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At least 109 records · Page 6Linked to original sources
PubMed1983

Leucocyte locomotion: comparison of random and directed paths using a modified time-lapse film analysis.

A semi-automated method, using a graphic digitizing tablet, for analysing the the tracks of cells taken from time-lapse film is described and illustrated with sample data. Three film sequences of neutrophil leucocytes moving on protein-coated substrata are analysed, and in one of these the cells are moving in a non-random fashion. The randomness of the tracks is tested by an objective method. Cells in the non-random (directed) sequence move faster and make smaller angled turns. No correlation between step length and turning angle could be shown for the random sequences. The method described here should make it possible to undertake visual analyses of cell locomotion with considerably less effort.

Animals↗
PubMed1985

Heavy-ion effects on mammalian cells: inactivation measurements with different cell lines.

In track segment experiments, the inactivation of different mammalian cells by heavy charged particles between helium and uranium in the energy range between 1 and 1000 MeV/u has been measured at the heavy ion accelerator Unilac, Darmstadt, the Tandem Van de Graaf, Heidelberg, and the Bevalac, Berkeley. The inactivation cross sections calculated from the final slope of the dose-effect curves are given as a function of the particle energy and the linear energy transfer.

Animals↗
PubMed1995

Tyrosine phosphorylation and cytoskeletal tension regulate the release of fibroblast adhesions.

We have investigated the mechanisms by which fibroblasts release their adhesions to the extracellular matrix substrata using a permeabilized cell system in which the adhesions remain relatively stable. A large number of different molecules were assayed for their effect on focal adhesion stability using immunofluorescence with antibodies against different focal adhesion constituents. ATP uniquely stimulates a rapid breakdown of focal adhesions, and at high ATP concentrations (> 5 mM), many cells are released from the dish. The remaining cells appear contracted with talin, alpha-actinin, and vinculin localized diffusely throughout the cell. Integrin containing tracks of variable intensity outline the regions where cells had resided before they detached from the substratum. At lower ATP concentrations (0.5-5 mM) the cells remain spread; however the focal adhesion components, including integrin, show an array of phenotypes ranging from diffusely localized throughout the cell to a localization in small, thin focal adhesions. Okadaic acid, a serine, threonine phosphatase inhibitor, enhances the contracted phenotype, even at low concentrations (0.5 mM) of ATP. The localization of focal adhesion components is different in okadaic acid-treated cells. In highly contracted cells, integrin is present in tracks where the cells resided before the contraction; however focal adhesions are no longer apparent. Talin, vinculin, and alpha-actinin localize in trabecular networks toward the periphery of the cell. Interestingly, phosphotyrosine staining as well as nascent, intracellular integrin precedes the recruitment of focal adhesion constituents into the trabecular network. The ATP-stimulated focal adhesion breakdown appears to operate through two mechanisms. First, ATP stimulates the tyrosine phosphorylation of several cytoskeletally associated proteins. These tyrosine phosphorylations correlated well with focal adhesion breakdown. Furthermore, addition of a recombinant, constitutively active tyrosine phosphatase inhibits both the tyrosine phosphorylations and the breakdown of the focal adhesions. None of the major tyrosine phosphoproteins are FAK, integrin, tensin, paxillin, or other phosphoproteins implicated in focal adhesion assembly. The second mechanism is cell contraction. High ATP concentrations, or lower ATP concentrations in the presence of okadaic acid induce cell contraction. Inhibiting the contraction by addition of a heptapeptide IRICRKG, which blocks the actin-myosin interaction, also inhibits focal adhesion breakdown. Neither the peptide nor the phosphatase inhibits focal adhesion breakdown under all conditions suggesting that both tension and tyrosine phosphorylations mediate the release of adhesions.

Adenosine Triphosphate↗
PubMed1978

Pathological findings in four cases of human angiostrongyliasis.

Three adults and a 3 1/2-year-old child presented with eosinophilic meningitis. A history of consumption of raw snails was elicited in 2; evidence of a constant diet of raw food, in the form of opisthorchiasis and taeniasis, as well as angiostrongyliasis, was present in the third; no history of raw food ingestion was obtained in the fourth, the child. Pathologic changes were similar in all 4 cases. There was infiltration of the meninges and around intracerebral vessels by varying proportions of lymphocytes, plasma cells and eosinophils. Numerous tracks and microcavities were found in the brains, and in the spinal cords in 2 cases, varying in size from 0.1 to 2 mm, and in age, with older tracks containing debris and gitter cells, newer tracks showing disruption of brain tissue, with and without haemorrhage. Numerous 4th and 5th stage Angiostrongylus larvae, alive and dead, were found in the meninges and brain tissue, sometimes in blood vessels or perivascular spaces, in 3 cases; in the fourth case a 5th stage larva was found on the surface of the right frontal lobe. In one case a degenerating larva was found in a pulmonary vessel. Cellular reaction was more often associated with dead larvae.

Adult↗
PubMed1994

Multiunit activity from the A9 and A10 areas in rats following chronic treatment with different neuroleptic drugs.

Effects of repeated twice daily i.p. administration of haloperidol (0.5 mg/kg), clozapine (3.0 mg/kg) and prothipendyl (1.0 mg/kg) on spontaneous A9 and A10 cell activity were studied using extracellular multiunit recording in rats, which offers relatively rapid access to neural activity in a large number of cells. Two cell types were identified, which probably represent the putative dopaminergic and non-dopaminergic neurons. Repeated neuroleptic treatment reduced the number of spontaneously active type 1 A10 cells per track. The effect of haloperidol was more pronounced than that of clozapine or prothipendyl. A9 cells were affected by haloperidol only. The frequency and amplitude of A9 and A10 active cells remained quite stable, except for a clozapine-induced increase of their values for type 1 A10 cells. Stability of spontaneously active type 1 A10 cells was significantly reduced by the chronic neuroleptic treatment. Collectively the activity of type 2 cells was not altered. Prothipendyl was classified as an atypical neuroleptic drug with potency comparable to clozapine.

Animals↗
PubMed1995

Regulation of the alginate biosynthesis gene algC in Pseudomonas aeruginosa during biofilm development in continuous culture.

Reporter gene technology was used to observe the regulation of the alginate biosynthesis gene, algC in a mucoid strain of Pseudomonas aeruginosa in developing and mature biofilms in continuous culture on Teflon and glass substrata. The plasmid pNZ63, carrying an algC-lacZ transcriptional fusion, was shown to not be diluted in continuous culture over a period of 25 days in the absence of selection pressure. Biofilm cells under bulk phase steady-state conditions demonstrated fluctuations in algC expression over a 16-day period, but no trend of increased or decreased expression over the time interval was indicated. In vivo detection of algC up-expression in developing biofilms was performed with a fluorogenic substrate for the plasmid-borne lacZ gene product (beta-galactosidase) by using microscopy coupled with image analysis. By this technique, cells were tracked over time and analyzed for algC activity. During the initial stages of biofilm development, cells already attached to a glass surface for at least 15 min exhibited up-expression of algC, detectable as the development of whole-cell fluorescence. However, initial cell attachment to the substratum appeared to be independent of algC promoter activity. Furthermore, cells not exhibiting algC up-expression were shown to be less capable of remaining at a glass surface under flowing conditions than were cells in which algC up-expression was detected.

Alginates↗
PubMed1984

Technetium 99m autoradiography of labelled white cells.

The cellular uptake of technetium 99m was determined on white blood cells (WBC) by autoradiography, after 'cold' tin pyrophosphate prelabelling followed by pertechnetate labelling. The autoradiographic method gave visible tracks of 99mTc internal conversion and Auger electrons. 75 +/- 5% of the treated WBC were labelled but none of the control WBC. The number and length of tracks per cell varied greatly. This was perhaps due to imaging conditions as well as to variations in cell uptake.

Autoradiography↗
PubMed1992

Behavioral responses of streamer F mutants of Dictyostelium discoideum: effects of cyclic GMP on cell motility.

Streamer F (stmF) mutants have a prolonged increase in intracellular cGMP in response to addition of the chemoattractant cAMP. The speed of movement and area of stmF cells were quantitated as the cells were stimulated with a rapid, uniform increase in extracellular cAMP. The speed of stmF cells rapidly drops as does that of the wild-type, but then requires about 300 seconds to recover. In contrast, the speed of the parental strain, XP55, recovers within 60-70 seconds. This prolonged drop in speed correlates with the time during which intracellular cGMP remains high, suggesting that intracellular cGMP induces this prolonged reduction in speed. Mutants from other streamer complementation groups do not show this altered response. Area measurements indicate that stmF cells do not cringe or round up as XP55 does, but spread with the same kinetics as XP55. Chemotactic orientation of the stmF cells in stable spatial gradients is similar to or slightly greater than that of the wild-type. Tracking of cells moving during aggregation indicates that the stmF cells show large drops in speed between pulses, resulting in the banding pattern seen in streams. The cells can still respond to new pulses, resulting in an aggregation time that is similar to that of XP55.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1991

Chronic continuous nicotine treatment causes decreased burst firing of nigral dopamine neurons in rats partially hemitransected at the meso-diencephalic junction.

Chronic continuous administration of nicotine (0.125 mg/kg/h, 14 days) to male Sprague-Dawley rats with a partial hemitransection at the meso-diencephalic junction caused a significant reduction in burst firing of remaining dopamine (DA) neurons in the zona compacta, substantia nigra, whereas neither the firing rate nor the number of spontaneously active DA cells per track were altered in comparison with saline-treated, hemitransected controls. The reduced functional activity of the remaining DA cells subjected to nicotine treatment provides a physiological correlate to the previously observed, reduced DA utilization in these neurons. It may also help to explain the increased nigral DA cell survival found after chronic nicotine treatment in similar lesion experiments.

Action Potentials↗
PubMed1993

Gene-marking to trace origin of relapse after autologous bone-marrow transplantation.

Bone marrow harvested for autologous bone-marrow transplantation may contain residual malignant cells even when it is judged to be in remission. Genetic marking and subsequent detection of these cells in recipients would give useful information about the origin of relapse after transplantation. We transferred the neomycin-resistance gene into bone-marrow cells harvested from children with acute myeloid leukaemia in remission. Two patients have relapsed since reinfusion of the marked cells. In both, the resurgent blast cells contained the neomycin-resistance gene marker; thus, remission marrow can contribute to disease recurrence. This method of tracking malignant cells should enable the development of better marrow purging strategies.

Bone Marrow Cells↗
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↗
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↗
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↗
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↗
PubMed1974

Biochemical localization of alkaline phosphatase in the cell wall of a marine pseudomonad.

The various layers of the cell envelope of marine pseudomonad B-16 (ATCC 19855) have been separated from the cells and assayed directly for alkaline phosphatase activity under conditions established previously to be optimum for maintenance of the activity of the enzyme. Under conditions known to lead to the release of the contents of the periplasmic space from the cells, over 90% of the alkaline phosphatase was released into the medium. Neither the loosely bound outer layer nor the outer double-track layer (cell wall membrane) showed significant activity. A small amount of the alkaline phosphatase activity of the cells remained associated with the mureinoplasts when the outer layers of the cell wall were removed. Upon treatment of the mureinoplasts with lysozyme, some alkaline phosphatase was released into the medium and some remained with the protoplasts formed. Cells washed and suspended in 0.5 M NaCl were lysed by treatment with 2% toluene, and 95% of the alkaline phosphatase in the cells was released into the medium. Cells washed and suspended in complete salts solution (0.3 M NaCl, 0.05 M MgSO(4), and 0.01 M KCl) or 0.05 M MgSO(4) appeared intact after treatment with toluene but lost 50 and 10%, respectively, of their alkaline phosphatase. The results suggest that the presence of Mg(2+) in the cell wall is necessary to prevent disruption of the cells by toluene and may also be required to prevent the release of alkaline phosphatase by toluene when disruption of the cells by toluene does not take place.

Alkaline Phosphatase↗