[Level of Binocular Pseudoaccommodation in Patients Implanted with an Apodised, Diffractive and Trifocal Multifocal Intraocular Lens]. / Grad der binokularen Pseudoakkommodation mit einer apodisierten, diffraktiven und trifokalen Multifokallinse.

PURPOSE: The aim of this study was to make an evaluation of the pseudoaccommodation span and clinical results after implantation of a diffractive, apodised and trifocal multifocal intraocular lens (MIOL). METHODS: In a prospective, single-centre study 28 eyes of 14 patients were evaluated after in the bag implantation of the Micro-F MIOL (PhysIOL, Belgium) during routine microsurgical cataract surgery. Two to four months postoperatively the final examinations were performed. Refraction, visual acuity monocular and binocular (near in 40 cm, intermediate in 80 cm and distance) as well as binocular defocus curves were evaluated. RESULTS: Mean monocular UDVA (uncorrected distance visual acuity) increased significantly (p < 0.0001) from 0.471 ± 0.22 logMAR to 0.144 ± 0.14 logMAR. For the monocular UNVA (uncorrected near visual acuity) and UIVA (uncorrected intermediate visual acuity) postoperative values of 0.127 ± 0.117 and 0.158 ± 0.20 logMAR compared to binocular results of 0.057 ± 0.137 and 0.094 ± 0.181 logMAR were found. In the analysis of the binocular defocus curve two peaks could be found between 0.0 and - 0.5 D with a visual acuity of 0.0 logMAR and at - 3.0 D with a visual acuity of 0.068 logMAR. In the intermediate range a constant pseudoaccommodation of 0.2 logMAR could be found. CONCLUSIONS: The trifocal, diffractive MIOL shows good functional results in all distances with a span of pseudoaccommodation of 3D and a mean visual acuity of 0.2 logMAR and better. Indeed it is offering a high level of spectacle independency without the typical intermediate gap of bifocal diffractive MIOLs.

[Refraction after Implantation of Multifocal and Presbyopia-Correcting Intraocular Lenses]. / Richtiges Refraktionieren nach Implantation von Multifokal- und presbyopiekorrigierenden Intraokularlinsen.

Nowadays, further developments in the field of intraocular lenses offer a higher level of spectacle independence for our patients. As light gets scattered on different focal points a wider range of defocus is created. This greater defocus area makes it more difficult for us to determine the objective or subjective refraction. This contribution is concerned with the difficulties of measuring visual acuity in different intraocular lens designs and different measurement distances. Measuring refraction after implantation of a multifocal intraocular lens is a complex procedure and the experience of the examiner plays a crucial role. Retinoscopy, keratometry and the defocus curve are reliable methods for testing, while the auto refractometer, bichromatic testing and the cross-cylinder have limitations.

[Implantation of a sulcus-fixated toric additive intraocular lens in a case of high astigmatism after a triple procedure]. / Implantation einer additiven Intraokularlinse in den Sulcus ciliaris zur Korrektur eines hochgradigen Astigmatismus nach Triple Procedure.

BACKGROUND: Residual refractive errors, especially high-grade astigmatism after penetrating keratoplasty, often lead to a significant loss of vision. If high anismetropia could not be corrected with glasses or contact lenses, different kinds of surgical procedures are available for visual rehabilitation (intraocular lens exchange, astigmatic keratotomy, Excimer laser treatment, intrastromal corneal ring segment implantation and additive intraocular lens implantation). Toric add-on IOLs are especially designed for sulcus implantation and correcting high astigmatism in pseudophakic eyes. All toric IOLs are individually manufactured according to subjective refraction and biometry. Depending on the underlying manufacturer high-grade astigmatism can be corrected with a cylindrical power up to + 30.0 D. CASE REPORT: A 74-year-old patient presented with endothelial decompensation and an uncorrected distance visual acuity (UDVA) of 1.0 logMAR for penetrating keratoplasty on the right eye due to a Fuchs endothelial dystrophy. Postoperatively, the uncorrected distance visual acuity improved to 0.8 logMAR, with pinhole correction to 0.5 logMAR. After removing the sutures a high and irregular corneal astigmatism of 21.0 D was found. The corrected distance visual acuity (CDVA) with a refraction of + 5.5 D sph, - 21.0 D cyl 90° was 0.24 logMAR. Therefore an individually manufactured toric additive intraocular lens of + 25.0 D cylindrical and - 18.0 D spherical power for sulcus implantation was chosen and implanted uneventfully. Eight months after surgery refractive astigmatism was reduced significantly to - 0.75 D with an UDVA of 0.08 logMAR and a CDVA of 0.02 logMAR. During the 8-months follow-up period the additive IOL remained centered and no IOL rotation could be observed. CONCLUSION: Toric add-on IOLs are a safe and successful method for reducing high astigmatism and anisometropia after penetrating keratoplasty. One of the main advantages is the reversibility of the procedure by an explantation of the IOL.

The aging heart: changes in the pharmacodynamic electrophysiological response to verapamil in aged rabbit hearts.

The aim of this study was to investigate whether the L-type calcium current (I(Ca.L)) may be altered in aged hearts and whether the classical calcium antagonist verapamil may exhibit altered pharmacological profile in aged hearts. We examined male New Zealand rabbits aged either 6 months or 26 months. To examine I(Ca.L) whole-cell patch-clamp technique was performed on isolated cells. Moreover, activation-recovery intervals (ARI) of isolated hearts (Langendorff method) were assessed using an epicardial 256 channel mapping system. We found that the I(Ca.L) density, normalised to the cell volume was significantly reduced (p<0.001). Maximum conductance was also significantly decreased (p=0.01) and steady state inactivation was shifted to more positive potentials in aged hearts (p<0.001). A slightly reduced effect of beta-adrenergic modulation of the I(Ca.L) in aged hearts, and a significantly reduced effect of carbachol on isoprenaline-stimulated I(Ca.L) in aged hearts was observed. L-type alpha 1c subunit, SERCA2-ATPase and the Na(+)/Ca(2+)-exchanger expression were neither significantly different in atrial and ventricular tissues nor between young and old animals. Using the mapping system, isolated hearts were exposed to verapamil (0.005, 0.01, 0.02, 0.05 microM/L). While verapamil did not affect ARI in young hearts, in aged hearts ARI was concentration-dependently reduced and the negative inotropic effect of verapamil was significantly attenuated in aged hearts (p<0.05). From these results we conclude that there are distinct alterations in the electrophysiology of I(Ca.L) (reduced maximum conductance, a shift of the steady state inactivation) in the aged heart which may influence the response to verapamil.

The Akoya pearl oyster shell as an archival monitor of lead exposure.

The Akoya pearl oyster (Pinctada imbricata) was experimentally exposed to (a) constant levels of lead (Pb) at 180 microg L(-1) for nine weeks, or (b) two short term (pulse) exposures of Pb at 180 microg L(-1) (three weeks each) with an intervening depuration period (three weeks), to assess its utility as an (i) accumulative monitor of Pb contamination and an (ii) archival monitor for discriminating constant versus pulsed Pb exposure events. P. imbricata showed similar reductions in growth (based on shell morphology and wet weight) and Pb accumulation patterns for whole tissue and shell in response to both Pb exposure regimes. Thus the whole oyster was deemed an inappropriate accumulative monitor for assessing short-term temporal variation of Pb exposure and effect. However, using secondary ion mass spectrometry, Pb was shown to accumulate in the successively deposited nacreous layers of the shell of P. imbricata, documenting the exposure history of constant versus pulsed Pb events. Patterns of Pb deposition not only reflected the frequency of Pb exposure events but also their relative durations. Thus, the shell of P. imbricata may be employed as a suitable biological archive of Pb exposure.

Distribution of a persistent sodium current across the ventricular wall in guinea pigs.

A tetrodotoxin-sensitive persistent sodium current, I(pNa), was found in guinea pig ventricular myocytes by whole-cell patch clamping. This current was characterized in cells derived from the basal left ventricular subendocardium, midmyocardium, and subepicardium. Midmyocardial cells show a statistically significant (P<0.05) smaller I(pNa) than subendocardial and subepicardial myocytes. There was no significant difference in I(pNa) current density between subepicardial and subendocardial cells. Computer modeling studies support a role of this current in the dispersion of action potential duration across the ventricular wall.

Profile and kinetics of L-type calcium current during the cardiac ventricular action potential compared in guinea-pigs, rats and rabbits.

The substantial interspecies differences in mammalian cardiac action potentials (APs) are attributed primarily to variations in K+ currents. In a comparative study on isolated ventricular myocytes from guinea-pigs, rabbits and rats, we investigated the influence of the species-based AP differences on the time course of the L-type Ca2+ current (ICa,L). In addition, we tested whether also species-dependent properties of the ICa,L contribute to its time course during the AP. In patch-clamp measurements, ICa,L was characterised using conventional square pulses and digitised APs as command voltages. Special interest was directed to the analysis of the actual time courses of ICa,L, and L-type channel activation and inactivation during APs. Although species-specific differences in AP shape strongly influence the amplitude and the time course of ICa,L, divergence in L-type channel inactivation was found as well. In each species ICa,L inactivation was related to Ca2+ influx via L-type channels. However, while L-type channels showed similar Ca2+ dependency in the rabbit and the rat, a 2-times higher Ca2+ influx was necessary to achieve a given degree of inactivation in the guinea-pig. Thus, inactivation of ICa,L is delayed in the guinea-pig, thereby contributing to the prolonged AP plateau in this species. Comparing the actual time course of ICa,L, and L-type channel activation and inactivation revealed that, in each species, fading of ICa,L during final repolarisation was caused by deactivation (i.e. closure of the channel's d-gate) rather than inactivation.

Membrane potential and currents of isolated heart muscle cells exposed to pulsed radio frequency fields.

The influence of radio frequency (RF) fields of 180, 900, and 1800 MHz on the membrane potential, action potential, L-type Ca(2+) current and potassium currents of isolated ventricular myocytes was tested. The study is based on 90 guinea-pig myocytes and 20 rat myocytes. The fields were applied in rectangular waveguides (1800 MHz at 80, 480, 600, 720, or 880 mW/kg and 900 MHz, 250 mW/kg) or in a TEM-cell (180 MHz, 80 mW/kg and 900 MHz, 15 mW/kg). Fields of 1800 and 900 MHz were pulsed according to the GSM-standard of cellular phones. The specific absorption rates were determined from computer simulations of the electromagnetic fields inside the exposure devices by considering the structure of the physiological test arrangement. The electrical membrane parameters were measured by whole cell patch-clamp. None of the tested electrophysiological parameters was changed significantly by exposure to RF fields. Another physical stimulus, lowering the temperature from 36 degrees C to 24 degrees C, decreased the current amplitude almost 50% and shifted the voltage dependence of the steady state activation parameter d(infinity) and inactivation parameter f(infinity) of L-type Ca(2+) current by about 5 mV. However, at this lower temperature RF effects (900 MHz, 250 mW/kg; 1800 MHz, 480 mW/kg) on L-type Ca(2+) current were also not detected.

Control of L-type calcium current during the action potential of guinea-pig ventricular myocytes.

1. During an action potential the L-type Ca2+ current (ICa,L) activates rapidly, then partially declines leading to a sustained inward current during the plateau phase. The reason for the sustained part of ICa,L has been investigated here. 2. In the present study the mechanisms controlling the ICa,L during an action potential were investigated quantitatively in isolated guinea-pig ventricular myocytes by whole-cell patch clamp. To measure the actual time courses of ICa,L and the corresponding L-type channel inactivation (fAP) during an action potential, action potential-clamp protocols combined with square pulses were applied. 3. Within the first 10 ms of the action potential the ICa,L rapidly inactivated by about 50 %; during the plateau phase inactivation proceeded to 95 %. Later, during repolarization, the L-type channels recovered up to 25 %. 4. The voltage-dependent component of inactivation during an action potential was determined from measurements of L-type current carried by monovalent cations. This component of inactivation proceeded rather slowly and contributed only a little to fAP. ICa,L during an action potential is thus mainly controlled by Ca2+-dependent inactivation. 5. In order to investigate the source of the Ca2+ controlling fAP, internal Ca2+ homeostasis was manipulated by the use of Ca2+ buffers (EGTA, BAPTA), by blocking Na+-Ca2+ exchange, or by blocking Ca2+ release from the sarcoplasmic reticulum (SR). Internal BAPTA markedly reduced the L-type channel inactivation during the entire action potential, whereas EGTA affected fAP only during the middle and late plateau phases. Inhibition of Na+-Ca2+ exchange markedly increased inactivation of L-type channels. Although blocking SR Ca2+ release decreased the fura-2-measured cytoplasmic Ca2+ concentration ([Ca2+]i) transient by about 90 %, it reduced L-type channel inactivation only during the initial 50 ms of the action potential. Thus, it is Ca2+ entering the cell through the L-type channels that controls the inactivation process for the majority of the action potential. Nevertheless, SR Ca2+-release contributes 40-50 % to L-type channel inactivation during the initial period of the action potential. However, the maximum extent of inactivation reached during the plateau is independent of Ca2+ released from the SR. 6. For the first time, the actual time course of L-type channel inactivation has been directly determined during an action potential under various defined [Ca2+]i conditions. Thereby, the relative contribution to ICa,L inactivation of voltage, Ca2+ entering through L-type channels, and Ca2+ being released from the SR could be directly demonstrated.

Overexpression of the sarcolemmal calcium pump in the myocardium of transgenic rats.

The plasma membrane calmodulin-dependent calcium ATPase (PMCA) is a calcium-extruding enzyme controlling Ca2+ homeostasis in nonexcitable cells. However, its function in the myocardium is unclear because of the presence of the Na+/Ca2+ exchanger. We approached the question of the physiological function of the calcium pump using a transgenic "gain of function" model. Transgenic rat lines carrying the human PMCA 4 cDNA under control of the ventricle-specific myosin light chain-2 promoter were established, and expression in the myocardium was ascertained at the mRNA, protein, and functional levels. In vivo hemodynamic measurements in adult homozygous animals showed no differences in baseline and increased cardiac performance recruited by volume overload compared with controls. No differences between transgenic and control cardiomyocytes were found in patch clamp voltage dependence, activation/inactivation behavior of the L-type Ca2+ current, or fast [Ca2+]i transients (assessed by the Fura-2 method). To test whether the PMCA might be involved in processes other than beat-to-beat regulation of contraction/relaxation, we compared growth processes of neonatal transgenic and control cardiomyocytes. A 1.6- and 2.3-fold higher synthesis rate of total protein was seen in cells from transgenic animals compared with controls on incubation with 2% FCS for 24 hours and 36 hours, respectively. An effect of similar magnitude was observed using 20 micromol/L phenylephrine. A 1.4-fold- and 2.0-fold-higher protein synthesis peak was seen in PMCA-overexpressing cardiomyocytes after stimulation with isoproterenol for 12 hours and 24 hours, respectively. Because pivotal parts of the alpha- and beta-adrenergic signal transduction pathways recently have been localized to caveolae, we tested the hypothesis that the PMCA might alter the amplitude of alpha- and beta-adrenergic growth signals by virtue of its localization in caveolae. Biochemical as well as immunocytochemical studies suggested that the PMCA in large part was colocalized with caveolin 3 in caveolae of cardiomyocytes. These results indicate that the sarcolemmal Ca2+-pump has little relevance for beat-to-beat regulation of contraction/relaxation in adult animals but likely plays a role in regulating myocardial growth, possibly through modulation of caveolar signal transduction.

The late component of L-type calcium current during guinea-pig cardiac action potentials and its contribution to contraction.

L-Type Ca2+ current (ICa,L) elicited during the action potential (AP) of guinea-pig ventricular myocytes exhibits an early and a late component. The whole-cell patch-clamp technique was used to characterize the process regulating the late ICa,L component and to assess its contribution to excitation-contraction coupling. A stepwise decrease in repolarization rate of AP-like voltage-clamp pulses led to an exponential increase in Ca2+ charge carried by ICa, L. This saturation behaviour was significantly reduced or absent when Ba2+ or monovalent cations were used as charge carriers, which suggests that the late component of ICa,L is controlled mainly by Ca2+-dependent processes. Simultaneously recording ICa,L and zero-load shortening or the internal Ca2+ concentration (fura-2) revealed that Ca2+ carried by the late component of ICa,L markedly contributes to the Ca2+ content of the sarcoplasmic reticulum (SR). Reducing the charge transfer by late ICa,L during a series of AP-like conditioning clamp pulses by 48% reduced the shortening amplitude during a subsequent test stimulation by 56%. This relationship was absent during long rectangular depolarizing conditioning clamps, during which Na+/Ca2+ exchange increased its influence on SR Ca2+ loading. The late component of ICa,L developed only a minor direct influence on the simultaneous cell shortening. Thus, the main contribution of the late ICa,L component is to supply Ca2+ for SR loading.

Rapid modulation of L-type calcium current by acutely applied oestrogens in isolated cardiac myocytes from human, guinea-pig and rat.

Gender-based differences in cardiovascular mortality may be due to a cardio-protective effect of oestrogens on the myocardium. However, mRNA expression of oestrogen receptors in myocardial tissue of the adult heart has yet to be demonstrated. Furthermore, a calcium antagonistic action of 17beta-oestradiol on myocardial tissue has been discussed. Therefore, two subjects were investigated in atrial myocytes of the human, and ventricular myocytes of guinea-pig and rat in this study. (1) Are oestrogen receptors expressed in adult myocardial cells? (2) Is there an influence of oestrogens on the L-type calcium current of cardiac myocytes? Expression of oestrogen receptors was investigated by reverse polymerase chain reaction. L-type calcium current was usually measured by the patch-clamp technique in whole-cell recording mode under selective recording conditions, i.e. overlapping currents were blocked. One series of experiments was performed in perforated patch configuration to avoid internal perfusion. 17beta-oestradiol inhibited L-type calcium current reversibly in all three species. At 10(-5) M, the inhibition was 15-20%. This inhibition was independent of the sex and the species. A full concentration response curve of 17beta-oestradiol on basal L-type current was recorded from female guinea-pig myocytes. The inhibition increased from 2% at 10(-7) M to about 30% at 10(-4) M 17beta-oestradiol. The values could be fitted by a sum of two sigmoidal functions with log EC50 values of -6.5 and -4.9 M and Hill slopes of 2.5 for both. The specificity of the 17beta-oestradiol action was tested by recording the L-type current in the presence of 17alpha-oestradiol and oestrone. 17alpha-oestradiol also inhibited the current, but with a maximal inhibition of only 17%. The concentration-response curve could be fitted by a single sigmoidal function (log EC50 -6-3 M; Hill slope 0.55). Oestrone did not influence the current at all. The decrease in L-type current after the application of 17beta-oestradiol via a rapid perfusion system developed with a time constant of 3-4 s, which was in the same range as that for the influence of isoprenaline. The isoprenaline-stimulated L-type current was much more susceptible to the inhibition by 17beta-oestradiol, i.e. in pre-stimulated cells (1) the inhibitory effect is significantly higher (e.g. at 10(-5) M, inhibition was 36.3% compared with 11.2% in untreated cells) and (2) an inhibitory effect can be seen with oestradiol concentrations as low as 10(-9) M. Although the concentrations needed to gain a calcium antagonistic influence on the basal current were much too high to explain a cardio-protective influence of oestrogens, the presence of oestrogen receptors in cardiac myocytes of all three species, together with the shift in concentration dependence following pre-stimulation by isoprenaline, suggest that myocytes are a potential target for oestrogen.

Modulation of L-type calcium current by internal potassium in guinea pig ventricular myocytes.

OBJECTIVES: The early phase of myocardial ischemia is characterized by a considerable K+ efflux from cardiac myocytes, causing decreasing internal ([K+]i) and increasing external ([K+]o) K+ concentrations. The change in [K+]i and [K+]o is one of the factors thought to initiate the ischemia-induced changes in electrical activity. Nevertheless, little is known about the influence of [K+]i and [K+]o on the L-type calcium current. METHODS: The whole-cell patch-clamp technique combined with an internal perfusion system was used to test possible actions of altered [K+]i and [K+]o on L-type current carried by Ca2+ and Ba2+ in isolated guinea pig ventricular myocytes. RESULTS: Changing the [K+]i in the range of 110-170 mM revealed a sigmoidal concentration-response relationship between the L-type current and [K+]i. The maximum change in current amplitude was more than 40% with a half-saturation concentration of 136 mM which is near the physiological [K+]i. Ca2+ influx during action potential clamp increased by approximately 42% after raising [K+]i from 130 to 170 mM. Internal perfusion with Cs+ demonstrated that Cs+ is less effective than K+ in regulating the L-type current. By using ATP-analogues, [K+]i was shown to affect the L-type channel in a phosphorylation-independent way. Changes in [K+]o only modulated the L-type current via alterations in [K+]i. CONCLUSIONS: The decrease in [K+]i during early ischemia is, per se, sufficient to reduce the L-type current by up to 15%, thereby decreasing the action potential duration, and Ca2+ influx into the cells. This may act in addition to well-known mechanisms such as changes in internal pH and falling ATP levels, which influence the L-type current. Moreover, the phenomenon may complicate the interpretation of electrophysiological measurements of L-type current under conditions where [K+]i is not precisely controlled.

Modulation of hypertensive heart disease by estrogen.

UNLABELLED: Left ventricular hypertrophy is an independent risk factor for morbidity and mortality in patients with hypertensive heart disease. Cardiac hypertrophy, associated with increased cardiac fibrosis and myocardial relaxation impairment, shows gender-based differences with significantly higher mortality in men. The role of estrogen in the pathogenesis of this process is poorly understood. After our previous demonstration that cardiac myocytes and fibroblasts contain functional estrogen receptors, we therefore investigated: 1) the influence of different estrogen metabolites on cardiac fibroblast growth; 2) the influence of different estrogen metabolites on the expression of the immediate early gene c-Fos; 3) the influence of estrogen on the L-type calcium channel in cardiomyocytes. METHODS: 1) Neonatal rat cardiac fibroblasts were incubated with 17 beta-estradiol, estrone, 2-hydroxyestrone, and 2-methoxyestradiol (all 10(-9) M). Bromodeoxyuridine incorporation was measured after 24 h. 2) c-Fos expression was demonstrated by immunoblotting. 3) L-type (Ca2+) current with and without 17 beta-estradiol was assessed in adult guinea pig cardiomyocytes by whole cell patch clamp. RESULTS: Cardiac fibroblast growth was stimulated by estrogen metabolites with 2-hydroxyestrone as the most potent activator; in addition, 10(-5) M 17 beta-estradiol reduced the L-type Ca2+ current by about 20% in cardiomyocytes. CONCLUSIONS: Estrogen induces both short term effects (non-genomic) and long term effects (genomic) on the heart and may therefore account for gender- and age-based differences in hypertensive heart disease.