Biomedical subjects

Z Yan

Publications and source records attributed to Z Yan.

At least 199 records · Page 11Linked to original sources

PubMed1995

[A new zoonosis--investigation of Gardnerella vaginalis disease of fox. II. Identification of pathogenic bacteria].

16 strains isolated from aborted foetus and vaginal exeretions of foxes were used for examination of cell morphology including fine structure of the cell wall and septa, test for homolysis, biochemical reactions and analysis of G+C content of the bacterial DNA. The cells are pleomorphic bacilli and coccobacilli, Gram stain reaction appear positive to variable, catalse and oxidase-negative, with a fermentative type of glucose metabolism, giving acetic and lactic acid as the major end products of fermentation. It's differentiated from the human strains of G. vaginalis by its less fastidious in growth requirements and being facultatively anaerobic to aerobic. We propose the name: a new subspecies--Gardnerella vaginalis subsp. fox, the type strain is U80.

Animals↗

PubMed1995

[Studies on elastase from Flavobacterium. I. Strain screening and enzyme purification].

132 strains bacteria secreting extracellular elastase were isolated from soil samples, 5 of them possessed considerably high elastiolytic activity of more than 100 u/ml. The highest-yield strain No. 17-87 was characterized as Flavobacterium odoratum, studies on the condition of elastase production revealed that its optimum carbohydrate and nitrogen source were glucose and casein respectively, and that it could utilize fowl ferther meal and wheat bran to give 80% relative yield. The culture exhibited maximum elastase activity at 26 degrees C for 21 hours, the productivity could be increased when the aeration was improved. The PAGE-homogenous elastase preparation was obtained from the culture broth by (NH4)2SO4 fractionation, DEAE-cellulose column chromatography and gel filtration on Sephadex G-75. The molecular weight was determined to be 21380 by SDS-PAGE, the elastiolytic activity was optimal at pH7.4 and 50 degrees C. The enzyme was stable over the range of pH4.5-9.5 and below 40 degrees C, but the activity was inhibited completely by Fe3+, Zn2+, Cu2+, Cr3+, Co2+, Ni2+, Hg2+, Ag+.

Flavobacterium↗

PubMed1995

[The comparison of positive rates and clinical significance of 8 bronchodilator testing parameters sarcoidosis].

Twenty asthmatic patients (with mild to severe attacks) were examined with bronchodilator test. Eight parameters, FVC, FEV1, PEF, FEF25-75%, FEF25-75% after inhaling bronchodilator (FEF25-75% Iso), thoracic gas volume (Vtg), airway resistance (Raw) and specific conductance (SGaw), were investigated, compared and analysed. The results showed that the positive rate (PR) of FEV1, the most commonly used parameter at present, was only 70%; the PR of two new parameters FEF 25-75% Iso and SGaw were 95% respectively, the change rate (%) of FEV1 was significantly related to that of many other parameters. The pathophysiology and clinical significance of each parameter were discussed.

Adult↗

PubMed1995

[Basic study on evaluation of the fundus with monochromatic photography].

By using the monochromatic fundus photographic system we developed, fundus pictures of 93 normal subjects were taken under the illumination of 10 lights with varying wavelengths. A densitometer was used for evaluating these photographic results. Optimal illumination lights were selected respectively for photography of different layers of fundus details. The results showed that the degrees of contrast at the macula, optic nerve fiber layer, physiological cup of papilla, retinal artery and vein, optic nerve head, choroid striae are the highest under the illumination of light with wavelength 478nm, 478nm, 530nm, 570nm, 628nm and 628nm respectively. The visibility of nerve fiber layer in the subjects over 50 years old is the highest under the illumination of light with a wavelength of 530nm. However, the degrees of contrast of all their fundus structural details, especially the macula and nerve fiber layer, are lower than those of subjects under 50 years old photographed with the corresponding lights with optimal wavelengths (P < 0.01).

Adolescent↗

PubMed1994

Structural requirements of platelet chemokines for neutrophil activation.

Using recombinantly expressed proteins and synthetic peptides, we examined the structural/functional features of the platelet chemokines, neutrophil-activating peptide-2 (NAP-2) and platelet factor 4 (PF4); that were important in their activation of neutrophils. Previous studies with the chemokine interleukin-8 (IL-8) had shown that the N-terminal region preceding the first cysteine residue was critical in defining neutrophil-activating properties. We examined whether NAP-2 and PF4 had similar structural requirements. In the Ale-glu-leu-arg (AELR) N-terminus of NAP-2, substitution of E or R abolished Ca2+ mobilization and elastase secretion. Unlike the parent molecule PF4, AELR/PF4, the hybrid formed by replacing the N-terminal sequence of PF4 before the first cysteine residue with the homologous sequence of NAP-2, stimulated Ca2+ mobilization and elastase secretion. Furthermore, the effect of amino acid substitutions in the ELR motif differed from those seen with NAP-2 in that conserved substitutions of E or R in NAP-2 abolished activity, but only reduced neutrophil activation in the hybrid. These studies show that just as with IL-8, the N-termini of NAP-2 and PF4 are critical for high-level neutrophil-activating function. Desensitization studies provided information on receptor binding. NAP-2, which binds almost exclusively to the type 2 IL-8 receptor (IL-8R), did not desensitize neutrophils to activation by IL-8 because IL-8 could bind to and activate via both type 1 and 2 IL-8R. AELR/PF4 appears to bind to both types of receptors because it desensitized neutrophils to NAP-2 activation; but was not desensitized by NAP-2, and because it desensitized to and was desensitized by IL-8. Thus, although NAP-2 and AELR/PF4 share approximately 60% amino acid homology, they have different receptor affinities. Studies were performed to define the role of the C-termini of these platelet chemokines in receptor binding. Heparin and a monoclonal antibody specific for the heparin-binding domain of PF4 both inhibited Ca2+ mobilization and elastase release, further suggesting that the C-terminus of these chemokines is important in receptor binding. Synthetic NAP-2(51-70) failed to mobilize Ca2+, whereas PF4(47-70) and PF4(58-70) induced Ca2+ mobilization and secretion of elastase at high concentrations. Pertussis toxin inhibited neutrophil activation by 40% to 50%, establishing a role for G-protein-coupled receptors such as the IL-8Rs in activation by the PF4 C-terminal peptides.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1994

Two different signal transduction pathways can be activated by transforming growth factor beta 1 in epithelial cells.

Signal transduction initiated by transforming growth factor beta 1 (TGF beta 1) was studied in two sublines of the same colon carcinoma cell line, which respond in opposite ways to TGF beta 1, by proliferation or by growth inhibition. TGF beta 1 activates ras proteins within 5 min of addition when it acts to inhibit growth but not when it acts as a mitogen. In both cases TGF beta 1 also rapidly modulates the activities of three protein kinases, detected by their in gel kinase activity on the mitogen-activated protein kinase (MAP kinase) substrate, myelin basic protein (MBP). When TGF beta 1 acts as a mitogen for U9 cells, it increases the activity of MBP kinases of 57, 105, and 130 kDa within 10 min of the addition without detectably activating ras proteins. When TGF beta 1 inhibits the growth of HD3 cells, it activates ras proteins and the 57-kDa MBP kinase within 5 min but inhibits the activity of the 105- and 130-kDa MBP kinases. In HD3 cells ras activation occurred in two signal transduction pathways, one from TGF beta 1 leading to growth inhibition and one from epidermal growth factor (EGF) leading to proliferation. In addition to ras proteins, EGF activates a different set of MBP kinases in HD3 cells than does TGF beta 1, MBP kinases of 85, 57, and 44 kDa. The latter is likely to be the 44-kDa MAP kinase extracellular signal-regulated kinase (erk) 1, because EGF treatment of HD3 cells activates erk1 by increasing its phosphotyrosine level. Therefore, in two closely related epithelial cell lines TGF beta 1 activates two different signal transduction pathways, one ras-dependent and one ras-independent, and modulates the activities of a set of MBP kinases.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed1994

Hydration forces and membrane stresses: cryobiological implications and a new technique for measurement.

Very large, repulsive forces are measured between various surfaces in water at separations of about a nanometer or less. These forces are important in cryobiology because extracellular freezing usually causes extreme osmotic dehydration of cells. This brings membranes and macromolecules into close approach, and imposes large, anisotropic stresses on them. It is therefore important to study these forces at freezing temperatures. We have studied the freezing and thawing behaviour of lamellar phases of egg yolk lecithin and D2O. Force-hydration and force-separation relations are obtained from the deuterium nuclear magnetic resonance signal as a function of temperature. From these measurements we estimate the magnitude of freezing-induced membrane stresses and discuss their effect on the response of cells and organelles to freezing and thawing.

Cell Membrane↗

PubMed1994

[Studies on triterpenoids of total glucosides of tripterygium wilfordii].

Three more triterpenoids were isolated from total glucosides of tripterygium wilfordii (T1). T16 and T17 were identified as salaspermic acid and as wilforlide B. T18 was a new compound. The structure of T18 was determined, as 3-oxo-22 alpha-hydroxy-delta 12-oleanen-29-oic acid by detail spectroscopic and chemical analysis, and named triptotriterpenonic acid A.

Drugs, Chinese Herbal↗

PubMed1994

The capacity for growth stimulation by TGF beta 1 seen only in advanced colon cancers cannot be ascribed to mutations in APC, DCC, p53 or ras.

Human colon cancer development is associated with the accumulation of mutations and deletions in the suppressor genes DCC, APC and p53 and mutations in the dominant oncogene K-ras, with loss of wild type alleles. In earlier studies we had observed that about half of the resected human colon cancers placed into primary culture were growth stimulated by TGF beta 1. This group included the more advanced cancers which were either poorly differentiated primary-site cancers or metastases. In contract, the more differentiated colon cancers were inhibited or unaffected by TGF beta 1, indicating that a switch in response to TGF beta 1 occurs during colon cancer progression. Different sublines of the HT29 colon carcinoma cell line model the resected cancers, responding to TGF beta 1 by proliferation, inhibition or no growth modulation. The current study shows that while the poorly differentiated, TGF beta 1-stimulated sublines are most tumorigenic, all the sublines have the same spectrum of mutations: truncating mutations in both APC (adenomatous polyposis coli) alleles, no activated ras genes, mutated and thus overexpressed p53, and very low expression of DCC compared to normal colon cells. Genes other than the four already implicated in colon carcinoma evolution are responsible for the mitogenic response to TGF beta 1 found in the more advanced cancers.

Base Sequence↗

PubMed1993

Saturable, stereospecific transport of 3,5,3'-triiodo-L-thyronine and L-thyroxine into GH4C1 pituitary cells.

The mechanism of uptake of the thyroid hormones, 3,5,3'-triiodo-L-thyronine (L-T3) and L-thyroxine (L-T4), was studied in rat pituitary GH4C1 cells. The major portion (approximately 65%) of L-T3 transport was stereospecific and saturable. Transport of L-T3 was 8-10 times more rapid than transport of D-T3. [125I]L-T3 transport was saturable at microM concentrations; a Lineweaver-Burk plot was linear with Km = 0.4 microM and Vmax = 4 pmol/min/10(6) cells. Unlabeled analogs competed with [125I]L-T3 uptake in the order L-T3 > or = L-T4 >> 3,3',5'-triiodo-L-thyronine (reverse-T3), D-T3, D-T4, and L-thyronine. L-T3 and L-T4 also both effectively inhibited [125I]L-T4 transport. Uptake of [125I]L-T3 was inhibited 40-55% by large neutral amino acids and 77% by 80 microM beta-2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid, an inhibitor selective for the L system of amino acid uptake. Conversely, L-T3 inhibited the transport of [3H]leucine by pituitary cells (IC50 = 2 microM), but D-T3 and 3,5,3'-triiodothyroacetic acid (Triac) did not. L-Leucine was transported much more efficiently (Vmax = 0.65 mumol/min/10(6) cells) than L-T3 by GH4C1 cells. The results show that L-T3 and L-T4 share the same stereospecific transport pathway in pituitary cells, that the transport mechanism is saturable at supraphysiological thyroid hormone concentrations, and that the L system is partially responsible for L-T3 transport.

Animals↗

PubMed1993

Tumor necrosis factor-alpha alters steroidogenesis and stimulates proliferation of human ovarian granulosal cells in vitro.

OBJECTIVE: To determine if tumor necrosis factor alpha (TNF-alpha) altered human granulosa-luteal cell proliferation and steroidogenesis. DESIGN: Aspirates of follicles from women undergoing in vitro fertilization were subjected to Percoll gradients to collect an enriched population of granulosa-luteal cells. The granulosa-luteal cells were subjected to culture for a period of 10 or 20 days in the presence or absence of various doses of human recombinant TNF-alpha (0.1 to 10.0 ng/mL). PATIENTS: Granulosa-luteal cells from nine patients were evaluated for their response to TNF-alpha in vitro. Patients with three follicles > 16 mm and a serum estradiol (E2) concentration of > 1,836 pmol/L were selected for study. RESULTS: Tumor necrosis factor-alpha increased granulosa-luteal cell number. By day 10 of culture, 10 ng TNF-alpha/mL doubled cell number and > 95% of the cells exhibited 3 beta-hydroxysteroid dehydrogenase. Tumor necrosis factor-alpha at 10 ng/mL increased progesterone (P) accumulation from day 4 through day 20 of culture. Tumor necrosis factor-alpha also increased E2 secretion but in a biphasic manner. During the first 14 days of culture, TNF-alpha increased E2, but thereafter E2 decreased to basal values by day 20. When steroidogenesis was expressed per 1,000 cells per days of culture, TNF-alpha did not increase P beyond controls but significantly increased E2 for the first 14 days of culture after which E2 per 1,000 cells declined. CONCLUSIONS: The results indicate that TNF-alpha stimulates granulosal-luteal cell growth and E2 secretion in vitro, and thus TNF-alpha may promote cellular events associated with formation of the corpus luteum; i.e., granulosa-cell proliferation and steroidogenesis.

Analysis of Variance↗

PubMed1993

No effect of carbohydrate feeding on glycogen synthase in human muscle during exercise.

The effect of carbohydrate (CHO) feedings on exercise-mediated changes in glycogen synthase fractional (GSF) activity has been investigated. Subjects cycled at approximately 70% of maximal oxygen uptake on two occasions: the first to fatigue (135 +/- 17 min; mean +/- SE) (control, CON), and the second at the same workload and duration as the first, but with the addition of frequent ingestion of CHO during exercise (0.27 g kg-1 body weight every 15 min). Biopsies were taken from the quadriceps femoris muscle before and immediately after exercise. Plasma glucose and insulin decreased during CON exercise, but remained elevated throughout CHO exercise (end of exercise: glucose = 4.4 +/- 0.2 mM CON vs. 5.8 +/- 0.2 CHO, P < 0.01; insulin = 9 +/- 1 uU ml-1 CON vs. 19 +/- 3 CHO, P < 0.05). Glycogen decreased to approximately 10% of the basal value during CON and to approximately 20% during CHO, and there was no significant difference in net glycogenolysis between treatments. GSF activity averaged 0.25 +/- 0.03 and 0.22 +/- 0.05 at rest, and increased to 0.51 +/- 0.08 and 0.48 +/- 0.09 after exercise in CON and CHO, respectively (P > 0.05 between treatments). It is concluded that under the present conditions CHO feedings do not alter the exercise-mediated changes in GSF activity. The increase in GSF during exercise is attributed at least in part to the decrease in muscle glycogen (which increases the suitability of GS as substrate for GS phosphatase).

Adolescent↗

PubMed1993

Regulation of glycogen synthase in human muscle during isometric contraction and recovery.

Six subjects performed isometric contraction (66% maximal force) to fatigue with the knee extensor muscles. Biopsies were taken from the quadriceps femoris muscle at rest, at fatigue and 1 min after termination of contraction. In three of the subjects recovery from contraction occurred in the presence of an intact circulation (non-occluded, NON) to the thigh, whereas in the other three the circulation during recovery was occluded (OCC). Glycogen synthase fractional activity (GSF) decreased in all subjects from (mean +/- SE) 0.53 +/- 0.06 at rest to 0.37 +/- 0.04 at fatigue (P < 0.001). In the OCC group GSF returned to the pre-exercise value within 1 min after termination of contraction (0.59 +/- 0.07 at rest vs. 0.57 +/- 0.04 at 1 min post-exercise), whereas in the NON group GSF increased to a higher extent (0.48 +/- 0.09 at rest vs. 0.70 +/- 0.06 at 1 min post-exercise). The increase in GSF during the 1-min recovery was almost three-fold higher in the NON group (0.15 +/- 0.02 vs. 0.38 +/- 0.03). Cyclic AMP-dependent protein kinase (cAMP-PK) (assayed at 0/100 microM and 0.2/100 microM cAMP) did not change at fatigue or during recovery in either group. Glycogen synthase phosphatase (GSP) increased at fatigue by approximately 30% (P < 0.05 vs. rest). It is concluded that isometric contraction mediated inactivation of GS (i.e. phosphorylation of GS) is due to activation of a protein kinase(s) but not cAMP-PK. The rapid activation of GS in the NON group demonstrates that a humoral factor(s), possibly insulin and/or oxygen, is responsible for this phenomenon.

Adolescent↗

PubMed1993

Neutrophil-activating intercrine secreted by porcine platelets is active without proteolytic processing.

A new member of the cytokine intercrine alpha-subfamily, porcine neutrophil-activating peptide 2 (pNAP-2), was isolated to homogeneity. Amino acid sequencing analysis showed two species of pNAP-2, a long form (pNAP-2-L) and a short form (pNAP-2-S). pNAP-2-L had seven more amino acids at the NH2-terminus than pNAP-2-S. The remaining amino acid sequences of the two molecules were identical. pNAP-2-S shared 65% homology with human neutrophil-activating peptide 2 (hNAP-2) including four cysteines in identical positions. Moreover, the NH2-terminal sequence Glu-Leu-Arg (E-L-R) was conserved in both molecules. Both pNAP-2-L and pNAP-2-S induced mobilization of cytosolic calcium in neutrophils and caused release of granulocyte elastase in a dose-dependent manner, although pNAP-2-L was less active. A desensitization study suggested that both hNAP-2 and pNAP-2-S may act on the same receptor. Whereas human platelets release inactive precursors that can be converted to hNAP-2 by cathepsin G from activated neutrophils, porcine platelets, upon stimulation with thrombin, appear to secrete active forms of pNAP-2. The activated neutrophils are not involved in the generation of pNAP-2.

Amino Acid Sequence↗

PubMed1993

Insulin-like growth factor immunoreactivity increases in muscle after acute eccentric contractions.

The purpose of the study was to note whether insulin-like growth factor (IGF) immunoreactivity increased after eccentric contractions. IGF immunoreactivity in the rat tibialis anterior muscle was measured on 5 successive days (4-5 rats/group, n = 28) after an acute bout of 192 eccentric contractions elicited by electrical stimulation. The muscle tissue sections were immunocytochemically processed with rabbit anti-human IGF-I serum. Immunoreactivity was analyzed with videomicroscopy and computer-aided image processing. Four days after eccentric contractions, IGF immunoreactivity was significantly higher than control [0.081 +/- 0.073 (SD) absorbance at 480 nm vs. 0.026 +/- 0.018; P < 0.05]. The increases in IGF-I immunoreactivity were mostly within the muscle fibers. These results suggest that an acute bout of eccentric exercise increases IGF-I immunoreactivity in rat type II muscle 4 days postexercise.

Animals↗

PubMed1993

Vascular endothelial growth factor (VEGF) messenger ribonucleic acid (mRNA) expression in luteinized human granulosa cells in vitro.

Vascularization is a prerequisit for corpus luteum formation. Angiogenesis is supposed to be regulated by vascular growth factors. Vascular endothelial growth factor (VEGF) induces specifically endothelial cell proliferation as well as angiogenesis and increases capillary permeability. With this study we demonstrate for the first time the presence of VEGF-mRNA in human luteinized granulosa cells by Northern blot technique. Granulosa cells were obtained from 11 individual patients undergoing ovarian stimulation for in vitro fertilization procedure. Two transcripts of VEGF-mRNA at 3.9Kb and at 4.3Kb could be detected in each case. Specific transcripts were expressed in different amounts. These results indicate that VEGF may promote at least in part vascularization of the human corpus luteum.

Cells, Cultured↗

PubMed1993

Phosphofructokinase activity in human skeletal muscle: effects of euglycaemic hyperinsulinaemia and fasting.

Euglycaemic (approximately 5.5 mmol l-1) hyperinsulinaemic (60 mU [m2]-1 min-1) clamps were performed for 2 h after a 10 h and after a 72 h fast on man. Biopsies were obtained from the quadriceps femoris muscle before and after each clamp and analysed in vitro for phosphofructokinase (PFK) activity under optimal (pH 8.2) and regulatory conditions (pH 7.0 and low substrate concentrations). Insulin stimulated, and fasting inhibited basal and insulin stimulated muscle glycolysis in vivo. However, PFK activity, measured in vitro, was not altered by any of the treatments (at pH 8.2: basal [10 h] = 102 +/- 5 mmol kg-1 dry wt min-1, clamp [10 h] = 104 +/- 6; basal [72 h] = 107 +/- 6, clamp [72 h] = 110 +/- 4 (at pH 7.0: basal [10 h] = 10.7 +/- 0.9, clamp [10 h] = 10.7 +/- 1.7; basal [72 h] = 11.7 +/- 2.4, clamp [72 h] = 9.7 +/- 1.6). Similarly, the activity ratio (7.0/8.2) was also not significantly altered by any of the treatments. Euglycaemic hyperinsulinaemia did not increase and fasting did not decrease the contents of activating hexose phosphates in muscle. The activity ratio increases after administration of epinephrine in rabbit muscle and the increase is thought to be mediated through a combination of increased hexose phosphates and adenine nucleotides (cyclic AMP) (Mansour TE. J Biol Chem 1972; 247: 6059-66). We confirmed that 2 h of epinephrine infusion also increased the activity ratio and hexose phosphates (but not fructose 2,6-P2) in human muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Colon carcinoma cells blocked in polarization exhibit increased expression of carcinoembryonic antigen.

Carcinoembryonic antigen (CEA) is an oncofetal protein whose regulation is poorly understood, although CEA is commonly expressed on many carcinoma cell types and enhances experimental metastases. The abundance of membrane-associated CEA was increased 3-fold when HD6 colon carcinoma cells were prevented from polarizing by culture for 3 days in low calcium medium. Polarization is an early event in HD6 cell differentiation, with the polarized cells forming a tight, laterally adherent monolayer by culture in normal calcium medium. Lateral adherence can occur because 3 days of culture in normal calcium medium increases expression of calcium-dependent intercellular adhesion proteins: a 35-fold increase in membrane abundance of LCAM and a 16-fold increase in membrane abundance of the desmosomal protein desmoglein I. Polarized HD6 cells exhibit low levels of CEA only at their apical luminal surface. Rounded, unpolarized HD6 cells do not exhibit increases in either LCAM or desmoglein I membrane expression, but express increased levels of CEA molecules throughout their cell surface, where they act as intercellular adhesion molecules, allowing unpolarized cells to form random cell to cell contacts. Cells cultured in low calcium medium form calcium-independent cell aggregates whose formation can be blocked by Fab' fragments of anti-CEA monoclonal antibody col-1. The familiar pattern of random, multilayered associations of tumor cells both in vitro and in xenographs in vivo may be due to intercellular adhesion mediated by CEA which is up-regulated and expressed throughout the cell surface of unpolarized tumor cells.

Calcium↗