Conformation of RNA in situ as studied by acridine orange staining and automated cytofluorometry

In lysate RNA digestion provides insights into the angiogenin's specificity towards transfer RNAs

Under adverse conditions, tRNAs are processed into fragments called tRNA-derived stress-induced RNAs (tiRNAs) by stress-responsive ribonucleases (RNases) such as angiogenin (ANG). Recent studies have reported several biological functions of synthetic tiRNAs lacking post-transcriptional modifications found on endogenous tiRNAs. Here we describe a simple and reproducible method to efficiently isolate ANG-cleaved tiRNAs from endogenous tRNAs. Using this in vitro method, more than 50% of mature tRNAs are cleaved into tiRNAs which can be enriched using complementary oligonucleotides. Using this method, the yield of isolated endogenous 5'-tiRNA^Gly-GCC was increased about fivefold compared to when tiRNAs were obtained by cellular treatment of ANG. Although the non-specific ribonuclease activity of ANG is much lower than that of RNase A, we show that ANG cleaves physiologically folded tRNAs as efficiently as bovine RNase A. These results suggest that ANG is highly specialized to cleave physiologically folded tRNAs. Our method will greatly facilitate the analysis of endogenous tiRNAs to elucidate the physiological functions of ANG.

Binding of fluorescent acridine dyes acridine orange and 9-aminoacridine to hemoglobin: Elucidation of their molecular recognition by spectroscopy, calorimetry and molecular modeling techniques

The molecular interaction between hemoglobin (HHb), the major human heme protein, and the acridine dyes acridine orange (AO) and 9-aminoacridine (9AA) was studied by various spectroscopic, calorimetric and molecular modeling techniques. The dyes formed stable ground state complex with HHb as revealed from spectroscopic data. Temperature dependent fluorescence data showed the strength of the dye-protein complexation to be inversely proportional to temperature and the fluorescence quenching was static in nature. The binding-induced conformational change in the protein was investigated using circular dichroism, synchronous fluorescence, 3D fluorescence and FTIR spectroscopy results. Circular dichroism data also quantified the α-helicity change in hemoglobin due to the binding of acridine dyes. Calorimetric studies revealed the binding to be endothermic in nature for both AO and 9AA, though the latter had higher affinity, and this was also observed from spectroscopic data. The binding of both dyes was entropy driven. pH dependent fluorescence studies revealed the existence of electrostatic interaction between the protein and dye molecules. Molecular modeling studies specified the binding site and the non-covalent interactions involved in the association. Overall, the results revealed that a small change in the acridine chromophore leads to remarkable alteration in the structural and thermodynamic aspects of binding to HHb.

Uptake and localisation of small-molecule fluorescent probes in living cells: a critical appraisal of QSAR models and a case study concerning probes for DNA and RNA

Small-molecule fluorochromes are used in biology and medicine to generate informative microscopic and macroscopic images, permitting identification of cell structures, measurement of physiological/physicochemical properties, assessment of biological functions and assay of chemical components. Modes of uptake and precise intracellular localisation of a probe are typically significant factors in its successful application. These processes and localisations can be predicted using quantitative structure activity relations (QSAR) models, which correlate aspects of the physicochemical properties of the probes (expressed numerically) with the uptake/localisation. Pay-offs of such modelling include better understanding and trouble-shooting of current and novel probes, and easier design of future probes ("guided synthesis"). Uptake models discussed consider adsorptive (to lipid or protein domains), phagocytic and pinocytotic endocytosis, as well as passive diffusion. Localisation models discussed include those for cytosol, endoplasmic reticulum, Golgi apparatus, lipid droplets, lysosomes, mitochondria, nucleus and plasma membrane. A case example illustrates how such QSAR modelling of probe interactions can clarify localisation and mode of binding of probes to intracellular nucleic acids of living cells, including not only eukaryotic chromatin DNA and ribosomal RNA, but also prokaryote chromosomes.

Flow cytometric analysis of marine bacteria with hoechst 33342

We investigated the accuracy and precision of flow cytometric (FCM) estimates of bacterial abundances using 4', 6-diamidino-2-phenylindole (DAPI) and Hoechst 33342 (HO342, a bisbenzamide derivative) on paraformaldehyde-fixed seawater samples collected from two stations near Oahu, Hawaii. The accuracy of FCM estimates was assessed against direct counts by using epifluorescence microscopy. DAPI and HO342 differ in two aspects of their chemistry that make HO342 better suited for staining marine heterotrophic bacteria for FCM analysis. These differences are most important in studies of open-ocean ecosystems that require dual-beam FCM analysis to clearly separate heterotrophic bacterial populations from populations of photosynthetic Prochlorococcus spp. Bacterial populations were easier to distinguish from background fluorescence when stained with HO342 than when stained with DAPI, because HO342 has a higher relative fluorescence quantum yield. A substantially higher coefficient of variation of blue fluorescence, which was probably due to fluorescent complexes formed by DAPI with double-stranded RNA, was observed for DAPI-stained populations. FCM estimates averaged 2.0 and 12% higher than corresponding epifluorescence microscopy direct counts for HO342 and DAPI-stained samples, respectively. A paired-sample t test between FCM estimates and direct counts found no significant difference for HO342-stained samples but a significant difference for DAPI-stained samples. Coefficients of variation of replicate FCM abundance estimates ranged from 0.63 to 2.9% (average, 1.5%) for natural bacterial concentrations of 6 x 10 to 15 x 10 cells ml.

Cell cycle kinetics of expanding populations of neural stem and progenitor cells in vitro

Neural stem cells (NSCs) are undifferentiated, primitive cells with important potential applications including the replacement of neural tissue lost due to neurodegenerative diseases, including Parkinson's disease, as well as brain and spinal cord injuries, including stroke. We have developed methods to rapidly expand populations of mammalian stem and progenitor cells in neurosphere cultures. In the present study, flow cytometry was used in order to understand cell cycle activation and proliferation of neural stem and progenitor cells in suspension bioreactors. First, a protocol was developed to analyze the cell cycle kinetics of NSCs. As expected, neurosphere cells were found to cycle slowly, with a very small proportion of the cell population undergoing mitosis at any time. Large fractions (65-70%) of the cells were detected in G1, even in rapidly proliferating cultures, and significant fractions (20%) of the cells were in G0. Second, it was observed that different culturing methods influence both the proportion of neurosphere cells in each phase of the cell cycle and the fraction of actively proliferating cells. The results show that suspension culture does not significantly alter the cell cycle progression of neurosphere cells, while long-term culture (>60 days) results in significant changes in cell cycle kinetics. This suggests that when developing a process to produce neural stem cells for clinical applications, it is imperative to track the cell cycle kinetics, and that a short-term suspension bioreactor process can be used to successfully expand neurosphere cells.

Analysis of micronuclei in the transferrin-receptor positive reticulocytes from peripheral blood of nasopharyngeal cancer patients undergoing radiotherapy by a single-laser flow cytometer

The automated micronucleus test is now accepted as a simple, objective, and accurate method for evaluating potential mutagenic effects caused by physical, chemical or biotic factors. This paper describes a single-laser flow cytometry, based on an immunomagnetic isolation technique in combination with acridine orange staining, to detect frequencies of micronucleated transferrin-receptor positive reticulocytes from human peripheral blood. Using this flow cytometric system, we detected the frequencies of micronucleated transferrin-receptor positive reticulocytes from 10 nasopharyngeal cancer patients undergoing radiotherapy and the baseline of the frequencies of micronucleated transferrin-receptor positive reticulocytes from 7 healthy donors. The results showed that the mean frequency of micronucleated transferrin-receptor positive reticulocytes from healthy donors was 0.236% and that from nasopharyngeal cancer patients before radiotherapy was 0.297%. After radiotherapy it was significantly elevated. When the cumulative dose of radiotherapy was about 20Gy, it reached a maximum of 6.905%, and then, as the cumulative dose of radiotherapy continued to increase to 30Gy, 40Gy and 50Gy, the frequency decreased to 6.258%, 5.119% and 5.007% respectively. Our results indicated that the single-laser flow cytometric system was quick, reasonable and acceptable for detecting the frequency of micronucleated transferrin-receptor positive reticulocytes from human peripheral blood.

Aspects of gene regulation in the diploid and tetraploid Odontophrynus americanus (Amphibia, Anura, Leptodactylidae)

Erythropoietic and hemoglobin DNA transcriptional activities were analyzed in the diploid and the tetraploid Odontophrynus americanus. Flow cytometric analyses of DNA, RNA and mitochondrial contents showed increased genic activity in both diploid and tetraploid animals during erythropoiesis in vivo elicited by pretreatment phenylhydrazine. Generally, higher values were seen in immature tetraploid erythroid cells. On the 10th day of recovery from anemia, large amounts of messenger RNA were found in both specimens. Based on the mitochondrial content, the tetraploid cells had more intense energy metabolism than the diploid cells. Diploid O. americanus had about three times more erythroid cells than tetraploid specimens, indicating that there were differences in the regulatory mechanisms of erythroid cells. Hematological parameters showed that tetraploid cells had 30% more hemoglobin than the diploid, suggesting a regulatory mechanism of hemoglobin synthesis at the transcriptional level. Cytoplasmic inclusions resembling Heinz bodies were found in both types of cells. In the tetraploid cells they were previously found associated with RNA or RNP, suggesting that other regulatory system which controls the accumulation of nontranslated RNA transcribed in excess must be present. These differences at the physiological and molecular levels during erythropoiesis reinforce the hypothesis that speciation is occurring between diploid and tetraploid O. americanus.

Use of acridine orange in: flow cytometric evaluation of erythropoietic cytotoxicity

Cytotoxic insult to bone marrow frequently impairs the proliferating and maturational abilities of erythroid cells. Typically, a ratio of enucleated, immature polychromatic erythrocytes (PCE) to mature normochromatic erythrocytes (NCE) is used to assess cytotoxicity in the micronucleus (MN) assay. The effects of cyclophosphamide (CP) on PCE/NCE ratio in rat bone marrow and spleen were assessed by a newly developed flow cytometric procedure using glutaraldehyde-fixed, acridine orange (AO)-stained cells, and compared to manual scoring of PCE/NCE in Wright stained slides. Comparison of methods showed that manual and flow cytometric determination of PCE were not statistically different. Several other parameters of cytotoxicity could be simultaneously assessed because the method allowed use of unfractionated whole bone marrow/spleen cell samples. Absolute numbers of total nucleated cells (TNC), a ratio of TNC to total erythrocytes (TE), and determination of RNA content within the PCE population demonstrated dose- and time-dependent effects with CP treatment. Shifts in RNA content were particularly sensitive, correctly identifying all CP-treated from control specimens, even in those samples where PCE/NCE ratio was similar. The AO methodology provided a more rapid, statistically-superior, and thorough approach in the assessment of bone marrow and spleen cytotoxicity than the conventional manual method of scoring PCE/NCE ratio alone.

Use of acridine orange in: flow cytometric assessment of micronuclei induction

The micronucleus assay is a widely accepted method for evaluation of clastogens and aneugens. In the current study, acridine orange (AO) supravital staining was adapted for flow cytometric usage to assess micronucleated cells in rat bone marrow and spleen. Cyclophosphamide was used as a positive control test compound and results were compared to manual scoring in Wright-stained slides. In bone marrow, both manual and flow cytometric methods demonstrated positive dose response-trends for micronucleated polychromatic erythrocytes (MNPCE). Significant elevations in MNPCE were observed at all doses of cyclophosphamide, and comparisons between methods in bone marrow were not statistically different. The flow cytometric method was more sensitive in spleen samples, showing dose- and time-related increases in micronuclei compared with manual scoring. AO proved to be a sensitive discriminator of RNA and DNA, allowing distinct separation of polychromatic erythrocytes (PCE), normochromic erythrocytes (NCE), total nucleated cells (TNC), and micronucleated populations within both PCE and NCE regions. These results support the use of AO-based flow cytometry to provide a rapid and sensitive indicator of micronuclei inducers.

Influence of the process parameters on the morphology and enzyme production of Aspergilli

Several papers have been published dealing with various fungi to determine their morphology, enzyme production or process performance. However, no publication considered all of these aspects simultaneously. In the case of the production of xylanase by Aspergillus awamori the interrelationship of various key parameters are investigated. The influence of the reactor type (shake flasks, stirred tank and airlift tower loop reactor), the medium composition (semisynthetic and complex medium with wheat bran of different sizes, respectively as well as different concentrations of phosphate), and the specific power input (stirrer speed) on the growth, morphology, physiology, and productivity of the fungus are investigated. The results reveal a complex interrelationship which explains why the published results are contradictory. Without considering all of the relevant parameters, it is not possible to make general conclusions.

Acridine orange as an indicator of bacterial susceptibility to gentamicin

We have studied the response of Escherichia coli NCTC10418 to gentamicin with flow cytometry. The susceptibility of individual bacterial cells to the antibiotic was assessed by differential staining using the metachromatic dye, acridine orange. Exponential phase cultures were exposed to the minimum bactericidal concentration of gentamicin and analysed at regular intervals over 90 min. Within 60 min of exposure to the drug, two sub-populations of organisms could be distinguished in cultures by their different acridine orange-associated fluorescence emissions of < 550 nm and > 550 nm. The number of bacteria exhibiting acridine orange-associated fluorescence at > 550 nm corresponded to counts of colony forming units.

The effects of burn blister fluid on cultured keratinocytes

OBJECTIVE

Previous studies have suggested that burn blister fluid (BBF) may be detrimental to the healing of the underlying wound bed. In this study, the effects of burn blister fluid on cultured keratinocyte proliferation and differentiation were examined and quantitated using various techniques.

METHODS

At three different concentrations (2%, 10%, 20% in 20% fetal bovine serum/complete culture medium), 19 BBFs were tested in triplicate using 12 populations of cultured keratinocytes. All BBFs were collected from partial thickness burns within 72 hours of injury,. BBF was added on day 4 of the keratinocyte culture. The effect on proliferation and viability was assessed using trypan blue dye exclusion. Multiparameter flow cytometric analysis was used to quantitate population kinetics and cell size distribution. Keratinocyte differentiation was determined using immunohistochemical staining of differentiation markers and quantitation of cornified envelope formation.

RESULTS

Relative to control fluid, the BBF caused a variable effect on proliferation, ranging from 67% inhibition to 103% stimulation with an overall 4% inhibition. The range of keratinocyte viability was narrower, with a similar overall 4% reduction. Using flow cytometry to analyze RNA/DNA content and cell size, the BBF caused a subtle shift in keratinocyte population kinetics and cell size distribution toward larger, less rapidly dividing cells. The BBF had no significant effect on expression of the differentiation markers, filaggrin and involucrin. Finally, the BBF did not alter terminal differentiation as it did not influence formation of cornified envelopes (BBF = 9.1 +/- 4.8%, control = 9.9 +/- 6.6%).

CONCLUSION

Previous biochemical analysis has shown that BBF consists primarily of human serum filtrate with locally produced acute reactants. Our study suggests that BBF is biologically similar to serum and does not significantly alter keratinocyte proliferation or differentiation in vitro.

Apoptosis overview emphasizing the role of oxidative stress, DNA damage and signal-transduction pathways

Apoptosis (programmed cell death) is a central protective response to excess oxidative damage (especially DNA damage), and is also essential to embryogenesis, morphogenesis and normal immune function. An understanding of the cellular events leading to apoptosis is important for the design of new chemotherapeutic agents directed against the types of leukemias and lymphomas that are resistant to currently used chemotherapeutic protocols. We present here a review of the characteristic features of apoptosis, the cell types and situations in which it occurs, the types of oxidative stress that induce apoptosis, the signal-transduction pathways that either induce or prevent apoptosis, the biologic significance of apoptosis, the role of apoptosis in cancer, and an evaluation of the methodologies used to identify apoptotic cells. Two accompanying articles, demonstrating classic apoptosis and non-classic apoptosis in the same Epstein-Barr virus-transformed lymphoid cell line, are used to illustrate the value of employing multiple criteria to determine the type of cell death occurring in a given experimental system. Aspects of apoptosis and programmed cell death that are not covered in this review include histochemistry, details of cell deletion processes in the sculpting of tissues and organs in embryogenesis and morphogenesis, and the specific pathways leading to apoptosis in specific cell types. The readers should refer to the excellent books and reviews on the morphology, biochemistry and molecular biology of apoptosis already published on these topics. Emphasis is placed, in this review, on a proposed common pathway of apoptosis that may be relevant to all cell types.

DNA and RNA content analysis by flow cytometry in the pathobiologic assessment of bone tumors

Studies of simultaneous DNA and RNA contents by flow cytometry in hematologic and some solid neoplasms have been shown to provide information that may be useful in the pathobiological evaluation of these neoplasms. We contend that similar analysis may be equally valuable in assessing bone tumors. Our data revealed significant statistical differences in DNA ploidy and proliferative fraction between benign and malignant bone neoplasms. Benign tumors manifested predominantly DNA diploidy and low proliferative activity, whereas the majority of malignant tumors were DNA aneuploid and showed high proliferation rate. No significant difference in the RNA content between different histopathologic categories was found. We observed, however, a distinct and consistently high RNA content pattern in giant cell tumors, aneurysmal bone cysts, and chondroblastomas that may be useful in their differential diagnosis. Analysis of different prognostic factors in malignant tumors indicated that histologic grade and DNA content are a significant prognostic factors. Further analysis of malignant tumors showed that a correlation between the proliferative activity and the clinical outcome in the low grade category and between RNA content and patients' survival in osteosarcomas. Our study also showed that preoperative treatment significantly impacted on the extent of the proliferative fraction in malignant tumors. We conclude that DNA/RNA analysis of bone tumor may assist in: (1) the differential diagnosis of certain bone tumors, (2) evaluation of treatment response, and (3) the biological assessment of osteosarcomas.

A simple fluorometric assay for the determination of cell numbers

A sensitive fluorometric assay was developed for the enumeration of cells in microtiter plates. This assay is based on the fluorescence enhancement of propidium iodide (PI) upon binding with double-stranded nucleic acids. This fluorochrome is compatible with a wide range of reagents commonly used in the laboratory, thus washing the cells before staining is not necessary. PI, together with Triton-X 100 and EDTA, was added directly to the cell culture. After 16-18 h incubation at room temperature, intensity of fluorescence was determined with a micro-plate fluorometer. This quick and simple method is sensitive for as little as 1.95 x 10(3) mononuclear leukocytes, and provides a linear correlation (r = 0.999) between cell number and fluorescence up to 1 x 10(6) cells. Since PI has a large Stokes shift with excitation wavelength at common visible range and emission wavelength far out in the red region of the spectrum, it allows simultaneous detection of DNA and other fluorescent compounds such as calcein and fluorescein. This assay may prove to be a valuable alternative for cell number determination.

Cell cycle dynamics of microcarrier cultures

In anchorage-dependent cell microcarrier cultures knowledge of the cell's growth kinetics is necessary in order to design and successfully operate bioreactors, particularly on a large scale. However, in addition to growth kinetics, an understanding of the physiological state of the culture is also important. In this paper the cell cycle progression of Vero and MRC-5 microcarrier cultures have been observed utilizing a flow cytometer. Flow cytometry analysis enabled the differentiation of the various phases of the cell cycle as the culture moved from initial inoculation to the stationary, or confluent stage. Not only was the flow cytometer able to distinguish contact inhibited cells from noncontact inhibited cells, but the measured fraction of contact inhibition cells were found to be in agreement with fractions predicted from a previously developed cellular automation model for microcarrier cultures. Further, the data from the stationary phase was used to quantify the death rate in microcarrier cultures.

Flow cytometric analysis of cytokinetics of L3-acute lymphoblastic leukemia/lymphoma

Cell kinetic differences have been described between acute lymphoblastic leukemia with L1 and L2 morphology. We now report cytokinetic and DNA ploidy findings of the rare L3 B-cell leukemia/lymphoma. Flow cytometry analysis of nineteen samples was performed by simultaneous DNA-RNA staining with acridine orange. RNA and DNA indices and cell cycle distributions were calculated. The RNA-index of the G0/G1 cells was 17.9 +/- 8.7 and the number of cells in S phase and S + G2M were 21 +/- 10.6 and 28.0 +/- 13.9 percent respectively. DNA aneuploidy was found in 6/19 (31.6%) and in two cases multiple aneuploid cell lines were observed. DNA aneuploidy and multiple abnormal stemlines adversely affected survival (p less than 0.05), while kinetic parameters did not affect survival (p greater than 0.05). The cytokinetic data are significantly different (S phase and RNA-I; p less than 0.001) than previously reported for the L1 and L2 ALL. Abnormal DNA stemlines were found in cases with no detected cytogenetic abnormalities. This study confirms that L3 ALL is characterized by significantly increased proliferation and provides a means for a flow cytometric identification of this subtype as compared to L1 and L2 ALL.

Increase in acridine orange (AO) fluorescence intensity of monocytes cultured in plastic tissue culture plates as measured by flow cytometry

Although the green-red fluorescence of AO is an accepted measure of DNA-RNA content, respectively, it is actually a measure of the fluorescence of dye bound to nucleic acids, and may vary with changes in accessibility to the dye. It has been shown for example that extraction of nuclear proteins results in a marked increase in DNA stainability. Moreover, in certain cell systems the binding of fluorochromes correlates with structural modifications in chromatin that accompany cell differentiation. We report here that changes in green & red fluorescence intensity also occur in long-term monocyte cultures. The increased red fluorescence intensity observed in cultured monocytes may reflect ribosomal RNA synthesis and the increased green fluorescence enhanced AO accessibility to DNA due to changes in chromatin organization. We compared cultured monocytes from bladder cancer patients and healthy donors. The results indicate a small but statistically significantly greater increase in mean green & red fluorescence of cultured monocytes from the cancer patients. These fluorescence variations may indicate differences in the immunologic status of cancer patients and/or be related to disease state.

Induction of transformational changes in normal endothelial cells by cultured human astrocytoma cells

Endothelial cell proliferation is a significant biological feature of malignant astrocytomas. The ability of the cells of these tumors to elaborate mitogenic angiogenesis factors has been well documented. However, less is known about the transformational effects that neoplastic astrocytes may have on the endothelial cells within malignant astrocytomas. In this study, the hypothesis that humoral factors elaborated by cells derived from malignant astrocytomas induce transformational changes in normal endothelial cells in vitro is investigated. Conditioned medium (CM) was prepared from exponentially growing cultures of a human glioblastoma cell line (UW18) and from two rat brain-tumor cell lines: an anaplastic astrocytoma (R175A) and a glioblastoma with sarcomatous elements (9L). Subconfluent target bovine aortic arch endothelial cells (BAEC's) were exposed for 48 hours to varying concentrations of CM prepared from each of these tumors, and then evaluated for transformational changes. Different molecular weight (MW) fractions of UW18 CM were prepared by molecular ultrafiltration, and each fraction was tested for transforming activity. Transformation endpoints included changes in cellular deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) content and distribution (measured by differential flow cytometry) and changes in de novo DNA synthesis determined by 3H-thymidine incorporation. Significant changes in the amount and distribution of DNA and RNA were observed in the BAEC's treated with UW18 CM compared to untreated BAEC's. At 10% concentrations of UW18 CM, changes in the RNA profile of target BAEC's were evident, and at 30% concentrations of UW18 CM, an irregular bimodal distribution was well established. Patterns of DNA were also altered in a concentration-dependent manner, with significant aneuploidy developing at UW18 CM concentrations of 20%. The DNA synthesis in BAEC's increased with increasing CM concentrations, up to a maximum of about 250% of control values at 30% concentrations of UW18 CM. The transformational changes induced after exposure of BAEC's to CM prepared from R175A and 9L were significantly less than those observed with UW18 CM. Molecular ultrafiltration was used to prepare UW18 CM fractions with MW cutoffs of less than 10 kD, 10 to 30 kD, and greater than 30 kD. Transformational activity was significant only in CM's with an MW of 10 to 30 kD. It is concluded that the UW18 human glioblastoma cell line elaborates a soluble factor, or group of factors, with an MW in the 10- to 30-kD range, capable of inducing transformational alterations in target normal endothelial cells, and that such transformation may account for some of the abnormal endothelial cell changes associated with malignant astrocytomas.

Single- and double-stranded RNA measurements by flow cytometry in solid neoplasms

We investigated the ability of single- and double-stranded RNA measurements to discriminate between neoplastic and non-neoplastic solid tissues. Sixty-one solid nonhematopoietic neoplasms, 10 reactive non-neoplastic lesions, and 26 normal tissue samples were the test materials. Single-stranded ribonucleic acid (s-RNA) levels and double-stranded ribonucleic acid (ds-RNA) excess in these specimens were defined in relationship to normal human lymphocytes. The mean s-RNA index in normal, reactive, benign, and diploid and aneuploid malignant tissue samples was 0.90, 1.54, 1.9, 1.2, and 2.2, respectively. For ds-RNA, the mean excess level for normal, reactive, benign, and diploid and aneuploid malignant specimens was 8.5%, 18.5%, 51.0%, 36.0%, and 41.3%, respectively. No statistical differences in s-RNA level were found between non-neoplastic and neoplastic tissue samples. A significant difference in ds-RNA excess was found between non-neoplastic and benign, and diploid and aneuploid malignant neoplastic tissue (P less than 0.001). The specificity of s-RNA level and ds-RNA excess was 94.4% and 100%, and the sensitivity was 29.5% and 67.2%, respectively. Notably, ds-RNA determinations identified 70.0% of the diploid neoplastic samples, in contrast to 20% by s-RNA. Our preliminary data suggest that ds-RNA may be a useful parameter and may complement DNA ploidy in identification of solid neoplasms, especially if the yield of intact cells is improved.

Analysis of the cellular DNA and RNA content in acute leukemias by flow cytometry

In the present study bone marrow samples from 573 patients with newly diagnosed acute myeloid (AML) and lymphoblastic or undifferentiated leukemias (ALL/AUL), were analysed for their cellular DNA and DNA/RNA content, respectively, by means of flow cytometry. From 237 patients with AML 35.4% revealed aneuploid DNA stemlines. While no relation of DNA aneuploidy with other pretherapeutic parameters, including FAB subtype, white blood cell count, lactate dehydrogenase, S-phase index and percentage of blasts in the bone marrow, was observed, cases with aneuploid DNA stemlines revealed a tendency towards longer remission duration. In ALL/AUL 21.8% of 280 patients expressed DNA aneuploidies, which were less frequently found in T-cell ALL (11.1%) as compared to common(C)-ALL (21.4%) or null-cell(null)-ALL (23.5%). DNA aneuploidy was not related with other clinically defined risk factors such as age, white blood cell count, and rapid achievement of remission. Patients with DNA indices less than 1.0, however, tended to have shorter remissions. A significant difference in RNA indices was observed between AML and ALL/AUL with median values of 14.4 and 10.1, respectively (P less than 0.05). These data indicate the usefulness of flow cytometric analyses of cellular DNA and RNA content for the characterization and classification of acute leukemias, complementing the identification of clinical risk factors, immuno-phenotyping and cytogenetics.

Appearance of the terminal senescent cell population in human diploid fibroblasts analyzed by flow cytometry

We studied changes in the distribution pattern of relative RNA content during the in vitro aging of TIG-3 cells by flow cytometry (FACS III). Propidium iodide (PI) does not stain total cellular RNA, but it intercalates specifically into double-helical regions of both DNA and RNA. In applying this principle to RNA, we stained double-stranded RNA (dsRNA) in whole cells with PI after DNA digestion with DNase. The results showed that dsRNA distribution patterns were relatively constant at 7-75 population doublings (PD) but were significantly altered after 77 PD. The distribution patterns were similar as those for cell volume measured with a Coulter Counter. The total cellular dsRNA contents increased linearly at the senescent phase of their in vitro life span. In contrast, the mean dsRNA contents (50% dsRNA contents) rapidly increased to 77-79 PD, but decreased somewhat at 81-83 PD. Two-dimensional histograms of the dsRNA contents versus cell size were little altered from 25 PD to 75 PD. However, a population with relatively larger cell volume and weaker fluorescence intensity appeared and increased after 79 PD. This cell population group may be categorized as "terminal senescent cells" that no more divide in respect that the dsRNA content decreases in spite of the increase of total RNA content.

Detection of bladder carcinoma in females by flow cytometry and cytology

The sensitivity of bladder wash flow cytometry (BWFCM), voided urinary cytology (VUC), and cytology of catheterized urine obtained at the time of cystoscopy (CUC) were reviewed on all women evaluated for bladder cancer at Memorial Sloan-Kettering Cancer Center between June 1985 and December 1986. This comprised sixty-four episodes of pathologically proven bladder cancer in 48 women. Considering positive and suspicious results jointly the sensitivities of BWFCM, CUC and 3 VUC were 75%, 64% and 56%, respectively. If only positive results were considered (i.e., suspicious results considered as negative), the sensitivities of BWFCM, CUC and 3 VUC were 64%, 31% and 32%, respectively. The sensitivities of these tests are less than for a predominantly male population, presumably related to the presence of squamous epithelium and greater frequency of pyuria. However, bladder wash flow cytometry and conventional cytology are still a very valuable addition to cystoscopic examination, and the combination of BWFCM with conventional cytology is more sensitive than either procedure alone.

Flow cytometry as a predictor of response and progression in patients with superficial bladder cancer treated with bacillus Calmette-Guerin

Simultaneous bladder wash flow cytometry, voided urinary cytology and cystoscopic examinations were performed at 3-month intervals during a median of 18 months (range 5.5 to 50 months) in 65 patients receiving intravesical bacillus Calmette-Guerin treatment for superficial bladder cancer. Of the 65 patients treated 36 (56 per cent) had a complete response, 12 (18 per cent) had no response and 17 (26 per cent) had progression. Results of examinations at 6 months suggested that a negative bladder wash flow cytometry (29 of 36 patients, r equals 0.73, p less than 10(-7) is a strong predictor of response to bacillus Calmette-Guerin, comparable with cytological (r equals 0.60, p less than 10(-7) or cystoscopic (r equals 0.38, p less than 0.005) examinations alone or combined with cytology (r equals 0.74, p less than 10(-7)). At 6 months a positive bladder wash flow cytometry (r equals 0.44, p less than 0.0005) is as strong a predictor of disease progression as a positive cystoscopic examination (r equals 0.43, p less than 0.0005). The combination of bladder wash flow cytometry and voided urinary cytology is not superior to positive bladder wash flow cytometry alone. Median estimated interval to progression for these patients treated with bacillus Calmette-Guerin was 38 months. In the subgroup with positive bladder wash flow cytometry at 6 months the median interval to progression was 30 months. With a negative bladder wash flow cytometry at 6 months the probability of survival free of progression at 30 months was 85 per cent (p less than 0.01). Thus, negative bladder wash flow cytometry at 6 months is a strong predictor of response to bacillus Calmette-Guerin and also survival free of progression.

Ethanol fixation of bladder irrigation specimens for flow cytometric analysis. A multiinstitutional study from the bladder cancer flow cytometry network

Ethanol preservation of voided and catheterized urine has long been the standard for urinary cytologic study. In this report ethanol preservation of bladder irrigation specimens was evaluated for flow cytometric analysis in a multiinstitutional study requiring specimen transport. Specimens from ten patients obtained at one center were preserved for varying periods of time in 50% ethanol, then distributed by express mail to four other participating centers, up to 3000 miles distant. On receipt, from 1 to 3 weeks after collection, the samples were processed and examined by flow cytometric study using propidium iodide as the fluorochrome. Forty-six of the 50 (92%) analyzed specimens gave satisfactory histograms. In 41 of the 46 adequate samples (89%), an aneuploid peak in the alcohol preserved (propidium iodide stained) specimen correlated well with the fresh (acridine orange stained) specimen. However, there was variable loss of DNA stainability with a broadening of the coefficient of variation in some alcohol-preserved specimens and an increase in cellular debris so that measurements of DNA index and percent hyperdiploid cells were considered unreliable. The authors conclude that ethanol preservation of bladder irrigation specimens for short periods of time may be a feasible alternative when flow cytometric analysis cannot be carried out on fresh specimens, but that this is not optimal fixation for specimens that must be transported and further studies of other fixatives are recommended.

Initial evaluation of a new epithelial antigen (T16) for bivariate flow cytometry of bladder irrigation specimens

Bivariate flow cytometry (FCM) was used to study immunofluorescent T16 mouse monoclonal antibody (Mab) binding simultaneously with propidium iodide DNA measurements in bladder irrigation specimens from 30 patients with a history of bladder cancer. Aliquots of the same samples were stained with acridine orange (AO) and examined by conventional FCM. T16 Mab is believed to be specific for epithelial cells in this type of specimen and stained from 13% of the cells in a patient with cystitis to 95% of the cells in a patient with an atypical papilloma. In combination with DNA measurements, this antibody increased the sensitivity of FCM in patients with severe cystitis and relatively small numbers of tumor cells, but the diagnostic specificity may be decreased and the criteria established for interpreting univariate flow cytometry may have to be re-evaluated and modified.

Flow cytometry and cytology as response indicators to M-VAC (methotrexate, vinblastine, doxorubicin and cisplatin)

We evaluated 23 patients treated with neoadjuvant methotrexate, vinblastine, doxorubicin and cisplatin for muscle invasive bladder carcinoma with serial bladder wash flow cytometry and serial urinary cytology. The sensitivities of bladder wash flow cytometry and cytology in detecting bladder cancer were 74 and 47 per cent, respectively, based on subsequent diagnosis from biopsy and cystectomy specimens. Exclusion of those cases without surface carcinoma increased the sensitivities of bladder wash flow cytometry and cytology to 93 and 60 per cent, respectively. Persistently positive bladder wash flow cytometry and cytology correctly predicted residual disease in 88 and 100 per cent, respectively. However, negative bladder wash flow cytometry and cytology after chemotherapy were not reliable indicators of disease-free status.

Cytometric analysis of growth-regulator-dependent transcription and cell-cycle progression in Petunia protoplast cultures

Acridine orange simultaneously stains DNA and RNA. Using flow cytometry, synthesis of these nucleic acids can be related throughout a culture time-course. This technique has been used with nuclei isolated from Petunia hybrida protoplasts during 48 h of culture. Nuclear RNA content has been evaluated with respect to DNA levels, namely the cell-cycle phase.Nuclear RNA synthesis was not dependent upon exogeneous hormones during the first 18 h of culture, but either auxin (2,4-dichlorophenoxyacetic acid, 2,4-D) or cytokinin (N(6)-benzyladenine) were necessary for entry into the S phase. Cytokinin alone could stimulate maximal RNA synthesis within each cell-cycle phase up to 24 h. In complete medium, DNA synthesis only began from a phase "G1B" having substantial RNA, although a subnormal amount of RNA (in protoplasts cultivated only with 2,4-D) did not prevent protoplast entry into the S phase. However, both hormones were necessary for highest RNA levels and G2 frequencies after 48 h. As in mammalian cells, the mean RNA level in plant 4C nuclei is double that of 2C nuclei. G2 nuclei are larger than G1 nuclei, but upon activation G1 nuclei in fact diminsh in size.This study aimed to identify restriction points in the cell cycle as affected by growth regulators and the specific synthesis of nucleic acids. For example, the RNA levels induced by N(6)-benzyladenine, although similar to those in complete medium, were not sufficient to induce mitosis. Conversely, 2,4-D action was probably limited by low nucleotide synthesis in the absence of cytokinin.

Different quiescence states of three culture cell lines detected by acridine orange staining of cellular RNA

Three cell lines (CHO, L-929, and R1H) were investigated for their growth kinetics and the difference of exponential and quiescent state of monolayers in medium with and without serum (L-929). The noncycling populations of L-929 and R1H in medium with serum contained increased G1-phase percentages but also considerable proportions of SQ and G2Q cells. Although about 90% of the cells excluded trypan blue, the viability tested by colony assay was clearly lower than for exponentially growing cultures. CHO cells showed similar fractions of cells in G1-, S-, and G2-Q compartments but in addition considerable cell loss. The RNA content of these cells was reduced in plateau phase by 7-48% depending on cell type and residence time in the noncycling state. The data suggest that the cells suffered from nutrition depletion and were arrested in all phases of the cycle. In contrast, L-929 cells in medium without serum reduced their RNA content down to one-third that of proliferating cells and still retained the full viability as shown by the same plating efficiency in a colony assay. Since about 90% of the cells had G1 DNA content, these cells resemble true G1Q or G0 cells controlled by growth factors rather than nutritional depletion.

In vivo and in vitro effects of hydralazine on cellular growth, differentiation, and chromatin structure

The effects of hydralazine (1-hydrazinophthalazine), an antihypertensive drug, on mammalian cell growth, viability, and differentiation were assessed using Friend leukemia cells, Chinese hamster ovary cells, human lymphocytes, and rat lymphocytes, testicular germ cells, and epididymal sperm. Cultured cells in exponential phase growth were more susceptible to hydralazine cytotoxicity than stationary phase (G0) cells. Growth inhibition was associated with a dose-related slowdown of cell progression through S phase and was observed prior to a decrease of cell viability. At high drug concentrations, progression in all phases of the cell cycle was partially or totally inhibited. Hydralazine did not have an effect on the proliferation and differentiation of testicular germ cells in spontaneously hypertensive rats receiving 0-90 mg/kg/day (up to 20 times the dose used in humans) of hydralazine for a 12-week period. Hydralazine-exposed, histone-containing somatic cells and protamine-containing sperm cells failed to show any alterations in stainability with a DNA-intercalating dye nor in the susceptibility of nuclear DNA to undergo acid-induced denaturation in situ. The data suggest that hydralazine causes a dose-related suppression of mammalian cell growth with S phase appearing to be the most susceptible to hydralazine cytotoxicity. Furthermore, the interaction of hydralazine with chromatin at concentrations leading to antigenicity did not inhibit DNA staining with the intercalating dye acridine orange, suggesting that the drug does not competitively intercalate at a detectable level. Association of hydralazine with chromatin did not cause a detectable level of stabilization or destabilization of the DNA to denaturation in situ.

Flow cytometry deoxyribonucleic acid determinations and cytology of bladder washings: practical experience

Flow cytometry deoxyribonucleic acid measurements of bladder washings, routine bladder irrigation cytology and cystoscopic results were compared in a prospective fashion during 33 months of clinical urology practice. Of the 204 patients (286 specimens) studied 74 had bladder tumors or a history of bladder tumors and 130 had other genitourinary pathological conditions, including hematuria, cystitis, benign prostatic hypertrophy or prostatic carcinoma. Flow cytometry and cytology agreed with the cystoscopic findings in 93 per cent of the cases, whereas flow cytometry agreed with cytology in 84.6 per cent. When combined, flow cytometry and cytology were negative in only 1 case when several papillomas or grade I papillary carcinomas were present on cystoscopy, yielding a diagnostic accuracy of 99 per cent. The false negative rates for flow cytometry and cytology were 4.3 and 5.2 per cent, respectively, with false positive rates of 4.2 and 3.1 per cent, respectively. As expected the specimens that were missed by cytology were low grade tumors and those missed by flow cytometry were usually ulcerated invasive tumors. We believe that flow cytometry is a valuable adjunct to cytology and cystoscopy in the diagnosis, management and followup of patients with known or suspected bladder cancer. In addition, criteria for the diagnosis of cancer are changed such that specimens with a deoxyribonucleic acid tail and a large amount of hyperdiploid cells without a distinct stem line are considered suspicious and indicative of bladder pathology but they are not synonymous with the presence of carcinoma.

Detection of carcinoma in the post-cystectomy urethral remnant by flow cytometric analysis

Following radical cystoprostatectomy for bladder cancer patients must be monitored for carcinoma of the urethral remnant. Cytological examination of urethral washings has proved to be a useful alternative to urethroscopy and urethrography. Urethral irrigation specimens also can be evaluated objectively by flow cytometry. In each of 4 patients in whom carcinoma developed in the urethral remnant analysis of urethral irrigation by flow cytometry was positive and comparable to results of urethral irrigation cytology. Flow cytometry is an objective and apparently reliable diagnostic test for malignancy in the urethral remnant.

The sensitivity of bladder wash flow cytometry, bladder wash cytology, and voided cytology in the detection of bladder carcinoma

The sensitivity of voided urinary cytology (VUC), bladder wash cytology (BWC), and bladder wash flow cytometry (BWFCM) in detecting cancer was studied in 70 patients with biopsy-proven bladder tumors. There were 11 Grade I papillomas, 14 Grade II TA, 18 Grade II-III TIS, 19 Grade II-III T1, and eight Grade II-III T2 carcinomas. One to five VUCs per patient (mean, 2.63) were obtained within the 24 hours preceding biopsy. At endoscopy a bladder wash specimen was obtained and divided for cytologic and flow cytometric examinations. For all tumor categories combined, the sensitivity for one, two, and three voided cytology examinations per patient was 41%, 41%, and 60%, respectively. The sensitivity of a single BWC was 61%, of a single BWFCM, 83%. Thus, one BWFCM is more sensitive than three VUC (binomial test; P = 0.006); one BWC is more sensitive than two VUC (P = 0.01); and one BWFCM is more sensitive than one BWC (P = 0.003). These findings remain significant when papillomas are excluded from the analysis (P less than or equal to 0.03) and when papillomas and T2 tumors are jointly excluded (P less than or equal to 0.02). Only four of 70 patients (6%) had their cancers detected by VUC and/or BWC rather than BWFCM. In summary, irrigation cytology specimens are more sensitive than voided urinary cytology, and bladder wash flow cytometry is more sensitive than either in diagnosing bladder cancer. Flow cytometry is more sensitive because of the better sampling of bladder irrigation compared with voided urine and because of the measurement technique itself.

Bladder cancer flow cytometry profiles in relation to histological grade and stage

Flow cytometry was used as an additional measurement to monitor 59 untreated patients with bladder cancer. The findings indicate that tumours belonging to the same stage and grade can demonstrate different flow cytometric profiles. Using this technique, together with routine histological assessment, we were able to subclassify bladder tumours in respect of their progress. Flow cytometric profiles are recommended for additional information about the aggressiveness of the tumour and the potential response to treatment.

The sensitivity of flow cytometry compared with conventional cytology in the detection of superficial bladder carcinoma

Three groups of patients with superficial bladder carcinoma were studied: 110 patients had carcinoma in situ (TIS), 54 had noninvasive papillary transitional cell carcinoma (TA), and 64 had transitional cell carcinoma infiltrating the lamina propria (T1). One to six conventional cytologic examinations per patient (mean 2.8) were obtained during the 24 hour period before biopsy. For all tumor categories combined, the sensitivity was 49%, 54%, 62%, and 66% for one, two, three, and four cytologic examinations per patient, respectively. Cytologic sensitivity varied according to tumor category; it was greater in the TIS and T1 categories than in the TA category. To compare with the cytologic results, a subset of 103 patients had bladder irrigation performed immediately before the biopsy which was subsequently analyzed by flow cytometry. The sensitivity of a single flow cytometric examination for all tumor categories combined was 78%. As with the cytologic examinations, the sensitivity of flow cytometry varied with tumor category; it was greater in TIS and T1 categories than in the TA category. The sensitivity of one flow cytometric examination was superior (binomial test, P less than or equal to 0.05) to that of one or two cytologic examinations for TA tumors and to that of one, two, or three cytologic examinations for TIS, T1, and all tumor categories combined. Only three of 103 patients had their cancers detected by cytologic examination and not by flow cytometry.

Flow cytometric analysis of primary adenocarcinoma of the bladder

The flow cytometric findings of bladder irrigation specimens from 4 patients with histologically confirmed primary adenocarcinoma of the bladder are reported. Cells in specimens from 3 patients showed deoxyribonucleic acid aneuploidy and a simultaneous preoperative urinary cytology study was positive. One patient had normal flow cytometry studies, whereas preoperative cytology results were suspicious. These findings indicate that at least some, perhaps most, primary adenocarcinomas of the bladder have abnormalities of deoxyribonucleic acid content. Flow cytometry should be of value in detecting and monitoring these cases, as it is for epidermoid (urothelial) carcinomas.

RNA, DNA, and cell surface characteristics of lesional and nonlesional psoriatic skin

We have measured the RNA and DNA content and examined cell surface characteristics of human epidermal cells derived from normal skin, and lesional and nonlesional areas of psoriatic skin prior to and following treatment on a modified Goeckerman protocol. Our results show that cells from active psoriatic lesions contain greater numbers of basal keratinocytes when compared with either nonlesional skin from the same patients or skin from healthy volunteers and individuals with other inflammatory skin lesions. Follow-up measurements 2-3 weeks after the initiation of therapy showed that the numbers of basal keratinocytes in resolving psoriatic lesions had decreased and approached normal levels. Multiparameter RNA/DNA flow cytometric analysis on parallel samples from the same psoriasis patients revealed an increased growth fraction and proportion of cycling cells in both the nonlesional and lesional skin compared with controls. Furthermore, the cellular RNA content was elevated in lesional psoriatic skin when compared with either nonlesional or normal skin. Flow cytometric examination of nonlesional and lesional epidermal cells obtained 2-3 weeks after the commencement of therapy revealed that the growth fraction and mean RNA content of the keratinocytes from resolving psoriatic plaques decreased in response to therapy. In contrast, the proportion of keratinocytes within the S + G2 + M phases of the cell cycle remained elevated. These data indicate that "uninvolved" psoriatic skin exhibits characteristics more closely resembling lesional psoriatic skin than normal skin. The results further suggest that quantitation of cellular RNA content and basal cell number might be sensitive indicators of early treatment response in psoriasis.

Application of pyronin Y(G) in cytochemistry of nucleic acids

Chinese hamster ovary (CHO) cells or isolated nuclei were stained with pyronin Y(PY) and analyzed by absorption or fluorescence microscopy, as well as by flow cytometry. Specificity of the staining reaction was assayed by testing sensitivity of the stainable material to RNase or DNase. The colored complexes detected by light absorption in fixed cells stained with PY are nonfluorescent and are most likely the products of condensation of single-stranded (ss) RNA by PY; the poly(rA) and poly(rA,rG) are the most sensitive to condensation. The products of PY interaction with double-stranded (ds) nucleic acids are fluorescent and can be detected in cells by cytofluorometry. PY used alone stains both DNA and RNA, and the staining capabilities of these nucleic acids vary depending upon the PY concentration at equilibrium; at a concentration above 330 microM, the RNA stainability decreases, perhaps due to its denaturation and condensation caused by the dye. In the presence of Hoechst 33342, PY can specifically stain RNA in fixed cells or isolated cell nuclei. Because only complexes of PY with ds RNA are fluorescent, this dye can be used as a probe of RNA conformation, e.g., to monitor denaturation of RNA in situ. The RNA stainability of mitotic cells is about 25% lower than that of cells in G2 phase, which indicates that during mitosis proportionately less cellular RNA is in the ds conformation. The advantages and limitations of the two cytochemical methods for DNA/RNA detection, one based on the use of Hoechst 33342 and PY, and another employing the metachromatic properties of acridine orange, are compared.

Monitoring intravesical bacillus Calmette-Guerin treatment of superficial bladder carcinoma by serial flow cytometry

Simultaneous urinary flow cytometry, cytologic, and cystoscopic examinations were performed at 3-month intervals for a minimum of 1 year on 29 patients receiving intravesical bacillus Calmette-Guerin (BCG) treatment of superficial bladder carcinoma. Flow cytometry (FCM) and cytology were concordant in 57 of 103 examinations; both FCM and cytology were positive in 38 instances, and carcinoma was confirmed by biopsy in 35 (92.1%). In 16 instances FCM and cytology were negative, but carcinoma was present on biopsy in 5 (31.3%). Three examinations were suspicious by both techniques. The 46 determinations with discordant FCM and cytology were subdivided into pathologically confirmed recurrences (25 instances) and no evidence of pathologic and/or cystoscopic disease (21 instances). In the 25 instances of recurrences, FCM was positive in 18 (72.0%), suspicious in 3 (12.0%), and negative in 4 (16.0%), while cytology was positive in 3 (12.0%), suspicious in 9 (36.0%), and negative in 13 (52.0%). Most patients had a severe BCG-induced inflammatory response that caused an elevation of the hyperdiploid population, believed secondary to epithelial regeneration and proliferation. In the 21 instances without detectable recurrence, hyperploidy led to a relatively high proportion of positive (15) and suspicious (4) results by FCM, but only eight had distinct aneuploid populations. It is possible that this latter group, at least, is harboring occult carcinoma. Conventional cytology in the nonrecurrent group was positive in 1 (4.8%), suspicious in 7 (33.3%), and negative in 13 (61.9%). In those instances when tumor was confirmed by biopsy, the false-negative rate for FCM was 19.7%; the false-negative rate for cytology was 40.9%. Thus, FCM appears to be more sensitive but less specific than conventional cytology, having a lower false-negative but a higher false-positive rate. Although serial FCM provides an objective quantitative measure of aneuploid stemlines and hyperdiploid populations in bladder irrigation specimens and can be helpful in following intravesical BCG therapy for superficial bladder carcinoma, it should still be used with conventional cytology. The greatest difficulty with FCM at present, as with conventional cytology, is in cases of marked inflammation. The results reported here were obtained under the most stringent conditions and represent the minimum level of accuracy. Potential improvements in the technique, with the addition of immunologic or other markers, hold hope of further increasing the accuracy of FCM.

Determination of the growth fraction in cell suspensions by flow cytometry using the monoclonal antibody Ki-67

A novel procedure for determining the growth fraction of cell suspensions by flow cytometry is described. This method identifies proliferating cells by binding the monoclonal antibody Ki-67 to a nuclear antigen present in all cells that are in the G1, S, G2, and M phase of the cell cycle, but not in the G0 phase. In a kinetic study of Na cell line U937 using concanavalin A for stimulation of peripheral blood mononuclear cells, a steady increase of Ki-67 positive cells evaluated by flow cytometry was observed. Simultaneously, the [3H]thymidine uptake of the ConA blasts was measured and compared to the expression of Ki-67. A linear correlation between the percentage of Ki-67 positive cells and the log transformed counts per minute was demonstrated, and staining with Ki-67 detected cell proliferation with the same sensitivity as 3H-TdR uptake. In addition, it was possible to stain Ki-67-labelled cells with a second cell marker if a second fluorescent dye coupled to an antibody was used. This provided the opportunity to define precisely the phenotype of proliferating cells. Conversely, the number of proliferating cells expressing certain preselected surface markers could be easily determined.

Detection of central nervous system relapse in acute leukemia by multiparameter flow cytometry of DNA, RNA, and CALLA

DNA/RNA flow cytometry studies were performed on the spinal fluid samples of thirty patients with acute leukemia or lymphoma at the time of clinical central nervous system relapse, and compared with similar studies of 56 patients (98 specimens) who had leukemia in remission with no evidence of CNS disease. Twelve of the 30 patients with CNS involvement had cells with abnormal DNA content in the spinal fluid (40%); the remaining eighteen had cells with diploid DNA content. In the group of 18 with diploid DNA, 10 had other abnormalities detected by flow cytometry. These included eight patients with acute leukemia who had cells with high RNA content, and two patients with non-Hodgkin's lymphoma who had markedly increased proliferation. Of the 22 patients studied by conventional cytology nine were negative for malignant cells, and in eight of these patients flow cytometry studies of DNA/RNA demonstrated abnormalities. Common ALL antigen was demonstrated by flow cytometry in three out of five cases studied. Thus, abnormal DNA content, increased RNA content, increased proliferation and/or expression of the cell surface antigen CALLA identified CNS relapse by flow cytometry in 22 of 30 patients with acute leukemia or lymphoma. The technique appears to be at least as sensitive as conventional cytology and identifies CNS relapse in some patients with negative cytology.

Load regulation of the properties of adult feline cardiocytes. The role of substrate adhesion

We have recently described rapid and reversible changes in cardiac structure, function, and composition in response to surgical load alteration in vivo. In the present study, we used a simple, well-defined in vitro experimental model system, consisting of terminally differentiated quiescent adult cat ventricular cardiocytes maintained in serum-free culture medium, to assess more definitively the role of loading conditions in regulating these same biological properties of heart muscle. Cardiocytes considered to be externally loaded were adherent throughout their length to a protein substrate, such that the tendency for the ends of the cells to retract was prevented. Cardiocytes considered to be unloaded were not adherent to a substrate and, thus, were free to assume a spherical shape. Cardiocyte structure and surface area were assessed, in initially identified cells, both by serial light microscopy and by terminal electron microscopy. Cardiocyte function was assessed in terms of the ability to exclude trypan blue, to remain quiescent with relaxed sarcomeres containing I-bands, and to shorten in response to electrical stimulation. Cardiocyte composition was first assessed by quantitative gel electrophoresis of proteins and then by microfluorimetric measurement of ribonucleic acid, protein, and deoxyribonucleic acid. In addition, cardiocyte incorporation of [3H]thymidine into deoxyribonucleic acid and [3H]uridine into ribonucleic acid were measured. Loading via substrate adhesion was found to be very effective in terms of each of these measurements in retaining the differentiated features of adult cardiocytes for up to 2 weeks in culture; unattached and thus unloaded cardiocytes quickly dedifferentiated. Conditions thought to stimulate cardiac growth, including catecholamine stimulation, were found to be ineffective. These experiments demonstrate that external load has a primary role in the maintenance of the basic differentiated properties of adult mammalian cardiocytes.

Stathmokinetic analysis of human epidermal cells in vitro

Proliferation kinetics of cultured human epidermal cells is characterized in quantitative terms. Three distinct subpopulations of keratinocytes, two of which are cycling, have been discriminated by two parameter DNA/RNA flow cytometry. Based on mathematical modelling, the cell cycle parameters of the cycling subpopulations have been assessed from stathmokinetic data collected at different time points after initiation of cultures (7-15 days). The first subpopulation is composed of low-RNA cells which resemble basal keratinocytes of epidermis and which show some characteristics of stem cells; these cells have a mean generation time of approximately 100 hr. The second subpopulation consists of high-RNA cells, resembling stratum spinosum cells of epidermis, which have an average generation time of approximately 40 hr. The third subpopulation consists of non-cycling cells with G0/G1 DNA content, with cytochemical features similar to those of cells in granular layer of epidermis. The results based on modelling can reproduce with acceptable accuracy the actual growth curve of the cultured cell population. Analysis of kinetics and differentiation of human keratinocytes is of interest in view of the recent application of cultured epidermal cell sheets for transplantation onto burn wounds. The results of this study also reveal the existence of regulatory mechanisms associated with proliferation and differentiation in the cultured epidermal cell population.