Seeing difference: market health reform in Europe

The comparative literature on health care reform has identified a convergence upon market models as nations respond to similar economic, technological, social, and demographic pressures. In this article I first challenge the conventional view by comparing "market" reforms of the late 1980s and early 1990s in the United Kingdom, the Netherlands, and Sweden. Though these nations did indeed converge upon the instrument of the market incentive, there was considerable divergence in the content and aims of their reform strategies. These nations designed their respective markets to make different tradeoffs among competing values. While all three exploited the principle of provider competition, they appointed different actors to judge the contest: the cost-conscious public authority in the United Kingdom, the quality-conscious patient in Sweden, and the optimizing consumer in the Netherlands. I argue that these countries were thus using common market tools to promote different health policy goals. Distinguishing these reforms further is the fact that--particularly in the Netherlands--there was a gap between market plans and the reality of implemented change. I then ask why nations responded so differently to such similar objective pressures. My contention is that this divergence reflects, in part, the different ideological orientations of the ruling party or coalition in each nation. Yet divergence is also the result of differences in both the design of political institutions and the structure of the pre-reform health system in each country.

Green fluorescent protein as a reporter for retrovirus and helper virus-free HSV-1 amplicon vector-mediated gene transfer into neural cells in culture and in vivo

Green fluorescent protein (GFP) is an effective marker for retrovirus and herpes virus vector-mediated gene transfer into various central nervous system-derived cells, both proliferative and non-proliferative, in culture and in vivo. Retrovirus vectors were used to stably transduce several rat and human glioma lines, and a multipotent mouse neural progenitor line in culture. Implantation of selected pools of transduced glioma cells into rodent brain allowed clear visualization of the tumor and the invading tumor edge. Helper virus-free HSV-1 amplicon vectors successfully transferred gfp into non-dividing primary neural cells in culture and in the rat brain. This study describes the versatility of GFP for: (i) labelling of glioma cells in experimental brain tumor models and neural progenitor cells by retrovirus vectors, and (ii) efficient, non-toxic delivery of genes to post mitotic cells of the nervous system using helper-virus free HSV-1 amplicon vectors.

Reactivity of a new HIV-1 group O third generation A-HIV-1/-2 assay with an unusual HIV-1 seroconversion panel and HIV-1 group O/group M subtyped samples

It was shown previously that about 97% of the anti-HIV-1 group O strain-positive samples were detected by crossreaction with native HIV-1 gp160 (Van Binsbergen et al., Evaluation of a new third generation anti-HIV-1/anti-HIV-2 assay with increased sensitivity for HIV-1 group O, J. Virol. Methods 60 (1996) 131-137). Fourteen out of 17 new anti-HIV-1 group O positive samples, selected with the Enzygnost HIV-1/2 plus assay, were already reactive when tested with HIV-1 gp160. When tested by the Vironostika HIV Uni-Form II plus O microELISA all 17 samples were reactive, demonstrating the necessity to implement an HIV-1 group O-specific antigen in the assay. On the other hand, it was surprisingly found that 40 out of 43 (93%) of anti-HIV-1 group M-positive samples, belonging to strain A, B, C, D, E or F, were detected by crossreaction with the HIV-1 group O (strain ANT70) synthetic peptide incorporated in the Vironostika HIV Uni-Form II plus O. Only HIV-1 subtype D-positive samples did not react with this peptide, presumably because of the presence of a histidine residue in the immunodominant region of HIV-1 subtype D gp41. Both crossreactions make the Vironostika HIV Uni-Form II plus O microELISA also sensitive for anti-HIV-1-positive samples originating from different geographical regions and resulting from different HIV-1 subtype infections. With an unusual seroconversion panel in which p24 Ag was present persistently, many anti-HIV-1/-2 assays produce alternating positive/negative results in anti-HIV antibody-positive bleeds. It was shown that the use of viral p24 and gp160 in a direct sandwich, allowing detection of anti-HIV IgG and IgM, explains the identification of all anti-HIV-positive bleeds by the Vironostika HIV Uni-Form II plus O. The high sensitivity of the plus O assay was confirmed with clinical samples of a so-called anti-HIV-1 low titer panel. The specificity of the Vironostika HIV Uni-Form II plus O determined in five blood transfusion centers, based on 135070 tests, was 99.97%.

Therapeutic efficiency and safety of a second-generation replication-conditional HSV1 vector for brain tumor gene therapy

A second-generation replication-conditional herpes simplex virus type 1 (HSV) vector defective for both ribonucleotide reductase (RR) and the neurovirulence factor gamma34.5 was generated and tested for therapeutic safety and efficiency in two different experimental brain tumor models. In culture, cytotoxic activity of this double mutant HSV vector, MGH-1, for 9L gliosarcoma cells was similar to that of the HSV mutant, R3616, which is defective only for gamma34.5, but was significantly weaker than that of the HSV mutant hrR3, which is defective only for RR. The diminished tumoricidal effect of the gamma34.5 mutants could be accounted for by their reduced ability to replicate in 9L cells. The MGH-1 vector did not achieve significant prolongation of survival in vivo in the syngeneic 9L rat gliosarcoma model for either single brain tumor focus or multiple intracerebral and leptomeningeal tumors, when the vector was applied intratumorally or intrathecally, respectively, and with or without subsequent ganciclovir (GCV) treatment. In identical 9L brain tumor models with single and multiple foci, application of hrR3 with or without GCV was previously shown to result in marked long-term survival. Contrary to the findings with intrathecal injection of hrR3, no vector-related mortality was observed in any animals treated with MGH-1. Thus, in these rat brain tumor models, the double mutant, replication-conditional HSV vector MGH-1 showed a higher therapeutic safety than the RR-minus vector, hrR3, but had clearly decreased therapeutic efficiency compared to hrR3. The development of new HSV vectors for brain tumor gene therapy will require a balance between maximizing therapeutic efficacy and minimizing toxicity to the brain. Standardized application in brain tumor models as presented here will help to screen new HSV vectors for these requirements.

Evidence of acute demyelination around a developmental venous anomaly: magnetic resonance imaging findings

The authors report on the occurrence of a focal demyelination showing a mass effect around a developmental venous anomaly in the cerebellum. Because the latter presented as a single lesion, the differentiation from intraparenchymal neoplasms or infarction was difficult. Follow-up magnetic resonance imaging and histology from a biopsy specimen give useful information to find the appropriate diagnosis.

MRI- and MRA-guided therapy of carotid and vertebral artery dissections

A high sensitivity and specificity has been shown for magnetic resonance imaging (MRI) and angiography (MRA) in the diagnosis of internal carotid (ICAD) and vertebral (VAD) artery dissections, where arteriography has been and still is the gold standard. Five patients (three with ICAD, two with VAD; age range 42-56 years) are presented, in whom diagnosis and follow-up management were exclusively based on non-invasive measures. In all patients, MRI demonstrated a typical intramural hematoma and MRA in 3D phase contrast technique showed loss or diminished flow. After anticoagulation (heparin) for 3 to 4 weeks follow-up, MRI showed a regression of the mural hematoma and MRA revealed reperfusion or improvement of flow. Depending on the extent of MRI-/MRA-pathology, three patients were put on antiplatelet therapy and two on Coumadin until normalization of MRI and MRA findings, which are assessed in 3-months intervals. We suggest, that with, (I) a suspicious history, symptoms and signs for cervical artery dissection (CAD), (II) typical MR-findings proven to indicate CAD, (III) improving or resolving at follow-up, (IV) in unusual location for atherosclerotic involvement, (V) in the absence of coexisting atherosclerotic lesions, the diagnosis has not to be confirmed with conventional arteriography. Therefore, safe MRI- and MRA-guided anticoagulation and antiplatelet therapy during serial follow-up measurements are possible.

Major activity of cladribine in patients with de novo B-cell prolymphocytic leukemia

PURPOSE

De novo B-cell prolymphocytic leukemia (B-PLL) is a distinct clinicopathologic entity usually characterized by marked lymphocytosis, massive splenomegaly, an aggressive course, and refractoriness to therapy. Cladribine (2-chlorodeoxyadenosine [2-CdA]; Ortho Biotech, Raritan, NJ) is a newer purine analog with potent activity against indolent lymphoproliferative disorders.

PATIENTS AND METHODS

We treated eight patients with cladribine 0.1 mg/kg/d for 7 days by continuous infusion or 0.14 mg/kg/d over 2 hours for 5 days, every 28 to 35 days, for a median of three courses (range, two to five). There were five men and three women, with a median age of 62 years and a median pretreatment duration of 6 months; four patients were previously untreated.

RESULTS

All eight patients were assessable: five achieved a complete response with a median response duration of 14 months (range, 1+ to 55+), and three achieved a partial response with a median duration of 3 months (range, 1 to 3). Of four patients who achieved a complete response and in whom a peripheral-blood immunophenotypic analysis was performed, two had no circulating B-PLL cells and one had no residual disease on Southern blot analysis. Myelosuppression and infection were the major toxicities: three patients developed grade 3 or 4 myelosuppression, four had bacterial infections, and two had herpes zoster infections.

CONCLUSION

In this small study of patients with de novo B-PLL, cladribine was an active agent that induced a high overall and complete response rate. These results require confirmation in larger numbers of B-PLL patients.

How neural interactions form neural responses in the salamander retina

A wide range of experimental data characterizing properties of individual salamander retinal cells and synaptic interactions are integrated to form a quantitative computational model of visual function in the salamander retina. The model is used to show how specific interactions between neurons and between networks of neurons can lead-to the integrated response behavior of individual cells deep in the retina. The model is also used to illustrate how the representation of moving and stationary stimuli is encoded in a series of layer-by-layer transformations leading to the final retinal output at the ganglion cell layer.

A BCNU-containing Regimen, Mini-BEAM, with GM-CSF is a Safe and Effective Mobilizing Regimen Pre-stem Cell Transplantation in Lymphoma Patients

Concern has been raised regarding the quality and engraftment potential of peripheral stem cells obtained from mobilizing regimens containing BCNU. We compared the mononuclear cell (MNC) yields and engraftment times of neutrophils and platelets in twenty-nine patients who received autologous peripheral blood stem cell transplants at our institution. Sixteen patients with either refractory or resistant Hodgkin's disease or non-Hodgkin's lymphoma, were mobilized with a BCNU-containing regimen, mini-BEAM (BCNU 60 mg/m(2) on day 1, etoposide 100 mg/m(2) on days 1-3, cytarabine 150 mg/m(2)q12h on days 1-3, and melphalan 30 mg/m(2) on day 3). Thirteen patients with various malignancies were mobilized with non-BCNU containing priming regimens. All patients received rhGM-CSF (Leukine, Immunex, Seattle, WA) 250μg/m(2) subcutaneously daily from 24 hours after completion of mobilizing chemotherapy through the completion of leukapheresis. The mean mononuclear cell yields in the BCNU versus non-BCNU containing regimens were 2.15 and 1.97 × 10(8) MNC/kg [95% CI -.32 to.68] after a median of 3 and 3 leukaphereses respectively. The median time post-stem cell infusion to an absolute neutrophil count (ANC) of ≥0.5 × 10(9)/1 were 11 days and 13 days [mean 11.7 and 12.2, p = 0.99, 95% CI -2.5, 1.6], days to an ANC of ≥1.0 x 10(9)/1 were 13 and 13 [mean 13.8 and 13.1, p = 0.47, 95% CI-1.8, 3.3], days to a platelet count of ≥20 × 10(9)/1 were 9 and 9 days [mean 11.4 and 9.8, p = 0.10, CI -0.6, 4.0], and days to a platelet count of ≥50 × 10(9)/1 were 14 and 15 days (p = 0.14) respectively. Mini-BEAM, as a mobilizing regimen, is easily administered as an outpatient. Stem cells mobilized with this regimen produces similar mononuclear cell yields as compared to non-BCNU containing regimens. There was no difference in the engraftment times for ANC or platelets from stem cells mobilized with BCNU versus non-BCNU containing regimens.

T-DNA integration patterns in co-transformed plant cells suggest that T-DNA repeats originate from co-integration of separate T-DNAs

Nicotiana protoplasts and Arabidopsis leaf discs or roots were co-cultivated with two Agrobacterium strains each carrying a different T-DNA. Co-transformed plants were selected and the integration of the different T-DNAs was analysed at the genetic and genomic level. Genetic analysis showed that the T-DNAs derived from different bacteria were frequently integrated at the same locus, independent of the plant species or transformation method used. Southern analysis revealed that 12 out of 27 Arabidopsis transformants contained the co-transferred T-DNAs linked to each other in all possible configurations but with a preference for those with at least one right border involved in linkage. Overall, our data support the hypothesis that ligation of separate T-DNAs is a dominant mechanism in formation of the frequently observed repeats of identical T-DNAs. We propose a scheme which could explain the formation of T-DNA repeats and the preferential involvement of right borders in T-DNA linkages.

Development of the multidimensional index of life quality. A quality of life measure for cardiovascular disease

OBJECTIVES

The purpose of this study was to design a multidimensional measure of health-related quality of life appropriate for patients with cardiovascular disease that was psychometrically sound, brief, and easy to administer.

METHODS

Qualitative interviews conducted with healthy subjects and patients with cardiovascular diseases identified nine major quality of life domains. Based on the responses of 129 cardiovascular disease patients recruited from hospitals and clinics, a criterion-based approach was used to select 35 questionnaire items that best tapped these domains. Psychometric properties of the Multidimensional Index of Life Quality (MILQ) were tested with a sample of 348 patients with various cardiovascular diseases.

RESULTS

Cronbach's alpha was 0.76 or higher for eight of the nine MILQ domains. Test-retest reliability coefficients were 0.73 or greater in all but two domains. Individual domain scores as well as a weighted overall quality of life index were correlated highly with self-assessed health and the number of heart-related symptoms.

CONCLUSIONS

The Multidimensional Index of Life Quality is a psychometrically reliable and valid instrument for measuring quality of life in patients with cardiovascular diseases. The MILQ also may be a suitable measure for other types of chronic diseases.

One-year follow-up of technetium-99m-HMPAO SPECT in mild head injury

We evaluated the predictive capacity of 99mTc-HMPAO SPECT for clinical outcome during a follow-up period of 12 mo after mild head injury.

METHODS

We prospectively evaluated 136 patients with mild head injury who underwent initial SPECT imaging (SPECTO) within 4 wk after the trauma. Re-evaluations were made 2.9-3.3 mo (T3mo), 5.7-6.3 mo (T6mo) and 11.9-12.6 mo (T12mo) postinjury. All patients with an abnormal SPECT underwent a repeat study at the subsequent time of evaluation. Patients with a previously normal SPECT scan did not undergo a repeat study. Clinical reassessments (CLIN) were performed as long as the earlier study had been positive or until patients were completely asymptomatic.

RESULTS

During all follow-up evaluations, SPECT had a high sensitivity and negative predictive value, increasing from 91% and 89%, respectively, at T3mo to 100% at T6mo and at T12mo. Clinical normalization occurred earlier than scintigraphic normalization. However, at 12 mo postinjury, we observed considerable improvement in the specificity and positive predictive value of SPECT (85% and 83%, respectively). The persistent lesions on the SPECT scan were related to their severity and to localization in the frontal cortex.

CONCLUSION

A normal 99mTc-HMPAO SPECT scan is a reliable tool in the exclusion of clinical sequelae of mild head injury. At 12 mo postinjury, a positive SPECT study is also a reliable predictor for clinical outcome.

[Varicella-zoster-virus myelitis without herpes. An important differential diagnosis of the radicular syndrome]

HISTORY AND CLINICAL FINDINGS

A 43-year-old woman was admitted with a 14-day history of general malaise, subfebrile temperature, radicular dysaesthesias in the "riding breeches" area, severe pain in the lumbar region and progressive disorders of bladder and rectal emptying. Physical examination showed a conus-cauda syndrome. Differential diagnosis was between myelitis (inflammatory or infectious), space-occupying intraspinal mass or vascular lesion.

INVESTIGATIONS

Cerebrospinal fluid contained 1700/3 cells and there was intrathecal antibody synthesis against varicella zoster virus (VZV) and positive VZV-DNA analysis in the polymerase chain reaction. Magnetic resonance imaging of the lumbar spine revealed an inflamed enlarged conal and epiconal area with small haemorrhagic spots. There was no evidence of an underlying immune-modulated disease.

TREATMENT AND COURSE

With the diagnosis of varicella zoster myelitis with cutaneous changes having been established the clinical signs and symptoms regressed almost completely with aciclovir administration (10mg/kg intravenously for 14 days).

CONCLUSION

VZV without cutaneous involvement should be considered in the differential diagnosis of the radicular pain syndrome. When clinical signs of beginning myelitis or encephalitis are present, immediate investigations and therapy are necessary.

Diaschisis of specific cerebellar lobules: pontine haematoma studied with high-resolution PET and MRI

Cerebellar glucose metabolism was studied in one patient with a hemipontine haematoma in order to investigate remote metabolic effects within the cerebellar lobules. In the patient, who suffered a circumscribed hemipontine haemorrhage, and in three normal subjects cerebellar glucose metabolisms was studied using 18F-2-fluoro-2-deoxy-D-glucose and high-resolution positron emission tomography (PET). Regions of interest were placed on sagittal brain slices of co-registered magnetic resonance images for quantitative evaluation of glucose metabolism in each cerebellar lobule. Interruption of corticopontine fibres caused inactivation of pontine nuclei with subsequent contralateral cerebellar diaschisis, mainly in the anterior lobe and the posterior portion of the quadrangular lobule. Damage within the ponto-cerebellar part of the cortico-ponto-cerebellar pathway, e.g. pontine nuclei and crossing ponto-cerebellar fibres from contralateral pontine nuclei, led to ipsi- and contralateral cerebellar diaschisis within the semilunar, gracile and biventral lobules. High-resolution PET is capable of demonstrating bilateral diaschisis involving specific cerebellar lobules to a different degree that is consistent with the pontine anatomy of the cortico-ponto-cerebellar pathway and with the location of the haemorrhagic lesion.

Interleukin-3 plus low-dose cytosine arabinoside for advanced myelodysplasia: a pilot study. EORTC Leukemia Group

In an attempt to reestablish normal hematopoiesis in symptomatic myelodysplasia (MDS) and to show the tolerability of a combination treatment of low-dose cytosine arabinoside (LD AraC) and interleukin-3 (IL-3), we treated 31 patients (pts., median age 65 years) who had more than 10% blasts in the bone marrow (BM) and hematopoietic failure with LD AraC (2 x 10 mg/m2 sc, day 1-14) plus IL-3 (once daily sc, day 8-21) at different dose steps (1.0, 2.5, 5.0, and 10.0 micrograms/kilogram body weight). The numbers of each 21-day cycle varied between 1 (3 pts.), 2 (6 pts.), 3 (8 pts.), 4 (1 pt.), 5 (5 pts.), and 6 (8 pts.), in total 116 cycles on an outpatient basis. Subjective tolerability was good in 20 cases (65%). Toxicities were fever (29 pts.), flu-like symptoms (17 pts.), infections (15 pts.), hepatic toxicity (10 pts.), and skin reactions (8 pts.). Overall response was seen in 13 cases (42%) and 5 complete responses (CR), while 10 pts. had stable disease (SD), 5 progressed (2 to acute leukemia), 2 were considered toxic deaths, and 1 died due to the disease. Median survival is 18 months, progression-free survival is 12.5 months (18.0 months in responding pts.), with an actuarial follow-up of 31 months. The data from this phase I/II study show that a combination of LD-AraC and IL-3 is well tolerated and that stable responses can be achieved in MDS by means of an easy outpatient therapy.

Amino acid uptake in ischemically compromised brain tissue

BACKGROUND AND PURPOSE

Multitracer positron emission tomography (PET) was used to investigate local amino acid accumulation in brain tissue surrounding focal ischemia.

METHODS

PET using 15O-labeled oxygen and water for measuring cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow (CBF), C15O for determination of blood volume (CBV) and calculation of oxygen extraction fraction, and L-[11C]methylmethionine (11C-MET) for the assessment of amino acid accumulation was applied in 14 patients (mean age, 52 +/- 9.1 years) with acute ischemic hemispheric stroke. Two multitracer PET studies were completed, the first 8 to 24 hours after onset of neurological symptoms and the follow-up study 14 +/- 1 days after the ischemic attack. Functional changes were compared with morphological damage on cranial CT or MRI. Three-dimensional matching and volume of interest evaluation procedures were used to study 11C-MET accumulation in relation to various physiological variables in infarcted and noninfarcted tissue.

RESULTS

Compared with contralateral mirror regions, initially increased regional 11C-MET uptake (21.2 +/- 10.9%, P < .001) was found in patchy areas in the immediate vicinity of infarction as well as in distant areas within the same hemisphere. In those areas, regional CBF (-11.4 +/- 21.2%, P < .01) and oxygen extraction fraction (2.8 +/- 29.1%, P = NS) were highly variable, and regional CMRO2 was preserved or slightly reduced (-12.4 +/- 16.0%, P < .001). CBF data comprised severely ischemic as well as high values (14.6 to 64.2 mL/100 g per minute). Cranial CT and coregistered MRI in five patients demonstrated preserved morphology. In all peri-infarct areas (n = 62), the 11C-MET uptake showed a positive correlation with delta CMRO2 as the relative improvement of ipsilateral CMRO2 between the two PET studies (r = .378, P < .01). Particularly in areas with increased oxygen extraction fraction (n = 42), the 11C-MET uptake showed a mild correlation with CMRO2 at follow-up measurement (r = .31, P < .05). In all peri-infarct areas, 11C-MET uptake showed a negative correlation with oxygen extraction fraction (r = -.672, P < .001) and a positive correlation with CBF (r = .4, P = .001). In all infarcted and peri-infarct areas, normalized initial 11C-MET uptake was positively correlated with CMRO2 at follow-up (r = .603, P < .001).

CONCLUSIONS

Focal increases of 11C-MET uptake seen in this study were generally mild. They might be seen in the core of ischemia, indicating breakdown of the blood-brain barrier with poor tissue prognosis, but they also frequently occurred during or after ischemic compromise in surviving brain tissue surrounding focal cerebral infarction, perhaps representing alterations of amino acid transport or protein synthesis in brain tissue with a favorable prognosis.

A screen for RAS mutations in individuals at risk of secondary leukaemia due to occupational exposure to petrochemicals

Occupational exposure to petrochemicals, in particular benzene, has been identified as a risk factor in the development of acute leukaemia. A cohort of exposed (n = 44) and non-exposed individuals (n = 19) from the same petrochemical installation were screened by polymerase chain reaction (PCR) followed by oligonucleotide hybridization (ONH) for the presence of mutations in the H, K, and NRAS cellular proto-oncogenes. A KRAS mutation was detected in one individual from the exposed group who was haematologically normal at the time of sampling. The presence of this mutation was confirmed by nude mouse tumorigenicity assay and positively identified as a K13 Gly-Asp substitution by cloning and sequencing.

FMS mutations in patients following cytotoxic therapy for lymphoma

Point mutations at codons 301 and 969 of the FMS proto-oncogene have been reported in both myelodysplasia (MDS) and acute myeloid leukaemia (AML). We report here the incidence of such mutations in patients at risk of developing secondary MDS and AML. Peripheral blood DNA from 70 patients in remission from lymphoma was screened for mutations by oligonucleotide (ONH) using mutant specific probes. Codon 969 mutations were detected in 11 of the 70 (15.7%) cases. No codon 301 mutations were detected. Five of these mutations were confirmed using an independent technique (single nucleotide primer extension analysis, SNPE) and a further mutation was detected in a single patient using single-stranded conformational polymorphism analysis (SSCP). No codon 969 mutations were detected in 62 lymphoma biopsy specimens from these patients or from three patients with detectable FMS mutations where pre-therapy marrow was investigated by ONH. No mutations at either codons 301 or 969 were detected by ONH in 61 normal controls. Somatic mutations at codon 969 of the FMS gene occur commonly following cytotoxic therapy for lymphoma and their detection indicates the presence of a clonally expanded population of abnormal cells.

Upregulation of p21 RAS levels in HL-60 cells during differentiation induction with DMSO, all-trans-retinoic acid and TPA

The role of p21 RAS in the proliferation and differentiation of myeloid cells has been studied by analysing the changes in the level of expression of p21 RAS proteins by flow cytometry upon differentiation down the granulocytic and monocytic pathways. Differentiation resulted in upregulated p21 RAS expression despite a marked decline in the number of dividing cells. On the other hand, growth inhibition, without differentiation, resulted in a decline in expression. Cell cycle analysis showed that the increase in p21 RAS occurred throughout the cell cycle. These results suggest that p21 RAS has a role in the process of myeloid differentiation.

RAS and FMS mutations following cytotoxic therapy for childhood acute lymphoblastic leukaemia

Patients who have received cytotoxic therapy for primary neoplastic disease are at an increased risk of developing secondary (therapy-related) acute myeloid leukaemia (AML) or myelodysplasia (MDS). RAS and FMS mutations have been observed in patients with AML and MDS. It has been suggested that the mutational status within these genes may be predictive of early secondary leukaemic disease. In this study we have screened 50 haematologically normal patients in complete remission from childhood acute lymphoblastic leukaemia (ALL) for activating point mutations in the RAS and FMS proto-oncogenes. Such patients may be considered at risk of therapy-related disease. Codons 12, 13 and 61 were screened in RAS and codon 969 in FMS using the polymerase chain reaction (PCR) followed by oligonucleotide hybridization (ONH). Three of the 50 patients (6%) were found to harbour N12 RAS mutations. One of these three patients (2%) had both a N12 RAS and FMS 969 mutation. Upon sequencing the RAS mutations, substitutions of serine, cysteine and aspartic acid for glycine were identified. The FMS 969 mutation was also confirmed, by sequencing, as a histidine substitution. RAS mutations were not detected in presentation samples indicating that these lesions have been somatically acquired presumably subsequent to cytotoxic therapy for the primary disease. Continued follow-up of these patients may indicate a role for these mutations in the development of secondary malignancies.

Intramolecular transmission of the ATP regulatory signal in Escherichia coli aspartate transcarbamylase: specific involvement of a clustered set of amino acid interactions at an interface between regulatory and catalytic subunits

Aspartate transcarbamylase from Escherichia coli is stimulated by ATP and feedback-inhibited by CTP and UTP. Previous work allowed the identification of the hydrophobic interface between the two domains of the regulatory chain as a structural element specifically involved in the transmission of the ATP regulatory signal toward the catalytic sites. The present work describes the identification of a cluster of amino acid interactions at an interface between the regulatory chains and the catalytic chains of the enzyme as another structural feature involved in the transmission of the ATP regulatory signal but not in those of CTP and UTP. These interactions involve residues 146 to 149 of the regulatory chain and residues 242 to 245 of the catalytic chain. Perturbations of these interactions also alter to various extents the co-operativity between the catalytic sites for aspartate binding. These findings are in agreement with the idea that the primary effect of ATP might consist, in part, of a modulation of the stability of the interfaces between regulatory and catalytic subunits, thereby facilitating the T to R transition induced by aspartate binding, as was put forward in two recently proposed models, the "effector modulated transition" model and the "nucleotide perturbation" model. This does not exclude that this cluster of interactions could also act as a relay to transmit the ATP regulatory signal to the catalytic sites according to the previously proposed "primary-secondary effects" model.