[New DIN and ISO norms for determination of visual acuity]. / Neue DIN- und ISO-Normen zur Sehschärfebestimmung.

Recently, three international norms (ISO) for visual acuity assessment were revised. The DIN EN ISO 8596:2018 stipulates the Landolt C eye chart as the standard optotype and specifies display characteristics. An informative annex lists clinical optotypes for the first time. These include the ETDRS chart, Snellen chart and pediatric optotypes; however, these clinical optotypes do not have the same status as the Landolt C chart, since even with identical font size and stroke width they may differ in recognizability. The technical report ISO/TR 19498:2015 complements DIN EN ISO 8596. A scientifically appropriate procedure is described, which enables a quantitative correlation of clinical optotypes with the Landolt C chart. The DIN EN ISO 10938:2016 describes the required optical quality of optotypes. For the first time, electronic devices are explicitly approved for standardized visual acuity tests. Consequently, according to this amendment electronic devices may be used for acuity assessment for ophthalmological expert opinions according to DIN 58220, part 3.

[Photopic contrast sensitivity. Local contrast perception]. / Photopisches Kontrastsehen. Ortliche Kontrastempfindlichkeit.

Contrast perception is an important visual function. Contrast sensitivity (CS) is affected by to optical reasons (aberrations, scatter, diffraction) or neural dysfunction (e.g., glaucoma, optic nerve diseases). In clinical practice the measurement of CS is relevant for disease monitoring, expert opinions, roadworthiness assessment, and recruitment screening. Furthermore, CS testing is often required in studies assessing optical quality, e.g., cataract or refractive surgery. Adding an appropriate glare source allows measurement of the glare-induced loss of CS (disability glare). Compared to high-contrast acuity, CS is more variable and strongly depends on the type of test, illumination, test strategy, and contrast definition; ceiling effects are quite common among many tests. Maximal standardization is important, especially for follow-up exams. In summary, CS testing cannot be regarded as a routine test. The present report by the DOG commission for quality management of psychophysical assessment covers the physiological background, testing principles, and strategies and presents a tabular overview of common tests.

[Analysis of spectacle lens prescriptions shows no increase of myopia in Germany from 2000 to 2015]. / Analyse der Brillenstärken zeigt keine Zunahme der Myopie in Deutschland von 2000 bis 2015.

OBJECTIVE: To determine whether the prevalence and magnitude of myopia among children and young adults wearing spectacles has increased in Germany from 2000 to 2015. MATERIAL AND METHODS: A total of 1,223,410 refraction values from 278,432 male and 333,273 female subjects between 5 and 30 years of age were analyzed. All subjects had received a new pair of spectacles between 1 January 2000 and 31 December 2015. The parameter studied was the spherical equivalent averaged over both eyes of each subject (N = 611,705). In order to identify temporal changes, the entire period of 16 years was divided into 4 time intervals of 4 years each. In the subjects three evaluation criteria were studied as a function of age: a) the frequency of myopic subjects among all spectacle wearers, b) the mean spherical equivalent and c) the distribution of the individual spherical equivalents. RESULTS: a) The frequency of myopic corrections among all spectacle wearers did not increase from 2000 to 2015. At 5 years of age, 9% of all children wearing glasses were myopic (≤-0.5 D) and 80% were hyperopic (≥+0.5 D). At the age of 10, 20 and 25 years, 46%, 75% and 79%, respectively, of all spectacle wearers were myopic and 42%, 13% and 10% hyperopic. b) The mean spherical equivalent, averaged across all spectacle wearers of the same age, did not show a myopic shift from 2000 to 2015. At the age of 5, 10.3 and 27 years, the mean spherical equivalent all subjects wearing glasses was +1.74 D, 0.0 D and -1.91D. c) The refractive power distribution of the individual spherical equivalents did not change significantly from 2000 to 2015. Neither low nor high myopias were more abundant in the period 2012-2015 compared to the previous years. CONCLUSION: The frequency and the refractive power of myopia did not increase in Germany over the last 16 years.

[Contrast vision-definitions, conversions, and equivalence tables]. / Kontrastsehen ­ Definitionen, Umrechnungen und Äquivalenztabelle.

Human contrast vision and its quantitative assessment are gaining more attention. Publications on this topic can be confusing due to the overabundance of differing definitions and quantification of contrast vision. As a case in point, in Germany, contrast ratios as required for certain driving licenses and the DIN-defined contrast ratio are reciprocal. In this article, the five most important definitions of luminance contrast and contrast vision (Michelson, Weber, contrast ratios, logCS) are presented. We detail the specific domains for them, give formulae to convert between all of them and provide a table with equivalent values. We recommend the unit logCS wherever possible.

[Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS). A new test to determine contrast sensitivity under variable ambient and glare luminance levels]. / Das "Frankfurt-Freiburg Contrast and Acuity Test System" (FF-CATS). Ein neuer Test zur Kontrastsensitivitätsbestimmung unter variablen Beleuchtungs- und Blendbedingungen.

BACKGROUND: The purpose of the present study was to evaluate a computerized test for measurement of contrast sensitivity thresholds under variable ambient and glare luminance levels. METHODS: A total of 40 eyes of 40 healthy subjects were examined with the FF-CATS and the Functional Acuity Contrast Test (FACT) at 0.167 cd/m(-2) (mesopic) and 167 cd/m(-2) (photopic). Measurements were performed twice with and without glare in a randomized fashion. Tests were evaluated according to three criteria: (1) repeatability, (2) discriminative ability, and (3) validity. RESULTS: The FF-CATS showed a higher discriminative ability between the two groups compared to the FACT charts. Under photopic conditions, the COR value was 0.39 for the FF-CATS and 0.26 for the FACT charts; under mesopic illumination, the COR value for the FF-CATS was 0.46 and 0.36 for the FACT charts. CONCLUSION: The FF-CATS is a reliable, sensitive, valid, and flexible test system for the determination of visual acuity and contrast sensitivity thresholds under variable ambient and glare luminance conditions.

Studies on megakaryocytes: isolation from rat and guinea pig and incorporation of 5-hydroxytryptamine.

A new, two step method is described for the isolation of megakaryocytes from bone marrow. By means of centrifugation in a PercollR density gradient megakaryocytes can be enriched by factor 68 or 24 starting from rat or guinea pig bone marrow, respectively. The purity of the megakaryocytes can be improved ca. 4 fold if gradient centrifugation is followed by separation in an Elutriator rotor.-The isolated megakaryocytes take up exogenous 5-hydroxytryptamine with a time and concentration dependent transport mechanism, K11=30 micrometer, K12=1.5 micrometer. As shown by electron microscopy the number and density of storage granules within the megakaryocytes is enhanced after incubation with 5-hydroxytryptamine. This finding suggests that 5-hydroxytryptamine is incorporated into the organelles.

Isolation of mouse megakaryocytes. I. Separation of two fractions enriched in different maturational stages.

Megakaryocytes (MK) were isolated from mouse bone marrow by centrifugation on discontinuous gradients of isotonic albumin or Percoll and characterized by acetylcholinesterase (AChE) staining. The apparent density distributions of MK varied greatly depending upon the nature of the gradient medium and the composition of the cell suspension buffer while the density range of the other bone marrow cells remained largely unchanged. The present findings also indicate that the unusual morphological and functional characteristics of MK may underlie the observed shift in their density profile. Thrombocytopoietic stimulatory factor (TSF) was administered to mice 18 h before killing to elevate the normally low numbers of earlier MK in the bone marrow and to improve the yield of immature MK during the subsequent isolation procedure. Cells belonging to earlier stages in maturation were separated from the more mature ones on discontinuous Percoll density gradients, providing a basis for further investigation of MK development.

Isolation of mouse megakaryocytes. II. Functional and metabolic aspects of two different maturational stages.

Functional and metabolic parameters were compared in immature and mature megakaryocytes (MK) isolated from bone marrow of the mouse by Percoll density gradient centrifugation. Comparison of metabolic parameters revealed that the ability to take up serotonin was equal in both megakaryocytic fractions. The uptake of radioactively labeled adenine was increased in immature MK as compared with mature MK. Total adenosine triphosphate (ATP) content was enhanced during the differentiation from MK to platelets: immature MK: 5, mature MK: 29, platelets: 63 nmol ATP/mg protein. Since MK, like platelets, released ATP upon stimulation, thrombin-induced release was used as functional parameter to differentiate between secretable and non-secretable ATP compartments. Upon thrombin stimulation both MK fractions released about 25% of their total ATP as compared with about 40% secreted by platelets. Although the actual size of the non-secretable ATP pool was different in mature MK and platelets, they demonstrated similar percentages of retained ATP (20-25%) in contrast to a much higher retention (62%) by immature MK. The present findings suggest that the bulk of ATP is acquired by immature MK as they gain maturity, although some ATP is still obtained during even later stages of differentiation. This growing ATP pool could be attributed mainly to the enlargement of the secretable compartment during the transition of immature MK to mature MK.

Intracellular distribution of adenine and 5-hydroxytryptamine in megakaryocytes isolated by density gradient and velocity sedimentation from bone marrow.

Megakaryocytes were isolated from rat and guinea pig bone marrow by Percoll density and/or elutriator centrifugation. As compared with the suspension of bone marrow an enrichment of factor 530 with a recovery of 34% can be achieved if a combination of both methods is applied.--The pattern of DNA percentage distribution in isolated cells paralleled the polyploidy found in megakaryocytes of the bone marrow. As determined by scanning cytophotometry and impulse cytophotometry the percentage distribution was maximal for the 16 C cells.--Exogenous [3H]adenine was incorporated by isolated megakaryocytes via a time and concentration dependent process showing two different affinities, Kt1 = 11 nM, V1 = 0.07 pmol/min per 10(5) cells; Kt2 = nM, V2 = 0.21 pmol/min per 10(5) cells.--Autoradiographic studies quantificated by means of the "probability circle" and "percent density" analysis showed that [3H]5-hydroxytryptamine (5-HT) accumulated in the osmiophilic dense bodies in contrast to [3H]adenine (metabolite) which was found mainly in the cytoplasm.

Effect of 1-aminoadamantanes on adenine nucleotide and serotonin storage in blood platelets.

The platelet release reaction, the liberation of adenine nucleotides and serotonin (5-HT) from osmiophilic dense granules, can be induced in human platelets by C-alkyl-derivatives of the antiviral and anti-Parkinson drug 1-aminoadamantane (D 1). The release-inducing activity is enhanced with increasing chain length and with the number of C-alkylsubstituents, respectively. The parent compound, D 1, liberates only 5-HT. Analyses of LDH activity in the incubation medium of the platelets and electron micrographs of platelets treated with 1-aminoadamantanes support the assumption that ATP, ADP, and 5-HT are released from the organelles by an exocytosis-like process rather than by destruction of the plasma and organelle membranes. The number of osmiophilic dense granules in platelets isolated from human and rabbit blood is decreased by the action of the drugs. This is in contrast to other subcellular structures where no morphological changes can be observed. The ADP-stimulated platelet aggregation is inhibited by preincubation with 1-aminoadamantanes. The inhibitory activity of the drugs on platelet aggregation parallels the effects observed after induction of the release reaction: the inhibition of platelet aggregation is enhanced with increasing C-alkylation. Hence, the inhibition of ADP-induced platelet aggregation can be used to screen for the releasing activity of 1-aminoadamantanes which have, as far as tested, similar effects on 5-HT storage in blood platelets and in the CNS. The time-, temperature, and concentration-dependent 5-HT uptake by platelets (K = 0.75 micro M; V max = 0.22 nmoles/min X 10 9 cells) is noncompetitively inhibited by the drugs with K1-values varying from 10 to 100 micro M depending on the degree of C-alkylation.

Increased number of high sensitive platelets in hypercholesterolemia, cardiovascular diseases, and after incubation with cholesterol.

The number of low density platelets was found to be increased in patients with hypercholesterolemia, as compared with the number in controls. The percentage increase of the low density platelet subpopulation was even more pronounced in patients with hypercholesterolemia when compared with that in patients suffering from myocardial infarction or angina. In vitro studies with control platelets incubated with cholesterol rich liposomes showed also an increase in the subpopulation of low density platelets. After incubation of control platelets with cholesterol rich liposomes, a higher membrane anisotropy and a higher cholesterol to phospholipid (C/P) molar ratio of the plasma membrane were found. Furthermore, cholesterol-enriched platelets were more sensitive upon thrombin stimulation. The results suggest that a shift of platelet subpopulations to a higher number of low density platelets could be caused by either the level of plasma cholesterol or an in-vitro incubation with cholesterol rich liposomes.

Absolute ocular fundus dimensions measured by multiple-beam interference fringes.

Multiple-beam interference fringes have been projected onto the retina to serve as a size reference for fundus photography. The absolute fringe spacing is determined by measurable parameters. The interference fringes are extremely narrow so that fringe maxima and fundus structures can be perceived equally well, and a high precision of measurement is achieved. The method has been applied to a model eye of varying ametropia (within +/- 7 diopters). The reproducibility of measurement is within 0.5%. In vivo measurements on human eyes demonstrate the clinical applicability.

Induction of the platelet release reaction by 1.3-dimethyl-5-aminoadamantane, a new adamantane derivative.

The amantadine derivative 1.3-dimethyl-5-aminoadamantane, D 145, induces in high concentrations of 2-10 mM the release reaction. Adenine nucleotides and 5-hydroxytryptamine (5-HT) are liberated to the same extent and in the same ratio as found after thrombin-induced release. The time course of release is very slow; maximal release is reached in 15-20 min. The process is temperature-dependent and dependent on energy derived from glycolysis and oxidative phosphorylation. Extracellular Ca++ does not promote the release process. D 145, in accordance with the mother-substance amantadine, inhibits 5-HT uptake non-competitively, KI = 0.15mM. In concentrations of 0.1-1 mM D 145 triggers only the liberation of 5-HT, adenine nucleotides are not liberated. The ADP induced platelet aggregation is completely inhibited after preincubation with a 1 mM solution of D 145.

Analysis of GTP-binding proteins, phosphoproteins, and cytosolic calcium in functional heterogeneous human blood platelet subpopulations.

The biochemical basis for the functional heterogeneity of human blood platelets was investigated in terms of protein phosphorylation, cytoplasmic calcium ([Ca2+]i), the ratio of 46 and 50 kDa vasodilator-stimulated protein (VASP), and GTP-binding proteins (G-proteins). Platelets were fractionated by density. Comparing resting low-density platelets (LDP) to high-density platelets (HDP) revealed higher phosphorylation of proteins in the 47, 31, and 24 kDa ranges. A higher phosphorylation of the 20 kDa protein in LDP compared to HDP was related to an enhanced [Ca2+]i, an increased ADP-ribosylation of the inhibitory G-protein (G(i alpha1-3)) and rhoA, and a decreased ADP-ribosylation of the stimulatory G-protein (G(s alpha)). The differences in the ribosylation patterns of the subpopulations were not influenced by thrombin stimulation or exposure to prostaglandin E1 (PGE1). An 18 kDa phosphoprotein was more highly phosphorylated in resting HDP than in LDP. Thrombin exposure caused dephosphorylation of the 18 kDa phosphoprotein in the HDP, but generally increased phosphorylation of both HDP and LDP in the 47, 31, 24, and 20 kDa bands. Preincubation with prostaglandin E1 or sodium nitroprusside diminished the subsequent thrombin-induced increase in phosphorylation, particularly in HDP. In unstimulated HDP, the 50 kDa VASP phospho form was enhanced, whereas in unstimulated LDP the 46 kDa VASP dephospho form was increased. Our findings suggest that the functional heterogeneity of platelets is partly derived from differences in signal transduction mechanisms reflected in varying phosphoprotein patterns and G-protein properties of platelet stimulatory and inhibitory pathways.

The lack of receptors for atrial natriuretic peptides on human monocytes prevents a rise of cGMP and induction of tumor necrosis factor-alpha synthesis.

Freshly harvested human monocytes were shown to produce tumor necrosis factor-alpha (TNF-alpha) in response to exogenously added or sodium nitroprusside-generated cGMP. In contrast, atrial natriuretic peptide (ANP) that acts by elevating cGMP in a variety of cells, was incapable of inducing TNF-alpha synthesis. This failure was due to a lack of ANP receptors and thus, to the inability of ANP to raise cGMP in human monocytes.

Modulation of serotonin binding in rat brain by membrane fluidity.

Preincubation of rat brain homogenates with increasing concentrations of n-hexanol reduced specific serotonin (5-HT) binding and increased membrane fluidity as measured by fluorescence depolarization using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe. At 5 mM ascorbate maximal reductions of both membrane fluidity and specific 5-HT binding were observed. Both effects were enhanced in the presence of ferrous sulphate and oxygen. In the presence of ascorbate (5.7 mM) only one 5-HT binding site was observed in contrast with high and low affinity binding sites (K(D1) = 0.08 +/- 0.04 nM, K(D2) = 28.8 +/- 1.3 nM) found in the absence of ascorbate. The ascorbate induced decrease of specific 5-HT binding may be explained by lipid peroxidation, which decreases membrane fluidity, and by ascorbate's reducing properties. Since different correlations were found between membrane fluidity and specific 5-HT binding depending upon the presence of ascorbate or n-hexanol, the results suggest that membrane fluidity is a critical factor, however, just one of several determinants in 5-HT binding studies.

Circadian and seasonal rhythms of 5-HT receptor subtypes, membrane anisotropy and 5-HT release in hippocampus and cortex of the rat.

Specific serotonin binding (5-HT1, 5-HT1A, and 5-HT2 subtypes) and membrane anisotropy were measured at 2 h intervals over a 24 h period in the hippocampus and cortex of Wistar WU rats, housed under a 12 h light-dark cycle, with lights on at 07.00. All experiments were performed both in March and December. In the hippocampus significant circadian rhythms could be ascertained for 5-HT1 binding sites in March and December while for 5-HT1A (subtype of 5-HT1) binding sites the circadian rhythm was only significant in March. The membrane anisotropy also showed significant variations only in March. Circadian rhythms were also found in the cortex for 5-HT1 (December) and 5-HT2 (March and December) binding sites as well as for the membrane anisotropy (December). A correlation was found between membrane anisotropy and 5-HT1 and 5-HT2 binding sites in hippocampus and cortex, respectively. A circadian rhythmicity was also observed for serotonin release as measured by in vivo voltammetry in both brain areas. The results obtained on the diurnal variations of serotonin receptor subtypes and serotonin release and the probable inverse relationship of these two parameters may be relevant in understanding the coupling of pre- and postsynaptic activity.

Effect of transient reduction of cerebral blood flow on membrane anisotropy and lipid peroxidation in different rat brain areas.

Light-microscopical studies revealed that oligemic hypoxia for 24 and 60 min as produced by bilateral clamping of the carotid arteries (BCCA) in normotension does not produce neuronal cell necrosis in the vast majority of rat brain. Less than 5% of cases showed a pattern of mild selective neuronal necrosis as would be expected in ischemia. However, significant changes in both lipid peroxidation (as measured by MDA formation) and membrane anisotropy (measured by DPH or TMA-DPH, respectively, as a fluorescence probe) in cortical and striatal, but not in hippocampal, membrane fractions could be measured in ex vivo studies. Twenty-four and 60 min of BCCA without reperfusion decreased lipid peroxidation in the cerebral cortex but not in the striatum. BCCA, either for 24 or 60 min, and 60 min of reperfusion produced no changes in lipid peroxidation in either structure. However, 24 and 60 min of BCCA followed by 14 days of reperfusion led to a significant increase in MDA formation in the striatum, while lipid peroxidation in the cortex was only increased after 60 min of BCCA. Cortical as well as striatal membrane anisotropy increased significantly 14 days later in rats submitted to BCCA for 24 or 60 min. The study shows an increased lipid peroxidation 2 weeks after a transient reduction in cerebral blood flow although no neuronal necrosis could be observed in general.

Alterations of blood platelet MAO-B activity and LSD-binding in humans after sleep deprivation and recovery sleep.

Sleep deprivation (SD) is an effective, however short-lived, method of treatment of depression. Preliminary findings suggest that the antidepressive effect of sleep deprivation is mediated by serotoninergic (5-HT) mechanisms. We therefore assessed serotoninergic activity before and after total SD (TSD) as well as after the following night sleep by investigating platelet LSD-binding, MAO B-activity, and 5-HT-content as well as plasma norepinephnne (NE) in 10 healthy men (age: 27.4 +/- 2.8 years). Blood samples were drawn on three consecutive days at 0700, 1300 and 1900 h, respectively. After TSD, a significant increase of LSD-binding KD and Bmax as well as of MAO-B KM and plasma NE could be observed, which, however, vanished after consecutive night sleep. Our findings favour an increased serotoninergic transmission after TSD and thus support the hypothesis, that sleep deprivation exerts its antidepressant effects by pro-serotoninergic mechanisms.

Regulation of cerebral serotonin binding and metabolism in sleep-deprived rats.

Two different binding sites are found for serotonin binding to crude membrane fractions isolated from rat brain. After 12 h sleep deprivation (SD) the dissociation constant of the high affinity binding KD1 = 1.4 mM, remains unchanged whereas the dissociation constant, KD2, of the low affinity binding increased from 26 to 42 nM. The number of binding sites are only moderately affected. The dissociation constant of the low affinity binding, KD2, is decreased towards control values if SD is followed by 1 or 4 h sleep. As indicated by serotonin and 5-hydroxyindoleacetic acid analyses, a statistically significant increase in serotonin metabolism is found only, if SD is followed by 1 h recovery sleep.