A program for automatic acquisition and processing of electroretinograms obtained in vivo in albino rats.

A program sequence has been developed on a microcomputer that affords automatic acquisition and processing of electroretinogram (ERG) obtained in vivo in dark-adapted albino rats. A 50-Hz digital filter and an averaging summation remove the background noise.

Light-induced variations of retinal sensitivity in rats.

PURPOSE: ERG responses were measured as a function of Ganzfeld luminance to evaluate functional damage induced by light on rat retinas. METHODS: Wistar rats were exposed to a fluorescent light of 1700 lux for 12 h, 24 h, 48 h and 72 h. We recorded ERGs before and one night after exposure, then 3, 8, 15, 22 and 29 days later. The b- and PIII-wave amplitudes were plotted against luminance for each group at each recovery time. RESULTS: The retinal damage induced by a pupillary illuminance of 1700 lux ranged from low to severe as exposure duration increased from 12 h to 72 h, respectively. We observed an effect immediately after light exposure but no improvement during the recovery period. The b-wave amplitude was reduced by 40, 60, 80 and 90 percent after 12, 24, 48 and 72 h of light exposure, respectively; the PIII-wave amplitude was reduced by 30, 40, 70 and 90 percent after these respective exposures. The Ganzfeld luminance eliciting a 50 microV b-wave amplitude increased significantly with exposure duration, but the luminance eliciting the maximal b-wave amplitude was not dependent on this duration. Hence we suggest that the ERG decrease is due to a reduction in photoreceptor number. CONCLUSIONS: We present a full analysis of the electrophysiological parameters recorded from light-exposed or non-exposed rats. This model is a useful tool to study in vivo retinal degeneration.

Comparison of intraocular treatment of DMTU and SOD following retinal ischemia in rats.

The effect of intravitreal injections of DMTU (dimethylthiourea) and SOD (superoxide dismutase), two free radical scavengers, was evaluated in a rat model of retinal ischemia induced by elevated intraocular pressure. The drugs were administered just before or just after a 60 min ischemia. At days 2 and 7 after reperfusion, retinal recovery was evaluated by electroretinography. At day 7, layer thicknesses and cell rows were measured from histologic sections of paraffin-embedded retinas. In the vehicle-treated control group, we observed a decrease in the inner retinal layers and b-wave amplitude impairment. SOD injection (6 units/eye) protected the retina from ischemia/reperfusion injury. At day 2 after reperfusion, electroretinographic recovery was more efficient when SOD was administered just after ischemia (99%) than after pretreatment with SOD (81%) (p<0.03). In the DMTU-treated group (75 microg/eye), only the pretreatment induced significant electrophysiologic (40%) (p<0.001) and morphologic recovery.

Effects of leukotrienes on the electroretinographic profile of the isolated rat retina.

The isolated retina represents an excellent membrane model since it provides a specific electrophysiological response that is easy to quantify. Therefore the authors have tested the effects of B4, C4 and D4 leukotrienes on this model. In the presence of leukotrienes, electrical response generally decreases and survival duration of the isolated retina is generally shortened. No significant difference between the effects of the three tested products has been found. These results are discussed in relation to, on the one hand, the mechanism of intraretinal generation of its electrophysiological signal and, on the other hand, the leukotrienes' role in inflammatory diseases of the retina.

An automatic stimulus generation system for electroretinogram capture and processing.

An automated system is presented for on-line capture and processing of the analog signal obtained in response to light or X-ray stimulation of isolated rat retina maintained in survival by perfusion. The most important part of the system is a microcomputer Apple II (48 K Europlus) equipped with interface boards. Basic and assembler programs automatically deliver light or X-ray stimulation every 5 min. Data capture and data processing are carried out following each retinal response. Calculated parameters of the ERG, and 200 values obtained after sampling of an ERG are placed in a data file on a floppy disc. One hundred ERGs can be stored in this way.

[Parathyroidectomy by elective route with perioperative measurement of parathyroid hormone. Report of 80 cases]. / Parathyroïdectomie par voie élective avec dosage peropératoire de la parathormone intacte. A propos de 80 cas.

STUDY AIM: The aim of this study was to report a series of 80 patients treated by unilateral neck exploration for a sporadic primary hyperparathyroidism. PATIENTS AND METHOD: Between April 1992 and November 1998, 80 patients (65 women and 15 men, mean age: 63.5 years) with a single gland enlargement localized by ultrasonography, were operated on through a short unilateral neck incision, under general anesthesia in 72 cases and local in eight cases. The enlarged gland was removed with intraoperative pathological examination and intraoperative monitoring of parathyroid hormone. RESULTS: Mean duration of surgery was 25 minutes. There was no postoperative mortality or morbidity. Mean duration of hospital stay was two days. The enlarged gland was an adenoma in 75 cases and an hyperplasia in five. Adequate intraoperative parathyroid hormone decrease was observed. Postoperative calcemia was normal in 78 patients (97.5%). Among 76 surviving patients, with a 31-month follow-up, there was only a suspicion of persistent hyperparathyroidism in two patients. CONCLUSIONS: Minimal invasive approach by unilateral neck exploration may be performed with safety and efficiency in patients with a single gland enlargement under intraoperative monitoring of parathyroid hormone.

[Effects of oxygenated free radicals on the electrophysiological activity of the isolated retina of the rat]. / Effets des radicaux libres oxygénés sur l'activité électrophysiologique de la rétine isolée de rat.

Particularly rich in polyunsaturated fatty acids, the retina constitutes an excellent model for testing the functional consequences of membrane lipoperoxidation. The effects could be quantified by measuring the amplitude of the electroretinogram which represents the characteristic response of the retina to its physiological stimulus (light photons). The authors report results obtained on isolated rat retina maintained in survival by perfusion. The membrane lipid peroxidation is induced by the non enzymatic catalytic system (Fe2+ + ascorbate). In the presence of such a system, the amplitude of the b-wave of the electroretinogram rapidly decreases and the survival time is notably shortened. These results are discussed with regards to the mechanism generating the electroretinogram and the specific role played by the disk membrane and plasmic membrane of the rod outer segment. Finally, the authors test the radical scavenger properties of a Ginkgo biloba extract. The results indicate that such an extract develops an antiperoxidative effect probably connected with its flavonoid composition. With this extract the survival time of the isolated retina is significantly increased and this result could be related to the retinal cell membrane disorders observed in diabetes.

Experimental study of the retinal toxicity of hemoglobinic iron.

The functional consequences of vitreous hemorrhage on the retina were studied using a rabbit experimental model. The repartition of hemoglobinic iron inside the retina was assessed after the intravitreous injection of 59Fe-labeled erythrocytes. Electroretinographic studies were performed both in vivo after the intravitreous injection of labeled blood and in vitro on albino rat isolated retina treated with Fe ions. Results indicate that hemoglobinic iron migrates from the vitreous to the retina and inside the retinal tissue from ganglion cells to deeper layers. It is also demonstrated that hemoglobinic iron has a significant functional toxicity on the retina.

Electrophysiological consequences of leukotrienes applied on isolated rat retina.

Scotopic vision is the result of a cascade of light-dependent biochemical events in rod outer segments (ROS) involving mainly a cGMP-modulation of sodium current. This modification of ionic currents induces changes of membrane potential which generates electroretinographic (ERG) waves. As (i) ERG disturbances are commonly recorded in hypoxic and inflammatory retinal diseases (ii) leukotrienes (LTs), a very potent mediators of inflammation, disturb ionic exchanges in several artificial or natural membrane systems, we undertook the investigation of the effects of LTs on ERG record in mammalian isolated retina. LTB4, LTC4 and LTD4, all induced a dose-dependent marked reduction of the b wave amplitude of ERG. This effect is correlated with a significant decrease in the survival time of the retina. The analysis of the modification of ERG indicates that LTs exhibit a real toxic effect since b wave is mainly affected while P III wave is unchanged. Comparatively with other nervous cells, this phenomenon may be attributed to an increase in Na+ permeability of ROS. It is suggested that LTs may be involved in the development of inflammatory or ischemic retinal diseases.

Effect of Gingko biloba extract (EGb 761) on chloroquine induced retinal alterations.

Electroretinography was used to investigate the preventive action of Ginkgo biloba extract (EGb 761) in experimental chloroquine-induced retinopathy in rats. EGb 761 contains flavones and anthocyanosides known for their oxygenated radical scavenging properties. Chronic administration of chloroquine (20 days) caused an overall lengthening of the duration of the ERG b-wave, together with delayed peaking. These anomalies became more marked with increased duration of treatment. In rats treated simultaneously with chloroquine and EGb 761 no such modification of the electroretinogram (ERG) was observed. These results suggest that retinal toxicity may be related to a localized inflammation releasing oxygenated free radicals and/or PAF. EGb 761 may thus afford a useful preventive treatment for chloroquine-induced retinopathy, and generally for xenobiotic retinotoxicities.

Evidence of 3 beta-hydroxysteroid dehydrogenase activity in several murine embryonal carcinoma cell lines.

This report describes, for the first time to our knowledge, a possible steroidogenic activity in established murine embryonal carcinoma cell lines (PCC3, PCC4, F9), revealed by a 3 beta-hydroxysteroid dehydrogenase activity (revelation of NADH2 by staining, and RIA assessment of delta 4-androstenedione). The remarkable analogy between such totipotent cells and embryonal cells may suggest that this activity could be present before histologic organization of the embryonal testis. Nonmalignant embryonal cells such as fibroblasts (3/A/1/D-3) or myoblasts (T984) were also found to possess a 3 beta-hydroxysteroid dehydrogenase activity, thus suggesting that this enzyme is not specific to hormone-secreting cells, but the sign of a more general phenomenon.