Long-term light history modulates the light response kinetics of luminosity (L)-type horizontal cells in the roach retina

Stomata are cellular pores on the leaf epidermis that allow plants to regulate carbon assimilation and water loss. Stomata integrate environmental signals to regulate pore apertures and optimize gas exchange to fluctuating conditions. Here, we quantified intraspecific plasticity of stomatal gas exchange and anatomy in response to seasonal variation in Brachypodium distachyon. Over the course of two years we (i) used infrared gas analysis to assess light response kinetics of 120 Bd21-3 wild-type individuals in an environmentally fluctuating greenhouse and (ii) microscopically determined the seasonal variability of stomatal anatomy in a subset of these plants. We observed systemic environmental effects on gas exchange measurements and remarkable intraspecific plasticity of stomatal anatomical traits. To reliably link anatomical variation to gas exchange, we adjusted anatomical gsmax calculations for grass stomatal morphology. We propose that systemic effects and variability in stomatal anatomy should be accounted for in long-term gas exchange studies.

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Intrinsic Cone Adaptation Modulates Feedback Efficiency from Horizontal Cells to Cones

The Journal of General Physiology ◽

10.1085/jgp.114.4.511 ◽

1999 ◽

Vol 114 (4) ◽

pp. 511-524 ◽

Cited By ~ 17

Author(s):

I. Fahrenfort ◽

R.L. Habets ◽

H. Spekreijse ◽

M. Kamermans

Keyword(s):

Membrane Potential ◽

Time Constant ◽

Calcium Current ◽

Horizontal Cell ◽

Light Response ◽

Horizontal Cells ◽

Spectral Processing ◽

Kinetics Of ◽

Feedback Pathway ◽

Cone Adaptation

Processing of visual stimuli by the retina changes strongly during light/dark adaptation. These changes are due to both local photoreceptor-based processes and to changes in the retinal network. The feedback pathway from horizontal cells to cones is known to be one of the pathways that is modulated strongly during adaptation. Although this phenomenon is well described, the mechanism for this change is poorly characterized. The aim of this paper is to describe the mechanism for the increase in efficiency of the feedback synapse from horizontal cells to cones. We show that a train of flashes can increase the feedback response from the horizontal cells, as measured in the cones, up to threefold. This process has a time constant of ∼3 s and can be attributed to processes intrinsic to the cones. It does not require dopamine, is not the result of changes in the kinetics of the cone light response and is not due to changes in horizontal cells themselves. During a flash train, cones adapt to the mean light intensity, resulting in a slight (4 mV) depolarization of the cones. The time constant of this depolarization is ∼3 s. We will show that at this depolarized membrane potential, a light-induced change of the cone membrane potential induces a larger change in the calcium current than in the unadapted condition. Furthermore, we will show that negative feedback from horizontal cells to cones can modulate the calcium current more efficiently at this depolarized cone membrane potential. The change in horizontal cell response properties during the train of flashes can be fully attributed to these changes in the synaptic efficiency. Since feedback has major consequences for the dynamic, spatial, and spectral processing, the described mechanism might be very important to optimize the retina for ambient light conditions.

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Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

Nuklearmedizin ◽

10.1055/s-0037-1620603 ◽

1977 ◽

Vol 16 (01) ◽

pp. 30-35 ◽

Cited By ~ 1

Author(s):

N. Agha ◽

R. B. R. Persson

Keyword(s):

Complex Formation ◽

Significant Influence ◽

Room Temperature ◽

Ph Value ◽

Maximum Activity ◽

Reduction Step ◽

Labelling Yield ◽

Different Temperatures ◽

Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

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Automated Microscopy: Macro Language Controlling a Confocal Microscope and its External Illumination: Adaptation for Photosynthetic Organisms

Microscopy and Microanalysis ◽

10.1017/s1431927616000556 ◽

2016 ◽

Vol 22 (2) ◽

pp. 258-263 ◽

Cited By ~ 4

Author(s):

Gábor Steinbach ◽

Radek Kaňa

Keyword(s):

Light Sources ◽

Light Conditions ◽

Photosynthetic Organisms ◽

Automated Microscopy ◽

Photosynthetic Microorganisms ◽

Arduino Microcontroller ◽

Microscopy Data ◽

Kinetics Of ◽

Photosynthetic Cells

AbstractPhotosynthesis research employs several biophysical methods, including the detection of fluorescence. Even though fluorescence is a key method to detect photosynthetic efficiency, it has not been applied/adapted to single-cell confocal microscopy measurements to examine photosynthetic microorganisms. Experiments with photosynthetic cells may require automation to perform a large number of measurements with different parameters, especially concerning light conditions. However, commercial microscopes support custom protocols (throughTime Controlleroffered by Olympus orExperiment Designeroffered by Zeiss) that are often unable to provide special set-ups and connection to external devices (e.g., for irradiation). Our new system combining an Arduino microcontroller with theCell⊕Findersoftware was developed for controlling Olympus FV1000 and FV1200 confocal microscopes and the attached hardware modules. Our software/hardware solution offers (1) a text file-based macro language to control the imaging functions of the microscope; (2) programmable control of several external hardware devices (light sources, thermal controllers, actuators) during imaging via the Arduino microcontroller; (3) theCell⊕Findersoftware with ergonomic user environment, a fast selection method for the biologically important cells and precise positioning feature that reduces unwanted bleaching of the cells by the scanning laser.Cell⊕Findercan be downloaded fromhttp://www.alga.cz/cellfinder. The system was applied to study changes in fluorescence intensity inSynechocystissp. PCC6803 cells under long-term illumination. Thus, we were able to describe the kinetics of phycobilisome decoupling. Microscopy data showed that phycobilisome decoupling appears slowly after long-term (>1 h) exposure to high light.

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Long-Term Clinical Effects, Bioavailability, and Kinetics of Minoxidil in Relation to Renal Function

The Journal of Clinical Pharmacology ◽

10.1002/j.1552-4604.1978.tb01578.x ◽

1978 ◽

Vol 18 (10) ◽

pp. 500-508 ◽

Cited By ~ 17

Author(s):

DAVID T. LOWENTHAL ◽

GADDO ONESTI ◽

ROBERT MUTTERPERL ◽

MELTON APFRIME ◽

EDUARDO W. MARTINEZ ◽

...

Keyword(s):

Renal Function ◽

Clinical Effects ◽

Kinetics Of

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Phosphorus removal by apatite in horizontal flow constructed wetlands for small communities: pilot and full-scale evidence

Water Science & Technology ◽

10.2166/wst.2011.250 ◽

2011 ◽

Vol 63 (8) ◽

pp. 1629-1637 ◽

Cited By ~ 8

Author(s):

N. Harouiya ◽

S. Martin Rue ◽

S. Prost-Boucle ◽

A. Liénar ◽

D. Esser ◽

...

Keyword(s):

Constructed Wetlands ◽

Particle Surface ◽

Full Scale ◽

Retention Capacity ◽

Small Communities ◽

Lab Experiments ◽

Apatite Mineral ◽

Kinetics Of ◽

P Removal

Phosphorus (P) removals in constructed wetlands (CWs) have received particular attention in recent decades by using specific materials which promote adsorption/precipitation mechanisms. Recent studies have shown interest in using apatite materials to promote P precipitation onto the particle surface. As previous trials were mainly done by lab experiments, this present study aims to evaluate the real potential of apatites to remove P from wastewater in pilot units and a full-scale plant over a 2 year period. P retention kinetics of two qualities of apatites are presented and discussed. In this work apatite appears to have high retention capacity (>80% of P removal) and is still an interesting way for P removal in CWs for limiting the risk of eutrophication downstream of small communities. Nevertheless, the apatite quality appears to be of great importance for a reliable and long term P removal. The use of materials with low content of apatite mineral (40–50%) seems to be not economically relevant.

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Wavelength-dependent temporal properties of retinal horizontal cells in turtles

Visual Neuroscience ◽

10.1017/s0952523800005186 ◽

1990 ◽

Vol 4 (05) ◽

pp. 427-435 ◽

Cited By ~ 1

Author(s):

C.A. Dvorak ◽

A.M. Granda

Keyword(s):

Temporal Integration ◽

Monochromatic Light ◽

Maximum Amplitude ◽

Light Response ◽

Chelonia Mydas ◽

Sea Turtle ◽

Horizontal Cells ◽

Freshwater Turtle ◽

L Cells ◽

Pseudemys Scripta

AbstractElectrical reponses of luminosity horizontal cells (L cells) to monochromatic stimuli were analyzed by intracellular recordings in the retinas of the freshwater turtle (Pseudemys scripta elegans) and of the sea turtle (Chelonia mydas mydas). Light intensity, duration, and wavelength were varied to assess temporal effects. For a given intensity of monochromatic light, response amplitude increased with stimulus duration until maximum amplitude occurred at a specific duration. This suprathreshold metric of temporal integration is calledhere summation time, and it is wavelength-dependent.L cells always had some level of red-sensitive cone input, although in some cells inputs from green- and blue-sensitive cones were also observed. For these latter cells, summation times were shorter for 640-nm than for 540-nm or 450-nm lights. These results were most evident in cells that received dominant inputs from blue- or green-sensitive cones.Responses of some other L cells were almost completely dominated by inputs from red-sensitive cones. Summation times of these cells were not wavelength-dependent. But when these inputs also included green-sensitive cones, shorter summation times were obtained to 640-nm light than to 540-nm light, even though dominant inputs were still from red-sensitive cones. These results, obtained from both retinal and 3,4-dehydroretinal photopigment systems, are consistent with reported observations inPseudemys scripta elegansthat show linear responses of red-sensitive cones to have shorterintegration times and times-to-peakthan green-sensitive cones.Responses from horizontal cells dominated by blue-sensitive cone inputs were the most sensitive of all; they also had the longest summation times. These results support the hypothesis that a gain in sensitivity occurs from the integration of absorbed photons over longer periods of time.These intracellular responses are of particular importance because behavioral critical durations in turtle, as defined by Bloch&'s law, are similarly wavelength-dependent.

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Depolarizing actions of GABA and glycine on amphibian retinal horizontal cells

Journal of Neurophysiology ◽

10.1152/jn.1991.65.3.680 ◽

1991 ◽

Vol 65 (3) ◽

pp. 680-692 ◽

Cited By ~ 27

Author(s):

R. A. Stockton ◽

M. M. Slaughter

Keyword(s):

Gabaa Receptor ◽

Gaba Receptors ◽

Ganglion Cells ◽

Light Response ◽

Feedback System ◽

Horizontal Cells ◽

Gaba Uptake ◽

Gamma Aminobutyric Acid ◽

Ion Substitution ◽

Chemical Coupling

1. The effects of inhibitory amino acid transmitters on horizontal cells in the superfused amphibian retina were studied by the use of conventional intracellular recording techniques. 2. Gamma-aminobutyric acid (GABA) caused a calcium-independent depolarization of horizontal cells in mud puppy and tiger salamander. This action was mimicked by muscimol but not baclofen (BAC) and blocked by bicuculline and picrotoxin (PTX), matching the GABAa receptor profile. 3. The purported GABA uptake inhibitors nipecotate (NPA) and guvacine (GUV) acted as GABAa agonists, having pharmacological properties very similar to GABA itself. These agents also activated receptors of amacrine and ganglion cells, causing membrane polarizations similar to GABA. Concentrations of these analogues that did not activate the GABAa receptor (submillimolar) did not lower the effective dose of GABA, even after prolonged application. 4. Glycine (GLY) also depolarized horizontal cells, but only in approximately 25% of the horizontal cells was the amplitude of the depolarization as great as GABA. The glycine response was blocked by both strychnine (STR, 10 microM) and PTX (100 microM). In contrast, the action of GABA was unaffected by STR. 5. Ion substitution and channel-blocking agents indicated that the effects of applied GABA and GLY were independent of both external sodium and calcium. 6. The results suggest that GABA receptors on horizontal cells may act 1) as a positive feedback system to modulate the light response and 2) as a mechanism for chemical coupling between horizontal cells.

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