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Biomedical subjects

R Hoffman

Publications and source records attributed to R Hoffman.

At least 271 records · Page 15Linked to original sources
PubMed1989

Clinical and molecular impact of inhibition of IMP dehydrogenase activity by tiazofurin.

The impact of tiazofurin on inhibition of IMP dehydrogenase was discussed at the clinical and molecular levels. 1. Evidence was provided for the role of IMP dehydrogenase and guanylates in the expression of the neoplastic program in cancer cells with particular relevance to human leukemic cells. 2. The argument for expecting an impact of tiazofurin in human myelocytic cells was provided. 3. Similarity of the kinetics of human leukemic cell IMP dehydrogenase to the rat hepatoma enzyme was documented. 4. New evidence was provided for the role of salvage in chemotherapy and the function of hypoxanthine in inhibiting guanine salvage. 5. The action of tiazofurin and retinoic acid was reported in HL-60 leukemic cells. 6. The effect of tiazofurin and retinoic acid on proliferation and cytotoxicity was outlined for hepatoma 3924A cells. 7. The effect of guanine on induced differentiation by tiazofurin and retinoic acid was examined. 8. Biochemical basis was provided for the lack of development of resistance in patients treated with tiazofurin. 9. Presumptive evidence was provided that tiazofurin treatment induced differentiation of leukemic cells in the patients. 10. The molecular biology of tiazofurin-induced differentiation in K-562 cells was reviewed with the possible relevance to clinical treatment that tiazofurin might also act through down-regulation of ras oncogene.

Animals↗
PubMed1989

IMP dehydrogenase: inhibition by the anti-leukemic drug, tiazofurin.

Tiazofurin through its active metabolite thiazole-4-carboxamide adenine dinucleotide (TAD) inhibits IMP dehydrogenase, the rate-limiting enzyme of GTP biosynthesis. IMP dehydrogenase activity in human leukemic cell extracts (33.4 +/- 0.1 nmol/h/mg protein) was increased 11-fold compared to normal leukocytes (3.1 +/- 0.5). Km values for IMP and NAD+ of leukemic IMP dehydrogenase were 22.7 and 44.0 microM, respectively. XMP inhibited competitively with IMP and noncompetitively with NAD+. NADH exerted mixed type inhibition with respect to both IMP and NAD+. The inhibitory pattern of TAD was quite similar to that of NADH; however, the affinity of TAD to leukemic IMP dehydrogenase (Ki = 0.1 microM) was three orders of magnitude higher than the natural product NADH (Ki = 150 microM). These results contribute to an understanding of the mechanism of action of tiazofurin in the treatment of leukemia.

Adenine Nucleotides↗
PubMed1989

Psychosocial outcomes of breast cancer therapies: lumpectomy versus mastectomy.

The psychological status of 50 patients who had been treated for breast cancer was assessed an average of 21 months after treatment. The patients were grouped according to major treatment modalities: mastectomy with breast reconstruction, mastectomy without breast reconstruction, or lumpectomy. Lumpectomy patients had a significantly more intact body image (p less than .008) and a greater sense of sexual desirability (p less than .009) than patients in the other groups. The patients did not differ on frequency of sexual relations or on emotional symptomatology. The results of this study generally validate those found in comparable studies showing that lumpectomy promotes a more intact body image but that no surgical procedure either produces or inhibits psychological symptomatology.

Adult↗
PubMed1989

Afferent and efferent pathways in T cell responses to MHC class I+, II-hepatocytes.

We have previously reported that purified hepatocytes stimulate significant in vitro allospecific cytotoxicity when cocultured with naive responder splenocytes in the mixed lymphocyte hepatocyte culture (MLHC). In this report we examined the expression of MHC antigens on the surface of hepatocytes, the phenotypic lymphocyte subset(s) that respond(s) to allogeneic hepatocytes, and the phenotype of allospecific cytolytic effectors generated in MLHC. Hepatocytes expressed MHC class I but not MHC class II antigens by immunofluorescent microscopy and fluorescence activated cell sorting. The lack of MHC class II on the surface of hepatocytes was also indirectly supported by the inability of hepatocytes to stimulate proliferation of a class II-directed allospecific helper T cell clone. The generation of allospecific cytotoxicity in MLHC required the participation of L3T4+, Ly2- T cells and L3T4-, Ly2+ T cells in the naive responder splenocyte population since depletion of these subsets with mAb and complement abrogated the development of allo-CTLs. Furthermore, adherent accessory cells in the naive responder splenocyte population appeared to play a role in the generation of allospecific cytotoxicity in MLHC since depletion of this population by plastic adherence and passage through a Sephadex G10 column resulted in significantly reduced allospecific cytotoxicity. Depletion of day 5 allosensitized cells of Ly2+ but not L3T4+ T cells by mAb and complement eliminated allospecific cytotoxicity--indicating that cytolytic effectors generated in MLHC appear to be L3T4-, Ly2+ T cells.

Animals↗
PubMed1989

Effectiveness of influenza vaccine when given during an outbreak of influenza A/H3N2 in a nursing home.

An explosive outbreak of influenza A/H3N2 began in a nursing home in the Denver area early in November, 1987. Residents had not been vaccinated at that time. Vaccine was administered on November 11th. Two weeks after the vaccine was given, the attack rate differed between the vaccinated and unvaccinated individuals. There were 40 cases of influenza among the 98 elderly residents, 12 cases of pneumonia, and seven deaths. Vaccine efficacy two weeks after it was given was estimated to be 65.4% in preventing clinical illness. There were no cases of pneumonia and no deaths among people who were vaccinated more than two weeks before. The virus was identified as influenza A by complement fixation tests with convalescent sera from 16 individuals who had been ill. Many also had hemagglutination inhibition titers for A/Colorado/1/87, which were as high as titers for A/Leningrad/87. A/Colorado/1/87 closely resembled A/Sichuan/87.

Aged↗
PubMed1989

Serum from patients with various thrombopoietic disorders alters terminal cytoplasmic maturation of human megakaryocytes in vitro.

Human bone marrow was depleted of progenitors (CFU-MK), but enriched for recognizable megakaryocytes (MK), and placed in cultures with serum from either normal donors (NABS) or patients with primary (PTS) or secondary (STS) thrombocytosis, autoimmune thrombocytopenia (ATS) or aplastic anemia (AAS). Mean MK diameters shifted during the 3-4 days of incubation. Endomitotic figure were visible and mean ploidy increased slightly during cytoplasmic maturation, where decreases in immature cells (stages 1 and 2) were accompanied by increases in the mature MK (stages 3 and 4). Cytoplasmic maturation was faster in AAS, ATS and STS than PTS or NABS; mean size and ploidy were similar in all cultures. Recognizable MK were not forced to undergo additional endoreduplication in response to stimulation. Only AAS augmented MK colony formation, which indicated that at least two humoral factors can regulate megakaryocytopoiesis at separate levels, the progenitors and morphologically recognizable MK.

Anemia, Aplastic↗
PubMed1989

Dose-intensive chemotherapy in refractory germ cell cancer--a phase I/II trial of high-dose carboplatin and etoposide with autologous bone marrow transplantation.

Between September 1986 and March 1988, 33 patients with refractory germ cell cancer were entered on a phase I/II trial of two courses of high-dose carboplatin plus etoposide with autologous bone marrow support. All patients had extensive prior treatment and had either cisplatin-refractory disease (67%) defined as progression within 4 weeks of the last cisplatin dose or failed at least two cisplatin-based regimens (35%) including a cisplatin-ifosfamide salvage regimen. Patients received a fixed total dose of etoposide of 1,200 mg/m2 with each cycle. The carboplatin dose ranged from 900 mg/m2 to 2,000 mg/m2. Twenty of the 33 patients received the second cycle of therapy. Despite extensive prior therapy with cisplatin, neurotoxicity, nephrotoxicity, or hearing impairment with high-dose carboplatin and etoposide was unusual. The most common nonhematologic toxicity was moderate enterocolitis. The hematologic toxicity of this regimen was substantial at each dose level. All 53 courses were accompanied by granulocytopenic fevers. Seven of the 33 patients (21%) died from treatment. All of these deaths occurred during the granulocyte nadir, and five were related to documented sepsis. Overall, 14 of 32 patients (44%) evaluable for response obtained an objective response, including eight complete remissions. Four patients remain in complete remission, with three patients being continuously free of disease in excess of 1 year. Eight responders (including four complete remissions) had progressed while receiving cisplatin. We conclude that carboplatin and etoposide can be administered in combination at high dosages and this regimen may have curative potential for patients with germ cell tumors resistant to conventional-dose cisplatin-based therapies.

Adolescent↗
PubMed1989

Characterization of the human burst-forming unit-megakaryocyte.

Two classes of human marrow megakaryocyte progenitor cells are described. Colony-forming unit-megakaryocyte (CFU-MK)-derived colonies appeared in vitro after 12-day incubation; burst-forming unit-megakaryocyte (BFU-MK)-derived colonies appeared after 21 days. CFU-MK-derived colonies were primarily unifocal and composed of 11.6 +/- 1.2 cells/colony; BFU-MK-derived colonies were composed of 2.3 +/- 0.4 foci and 108.6 +/- 4.4 cells/colony. CFU-MK and BFU-MK were separable by counterflow centrifugal elutriation. CFU-MK colony formation was diminished by exposure to 5-fluorouracil (5-FU); BFU-MK colony formation was unaffected. CFU-MK and BFU-MK were immunologically phenotyped. CFU-MK expressed the human progenitor cell antigen-1 (HPCA-1, CD34, clone My10) and a major histocompatibility class II locus, HLA-DR, and BFU-MK expressed only detectable amounts of CD34. BFU-MK colony formation was entirely dependent on addition of exogenous hematopoietic growth factors. Recombinant granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) possessed such colony-stimulating activity, whereas recombinant erythropoietin (Epo), G-CSF, IL-1 alpha, IL-4, and purified thrombocytopoiesis-stimulating factor did not. These studies indicate the existence of a human megakaryocyte progenitor cell, the BFU-MK, which has unique properties allowing it to be distinguished from the CFU-MK.

Antigens, CD34↗
PubMed1989

A prospective trial of new versus refurbished cardiac pacemakers: a Canadian experience.

Pacemaker reimplantation in the same patient is common, and pacemaker transplantation or reuse in a second patient has been reported. No report prospectively compares the long term costs, the impact of reuse on the number of pacemakers implanted, the pacemaker related complications, the types of patients selected and the patient survival of those who receive new versus a refurbished pacemaker. The authors implanted 70 pacemakers of which 75% (52) were new and 25% (18) were refurbished. The refurbished pacemakers were implanted in older patients (P less than 0.02), with a mean +/- SD of 77 +/- 8 versus 69 +/- 13 years of age. During a follow-up period of 36 months, the rate of pacemaker related complications was the same in both groups, with no unusual or unexpected problems arising in the refurbished group. There were 12 (23%) complications in the new pacemaker group and four (22%) complications in the refurbished pacemaker group. There were no major pacemaker related complications, no pacemaker battery depletions and no pacemaker related deaths. The refurbished pacemakers saved $33,000. After three years the cumulative probability of survival in the new group tended to be higher (P = 0.08) with a mean (SE) of 0.62 (0.12) versus 0.44 (0.15). New and refurbished pacemakers are similar with respect to pacemaker related survival and complications. Refurbished pacemakers effect a major reduction in pacemaker costs while maintaining health care standards.

Arrhythmias, Cardiac↗
PubMed1989

Effect of interleukin 6 on in vitro human megakaryocytopoiesis: its interaction with other cytokines.

The effects of human recombinant interleukin 6 (rIL-6) on in vitro human megakaryocytopoiesis were studied utilizing a serum-depleted culture system. Recombinant IL-6 increased both the number of megakaryocyte (MK) colonies formed and the number of cells comprising individual MK colonies cloned from normal low-density bone marrow (LDBM) cells. This stimulation of MK colony number and size was significantly less than that observed following the addition of recombinant interleukin 3 (rIL-3) or granulocyte-macrophage colony-stimulating factor (rGM-CSF). The addition of either rIL-3 or rGM-CSF, but not rIL-6 promoted MK colony formation by nonadherent, low-density, T-cell-depleted (NALDT-) marrow cells. Recombinant interleukin 1 alpha (rIL-1 alpha) and interleukin 4 (rIL-4) failed either to promote LDBM MK colony formation when added alone or to significantly increase rIL-6-promoted MK colony formation. MK colony formation promoted by optimal doses of rIL-6 was, in fact, significantly inhibited by rIL-1 alpha at all concentrations tested. Addition of either recombinant erythropoietin (rEpo) or purified thrombocytopoiesis-stimulating factor (TSF) to assays containing rIL-6 also resulted in significant inhibition of MK colony formation. The effect of suboptimal concentrations of rIL-6 on MK colony formation was additive to that of rIL-3 but not rGM-CSF. The addition of transforming growth factor beta (TGF-beta) resulted in a 58% reduction of rIL-6-promoted MK colony formation by LDBM. These data suggest that rIL-6 can promote in vitro megakaryocytopoiesis and that this effect can be either augmented or inhibited by the addition of several other cytokines. Recombinant IL-6, however, might affect the MK colony-forming unit (CFU-MK) by acting through bone marrow accessory cells or requiring the presence of as yet unidentified additional cytokines.

Biological Factors↗
PubMed1989

Effects of thrombocytopoiesis-stimulating factor on terminal cytoplasmic maturation of human megakaryocytes.

Aplastic anemia serum (AAS) contains humoral factors that alter both proliferation and maturation of human megakaryocytes (MK). The ability of AAS to augment MK colony formation (colony-forming unit, CFU-MK) was neutralized by an antiserum against MK colony-stimulating factor (MK-CSF), a glycoprotein isolated from AAS. The adsorbed AAS still retained the ability to accelerate cytoplasmic maturation of recognizable MK. Similar experiments were done with thrombocytopoiesis-stimulating factor (TSF) and an anti-TSF antiserum to further define the activity in AAS responsible for accelerating cytoplasmic maturation. Bone marrow fractions enriched for recognizable human MK, but devoid of CFU-MK, were obtained by centrifugal elutriation and placed in short-term liquid cultures. MK progressed through identifiable maturation stages (1-4) more quickly in the presence of either TSF or AAS. TSF slightly enhanced the cloning efficiencies of CFU-MK, but did not alter the number of MK in individual colonies derived from non-adherent, low-density, T-cell-depleted bone marrow. In contrast, granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 3 (IL-3), and crude AAS substantially augmented both MK colony formation and cells per colony. TSF also doubled the percent 35S incorporation into platelets of immunothrombocythemic mice, but stimulation was completely abolished by anti-TSF. Anti-TSF antiserum was then used to analyze the promotion of MK colony formation by cytokines. Cloning efficiencies of CFU-MK were reduced to baseline values when TSF was pretreated with anti-TSF; however, the MK colony-stimulating activity (MK-CSA) of GM-CSF, IL-3, or AAS was not altered by adsorption with anti-TSF. In contrast, the cytoplasmic maturation of recognizable MK was slower, and fewer mature stage-4 cells were present at days 1-3 in AAS adsorbed with anti-TSF than MK cultured in AAS treated with normal rabbit serum or untreated AAS. Therefore, TSF appears to be a major factor in AAS that accelerates terminal maturation of human MK. TSF primarily affects megakaryocytopoiesis by promoting MK maturation rather than enhancing CFU-MK proliferation.

Anemia, Aplastic↗
PubMed1988

KRAS2 oncogene overexpression in myelodysplastic syndrome with translocation 5;12.

The factors that initiate and maintain the abnormal hematopoietic clone in the myelo-dysplastic syndromes (MDS) remain largely unknown. We describe a patient with MDS associated with an abnormal karyotype, 46,XY,t(5;12)(q31;p12). According to the FAB cooperative group classification, the patient was classified as chronic myelomonocytic leukemia. Because of the particular chromosomal translocation, the structure-function relationship of three genes relevant to the translocation breakpoints, CSF2, FMS, and KRAS2, was studied in bone marrow and peripheral blood lymphocytes in this patient. No major structural alterations were observed at these three genetic loci. Although the levels of expression of the CSF2 and FMS genes remained unaltered, the KRAS2 oncogene was overexpressed approximately six-fold in bone marrow cells from the MDS patient compared with normal donors. We postulate that the RAS oncogene activation may be instrumental in the genesis of MDS.

Adult↗
PubMed1988

Temporal adaptation of neutrophil oxidative responsiveness to n-formyl-methionyl-leucyl-phenylalanine. Acceleration by granulocyte-macrophage colony stimulating factor.

This investigation was undertaken to clarify the mechanism by which purified recombinant human granulocyte-macrophage colony stimulating factor (GM-CSF) potentiates neutrophil oxidative responses triggered by the chemotactic peptide, FMLP. Previous studies have shown that GM-CSF priming of neutrophil responses to FMLP is induced relatively slowly, requiring 90 to 120 min of incubation in vitro, is not associated with increased levels of cytoplasmic free Ca2+, but is associated with up-regulation of cell-surface FMLP receptors. We have confirmed these findings and further characterized the process of GM-CSF priming. We found that the effect of GM-CSF on neutrophil oxidative responsiveness was induced in a temperature-dependent manner and was not reversed when the cells were washed extensively to remove the growth factor before stimulation with FMLP. Extracellular Ca2+ was not required for functional enhancement by GM-CSF and GM-CSF alone effected no detectable alteration in the 32P-labeled phospholipid content of neutrophils during incubation in vitro. Our data indicate that GM-CSF exerts its influence on neutrophils by accelerating a process that occurs spontaneously and results in up-regulation of both cell-surface FMLP receptors and oxidative responsiveness to FMLP. Thus, the results demonstrate that, with respect to oxidative activation, circulating endstage polymorphonuclear leukocytes are nonresponsive or hyporesponsive to FMLP; functional responsiveness increases dramatically as surface FMLP receptors are gradually deployed after the cells leave the circulation. Thus, as neutrophils mature, their responsiveness to FMLP changes in a manner which may be crucial for efficient host defense. At 37 degrees C, this process is markedly potentiated by GM-CSF. We conclude that endogenous GM-CSF, released systemically or at sites of infection and inflammation, potentially plays an important role in host defense by accelerating functional maturation of responding polymorphonuclear leukocytes.

Cell Differentiation↗
PubMed1988

Synergistic interaction between complement receptor type 2 and membrane IgM on B lymphocytes.

We sought biochemical evidence for a role of C receptors types 1 (CR1) and 2 (CR2) in B cell activation. A flow cytometer was used to measure the fluorescence of tonsillar cells that had been loaded with the calcium-dependent indicator indo-1, and cells were stimulated by cross-linking cell-bound DA4.4 anti-IgM, Yz-1 anti-CR1 or HB5 anti-CR2 with goat anti-mouse IgG. There was a direct dose-response relationship between the proportion of cells having increased cytoplasmic free calcium concentration (Cai) after addition of second antibody and the amount of cell-bound Fab' DA4.4. In contrast, no rise in Cai was observed after cross-linking bound Yz-1 or HB5. To determine whether CR1 or CR2 could modify the increase in Cai induced by cross-linking membrane IgM, Cai was monitored after addition of second antibody to cells bearing combinations of either Yz-1 or HB5 with a limited amount of DA4.4. The combination of Yz-1 with DA4.4 yielded little or no further increase in the percentage of cells responding to cross-linking with elevated Cai compared with DA4.4 alone. However, the combination of HB5 with limited DA4.4 synergistically enhanced this response, resulting in stimulation that was equivalent to that obtained with optimal concentrations of DA4.4. The synergistic effect of CR2 was also observed with avidin as the cross-linking reagent for bound biotinylated HB5 and DA4.4, occurred in the presence of EGTA, and did not require T cells. Studies of the proliferation of B cell-enriched PBMC demonstrated that, whereas HB5 coupled to Sepharose alone induced little or no DNA synthesis, the combination of HB5 with limited DA4.4 on Sepharose induced a dose-related synergistic increase in the incorporation of [3H]thymidine.

B-Lymphocytes↗