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[Comparison of 2 techniques for measuring lymphocyte proliferation: tritiated methyl-thymidine incorporation and propidium iodide fluorometry].

In vitro lymphocyte mitogenic stimulation by phytohemagglutinin A was determined in 20 subjects, comparing tritiated thymidine incorporation and nuclear propidium iodide fluorescence. Unexpectedly, no correlation could be found between the two measures. The pitfalls of both methods are reviewed and discussed. The inability to validate one test by the other restricts the interpretation of the results obtained with one method and prevents their generalization. Without another gold-standard at the present time, specific and limited method-dependent norms should be defined.

Fluorometry↗

Dual DNA staining assessment of bovine sperm viability using SYBR-14 and propidium iodide.

A new membrane-permeant DNA stain, SYBR-14, was used in combination with propidium iodide (PI) to estimate the proportion of living sperm in bovine semen. The SYBR-14 stained living sperm while PI only stained degenerate cells that had lost their membrane integrity. Staining with SYBR-14 resulted in the nuclei of living sperm fluorescing bright green. Aliquots containing nearly all living bovine sperm were prepared using glass wool/Sephadex filtration to remove dead and damaged cells. A portion of this filtered sample was killed by unprotected freeze-thawing and used to provide mixed aliquots containing known ratios of living and dead sperm. Flow cytometry was used to assess the green and red fluorescence of these mixtures. The percentages of living sperm, as determined by the log of green fluorescence, were 85.1, 68.8, 39.8, 20.7, and 1.4 for ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 of the filtered, killed mixtures. Also, bovine semen was diluted 1:60 in HEPES-0.1% bovine serum albumin and incubated for 0, 3, 6, and 24 hours at 36 degrees C to assess changes in cell viability. As cell death occurred during this incubation period, a relatively rapid transition of staining from green to red occurred as sperm died. Three replicates of cryopreserved sperm from six bulls were also examined using SYBR-14 and PI to assess the proportion of living and dead cells. Flow cytometric analyses of these samples, which had been processed and stored in homogenized milk, indicated that this stain combination was useful in assessing the quality of cryopreserved sperm. The combination of SYBR-14 and PI was determined to be an effective tool for assessing the viability of fresh or cryopreserved sperm.

Animals↗

[Simultaneous staining with fluorescein diacetate-propidium iodide to determine isolated cochlear outer hair cell viability of guinea pig].

A simultaneous double-staining procedure using fluorescein diacetate (FDA) and propidium iodide (PI) is discribed for use in the determination of isolated cochlear outer hair cell viability. With exciter light, viable cells fluoresce bright green, while nonviable cells are bright red. In cell culture and cytotoxicity studies, double-staining with FDA-PI is a accurate method to discriminate between live and nonviable cells.

Animals↗

Propidium iodide quenches the fluorescence of TdT-incorporated FITC-labeled dUTP in apoptotic cells.

Apoptotic cells with frequent DNA strand breaks may be detected by tagging with directly or indirectly labeled nucleotides incorporated by the use of terminal deoxynucleotidyl transferase (TdT). Propidium iodide (PI) is typically added for the simultaneous assessment of DNA content. PI was found to quench the specific in situ FITC-fluorescence of apoptotic cells which were labeled by TdT with FITC-conjugated dUTP, biotin-dUTP followed by streptavidin-FITC, or digoxigenin-dUTP followed by FITC-labeled anti-digoxigenin antibodies as measured by flow cytometry. The effect was concentration-dependent, with 50% quenching occurring at 0.8 microg/ml, 1.5 microg/ml, and 5 microg/ml PI, respectively, at approximately 1 x 10(6) cells/ml. Spectrofluorimetry in solution revealed that 15 microg/ml PI was required to quench 50% of the fluorescence of ss FITC-labeled poly(dU)35. In contrast, the fluorescence of ds FITC-labeled poly(dU)35-poly(dA) was quenched to 50% at 3 microg/ml PI. The maximum of the fluorescence excitation spectrum of PI shifted from 490 nm to 535 nm upon binding to ds DNA as well as ss poly(dU)35, and the fluorescence yield of PI at 610 nm increased, but the binding required 10-fold higher concentrations of poly(dU)35 as compared to ds DNA. The spectroscopic properties of PI are therefore similar whether bound to poly(dU) or to double-stranded DNA, but the binding to poly(dU) is much weaker. The observed quenching in situ therefore cannot be explained by direct binding of PI to the poly(dU) tails synthesized by TdT in situ in apoptotic cells, but may rather be due to radiationless energy transfer from FITC to PI bound to double-stranded DNA close to the nicks where TdT is known to start polymerization.

Apoptosis↗

A flow cytometric method for measuring lymphocyte proliferation directly from tissue culture plates using Ki-67 and propidium iodide.

A new method for measuring lymphocyte proliferation in response to mitogens and allogeneic cells without using radiolabelling is described. It utilizes flow cytometry and the monoclonal antibody, Ki-67, which detects a nuclear proliferation antigen. The entire test is performed in standard, 96-well tissue culture plates. Stable, clean nuclear suspensions rather than whole cells were used to avoid non-specific staining. The nuclei were stained by the indirect fluorescent method. Simultaneous measurements of DNA content were possible by dual staining with propidium iodide (PI). The percentage of Ki-67-positive nuclei correlated well with [3H]thymidine uptake and morphologic quantitation of blasts. This method avoids use of radioactive material and is less time consuming.

Antibodies, Monoclonal↗

Assessment of acrosome-reacted boar spermatozoa using monoclonal antibody GB 24 and propidium iodide.

Fluorescein-labeled GB 24, a mouse monoclonal antibody, was evaluated as an acrosomal dye for boar spermatozoa that had previously been stained with propidium iodide (PI) to assess sperm viability. A specific sperm-staining pattern with fluorescein-labeled GB 24 was shown to be associated with acrosome reaction on freshly ejaculated sperm when fixed with acetone or induced with ionophore A 23187, whereas the presence of PI staining was typical of dying spermatozoa. The GB 24-PI procedure was as accurate as the glutaraldehyde method in assessing acrosomal presence or absence on freshly ejaculated spermatozoa when spontaneous or A 23187-induced acrosomal reactions were considered. Approximately half of A 23187-induced spermatozoa with acrosomal loss did not exhibit a PI fluorescence; these were potentially viable acrosome-reacted spermatozoa. On semen diluted in a boar sperm-specific diluent (BTS-A) and stored, percentages of spermatozoa with nonintact acrosome from glutaraldehyde and GB 24-PI were not significantly different. Conversely, data from GB 24-PI was significantly lower than those from glutaraldehyde when semen were undiluted. This suggested that spermatozoa with reacted acrosome gradually lost their ability to bind with GB 24. Providing unequivocal and rapid scoring of acrosome-reacted spermatozoa, the GB 24-PI procedure may be a valuable tool in the evaluation of the acrosomal status of porcine fresh spermatozoa.

Journal Article↗

Rapid flow cytofluorometric analysis of mammalian cell cycle by propidium iodide staining.

A rapid method for the flow microfluorometric determination of the DNA content per cell is described. Incubation of cells in a hypotonic solution of propidium iodide results in disruption of the cell membrane and rapid staining of nuclear chromatin. DNA distribution histograms generated from cells stained by this method are identical to those generated after fixation and RNase digestion. In contrast to some earlier described methods, the present technique is rapid (5 min of processing), requires a minimal amount of material, and avoids formation of cell clumps.

Bone Marrow↗

Flow microfluorometric system for screening gynecologic cytology specimens using propidium iodide-fluorescein isothiocyanate.

Seventy cervical cytology specimens have been screened by a xero resolution flow analyzer-sorter using propidium iodide and fluorescein isothiocyanate as fluorochromes for nucleus and cytoplasm, respectively. This system shows a 1% sensitivity for detection of abnormal cells using only crude visual data analysis. Screening of clinical specimens was performed on the instrument with a 5.8% false negative rate and a 11.8% false positive rate by comparison with routine visual cytologic evaluation of the same samples.

Adenocarcinoma↗

[Importance of determining the propidium-iodide index of plasmacytes in multiple myeloma. II. Relation to disease extent and activity].

The authors evaluated in a group of 50 patients with multiple myeloma (MM), examined when the diagnosis was established before onset of treatment, and in a group of 85 patients examined in different stages of MM the relationship of proliferative characteristics of myeloma plasmocytes assessed by means of the propidium-iodide index PI/CD38, PI/"UHKT" and PI/B-B4(CD138) with the progression, "performance status" and the activity of the disease. With the exception of a different value of the PI/CD38 index between stages 1 and 3 evaluated according to Durie-Salmon, in the whole group of patients no relationship was found with the progress of the disease. When evaluating the whole group the authors observed a difference between sub-stages A and B (i.e. between patients without and with a serious impairment of renal function) when using indexes PI/CD38 and PI/B-B4(CD138). Only in the whole group of 85 patients the authors found a significant relationship of all proliferation indexes (PI/CD38PI/"UHKT" and PI/B-B4) with the "performance status" according to ECOG score to or > or = 3 vs. < 3. In both groups there was a very close statistically significant relationship without the activity of the disease whichever of the three proliferation indexes was used. It was revealed that patients with the active but stable form of the disease have different PI/CD38 and PI/B-B4(CD138) indexes within the framework of the same stage of MM (stages 1 + 2 vs. 3). From the investigation ensues that examination of the PI proliferation index, in particular PI/B-B4(CD138) or possibly PI/CD38 using multiparametric flow cytometry is a valuable method extending hitherto used examination procedures in MM, and that it replaces adequately former autoradiographic and microscopic immunofluorescent techniques.

Adult↗

Green fluorescent protein-propidium iodide (GFP-PI) based assay for flow cytometric measurement of bacterial viability.

BACKGROUND: Several staining protocols have been developed for flow cytometric analysis of bacterial viability. One promising method is dual staining with the LIVE/DEAD BacLight bacterial viability kit. In this procedure, cells are treated with two different DNA-binding dyes (SYTO9 and PI), and viability is estimated according to the proportion of bound stain. SYTO9 diffuses through the intact cell membrane and binds cellular DNA, while PI binds DNA of damaged cells only. This dual-staining method allows effective separation between viable and dead cells, which is far more difficult to achieve with single staining. Although SYTO9-PI dual staining is practical for various bacterial viability analyses, the method has a number of disadvantages. Specifically, the passage of SYTO9 through the cell membrane is a slow process, which is significantly accelerated when the integrity of the cell membrane is disrupted. As a result, SYTO9 binding to DNA is considerably enhanced. PI competes for binding sites with SYTO9 and may displace the bound dye. These properties diminish the reliability of the LIVE/DEAD viability kit. In this study, we investigate an alternative method for measuring bacterial viability using a combination of green fluorescent protein (GFP) and PI, with a view to improving data reliability. METHODS: Recombinant Escherichia coli cells with a plasmid containing the gene for jellyfish GFP were stained with PI, and green and red fluorescence were measured by FCM. For comparison, cells containing the plasmid from which gfp was removed were stained with SYTO9 and PI, and analyzed by FCM. Viability was estimated according to the proportion of green and red fluorescence. In addition, bioluminescence and plate counting (other methods to assess viability) were used as reference procedures. RESULTS: SYTO9-PI dual staining of bacterial cells revealed three different cell populations: living, compromised, and dead cells. These cell populations were more distinct when the GFP-PI combination was used instead of dual staining. No differences in sensitivity were observed between the two methods. However, substitution of SYTO9 with GFP accelerated the procedure. Bioluminescence and plate counting results were in agreement with flow cytometric viability data. CONCLUSIONS: In bacterial viability analyses, the GFP-PI combination provided better distinction between current viability stages of E. coli cells than SYTO9-PI dual staining. Additionally, the overall procedure was more rapid. No marked differences in sensitivity were observed.

Escherichia coli↗