Modulation of the antitumor activity of 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosoure a by O(6)-methyl-2'-deoxyguanosine--a new inhibitor of O(6)-alkylguanine-DNA-alkyltransferase

O6-Methyl-2'-deoxyguanosine (O6-MedG), a novel inhibitor of O6-alkylguanine-DNA alkyltransferase (O6-AGT), has been synthesized. The ability of O6-MedG to deplete the O6-AGT activity in leukemia L1210 and melanoma B16 cells in vivo has been studied. After intraperitoneal administration of O6-MedG to mice bearing leukemia L1210 or melanoma B16, the activity of O6-AGT in tumour cells decreased by 50%. Pretreatment of leukemia L1210 bearing mice with O6-MedG (200 mg/kg) 24 hours prior to ACNU (15 mg/kg) administration resulted in six out of seven 60-day survivors. Treatment of mice with ACNU (15 mg/kg) alone increased the life span by 200%. Treatment of melanoma B16 bearing mice with O6-MedG and 3 hours thereafter with ACNU resulted in a 50% inhibition of tumour growth, whereas the inhibiting effect of ACNU alone was 16%. There was no difference in leukemia growth when L1210/BCNU bearing mice were treated with O6-MedG followed by ACNU treatment. In vivo ACNU (15 mg/kg) produced a deep and prolonged inhibition of DNA, RNA and protein synthesis in leukemia L1210 cells. The DNA synthesis in leukemia L1210/BCNU cells was shown to recover more rapidly than in L1210 cells. The activities of DNA-polymerases alpha and beta and, especially, of O6-AGT were elevated in ACNU-resistant leukemia cells as compared with ACNU-sensitive cells. The activation of some repairing enzymes, such as O6-AGT, DNA-polymerases alpha and beta as well as increased levels of GSH may play a role in the development of drug resistance to ACNU.     

Intrathecal ACNU against experimental leptomeningeal tumors

Therapeutic efficacy and cell kinetics of intrathecal ACNU, 3-(4-amino-2-methyl-5-pyrimidinyl) methyl-1-(2-chloroethyl)-1-nitrosourea, were investigated in experimental meningeal carcinomatosis rats. Therapeutic effect of intrathecal ACNU (IT ACNU) against meningeal carcinomatosis model was evaluated in rats induced by intracisternal inoculation of Walker 256 carcinosarcoma cells. The median survival time of the rats treated with IT ACNU 1.5 mg/kg on day 5 after tumor inoculation was significantly increased by 145% as compared with that of non-treatment rats. The cell kinetics was studied immunohistochemically using indirect immunoperoxidase method with bromodeoxyuridine (BrdU) and anti-BrdU monoclonal antibody (Becton-Dickinson). The meningeal carcinomatosis rats were treated with IT ACNU (1.5 mg/kg) on the fifth day after tumor inoculation. Before and 12, 24, 48, 96 or 144 hours after treatment, the rats received intravenous BrdU (200 mg/kg) injection. Thirty minutes later, the rats were sacrificed and the brains were removed. Brain sections were stained immunohistochemically with anti-BrdU monoclonal antibody. Labeling index (LI) which represented the percentage of tumor cells in synthetic phase was obtained by counting immunoreactive cells under the microscope. Before treatment, LI was around 34% on day 5 after tumor inoculation and dropped to below 20% 12 to 48 hours after IT ACNU. However, it increased to around 36% on day 4 after IT ACNU. The antineoplastic effect of IT ACNU against meningeal carcinomatosis rats might be expected in the early stage of intrathecal administration.     

Central nervous system involvement of leukemia and systemic lymphoma in children: CT and MR findings

The purpose of this paper is to retrospectively evaluate CT and MR findings of central nervous system (CNS) involvement of leukemia and systemic lymphoma in children. Over a 12-year period, sixty-five patients with leukemia and fifteen patients with systemic lymphoma underwent cerebral CT and/or MR imaging. Nine patients (11.3%) were diagnosed as CNS involvement of leukemia and lymphoma. The diagnostic criteria of CNS involvement were as follows; 1) Histological proof was confirmed by surgery, 2) Tumor cells were found in the cerebrospinal fluid examinations, 3) Increase in size of the lesion during observation without specific treatment, and 4) Response to the treatment for leukemia or lymphoma. All of nine patients fulfilled more than two criteria of 1)-4). The CT and MR abnormalities in these patients were correlated with the findings of histology, cerebrospinal fluid cytology, and/or treatment. The age of the patients ranged from 0 to 15 years old. They consisted of 6 boys and 3 girls. The CT examinations were performed before and after contrast administration. MR examinations were performed on a 1.5-T unit, and T1-weighted, T2-weighted, and proton density-weighted images were obtained using spin-echo or fast spin-echo sequences. Tumor masses were present in seven with leukemia (acute lymphoblastic leukemia 4; acute myeloblastic leukemia 1; acute promyelocytic leukemia 1; acute monocytic leukemia 1), and in two with malignant lymphoma. On the CT scan, tumor masses were hyperdense with contrast enhancement. On the MR images, their signals were variable. In all of nine patients, tumor masses were contiguous with a meningeal surface. Postcontrast T1 weighted images were valuable in demonstrating meningeal infiltration. Tumoral hemorrhage was found in two patients. In a patient with tumor at the superior sagittal sinus, venous infarct was observed. CNS leukemic and lymphomatous masses are almost hyperdense on the CT and they are characteristically contiguous with a meningeal surface. MR imaging was valuable in demonstrating meningeal infiltration. Findings of CT and MR imaging, cerebrospinal fluid examinations, and response to the treatment are useful in the differentiation of CNS involvement of leukemia and lymphoma from other lesions such as infectious diseases and leukoencephalopathy.     

Molecular basis for thymidine modulation of the efficacy and toxicity of alkylating agents

The antitumor activity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in mice previously was shown to be markedly enhanced by co-administration of thymidine. We have examined the cellular mechanisms underlying the augmentation effect of thymidine. It was found that thymidine did not increase the cytotoxicity of BCNU for B16/F10 melanoma or L1210 leukemia cells in vitro. Instead, thymidine appeared to augment the activity of tumor-specific cytotoxic T-cells in tumor-bearing mice, which specifically rejected a secondary challenge with the B16/F10 tumor. Thus, development of an antitumor immune response is facilitated by thymidine in BCNU-induced immunosuppressed mice. These preclinical studies suggested that combination therapy with alkylating agents and thymidine may be a more efficacious and less toxic anticancer therapy. The potential efficacy of the sequential administration of dacarbazine (DTIC), BCNU, and thymidine in patients with advanced malignant melanoma was investigated. As predicted from animal studies, sequential administration of DTIC, BCNU, and thymidine is a relatively nontoxic therapy for metastatic melanoma. This treatment induced durable responses in up to 35% of patients, and hence is superior to many commonly used toxic combination chemotherapies. The mechanism of action, although not well characterized, is thought to be mediated through protection of the cellular immune process, as well as organ function, from alkylating agent toxicity through modulation of DNA repair enzymes such as O(6)-alkylguanine-DNA alkyltransferase in normal tissue. Thus, thymidine is a biomodulator, which not only protects patients from hematologic, pulmonary, and hepatic toxicities associated with DTIC and BCNU chemotherapy, but also potentiates therapeutic efficacy.     

The effect of benzylpenicillin and doxycycline on toxicity and antineoplastic action of cyclophosphamide and methotrexate in mice

The effect of benzylpenicillin and doxycycline on toxicity and anticancer activity of cyclophosphamide and methotrexate in mice was studied. Benzylpenicillin applied both at once repeatedly enhances anticancer activity of cyclophosphamide against L 1210 leukemia within limited range of CP. Benzylpenicillin does not change anticancer activity of methotrexate, but doxycycline of both cyclophosphamide and methotrexate, against L 1210 leukemia in mice.     

The SPINRPHEX club

A 3-year-old Japanese domestic cat with a diagnosis of lymphocytic leukemia showed severe generalized seizures in the course of chemotherapy after leukemic condition was improved clinically. Computed tomography (CT) and magnetic resonance (MR) imaging of the brain were carried out. Both contrast procedures disclosed enhancements at the falx cerebri and the margin of cerebral cortex. Among these procedures contrast MR imaging demonstrated the lesion most clearly. Cytological examination of cerebrospinal fluid obtained by spinal puncture showed the infiltration of malignant cells and the diagnosis of meningeal syndrome associated with lymphocytic leukemia was defined. Intrathecal administration of cytosine arabinoside partially improved the neurologic dysfunction. Autopsy and histopathological examination confirmed the infiltration of leukemic cells in the areas of meningeal lesion demonstrated with contrast CT and MR imaging. Thus these imaging techniques, especially contrast MR imaging, are useful tools for rapid and precise diagnosis of meningeal syndrome.     

Effect of dose, schedule, and route of administration on the in vivo toxicity and antitumor activity of two activated sulfhydryl derivatives of cyclophosphamide

Two cyclophosphamide (CP) derivatives, 4-S-(hexane-6-ol)-sulfidocyclophosphamide (C-1) and 4-S-(propionic acid)-sulfidocyclophosphamide (C-2), that hydrolyze spontaneously under physiological conditions to 4-hydroxycyclophosphamide, are compared to CP for antitumor activity in male C57BL/6 x DBA/2 F1 mice with ascites L1210 leukemia or solid Lewis lung carcinoma. When C-1 or C-2 is administered i.p. as a single injection at 10% lethal dose (approximately LD10) to mice bearing L1210 (1 x 10(5) cells i.p.), early treatment produces a 5- to 6-log tumor cell kill and results in substantial numbers of long-term survivors (greater than or equal to 30 days). Such antitumor activity is comparable to that of CP treatment. However, i.p. administration of either sulfido derivative produces liver atrophy and fibrosis of hepatic capsular structures. Hepatotoxicity is eliminated if single-dose C-2 (less than or equal to LD10) is administered i.v.; however, when administered by this route, C-2 results in only a 1-log cell kill of i.v. implanted leukemic cells as compared to the 4-log tumor cell kill obtained with CP given i.v. In addition to hepatotoxicity, C-2 causes an acute and dose-limiting toxicity in mice, manifested by severe muscular spasms and cessation of breathing. In the treatment of advanced L1210, C-2 shows no therapeutic advantage over CP. When mice bearing s.c. Lewis lung carcinoma receive early i.p. treatment with CP, C-1, or C-2, each drug results in long-term tumor-free survivors. However, CP (< LD10) consistently cures all mice, whereas C-1 or C-2 (approximately LD10) produces only 10 to 30% tumor-free survivors. These data suggest that, in the L1210 and Lewis lung tumor systems studied, the two activated CP derivatives offer no therapeutic advantage over CP. In addition, two forms of toxicity occur with these derivatives that do not occur with CP.     

Value of radiotherapy in disseminated high-grade non-Hodgkin''s lymphoma]

The usefulness of immunohistochemical demonstration with anti-bromodeoxyuridine (BrdU) monoclonal antibody for estimating proliferative activity was evaluated in experimental meningeal carcinomatosis model. The experimental model was developed by inoculation of 1 x 10(4) Walker 256 carcinosarcoma cells into the cisterna magna of female Wistar rats. Every consecutive day after tumor inoculation, the rat was perfused by saline and then sacrificed 30 min after intravenous BrdU (200 mg/Kg) injection. The brain was removed, fixed in 80% ethanol and embedded in paraffin. Coronal sections of the brain 6 mu in thickness were obtained and stained immunohistochemically using the indirect immunoperoxidase (ABC) method with anti-BrdU monoclonal antibody (Becton-Dickinson). The sections were counterstained by hematoxylin. Labeling index (LI) which represented the percentage of tumor cells in synthetic phase was obtained by counting immunoreactive cells under the microscope. LI was as low as 10.8% to 16.9% in the first 3 days after tumor inoculation. Four to 6 days after tumor inoculation when tumor cells grew several layers in the subarachnoid space, LI was 24.0% to 40.1%. LI increased to reach a plateau around 40.7% to 48.2%, 7 to 9 days after tumor inoculation. Ten days after inoculation when necrosis appeared in the tumor, BrdU-positive cells declinded and LI was between 29.1% to 35.0%. It is a useful method to estimate the proliferative activity of the experimental brain tumors, design treatment modalities and evaluate the effect of chemotherapeutic agents by using immunohistochemical demonstration with anti-BrdU monoclonal antibody. Therefore, we suggest that chemotherapy against malignant leptomeningeal tumors shall be carried out in early or intermediate stage before the proliferative activity reaches its plateau stage.     

Nitrosoureas in multiple myeloma

A number of cooperative-group and single-institution studies have shown that BCNU used in combination with prednisone alone or with melphalan,cyclophosphamide, and prednisone is useful for remission induction in patients with previously untreated multiple myeloma. In this setting, results with BCNU (and probably CCNU) are as good as (but not superior to)the results obtained to the frequency of remission induction, duration of remission, and survival. BCNU plus prednisone also appears to be equal to melphalan plus prednisone for remission-maintenance therapy, although it is still unclear whether maintenance therapy is superior to discontinuation of therapy during remission. At the present time, the major use of the nitrosoureas in multiple myeloma appears to be for patients who enter remission with conventional alkylating-agent therapy and later relapse. BCNU and CCNU are occasionally effective when used as single agents or in combination with other alkylating agents for relapsing patients. Results of a pilot study at the University of Arizona with low doses of BCNU and adriamycin for patients relapsing on alkylating-agent therapy have been encouraging, with a 54% (seven of 13 patients) incidence of CRs and PRs. The use of this combination in conjunction with vincristine and prednisone for relapsing patients is under investigation by the Southwest Oncology Group.     

Possibility of the use of perfluorochemicals (fluorocarbons) as adjuvants in chemotherapy of cancer

In Fischer 344 rats weighing about 100 gr., 7 X 10(5) 9L tumor cells were implanted into right cerebral hemisphere. BCNU. Fluosol-43 (perfluorochemicals blood substitute), or combined therapy BCNU and Fluosol-43 were initiated on Day 7 postimplantation and its therapeutic effect was studied. Mean survival time of control animals was 15.23 +/- 2.84 (SD) days, the group of Fluosol-43 treated in oxygen chamber (95% Oxygen & 5% Carbon Dioxide) was 15.30 +/- 2.11 (SD) days. BCNU treatment alone prolonged the mean survival time to 20.90 +/- 3.80 (SD) days, BCNU plus Fluosol-43 in normal aeration was 21.20 +/- 2.63 (SD) days. On the other hand, BCNU plus Fluosol-43 in oxygen chamber showed a significant increase of mean survival time of 32.27 +/- 4.80 (SD) days (p less than 0.005). From these results, it was concluded that Fluosol-43 (perfluorochemicals) with oxygen might have a synergistic effect for BCNU chemotherapy.     

Topical treatment of early cutaneous T-cell lymphoma

The two major topical treatment modalities for cutaneous T-cell lymphoma (CTCL) are mechlorethamine (nitrogen mustard) and topical carmustine (BCNU). Topical mechorethamine hydrochloride has been used since the late 1950s as therapy for CTCL. Topical BCNU solution is a highly effective treatment for early stage mycosis fungoides. This article describes these two modalities.     

Secretion of parathyroid hormone by abnormal human parathyroid glands in vitro

Radiation survival curves for Lewis lung tumours in the lungs ranging in size from 0-5 to 20 mm3 have been obtained, and a size-dependent variation in hypoxic fraction was found. Cell-survival studies following treatment of various sizes of s.c. tumours indicated that the effects of 60Co gamma-rays and the chemotherapeutic agents 1,3-bas(2-chloroethyl)-1-nitrosourea (BCNU) and cyclophosphamide are all size-dependent. Large pulmonary nodules which had regressed but had not been cured by cyclophosphamide regrew with a radiosensitivity that was characteristic of previously untreated tumours. The results give additional experimental support to the clinical interest in early adjuvant therapy of micrometastases, and sequential combined modality therapy for larger tumours.     

Combination of dihydroxyanthraquinone and radiation on L1210 murine leukemia

A new synthetic anthraquinone, dihydroxyanthraquinone (DHAQ), was tested as a single agent and in combination with whole-body x-irradiation in mice bearing L1210 leukemia in the ascites form. DHAQ alone had significant antitumor activity as evidenced by prolonged mean survival times; radiation was ineffective. The combination of the two modalities produced a therapeutic benefits greater than that produced by either agent alone: mean survival times were increased and a number of cures (animals alive at 30 days) produced. These results suggest the potential of using DHAQ and radiation in a combined modality therapeutic approach.     

Computed tomography-guided biopsy of the spine. A review of 103 patients

PURPOSE: This study was performed to evaluate relations among neutrophil count (including its course), type of lesion, treatment, and prognosis in patients with leukemia and perianal infection. METHODS: Medical records of patients with acute and chronic leukemia who were followed during the last five years were reviewed retrospectively. RESULTS: The incidence of perianal infections was found to be 7.3 percent in 259 patients with acute leukemia. Only 1 of 108 patients with chronic leukemia suffered from this problem. Twenty percent of all patients with this complication died as a result of sepsis. Perianal abscess was the sole and obligatory indication for surgical treatment in our patients. There were ten patients in each treatment group. The operative group had better results (9 cures, 1 complication vs. 3 cures, 7 complications). However, median neutrophil count at diagnosis was notably higher in the operative group 1,280/mm3 vs. 96/mm3; P = 0.075). Also, significantly more frequent abscess formations and, consequently, operative treatments were performed in patients with a period of normal neutrophil counts during the infection compared with continuously neutropenic patients (9 operative, 4 nonoperative vs. 1 operative, 6 nonoperative; P = 0.057). Ten cures, three complications vs. two cures, five complications (3 mortalities) were present in patients with and without normal neutrophil counts, respectively (P = 0.062). When only severely neutropenic patients were considered, four patients in the surgery group had normal neutrophil counts before or shortly after surgery. However, only two of eight patients with perianal cellulitis had normal counts during full-course infection (P = 0.06). CONCLUSIONS: The course of the neutrophil count during infection was an important factor affecting the perianal lesion, and indirectly, choice of treatment and prognosis. A period of normal counts during infection usually led to well bordered and fluctuant lesions, and the prognosis was acceptable with operative treatment. However, continuously neutropenic patients developed nonfluctuating indurations. We found disappointing results with nonoperative treatment of such patients. In all studies, regarding treatment of perianal infections in neutropenic patients, the course of the neutrophil count and indications for surgery should be clarified to get reliable results.     

Survival of multiple myeloma patients who are potential candidates for early high-dose therapy intensification/ autotransplantation and who were conventionally treated

PURPOSE: To analyze the outcome of patients with multiple myeloma (MM) who were potential candidates for early high-dose therapy (HDT) intensification followed by autotransplantation from a series treated with conventional chemotherapy. PATIENTS AND METHODS: From January 1985 through December 1989, 487 patients with symptomatic MM were entered onto a randomized study to compare melphalan and prednisone (MP) versus vincristine, cyclophosphamide, melphalan, and prednisone (VCMP) /vincristine, carmustine (BCNU), doxorubicin, and prednisone (VBAP). The sub-group of 77 patients who could have been candidates for early intensification with HDT followed by stem-cell support (ie, < 65 years of age, stage II or III disease, performance status < 3, and objective or partial response to initial chemotherapy) are the subjects of this report. RESULTS: Seventy-seven of 487 patients could have been candidates for early intensification. The median age was 56 years (range, 27 to 64). At diagnosis, 12% had abnormal renal function, 16% hypercalcemia, and 42% serum beta 2-microglobulin level > or = 6 mg/L; 62% had stage III disease at diagnosis. Thirty-six patients were initially treated with MP and 41 with VCMP/VBAP. The median response duration to initial chemotherapy was 22 months, and the actuarial probability of being in continued first response at 5 years was 14%. After a median follow-up time of 58 months, 59 patients have died, one was lost to follow-up evaluation, and 17 are still alive 69 to 119 months after initial chemotherapy. The median survival time from initiation of treatment was 60 months and from the time when autotransplantation would be considered, 52 months. The only independent prognostic parameter for survival was renal function at diagnosis. CONCLUSION: The median survival time of patients with MM who are less than 65 years of age and who respond to initial chemotherapy is 5 years. This survival duration is similar to that reported in selected series of patients given early HDT and stresses the importance of ongoing randomized trials to determine the role of HDT in the treatment of younger myeloma patients.     

Treatment of acute lymphoblastic leukemia. 30 years' experience at St. Jude Children's Research Hospital

BACKGROUND: Therapy for childhood lymphoblastic leukemia has evolved during the past three decades, but key questions about what are the least toxic, most effective forms of treatment remain unanswered because of the lack of comprehensive follow-up information. METHODS: To assess long-term outcome in the series of clinical trials conducted at St. Jude Hospital, we compared the results of treatment typical of four eras: exploratory combination chemotherapy (era 1, 1962 to 1966; 91 patients), regimens for the control of meningeal leukemia (era 2, 1967 to 1979; 825 patients), limited intensification of therapy (era 3, 1979 to 1983; 428 patients), and extended intensification of therapy (era 4, 1984 to 1988; 358 patients). ("Intensification" refers to strategies of systemic chemotherapy that are more aggressive than conventional ones.) The major end points were survival and event-free survival; we also calculated the relative risk of treatment failure and the rate of relapse or death after treatment ended (post-treatment failure rate). RESULTS: The probability of event-free survival improved significantly in each successive era (P < 0.001 by the log-rank test), reaching 71 percent in era 4. There was a decrease of approximately 50 percent in the risk of treatment failure from one era to the next in each subgroup of patients defined according to different combinations of the leukocyte count, race, age, and sex. Leukemia appeared to be eradicated in patients who remained in complete remission for three years or more after treatment in era 4. The incidence of death due to nonleukemic causes remained 4 to 6 percent despite the trend toward more intensive treatment. An estimated 765 patients (45 percent) are long-term survivors; most of them (80 percent) have no health problems related to leukemia or its treatment. CONCLUSIONS: The development and successful application of preventive therapy for meningeal leukemia, followed by the intensification of systemic chemotherapy, has progressively improved the rate of cure of childhood lymphoblastic leukemia, with relatively few adverse sequelae.     

Risperidone compared with new and reference antipsychotic drugs: in vitro and in vivo receptor binding

Risperidone and its active metabolite 9-OH-risperidone were compared to reference antipsychotic drugs (haloperidol, pipamperone, fluspirilene, clozapine, zotepine) and compounds under development (olanzapine, seroquel, sertindole, ORG-5222, ziprasidone) for in vitro binding to neurotransmitter receptors in brain tissue and on membranes of recombinant cells expressing cloned human receptors and for in vivo occupancy of neurotransmitter receptors in rat and guinea-pig brain following acute treatment (2 h., s.c.). An ex vivo autoradiography technique was applied to determine the receptor occupancy by the drugs administered in vivo. Of particular interest are the central 5HT2A receptors and D2-type receptors. Predominant 5HT2A receptor antagonism is supposed to add to an atypical profile of the antipsychotics (treatment of the negative symptoms, low incidence of extrapyramidal side effects). D2 antagonism is required the treatment of positive symptoms. A contribution of the new dopamine receptor subtypes D3 and in particular D4 receptors has been proposed. In vitro, all compounds, except the 'typical' antipsychotics haloperidol and fluspirilene, showed higher affinity for 5HT2A than for D2 receptors. Subnanomolar affinity for human 5HT2A receptors was observed for ORG-5222, sertindole, risperidone, 9-OH-risperidone and ziprasidone. Fluspirilene, ORG-5222, haloperidol, ziprasidone, risperidone, 9-OH-risperidone and zotepine displayed nanomolar affinity for human D2 receptors. Sertindole and olanzapine were slightly less potent. Pipamperone, clozapine and seroquel showed 2 orders of magnitude lower D2 affinity in vitro. Clozapine, but even more so pipamperone, displayed higher affinity for D4 than for D2 receptors. For most other compounds, D4 affinity was only slightly lower than their D2 affinity. Seroquel was totally devoid of D4 affinity. None of the compounds had nanomolar affinity for D1 receptors; their affinity for D3 receptors was usually slightly lower than for D2 receptors. In vivo, ORG-5222, risperidone, pipamperone, 9-OH-risperidone, sertindole, olanzapine, zotepine and clozapine maintained a higher potency for occupying 5HT2A than D2 receptors. Risperidone and ORG-5222 had 5HT2A versus D2 potency ratio of about 20. Highest potency for 5HT2A receptor occupancy was observed for ORG-5222 followed by risperidone and olanzapine. Ziprasidone exclusively occupied 5HT2A receptors. ORG-5222, haloperidol, fluspirilene and olanzapine showed the highest potency for occupying D2 receptors. No regional selectivity for D2 receptor occupancy in mesolimbic versus nigrostriatal areas was detected for any of the test compounds. Risperidone was conspicuous because of its more gradual occupancy of D2 receptors; none of the other compounds showed this property. The various compounds also displayed high to moderate occupancy of adrenergic alpha 1 receptors, except fluspirilene and ziprasidone. Clozapine, zotepine, ORG-5222 and sertindole occupied even more alpha 1 than D2 receptors. Clozapine showed predominant occupancy of H1 receptors and occupied cholinergic receptors with equivalent potency to D2 receptors. A stronger predominance of 5HT2A versus D2 receptor occupancy combined with a more gradual occupancy of D2 receptors differentiates risperidone and its 9-OH-metabolite from the other antipsychotic compounds in this study. The predominant 5HT2A receptor occupancy probably plays a role in the beneficial action of risperidone on the negative symptoms of schizophrenia, whereas maintenance of a moderate occupancy of D2 receptors seems adequate for treating the positive symptoms of schizophrenia. A combined 5HT2A and D2 occupancy and the avoidance of D2 receptor overblockade are believed to reduce the risk for extrapyra     

Granulocyte colony-stimulating factor enhances bone marrow stem cell damage caused by repeated administration of cytotoxic agents

Despite the increasing use of cytokines to circumvent the acute dose-limiting myelotoxicity of cancer treatment, little is known about the combined effects of cytotoxic agents and cytokines on the primitive stem cells responsible for long-term hematopoiesis. In an experimental model, we administered cytotoxic agents that have variable effects on primitive stem cells in C57BL/6 (B6)-mice. Mice received six every-other-week doses of cyclophosphamide (CY, 84 mg/kg), VP-16 (24 mg/kg) + cisplatinum (2.4 mg/kg), carboplatinum (50 mg/kg), chlorambucil (12 mg/kg), BCNU (13.2 mg/kg), or TBI (80 cGy). Granulocyte colony-stimulating factor (G-CSF; 250 microg/kg/day) was administered subcutaneously twice daily on days 3 to 6 after each dose of the cytotoxic agent. Comparison with animals receiving the cytotoxic agent alone was made to investigate the effects of G-CSF on long-term hematopoiesis. Hematopoiesis was measured 20 weeks after the last dose of the cytotoxic agent by assessment of peripheral blood counts, marrow cellularity, progenitor cell content (colony-forming units-spleen; CFU-S), and primitive stem cell number (long-term repopulating ability and day 28 and day 35 cobblestone area-forming cell [CAFC] frequencies). Exposure to cytotoxic agents alone resulted in a significant decrease in primitive stem cells (as measured by repopulating units [RU] and day 28 and day 35 CAFC content) in animals given carboplatinum, chlorambucil, BCNU, and TBI, but not in animals treated with cyclophosphamide or VP-16 and cisplatinum. The addition of G-CSF resulted in a significant decrease in stem cell content when compared with no G-CSF administration in animals treated with chlorambucil, BCNU, or TBI. Thus, G-CSF administered after repeated exposure to cytotoxic agents, appeared to damage the primitive stem cell compartment when used in combination with agents known to damage primitive stem cells. These results, although obtained in an experimental model, should raise concerns for the indiscriminate use of G-CSF in the clinic.     

Comparison of supercritical fluid extraction and conventional liquid-solid extraction for the determination of benzo[a]pyrene in water-soluble smoke

In patients undergoing bone marrow transplantation cryptococcosis is rarely encountered. We report a fatal case of Cryptococcus meningitis in a 12-year-old girl with acute lymphoblastic leukemia (ALL) in second remission who had a transplant from a human leukocyte antigen (HLA)-identical unrelated bone marrow donor. The conditioning regimen was thiotepa, cyclophosphamide, and total body irradiation (TBI); graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporin A, methotrexate, and antilymphocyte globulin (ALG). The patient experienced stage III GVHD responsive to high-dose corticosteroids. On day +54 a thrombotic microangiopathy occurred. On day +64 neurological status worsened; a brain computed tomographic (CT) scan showed hyperdense lesions suggesting fungal infection. Detection of cryptococcal antigen by latex agglutination was positive but India ink stain and culture were negative. Despite treatment with amphotericin B, 5-flucytosine, and granulocyte-macrophage colony-stimulating factor, the patient died 13 days after the diagnosis.     

Induction of specific-locus and dominant lethal mutations in male mice by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)

1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) induced dominant lethal and specific-locus mutations in male mice. For both compounds the germ cell stage sensitive to the induction of dominant lethal mutations was dose dependent. A dose of 5 mg BCNU per kg b.wt. induced dominant lethal mutations primarily in spermatocytes, whereas higher doses of BCNU induced dominant lethals in spermatids and spermatocytes. Following doses of 5 and 10 mg CCNU per kg b.wt. dominant lethals were induced in spermatids and spermatocytes similar to the results for higher doses of BCNU. Higher dose exposure to BCNU and CCNU was associated with dominant lethals expressed as pre-implantation loss (reduction in total number of implants). In addition, higher doses of CCNU showed a cytotoxic effect in differentiating spermatogonia. Both compounds induced specific-locus mutations in post-spermatogonial germ cell stages of mice. However, CCNU increased also the specific-locus mutation frequency in spermatogonia in two out of three experiments. We conclude in analogy with criteria developed by IARC, that BCNU and CCNU are potential human mutagens.