Phosphoinositide detection at synapses of fixed murine hippocampal neurons

The minor phospholipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is crucial for neurotransmission and has been implicated in Parkinson's disease. Here, we present a staining protocol for the analysis of activity-dependent changes of PI(4,5)P2 at synapses. We describe steps for stimulating and fixing murine hippocampal neurons, staining with probes for PI(4,5)P2 and a synaptic marker, and analysis by high-resolution microscopy. Our approach gives insights into local PI(4,5)P2 synthesis and turnover at synapses and can be extended to phosphoinositide lipids other than PI(4,5)P2. For complete details on the use and execution of this protocol, please refer to Bolz et al.1.

Synaptotagmin 1-triggered lipid signaling facilitates coupling of exo- and endocytosis

Exocytosis and endocytosis are essential physiological processes and are of prime importance for brain function. Neurotransmission depends on the Ca2+-triggered exocytosis of synaptic vesicles (SVs). In neurons, exocytosis is spatiotemporally coupled to the retrieval of an equal amount of membrane and SV proteins by compensatory endocytosis. How exocytosis and endocytosis are balanced to maintain presynaptic membrane homeostasis and, thereby, sustain brain function is essentially unknown. We combine mouse genetics with optical imaging to show that the SV calcium sensor Synaptotagmin 1 couples exocytic SV fusion to the endocytic retrieval of SV membranes by promoting the local activity-dependent formation of the signaling lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) at presynaptic sites. Interference with these mechanisms impairs PI(4,5)P2-triggered SV membrane retrieval but not exocytic SV fusion. Our findings demonstrate that the coupling of SV exocytosis and endocytosis involves local Synaptotagmin 1-induced lipid signaling to maintain presynaptic membrane homeostasis in central nervous system neurons.

SynActJ: Easy-to-Use Automated Analysis of Synaptic Activity

Neuronal synapses are highly dynamic communication hubs that mediate chemical neurotransmission via the exocytic fusion and subsequent endocytic recycling of neurotransmitter-containing synaptic vesicles (SVs). Functional imaging tools allow for the direct visualization of synaptic activity by detecting action potentials, pre- or postsynaptic calcium influx, SV exo- and endocytosis, and glutamate release. Fluorescent organic dyes or synapse-targeted genetic molecular reporters, such as calcium, voltage or neurotransmitter sensors and synapto-pHluorins reveal synaptic activity by undergoing rapid changes in their fluorescence intensity upon neuronal activity on timescales of milliseconds to seconds, which typically are recorded by fast and sensitive widefield live cell microscopy. The analysis of the resulting time-lapse movies in the past has been performed by either manually picking individual structures, custom scripts that have not been made widely available to the scientific community, or advanced software toolboxes that are complicated to use. For the precise, unbiased and reproducible measurement of synaptic activity, it is key that the research community has access to bio-image analysis tools that are easy-to-apply and allow the automated detection of fluorescent intensity changes in active synapses. Here we present SynActJ (Synaptic Activity in ImageJ), an easy-to-use fully open-source workflow that enables automated image and data analysis of synaptic activity. The workflow consists of a Fiji plugin performing the automated image analysis of active synapses in time-lapse movies via an interactive seeded watershed segmentation that can be easily adjusted and applied to a dataset in batch mode. The extracted intensity traces of each synaptic bouton are automatically processed, analyzed, and plotted using an R Shiny workflow. We validate the workflow on time-lapse images of stimulated synapses expressing the SV exo-/endocytosis reporter Synaptophysin-pHluorin or a synapse-targeted calcium sensor, Synaptophysin-RGECO. We compare the automatic workflow to manual analysis and compute calcium-influx and SV exo-/endocytosis kinetics and other parameters for synaptic vesicle recycling under different conditions. We predict SynActJ to become an important tool for the analysis of synaptic activity and synapse properties.

Einfluss der apparativen intermittierenden Kompression auf die venöse Hämodynamik

Ziel der Arbeit war, den hämodynamischen Effekt von apparativer intermittierender Kompression (AIK) bei Phlebödemen mittels des veno-arteriellen Flow-Index (VAFI) zu quantifizieren. Patienten, Methode: Bei 33 Patienten (C3-6, EP,S, AS,D,P, PO,R), die trotz Kompression Phlebödeme aufwiesen und 20 Venengesunden wurde vor (VAFI-0), 30 min (VAFI-1) und 2 h nach AIK (VAFI-2) der VAFI als Quotient aus venösem und arteriellem Stromzeitvolumen der Vena und Arteria femoralis communis berechnet. In der Patientengruppe erfolgte eine Woche nach 19 ambulant durchgeführten AIK (2-3 pro Woche) eine erneute Messung (VAFI-20). Ergebnisse: Bei den Patienten mit Plebödem war der mittlere VAFI-0 mit 1,49 ± 0,29 signifikant erhöht (p <0,001). Nach AIK zeigte sich eine signifikante Reduktion (p <0,001) auf 0,96 ± 0,25 (VAFI-1), die stabil blieb. VAFI-2 betrug 1,07 ± 0,15, VAFI-20 1,07 ± 0,18. Bei Venengesunden waren VAFI-0 0,87 ± 0,07, VAFI-1 0,84 ± 0,07 und VAFI-2 0,86 ± 0,07. Es zeigte sich keine signifikante Änderung (p = 0,40). Schlussfolgerung: Die zusätzlich zur Kompression durchgeführte AIK bewirkt bei Phlebödemen eine dauerhafte Verbesserung der venösen Hämodynamik, erkennbar an der signifikanten Reduktion des VAFI.

Quantitative Analyse des Einflusses von standardisiertem Gehen auf die venöse Hämodynamik bei postthrombotischem Syndrom

Ziel der Arbeit war, den hämodynamischen Einfluss von ruhigem Gehen mit und ohne Kompression bei postthrombotischem Syndrom (PTS). Patienten und Methode: Bei 30 PTS-Patienten (C4-6, ES, ADSP, PRO) und 20 Gesunden wurde duplexsonographisch das Stromzeitvolumen der Vena und Arteria femoralis communis gemessen und aus dem Quotient der venoarterielle Flow-Index (VAFI-1) berechnet. Nach standardisierter Gehleistung (10 min; 2,0 km/h) wurde VAFI-2 gemessen. Anschließend wurde für 30 min ein Kompressionsverband angelegt und unter Kompression VAFI-3 bestimmt. Die Gehleistung wurde mit Kompression wiederholt und danach VAFI-4 gemessen. Ergebnisse: Bei PTS war der mittlere VAFI 1,56 ± 0,32. Nach 10-minütigem Gehen reduzierte sich VAFI-2 auf 1,27 ± 0,37 und nach 30-minütiger Kompression (VAFI-3) auf 1,12 ± 0,27. Nach Gehen mit Kompression reduzierte sich VAFI-4 weiter auf 1,05 ± 0,26. Alle Indexwerte nach Gehen und/oder Kompression unterschieden sich hoch signifikant von VAFI-1 (p <0,001), nicht jedoch untereinander. VAFI-4 bei PTS unterschied sich nicht von den Indexwerten der Kontrollgruppe (p = 0,09). VAFI war in der Kontrollgruppe 0,94 ± 0,18 und änderte sich nicht nach Gehen mit oder ohne Kompression. Schlussfolgerung: Gehen ohne Kompression sowie eine 30-minütige Kompression führen zu einer signifikanten Verbesserung der venöser Hämodynamik bei PTS. Die Kombination von Kompression und Gehen bewirkt eine Absenkung des VAFI auf ein nahezu gesundes Niveau.

Die Reproduzierbarkeit des veno-arteriellen FlowIndex für die quantitative Erfassung des hämodynamischen Schweregrads von venösen Erkrankungen

Background: The ratio of volume flow in the common femoral vein and artery denoted as venous-arterial Flowindex (VAFI) is significantly increased in venous insufficiency according the clinical grade of the disease. This study was done to investigate the reliability and reproducibility of VAFI as quantitative pattern. Patients and methods: In 43 patients with varicose veins C4–6 EPAS,D,PPR (PVV), 40 with postthrombotic syndrome C4–6 ESAS,D,PPR,O (PTS) and 48 healthy volunteers volume flow in the common femoral vein (VFV) and artery (VFA) were measured by duplex. Division of VFV by VFA calculated VAFI. VAFI-measurement was repeated 5 times at an interval of ten minutes in 63 subjects (23 PVV, 20 PTS, 20 healthy) and it was performed at three different days in 68 subjects (20 PVV, 20 PTS, 28 healthy). Results: Mean VAFI ± standard deviation was 1.39 ± 0.26 in PVV, 1.42 ± 0.26 in PTS and 0.93 ± 0.13 in healthy veins (p < 0.001). VAFI remained stable and significantly increased (p < 0.001) in PVV and PTS compared to healthy veins during 40 minutes and also within three different days. Conclusion: The venous-arterial flowindex VAFI is a reproducible pattern of the hemodynamic severity in venous insufficiency.

Differential validity of the Defense Mechanism Manual for the TAT between Asian Americans and Whites. Thematic Apperception Test

Thematic Apperception Test (Murray, 1943) responses of 69 Asian American (hereafter, Asian) and 83 White students were coded for defenses according to the Defense Mechanism Manual (Cramer, 1991b) and studied for differential validity in predicting paper-and-pencil measures of relevant constructs. Three tests for differential validity were used: (a) differences between validity coefficients, (b) interactions between predictor and ethnicity in criterion prediction, and (c) differences between groups in mean prediction errors using a common regression equation. Modest differential validity was found. It was surprising that the DMM scales were slightly stronger predictors of their criteria among Asians than among Whites and when a common predictor was used, desirable criteria were overpredicted for Asians, whereas undesirable ones were overpredicted for Whites. The results were not affected by acculturation level or English vocabulary among the Asians.

Monoclonal antibodies directed against conserved epitopes on the nucleocapsid protein and the major envelope glycoprotein of equine arteritis virus

We recently developed a highly effective immunization procedure for the generation of monoclonal antibodies (MAbs) directed against the porcine reproductive and respiratory syndrome virus (E. Weiland, M. Wieczorek-Krohmer, D. Kohl, K. K. Conzelmann, and F. Weiland, Vet. Microbiol. 66:171-186, 1999). The same method was used to produce a panel of 16 MAbs specific for the equine arteritis virus (EAV). Ten MAbs were directed against the EAV nucleocapsid (N) protein, and five MAbs recognized the major viral envelope glycoprotein (G(L)). Two of the EAV G(L)-specific MAbs and one antibody of unknown specificity neutralized virus infectivity. A comparison of the reactivities of the MAbs with 1 U.S. and 22 newly obtained European field isolates of EAV demonstrated that all N-specific MAbs, the three nonneutralizing anti-G(L) MAbs, and the weakest neutralizing MAb (MAb E7/d15-c9) recognized conserved epitopes. In contrast, the two MAbs with the highest neutralization titers bound to 17 of 23 (MAb E6/A3) and 10 of 23 (MAb E7/d15-c1) of the field isolates. Ten of the virus isolates reacted with only one of these two MAbs, indicating that they recognized different epitopes. The G(L)-specific MAbs and the strongly neutralizing MAb of unknown specificity (MAb E6/A3) were used for the selection of neutralization-resistant (NR) virus variants. The observation that the E6/A3-specific NR virus variants were neutralized by MAb E7/d15-c1 and that MAb E6/A3 blocked the infectivity of the E7/d15-c1-specific NR escape mutant confirmed that these antibodies reacted with distinct antigenic sites. Immunoelectron microscopy revealed for the first time that the antigenic determinants recognized by the anti-G(L) MAbs were localized on the virion surface. Surprisingly, although the immunofluorescence signal obtained with the neutralizing antibodies was relatively weak, they mediated binding of about three times as much gold granules to the viral envelope than the nonneutralizing anti-G(L) MAbs.

Chronic increases in transmural pressure reduce NO-mediated dilations in isolated resistance arteries of the hamster

It is unclear whether the impairment of NO-mediated dilation in hypertension is the cause or the consequence of high blood pressure. We therefore studied in isolated resistance arteries whether elevated transmural pressure affects NO-mediated dilation. Arteries (n=5-7) were perfused at hydrostatic pressures of either 45, 120 or 160 mmHg for 48 h. Subsequently, diameter and calcium responses (fura 2) were studied at a transmural pressure of 45 mmHg. Pre-exposure to 120 and 160 mmHg reduced resting diameters and minimal diameters after stimulation with noradrenaline and significantly increased corresponding intracellular free calcium levels in vascular smooth muscle. Moreover, the NO-mediated dilation in response to acetylcholine was significantly reduced although the increase in endothelial calcium was not altered. Dilations induced by the NO donor SNP were not affected. It is concluded that chronically elevated pressure per se impairs endothelial NO production by a mechanism distal to receptor-dependent calcium increases.

Subcellular distribution of glucose transporter (GLUT-1) during development of the blood-brain barrier in rats

Electron microscopy was used to quantify the subcellular distribution of the GLUT-1 isoform of the glucose transporter in developing microvessels of the brain of embryonic rats from E (embryonic stage) 13 to E19 and in adult rats. Gold-conjugated secondary antibodies were used to localize, on ultrathin sections of brain, a rabbit polyclonal antiserum (anti-GLUT-1) raised against a synthetic peptide encoding 13 amino acids of the C-terminus of the human glucose transporter. Staining was weak at E13 but increased in density during development into adulthood. The increase represented an increase in the absolute amount of transporter per vessel profile, with a concomitant decrease in vessel size with the narrowing of the wall. At early stages, the percentages of total particles per profile of lumenal membrane, ablumenal membrane, and cytoplasm were approximately equivalent. The ratio of lumenal to ablumenal particle density then shifted from below 1 at E13 to above 2 at E19 and to 4 in the adult. In contrast, vessels of the choroid plexus were devoid of labeling, but the choroid plexus epithelium stained as early as E15. In the brain, no astrocytes, neurons, or pericytes were stained at any stage examined. Developmental upregulation of the GLUT-1 glucose transporter therefore seems to occur at the blood-brain barrier, and the modulation of the subcellular distribution of the transporter can be correlated with other observed changes in the microvessels as they develop the blood-brain barrier phenotype.

First appearance of orthogonal arrays of particles in Müller cell membranes depends on retina maturation

A freeze-fracture analysis was undertaken to investigate both the appearance of orthogonal arrays of particles (OAP) in the Müller cell endfoot membrane at the retina-vitreous border and the endfoot size during development of two avian species. Chickens and pigeons have a common length of development until hatching (21 days), but differ in maturation velocity. In the chicken, the first OAP appear in the central retina at embryonic day 18 (E18), in the peripheral retina at E19. The OAP density increases rapidly. In the pigeon, the first OAP appear 6 days after hatching when the eyes are opened. In both species, the size of endfeet is maximal when the OAP first appear and is reduced thereafter. In the chicken, during the time up to adulthood both the mean endfoot size and the retina area increase 6-fold suggesting that the number of endfeet remains constant during growth of their individual area. In the pigeon, after an initial increase of mean endfoot area this decreases until adulthood, despite continuous growth of the eye. This strongly suggests that during retina growth the number of Müller cell endfeet increases. It is concluded that these alterations of Müller cell membranes reflect some functional aspects of retina maturation.

Use of monoclonal antibody KP1 for identifying normal and neoplastic human mast cells

The monoclonal antibody KP1 (CD68) was used to stain normal and neoplastic monocytes and macrophages in routinely processed, paraffin wax embedded tissue: mast cells also exhibited strong, consistent cytoplasmic immunoreactivity. Light microscopic findings were corroborated by electron microscopical and immunocytochemical findings. The predominant sites of immunoreactivity were the specific intracytoplasmic granules of the mast cells. All mast cell subtypes--that is, normal and reactive mast cells, such as those in lymph nodes exhibiting chronic non-specific lymphadenitis, and malignant or neoplastic mast cells in various types of mastocytosis--reacted with this antibody. This finding is of diagnostic importance, because mast cell proliferation could be mistaken for histiocyte proliferation. It also supports the hypothesis that mast cells derive from the bone marrow.