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PubMed1997

Cell proliferation as an independent predictor of survival for patients with advanced nasopharyngeal carcinoma.

Commonly used clinical and pathologic criteria are often of limited value in predicting the outcome of patients with undifferentiated nasopharyngeal carcinoma, and new parameters related to the biology of growth of neoplastic cells are still required for better definition of the aggressiveness of these tumors. The prognostic significance of DNA ploidy, measured by image cytometry on isolated cells, and of the mitotic index, proliferating cell nuclear antigen, and p53 protein, all measured by image cytometry in histologic sections, were evaluated on archival tumor tissues from 53 patients with Stage III or IV nasopharyngeal carcinomas. Patients were staged according to the criteria of the International Union Against Cancer and were irradiated according to a conventional radiotherapy schedule. No significant associations were found between biologic parameters and clinical features. Only the stage and the mitotic index were related to patient survival, and, when examined in a proportional hazard regression analysis, both provided independent information. When patients with compromised skull and/or cranial nerves (T4 tumors), who had a very short survival, were eliminated from the analysis, only the mitotic index and proliferating cell nuclear antigen allowed discrimination of a subset of patients with poor prognoses. This study shows that the assessment of cell proliferative activity can provide useful information for better predicting the clinical course of high-risk patients with nasopharyngeal carcinomas and improve therapeutic strategies.

Adolescent↗
PubMed1997

The role of deoxyribonucleic acid image cytometric and interphase cytogenetic analyses in the differential diagnosis, prognosis, and clinical follow-up of hydatidiform moles. A report from the Central Molar Registration in The Netherlands.

OBJECTIVES: To assess the value of deoxyribonucleic acid ploidy in the differential diagnosis and clinical follow-up of hydatidiform moles, the histopathologic features, deoxyribonucleic acid ploidy, and clinical follow-up were compared in 347 cases: 143 complete moles, 52 partial moles, and 152 abortions, of which 56 cases were hydropic abortions with histologic features of triploidy but lacked trophoblastic hyperplasia. STUDY DESIGN: In all cases deoxyribonucleic acid image cytometry was performed, and in 85 of these cases interphase cytogenetics was also performed. RESULTS: With use of deoxyribonucleic acid image cytometry and interphase cytogenetics, a bimodal polyploid deoxyribonucleic acid pattern was present in 97% of complete moles, 27% of partial moles, and 4% of abortions. All these cases of partial mole were reclassified to complete mole on the basis of this deoxyribonucleic acid pattern and the histopathologic features in spite of the presence of fetal blood cells, amnion, or yolk sac. Deoxyribonucleic acid triploidy was found in 95% of the remaining partial moles, in 77% of hydropic abortions with histologic features of triploidy, and in 14% of the remaining abortions. Reliable differentiation between deoxyribonucleic acid triploid partial moles and hydropic abortions with histologic features of triploidy was not possible on basis of the histopathologic features (trophoblastic hyperplasia) or 3.5c exceeding rates. Deoxyribonucleic acid diploidy was found in 1% of complete moles, 23% of hydropic abortions with features of triploidy, and 78% of the remaining abortions. Deoxyribonucleic acid tetraploidy was rarely found (1% of complete moles, 2% of partial moles, 1% of abortions). Persistent gestational trophoblastic disease developed in 33% of the bimodal deoxyribonucleic acid polyploid cases (all complete moles), in 1% of the diploid cases (concerning one of the two diploid complete moles), and in 1% of the triploid cases (partial moles). CONCLUSION: Deoxyribonucleic acid analysis is essential in the diagnosis of hydatidiform moles to decide on clinical follow-up.

Chromosome Aberrations↗
PubMed1999

Benign, preinvasive and invasive ductal breast lesions. A comparative study with quantitative techniques: morphometry, image- and flow cytometry.

The histological distinction between ductal hyperplasia of the breast, atypical ductal hyperplasia and ductal carcinoma in situ is difficult and subjective. To gain a better understanding of these lesions, we performed a comparative study comprising 20 cases of ductal hyperplasia without atypia, 20 cases of ductal hyperplasia with atypia, and 30 cases of ductal carcinoma in situ (well-, moderately- and poorly-differentiated), using quantitative techniques: image cytometry analysis, morphometry and DNA analysis, and DNA flow cytometry. Our results confirm that the mean nuclear area and volume progressively decreased from ductal carcinoma in situ to ductal hyperplasia without atypia. The difference was significant (p < 0.05) when comparing hyperplasia without atypia with hyperplasia with atypia and hyperplasia with atypia with poorly differentiated ductal carcinoma in situ. Atypical ductal hyperplasia values were comparable to those of well-differentiated ductal carcinoma in situ. DNA image cytometry proved significant (p < 0.05) when comparing hyperplasia without atypia with hyperplasia with atypia and hyperplasia with atypia with moderately- and poorly-differentiated ductal carcinoma in situ. DNA flow cytometry revealed significant differences only in the distribution of the DNA ploidy patterns (p < 0.05) when comparing hyperplasia without atypia with moderately- and poorly-differentiated DCIS. A comparison of the results obtained by image and flow cytometry showed that in 90% of the cases the IC and FC values were coincident, whereas in the remaining cases the DNA index was aneuploid by IC and diploid by FC.

Breast Neoplasms↗
PubMed2003

DNA cytometric features in biopsies of TaT1 urothelial cell cancer predict recurrence and stage progression more accurately than stage, grade, or treatment modality.

OBJECTIVES: To compare retrospectively the predictive value for recurrence and stage progression of DNA ploidy and S-phase fraction by flow cytometry and highly automated ultrafast image cytometry (ICM) in biopsies of TaT1 urothelial cell carcinomas (UCCs) of the urinary bladder with stage, grade, other pathologic features, and treatment. METHODS: Three experienced pathologists reviewed the stage and grade of 228 UCCs; 193 (85%) consensus cases were analyzed further. We had enough material for single-cell suspensions for both flow cytometry and ICM in 183 cases (94.8%). The 2001 European Society for Analytical Cellular Pathology standards for DNA ICM were followed. The predictive value of DNA features, classic prognosticators (stage, grade, carcinoma in situ, multicentricity), and treatment modality for recurrence and stage progression were analyzed with univariate (Kaplan-Meier) survival and multivariate (Cox model) regression analysis. Ta and T1 cases were analyzed separately. RESULTS: Of the 228 cases, 88 (51.5%) recurred and 13 (7.6%) progressed. On univariate analysis, most of the DNA features studied were statistically significant. Treatment modality and grade were only prognostic for progression (not for recurrence) and only in Ta cases. On multivariate analysis, DNA ICM features performed best; the strongest recurrence predictor for Ta UCC was a DNA index (DI) of 1.0 versus all others, and for T1 UCC, a DI of less than 1.3 versus 1.3 or greater. The best stage progression predictor for Ta UCCs was a DI of 1.0 plus an S-phase fraction of less than 10%, and for T1 UCCs, a DI of less than 1.3 versus 1.3 or greater. With multivariate analysis, sex, age, grade, carcinoma in situ, multicentricity, and treatment modality were excluded once the DNA ICM features were selected. CONCLUSIONS: DNA image cytometric features predict recurrence and stage progression in TaT1 UCC biopsies more accurately than classic prognostic factors, independent of treatment modality.

Aged↗
PubMed1989

Grading and prognosis of invasive ductal mammary carcinoma by nuclear image analysis in tissue sections.

In primary tumours of 84 patients with invasive ductal carcinomas the prognostic significance of the nuclear image was assessed. Feulgen stained tissue sections were investigated by image cytometry. At least 150 tumour cell nuclei as well as 50 lymphocytes or trout erythrocytes for diploid reference were measured in each specimen. 35 morphological features, including those of the chromatin pattern, were derived from the digitized nuclear images. By means of multivariate discriminant analysis, significant differences could be found between tumours of 41 node-negative and 43 node-positive patients. The differences were sufficiently large to distinguish subgroups with low and high risk of lymph node involvement. Irrespective of lymph node status, 66 patients with an adequate 5 year follow-up were divided into two groups according to their survival time. The classification results revealed a clear relationship between characteristics of the nuclear image and prognosis. By image cytometry it is thus possible to separate both node-positive and node-negative patients into subgroups with increasing risk of recurrence. The results indicate that nuclear image analysis provides prognostic information in addition to established prognostic factors, such as histological grade and tumour stage.

Adult↗
PubMed2004

Automated detection of immunofluorescently labeled cytomegalovirus-infected cells in isolated peripheral blood leukocytes using decision tree analysis.

BACKGROUND: Cytomegalovirus (CMV) infection continues to be a major problem for immunocompromised patients. Detection of viral antigens in leukocytes (antigenemia assay) is widely used for the diagnosis of CMV infection and for guiding antiviral therapy. The antigenemia technique, contingent upon the manual microscopic analysis of rare cells, is a laborious task that is subject to human error. In this study, we combine automated microscopy with artificial intelligence for reliable detection of fluorescently labeled CMV-infected cells. METHODS: Cytospin preparations of peripheral blood leukocytes were immunofluorescently labeled for the CMV lower matrix phosphoprotein (pp65) and scanned in the Rare Event Imaging System (REIS), a fully automated image cytometer. The REIS detected potential positive objects and digitally recorded 49 measured cellular features for each identified case. The measurement data of these objects were analyzed by the See5 decision tree (DT) algorithm to ascertain whether they were true-positive detections. RESULTS: The DT was built from the measurement data of 2,047 true- and 2,028 false-positive detections, collected from 32 patient samples. By designating misclassifications of false-negatives three times more costly, the 10-fold cross-validation sensitivity, specificity, and misclassification error of the assay was 94.3%, 56.2%, and 25%, respectively. The method was also validated using an independent test set of 21 patient samples, in which similar results were obtained. CONCLUSIONS: To our knowledge, this study represents the first attempt to improve the accuracy of rare event image cytometry through the implementation of artificial intelligence methodology. Results suggest that cost-sensitive decision tree analysis of digitally measured cellular features vastly improves the performance of rare event image cytometry.

Artificial Intelligence↗
PubMed1989

Quantification and topographical description of Ki-67 antibody labelling during the cell cycle of normal fibroblastic (MRC-5) and mammary tumour cell lines (MCF-7).

The expression of a human nuclear antigen associated with cell proliferation and recognized by monoclonal antibody Ki-67 was investigated during the cell cycle in a breast cancer cell line (MCF-7) and in a normal human fibroblastic cell line (MRC-5). Image cytometry was used to determine Ki-67 antigen and DNA amounts at the cell level. Results confirm Ki-67 antibody specificity for proliferating cells. The antigen expression increases with cell progression through the cycle. Image cytometry also permits the description of the Ki-67 topographic distribution at the various phases of the cell cycle. Ki-67 antigen is essentially localized in the nucleoli at G1 phase. A nucleoplasmic distribution appears later in the cell cycle. The parameters measured on the labelling allow the calculation of the growth fraction and an evaluation of the phase fractions. Other results in this study strongly suggest that nucleolar rRNA synthesis is required for Ki-67 antigen expression. Hypotheses on Ki-67 functions are proposed.

Antibodies, Monoclonal↗
PubMed1992

DNA ploidy of oncocytic-granular renal cell carcinomas and renal oncocytomas by image analysis.

DNA ploidy analysis of five renal oncocytomas, six pure oncocytic-granular renal cell carcinomas, 15 pure clear cell renal carcinomas, and two cases of mixed oncocytic-granular and clear cell heterogenous renal cell carcinomas were determined on Feulgen-stained paraffin sections using the (CAS-200 image Analyzer). All five renal oncocytomas were diploid, as were six oncocytic-granular renal cell carcinomas. Three of the 15 clear renal cell carcinomas were aneuploid. In one heterogeneous renal cell carcinoma, the oncocytic-granular foci were diploid and the clear cell focus was aneuploid. The other heterogeneous renal cell carcinoma was uniformly diploid. In 21 renal cell carcinomas, one of 14 stage I tumors was aneuploid, all four stages II and III tumors were diploid, and two of three stage IV cases were aneuploid. All stages I, II, and III patients were free of disease 3 to 48 months after surgery. All three stage IV cases were dead of their disease within 36 months of surgery. We conclude that DNA analysis by image cytometry best identifies the heterogeneity of ploidy patterns in mixed cell type carcinomas, generally correlates with the stage of disease, and may be of value in predicting overall prognosis of renal epithelial neoplasms. DNA analysis by image cytometry, however, did not reveal significant differences between oncocytic granular cell carcinoma and oncocytoma, since both lesions were generally diploid. The distinction between the two tumors is best made on morphologic grounds.

Adenoma↗
PubMed1997

A rule-based expert system for the automatic classification of DNA "ploidy" histograms measured by the CAS 200 image analysis system.

DNA "ploidy" histogram interpretation is one of the most important sources of variation in DNA image cytometry and is influenced by multiple technical factors such as scaling, selection of peaks, and variable classification criteria. A rule-based expert system was developed to automate and eliminate subjectivity from this interpretative process. Ninety-eight Feulgen stained histologic sections from patients with breast, colon, and lung cancer were measured with the CAS 200 image analysis system (Becton Dickinson, Santa Clara, CA); they included diploid (n = 42), aneuploid (n = 46), tetraploid (n = 7), and multiploid (n = 3) examples. The data was converted from listmode format into ASCII with the aid of CELLSHEET software (JVC Imaging, Elmhurst, IL). Individual microphotometric nuclear measurements were sorted to one of 64 bins based on DNA index. The 64 bins were then divided into 5 semi-arbitrarily defined ranges: hypodiploid, diploid, aneuploid, tetraploid, and hypertetraploid. The nuclear percentages in each range were calculated with EXCEL 4.0 (Microsoft, Redmond, WA). The histograms were divided into 2 equal sets: training and testing. The data from the training set were used to develop 16 IF-THEN rules to classify the histograms into diploid, aneuploid, or tetraploid. A macro was programmed in EXCEL to automate all these operations. The rule-based expert system classified correctly 45/50 histograms of the training set. Two tetraploid histograms were classified as aneuploid. Three multiploid histograms were classified as tetraploid. All histograms in the testing set were correctly classified by the expert system. The potential role of rule-based expert system technology for the objective classification of DNA "ploidy" histograms measured by image cytometry is discussed.

Automation↗
PubMed2001

Simultaneous paired analysis of numerical chromosomal aberrations and DNA content in osteosarcoma.

Relatively little is known about the biologic relevance of numerical chromosomal changes in relation to DNA content in osteosarcoma. In this study, by using a series of human osteosarcoma cell lines, we standardized a method for the assessment, on the same nuclei specimen, of both specific chromosome copy numbers by fluorescence in situ hybridization (FISH) and the DNA content by static cytofluorometry or image cytometry. On the same cell lines, we also evaluated the DNA content by using flow cytometry and the chromosome number distribution by metaphase analysis. Comparison between these different methods showed that DNA ploidy level as determined by FISH or metaphase analysis is frequently lower than the ploidy pattern as defined by cytometric methods. By using comparative genomic hybridization, we were able to demonstrate that these discrepancies were due to the presence of several unbalanced chromosome aberrations, specifically gains and high-level amplifications, which affect the total DNA content with less effect on the total chromosome number. Thus, evaluation of DNA ploidy in osteosarcoma cells is needed for a correct interpretation of FISH or cytogenetic data concerning numerical chromosomal changes. Evaluation of tumor ploidy in a series of clinical samples demonstrated that in high-grade osteosarcoma, flow cytometry sometimes may give false results because of the presence of high proportions of contaminating, nonneoplastic cells that cannot be excluded from the flow cytometric assessment but that do not interfere with the evaluation of DNA ploidy by static cytofluorometry or image cytometry, in which only tumor cells are selected for the analysis. The possibility of using this method to evaluate, on the same nuclei sample, both specific chromosomal aberrations and DNA ploidy may allow a better determination of numerical chromosomal changes that may be relevant for the biologic behavior of osteosarcoma.

Bone Neoplasms↗
PubMed1992

Application of low magnification image analysis cytometry to prostatic tissue.

Determination of the volume percentage of epithelial tissue present in prostatic tissue samples obtained by transurethral resection presents difficulties for high magnification (0.2-0.5 microns per pixel) measurement techniques due to the random orientation of tissue fragments when sectioned and the necessity of having to select "representative" areas for measurement. A low magnification (110 microns per pixel) image analysis technique was used to overcome these difficulties by allowing measurement of the epithelial tissue component to be made from the entire area of tissue available for microscopic examination. This technique which utilizes standard hematoxylin and eosin preparations was applied to 89 consecutive cases of benign prostatic hyperplasia, with measurement times of four mins per slide being obtained. Replicate measurement of 20 of these samples showed an average absolute difference between replicates of +/- 5.1 percent epithelial tissue. This method thus offers a simple, fast and practical alternative to high magnification methods of estimating the volume percentage of epithelial tissue when the selection of "representative" areas for measurement is complicated by specimen heterogeneity or when large numbers of specimens must be examined.

Epithelium↗
PubMed1992

Selective cutaneous hyperpigmentation in mice following zidovudine administration.

BACKGROUND AND DESIGN: C57BL/6N mice fed zidovudine in their drinking water develop selective hyperpigmentation of the tails and footpads. Zidovudine-fed and identical control mice were observed and sequential biopsy specimens were obtained. Routine light microscopy, electron microscopy, and image analysis of unstained biopsy specimens were used to evaluate the extent, nature, and amount of cutaneous hyperpigmentation. RESULTS: Beginning at day 14 selective hyperpigmentation of the tails and footpads of the mice was noted. Histologic evaluation revealed a gradual increase in melanin, beginning in the lower levels of the epidermis, with eventual pigmentation of the stratum corneum. Electron microscopy demonstrated a sixfold increase in melanosomes in the tail skin of the zidovudine-fed mice. Using image cytometry, melanin was quantitatively shown to increase, paralleling the clinically apparent hyperpigmentation. The hyperpigmentation was reversible on discontinuation of zidovudine. CONCLUSIONS: This animal model parallels the human in developing reversible and selective hyperpigmentation on administration of zidovudine. In this model the increased pigmentation is due to increased numbers of melanosomes within epidermal keratinocytes. Image cytometry may be useful in semiquantitatively studying the pathogenesis of various disorders of hyperpigmentation.

Animals↗
PubMed1983

Centromeric index measurement by slit-scan flow cytometry.

We report here the application of slit-scan flow cytometry (SSFCM) in the classification of muntjac, Chinese hamster, and human chromosomes according to centromeric index (CI) and total fluorescence. Chromosomes were isolated from mitotic cells, stained with propidium iodide and processed through the SSFCM where fluorescence profiles were measured. The centromere for each profile was taken as the point of maximum difference between the measured profile and a standard profile having no centromeric dip. The areas under the profile on either side of the centromere were then calculated and the CI was calculated as the ratio of the larger area to the total area under the profile. Relative DNA contents for each chromosome were taken to be proportional to the total fluorescence. Mean CI's for muntjac chromosomes 1, 2, and X + 3 were 0.52, 0.88, and 0.73, respectively; CI's for Chinese hamster M3-1 chromosomes 1, 2, 5, 8, and M2 were 0.53, 0.55, 0.57, 0.77, and 0.86, respectively; and average CI's for chromosome groups 4 + t (X;5), 6 + 7 + Y, 9 + M1, and 10 + 11 were 0.56, 0.82, 0.58, and 0.60, respectively. These results were, on average, within 4.4% of CI measurements made by image cytometry. CI's measured for human chromosomes 9 through 12, were, on average, within 2.0% of those made by image cytometry.

Animals↗
PubMed1994

Nuclear texture: can it be used as a surrogate endpoint biomarker?

Nuclear texture measurements are suggested to predict the progression/regression of precancerous lesions in breast, cervix, lung, and possibly other tissues. Nuclear texture features describe DNA distribution patterns in cell nuclei, and can be reliably measured by high resolution image cytometry, both in tissue sections as well as in single cell preparations such as smears from fine needle aspirates (FNAs) or cell suspension preparations. The cells must be stained with a stoichiometric DNA stain. For absorbance staining, the Feulgen-Thionin stain is one of the best performers used for DNA ploidy measurements using conventional image cytometry. Regression/progression information can be obtained from either diagnostic cell nuclei or from cell nuclei of normal surrounding tissue. Subtle changes in normal-appearing cells adjacent to malignant tumors are called malignancy associated changes (MACs) and can be detected by nuclear texture measurements. We postulate that measurements of texture features can also be employed as surrogate endpoint biomarkers (SEBs).

Anticarcinogenic Agents↗
PubMed2001

Microspectrofluorometry of autofluorescence emission from human leukemic living cells under oxidative stress.

Image cytometry was applied to study the intracellular localization of autofluorescence and the influence of an oxidative stress on this emission. K562 erythroleukemia cancer cells were analyzed with a microspectrofluorometer, coupled with a Argon laser (Ar+) (363 nm). From each cell, 15 x 15 emission spectra were recorded in the 400-600 nm spectral range to generate a spectral image of autofluorescence. The intracellular locations of the autofluorescence emission and of the specific mitochondrial probe rhodamine 123 (R123) were matched. Under a 363 nm excitation, all spectra from K562 cells show equivalent profiles with a 455 nm maximum emission, near of reduced nicotinamide adenine dinucleotide-(Phosphate) solution (NAD(P)H) (465 nm maximum emission). The spatial distribution of autofluorescence is homogeneous and different from the one of R123. Hydrogen peroxide (H2O2) (200 microM) and menadione (Men) (5 microM) induce a weak spectral change and a decrease in autofluorescence intensity, down to 40% of the initial emission. Doxorubicin (Dox) induces a dose-dependent decrease in autofluorescence emission and a release of intracellular free radicals. When cells were pre-treated 1 h with 1 mM glutathione (GSH), Dox induces a lower free radicals release, no significant variation of autofluorescence intensity and a lower growth inhibitory effect. Images cytometry of autofluorescence suggest that the intracellular NAD(P)H would not be restricted to mitochondrial compartments. The release of free radicals was associated with a decrease in autofluorescence intensity, mainly attributed to NAD(P)H oxidation both inside and outside mitochondria.

Dose-Response Relationship, Drug↗
PubMed2004

DNA ploidy and S-phase fraction in the patients of chronic HCV and hepatocellular carcinomas.

Four hundred blue Fulgen-stained nuclei were measured from each lesion by using DNA image cytometry. The histopathological and cytopathological observations revealed that (52 cases, 69.3%) had a variable degrees of chronic hepatitis, (12cases 16 %) were emerging into cirrhosis, while (11 cases 14.7%) represented different grades of HCC. Most of the cases with minimal or mild chronic hepatitis were female, while most of male had moderate or severe chronic hepatitis, cirrhosis and HCC. DNA image analysis data gave the support of to the histological observations. All of chronic hepatitis C and cirrhotic cases showed normal diploid and/or tetraploid histograms, although increasing S-phase fraction s' values of the highly diseased chronic hepatitis and cirrhotic cases. Hepatocellular carcinomas and one cirrhotic case only revealed aneuploidy (diploid and tetraploid), while one case of poorly differentiated HCC revealed multiploid histogram. So, histopathological severity in cases of progressive chronic hepatitis seems to be associated with the age and sex of Egyptian society. Also, demonstrates the potential usefulness of image cytometry for the evaluation of the different histopathological problems.

Biopsy, Needle↗
PubMed2003

Analysis of ploidy in hypopharyngeal cancer by laser scanning cytometry on fine needle aspirate biopsies.

AIM: To test laser scanning cytometry (LSC) for the analysis of ploidy in squamous cell carcinoma of the hypopharynx (SCCH) and to develop a routine application for minimal samples such as fine needle aspirate biopsies (FNABs). METHODS: From 11 individuals 30 FNABs of primary tumors (n=11) and lymphatic metastases of SCCH (n=11) and non-metastatic lymph nodes (n=8) are analyzed by LSC. This microscope based instrument scans the cells after immobilization on a glass slide and after double staining of cytokeratin and DNA. The location of each cell is stored with the fluorescence data. Therefore the morphology of every cell can be documented by re-staining with H & E; and re-localization on the slide. Additionally, aliquots are Feulgen-stained for image cytometry in 8 specimens. RESULTS: The diploid reference peak is identified taking leukocytes as internal standard. The DNA-index of the carcinoma cells ranges from 0.4 to 3.8. Comparison with image cytometry shows good correlation (r=0.89). CONCLUSION: LSC provides a reliable and objective way to determine the ploidy of SCCH pre-operatively. Colour figures can be viewed on http://www.esacp.org/acp/2003/25-2/gerstner.htm.

Biopsy↗
PubMed1996

Discrimination of respiratory dysfunction in yeast mutants by confocal microscopy, image, and flow cytometry.

Living yeast cells can be selectively stained with the lipophilic cationic cyanine dye DiOC6(3) in a mitochondrial membrane potential-dependent manner. Our study extends the use of flow cytometric analysis and sorting to DiOC6(3)-stained yeast cells. Experimental conditions were developed that prevented the toxic side effect of the probe and gave a quantitative correlation between fluorescence and mitochondrial membrane potential, without any staining of other membranes. The localization of the fluorochrome was checked by confocal microscopy and image cytometry. The mitochondrial membrane alterations were also tested through cardiolipin staining with nonyl acridine orange. Differences in light scattering and in fluorescence were detected in mutants (rho-, rho degrees, mit-, or pet-) and wild-type (rho+mit+) populations of yeast. The dye uptake of respiratory-deficient yeast strains was significantly reduced as compared to that of the wild-type. Application of an uncoupler (mCICCP), which collapsed the mitochondrial membrane potential (alphapsi(m)), led to a drastic reduction of the dye uptake. It was observed that a decrease in deltapsi(m), was usually correlated with a decrease in cardiolipin stainability by nonyl acridine orange (NAO). Quantitative flow cytometry is a fast and reproducible technique for rapid screening of yeast strains that might be suspected of respiratory dysfunction and/or mitochondrial structural changes. We give evidence that it is an adequate method to characterize and isolate respiratory mutants through sorting procedure, with selective enrichment of the population studied in respiring or non-respiring yeast cells. Confocal microscopy and image cytometry corroborate the flow cytometry results.

Acridine Orange↗