[Mechanical dilatation of the pupil in phacoemulsification surgery: first experiences with the 6.25 mm Malyugin-ring]. / Mechanische Pupillenerweiterung zur Kataraktoperation: erste Erfahrungen mit dem 6,25 mm Malyugin-Ring.

PURPOSE: Inadequate mydriasis may cause major problems in phacoemulsification surgery. Usually 4 iris retractors are used to allow adequate pupillary dilatation. Implantation of a Malyugin ring to maintain a 6.25 mm pupil is a new alternative. PATIENTS AND METHODS: A Malyugin ring was used in 46 eyes of 39 patients (aged 80.1 ± 6.2 years). The ring is im- and explanted with a disposable shooter through the main incision. Indications for the use of the ring were inadequate mydriasis due to pseudoexfoliation (n = 27), intraoperative floppy iris syndrome (n = 5), the combination of PEX and IFIS (n = 11), extensive posterior synechiae (n = 2) or inadquate mydriasis after long-term pilocarpine treatment (n = 1). RESULTS: In 44/46 eyes phacoemulsification with implantation of foldable posterior chamber lens was performed without complications. In 2 eyes with massive phakodonesis an Artisan anterior chamber lens had to be implanted after anterior vitrectomy because of total zonulolysis. There where no complications associated to the use of the device and with increasing experience duration of implantation as well as explantation was reduced to 2 - 4.5 min (median 2:51 min). CONCLUSIONS: In cases of phacoemulsification surgery with inadequate mydriasis implantation of a Malyugin ring is a simple, safe and fast alternative to iris-retractors; it allows better pupil-size without additional stab incisions.

[Effect of insulin on retinal glycogen content]. / Die Wirkung des Insulins auf den Glykogengehalt der Netzhaut.

BACKGROUND: The effect of insulin on glucose and glycogen metabolism in peripheral organs is well known. However, information about the action of this peptide in the retina is incomplete. We addressed the questions whether insulin influences glycogen content in the cat retina and whether glycogen breakdown is triggered by lack of glucose. MATERIAL AND METHODS: Eyes from adult cats were enucleated under deep barbiturate and fentanylanesthesia. Retinas were snap frozen either before or following arterial in vitro perfusion. Three conditions were studied: a) Perfusion with a glucose- and insulin-free medium; b) perfusion with the addition of physiologic glucose concentration; and c) in combination with insulin. Glycogen content was determined by in vitro measurement of glucose converted from glycogen. RESULTS: The reference value for retinal glycogen after enucleation (10 min of ischemia) is 2.4 micrograms glucose/mg protein. Glucose- and insulin-free perfusion for 80 min following "normoglycemia" reduced the amount of retinal glycogen by one third. Perfusion for 3 h with 5.5 mM glucose led to a small increase of the partly depleted glycogen stores. Insulin, in contrast, markedly augmented the glycogen content. CONCLUSIONS: Insulin led to an increase in retinal glycogen content, indicating an influence of this peptide on retinal glucose and glycogen metabolism. However, it appears that glycogen might play a dynamic role in retinal metabolism as a buffer between abrupt changes in focal metabolic demands that occur during normal glucose supply rather than acting solely as an emergency energy reserve for neural function during hypoglycemia.

[Stargardt's disease and its intrafamilial variability]. / Morbus Stargardt mit intrafamiliärer Variabilität.

BACKGROUND: Because of its considerable differential diagnosis and a wide range of phenotypic variation, Stargardt's disease (juvenile macular dystrophy) can cause diagnostic problems. Moreover, ample variability in course and outcome of the disease has been described. PATIENTS AND METHODS: The diagnosis and variable course of Stargardt's disease of three affected siblings have been documented by clinical manifestation, fluorescein angiography and Ganzfeld-ERG including the ISCEV standard protocol. RESULTS: All three siblings presented with retinal abnormalities. However, only the youngest brother revealed symptoms for more than 10 y in terms of reduced visual acuity. The two elder ones had preserved central vision. Classical findings of contact lens biomicroscopy, fluorescein angiography and changes in the Ganzfeld-ERG confirmed the diagnosis of Stargardt's disease. CONCLUSIONS: The diagnosis of Stargardt's disease can be made as late as in the 7th decade of life. Tremendous variability can occur in course and outcome even within the same family. Therefore, visual prognosis is uncertain and has to be made with caution. In most cases the diagnosis can be established with the above mentioned methods.

The retina of c-fos-/- mice: electrophysiologic, morphologic and biochemical aspects.

PURPOSE: Mice without a functional c-Fos protein (c-fos-/- mice) do not exhibit light-induced apoptotic cell death of rods in contrast to their wild-type littermates (c-fos+/+ mice). To analyze the consequences of the absence of c-fos in the retina, we investigated whether the retinas of c-fos-/- mice have a reduced capacity to absorb and transduce light compared with c-fos+/+ mice. METHODS: Retinal function was evaluated in dark-adapted mice by full-field electroretinograms (ERGs) over more than 6 log units of intensity. Retinal morphology was studied by light- and electron microscopy. Arrestin and the heat shock protein 70 (Hsp70) were detected by Western blot analysis. The rhodopsin content and the kinetics of rhodopsin regeneration were determined in retinal extracts. RESULTS: Although the configuration of the ERGs was comparable in both groups of mice, c-fos-/- mice showed a marked variability in all quantitative ERG-measures with lower mean amplitudes, longer latencies, and a 0.9-log-unit lower b-wave sensitivity on average. Morphometry showed that c-fos-/- mice have 23% fewer rods on average, whereas the number of cones was comparable among c-fos+/+ and c-fos-/- mice. Arrestin levels appeared slightly reduced in c-fos-/- mice when compared with c-fos+/+ mice, whereas Hsp70 levels were comparable in both genotypes. The kinetics of rhodopsin regeneration were similar, but c-fos-/- mice had a 25% lower rhodopsin content on average. CONCLUSIONS: Compared with c-fos+/+ mice, retinal function in c-fos-/- mice is attenuated to a variable but marked degree, which may be, at least in part, related to the reduced number of rods and the reduced rhodopsin content. However, c-fos does not appear to be essential for the ability to absorb photons, nor for phototransduction or the function of second-order neurons. The resistance to light-induced apoptosis of photoreceptor cells in c-fos-/- mice may result from the acute deficit of c-fos in the apoptotic cascade rather than from developmental deficits affecting rod photoreceptor function.

Light-induced cell death of retinal photoreceptors in the absence of p53.

PURPOSE: Cell death by apoptosis is essential for normal development and tissue homeostasis, and it is involved also in a variety of pathologic processes. Apoptosis is the final common pathway of photoreceptor cell death in retinal dystrophies and degeneration. So far, little is known about genes regulating apoptosis in the retina. The tumor-suppressor gene product p53 is a potent regulator of apoptosis in numerous systems. However, p53-independent apoptotic pathways also have been described. In this study the authors investigated the role of p53 in the light-induced apoptosis of retinal photoreceptors using mice lacking p53. METHODS: Free-moving p53-/- and p53+/+ mice were dark adapted and were exposed to 8,500 or 15,000 lux of diffuse, cool, white fluorescent light for 2 hours. Animals were killed before and immediately after light exposure or at 12 hours in darkness after light exposure. Eyes were enucleated and processed for light and electron microscopy and histochemistry (TdT-dUTP terminal nick-end labeling method). Isolated retinas were subjected to the extraction of total retinal DNA. Electroretinogram (ERG) recordings were performed at all time points. RESULTS: Morphologic, biochemical, histochemical, and ERG analysis showed that the retinas of untreated p53-/- mice and wild-type control mice were structurally and functionally indistinguishable. After exposure to diffuse white fluorescent light, light-induced photoreceptor cell death was analyzed and was found to be the same in both groups of mice. CONCLUSIONS: These data suggest that light-induced apoptosis of photoreceptors is independent of functional p53.

The mouse ERG before and after light damage is independent of p53.

Death of retinal photoreceptors by apoptosis is observed under many physiological and pathological conditions such as histogenesis, retinal dystrophies and light-induced photoreceptor degeneration. To date, little is known about regulatory mechanisms for apoptosis in the retina. The tumor suppressor gene p53 is a regulator of apoptosis in a number of systems, however, p53-independent apoptosis has also been described. We have therefore investigated whether the lack of p53 influences the dark-adapted ERG in C57BL/6 p53-/- mice compared to p53+/+ control littermates under physiological (regular light-dark cycle) conditions. We also recorded ERGs at 12 to 14 h in darkness following diffuse bright light exposure to 8,000 or 15,000 lux for 2 h. ERG analysis over a range of 6 logarithmic units of light intensity revealed normal and virtually identical a-, b-, c-waves and oscillatory potentials in dark-adapted p53+/+ and p53-/- mice. After exposure to diffuse white fluorescent light strong decreases of all ERG components were found to be very similar in both genotypes. These data support the notion that the p53 protein is neither essential for normal retinal function nor for processes involved in light-induced depression of the ERG in mice.

Effects of insulin under normal and low glucose on retinal electrophysiology in the perfused cat eye.

PURPOSE: To investigate the short-term effects of fast-acting insulin on the electroretinogram-b-wave, optic nerve response, standing potential, and flow rate in the arterially perfused cat eye under normal conditions and during low glucose levels. METHODS: Enucleated cat eyes were perfused with a glucose- and insulin-free tissue culture medium, to which glucose was applied at normal (5.5 mM) and reduced (2 and 1 mM) concentrations. Photic stimulation was performed in the rod-matched intensity range before, during, and after insulin application at postprandial (5 ng/ml) and at 10 and 20 x higher concentrations. RESULTS: Insulin failed to affect retinal signals at normal glucose levels. However, insulin enhanced the low glucose-induced decrease in rod-driven b-wave amplitude (P < 0.05 at 2 mM; P < 0.01 at 1 mM) without affecting the corresponding changes in the optic nerve response. The standing potential increased by as much as 0.75 mV in response to insulin. The perfusate flow rate was not altered by insulin. CONCLUSIONS: Insulin was not required for normal retinal function as observed during 10 hours of perfusion. The differential responsiveness to insulin under low glucose of the b-wave versus the optic nerve response is thought to reflect suppression of glucose use by Müller (glial) cells rather than neuromodulation, as the neuronal optic nerve response is unaffected. The postulated insulin sensitivity of Müller cells (changes in b-wave amplitude) indicates a possible difference in the mechanism of glucose metabolism of glia versus neurons. The electrophysiological effect of insulin under low glucose suggests its passage across the blood-retina barrier. The increase in the standing potential is likely to be a receptor-mediated retinal pigment epithelium effect. These results provide evidence in the retina for the reported multifunctional nature of the insulin receptor.

beta-Casomorphin-immunoreactivity in the brain stem of the human infant.

Using a peptide extraction procedure, reversed phase high performance liquid chromatography, and a radioimmunoassay that utilized an antibody raised specifically against human beta-casomorphin-8 (BC8), BC-immunoreactivity (BCIR) was detected in rostrocaudally increasing levels in nineteen microscopically distinct and functionally relevant areas of mesencephalon, pons cerebri, and medulla oblongata of eight infants. On the basis of the methodology used, it can be concluded, that the BCIR present in their brain stem was due to BC8 and/or to some of its congeners. Data in the literature together with those of this study indicate that beta-casomorphins could be transported by specific mechanisms from the blood into the brain stem and that they could play a role in the central regulation of various physiological phenomena.

A novel two-site enzyme immunoassay for the sensitive detection of beta-endorphin in specific human brain stem regions.

On the line of experiences previously made in the development of a two-site immunoradiometric assay (TS-IRMA), we generated, in the present study, a novel, sequential, noncompetitive two-site immunoenzymometric assay (TS-IEMA) for the determination of the non-acetylated form of human beta-endorphin (beta h-EP). At variance with other assays reported in the literature, but in analogy to the TS-IRMA, the TS-IEMA does not require previous separation of beta h-EP. The TS-IEMA detects beta h-EP in central nervous tissues at a very low detection limit, and to a high degree of reproducibility, precision, sensitivity, and accuracy. The newly developed assay was then used to determine beta h-EP levels in the tissues of distinct brainstem regions. Tissues were collected, by the Palkovits's punching technique, from a series of victims of "Sudden Infant Death Syndrome" and of miscellaneous infections. The TS-IEMA, combined with the punching technique, has revealed, in the measure of its application in the present study, an unprecedented high degree of resolution of the neurochemical architecture of beta h-EP in the human infantile brainstem.