Isomer depletion as experimental evidence of nuclear excitation by electron capture.

The atomic nucleus and its electrons are often thought of as independent systems that are held together in the atom by their mutual attraction. Their interaction, however, leads to other important effects, such as providing an additional decay mode for excited nuclear states, whereby the nucleus releases energy by ejecting an atomic electron instead of by emitting a γ-ray. This 'internal conversion' has been known for about a hundred years and can be used to study nuclei and their interaction with their electrons. In the inverse process-nuclear excitation by electron capture (NEEC)-a free electron is captured into an atomic vacancy and can excite the nucleus to a higher-energy state, provided that the kinetic energy of the free electron plus the magnitude of its binding energy once captured matches the nuclear energy difference between the two states. NEEC was predicted in 1976 and has not hitherto been observed. Here we report evidence of NEEC in molybdenum-93 and determine the probability and cross-section for the process in a beam-based experimental scenario. Our results provide a standard for the assessment of theoretical models relevant to NEEC, which predict cross-sections that span many orders of magnitude. The greatest practical effect of the NEEC process may be on the survival of nuclei in stellar environments, in which it could excite isomers (that is, long-lived nuclear states) to shorter-lived states. Such excitations may reduce the abundance of the isotope after its production. This is an example of 'isomer depletion', which has been investigated previously through other reactions, but is used here to obtain evidence for NEEC.

Factors influencing hematopoietic spleen colony formation in irradiated mice. 3. The effect of repetitive irradiation upon proliferative ability of colony-forming cells.

Mice were irradiated repetitively at 6 wk intervals. The proliferative capacity of the hematopoietic stem cell compartment was studied after each irradiation and compared to that of age-matched controls which had been irradiated only once. Hematopoietic proliferation capacity was measured by determining the number of spleen colonies, splenic iron uptake, spleen weight, and volume of packed red cells 10 days after irradiation. 6 wk after the first irradiation, the hematopoietic compartment was apparently supranormal in size for, when such mice were again irradiated, their postirradiation hematopoiesis was in excess of that of the controls. Thereafter, there was a steady decline in regenerative capacity with each sequential irradiation. After the sixth irradiation, the number of spleen colonies and iron uptake were reduced to one-fifth of that of singly irradiated controls. A decline in body weight and an increase in irradiation mortality accompanied the decline in postirradiation hematopoiesis. The degree of measured decline in hematopoietic proliferative ability was less than that observed by other investigators who studied the effect of serial transplantation of cells upon their ability to proliferate. Furthermore, even after the sixth irradiation, a marked stimulation of postirradiation hematopoiesis was induced by bleeding the animals before irradiation.

Factors influencing hematopoietic spleen colony formation in irradiated mice. II. The effect of foreign materials.

Normal dog plasma and serum, human, rat, and Swiss-Webster mouse plasma, phytohemagglutinin, sheep red cells, mumps and influenza vaccine, fibrinogen, and endotoxin injected before irradiation led to an increased number of endogenously derived spleen colonies in irradiated mice. Spleen weight and uptake of radioactive iron and iododeoxyuridine into such spleens were also increased. The relationship between these parameters of splenic hematopoiesis was unchanged by plasma injection suggesting that, while the number of colonies was increased, the composition of individual colonies was unchanged. This conclusion was supported by studies on plethoric mice in which splenic erythropoiesis is abolished. Increased splenic hematopoiesis was accompanied by an increase in the volume of packed red blood cells 10 days after irradiation. The total volume of plasma injected, the number of days of plasma injection preceding irradiation, and the route of administration were all important variables influencing the effect of plasma injections. Crude fractions of human albumin and gamma globulin, cortisol, C57BL (maternal) and DBA (paternal) mouse plasma, and isogeneic plasma were without effect. The ineffectiveness of isogeneic and closely related allogeneic plasma rendered unlikely the hypothesis that this effect represented the presence of homeostatic hematopoietic regulating factors in plasma. The increased hematopoiesis induced with plasma appeared to be limited to the spleen, for increased bone marrow hematopoiesis was not detected. Certain observations suggested that the effect of plasma may not be due to an antigenic or an inflammatory effect. From current observations, it was unclear whether the increased colonies induced by plasma were representative of expansion of the colony-forming cell pool or of increased efficiency of growth of the fraction surviving irradiation.

Factors influencing hematopoietic spleen colony formation in irradiated mice. I. The normal pattern of endogenous colony formation.

Data pertaining to the endogenous mouse spleen colony system, 10 days postirradiation, are presented. The D(o) for visible colonies is 78 R, while that for 6 hr iron uptake over a range of 600-800 R is 50 R. The D(o) for spleen weight is 196 R and that for IUdR uptake is 193 R. These measurements increase with the age of the mouse. Hypertransfusion decreases spleen iron uptake and colony number. DF-(32)P and sodium sulfate-(35)S are not useful indicators of splenic hematopoiesis in this system. Visible hematopoietic colonies in the spleen are not produced by vinblastine, nitrogen mustard, methotrexate, or cyclophosphamide.

Aplastic anaemia in association with coeliac disease: a series of three cases.

We report a series of three patients in whom the diagnoses of aplastic anaemia (AA) and coeliac disease were made concurrently. Haematological manifestations of coeliac disease are well described but this is the first report to suggest an association with aplastic anaemia. 'Silent/atypical coeliac disease', in the absence of gastrointestinal symptoms, is increasingly recognised and patients may present with generalised symptoms, such as malaise and fatigue, which are easily attributable to AA. Immunosuppressive therapy for AA could modulate the course of celiac disease. We recommend clinicians should be vigilant for signs of coeliac disease in patients with AA.

Neutrophil kinetics in acute infection.

Neutrophil kinetics of acute experimental infection were studied with diisopropylfluorophosphate-(32)P labeling in 31 dogs inoculated intrabronchially with pneumococci. In vitro neutrophil labeling indicated a rapid transit time through the blood in early infections, with an elevated marginal granulocyte pool sometimes preceding an elevation of the circulating granulocyte pool. 13 hr after infection, the circulating and total blood granulocyte pools were increased but the rate of neutrophil transit through the blood was normal. During the recovery from infection there was a marked prolongation of neutrophil blood transit time, suggesting virtually complete cessation of bone marrow release of neutrophils into the blood. Labeling of neutrophils in vivo indicated an increased rate of emptying of the bone marrow storage pool proportional to the severity of infection as measured by the fever index. The change in the blood ratio of nonsegmented to segmented neutrophils was a much more accurate index of the severity of infection than the blood granulocyte concentration, correlating significantly with the fever index.

Lack of clinical efficacy of rituximab in the treatment of autoimmune neutropenia and pure red cell aplasia: implications for their pathophysiology.

We describe 11 patients with severe refractory autoimmune cytopenias treated with the anti-CD20 monoclonal antibody rituximab. Six patients had autoimmune neutropenia (AIN), two had pure red cell aplasia (PRCA), one had AIN and autoimmune haemolytic anaemia, one had AIN and immune thrombocytopaenia purpura (ITP) and one had PRCA and ITP. Rituximab was administered at a dose of 375 mg/m(2) as an intravenous infusion weekly for 4 weeks. Six of eight patients with AIN and all three patients with PRCA did not respond. Two patients died: one with resistant AIN and autoimmune haemolytic anaemia died of pneumocytis pneumonia infection, and one with PRCA and ITP died of an acute exacerbation of bronchiectasis. Rituximab in AIN and PRCA appears to be less effective than Campath-1H when compared to historical data from our group. This supports the hypothesis that T cells may be important in the pathophysiology of AIN and PRCA.

Low dose antithymocyte globulin for the treatment of older patients with aplastic anaemia.

We report 14 older patients with aplastic anaemia (AA) who were treated with 'low dose' antithymocyte globulin (ATG). The aims of the study were to assess the efficacy and safety of reduced dose ATG in patients over the age of 60 years. Median age was 71 years (range 62-74 years). At the study endpoint (response to treatment at 6 months) 12 patients were evaluable. All patients received lymphoglobuline (horse ATG; Genzyme) at a dose of 0.5vials/10kg/day for 5 days (5mg/kg/day, equivalent to one-third of the standard dose). There were no deaths attributed to ATG. Two patients died during follow-up, from sepsis and anaphylaxis following platelet transfusion, respectively. Only one of the 12 evaluable patients responded to treatment and remains transfusion independent at 14 months after ATG. These results suggest that this lower dose of ATG, though well tolerated, had low efficacy in the treatment of AA.

Bone marrow transplants from mismatched related and unrelated donors for severe aplastic anemia.

For patients with acquired severe aplastic anemia without a matched sibling donor and not responding to immunosuppressive treatment, bone marrow transplantation from a suitable alternative donor is often attempted. We examined risks of graft failure, graft-versus-host disease and overall survival after 318 alternative donor transplants between 1988 and 1998. Sixty-six patients received allografts from 1-antigen and 20 from >1-antigen mismatched related donors; 181 from matched and 51 from mismatched unrelated donors. Most patients were young, had had multiple red blood cell transfusions and poor performance score at transplantation. We did not observe differences in risks of graft failure and overall mortality by donor type. The probabilities of graft failure at 100 days after 1-antigen mismatched related donor, >1-antigen mismatched related donor, matched unrelated donor and mismatched unrelated donor transplants were 21, 25, 15 and 18%, respectively. Corresponding probabilities of overall survival at 5 years were 49, 30, 39 and 36%, respectively. Although alternative donor transplantation results in long-term survival, mortality rates are high. Poor performance score and older age adversely affect outcomes after transplantation. Therefore, early referral for transplantation should be encouraged for patients who fail immunosuppressive therapy and have a suitable alternative donor.

Comparison of the sensitivities of human, canine, and murine hematopoietic precursor cells to adriamycin and N-trifluoroacetyladriamycin-14-valerate.

The sensitivities of leukocyte-committed stem cells of human, dog, and mouse bone marrow to an 18-hr exposure to Adriamycin (ADR) and N-trifluoroacetyladriamycin-14-valerate (AD32) were compared using the agar diffusion chamber assay. The survival of in situ mouse marrow stem cells following the drugs was also measured. The in vivo doses required to produce 37% survival of hematopoietic precursor cells for human, dog, mouse, and in situ mouse marrow stem cells for ADR were 9.5, 3.5, 8, and 8 mg/kg, respectively, while those for AD32 were 22, 17, 37, and 40 mg/kg. Mouse bone marrow cellularity was reduced to 50% by drug doses producing 3 and 7% stem cell survival. AD32 given i.p. to mice was less effective than i.v. drug in producing marrow stem cell death, reduction of marrow cellularity, or acute lethality. Although more AD32 than ADR was required to kill marrow stem cells from each species and canine marrow stem cells were the most sensitive to either drug, human stem cells were relatively more sensitive to AD32 than were mouse stem cells. The reverse was true for ADR. Granulocytopenia may be an important limiting toxicity in the clinical use of AD32.

The effects of cancer chemotherapeutic agents on normal hematopoietic precursor cells: a review.

The effects of antineoplastic agents, singly or in combination, on normal hematopoietic precursor cells have been reviewed. Following a description of the assays used (e.g., spleen colony, in vitro colony, repopulating ability), the dose response and/or time response for each drug are presented by species and by assay as available. The schedule of drug administration, the time of the assay, and the proliferative state of the target population are the most important determinants. Alkylating agents, antitumor antibiotics, and 5-fluorouracil have exponential dose survival curves. "Phase-specific" agents such as antimetabolites, Vinca alkaloids, and ribonucleotide reductase inhibitors have plateaus in their dose survival curves, although the level of this plateau is different for different agents. Most drugs are more effective against rapidly proliferating cells although busulfan is less effective. Direct interspecies comparisons are possible with some of the clonogenic assays, which may allow prediction of the magnitude of human hematological toxicity for new agents or combinations.

In vivo drug sensitivity assay of clonogenic human melanoma cells and correlation with treatment outcome.

In vitro tests of tumor cell drug sensitivity have been suggested as a means of selecting more appropriate clinical strategies against human cancer and improving preclinical drug development. The lack of biotransformation in these in vitro assays precludes the meaningful assessment of several major chemotherapeutic agents, including dacarbazine and cyclophosphamide. In vivo drug exposure of tumor cells in agar diffusion chambers placed in mice offers a possible solution to problems of drug biotransformation and pharmacokinetics. We have prospectively used this system as an assay for sensitivity of clonogenic human melanoma cells. Tumor cells were tested fresh, cryopreserved, and/or cultured in vitro before or after clinical use of dacarbazine, semustine, and mitolactol in 41 patient-drug combinations in which a clinical correlation could be made. Tumor cell drug sensitivity in the assay using fresh or cryopreserved tumor cells was highly correlated with clinical response and resistance with clinical nonresponse. Cultured melanoma cells exhibited enhanced plating efficiency in comparison to both fresh and cryopreserved cells of the same tumor. Cultured cells also showed increased drug sensitivity which did not correlate with drug sensitivity of the same fresh or cryopreserved tumor or with clinical response. Tumor cell drug sensitivity assays carried out in vivo provide a possible basis for preclinical evaluation of drugs which are unsuitable for in vitro testing.

Relationship of Bacillus Calmette-Guérin-induced suppressor cells to hematopoietic precursor cells.

Bacillus Calmette-Guérin (BCG) stimulated the proliferation of granulocyte-macrophage colony-forming cells (CFU) and activated suppressor cells that inhibit the immunization of T-lymphocytes in vitro. Increases in both CFU concentration and suppressor cell activity were moderate in the bone marrow and marked in the spleen of mice given BCG i.v. In the bone marrow, these increases were apparent 2 days after treatment with BCG, while in the spleen they did not occur until 7 days after BCG. A BCG strain that produced no increases in CFU concentration also produced no activation in suppressor cell activity. Fractionation of spleen cells through nylon wool and density gradients revealed that cell populations enriched in CFU were also enriched in suppressor cell activity. The paralelism in the response to CFU and suppressor cells to BCG indicates that there is a close relationship between these two cell populations.

Sensitivity of bone marrow hematopoietic colony-forming cells from mice, dogs, and humans to carminomycin, marcellomycin, aclacinomycin A, and N,N-dibenzyldaunorubicin and its relationship to clinical toxicity.

The sensitivity of bone marrow granulocyte-macrophage colony-forming cells to 4 anthracyclines, carminomycin, marcellomycin, aclacinomycin A, and N,N-dibenzyldaunorubicin, was studied using the agar diffusion chamber technique which allows exposure of target cells to drug metabolized by the chamber-bearing host after i.v. injection. Colony-forming cells from mice, dogs, and humans were all found to have exponential dose-response curves for the agents studied, with variation of the slopes between species and agents. Species sensitivities as determined by the assay related well to the available toxicological and clinical data for specific drugs. The rank order of sensitivity of human marrow colony-forming cells to five anthracyclines tested in this and a previous study related very closely to doses producing moderate leukopenia in Phase I and II clinical studies. A dose of 200 mg/sq m of N,N-dibenzyldaunorubicin would be expected to produce moderate leukopenia in future clinical trials. This assay may be useful in predicting human bone marrow toxicity of new agents before actual clinical trial because of the ability to study the survival of human colony-forming cells directly.

Antitumor activity of the 3'-chloroethylnitrosourea analog of thymidine and the prevention by co-administered thymidine of lethality but not of anticancer activity.

The effect of the 3'-nitrosourea analog of thymidine (3'-[3-(2-chloroethyl)-3-nitrosoureido]-3'-deoxythymidine; 3'-CTNU) on the growth of the murine L1210 and P388 leukemias in mice was investigated. A single injection of 3'-CTNU (40 mg/kg) was minimally toxic to mice bearing the L1210 leukemia and produced 60-day survivors. The coadministration of thymidine did not prevent the initial loss of weight caused by 3'-CTNU but did prevent the lethality otherwise produced in non-tumor-bearing mice. A single dose of thymidine (2 g/kg) administered to L1210-bearing mice had no anticancer activity and when coadministered with 3'-CTNU had no detrimental effect on the potent antitumor effects of 3'-CTNU. Similar results were obtained against P388 leukemia. The hematopoietic toxicity produced by the administration of 3'-CTNU to non-tumor-bearing mice, as evidenced by changes in the white blood cells, neutrophil, and agar diffusion chamber precursor cell concentrations in the hematocrit and in bone marrow cellularity, could not be prevented by thymidine. Therefore, the lethality produced by 3'-CTNU is probably not related to hematopoietic toxicity since the coadministration of thymidine completely prevented any lethality.

Evaluation of some anthracycline antibiotics in an in vivo model for studying drug-induced human leukemia cell differentiation.

Human acute promyelocytic leukemia cells (HL-60) were induced to undergo terminal differentiation by treatment in vivo with marcellomycin. This was accomplished by cloning HL-60 cells in 0.3% agar in diffusion chambers, which were subsequently implanted in the peritoneal cavities of mice. These animals were given injections i.v. with anthracycline antibiotics, and the chambers were transferred to a second recipient 24 hr later. After an additional 8 days, the chambers were removed, the cloning efficiency was determined, and colonies were scored for the presence of differentiated cells based on their ability to reduce nitro blue tetrazolium (NBT). Marcellomycin produced dose-dependent decreases in cloning efficiency and increases in the number of differentiated cells present in chambers. At all dose levels of marcellomycin tested, three types of colonies were observed; these were colonies consisting entirely of undifferentiated cells and approximately equal numbers of colonies consisting of solely differentiated cells and those with mixtures of both differentiated and undifferentiated cells. An 8-fold increase in colonies containing differentiated cells (both pure and mixed) was observed after a single injection of marcellomycin (10 mg/kg), a dose which reduced cloning efficiency by 40%. At that dosage level, aclacinomycin A also induced differentiation, while doxorubicin was ineffective, a finding consistent with the effects of these anthracyclines on HL-60 cells in suspension culture. In addition to the functional changes accompanying differentiation, commitment was characterized by a limitation in proliferative potential. Thus, the average size of uniform NBT-positive colonies was approximately 16 cells, and few clones of NBT-positive cells greater than 32 cells in number were observed; this contrasted with NBT-negative clones which contained up to 100 cells. This finding suggests that HL-60 cells undergo an average of four and a maximum of five divisions upon commitment to granulocytic differentiation. The in vivo system described may be useful in further evaluation of differentiation-inducing agents for therapeutic potential after an initial in vitro screen to identify active compounds.

Pharmacological studies with vinblastine in the dog.

Tritiated vinblastine was prepared by catalytic exchange and its metabolism was studied in dogs. Plasma levels of drug fell in biphasic mode with initial and secondary phase half-lives of 17 to 38 min and 3 to 5 hr, respectively. Between 28.6 and 79.1% of plasma tritium was precipitable with cold trichloroacetic acid and thus was presumably protein bound. Blood leukocytes had levels of intracellular tritium between 2.4 and 11.8 times those of the coincident plasma samples. Over a 9-day period, urinary excretion accounted for 12.1 to 16.8% and fecal excretion accounted for 30.1 to 36.1% of the administered radioactivity. Ratios of biliary to plasma radioactivity varied between 7.3 and 56.9, with unchanged vinblastine being the mamor component (46.8 to 80.7%) in the bile.

Phase I studies with trimetrexate: clinical pharmacology, analytical methodology, and pharmacokinetics.

Twenty-two patients with advanced solid tumors were treated with a quinazoline folate antagonist, trimetrexate, to determine the toxicity spectrum, the maximal tolerated dose, and the pharmacokinetics of the drug. Negligible toxicity was seen with single doses of 10-70 mg/m2 given as a 1-h infusion. Single doses of 120 mg/m2 infused over 1 h caused moderate to grade 4 toxicity in five of nine patients treated. Two patients who had no toxicity at this level were escalated to a dose of 213 mg/m2 with mild to moderate toxicity. The primary dose-limiting toxicity was myelosuppression. Moderate transaminase elevations, rash, anorexia, nausea and vomiting, and mucositis were occasionally seen. Although there was variation in dose tolerance to this drug, with selected patients able to tolerate higher doses, we consider 120 mg/m2 every 2 weeks to be the maximal tolerated dose, and the recommended Phase II starting dose. Trimetrexate plasma concentration-time curves were best described as biphasic (N = 9) or triphasic (N = 5) in form. The half-life of the terminal elimination-phase was 16.4 h. The mean residence time was 17.8 h. The volume of distribution of the plasma compartment and the volume of distribution at steady-state were 0.17 and 0.62 liter/kg, respectively. Plasma clearance was 53 ml/min. Plasma concentrations as determined by dihydrofolate reductase enzyme inhibition assay and high-performance liquid chromatography were initially identical, but diverged at later times. Divergences were seen also in urinary recovery as determined by the two methods. Both results suggest the appearance of metabolite(s) of trimetrexate which can inhibit dihydrofolate reductase. Measurable objective solid tumor responses were not seen in this Phase I study, although three patients with colon cancer had stable disease lasting 18, 26, and 26 weeks, respectively.

Clinical effects and pharmacokinetics of different dosage schedules of adriamycin.

Adriamycin was administered to 60 adults and 21 children by 3 different dosage schedules: 22.5 mg/sq m (0.6 mg/kg) daily for 4 days, 15 mg/sq m (0.4 mg/kg) every 8 hr for a total of 6 doses, and 50 to 120 mg/sq m as a single dose every 3 to 4 weeks. Objective responses lasting more than 1 month occurred in 5 subjects with acute leukemias or lymphoma, 3 with transitional cell carcinomas, 2 with sarcomas, 2 with Ewing's sarcoma and 1 each with bronchogenic carcinoma, orchidoblastoma, and thymoma. Toxic reactions included nausea, vomiting, stomatitis, alopecia, and hematopoietic depression, but significant cardiac toxicity occurred in only 1 patient. Pharmacokinetic data, collected in 25 patients by fluorometric and chromatographic assay, suggested a biphasic plasma clearance of drug with initial and secondary half-lives of about 1.5 and 14 to 21 hr, respectively. When drug was given every 8 hr there was evidence of loss of an initial very rapid phase of distribution of adriamycin and its metabolites. Urinary excretion accounted for 3.4 to 38.1% of administered fluorescence over a 72-hr period; in the first 24 hr, between 48.2 and 100% of this urinary material was in the form of adriamycin; leter, this fraction declined. No adriamycin or its fluorescent metabolites could be extracted from the stools.