Mechanotransduktion im Alter und bei Osteoporose

Knochen wird permanent an die alltäglichen mechanischen Kräfte adaptiert, um für die natürlichen Gegebenheiten eine optimale Frakturresistenz zu gewährleisten. Osteoporose ist eine Erkrankung, bei der unter Alltagsbedingungen Fragilitätsfrakturen entstehen. Ursache dafür sind strukturelle und qualitative Defizite und eine Verminderung der Knochenmasse. Es handelt sich somit um eine Dysadaptation des Organs, verursacht entweder durch ungenügenden Krafteintrag oder durch eine Störung der Mechanosensitivität der Osteoblasten und Osteozyten. Kraft durch Dehnung, Kompression oder Flüssigkeits-Scher-Stress wird über Adhäsionsmoleküle, Rezeptoren, Kanäle und über das Zytoskelett auf die Zelle übertragen. Die Umwandlung in biologische Signale geschieht durch Signaltransduktionskaskaden bis hin zur Genregulation im Zellkern. Neben den membranständigen molekularen Strukturen werden auch subzelluläre Organell-Strukturen wie z.B. das primäre Zilium als Übermittler mechanischer Signale diskutiert. Bei Osteoporose sind häufig Signalwege gestört, die mit der Mechanotransduktion zusammenhängen, was man an den Hauptrisikofaktoren der Osteoporose ablesen kann. Östrogene wirken als Mechanosensitizer, so dass nach der Menopause die Gefahr der Dysadaptation steigt. Zelluläre Alterung ist mit Störungen der Mechanotransduktion verknüpft, wie am Beispiel von Laminopathien gezeigt werden konnte, präklinischen und klinischen Modellerkrankungen für vorzeitiges Altern. Die als Haupt-Risikogene für den genetischen Hintergrund der Osteoporose identifizierten Kandidaten sind fast sämtlich molekular in die Regulation der Mechanotransduktion eingebunden. Es gibt präklinische und klinische Evidenz dafür, dass z.B. die anabole Therapie mit Parathormon/Teriparatid nur unter Einwirkung mechanischer Kräfte wirklich wirksam ist. Ein überwältigender Hinweis für das Vorliegen fundamentaler Störungen der Regulation der Mechanosensitivität bei der Osteoporose ist die Tatsache, dass meistens der Gewinn von Knochenmasse durch die verfügbaren therapeutischen Prinzipien nicht wirklich nachhaltig ist. Antiresorptive und anabole Prinzipien der Therapie der Knochenmasse sind bereits auf dem Markt, weitere sind in der Entwicklung. Ein Medikament, das die Mechanosensitivität des Knochens beeinflusst, wäre das ideale Werkzeug, um per se anabol zu wirken und/oder den Therapieerfolg mit anderen Medikamenten zu erhalten. Die Forschung hierüber ist daher von hoher klinischer Relevanz.

Effects of high hydrostatic pressure and temperature increase on Escherichia coli spp. and pectin methyl esterase inactivation in orange juice

The aim of this study was to evaluate the effect of high hydrostatic pressure treatment combined with moderate processing temperatures (25 ℃-50 ℃) on the inactivation of Escherichia coli O157: H7 (ATCC 700728), E. coli K12 (ATCC 23716), and pectin methyl esterase in orange juice, using pressures of 250 to 500 MPa with times ranging between 1 and 30 min. Loss of viability of E. coli O157:H7 increased significantly as pressure and treatment time increased, achieving a 6.5 log cycle reduction at 400 MPa for 3 min at 25 ℃ of treatment. With regard to the inactivation of pectin methyl esterase, the greatest reduction obtained was 90.05 ± 0.01% at 50 ℃ and 500 MPa of pressure for 15 min; therefore, the pectin methyl esterase enzyme was highly resistant to the treatments by high hydrostatic pressure. The results obtained in this study showed a synergistic effect between the high pressure and moderate temperatures in inactivating E. coli cells.

FT-IR product study of the reactions of NO3 radicals with ortho-, meta-, and para-cresol

Product analyses of the NO3 radical-initiated oxidation of ortho-, meta-, and para-cresol have been performed in large-volume chamber systems at the University of Wuppertal (1080 L quartz glass reactor: QUAREC) and the European Photoreactor (EUPHORE), Valencia, Spain. The reaction of O3 with NO2 was used for the in situ generation of NO3 radicals in both QUAREC and EUPHORE. In the QUAREC experiments the gas-phase reaction of ortho-cresol isomer with NO3 yielded (11.5 ± 0.8) % 6-methyl-2-nitrophenol (6M2NP), (4.4 ± 0.3) % methyl-1,4-benzoquinone (MQUIN) and (77.2 ± 6.3) % HNO3. The reaction of NO3 radicals with meta-cresol yielded (21.2 ± 1.4) % 3-methyl-2-nitrophenol (3M2NP), (22.8 ± 1.8) % 3-methyl-4-nitrophenol (3M4NP), (23.5 ± 1.8) % 5-methyl-2-nitrophenol (5M2NP), (4.2 ± 0.7) % MQUIN and (72.3 ± 6.4) % HNO3. In the reaction of NO3 radicals with para-cresol, 4-methyl-2-nitrophenol (4M2NP) and HNO3 were identified as products with yields of (41.3 ± 3.7) % and (85.0 ± 10.2) %, respectively. In the EUPHORE chamber not all products were formed at levels above the detection limit, however, in cases where detection was possible similar product yields were observed. The product formation yields determined in both chambers are compared with available literature data and a gas-phase mechanism is proposed to explain the formation of the products observed from the reaction of NO3 and with cresol isomers.

Organic aerosol formation during the atmospheric degradation of toluene

Organic aerosol formation during the atmospheric oxidation of toluene was investigated using smog chamber systems. Toluene oxidation was initiated by the UV irradiation of either toluene/air/NOx or toluene/air/CH3ONO/NO mixtures. Aerosol formation was monitored using scanning mobility particle sizers and toluene loss was monitored by in-situ FTIR spectroscopy or GC-FID techniques. The experimental results show that the reaction of OH radicals, NO3 radicals and/or ozone with the first generation products of toluene oxidation are sources of organic aerosol during the atmospheric oxidation of toluene. The aerosol results fall into two groups, aerosol formed in the absence and presence of ozone. An analytical expression for aerosol formation is developed and values are obtained for the yield of the aerosol species. In the absence of ozone the aerosol yield, defined as aerosol formed per unit toluene consumed once a threshold for aerosol formation has been exceeded, is 0.075 +/- 0.004. In the presence of ozone the aerosol yield is 0.108 +/- 0.004. This work provides experimental evidence and a simple theory confirming the formation of aerosol from secondary reactions.

[Self assessment and actual intelligibility of speech audiometry test material]

Self-estimated and measured intelligibility were compared using different instructions in speech audiometric tests. The results of 69 tested persons reveal that there exist speech levels in both test procedures where the intelligibility reaches 0% or 100%, respectively. In general, self-estimated intelligibility was significantly higher than real identification. Therefore, the self-estimation of intelligibility does not appear as an appropriate procedure to automated speech audiometry. The results are a speech audiometric equivalent of the subject's to have correctly understood speech in daily life in which in fact was misunderstood. Connections to central speech processing seem to be possible. Audiologists might be influenced by the effect of overestimation of speech intelligibility as well. However, preliminary investigations concerning pseudohypacusis show different results.

Changes in the central ANF-system of renovascular hypertensive rats

The central atrial natriuretic peptides (ANF)-system was investigated in volume-dependent, one-kidney, one-clip (1K1C) and renin-dependent two-kidney, one-clip (2K1C) renovascular hypertensive rats by radioimmunological measurement of ANF concentration in 18 selected brain areas. Significant changes were found in nine brain areas of 1K1C and in eight brain areas of 2K1C hypertensive rats. Except undirectional changes in the organum vasculosum laminae terminalis and the supraoptic nucleus, ANF concentration was changed in the opposite direction in all other brain areas, with an activation of the central ANF system in 1K1C and an inhibition in 2K1C hypertension. The localization of the alterations (circumventricular organs, anteroventral third ventricle region, hypothalamo hypophyseal system, brain stem) implies major differences in the central regulation of blood pressure and electrolyte and fluid homeostasis between these two models. The activation of the central ANF system in 1K1C hypertension may be a compensatory mechanism to prevent further increments in blood pressure and plasma volume. In contrast, the depression of the central ANF system in 2K1C hypertension may promote the elevation of the blood pressure.