The optical function of changes in the medium surrounding the cockroach rhabdom

Summary In the dark-adapted eye of the cockroachPeriplaneta, the fused rhabdom is surrounded by a clear watery palisade; in the light-adapted eye this is replaced by pigment. The refractive indices of the rhabdom and its surround have been measured. The physiological effects of this change in structure has been analysed by the electromagnetic theory of light guides. The optical constants are theoretically consistent with the measured tenfold change in sensitivity and changes in acceptance angle of the retinula cells from 6.7 ° ¦(dark-adapted) to 2.4 ° (light-adapted).     

Angular sensitivity of the retinula cells of dark-adapted worker bee

Summary Electrophysiological determination of the angular sensitivity of 16 worker bee retinula cells gives a value for horizontal acceptance angle of 2.5°±0.4° (S.D.) and for vertical acceptance angle of 2.7°±0.8° (S.D.).This value is in agreement with previous behavioural studies, but is clearly at variance with a recent analysis of the ommatidial dioptric by ray optics, which gives a value of 5° for the acceptance angle. It is suggested that this results from the failure of ray optics to take diffraction effects into account.     

Light and dark adaptation influences GABA receptor sites in the chick retina

The aim of the present study was to investigate the effect of environmental conditions such as light-and-dark-adaptation on the plasticity of GABA receptor sites in the chick retina. In chicks exposed to light for 5 hr (light-adapted), specific [³H]GABA binding was increased by 35% in comparison to the binding found in chicks maintained in darkness (dark-adapted). Conversely, in the retina of chicks exposed to darkness for 5 hr, specific [³H]GABA binding was decreased by 28% with respect to that found in chicks kept in the light. Scatchard analysis of the binding data revealed that the affinity of GABA for its receptor binding site was higher in the retinas of light-adapted chicks than in those of dark-adapted chicks (K _d values of 19.20±1.23 and 27.20±1.47 nM, respectively). On the contrary, the maximal number of binding sites (B_max) remained unchanged in light- and dark-adapted chicks (5.2±0.10 and 5.3±0.15 pmol/mg protein, respectively). These results suggest the involvement of GABA receptors in the regulation of visual function.Special Issue dedicated to Prof. Eduardo DeRobertis     

Adaptations for vision in dim light: impulse responses and bumps in nocturnal spider photoreceptor cells (<Emphasis Type="Italic">Cupiennius</Emphasis><Emphasis Type="Italic">salei</Emphasis> Keys)

The photoreceptor cells of the nocturnal spider Cupiennius salei were investigated by intracellular electrophysiology. (1) The responses of photoreceptor cells of posterior median (PM) and anterior median (AM) eyes to short (2 ms) light pulses showed long integration times in the dark-adapted and shorter integration times in the light-adapted state. (2) At very low light intensities, the photoreceptors responded to single photons with discrete potentials, called bumps, of high amplitude (2–20 mV). When measured in profoundly dark-adapted photoreceptor cells of the PM eyes these bumps showed an integration time of 128 ± 35 ms (n = 7) whereas in dark-adapted photoreceptor cells of AM eyes the integration time was 84 ± 13 ms (n = 8), indicating that the AM eyes are intrinsically faster than the PM eyes. (3) Long integration times, which improve visual reliability in dim light, and large responses to single photons in the dark-adapted state, contribute to a high visual sensitivity in Cupiennius at night. This conclusion is underlined by a calculation of sensitivity that accounts for both anatomical and physiological characteristics of the eye.     

Volume and surface changes of smooth endoplasmic reticulum in crayfish retinula cells upon light- and dark-adaptation

Summary Adaptation to light and darkness involves major transformations of the smooth endoplasmic reticulum (SER) in the retinula cells of the crayfish and other invertebrates, the mechanisms of which are unknown. This paper presents measurements of SER stereological parameters at three levels along the main axis of light-adapted and dark-adapted retinula cells of the crayfish. Both the volume density and the surface density of SER in the perinuclear region of dark-adapted cells are more than double the values found in light-adapted cells. This relationship is inverted in the axoplasm above and below the basement membrane, where SER volume and surface in dark-adapted cells are approximately half of the quantities measured in light-adapted cells. Although this proportional correspondence between changes in separate regions of the cells might suggest merely an intracellular shifting of SER membrane, calculation of the approximate absolute amounts of membrane involved makes this possibility very unlikely. It is concluded that the vast increase of SER in the perinuclear region of dark-adapted cells implies a large input of membrane, which is subsequently removed during light-adaptation.Abbreviation SER smooth endoplasmic reticulum     

Fine structural changes in dark-light adaptation in relation to unit studies of an insect compound eye with a crustacean-like rhabdom

Structural changes in dark-light adaptation of the compound eye of the beetle Creophilus erythrocephalus, have been investigated by electron microscopy. Their functional consequences have been studied by means of intracellular electrophysiological recordings from retinula cells. In the dark-adapted state the intercellular spaces between the retinula cells swell considerably and produce a palisade of extracellular origin around the rhabdom. Units from dark-adapted eyes are approximately ten times more sensitive than those from light-adapted animals and have larger acceptance angles (7·037° ± 1·23 S.D. compared with 5·135° ± 0·99 S.D. for the light-adapted insect). A spikegenerating unit, inhibited by light, was found once. Although the rhabdom is of the ‘banded’ type, polarization sensitivity was found to be unexpectedly low: 2·31 ± 1·54 S.D. It is concluded that electrical coupling, useful for dim light conditions and eyes with tiny apertures, most likely appears to be the reason for the low average polarization sensitivity.     

Angular and spectral sensitivity of fly photoreceptors. III. Dependence on the pupil mechanism in the blowfly<Emphasis Type="Italic"> Calliphora</Emphasis>

A wave optics model for the facet lens-rhabdomere system of fly eyes is used to analyze the dependence of the angular and spectral sensitivity of R1–6 photoreceptors on the pupil mechanism. This assembly of light-absorbing pigment granules in the soma interacts with the waveguide modes propagating in the rhabdomere. A fly rhabdomere carries two modes in the middle wavelength range and four modes at short wavelengths, depending on the rhabdomere diameter and the angle of the incident light flux. The extension of the mode to outside the rhabdomere strongly depends on wavelength, and this dependence plays a determinant role in the light control function of the pupil. The absorbance spectrum of the pigment in the pupil granules is severely depressed at short wavelengths by waveguide effects, resulting in a distinct blue peak. Accordingly, pupil closure suppresses the photoreceptors spectral sensitivity much more in the blue-green than in the UV. The pupil only narrows the angular sensitivity at short wavelengths. The geometrical size of the rhabdomere governs the angular sensitivity of fly photoreceptors in the dark-adapted state, but diffraction takes over in the fully light-adapted state.     

Comparison of dark- and light-adapted carp retinas with NADPH diaphorase staining

The carp retina was examined by NADPH diaphorase histochemistry to determine if the staining pattern of retinal cells was changed depending on the adaptation state of the retina. When dark-adapted for 5 h, ellipsoids of inner segments of both rods and cones and some horizontal cells were heavily stained. Staining was also found in subpopulations of amacrine cells and ganglion cells. In addition, Muller cells were strongly positive for NADPH diaphorase. When light-adapted for 5h, ellipsoids of photoreceptors and ganglion cells were less intensely stained, whereas Muller cells and horizontal cells became negative for NADPH diaphorase. Furthermore, rod ON-center bipolar cells were clearly stained. The difference of staining of amacrine cells between dark- and light-adapted retinas was not significant. The differences in diaphorase-staining pattern between dark- and light-adapted retinas suggest that Muller cells, some horizontal cells and rod ON-center bipolar cells contain inducible nitric oxide synthase,     

On spiking units in the first optic chiasm of the blowfly

We recorded from the spiking sustaining unit in the optic chiasm between lamina and medulla in the brain of the blowfly Calliphora vicina, and investigated both temporal and spatial properties of the light-adapted cell. The sustaining unit fails to follow the highest temporal frequencies followed by the photoreceptor, but its temporal resolution is substantially better than that of the on-off unit. The sustaining unit does not display the fast temporal adaptation as previously described in the on-off unit. As compared with the on-off unit, the sustaining unit has a high sensitivity to small contrasts. Although the sustaining unit continues spiking as long as the light is on, its response is also transient as it adapts rapidly after a change of intensity. The receptive field and the line spread function of the sustaining unit have a similar size and profile: a central lobe with a half-width of approximately 2° surrounded by a circular inhibitory zone located at about 3° off-axis.     

草地贪夜蛾成虫复眼明暗适应及黄光照射下明适应状态转化率

【目的】蛾类昆虫的趋光性与复眼明暗适应状态的转化有着直接的关系，本研究旨在阐明光照与草地贪夜蛾Spodotera frugiperda复眼明暗适应状态转化的关系。【方法】在光、暗适应条件和不同光照强度黄光照射下，在不同时间段，用相机迅速拍照，观察统计草地贪夜蛾成虫复眼的明暗适应状态及明、暗适应状态转化率。【结果】在明适应状态下，草地贪夜蛾成虫经黄光照射1 h后，随光照强度的增加，复眼明适应状态保持率逐步升高：雄成虫复眼在0.1~0.5 lx时明适应状态保持率为67.77%(有32.23%的转化为暗适应状态与中间状态)，4~6 lx时明适应状态保持率达到100%；雌成虫复眼在7~10 lx时，明适应状态保持率达98.90%。在明适应状态下，经黄光照射3 h后，草地贪夜蛾成虫复眼明适应状态保持率亦随着光照强度的增加逐步升高，在0.1~0.5 lx时雄成虫复眼明适应状态保持率为50.00%,雌成虫为32.23%；在光照强度7~10 lx时，雌雄成虫复眼明适应状态保持率分别为90.00%和100%。在暗适应状态下，草地贪夜蛾成虫经不同光照强度的黄光照射30 min后，成虫复眼向明适应状态逐渐转化：在0.1~0.5 lx光照强度时雌、雄成虫复眼明适应状态转化率均为93.33%；当光照强度达到0.6~0.9 lx时雌成虫复眼的明适应状态转化率达到100%，雄成虫复眼则在1~2 lx时达到100%。【结论】结果说明，草地贪夜蛾成虫有较强的光敏感性，且雌虫对黄光的光敏感性略强于雄虫。     

Photocycles of bacteriorhodopsin in light- and dark-adapted purple membrane studied by time-resolved absorption spectroscopy.

Nanosecond time-resolved absorption spectra have been measured throughout the photocycle of bacteriorhodopsin in both light-adapted and dark-adapted purple membrane (PM). The data from dark-adapted samples are interpretable as the superposition of two photocycles arising independently from the all-trans and 13-cis retinal isomers that coexist in the dark-adapted state. The presence of a photocycle in dark-adapted PM which is indistinguishable from that observed for light-adapted PM under the same experimental conditions is demonstrated by the observation of the same five relaxation rates associated with essentially identical changes in the photoproduct spectra. This cycle is attributed to the all-trans component. The cycle of the 13-cis component is revealed by scaling the data measured for the light-adapted sample and subtracting it from the data on the dark-adapted mixture. At times less than 1 ms, the resulting difference spectra are nearly time-independent. The peak of the difference spectrum is near 600 nm, although there appears to be a slight (approximately 2 nm) blue-shift in the first few microseconds. Subsequently the amplitude of this spectrum decays and the peak of the difference spectrum shifts in two relaxations. Most of the amplitude of the photoproduct difference spectrum (approximately 80%) decays in a single relaxation having a time constant of approximately 35 ms. The difference spectrum remaining after this relaxation peaks at approximately 590 nm and is indistinguishable from the classical light-dark difference spectrum, which we find, in experiments performed on a much longer time scale, to peak at 588 nm. The decay of this remaining photo-product is not resolvable in the nanosecond kinetic experiments, but dark adaptation of a completely light-adapted sample is found to occur exponentially with a relaxation time of approximately 2,000 s under the conditions of our experiments.     

Neuromuscular efficiency during sit to stand movement in women with knee osteoarthritis

The purpose of this study was to investigate the neuromuscular efficiency of women with knee osteoarthritis (OA) when performing a sit-to-stand movement and during maximum strength efforts. Twelve women with unilateral knee OA (age 60.33 ± 6.66 years, height 1.61 ± 0.05 m, mass 77.08 ± 9.2 kg) and 11 controls (age 56.54 ± 5.46 years, height 1.64 ± 0.05 m, mass 77.36 ± 13.34 kg) participated in this study. Subjects performed a sit-to-stand movement from a chair while position of center of pressure and knee angular speed were recorded. Furthermore, maximal isokinetic knee extension and flexion strength at 60°/s, 120°/s and 150°/s was measured. Surface, electromyography (EMG) from the biceps femoris (BF), vastus lateralis (VL) and vastus medialis (VM) was recorded during all tests. Analysis of variance (ANOVA) showed that during the sit-to-stand OA group demonstrated significantly lower knee angular speed (44.49 ± 9.61°/s vs. 71.68 ± 19.86°/s), a more posterior position of the center of pressure (39.20 ± 7.02% vs. 41.95 ± 2.49%) and a higher antagonist BF activation (57.13 ± 20.55% vs. 32.01 ± 19.5%) compared with controls (p < 0.05). Further, women with knee OA demonstrated a lower Moment-to-EMG ratio than controls in extension and eccentric flexion at 60°/s and 150°/s, while the opposite was found for concentric flexion at 60°/s (p < 0.05). Among other factors, the slower performance of the sit-to-stand movement in women with OA is due to a less efficient use of the knee extensor muscles (less force per unit of EMG) and, perhaps, a higher BF antagonist co-activation. This may lead subjects with OA to adopt a different movement strategy compared with controls.     

Critical thermal maxima of diploid and triploid brook charr, Salvelinus fontinalis

The purpose of this experiment was to determine whether diploid and triploid brook charr, Salvelinus fontinalis, differ in their critical thermal maxima (CTM). Two age classes were tested (underyearlings, having average weight of 25 g, and yearlings, having average weight of 668 g) at two rates of temperature increase (2° C h^-1 and 15° C h^-1). No effect of ploidy on CTM was found. Fish exposed to the faster rate of temperature increase had higher CTM values than those exposed to the slower rate (underyearlings: 29.5 ± 0.1° C versus 29.1 ± 0.1° C in one trial and 29.8 ± 0.1° C versus 28.3 ± 0.1° C in a second trial; yearlings: 29.3 ± 0.1° C versus 27.7 ± 0.1° C in two trials, p < 0.001 in all cases). Underyearlings had higher CTM values than yearlings (29.2 ± 0.1° C versus 28.5 ± 0.1° C, p < 0.05). Female yearlings, which were immature, had higher CTM values than males, which had previously matured as one-year-olds (28.8 ± 0.1° C versus 28.3 ± 0.1° C, p < 0.001).     

Receptive field properties of rod-driven horizontal cells in the skate retina

The large receptive fields of retinal horizontal cells result primarily from extensive intercellular coupling via gap (electrical) junctions; thus, the extent of the receptive field provides an index of the degree to which the cells are electrically coupled. For rod-driven horizontal cells in the dark-adapted skate retina, a space constant of 1.18 +/- 0.15 mm (SD) was obtained from measurements with a moving slit stimulus, and a comparable value (1.43 +/- 0.55 mm) was obtained with variation in spot diameter. These values, and the extensive spread of a fluorescent dye (Lucifer Yellow) from the site of injection to neighboring cells, indicate that the horizontal cells of the all-rod retina of skate are well coupled electrically. Neither the receptive field properties nor the gap-junctional features of skate horizontal cells were influenced by the adaptive state of the retina: (a) the receptive field organization was unaffected by light adaptation, (b) similar dye coupling was seen in both dark- and light-adapted retinae, and (c) no significant differences were found in the gap-junctional particle densities measured in dark- and light-adapted retinas, i.e., 3,184 +/- 286/microns 2 (n = 8) and 3,073 +/- 494/microns 2 (n = 11), respectively. Moreover, the receptive fields of skate horizontal cells were not altered by either dopamine, glycine, GABA, or the GABAA receptor antagonists bicuculline and picrotoxin. We conclude that the rod-driven horizontal cells of the skate retina are tightly coupled to one another, and that the coupling is not affected by photic and pharmacological conditions that are known to modulate intercellular coupling between cone-driven horizontal cells in other species.     

A comparison of the second harmonic generation from light-adapted, dark-adapted, blue, and acid purple membrane.

The second order nonlinear polarizability and dipole moment changes upon light excitation of light-adapted bacteriorhodopsin (BR), dark-adapted BR, blue membrane, and acid purple membrane have been measured by second harmonic generation. Our results indicate that the dipole moment changes of the retinal chromophore, delta mu, are very sensitive to both the chromophore structure and protein/chromophore interactions. Delta mu of light-adapted BR is larger than that of dark-adapted BR. The acid-induced formation of the blue membrane results in an increase in the delta mu value, and formation of acid purple membrane, resulting from further reduction of pH to 0, returns the delta mu to that of light-adapted BR. The implications of these findings are discussed.     

Resonance Raman study of the dark-adapted form of the purple membrane protein.

The resonance Raman spectrum of the dark-adapted form of the purple membrane protein (bacteriorhodopsin) has been obtained and is compared to the light-adapted pigment and model chromophore spectra. As in the light-adapted form, the chromophore-protein linkage is found to be a protonated Schiff base. Electron delocalization appears to play the dominant role in color regulation. The dark-adapted spectrum indicates a conformation closer to 13-cis than the light-adapted spectrum.     

Immunocytochemical localization of phosphatidylinositol-4,5-bisphosphate in dark- and light-adapted rat retinas

Light-mediated hydrolysis of phosphatidylinositol-4,5-bisphosphate (TPI) to 1,2-diacylglycerol and D-myo-inositol 1,4,5-triphosphate (IP3) has been reported in the visual photoreceptor cells. We have investigated the localization of the TPI antigenic sites in dark- and light-adapted rat retinas using rabbit anti TPI antibodies (Ab). Sprague-Dawley rats were dark-, or light-adapted, or were exposed to a light flash. The eyes were fixed immediately and the tissue sections stained with the rabbit anti TPI Ab. The peroxidase-antiperoxidase method was used to find the localization of the TPI antigenic site. Image analysis of the sections was performed to obtain optical density profiles of the stain. Dark-adapted retinas showed intense staining of the rod outer segment (OS) layer but much less staining of the rod inner segment layer. Compared with the OS of dark-adapted retinas, those of the flash-bleached retinas were stained much less. The OS of fully bleached retinas showed little or no staining. The anti TPI Ab-protein A-gold conjugate intensely stained disks from dark-adapted retina but those from bleached retina much less. Our results suggest that rapid hydrolysis of TPI in rat rod outer segments occurs in vivo in response to light.     

Polarized-light sensitivity in rainbow trout (Oncorhynchus mykiss): characterization from multi-unit responses in the optic nerve

Integrated spike activity of axons from the optic nerve was measured in an investigation of the e-vector sensitive mechanism underlying the ability of rainbow trout (Oncorhynchus mykiss) for orientation in downwelling, linearly-polarized light. In anaesthetized, immobilized fish, one eye was exposed to incremental light flashes which were superimposed over closely controlled background conditions. Under scotopic and various photopic conditions, intensity/response curves were generated from the on-response of the optic nerve. Relative sensitivity curves were then obtained as a function of e-vector direction for the 5 kinds of receptor cells in this trout's retina: rods, ultraviolet cones (UV), short wavelength cones (S), medium wavelength cones (M), and long wavelength cones (L).Under scotopic conditions, no sensitivity to e-vector was apparent: thus, rods do not mediate polarization sensitivity. Under photopic conditions, parr weighing 8–10 g exhibited e-vector sensitivity in two orthogonal channels. A UV stimulus (380 nm) on a white background evoked a three-peaked response (0°, 90°, and 180°) to the e-vector orientations presented in 30° increments between 0° and 180°. In contrast, when the background was illuminated with appropriate short and long wavelength cut-off filters, M-and L-cones showed maximum responses only to the horizontal (90°) plane whether they were stimulated at their -absorption band or their -absorption band in the near UV. Isolated UV-cones gave maximum responses to the vertical (0° and 180°) e-vector, thus corresponding to a second channel. The blue sensitive, S-cones, did not show evidence of polarization sensitivity. As well, no evidence of the polarization sensitivity was observed under UV isolating background conditions in larger individuals, 50–78 g smolts, although the other cone mechanisms responded as in smaller individuals.     

Light and dark adaptation of halorhodopsin

Dark incubation of envelope vesicles derived from a strain of Halobacterium halobium that lacks bacteriorhodopsin but contains halorhodopsin and a third rhodopsin-like pigment caused a decrease in the flash yield [the amplitude of a transient absorbance change of flash reactive component(s) by flash] of halorhodopsin but not the rhodopsin-like pigment. The flash yield decreased to reach a low steady level after incubation for about 4 days in the dark. The flash yield of halorhodopsin at any stage of dark incubation was increased by actinic illumination of the vesicles. The flash yield at 490 nm (absorbance increase) was found to be approximately proportional to that at 590 nm (absorbance decrease). These results indicate that halorhodopsin in the envelope vesicles has two forms, dark and light adapted, and that the halorhodopsin phototransient absorbing at 490 nm is originated from the light-adapted form. A difference spectrum between these two forms of halorhodopsin shows that the light-adapted halorhodopsin was red-shifted from the dark-adapted form. The light-induced membrane potential was measured by tetraphenylphosphonium uptake. The uptake by the dark-adapted vesicles was slower than that by the light-adapted vesicles, suggesting that only the light-adapted halorhodopsin has ion-transporting activity.     

Directionality of a one way movement detector in the crayfishCherax destructor

Summary Directionality curves for vertical one way movement detector neurons in the crayfish were obtained during whole animal oscillation around continuously varying horizontal axes. Results are presented in detail for one easily monitored unit, M.D.I. In a fresh animal, maximum sensitivity was shown to rotation in the rolling plane. In an adapted animal, the maximum sensitivity, was shifted by 45° and the directionality curve became markedly asymmetrical. Right and left adapted M.D.I cells have axes for maximum response 90° apart. The results can be explained simply by a reduction in excitability of input cells coding the set of orthogonal components of a rotation at 45° to the pitch and roll set of orthogonal components.