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X L Yang

Publications and source records attributed to X L Yang.

At least 109 records · Page 6Linked to original sources
PubMed1993

Localization and modulatory actions of zinc in vertebrate retina.

Zinc ions are colocalized with glutamatergic synaptic vesicles in vertebrate photoreceptors and may act as a diffusible molecular switch regulating neurotransmitter signaling at two distinct sites in the outer retina. In the dark, extracellular zinc acts presynaptically at rods and cones to minimize the depletion of tonically released glutamate, and selectively reduces GABA-mediated depolarization in horizontal cells, accelerating the response kinetics of the second-order cells. The discovery of zinc ions in photoreceptors provides a mechanism for gain control, kinetics modulation, and the balance of rod vs cone output at the first synapse in the visual system.

Animals↗
PubMed1993

Relative contribution of rod and cone inputs to bipolar cells and ganglion cells in the tiger salamander retina.

1. The relative contribution of rod and cone inputs to bipolar and ganglion cells were studied by comparing the response-irradiance relations, spectral sensitivities, and response waveforms of these neurons recorded from the isolated, flat-mounted tiger salamander retina under dark-adapted conditions. 2. Bipolar cells could be differentiated both on the basis of the polarity of the light response and on their relative rod/cone input. Thus some depolarizing bipolar cells appeared more strongly influenced by rod input (DBCR), whereas others were more influenced by cone input (DBCC). Similarly, hyperpolarizing bipolar cells could be divided into those that received rod-dominant input (HBCR) or cone-dominant input (HBCC). 3. The light onset response of sustained-ON ganglion cells reflected both rod-dominant input from DBCRs and cone-dominant input from DBCCs. 4. OFF ganglion cells displayed both a rod-dominant sustained light offset response and a cone-dominant transient light offset response, suggesting input from both HBCRs and HBCCs. 5. In ON-OFF ganglion cells, the light onset response was strongly rod dominated and was presumably mediated by DBCRs, whereas the light offset response displayed both rod and cone influence, suggesting input from HBCRs and HBCCs. The contribution of cones to the light onset response of ON-OFF ganglion cells was only observed in the presence of a rod-adapting background light. 6. A suppression of the light offset responses of OFF and ON-OFF ganglion cells was observed, which was dependent both on the wavelength and irradiance of the light stimulus. 7. These results indicate that the photoreceptor inputs to bipolar cells in the tiger salamander retina are segregated such that they form separate rod-dominant and cone-dominant pathways. Thus the response properties of the different types of ganglion cells are influenced not only by the excitatory and inhibitory inputs they receive from the bipolar and amacrine cells but also whether these inputs are provided through rod-dominant or cone-dominant pathways. The functional implications of these findings are discussed.

Ambystoma↗
PubMed1993

Identification of glutamate receptor subtypes mediating inputs to bipolar cells and ganglion cells in the tiger salamander retina.

1. The effects of glutamate receptor agonists and antagonists on bipolar cells and ganglion cells were studied with the use of intracellular and extracellular recording in the superfused, isolated, flat-mounted tiger salamander retina. The goal of the experiments was to correlate glutamate receptor subtypes with their localization at specific synaptic sites in the tiger salamander retina. The drugs tested were the kainate/alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), the N-methyl-D-aspartate (NMDA) receptor antagonist 3-(C+/-)-2-carboxy-piperazin-4-yl)-propyl-1-phosphonic acid (CPP) and L-2-amino-4-phosphonobutyrate (L-AP4). 2. The light responses of hyperpolarizing bipolar cells were suppressed by 20 microM CNQX, whereas L-AP4 had no effect on their light responses. In contrast, 20 microM CNQX had no effect on depolarizing bipolar cells, whereas L-AP4 abolished the light responses of these cells. 3. The light offset responses of OFF and ON-OFF ganglion cells were completely blocked by concentrations of CNQX as low as 5 microM. The light onset responses of ON-OFF ganglion cells were blocked when the concentration of CNQX was raised to 20 microM. In addition, 30 microM CPP partially blocked the light onset responses of ON-OFF ganglion cells but had a lesser effect on the light offset responses. 4. Twenty micromolars of CNQX blocked a transient component, and 20 microM CPP blocked a sustained component of the light response of sustained-ON ganglion cells.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1993

[Percutaneous balloon angioplasty in the treatment of membranous obstruction of the inferior vena cava].

Percutaneous transluminal angioplasty (PTA) was performed with Inoue balloon catheter in 20 patients with membranous obstruction of the inferior vena cava (MOVC) including 4 postoperative recurrent cases. 9 patients had complete and 11 had incomplete MOVC. The thickness of the membrane or web measured 1-5mm. one patient died of massive pulmonary embolism after successful PTA. The remaining 19 patients remained asymptomatic during 6-38 months. Two-dimensional ultrasonograms showed no recurrence of MOVC or thrombosis. The caval diameter at the site of MOVC increased from 1.7 +/- 1.5 to 20.3 +/- 2.6mm (P < 0.0001), and the caval pressure below the MOVC decreased from 340 +/- 76 to 160 +/- 72mm H2O (P < 0.0001), respectively.

Adolescent↗
PubMed1993

[Effect of baoyuantang on level of serum lipid peroxide and vitamin E in chronic glomerulonephritis].

Serum lipid peroxide (LPO) and vitamin E (VE) were determined in 18 patients with chronic glomerulonephritis (CGN) before and after treatment with Baoyuantang (BYT). It was found that before treatment the level of serum LPO (4.89 +/- 1.85 mumol/L) was higher, while the content of serum VE (4.27 +/- 1.84 micrograms/ml) was lower than those of normal controls (3.36 +/- 0.59 mumol/L, P < 0.001; 7.03 +/- 0.69 microgram/ml, P < 0.05). After treatment with BYT, the level of LPO lowered to 3.76 +/- 1.49 mumol/L, P < 0.05, as compared with the value before treatment, while the content of VE was increased to 5.33 +/- 2.45 micrograms/ml, but without statistical significance. A negative correlation was found between LPO level and VE content both before and after treatment (r = -0.495,P < 0.05; r = -0.522, P < 0.05). The results indicated chronic deficiency of VE in association with an increase in the level of LPO in the kidney in CGN patients and inhibition of LPO by BYT. After treatment complete remission was observed in 5 cases, basic remission in 3, and partial remission in 7.

Adult↗
PubMed1992

Modulation of synaptic gain by light.

Although synaptic transmission in the retina has been assumed to be static, it appears that the voltage gains of the synapses between photoreceptors and second-order cells can be enhanced by light. Voltage gains of the synapses between rods and bipolar (or horizontal) cells are about 10 times higher in the presence of dim background light than in darkness. This increase in synaptic gain may compensate for the loss of rod light responsiveness caused by weak background light so that the animal can maintain good rod sensitivity under moonlight or starlight, the natural lighting condition for mating and food catching.

Ambystoma↗
PubMed1992

Nonoperative treatment of membranous obstruction of the inferior vena cava by percutaneous balloon transluminal angioplasty.

Percutaneous transluminal angioplasty (PTA) was performed with the Inoue balloon catheter in nine patients with membranous obstruction of the inferior vena cava (MOVC) between November 1988 and April 1991. There were five men and four women, aged 30.8 +/- 8.5 years. Two patients had had previous surgical treatment. Three patients had complete and six had incomplete MOVC. The caval pressure below the MOVC was 24.0 +/- 5.6 and 11.8 +/- 5.3 mm Hg (p less than 0.0001) before and after PTA, respectively. The caval diameter at the site of MOVC increased from 1.5 +/- 1.7 to 20.3 +/- 2.6 mm (p less than 0.0001), and the maximal caval diameter below the MOVC decreased from 28.7 +/- 12.9 to 19.8 +/- 9.9 mm (p = 0.006), before and after PTA, respectively. One patient died of massive pulmonary embolism following successful PTA. All the other eight patients remained asymptomatic during an 18.5 +/- 11.5 months (range 3.5 to 32) follow-up period. Two-dimensional ultrasonograms showed no recurrence of MOVC. We conclude that PTA with the Inoue balloon catheter is an effective and safe alternative to surgical treatment of MOVC.

Adult↗
PubMed1992

Relationship of the cAMP-dependent protein kinase pathway to the SNF1 protein kinase and invertase expression in Saccharomyces cerevisiae.

The SNF1 protein kinase and the associated SNF4 protein are required for release of glucose repression in Saccharomyces cerevisiae. To identify functionally related proteins, we selected genes that in multicopy suppress the raffinose growth defect of snf4 mutants. Among the nine genes recovered were two genes from the cAMP-dependent protein kinase (cAPK) pathway, MSI1 and PDE2. Increased dosage of these genes partially compensates for defects in nutrient utilization and sporulation in snf1 and snf4 null mutants, but does not restore invertase expression. These results suggest that SNF1 and cAPK affect some of the same cellular responses to nutrients. To examine the role of the cAPK pathway in regulation of invertase, we assayed mutants in which the cAPK is not modulated by cAMP. Expression of invertase was regulated in response to glucose and was dependent on SNF1 function. Thus, a cAMP-responsive cAPK is dispensable for regulation of invertase.

Blotting, Northern↗
PubMed1992

Effects of neuropeptide Y injected into A1 noradrenergic nucleus on blood pressure and catecholamines in plasma of cats.

The microinjection of neuropeptide Y (NPY) 0.75 and 1.5 micrograms into A1 noradrenergic nucleus of cats produced dose-dependent falls in mean arterial blood pressure of 2.0 +/- 0.6 and 4.9 +/- 2.4 kPa, respectively. NPY microinjection (1.5 micrograms) also produced marked decreases in noradrenaline (5 +/- 4 pmol.ml-1) and adrenaline (23 +/- 8 pmol.ml-1), but no significant change in dopamine in blood plasma. The results suggest that the depressor effect of NPY in A1 noradrenergic nucleus may be realized by not only reducing the release of noradrenaline in sympathetic terminals around the peripheral vascular beds but also inhibiting the sympathetico-adrenal system.

Animals↗
PubMed1992

[Effects of prolonged darkness and background illumination on cone horizontal cells in carp retina: a correlative study of morphology and physiology].

Using intact, immobilized carp preparations, changes in light responsiveness of cone horizontal cells and ultrastructures of their terminals in cone pedicles (HCTs) were correlatively examined in prolonged (greater than 2 h) darkness and after the presentation of a dim background light. Following background illumination cone horizontal cells exhibit high light responsiveness and HCTs give rise to a lot of long, fingerlike or ball-like extensions, called slender or round spinules. When the retina is left in the dark for more than 2 h, the light responsiveness of these cells is depressed, which is accompanied by a dramatic decrease of spinules. Thus light responsiveness of the cone horizontal cells seems to be well correlated with the number of spinules. The results suggest that spinules may play an important role in regulating light responsiveness of cone horizontal cells following background illumination by altering the efficacy of signal transfer across the synapses between cone photoreceptors and cone horizontal cells.

Animals↗
PubMed1992

[The expression of kainate and GABA receptors in oocytes of Bufo bufo gargarizans].

Oocytes of Bufo bufo gargarizans were used as an expression system for analyzing structure of exogenous membrane protein and their functions. Poly (A)+ mRNA isolated from rat brain was injected into Toad (Bufo bufo gargarizans) oocytes (50 ng/oocyte). Rat brain kainic acid and gamma-aminobutyric acid(GABA) receptors expressed by the injected mRNA were integrated in the oocyte membrane 48 h after the injection at 19 degrees C. Membrane currents induced by kainic acid (5 x 10(-5) mol/L) and GABA (10(-4) mol/L) were 294.0 +/- 6.4 nA (n = 5) and 309.5 +/- 4.9 nA (n = 4) respectively. The kainic acid induced current reached its maximum value at about 10(-3) mol/L. Moreover, it was observed that the 36Cl- influx of the oocytes microinjected with mRNA was one-fold more rapid than the control oocytes. These results indicate that the oocytes of Bufo bufo gargarizans as those of Xenopus laevis can be used to express membrane proteins (receptors & transports) to acquire their proper functions from exogenous mRNA.

Animals↗
PubMed1992

[Central analgesic action of calcitonin and its relationship with central monoamine transmitters].

The analgesic action of calcitonin (0.25 MRC units.kg-1) injected into lateral cerebral ventricle was investigated in rats. The pain threshold was evaluated by the tail-flick test. The influences of icv naloxone 5 micrograms/rat, a blocker of opiate receptor, on the analgesic action of calcitonin were observed. The results showed that icv calcitonin produced a significant analgesic action, which was reversed by naloxone. While the pain threshold was raised by calcitonin, the contents of central monoamines (5-HT, NE, DA) in brain (diencephalon, brain stem) were examined by fluorophotometry, which were increased remarkably. It is suggested that calcitonin-induced analgesia is related to the opiate receptors and the contents of 5-HT, NE, and DA in CNS.

Analgesics↗
PubMed1992

Rod-cone interaction in carp retina: an analysis of electroretinographic B-waves.

Changes in electroretinographic b-wave in the presence of background lights of increasing intensity were examined in isolated, superfused carp retinas. Within a certain range of ambient illumination b-waves elicited by red (695 nm) test flashes against dimmer background lights were smaller in size than against brighter ones. Accordingly, incremental thresholds for red flashes decreased as the intensity of background lights increased within this intensity range. The results suggest that cone pathways may be suppressed by rods in darkness and dim illumination. The phenomenon was absent for photoreceptor potentials (PIII components), indicating that the rod-cone interaction occurs in second-order retinal neurons.

Animals↗
PubMed1991

Feedforward lateral inhibition in retinal bipolar cells: input-output relation of the horizontal cell-depolarizing bipolar cell synapse.

Lateral inhibition is the ubiquitous strategy used by visual neurons for spatial resolution throughout the animal kingdom. It has been a puzzle whether lateral inputs in retinal bipolar cells are mediated by the horizontal cell (HC)-cone feedback synapse, by the HC-bipolar cell feedforward synapse, or by both. By blocking the central inputs of the depolarizing bipolar cells (DBCs) with L-2-amino-4-phosphonobutyrate, we were able to eliminate the contribution of the feedback synapse and to demonstrate the postsynaptic light response in DBCs mediated by the HC-DBC feedforward synapse. The HC-DBC feedforward synapse contributes roughly one-third of the surround response whereas the HC-cone-DBC feedback synapse probably contributes the rest.

Ambystoma↗
PubMed1991

Modulation of synaptic transmission in the retina.

Synaptic transmission between photoreceptors and horizontal cells can be modulated in at least two domains: amplitude and time. In teleost fish, synaptic transmission is modulated mainly in the amplitude domain. Cone-driven horizontal cells in this species require background illumination to maintain high light responsiveness, and they are strongly suppressed in prolonged darkness. Moreover, in light, cone horizontal cells are extensively coupled via gap junctions, and the coupling is reduced in strength after prolonged darkness. The dopaminergic interplexiform cells play a major role in the regulation of cone horizontal cell activity. They may release dopamine tonically in darkness, which suppresses the light responsiveness of horizontal cells and uncouples them. In amphibians, whose horizontal cells receive input from both rods and cones, the modulation appears to be in the time domain, i.e., the rise time of horizontal cell responses is slow in prolonged darkness and accelerated after background illumination. gamma-aminobutyric acid and glycine may mediate the changes in response rise time. Despite the differences of the neuromodulators involved, these species provide two complementary modes of modulation of synaptic transmission in the retina.

Animals↗
PubMed1991

Coexistence and function of glutamate receptor subtypes in the horizontal cells of the tiger salamander retina.

Effects of the major glutamate receptor agonists, kainate (KA), alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), quisqualate (QA), N-methyl-D-aspartate (NMDA), L-alpha-amino-4-phosphonobutyrate (L-AP4), and trans-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) on horizontal cells (HCs) were studied in superfused larval tiger salamander retina. 20 microM of KA, AMPA, and QA mimicked the action of 3 mM glutamate in the absence and presence of 1 mM Co2+. 20 microM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocked the actions of KA and AMPA, but not those of QA and glutamate, indicative of the existence of CNQX-resistant QA receptors in the tiger salamander HCs. Prolonged application of ACPD hyperpolarized the HCs and enhanced the light responses, probably by shifting the resting HC voltage (Er) to a more hyperpolarized position. It is possible that the KA, AMPA, and CNQX-resistant QA receptors are involved in mediating the postsynaptic light responses in HCs, and ACPD receptors are involved in sensitivity adjustment of the HC responses.

Animals↗
PubMed1991

[Light adaptation properties of receptor potentials of cyprinid retina].

It was previously reported that changes in sensitivities of electroretinographic b-wave in the course of light adaptation depended on the intensity of background lights. B-wave sensitivity decreased with time by dimmer background lights, while it recovered during illumination with background lights of higher intensities. In this work we examined light adaptation properties of glutamate-isolated receptor potentials (P III components), using isolated and superfused cyprinid retinas. During dimmer background illumination, P III components were unchanged. When background lights were increased above certain levels, P III components showed partial recovery with time in the light. A detailed analysis of spectral sensitivities of P III components and their increment thresholds for several wavelengths indicated that the recovery of P III sensitivity appeared with background lights at which rod function was taken over by cone function. The results suggest that the recovery of b-wave sensitivity during brighter background illumination is partially a reflection of the adaptation property of cone photoreceptors.

Adaptation, Ocular↗