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PubMed1983

Factors altering the ability of multipotential hemopoietic colony-forming cells to self-generate or form progenitor cells.

Individual in vitro colonies grown from multipotential cells have been analysed for their content of colony-forming cells including BFU-E, Mix-CFC and non-erythroid CFC. The CFC content of mixed colonies was higher in colonies grown from spleen cells than in colonies grown from bone marrow cells and was unaffected by the addition of thymocytes or postendotoxin serum. When the incubation period was extended from 7 to 14 days, CFC content of mixed colonies increased. However, plate mapping and reculturing of individual mixed colonies demonstrated that different subsets of mixed colonies were present in day 7 and day 14 cultures. Although the number of mixed colonies developing decreased when stimulated by decreasing concentrations of pokeweed mitogen-stimulated spleen cell conditioned medium (SCM) the mean number of cells per colony remained unaltered and the content of CFC in such colonies increased. With the SCM concentration range tested, as the SCM concentration was decreased, the absolute number of mixed colonies containing CFC rose from 0.6 per culture to 2.4 per culture. Over this same SCM concentration range the mean number of CFC per mixed colony increased from 1.3 to 185.2. These data suggest that amplification within mixed colonies of the number of cells capable of colony formation may occur at the expense of the production of differentiating cells.

Animals↗
PubMed1986

Declining sensitivity to interleukin 3 of murine multipotential hemopoietic progenitors during their development. Application to a culture system that favors blast cell colony formation.

When spleen cells of 5-fluorouracil (5-FU)-treated mice were cultured in the presence of interleukin 3 (IL-3), most colonies revealed IL-3 concentration-dependent colony formation except for mast cell colonies and blast cell colonies. While most colonies were smaller in lower concentrations of IL-3, the size of the blast cell colonies were similar between high and low IL-3 groups. These data suggested that blast cell colony development requires less IL-3 than the development of multilineage colonies from blast cell colonies. This notion was supported by experiments in which IL-3 was added twice to cultures of spleen cells of 5-FU-treated mice. When low concentrations of IL-3 were added on day 7, there was a reduction in the number of multilineage colonies formed without an effect on the number of blast cell colonies. Using this information, we developed a culture system that favors blast cell colony formation by cells of normal mice. When low (20 U/ml) concentrations of IL-3 were added to cultures of spleen cells of normal mice on day 7 of incubation in media containing 2-5% fetal calf serum, blast cell colonies were the predominant colony type. The blast cell colonies revealed high but variable secondary replating efficiencies. These data suggest that multipotential progenitors may become less sensitive to IL-3 as they differentiate in culture.

Animals↗
PubMed1989

Effect of recombinant GM-CSF and recombinant G-CSF on colony formation of blast progenitors in acute myeloblastic leukemia.

The colony-promoting activities of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) and recombinant granulocyte colony-stimulating factor (rG-CSF) on primary and secondary colony formation by blast progenitors (leukemic colony-forming units [L-CFU]) from 21 patients with acute myeloblastic leukemia (AML) were examined using blast colony assay and compared to colony promotion stimulated by phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM). Recombinant GM-CSF stimulated blast colonies in 13 out of 20 cases examined (1 case not done). The magnitude of stimulation by rGM-CSF varied significantly according to the type of AML, but in general was lower than that of PHA-LCM. Blast cells of type M1 did not form any colonies with rGM-CSF, although numerous colonies were produced with PHA-LCM. Type M4 blasts formed fairly large numbers of colonies, though slightly less than those stimulated by PHA-LCM. Blasts of type M2 and M5 formed colonies with the stimulation of rGM-CSF, but the numbers were considerably smaller than type M4 and those stimulated with PHA-LCM. Recombinant G-CSF stimulated blast colonies in only 5 out of 21 cases, 3 of them being type M2. The number of cases responding to rG-CSF was significantly smaller than that responding to rGM-CSF, and even in cases in which colonies were formed, the magnitude of stimulation was minimal. From these results it seems likely that blast cells of different types of AML require a different kind of CSF for their optimal growth; type M4 blasts responded to the stimulation of rGM-CSF well, but blasts of other types of AML responded poorly. Thus, except for type M4, CSF(s) other than rGM-CSF seems to be required for the sufficient growth of L-CFU. Recombinant G-CSF is not likely to play an essential role in the proliferation of leukemic blasts of most types. Previous exposure to rGM-CSF and rG-CSF did not alter the self-renewal capacity, cellular phenotype, and morphology of colony cells, indicating that the direction and degree of differentiation of L-CFU stimulated by rGM-CSF or rG-CSF were not different from those stimulated with PHA-LCM.

Colony-Stimulating Factors↗
PubMed1993

Blast colony-forming cells in myelodysplastic syndrome: decreased potential to generate erythroid precursors.

In vitro colony-forming abilities of highly purified primitive hematopoietic cells in eight cases of myelodysplastic syndrome (MDS) were studied using the blast cell colony assay. Blast cell colony formation from seven normal bone marrow (NBM) samples was studied in parallel. Blast cell colonies were formed in 7/8 cases of MDS, the numbers not significantly differing from those generated by NBM. In contrast the more mature hematopoietic progenitors (granulocyte-erythroid-macrophage-megakaryocyte colony-forming unit, CFU-GEMM; erythroid burst-forming units, BFU-E; granulocyte colony-forming units, CFU-G; eosinophilic colony-forming units, CFU-Eo) were severely depressed in numbers in MDS marrow. After replating of blast cell colonies in secondary cultures, colonies were obtained in 5/8 MDS cases. A marked difference was evident in the composition of the secondary colonies between MDS and normal marrow. Whereas secondary colonies derived from normal blast cell colonies consisted of about 45% of erythroid cells, MDS blast colonies generated mainly colonies of the granulocytic-monocytic lineage and no erythroid colonies. The normal quantitative level of CFU-blast progenitors in MDS in the context of their impaired ability to generate lineage specific progeny upon secondary plating suggests that the incompetence of maturation of MDS may reside in the CFU-blast progenitor cell being incapable of properly responding to growth factor stimulation.

Adult↗
PubMed1986

Chromosome analysis of trifluorothymidine-resistant L5178Y mouse lymphoma cell colonies.

Cells from small (sigma) and large (lambda) trifluorothymidine-resistant (TFTr) colonies induced by chemical mutagen treatment of TK+/-L5178Y mouse lymphoma cells were examined for chromosomal abnormalities. Analysis of G-banded metaphase chromosomes from 34 sigma-TFTr colonies revealed that cells from 20 (59%) possessed one or more chromosomal abnormalities. The most frequent (16/20 colonies) abnormality observed in cells from sigma-TFTr colonies involved the addition of extra chromatin to the distal region of one chromosome number 11. In 13 of these 16 colonies, the origin of the chromatin translocated to chromosome number 11 could not be identified; the chromatin was not missing elsewhere in the genome. The remaining three sigma-TFTr colonies with an abnormal chromosome number 11 had apparently whole chromosomes translocated, in tandem, to the distal region of chromosome number 11. Chromosomal abnormalities observed in cells from sigma-TFTr colonies with normal number 11 chromosomes included 2N/4N and 2N/4N/8N mosaicism (two colonies), a Robertsonian translocation involving chromosome 10 and a marker chromosome (one colony), and trisomy 7 (one colony). In most (14/16) sigma-TFTr colonies with structural damage to chromosome number 11, the cells within a colony were heterogeneous in that some possessed chromosomal damage whereas others were apparently normal. Analysis of chromosomes in cells from eight lambda-TFTr colonies revealed one colony in which all cells had a Robertsonian translocation involving chromosomes 1 and 16 plus other structural abnormalities. The chromosomes of cells from the remaining lambda-TFTr colonies were apparently normal.

Animals↗
PubMed1979

Colony formation in agar by multipotential hemopoietic cells.

Agar cultures of CBA fetal liver, peripheral blood, yolk sac and adult marrow cells were stimulated by pokeweed mitogen-stimulated spleen conditioned medium. Two to ten percent of the colonies developing were mixed colonies, documented by light or electron microscopy to contain erythroid, neutrophil, macrophage, eosinophil and megakaryocytic cells. No lymphoid cells were detected. Mean size for 7-day mixed colonies was 1,800-7,300 cells. When 7-day mixed colonies were recloned in agar, low levels of colony-forming cells were detected in 10% of the colonies but most daughter colonies formed were small neutrophil and/or macrophage colonies. Injection of pooled 7-day mixed colony cells to irradiated CBA mice produced low numbers of spleen colonies, mainly erythroid in composition. Karyotypic analysis using the T6T6 marker chromosome showed that some of these colonies were of donor origin. With an assumed f factor of 0.2, the mean content of spleen colony-forming cells per 7-day mixed colony was calculated to vary from 0.09 to 0.76 according to the type of mixed colony assayed. The fetal and adult multipotential hemopoietic cells forming mixed colonies in agar may be hemopoietic stem cells perhaps of a special or fetal type.

Animals↗
PubMed1980

Colony formation in agar by adult bone marrow multipotential hemopoietic cells.

Erythroid colony formation in agar cultures of CBA bone marrow cells was stimulated by the addition of pokeweed mitogen-stimulated spleen conditioned medium (SCM). Optimal colony numbers were obtained when cultures contained 20% fetal calf serum and concentrated spleen conditioned medium. By 7 days of incubation, large burst or unicentric erythroid colonies occurred at a maximum frequency of 40--50 per 10(5) bone marrow cells. In CBA mice the cells forming erythroid colonies were also present in the spleen, peripheral blood, and within individual spleen colonies. A marked strain variation was noted with CBA mice having the highest levels of erythroid colony-forming cells. In CBA mice erythroid colony-forming cells were mainly non-cycling (12.5% reduction in colony numbers after incubation with hydroxyurea or 3H-thymidine). Erythroid colony-forming cells sedimented with a peak of 4..5 mm/hr, compared with CFU-S, which sedimented at 4.25 mm/hr. The addition of erythropoietin (up to 4 units) to cultures containing SCM did not alter the number or degree of hemoglobinisation of erythroid colonies. Analysis of the total number of erythroid colony-forming cells and CFU-S in 90 individual spleen colonies gave a correlation coefficient of r = 0.93 for these two cell types. In addition to benzidine-positive erythroid cells, up to 40% of the colonies contained, in addition, varying proportions of neutrophils, macrophages, eosinophils, and megakaryocytes. Taken together with the close correlation between the numbers of CFU-S in different adult hemopoietic tissues, including individual spleen colonies, the data indicate that the erythroid colony-forming cells expressing multiple hemopoietic differentiation are members of the hemopoietic multipotential stem cell compartment.

Animals↗
PubMed1976

Regulation of the induction of colonies in vitro by normal human lymphocytes.

Lymphocytes isolated from normal human peripheral blood can be induced to form colonies in vitro by incubation with the appropriate inducer. Phytohemagglutinin can induce colonies with T (thymus-derived) lymphocytes. Optimun colony formation with about two colonies per 10(2) peripheral blood lymphocytes was obtained by adding, in addition to phytohemagglutinin, autologous plasma, autoologous red blood cells, and fresh L-glutamine or L-cystine. In the absence of these fresh amino acids, no colonies were formed at seeding levels below 10(5) cells per 35 mm petri dish. The addition of either of these amino acids gave a 10-fold decrease in the minimum number of cells that had to be seeded for colony formation. Lipopolysaccharide did not induce the formation of colonies, but enhanced the formation of T cell colonies by phytohemagglutinin. The mixing of lymphocytes from persons with and deficient in glucose-6-phosphate-dehydrogenase (EC 1-1-1-49) has shown that phytohemagglutinin-induced colonies can be derived from single cells and are, therefore, clones. No colonies were formed by lethally irradiated cells. Incubation with pokeweed mitogen also induced the formation of colonies. With autologous plasma and autologous red blood cells, pokeweek mitogen induced about one colony per 5 X 10(3) cells seeded and no colonies at seeding levels below 10(5) cells per petri dish. The minimum number of cells needed for colony formation by pokeweed mitogen was not decreased by fresh L-glutamine or L-cystine. The results indicate that normal human lymphocytes can be cloned in vitro and that induction of these lymphocyte colonies can be regulated by lectins and other specific factors.

Blood↗
PubMed2006

Microarray analysis distinguishes differential gene expression patterns from large and small colony Thymidine kinase mutants of L5178Y mouse lymphoma cells.

BACKGROUND: The Thymidine kinase (Tk) mutants generated from the widely used L5178Y mouse lymphoma assay fall into two categories, small colony and large colony. Cells from the large colonies grow at a normal rate while cells from the small colonies grow slower than normal. The relative proportion of large and small colonies after mutagen treatment is associated with a mutagen's ability to induce point mutations and/or chromosomal mutations. The molecular distinction between large and small colony mutants, however, is not clear. RESULTS: To gain insights into the underlying mechanisms responsible for the mutant colony phenotype, microarray gene expression analysis was carried out on 4 small and 4 large colony Tk mutant samples. NCTR-fabricated long-oligonucleotide microarrays of 20,000 mouse genes were used in a two-color reference design experiment. The data were analyzed within ArrayTrack software that was developed at the NCTR. Principal component analysis and hierarchical clustering of the gene expression profiles showed that the samples were clearly separated into two groups based on their colony size phenotypes. The Welch T-test was used for determining significant changes in gene expression between the large and small colony groups and 90 genes whose expression was significantly altered were identified (p < 0.01; fold change > 1.5). Using Ingenuity Pathways Analysis (IPA), 50 out of the 90 significant genes were found in the IPA database and mapped to four networks associated with cell growth. Eleven percent of the 90 significant genes were located on chromosome 11 where the Tk gene resides while only 5.6% of the genes on the microarrays mapped to chromosome 11. All of the chromosome 11 significant genes were expressed at a higher level in the small colony mutants compared to the large colony mutants. Also, most of the significant genes located on chromosome 11 were disproportionally concentrated on the distal end of chromosome 11 where the Tk mutations occurred. CONCLUSION: The results indicate that microarray analysis can define cellular phenotypes and identify genes that are related to the colony size phenotypes. The findings suggest that genes in the DNA segment altered by the Tk mutations were significantly up-regulated in the small colony mutants, but not in the large colony mutants, leading to differential expression of a set of growth regulation genes that are related to cell apoptosis and other cellular functions related to the restriction of cell growth.

Animals↗
PubMed1999

Redox control in development and evolution: evidence from colonial hydroids

Redox chemistry, involving the transfer of electrons and hydrogen atoms, is central to energy conversion in respiration, and the control of gene expression by redox state commonly occurs in bacteria, allowing rapid responses to environmental changes, for instance, in the food supply. Colonial metazoans often encrust surfaces over which the food supply varies in time or space; hence, in these organisms, redox control of the development of feeding structures and gastrovascular connections could be similarly adaptive, allowing colonies to adjust the timing and spacing of structures in response to a variable food supply. To investigate the possibility of redox control of colony development, the redox states of hydractiniid hydroid colonies were manipulated experimentally. As in many colonial animals, hydractiniid hydroids display a range of morphological variation from sheet-like forms (i.e. closely spaced polyps with high rates of stolon branching) to runner-like forms (i. e. widely spaced polyps with low rates of stolon branching). In the runner-like Podocoryna carnea, azide, a blocker of the electron transport chain, and dinitrophenol, an uncoupler of oxidative phosphorylation, diminished the largely polyp-driven gastrovascular flow to a similar extent. Measures of the redox state of the polyp epitheliomuscular cells using the fluorescence of NAD(P)H suggest that azide shifts the redox state in the direction of reduction, while dinitrophenol shifts the redox state in the direction of oxidation. Colony development corresponds to redox state in that azide-treated colonies were more runner-like, while dinitrophenol-treated colonies were more sheet-like. Nevertheless, the functional role of polyps in feeding and generating gastrovascular flow probably contributed to a trade-off between polyp number and size such that azide-treated colonies had few large polyps, while dinitrophenol-treated colonies had many small polyps. Regardless of the treatment, P. carnea colonies developed to maturity and produced swimming medusae in the normal fashion. In the sheet-like Hydractinia symbiolongicarpus, treatment with azide resulted in complete suppression of the development of both the stolonal mat and the blastostyles, the reproductive polyps. Azide-treated H. symbiolongicarpus colonies therefore developed in a juvenilized, runner-like manner and much resembled colonies of P. carnea. Following cessation of azide treatment in H. symbiolongicarpus, normal colony development ensued, and both a stolonal mat and blastostyles formed. In both hydroid species, relative oxidization favors sheet-like growth, while relative reduction favors runner-like growth. Since feeding triggers strong contractions of polyp epitheliomuscular cells and results in relative oxidation, this experimental evidence supports the hypothesis of adaptive redox control of colony development and evolution.

Journal Article↗
PubMed1985

LPF-induced T cell colony formation: effect of PMA and interleukin-2, and surface marker analysis.

We demonstrated that a primary exposure to the lymphocytosis promoting factor (LPF) of Bordetella pertussis-induced T cell colony formation. Colony formation was observed when mononuclear cells (MNC) were cultured at concentrations of more than 1 X 10(6)/ml, and reached a peak on day 8. However, the number of colonies generated with LPF was about one-third induced with phytohaemagglutinin (PHA). Removal of monocytes from MNC or T cells resulted in the failure of colony formation, but colony growth could be restored by the addition of monocytes or B enriched cells, indicating that they were required for the optimal colony growth induced by LPF. In the absence of accessory cells, optimal colony growth from monocyte depleted T cells could be obtained when an appropriate concentration of phorbol myristate acetate (PMA) or interleukin-2 (IL-2) was added in the cultures with LPF. PMA did not enhance LPF-induced colony formation in the cultures containing a sufficient amount of exogeneous IL-2. These findings suggest that IL-2 is essential to LPF-induced colony formation. Surface marker analysis showed that most of LPF-induced colony cells were T cells. The percentages of T4+ and T gamma cells of LPF-induced colony cells were more, and T8+ cells less, than those of PHA-induced colony cells. Ia1, T9 and Tac antigens were detected on many colony cells induced by LPF or PHA. These results indicate that the phenotype of LPF-induced colony cells differs from those of PHA, but the sequential antigen expression on lymphocytes triggered by IL-2 might be similar in both LPF- and PHA-induced colony formation.

Antigens, Surface↗
PubMedDate not supplied

Phytohemagglutinin-induced human T-lymphocyte colonies: cellular and T-cell growth factor requirements are the same as for suspension culture growth.

Both T-cell colony formation and T-cell growth in liquid culture requires phytohemagglutinin, either adherent cells or conditioned medium from mononuclear cells, and perhaps other cooperating cells. Despite these similarities, there are some data that the two systems may differ. While it is clear that a source of T-cell growth factor (TCGF) is an absolute requirement for the growth of T cells in liquid culture, less is known of the factors influencing T-cell colony formation. In these studies, production of TCGF during T-cell colony formation was determined. High levels of TCGF can be extracted from methylcellulose when colony formation is rapidly increasing. When colony size is at its maximum, measurable levels of TCGF decline and after 2 weeks little or no TCGF is detectable, suggesting that the factor is used by colony-forming cells. The only requirement for these colony-forming cells to form secondary colonies in replating experiments is exogenous TCGF- The need for adherent cells in primary colony formation can be substantially replaced by interleukin 1, a factor which is produced by adherent cells and functions by amplifying TCGF production. Other promoters of T-cell colony formation may also amplify TCGF production. Addition of dexamethasone to the assay decreases the number and size of the T-cell colonies formed by 75-90%, and colony formation can be completely restored by the addition of purified TCGF. The addition of antigen, lectin, 12-O-tetradecanoyl-phorbol-13-acetate or interleukin 1 cannot overcome the specific dexamethasone-mediated inhibition of colony formation. Although there may be additional requirements for colony formation depending upon the T-cell subset and state of differentiation of the cells, it appears that TCGF is the ultimate proliferative signal in both liquid and colony T-cell growth.

Cell Division↗
PubMed1980

Functional differences between cells from MLR colonies grown in soft agar cultures.

This report describes a method of growing soft agar colonies of human T lymphocytes activated in the MLR. Two types of colonies were demonstrated: lower colonies grew within the agar layer, and upper colonies grew on the surface of the agar layer. Three days of priming the lymphocytes in the MLR and the use of supernatants of day-3 MLR cultures to provide T cell colony growth factor were necessary for optimal colony formation. Lymphocytes obtained from colonies were grown in long-term (2 to 4 weeks) cultures to generate sufficient numbers of cells to be tested in different functional assays. Cells from both types of colonies exhibited PLT activity. Upper colony cells showed considerably higher CML activity than lower colony cells (mean percent cytotoxicity 37 +/- 5 vs 6 +/- 3). Cells from both types of colonies contained radiosensitive suppressor cell activity that inhibited the primary MLR. The suppressor cell effect of lower colony cells was specific for the original stimulator, but upper colony cells displayed nonspecific suppressive effects. For both types of colony cells, it appeared that suppressive effects were unrelated to the CML activity of these cells. These data suggest that the soft agar colony assay offers a promising approach to separate subpopulations of lymphocytes activated in the MLR.

Agar↗
PubMed1976

Cytologie and cytochemistry of colony cells in soft agar gel culture from normal and leukemic bone marrow.

In order to judge differentiation of cells in soft agar colonies, cytological and cytochemical classification of single cells within these colonies is necessary. In this study, 1,026 colonies from 15 normal and 95 leukemic bone marrows have been evaluated using cytological, cytochemical, and immunocytochemical techniques. In 180 colonies from 15 normal controls no segmented neutrophils have been observed. The colonies mostly consisted of monocytes and macrophages, rarely pure eosinophil colonies were observed. The number of monocyte/macrophage colonies in untreated AML and the percentage of pure eosinophil colonies in AML and ALL in remission are reduced, as compared to normal controls. In 174 colonies from a total of 926 colonies derived from bone marrows of leukemic patients, plasma cells and in 20 colonies, blast cells have been observed. In contrast to normal colonies, growth of colonies containing blast cells does not depend upon the conditioned medium of the leukocyte feederlayer. This investigation has demonstrated the necessity of cytological and cytochemical classification in addition to quantiative evaluation of soft agar colonies when studying the effect of factors on proliferation and differentiation of normal and leukemic stem cells.

Bone Marrow Cells↗
PubMed1985

Characterization of normal peripheral blood T- and B-cell colony-forming cells: growth factors(s) and accessory cell requirements for their in vitro proliferation.

The biological properties of normal peripheral lymphoid precursors were studied using separate colony assays for T- and B-cell colony-forming cells (T-CFC and B-CFC, respectively). Cell fractions, selected by complement-mediated cytotoxicity with monoclonal antibodies, were cultured in methylcellulose using different sources of growth factors containing (PHA-LCM2 and PHA-LCM7) or not (PHA-TCM) Interleukin-2 (IL-2). Well-differentiated T-cell colonies were only observed with IL-2-containing conditioned media (CM). Normal T-CFC displayed either an immature (E-T11-OKT3-Ia-) or mature (E+) phenotype, were quiescent cells presenting different radiosensitivity (D0 = 80 and 155 rads, respectively). B-CFC displayed the E-T11-OKT3-B1-Ia+ surface phenotype, were in DNA synthesis and were more radioresistant (D0 = 300 rads) than T-CFC. B-cell colonies could be obtained in the presence of allogeneic irradiated T cells and PHA-TCM, but not with IL-2-containing CM. When E-T11-OKT3- cells were seeded with PHA-TCM supplemented with increasing amounts of semipurified IL-2 in the presence of a fixed number of irradiated T cells, the B-cell colony growth (as assessed by the frequency of sIg+ colony cells) progressively decreased whereas that of T-cell colonies increased. IL-2-free CM (PHA-TCM) was able to induce T-cell colony growth from E-T11-OKT3- cells but addition of allogeneic irradiated T cells induced B-cell colony formation in a dose-dependent manner. Conversely, T cells enhanced T-cell colony growth in the presence of IL-2-containing CM. Furthermore, adherent cell depletion of E-T11-OKT3- cells inhibited T- but not B-cell colony growth. These results taken together suggest that T- and B-cell colonies derive from different progenitor cells which have different growth factor(s) and accessory cell requirements and indicate that T-cell colony growth is associated with inhibition of B-cell colony formation.

Antigen-Presenting Cells↗
PubMed1997

Molecular analysis of hematopoietic colonies derived from chronic myeloid leukemia patients: interphase fluorescence in situ hybridization compared with RT-PCR.

In this study we compared interphase fluorescence in situ hybridization (I-FISH) with reverse transcription polymerase chain reaction (RT-PCR) for the molecular analysis of hematopoietic colonies derived from patients with chronic myeloid leukemia (CML). Molecular analysis of individual colonies is often performed to monitor purging efficacy in CML. We harvested individual colony-forming unit granulocyte-macrophage (CFU-GM) colonies. One half was analyzed with I-FISH, for the presence of bcr-abl fusion gene. The other half was analyzed with RT-PCR for the presence of the bcr-abl mRNA. We wanted to address the following questions: (1) is the bcr-abl gene always expressed in CFU-GM colonies and (2) which technique has to be preferred to analyze individual CFU-GM colonies? In total, 133 colonies, derived from six CML patients, could be analyzed both with I-FISH and RT-PCR. We found a positive correlation in 89% of the cases: 118 colonies showed the same results with both techniques. However, 15 of the 106 I-FISH-positive colonies were negative in the RT-PCR. Serial analysis of the cDNA derived from 22 colonies showed in each round of amplification 21-29% RT-PCR-negative but I-FISH-positive colonies. However, all I-FISH-positive colonies showed at least one positive RT-PCR, either in the first, second or third round of amplification. These results indicate that the bcr-abl gene is probably always transcriptionally active in CFU-GM colonies. Reliable analysis with RT-PCR is possible but likely to generate false negative results. We conclude that: (1) I-FISH offers a reliable alternative to RT-PCR for analyzing individual hematopoietic colonies and (2) results obtained with RT-PCR should only be interpreted with caution.

Adult↗
PubMed1987

Tumor cell heterogeneity: divided-colony assay for measuring drug response.

In vitro tests for predicting the response of tumors to chemotherapeutic agents might be improved if they were modified to take into account tumor-cell heterogeneity. We have studied the heterogeneity of cellular growth rate and drug response in mouse fibroblast NIH 3T3 cells and in NIH 3T3 cells transformed with the human HRAS gene (homologue of the Harvey sarcoma virus oncogene v-Ha-ras) from the EJ human bladder carcinoma cell line. Growth-rate heterogeneity was detected as a broad distribution of numbers of cells per colony. In spite of this heterogeneity, secondary colonies have numbers of cells per colony that resemble that of the primary colony from which they were derived. The variance between unrelated secondary colonies is increased by HRASEJ. Colony-size measurements are reliable because primary colonies divided in half formed two groups of secondary colonies (on two separate plates) that had indistinguishable mean colony sizes. Based on these observations, a divided-colony procedure was devised to detect the drug response of heterogeneous cell populations. Primary colonies are divided into two groups of cells, one of which is treated with a drug and the other is left untreated as a control. The size distribution of treated secondary colonies is then compared to that of the untreated control and to that of the primary colony from which it was derived. The divided-colony procedure is proposed as a modification of the human-tumor-cloning system to increase the sensitivity and reliability of in vitro procedures used to determine the drug response of heterogeneous tumor-cell populations.

Animals↗
PubMed2002

Evidence for protection of nitrogenase from O(2) by colony structure in the aerobic diazotroph Gluconacetobacter diazotrophicus.

Gluconacetobacter diazotrophicus is an endophytic diazotroph of sugarcane which exhibits nitrogenase activity when growing in colonies on solid media. Nitrogenase activity of G. diazotrophicus colonies can adapt to changes in atmospheric partial pressure of oxygen (pO(2)). This paper investigates whether colony structure and the position of G. diazotrophicus cells in the colonies are components of the bacterium's ability to maintain nitrogenase activity at a variety of atmospheric pO(2) values. Colonies of G. diazotrophicus were grown on solid medium at atmospheric pO(2) of 2 and 20 kPa. Imaging of live, intact colonies by confocal laser scanning microscopy and of fixed, sectioned colonies by light microscopy revealed that at 2 kPa O(2) the uppermost bacteria in the colony were very near the upper surface of the colony, while the uppermost bacteria of colonies cultured at 20 kPa O(2) were positioned deeper in the mucilaginous matrix of the colony. Disruption of colony structure by physical manipulation or due to 'slumping' associated with colony development resulted in significant declines in nitrogenase activity. These results support the hypothesis that G. diazotrophicus utilizes the path-length of colony mucilage between the atmosphere and the bacteria to achieve a flux of O(2) that maintains aerobic respiration while not inhibiting nitrogenase activity.

Acetobacteraceae↗