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Biomedical subjects

B Palcic

Publications and source records attributed to B Palcic.

At least 73 records · Page 4Linked to original sources
PubMed1990

Effect of focus on cell detection and recognition by the Cell Analyzer.

The effect of defocusing on the quality of signals from live cells detected by an automated image cytometry device, the Cell Analyzer, was examined. The influence of these effects on the ability of this device to automatically locate cells plated into a tissue culture flask was then determined by measuring the performance of cell detection and recognition procedures as a function of focus setting. Acceptable limits for deviation from the optimal focus setting (as determined by microscope objective position) were found to be similar for both these procedures, ranging from 40 microns below to 25 microns above the optimal focus position. These limits were asymmetrical about ideal focus due to a pronounced asymmetry in the effects of positive and negative defocusing on the cell signal.

Animals↗
PubMed1990

The effect of retinoids, carotenoids and phenolics on chromosomal instability of bovine papillomavirus DNA-carrying cells.

Antioxidants were found to protect against the genotoxic effects of chemical and physical mutagenic and clastogenic agents. This study focused on the capacity of antioxidants to reduce an intrinsic and persistent chromosome instability. As a model system, strains of C127 cells, which were transformed by bovine papillomavirus (BPV) DNA and which carry BPV DNA varying from 20 to 160 copies, were used. Transformed cells of 10 different strains showed a persistently high incidence of mitotic irregularities detectable at anaphase and telophase (27.3-58.9%), an elevated frequency of cells with micronuclei (6.6-34.7%), and a broad spectrum of nuclear sizes, as measured by image analysis. A 3-day exposure to retinoic acid, retinol, beta-carotene, canthaxanthin, ascorbic acid and ellagic acid greatly reduced the degree of chromosome instability, whereas catechin, eugenol and pyrogallol showed a smaller inhibitory effect, and curcumin had no detectable effect on the frequency of mitotic irregularities. After withdrawal of retinoic acid treatment, the high levels of chromosome instability reappeared. The possibility that the protective effect of the retinoids and carotenoids examined in the model system points to their beneficial administration to human cells with an intrinsic or acquired chromosome instability is discussed.

Antioxidants↗
PubMed1990

The effects of low density lipoproteins on uptake of Photofrin II.

The cellular uptake of Photofrin II (PII) was studied using fluorescence imaging and chemical extraction. The influence of serum and low density lipoproteins (LDL) was examined under a variety of experimental conditions employing cultured human cells of different origins as well as a subcutaneously SMT-F tumor implanted in mice. Results showed that serum inhibited PII uptake. In general, LDL also inhibits PII uptake with the exception of an initial increase in the first 10-30 min when the cellular concentration of PII was measured by fluorescence imaging instead of chemical extraction. Our results suggest a possible de-aggregation process occurring upon internalization or binding of PII to LDL.

Animals↗
PubMed1990

Detection of early lung cancer using low dose Photofrin II.

Fluorescence imaging using hematoporphyrin derivative (HpD) or Photofrin II as a tumor marker has been used for localization of early bronchogenic carcinoma. Wider clinical application of HpD or Photofrin II as a cancer imaging agent has been hampered by the potentially serious and prolonged skin photosensitivity. Using a sensitive fluorescence bronchoscope system with a ratio fluorometer probe, carcinoma in situ was detected in four patients with low dose Photofrin II (0.25 mg/kg) with no apparent skin phototoxicity to 30 J/cm2 visible light on skin photosensitivity test.

Aged↗
PubMed1990

Fractal texture features based on optical density surface area. Use in image analysis of cervical cells.

The spatial distribution of the optical density of an image of a cell nucleus can be imagined to resemble a rugged surface in a three-dimensional space. The area of this surface can be measured using different unit-sized squares, yielding different values for the total area depending on the unit size. A fractal dimension can be calculated from the relationship between the unit size and the overall area measured; this fractal dimension is characteristic of the surface measured. This technique was applied to extract three new nuclear features from stained cervical cells. These new features were useful for the computer discrimination of normal and premalignant cervical cells. The features are defined, and their discriminating power is compared to that of some other nuclear features.

Cell Membrane↗
PubMed1990

Quantitation of chromatin patterns by image analysis as a predictive tool in chemopreventive trials with vitamin A.

Nuclear textures of oral mucosal cells were quantitated by image analysis, and their suitability as markers in a chemopreventive trial explored. Subjects were chewers of tobacco-containing betel quids with well established oral leukoplakias. Treatment consisted of a weekly oral administration of vitamin A (200,000 IU/week) for six months. Leukoplakias regressed in 57.1% of the 21 trial participants. The original leukoplakias did not redevelop within four months after termination of treatment. For image analysis, biopsies were taken from leukoplakias of five chewers before administration of vitamin A, at the end of the administration, and four months after termination of treatment. Sections of paraffin-embedded biopsies were stained with the Feulgen reaction and submitted to quantitative image analysis of two parameters: variance of intensity and entropy. Both these parameters were significantly reduced in all five trial participants as a result of the six-month vitamin A treatment. During the post-treatment period, nuclei with condensed chromatin, as measured by the variance of intensity, reappeared in the mucosa of four of the five chewers examined, although no leukoplakias were detectable on visual examination of the oral cavity. The results indicate that the quantitation of nuclear textures in a small subpopulation of a chemopreventive trial could conceivably be a simple marker with a predictive value.

Biomarkers, Tumor↗
PubMed1990

Pharmacological modulation of human subconjunctival fibroblast behavior in vitro.

The response of human subconjunctival fibroblasts to a variety of pharmacological agents was evaluated utilizing a novel in vitro wound assay and a separate proliferation assay. Both colchicine and cytochalasin B dramatically arrested wound closure at concentrations greater than or equal to 0.01 micrograms/ml and 2 micrograms/ml, respectively (p less than 0.05). At lower doses these drugs altered fibroblast morphology and inhibited directed cell migration. Dexamethasone and 6-MP delayed wound closure at concentrations greater than or equal to 100 micrograms/ml and 1000 micrograms/ml, respectively (p less than 0.05). Effective antiproliferative agents, in order of decreasing potency (based on unit weight), were Cytarabine (cytosine arabinoside), doxorubicin (Adriamycin), colchicine, 5-fluorouracil, cytochalasin B, cyclosporin (Sandimmune), 6-mercaptopurine, and dexamethasone. The antiprotease agents and methotrexate were ineffective as determined by both assays. We conclude that the wound assay is well suited for rapid screening of drugs for their effect on fibroblast morphology, motility, and proliferation, and that colchicine and cytochalasin B, in doses well below those documented to produce ocular toxicity, are effective in inhibiting directed migration and proliferation of subconjunctival fibroblasts in vitro. Differences in mechanism, onset of action, therapeutic range, and cytotoxicity of drugs could be exploited in controlling ocular fibroblast behavior in vivo.

Antineoplastic Agents↗
PubMed1990

An edge relocation segmentation algorithm.

An automated procedure that refines the nuclear contour of a previously segmented nucleus is described. The algorithm makes use of intensity information, edge magnitude information and both object and edge connectivity information. This automated procedure generates a closed contour precisely along the edge of the nucleus. The procedure was tested on a database of 3,680 red-green-blue images of thionin-SO2 and orange II-stained cervical cells obtained from normal and dysplastic samples. When used in conjunction with a simple threshold selection algorithm and an artifact removal routine, this edge relocation algorithm resulted in the correct segmentation of over 98% of the nuclei. Only 63 (1.7%) of all nuclei were incorrectly segmented.

Algorithms↗
PubMed1989

Automated detection and recognition of live cells in tissue culture using image cytometry.

An automated image cytometry device, the Cell Analyzer, was used to locate live V79 cells plated at low densities in a tissue culture flask. Cells and other objects were detected by moving the flask in steps across a linear solid-state image sensor. The step size was selected to be small enough to allow detection of all the cells in the area being scanned but sufficiently large so that most cells would be detected on only one image line. To distinguish cells from other detected objects, a recognition algorithm utilizing 18 characteristic cell signal features was developed. The algorithm first tests whether a set of feature values falls within specified upper and lower bounds, and then applies a linear discriminant function to the remaining data to further discriminate cells from debris. False-positive errors of 5% or less were achieved with this method, whereas 15-35% of cells were misclassified as debris.

Algorithms↗
PubMed1989

The interaction of trans-DDP [PtCl2(NH3)2] with low doses of radiation in mammalian cells.

Trans-DDP, a less toxic isomer of cisplatin, was examined for its radiosensitizing activity at high and low doses of ionizing radiation. Cells were exposed to the drug to produce low toxicity before exposure to X rays. A sensitive assay using the DMIPS Cell Analyzer was employed to measure cell survival response in low dose region (0-4 Gy) and conventional assay was used for high doses (4-25 Gy). The results show that trans-DDP is a much more effective radiosensitizer at low doses than at high doses, whether or not cytotoxicity was pronounced. This is in contrast to any other sensitizer studied to date, including oxygen, misonidazole, SR-2508 and Ro-03-8799, regardless of prior incubation and/or cytotoxicity.

Animals↗
PubMed1989

Adaptive color basis transformation. An aid in image segmentation.

Multispectral images of stained cells enable the use of color differences to segment and/or to discriminate between image components, such as cell types and cellular subcomponents. When the spectral characteristics of the image components do not change over the area of a slide or from slide to slide, one can create a constant weighted linear combination of spectral images to generate one-dimensional or two-dimensional images that have the desired contrast between the image components that must be discriminated. However, when the spectral characteristics are not constant, i.e., when they vary from image to image, a constant weighted linear combination cannot be employed; instead, an appropriate solution must be found for each selected image. This is usually a time-consuming, manual procedure that cannot be employed in a fully automated process of discriminating and segmenting stained cells. This paper describes an algorithm that uses principal components decomposition basis vectors to generate a nonstatic weighted linear combination of color images that can be used by an automated system. This algorithm relies on a semiconstant relationship between the areas (sizes) of the image components that are to be discriminated and/or segmented. The technique has been successfully applied as an aid in the segmentation of images of stained cervical smears; the images were acquired with a three-chip CCD camera that generates three broad-band color images.

Algorithms↗
PubMed1989

Oxygen enhancement ratio of fractionated regimens in vitro.

The oxygen enhancement ratio (OER) of proliferating and nonproliferating cells grown in vitro was measured using accelerated fractionated regimens. Irradiations were performed either twice daily or three times per day, with a minimum of 6 h between the consecutive fractions. The dose delivered was 2.3 Gy per fraction. Two significant observations were made: (i) the OER of accelerated fractionation regimens for proliferating cells is lower than that obtained from single-exposure experiments at 2.3 Gy (approximately 1.4 vs 2.4, respectively), while for nonproliferating cells it is approximately the same (2.3); (ii) the fractionated regimen does not spare proliferating cells irradiated under hypoxic conditions, and thus the fractionated survival curve lies below the single-exposure curve. For cells irradiated under aerobic conditions or for nonproliferating cells, irradiated under either hypoxic or aerobic conditions, the fractionated survival curve lies above the single-exposure curves as expected.

Animals↗
PubMed1988

Measurement of cell motility and morphology with an automated microscope system.

A method is presented which provides quantitative descriptions of the morphology and motility behaviour of a large number of unperturbed individual cells. For that, a microscope system has been developed that performs automated tracking of motile mammalian cells in tissue culture and the concurrent measurement of cell morphology. Experiments using 3T3 mouse fibroblasts show that simple global morphological features, such as degree of cell elongation, correlate with the motile behaviour of individual cells. Combined data from many cells following trypsinization and replating show the time course of the spreading of cells, measured by increase in average cell area, and the onset of cell polarization, measured by change in average cell circularity. Methods for describing fibroblast morphology and changes in morphology are discussed.

Animals↗
PubMed1988

Imaging system for morphometric assessment of absorption or fluorescence in stained cells.

An image acquisition and processing system has been developed for quantitative microscopy of absorption or fluorescence in stained cells. Three different light transducers are used in the system to exploit the best characteristics of these sensors for different biological measurements. A digital scanner, in the form of a linear array charge-coupled device (CCD), acquires data with high spatial and photometric resolution. A color (RGB) camera is employed when spectral information is required for the segmentation of cellular subcomponents. An image-intensified charged-injection device (CID) camera provides for very low light intensity measurements, primarily for fluorescence-labeled cells. Properties of these transducers, such as contrast transfer function, linearity, and photo-response nonuniformity, have been measured. Two dedicated image processing units were incorporated into the system. The front-end processor, based on a digital signal processor, provides functions such as object detection, raw image calibration, compression, artifact removal, and filtering. The second image processor is associated with the frame memory and includes a histogram processor, a dedicated arithmetic logic unit for image processing functions, and a graphics module for one-bit overlay functions. An interactive program was developed to acquire cell images and to experiment with a range of segmentation algorithms, feature extractions, and other image processing functions. The results of any image operation are displayed on the video monitor. Once a desired processing sequence is determined, the sequence may be stored to become part of a command library and can be executed thereafter as a single instruction.

Algorithms↗
PubMed1988

A comparison of some quick and simple threshold selection methods for stained cells.

The segmentation accuracy of four fast and simple gray-scale threshold selection methods were compared using a data base of stained cervical cell images. Some postprocessing was applied to the segmented images to increase the accuracy of the nuclear segmentation. The most accurate method correctly segmented the cytoplasm of 81% of the cell images and the nuclei of 78% of the cell images in the data base.

Algorithms↗
PubMed1987

3T3 cell motility in the temperature range 33 degrees C to 39 degrees C.

The phenomena of mammalian cell motility in tissue culture is an integrated function of many cellular components. As such, cell motility is very sensitive to external stimuli and perturbation. In this article we report the effect of temperature in the range 33 degrees C to 39 degrees C on cell motility. For this 3T3 cells were plated in plastic tissue culture flasks. A large number of individual cells (60 per experiment) were tracked as a function of time by means of an automated device, the Cell Analyzer. The data show a peak in the average cell speed in the range 36.5 degrees C to 38.5 degrees C, falling off sharply at lower and higher temperatures. The average rate of cell motility closely correlates to the average cell proliferation rate in the range 33 degrees C to 39 degrees C.

Animals↗
PubMed1986

Ocular penetration, toxicity, and radiosensitization effects of two hypoxic cell radiosensitizers on retinoblastoma.

Two new radiosensitizing drugs, SR-2508 and SR-2555, were studied for their in vivo toxicity and absorption properties. For both drugs, 100 mg dissolved in 0.5 mL of normal saline resulted in the maximum acceptable level of toxicity when injected subconjunctivally in rabbit eyes as determined by ocular and histopathologic changes. SR-2508 showed higher ocular and systemic absorption than SR-2555. The radiosensitizing ability of these drugs was studied using Chinese hamster ovary cells and the retinoblastoma cell line, V79c6. Results of the in vitro radiation experiments indicate that both drugs are comparable with misonidazole in their radiosensitizing ability, with SR-2508 being slightly more effective than SR-2555. Because of their relative high ocular absorption and low toxicity in comparison with misonidazole, these two drugs, particularly SR-2508, may be of clinical value and could be considered for adjunctive use as radiosensitizers of hypoxic tumors such as retinoblastoma.

Absorption↗