Variability of the thrombin- and ADP-induced Ca2+ response among human platelets measured using fluo-3 and fluorescent videomicroscopy

The intracellular free Ca2+ concentration ([Ca2+]cyt) of individual human platelets localized between siliconized glass cover slips was determined at rest and after stimulation with thrombin and ADP using the Ca2+ indicator fluo-3 (0.97 +/- 0.30 mmol/l cell volume) with fluorescence video microscopy. Resting [Ca2+]cyt in the presence of 2 mM external Ca2+ showed only small inter-platelet variability ([Ca2+]cyt = 86 +/- 30 (S.D.) nM). Resting [Ca2+]cyt of individual fluo-3-loaded platelets measured as a function of time had a S.D. of 10 nM or 12% (S.D./mean). Individual platelets showed no affinity for the siliconized support and their [Ca2+]cyt showed no tendency to oscillate in either the resting or in the activated state. When 0.2 U/ml thrombin or 20 microM ADP were added, all platelets showed a characteristic Ca2+ transient whereby [Ca2+]cyt increased to peak values within 8-12 sec and then declined. The Ca2+ transients measured with fluo-3 were in approximate synchrony but peak [Ca2+]cyt values showed large inter-platelet variability. The ensemble average peak [Ca2+]cyt for thrombin and ADP were 672 +/- 619 (S.D.) nM and 640 +/- 642 (S.D.) nM, respectively. Thus inter-platelet variations (S.D./mean) were 92% or 100% as large as the average measured values. Mathematically-constructed averages of the single platelet experiments agreed reasonably well with platelet-averaged values obtained in parallel experiments with stirred platelet suspensions in a plastic cuvette, measured with a conventional spectrofluorometer. Peak [Ca2+]cyt values reflecting dense tubular Ca2+ release alone (external Ca2+ removed) also showed large interplatelet variation (171 +/- 105 (S.D.) nM with thrombin and 183 +/- 134 (S.D.) nM with ADP). Dense tubular Ca2+ release induced by cyclopiazonic acid (a dense tubular Ca2+-ATPase inhibitor) gave peak [Ca2+]cyt of 289 +/- 170 nM. Thus the size of the dense tubular Ca2+ pool has an inter-platelet variation of 59% (S.D./mean). Variability of the dense tubular pool size accounts for some, but not all, of the large interplatelet variation in peak (Ca2+]cyt seen with thrombin and ADP activation.

Different pathways of inhibitory effects of wortmannin on exocytosis are revealed by video-enhanced light microscope

Exocytosis of secretory granules, including histamine, in rat basophilic leukemia (RBL-2H3) cells, which exhibit Ca(2+)-dependent secretion of granules when stimulated with antigen or Ca(2+)-ionophore (A23187), was observed under a video-enhanced light microscope. Exocytotic events of individual granules including fusion, extrusion, and membrane retrieval were visualized in individual cells stimulated with antigen or A23187. Exocytosis of granules stimulated with A23187 showed two peaks in its time courses. The earlier one of the peaks was inhibited by wortmannin ( > 100 nM), as an inhibitor of myosin light chain kinase (MLCK), and the other was not. Exocytosis by antigen-stimulation, however, showed only one peak, which was inhibited by low concentration of wortmannin ( < 50 nM) as an inhibitor of phosphatidylinositol 3-kinase (PI3-kinase). These results indicate that quantitative analysis of exocytosis visualized by video-enhanced light microscope reveals two different pathways, through P13-kinase and MLCK, of inhibitory effects on exocytosis by wortmannin in RBL-2H3 cells.

Gallbladder carcinoma: a video image analysis of AgNOR distribution and its relation to tumour stage and grade

The amount and distribution of interphase argyrophilic nucleolar organizer regions (AgNORs) was studied in 51 gallbladder surgical specimens including 32 primary carcinomas, 10 adenomas and 9 cases of chronic cholecystitis with calculi. The mean nuclear AgNOR area (NORA) and the AgNOR distribution score (NORDS), i.e. the percentage of cells carrying nucleolar aggregates with more than 6 distinct silver dots, were evaluated in 200 epithelial nuclei per specimen by means of automated image analysis and direct counting respectively. Statistical analysis (variance analysis and Student-Neuman-Keuls' test) performed on the pooled mean AgNOR values showed a significant difference (p < 0.001) between carcinomas and non-carcinomatous lesions. Both NORA and NORDS highly discriminated carcinomas with histopathological grade 4 versus cases with grade 1, 2 or 3 (p < 0.001); a less statistically significative p value (< 0.05) was encountered when NORDS values of well differentiated grade 1 carcinomas and adenomas were compared. The NORA parameter permitted the discrimination of stage IV versus stage I carcinomas (p < 0.001), while carcinomas in stage IV and those in stage II were distinguished with a p < 0.05; the NORDS parameter allowed also to distinguish stage IV from both stage I or II tumours (p < 0.001). Our results indicate that the above-mentioned AgNOR parameters may be utilized as additional, more objective quantitative criteria in the clinical-pathological assessment of the outcome of gallbladder carcinomas.

Regulation of cell volume by beta2-adrenergic stimulation in rat fetal distal lung epithelial cells

Cell-volume changes induced by terbutaline (a specific beta2-agonist) were studied morphometrically in rat fetal distal lung epithelium (FDLE) cells. Cell-volume changes qualitatively differed with the concentration of terbutaline. Terbutaline of 10(-10)-10(-8) M induced transient cell swelling. Terbutaline of 10(-7) M induced transient cell swelling followed by slow cell shrinkage. Terbutaline of 10(-6)-10(-5) M induced rapid cell shrinkage followed by slow cell shrinkage. Terbutaline of 10(-3) M induced transient cell shrinkage; then cell volume oscillated during stimulation. Benzamil of 10(-6) M suppressed the cell swelling induced by 10(-10)-10(-8) M terbutaline and quinine of 10(-3) M inhibited the cell shrinkage induced by 10(-6)-10(-5) M terbutaline. These results suggest that cell swelling would be induced by NaCl influx and the cell shrinkage is by KCl efflux. Dibutyryl cyclic AMP (DBcAMP) also induced similar cell-volume changes over a wide range of concentrations (10(-9)-10(-3) M): a low concentration induced transient cell swelling; a high concentration, rapid and slow cell shrinkage. Forskolin (10(-4) M), like terbutaline (10(-5) M), induced rapid cell shrinkage followed by slow cell shrinkage, and this decrease in the cell volume was enhanced by the presence of benzamil. On the other hand, cell shrinkage was induced by ionomycin (even low concentration; 3 x 10(-10) M ionomycin), and after that cell volume remained at a plateau level. Removal of extracellular Ca2+ abolished the cell swelling caused by terbutaline of 10(-10)-10(-8) M. With removal of extracellular Ca2+, the initial, rapid cell shrinkage induced by 10(-5) M terbutaline became transient, but we still detected slow cell shrinkage similar to that in the presence of extracellular Ca2+. Overall, at low concentrations (10(-10)-10(-8) M), terbutaline induced benzamil-sensitive cell swelling in FDLE cells, which was cAMP- and Ca2+-dependent; high concentrations (> or =10(-6)) induced quinine-sensitive rapid cell shrinkage, which was Ca2+-dependent; high concentrations (> or = 10(-7)) induced slow cell shrinkage, which was cAMP-dependent. These findings suggest that terbutaline regulates cell volume in FDLE cells by cytosolic cAMP and Ca2+ through activation of Na+ and K+ channels.

[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.

Quantifying cell mono-layer cultures by video imaging

A method is described in which the relative number of adherent cells in multi-well tissue-culture plates is assayed by staining the cells with Giemsa and capturing the image of the stained cells with a video camera and charged-coupled device. The resultant image is quantified using the associated video imaging software. The method is shown to be sensitive and reproducible and should be useful for studies where quantifying relative cell numbers and/or proliferation in vitro is required.

[The use of the television microscopicanalysis for the serodiagnosis of salmonellosis and brucellosis]

The possibility of using TV microscopic analysis for the laboratory diagnosis of salmonellosis and brucellosis is considered. The comparative analysis of this method and standard serodiagnostic methods was made in the study of sera taken from 134 salmonellosis patients 69 chronic brucellosis patients. The study demonstrated the advantages of the method of MIA (rapidity, high sensitivity, specificity), making it possible to recommend its wide use for the laboratory diagnosis of salmonellosis and brucellosis.

Video light microscopy of 670-kb DNA in a hanging drop: shape of the envelope of DNA

Although its conformation has not been observed directly, double-stranded DNA in solution is usually assumed to be randomly coiled at the level of the DNA double helix. By video light microscopy of ethidium-stained DNA at equilibrium in a nonturbulent hanging drop, in the present study, the 670 kb linear bacteriophage G DNA is found to form a flexible filament that has on average 17 double helical segments across its width. This flexible filament 1) has both asymmetry and dimensions expected of a random coil and 2) has ends that move according to the statistics expected of a random walk. After unraveling the flexible filament-associated DNA double helix near the surface of a hanging drop, recompaction occurs without perceptible rotation of the DNA. Both conformational change and intermolecular tangling of the DNA are observed when G DNA undergoes nondiffusive motion in a hanging drop. The characteristics of the G DNA flexible filament are explained by the assumption that the flexible filament is a random coil of double helical segments that are unperturbed by motion of the suspending medium.

Digital photography for the light microscope: results with a gated, video-rate CCD camera and NIH-image software

In this report, we describe a relatively inexpensive method for acquiring, storing and processing light microscope images that combines the advantages of video technology with the powerful medium now termed digital photography. Digital photography refers to the recording of images as digital files that are stored, manipulated and displayed using a computer. This report details the use of a gated video-rate charge-coupled device (CCD) camera and a frame grabber board for capturing 256 gray-level digital images from the light microscope. This camera gives high-resolution bright-field, phase contrast and differential interference contrast (DIC) images but, also, with gated on-chip integration, has the capability to record low-light level fluorescent images. The basic components of the digital photography system are described, and examples are presented of fluorescence and bright-field micrographs. Digital processing of images to remove noise, to enhance contrast and to prepare figures for printing is discussed.

Steps in tumor metastasis: new concepts from intravital videomicroscopy

Metastases are responsible for the majority of failures in cancer treatment. Clarifying steps in metastasis and their molecular mechanisms will be important for the development of anti-metastasis therapeutic strategies. Considerable progress has been made in identifying molecules involved in metastasis. However, because of the nature of assays that have been available, conclusions about steps in metastasis and their molecular bases have been drawn primarily from inference. In order to complete the picture of how metastases form, a technique is needed to directly watch the process in vivo as it occurs over time. We have developed an intravital videomicroscopy (IVVM) procedure to make such observations possible. Results from IVVM are providing us with new conceptual understanding of the metastatic process, as well as the nature and timing of the contributions of molecules implicated in metastasis (e.g. adhesion molecules and proteinases). Our findings suggest that early steps in metastasis, including hemodynamic destruction and extravasation, may contribute less to metastatic inefficiency than previously believed. Instead, our results suggest that the control of post-extravasation growth of individual cancer cells is a significant contributor to metastatic inefficiency. Thus, this stage may be an appropriate target for design of novel strategies to prevent metastases.

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.

Determination of microtubule polarity in vitro by the use of video-enhanced differential-interference contrast light microscopy and Chlamydomonas flagellar axonemal pieces

Microtubules nucleated by sea urchin sperm-tail axonemes have polar ends that differ both functionally and structurally but cannot be distinguished from one another when viewed by light microscopy. Ambiguity and circularity surround any classification of microtubule polarity by conventional methods. Chlamydomonas flagellar axonemal pieces have distinct morphological differences at their plus- and minus-ends, and microtubules nucleated from these pieces can be distinguished as plus- or minus-ended based on the morphological differences present in the Chlamydomonas flagellar axonemal pieces. Plus- and minus-ended microtubules were polymerized in this fashion and analyzed for differences in growth rates, shortening rates, and frequencies of transitions. The results were in good agreement with similar data generated by the more time-consuming and difficult use of kinesin-coated beads (R. J. Kowalski, and R. C. Williams, Jr. (1993) Cell Motil. Cytoskeleton 26, 282-290) to determine microtubule polarity. This is a relatively simple and effective method for determining the polarity of microtubules in vitro by video-enhanced differential-interference contrast light microscopy.

An agarose slide method to follow the fate of bacteria within digestive vacuoles of protozoa

A method to follow the fate of ingested bacteria within digestive vacuoles of protozoa is presented. Tetrahymena pyriformis, previously fed with bacteria, is deposited onto glass microscope slides covered with a film of nutritive agarose. The protozoa lyse and the digestive vacuoles containing the bacteria stay undamaged and can be observed microscopically. After incubation, microcolonies reveal those vacuoles which contained living bacteria. The method can be used to study the survival ability of the ingested bacteria. It is a potentially valuable technique for studies on digestion efficacy, virulence ability, or escape mechanisms of bacteria from digestion.

A study of spermatozoal motility in type 1 diabetes mellitus

The aim of the study was to examine an aspect of male fertility in patients with Type 1 diabetes mellitus (n = 17) compared to healthy control subjects (n = 16) using parameters of sperm motility, measured using a computerized image analysis system (the Hamilton Thorn Research HTM-2030 Motility Analyzer), as indicators of potential fertility. Within the diabetic group no correlations were found between sperm motility and age, age of onset of diabetes, duration of diabetes or glycated haemoglobin. When the diabetic and control groups were compared, track speed, path velocity, progressive velocity, and lateral head displacement were not significantly different, whereas linearity and linear index, measures of straightness of swimming, were significantly greater in the diabetic subjects (59.2% vs 69.8%, p = 0.0005 and 76.4% vs 83.6%, p = 0.0016, respectively). We conclude that diabetic men, in the absence of complications, do not appear to be at a disadvantage in terms of sperm motility compared to healthy individuals.

Stochastic behavior of organelle motion in Nitella internodal cells

The stochastic behavior of organelles during the recovery process of protoplasmic streaming is investigated in Nitella internodal cells at a nanometer space resolution. The motions of organelles in the components parallel and perpendicular to the alignment of actin filaments in the cell are analysed from the traces of displacement of 860 organelles in 1/30s (= video rate). The analysis of those traces shows that the generation of motive forces to the organelle follows the Poisson process. Therefore, we have been able to estimate the step size corresponding to the single force generation as approximately 100 nm.

Persistent Na+ conductance in medium-sized neostriatal neurons: characterization using infrared videomicroscopy and whole cell patch-clamp recordings

1. In the present study we investigate the expression of a persistent Na+ conductance (INaP) in identified medium-sized neostriatal neurons. Nomarski optics and infrared videomicroscopy were used for cell visualization and identification in thick slices (350 microns). Current- and voltage-clamp recordings were obtained utilizing whole cell patch-clamp methodology. 2. Application of depolarizing ramp voltage commands from a holding potential of -70 mV induced a slow, noninactivating inward current that occurred before and independent of the rapidly inactivating sodium current that subserves action potential generation. INaP began to activate at potentials less negative than -70 mV and peaked at -34 +/- 1 (SE) mV. Its average peak amplitude was -100 +/- 17 pA. INaP was abolished by tetrodotoxin (TTX, 0.5-1 microM) or an Na(+)-free solution. In contrast, it was not affected by Ca2+ channel blockers. Depolarizing ramp commands also induced tetraethylammonium-sensitive outward currents. 3. Dopamine (DA) (20-100 microM) produced a significant reduction of INaP. 4. These results demonstrate the existence of a TTX-sensitive persistent Na+ conductance in medium-sized neostriatal neurons. This conductance is modulated by DA and could play a role in the generation of rhythmic oscillations and in supporting repetitive firing.

Robert Feulgen Prize Lecture 1995. Electronic light microscopy: present capabilities and future prospects

Electronic light microscopy involves the combination of microscopic techniques with electronic imaging and digital image processing, resulting in dramatic improvements in image quality and ease of quantitative analysis. In this review, after a brief definition of digital images and a discussion of the sampling requirements for the accurate digital recording of optical images, I discuss the three most important imaging modalities in electronic light microscopy--video-enhanced contrast microscopy, digital fluorescence microscopy and confocal scanning microscopy--considering their capabilities, their applications, and recent developments that will increase their potential. Video-enhanced contrast microscopy permits the clear visualisation and real-time dynamic recording of minute objects such as microtubules, vesicles and colloidal gold particles, an order of magnitude smaller than the resolution limit of the light microscope. It has revolutionised the study of cellular motility, and permits the quantitative tracking of organelles and gold-labelled membrane bound proteins. In combination with the technique of optical trapping (optical tweezers), it permits exquisitely sensitive force and distance measurements to be made on motor proteins. Digital fluorescence microscopy enables low-light-level imaging of fluorescently labelled specimens. Recent progress has involved improvements in cameras, fluorescent probes and fluorescent filter sets, particularly multiple bandpass dichroic mirrors, and developments in multiparameter imaging, which is becoming particularly important for in situ hybridisation studies and automated image cytometry, fluorescence ratio imaging, and time-resolved fluorescence. As software improves and small computers become more powerful, computational techniques for out-of-focus blur deconvolution and image restoration are becoming increasingly important. Confocal microscopy permits convenient, high-resolution, non-invasive, blur-free optical sectioning and 3D image acquisition, but suffers from a number of limitations. I discuss advances in confocal techniques that address the problems of temporal resolution, spherical and chromatic aberration, wavelength flexibility and cross-talk between fluorescent channels, and describe new optics to enhance axial resolution and the use of two-photon excitation to reduce photobleaching. Finally, I consider the desirability of establishing a digital image database, the BioImage database, which would permit the archival storage of, and public Internet access to, multidimensional image data from all forms of biological microscopy. Submission of images to the BioImage database would be made in coordination with the scientific publication of research results based upon these data.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of the centrosome in mitosis: UV micro-irradiation study

Ultraviolet micro-irradiation (UV-MI) of the PK (pig kidney embryo) cell centrosome (lambda max = 280 nm, spot diameter 1.6 mm, exposure time 5-15 s) at metaphase and anaphase resulted in functional damage of the centrosome. After UV-MI of the centrosome at early metaphase, chromosomes quickly (in 1-3 min) moved away from the irradiated pole and then encircled the non-irradiated pole. Within 10 min after UV-MI the spindle disassembled and chromosomes remained unseparated. The minimal dose inducing this effect in 90% of cells was accumulated in 5 s. After the same UV-MI at late metaphase, chromosomes shifted towards the non-irradiated pole; however, anaphase started and chromosome motion towards the non-irradiated pole continued normally. UV-MI of the centrosome at early anaphase for 5-15 s slowed down and then stopped chromosome motion towards the irradiated pole. This was a result of rapid (within 2-3 min) disorganization of the half-spindle. Chromosomes continued to move towards the opposite pole normally, while cytokinesis was significantly retarded. No visible lesion was revealed by electron microscopy after 5 s UV-MI, while 15 s irradiation resulted in the truncation of the microtubule bundles 1.5-2 microns from the centrosome. We concluded that UV-MI inactivates the centrosome and induces disaggregation of microtubule initiation sites. The critical point (checkpoint) in mitosis up to which this damage induces mitotic arrest is mid-metaphase.

A new design intended to relate high pressure treatment to yeast cell mass transfer

A new optical device has been developed to allow the observation of microorganisms during a high pressure treatment up to 700 MPa. To measure cell volume variation during the high pressure application, an image analysis system was connected with the light microscope. With this device, growth of Saccharomyces cerevisiae was studied at moderate pressure (10 MPa) through the observation of individual cell budding. Cell volume variations were also measured on the yeast Saccharomycopsis fibuligera on fixed cells as well on a population sample and a shrinkage in average cell volume was observed consequently to a pressure increase of 250 MPa. The observed compression rate (25%) under pressure and the partial irreversibility of cell compression (10%) after return to atmospheric pressure lead to the conclusion that a mass transfer between cell and cultivation medium occurred. The causes of this transfer could be explained by a modification of membrane properties, i.e., disruption or increase in permeability.

Isolation of small polarized bile duct units

Fragments of small interlobular bile ducts averaging 20 microns in diameter can be isolated from rat liver. These isolated bile duct units form luminal spaces that are impermeant to dextran-40 and expand in size when cultured in 10 microM forskolin for 24-48 hr. Secretion is Cl- and HCO3- dependent and is stimulated by forskolin > dibutyryl cAMP > secretion but not by dideoxyforskolin, as assessed by video imaging techniques. Secretin stimulates Cl-/HCO3- exchange activity, and intraluminal pH increases after forskolin administration. These studies establish that small polarized physiologically intact interlobular bile ducts can be isolated from rat liver. These isolated bile duct units should be useful preparations for assessing the transport properties of small bile duct segments, which are the primary site of injury in cholestatic liver disorders, known as "vanishing bile duct syndromes."