Pupil adjustments in the eye of the common backswimmer

1995 ◽  
Vol 198 (1) ◽  
pp. 71-77 ◽  
Author(s):  
AI Ro ◽  
DE Nilsson
Keyword(s):  
Dark Adaptation ◽  
Water Surface ◽  
Light Adaptation ◽  
Dynamic Range ◽  
Living Animal ◽  
Control Range ◽  
Non Invasive ◽  
Endogenous Circadian Rhythm ◽  
Sensitivity Range ◽  
The Common

The pupil mechanism in the acone apposition eye of the semi-aquatic common backswimmer Notonecta glauca (Hemiptera) was investigated with infrared reflectometry of the pseudopupil. This method allows non-invasive continuous measurements of pupil responses in the living animal. The dynamic range of the pupil sensitivity is about 7 log units during daytime and 6 log units at night. During the day, the sensitivity range of the pupil covers the normal daylight intensities in the animal's habitat, just under the water surface (I50=10(19.2) photons m-2 sr-1 s-1). At night, the sensitivity is 1 log unit lower (I50=10(20.2) photons m-2 sr-1 s-1), ensuring that the pupil is maximally open when light intensities are low. During daytime, light adaptation is completed in slightly less than 40 min, and dark adaptation takes approximately 50 min. The pupil response is only slightly slower at night. The speed of the response as well as the pupil sensitivity are dependent on the preceding adaptation history. An endogenous circadian rhythm determines the control range of the pupil aperture. However, the rhythm is easily disturbed, especially within a 3 h period before dusk and dawn. The results are compared with corresponding results from other insects with the same type of pupil mechanism.

scholarly journals THE REGENERATION OF VISUAL PURPLE IN THE LIVING ANIMAL

1942 ◽  
Vol 26 (1) ◽  
pp. 27-47 ◽  
Author(s):  
James C. Peskin
Keyword(s):  
Vitamin A ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Living Animal ◽  
First Order ◽  
Visual Threshold ◽  
Isolated Retina ◽  
Lower Temperature ◽  
Initial Delay ◽  
Sigmoid Shape

1. The accumulation of visual purple in the retina after bleaching by light has been studied in the intact eye of the frog. The data show that duration and intensity of light adaptation, which influence the course of human dark adaptation as measured in terms of visual threshold, have a similar influence on the course of visual purple regeneration. 2. At 25°C. frogs which have been light adapted to 1700 millilamberts and then placed in the dark, show an increase in visual purple concentration which begins immediately and continues for 70 minutes until a maximum concentration is attained. The increase, although beginning at once, is slow at first, then proceeds rapidly, and finally slows up towards the end. Frogs which have been adapted to 9500 millilamberts show essentially the same phenomenon except that the initial slow period is strongly delayed so that almost no visual purple is formed in the first 10 minutes. 3. At 15°C. the initial delay in visual purple regeneration occurs following light adaptation to both 1700 and 9500 millilamberts. The delay is about 10 minutes and is slightly longer following the higher light adaptation. 4. The entire course of visual purple accumulation in the dark takes longer at the lower temperature than at the higher. The temperature coefficient for 10°C. is about 1.8. 5. In contrast to the behavior of the isolated retina which has small amounts of vitamin A and large amounts of retinene immediately after exposure to light, the intact eye has large amounts of vitamin A and little retinene after exposure to light for 10 minutes. In the intact eye during dark adaptation, the amount of vitamin A decreases markedly while retinene decreases only slightly in amount. If retinene is formed in the intact eye, the change from retinene to vitamin A must therefore occur rapidly in contrast to the slow change in the isolated retina. 6. The course of visual purple regeneration may be described by the equation for a first order autocatalyzed reaction. This supposes that the regeneration of visual purple is catalyzed by visual purple itself and accounts for the sigmoid shape of the data.

The Utility of Non-invasive Tests for Detection of Previous Proximal-vein Thrombosis

1995 ◽  
Vol 73 (04) ◽  
pp. 592-596 ◽  
Author(s):  
Sabina Villalta ◽  
Paolo Prandoni ◽  
Alberto Cogo ◽  
Paola Bagatella ◽  
Andrea Piccioli ◽  
...  
Keyword(s):  
Clinical Evaluation ◽  
Femoral Vein ◽  
Clinical Score ◽  
Diagnostic Methods ◽  
Popliteal Vein ◽  
Venous Reflux ◽  
Study Objective ◽  
Vein Thrombosis ◽  
Non Invasive ◽  
The Common

SummaryBackground. Despite the availability of several diagnostic methods for the detection of deep-vein thrombosis (DVT), the identification of previous episodes of DVT remains a diagnostic challenge.Study objective. To assess the reliability of a combination of a standardized clinical score with three non-invasive tests: compression ultrasonography (CUS), Doppler ultrasound (DUS), and photoplethysmography (PPG), in determining the presence or the absence of previous proximal DVT.Methods. One hundred consecutive unselected outpatients were identified, who had undergone contrast venography six to nine years previously because of the clinical suspicion of DVT (confirmed in 43). They were blindly reinvestigated by a panel of trained operators unaware of venography results. They underwent a clinical evaluation of the lower limb, by applying a standardized score to five symptoms and six signs (grading each item from 0 to 3); a PPG test to determine the venous refilling time; a DUS test to determine the venous reflux separately in the common femoral and the popliteal vein; and a CUS test to determine vein compressibility in the same regions.Results. An abnormal CUS test and/or the demonstration of venous reflux in the popliteal region and/or a high clinical score (≥ 8) identified twenty-four of the 43 (56%) DVT + patients with a specificity of 89%. The combination of normal CUS with the absence of venous reflux in both the common femoral and popliteal vein and a low clinical score excluded previous thrombosis in 45 (79%) of the 57 DVT- patients (negative predictive value, 78%). Abnormal venous reflux in the isolated common femoral vein did not reliably predict the presence or absence of previous DVT. However, this occurred in only 13 (13%) patients. The PPG determination of venous refilling time did not improve the results obtained with the other tests.Conclusions. The combination of a standardized clinical evaluation with the results of CUS and DUS can reliably diagnose or exclude previous proximal-vein thrombosis in almost 90% of patients with previous episodes of suspected DVT.

scholarly journals POS1388 ULTRASOUND FOR PANNICULITIS

2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 977.1-977
Author(s):  
A. Potapova ◽  
O. Egorova ◽  
O. Alekseeva ◽  
A. Volkov ◽  
S. Radenska-Lopovok
Keyword(s):  
Dynamic Range ◽  
Subcutaneous Fat ◽  
Diagnostic Value ◽  
High Energy ◽  
Contralateral Side ◽  
Imaging Method ◽  
Non Invasive ◽  
M 12

Background:Ultrasound (US) is a non-invasive and safe imaging method that allows in vivo differentiation of the morphological structures of subcutaneous fat (SCF) tissue in in normal and pathology.Objectives:Reveal features of ultrasound changes in SCF in panniculitis (Pn).Methods:57 patients (f – 45, m - 12) aged 18 - 67 years with an initial diagnosis of erythema nodosum and a disease duration of 3.6 ± 1.4 years were examined. In addition to the general clinical examination, a computed tomography of the chest organs and a pathomorphological examination of a skin biopsy from the site of the node were performed. Ultrasound was performed on a MyLabTwice apparatus (ESAOTE, Italy) using a multi-frequency linear transducer (10-18 MHz) with the PD technique, the parameters of which were adapted for recording low-speed flows (PRF 300-600 Hz, low filter, dynamic range - 20-40 dB), the presence of vascularization was assessed not only in the affected area, but also on the contralateral side using high-energy Doppler.Results:33 patients were diagnosed with septal Pn (SPn), 24 - lobular Pn (LPn). In all cases, the diagnosis was verified by histological examination. Ultrasound made it possible to assess the thickness, echoicity and vascularization of the SCF. In 35 patients, significant thickening of the SCF was revealed (as compared to the contralateral side), of which in 14 cases with SPn, in 21 - with LPn. Significant diffuse thickening of the SCF with the contralateral side was observed in 18 patients, incl. in 12 (66%) patients with LPn. Limited thickening was more typical for SPn (73%). A significant increase in the echoicity of the SCF was noted in all forms of Pn. A “lobular” echo pattern with an anechogenic environment was observed in 25 patients, of which 18 (72%) had LPn. An increase in vascularization compared to the contralateral side was recorded in 30 cases (SPn-17, LPn-13).Conclusion:The obtained preliminary results indicate the important role of ultrasound in assessing the depth and prevalence of the inflammatory process at Pn. To clarify the diagnostic value of this method, further studies are needed on a larger sample of patients.Disclosure of Interests:None declared

The Cockroach DCMD Neurone: I. Lateral Inhibition and the Effects of Light- and Dark-adaptation

1982 ◽  
Vol 99 (1) ◽  
pp. 61-90 ◽  
Author(s):  
DONALD H. EDWARDS
Keyword(s):  
Lateral Inhibition ◽  
Dark Adaptation ◽  
Light Adaptation ◽  
Absolute Intensity ◽  
Recurrent Network ◽  
Light Spot ◽  
Movement Detector ◽  
Threshold Response ◽  
Inhibitory Network ◽  
Local Background

1. The responses of the cockroach descending contralateral movement detector (DCMD) neurone to moving light stimuli were studied under both light- and dark-adapted conditions. 2. With light-adaptation the response of the DCMD to two moving 2° (diam.) spots of white light is less than the response to a single spot when the two spots are separated by less than 10° (Fig. 2). 3. With light-adaptation the response of the DCMD to a single moving light spot is a sigmoidally shaped function of the logarithm of the light intensity (Fig. 3a). With dark-adaptation the response of a DCMD to a single moving light spot is a bell-shaped function of the logarithm of the stimulus intensity (Fig. 3b). The absolute intensity that evokes a threshold response is about one-and-a-half log units less in the dark-adapted eye than in the light-adapted eye. 4. The decrease in the DCMD's response that occurs when two stimuli are closer than 10°, and when a single bright stimulus is made brighter, indicates that lateral inhibition operates among the afferents to the DCMD. 5. It is shown that this inhibition cannot be produced by a recurrent lateral inhibitory network. A model of the afferent path that contains a non-recurrent lateral inhibitory network can account for the response/intensity plots of the DCMD recorded under both light-adapted and dark-adapted conditions. 6. The threshold intensity of the DCMD is increased if a stationary pattern of light is present near the path of the moving spot stimulus. This is shown to be due to a peripheral tonic lateral inhibition that is distinct from the non-recurrent lateral inhibition described earlier. 7. It is suggested that the peripheral lateral inhibition acts to adjust the threshold of afferents to local background light levels, while the proximal non-recurrent network acts to enhance the acuity of the eye to small objects in the visual field, and to filter out whole-field stimuli.

Markers of steroid resistance of the primary nephrotic syndrome in children

2021 ◽  
Vol 19 (1) ◽  
pp. 15-21
Author(s):  
S. L. Morozov ◽  
◽  
V. V. Dlin ◽  
Keyword(s):  
Nephrotic Syndrome ◽  
Steroid Therapy ◽  
Molecular Genetic ◽  
Clinical Importance ◽  
Recent Decade ◽  
Immunosuppressive Drugs ◽  
Steroid Resistance ◽  
Primary Nephrotic Syndrome ◽  
Non Invasive ◽  
The Common

The global task of the recent decade is to search for clinical and laboratory markers accurately showing a patient’s reaction to steroid therapy and other immunosuppressive drugs. It is important the applied methods and tests to be non-invasive and simple to use. The article considers various biomarkers used to verify the type of nephrotic syndrome depending on the sensitivity to steroid therapy. Besides the common markers, which are used in clinical practice or have shown a significant result, the work highlights the molecular- genetic markers of resistance to steroid therapy, which are of special clinical importance today. Also, the article presents authors’ own results in diagnosing the steroid resistance of the primary nephrotic syndrome.

scholarly journals An improved AC-amplifier for electrophysiology

2009 ◽  
Vol 19 (1) ◽  
pp. 7-12
Author(s):  
Nikola Jorgovanovic ◽  
Dubravka Bojanic ◽  
Vojin Ilic ◽  
Darko Stanisic
Keyword(s):  
Dynamic Range ◽  
Cutoff Frequency ◽  
Instrumentation Amplifier ◽  
Single Chip ◽  
Common Mode ◽  
Differential Signal ◽  
Op Amp ◽  
Chip Technology ◽  
The Common ◽  
Dc Component

We present the design, simulation and test results of a new AC amplifier for electrophysiological measurements based on a three op-amp instrumentation amplifier (IA). The design target was to increase the common mode rejection ratio (CMRR), thereby improving the quality of the recorded physiological signals in a noisy environment. The new amplifier actively suppresses the DC component of the differential signal and actively reduces the common mode signal in the first stage of the IA. These functions increase the dynamic range of the amplifier's first stage of the differential signal. The next step was the realization of the amplifier in a single chip technology. The design and tests of the new AC amplifier with a differential gain of 79.2 dB, a CMRR of 130 dB at 50 Hz, a high-pass cutoff frequency at 0.01 Hz and common mode reduction in the first stage of the 49.8 dB are presented in this paper.

The Effect of Changed Extracellular Calcium and Sodium Concentration on the Electroretinogram of the Crayfish Retina

1980 ◽  
Vol 35 (3-4) ◽  
pp. 308-318 ◽  
Author(s):  
H. Stieve ◽  
I. Claßen-Linke
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Calcium Concentration ◽  
Light Adaptation ◽  
Sodium Concentration ◽  
Strong Increase ◽  
Calcium Stores ◽  
Half Time ◽  
Astacus Leptodactylus ◽  
External Calcium

Abstract The electroretinogram (ERG) of the isolated retina of the crayfish Astacus leptodactylus evoked by strong 10 ms light flashes at constant 5 min intervals was measured while the retina was continuously superfused with various salines which differed in Ca2+ -and Na+ -concentrations. The osmotic pressure of test- and reference-saline was adjusted to be identical by adding sucrose. Results: 1. Upon raising the calcium-concentration of the superfusate in the range of 20-150 mmol/l (constant Na+ -concentration: 208 mmol/l) the peak amplitude hmax and the half time of decay t2 of the ERG both decrease gradually up to about 50% in respect to the corresponding value in reference saline. 2. The recovery of the ERG due to dark adaptation following the “weakly light adapted state” is greatly diminished in high external [Ca2+]ex. 3. Lowering the external calcium-concentration (10 →1 mmol/l) causes a small increase in hmax and a strong increase of the half time of decay t2 (about 180%). Upon lowering the calcium concentration of the superfusate to about 1 nmol/l by 1 mmol/l of the calcium buffer EDTA, a slowly augmenting diminution of the ERG height hm SLX occurs. How­ever, a strong retardation of the falling phase of the ERG characterized by an increase in t2 occurs quickly. Even after 90 min stay in the low calcium saline the retina is still not inexcitable; hmax is 5 - 10% of the reference value. The diminution of hmax occurs about six-fold faster when the buffer concentration is raised to 10 mmol/l EDTA. 4. Additional lowering of the Na+ -concentration (208 →20.8 mmol/l) in a superfusate with a calcium concentration raised to 150 mmol/l causes a strong reduction of the ERG amplitude hmax to about 10%. 5. In a superfusate containing 1 nmol/l calcium such lowering of the sodium concentration (208 → 20.8 mmol/l) causes a diminution of the ERG height to about 40% and the shape of the ERG to become polyphasic; at least two maxima with different time to peak values are observed. Interpretation: 1. The similarity of effects, namely raising external calcium concentration and light adaptation on the one hand and lowering external calcium and dark adaptation on the other hand may indicate that the external calcium is acting on the adaptation mechanism of the photoreceptor cells, presumably by influencing the intracellular [Ca2+]. 2. The great tolerance of the retina against Ca2+ -deficiency in the superfusate might be effected by calcium stores in the retina which need high Ca2+ -buffer concentrations in the superfusate to become exhausted. 3. In contrast to the Limulus ventral nerve photoreceptor there does not seem to be an antagonis­ tic effect of sodium and calcium in the crayfish retina on the control of the light channels. 4. The crayfish receptor potential seems to be composed of at least two different processes. Lowering calcium-and lowering external sodium-concentration both diminish the height and change the time course of the two components to a different degree. This could be caused by in­ fluencing the state of adaptation and thereby making the two maxima separately visible.

Changes of Acuity during Light and Dark Adaptation in the Dragonfly Compound Eye

1990 ◽  
Vol 45 (1-2) ◽  
pp. 137-142 ◽  
Author(s):  
Eric J. Warrant ◽  
Robert B. Pinter
Keyword(s):  
Dark Adaptation ◽  
Time Course ◽  
Light Adaptation ◽  
Compound Eye ◽  
Sensitivity Function ◽  
The State ◽  
Intracellular Recordings ◽  
Acceptance Angle ◽  
Angular Sensitivity ◽  
Rapid Reduction

Abstract Intracellular recordings of angular sensitivity from the photoreceptors of Aeschnid dragonflies (Hemianax papuensis and Aeschna brevistyla) are used to determine the magnitude and time course of acuity changes following alterations of the state of light or dark adaptation. Acuity is defined on the basis of the acceptance angle, Δρ (the half-width of the angular-sensitivity function). The maximally light-adapted value of Δρ is half the dark-adapted value, indicating greater acuity during light adaptation. Following a change from light to dark adaptation, Δρ increases slowly, requiring at least 3 min to reach its dark-adapted value. In contrast, the reverse change (dark to light) induces a rapid reduction of Δρ , and at maximal adapting luminances, this reduction takes place in less than 10 sec.

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