P-glycoprotein is downregulated in KG1a-primitive leukemia cells by LDL cholesterol deprivation and by HMG-CoA reductase inhibitors

OBJECTIVE: P-glycoprotein (pgp) is a membrane transporter encoded by the multidrug resistance (MDR1, ABCB1) gene. Pgp is a poor prognostic factor in elderly patients with acute myeloid leukemia (AML). In addition to its role in drug efflux, pgp has been implicated in cellular cholesterol homeostasis. We investigated the effects of exogenous cholesterol removal on pgp expression and function. METHODS: KG1a drug-na?ve, primitive leukemia cells were cultured in serum-free medium with or without the addition of low-density lipoprotein (LDL) cholesterol. After 72 hours, pgp expression and function was assessed by flow cytometry and total cholesterol content of the KG1a cells was determined by the Amplex Red cholesterol assay. The addition of clinically available cholesterol-lowering agents, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors to KG1a cells was also assessed. RESULTS: There was a 39% (SEM = 8.3%; p = 0.03) decrease in pgp protein expression after 3 days of serum-free culture. The decrease was also observed at the message and functional levels. In the presence of low-density lipoprotein cholesterol, pgp expression was restored to 86% of the basal value. Addition of a HMG-CoA reductase inhibitor to KG1a cells resulted in an additional 26% (lovastatin, p = 0.03) and 16% (pravastatin, p = 0.05) reduction in pgp, respectively. Furthermore, toxicity of the pgp substrate drug daunorubicin was enhanced following lovastatin preculture (p = 0.04). CONCLUSION: LDL cholesterol contributes to pgp expression and chemoresistance in primitive leukemia cells. Use of HMG-CoA reductase inhibitors may be of clinical value in lowering pgp expression in AML.     

Mandatory Nap Times and Group Napping Patterns in Child Care: An Observational Study

Policy provision for naps is typical in child care settings, but there is variability in the practices employed. One practice that might modify children’s early sleep patterns is the allocation of a mandatory nap time in which all children are required to lie on their beds without alternate activity permitted. There is currently limited evidence of the effects of such practices on children’s napping patterns. This study examined the association between duration of mandatory nap times and group-level napping patterns in child care settings. Observations were undertaken in a community sample of 113 preschool rooms with a scheduled nap time (N = 2,114 children). Results showed that 83.5% of child care settings implemented a mandatory nap time (range = 15–145 min) while 14.2% provided alternate activities for children throughout the nap time period. Overall, 31% of children napped during nap times. Compared to rooms with ≤ 30 min of mandatory nap time, rooms with 31–60 min and > 60 min of mandatory nap time had a two-and-a-half and fourfold increase, respectively, in the proportion of children napping. Nap onset latency did not significantly differ across groups. Among preschool children, exposure to longer mandatory nap times in child care may increase incidence of napping.     

Risk of ovarian failure and fertility preserving methods in girls and adolescents with a malignant disease

Girls and young women suffering from a malignant disease that requires treatment with chemo- and/or radiotherapy are at risk of losing fertility. The most significant risk factors are age and type of treatment given. Preserving fertility is of high priority to both the young patient and her parents. This article reviews the effect of chemo- and radiotherapy on gonadal function, and thus fertility, and offers different fertility preserving methods based on the literature. Cryopreservation of ovarian tissue is a possible way of preserving fertility in this group of patients in the future.     

Intrathecal methotrexate overdose

We report two cases of intrathecal methotrexate overdose. A 3-y-old girl with acute lymphoblastic leukaemia and a 4-y-old boy with Burkitt's lymphoma were to receive an intrathecal injection of methotrexate after completion of intravenous methotrexate infusion. Instead of 12.5 mg, they both received a dose of 125 mg. Both children developed generalized convulsion 3 h after the overdose, but afterwards recovered completely. Intravenous folinic acid and dexamethasone rescue were employed, but no attempt was made to exchange the cerebrospinal fluid. In addition to the staffs failure to check the drug label carefully, the marked resemblance of the two dose preparations of methotrexate (50 mg/5 ml and 500 mg/5 ml) may have been contributory.     

Pharmacological FMRI: measuring opioid effects on the BOLD response to hypercapnia.

Opioid binding to the cerebral blood vessels may affect vascular responsiveness and hence confound interpretation of blood oxygen level-dependent (BOLD) responses, which are usually interpreted as neuronal in origin. Opioid binding varies in different brain regions. It is unclear whether opioids alter neurovascular coupling, or whether their effects are purely neuronal. This study used BOLD functional magnetic resonance imaging (FMRI) to investigate the effect of a mu-opioid agonist remifentanil, on cerebrovascular CO(2) reactivity (being one component of neurovascular coupling). Hypercapnic challenges were delivered to human volunteers, while controlling potential opioid-induced respiratory depression. The BOLD signal increase to hypercapnia was compared before and during remifentanil administration. Remifentanil was shown not to have a generalised effect on CO(2) responsiveness in the cerebral vasculature. However, it caused a significant reduction in the positive BOLD response to hypercapnia in the bilateral primary sensorimotor cortices, bilateral extrastriate visual areas, left insula, left caudate nucleus, and left inferior temporal gyrus. We conclude that remifentanil does not modulate cerebrovascular CO(2) reactivity, as we saw no difference in BOLD response to hypercapnia in areas with high opioid receptor densities. We did however see a focal reduction in areas related to motor control and putative task activation, which we conclude to be related to changes in neuronal activity related to the sedative effects of remifentanil. Our method of controlling CO(2) levels effectively mitigated the potential confound of respiratory depression and allowed comparison over a similar range of CO(2) levels. We suggest that similar methodology should be used when investigating other potentially vasoactive compounds with FMRI.