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Biomedical subjects

P Celano

Publications and source records attributed to P Celano.

33 records · Page 2Linked to original sources
PubMed1990

Separation of pluripotent haematopoietic stem cells from spleen colony-forming cells.

Long-term reconstitution of the lymphohaematopoietic cells of a mouse after lethal irradiation requires the transplantation of at least (5-10) x 10(3) bone marrow cells. Several cell-separation techniques based on cell-surface characteristics have been used in attempts to identify the pluripotent haematopoietic stem cells (PHSC), and have allowed the long-term engraftment of lethally irradiated mice with an enriched fraction of fewer than 200 marrow cells. But these techniques enrich not only for PHSC but also for haematopoietic progenitors, especially day-12 spleen colony-forming units (CFU-S). Although day-12 CFU-S have been postulated to be primitive multipotential haematopoietic progenitors, with day-8 CFU-S representing later, more committed progenitors, recent evidence suggests that neither of these CFU-S represents mouse PHSC. Here we report that counterflow centrifugal elutriation, which sorts cells on the basis of size and density, can separate PHSC from these less primitive progenitors. The fraction containing the largest cells was enriched for the granulocyte-macrophage colony-forming units (CFU-GM), but gave only transient, early engraftment and was therefore depleted of PHSC. The intermediate fraction was enriched for CFU-S, but depleted of CFU-GM. Despite being devoid of CFU-GM and CFU-S, the fraction consisting of only morphological lymphocytes gave sustained, albeit delayed, reconstitution of all lymphohaematopoietic cells, and was therefore enriched for PHSC. We conclude that there are two vital classes of engrafting cells: committed progenitors, which provide initial, unsustained engraftment, and PHSC, which produce delayed, but durable, engraftment. Therefore for late haematological reconstitution, PHSC must be transplanted with a distinguishable source of early engrafting cells, thereby allowing the lethally irradiated host to survive initial aplasia.

Animals↗
PubMed1989

Modulation of growth gene expression by selective alteration of polyamines in human colon carcinoma cells.

The biosynthesis of the polyamines, putrescine, spermidine and spermine, is temporally linked with expression of many growth related genes. Our previous studies have shown that generalized polyamine depletion of the human colon cancer cell line COLO 320 by 2-difluoromethylornithine is associated with decreased transcription of the c-myc, c-fos, and ornithine decarboxylase (ODC) genes. In the current study, the role of individual polyamines was further defined by the use of a specific inhibitor of spermidine synthase, S-adenosyl-1,8, diamino-3-thio-octane (AdoDATO), and a spermine analogue, N1,N12 bis(ethyl)spermine. Our data demonstrate that depletion of spermidine results in a 60-90% decrease in c-myc mRNA steady state levels. In contrast, c-fos mRNA levels are decreased only when both spermidine and spermine are diminished. Furthermore, ODC mRNA levels are increased when all polyamines are decreased by DFMO, but are unaffected by a selective reduction in intracellular spermidine levels by AdoDATO. These studies suggest that individual polyamines may have a selective role in the expression of specific growth related genes.

Adenosine↗
PubMed1989

Differential induction of spermidine/spermine N1-acetyltransferase in human lung cancer cells by the bis(ethyl)polyamine analogues.

We have investigated the induction of an important polyamine metabolic enzyme, spermidine/spermine N1-acetyltransferase, in two human lung cancer cell lines which respond differently to treatment with the bis(ethyl)polyamine analogues. The human small cell lung carcinoma line NCI H82 has previously been shown to be minimally affected by treatment with these analogues, whereas the large cell undifferentiated lung carcinoma line, NCI H157, responds in a rapid cytotoxic manner (R.A. Casero, Jr., S. J. Ervin, P. Celano, S. B. Baylin, and R. J. Bergeron, Cancer Res., 49:639-643, 1989). The mechanisms underlying the differential response are unknown. In the responsive NCI H157 cells, the bis(ethyl)polyamines were found to induce spermidine/spermine N1-acetyltransferase in a time- and dose-dependent manner to maximum levels greater than 1700-fold over baseline. By contrast, the unresponsive NCI H82 cells exhibit minimal induction of spermidine/spermine N1-acetyltransferase to less than 7-fold increase after bis(ethyl)polyamine treatment, regardless of time or concentration examined. The results of the current study suggest that the differential induction of this key enzyme, which is rate limiting in the back conversion pathway of polyamine metabolism, may play a role in determining cell specific to the bis(ethyl)polyamine analogues.

Acetyltransferases↗
PubMed1989

Polyamines differentially modulate the transcription of growth-associated genes in human colon carcinoma cells.

Increases in the transcription of genes important to cell growth frequently occur in concert with increases in intracellular polyamines after a mitogenic stimulus. Previously, we have shown that depletion of intracellular polyamines by 2-difluoromethylornithine in COLO 320 cells resulted in a significant decrease in c-myc mRNA steady state levels. We demonstrate here that polyamines have a predominant role in the regulation of transcription of c-myc, c-fos, and histone 2A, while they appear to have both a transcriptional and post-transcriptional role in expression of c-myb, ornithine decarboxylase, and beta-actin mRNA levels. We further analyzed the effect of spermidine in overall and specific RNA transcription in isolated nuclei from COLO 320 cells. In nuclei from control cells, the addition of spermidine resulted in a 3-4 increase in overall [alpha-32P]UTP incorporation and a 4-8-fold increase in c-myc, c-fos, and histone 2A transcription. In contrast, ornithine decarboxylase and c-myb gene transcription were unaffected. Furthermore, in nuclei from 2-difluoromethylornithine-treated COLO 320 cells, spermidine addition resulted in less than a 2-fold increase in RNA transcription and had no effect on any specific gene analyzed. These results indicate that polyamines may have an important role in the transcription of specific growth related genes, especially c-myc and c-fos, and this role may be one mechanism by which polyamines modulate cell growth.

Actins↗
PubMed1989

Differential response to treatment with the bis(ethyl)polyamine analogues between human small cell lung carcinoma and undifferentiated large cell lung carcinoma in culture.

We have compared the effects of treatment with each of three bis(ethyl)polyamine analogues on a human small cell lung carcinoma (SCLC) line, NCI H82, and a non-small cell line, NCI H157, an undifferentiated large cell lung carcinoma. The bis(ethyl)polyamines have been shown to interfere with polyamine metabolism, presumably by regulation of the polyamine biosynthetic pathway in a manner similar to the natural polyamines, in contrast to direct inhibition of specific enzymes, such as ornithine decarboxylase. Each of these compounds was found to be relatively inactive in reducing growth rate, polyamine levels, or polyamine biosynthetic enzyme activity in the SCLC cells, a line which we have previously shown to be particularly sensitive to inhibition of polyamine biosynthesis by the direct ornithine decarboxylase inhibitor difluoromethylornithine. By contrast, each of the bis(ethyl)polyamines tested was found to be markedly cytotoxic (at concentrations of only 10 microM) to the non-SCLC line, NCI H157. Interestingly, the non-SCLC line has previously been demonstrated to be resistant to polyamine depletion by difluoromethylornithine. For each bis(ethyl)polyamine, cytotoxicity was accompanied by nearly complete depletion of all intracellular polyamines and a decrease in ornithine decarboxylase activity to undetectable levels. The current study emphasizes the phenotypic variability which can exist in response to inhibitors of polyamine biosynthesis and suggests a class of agents which may have clinical utility against the treatment-resistant non-SCLC lung cancers.

Adenosylmethionine Decarboxylase↗
PubMed1989

Two phases of engraftment established by serial bone marrow transplantation in mice.

Serially transplanted bone marrow eventually fails to reconstitute lethally irradiated mice. The reasons for this loss of repopulating ability are unknown. We showed that serial bone marrow transplantation changed the ratio of hematopoietic progenitors in bone marrow. The numbers of granulocyte-macrophage colony-forming units (CFU-GM) in the bone marrow did not change with serial transplantation. Spleen CFU (CFU-S) numbers decreased with serial transfer but remained at levels which should be associated with engraftment, even on the transfers which were unsuccessful. The CFU-S, therefore, did not appear to be the cells responsible for long-term hematopoietic repopulation. The number of successful serial transfers was dependent on the size of the grafts, and prolonging the time interval between transfers reestablished the ability of the serially transplanted marrow to reconstitute lethally irradiated recipients. Serial bone marrow transplantation dissociated two phases of engraftment. The first unsustained phase was maintained with repeated serial transfer and appeared to be produced by committed progenitors. The second sustained phase was eventually lost with repeated serial transfer and was apparently due to the pluripotent stem cell.

Animals↗
PubMed1988

Effect of polyamine depletion on c-myc expression in human colon carcinoma cells.

Polyamine depletion generally results in an inhibition of cell growth. However, the precise role of polyamines in the regulation of cell proliferation is unknown. In the present study, we demonstrate that polyamine depletion induced by 2-difluoromethylornithine in COLO 320 human colon carcinoma cells results in a greater than 90% decrease in expression of a key gene in the maintenance of cell growth, the c-myc protooncogene. The decrease in c-myc expression accompanying polyamine depletion appears to occur at the transcriptional level. It is not simply a result of decreased growth rate since growth-inhibited cells at confluence maintain a high level of c-myc expression. It is also due to a change in cell cycle phase distribution and is not a reflection of a generalized decrease in gene expression which accompanies a decrease in cellular proliferation. Thus, the expression of the histone H2A gene was similar to and temporally paralleled the growth status of both treated and untreated cells, while the beta-actin and ornithine decarboxylase genes actually had increased expression during polyamine depletion. These studies demonstrate that polyamines may be critical to the expression of c-myc and suggest one mechanism by which they modulate cell growth.

Actins↗
PubMed1987

Progenitor cell assays predict hematopoietic reconstitution after syngeneic transplantation in mice.

Hematopoietic reconstitution following syngeneic bone marrow transplantation with graded doses of untreated and drug-treated bone marrow was studied in B6D2F1 mice. Granulocyte-macrophage colony-forming units (CFU-GM) and spleen colony-forming units (CFU-S) showed similar in vitro drug sensitivities. Both the speed of hematologic recovery and survival of mice transplanted with untreated or drug-treated bone marrow were directly related to the number of CFU-GM or CFU-S transplanted. Similar hematologic recovery was seen for untreated marrow transplants and treated transplants that had similar CFU-GM or CFU-S content. There is a minimum number of transplanted CFU-GM or CFU-S that allows survival of lethally irradiated mice. This number is present in a marrow transplant containing the equivalent of 5 X 10(3) untreated cells or producing one to two spleen colonies. There also exists a maximum value for the number of hematopoietic progenitors in a marrow graft, above which the rate of hematologic recovery following transplantation is rapid and no detectable increase in the rate is seen with increasing CFU-GM or CFU-S content. The presence of this maximum value for transplanted progenitors and variations in culture techniques are probably the reasons previous studies have not always shown a correlation between CFU-GM content and hematologic recovery after bone marrow transplantation.

Animals↗
PubMed1983

Bias in treatment assignment in controlled clinical trials.

Controlled clinical trials of the treatment of acute myocardial infarction offer a unique opportunity for the study of the potential influence on outcome of bias in treatment assignment. A group of 145 papers was divided into those in which the randomization process was blinded (57 papers), those in which it may have been unblinded (45 papers), and those in which the controls were selected by a nonrandom process (43 papers). At least one prognostic variable was maldistributed (P less than 0.05) in 14.0 per cent of the blinded-randomization studies, in 26.7 per cent of the unblinded-randomization studies, and in 58.1 per cent of the nonrandomized studies. Differences in case-fatality rates between treatment and control groups (P less than 0.05) were found in 8.8 per cent of the blinded-randomization studies, 24.4 per cent of the unblinded-randomization studies, and 58.1 per cent of the nonrandomized studies. These data emphasize the importance of keeping those who recruit patients for clinical trials from suspecting which treatment will be assigned to the patient under consideration.

Clinical Trials as Topic↗
PubMed1980

Demonstration of a difference in expression of maximal lactase and sucrase activity along the villus in the adult rat jejunum.

Lactase and sucrase are two disaccharidases that differ not only in their substrate specificity and developmental patterns, but also in their resistance to mucosal insult. In this experiment, we tested the hypothesis that there might be a dichotomy in expression of enzyme activity along the jejunal villuscrypt unit. Sectioning of the villus-crypt unit in a cryostat enabled direct comparison of the distribution of lactase and sucrase enzyme activities in the adult rat. There is a stepwise increase in mean lactase/sucrase ratio going from crypt to villus. The data indicate that unlike sucrase activity, which is expressed maximally in enterocytes along the entire villus, maximal lactase activity is not attained until midvillus. The delay in expression of maximal lactase activity might help to explain the vulnerability of this enzyme to acute mucosal insult such as occurs in viral gastroenteritis.

Animals↗
PubMed1977

Prenatal induction of sucrase activity in rat jejunum.

Daily application of cortisone acetate (10mg/100g body wt.) or L-tri-iodothyronine (20 microng/100g body wt.) to female rats in the last (third) week of pregnancy elicits a precocious appearance of jejunal sucrase in their foetuses.

Animals↗
PubMed1977

Effect of cortisone or L-triiodothyronine administration to pregnant rats on the activity of fetal intestinal disaccharidases and lysosomal acid beta-galactosidase.

Activities of maltase, sucrase, lactase and acid-beta-galactosidase were studied in jejunum and ileum of term rat fetuses obtained by cesarian section. Female rats were either untreated or injected daily in the last (3rd) week of pregnancy with cortisone acetate (10 or 50 mg/100 g body weight) or L-triiodothyronine (20 or 50 microgram/100 g body weight). Two other control groups were injected with appropriate solvents. Cortisone or T3 treatment to mothers increased sucrase and maltase activity in jejunum and ileum of the offspring. Generally, higher doses of hormone were more effective. Lactase activity was increased by 25% in the jejunum by the higher dose of cortisone. Both doses of cortisone increased ileal lactase. Jejunal acid-beta-galactosidase activity was decreased in fetuses of T3-treated mothers.

Animals↗
PubMed1977

Thyroxine-evoked decrease of jejunal lactase activity in adult rats.

Daily administration of L-thyroxine (20 micrograms or 200 micrograms/100 g body weight) to adult male rats decreased jejunal lactase activity by 35% after 2-, 3-, 4- and 10 days. Four days of injections of D-thyroxine (200 micrograms/100 g body weight/day) produced a similar decrease of lactase activity. Sucrase activity was uninfluenced except for a 30% increase after daily injections of L-thyroxine (200 micrograms/100 g body weight) for 10 days. Acid beta-galactosidase activity was unaffected by either D- or L-thyroxine.

Animals↗