Search PubMed⌕ Search

Biomedical subjects

Z Yan

Publications and source records attributed to Z Yan.

At least 127 records · Page 7Linked to original sources
PubMed1999

[Application of derivative technique in the signal processing of gas chromatography].

An application of derivative technique in the signal processing of gas chromatography(GC) is described. TCD's sensitivity of the derivative GC was 270 kV.L/kg, and its susceptibility was 0.3 microgram/L In comparison with the conventional GC, there was a 7-40 fold increase in sensitivity and a 24-40 fold decrease in susceptibility. The noise of the derivative GC was equal to or smaller than the conventional one. The minimum resolution for a pair of substances most difficulty to be separated in conventional GC, which was separated completely in the derivative GC, was 2.8. The linear range of n-butanol was 10(2) and the peak area correlation coefficient of the derivative GC was 0.9991.

1-Butanol↗
PubMed1999

[Different protein forms of purple membrane produced by Halobacterium halobium under various nutritional condition].

The extremely halophilic bacterium, purple membrane producing Halobacterium halobium strain R1 were cultured in four liquid media which consist of different constituents. After the purple membrane is harvested by ultracentrification and purified by sucrose density gradient ultracentrification, and run on SDS-PAGE, the result of Coomassie blue staining showed different bR protein forms: three bands with molecule weight ranging from 26.0 to 27.5 kD in peptone medium, while only one band with MW 26.0 kD in other three media-complex, synthetic and artificial seawater media, which corresponded to the mature form in peptone medium. The result of Western blotting not only confirmed the different protein forms of Coomassie blue staining in the four media, but also gave additional bands that Coomassie blue can not detect due to its lower sensitivity: 1) in the complex, synthetic and artificial seawater media, a faint 28.0 kD band existed, while in the peptone medium it did not exist; and 2) in the four media, it appeared that a faint 23.0-24.0 kD band exited. The different bR protein forms of purple membrane which result from the difference of nutritional constituents in these four media might be caused by different precursor processing enzymes or different activities of precursor processing enzyme(s) under these different nutritional conditions.

Culture Media↗
PubMed1999

[Screening of acidic xylanase producing strain and studies on its enzyme production conditions].

From 150 fungal strains, the authors found 8 strains contained mainly of xylanase activity over 100 U/mL in which the No. 149 strain was the highest xylanase producer. Which tentatively identified as Aspergillas niger. The appropriate medium composition was as follows: wheat bran hemicellulose 4%; NaNO3 1%; wheat bran 1% prepared in Mandels nutritional solution without (NH4)2SO4 and urea. After cultivated in shake-flask at 28 degrees C-32 degrees C for 60 h, the activity reached the highest value of 357.2 U/mL. The optimum pH of xylanase was 4.6 and it was stable at pH3-11. The fermented broth of strain 149 contained in addition to xylanase (relative activity 100) also included amylase(1.8), mannanase(0.98), beta-xylosidase(0.94) and cellulase(0.17).

Aspergillus niger↗
PubMed1999

[Finding of new FCC1/HN antigenic expressed sequence tag(ESTs) of Plasmodium falciparum].

AIM: To sequence the strong positive clones obtained by immuno-screening of Plasmodium falciparum FCC1/HN lambda gt11 cDNA expression library, and to elucidate the antigenic expressed sequence tags through sequencing the cDNA insert of these positive clones, and new antigenic ESTs could serve as a resource to pursue their corresponding antigen genes. METHODS: cDNA inserts of positive lambda gt11 phage clones were amplified by PCR. The PCR products, after purification, were cloned into the M13 mp18 sequencing vector. Single-stranded M13 DNA was prepared and sequenced. Then the acquired sequences were compared in homologies with EMBL/GenBank database on the PC/GENE software system and searched in NCBI (National Center for Biotechnology Information) GenBank using BLAST (Basic Local Alignment Search Tool) commond. RESULTS: Sequence C03 was part of the known P. falciparum antigenic heat shock protein 70 (Pfhsp70) gene, while the other 5 sequences were new P. falciparum antigenic expressed sequence tags (ESTs). CONCLUSION: The 5 new antigenic ESTs generated could serve as the breaking through points in our efforts to find out new P. falciparum antigen genes.

Animals↗
PubMed1999

[One-stage reconstruction with the pedicle skin flap of forehead for defective tissue of head-neck tumors dissection].

OBJECTIVE: To discuss the feasibility on reconstructing the defective tissue with the pedicle skin flap of forhead after head-neck tumors dissection. METHOD: 14 patients with advanced head-neck tumors were studied, whose defective tissues were reconstructed by their forehead skin flaps. The flap area ranged from 5 cm x 11 cm to 7 cm x 16 cm. RESULT: 2 cases of them were partial necrosis, 3 years and 5 years survival rates were 76.9% and 63.6% respectively. The function of breath through nose or mouth and the function of swallow were satisfactory. CONCLUSION: The forehead skin flap should be a good selection for the reconstruction of defective tissue after basicranial and nasalfacial dissection.

Adolescent↗
PubMed1999

Differential responsiveness to autocrine and exogenous transforming growth factor (TGF) beta1 in cells with nonfunctional TGF-beta receptor type III.

The two major intestinal epithelial cell lineages are columnar fluid-absorbing cells and mucin-producing goblet cells. High levels of transforming growth factor (TGF) beta1 are found surrounding postmitotic cells in the colonic crypt, suggesting that TGF-beta1 mediates the maturation and growth inhibition of both epithelial cell types. However, we now show that the injection of recombinant TGF-beta1 into mice leads to an enrichment of goblet cells, indicating that these normal epithelial cells are resistant to TGF-beta1. In support of this interpretation, each of two independently isolated cell lines modeling normal colon goblet cells was also growth resistant to exogenous TGF-beta1 but made levels of TGF-beta receptor (TbetaR) I, TbetaRII, and TbetaIII mRNA and protein equal to those made by two TGF-beta1-sensitive cell lines. No mutations were found in the alk5 or alk2 forms of TbetaRI or in TbetaRII; these receptors were found on the cell surface, although they could not bind 125I-labeled TGF-beta1. TbetaRIII binds TGF-beta1, concentrates it, and presents it to TbetaRII. The major TbetaRIII form, betaglycan, did not undergo normal posttranslational modification in either of the goblet cell lines and could not bind 125I-labeled TGF-beta1; thus, it was nonfunctional. TGF-beta resistance was overcome by raising TGF-beta1 levels 100-fold, at which point TbetaRII could bind TGF-beta1. Signaling initiated by these higher TGF-beta1 levels was blocked by the expression of dominant negative TbetaRII, demonstrating that TbetaRII and TbetaRI were functional. Cells resistant to exogenous TGF-beta1 maintained functional cell surface TbetaRI and TbetaRII to mediate responses to autocrine TGF-beta1, which controlled the maturation of the adhesion protein integrin beta1. Expression of dominant negative TbetaRII in goblet cells greatly inhibited the conversion of the beta1 integrin from its precursor to its mature form. Thus, in normal intestinal epithelial goblet cells, TbetaRI and TbetaRII can respond to autocrine but not exogenous TGF-beta without the participation of TbetaRIII. Absorptive epithelial cells are growth inhibited by TGF-beta1 both in vivo and in vitro; therefore, the loss of functional TbetaRIIIs on goblet cells allows differential regulation of the two major intestinal epithelial cell types.

Activin Receptors, Type I↗
PubMed1998

Polarity influences the efficiency of recombinant adenoassociated virus infection in differentiated airway epithelia.

To better understand mechanisms that limit rAAV transduction in the lung, we have evaluated several unique features of rAAV infection in polarized primary airway epithelial cultures. rAAV was found to transduce the basolateral surface of airway epithelia 200-fold more efficiently than the apical membrane. These differences in membrane infection correlated with the abundance of apical heparan sulfate proteoglycan (AAV-2 receptor) and virus binding. UV irradiation augmented rAAV transduction greater than 20-fold, only when virus was applied to the apical membrane. Ultrastructural analysis of UV-irradiated primary cultures demonstrated significant changes in microvilli architecture following exposure to 25 J/m2 UV. Although virus binding and the abundance of heparan sulfate proteoglycan were not increased at the apical membrane following UV irradiation, increased receptor-independent endocytosis of fluorescent beads was seen at the apical membrane following UV irradiation. We hypothesize that endocytotic processes associated with apical membrane-specific pathways of viral entry, and/or processing of virus to the nucleus, may be altered following UV irradiation. Interestingly, UV irradiation had an inhibitory effect on rAAV transduction from the basolateral membrane, which correlated with a decrease in the abundance of heparan sulfate proteoglycan at the basal membrane. In summary, these findings suggest that independent pathways of viral transduction may occur in the apical and basolateral compartments of polarized airway epithelia.

Bronchi↗
PubMed1998

[A study of correlation between essential hypertension and HLA-DQA1 alleles].

OBJECTIVE: To analyse the hereditary susceptibility by genotyping of HLA-DQA1 alleles in essential hypertensives. METHODS: The allelic types of HLA-DQA1 were detected by PCR-SSP technic in 52 cases of essential hypertensives and 86 normal individuals as the control. RESULTS: The frequency of HLA-DQA1*0302 allele in hypertensive group was markedly higher than that in normal control group (17.9572 vs 3.5531), but the frequency of HLA-DQA1*0103 allele in normal group was higher than that in hypertensive group. CONCLUSION: HLA-DQA1*0302 may be a correlative gene of essential hypertension, whereas HLA-DQA1*0103 may be a defence gene of hypertension.

Adult↗
PubMed1998

Inwardly rectifying potassium (IRK) currents are correlated with IRK subunit expression in rat nucleus accumbens medium spiny neurons.

Inwardly rectifying K+ (IRK) channels are critical for shaping cell excitability. Whole-cell patch-clamp and single-cell RT-PCR techniques were used to characterize the inwardly rectifying K+ currents found in projection neurons of the rat nucleus accumbens. Inwardly rectifying currents were highly selective for K+ and blocked by low millimolar concentrations of Cs+ or Ba2+. In a subset of neurons, the inwardly rectifying current appeared to inactivate at hyperpolarized membrane potentials. In an attempt to identify this subset, neurons were profiled using single-cell RT-PCR. Neurons expressing substance P mRNA exhibited noninactivating inward rectifier currents, whereas neurons expressing enkephalin mRNA exhibited inactivating inward rectifier currents. The inactivation of the inward rectifier was correlated with the expression of IRK1 mRNA. These results demonstrate a clear physiological difference in the properties of medium spiny neurons and suggest that this difference could influence active state transitions driven by cortical and hippocampal excitatory input.

Animals↗
PubMed1998

E2F3 activity is regulated during the cell cycle and is required for the induction of S phase.

Previous work has demonstrated the important role of E2F transcription activity in the induction of S phase during the transition from quiescence to proliferation. In addition to the E2F-dependent activation of a number of genes encoding DNA replication activities such as DNA Pol alpha, we now show that the majority of genes encoding initiation proteins, including Cdc6 and the Mcm proteins, are activated following the stimulation of cell growth and are regulated by E2F. The transcription of a subset of these genes, which includes Cdc6, cyclin E, and cdk2, is also regulated during the cell cycle. Moreover, whereas overall E2F DNA-binding activity accumulates during the initial G1 following a growth stimulus, only E2F3-binding activity reaccumulates at subsequent G1/S transitions, coincident with the expression of the cell-cycle-regulated subset of E2F-target genes. Finally, we show that immunodepletion of E2F3 activity inhibits the induction of S phase in proliferating cells. We propose that E2F3 activity plays an important role during the cell cycle of proliferating cells, controlling the expression of genes whose products are rate limiting for initiation of DNA replication, thereby imparting a more dramatic control of entry into S phase than would otherwise be achieved by post-transcriptional control alone.

CDC2-CDC28 Kinases↗
PubMed1998

Cdc6 is regulated by E2F and is essential for DNA replication in mammalian cells.

Cdc6 has a critical regulatory role in the initiation of DNA replication in yeasts, but its function in mammalian cells has not been characterized. We show here that Cdc6 is expressed selectively in proliferating but not quiescent mammalian cells, both in culture and within tissues of intact animals. During the transition from a growth-arrested to a proliferative state, transcription of mammalian Cdc6 is regulated by E2F proteins, as revealed by a functional analysis of the human Cdc6 promoter and by the ability of exogenously expressed E2F proteins to stimulate the endogenous Cdc6 gene. Immunodepletion of Cdc6 by microinjection of anti-Cdc6 antibody blocks initiation of DNA replication in a human tumor cell line. We conclude that expression of human Cdc6 is regulated in response to mitogenic signals though transcriptional control mechanisms involving E2F proteins, and that Cdc6 is required for initiation of DNA replication in mammalian cells.

Animals↗
PubMed1998

Genetic dissection of retinal development.

Retinal development depends on complex interactions between products of thousands of genes and numerous cellular and environmental factors. We are using novel quantitative genetic methods to map and characterize genes that are responsible for the pervasive quantitative differences in the architecture of the eye and the retina. These genes, known as quantitative trait loci (QTLs), may also determine susceptibility to common eye diseases. To map QTLs that generate variation among normal individuals we have analyzed several traits in a wide variety of mice, including standard inbred strains, recombinant inbred strains, wild mice, F1 hybrids and intercross progeny. Here we review this approach and give three specific examples of how genes with well-defined functions in retinal development are being mapped and characterized.

Animals↗
PubMed1998

Expression of intercellular adhesion molecule-1 in immune response of inner ear.

To understand the role of intercellular adhesion molecule-1 (ICAM-1) in immune response of the inner ear, inner ear immune response was induced in rats by inoculation of keyhole limpet hemocyanine (KLH) into the scala tympani of the animals who had been systemically sensitized. The expression of ICAM-1 in the inner ear was immunohistochemically examined. ICAM-1 was found in the epithelium of the spiral modiolar vein (SMV) with its collecting venules (CVs) as early as 6 h after challenge. Expression of ICAM-1 was observed on the epithelium of the endolymphatic sac (ES) and perisaccular region at 12 h. The intensity of ICAM-1 staining reached its peak within 24-48 h in these sites of the inner ear. By day 28, most specimens were devoid of appreciable staining for ICAM-1. Our study demonstrates that adhesion molecules play an important role in extravasation of inflammatory cells from the systemic circulation in the process of inner ear immune response. It also shows that cytokines that control expression of adhesion molecules may be released by cells outside ES, besides those cells in the ES.

Animals↗
PubMed1998

Aborted leiomyosarcoma after treatment with leuprolide acetate.

BACKGROUND: Leuprolide acetate has been used to decrease uterine size and shrink leiomyomata. In carefully selected patients, its treatment benefits are well recognized. However, if leuprolide acetate is inadvertently given to a patient with an unsuspected leiomyosarcoma, complications may occur. CASE: A patient presumed to have leiomyomata was treated with monthly injections of leuprolide acetate. In the third month of treatment, unusual manifestations, including increased bleeding, aborting mass, urinary retention, and severe pain, occurred suggesting a possible malignancy and requiring immediate operation. CONCLUSION: The use of leuprolide acetate can delay the diagnosis and treatment of leiomyosarcoma and thus may increase the risk of morbidity and affect the treatment outcome of patients with leiomyosarcoma. The histologic changes ascribed to leuprolide acetate treatment in leiomyomata also were seen in this leiomyosarcoma.

Antineoplastic Agents, Hormonal↗
PubMed1998

Evidence for the preferential localization of glutamate receptor-1 subunits of AMPA receptors to the dendritic spines of medium spiny neurons in rat striatum.

Although immunohistochemical studies have typically found the perikarya of striatal projection neurons to be devoid of immunohistochemical labelling for the GluR1 AMPA type glutamate receptor subunit, the striatal neuropil is rich in GluR1 immunolabelling and in situ hybridization histochemistry has indicated the presence of GluR1 message in many striatal neurons. To explore the possibility that GluR1 subunits may be synthesized by many striatal projection neurons, but selectively localized to their dendrites, we have used light-microscopic and electron-microscopic immunohistochemistry in combination with single-cell reverse transcription-polymerase chain reaction. Light-microscopic immunohistochemical studies confirmed the presence of abundant GluR1 immunoreactivity in the striatal neuropil in rats. Perikaryal labelling was restricted to neurons previously identified as parvalbuminergic neurons. Single-cell reverse transcription-polymerase chain reaction for individual striatal neurons in rats confirmed that most striatal projection neurons (i.e. containing either or both substance P message or enkephalin message) make GluR1 message. For example, 94% of enkephalin-containing neurons, 75% of substance P-containing neurons, and 87% of enkephalin and substance P co-containing neurons expressed GluR1 messenger RNA. Electron-microscopic immunohistochemistry revealed that GluR1 immunolabelling was prominent in 61% of dendritic spines and 53% of dendritic shafts. While prominent perikaryal GluR1 immunolabelling was observed only in a small population of interneurons, sparse perikaryal GluR1 immunolabelling was found associated with the rough endoplasmic reticulum, the Golgi apparatus, the outer membranes of the mitochondria, and the outer envelope of the nucleus of about 30% of striatal projection neurons (identified by their non-indented nuclei). These results indicate that striatal projection neurons selectively target GluR1 subunits to their spines and dendritic shafts. Our finding has implications for the functioning of striatal projection neurons and for the general issue of whether neurons can control the subcellular localization of glutamate receptors.

Animals↗