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Results for “Laser Scanning Cytometry”

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PubMed1991

Antibodies to tubulin and actin bind to the surface of a human monocytic cell line, U937.

Intermittent reports of cytoskeleton proteins (actin and tubulin) on the cell surface have appeared over the last 13 years. Whereas most have concentrated on lymphocytes, this study provides evidence for the presence of these proteins on the surface of a human cultured monocyte-like cell line, U937. Both actin and tubulin were detected on the surface of U937 cells by flow cytometry, using an indirect staining procedure based on biotin-streptavidin-phycoerythrin, chosen for greater sensitivity. By use of this procedure, the majority of viable unstimulated U937 cells stained positively for actin and tubulin, although the level of fluorescence intensity was low. With an antibody specific for tyrosine-tubulin, most of the surface tubulin was also found to be tyrosinylated. For vimentin, an intermediate filament protein abundantly present in the cytoplasm of U937 cells, no staining could be detected. Confirmation of the flow cytometry data for surface actin and tubulin on unstimulated U937 cells was achieved by direct vesualization using a confocal laser scanning microscope. When U937 cells were activated with PMA and LPS, a marked reduction in the level of cell surface actin and tubulin occurred. The role of cell surface actin and tubulin on unstimulated U937 cells, in terms of monocyte function, remains to be elucidated.

Actins↗

PubMed2005

Delivery of TAT/PTD-fused proteins/peptides to islets via pancreatic duct.

Delivering cytoprotective proteins/peptides into pancreata prior to islet isolation through protein transduction (PT) is a novel strategy to enhance the yield of viable transplantable islets. Previous work has shown that the protein transduction domain PTD-5 efficiently transduced islets via the pancreatic duct. TAT/PTD is a well-characterized PTD with the capability to cross even the hemato-encephalic barrier. In this study, we investigated the utilization of the 11-aa TAT protein transduction domain (TAT/PTD) to deliver peptides or proteins of different sizes ranging from 1.2 to 120 kDa, as the TAT/PTD and TAT/PTD-BH4 peptide, or the TAT/PTD-beta-galactosidase fusion protein, into islets through the pancreatic duct. Using flow cytometry analysis we found that TAT/PTD derivatives transduced practically 100% of the islet cell population. Moreover, confocal laser scanning microscopy in live, nonfixed islets confirmed these results assessing transduction of TAT/PTD molecules into intact nondisaggregated islets. TAT-beta-galactosidase peptide conjugated to FITC was not compartment selective, as both cytoplasmic and nucleic cellular compartments were positively stained. Furthermore, TAT-beta-galactosidase peptide delivery was highly effective, as even cells located in the inner core region of the islets were transduced. Finally, transduced TAT-beta-galactosidase fusion protein was biologically active after islet isolation and manipulation, and islet insulin secretion capability was not compromised by peptide transduction. These findings suggest that the transduction of chimeric TAT/PTD proteins can represent an efficient tool of molecular delivery independent of the size, to enhance or modify a specific phenotype at the nuclei or cytoplasmic level.

Animals↗

PubMed1996

Surface annexin II on placental membranes of the fetomaternal interface.

PROBLEM: The phospholipidbinding membrane protein annexin II has been demonstrated to possess FcR activity for IgG and has been localized to the outer part of the syncytiotrophoblast cell layer. The question has arisen whether annexin II is exposed on the surface of syncytiotrophoblast cells thus enabling it to take part in the transport of IgG across the maternal barrier. METHOD: Syncytiotrophoblast microvillous plasma membranes were analyzed by flow cytometry for annexin II as well as established surface molecules. Fresh, fixed placental tissue was preincubated with antibodies to annexin II or known trophoblast surface molecules, and analyzed by confocal laser scanning microscopy. RESULTS: Annexin II and its subunit p11 were expressed on the surface of the syncytiotrophoblast microvillous plasma membranes as were other established surface proteins (CD46, CD59, placental alkaline phosphatase), using both flow cytometry and confocal microscopy. Annexin was not detected on the surface of viable cultured trophoblast cells. CONCLUSION: Annexin II is exposed on the surface of syncytiotrophoblast cells as a heterotetramer together with its light chain p11. It is exposed to maternal blood and may be instrumental in IgG transport across the placental barrier by binding.

Alkaline Phosphatase↗

PubMed1994

A method for isolating human lung macrophages and observations of fluorescent phagocytes from the lungs of habitual cigarette smokers.

We report the development of a simple, efficient, expedient, and inexpensive procedure for isolating a large and relatively pure population of macrophages (Mphi) from residual (i.e., non-tumor) lung tissue obtained from lung cancer patients undergoing either a lobectomy or pneumonectomy. The proposed technique was founded on observations by fluorescent microscopy of fresh, non-fixed, and non-stained human lung tissue. Examinations of 74 specimens from different patients revealed that most of the Mphi reside as non-adherent cells within the sponge-like lung stroma. Very few Mphi were observed in the lungs of nonsmokers. In contrast, many Mphi were visible in the lungs of habitual smokers. For most specimens from smokers, a few of the Mphi were present as randomly distributed single cells; the majority of the Mphi, however, were in clusters that ranged from a dozen to several hundred cells. The Mphi could be released readily by different mechanical techniques. In the procedure reported herein, pulmonary leukocytes (> 75% Mphi) were dislodged easily from lung tissue with the use of an inexpensive, hand-operated, tissue grinder. The grinder consisted of a glass mortar and Teflon pestle that provided sufficient clearance between the mortar and pestle so as to avert damaging the displaced leukocytes. The leukocytes were then segregated by centrifugation on a density gradient. Further purification was achieved by harvesting Mphi that had been allowed to adhere to serum-coated polystyrene culture dishes (> 90% Mphi). In most experiments, the Mphi yield (approximately 5 x 10(6) Mphi /gr of lung) and Mphi viability (> 85%) were good. A significant advantage of this technique is that it avoids jeopardizing the cells to the hazards associated with enzymes that have been used in techniques employed previously for isolating Mphi from the lung and other organs. Thus, the proposed method provides numerous lung Mphi for detailed studies of their morphology, phenotype, and function. Moreover, lung Mphi were cultured as non-adherent, single cells in a serum- and cytokine-free tissue culture medium for more than 6 weeks. Lung Mphi from habitual smokers displayed a high level of fluorescence that was readily apparent when viewed with a fluorescence microscope that had been configured with either a fluorescein or rhodamine filter. Serial sections of single, living Mphi obtained with the use of a confocal laser scanning microscope revealed that the fluorescence originated from cytoplasmic inclusions. Relative fluorescence intensity was measured by cytometry.(ABSTRACT TRUNCATED AT 400 WORDS)

Bronchoalveolar Lavage Fluid↗

PubMed2000

Feasibility study of an online toxicological sensor based on the optical waveguide technique.

Morphological properties of the cells often change as an early response to the presence of a pharmacologically acting toxic substance [Etcheverry, S.B., Crans, D.C., Keramidas, A.D., Cortizo, A.M., Arch. Biochem. Biophys. 338 (1997) 7-14]. Recently it has been shown that living animal cell adhesion and spreading can be monitored online and quantitatively via the interaction of the cells with the evanescent electromagnetic field present at the surface of an optical waveguide [Ramsden, J.J., Li, S.Y., Heinzle, E., Prinosil, J.E. Cytometry 19 (1995) 97-102]. In the present study, optical waveguide lightmode spectroscopy (OWLS) and confocal laser scanning microscopy (CLSM), which provides information about the shape of the cells at the surface, were compared under identical experimental conditions. This allowed for the correlation between the cell-shape information from CLSM and the cell-surface interaction measurements from OWLS. The proposed design of the microsystem sensor involves the establishment of a cell layer on the surface of the waveguide and the subsequent online measurement of the morphological response of the cells to various toxic substances. In the present study, the setup was evaluated using cells from an osteoblastic MC 3T3-E1 cell line, and sodium hypochlorite was used as model toxic substance. Comparing the OWLS signal to the morphological response measured by CLSM reveals that OWLS is effective in monitoring not only cell attachment and spreading but also the cellular response to toxic compounds (i.e. by means of change in cell morphology). For the model toxin, the OWLS measurements indicate that, at concentrations above 0.01%, the cells exhibit a clearly discernable morphological effect (i.e. a decrease in average cell contact area). Thus, the potential of an on-line sensor based on OWLS to applications in toxicology, pharmacy and biocompatibility was demonstrated.

3T3 Cells↗

PubMedDate not supplied

Encystation in Acanthamoeba castellanii: development of biocide resistance.

Since the early 1960s, axenic culture and the development of procedures for the induction of encystation have made Acanthamoeba spp. superb experimental systems for studies of cell biology and differentiation. More recently, since their roles as human pathogens causing keratitis and encephalitis have become widely recognized, it has become urgent to understand the parameters that determine differentiation, as cysts are much more resistant to biocides than are the trophozoites. Viability of trophozoites of the soil amoeba Acanthamoeba castellanii (Neff), is conveniently measured by its ability to form plaques on a lawn of Escherichia coli. Use of confocal laser scanning microscopy with Calcofluor white, Congo Red or the anionic oxonol dye, DiBAC4(3) or flow cytometry with propidium iodide diacetate and fluorescein or oxonol provides more rapid assessment. For cysts, the plaque method is still the best, because dye exclusion does not necessarily indicate viability and therefore the plate count method has been used to study the sequence of development of biocide resistance during the differentiation process. After two hours, resistance to HCl was apparent. Polyhexamethylene biguanide, benzalkonium chloride, propamidine isethionate, pentamidine isethionate, dibromopropamine isethionate, and H2O2 and moist heat, all lost effectiveness at between 14 and 24 h after trophozoites were inoculated into encystation media. Chlorhexidine diacetate resistance was observed at between 24 and 36 h. The molecular biology and biochemistry of the modifications that underlie these changes are now being investigated.

Acanthamoeba↗

PubMed2004

[Regulation of growth inhibition by transforming growth factor beta1 in rhabdomyosarcoma RD cell line].

OBJECTIVE: To study the regulatory effect of TGF-beta1 on growth of rhabdomyosarcoma RD cell line. METHODS: After various durations of TGF-beta1 treatment, the viability of RD cell line was examined by growth rate measurement, MTT assay and (3)H-thymidine incorporation. The cell cycle was analyzed by flow cytometry. Immunofluorescent staining was used to localize p15, p21 and p27 in RD cell line under laser scanning confocal microscope. The protein and mRNA of p15, p21 and p27 in RD cell line were detected by western blot and reverse transcriptase-polymerase chain reaction respectively. RESULTS: The viability of RD cell line treated with TGF-beta1 was obviously decreased. RD cell line was arrested in G(1) phase by TGF-beta1. There was increased expression of p21 and p27 in RD cell line with TGF-beta1 treatment at protein and mRNA levels. The expression of p21 in RD cell line was seen in both nucleus and cytoplasm after 24 hours of TGF-beta1 treatment. The expression of p15 showed no obvious changes upon TGF-beta1 treatment. CONCLUSIONS: TGF-beta1 inhibits growth of RD cell line and induces G(1)-arrest. It up-regulates protein and mRNA of p21 and p27 and shows no obvious influence on p15 expression. The growth arrest of RD cell line may result from the up-regulation of p21 and p27 by TGF-beta1.

Cell Line, Tumor↗

PubMed2002

Imaging technique implemented in CellTracks system.

BACKGROUND: We developed the CellTracks cell analysis system that, similar to flow cytometry, yields multiparameter information by which the cells can be differentiated. We describe the implementation of a laser scanning imaging method in the system. Image analysis of the cells improves the specificity of cell classification, especially in cases where the particular cells are found relatively infrequently and one has to discriminate between artifacts and real events. METHODS: Fluorescent images of immunomagnetically labeled and aligned cells are obtained by passing the cells through a laser focus. The laser focus is smaller than the objects and subsequent frames captured by a regular surveillance CCD camera with a frame grabber board represent different parts of the cells. Complete images of the cells are constructed by shifting each image with respect to each other and adding individual pixel values. RESULTS: The power of combining a fluorescent image with multiparametric data is demonstrated by imaging fluorescent and magnetically labeled beads and cells. The image gives additional information about the dye distribution across the objects. Changes in dye distribution as a function of time were observed in leukocytes labeled with the red fluorescent label, Oxazine750, which are imaged at different time intervals. CONCLUSIONS: An imaging technique implemented in the CellTracks system provides high-resolution fluorescent images of events previously identified by the system. The images of the fluorescent cells enhance the ability to classify rare events.

Blood Cells↗

PubMed2004

A rare-cell detector for cancer.

Although a reliable method for detection of cancer cells in blood would be an important tool for diagnosis and monitoring of solid tumors in early stages, current technologies cannot reliably detect the extremely low concentrations of these rare cells. The preferred method of detection, automated digital microscopy (ADM), is too slow to scan the large substrate areas. Here we report an approach that uses fiber-optic array scanning technology (FAST), which applies laser-printing techniques to the rare-cell detection problem. With FAST cytometry, laser-printing optics are used to excite 300,000 cells per sec, and emission is collected in an extremely wide field of view, enabling a 500-fold speed-up over ADM with comparable sensitivity and superior specificity. The combination of FAST enrichment and ADM imaging has the performance required for reliable detection of early-stage cancer in blood.

Biomarkers, Tumor↗

PubMed2005

[Inhibition effects of par-4 antisense oligodeoxynucleotide on apoptosis of PC12 cell induced by glutamate is mediated by ERK1/2].

OBJECTIVE: To investigate the inhibition effects of par-4 antisense oligodeoxynucleotide on apoptosis of PC12 cell induced by glutamate and its signal transduction mechanism. METHODS: (1) Cationic lipid-mediated par-4 antisense oligodeoxynucleotide (Par-4-AS-ODN) was transfected into PC12 cells before they were treated with glutamate. Mismatch oligodeoxynucleotide (MS-ODN) were also transfected into cells as controls. (2) Morphological observation and the detection of anti-apoptosis effects of par-4-AS-ODN on PC12 cells were done with the Laser Scanning confocal Microscope by double staining the cells with acridine orange/ethidium bromide (AO/EB), addition to with flow cytometry. (3) Western blot was used to detect the protein levels of par-4 and phosphorylated ERK(1/2) at threonine-202 and Tyrosine-204. RESULTS: (1) Par-4-AS-ODN significantly suppressed up-regulation of the par-4 protein levels induced by glutamate in PC12 cells. (2) Par-4-AS-ODN could resist the decrease of phosphorylated ERK(1/2) (Thr202/Tyr204) induced by glutamate in PC12 cells. (3) Par-4 AS-ODN could inhibit apoptosis of PC12 cells induced by glutamate. But its inhibition effect could be eliminated by PD98059, a selective MEK(1) inhibitor which could inhibit phosphorylation of ERK(1/2). CONCLUSION: Par-4 AS-ODN may inhibit apoptosis of PC12 cells induced by glutamate, and its inhibition effects may be medicated by the activation of ERK(1/2).

Animals↗

PubMed2005

[The cloning of human Smac gene and its pro-apoptotic effect on Burkitt's lymphoma cells].

OBJECTIVE: Second mitochondria-derived activator of caspase (Smac) is a recently identified, novel pro-apoptotic molecule, which is released from mitochondria into the cytosol during apoptosis. Smac promotes activation of caspases by neutralizing members of the inhibitor of apoptosis proteins (IAPs) family, such as X-linked inhibitor of apoptosis protein (XIAP). The objective of the study was to examine the pro-apoptotic effect of human Smac gene on Burkitt's lymphoma Raji cells. METHODS: The full length cDNA of human Smac gene was amplified by reverse transcription-PCR from total RNA of HEK-293 cells. The PCR product was ligated with linearized vector pGEM-T-easy supplied in the TA cloning kit and sequenced. The correct cDNA of full length Smac was subcloned into eukaryocytic expression vector pcDNA3.1/myc-his and transfected into human Burkitt's lymphoma cell line Raji by lipofectamine-mediated transfection. The expression of full length Smac was determined by Western blot. Morphological observation was done with the laser scanning confocal microscope by double staining the Raji cells with Hoechest 33,258 and propidium iodide. Flow cytometry was used to evaluate apoptosis. Relative caspase-3 activity was determined by colorimetric assay. RESULTS: Recombinant eukaryocytic expression vector pcDNA3.1/Smac, which contained full length Smac, was successfully constructed. After pcDNA 3.1/Smac was transfected into human Burkitt's lymphoma Raji cell line for 24 hours, Raji cells showed apparent apoptosis with a percentage of (43.7 +/- 2.5)%, which was higher than that of non-transfected group and free vector-transfected group (P < 0.05). Compared with non-transfected group (0.136 +/- 0.036) and free vector-transfected group (0.138 +/- 0.026), the relative caspase-3 activity of Raji cells transfected by pcDNA3.1/Smac (0.936 +/- 0.041) was significantly enhanced (P < 0.05). CONCLUSION: Transfection and expression of human Smac gene could significantly induce apoptosis of human Burkitt's lymphoma Raji cells. The mechanism is associated with the increase of caspase-3 activity.

Apoptosis↗

PubMed2006

[Changes of reactive oxygen species in mitochondria of retinal endothelial cells and pericytes induced by high glucose].

OBJECTIVE: To study changes of reactive oxygen species (ROS) in mitochondria of bovine retinal endothelial cells and pericytes cultured in high-glucose and its relevance with the pathogenesis of diabetic retinopathy. METHODS: Bovine retinal endothelial cells and pericytes were cultured with selective culture media. ROS changes in mitochondria of retinal endothelial cells and pericytes in response to different concentrations of glucose were detected with scanning laser confocal microscope. The mitochondria membrane potential (MMP) and cell death ratio (CDR) were measured with flow cytometry. Expression of MnSOD and uncoupling protein (UCP) were detected with reverse-transcriptase PCR (RT-PCR). RESULTS: In high-glucose, increased ROS was seen in mitochondria of retinal endothelial cells and pericytes. However MMP and CDR only increased in endothelial cells, no change was found in pericytes. UCP1, 2 mRNA expressed in cultured cells whereas UCP3 was negative. The expression of UCP1, 2, MnSOD mRNA changed with the variation of glucose concentrations. CONCLUSIONS: Increasing of ROS production in mitochondria of retinal endothelial cells and pericytes can be induced by high glucose. There is feedback accommodation mechanism between ROS increasing and MMP elevation in endothelial cells. The different features of endothelial cells and pericytes in high glucose demonstrate their roles in pathogenesis of diabetic retinopathy are different.

Animals↗

PubMed2002

Tubuloside B from Cistanche salsa rescues the PC12 neuronal cells from 1-methyl-4-phenylpyridinium ion-induced apoptosis and oxidative stress.

The neuroprotective effects of tubuloside B, one of the phenylethanoids isolated from the Chinese herbal medicine Cistanche salsa, on 1-methyl-4-phenylpyridinium ion (MPP +)-induced apoptosis and oxidative stress in PC12 neuronal cells were investigated. PC12 cells treated with MPP + underwent apoptotic death as determined by MTT assay, flow cytometry and DNA agarose gel electrophoresis; intracellular accumulation of reactive oxygen species (ROS) was measured by DCFH-DA staining with laser scanning confocal microscopy (LSCM). Simultaneous treatment with tubuloside B markedly attenuated MPP +-induced cytotoxicity, DNA fragmentation, and intracellular accumulation of ROS. These results strongly indicate that tubuloside B prevents MPP +-induced apoptosis and oxidative stress. Tubuloside B may be applied as an antiparkinsonian agent.

1-Methyl-4-phenylpyridinium↗

PubMed2001

Statistical evaluation of confocal microscopy images.

BACKGROUND: The coefficient of variation (CV) is defined as the standard deviation (sigma) of the fluorescent intensity of a population of beads or pixels expressed as a proportion or percentage of the mean (mu) intensity (CV = sigma/mu). The field of flow cytometry has used the CV of a population of bead intensities to determine if the flow cytometer is aligned correctly and performing properly. In a similar manner, the analysis of CV has been applied to the confocal laser scanning microscope (CLSM) to determine machine performance and sensitivity. METHODS: Instead of measuring 10,000 beads using a flow cytometer and determining the CV of this distribution of intensities, thousands of pixels are measured from within one homogeneous Spherotech 10-microm bead. Similar to a typical flow cytometry population that consists of 10,000 beads, a CLSM scanned image consists of a distribution of pixel intensities representing a population of approximately 100,000 pixels. In order to perform this test properly, it is important to have a population of homogeneous particles. A biological particle usually has heterogeneous pixel intensities that correspond to the details in the biological image and thus shows more variability as a test particle. RESULTS: The bead CV consisting of a population of pixel intensities is dependent on a number of machine variables that include frame averaging, photomultiplier tube (PMT) voltage, PMT noise, and laser power. The relationship among these variables suggests that the machine should be operated with lower PMT values in order to generate superior image quality. If this cannot be achieved, frame averaging will be necessary to reduce the CV and improve image quality. There is more image noise at higher PMT settings, making it is necessary to average more frames to reduce the CV values and improve image quality. The sensitivity of a system is related to system noise, laser light efficiency, and proper system alignment. It is possible to compare different systems for system performance and sensitivity if the laser power is maintained at a constant value. Using this bead CV test, 1 mW of 488 nm laser light measured on the scan head yielded a CV value of 4% with a Leica TCS-SP1 (75-mW argon-krypton laser) and a CV value of 1.3% with a Zeiss 510 (25-mW argon laser). A biological particle shows the same relationship between laser power, averaging, PMT voltage, and CV as do the beads. However, because the biological particle has heterogeneous pixel intensities, there is more particle variability, which does not make as useful as a test particle. CONCLUSIONS: This CV analysis of a 10-microm Spherotech fluorescent bead can help determine the sensitivity in a confocal microscope and the system performance. The relationship among the factors that influence image quality is explained from a statistical endpoint. The data obtained from this test provides a systematic method of reducing noise and increasing image clarity. Many components of a CLSM, including laser power, laser stability, PMT functionality, and alignment, influence the CV and determine if the equipment is performing properly. Preliminary results have shown that the bead CV can be used to compare different confocal microscopy systems with regard to performance and sensitivity. The test appears to be analogous to CV tests made on the flow cytometer to assess instrument performance and sensitivity. Published 2001 Wiley-Liss, Inc.

Calibration↗

PubMedDate not supplied

Cyanine-labeling reagents: sulfobenzindocyanine succinimidyl esters.

A synthetic method for shifting the absorption and emission wavelengths of cyanine dye labels by 15-30 nm to the red has been developed. This step significantly increases the potential for preparing fluorescent probes for multiparameter analysis in cytometry and diagnostics. The new sulfobenzindocyanine dyes contain succinimidyl esters as reactive groups and can be readily conjugated to antibodies, avidin, modified DNA, and other amino group-containing materials. The labeling reagents are water soluble, and their fluorescence is not sensitive to pH. One of the reagents, Cy3.205, can be optimally excited with the 568 nm Kr laser line and is useful for confocal microscopy and flow cytometry. Another dye, Cy5.205, can be excited with the 633 He-Ne or 647 nm Kr laser lines available with many flow cytometers and laser-scanning microscopes. New laser diodes emitting near 660-690 nm should also be excellent excitation sources for Cy5.205.

Animals↗

PubMed1997

Theoretical and practical considerations for the measurement of P-glycoprotein function in acute myeloid leukemia.

This paper summarizes experimental data and theoretical considerations, that are important for the measurement of P-glycoprotein (Pgp) function in acute myeloid leukemia (AML). The data are presented in subdivisions based on the techniques used, which will facilitate finding specific information. Based on our extensive experience with Pgp analysis, which includes radioactive assays, flow cytometry and fluorescence microscopy, we recommend a flow cytometry-based assay, that measures the effect of 2 microM PSC 833 on rhodamine 123 (R123) accumulation as the most practical and sensitive functional Pgp test. In combination with the flow cytometric measurement of Pgp using an antibody against an extracellular epitope (eg MRK16), this offers a sensitive and reproducible method for Pgp detection in AML, which is also rapid and practical. Furthermore, an R123 accumulation assay is specific for Pgp, because R123 is transported much less efficiently by the multidrug resistance protein (MRP) than by Pgp. Another probe of similar sensitivity and specificity is 3,3'-diethyloxacarbocyanine iodide. Alternatively, especially for the analysis of small numbers of cells (for example sorted subpopulations of leukemic cells), convenient and sensitive procedures are being developed by using DNA-binding Pgp substrates which remain fixed in the nuclei of the cells upon formaldehyde exposure for quantitative fluorescence laser scanning microscopy with image analysis. Less experimental data have been published to establish the optimal conditions for dual parameter flow cytometry (Pgp function, in eg Pgp+ or CD34+ cells). However, laboratories with flow cytometry experience will be able to implement this useful option to analyze subpopulations of cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2005

Colonization of tomato root seedling by Pseudomonas fluorescens 92 rkG5: spatio-temporal dynamics, localization, organization, viability, and culturability.

The localization, viability, and culturability of Pseudomonas fluorescens 92 rkG5 were analyzed on three morphological root zones (root tip + elongation, root hair, and collar) of 3-, 5-, and 7-day-old tomato plants. Qualitative information about the localization and viability was collected by confocal laser scanning microscopy. Quantitative data concerning the distribution, viability, and culturability were obtained through combined dilution plating and flow cytometry. Colonization by P. fluorescens affected root development in a complex way, causing a general increase in the length of the collar and early stimulation of the primary root growth (3rd day), followed by a reduction in length (7th day). The three root zones showed different distribution, organization, and viability of the bacterial cells, but the distribution pattern within each zone did not change with time. Root tips were always devoid of bacteria, whereas with increasing distance from the apex, microcolonies or strings of cells became more and more prominent. Viability was high in the elongation zone, but it declined in the older parts of the roots. The so-called viable but not culturable cells were observed on the root, and their proportion in the distal (root tip + elongation) zone dramatically increased with time. These results suggest the existence of a specific temporal and spatial pattern of root colonization, related to cell viability and culturability, expressed by the plant-beneficial strain P. fluorescens 92 rkG5.

Culture Media↗

PubMed1979

Slit-scan flow cytometry of mammalian chromosomes.

A flow cytometer has been constructed which measures total fluorescence and the distribution of fluorescence along isolated, stained mammalian chromosomes. In this device, chromosomes flow lengthwise at 4 m/sec through a 1-micrometer thick laser beam. The fluorescence from each chromosome is recorded at 10 nsec intervals; the sequence of recorded values represents the distribution of fluorescence along the chromosome and is stored in the memory of a waveform recorder. The total fluorescence of each chromosome is also measured and recorded. Preliminary studies show that doublets of 1.83 micrometers diameter microspheres flow with their long axes parallel to the direction of flow and that the two microspheres are resolved in the slit-scan profile. Ethidium bromide stained Muntjac and Chinese hamster chromosomes have also been slit-scanned. Centromeres were resolved in many of the Nos. 1 and 2 Chinese hamster chromosomes and the Nos. 1 and X + 3 Muntjac chromosomes.

Animals↗