Biomedical subjects

X Xi

Publications and source records attributed to X Xi.

34 records · Page 2Linked to original sources

PubMed1999

[Design of CXLY-II low frequency magnetic fields pulse generator].

An experimental device, low frequency magnetic fields pulse generator, has been designed and accomplished in our department. It can provide low frequency magnetic fields pulse with the intensity from 150mT to 800mT and the frequency from 0 to 100Hz. This device is easy to operate and performs reliably. It can stably work for a long time and has been successful used in the experiment of magnetic biological effect.

Electromagnetic Phenomena↗

PubMed1999

[The influence of pulsed magnetic fields on SOD's activity and MDA value in metabolism of mice].

This experiment aimed to investigate the influence of pulsed extremely-low-frequency-magnetic fields on free radical metabolism of mice. Thirty-two mice were randomly divided into four groups and were exposed to 0 T, 0.25 T, 0.34 T and 0.64 T intensity pulsed magnetic fields of 20 Hz for 40 min. The 0 T exposed group was the control group. The free radical metabolism, SOD's activity and MDA, of mice were measured respectively. The result showed the SOD's activity and MDA of the 0.34 T exposed group were both significantly lower (P < 0.01, P < 0.05) than that of the control group, while the 0.25 T and 0.64 T exposed groups were not significantly different from the control group. This demonstrates that the biological effect of pulsed extremely-low-frequency magnetic fields on free radical metabolism of mice varies and depends on the intensity of the fields. The "window" effect may exist.

Animals↗

PubMed1997

High resolution multichannel fluorescence detection for capillary electrophoresis. Application to multicomponent analysis.

A wavelength-resolved fluorescence detector for laser-induced fluorescence detection in capillary electrophoresis (CE) is described that uses a charge injection device (CID) array detector Post-column fluorescence detection occurs using a sheath flow cell. The limit of detection for fluorescein is 4.8 x 10(-11) M (29,000 molecules), the spectral resolution is 0.56 nm/pixel, and the spectrograph/CID monitors a 250 nm spectrum throughout the 250-875 nm range. Custom array readout, data manipulation and data processing methods are described to convert wavelength/spatial CID images into electropherograms. The application of the system to characterizing bilirubins in human serum is described, demonstrating the ability to match electrophoretic peaks to standards using spectral information.

Bilirubin↗

PubMed1997

Simple sheath flow reactor for post-column fluorescence derivatization in capillary electrophoresis.

A system for post-column fluorescence derivatization in capillary electrophoresis is described. The post-column reactor uses a sheath flow detection cell where the reagents, o-phthaldialdehyde and beta-mercaptoethanol, are added to the sheath buffer and mix by diffusion with the analytes effusing from the separation capillary. Reaction progress is monitored and optimized by imaging a large portion of the sheath flow cuvette using an extended UV source and a CCD camera. Significantly, this design provides the ability to switch between the analysis of pre- and post-column derivatized amino acids and peptides easily and without sacrificing system performance. The lack of turbulent flow in this system minimizes post-separation band broadening. The limit of detection for glycine is 9.4 x 10(-8) M (110 amol) with a separation efficiency of 190,000 theoretical plates, without stacking. The performance of the system for a series of amino acids was evaluated using post-column and pre-capillary derivatization.

Amino Acids↗

PubMed1996

Direct and reversible inhibition of platelet factor 4 on megakaryocyte development from CD34+ cord blood cells: comparative studies with transforming growth factor beta1.

Mechanisms of the action of platelet factor 4 (PF4) on the growth of megakaryocyte (MK) progenitor cells in CD34+ cord blood (CB) cells were studied in comparison with transforming growth factor beta1 (TGFbeta1). Development of MK from CD34+ CB cells in both plasma clot culture and liquid culture was significantly inhibited by either purified human PF4 and by recombinant human TGFbeta1. Inhibition of MK colony formation by PF4 was reversible because CD34+ cells preincubated with PF4 could regenerate colonies after washing and replating into secondary cultures. In contrast, TGFbeta1-preincubated CD34+ cells gave rise to few colonies following replating. Moreover, incubation of CD34+ cells with PF4 in liquid culture caused the increased number of both stem cell factor (SCF)-binding cells and CD34 antigen-bearing cells. In addition, PF4-preincubated CD34+ cells exhibited a higher potential in MK colony formation in the presence of 5-fluorouracil (5FU). These results demonstrate that both PF4 and TGFbeta1 inhibit MK development from CD34+ CB cells by different mechanisms, and suggest that PF4, unlike TGFbeta1, exerts its inhibitory effect on the growth of the target cells in a reversible manner which results in a preservation of a more immature and 5FU-resistant cell population.

Antigens, CD34↗

PubMed1995

Differential effects of recombinant human interleukin-13 on the in vitro growth of human haemopoietic progenitor cells.

Effects of recombinant human interleukin (IL)-13 on in vitro haemopoiesis from non-adherent mononuclear cells (NAMC) or highly enriched CD34+ cells of human cord blood (CB) were studied. IL-13 significantly increased megakaryocyte (MK) colony formation from either NAMC or CD34+ cells cultured in a plasma clot system supplemented with aplastic anaemia serum (AAS) and phytohaemagglutinin-stimulated human peripheral blood leucocyte-conditioned medium (PHA-LCM) in a dose-dependent manner. Experiments using a modified plasma clot culture, in which normal AB serum and various cytokines were added to replace AAS and PHA-LCM, demonstrated an increased MK colony number in the presence of IL-13, especially in combination with IL-3. However, IL-13 had no stimulatory effect, but rather a slight inhibitory effect in some cases on granulocyte-macrophage (GM) colony formation in both plasma clot cultures. Furthermore, the growth of GM progenitor cells in a methylcellulose culture system in the presence of IL-3, GM-CSF, Epo, G-CSF or in combination was significantly inhibited by the addition of IL-13. On the other hand, high concentrations (100 ng/ml) of IL-13 were needed to cause a slight inhibition on the growth of BFU-E-derived colonies under the same methylcellulose culture. These results indicate that IL-13, alone and synergistically with the effect of IL-3, promotes MK colony formation, but it inhibits the growth of GM and erythroid progenitor cells in vitro.

Cells, Cultured↗

PubMed1995

[ACh and ATP induced calcium mobilization in outer hair cells of the guinea pig cochlea: confocal microscopy].

Effects of acetylcholine (ACh) and ATP as the candidates of efferent neurotransmitter on intracellular Ca2+ concentrations ( [Ca2+]i) of the isolated outer hair cells (OHCs) from guinea pig cochlea were studied with laser scanning confocal microscope. The OHCs were loaded with Ca2+ sensitive dye Fluo-3, whose fluorescent intensity was strongest at the basal end in resting OHC. The presence of ACh gradually increased [Ca2+]i to a higher level at the basal end of OHCs. Continuous application of ATP caused a rapid [Ca2+]i increase followed by a gradual exhaustion throughout the whole OHC. Magnitude of the increase at the apex was greater than that at the base. In OHCs whose calcium had been exhausted by ATP, ACh induced a temporary increase in [Ca2+]i. It seems likely that the ACh-induced [Ca2+]i rise is partly due to an influx of extracellular Ca2+. The bursting nature of ATP-induced [Ca2+]i rise may be a consequence of Ca2+ influx through the ATP-gated cation channels and of the mobilization of intracellular store mediated by ATP.

Acetylcholine↗

PubMed1995

[Confocal images of cochlear outer hair cells in the guinea pigs].

The effects of ACh, ATP and high K+ on intracellular calcium concentration Ca2+ in outer hair cells (OHC) of the guinea pig cochleae were observed with the use of Ca2+ sensitive dye Fluo-3 and laser scanning confocal microscope. Ca2+ increase induced by these chemicals had individual temporal and spatial features. Moreover, high K+ solutions induced contraction and bending of OHC too. Taking advantage of the "optical sectioning" facility of confocal microscopy, morphography of Fluorescein-labelled living OHC and PI-dyed nuclei was reconstructed three-dimensionally. The application of confocal microscopy in OHC physiological and morphological research was discussed.

Animals↗

PubMed1995

[Platelet factor 4, reversible inhibitor of megakaryocytogenesis, protector of megakaryocytes during chemotherapy].

Development of megakaryocyte (MK) from CD34+ cord blood (CB) cells in both plasma clot culture and liquid culture was significantly inhibited by human platelet factor 4 (PF4) and human transforming growth factor beta 1 (TGF beta 1). Inhibition of cell growth by PF4 was reversible judging from the fact that the CD34+ cells preincubated with PF4 could regenerate colonies after washing and replating into the cultures. By contrast, TGF beta 1-pretreated CD34+ cells gave rise to few colonies following replating. Moreover, incubation of CD34+ cells with PF4 in liquid culture caused an increase in the number of both stem cell factor (SCF)-binding cells and CD34 antigen-bearing cells, and exhibited greater capacity to form MK colonies than control after the treatment of 5-FU. In vivo in mice, twice injections of PF4 at 40 micrograms/kg resulted in a significant increase in the number of colony-forming cells with high proliferative potential (HPP-CFC) and colony-forming unit-megakaryocyte (CFU-MK) in bone marrow. In exponentially growing human erythroleukemia cells (HEL), the addition of PF4 prolonged cell cycle progression and therefore resulted in an increased cell population in S phase, as determined by flow cytometric analysis. Different from PF4, TGF beta 1 blocked more cells in G1 phase. These results demonstrate that PF4 and TGF beta 1 inhibit MK development from CD34+ CB cells by different mechanisms and suggest that PF4, unlike TGF beta 1, exerts its inhibitory effect on cell growth in a reversible and S phase-specific manner by which it protects stem cells and MK progenitor cells from 5-FU cytotoxicity.

Animals↗

PubMed1994

Electrophysiological properties of canine cardiac ganglion cell types.

Intracellular recordings were made from 110 canine cardiac ganglion cells to study their electrophysiological properties. According to their discharge responses to depolarizing currents, these neurons were classified as tonic, phasic and non-discharging cells. Of these cell types, the order of the resting membrane potentials was non-discharging > phasic > tonic cells, which was the reverse of the order of their input resistances. Tonic and phasic cells could not be distinguished by the nature of their after hyperpolarizations which involved Ca(2+)-sensitive K+ currents. Although both cell types demonstrated fast Na+ and slow Ca(2+)-mediated action potentials, the tonic cells' action potentials were more sensitive to tetrodotoxin than those of the phasic cells.

Action Potentials↗

PubMed1994

[Evaluation of postural sway in normals and patients with vertigoes].

A measurable parameter in the study of static equilibrium was described. The locus of postural sway was measured with a set of computer during 1 minute period in 68 normal subjects and 82 patients suffering from central and peripheral vertigoes with eyes closed. The results demonstrated: 1) There are five patterns of postural sway: centripetal, forward-backward, right-left, diffuse and multicentric patterns; centripetal pattern was the most prominent figure pattern in the normal subjects, diffuse pattern was the most prominent figure pattern in the central vertigoes. 2) Length of locus and velocity of postural sway of the patients were significantly increased in comparison with normal subjects. 3) The length of locus was the shortest and velocity of sway was the slowest in the 20-year group. There was difference between 20- year and 10-year group (P < 0.05), the difference between 20-year and 50-year was more significant (P < 0.01).

Adolescent↗

PubMed1993

Antiplatelet granule membrane protein (GMP-140) autoantibodies detected in plasma from patients with idiopathic thrombocytopenic purpura.

Plasma from 92 patients with idiopathic thrombocytopenic purpura (ITP) was tested for autoantibodies against granule membrane protein 140 (GMP-140) using an antigen specific immunoassay. Results showed that autoantibodies to GMP-140 existed in 17 of these patients (18.5%). Incubation of patient plasma with purified GMP-140, immobilized on nitrocellulose strips by SDS-PAGE and Western blotting, revealed a staining band at the level of GMP-140 in two of 8 plasmas. Autoantibodies to GMP-140 often coexisted with other autoantibodies, in particular towards GP Ib/IX (3 cases), GP IIb-IIIa (5 cases) or both (3 cases). This study provides direct evidence for the presence of anti-platelet GMP-140 autoantibodies in some patients with ITP.

Adult↗

PubMed1992

Competitive binding of a monoclonal antibody SZ-21 with anti-PLA1 antibodies and its potential for clinical application.

Both intact IgG and Fab fragments of a monoclonal antibody SZ-21, directed against platelet glycoprotein (GP) IIIa, inhibited binding of anti-PLA1 antibodies to PLA1-positive platelets in a dose dependent manner. Conversely, the binding capacity of the platelets for SZ-21 was decreased in the presence of anti-PLA1 antibodies. In Western blots, the determinant for SZ-21 was present on GPIIIa from either PLA1 or PLA2 homozygotes, but SZ-21 did not affect the interaction of anti-Yukb alloantibodies with their target antigen on GPIIIa. These results suggest that SZ-21 reacts with an epitope on the GPIIIa molecule very close to but not identical with that for anti-PLA1. The existence of PLA1-reactive alloantibodies in serum could be demonstrated by their competitive effect on the binding of SZ-21.

Antibodies, Monoclonal↗

PubMed1991

Morphology of intracellularly labeled canine intracardiac ganglion cells.

The purpose of this study was to determine the morphological organization and structure-function correlation of mammalian intracardiac ganglion cells. Conventional intracellular microelectrode techniques were applied to the tissue whole mount preparation of canine intracardiac ganglia. Forty neurons were intracellularly recorded and labeled by means of horseradish peroxidase iontophoresis. Cell morphology was quantitatively analyzed by light microscopy and camera lucida technique. Somata were elongated (mean 62 x 40 microns) and had 2-12 primary dendrites restricted within the ganglion. Almost half of the neurons had either a short axon that was traced only within the ganglion or no axon distinguishable. These neurons may have perhaps been intraganglionically active neurons. The other cells had a long axon that either coursed out of the ganglion to peripheral cardiac tissue or exited the ganglion via interganglionic nerve to innervate more remote cardiac tissue or cells in other intracardiac ganglia. Interaction between neurons was suggested by the close proximity of processes from different neurons. Previously defined electrophysiological cell types (R-, S-, and N-cells), which were significantly different in their passive and active membrane properties, had different morphological features of the somata but not the axonal or dendritic processes. Intraganglionic or long axon neurons were not associated with a particular electrophysiological cell type. These findings provide the possibility of ganglionic modulation of vagal efferent activity in mammalian heart and also provide some morphological basis for the electrophysiological cell types.

Animals↗

PubMed1991

Intracellular recording of spontaneous activity of canine intracardiac ganglion cells.

Intracellular recordings were made from 302 canine intracardiac ganglion cells with intact synaptic connections. Fifty-two % of these cells exhibited spontaneous membrane potential changes consisting primarily of miniature excitatory postsynaptic potential (EPSP)-like depolarizations upon which an action potential or burst of action potentials was sometimes evoked. Most of the spontaneous potential changes are presumed to be synaptically mediated involving nicotinic mechanisms because they were blocked by low Ca2+/high Mg2+ and hexamethonium solutions.

Action Potentials↗

PubMed1990

Preparation of a monoclonal antibody, SZ-51, that recognizes an alpha-granule membrane protein (GMP-140) on the surface of activated human platelets.

To identify the changes on the platelet plasma membrane after platelet activation, we prepared monoclonal antibodies specific for activated platelets. Hybridoma cell line SZ-51 was screened for antibodies which bound to thrombin activated platelets but not to resting platelets. 125I-SZ-51, and IgG1, bound 780 molecules/platelet on resting platelets. However, it bound 11,000 molecules/platelet on thrombin activated platelets with high affinity (4.2 nmol/L). The isolated protein using affinity chromatography showed a single band in both periodic acid-Schiff and Coomassie blue staining. Immunoblot analysis revealed that SZ-51 reacted with a 140,000 molecular weight protein which was identified to be alpha-granule membrane protein (GMP-140) in radioimmunoassay. These results demonstrate that the antigen recognized by SZ-51 is GMP-140, which is expressed on the plasma membrane of activated platelets.

Antibodies, Monoclonal↗