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Results for “Cell Tracking”

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At least 595 records · Page 33Linked to original sources

PubMed1979

Ultrastructure of gliding bacteria: scanning electron microscopy of Capnocytophaga sputigena, Capnocytophaga gingivalis, and Capnocytophaga ochracea.

When examined by both light and scanning electron microscopy, Capnocytophaga gingivalis, C. sputigena, and C. ochracea displayed three distinct growth zones: the original streak, an intermediate zone, and the advancing edge, or halo zone. On Trypticase (BBL Microbiology Systems)-soy-blood agar, the cells translocated by gliding. C. gingivalis and C. sputigena formed large, irregular isolated colonies, while C. ochracea formed a more confluent cell mass. The cells within the streak zone and in most of the intermediate zone were heaped into mounds, with the individual cells displaying a definite flow pattern, the latter characteristic of C. sputigena and C. gingivalis. The halo zone consisted of tracks of cells which appeared to have translocated back upon themselves, or were restricted in their outward movements by adjacent cells. Also present within the halo zone were small aggregates of cells, referred to as pioneer colonies. The cell surfaces of C. gingivalis and C. ochracea were smooth and free of any apparent extracellular material, whereas C. sputigena was covered with a thick amorphous material, as well as long, thick, cell surface-associated fibrils.

Bacteroidetes↗

PubMed2026

Tracking GAD-specific T-cell expansions in Type 1 diabetes by intradermal GAD-Alum challenge.

Identifying and monitoring autoreactive T cells that drive beta cell destruction remains a major obstacle to developing effective immunotherapies for type 1 diabetes (T1D). These cells are extremely rare in peripheral blood and cannot be accessed directly from the pancreas. We used intradermal injection of Glutamic Acid Decarboxylase (GAD)-Alum to recruit GAD-specific T cells to accessible sites in the skin and skin-draining lymph nodes (LNs), sampled by skin suction blisters and ultrasound-guided LN aspiration. Peripheral blood samples obtained before GAD injection were restimulated with GAD in vitro to detect reactive CD4+ T cells. Single-cell RNA sequencing (scRNAseq) followed by re-expression of selected T cell receptors (TCRs) confirmed antigen specificity. Up to 70% of T cells at the skin injection site were clonally-expanded and 4 of 14 (28%) re-expressed TCRs were GAD-reactive. In LNs 1 of 14 (4%) clonally-expanded TCRs was GAD-reactive, representing ~0.08% of all T-cells. GAD-reactive cells across compartments displayed Th1 and Th17-associated transcription signatures. These results demonstrate the intradermal autoantigen challenge and scRNAseq, enable direct identification and molecular profiling of autoreactive T cells in vivo. This minimally invasive approach provides a powerful platform for tracking antigen-specific T cells to monitor disease activity and evaluate immune interventions in T1D.

Autoimmunity↗

PubMed1996

Telomerase is activated in the prostate and seminal vesicles of the castrated rat.

Telomeres, the repetitive non-coding DNA sequences found at the ends of all eukaryotic chromosomes, shorten with each cell division. It has been proposed that telomere shortening may be the counting element of a mitotic clock that keeps track of cell divisions; with shortening to a critical length acting as a senescence signal underlying cellular aging. The enzyme telomerase functions to maintain telomere length, thus allowing unlimited cell division, and has been associated with cellular immortalization and cancer. Stem cells have large, perhaps unlimited, replicative capacities. Since these cells are potentially immortal, we reasoned that they might posses active telomerase. We therefore assayed for telomerase activity in the stem cell enriched pools of the androgen-depleted sex accessory tissues in the castrated male rat. Following castration, the ventral prostate and seminal vesicles of the rat involute, losing approximately 90% of their cells by 21 days. These residual glands persist, and are enriched for stem cells, being capable of fully regenerating these glands if testosterone is re-introduced into the animal. We assayed telomerase activity in extracts from normal, involuted, and regenerating ventral prostate and seminal vesicles. Normal glands were found to be telomerase negative, whereas telomerase activity appeared as these glands involuted following castration. Conversely, telomerase activity disappeared during testosterone-induced regeneration of these residual glands. These results provide strong evidence for the ability of androgen to negatively-regulate telomerase activity in stem cell populations of the rat ventral prostate and seminal vesicles. and represent the first in vivo model system for the modulation of telomerase activity.

Animals↗

PubMed1994

The regulation of chemotaxis and chemokinesis in Dictyostelium amoebae by temporal signals and spatial gradients of cyclic AMP.

The tactic and kinetic locomotion of Dictyostelium discoideum amoebae were examined in cyclic AMP (cAMP) spatial gradient and temporal signal fields. The distributions of migrating cells were examined within 150 microns-thick micropore filters after incubation with different cAMP concentrations, [cAMP], applied in three ways across the fields: as positively or negatively developing gradients, generated either by increasing or decreasing the [cAMP] on one side of the filter, respectively, or as static, linear gradients after negative development. Chemotaxis was only induced by oriented, temporally increasing [cAMP]. Pulses propagated by molecular diffusion or mechanical flow were equally effective. Negatively developing cAMP gradients had no initial effect on cell accumulation. However, if the subsequent static spatial gradient was maintained by an infusion system, some gradients also induced cell accumulation, whose degree and direction depended on the gradient [cAMP]. The basis of this new effect was examined by tracking individual cells by computer-assisted videomicroscopy during locomotion in different [cAMP]. Cells produced a triphasic [cAMP]-dependent response, with optimal cell motility induced by 10-30 nM. The results demonstrate that cell accumulation either up-field or down-field in spatial gradients is governed by the field locations of the attractant concentrations that induce the relative locomotory maxima and minima in the gradient field. Cells perceive the ambient [cAMP], but cannot read the spatial gradient orientation in static or yet steeper regions of developing gradients. Accumulation in static spatial gradients is a function of klino- and orthokinesis, but chemotaxis requires an oriented cAMP pulse or impulse.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed2001

Dependence of the yield of DNA double-strand breaks in Chinese hamster V79-4 cells on the photon energy of ultrasoft X rays.

Induction of DNA DSBs by low-LET radiations reflects clustered damage produced predominantly by low-energy, secondary electron "track ends". Cell inactivation and induction of DSBs and their rejoining, assayed using pulsed-field gel electrophoresis, were determined in Chinese hamster V79-4 cells irradiated as a monolayer with characteristic carbon K-shell (CK) (0.28 keV), aluminum K-shell (AlK) (1.49 keV), and titanium K-shell (TiK) (4.55 keV) ultrasoft X rays under aerobic and anaerobic conditions. Relative to (60)Co gamma rays, the relative biological effectiveness (RBE) for cell inactivation at 10% survival and for induction of DSBs increases as the photon energy of the ultrasoft X rays decreases. The RBE values for cell inactivation and for induction of DSBs by CK ultrasoft X rays are 2.8 +/- 0.3 and 2.7 +/- 0.3, respectively, and by TiK ultrasoft X rays are 1.5 +/- 0.1 and 1.4 +/- 0.1, respectively. Oxygen enhancement ratios (OERs) of approximately 2 for cell inactivation and induction of DSBs by ultrasoft X rays are independent of the photon energy. The time scale for rejoining of DNA DSBs is similar for both ultrasoft X rays and 60Co gamma rays. From the size distribution of small DNA fragments down to 0.48 kbp, we concluded that DSBs are induced randomly by CK and AlK ultrasoft X rays. Therefore, ultrasoft X rays are more efficient per unit dose than gamma radiation at inducing DNA DSBs, the yield of which increases with decreasing photon energy.

Animals↗

PubMed2002

Using the Australian Childhood Immunisation Register to track the transition from whole-cell to acellular pertussis vaccines.

From 1997 to 1999, Australia changed from a whole-cell based pertussis vaccination program to an acellular one. This paper tracks the transition from whole-cell to acellular pertussis vaccines by calculating the number of whole cell (DTPw) and acellular (DTPa) pertussis vaccines recorded on the Australian Childhood Immunisation Register (ACIR) each month from January 1996 to August 2000. The number of combined diphtheria-tetanus (CDT) vaccines, recommended where DTP is contraindicated and for the fifth dose prior to 1994, was also calculated. The use of DTPa increased following its licensing in 1997, with a corresponding decrease in the use of DTPw. The increase was initially greatest in its use as a fourth and fifth dose, for which it was funded at a national level in 1997. Subsequently, a steep increase in its use for the first three doses followed in 1999, coinciding with it becoming free of charge for infants nationally. The use of CDT has decreased markedly since January 1996 and, since March 2000, fewer than 100 CDT vaccines per month were recorded on the ACIR, suggesting that this vaccine is not being inappropriately used.

Australia↗

PubMed1981

Mammalian cell survival and radiation quality: analysis with allowance for delta tracks.

The RBE for mammalian cell survival is analysed in relation to the distribution of LET. Complex target theory is described, together with a procedure for applying LET distributions to experimental findings in order to estimate the modes of cellular inactivation. Track segment theory is shown to have previously unrecognised limitations. The stepwise method is adopted to calculate the LET distributions for the radiations (alpha-particles, deuterons and x-rays) used by Barendsen et al (1966) in their study of the survival of T1 cells of human origin. Satisfactory fits of theory to experiment are obtained. Three distinctive modes of cellular inactivation, with independent energy transfers (direct and indirect) to complex targets comprising 2, 4 adn 6 elements respectively, appear to be involved overall. At 'low dose', no contribution from the 2-transfer-mode can be discerned; only this mode is reparable. Saturation cross-sections (at high LET) for the 2- and 4-transfer-, but not the 6-transfer-mode, are oxygen-dependent. All three modes of inactivation might entail unrepaired double strand breaks and/or some form of mutation in DNA, at 1, 2 and 3 vulnerable sections, respectively.

Alpha Particles↗

PubMed1999

Allergic contact dermatitis: correlation of in vivo confocal imaging to routine histology.

BACKGROUND: Allergic contact dermatitis (ACD) is a common and often challenging clinical problem. In vivo near-infrared confocal reflectance microscopy (CM) is a new vital microscopy technique. OBJECTIVE: CM was used to evaluate acute ACD. METHODS: Patch testing by means of Finn Chambers technique was performed in 5 subjects to induce an acute allergic skin reaction. Noninvasive CM images from normal and eczematous skin were sequentially recorded before and after removal of the Finn Chambers. RESULTS: The epidermis and papillary dermis were clearly seen in high resolution. Retention of nuclei in stratum corneum, epidermal edema with microvesicle formation, and transepidermal migration of inflammatory cells were observed in vivo. Isolated dendritic cells were present in the ACD sites of 2 subjects, with morphology, size, and location consistent with Langerhans cells. Dermal vasodilation was observed as well. CONCLUSION: CM is a useful tool to study ACD and may be able to track Langerhans cell activation.

Blister↗

PubMed2006

Individual stem cells with highly variable proliferation and self-renewal properties comprise the human hematopoietic stem cell compartment.

Hematopoiesis requires tight regulation of the hematopoietic stem cell (HSC) population; however, the dynamics of HSC use at steady state are uncertain. Over 3-7 months, we evaluated the repopulation and self-renewal of more than 600 individual human 'severe combined immunodeficiency mouse-repopulating cells' (SRCs), tracked on the basis of lentiviral integration sites, in serially transplanted immune-deficient mice, as well as of SRC daughter cells that migrated to different marrow locations in a single mouse. Our data demonstrate maintenance by self-renewing SRCs after an initial period of clonal instability, a result inconsistent with the clonal succession model. We found wide variation in proliferation kinetics and self-renewal among SRCs, as well as between SRC daughter cells that repopulated equivalently, suggesting that SRC fate is unpredictable before SRCs enter more rigid 'downstream' developmental programs.

ADP-ribosyl Cyclase 1↗

PubMed2006

Allocation of cells in mouse blastocyst is not determined by the order of cleavage of the first two blastomeres.

The second cleavage of the mouse embryo is asynchronous. Some recent investigators have proposed that the sequence of division of blastomeres in two-cell embryos may predict the ultimate location of the descendants of these blastomeres within the blastocyst. To verify this model, we tracked the cells derived from two-cell stage blastomeres using tetramethylrhodamine-conjugated dextran as a lineage tracer. In the first variant of the experiment, we labeled one of two blastomeres in two-cell embryos and subsequently recorded which blastomere cleaved first. In the second variant of the experiment, fluorescent dextran was injected at the three-cell stage into the blastomere that had not yet cleaved. Subsequently, the fate of the progeny of labeled and unlabeled blastomeres was followed up to the blastocyst stage. Our results suggest that allocation of cells into the embryonic and abembryonic parts of the blastocyst is not determined by the order of cleavage of the first two blastomeres.

Animals↗

PubMed2006

Moving toward the light: using new technology to answer old questions.

Fluorescence microscopy has become a principle methodology in the field of developmental biology. Recent technological advances have led to the design of high-speed and high-resolution confocal and multiphoton microscopes that enable researchers to obtain three- and four-dimensional information in living cells and whole embryos. Paralleling this progress, the development of stable and bright vital fluorescent probes has revolutionized the ability to track individual cells in vitro and in vivo and to visualize intercellular and subcellular molecular interactions in real time. Combining imaging modalities and labeling techniques that are increasingly unobtrusive to cell and whole animal function, our understanding of how proteins interact, tissues take form, and organs synchronize to create a functioning animal is reaching a whole new level.

Animals↗

PubMed2003

Spatiotemporal tuning of motor cortical neurons for hand position and velocity.

A pursuit-tracking task (PTT) and multielectrode recordings were used to investigate the spatiotemporal encoding of hand position and velocity in primate primary motor cortex (MI). Continuous tracking of a randomly moving visual stimulus provided a broad sample of velocity and position space, reduced statistical dependencies between kinematic variables, and minimized the nonstationarities that are found in typical "step-tracking" tasks. These statistical features permitted the application of signal-processing and information-theoretic tools for the analysis of neural encoding. The multielectrode method allowed for the comparison of tuning functions among simultaneously recorded cells. During tracking, MI neurons showed heterogeneity of position and velocity coding, with markedly different temporal dynamics for each. Velocity-tuned neurons were approximately sinusoidally tuned for direction, with linear speed scaling; other cells showed sinusoidal tuning for position, with linear scaling by distance. Velocity encoding led behavior by about 100 ms for most cells, whereas position tuning was more broadly distributed, with leads and lags suggestive of both feedforward and feedback coding. Individual cells encoded velocity and position weakly, with comparable amounts of information about each. Linear regression methods confirmed that random, 2-D hand trajectories can be reconstructed from the firing of small ensembles of randomly selected neurons (3-19 cells) within the MI arm area. These findings demonstrate that MI carries information about evolving hand trajectory during visually guided pursuit tracking, including information about arm position both during and after its specification. However, the reconstruction methods used here capture only the low-frequency components of movement during the PTT. Hand motion signals appear to be represented as a distributed code in which diverse information about position and velocity is available within small regions of MI.

Action Potentials↗

PubMed2006

Efficient tracking of non-iron-labeled mesenchymal stem cells with serial MRI in chronic stroke rats.

BACKGROUND AND PURPOSE: Although stem cell-based treatments for neurodegenerative diseases have advanced rapidly, there is currently no clinically available method to monitor the fate of transplanted cells in the brain. METHODS: To use magnetic resonance imaging for tracking transplanted stem cells in the ischemic rat brain, we used the cellular labeling substance Effectene to transfect a standard contrast agent (Gd-DTPA) into immortalized human bone marrow stromal cells. RESULTS: The transfection efficiency of this method was up to 90%, which is substantially better than pure spontaneous endocytosis or other transfection agents. In addition, cellular uptake of Gd-DTPA in vitro was maintained for >28 days. Therefore, we could follow transplanted stem cell migration and homing into the penumbric area. Using double immunofluorescence, the transplanted cells were seen to differentiate into glial cells, neurons and vascular endothelial cells. Cortical neurochemical activity as evaluated by proton magnetic resonance spectroscopy ((1)H-MRS) also increased considerably after immortalized human bone marrow stromal cell transplantation. CONCLUSIONS: This method of tracking immortalized human bone marrow stromal cells is highly efficient and allows for nontoxic labeling of cells.

Animals↗

PubMedDate not supplied

DNA damage responses in cell cycle G2 phase and mitosis--tracking and targeting.

BACKGROUND: In order to determine temporal responses of cell cycle populations to DNA damage, a rational combination of cell cycle analyses is critical. Moreover, the targeting of cell cycle checkpoint responses may modify the cytotoxic effect of DNA damage. MATERIALS AND METHODS: The characteristics of cell cycle populations (DNA content, cell cycle transitioning of S phase cells and size of mitotic cell fraction within the total G2/M phase population) in HeLa cells exposed to ionizing radiation were analyzed using three individual flow cytometry-based assays. The potential radiosensitization from inhibiting DNA damage responses was assessed by the colony formation assay. RESULTS: Irradiation resulted in an initial accumulation of S phase cells in G2 phase, from which the arrested cells were subsequently released to enter mitosis. Upon drug inhibition of G2 checkpoint signaling or mitotic progression, the cytotoxic effect of ionizing radiation on the HeLa cells was amplified. CONCLUSION: DNA damage-induced cell cycle responses, analyzed by selected cytometry assays and modified by specific targeting, might contribute to an understanding of how to improve radiotherapy outcome.

Cell Division↗

PubMed2006

Tracking individual proteins in living cells using single quantum dot imaging.

Single quantum dot imaging is a powerful approach to probe the complex dynamics of individual biomolecules in living systems. Due to their remarkable photophysical properties and relatively small size, quantum dots can be used as ultrasensitive detection probes. They make possible the study of biological processes, both in the membrane or in the cytoplasm, at a truly molecular scale and with high spatial and temporal resolutions. This chapter presents methods used for tracking single biomolecules coupled to quantum dots in living cells from labeling procedures to the analysis of the quantum dot motion.

Absorption↗

PubMed1992

Segregation of global and local motion processing in primate middle temporal visual area.

The early stages of primate visual processing appear to be divided up into several component parts so that, for example, colour, form and motion are analysed by anatomically distinct streams. We have found that further subspecialization occurs within the motion processing stream. Neurons representing two different kinds of information about visual motion are segregated in columnar fashion within the middle temporal area of the owl monkey. These columns can be distinguished by labelling with 2-deoxyglucose in response to large-field random-dot patterns. Neurons in lightly labelled interbands have receptive fields with antagonistic surrounds: the response to a centrally placed moving stimulus is suppressed by motion in the surround. Neurons in more densely labelled bands have surrounds that reinforce the centre response so that they integrate motion cues over large areas of the visual field. Interband cells carry information about local motion contrast that may be used to detect motion boundaries or to indicate retinal slip during visual tracking. Band cells encode information about global motion that might be useful for orienting the animal in its environment.

Animals↗

PubMed2002

Modeling the effects of vaccination on chronically infected HIV-positive patients.

T-cell activation plays a critical role in the initiation and propagation of HIV-1 infection and yet transient activation of the immune system is a normal response to immunization. While it is now considered wise to vaccinate HIV-1-positive patients, it is crucial to anticipate any lasting effects of vaccination on plasma HIV-1 RNA levels and on infected T-cell populations. We extend a simple dynamic model of HIV infection to include T-cell activation by vaccination. We show that the model can reproduce many but not all of the features of the post-tetanus immunization rise in viral load observed and reported on by Stanley et al. in 1966 ( 334:1222-1230). Amplitudes and approximate timing of postimmunization peak viral loads were matched in 10 of 12 cases; in patients with double postimmunization peaks of nearly equal amplitude the later peaks were matched. Furthermore, our simulations suggest that productively infected cell populations track postvaccination increases in plasma viral load, rising and falling in concert over a period of about 4 weeks, whereas chronically infected cells peak later and remain elevated over baseline levels for up to 6 weeks postvaccination.

AIDS Vaccines↗

PubMed1999

Green fluorescent protein as a selectable marker of retrovirally transduced hematopoietic progenitors.

Recombinant retroviruses are most commonly used in hematopoietic stem cell gene therapy trials, but gene transfer efficiency is still inadequate with the present vectors. One approach for overcoming this problem is to develop methods of selecting and enriching the successfully transduced cells. We investigated the feasibility of using the green fluorescent protein (GFP) gene as a selectable marker of hematopoietic cells. When M1 murine leukemia cells were electroporated with GFP expression vectors, a red-shifted mutant (S65T) GFP showed several-fold greater fluorescence than the wild-type GFP and generated readily detectable green light under control of SRalpha or CAG promoter. We then inserted an SRalpha-S65T GFP cassette into the MSCV retrovirus vector and established virus producer cells. Infection of primary murine bone marrow cells resulted in a distinct population with green fluorescence, which was separated by fluorescence-activated cell sorting. The fractionated bright cells gave rise to fluorescent spleen colonies in lethally irradiated mice, while the fluorescence-negative cells yielded only dark colonies. These results indicated that GFP is a faithful marker in gene transfer into hematopoietic progenitor/stem cells, facilitating selection of the transduced cells and tracking of their progeny in vivo.

3T3 Cells↗