998

[Effect of total saponins of Panax notoginseng (TSPNS) on myocardial intracellular Ca2+ and activity of calcium pump of membrane of sarcoplasmic reticulum in SHR].

A comparative study was conducted on the action of TSPNS, NS and Captopril in treating SHR, with WKY of similar ages taken as normal control. The results demonstrate that TSPNS helps increase the effect of calcium pump on the membrane of sarcoplasmic reticulum, decrease the myocardial intracellular Ca2+ and reduce the mass of the left ventricular muscle.

Animals↗
PubMed1997

Large-cage zeolite structures with multidimensional 12-ring channels

Zeolite type structures with large cages interconnected by multidimensional 12-ring (rings of 12 tetrahedrally coordinated atoms) channels have been synthesized; more than a dozen large-pore materials were created in three different topologies with aluminum (or gallium), cobalt (or manganese, magnesium, or zinc), and phosphorus at the tetrahedral coordination sites. Tetragonal UCSB-8 has an unusually large cage built from 64 tetrahedral atoms and connected by an orthogonal channel system with 12-ring apertures in two dimensions and 8-ring apertures in the third. Rhombohedral UCSB-10 and hexagonal UCSB-6 are structurally related to faujasite and its hexagonal polymorph, respectively, and have large cages connected by 12-ring channels in all three dimensions.

Journal Article↗
PubMed1997

IRAK (Pelle) family member IRAK-2 and MyD88 as proximal mediators of IL-1 signaling.

The interleukin-1 receptor (IL-1R) signaling pathway leads to nuclear factor kappa B (NF-kappaB) activation in mammals and is similar to the Toll pathway in Drosophila: the IL-1R-associated kinase (IRAK) is homologous to Pelle. Two additional proximal mediators were identified that are required for IL-1R-induced NF-kappaB activation: IRAK-2, a Pelle family member, and MyD88, a death domain-containing adapter molecule. Both associate with the IL-1R signaling complex. Dominant negative forms of either attenuate IL-1R-mediated NF-kappaB activation. Therefore, IRAK-2 and MyD88 may provide additional therapeutic targets for inhibiting IL-1-induced inflammation.

Adaptor Proteins, Signal Transducing↗
PubMed1997

The human extracellular matrix gene 1 (ECM1): genomic structure, cDNA cloning, expression pattern, and chromosomal localization.

The Ecm1 gene encodes an 85-kDa protein of unknown function that was originally identified as a secretory protein of the murine osteogenic stromal cell line MN7. This paper describes the isolation of a genomic clone containing the human ECM1 gene from a chromosome 1 cosmid library and the characterization of its exon-intron structure. The protein coding region comprises 10 exons. The ECM1 gene maps at chromosome 1q21 outside the epidermal differentiation complex region. The ECM1 gene appears to be expressed as a 1.8-kb transcript predominantly in placenta and heart, while an additional 1.4-kb alternatively spliced message was detected in tonsils. The full-length human ECM1 transcript contains 1838 bp and has an overall homology of 79.6% with the mouse Ecm1 cDNA. This transcript codes for a protein of 540 amino acids that is 69.4% identical and 81.3% similar to the corresponding mouse protein. The alternatively spliced variant, 1450 bp long, encodes a protein of 415 amino acids.

Alternative Splicing↗
PubMed1997

Decreased dorsal raphe nucleus neuronal activity in adult chloral hydrate anesthetized rats following neonatal clomipramine treatment: implications for endogenous depression.

Although the biological cause of endogenous depression is unknown, one commonly held hypothesis proposes that depression results, in part, from decreased central serotonin (5-HT) neurotransmission. Previous research found that clomipramine (CLI) treatment of neonatal rats produced, in adult rats, a variety of behavioral and physiological dysfunctions resembling those found in human endogenous depression. It was later reported that adult CLI-treated rats exhibited a decreased discharge of 5-HT neurons in the dorsal raphe nucleus (DRN) compared with control rats. This finding, however, was not replicated in subsequent studies that detected differences in DRN receptor function. Several factors were identified that may have contributed to the inability of the latter studies to detect CLI vs. control differences in DRN firing rates and interspike interval histograms (ISIH). Among these were the anesthetic used, the age at which the adult rats were tested, and the location of the recording electrode. The present study controlled these variables by using chloral hydrate anesthesia, testing 'depressed' rats at both 2 and 3 months of age, and verifying electrode location using standard histological techniques. We found that DRN unit firing in 'depressed' rats (0.417 +/- 0.071 spikes/s) was less than half that of 'non-depressed' control rats (i.e. neonatal saline treatment 0.968 +/- 0.12 spikes/s). Additionally, ISIH's indicated that, in addition to the lower firing rate of 5-HT DRN neurons, adult CLI rats had an altered temporal discharge pattern of these neurons. Thus, the ISIH of 5-HT DRN neurons recorded from CLI rats was characterized by a flat distribution suggesting random temporal firing patterns. These results confirm previous findings of decreased DRN firing rates and flat ISIH's in 'depressed' rats and extend previous findings to younger rats of a different strain. The results thereby lend support to the hypothesis of a role for decreased central 5-HT as a substrate for the behavioral deficiencies observed in endogenous depression and suggest that these deficiencies may also result, in part, from a random, rather than orderly, temporal pattern of discharge in these neurons.

Anesthesia↗
PubMed1997

Impact of molecular biology on the detection of foodborne pathogens.

Molecular biological methods that use antibodies and nucleic acids to detect specific foodborne bacterial pathogens were scarcely known a decade and a half ago. Few scientists could have predicted that these tools of basic research would come to dominate the field of food diagnostics. Today, a large number of cleverly designed assay formats using these technologies are available commercially for the detection in foods of practically all major established pathogens and toxins, as well as of many emerging pathogens. These tests range from very simple antibody-bound latex agglutination assays to very sophisticated DNA amplification methods. Although molecular biological assays are more specific, sensitive, and faster than conventional (often cultural) microbiological methods, the complexities of food matrices continue to offer unique challenges that may preclude the direct application of these molecular biological methods. Consequently, a short cultural enrichment period is still required for food samples prior to analysis with these assays. The greater detection sensitivity of molecular biological methods may also affect existing microbiological specifications for foods; this undoubtedly will have repercussions on the regulatory agencies, food manufacturers, and also consumers.

Antibodies, Bacterial↗
PubMed1997

Postnatal ontogeny of the thyrotropin-releasing hormone receptor messenger ribonucleic acids in the rat forebrain.

Postnatal developmental change of the thyrotropin-releasing hormone receptors (TRHR) in the rat forebrain was investigated using TRH binding assays and Northern blot analyses from postnatal day 8 to the age of 2 years. TRH binding assays, with [3H]MeHisTRH as the radioactive ligand, demonstrated that the binding capacity in the forebrain was lowest at postnatal day 8 and increased to a maximum level at postnatal day 20. The TRH binding significantly decreased to adult levels between days 20 and 35, and no significant change was observed thereafter. Northern blot analysis, with a 32P-labeled TRHR cRNA probe, revealed that expression of the TRHR gene in the forebrain was not detectable on day 8 after birth, whereas apparent gene expression could be detected in the anterior pituitary. In contrast to the binding capacities, TRHR mRNA levels were very low until postnatal day 20, and increased significantly between days 20 and 35. No significant alteration in mRNA levels was observed after day 35. These results indicated that: (1) TRH binding capacities in the forebrain increased to a maximum levels between the second and third postnatal week and thereafter decreased to adult level, (2) the levels of TRHR mRNA and the TRH-binding capacities did not correlate in that period, suggesting that the TRHR number in the immature forebrain might be regulated by a posttranscriptional mechanism, and (3) expression of the TRHR gene in the forebrain and pituitary seemed to be regulated differentially during development.

Aging↗
PubMed1997

The detection of thyrotropin-releasing hormone (TRH) and TRH receptor gene expression in Siberian hamster testes.

Thyrotropin-releasing hormone (TRH) from the hypothalamus is the major regulator of TSH synthesis and secretion. Most recently, TRH and TRH receptors (TRH-R), as well as their mRNAs, have been identified in rat testis. To expand our knowledge on the testicular TRH and TRH receptor gene expression in different species, in the present study the mRNA levels of testicular TRH and TRH-R were investigated in Siberian hamsters. To further localize the cellular sites of the gene expression, the animal model was treated with a single injection of ethylene dimethane sulfonate (EDS) (i.p., 80 mg/kg body weight), a compound known as to specifically eliminate testicular Leydig cells. The elimination of Leydig cells induced by EDS treatment was confirmed by histological studies of the testis sections and by serum hormonal analyses, which showed a dramatic reduction of serum testosterone (T) levels and significantly elevated serum LH concentrations. Messenger RNA levels of TRH and TRH-R in the testes were determined by Northern blot analyses quantitated with densitometry scanning. The results showed that specific TRH-R mRNA, 3.8 kb in size, was identified in Siberian hamster testes and the mRNA levels were significantly elevated in the EDS-treated testes compared to the controls (p < 0.01). Testicular TRH mRNA was also detected; however, no significant differences in TRH mRNA levels were found between EDS-treated and control groups. The size of TRH mRNA was characterized as about 1.2 kb in hamster testes, which was smaller than that observed in the rat hypothalamus (1.6 kb) and in the rat testis (2.0 kb). Further studies by RNase H digestion revealed the presence of smaller TRH transcripts in the hamster testes than those in the rat testis. No hybridization signal for TRH mRNA was detected by RNase protection assay, when a rat TRH riboprobe was applied to hamster testis RNA, suggesting the limited homology of TRH gene sequences between these two species. Our results demonstrate that both TRH and TRH-R genes are expressed in Siberian hamster testes, and a significant increase of TRH-R mRNA levels occurs in the Leydig cell eliminated hamster testes. Unlike the rat testicular TRH mRNA mainly detected in Leydig cells, in hamster TRH mRNA could also be detected in other testicular compartment.

Animals↗
PubMed1997

Regulation of the human TRH (hTRH) gene by human thyroid hormone receptor beta 1 (hTR beta 1) mutants.

TRH is negatively regulated by T3 both in the hypothalamic paraventricular nucleus and transient transfection models. Mutations in hTR beta 1 genes are associated with the syndrome of generalized resistance to thyroid hormone. To investigate potential effects of mutant TRs on T3 regulation of the hTRH gene, transient gene expression assays were performed in human neuroblastoma (HTB-11) cells with an hTRH promoter-luciferase construct, wild type (WT) hTR beta 1, and three qualitatively distinct hTR beta 1 mutant forms (ED, OK and PV). In the presence of T3 (10(-9) M), liganded WT-hTR beta 1 inhibited hTRH promoter activity significantly (40%). Cotransfection of each of the two mutants (ED and OK) achieved similar levels of inhibition only at 10 to 100 fold increased T3 concentrations. Of interest, a 10x excess of mutant ED or OK could also exert dominant negative effects upon WT hTR beta 1-T3 mediated inhibitory actions on the hTRH promoter. In contrast, mutant TR-PV exerted neither inhibitory nor dominant negative effects at even higher concentrations of T3. Moreover, all three unliganded mutant forms stimulated TRH promoter activity significantly in the absence of T3, despite their different mutations in the ligand-binding domain (LBD). These data demonstrate that thyroid hormone resistance at the level of TRH gene regulation, due to reduced inhibitory actions of mutant TR-T3 complexes, as well as dominant negative effects upon WT hTR beta 1 mediated inhibition, likely contribute to elevated TSH values observed in the syndrome of thyroid hormone resistance.

Dose-Response Relationship, Drug↗
PubMed1997

Molecular characterization of the gene encoding H antigen in Escherichia coli and development of a PCR-restriction fragment length polymorphism test for identification of E. coli O157:H7 and O157:NM.

Recent outbreaks of disease caused by Escherichia coli O157:H7 have focused much attention on this newly emerged pathogen. Identification of the H7 flagellar antigen is critical for the confirmation of E. coli O157:H7; however, clinical isolates are frequently nonmotile and do not produce detectable H antigen. To further characterize nonmotile isolates (designated NM), we developed a PCR-restriction fragment length polymorphism (PCR-RFLP) test to identify and characterize the gene encoding the H antigen (fliC) in E. coli. The entire coding sequence of fliC was amplified by PCR, the amplicon was restricted with RsaI, and the restriction fragment pattern was examined after gel electrophoresis. Two hundred eighty E. coli isolates representing serotypes O157:H7 and O157:NM, flagellar antigen H7 groups associated with other O serogroups, and all other flagellar antigen groups were analyzed. A single restriction pattern (pattern A) was identified for O157:H7 isolates, O157:NM isolates that produced Shiga toxin (formerly Shiga-like toxin or verotoxin), and 16 of 18 O55:H7 isolates. Flagellar antigen group H7 isolates of non-O157 serotypes had one of three banding patterns distinct from pattern A. A wide variety of patterns were found among isolates of the other 52 flagellar antigen groups; however, none was identical to the O157:H7 pattern. Thirteen of 15 nonmotile strains that did not produce the A pattern had patterns that matched those of other known H groups. The PCR-RFLP in conjunction with O serogroup determination will be useful in identifying E. coli O157:H7 and related strains that do not express immunoreactive H antigen and could be expanded to include other clinically important E. coli strains.

Antigens, Bacterial↗
PubMed1997

[Molecular cloning of the imipenem resistant gene in bacteroides fragilis].

Imipenem, as a representative of-cabapenem, is one of the most effective beta-Lactam agents against Bacteroides, but recently there have been a few reports on the resistant strains of Bacteroides. To explore the mechanism of imipenem resistance (IMPr) at the molecular level, we extracted chromosome DNA of the resistant strains and acquired a 1.7 kb fragment of resistant gene of imipenem. Recombinant plasmid was stably reserved in generation after generation in E. coli DH5. Resistant gene of imipenem was labeled with Dig-11-dUTP by way of random prime, and 40 strains of clinically isolated Bacteroides were detected by the prepared DNA probe. Two IMPr strains showed hybridization signal, whereas 38 IMPr strains did not show such a signal. The result suggests that the Dig-labeled IMPr gene probe can be used in molecular epidemiology for investigating IMPr strains.

Bacteroides fragilis↗