Conditioned Pain Modulation bei Patienten mit komplexem regionalen Schmerzsyndrom im Vergleich zu Gesunden und Patienten mit unilateralen Nervenschmerzen der oberen Extremität

Ein möglicher pathologischer Mechanismus des komplexen regionalen Schmerzsyndroms (CRPS) ist die Störung des endogenen schmerzhemmenden Systems. Diese Studie untersucht das System mittels Conditioned Pain Modulation (CPM) bei 24 Patienten mit CRPS, 17 Patienten mit Neuralgien und 23 gesunden Probanden. CPM wurde mittels eines Hitzeschmerzes als Teststimulus (TS) und eines Kälteschmerzes als konditionierendem Stimulus (CS) untersucht. Alle drei Gruppen zeigten einen signifikanten frühen CPM Effekt. Im Vergleich zu den gesunden Probanden verlief die Abnahme des Hitzeschmerzes bei Patienten mit CRPS signifikant steiler. Nur bei Patienten mit CRPS war eine erniedrigte Kälteschmerzschwelle mit einem erhöhten frühen CPM Effekt korreliert. Eine Störung des Systems erklärt nicht das Schmerzausmaß in der frühen Phase des CRPS. Dem unerwartet hohen CPM-Effekt der Patienten mit CRPS könnte eine Aktivierung der intakten absteigenden Bahnen als Folge einer zentralen Sensitivierung zugrunde liegen

Investigation of inter- and intra-day variability of tear fluid regarding flow rate, protein concentration as well as protein composition

$\bf Purpose:$ The purpose of this study was to present the determination of inter- and intra-day variations in tear flow rate, and tear fluid protein concentration, as well as protein composition regarding their impact for future biomarker studies. $\bf Methods:$ Tear fluid was collected noninvasively from 18 healthy subjects by performing Schirmer tests at 4 different time points repetitive in a period of 2 days. The tear flow rate on the Schirmer test strips was measured. Proteins were extracted from strips and quantified using amino acid analysis. Protein composition was analyzed by the strips data-independent (DIA) based mass spectrometry. To exclude any impairments to health, volunteers underwent a detailed neurological as well as an ophthalmological examination. $\bf Results:$ Whether tear fluid was collected from oculus sinister or oculus dexter did not affect the tear flow rate ($\it P$ $\thickapprox$ 0.63) or protein concentration ($\it P$ $\thickapprox$ 0.97) of individual subjects. Moreover, protein concentration was independent from the tear volume, so that a change in volume may only influence the total protein amount. When the examination days were compared, investigation of tear flow rate ($\it P$ $\thickapprox$ 0.001) and protein concentration ($\it P$ $\thickapprox$ 0.0003) indicated significant differences. Further, mass spectrometric analysis of tear fluid revealed 11 differentially regulated proteins when comparing both examination days. $\bf Conclusions:$ Our findings provide evidence of inter-day variation in tear flow rate, tear proteome concentration, and composition in healthy subjects, suggesting that inter-day variation needs to be taken into consideration in biomarker research of tear fluid. Identified proteins were assigned to functions in the immune response, oxidative and reducing processes, as well as mannose metabolism