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At least 361 records · Page 20Linked to original sources
PubMed1999

Action spectrum for the photophobic response of Ciona intestinalis (Ascidieacea, Urochordata) larvae implicates retinal protein.

Ascidian tadpole larvae change swimming behavior during the course of development. The photic behavior of the larvae of Ciona intestinalis was monitored by a computerized cell-tracking system with a time resolution of 0.1 s. Newly hatched larvae swim at an average speed of 1.4 mm/s but show no response to light stimuli. The swimming speed of the larvae became slower (0.4 mm/s) 3 h after hatching and they were induced to swim more rapidly by a sudden decrease in light intensity 4 h after hatching. During the course of development, the maximal speed of swimming behavior increased with time until 8 h after hatching and then plateaued. The action spectrum for the step-down photophobic response of the larvae was determined at around 8 h after hatching and was fitted to Dartnall's nomogram with the absorbance maximum of the pigment located at 505 nm. These results suggest retinal proteins in the ocellus of the larvae are the photoreceptors for the photobehavior.

Animals↗
PubMed2004

Biomedical applications of fluorescence imaging in vivo.

Optical imaging can advance knowledge of cellular biology and disease at the molecular level in vitro and, more recently, in vivo. In vivo optical imaging has enabled real-time study to track cell movement, cell growth, and even some cell functions. Thus, it can be used in intact animals for disease detection, screening, diagnosis, drug development, and treatment evaluation. This review includes a brief introduction to fluorescence imaging, fluorescent probes, imaging devices, and in vivo applications in animal models. It also describes a quantitative fluorescence detection method with a reconstruction algorithm for determining the location of fluorophores in tissue and addresses future applications of in vivo fluorescence imaging.

Algorithms↗
PubMed1984

Invasion of collagen gels by mouse lymphoid cells.

Small mouse lymphocytes from lymph nodes rapidly invaded three-dimensional collagen gels (in the absence of any added chemical attractant). In short-term assays (2-8 hr) this property was restricted to 20-25% of the cell population. Invasion was an active process involving cell locomotion. Time-lapse cinematography revealed that movement was erratic with frequent changes in cell speed. Tracks of cell paths within collagen gels demonstrated that lymphocytes made narrow angles of turn and thus showed a 'persistent random-walk' similar to other cell types moving on plane substrata. Analysis of lymphocyte movement within aligned collagen gels demonstrated that locomotion was biased in the axis of fibre alignment, i.e. lymphocytes showed contact guidance. Separated B lymphocytes invaded collagen gels at a slower rate than unseparated lymph node cells, as also did T cells purified by filtration through nylon wool columns. This latter anomaly implied that nylon wool filtration selectively depleted cells with invasive characteristics from a heterogeneous lymphocyte population. A comparison of Peyer's patch and lymph node lymphocytes showed that both populations invaded at the same rate but the latter cell type did this in greater numbers. This difference may reflect the different proportions of B and T lymphocytes in the two tissues. Lymphocytes from oxazolone-stimulated lymph nodes showed greatly increased movement into collagen matrices compared to unstimulated control lymph node lymphocytes. This increase was demonstrated to be a property of the blast cell population by separating the cells on Percoll gradients into lymphoblast-enriched and -depleted populations.

Animals↗
PubMed1996

Incudal folds and epitympanic aeration.

Thirty-seven temporal bones were dissected, and the posterior tympanic and epitympanic folds recorded and photographed. Histologic details were documented from four serially sectioned temporal bones, two normal and two inflamed. Of these 41 specimens, 31 were normal, and 10 showed signs of inflammation. The type for the lateral fold was incudomalleal in 16 and incudal in 25 ears. Incus intercrural and incudostapedial folds appeared only exceptionally. Medial and superior incudal folds were not present in normal ears. The anterior tympanic isthmus was a constant, large aeration pathway. In chronically inflamed ears, its partial or total block was caused by polypoid or large sheet-like folds. Inactive sequelae appeared as mature, simple, one-layer or extensive multilayer networks of webs, connected with a deeply indrawn incudomalleal fold. The small posterior isthmus was open to the incudal fossa in 13 ears, and in 28, it was sealed off by a posterior incudal fold. The mastoid air cell tracks were (in ten of 37 dissected ears) open to the incudal fossa, or directly, to the posterior tympanum. Auxiliary pathways due to membrane defects were found in both the horizontal and descending portions of the incudomalleal fold. Excepting the chordal, incudomalleal, and posterior incudal folds, fold-like webs in the posterior tympanum and epitympanum are of inflammatory origin.

Cholesteatoma↗
PubMed2007

Sensitivity of magnetic resonance imaging of dendritic cells for in vivo tracking of cellular cancer vaccines.

Success of immunotherapy with dendritic cells (DC) to treat cancer is highly dependent on their interaction with and activation of antigen specific T cells. To maximize DC-T cell contact accurate delivery of the therapeutic cells into the lymph node, or efficient trafficking of DC to the lymph nodes of the patient is essential. Since responses are seen in some patients but not in others, monitoring of the injected cells may be of major importance. Tracking of cells with magnetic resonance (MR) imaging is a non-invasive method that provides detailed anatomical information and is therefore more informative for the evaluation of the localization of therapeutic cells after injection than e.g. scintigraphic imaging. To challenge the sensitivity of this novel technique, we investigated the minimum amount of label and the number of cells required for MR imaging and the effect of labeling on DC function. DC were labeled with different concentrations of a clinically approved MR contrast agent consisting of superparamagnetic iron oxide particles and were imaged at both 3 and 7 T. Our results demonstrate the following: (i) When loaded with 30 (+/-4) pg Fe/cell, cell numbers as low as 1,000 cells/mm3 at 3 T and 500 cells/mm3 at 7 T could be readily imaged; (ii) Labeling does not affect cell viability and function; (iii) Because of its high spatial resolution and sensitivity, MRI is ideally suited to track therapeutic cells in vivo.

Cancer Vaccines↗
PubMed1996

The effect of track structure on cell inactivation and chromosome damage at a constant LET of 120 keV/micrometer.

The influence of track structure on chromosome damage and cell inactivation are being investigated. Plateau-phase normal human fibroblast cultures were irradiated with gamma rays, and He, Ne and Ar ions. Particle velocities were chosen so that all beams had an LET of 120 keV/micrometer. In this constant-LET experimental design, the radial distribution of excitations and ionizations about the particle track is the most significant variable. Using premature chromosome condensation, chromatin breaks were measured at two time points, promptly after irradiation and after a prolonged incubation to allow for repair. These measurements give an indication of both initial chromosomal damage and also residual damage that is either not repaired or is misrepaired. Survival was measured under the same conditions. Results indicate that the RBEs for both cell inactivation and, to a lesser extent, chromosome damage decrease as particle energy increases.

Alpha Particles↗
PubMed1996

Ca2+ triggers massive exocytosis in Chinese hamster ovary cells.

We have tracked the cell surface area of CHO cells by measuring the membrane capacitance, Cm. An increase in cytosolic [Ca2+], [Ca2+]i, increased the cell surface area by 20-30%. At micromolar [Ca2+]i the increase occurred in minutes, while at 20 microM or higher [Ca2+]i it occurred in seconds and was transient. GTPgammaS caused a 3% increase even at 0.1 microM [Ca2+]i. We conclude that CHO cells, previously thought capable only of constitutive exocytosis, can perform Ca2+-triggered exocytosis that is both massive and rapid. Ca2+-triggered exocytosis was also observed in 3T3 fibroblasts. Our findings add evidence to the view that Ca induces exocytosis in cells other than known secretory cells.

Animals↗
PubMed2006

Gadofluorine m uptake in stem cells as a new magnetic resonance imaging tracking method: an in vitro and in vivo study.

OBJECTIVES: Cell tracking using ultrasmall iron particles is well established in magnetic resonance imaging (MRI). However, in experimental models, intrinsic iron signals derived from erythrocytes mask the labeled cells. Therefore, we evaluated Gadofluorine M with other gadolinium chelates for a T1-weighted positive enhancement for cell tracking in vitro. In addition, Gadofluorine M was tested in vivo. MATERIAL AND METHODS: Gadofluorine M and other gadolinium chelates were used to label stem cells with and without uptake-mediating agents in vitro and in vivo using a 1.5 T MRI. In addition, histology and molecular modeling was investigated. RESULTS: Gadofluorine M revealed comparable properties to an uptake mediating agent in molecular modeling. Without an uptake-mediating agent Gadofluorine M-labeled cells were detected as a T1-weighted positive contrast in vitro and in vivo. Histology confirmed a 100% success rate for intracellular labeling. CONCLUSION: This study describes a novel contrast agent with the capability of intracellular accumulation without an uptake mediator providing a T1-positive MRI signal at 1.5 T and may be suitable for cell tracking in animal models with intraparenchymal hemorrhages such as stroke or malignant tumors.

Adipose Tissue↗
PubMed1983

Cell motility and microtubules in cultured fibroblasts from patients with Kartagener syndrome.

Patients with Kartagener syndrome (KS) show defects in ciliary and flagellar movement that are usually associated with the partial or total absence of dynein side arms from axonemal microtubules. Dynein is essential for such movements, but its involvement in other cellular (particularly microtubule-related) processes is unknown. It has recently been reported that neutrophils from KS patients show impaired motility including responses to chemotactic stimuli, suggesting that dynein-like proteins may be generally involved in motile processes. In support of this, we have now found that spontaneous motility of cultured skin fibroblasts from KS patients is also markedly impaired. Three cell lines derived from skin explants of KS patients with deficient dynein side arms in nasal cilia and eight cell lines derived from normal volunteers were studied. Fibroblasts were seeded into dishes containing colloidal gold-coated cover glasses [Albrecht-Buehler, 1977], incubated for 24h at 37 degrees C, and the area of cell "phagokinetic" tracks determined. Each cell line studied in this manner reproducibly displayed an amount of spontaneous motility characteristic for that cell line. The mean track area (+/- SE) for all control cells studied was 14.6 +/- 0.5 X 10(3) micron2 whereas for KS fibroblasts was 8.7 +/- 0.4 X 10(3) micron2 (P less than 0.001). Immunofluorescence microscopy using antitubulin and antihuman 210 K MAP antibodies revealed no differences in the staining patterns between control and KS fibroblasts. Pinocytic rates were identical, and the complement of tubulin and major microtubule associated proteins as seen on one-dimensional SDS polyacrylamide gel autoradiographs appeared similar for control and KS cells. Thus, the observed motility defect is probably not the result of alterations in the occurrence or distribution of microtubules or in the occurrence or binding of the major microtubule-associated proteins. This defect in cellular motility may be related to the absence of dynein or may reflect another independent cellular defect.

Adenosine Triphosphatases↗
PubMed2005

Chromatin dynamics in interphase cells revealed by tracking in a two-photon excitation microscope.

Increasing evidence points to a dynamical compartmentalization of the cell nucleus, yet the mechanisms by which interphase chromatin moves and is positioned within nuclei remain unclear. Here, we study the dynamics of chromatin in vivo applying a novel particle-tracking method in a two-photon microscope that provides approximately 10-fold higher spatial and temporal resolutions than previous measurements. We followed the motion of a chromatin sequence containing a lac-operator repeat in cells stably expressing lac repressor fused with enhanced green fluorescent protein, observing long periods of apparent constrained diffusion interrupted by relatively abrupt jumps of approximately 150 nm lasting 0.3-2 s. During these jumps, the particle moved an average of four times faster than in the periods between jumps and in paths more rectilinear than predicted for random diffusion motion. Additionally, the jumps were sensitive to the temperature and absent after ATP depletion. These experimental results point to an energy-dependent mechanism driving fast motion of chromatin in interphase cells.

Animals↗
PubMed2004

Level set analysis for leukocyte detection and tracking.

We propose a cell detection and tracking solution using image-level sets computed via threshold decomposition. In contrast to existing methods where manual initialization is required to track individual cells, the proposed approach can automatically identify and track multiple cells by exploiting the shape and intensity characteristics of the cells. The capture of the cell boundary is considered as an evolution of a closed curve that maximizes image gradient along the curve enclosing a homogeneous region. An energy functional dependent upon the gradient magnitude along the cell boundary, the region homogeneity within the cell boundary and the spatial overlap of the detected cells is minimized using a variational approach. For tracking between frames, this energy functional is modified considering the spatial and shape consistency of a cell as it moves in the video sequence. The integrated energy functional complements shape-based segmentation with a spatial consistency based tracking technique. We demonstrate that an acceptable, expedient solution of the energy functional is possible through a search of the image-level lines: boundaries of connected components within the level sets obtained by threshold decomposition. The level set analysis can also capture multiple cells in a single frame rather than iteratively computing a single active contour for each individual cell. Results of cell detection using the energy functional approach and the level set approach are presented along with the associated processing time. Results of successful tracking of rolling leukocytes from a number of digital video sequences are reported and compared with the results from a correlation tracking scheme.

Algorithms↗
PubMedDate not supplied

Tracking of individual cell cohorts in asynchronous Saccharomyces cerevisiae populations.

A novel flow cytometric procedure has been developed with the aim to obtain the growth properties of individual Saccharomyces cerevisiae cells in asynchronous culture. The method is based on labeling of the cell surface with FITC-conjugated concanavalin A and detection of the single-cell fluorescence with flow cytometry after cell exposure to growth conditions. Because the formation of new cell wall material in budded cells is restricted to the bud tip, exposure of the stained cells to growth conditions results in three cell types: (i) stained cells, (ii) partially stained cells, and (iii) unstained cells. Analysis of the staining pattern over time permits the determination of the specific growth rate of the cell population, the length of the budded cell cycle phase, and the growth pattern during the cell cycle of newly formed, partially stained daughter cells. The procedure has been tested with yeast cell populations growing at different rates. The data suggest an exponential increase in the size of individual cells during the cell cycle, as reflected by the forward angle light scattering (FALS) signals. It has been found that the apparent single-cell specific cell size growth rates, determined by FALS intensity, are significantly lower than the specific growth rates of the overall population. This could indicate that the tracking of a cohort of cells is significantly perturbed by a distribution of staining levels of daughter cells at cell division and that FALS may not be a good indicator of the cell size.

Cell Cycle↗
PubMed2004

Renal cell carcinoma of the grafted kidney: how to improve screening and graft tracking.

Renal cell carcinoma of transplanted kidneys is rare. We report three such cases among 1,250 kidney grafts that were performed or followed from 1968 to 2002. A strategy to diagnose these lesions is needed because of their rarity, late detection, and therapeutic repercussions. At the least, the strategy should include annual ultrasonography of the graft throughout its lifespan. Because the risk of tumor development in another organ from the same donor is not negligible, a national registry should be established to rapidly alert graft recipients with the same donor and other transplantation centers about the risk of graft tumors.

Adolescent↗
PubMed2006

Neuroprotection by GDNF-secreting stem cells in a Huntington's disease model: optical neuroimage tracking of brain-grafted cells.

The use of stem cells for reconstructive or neuroprotective strategies can benefit from new advances in neuroimaging techniques to track grafted cells. In the present work, we analyze the potential of a neural stem cell (NSC) line, which stably expresses the glial cell line-derived neurotrophic factor (GDNF) and the firefly luciferase gene (GDNF/Luc-NSC), for cell therapy in a Huntington's disease mouse model. Our results show that detection of light photons is an effective method to quantify the proliferation rate and to characterize the migration pathways of transplanted NSCs. Intravenous administration of luciferine, the luciferase substract, into the grafted animals allowed the detection of implanted cells in real time by an optical neuroimaging methodology, overpassing the limits of serial histological analyses. We observed that transplanted GDNF/Luc-NSCs survive after grafting and expand more when transplanted in quinolinate-lesioned nude mouse striata than when transplanted in non-lesioned mice. We also demonstrate that GDNF/Luc-NSCs prevent the degeneration of striatal neurons in the excitotoxic mouse model of Huntington's disease and reduce the amphetamine-induced rotational behavior in mice bearing unilateral lesions.

Animals↗
PubMed2006

In vivo tracking of macrophage activated killer cells to sites of metastatic ovarian carcinoma.

Radio-labelling of blood cells is an established technique for evaluating in vivo migration of normal cells to sites of pathology such as infection and haemorrhage. A limitation of cellular immunotherapies to induce anti-tumour responses is in part due to the uncertain ability of cellular effectors to reach their intended target. We extended the approach of cell radiolabelling to accurately examine the in vivo distribution of cellular immunotherapy with ex-vivo macrophage activated killer (MAK) cells. We describe the use of two methods of cell labelling for tracking the destination of autologous-derived macrophage activated killer (MAK) cells linked to the bi-specific antibody MDX-H210 delivered either by intravenous (i.v.) or intraperitoneal (i.p.) injection in ten patients with peritoneal relapse of epithelial ovarian carcinoma. Our results demonstrate the feasibility of generating high numbers and purity of GMP quality MAK cells, which can be radiolabelled with (18)F-FDG or (111)In-oxime. MAK cell administration produced minimal infusional toxicity and demonstrated a reproducible pattern of in vivo distribution and active in vivo tracking to sites of known tumour following 8 of 16 i.v. infusions or 4 of 6 i.p. infusions. However, the leakage of (18)F-FDG limited the ability to confidently confirm the tracking of MAK cells to tumour in all cases and improved PET labels are required. The addition of MDX-H210 bispecific antibody did not alter the distribution of cells to tumour sites, but did accelerate the clearance of i.v. administered MAK cells from the pulmonary circulation. This data demonstrates that cellular cancer immunotherapies may be successfully delivered to the sites of active tumour following either i.v. or i.p. injection in a proportion of patients with metastatic cancer. Incorporation of tracking studies in early cycles of cellular immunotherapy may allow selection of patients who demonstrate successful targeting of the immunotherapy for ongoing treatment.

Antibodies, Bispecific↗
PubMed2002

Biological effectiveness of isolated short electron tracks: V79-4 cell inactivation following low dose-rate irradiation with Al(K) ultrasoft X-rays.

PURPOSE: To investigate the biological effect of single, isolated, short electron tracks (<70 nm) relevant to practical human exposures to low-linear energy transfer radiation. MATERIALS AND METHODS: An irradiation rig was constructed that allowed environmentally controlled, protracted irradiations with an individually prescribed dose to up to 20 samples over a period of days. Inactivation of V79-4 mammalian cells by Al(K) ultrasoft X-rays was studied at high and low dose-rates with a maximum exposure time of 42 h. RESULTS: A significant increase in clonogenic survival was observed at the higher doses when the exposure time was increased from <6 min to 21 h, with no further increase observed for 42-h exposures. Despite the short range of the low-energy electrons produced (<70 nm), significant cell inactivation was observed for these low dose-rate exposures. CONCLUSIONS: The results are consistent with the hypothesis that even individual tracks can be biologically effective.

Aluminum↗