Loss of division potential in vitro: aging or differentiation?

We have examined the hypothesis that diploid cells grown in vitro age, and propose that only proliferative potential and not life-span is telescoped. We suggest that explanted or transplanted diploid cells are driven to divide by the process of subculturing in vitro or in vivo and, in response to this pressure, also complete their differentiation and become refractory to further mitotic stimulation. We conclude that differentiation rather than "mortality" distinguishes diploid from transformed cells and that the former may not age in vitro, but are lost because culture methods are selective for cycling cells.

Measuring the wavelength-dependent divergence of transmission through sub-wavelength hole-arrays by spectral imaging.

We present a study on the far-field patterns of light transmitted through sub-wavelength metallic hole-arrays. Spectral imaging measurements are used here on hole arrays for the first time. It provides both spatial and spectral information of the transmission in far-field. The visibility of the images, measured in two illumination modes: Köhler and collimated, is calculated for different planes in and out of focus. The transmission under collimated illumination reveals that 75% of the beam if non-divergent. The results are in agreement with the low divergence measured by Lezec [Science 297, 820 (2002)].

Proof without prejudice: use of the Kolmogorov-Smirnov test for the analysis of histograms from flow systems and other sources.

In this paper the Kolmogorov-Smirnov statistical test for the analysis of histograms is presented. The test is discussed for both the two-sample case (comparing fn1(X) to fn2 (X)) and the one-sample case (comparing fn1 (X) to f(X)). Presentation of the specific algorithmic steps involved is done through development of an example where the data are from an experiment discussed elsewhere in this issue. It is shown that the two histograms examined come from two different parent populations at the 99.9% confidence level.

The automated classification of mitotic phase for human chromosome spreads.

A system has been developed that automatically recognizes the mitotic phase of human chromosome spreads for karyotyping. Suitable spreads are classified into one of five subphases of mitosis. Classification is performed on the basis of summed chromosome length and most probable chromosome width. Classification requires 100-500 msec. A television camera scans the spread through microscope optics; computer and special purpose electronics process the video signals to generate run length histograms. The histograms are used to determine mitotic phase. Unbanded spreads, 133, were classified with a 4.5% error rate. One hundred banded spreads were classified with a 15% error rate.

An immunocytochemical approach to cell kinetics automation.

Antibodies specific for 5-bromodeoxyuridine (BrdUrd) can be used to measure labeling indices in an automated system by image analysis. The antibody, used with an indirect immunoperoxidase technique, will detect de novo DNA synthesis subsequent to growing the cells for various time intervals in 5-bromodeoxyuridine-containing medium. Asynchronously growing CHO cells were pulsed with 3H-5-bromodeoxyuridine, fixed, denatured and then stained with anti-bromouridine antiserum. Peroxidase-coupled goat anti-rabbit IgG was used as the secondary antibody, and slides were stained with diaminobenzidine. Cells which are positive display a reticular pattern indicative of replicating chromatin. "Labeling indices" were generated by scanning the nuclei by TV image analysis. The percentage of labeled cells by the immunocytochemical technique correlates well with that found by autoradiography. Some of the applications of this automated method include cell kinetics and analysis of S-phase by pattern recognition technique.

A technique for multiple-cell chromosome karyotyping.

A new approach to a system for chromosome karyotyping is presented. The system assembles the information about chromosomes from several cells at a time, thereby filtering out noise due to variations in the slide preparations. The system makes i possible to use metaphase spreads which are incomplete due to missing chromosomes, touching and overlapping chromosomes and stain particles. The system gives a precise description of the chromosome complement in terms of distribution function parameters, with the uncertainty of the parameters specificed. The system is adaptive with respect to the initial reference parameter set so that both recognition of normal chromosomes, in spite of the variation displayed among individuals, and identification of aberrant chromosomes are possible. The precise chromosome descriptors can be used to detect differences between the tested individual and various references, in order to find chromosomal abnormalities.

Transformation of nuclear morphology during cellular maturation.

Using in vivo labeling of mouse leukocytes with tritiated thymidine, cells in the neutrophilic series were studied to determine the change in their nuclear shape as a function of maturation level. Several morphologic shape parameters including perimeter and bending energy were used to quantify the distribution of the nuclear morphology in a given age cohort. The change in these distributions as a function of calender age level was determined. The two parameters named above were used to test the possibility of inferring the age from the quantitative morphology.

Automatic detection and localization of sister chromatid exchanges.

Sister chromatids of human metaphase chromsomes from cells which have replicated twice in medium containing 5-bromodeoxyuridine exhibit unequal fluorescence when stained with the dye 33258 Hoechst. Sister chromatid exchanges occurring in these chromosomes are apparent as interchanges of brightly and dully fluorescing chromatids. A technique for detecting such exchanges by computer analysis of chromsome images has been developed and found to campare favorably with manual methods. The exchanges have been localized in the context of quinacrine banding patterns.

3D restoration with multiple images acquired by a modified conventional microscope.

A problem in high magnification microscopy is the blurring in the imaging of an object. In this article, we demonstrate a restoration technique that simultaneously makes use of the confocal image and the wide-field image. These images can be acquired by a modified conventional microscope. In front of the light-source, there is an array of pinholes. There are no pinholes at the detection plane. Instead, one or more pixels from the CCD camera are used, where the pinholes would have been. Using all pixels gives the wide-field image, but using a selected subset can give a confocal image. The array is used to speed up the process of acquiring the image. Note that the speed of acquisition is proportional to the number of pinholes. We show that the restoration from the two images can lead to a better result than using only one of the images. If this is the case, we show that a distance of 5 times the diameter of the pinholes can give the same results as a distance of 20 times after deconvolution. This offers an increase in acquisition time of a factor 16.

An analysis technique for biological shape-III.

The motivation for a syntactic theory of shape was a belief that computer shape analysis could mimic human recognition procedures. The results described here suggest that heuristic techniques can be used to decompose and analyze complex objects. The derived decomposition algorithm gives quite good results when compared with human lobe determinations. In addition, it seems to follow closely the actual procedures used by observers in classifying shapes. The list structure output of the program clearly describes each shape element and greatly facilitates further analysis. Extensions of this work should be directed toward the development of more specific "rules" for shape decomposition, and more complete orientation information in the output list structure.

An analysis technique for biological shape-II.

A discrete function representing the curvature of closed contours has been derived. The function is easily computable and has properties desirable for use in shape analysis. Two curvature measures (as well as the traditional P2A) have then been applied to a set of shapes extracted from leukocyte nuclei in order to evaluate their effectiveness as numeric descriptors of shape complexity. Bending energy, (BEN), was shown to be, on the average, the most sensitive indicator of complex shape, normalized mean absolute curvature (NMAC) was next, and P2A was last. Bending energy could also have important biolgical significance due to its possible relation to developmental processes. Further studies on bending energy will be necessary in order to substantiate this possibility. Many of the discrepancies between P2A, NMAC, BEN, and the study subjects are explainable by the lack of "syntactic", or form, information used by the computer features. If an observer really classifies an object by decomposing it into simpler pieces, then a more sophisticated shape analysis procedure must be used. Such a procedure will be described in a sequel to this paper.

3D base: a geometrical data base system for the analysis and visualisation of 3D-shapes obtained from parallel serial sections including three different geometrical representations.

In this paper we discuss a geometrical data base that includes three different geometrical representations of one and the same reconstructed 3D shape: the contour-pile, the voxel enumeration, and the triangulation of a surface. The data base is tailored for 3D shapes obtained from plan-parallel serial sections. It is explained how this geometrical data base is useful with the different processing approaches of a 3D shape, such as analysis and visualisation. Methods of conversion between the geometrical representations are discussed. Examples of the operation of the data base as it is embedded in a data base management system are given by illustrations of retrieval of geometrical information.

Characterizing the three-dimensional organization of telomeres.

BACKGROUND: Quantitative analysis can be used in combination with fluorescence microscopy. Although the human eye is able to obtain good qualitative results, when analyzing the spatial organization of telomeres in interphase nuclei, there is a need for quantitative results based on image analysis. METHODS: We developed a tool for analyzing three-dimensional images of telomeres stained by fluorescence in situ hybridization in interphase nuclei with DNA counterstained with 4',6-diamidino-2-phenylindole. After deconvolution of the image, we segmented individual telomeres. From the location of the telomeres we derived a distribution parameter rhoT, which indicated whether the telomeres were in a disk (rhoT >> 1) or not (rhoT approximately 1). We sorted mouse lymphocyte nuclei and measured rhoT. We also performed a bromodeoxyuridine synchronous cell sorting experiment on live cells and measured rhoT at several instances. RESULTS: Measuring rhoT for nuclei in G0/G1, S, and G2 produced 1.4 +/- 0.1, 1.5 +/- 0.2, and 14 +/- 2, respectively, showing a significant difference between G2 and G0/G1 or S. For the bromodeoxyuridine synchronous cell sorting experiment, we found a cell cycle dependency of rhoT and a correlation between rhoT and an observer. CONCLUSIONS: In this study we present a quantitative method to characterize the organization of telomeres using three-dimensional imaging, image processing, and image analysis.

Sampling density and quantitative microscopy.

The sampling densities required for the quantitative analysis of digitized microscope images is discussed. It is shown that the Nyquist sampling theorem is not the proper reference point for determining the sampling density when the goal is measurement, although it may be a proper reference point when the goal is image filtering and reconstruction. The problems associated with signal truncation--the use of a finite amount of data--and the finite amount of time available for computation make it impossible to reconstruct an arbitrary image, even if it is bandlimited. Two examples taken from straightforward measurement problems exhibit the fundamental problems associated with the measurement of analog quantities from digital data and the role played by the sampling density.

Shading correction: compensation for illumination and sensor inhomogeneities.

The interaction between objects in real space, the illumination, and the camera frequently leads to a situation in which a microscope image exhibits significant shading across the field of view. In general this shading effect is undesirable and requires elimination, especially for quantitative microscopy. Starting with a simple mathematical model, this unit develops procedures to correct images for the shading thus introduced in the image-formation process. Two cases are distinguished: the a priori, which assumes the availability of calibration images in addition to the images of interest; and the a posteriori, which assumes that only the recorded images of interest are available.