scholarly journals Cellular mechanisms that underlie bleaching and background adaptation.

1990 ◽  
Vol 96 (2) ◽  
pp. 345-372 ◽  
Author(s):  
M C Cornwall ◽  
A Fein ◽  
E F MacNichol
Keyword(s):  
Steady State ◽  
Visual Pigment ◽  
Outer Segment ◽  
Tiger Salamander ◽  
Cellular Mechanisms ◽  
Rod Photoreceptors ◽  
Background Adaptation ◽  
Before And After ◽  
Space Constant ◽  
Local Test

Experiments were performed on rod photoreceptors isolated from the eye of the larval tiger salamander to determine if the same or different mechanisms underlie the desensitization produced by dim background light (background adaptation) and that which persists in the steady state in darkness after a significant fraction of the photopigment is bleached (bleaching adaptation). We have examined adaptational effects after light that bleached between approximately 50% and 95% of the photopigment under conditions which preclude pigment regeneration. The steady-state desensitization, far greater than that predicted by quantum-catch loss, is relieved upon regeneration of the visual pigment with 11-cis retinal. We measured the spread of desensitization along the long axis of the rod after a local bright bleach at one end by comparing responses to dim local test flashes elicited in different regions of the outer segment, before and after bleaching. The space constant for this spread was less than 2.5 microns. We have previously measured the space constant for the longitudinal spread of desensitization during a local dim background in Ambystoma rods to be 7 microns. This is similar to a space constant of 6 microns measured under similar conditions in Bufo rods by Lamb et al. (1981. J. Physiol. 319:463-496). If calcium carries the signal for background desensitization, this difference in space constant for background and bleaching adaptation precludes it as the messenger for the steady component of bleaching adaptation. Experiments with isobutylmethyl xanthine (IBMX) also indicate that Ca2+ as well as c-GMP are unlikely regulators of bleaching desensitization, since elevation of cytosolic levels of both of these internal messengers by IBMX has little effect on sensitivity in bleach-adapted cells. All of our findings are consistent with the notion that bleaching adaptation is not mediated by a freely diffusible cytoplasmic messenger.

Effect of hydroxylamine on the subcellular distribution of arrestin (S-antigen) in rod photoreceptors

1994 ◽  
Vol 11 (3) ◽  
pp. 561-568 ◽  
Author(s):  
Nancy J. Mangini ◽  
Grady L. Garner ◽  
Tinging L. Okajima ◽  
Larry A. Donoso ◽  
David R. Pepperberg
Keyword(s):  
Visual Pigment ◽  
Driving Force ◽  
Outer Segment ◽  
Processing System ◽  
Bright Light ◽  
Photoreceptor Outer Segment ◽  
Rod Photoreceptors ◽  
Average Value ◽  
Secondary Antibodies ◽  
Microscopic Image Processing

AbstractThe immunocytochemical labeling of arrestin (S-antigen) in photoreceptors of the ovine retina was examined following incubation of the retina with hydroxylamine (NH2OH), an agent known to inhibit the phosphorylation of photoactivated rhodopsin. Intact, isolated retinas bathed in medium containing 20 mM NH2OH, or in control medium lacking NH2OH, were maintained in darkness or exposed to bright light for 3 min (dark-adapted and light-adapted conditions, respectively); further incubated in darkness for 10 min; and then fixed and prepared for cryosectioning. Cryosections were incubated with anti-S-antigen monoclonal antibody MAb A2G5; with secondary antibodies that were conjugated with horseradish peroxidase; and with either 3–amino-9–ethyl carbazole or diaminobenzidine as chromogen. Anti-arrestin labeling in cryosections was then analyzed densitometrically using a light-microscopic image processing system. In dark-adapted control retinas, labeling density of the photoreceptor outer segment (OS) layer (0.061 ± 0.004; average ± S.e.m.) was less than that of the inner segment (IS) layer (0.138 ± 0.011). In light-adapted control retinas, OS labeling density (0.139 ± 0.007) exceeded IS labeling density (0.095 ± 0.005). Incubation with NH2OH eliminated this light-dependent increase in labeling of the OS relative to that of the IS, i.e. eliminated the increase in relative OS/IS labeling. Densities of labeling were 0.110 ± 0.006 (OS) and 0.183 ± 0.006 (IS) in NH2OH-treated dark-adapted retinas vs. 0.078 ± 0.004 (OS) and 0.182 ± 0.008 (IS) in NH2OH-treated light-adapted retinas. Anti-arrestin labeling was also examined in retinas that were exposed to 3 min or 13 min of bright light and then immediately fixed. Among retinas incubated in the absence of NH2OH, an increase in OS/IS labeling density was evident after 3 min of illumination, and retinas illuminated for 13 min exhibited an even larger increase in OS/IS labeling. An increase in OS/IS labeling was also exhibited by NH2OH-treated retinas that had been illuminated for 3 min; by comparison with dark-adapted NH2OH-treated controls (average value of OS/IS labeling: 0.60), OS/IS labeling in these illuminated retinas was 0.97. However, OS/IS labeling in NH2OH-treated retinas that had been illuminated for 13 min (average value: 0.35) was lower than that of the dark-adapted controls. The results indicate that, within intact rods, NH2OH inhibits the light-dependent increase in OS/IS anti-arrestin labeling that is ordinarily expressed at long times (~10 min) after major bleaching of the visual pigment. Among the possible bases for the effect of NH2OH are a reduction in the driving force for the movement of arrestin from the inner to the outer segment and/or a facilitation of the degradation of arrestin in the outer segment.

Movement of retinal along cone and rod photoreceptors

1994 ◽  
Vol 11 (2) ◽  
pp. 389-399 ◽  
Author(s):  
Jing Jin ◽  
Gregor J. Jones ◽  
M. Carter Cornwall
Keyword(s):  
Cell Body ◽  
Dark Adaptation ◽  
Visual Pigment ◽  
Outer Segment ◽  
Light Adaptation ◽  
Rod Photoreceptors ◽  
Rod Outer Segment ◽  
Rods And Cones ◽  
Outer Segments ◽  
Rod Cell

AbstractSingle isolated photoreceptors can be taken through a visual cycle of light adaptation by bleaching visual pigment, followed by dark adaptation when supplied with 11–cis retinal. Light adaptation after bleaching is manifested by faster response kinetics and a permanent reduction in sensitivity to light flashes, presumed to be due to the presence of bleached visual pigment. The recovery of flash sensitivity during dark adaptation is assumed to be due to regeneration of visual pigment to pre-bleach levels. In previous work, the outer segments of bleached, light-adapted cells were exposed to 11–cis retinal. In the present work, the cell bodies of bleached photoreceptors were exposed. We report a marked difference between rods and cones. Bleached cones recover sensitivity when their cell bodies are exposed to 11–cis retinal. Bleached rods do not. These results imply that retinal can move freely along the cone photoreceptor, but retinal either is not taken up by the rod cell body or retinal cannot move from the rod cell body to the rod outer segment. The free transfer of retinal along cone but not along rod photoreceptors could explain why, during dark adaptation in the retina, cones have access to a store of 11–cis retinal which is not available to rods. Additional experiments investigated the movement of retinal along bleached rod outer segments. The results indicate that retinal can move along the rod outer segment, but that this movement is slow, occurring at about the same rate as the regeneration of visual pigment.

scholarly journals Metabolic constraints on the recovery of sensitivity after visual pigment bleaching in retinal rods

2009 ◽  
Vol 134 (3) ◽  
pp. 165-175 ◽  
Author(s):  
Kiyoharu J. Miyagishima ◽  
M. Carter Cornwall ◽  
Alapakkam P. Sampath
Keyword(s):  
Time Constant ◽  
Visual Pigment ◽  
Outer Segment ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Bright Light ◽  
Primary Source ◽  
Retinal Rods ◽  
Before And After ◽  
Active Intermediates ◽  
Phototransduction Cascade

The shutoff of active intermediates in the phototransduction cascade and the reconstitution of the visual pigment play key roles in the recovery of sensitivity after the exposure to bright light in both rod and cone photoreceptors. Physiological evidence from bleached salamander rods suggests this recovery of sensitivity occurs faster at the outer segment base compared with the tip. Microfluorometric measurements of similarly bleached salamander rods demonstrate that the reduction of all-trans retinal to all-trans retinol also occurs more rapidly at the outer segment base than at the tip. The experiments reported here were designed to test the hypothesis that these two phenomena are linked, e.g., that slowed recovery of sensitivity at the tip of outer segments is rate limited by the reduction of all-trans retinal and results from a shortage of cytosolic nicotinamide adenine dinucleotide phosphate (NADPH), the reducing agent for all-trans retinal reduction. Extracellular measurements of membrane current and sensitivity were made from isolated salamander rods under dark-adapted and bleached conditions while intracellular NADPH concentration was varied by dialysis from a micropipette attached to the inner segment. Sensitivity at the base and tip of the outer segment was assessed before and after bleaching. After exposure to a light that photoactivates 50% of the visual pigment, rods were completely insensitive for nearly 10 minutes, after which the base recovered sensitivity and responsiveness with a time constant of ∼200 seconds, but tip sensitivity recovered more slowly with a time constant of ∼680 seconds. Dialysis of 5 mM NADPH into the rod promoted an earlier recovery and eliminated the previously observed tip/base difference. Dialysis of 1.66 mM NADPH failed to eliminate the tip/base recovery difference, suggesting the steady-state NADPH concentration in rods is ∼1 mM. These results indicate the inner segment is the primary source of reducing equivalents after pigment bleaching, with the reduction of all-trans retinal to all-trans retinol playing a key step in the recovery of sensitivity.

The Study of Dynamic Response to Acute Hemorrhage by Pulse Spectrum Analysis

2006 ◽  
Vol 34 (03) ◽  
pp. 449-460 ◽  
Author(s):  
Yu Hsin Chang ◽  
Chia I Tsai ◽  
Jaung Geng Lin ◽  
Yue Der Lin ◽  
Tsai Chung Li ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Steady State ◽  
Arterial Blood Pressure ◽  
Mean Arterial Blood Pressure ◽  
Spectrum Analysis ◽  
Pulse Spectrum ◽  
Acute Hemorrhage ◽  
Arterial Blood ◽  
Percentage Difference ◽  
Before And After

Traditional Chinese Medicine (TCM) holds that Blood and Qi are fundamental substances in the human body for sustaining normal vital activity. The theory of Qi, Blood and Zang-Fu contribute the most important theoretical basis of human physiology in TCM. An animal model using conscious rats was employed in this study to further comprehend how organisms survive during acute hemorrhage by maintaining the functionalities of Qi and Blood through dynamically regulating visceral physiological conditions. Pulse waves of arterial blood pressure before and after the hemorrhage were taken in parallel to pulse spectrum analysis. Percentage differences of mean arterial blood pressure and harmonics were recorded in subsequent 5-minute intervals following the hemorrhage. Data were analyzed using a one-way analysis of variance (ANOVA) with Duncan's test for pairwise comparisons. Results showed that, within 30 minutes following the onset of acute hemorrhage,the reduction of mean arterial blood pressure was improved from 62% to 20%. Throughout the process, changes to the pulse spectrum appeared to result in a new balance over time. The percentage differences of the second and third harmonics, which were related to kidney and spleen, both increased significantly than baseline and towards another steady state. Apart from the steady state resulting from the previous stage, the percentage difference of the 4th harmonic decreased significantly to another steady state. The observed change could be attributed to the induction of functional Qi, and is a result of Qi-Blood balancing activity that organisms hold to survive against acute bleeding.

scholarly journals Light-dependent binding of G-protein to outer segment membranes of toad photoreceptors.

1986 ◽  
Vol 88 (5) ◽  
pp. 675-694 ◽  
Author(s):  
N J Mangini ◽  
D R Pepperberg ◽  
W Baehr
Keyword(s):  
G Protein ◽  
Visual Pigment ◽  
Outer Segment ◽  
Tight Binding ◽  
Beta Subunits ◽  
Hypotonic Medium ◽  
Intense Light ◽  
Low Levels ◽  
Toad Bufo ◽  
Peak Value

Light-dependent changes in the binding of G-protein were analyzed in outer segment disk membranes obtained from photoreceptors of the toad (Bufo marinus) retina. Isolated, intact retinas, incubated in oxygenated Ringer's solution at 23 +/- 1 degree C, were subjected to various conditions of illumination and then incubated in darkness for specified periods. The retinas were then chilled (0-4 degrees C) and the receptor outer segments (ROS) were isolated. Binding of the alpha- and beta-subunits of G-protein to the ROS membranes was analyzed by quantitating G alpha and G beta extracted from the membranes with hypotonic medium lacking GTP vs. hypotonic medium containing GTP (H and HG extracts, respectively). For retinas illuminated and then immediately chilled for analysis, the extent of G binding (relative abundance of G alpha, beta in the HG extract) increased with the extent of bleaching of the visual pigment. Near-maximal binding was observed after bleaches of greater than or equal to 30%. With an increasing period of incubation in darkness after approximately 70% bleaching, the extent of binding declined gradually to low levels characteristic of unbleached retinas. The period required for half-completion of the decline was approximately 10(3) s. A gradual decline in G binding, from a rapidly developing peak value, was also observed with an increasing period of exposure to intense light. Viewed in the context of previous electrophysiological data, our results indicate that sustained bleaching desensitization of the rods does not depend upon a persisting state of "tight binding" (immobilization) of G-protein by bleached visual pigment.

Light-Evoked Electrical Potentials from the Eye and Optic Nerve of Strombus: Response Waveform and Spectral Sensitivity

1974 ◽  
Vol 60 (2) ◽  
pp. 383-396
Author(s):  
HOWARD L. GILLARY
Keyword(s):  
Steady State ◽  
Optic Nerve ◽  
Spectral Sensitivity ◽  
Visual Pigment ◽  
Synaptic Inhibition ◽  
Nerve Fibres ◽  
Electrical Potentials ◽  
Peak Absorption ◽  
Negative Erg ◽  
Sensitivity Studies

1. The cornea-negative ERG of the eye of Strombus exhibited two distinct ‘on’ peaks, a steady state during sustained illumination, and small rhythmic oscillations following the cessation of stimulation. 2. In certain afferent optic nerve fibres, illumination evoked phasic and tonic ‘on’ responses; others, whose activity was inhibited by light, responded with repetitive ‘off’ bursts which tended to occur in phase with the rhythmic ERG oscillations. 3. Spectral sensitivity studies indicate the presence of a single visual pigment with a peak absorption of about 485 nm. 4. The effects on the response of temperature and stimulus intensity and frequency were also examined. 5. The results indicate photo-excitation and synaptic inhibition of the receptors, and excitatory coupling between them.

scholarly journals Comparison of Infant Test-Weighing and Hourly Breast Expression in Measuring Maternal Milk Production (P11-041-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Dayna Roznowski ◽  
Erin Wagner ◽  
Sarah Riddle ◽  
Laurie Nommsen-Rivers
Keyword(s):  
Steady State ◽  
Production Rate ◽  
Milk Production ◽  
Production Capacity ◽  
Limits Of Agreement ◽  
Term Infants ◽  
Maternal Milk ◽  
Milk Output ◽  
Before And After ◽  
The Difference

Abstract Objectives Measuring maternal milk production is cumbersome. Our objectives were to: 1) confirm that milk production rate reaches steady state at hour 2 of hourly breast emptying; and 2) compare agreement in milk production when measured using the well-established test-weighing method versus the more efficient hourly breast emptying method (Lai, et al., Breastfeeding Medicine, 2010). Methods Eligible mothers were 4–10 weeks postpartum and exclusively breastfeeding their healthy, singleton, term infants. A subset of mothers test-weighed (TW) their infant (± 2 g) before and after breastfeeding for 48h. Within 1 week of TW, mothers had a morning visit at the research clinic for hourly breast expression measurements. Mothers emptied both breasts at baseline (h0), and 1, 2, and 3 hours after baseline (h1, h2, h3) using a hospital-grade pump. We recorded hourly milk output ± 1 g and adjusted production rate (g/h) to exact interval (minutes from end of previous to end of current expression). We used paired t-test to compare g/h at h3 versus h0, h1, and h2. We estimated mother's steady-state milk production rate (MPR, g/h) as mean (h2, h3). We used the Bland-Altman method for determining the 95% limits of agreement in measuring milk production (g/24h) using TW versus MPRx24. Results 23 mothers (65% primiparous) were 54 ± 14 days postpartum. Milk output was 185 ± 55 g at h0 and 60 ± 26, 47 ± 13, 44 ± 13 g/h at h1, h2, and h3, respectively. Mean paired difference (vs. h3) was significant at h0 and h1 (P < 0.05), but not at h2 (P > 0.05, h3 - h2 = 3 ± 10 g/h). In the subset with TW data (n = 16), mean TW milk output was 717 ± 119 g/24h, and mean MPRx24 was 1085 ± 300 g/24h. Mean difference, MPRx24 - TW [± 95% limits of agreement], was 368 [± 468] g/24h; and mean ratio, MPRx24/TW, was 1.5 [± 0.4]. Both difference and ratio significantly increased as MPR increased (P < 0.05). Conclusions Hourly milk production reaches steady state at h2; thus, mean (h2, h3) is a valid measure of current maternal milk production capacity. However, there was not homogeneous agreement between MPR and TW, and the 95% limits of agreement were very wide: -91 to 459 g/24h when expressed as the difference, and 0.9 to 1.9-fold as a ratio. Thus, MPR is feasible for researching variation in maternal milk production but not for researching variation in infant intake. Funding Sources None. Supporting Tables, Images and/or Graphs

Relative peripheral and central chemosensory responses to metabolic alkalosis

1983 ◽  
Vol 245 (6) ◽  
pp. R873-R880 ◽  
Author(s):  
M. Pokorski ◽  
S. Lahiri
Keyword(s):  
Steady State ◽  
Metabolic Alkalosis ◽  
Central Effect ◽  
Co2 Partial Pressure ◽  
Ventilatory Responses ◽  
Relative Contribution ◽  
Before And After ◽  
Ventilatory Effect ◽  
Peripheral Effect ◽  
Steady State Levels

We investigated the relative contribution of peripheral and central chemosensory mechanisms to ventilatory responses to metabolic alkalosis in anesthetized cats by simultaneously measuring steady-state carotid body chemosensory activity and ventilation. The effects of graded steady-state levels of metabolic alkalosis at constant levels of arterial O2 and CO2 partial pressure (PaO2 and PaCO2, respectively) were studied first. Then the responses to isocapnic hypoxia and hyperoxic hypercapnia before and after the induction of a given level of metabolic alkalosis were studied. From the relationship between the carotid chemosensory activity and ventilation, the contribution of the two chemosensory mechanisms was estimated. The depression of ventilation that could not be accounted for by a decrease in the carotid chemosensory activity is attributed to the central effect. We found that metabolic alkalosis decreased both carotid chemosensory activity and ventilation at all levels of PaO2 or PaCO2. The ventilatory effect of alkalosis increased during hypoxia due to suppression of both peripheral chemosensory input and its interaction with the central CO2-H+ drive. During hyperoxia the central effect of alkalosis was predominant, although the peripheral effect increased with hypercapnia. We conclude that acute metabolic alkalosis suppresses both peripheral and central chemosensory drives, and its ventilatory effect grows larger with decreasing PaO2.

Effects of hypercapnia and hypoxia on inspiratory and expiratory diaphragmatic activity in conscious cats

1994 ◽  
Vol 77 (4) ◽  
pp. 1644-1652 ◽  
Author(s):  
M. Bonora ◽  
M. Boule
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Steady State ◽  
Electromyographic Activity ◽  
Large Reduction ◽  
Before And After ◽  
The Central Nervous System ◽  
State Changes ◽  
Chemical Stimuli ◽  
Adult Cats

The influence of steady-state changes in chemical stimuli on ventilation and electromyographic activity of the diaphragm during both inspiration (total DI) and expiration (total DE) was studied in unanesthetized intact adult cats before and after carotid denervation. In intact animals, during hypercapnia (2 4, and 6% CO2), tidal volume (VT) and total DI increase, whereas total DE did not consistently change. During ambient hypocapnic hypoxia (14, 12, and 10% O2), VT increased only at 10% O2, whereas total DI increased at all levels studied. Total DE increased substantially at 14% O2, persisting up to the end of expiration with 12 and 10% O2. This effect was markedly attenuated during normocapnic hypoxia. During CO hypoxemia (1,700 ppm in air), VT as well as total DI and total DE decreased because of a large reduction in inspiratory and expiratory time elicited by tachypneic breathing. The effects of hypercapnia and hypoxia persisted after carotid denervation. Therefore, 1) in contrast to hypercapnia, hypoxia markedly enhances the expiratory diaphragmatic activity, 1) this expiratory braking mechanism depends on the severity of hypoxia and is partly due to hypocapnia secondary to hypoxia; and 3) because this effect was observed after carotid denervation and during CO hypoxemia, it may arise in the central nervous system, possibly in bulbopontine structures.

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