Frog Eye Research Articles

Huasteca 600, Variedad de soya para el sur de Tamaulipas

La demanda de soya [Glycine max (L.) Merr.] en México exige el desarrollo de variedades más productivas que contribuyan a disminuir las importaciones de dicha oleaginosa, y la consecuente fuga de divisas. Por lo que el objetivo del presente trabajo fue desarrollar una variedad de soya con periodo largo de formación de vainas y llenado de grano (R4-R7) y que se ubique cerca del mes de septiembre, para así potenciar un rendimiento superior a las variedades testigo. La variedad de soya Huasteca 600 se originó a partir de la hibridación de H88-1880 x H88-3868, líneas adaptadas a ambientes tropicales (grupo de madurez IX), que se realizó en 1994. Es de temporal y está recomendada para el sur de Tamaulipas y regiones cálido húmedas y subhúmedas de México. Es de porte medio a alto, con buena ramificación y hábito de crecimiento determinado; los foliolos de las hojas son ovoides medianos y color verde medio, las flores son color violeta, la semilla es mediana (100 semillas pesan 15.7 g), de forma subesférica, color amarillo e hilio café. Presenta 48 días a R2, permitiéndole desarrollar el periodo de R4 a R7 en la época de mayor probabilidad de lluvias, ventaja que contribuye a la obtención de mayor rendimiento. El contenido de aceite y proteína es de 20.6% y 36.9% respectivamente. Presenta buen nivel de resistencia al acame y al desgrane, a plagas defoliadoras y a la enfermedad “ojo de rana”, además tolera “mildiu velloso”, “tiro de munición” y “antracnosis”. Tiene un potencial de rendimiento de 2988 kg ha-1, 25% más que la variedad testigo Huasteca 200.
 

Stability analysis for seed yield and related traits in soybean (Glycine max L. Merrill)

In the present study, ten soybean strains were evaluated along with four standard checks during kharif 2013 and 2014 at two locations viz., Palampur and Kangra of Himachal Pradesh. The analysis of variance revealed highly significant differences due to genotypes, environments and genotype x environment interaction for all the traits studied when tested against pooled error. G x E (L) was significant for plant height and number of branches per plant. The magnitude of G x E (linear) was more than non-linear component (pooled deviation) for days to maturity, plant height, number of branches per plant and 100-seed weight suggesting its importance in the expression of these traits. The genotype P1–4 was suitable for favorable environment and resistant to yellow mosaic virus, frog eye leaf spot and pod blight. The genotype SL-958 was found suitable for unfavorable environment and it was resistant to yellow mosaic virus and pod blight.

A frog's eye view: logging roads buffer against further diversity loss

A frog's eye view: logging roads buffer against further diversity loss

Expression, Purification and Properties of Redox-Sensitive Eye Lens Zeta-Crystallin of Arabian Camel.

The high protein concentration, unique composition and complex geometry of the lens makes it transparent. α-, β-, and γ-crystallins are present in all the lenses. In addition, taxon-specific crystallins are present in lenses in bulk quantity. Zeta (ζ)-crystallin is an NADPH-dependent quinone oxidoreductase, which constitutes nearly 10 % of the total eye lens protein in the evolutionary divergent animals (Camel, guinea pig and Japanese frog eye lenses) living in different ecological conditions. ζ -Crystallin is also present in human and other animal lenses but at catalytic amount. The physiological role of γ-crystallin in the eye lens is not well understood, however, truncated ζ-crystallin causes congenital cataract in guinea pig. In earlier study, redox regulated reversible activity of ζ-crystallin was reported. In this study, recombinant camel ζ-crystallin was overexpressed in E.coli and purified to homogeneity. Effect of different concentrations of reducing agent, dithiothretol (DTT) on the quinone oxidoreductase activity of recombinant ζ-crystallin was studied by enzymatic assay. To evaluate the effect of the reducing agent on the ζ-crystallin conformation, we have used far-UV and near-UV CD, intrinsic fluorescence, ANS binding assay and size exclusion chromatography. Our results showed that nearly 50% of the of ζ-crystallin activity was lost at 50 µM DTT. However, no detectable changes in secondary structure were observed. No changes in the tertiary structure and surface hydrophobicity of ζ-crystallin were detected; however, marginal changes were seen at saturating concentration of DTT (1 mM).

In vivo intrinsic optical signal imaging of mouse retinas.

Intrinsic optical signal (IOS) imaging is a promising noninvasive method for advanced study and diagnosis of eye diseases. Before pursuing clinical applications, more IOS studies employing animal models are necessary to establish the relationship between IOS distortions and eye diseases. Ample mouse models are available for investigating the relationship between IOS distortions and eye diseases. However, in vivo IOS imaging of mouse retinas is challenging due to the small ocular lens (compared to frog eyes) and inevitable eye movements. We report here in vivo IOS imaging of mouse retinas using a custom-designed functional OCT. The OCT system provided high resolution (3 μm) and high speed (up to 500 frames/s) imaging of mouse retinas. An animal holder equipped with a custom designed ear bar and bite bar was used to minimize eye movement due to breathing and heartbeats. Residual eye movement in OCT images was further compensated by accurate image registration. Dynamic OCT imaging revealed rapid IOSs from photoreceptor outer segments immediately (<10 ms) after the stimulation delivery, and unambiguous IOS changes were also observed from inner retinal layers with delayed time courses compared to that of photoreceptor IOSs.

The works of professor N.P. Kravkov in the area of endocrinology

This article describes the academic works of the N.P. Kravkov (1865–1924), a prominent Russian pharmacologist, on the study of the endocrine glands.In N.P. Kravkov’s laboratory, via experiments on rabbits and dogs, a method of isolating the pancreas and extracting its perfusate was developed based on passing Ringer-Locke’s solution through the vessels of the isolated gland. It was discovered that the perfusate contains a substance that reduces the level of glucose in the blood of healthy animals and, in large doses, causes hypoglycaemic coma. N.P. Kravkov called this substance pancreotoxin.The experiments of N.P. Kravkov’s followers on the isolated hearts of animals showed that, for a heart in the normal condition, pancreotoxin decelerates the heartbeat and reduces the amplitude of contractions, whereas for the heart tired above a certain threshold, the opposite effect is observed.The study of the blood vessels in isolated ears of rabbits and the eyes of frogs revealed antagonism between pancreotoxin and adrenalin: pancreotoxin weakens the vasoconstrictive effect of adrenalin and reduces its influence on the size of the pupil in frogs. It was also shown that passing the perfusate containing pancreotoxin through the adrenal gland increases the secretion of adrenalin.Later, pancreotoxin was obtained in the dried form and used to prepare a drug prescribed to patients with diabetes in hospitals.From its properties, pancreotoxin turned out to be insulin. It should be noted that the news that insulin had been isolated from the pancreas by the Canadian researchers F. Banting and C. Best reached Russia only after the researchers in N.P. Kravkov’s laboratory had extracted and studied pancreotoxin from isolated pancreases. Thus, N.P. Kravkov and foreign researchers discovered this hormone independently.In experiments on the isolated adrenal glands of cattle, N.P. Kravkov and his collaborators obtained the perfusate containing an adrenalin-like substance produced in the medulla of the adrenal gland and a muscarine-like substance produced by the suprarenal cortex.The research by N.P. Kravkov and his followers on the physiology, pathology and pharmacology of the glands of internal secretion at the beginning of the 20th century has proved to be of great importance for the development of endocrinology in Russia.

Early Detection of &amp;lt;i&amp;gt;Cercospora&amp;lt;/i&amp;gt; Species in Soybean Plants: Immunologic and Molecular Methods

Late-cycle diseases (LCD) cause a significant deterioration in quality and reduce yields in soybean crops. In Argentina, in particular, leaf blight and purple seed stain, caused by the agent Cercospora kikuchii, and frog eye spot, caused by C. sojina, are the prevailing sources of diseases. The early, rapid and accurate detection of these phytopathogens becomes essential, and would contribute to preserving both the environment and the health of humans and animals by preventing the wasteful or improper use of chemicals such as pesticides. In order to detect Cercospora species in soybean plants at an early stage, immunochemical and molecular techniques were developed in this work. Strains from the NITE Biological Resource Center collection (Japan): Cercospora kikuchii NBRC 6711 and Cercospora sojina NBRC 6715 and regional isolates of C. kikuchii were used. To develop Dot-Blot and PCR techniques, experiments with plants undergoing different treatments were carried out: those experimentally inoculated with these fungi, those treated with sterile water and healthy plants as well. Both techniques allowed the detection, at early stages, of Cercospora species involved in two of the most frequent LCD in the country, when the cercosporin concentration produced by the fungus was higher than 3.93 ± 0.39 nmol·cyl-1 ±SD. The sensitivity between both techniques was very different. While Dot-Blot allowed the detection of the disease 4 days after inoculation, PCR detected it after 4 hours, even without visible symptoms of the disease.

Frog eyes show prowess as quantum sensors

Frog eyes show prowess as quantum sensors

Frog eyes show prowess as quantum detectors

Nearly one out of every three photons that reach the frog's photoreceptor cells elicits a neuronal spike. Nearly one out of every three photons that reach the frog's photoreceptor cells elicits a neuronal spike.

Early prenatal diagnosis of the OEIS complex with different appearance in early compared with late pregnancy before spontaneous rupture of the cloacal membrane

The OEIS complex is a rare variant of the exstrophy–epispadias complex. It is most often diagnosed in second trimester screening by typical sonographic features of omphalocele together with exstrophy of the fetal bladder, imperforate anus and spinal anomalies that have created its acronym. Firsttrimester sonography is now widely accepted not only as screening for aneuploidies but also for major structural anomalies. The typical feature of each disorder must be kept in mind as several structural defects show different sonographic features in the first compared with the second trimester. For example, whereas spina bifida is indirectly diagnosed by scalloping of the frontal bones (‘lemon sign’) and caudal displacement of the cerebellum (‘banana sign’) in the second trimester, the characteristic indirect feature of spina bifida in first trimester is the absence of the intracranial translucency and the displacement of the brain stem, respectively. Furthermore, direct visualization of the spinal defect in early gestation is difficult, in particular due to the small size of the cele during the first trimester. The same is true for fetal exencephaly–anencephaly: in the first trimester, the cerebral lobes are present and floating in the amniotic fluid, resembling the face of Mickey Mouse in the coronal plane; whereas in the second trimester, lack of any tissue and cranium above the level of the orbits due to perishing of the fetal brain similar a frog head or frog eye appearance by the bulging orbits. Similar, cloacal extrophy and lower urinary tract obstruction (LUTO) show another clinical picture in the first trimester than in the second trimester, as both present as large cystic mass in the abdomen in the first trimester and change appearance upon their rupture. A 35-year-old gravida II/para I was referred for fetal assessment at 14 + 1weeks of gestation due to a large cystic mass initially diagnosed in 12 + 5weeks of gestation in the lower abdomen of the fetus (Figure 1A). Medical history and course of the pregnancy had been uneventful. Detailed ultrasound examination of the fetus revealed inappropriate fetal growth (BPD: 26.1mm; CRL: 69.8mm) and a 41 × 34mm large cystic structure in the lower abdomen with an intact lower abdominal wall. The membrane of the cyst was very thin similar to an amnion membrane and occupied the entire abdomen of the fetus pushing the adjacent organs cranially (Figure 1A). No urinary bladder could be visualized. Amniotic fluid was in normal range. Differential diagnoses included LUTO due to posterior urethral valves, a nonruptured cloacal membrane and an amniotic band syndrome affecting the infraumbilical part of the body. Vesicocentesis is a useful diagnostic procedure for evaluation of the tubular renal function and has been shown to be a sufficient treatment in some case of megacystis. Hence, puncture of the cyst with drainage of 25ml fluid was performed revealing features of fetal urine (sodium level: 118mmol/L; chloride level: 105mmol/L; β2-microglobulin level: 6.40mg/L; cystatin C: 0.96mg/L). After puncture of the cyst, repeated ultrasound examination showed a decompression of the abdominal organs and a thick-walled folded membrane floating within the amniotic fluid in front of the ventral abdominal wall of the fetus (Figure 1B). The fetus showed classical features of the OEIS complex with a large infraumbilical anterior midline defect with a protruding omphalocele, (elephant-trunk appearance), bladder exstrophy below the omphalocele in an area of 3.7mm and sacral spina bifida as well as a singular umbilical artery. Consequently, the diagnosis of an OEIS complex with intact cloacal membrane was made. Two weeks later, a missed abortion was diagnosed and labor was induced. Postnatal visual examination of the fetus was performed and confirmed the diagnosis of OEIS.

A Method for Mechanism Analysis of Frog Swimming Based on Motion Observation Experiments

For understanding the mechanism of frog swimming under water and designing a frog-inspired swimming robot, kinematics of the frog body and trajectories of joints should be obtained. In this paper, an aquatic frog, Xenopus laevis, was chosen for analysis of swimming motions which were recorded by a high speed camera, and kinematic data were processed in a swimming data extraction platform. According to the shape features of the frog, we propose a method that the frog eyes are set as the natural data extraction markers for body motion, and kinematic data of joint trajectories are calculated by the contour points on the limbs. For the data processing, a pinhole camera model was built to transform the pixel coordinate system to world coordinate system, and the errors caused by the water refraction were analyzed and corrected. Finally, from the developed data extraction platform, the kinematic data for the analysis of swimming mechanism and design of frog-inspired robot were obtained.

Receptive fields of visual neurons: the early years.

This paper traces the history of the visual receptive field (RF) from Hartline to Hubel and Wiesel. Hartline (1938, 1940) found that an isolated optic nerve fiber in the frog could be excited by light falling on a small circular area of the retina. He called this area the RF, using a term first introduced by Sherrington (1906) in the tactile domain. In 1953 Kuffler discovered the antagonistic center-surround organization of cat RFs, and Barlow, Fitzhugh, and Kuffler (1957) extended this work to stimulus size and state of adaptation. Shortly thereafter, Lettvin and colleagues (1959) in an iconic paper asked "what the frog's eye tells the frog's brain". Meanwhile, Jung and colleagues (1952-1973) searched for the perceptual correlates of neuronal responses, and Jung and Spillmann (1970) proposed the term perceptive field (PF) as a psychophysical correlate of the RF. The Westheimer function (1967) enabled psychophysical measurements of the PF center and surround in human and monkey, which correlated closely with the underlying RF organization. The sixties and seventies were marked by rapid progress in RF research. Hubel and Wiesel (1959-1974), recording from neurons in the visual cortex of the cat and monkey, found elongated RFs selective for the shape, orientation, and position of the stimulus, as well as for movement direction and ocularity. These findings prompted the emergence in visual psychophysics of the concept of feature detectors selective for lines, bars, and edges, and contributed to a model of the RF in terms of difference of Gaussians (DOG) and Fourier channels. The distinction between simple, complex, and hypercomplex neurons followed. Although RF size increases towards the peripheral retina, its cortical representation remains constant due to the reciprocal relationship with the cortical magnification factor (M). This constitutes a uniform yardstick for M-scaled stimuli across the retina. Developmental studies have shown that RF properties are not fixed. RFs possess their full response inventory already at birth, but require the interaction with appropriate stimuli within a critical time window for refinement and consolidation. Taken together these findings paved the way for a better understanding of how objective properties of the external world are encoded to become subjective properties of the subjective, perceptual world.

Effects of dopamine receptor blockade on the intensity-response function of electroretinographic b- and d-waves in light-adapted eyes

The effects of dopamine receptor blockade by sulpiride (D2-class antagonist) and sulpiride plus SCH 23390 (D1-class antagonist) on the V - log I function of the electroretinographic (ERG) b- and d-waves were investigated in light-adapted frog eyes. Sulpiride significantly decreased the absolute sensitivity of the b- and d-waves. The amplitude of the both waves was diminished over the whole intensity range studied. A similar effect on the b-, but not d-wave amplitude was seen during the perfusion with sulpiride plus SCH 23390. The effect on the d-wave amplitude depended on stimulus intensity. The threshold of the d-wave was not significantly altered. The suprathreshold d-wave amplitude was enhanced at the lower stimulus intensities and remained unchanged at the higher ones. The results obtained indicate that the action of endogenous dopamine on the photopic ERG shows clear ON-OFF asymmetry. Participation of different classes of dopamine receptors is probably responsible for this difference.

Structural changes in rod outer segments of frog and mouse after illumination

Intact eyes of frog and mouse were studied by X-ray diffraction. Light-induced changes in the reflections from the rod outer segments (ROS) were recorded at a time resolution of 0.1 and 1 s in frog and mouse, respectively. Lamellar diffraction from disk membranes was observed to the 10th order. In frog, the intensities of seven reflections were found to change significantly on 7-s intense illumination and the lamellar spacing, which was 30.4 nm in darkness, decreased by 0.5%. Time courses of changes in the intensity and the lamellar spacing were similar, saturating at about 7 s. Most of the intensity changes could be attributable to the spacing change. Thus, the effect of light on the electron density distribution was smaller than previously reported. The decrease in the lamellar spacing is attributed to changes in the intracellular ionic concentrations due to the blockage of the dark current. This may be a useful index to study the ionic movements in the cell. Mouse ROS's had a lamellar spacing larger than frog (32.4 nm). The structural changes after illumination were similar to those in frog ROS. This X-ray diffraction technique may be utilized to study functions of photoreceptor cells in transgenic mice and other animals.

In vivo Optical Coherence Tomography of Light-Driven Melanosome Translocation in Retinal Pigment Epithelium

Optical coherence tomography (OCT) may revolutionize fundamental investigation and clinical management of age-related macular degeneration and other eye diseases. However, quantitative OCT interpretation is hampered due to uncertain sub-cellular correlates of reflectivity in the retinal pigment epithelium (RPE) and photoreceptor. The purpose of this study was twofold: 1) to test OCT correlates in the RPE, and 2) to demonstrate the feasibility of longitudinal OCT monitoring of sub-cellular RPE dynamics. A high resolution OCT was constructed to achieve dynamic imaging of frog eyes, in which light-driven translocation of RPE melanosomes occurred within the RPE cell body and apical processes. Comparative histological examination of dark- and light-adapted eyes indicated that the RPE melanin granule, i.e., melanosome, was a primary OCT correlate. In vivo OCT imaging of RPE melanosomes opens the opportunity for quantitative assessment of RPE abnormalities associated with disease, and enables longitudinal investigation of RPE kinetics correlated with visual function.

Effects of dopamine receptor blockade on the intensity-response function of ERG b- and d-waves in dark adapted eyes

The effects of dopamine receptor blockade by sulpiride (D2-class antagonist) and sulpiride plus SCH 23390 (D1-class antagonist) on the V - log I function of the ERG b- and d-waves were investigated in dark adapted frog eyes. We observed that sulpiride enhanced the amplitude of the suprathreshold b- and d-waves in the lower intensity range, where the responses were mediated by rods, but diminished it in the higher intensity range, where the responses were mediated by cones. A similar effect on the b-, but not d-wave amplitude was seen during the perfusion with sulpiride plus SCH 23390. The d-wave amplitude was enhanced over the whole intensity range with the exception of the highest intensities during the combined D1 and D2 receptor blockade. The results obtained indicate that the endogenous dopamine has an overall inhibitory action on the suprathreshold rod-mediated ON and OFF responses, while its action on the cone-mediated responses shows clear ON-OFF asymmetry. It is excitatory upon the ON responses, but inhibitory upon the OFF responses except for those in the highest intensity range. Participation of different types of dopamine receptors (predominantly D2 for the ON versus D1 for the OFF response) is probably responsible for this difference.

In vivo confocal intrinsic optical signal identification of localized retinal dysfunction.

The purposes of this study were to investigate the physiological mechanism of stimulus-evoked fast intrinsic optical signals (IOSs) recorded in dynamic confocal imaging of the retina, and to demonstrate the feasibility of in vivo confocal IOS mapping of localized retinal dysfunctions. A rapid line-scan confocal ophthalmoscope was constructed to achieve in vivo confocal IOS imaging of frog (Rana pipiens) retinas at cellular resolution. In order to investigate the physiological mechanism of confocal IOS, comparative IOS and electroretinography (ERG) measurements were made using normal frog eyes activated by variable-intensity stimuli. A dynamic spatiotemporal filtering algorithm was developed to reject the contamination of hemodynamic changes on fast IOS recording. Laser-injured frog eyes were employed to test the potential of confocal IOS mapping of localized retinal dysfunctions. Comparative IOS and ERG experiments revealed a close correlation between the confocal IOS and retinal ERG, particularly the ERG a-wave, which has been widely used to evaluate photoreceptor function. IOS imaging of laser-injured frog eyes indicated that the confocal IOS could unambiguously detect localized (30 μm) functional lesions in the retina before a morphological abnormality is detectable. The confocal IOS predominantly results from retinal photoreceptors, and can be used to map localized photoreceptor lesion in laser-injured frog eyes. We anticipate that confocal IOS imaging can provide applications in early detection of age-related macular degeneration, retinitis pigmentosa, and other retinal diseases that can cause pathological changes in the photoreceptors.

TheXenopushomeobox genepitx3impinges upon somitogenesis and laterality

Pitx3 has been identified as the causative locus in a developmental eye mutation associated with mammalian anterior segment dysgenesis, congenital cataracts, and aphakia. In recent studies of frog eye development we discovered that pitx3 expresses symmetrically in the somites and lateral plate mesoderm and asymmetrically during cardiac and gut looping. We report that disruption of pitx3 activity on one side of an embryo relative to the other, either by over- or underexpression of pitx3, elicits a crooked dorsal axis in embryos that is a consequence of a retarded progression through somitogenesis. Unlike in amniotes, Xenopus somites form as cohorts of presomitic cells that rotate perpendicular to the dorsal axis. Since no vertebral anomalies have been reported in mouse and human Pitx3 mutants, we attempt to distinguish whether the segmentation clock is uniquely affected in frog or if the pitx3 perturbation inhibits the cellular changes that are necessary to rotation of presomitic cells. In Xenopus, pitx3 appears to inhibit the rotation of presomitic cell cohorts and to be necessary to the bilaterally symmetric expression of pitx2 in somites.

Effects of dopamine D 1 receptor blockade on the intensity-response function of ERG b- and d-waves under different conditions of light adaptation

The effect of dopamine D 1 receptor blockade by SCH 23390 on the V–log I function of the ERG b- and d-waves was investigated in dark and light adapted frog eyes. We obtained that the blocker enhanced the amplitude of the b- and d-waves in both conditions of adaptation. The enhancing effect of the blocker was more pronounced on the rod- than cone-dominated responses for the both ERG waves. The absolute sensitivity of the b-wave was not altered, but that of the d-wave was significantly increased. The intensity-response function of the b-wave, but not that of the d-wave, was shifted to the left along the intensity axis. The b-wave V–log I function had steeper slope and narrower dynamic range in both dark and light adapted eyes after the D 1 receptor blockade. The results obtained indicate that the endogenous dopamine, acting through D 1 receptors, does not play a crucial role in the process of retinal adaptation, although it changes in a specific manner the intensity-response function of both the ERG b- and d-waves.

Giacomo Rizzolatti

Giacomo Rizzolatti