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Biomedical subjects

R K Stuart

Publications and source records attributed to R K Stuart.

At least 55 records · Page 3Linked to original sources
PubMed1985

Autologous bone marrow transplantation in acute leukemia: a phase I study of in vitro treatment of marrow with 4-hydroperoxycyclophosphamide to purge tumor cells.

This phase I study was conducted to determine the maximal safe concentration of 4-hydroperoxycyclophosphamide (4HC) that could be used for in vitro treatment of bone marrow from patients with acute leukemia undergoing autologous bone marrow transplantation. Concentrations of 40 to 120 micrograms/mL of 4HC were used in 30 patients with relapsed or high-risk acute leukemia and in six patients with nonleukemic malignancies. All patients received marrow-lethal cytoreductive therapy followed by infusion of the 4HC-treated marrow. Complete inhibition of granulocyte and macrophage colony-forming cells was obtained at 80 micrograms/mL. Nevertheless, only one transplant-related death and otherwise full hematologic recovery was observed at concentrations of 4HC up to 100 micrograms/mL. At 120 micrograms/mL, there were three transplant-related deaths, including two of the three patients who required the infusion of reserve marrow. Among the acute leukemia patients, three remain in complete remission at 1,337, 1,017, and 967 days after transplant. Among the nonleukemic patients, two remain in complete remission at 1,081 and 1,017 days after transplant. At the maximum safe concentration of 4HC (100 micrograms/mL), satisfactory hematologic recovery can be obtained, despite elimination of detectable hematopoietic progenitors.

Acute Disease↗
PubMed1985

Human multilineage progenitor cell sensitivity to 4-hydroperoxycyclophosphamide.

This institution has documented consistent reconstitution of hematopoiesis in patients treated with marrow lethal chemoradiotherapy who are "rescued" by reinfusion of autologous cryopreserved marrow cells incubated with 4-hydroperoxycyclophosphamide (4-HC) for in vitro purging of occult tumor cells. After 4-HC incubation, the reinfusion marrow cells showed marked reduction in committed progenitor cell (BFU-E, CFU-GM) frequency, and often total absence of detectable progenitors, without significant loss of marrow reconstituting ability. Since BFU-E and CFU-GM assays did not predict marrow reconstituting ability after 4-HC incubation, we sought to determine whether multilineage progenitor cells (CFU-GEMM) might be more resistant to 4-HC incubation and therefore a more reliable predictive assay in this setting. We found that BFU-E, CFU-GM, and CFU-GEMM all show similar dose-related sensitivity to in vitro incubation with 4-HC and do not appear representative of the cell(s) responsible for marrow reconstitution.

Cells, Cultured↗
PubMed1984

Nutritional assessment by isotope dilution analysis of body composition.

The three components of body mass, body cell mass (BCM), extracellular fluid (ECF), and fat + extracellular solids (ECS: bone, tendon, etc) can be quantified using established isotope dilution techniques. With these techniques, total body water (TBW) and ECF are measured using 3H2O and 82Bromine, respectively, as tracers. BCM is calculated from intracellular fluid (ICF) where ICF = TBW - ECF. Fat + ECS is estimated as: body weight - (BCM + ECF). TBW and ECF can be determined by either of two calculation methods, one requiring several timed plasma samples (extrapolation method) and one requiring a single plasma sample and a 4-h urine collection (urine-corrected method). The comparability of the two calculation methods was evaluated in 20 studies in 12 bone marrow transplant recipients. We found that for determination of TBW and ECF there was a very strong linear relationship (r2 greater than 0.98) between the calculation methods. Further comparisons (by t test, 2-sided) indicated that for the determination of ECF, the methods were not significantly (p greater than 0.90) different; however, TBW determined by the urine-corrected method was slightly (0.1 to 6%), but significantly (p less than 0.01) greater than that determined by the extrapolation method. Therefore, relative to the extrapolation method, the urine-corrected method "over-estimates" BCM and "under-estimates" fat + ECS since determination of these compartment sizes depends on measurement of TBW. We currently use serial isotope dilution studies to monitor the body composition changes of patients receiving therapeutic nutritional support.

Adipose Tissue↗
PubMed1983

Phorbol ester-stimulated murine myelopoiesis: role of colony-stimulating factors.

Tumor promoting phorbol esters, such as 12-0-tetradecanoyl-phorbol-13-acetate (TPA), stimulate colony formation in vitro by murine granulocyte-macrophage progenitors (GM-CFC) without added colony stimulating factors (CSF). To determine whether TPA induces CSF production in vitro, marrow cells were cultured for 1 to 7 days in liquid medium with or without TPA. No CSF was detected in any sample by a double antibody radioimmunoassay (sensitivity = 2 units/0.1 ml), however, colony-stimulating activity was detected in supernatant fluid from all TPA containing cultures by bioassay. This activity appeared to result from a direct effect of TPA rather than from production of CSF, as equivalent activity was found in TPA-containing medium incubated in the absence of marrow cells. Rabbit antiserum to purified L-cell CSF inhibited colony formation stimulated by L-cell CSF and WEHI-3 CSF, but had no effect on colony formation induced by TPA. Cells from long-term marrow cultures responded to TPA with colony formation, despite culture conditions and cell fractionation procedures that reduced the frequency of CSF-producing macrophages to less than 1.0%. TPA inhibited binding of radioiodinated L-cell CSF to marrow cells, especially if the cells were first exposed to TPA. These results do not support induction of CSF production as the major mechanism of phorbol ester stimulation of myelopoiesis. Phorbol esters may directly stimulate GM-CFC and/or enhance their response to CSF by a mechanism involving CSF binding sites.

Animals↗
PubMed1983

Effect of several antiviral agents on human lymphocyte functions and marrow progenitor cell proliferation.

Toxicity to hematopoiesis and lymphocytic function are major considerations in the clinical applicability of antiviral agents. We have examined the toxicities of five antiviral agents showing activity against herpesviruses: vidarabine, acyclovir, (E)-5-(2-bromovinyl)-2'-deoxyuridine, trifluorothymidine, and (S)-9-(2,3-dihydroxypropyl)adenine. The drugs were tested in vitro for inhibition of herpes simplex virus type 1 and human cytomegalovirus replication, effects on marrow progenitor cell growth, effects on lymphocyte responses to mitogen and alloantigen stimulation, and effects on several lymphocyte cytotoxic responses. In general, lymphocyte proliferative responses were inhibited by the various drugs at lower concentrations than were cytotoxic activities. Acyclovir and (E)-5-(2-bromovinyl)-2'-deoxyuridine were the least toxic drugs tested, with antiviral indices exceeding 10,000. Vidarabine and trifluorothymidine were more toxic, with antiviral indices generally between 10 and 100. (S)-9-(2,3-dihydroxypropyl)-adenine was the most toxic, with several antiviral indices between 1 and 10.

Antiviral Agents↗
PubMed1983

Antigenic analysis of hematopoiesis. I. Expression of the My-1 granulocyte surface antigen on human marrow cells and leukemic cell lines.

Five monoclonal antibodies that identify the My-1 human granulocyte surface antigen were not reactive with other peripheral blood cells. These antibodies effected complement-dependent cytolysis of a large fraction of normal human marrow leukocytes. This My-1-positive marrow cell population consisted of morphologically identifiable granulocytic precursor cells. Colony-forming cells of the granulocyte-monocyte lineage (CFC-GM) did not express My-1, suggesting that the My-1 antigen is expressed later in normal granulocytic maturation. However, these antibodies did react with myeloid leukemic cell lines. The significance and potential utility of these probes for the understanding of granulopoietic differentiation is discussed.

Animals↗
PubMed1982

Abnormal fatty acid breath tests in cancer patients, with nutritional correlation.

In a group of cancer patients selected to exclude common causes of abnormal lipid absorption, we have examined this function using a breath test. Abnormal breath tests of fatty acid absorption (FABT) are found in most cancer patients, as has been previously claimed. These tests are abnormal in both quality (delayed peak in nine of ten patients, and quantity (reduced maximum peak in five of ten patients) of fatty acid absorption. In many patients abnormal FABT is not due to chemotherapy. Our preliminary results indicate no definite malabsorption mechanism but more stringent tests of absorption need to be applied. Malnutrition is common in cancer patients, even in those with little or no weight loss, and some of the malnutrition may be related to abnormal lipid absorption or to other disturbed aspects of lipid metabolism.

Adult↗
PubMed1982

Fatty acid breath test values in the malabsorption range in cancer patients.

Fatty acid absorption breath tests (FABT) were found to be abnormal in most subjects in a group of cancer patients selected to exclude common causes of abnormal lipid absorption, including chemotherapy and radiation therapy. The breath tests were abnormal in both quality (delayed peak in 9 of 10 patients) and quantity (reduced maximum peak in 5 of 10 patients) of fatty acid absorption. Retrospective separation of patients into 2 groups (normal or low maximum peak height FABT), either at a common time after the start of the test or at each individual's maximum peak height FABT regardless of time, was significant at 0.005 and 0.001, respectively. The low maximum peak heights were in the range of the malabsorption syndrome. Further studies of pancreatic function and fat malabsorption are warranted before the abnormal results can be ascribed to altered intermediary metabolism or peripheral utilization of lipids.

Adult↗
PubMed1982

Pseudomonas aeruginosa exotoxin A inhibits proliferation of human bone marrow progenitor cells in vitro.

Pseudomonas aeruginosa exotoxin A, a potent inhibitor of eukaryotic protein synthesis, is produced in vivo during human infection. We tested the hypothesis that exotoxin A may be responsible for the leukopenia which sometimes accompanies pseudomonas disease by examining the in vitro toxicity of exotoxin A for human bone marrow granulocyte-macrophage progenitor cells (colony-forming units in culture [CFU-c] in the soft agar cloning system. Colony formation by freshly obtained marrow cells from five normal subjects was inhibited by exotoxin A in a concentration-dependent manner. The mean 50 and 100% inhibitory concentrations of toxin were 1.4 x 10(-10) and 1.4 x 10(-8) M, respectively, and significant inhibition was observed at a toxin concentration as low as 1.4 x 10(-13) M in two subjects. The inhibitory effect of exotoxin A on colony formation was specifically neutralized by antiserum to exotoxin A. Although mouse CFU-c were somewhat less sensitive to exotoxin A in vitro compared with human CFU-c, exotoxin A produced significant leukopenia in vivo in mice. These data suggest a possible mechanism for the leukopenia which sometimes occurs in human pseudomonas disease.

ADP Ribose Transferases↗
PubMed1981

Tumor-promoting phorbol esters stimulate myelopoiesis and suppress erythropoiesis in cultures of mouse bone marrow cells.

Tumor-promoting phorbol esters affect the ability of mouse hematopoietic progenitor cells to form morphologically recognizable colonies in culture. They induce myeloid progenitor cells to form colonies of the monocyte/macrophage type in the absence of exogenous granulocyte/macrophage colony-stimulating factor. Conversely, similar concentrations of tumor-promoting phorbol esters inhibit the formation of colonies (bursts) by early erythroid progenitor cells, even when the culture medium contains saturating amounts of burst-promoting activity and erythropoietin. However, late erythroid progenitor cells, are not affected by phorbol esters. Only a temporary (45 min) exposure of marrow cells to phorbol esters is necessary to produce both stimulation of myeloid colony growth and inhibition of erythroid burst formation. Experiments with a radioactively labeled phorbol ester indicate a high affinity for cellular binding sites. The ability of various phorbol esters to stimulate myeloid colony growth and to inhibit erythroid burst formation correlates well with their ability to promote skin tumors in mice. The different responses of two developmentally closely related hematopoietic progenitor cells to the same phorbol esters indicate the usefulness of these substances in the further analysis of regulatory events affecting hematopoiesis.

Animals↗
PubMed1981

Activity of trifluorothymidine against cytomegalovirus.

Trifluorothymidine (TFT) was tested for antiviral activity against mouse cytomegalovirus (MCMV) and human cytomegalovirus (HCMV) in one-step replication assays. The TFT concentration required to reduce virus yield by 50% (ID50) was 0.22 microM for MCMV and 0.012 microM for HCMV. The antiviral activity of TFT against MCMV was reversed by addition of equimolar thymidine, and no antiviral activity was demonstrable in a host cell line lacking thymidine kinase. Thus, TFT's anti-MCMV activity is dependent on a host cell TK since this herpesvirus lacks thymidine kinase. A continuous subcutaneous infusion of TFT achieving a serum concentration of 1 microM failed to protect mice from lethal MCMV infection, perhaps because serum levels of thymidine were comparable to the drug level. Comparison of the ID50 against HCMV and the ID50 against human bone marrow progenitor cells resulted in an in vitro therapeutic ratio of 108, suggesting that TFT might offer some promise as a clinically useful anti-HCMV agent.

Animals↗
PubMed1980

Tumor-promoting phorbol esters stimulate hematopoietic colony formation in vitro.

Tumor-promoting phorbol esters stimulated mouse bone marrow cells to form myeloid colonies in agar cultures without added colony-stimulating factors. The colony-stimulating ability of various phorbol esters correlated well with their ability to promote skin tumors in vivo. These results suggest that phorbol esters mimic the action of specific colony-stimulating factors that regulate growth.

Animals↗
PubMed1980

Carbenicillin-trimethoprim/sulfamethoxazole versus carbenicillin-gentamicin as empiric therapy of infection in granulocytopenic patients. A prospective, randomized, double-blind study.

The results of therapy with carbenicillin plus trimethoprim-sulfamethoxazole (C-T/S) were compared to those obtained with carbenicillin plus gentamicin (C-G) in a prospective double-blind study of empiric antibiotic therapy in granulocytopenic patients. Patients were stratified into two groups: favorable-prognosis, group 1 (carcinoma, lymphoma, multiple myeloma), or unfavorable-prognosis, group 2 (acute leukemia, bone marrow transplantation), based on anticipated duration of granulocytopenia. Over-all, empiric antibiotic trials were more often successful (P = 0.004) in group 1 (55 of 62 patients or 89 per cent) than in group 2 (42 of 64 patients, 66 per cent)mwithin group 1, there was a favorable outcome in 30 of 32 (94 per cent) C-T/S trials and in 25 of 30 (83 per cent) C-G trials (P = 0.25); within group 2, there was a favorable outcome in 23 of 30 (77 per cent) C-T/S trials and in 19 of 34 (56 per cent) C-G trials (P = 0.14), Combined results in both groups indicated a higher proportion of favorable outcome in C-T/S trials (53 of 62, 85 per cent) than in C-G trials (44 of 64, 69 per cent). Further analysis (Manetl-Naenszel test) showed the over-all difference in outcome to be significant (P = 0.049), but the general applicability of this result may be limited by the rather low incidence of gram-negative bacterial infections in this study. There was no difference between the treatment regimens in antibiotic toxicity, and serious superinfection occurred only in group 2 patients (21 per cent of trials), equally divided between treatment arms. Initial protocol dosing achieved target plasma levels of trimethoprim (3 to 8 micrograms/ml) or gentamicin (4 to 10 micrograms/ml) in 57 of 68 (84 per cent) C-T/S trials compared to 21 of 60 (35 per cent) C-G trials.

Adult↗
PubMed1980

Regulation of hematopoiesis: helper and suppressor influences of the thymus.

Thymocytes from normal mice strains as well as from genetically determined stem cell defective W/Wv anemic mice were cocultured with syngeneic (or congeneic) bone marrow cells. We assayed these cocultures for the proliferation of erythroid progenitor cell types (BFU-E and CFU-E) using the plasma clot technique. Results indicate that when concentrations of thymocytes were lower than bone marrow cells, significant suppression of erythroid growth was observed. However, when the concentration of thymocytes exceeded that of the bone marrow cells in culture (greater than 1:1), significant enhancement of erythroid growth was demonstrated. The W/Wv anemic bone marrow appears to respond to this interaction by enhancement at all concentrations of added normal thymocytes. The regulatory functions observed can be diminished by treatment of the thymocytes in vitro with anti-theta serum plus complement. Thus, we establish regulatory functions for anti-theta-sensitive regulatory cells (TSRC) with both positive (enhancement) and negative (suppression) components.

Animals↗
PubMed1979

Adverse effects of nutritional deprivation on transplanted hematopoietic cells.

We studied the effect of food deprivation on hematopoietic reconstitution of B6D2F1 mice given 900 rad total body irradiation followed by 2 x 10(5) syngeneic bone marrow cells. Animals deprived of food from the day of cell transfer to the day of sacrifice were compared to control animals allowed ad libitum laboratory chow. The body weight of food deprived mice decreased by 36% on day 7 as compared to a 9% decrease in fed controls. The mean number of nucleated cells/femur on day 7 was only 22% of that found in fed controls. The spleen weight in the experimental animals was only 48% of that in the controls. Food deprived animals showed complete suppression of macroscopic hematopoietic spleen colony formation. Both marrow and spleen from the primary recipients, when studied for content of CFU-s in secondary ad libitum fed recipients, showed that food deprived animals had less than 25% of the number seen in controls. A third group of animals receiving vitamin supplements and small amounts of dextrose, but no protein, showed hematopoietic suppression similar to that seen in the totally food deprived mice.

Animals↗