GABA uptake into astrocytes is not associated with significant metabolic cost: implications for brain imaging of inhibitory transmission

Synaptically released glutamate has been identified as a signal coupling excitatory neuronal activity to increased glucose utilization. The proposed mechanism of this coupling involves glutamate uptake into astrocytes resulting in increased intracellular Na+ (Nai+) and activation of the Na+/K+-ATPase. Increased metabolic demand linked to disruption of Nai+ homeostasis activates glucose uptake and glycolysis in astrocytes. Here, we have examined whether a similar neurometabolic coupling could operate for the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), also taken up by Na+-dependent transporters into astrocytes. Thus, we have compared the Nai+ response to GABA and glutamate in mouse astrocytes by microspectrofluorimetry. The Nai+ response to GABA consisted of a rapid rise of 4-6 mM followed by a plateau that did not, however, significantly activate the pump. Indeed, the GABA transporter-evoked Na+ influxes are transient in nature, almost totally shutting off within approximately 30 sec of GABA application. The metabolic consequences of the GABA-induced Nai+ response were evaluated by monitoring cellular ATP changes indirectly in single cells and measuring 2-deoxyglucose uptake in astrocyte populations. Both approaches showed that, whereas glutamate induced a robust metabolic response in astrocytes (decreased ATP levels and glucose uptake stimulation), GABA did not cause any measurable metabolic response, consistent with the Nai+ measurements. Results indicate that GABA does not couple inhibitory neuronal activity with glucose utilization, as does glutamate for excitatory neurotransmission, and suggest that GABA-mediated synaptic transmission does not contribute directly to brain imaging signals based on deoxyglucose.     

Decreased turnover aspirin resistance by bidaily aspirin intake and efficient cytoreduction in myeloproliferative neoplasms

Essential thrombocythemia (ET) and polycythemia vera (PV) are myeloproliferative neoplasms (MPN) with an increased risk of arterial and venous thrombosis. Aspirin is recommended to reduce this risk, but resistance to antiplatelet therapy seems to hamper its efficacy in some patients. We have previously shown that multiple electrode aggregometry (MEA) was a valuable tool to assess aspirin resistance in MPN. In this study, MEA was used to assess the reduction in aspirin resistance after bi-daily (BID) aspirin intake or cytoreduction.

Fifty one MPN patients (31 ET and 20 PV) receiving 75 mg aspirin once daily (OD) or BID, with or without cytoreductive treatment, were analyzed. Aspirin resistance was assessed using whole blood MEA (Multiplate®, Roche Diagnostics, Meylan, France).

In all patients, global aspirin resistance consisted mainly of turnover resistance (TOR). 94% of patients with OD aspirin intake and without cytoreduction displayed biological aspirin resistance. By switching to a BID aspirin regimen, the proportion of resistant patients reduced to 47%. Cytoreduction also contributed to reduce aspirin resistance in a similar way (50% of aspirin resistant patients). Combining cytoreduction and BID aspirin regimen was the most efficient way to reduce aspirin resistance yielding to 12% resistant patients. Moreover, a nonlinear correlation was observed between TOR and naive platelet counts regardless of aspirin regimen. Last, mutational status did not seem to affect TOR.

This study confirmed that BID aspirin is biologically more effective than OD aspirin in reduction of aspirin resistance. The latter was achieved through a reduction in TOR which was also decreased by cytoreductive therapy.     

Ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) continues to complicate the course of 8 to 28% of patients receiving mechanical ventilation (MV). In contrast to infections of more frequently involved organs (e.g., urinary tract and skin), for which mortality is low, ranging from 1 to 4%, the mortality rate for VAP ranges from 24 to 50% and can reach 76% in some specific settings or when lung infection is caused by high-risk pathogens. The predominant organisms responsible for infection are Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacteriaceae, but etiologic agents widely differ according to the population of patients in an intensive care unit, duration of hospital stay, and prior antimicrobial therapy. Because appropriate antimicrobial treatment of patients with VAP significantly improves outcome, more rapid identification of infected patients and accurate selection of antimicrobial agents represent important clinical goals. Our personal bias is that using bronchoscopic techniques to obtain protected brush and bronchoalveolar lavage specimens from the affected area in the lung permits physicians to devise a therapeutic strategy that is superior to one based only on clinical evaluation. When fiberoptic bronchoscopy is not available to physicians treating patients clinically suspected of having VAP, we recommend using either a simplified nonbronchoscopic diagnostic procedure or following a strategy in which decisions regarding antibiotic therapy are based on a clinical score constructed from seven variables. Selection of the initial antimicrobial therapy should be based on predominant flora responsible for VAP at each institution, clinical setting, information provided by direct examination of pulmonary secretions, and intrinsic antibacterial activities of antimicrobial agents and their pharmacokinetic characteristics. Further trials will be needed to clarify the optimal duration of treatment and the circumstances in which monotherapy can be safely used.     

Long-term outcome after bone marrow transplantation for severe aplastic anemia

From January 1978 to December 2001, 133 patients with severe aplastic anemia (SAA) underwent non-T cell-depleted allogeneic bone marrow transplantation from an HLA-identical sibling donor, at the Hospital Saint Louis using either the combination of cyclophosphamide (Cy) and thoracoabdominal irradiation (TAI; n=100) or Cy and antithymocyte globulin (ATG; n=33), as a conditioning regimen. With 13.6 years of follow-up, the 10-year survival estimate was 64%. Four factors were associated with lower survival: older age, use of Cy-TAI, any form of treatment prior to transplantation (either androgens or immunosuppressive therapy, [IST]), and grade II to IV acute graft-versus-host disease (GvHD). TAI was the sole factor associated with the occurrence of acute GvHD. The risk of cancers (15-year cumulative incidence, 10.9%) was associated with older age and with the use of cyclosporine as IST before transplantation. Cumulative incidences and risk factors of nonmalignant late effect including avascular osteonecrosis and late bacterial, viral, and fungal infection were also analyzed. Improved results using Cy-ATG as conditioning can lead to more than 90% chance of cure in patients with SAA. Even if, in our experience, the role of Cy-ATG versus that of Cy-TAI remained inextricably related to the year of transplantation, the major detrimental role of the GvHD disease in the long-term outcome and its relation to TAI supports avoidance of irradiation in the conditioning regimen. Furthermore, avoidance of any IST before transplantation in patients with a sibling donor is a prerequisite for attaining such excellent results.     

Junior versus senior physicians for informing families of intensive care unit patients

To compare the effectiveness of information delivered to family members of critically ill patients by junior and senior physicians, we performed a prospective randomized multicenter trial in 11 French intensive care units. Patients (n = 220) were allocated at random to having their family members receive information by only junior or only senior physicians throughout the intensive care unit stay; there were 92 and 93 evaluable cases in the junior and senior groups, respectively, with no significant differences in baseline characteristics. Between Days 3 and 5, one family representative per patient was evaluated for comprehension of the diagnosis, prognosis, and treatment in the patient; satisfaction with information and care; and presence of symptoms of anxiety and depression. No significant differences were found between the two groups for any of these three criteria. Family members informed by a junior physician were more likely to feel they had not been given enough information time (additional time wanted: 3 [0-6.5] vs. 0 [0-5] minutes, p = 0.01) and to have sought additional explanations from their usual doctor (48.9 vs. 34.4%, p = 0.004). Specialty residents, if given opportunities for acquiring experience, can become proficient in communicating with families and share this task with senior physicians.     

Early matched sibling hematopoietic cell transplantation for adult AML in first remission using an age-adapted strategy: long-term results of a prospective GOELAMS study

The LAM2001 phase 3 trial, involving 832 patients with acute myeloid leukemia (AML; median: 46 years) proposed HLA-identical sibling allograft HSCT for all patients with an identified donor. The trial compared reduced-intensity conditioning (RIC) for patients older than 50 years of age (N = 47) and myeloablative conditioning for younger patients (N = 117). BM HSCT was performed in the younger patients, while the older ones received a consolidation course, followed by peripheral blood allo-HSCT using RIC. The incidence of grade II-IV acute GVHD, was 51.9% (95% confidence interval [CI]: 42.1-61.8) and 11.3% (1.6-21.2) after myeloablative or RIC, respectively (P < .0001) and that of chronic GVHD 45.8% (95% CI: 34.8-56.7) and 41.7% (24.7-58.6; NS). Cumulative incidence of nonrelapse mortality at 108 months was 15.8% (95% CI: 9.8-23.2) for myeloablative, and 6.5% (0.2-16.2) for RIC (NS). CI of relapse at 108 months was 21.7% (95% CI: 13.9-28.6) and 28.6% (16.5-43.4; NS). Overall survival at 108 months was 63.4% (95% CI: 54.6-72.2) and 65.8% (52.2-72.2), respectively, after myeloablative or RIC (NS). RIC peripheral blood stem cell allo-HSCT is prospectively feasible for patients between the ages of 51 and 60 years without excess of relapse or nonrelapse mortality, and compares favorably with myeloablative marrow allo-HSCT proposed to younger patients.     

Bortezomib combined with low-dose cytarabine in Intermediate-2 and high risk myelodysplastic syndromes. A phase I/II Study by the GFM

Marrow cells from patients with higher-risk myelodysplastic syndrome (MDS) exhibit constitutive nuclear factor (NF)-κB activation. The proteasome inhibitor, bortezomib, has limited efficacy as a single agent in acute myeloid leukaemia. Its activity on leukaemic cell lines is potentiated by chemotherapy. We treated 43 higher-risk MDS patients with bortezomib (1·5 mg/m(2) , days 1, 4, 8 and 11) and low dose cytarabine arabinoside (LDAC; 10 mg/m(2) , then 20 mg/m(2) from days 1-14), every 28 d for four cycles. Median follow-up was 29·7 months. Responses were seen in 12 of the 43 patients (28%), including complete response (CR, n = 1), marrow-CR (n = 3), partial response (PR, n = 5) and haematological improvement (HI, n = 3). Responses were seen in 12 (36%) of the 33 previously untreated patients (11% CR, 13% PR, 2·5% HI), compared to none in the 12 previously treated patients (P < 0·01). Responders had better overall survival (median 18·2 vs. 10 months). One CR and 3 marrow-CRs were seen in patients with complex karyotypes. Main toxicity was haematological, responsible for infection in six patients and bleeding in 3. Three patients with Grade 1-2 pre-treatment haematotoxicity developed Grade 3-4 toxicity. Neuropathy was seen in 12% of patients. The addition of bortezomib to LDAC in higher-risk MDS may improve results obtained with LDAC alone, especially in patients with unfavourable karyotypes.