The Duplex Nature of the Retina of the Nocturnal Gecko as Reflected in the Electroretinogram

The effect of light and dark adaptation on the electrical activity in two species of nocturnal gecko, Hemidactylus turcicus and Tarentola mauritanica was studied. The electroretinogram of both species changes from the scotopic type in the dark-adapted state to the photopic type after strong light adaptation. For the scotopic response fusion frequencies up to 18 flashes per sec. are obtained in both species. For the photopic response fusion frequencies up to 50 flashes per sec. are seen in Tarentola, and up to 25 flashes per sec. in Hemidactylus. Proceeding from dark to light adaptation the increment threshold (dI) is measured at different levels of adaptive illumination (I). At low levels of illumination the dI/I ratio is found to be small and at high levels of illumination to be large. No difference in the dI/I ratio is obtained for test lights of 462 and 605 mµ. During dark adaptation the change of threshold after exposure to moderate and weak lights (up to 10³ times dark threshold) is rather fast. After light adaptation to strong light (10⁶ times dark threshold) duplex dark adaptation curves are seen with a break separating a fast and a slow phase of dark adaptation. The significance of these results from a retina which possesses sense cells of only one type is discussed.     

The DC-Recorded Dog Electroretinogram in Ketamine -Medetomidine Anaesthesia

A new selective alpha 2-adre-noreceptor agonist, medetomidine hydrochloride was combined with low dosage ketamine hydrochloride and vecuronium bromide for d.c. (direct current) recordings of fast electroretinographic (ERG) components in nine ophthalmoscopically healthy dark adapted dogs. The dogs were tracheally intubated and manually ventilated. They were given full field single flash stimuli of different intensities starting with near b-wave threshold blue light (tests 1-3), followed by white light (tests 4-6) and 30 Hz photopic flicker (test 7). The a- and b-wave amplitudes and flicker responses were measured from the base line. The latencies were measured from the stimulus moment to the highest point of the different waves. Statistical analysis of results gave individual differencies which had a good constancy. This showed that the dogs had an individual ERG profile according to the standardized method. The latencies varied very little as expected, but the amplitudes differed individually and showed a good constancy as seen by reproducibility tests made nine to ten days later on three of the dogs’ ipsilateral eyes. The combination of drugs used in this study was considered suitable for short term (10-12 minutes) stable d.c.–ERG recordings in dogs as the rod and cone responses had higher amplitudes when compared to an identical examination made with other anaesthetic combinations on the same dogs. Involuntary eye movements and other involuntary muscular activity caused by ketamine in dogs were negligible when using medetomidine premedication and was completely absent when using vecuronium. The anaesthetic method described can be recommended for ambulatory ERG recordings in dogs because of the above mentioned advantages.     

中药材蛤蚧的特异性PCR鉴定

以线粒体Cytb、COI、12SrRNA、16SrRNA基因序列为基础,探讨特异性PCR技术鉴定蛤蚧及伪品的可行性。本研究以所扩增的16条COI序列为引物设计依据序列设计了1对位点特异性引物COISF,COISR,同时从Gen-Bank上下载30条序列,设计了CytbSF,CytbSR;16S rRNASF,16S rRNASR;12S rRNASF,12S rRNASR另外3对位点特异性引物,因此共用4对位点特异性引物分别扩增蛤蚧及伪品实验样本。结果表明在复性温度为65℃时,4对引物都出现了理想的结果,即蛤蚧正品出现了扩增条带,而伪品没有扩增条带。同时对市售的蛤蚧商品进行了检测,在所供的7号标本中,有4号为蛤蚧正品,其余3号为蛤蚧伪品。本研究所设计的位点特异性引物可快捷、准确的鉴定蛤蚧及伪品,且在药检工作中具有极大的应用前景。     

Quantum Relations of the Rat Electroretinogram

The rat retina is uniform and contains almost exclusively rods. Therefore the rat eye, when uniformly illuminated, produces a gross electroretinogram (ERG) which is simply related to the activity of the individual retinal sources of the ERG. Characteristics of ERG's are shown on an intensity scale of the average number of quanta absorbed per rod per stimulus flash obtained by direct accurate measurement of all quantities involved. An independent check on the accuracy of these measurements is applied to pigment-bleaching data reported by Dowling (1963). When ERG characteristics are placed on this scale it is found that: (a) The b-wave can usually be observed when fewer than one out of two hundred rods absorbs a quantum, the threshold being determined by the noise of the preparation. (b) Near threshold the b-wave amplitude is proportional to intensity. (c) The a-wave appears when there are more than two to four absorptions per rod per flash. (d) The b-wave latency decreases with intensity, and the amplitude becomes proportional to the logarithm of intensity when fewer than one out of ten rods absorbs a quantum. This implies that the b-wave sources must combine excitation from more than one rod (probably more than seven). Therefore the b-wave cannot arise from independent rods or rod-bipolar synapses, but probably reflects activity of entire inner nuclear layer cells.     

Spectral Sensitivity Measured with Electroretinogram Using a Constant Response Method

A new method is presented to determine the retinal spectral sensitivity function S(λ) using the electroretinogram (ERG). S(λ)s were assessed in three different species of myomorph rodents, Gerbils (Meriones unguiculatus), Wistar rats (Ratus norvegicus), and mice (Mus musculus). The method, called AC Constant Method, is based on a computerized automatic feedback system that adjusts light intensity to maintain a constant-response amplitude to a flickering stimulus throughout the spectrum, as it is scanned from 300 to 700 nm, and back. The results are presented as the reciprocal of the intensity at each wavelength required to maintain a constant peak to peak response amplitude. The resulting S(λ) had two peaks in all three rodent species, corresponding to ultraviolet and M cones, respectively: 359 nm and 511 nm for mice, 362 nm and 493 nm for gerbils, and 362 nm and 502 nm for rats. Results for mouse and gerbil were similar to literature reports of S(λ) functions obtained with other methods, confirming that the ERG associated to the AC Constant-Response Method was effective to obtain reliable S(λ) functions. In addition, due to its fast data collection time, the AC Constant Response Method has the advantage of keeping the eye in a constant light adapted state.     

Recent Physical Encounters Affect Chemically Mediated Retreat-Site Selection in a Gecko

Chemoreception is well documented in a range of animals but the effects of recent behavioural interactions on an animal's response to subsequent chemical information are poorly understood. Using a series of laboratory experiments with a rock‐dwelling gecko (Oedura lesueurii), we examined whether latest social experience affects how animals used chemoreception to mediate microhabitat selection. Males of this species defend retreat‐sites and the outcomes of physical duels are maintained during second physical contests staged up to 1 wk after first contests. Retreat‐site selection experiments showed that past social experience affects the behavioural responses of adult male geckos to chemical cues from conspecific male lizards. When offered a choice between retreat‐sites labelled with chemicals from an unknown male vs. the opponent from a recent contest, geckos that won their previous fight selected retreat‐sites at random. In contrast, under the same conditions, geckos that lost their previous fight significantly preferred retreat‐sites scented with an unknown male conspecific over those scented with the winning opponent. During these experiments males that lost their previous fight were significantly more vigilant, and spent greater time near the retreat‐site of the unknown male, compared with males that won their previous fight. These results support the notion that recent physical social encounters can affect the way that animals respond to chemical information from potential competitors.     

壁虎药用价值的研究进展

壁虎是对蜥蜴亚目壁虎科所有蜥蜴的通称,其作为中药材使用具有悠久的历史。结合近年来国内外对壁虎药用价值的研究成果,综 述了壁虎在抗肿瘤、调节机体免疫力和促进再生等方面的活性及相关机制研究进展,旨在为壁虎药用价值的深入探索提供参考。     

A Biomimetic Climbing Robot Based on the Gecko

1 Introduction The locomotion, sensing, navigation, and adapta- tion capabilities in animals have long inspired humans to emulate them in robots. The purpose of this study was to determine the potential of climbing robots for both ter- restrial and extra-terrestrial explorations. Robots similar to their biological counterparts require extensive sys- tems for power, locomotion, and actuation, with com- putation, sensing, and autonomy. From animal research and current technologies, the possibili…     

Electroretinogram in the nocturnal Prosimian Perodicticus potto]

There is histological evidence for the presence of cones in potto's retina: about 1 cone for 300 rods. The ERG of the dark adapted animal resembles that of the night monkey. In the potto's retina some red sensitive elements respond to wavelenghts beyond those which affect visual purple. The ERG evoked by these long wavelenghts differs from that produced by white light, suggesting a duplex character of the retina. These red sensitive receptors dark adapt faster than the others. However their fusion frequency is low, if compared with that in other species with a duplex retina. Nevertheless in potto the critical fusion frequency is higher for red light than for blue light.     

Gecko Adhesion on Wet and Dry Patterned Substrates

Perhaps one of the most astounding characteristics of the gecko adhesive system is its versatility. Geckos can locomote across complex substrates in a variety of conditions with apparent ease. In contrast, many of our synthetic pressure sensitive adhesives fail on substrates that are dirty, wet or rough. Although many studies have investigated the effect of environmental challenges on performance, the interaction of multiple, potentially compromising variables is studied less often. Here we focus on substrate structure and surface water, both of which are highly relevant to the biological system and to synthetic design. To do this we utilized a highly controlled, patterned substrate (Sharklet^®, by Sharklet^® Technologies Inc.). This allowed us to test independently and jointly the effects of reduced surface area substrates, with a defined pattern, on adhesion in both air and water. Our results show that adhesion is not significantly impaired in air, whereas surface area and pattern significantly affect adhesion in water. These findings highlight the need to study multiple parameters that are relevant to the gecko adhesive system to further improve our understanding of the biological system and to design better, more versatile synthetics.     

Oscillations of Potential in the Electroretinogram of the Lobster

The electroretinogram (ERG) evoked in the lobster by a short flash of light consists of a highly damped, slow oscillation of potential, triggered apparently by a single excitatory process. Near the threshold, only one wave may be evident; but as the intensity of stimulus rises, a prior wave appears, and grows so much more rapidly as to become dominant. Simultaneously third and later waves appear, so that at high intensities the response may include five to seven waves. Dark adaptation favors the second and later waves relative to the first; light adaptation tends to suppress them. On turning on a steady light the oscillations are superimposed on the early stages of development of a maintained, steady-state potential (on-response). Turning off the light causes a rapid fluctuation of potential followed by a similarly damped slow oscillation (off-response). These phenomena resemble in part oscillations recently observed in the b wave of the ERG of many vertebrates including man.     

Conscientiousness is a Predictor of Diurnal Preference

The relationship between diurnal preference, as measured by the Horne‐Östberg questionnaire, and quantifiable personality traits was investigated in 617 participants. A hierarchical multiple regression analysis demonstrated that out of the personality variables, conscientiousness was the single biggest predictor of diurnal preference (β=0.246), after controlling for depression, sleep disorders, shift work, age, gender, and demographic characteristics. Morningness has previously been associated with physiological parameters of the circadian clock and with polymorphisms in circadian clock genes, suggesting the possibility that conscientiousness, too, may be linked to the same parameters.