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In the course of the Raiselife project, three uncoated and twelve black coated tubular solar Receiver samples are investigated in an accelerated ageing test campaign to evaluate their durability . Thermal cycling tests are carried out, in which sample surfaces are exposed to concentrated solar flux at a modified solar dish system located at PSA in the south of Spain. Sample surface temperature needs to be controlled during cycling tests to be maintained below a maximum temperature setpoint, characterize possible degradation mechanisms and improve knowledge about the thermal cycling test procedure. Two approaches for surface temperature measurement are applied. The existing temperature measurement system consisting of thermocouples and a tool to estimate the temperature Gradient between the embedded thermocouple and sample surface. This method is enhanced by a simulation using ANSYS Thermal, confirming its applicability. A second temperature measurement system consisting of a solar blind IR camera is implemented. After confirming its calibration and applicability under the desired circumstances, an IR image is taken during cycling. Measured raw values of sample surface temperature are weighted with their specific thermal emittance in the wavelength range of the camera. Coated samples show stable thermal emittance values throughout cycling tests. Uncoated samples show optical degradation influencing the outcome of IR image processing, allowing the applicability of precise thermographic measurements to only be ensured for coated samples. A refinement of ANSYS Thermal properties promises more reliable simulation results. An improvement on the optical characterization process of sample surfaces promises more reliable thermographic measurements, in order to decrease its sensitivity with respect to emittance.

In the course of the Raiselife project, four solar absorber coatings are to be evaluated after thermal cycling at a dish facility. One key parameter is the thermal emittance. Optical measurements carried out at PSA show a deviation between two complementary spectrophotometers. Different approaches for the mismatch correction are applied. After the successful correction, a new measurement routine following DIN EN ISO 22795-3 is defined and the corrected values are evaluated with a round robin campaign. The standard deviation of thermal emittance values determined by different participating laboratories can be reduced by implementing a common processing of spectral data. The postprocessed DLR/CIEMAT value deviates around 2.1 % from the mean value determined within the round robin campaign. A new calibrated reference standard promises a further reduction of the deviation and hence an improvement in the absorber coatings’ thermal efficiency characterisation.

Die hypoxische pulmonale Vasokonstriktion (HPV) ist eine physiologische Anpassungsreaktion der Lungengefäße an Hypoxie. Dieser als von-Euler-Liljestrand-Mechanismus bekannte Vorgang dient zur Optimierung des Gasaustausches. Unter chronischer Hypoxie (z.B. COPD, Höhenaufenthalt) kommt es jedoch zu pathologischen Umbauvorgängen, die zu vaskulärem Remodeling und pulmonaler Hypertonie führen können. Als Sensor- und Effektorzellen konnten pulmonalarterielle glatte Gefäßmuskelzellen (PASMCs) identifiziert werden, welche durch Ca2+-Einstrom kontrahieren und angeregt durch Transkriptionsfaktoren, wie z.B. HIF proliferieren. Mitochondrien sind sowohl am akuten Sauerstoffsensing als auch bei den chronischen Remodelingprozessen beteiligt. Möglicherweise spielen dabei die mitochondriale ROS-Produktion und metabolische Veränderungen eine Rolle. Ziel dieser Arbeit war es daher zu untersuchen, ob sich die mitochondriale Atmung sowie der Redox-Status mitochondrialer Atmungskettencytochrome in PASMCs unter chronischer Hypoxie verändern. Verglichen wurden die Ergebnisse mit Veränderungen in aortalen SMCs (ASMCs). In einer kombinierten Messung aus Respirometrie und Remissions-Spektrophotometrie wurden die mitochondriale Sauerstoffaffinität, die mitochondriale Atmung und der Redox-Status der Cytochrome untersucht. Nach Etablierung eines validen Zellkulturmodels wurden Messungen an 24 Std und 48 Std hypoxisch (1 % O2) inkubierten Zellen durchgeführt. Es konnte gezeigt werden, dass bei Verwendung von 10 % FCS im Versuchsmedium die Zellkulturbedingungen hinsichtlich Aussaat oder Passage keinen Einfluss auf die Sauerstoffaffinität (p50) oder den maximalen Sauerstoffverbrauch (Vmax) haben. Serumarme Zellen (1 % FCS) dagegen wiesen im Vergleich zu serumreichen Zellen (10 % FCS) niedrigere Werte für beide Parameter auf. Nach hypoxischer Inkubation wurde nach 24 Std eine Abnahme von Vmax gesehen, welche nach 48 Std zunahm. Eine Reduktion der Sauerstoffaffinität konnte nach 48 Std hypoxischer Inkubation detektiert werden. Dabei veränderte sich die Mitochondrienzahl, gemessen an der Citrat-Synthase-Aktivität, nicht. In aortalen Vergleichszellen nahm die Sauerstoffaffinität nach 24 Std hypoxischer Inkubation stärker als in PASMCs ab, der maximale Sauerstoffverbrauch war vergleichbar mit demjenigen in PASMCs. In der Spektrophotometrie zeigte sich kein Unterschied in der pO2-abhängigen cytochromalen Reduktion bei hypoxisch inkubierten Zellen. Zusammenfassend zeigte sich eine verminderte Atmung und Sauerstoffaffinität hypoxisch inkubierter PASMCs, die möglicherweise Auswirkungen auf die Proliferation und das vaskuläre Remodeling unter chronischer Hypoxie haben. Hypoxic pulmonary vasoconstriction (HPV) is a physiological response of the lung to hypoxia and is also known as von-Euler-Liljestrand-mechanism, which optimizes blood perfusion to ventilation. In contrast, chronic hypoxia (as occuring in COPD or high altitude) leads to pathological changes and can result in pulmonary hypertension (PH) and vascular remodeling. The precapillary pulmonary artery smooth muscle cells (PASMCs) could be identified as sensor- and effector cells as they contract and proliferate in response to hypoxia mediated by Ca2+-entry and transcription factors, e.g. HIF. Mitochondria take part in both, acute oxygen sensing and chronic remodeling processes. Mitochondrial ROS-production and metabolic changes are discussed to be essential for these alterations. Aim of this dissertation was to investigate, if mitochondrial respiration and cytochromal redox-state of the mitochondrial respiratory chain complexes in PASMCs show alterations under conditions of chronic hypoxia. These results were compared to aortal SMCs (ASCMs). The protocol consisted of a combination of respirometry and remissions-spectrophotometry to analyze mitochondrial oxygen affinity, oxygen consumption and cytochromal redox state. After establishment of a valid cell culture model, measurements in cells after 24 and 48 hours of hypoxic incubation (1 % O2) were performed. It could be shown that cell culture conditions with regard to passage or sowing did not have any effect on oxygen affinity (p 50) or oxygen consumption (Vmax). Cells incubated with 1 % FCS showed a decrease in both values compared to cells cultured with 10 % FCS. After hypoxic incubation (1 % O2), a decrease in Vmax after 24 hours could be detected, which was increased after 48 hours. In contrast, a decrease of oxygen affinity only could be seen after 48 hours of hypoxic incubation. During 24 hours hypoxic incubation, the number of mitochondria was constant, measured by citrate synthase activity. In comparison to pulmonary artery cells, in aortal cells oxygen affinity was more reduced after 24 hours of hypoxic incubation with similar values of oxygen consumption. In spectrophotometry, no significant difference in pO2-dependent reduction of cytochromes could be found. In conclusion, pulmonary artery smooth muscle cells showed a decrease in respiration and oxygen affinity after hypoxic incubation. This may affect proliferation and vascular remodeling in conditions of chronic hypoxia.

Die hypoxische pulmonale Vasokonstriktion (HPV) ist eine physiologische Anpassungsreaktion der Lungengefäße an Hypoxie. Dieser als von-Euler-Liljestrand-Mechanismus bekannte Vorgang dient zur Optimierung des Gasaustausches. Unter chronischer Hypoxie (z.B. COPD, Höhenaufenthalt) kommt es jedoch zu pathologischen Umbauvorgängen, die zu vaskulärem Remodeling und pulmonaler Hypertonie führen können. Als Sensor- und Effektorzellen konnten pulmonalarterielle glatte Gefäßmuskelzellen (PASMCs) identifiziert werden, welche durch Ca2+-Einstrom kontrahieren und angeregt durch Transkriptionsfaktoren, wie z.B. HIF proliferieren. Mitochondrien sind sowohl am akuten Sauerstoffsensing als auch bei den chronischen Remodelingprozessen beteiligt. Möglicherweise spielen dabei die mitochondriale ROS-Produktion und metabolische Veränderungen eine Rolle.Ziel dieser Arbeit war es daher zu untersuchen, ob sich die mitochondriale Atmung sowie der Redox-Status mitochondrialer Atmungskettencytochrome in PASMCs unter chronischer Hypoxie verändern. Verglichen wurden die Ergebnisse mit Veränderungen in aortalen SMCs (ASMCs). In einer kombinierten Messung aus Respirometrie und Remissions-Spektrophotometrie wurden die mitochondriale Sauerstoffaffinität, die mitochondriale Atmung und der Redox-Status der Cytochrome untersucht. Nach Etablierung eines validen Zellkulturmodels wurden Messungen an 24 Std und 48 Std hypoxisch (1 % O2) inkubierten Zellen durchgeführt. Es konnte gezeigt werden, dass bei Verwendung von 10 % FCS im Versuchsmedium die Zellkulturbedingungen hinsichtlich Aussaat oder Passage keinen Einfluss auf die Sauerstoffaffinität (p50) oder den maximalen Sauerstoffverbrauch (Vmax) haben. Serumarme Zellen (1 % FCS) dagegen wiesen im Vergleich zu serumreichen Zellen (10 % FCS) niedrigere Werte für beide Parameter auf. Nach hypoxischer Inkubation wurde nach 24 Std eine Abnahme von Vmax gesehen, welche nach 48 Std zunahm. Eine Reduktion der Sauerstoffaffinität konnte nach 48 Std hypoxischer Inkubation detektiert werden. Dabei veränderte sich die Mitochondrienzahl, gemessen an der Citrat-Synthase-Aktivität, nicht. In aortalen Vergleichszellen nahm die Sauerstoffaffinität nach 24 Std hypoxischer Inkubation stärker als in PASMCs ab, der maximale Sauerstoffverbrauch war vergleichbar mit demjenigen in PASMCs. In der Spektrophotometrie zeigte sich kein Unterschied in der pO2-abhängigen cytochromalen Reduktion bei hypoxisch inkubierten Zellen. Zusammenfassend zeigte sich eine verminderte Atmung und Sauerstoffaffinität hypoxisch inkubierter PASMCs, die möglicherweise Auswirkungen auf die Proliferation und das vaskuläre Remodeling unter chronischer Hypoxie haben., Hypoxic pulmonary vasoconstriction (HPV) is a physiological response of the lung to hypoxia and is also known as von-Euler-Liljestrand-mechanism, which optimizes blood perfusion to ventilation. In contrast, chronic hypoxia (as occuring in COPD or high altitude) leads to pathological changes and can result in pulmonary hypertension (PH) and vascular remodeling. The precapillary pulmonary artery smooth muscle cells (PASMCs) could be identified as sensor- and effector cells as they contract and proliferate in response to hypoxia mediated by Ca2+-entry and transcription factors, e.g. HIF. Mitochondria take part in both, acute oxygen sensing and chronic remodeling processes. Mitochondrial ROS-production and metabolic changes are discussed to be essential for these alterations.Aim of this dissertation was to investigate, if mitochondrial respiration and cytochromal redox-state of the mitochondrial respiratory chain complexes in PASMCs show alterations under conditions of chronic hypoxia. These results were compared to aortal SMCs (ASCMs). The protocol consisted of a combination of respirometry and remissions-spectrophotometry to analyze mitochondrial oxygen affinity, oxygen consumption and cytochromal redox state. After establishment of a valid cell culture model, measurements in cells after 24 and 48 hours of hypoxic incubation (1 % O2) were performed. It could be shown that cell culture conditions with regard to passage or sowing did not have any effect on oxygen affinity (p 50) or oxygen consumption (Vmax). Cells incubated with 1 % FCS showed a decrease in both values compared to cells cultured with 10 % FCS. After hypoxic incubation (1 % O2), a decrease in Vmax after 24 hours could be detected, which was increased after 48 hours. In contrast, a decrease of oxygen affinity only could be seen after 48 hours of hypoxic incubation. During 24 hours hypoxic incubation, the number of mitochondria was constant, measured by citrate synthase activity. In comparison to pulmonary artery cells, in aortal cells oxygen affinity was more reduced after 24 hours of hypoxic incubation with similar values of oxygen consumption.In spectrophotometry, no significant difference in pO2-dependent reduction of cytochromes could be found. In conclusion, pulmonary artery smooth muscle cells showed a decrease in respiration and oxygen affinity after hypoxic incubation. This may affect proliferation and vascular remodeling in conditions of chronic hypoxia.

The biological properties of a protein critically depend on its conformation, which can vary as a result of changes in conditions such as pH or following the addition of various substances. Being able to reliably assess the quality of protein structures under various conditions is therefore of crucial importance. Infrared (IR) spectroscopy of the Amide I band of proteins is a powerful method for the determination of protein conformations and further allows the analysis of continuously flowing solutions of the target molecule. Here, a commercial Fourier-transform infrared spectrometer was coupled to a microfluidic mixer to allow the on-line monitoring of protein conformation under varying conditions. The validity of the concept was demonstrated by continuously recording the variations of the IR spectrum of poly-L-lysine resulting from repetitive, pH-induced conformational changes.

The diagnostic investigation of CT-negative subarachnoid haemorrhage (SAH) is a particular challenge in clinical neurology. Cerebrospinal fluid (CSF) analysis via lumbar puncture is the method of choice. The diagnosis of SAH in CSF is based on a bloody or xanthochromic discoloration of the CSF as well as on findings in non-automated CSF cytology including the detection of erythrophages and siderophages. The automated determination of CSF ferritin concentrations or spectrophotometric detection of xanthochromia may contribute to the diagnosis but are only useful with regard to the overall clinical picture. Generally, the knowledge of the time flow of CSF changes associated with SAH is essential for a correct interpretation of CSF findings.

In Ländern wie Norwegen und dem Vereinigten Königreich hat die Farmhaltung von Salzwasserfischen, speziell Lachsen, in den zurückliegenden 10 bis 15 Jahren große wirtschaftliche Bedeutung erlangt. Aus diesen Ländern wurde in den zurückliegenden 8 Jahren vermehrt über eine zunehmende Rate von Kataraktausbildung bei Lachsen berichtet. Die Katarakte können aus den bisherigen Kenntnissen der Fischlinsenphysiologie und –morphologie nicht erklärt werden. In der vorliegenden Arbeit werden verschiedene Schritte der Glykolyse in der Fischlinse (anhand von Bestimmung der spezifischen Aktivität von 5 Enzymen in definierten Linsenschnitten) spektrophotometrisch untersucht. Es werden erste Einblicke in die Stoffwechsel-Physiologie der Fischlinse gezeigt und Voraussetzungen für die spätere gezielte Untersuchung von möglichen Kataraktnoxen benannt. Der Linsenstoffwechsel der Lachse verläuft ähnlich dem der Säugetiere. Die gemessenen Enzymaktivitäten liegen in der Fischlinse deutlich unterhalb derer, die von Säugetierlinsen bekannt sind. Die niedrigen Enzymaktivitäten können Ausdruck einer Anpassung an die umgebende Wassertemperatur sein. Die relativ hohen LDH-Aktivitäten und PFK-Aktivitäten beweisen das Stattfinden der Glykolyse in der Augenlinse von Lachsen. Die niedrigeren PFK-Aktivitäten in den kataraktösen Farmlachslinsen können die Hemmung dieses Enzyms durch ein Überangebot an Glukose oder eine Entkopplung der Glykolyse beispielsweise durch Organophosphate anzeigen. Die G6P-DH liefert ein Indiz für das Vorhandensein des Pentosephosphatweges. Eine erhöhte AR-Aktivität weist auf einen latenten Typ II-Diabetes hin. Dies ist bei den unveränderten Linsen der Farmlachse und bei Kataraktlinsen gezeigt worden und deutet darauf hin, dass der Farmlachs ein ständiges Nahrungsüberangebot nicht verstoffwechseln kann. Eine hohe SDH-Aktivität bei den nur kurzfristig unter Stress stehenden WSS könnte eine Schutzfunktion anzeigen. Nimmt der WSS kurzfristig viele Kohlenhydrate zu sich, könnte die SDH verstärkt arbeiten, um ein Überangebot an Sorbit zu verhindern. Der Farmlachs dagegen weist nur geringe SDH-Aktivitäten auf, was Ausdruck eines Unvermögens ist, mit dem ständigen Glukoseüberangebot zurechtzukommen. Im Gegensatz zum Wildlachs steht der Lachs in der kommerziellen Fischzucht aufgrund von unnatürlichen Haltungsbedingungen (hohe Besatzdichte, permanentes Futterangebot, künstliche Belichtung) ständig unter Stress. Der Stoffwechsel scheint durch die Futteraufnahme – bei bereits gedecktem Bedarf – zu entgleisen. Als Argument für diese Hypothese wird die Assoziation von BMI (Verhältniszahl zwischen Körpergröße und Gewicht) und Katarakthäufigkeit beim Menschen angeführt. Der schädigende Einfluss von regelmäßig eingesetzten Pestiziden (Organophosphate) auf die Augenlinse ist wahrscheinlich und sollte in späteren Arbeiten gezielt untersucht werden. Die Linse scheint den intraokularen Parasitenbefall zu tolerieren. Dies zeigte sich dadurch, dass der Parasitenbefall weder auf das LFG (ungestörtes Wachstum) noch auf die Transparenz der Linse im Sinne kataraktogener Veränderungen Einfluss genommen hat. In der vorliegenden Arbeit wird auf die Prüfung triploider Fische hinsichtlich der Zuchteignung hingewiesen und es werden die Faktoren (osmotischer) Stress, Pestizide, Nahrungszusammensetzung, Temperatur, UV-Licht, oxidative Prozesse, Besatzdichte und Wachstumsgeschwindigkeit als mögliche Kataraktursachen aufgeführt. Deren weitere monokausale Überprüfung hinsichtlich Kataraktogenität ist notwendig., In countries such as Norway and the United Kingdom, fish farming of salt-water fish, especially salmon, has gained great economic importance in the past 10 to 15 years. A greater rate of cataract formation has been increasingly reported in salmon in these countries over the past 8 years. The increase in cataract frequency, however, cannot be explained using knowledge about fish lens physiology and morphology gained up until now. In the work presened here, the various stages of glycolysis in the fish lens (based on a determination of the specific activity of 5 enzymes in defined lens sections) were investigated using spectrophotometry. Using this methodology, it was possible to gain an initial insight into the metabolic physiology of the fish lens and the prerequisites for later investigations of possible cataract noxae could be defined. The metabolism of the lens of the salmon is similar to that of mammals. But, the enzyme activities measured in the fish lens are clearly lower than those found in the lenses of mammals. The lower enzyme activities may represent the expression of an adaptation to the surrounding water temperature. The relatively high LDH activity and PFK activity demonstrate that glycolysis takes place in the crystalline lens of the salmon. The lower PFK activities in the eyes of farm salmon with cataracts may show blockage of this enzyme due to excessive glucose or decoupling of glycolysis due, for example, to organic phosphates. G6P-DH provides an indication of the presence of a pentose phosphate pathway. Increased AR activity indicates a latent type II diabetes. This is present in normal lenses of farmed fish and cataract lenses and is an indication that salmon in fish farms is not able to cope with a constant excessive supply of food. Increased SDH activity with an only short-term WSS existing under stress may indicate a protective function. If a WSS takes up to much carbohydrate, then the SDH could work effectively in order to prevent an excessive accumulation of sorbitol. The salmon in fish farms, in contrast, only show low SDH activity, which is a sign of an inability to cope with the constant over supply of glucose. In contrast to wildsalmon, the salmon used for commercial breeding are on account of unnatural conditions (population density, excessive supply of food, light) under constant stress. The metabolism appears – with an already satisfied requirement – to go out of control. As an argument in favour of this hypothesis, the association of BMI (the ratio between height and weight) with frequency of cataracts in humans is cited. A damaging influence of the regular use of pesticides (organophosphates) on the crystalline lens is probable and will be specifically investigated in future studies. The lens appears to tolerate intra-ocular infections with parasites. This could be demonstrated by the absence of any influence of parasites on lens fresh weight (undisturbed tissue growth) or its transparency. In this study reference is made to testing triploid fish for breeding suitability and (osmotic) stress, pesticides, diet, temperature, UV light, oxidative processes, population density and growth speed lised as possible contributory factors to cataracts. Further monocausal examination where cataracts and their origins are concerned is essential.

In the 1990s, there was great optimism due to the development of devices for measuring tooth shade. The frequently not so simple, visual determination of the shade of a tooth was to be done with the aid of a device which recognizes the shade and describes it accurately by reference to a color chart. However, the skepticism towards such devices was also great. It is known that the color effect frequently differs strongly when comparing a tooth from the shade guide with a metal ceramic crown, despite identical shade designation. Anyone who considers visual shade determination to be inadequate and places his hopes in digital shade matching devices will be disappointed. It is the shade-generating structures of the metal ceramic and frequently of the veneer layers that turn out to be too thin which, despite correct shade selection, cause a different color perception. Such problems have been reduced decisively with the development of fracture-proof hard porcelain caps (Vita In-Ceram) with optical characteristics similar to teeth. In addition, the Vita System 3D-Master tooth shade system developed in 1998 by Vita in cooperation with Dr. Hall from Australia, leads the practitioner to a better understanding of the primary tooth shade characteristics of "brightness (value)", "color intensity (chroma)" and "color (wave length of the visible light, hue)". These two innovations allow a more accurate estimate of the basic shade of a natural tooth (reference tooth) and the imitation in the laboratory of its natural, shade-generating structures. If digital shade measurement supplements the visual shade estimate, then a further improvement can be expected--especially in the recognition of the basic shade. Qualitative descriptions of subjective shade measurement of a natural tooth and of its imitation in the dental laboratory by ceramics can be found frequently in professional journals and publications. With digital tooth shade matching devices, which apart from the color code of the color chart also reproduce exact, colorimetric values, such work processes can be recorded quantitatively and objectively. Reports about this type of controlled shade determination and generation are found rarely in the literature, which is surprising in view of the large number of tooth shade matching devices and dental ceramic systems available. In the present paper, the influence of the individual ceramic layers on color perception is measured and described under standardized conditions. The creation of the basic shade as it results from the composition of the various ceramic layers is traced with a spectrophotometer. The Vita In-Ceram Alumina infiltration ceramic and the VitaVM7 veneer ceramic were selected as the ceramic system. MHT-SpectroShade and Vita Easyshade were used as shade matching devices.

In the literature currently available monitoring devices are usually divided into two major groups: those for monitoring perfusion and those for measuring tissue oxygenation. The O(2)C (oxygen to see) system combines these two ways of monitoring free flap viability. The aim of this prospective study was to determine the necessity of flap revision and when unnecessary revision can be avoided. Another point of interest was the question of whether critical values for the successful course of free flaps could be defined and in addition whether such values would differ for different flap types.In a prospective study 82 free flaps (61 radial forearm flaps and 21 fibula flaps) were monitored with the O(2)C monitoring unit. Measurements were carried out intraoperatively and postoperatively up to 14 days.Perfusion compromise occurred in 12 (14.6%) of 82 monitored free flaps. Operative exploration was performed in seven cases, in five of them successfully. Five flaps (three radial forearm and two fibula flaps) were lost due to vascular compromise, which led to an overall success rate of 93.4%. Venous congestion was identified by a rapid increase in hemoglobin concentration of more than 30%. An abrupt decline of blood flow and hemoglobin oxygenation indicated arterial occlusion. Vascular complications were detected in all cases prior to clinical assessment with no false positive or negative results. For radial forearm flaps a hemoglobin oxygenation of 15%, a superficial flow of 10 AU, and a deep flow of 20 AU were identified as minimum values for flap viability. For fibula flaps a hemoglobin oxygenation of 10%, a superficial flow of 5 AU, and a deep flow of 15 AU were determined as minimum values.O(2)C combines laser Doppler flowmetry and tissue spectrophotometry and for the first time allows simultaneous measurement of the microcirculatory parameters including blood flow, flow velocity, hemoglobin concentration, and hemoglobin oxygenation. We found this new noninvasive technique to be a reliable and accurate method for evaluating flap viability and improving the success rate in free flap transfer.

Noninvasive investigation of skin functions is increasingly employed in dermatology and cosmetology. It enables one to study aspects of skin functions that cannot always be appreciated by sensory perception. Noninvasive methods permit objective and reproducible investigation of distinct biophysical parameters. In the age of evidence-based medicine this becomes more and more important. Biophysical data can be quantified, analyzed, and stored electronically. In an overview, selected noninvasive techniques of skin function testing are introduced and their relevance in dermatology, dermatopharmacology, and cosmetology is discussed.

Currently, there are no data on how the topical application of amino acids influences the complex moisture retaining system of the skin in vivo.An open study was performed to investigate the effects of topical application of arginine hydrochloride on epidermal stratum corneum urea content, transepidermal water loss, skin hydration, and clinical status of patients with atopic dermatitis and dry elderly skin.Treatment of patients with atopic dermatitis with 2.5% arginine hydrochloride ointment over 4 weeks showed a significant increase in urea in the stratum corneum as well as a continuous increase in skin moisture.The urea deficit in the stratum corneum in atopic dermatitis and elderly skin was corrected not by applying the moisturizer urea itself but instead by using arginine - its precursor in the Krebs-Henseleit urea cycle. This topical treatment also improved the clinical symptoms of dry skin.