Search PubMed⌕ Search

Biomedical subjects

X L Yang

Publications and source records attributed to X L Yang.

At least 19 recordsLinked to original sources
PubMed2003

Interference of four umbrellalike beams by a diffractive beam splitter for fabrication of two-dimensional square and trigonal lattices.

A simple optical interference method for fabricating two-dimensional square and trigonal lattices is demonstrated. A general formula for the interference contrast formed by two arbitrary polarized elliptical waves is deduced, the relation between wave vectors of incident light and the resultant pattern is analyzed, and polarization optimization of all beams to ensure uniform contrast is given.

Journal Article↗
PubMed2003

Cholinergic and dopaminergic amacrine cells differentially express calcium channel subunits in the rat retina.

Immunofluorescence labeling was performed to study the expression of high voltage-activated Ca(2+) channel subunits on rat retinal cholinergic and dopaminergic amacrine cells, which were double labeled with antibodies against choline acetyltransferase and tyrosine hydroxylase, respectively. The alpha(1A) subunit was predominantly expressed on the processes but not on the somata of cholinergic amacrine cells, whereas staining for alpha(1B) and alpha(1E) was observed in both structures of the cells. Immunoreactivity of alpha(1C) and alpha(1D) was not found in the cholinergic amacrine cells. Dopaminergic amacrine cells, on the other hand, exhibited a differential expression pattern of the Ca(2+) channel subunits, with alpha(1A), alpha(1C) and alpha(1E) being expressed on both somata and processes and alpha(1B) predominantly on the processes of the cells. No alpha(1D) labeling was seen. These results suggest that Ca(2+) channel subunits differentially expressed on the cholinergic and dopaminergic amacrine cells may endow these two cell types with different physiological properties.

Acetylcholine↗
PubMed2002

Glycinergic synaptic transmission to bullfrog retinal bipolar cells is input-specific.

Glycinergic inhibitory postsynaptic currents (IPSCs) focally elicited at the dendrites and axon terminals were recorded from bipolar cells in the bullfrog retinal slice, using the whole-cell clamp technique. IPSCs driven by input from interplexiform cells at bipolar cell dendrites (ipc-IPSCs) had a much slower decay time constant (25.2 +/- 7.8 ms) than IPSCs driven by input from amacrine cells at bipolar cell axon terminals (ac-IPSCs) (14.7 +/- 5.5 ms). Furthermore, peak-scaled non-stationary noise analysis revealed that the weighted mean single-channel conductance of the glycine receptors underlying bipolar cell dendritic ipc-IPSCs (20.8 +/- 6.6 pS) was significantly larger than that of those underlying bipolar cell axon terminal ac-IPSCs (12.9 +/- 2.9 pS). These results demonstrate that glycinergic synaptic transmission with different properties at bipolar cell dendrites and axon terminals differentially mediates intraretinal centrofugal signal transfer from the inner retina to the outer retina provided by interplexiform cells and lateral inhibition offered by amacrine cells in the inner retina.

Animals↗
PubMed2002

Photo-induced cytotoxicity of malonic acid [C(60)]fullerene derivatives and its mechanism.

The biological activities of fullerenes have attracted extensive attention in recent years. The aim of this paper is to study the relation of the photo-induced cytotoxicity of fullerene derivatives to their chemical structures as well as the possible cellular mechanism involved in the photocytotoxicity. Three C(60) derivatives with two to four malonic acid groups (DMA C(60), TMA C(60) and QMA C(60)) were prepared and the cytotoxicity of these compounds against HeLa cells was determined by MTT. Cell cycle was measured by flow cytometry. The results showed that the cytotoxicity of the malonic acid C(60) derivatives was irradiation- and dose-dependent. The sequence of their photo-induced growth inhibition was DMA C(60)>TMA C(60)>QMA C(60). Hydroxyl radical quencher mannitol (10mM) was not able to prevent cells from the damage induced by irradiated DMA C(60). DMA C(60), together with irradiation, was found to have an ability of inducing a decrease in the number of G(1) cells from 63 to 42% and a rise in that of G(2)+M cells from 6 to 26%. These data indicated that the number of malonic acid molecules added to C(60) played an important role in the phototoxicity, and the blockage of cell cycle might be a mechanism of this activity.

Carbon↗
PubMed2002

Formation of three-dimensional periodic microstructures by interference of four noncoplanar beams.

A newly reported method of making three-dimensional microstructures or photonic crystals by holographic lithography has some obvious advantages over other techniques with the same purpose. A systematic and comprehensive analysis of interference of four noncoplanar beams (IFNB) is provided. It shows that all 14 Bravais lattices can be formed by means of IFNB and gives explicit relationships between each lattice and the corresponding recording geometry. The concept of pattern contrast is extended to the case of IFNB, and it is indicated that a uniform contrast for each interference term can be obtained by properly choosing the beam ratio and polarization. A calculation algorithm is then developed to optimize the direction of polarization of each beam to ensure maximum uniform contrast. These results, verified by computer simulations, may lay a theoretical foundation for fabrication of photonic crystals with the approach of IFNB.

Journal Article↗
PubMed2001

Glutamate transporter EAAC1 is expressed on Müller cells of lower vertebrate retinas.

The expression of glutamate transporter EAAC1 was investigated in carp and bullfrog retinas using Western blotting, immunofluorescence double labeling and confocal laser scanning microscopic techniques. In addition to a variety of retinal neurons, radially oriented elements spanning the whole neural retinas of carp and bullfrog were also EAAC1-immunoreactive, and EAAC1 was found to be predominantly on the cell membrane. Virtually all EAAC1-labeled radial elements were immunopositive to glial fibrillary acidic protein (GFAP), a specific marker for retinal Müller cells of carp and bullfrog, indicating that they were Müller cells. This finding suggests that EAAC1, which has been thought to be an exclusively neuronal type, may be a glial transporter as well. EAAC1 of Müller cells may play an important modulatory role in the retina by making contributions to glutamate homeostasis.

Amino Acid Transport System X-AG↗
PubMed2001

Release of hydrogen chloride from combustibles in municipal solid waste.

Study of the inorganic chlorides in municipal solid waste (MSW) shows that the main source of inorganic chlorides in MSW is food. The main organic source of HCl emission from MSW is plastic. But wood, textiles, and food also produce a large amount of HCl when they are combusted. Each combustible shows a different HCl releasing temperature range. At 973 K, there are 30-70% of the total chlorine left in the char of each combustibles in MSW.

Air Pollutants↗
PubMed2001

Zn2+ differentially modulates signals from red- and short wavelength-sensitive cones to horizontal cells in carp retina.

The effects of Zn2+ were studied while recording intracellularly from L-type horizontal cells (LHCs) in the isolated, superfused carp retina. In darkness, 25 microM Zn2+ hyperpolarized LHCs and potentiated responses of these cells to 500 nm flashes, but decreased those to 680 nm flashes. Zn2+ did not change photopic electroretinographic P III responses. The differential modulation by Zn2+ persisted when the Zn2+-induced membrane hyperpolarization was compensated by lowering Ca2+ concentration in the perfusate, but it was abolished in the presence of background illumination. Furthermore, the differential modulation no longer existed in the presence of bicuculline, suggesting the involvement of gamma-aminobutyric acid(A) (GABA(A)) receptors. We speculate that the differential modulation may be a consequence of multiple changes caused by Zn2+. Decreased glutamate release from the cone terminal by Zn2+ results in a reduction of cone signals. Zn2+ antagonizes GABA receptors on LHCs, leading to cone signal reduction. On the other hand, Zn2+ may reduce the strength of the negative feedback from LHCs to cones by downregulating the activity of GABA receptors on the cone terminal, which causes a potentiation of LHC light responses. Cone- or wavelength-relevance of the Zn2+-induced feedback strength change may account for the differential modulation.

Animals↗
PubMed2001

Melatonin modulates gamma-aminobutyric acid(A) receptor-mediated currents on isolated carp retinal neurons.

Modulation by melatonin of gamma-aminobutyric acid(A) (GABA(A)) receptor-mediated responses was studied in bipolar and amacrine-like cells acutely isolated from carp retina, using the whole-cell patch-clamp technique. Melatonin of 1 mM accelerated desensitization of the GABA(A) receptors at both bipolar and amacrine-like cells. In addition, 1 mM melatonin hardly changed the GABA(A) receptor-mediated response amplitude of bipolar cells, while it increased or decreased that of amacrine-like cells, depending on the concentration of GABA applied. These modulatory effects, which can not be blocked by luzindole, a melatonin receptor antagonist, may be due to the allosteric action caused by melatonin bound to a site of the GABA(A) receptors.

Animals↗
PubMed2001

Forskolin modulation of desensitization at GABA(A) and glycine receptors is not mediated by cAMP-dependent protein kinase in isolated carp amacrine-like cells.

The effects of forskolin on gamma-aminobutyric acid type-A (GABA(A)) and glycine receptors in amacrine-like cells of carp (Carassius auratus) retina were studied using patch-clamp techniques. Application of 50 microM forskolin markedly accelerated the desensitization of whole-cell responses induced by 100 microM GABA or glycine without changing the peak amplitude of the response. Both 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP) and 3-isobutyl-1 -methylxanthine (IBMX) (500 microM) failed to accelerate the desensitization of these two receptors. Protein kinase A (PKA) inhibitors, N- [2-[(p-bromocinnamyl)amino]ethyl)-5-isoquinolinesulfonamide dihydrochloride (H-89) and N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H-8), could not block these effects of forskolin. An inactive analogue of forskolin, 1,9-dideoxyforskolin (DFSK), accelerated the desensitization effectively. These results suggest that forskolin's effects are not mediated by activation of the PKA pathway. Moreover, similar results were obtained using excised outside-out patches of these cells, suggesting that forskolin may act on an extracellular site(s). The neurosteroids 5alpha-pregnane-3alpha,21 -diol-20-one (THDOC) and 5-pregnen-31 -ol-20-one sulfate sodium (PS), structural analogues of forskolin, accelerated the desensitization of these receptors without changing the peak amplitudes, thus mimicking forskolin's effects. Furthermore, PS interacted with forskolin on these receptors so as to slow down the responses. These results raise the possibility that forskolin acts directly on an extracellular site(s) of the GABA(A) and glycine receptors, shared with neurosteroids, in carp amacrine-like cells.

Animals↗
PubMed2001

Signals from cone photoreceptors to L-type horizontal cells are differentially modulated by low calcium in carp retina.

Ca2+ plays crucial roles in both phototransduction and calcium-dependent glutamate release from the photoreceptor terminal. Modulation, by lowering extracellular Ca2+, of red-sensitive (R-) and short wavelength-sensitive (S-) cone-driven light responses of L-type horizontal cells (LHCs) was studied in the isolated superfused carp retina using intracellular recording techniques. Low Ca2+ (nominally Ca2+-free) Ringer's reduced responses of LHCs to both green (500 nm) and red (680 nm) flashes in darkness, with the former being suppressed more substantially than the latter. This differential suppression became more significant when contribution of R-cones to the green-light-induced responses was diminished by a moderate red (680 nm) background light. Application of IBMX, an inhibitor of phosphodiesterase (PDE), increased LHC responses to both red and green flashes equally, resembling the effect of low Ca2+ on phototransduction. In addition, photopic electroretinographic P III responses, reflecting the activity of cones, to red flashes were more potentiated by low Ca2+, compared to those to green flashes, whilst they were both equally potentiated by IBMX. Furthermore, low Ca2+ caused a more pronounced suppression of LHC responses to red flashes than those to green flashes in the presence of IBMX. It is postulated that reduction of LHC responses in low Ca2+ may be due to the 'saturation suppression' caused by the increased glutamate release from the photoreceptor terminal and the differential modulation may reflect a consequence of the dual action of low Ca2+ on the PDE activity in the photoreceptor outer segment and the synaptic strength between cones and LHCs.

1-Methyl-3-isobutylxanthine↗
PubMed2001

Resistance to fulminant hepatitis and carcinogenesis conferred by overexpression of retinoblastoma protein in mouse liver.

Previously, retinoblastoma (Rb) transgenic mice were produced under the control of the Rb gene promoter and showed dwarf characteristics. Here, we created transgenic mice, in which the human Rb gene was controlled by the hepatocyte nuclear factor-1 gene promoter/enhancer and was expressed primarily in the liver. The liver of these novel transgenic mice was normally developed. Intriguingly, these mice showed resistance to fulminant hepatitis induced by anti-Fas antibody as well as resistance to chemical carcinogenesis in the liver. These results show that the Rb protein acts as an anti-apoptotic and anti-oncogenic agent in vivo. Our novel construct may be useful as a gene cassette in gene therapy for prevention of fulminant hepatitis and hepatoma.

Animals↗
PubMed2001

[Zinc ions: an endogenous neuromodulator].

Zinc ions are widely distributed in the central nervous system. Zinc ions are released from neurons in a calcium-dependent manner. In recent years abundant evidence indicates that zinc ions modulate not only the release of transmitters, but also the voltage- and ligand (excitatory and inhibitory amino acids)-gated channels, suggesting that these ions may serve as an important endogenous neuromodulator.

Animals↗
PubMed2001

[Studies on the properties of energy upconversion of the rare earth ErYb and HoYb in the oxyfluoride glass].

Er and Yb, Ho and Yb codoped in the oxyfluoride were burnt on in the specific temperature, and got two kinds of samples. Using 930 nm as an exciting light, the emitting fluorescent spectra of two kinds of the samples were measured, and observed the red band and green band fluorescent spectra, respectively. According to the detected absorption spectra of Er2O3, Ho2O3, Yb2O3 and the rule of energy jump, the mechanism and the properties of the energy upconversion of two kinds of the samples were explained. As can be seen, energy upconversion properties were determined mainly by the absorbtion spectra of Er2O3, Yb2O3. Energy upconversion efficiency were determined by excitative photons.

Energy Transfer↗