Red Flashes Research Articles

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.

Effects of Halothane on Children's Electroretinograms

At times, anesthesia is necessary to test children's electroretinographic (ERG) responses. Halothane, an anesthetic commonly used for pediatric patients, affects some aspects of ERG responses, but it is unknown if halothane affects ERG parameters evaluated by contemporary clinical protocols. Scotopic and photopic ERG responses were recorded from children when awake and then under halothane. Halothane has no effect on scotopic b-wave stimulus/response parameters, including amplitude, sensitivity, and implicit time. Scotopic a-wave amplitudes, implicit times, model parameters, and ratio of a- to b-wave amplitudes are unaffected by halothane. The amplitudes and implicit times of photopic responses to red flashes and 30 Hz flickering white light are not altered by halothane. Halothane causes no significant change in amplitudes and implicit times of the oscillatory potential wavelets. These results suggest that significant departures of ERG responses (studied with the protocol described herein) from a laboratory's normal values cannot be attributed to halothane.

Modification of Petunia Seedling Carbohydrate Partitioning by Irradiance

Petunia × hybrida Villm. `Red Flash' plants received either 10 or 20 mol·day-1 photosynthetic photon flux (PPF) in growth chambers at: 175 μmol·m-2·s-1 for 16 hours, 350 μmol·m-2·s-1 for 8 or 16 hours, or 350 μmol·m-2 s-1 for 8 hours plus 8 hours of incandescent photoperiod extension (5 μmol·m-2·s-1 PPF). The irradiation components of peak, total, and duration were examined. Doubling total PPF increased total carbohydrate (CHO) production by 60%, seedling dry weight (DW) by 30%, rate of seedling growth by 25%, and acid invertase activity by 50% compared to the other treatments, once the seedlings had reached the two-leaf stage. Seedlings receiving 20 mol·day-1 PPF partitioned 14% more CHO into ethanol soluble sugars rather than starch, which may explain the increase in relative growth rate observed with supplemental irradiance treatments. Extending the photoperiod for 8 hours with 5 μmol·m-2·s-1 PPF reduced total CHO production by 50% compared to the same treatment without photoperiodic lighting. Treatment with 350 μmol·m-2·s-1 for 8 hours resulted in the highest O2 evolution (8.8 μmol O2/min per dm2). Increasing the photoperiod from 8 to 16 hours gave the lowest rate of O2 evolution (4.5 μmol O2/min per dm2). Previous reports of the importance of photosynthetic period in controlling partitioning between starch and sugars may have simply observed a decreasing rate of starch accumulation due to increased total PPF.

Improving the diagnostic power of electroretinography by transient alteration of the ocular perfusion pressure.

In this report we present the results of a series of studies focusing on the effects of transient changes in the ocular perfusion pressure (OPP) on retinal function in normals as assessed by the flash electroretinogram (ERG). A transient increase or decrease in the OPP affected by body inversion and compression/suction ophthalmodynamometry (ODM), respectively, is shown to affect differentially the b-wave of scotopic and photopic ERG's. However, under dark-adapted conditions, the cone component of the red flash ERG b-wave exhibited a vulnerability to decreased OPP which approached that seen for the b-wave of the scotopic blue flash ERG b-wave. Similar test procedures used to investigate the functional response of the inner plexiform layer during altered OPP revealed component-specific changes in white flash scotopic oscillatory potentials (OP's). The results of these provocative tests of retinal function offer new insights into basic retinal physiology and encouraging prospects for practical clinical diagnostic procedures with enhanced sensitivity and specificity for subclinical retinal disorders.

Influence of transiently altered retinal vascular perfusion pressure on rod/cone contributions to scotopic oscillatory potentials

The oscillatory potentials (OPs) are sensitive to vascular disturbances in the retina. Rods in man are more susceptible than cones to ischaemia. The findings in a recent study showed that the white flash OP-5 had a heightened sensitivity to altered retinal vascular perfusion pressure (RVPP), compared with earlier OPs and the b-wave. In the present study, a comparison was made of the sensitivity of scotopically matched blue and red flash OPs to dim white flash OPs, to transient stepwise changes in the RVPP, in 10 healthy young adults. After 30 minutes of dark adaptation, two consecutive 0.3 Hz flash groups (n = 20) were filtered and averaged to obtain 100 ms flash ERGs and OPs simultaneously via DTL fibre electrodes for white, blue, and red flashes. To minimize any carry-over effects across flash colour, or repeated testing, the retinal responses to each of these stimuli were measured in separate test sessions several hours to days apart. The RVPP was increased or decreased by 20% and 40% non-invasively by body inversion and scleral suction respectively. For the flash intensities used, blue and red flash OPs appeared more variable than white flash OPs. The OP index increased or decreased across all flash colours when the RVPP was increased, with blue OPs showing the greatest spread of data. Retesting in five subjects using white and red flashes against a blue background disclosed the input of both rods and cones to the white flash scotopic OPs. The provocative test conditions described here offer a potentially profitable approach for studies attempting to differentiate the effects of vascular disorders on rod versus cone function.

Influence of transiently altered retinal vascular perfusion pressure on rod/cone contributions to scotopic oscillatory potentials

The oscillatory pntentials (Ops) are sensitive to vascular disturbances in the retina. Rods in man are more susceptible than cones to ischaemia. The findings in a recent study showed that the while flash OPs had a heightened sensitivity to altered retinal vascular perfusion pressure (RVPP), compared with earlier OPs and the h-wave. In the present study, a comparison was made of the sensitivity of scotopically matched blue and red flash OPs to dim white flash OPs, to transient stepwise changes in the RVPP, in 10 healthy young adults. After 30 minutes of dark adaptation, two consecutive 0.3 Hz Hash groups (n= 20) were filtered and averaged to obtain 100 ms flash ERGs and OPs simultaneously via DTL, fibre electrodes For white, blue, and red flashes. To minimize any earn-over effects across flash colour, or repeated testing, the retinal responses to each of these stimuli were measured in separate test sessions several hours to days apart. The RVPP was increased or decreased by 20% and 40% non-invasively by body inversion and scleral suction respectively. For the flash intensities used, blue and red Hash OPs appeared more variable than white flash OPs. The OP index increased or decreased across all flash colours when the RVPP was increased, with blue OPs showing the greatest spread of data. Retesting in five subjects using white and red flashes against a blue background disclosed the input of both rods and cones to the while flash scotoptc OPs. The provocative test conditions described here offer a potentially profitable approach for studies attempting to differentiate the effects of vascular disorders on rod versus cone function.

Sequential stimuli and relative numerosity discriminations in pigeons.

Pigeons were trained in symbolic matching-to-sample procedures. The sample stimuli were sequences of red and blue flashes of light. If more blue flashes appeared in a sequence, then one side key was correct and provided occasional reinforcement, and the other side key produced a short blackout. If there were more red flashes, these contingencies were reversed. The number of flashes, their ordering, flash durations, and gaps between flashes were varied in 3 experiments. The proportion of «more blue» responses was an orderly function of the proportion of blue stimuli. Varying the gaps between flashes showed that both temporal and ordinal locations were important variables. Increasing the duration of flashes increases their salience. Mechanisms for discriminating the relative numerosity of successive stimuli are discussed

High Pressure Sodium Irradiation and Infrared Radiation Accelerate Petunia Seedling Growth

The increase in photosynthetic photon flux (PPF) and plant temperature associated with supplemental high pressure sodium (HPS) irradiation were investigated during Petunia × hybrids Villm. `Red Flash' seedling development. Seedlings were treated for 14 days following emergence or 5 days after the first true leaf had expanded to 1 mm. Treatments consisted of continuous infrared (IR) radiation (Ambient + IR), ambient conditions with spill-over radiation from adjacent treatments (Ambient - IR), root zone heating to 19.5C (RZ Heat), continuous HPS irradiation at 167 μmol·s-1.m-2 PPF (HPS + IR) or continuous HPS irradiation at 167 μmol-1·m-2 PPF filtered through a water bath to remove IR (HPS - IR). Linear regression of natural log-transformed fresh weights indicated that increasing ambient PPF 53% and elevating plant temperature 4.3C (HPS + IR) increased seedling relative growth rate (RGR) by 45% compared with the control (Ambient - IR). Elevating plant temperature with + IR by 4.8C without supplementing PPF (Ambient + IR) increased RGR by 31% but failed to increase fresh weight (FW) above controls and resulted in etiolated plants that were unsuitable for transplanting. Once plants were removed from supplemental treatment and returned to ambient conditions, RGR for all treatments was similar. The increased FW promoted by IR and HPS treatments was maintained for up to 7 days after treatment. Therefore, the increased seedling growth responses observed with HPS treatment were due primarily to an increase in RGR during HPS treatment that is not sustained beyond treatment.

The VER as a Diagnostic Marker for Childhood Abdominal Migraine

Abdominal migraine is a common childhood migraine equivalent, for which diagnostic criteria have not been defined. As in other children with migraine equivalents this leads to difficulties in diagnosis and determination of prevalence. By recording the fast wave activity (beta rhythmn) in the visual evoked response (VER) to red and white flash, the pattern stimulation, 27 out of 28 children with clinically diagnosed abdominal migraine revealed significant differences compared with normal controls, outside the attack phase. Comparisons with children diagnosed as migraine with or without aura revealed, from the VER findings of higher amplitude fast wave activity and the presence of paroxysmal sharp wave activity, that abdominal migraine appears to be a specific form of childhood migraine. We found that both clinically and electrophysiologically, abdominal migraine changes with age; older children exhibiting a shorter duration of abdominal pain during attacks, and less evidence of sharp wave activity in the VER.

EFFECT OF TRANSPLANTING PETUNIA PLUGS AT DIFFERENT STAGES OF DEVELOPMENT

Petunia seeds of `White Cascade', `Red Flash', and `Red Madness' were sown in 406 plug trays on the same date. The first transplanting occurred when the plants could be removed from the cells without root damage. Subsequent transplanting occurred for four weeks. The first transplanting of `White Cascade' flowered two weeks earlier than the second while the third transplanting was one week behind the second. `Red Flash' flowered two weeks earlier for the first transplanting. There was no effect on time to flower for the `Red Madness'. The highest fresh and dry weights corresponded to the earliest flowering transplants. Optimum growth and development for most petunia cultivars was obtained with the earliest transplanting without root damage.

PETUNIA SEEDLING GROWTH - HPS PHOTOPERIOD STUDY

Petunia `Red Flash' seedling were grown under HPS (175 μmolm-2 s-1) photoperiod treatments of 10, 12, 14 or 16 hr at 20C soil temperature in a shaded glasshouse where the maximum peak PPF was reduced to 150 μmolm-2s-1. Seedling dry weight and individual leaf area were determined daily. The photosynthetic rate was determined when seedlings reached the second true leaf stage.The dry weight response to increasing photoperiod durations was cubic with a peak at 14 hr. Seedling dry weight increased slowly during days 5 through 10 then increased rapidly during the next 7 to 10 days. This increase coincided with the unfolding of leaves one through four. The total leaf area showed a cubic response to the photoperiod treatments. The leaf area increased slowly then began an exponential increase after day 10. The photosynthetic rate per gram dry weight was increased by the 10 hr photoperiod treatment when compared to the 16 hr treatment. The increased photosynthetic rate was not observed when the data was calculated on a fresh weight or leaf area basis.

PETUNIA SEEDLING GROWTH - FLOWERING RESPONSE

Petunia `Red Flash' seedlings were grown under HPS (175 μmol m-2 s-1) photoperiod treatments of 10, 12, 14 or 16 hr at 20C soil temperature in a shaded glasshouse where the maximum peak PPF was reduced to 150 μmolm-2s-1. Seedling were transplanted after they had unfolded a specific number of leaves and grown under natural days or placed under photoperiod treatments which consisted of an 8 hr natural day with incandescent day extension treatments of 1 to 6 hours.A 16 hr HPS treatment decreased the days to transplant (DTT) by more than 4 days and reduced the days from transplant to flower (DTF) by more than 5 days. The total reduction in days from sowing to flower (DSTF) was at least 8 days. When compared to unlighted controls, the reduction in DSTF was 26 days. The longer the seedlings remained under the HPS treatments, the shorter the DTF and DSTF. Premature shifting of plants to natural days resulted in up to a 9 day delay in DSTF. At photoperiods greater than 13 hr, the number of nodes subtending the inflorescence becomes constant regardless of number of leaves at transplant.

TEMPERATURE, TRANSPLANT TIME, AND PLUG SIZE EFFECTS ON GROWTH AND DEVELOPMENT OF PANSY, PETUNIA, VINCA, AND IMPATIENS

Petunia `Red Flash', Vinca `Little Blanch', Pansy `Magestic Giant Purple', and Impatien `Super Elfin Red' plugs were held in the greenhouse after they reached the saleable size in 200, 406, 512, and 800 for 1 to 3 weeks Pansy plugs were held in coolers at 40, 50, or 60F under fluorescent light for 16 hrs photoperiod for 1 to 3 weeks in 200, 406, 512, or 800 plug trays. All plants ware transplanted weekly and were grown in the greenhouse until flowering and data were collected. For plants bald in the greenhouse, plants were affected by transplanting time. As the holding time increased the final height, diameter, flower number, and fresh and dry weight of plants decreased. The flowering time was delayed by increase the holding time, regardless of plant variety, As cell size decreased, plant height, diameter, flower number, and fresh and dry weight decreased. For plants held in the coolers, the flowering time was delayed by the transplant time, regardless of cooler temperatures Plant quality was not affected by the treatment. The height, diameter, flowers number, and fresh and dry weight of plants showed a little effects by temperatures, cell size, and transplanting time.

TEMPERATURE, TRANSPLANT TIME, AND PLUG SIZE EFFECTS ON GROWTH AND DEVELOPMENT OF PANSY, PETUNIA, VINCA, AND IMPATIENS

Petunia `Red Flash', Vinca `Little Blanch', Pansy `Magestic Giant Purple', and Impatien `Super Elfin Red' plugs were held in the greenhouse after they reached the saleable size in 200, 406, 512, and 800 for 1 to 3 weeks Pansy plugs were held in coolers at 40, 50, or 60F under fluorescent light for 16 hrs photoperiod for 1 to 3 weeks in 200, 406, 512, or 800 plug trays. All plants ware transplanted weekly and were grown in the greenhouse until flowering and data were collected. For plants bald in the greenhouse, plants were affected by transplanting time. As the holding time increased the final height, diameter, flower number, and fresh and dry weight of plants decreased. The flowering time was delayed by increase the holding time, regardless of plant variety, As cell size decreased, plant height, diameter, flower number, and fresh and dry weight decreased. For plants held in the coolers, the flowering time was delayed by the transplant time, regardless of cooler temperatures Plant quality was not affected by the treatment. The height, diameter, flowers number, and fresh and dry weight of plants showed a little effects by temperatures, cell size, and transplanting time.

Modification of Petunia seedling Carbohydrate Partitioning by Irradiance

Petunia × hybrida Villm. `Red Flash' plants were irradiated for either 10 or 20 mol day1 photosynthetic photon flux (PPF) in growth chambers using one of the following treatments: 175 μmol m-2 s-1 for 16 h, 350 μmol m-2 s-1 for 8 or 16 h or 350 μmol m-2 s-1 for 8 h plus 8 h incandescent day extension (5 μmol m-2 s-1 PPF). These four treatments were designed to examine the effects of increased peak and total daily integrated PPF as well as increased photosynthetic (Pn) period and photoperiod resulting from supplemental irradiance treatment of seedlings. Previous seedling petunia research indicated a greater response to supplemental lighting during expansion of the second true leaf. Therefore, seedlings were sampled for analysis at the two leaf stage and also later at the four leaf stage to examine effects at a later stage of growth.Increasing total integrated PPF increased total carbohydrate production, seedling dry weight, rate of seedling growth, and acid invertase activity once the seedlings reached the two leaf stage. Increasing total PPF resulted in greater partitioning into ethanol soluble sugars rather than starch at the two leaf stage. Increasing the photoperiod only, with an incandescent day extension treatment, reduced total carbohydrate production at the two leaf stage.Maximal oxygen evolution was observed when seedlings received 350 μmolm-2s-1 for 8 h when expressed on a leaf area or dry weight basis. The use of an 8 h day extension treatment to extend the photoperiod from 8 to 16 h resulted in the lowest rates of oxygen evolution on a leaf area basis.

Visuell evozierte Diskriminationspotentiale im Kindesalter

70 children without visual, developmental or neurological handicap in the age of 3 to 92 months were investigated. Using red and white light flashes non-target event-related evoked potentials have been registrated, white light serving as rare (20%) stimulus

Time characteristics of the interaction between phytochrome and the blue light photoreceptor system in Mougeotia

The interaction between cryptochrome and phytochrome which induces the face-to-profile movement of Mougeotia chloroplasts was investigated. The response was induced with combinations of blue and red light flashes, both in the millisecond range. After the flash sequence a dark period of varied duration was applied, after which the gradient of the far-red absorbing form of phytochrome (P fr) was cancelled by far-red light. The results support the hypothesis that in the blue-light cryptochrome-mediated reaction a photoproduct is formed which interacts with the P fr gradient. The lifetime of the photoproduct was estimated to be about 100 s on a level of reduction of the response to 30%. A similar time is required for this photoproduct to interact with the P fr gradient in order to induce a full response. Thereafter the P fr gradient is no longer necessary. Involvement of the intermediates of the phytochrome phototransformation was excluded in experiments with red flashes preceding blue flashes.

Photoreceptor responses of patients with congenital stationary night blindness

The present study examines the hypothesis that the electroretinogram (ERG) a-wave of patients with congenital stationary night blindness with myopia (CSNB) is solely cone mediated. The subjects include four patients with x-linked recessive inheritance, two patients with no family history, and thirteen age-matched normal subjects. Because normal subjects have relatively large b-waves (which can influence the measurement of the PIII component of the a-wave), the main response parameter studied was the slope of the a-wave. The results for the CSNB patients show that in the light adapted condition, the ratio of the responses to photopically balanced blue and red flashes was nearly unity; whereas, in the dark-adapted condition, the ratio was ~3 times greater. The ratios for the normal subjects were similar to those of the CSNB patients. These results lead to the conclusion that, in patients with CSNB, the ERG a-wave is not solely mediated by cones.

Response properties of C-type horizontal cells in the retina of the bowfin.

Intracellular recordings were obtained from biphasic- and triphasic-type horizontal cells (C cells) in the retina of the bowfin. For steady-state responses, both cell types displayed a linear stimulus-response function for responses up to at least 20% of maximum. In the linear range, responses to red/green mixtures were well predicted from the assumption that opposed inputs combine by simple summation. Action spectra were measured in the linear range for 30 biphasic and 12 triphasic cells. Biphasic cells showed their peak hyperpolarization near 530 nm and peak depolarization near 680 nm. Triphasic cells showed peak hyperpolarization near 450 nm, peak depolarization near 570 nm and small hyperpolarizing responses to deep red flashes (greater than 670 nm). The response to deep red test flashes was reduced by chromatic backgrounds which either depolarized or hyperpolarized the cell, in contrast to past findings in carp triphasic cells. In both classes of cells, the depolarizing input mechanism had a shorter latency than the hyperpolarizing mechanism, a result not previously observed in other fish retinas. Color opponency was maintained in both classes of C cells for stimuli of small diameter. The findings in bowfin and other species suggest that both feedback and direct pathways shape the depolarizing response of C cells.

Single- and Double-flash Photoconversion of Phytochrome in vivo and in vitro

Native (124 kDa) phytochrome was isolated from etiolated oat seedlings ( Avena sativa L., cv. «Pirol»). Photoconversion of the red absorbing form (P r ) to the far-red absorbing form (P fr ) by single- and double-flash or pulse irradiation was compared with induction of germination of positive photoblastic lettuce seeds ( Lactuca sativa L., cv. «Perax») by the same irradiation program. Fluence-response curves for single-flash irradiation (12 ms) in vitro were recorded for 618, 666 and 697 nm, saturating at 200 to 500 Jm −2 with the saturation levels of P fr /P tot around 48 %, 52 %, and 43 %, respectively. The corresponding values for pulse irradiation in the range of minutes were 90 %, 87 %, and 67 %, respectively. The low saturation levels, for single-flash irradiation, are explained by a photoequilibrium P r ⇌ meta-Ra, established during the ms-flash. Double-flash irradiation with 10 s dark interval increased the saturation level, for all tested wavelengths, over that measured for single-flash irradiation. This is explained by assuming that for double-flash irradiation the photoequilibrium P r ⇌ meta-Ra can be established twice. For induction of seed germination similar characteristics were reported using single- and double-flash or pulse irradiation. Kinetics for double-flash irradiation show a biphasic shape. Extending the dark interval between the two flashes from about 10 ms to 1 s, first the effect increases, but from 1 to 10 s it decreases. The same pattern is obtained if the initial red flash is followed by a 710 nm flash. If the second flash is at 744 nm, the kinetics show a permanent drop from about 10 ms to 10 s. The effects are explained by photoreversibility of the intermediates meta-Ra and meta-Rc as well as of P r and P fr . Kinetic data, obtained in vitro at 8 or 10 °C, show similar pattern to the photoinduced germination in lettuce at 24.5 °C. An expected temperature effect may be partly compensated for by deviating viscosity of the phytochrome environment in vivo (in seeds) versus in vitro (in solution).