We have previously shown that hypoxia induces both acute and chronic epileptogenic effects that are age dependent. Global hypoxia (3-4% O2) induces seizure activity in the developing brain [postnatal day (P)10-12] but not at younger or older ages. Adult rats with prior seizures induced by hypoxia at P10 show increased seizure susceptibility to chemical convulsants compared with controls. In the present study, we tested the hypothesis that acute and chronic epileptogenic effects of hypoxia are demonstrable in hippocampus both in vivo and in vitro. Depth electrode recordings confirmed the presence of ictal activity within hippocampus in P10 rats during global hypoxia. Hippocampal slices prepared from P10 pups killed at 10 min after recovery from hypoxia showed evidence of increased excitability. Extracellular field recordings revealed that the amplitude and duration of long-term potentiation (LTP) was increased significantly in area CA1 of hippocampal slices removed from hypoxic pups. In addition, extracellular recordings within areas CA1 and CA3 showed significantly longer afterdischarge durations in response to kindling stimuli in slices from hypoxic pups compared with controls. To evaluate whether there were also long-term changes in hippocampal excitability, hippocampal slices were prepared from adult rats that had underwent hypoxia at P10 and compared with slices from adult litter-mate controls. A Mg2+-free medium was superfused to induce epileptiform activity within the slices. Extracellular recordings from stratum pyramidale of area CA1 showed that Mg2+-free media induced significantly more frequent ictal discharges in slices from previously hypoxic rats compared with controls. These results provide evidence that the naturally occurring stimulus of hypoxia can result in both acute and chronic changes in the excitability of the CA1 neuronal network. These results parallel our previous in vivo studies demonstrating that global hypoxia acutely increases excitability in the immature brain and that hypoxia during the age window approximately P10 results in long-lasting increases in seizure susceptibility within hippocampus. Our results suggest that the age-dependent epileptogenic effects of hypoxia are in part mediated by a direct and permanent effect on neuronal excitability within hippocampal neuronal networks.

Clinically, and in experimental models, perinatal hypoxic encephalopathy is commonly associated with seizures. We previously described a rat model in which hypoxia induces seizures and permanently increases in seizure susceptibility in immature rats [postnatal day (P) 10-12] but not in older rats. In the present study, we compared the effect of pretreatment with the excitatory amino acid antagonists MK-801 and NBQX versus lorazepam in our rat model of perinatal hypoxia. Animals exposed to hypoxia at P10 without treatment have frequent seizures during hypoxia and subsequently exhibit increased seizure susceptibility to flurothyl. Treatment with 6-nitro-7-sulfamoylbenzo(f)quinoxaline-2,3-dione (NBQX 20 mg/kg) effectively suppressed hypoxia-induced seizures in immature rats and also protected against permanent changes in flurothyl threshold in adulthood, whereas treatment with MK-801 (1 mg/kg) or lorazepam (LZP 1 mg/kg) did not prevent these hypoxia-related epileptogenic effects. These results suggest that activation of alpha-amino-3-hydroxy-5-methyl-4-isoxazol propionic acid (AMPA) receptors may partly mediate the age-dependent epileptogenic effect of hypoxia in the perinatal period.

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Summary.We report the response to immunosuppressive therapy with antithymocyte globulin (ATG) and cyclosporin or oxymetholone in 13 cases of aplastic anaemia (AA) with an abnormal cytogenetic clone detected at or sometime after diagnosis. Blood and bone marrow examination showed no distinctive morphological features of myelodysplasia (MDS) at diagnosis. Haematological response occurred promptly in eight cases; the remainder responded after additional immunosuppression with or without oxymetholone. Three patients had a late relapse of AA, treated successfully by allogeneic bone marrow transplantation in one; the others responded to oxymetholone. Transformation to MDS or acute leukaemia was not observed after a median follow-up of 4·1 years (range 1·2-11·2). In four patients the cytogenetic clone disappeared after treatment.

Long-term bone marrow culture (LTBMC) was used to investigate the proliferative behaviour of marrow cells from a spectrum of cases of the myelodysplastic syndrome (MDS), and the results compared with those obtained in the conventional short-term clonal assay. Two broad patterns of growth were revealed in LTBMC. In one group the incidence of haemopoietic progenitor cells steadily declined to abnormally low levels at 4 weeks, while in a second group they were maintained near normal levels for periods of up to 7 weeks. These growth patterns, which were not predictable from clonogenic assays on the marrow cells prior to LTBMC, or from the morphology of the bone marrow, may reflect the stage of evolution of the disease. Further studies of clonality are required to establish whether or not patients exhibiting the second pattern have a potentiality to harbour residual normal haemopoiesis. LTBMC was also used to study the function of MDS marrow stroma in terms of its ability to sustain the growth of normal haemopoietic progenitor cells. Although the phenotype of the cultured adherent cell layer, obtained from some patients, was atypical, no consistent functional defect of MDS stroma could be identified by studying the level of haemopoiesis reached by normal cells seeded into MDS stroma.

Between June 1977 and July 1983 51 patients with Ph1-positive chronic granulocytic leukaemia (CGL) in transformation were treated either by chemotherapy or by chemoradiotherapy followed by autografting with haemopoietic stem cells collected from their peripheral blood at the time of diagnosis. Forty-eight patients were restored to a second chronic phase. The median duration of survival after autografting was 26 weeks (range 2-152 weeks). Twenty-one patients with relatively long durations of second chronic phase were treated again by autografting as consolidation or when transformation recurred; this selected group of patients survived longer than the 30 patients treated by autografting only once (medians 52 v. 13 weeks respectively, P less than 0.01). There was no significant influence of the patients' age, splenectomy status, type of transformation, treatment pre-autograft or number of nucleated cells autografted on the duration of survival. Three patients treated in myeloid blastic transformation were restored to partially Ph1-negative haemopoiesis. We conclude that this approach to the management of CGL in transformation can offer benefit for a minority of patients and that further chemotherapy and autografting for patients still in second chronic phase may be valuable.

Summary. Aplastic anaemia is a rare but serious disorder with a high morbidity and mortality rate. The causes of aplastic anaemia are, for the most part, unknown. We report on the hypothesis that aplastic anaemia may be caused by occupational and/or environmental exposures to certain chemicals. The UK Aplastic Anaemia Study was an interview-based case-control study covering the whole of Great Britain. Those patients diagnosed between 1 July 1993 and 20 October 1997, aged £75 years and born and diagnosed in the UK were eligible for the study. Two hundred eligible cases of aplastic anaemia were compared with 387 age-and sex-matched controls. A number of occupational exposures showed increases in risk. In a multivariate model of these exposures the odds ratios (ORs) for solvents/ degreasing agents, pesticides and radiation were >2 and statistically significant. Reported chemical treatment of houses within 5 years of diagnosis had a significantly raised risk for adults [OR ¼ 2AE51, 95% confidence interval (CI) 1AE02-12AE01], particularly for woodworm treatment (OR ¼ 5AE1, 95% CI 1AE5-17AE4). This study identified significant risks associated with self-reported exposure to solvents, radiation and pesticides in the workplace. Self-reported chemical treatment of houses was also associated with an increased risk of developing aplastic anaemia, in keeping with previous literature.

The natural history and haematological features of 18 patients with a chronic form of myelomonocytic leukaemia are described. The majority were elderly and, in this series, females predominated. Haematological prodomata, such as unexplained monocytosis, leucopenia, or thrombocytopenia were common, and the clinical onset was insidious. Splenomegaly was variable but tended to increase as the disease progressed. Anaemia was usually less than in the acute disease, unless compounded by iron deficiency. The blood film typically showed a mixed monocytosis and granulocytosis, cells in both lines showing abnormalities. 'Paramyeloid' cells, appearing in Romanowsky stained films intermediate between myelocytes and monocytes, were characteristic, although cytochemical and electron microscopical analysis suggests that these cells may be allotted to one or other cell line. The marrow aspirate was characteristically hypercellular, showed granulocytic hyperplasia, and, in contrast to the well-differentiated blood picture, the proportion of poorly differentiated cells, including blasts, was high. Serum lysozyme levels were usually raised. Five of the 18 cases survived more than 5 years, while 10 lived 2 years or longer. The morphological and clinical features form part of a spectrum including acute myelomonocytic leukaemia, into which several of the patients transformed. Recognition of the syndrome is important because the patients are probably best managed without intensive chemotherapy.