A5011305143- Retinal Development and Disorders
- Photoreceptor and optogenetics research
- Neurobiology and Insect Physiology Research
- Receptor Mechanisms and Signaling
- Retinal Diseases and Treatments
- Photochromic and Fluorescence Chemistry
- Neuroscience and Neural Engineering
- Neuroscience and Neuropharmacology Research
- Neural dynamics and brain function
- bioluminescence and chemiluminescence research
- Circadian rhythm and melatonin
- melanin and skin pigmentation
- Connexins and lens biology
- Olfactory and Sensory Function Studies
- Retinoids in leukemia and cellular processes
- Plant and Biological Electrophysiology Studies
- Antioxidant Activity and Oxidative Stress
- Electrochemical Analysis and Applications
- Ion channel regulation and function
- Biochemical Analysis and Sensing Techniques
- Visual perception and processing mechanisms
- Adipose Tissue and Metabolism
- Animal Behavior and Reproduction
- Cardiac electrophysiology and arrhythmias
- Ocular and Laser Science Research
Boston University
2010-2023
Boston Medical Center
2008
University Medical Center
2008
Medical University of South Carolina
1990-2007
The First Affiliated Hospital, Sun Yat-sen University
2007
National Eye Institute
2007
Sun Yat-sen University
2007
University of Cambridge
1996-2001
University of California, Los Angeles
1998-2001
University of Colorado Denver
2001
After visual-pigment bleaching, single isolated rod photoreceptors of Ambystoma tigrinum recover their sensitivity to light when supplied with 11-cis-retinal from liposomes or bound interphotoreceptor retinoid-binding protein. Bleached rods do not sensitivity, so only very slowly, after exposure 11-cis-retinol. The latter retinoid is "toxic" in that actually lose its presence. In contrast, bleached cone cells either supplied. It suggested the major pathway for rhodopsin regeneration during...
Abstract Using suction electrodes, photocurrent responses to 100-ms saturating flashes were recorded from isolated retinal rods of the larval-stage tiger salamander ( Ambystoma tigrinum ). The delay period T e ) that preceded recovery dark current by a criterion amount (3 pA) was analyzed in relation flash intensity I f ), and corresponding fractional bleach R* 0 /R tot visual pigment; compared with s at which peak level activated transducin approaches saturation. Over an approximately 8 In...
1. We have used suction electrode recording together with rapid steps into Li+ solution and 0.5 mM IBMX to estimate the rates of guanylyl phosphodiesterase (PDE) cyclase in isolated rods salamander, Ambystoma tigrinum. 2. show that both PDE velocities are accelerated by steady background light. The enzymes appear be saturating functions intensity. 3. Bleaching also accelerates cyclase. This effect is maintained long after bleaching stimulus removed (up 2 h) reversed only if photopigment...
The brilliantly coloured cone oil droplets of the avian retina function as long-pass cut-off filters that tune spectral sensitivity photoreceptors and are hypothesized to enhance colour discrimination improve constancy. Although it has long been known these pigmented with carotenoids, their precise composition remained uncertain owing technical challenges measuring very small, dense highly refractile optical organelles. In this study, we integrated results from high-performance liquid...
Simultaneous measurements of photocurrent and outer segment Ca2+ were made from isolated salamander cone photoreceptors. While recording the inner segment, which was drawn into a suction pipette, laser spot confocal technique employed to evoke fluorescence loaded with indicator fluo-3. When dark-adapted exposed intense illumination laser, circulating current completely suppressed fluo-3 rapidly declined. In more numerous red-sensitive cones this light-induced decay in best fitted as sum two...
Experiments were performed on rod photoreceptors isolated from the eye of larval tiger salamander to determine if same or different mechanisms underlie desensitization produced by dim background light (background adaptation) and that which persists in steady state darkness after a significant fraction photopigment is bleached (bleaching adaptation). We have examined adaptational effects between approximately 50% 95% under conditions preclude pigment regeneration. The steady-state...
A spot confocal microscope based on an argon ion laser was used to make measurements of cytoplasmic calcium concentration (Ca2+i) from the outer segment isolated rod loaded with fluorescent indicator fluo-3 during simultaneous suction pipette recording photoresponse. The decline in fluorescence a exposed saturating illumination best fitted by two exponentials approximately equal amplitude time constants 260 and 2,200 ms. Calibration situ yielded Ca2+i estimates 670 ± 250 nM dark-adapted 30...
Passive and active electrical properties of isolated rat adrenal glomerulosa fasciculata cells were studied by intracellular voltage-recording constant current stimulation. The average resting membrane potential was -78.9 +/- 4.2 mV for -77.8 5.0 cells. response the to changes in external K+ concentration stable reversible up 28 mM independent Cl-. relationship between log linear 4 mM, could be predicted a simplified form field equation with [K]i 138.5 PNa/PK 0.015 112.4 0.011 Under clamp...
The visual cycle is a chain of biochemical reactions that regenerate pigment following exposure to light. Initial steps, the liberation all-trans retinal and its reduction retinol by dehydrogenase (RDH), take place in photoreceptors. We performed comparative microspectrophotometric microfluorometric measurements on variety rod cone photoreceptors isolated from salamander retinae correlate rates photoproduct decay production. Metapigment rate was spatially uniform within outer segments 50–70...
Color vision in birds is mediated by four types of cone photoreceptors whose maximal sensitivities (λmax) are evenly spaced across the light spectrum. In course avian evolution, λmax most shortwave-sensitive cone, SWS1, has switched between violet (λmax > 400 nm) and ultraviolet < 380 multiple times. This shift SWS1 opsin accompanied a corresponding short-wavelength spectrally adjacent SWS2 cone. Here, we show that spectral tuning modulating ratio two apocarotenoids, galloxanthin...
Photoactivation of rhodopsin initiates both excitation and adaptation in vertebrate rod photoreceptors. Bleaching to free opsin all-trans-retinal isolated rods produces a stable desensitization (bleaching adaptation) that is much larger than expected from pigment depletion alone. In our experiments, 93% bleach produced 500-fold increase the light intensity required for saturation response. This component was 32-fold 16-fold 11-cis-Retinal, when delivered liposomes, combines with form...
The membrane response of isolated rat glomerulosa cells to the application angiotensin II (A II) has been studied using intracellular voltage measurements. is biphasic. first, brief phase involves an increase in conductance and a hyperpolarization from resting potential. second, long-lasting characterized by large decrease depolarization reversal potential for second –94 ±1.2 mV, linear relationship between external K+ indicates that A II-mediated predominantly inhibition permeability. can...
The response of cytosolic calcium [Ca2+]i to angiotensin II (AII) and potassium (K+) in individual rat glomerulosa cells was determined using the calcium-sensitive fluorescent dye, fura-2 digital imaging. Control (4 mM K+) levels were generally 80-120 nM range increased monotonically as [K+] from 4 12 mM. There no delay onset response. In most decreased its peak after 3-4 min, even presence superfusate containing elevated K+. time course change AII stimulation, on other hand, more variable....
Bleaching of a large fraction the rhodopsin in isolated rod outer segments results an irreversible desensitization rod. This is referred to as bleaching adaptation. The logarithm sensitivity during adaptation has been found by number workers be linearly related concentration unbleached rhodopsin. We have measured due produced spatially confined stimulus and that its effects are highly local. space constant for spread was less than 4 microns. small apparent beyond bleached regions probably...
Vision is the primary sensory modality of birds, and its importance evident in sophistication their visual systems. Coloured oil droplets cone photoreceptors represent an adaptation avian retina, acting as long-pass colour filters. However, we currently lack understanding how optical properties morphology component structures (e.g. droplet, mitochondrial ellipsoid outer segment) photoreceptor influence transmission light into segment ultimate effect they have on receptor sensitivity. In this...
Significance For decades, amplification at the step of rhodopsin–G protein (transducin) interaction in rod phototransduction has been believed to be ∼500, a high value often generalized other G protein-coupled receptor pathways. Recently, there have indications that this may considerably lower. Nonetheless, disputes persist because large variation estimates obtained by different groups, plus drawback some key measurements used such came from experiments on nonintact rods. As such, dogma...
We have used suction electrode recording together with rapid steps into 0.5 mM IBMX solution to investigate changes in guanylyl cyclase velocity produced by pigment bleaching isolated cones of the salamander Ambystoma tigrinum. Both backgrounds and bleaches accelerate time course current increase during IBMX. interpret this as evidence that is increased background light or after bleaching. Our results indicate increases nearly linearly increasing percent bleached but nonlinearly (and may...