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At least 37 records · Page 2Linked to original sources
PubMed1999

Gravitaxis in Chlamydomonas reinhardtii: characterization using video microscopy and computer analysis.

We characterized the gravitactic behavior of Chlamydomonas reinhardtii, a unicellular green alga, using a computer-analysis system in order to study directional swimming. The effects of the calcium-channel inhibitors gadolinium and diltiazem on graviorientation and swimming speed were examined. In addition, we studied directional swimming in the ptx1 strain of C. reinhardtii, a flagellar dominance mutant. Results indicate that Chlamydomonas reorients for gravitactic swimming through a mechanism different from the calcium-mediated pathway believed to be involved in gravity transduction in higher plants. We suggest that calcium-mediated gravitaxis originated in an organism that was more evolutionarily advanced than Chlamydomonas.

Animals↗
PubMed2000

Time-lapse video microscopy analysis reveals astral microtubule detachment in the yeast spindle pole mutant cnm67.

Saccharomyces cerevisiae cnm67Delta cells lack the spindle pole body (SPB) outer plaque, the main attachment site for astral (cytoplasmic) microtubules, leading to frequent nuclear segregation failure. We monitored dynamics of green fluorescent protein-labeled nuclei and microtubules over several cell cycles. Early nuclear migration steps such as nuclear positioning and spindle orientation were slightly affected, but late phases such as rapid oscillations and insertion of the anaphase nucleus into the bud neck were mostly absent. Analyzes of microtubule dynamics revealed normal behavior of the nuclear spindle but frequent detachment of astral microtubules after SPB separation. Concomitantly, Spc72 protein, the cytoplasmic anchor for the gamma-tubulin complex, was partially lost from the SPB region with dynamics similar to those observed for microtubules. We postulate that in cnm67Delta cells Spc72-gamma-tubulin complex-capped astral microtubules are released from the half-bridge upon SPB separation but fail to be anchored to the cytoplasmic side of the SPB because of the absence of an outer plaque. However, successful nuclear segregation in cnm67Delta cells can still be achieved by elongation forces of spindles that were correctly oriented before astral microtubule detachment by action of Kip3/Kar3 motors. Interestingly, the first nuclear segregation in newborn diploid cells never fails, even though astral microtubule detachment occurs.

Cell Division↗
PubMed1996

[Method of measurement of cadmium influx by fura-2 titration in MDCK cell evidenced. Fluorescence video-microscopy study].

Cadmium influx rate in mammal kidney cells (MDCK) is analyzed using an original method based on fura-2 titration. The method relies on the high affinity of the fluorophore for the metal. It follows that the excitation spectrum shift of fura-2 can be linearly correlated to the influx rate of cadmium. Fluorescence digital imaging microscopy allows the study at single cell and intra-cellular organite levels. Results show that the cadmium uptake seems to be carrier dependent. Metal fluxes are potential independent, with a temperature effect caracterized by a Q10 of 2.3 +/- 0.2. No effect of verapamil is noticed; however, cadmium transport is inhibited by external calcium. Apparent dissociation constant for the cadmium uptake is estimated at 4.5 10(-5) M at 20 degrees C. An additional passive transmembrane diffusion process is also evidenced.

Animals↗
PubMed1997

Time lapse video microscopy and ultrastructure of penetrating sporozoites, types 1 and 2 parasitophorous vacuoles, and the transformation of sporozoites to tachyzoites of the VEG strain of Toxoplasma gondii.

Videomicroscopy and transmission electron microscopy were used to study the interaction of Toxoplasma gondii sporozoites with cultured cardiopulmonary artery endothelial, embryonic bovine tracheal and Madin-Darby bovine kidney cells. No moving junction or exocytosis of rhoptries, micronemes, and dense granules was detected during the initial penetration of sporozoites into cultured cells, whereas constriction of the sporozoite and partial exocytosis of rhoptries occurred during movement of the sporozoite from the first parasitophorous vacuole (PV1) into the second vacuole (PV2). The PV1 was unusually large, lacked a tubulovesicular membrane network (TMN), and had an indistinct parasitophorous vacuolar membrane (PVM). Comparatively, the PV2 was small, had a distinct PVM, contained a well-developed TMN, and was surrounded by numerous host cell mitochondria. Sporozoites that passed completely through cells carried with them an envelope of host cell membranes and cytoplasm. Cultured cells occasionally endocytosed sporozoites that were enveloped by host cell material. After formation of the PV2, sporozoites replicated by endodyogeny to form tachyzoites.

Animals↗
PubMed1999

Maximization of skin capillaries during intravital video-microscopy in essential hypertension: comparison between venous congestion, reactive hyperaemia and core heat load tests.

Intravital capillary video-microscopy is a dynamic method for studying skin capillaries. The technique of direct intravital microscopy (without dyes) depends on the presence of red blood cells inside capillaries for their identification. The aim of the present study was to compare different techniques to try to establish the best method for maximizing the number of visible perfused capillaries during intravital capillary microscopy. We compared the effects of venous congestion with those of post-occlusive reactive hyperaemia (Study 1). We also investigated venous congestion followed first by post-occlusive reactive hyperaemia and then by a core heat load test (Study 2). Finally we investigated venous congestion followed by post-occlusive reactive hyperaemia combined with venous congestion (Study 3). In Study 1, capillary density increased with venous congestion from a baseline value of 74+/-2 (mean+/-S.E.M.) per field to 82+/-3 per field (P<0.0001; analysis of variance). With reactive hyperaemia, there was an apparent decrease in visible capillary density to 69+/-2 per field. In Study 2, baseline capillary density was 69+/-4 per field, and this increased significantly with venous congestion to 74+/-4 per field (P=0.01). With both reactive hyperaemia and core heat load, the apparent density was 62+/-4 per field. In Study 3 the baseline density was 70+/-2 per field, and this increased significantly with venous congestion to 80+/-3 per field (P<0.0001). With reactive hyperaemia combined with venous congestion, the density was 81+/-3 per field (P=0.328 compared with venous congestion alone). The results show that venous congestion at 60 mmHg for 2 min is the most effective method for visualization of the maximal number of perfused skin capillaries during intravital video-microscopy.

Adult↗
PubMed1985

Simultaneous assessment of red cell perfusion in skeletal muscle by laser Doppler flowmetry and video microscopy.

The objective of this study was to compare temporal and spatial variations of the laser Doppler flowmeter output (V) with the corresponding variations of perfusion (cells/mm3 X mm/s) evaluated by video microscopy. The flowmetry and video microscopy sampled 2 mm3 (approx.) and 0.84 mm3 surface volumes of the sartorius muscle in anesthetized frogs, respectively. The overall ranges of the output and perfusion measurements were from 0.01 to 0.72 V and from 45 to 1404 cells/mm3 X mm/s. Within these ranges, temporal variations induced by muscle contraction correlated well (overall r = 0.91), but the spatial variations associated with the resting state correlated poorly (overall r = 0.45). When the penetration of the laser light was limited to 0.3-0.4 mm (to make the volumes sampled by both techniques more comparable) the overall r of the spatial comparison increased to 0.86. It is concluded that the flowmeter (1) is affected by red cell perfusion below the tissue depth of 0.3-0.4 mm, and (2) can follow both the temporal and spatial variations of red cell perfusion in the tissue examined.

Capillaries↗
PubMed1995

Imaging of electrically induced fast motion by video microscopy and triggered flash illumination.

A simple and inexpensive method is described for imaging with video microscopy fast transient events that can be triggered electrically. An electronic system was developed that triggered stroboscopic illumination and generated an electrical step function. The essential feature was precise control of a sub-millisecond time delay between electrical stimulus and the following short pulse of light. With this technique (15 microseconds time resolution, 50 frames/s) different phases of the exocytosis and discharge of nematocysts from Hydra vulgaris can be visualized. It was shown that not only stenoteles, but also desmonemes, can discharge in less than 0.5 ms.

Animals↗
PubMed1994

Digital video microscopy for the undergraduate histology laboratory.

An undergraduate histology course was profoundly changed through the introduction of digital video microscopy. Students have access to a networked, Macintosh-based imaging laboratory where they can digitally capture, enhance, analyse, and media output microscope originated images. By increasing the access to image information, students are able to assume a more active inquiry mode in a microscope-based course. The technology allowed students to increase intellectual sharing among themselves and to leave 'digital legacies' for future classes.

Computer Communication Networks↗
PubMed1990

Observation of single influenza virus-cell fusion and measurement by fluorescence video microscopy.

We have used intensified video fluorescence microscopy and digital image processing to observe and quantitate influenza virus (A/PR8/34/H1N1) fusion to human erythrocyte membranes. Viruses labeled with the lipid probe octadecylrhodamine B (R18) were seen to undergo fluorescence dequenching and eventual disappearance after exposure to pH levels known to induce virus-cell membrane fusion. Quantitative intensity measurements of single individual particles were possible. From these fluorescence data it has been possible to calculate the fraction of R18 dye molecules transferred from the virus to the cell. The redistribution of the lipid probe upon fusion at pH 5.0 had a t1/2 of 46 s, longer than expected for a free-diffusion model. The R18 loss was approximately twice as fast at pH 5.0 as at pH 5.1. No obvious delay until the start of fluorescence dequenching was observed after the pH changes, suggesting that activation processes are faster than the time resolution, 1-5 s, of the current method.

Erythrocyte Membrane↗
PubMed2000

Axonal membrane proteins are transported in distinct carriers: a two-color video microscopy study in cultured hippocampal neurons.

Neurons transport newly synthesized membrane proteins along axons by microtubule-mediated fast axonal transport. Membrane proteins destined for different axonal subdomains are thought to be transported in different transport carriers. To analyze this differential transport in living neurons, we tagged the amyloid precursor protein (APP) and synaptophysin (p38) with green fluorescent protein (GFP) variants. The resulting fusion proteins, APP-yellow fluorescent protein (YFP), p38-enhanced GFP, and p38-enhanced cyan fluorescent protein, were expressed in hippocampal neurons, and the cells were imaged by video microscopy. APP-YFP was transported in elongated tubules that moved extremely fast (on average 4.5 micrometer/s) and over long distances. In contrast, p38-enhanced GFP-transporting structures were more vesicular and moved four times slower (0.9 micrometer/s) and over shorter distances only. Two-color video microscopy showed that the two proteins were sorted to different carriers that moved with different characteristics along axons of doubly transfected neurons. Antisense treatment using oligonucleotides against the kinesin heavy chain slowed down the long, continuous movement of APP-YFP tubules and increased frequency of directional changes. These results demonstrate for the first time directly the sorting and transport of two axonal membrane proteins into different carriers. Moreover, the extremely fast-moving tubules represent a previously unidentified type of axonal carrier.

Amyloid beta-Protein Precursor↗
PubMedDate not supplied

A triple electrode for simultaneous investigations of transcutaneous oxygen tension, laser-Doppler flowmetry and dynamic fluorescence video microscopy.

A newly designed triple probe is introduced for measurements of transcutaneous oxygen tension, laser Doppler flowmetry (LDF) and microangiodynamics of skin capillaries by dynamic video microscopy with and without fluorochromes. The performance of the triple probe was checked in 9 healthy volunteers (6 women, 3 men; mean age: 34 years) and 9 patients (5 women, 4 men; mean age: 67 years) with peripheral arterial occlusive disease (PAOD). The mean Doppler ankle/arm pressure ratio was 0.54 +/- 0.30. Six patients suffered from severe claudication, 2 from rest pain and 1 patient had toe and forefoot necrosis. The foot dorsum was selected as measuring site. After recording baseline values of skin surface PO2 (ssPO2) at 37 degrees C, LDF and capillary images, a suprasystolic compression at the ankle level was performed for 4 min. Thirty seconds before cuff opening 0.2 ml/1 l blood volume of 20% sodium fluorescein was injected in an antecubital vein. Sodium fluorescein arrival times, filling times and maximum fluorescent light intensity times were measured, and ssPO2 and LDF were recorded continuously during postocclusive reactive hyperemia (PORH). The results indicate an adequate function of the triple probe. The mean resting ssPO2 was 2.0 +/- 1.9 mm Hg in PAOD patients and 4.0 +/- 3.9 mm Hg in controls (p = 0.185). Maximum ssPO2 during PORH was significantly reduced (p = 0.008) in patients (3.1 +/- 2.1 mm Hg) compared to healthy subjects (11.8 +/- 7.7 mm Hg). Resting LDF values were 6.5 +/- 6.4 perfusion units (PU) in PAOD patients versus 10.3 +/- 8.2 AU in controls (p = 0.295). Peak LDF during PORH was significantly reduced (p = 0.005) in patients (19.5 +/- 6.4 PU) versus healthy subjects (33.8 +/- 11.5 PU.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗