Pharmacodynamics of minocycline against Acinetobacter baumannii studied in a pharmacokinetic model of infection.

Minocycline (MNO) is an old antibiotic that may have an important role in the treatment of multidrug-resistant Gram-negative bacterial infections as the burden of such infections increases. In this study, a single-compartment dilutional pharmacokinetic model was used to determine the relationship between MNO exposure and antibacterial effect, including the risk of resistance emergence, against strains of Acinetobacter baumannii. The mean ± standard deviation area under the unbound drug concentration-time curve to minimum inhibitory concentration ratio (fAUC/MIC) associated with a 24-h bacteriostatic effect was 16.4 ± 2.6 and with a -1 log reduction in bacterial load at 24 h was 23.3 ± 3.7. None of the strains reached a -2 log reduction over 48 h. Changes in population profiles were noted for two of the three strains studied, especially at fAUC/MIC ratios of >5-15. A reasonable translational pharmacodynamic target for MNO against A. baumannii could be an fAUC/MIC of 20-25. However, if maximum standard 24-h doses of intravenous MNO are used (400 mg/day), many strains would be exposed to MNO concentrations likely to change population profiles and associated with the emergence of resistance. Either MNO combination therapy or an increased MNO dose (>400 mg/day) should be considered when treating A. baumannii infections.

Acetylcholinesterase-induced fluorescence turn-off of an oligothiophene-grafted quartz surface sensitive to myristoylcholine.

Conjugated polyelectrolytes (CPEs) have recently emerged as label-free materials for biosensing due to their intrinsic ability to transduce an amplified optical signal in response to interactions with different analytes. Herein, the conformational change of an anionic oligothiophene is exploited to generate a unique fluorescent response upon interaction with myristoylcholine (MyrCh). The variations observed in spectroscopic signals are explained in terms of a synergistic combination of hydrophobic and electrostatic forces involving the oligothiophene chains and MyrCh molecules, inducing the disassembling of oligothiophene chains. The enzyme acetylcholinesterase (AChE) is able to reverse this effect by catalyzing the hydrolysis of MyrCh; hence, its enzymatic activity can be monitored through the variation of fluorescence emission of the system. The oligothiophene sensing probe retains its conformational sensitivity with regard to the AChE-mediated cleavage of MyrCh upon immobilization onto a quartz substrate, which is accomplished by a "grafting onto" approach based on click chemistry. These results are encouraging for the further development of such a label-free system towards the fabrication of sensing devices that would incorporate CPEs and would be potentially useful for the specific detection of a wide range of bioanalytes.

Comparative antibacterial effects of moxifloxacin and levofloxacin on Streptococcus pneumoniae strains with defined mechanisms of resistance: impact of bacterial inoculum.

OBJECTIVES: We aim to further define the impact of the mechanism of fluoroquinolone resistance and inoculum load on the pharmacodynamic effects of levofloxacin and moxifloxacin on Streptococcus pneumoniae. METHODS: The antibacterial effects of and emergence of resistance (EoR) to moxifloxacin (400 mg once daily) or levofloxacin (750 mg once daily or 500 mg twice daily) were compared using five S. pneumoniae strains containing no known resistance mechanisms, efflux resistance mechanisms, a parC mutation or parC and gyrA mutations, at high (10(8) cfu/mL) and low (10(6) cfu/mL) inocula. An in vitro pharmacokinetic model was used and simulations were performed over 96 h. After drug exposure, isolates were tested for the presence of efflux pumps and mutations in the quinolone resistance-determining regions. RESULTS: A high inoculum diminished the antibacterial effect of moxifloxacin and levofloxacin. Levofloxacin at both dosages produced EoR with all strains. Levofloxacin regimens with AUC/MIC ratios <100 produced EoR. Moxifloxacin produced EoR with the parC strain only. CONCLUSIONS: Levofloxacin dosing regimens with low AUC/MIC ratios select for efflux pump overexpression, leading to fluoroquinolone resistance. Levofloxacin dosing may select for gyrA mutations, inducing moxifloxacin resistance. These data confirm that a fluoroquinolone AUC/MIC ratio of >100 is required for prevention of EoR.

ADAR2-editing activity inhibits glioblastoma growth through the modulation of the CDC14B/Skp2/p21/p27 axis.

Grade IV astrocytoma or glioblastoma multiforme (GBM) is one of the most aggressive and lethal tumors affecting humans. ADAR2-mediated A-to-I RNA editing, an essential post-transcriptional modification event in brain, is impaired in GBMs and astrocytoma cell lines. However, the role of ADAR2 editing in astrocytomas remains to be defined. Here, we show that ADAR2 editing rescue in astrocytomas prevents tumor growth in vivo and modulates an important cell cycle pathway involving the Skp2/p21/p27 proteins, often altered in glioblastoma. We demonstrate that ADAR2 deaminase activity is essential to inhibit tumor growth. Indeed, we identify the phosphatase CDC14B, which acts upstream of the Skp2/p21/p27 pathway, as a novel and critical ADAR2 target gene involved in glioblastoma growth. Specifically, ADAR2-mediated editing on CDC14B pre-mRNA increases its expression with a consequent reduction of the Skp2 target protein, as shown both in vitro and in vivo. We found that, compared to normal brain, both CDC14B editing and expression are progressively impaired in astrocytomas from grade I to IV, being very low in GBMs. These findings (1) demonstrate that post-transcriptional A-to-I RNA editing might be crucial for glioblastoma pathogenesis, (2) identify ADAR2-editing enzyme as a novel candidate tumor suppressor gene and (3) provide proof of principle that ADAR2 or its substrates may represent a suitable target(s) for possible novel, more effective and less toxic approaches to the treatment of GBMs.

Correlation between ultrastructural and histochemical parameters in lymphokine-activated killer (LAK) cells reacting with target cells in vitro.

Ultrastructural and fluorescence data allowed us to study the most important moments of the interaction between lymphokine-activated killer (LAK) cells against target cells (Chang) in vitro. The LAK cells, maintained at low doses of recombinant interleukin-2, were able to recognize, bind and destroy the tumoral cells. Before the attack, the LAK cells were characterized by a cytoplasm with a high ribosomes content; after the identification and the interaction cell-cell, a degeneration of the tumoral cell was observed. These observations allowed us to suppose that the interaction between the two types of cells may be mediated by a receptoral membrane system without the action of lytic enzymes.

Respiratory function in precapillary pulmonary hypertension.

Since dyspnoea on exertion is very often the first symptom of precapillary pulmonary hypertension (PPH), either from chronic thromboembolic pulmonary hypertension (CTEPH) or from idiopathic pulmonary hypertension (IPH), these patients are often first examined in a pulmonary function laboratory. We carried out a retrospective study (1987-1992) on pulmonary function in 34 patients diagnosed to have PPH by means of specific diagnostic tools, out of 5,467 patients first attending our laboratory. Nine suffered from IPH, 10 from CTEPH and 15 from Eisenmenger physiology. This last group differed from the others, since its diagnosis had been known for a long time and the stage of the disease was more advanced, when pulmonary function tests were performed in our laboratory (with a view to transplantation). Respiratory function, blood gases and arterial oxyhaemoglobin saturation (HbSaO2) during exercise (Bruce protocol), diffusing capacity of the lungs for carbon monoxide (DLCO), shunt fraction (QS%) (approximation obtained from arterial oxygen tension (PaO2) after 100% oxygen breathing) had been evaluated. In the first two groups, in contrast to other reports, we could observe no obstructive defect. Only 20% of the subjects had restrictive defects, however mild. The typical functional picture of these patients revealed normal lung volumes, normal or slightly reduced DLCO, mild hypoxaemia with hypocapnia, severe HbSaO2 drops during exercise, and pathological QS%. We conclude that every time a patient presents with breathlessness at rest or on exercise, a normal chest X-ray and respiratory function tests, pulmonary hypertension must be suspected and subject to specific and invasive tests. More severe functional impairment was observed in the PPH from the Eisenmenger disorder. This might be due to a more advanced stage of this type of hypertension at the time of our observation and/or to the different mechanisms of the diseases themselves.

Chordoma-natural history, treatment and prognosis. The Florence Radiotherapy Department experience (1956-1990) and a critical review of the literature.

Fifteen cases of chordoma, seen between 1956 and 1990 at the Florence Radiotherapy Department are reported. Twelve of them were treated with radiotherapy and surgery, while one was left untreated. We analyzed the course of the disease in the treated cases, with particular emphasis on the problem of symptom control. The natural history of the disease seemed to be only marginally affected by the treatment and new therapeutic options are strongly needed. While actuarial survival rates at 5 and 10 years were 58% and 35% respectively (owing to the slow growth rate of this neoplasm), 10 years' symptomatic progression-free, symptom-free, and disease-free survival rates were only 25%, 17% and 8% respectively.

In vitro growth of bone marrow-derived multipotent and lineage-restricted hematopoietic progenitor cells in myelodysplastic syndromes.

The aim of the present study was to evaluate the incidence of bone marrow-derived multipotent (CFU-GEMM), megakaryocytic (CFU-Mk), erythroid (BFU-E), and granulocyte-macrophage (CFU-GM) progenitor cells in 22 patients with myelodysplastic syndromes (MDS), and to investigate the role of hematopoietic accessory cells (T-lymphocytes and monocytes) as a possible cause of growth derangement. As compared to normal controls (n = 15), growth values in the 22 patients (mean +/- SEM) were significantly reduced for CFU-GEMM (0.4 +/- 0.1 versus 7 +/- 1, P less than 0.0005), CFU-Mk (1.4 +/- 0.5 versus 18 +/- 4, P less than 0.0005), BFU-E (2.2 +/- versus 40 +/- 6, P less than 0.0005), and CFU-GM (19 +/- 5 versus 65 +/- 10, P less than 0.0005). The growth of CFU-GEMM was abnormal at an early stage in the clinical development of MDS, sometimes even when CFU-GM formation was still normal. Colony-formation was unaffected by removal of hematopoietic accessory cells. Although no correlation was found between the incidence of lineage-restricted progenitors and the degree of peripheral cytopenia, derangement of colony growth was more pronounced in patients with worse prognosis. We conclude that: (i) the grossly defective CFU-GEMM growth supports the concept of MDS as clonal disorders of hematopoietic multipotent stem cells; (ii) a progressive impairment of in vitro hematopoiesis occurs in association with the clinical progression of the myelodysplastic syndromes.

Changes in aerobic microflora of skin and gills of Mediterranean sardines (Sardina pilchardus) during storage in ice.

Sardines from the Adriatic Sea were examined fresh and after 4 and 8 days of storage in ice. A total of 1500 strains isolated were identified from the gills and the surface of the fish. Pseudomonadaceae, Neisseriaceae, Flavobacterium/Cytophaga, Enterobacteriaceae, coryneform bacteria and Micrococcaceae were the most common bacteria in fresh fish. During storage the pseudomonads (mainly the non-fluorescent strains) increased and became the dominating microflora; the Neisseriaceae (Moraxella, Psychrobacter and Acinetobacter) showed a distinct increase during the first 4 days in ice; the percentage of the other bacterial groups clearly decreased. On the gills the quantitative changes in the microflora were less pronounced than on the surface.