Statistical mechanics of Hamiltonian adaptive resolution simulations.

The Adaptive Resolution Scheme (AdResS) is a hybrid scheme that allows to treat a molecular system with different levels of resolution depending on the location of the molecules. The construction of a Hamiltonian based on the this idea (H-AdResS) allows one to formulate the usual tools of ensembles and statistical mechanics. We present a number of exact and approximate results that provide a statistical mechanics foundation for this simulation method. We also present simulation results that illustrate the theory.

Proton Wires via One-Dimensional Water Chains Adsorbed on Metallic Steps.

The process of proton transfer is here analyzed for one-dimensional water chains adsorbed on metallic steps. When the water chain contains a hydronium and a hydroxyl ion, two different mechanisms are possible, depending on the metal substrate. On coinage metals (Ag, Au), recombination is observed through a spontaneous Grotthuss mechanism. On more reactive surfaces (Pd and Pt), the hydronium ion is unstable and releases a proton that adsorbs onto the metal, leaving the negatively charged OH(-) unbalanced. In this case, the negative charge can be transferred along the wire with very low activation barriers.

Evolution of the structure of amorphous ice: from low-density amorphous through high-density amorphous to very high-density amorphous ice.

We report results of molecular dynamics simulations of amorphous ice for pressures up to 22.5 kbar. The high-density amorphous ice (HDA) as prepared by pressure-induced amorphization of I(h) ice at T=80 K is annealed to T=170 K at various pressures to allow for relaxation. Upon increase of pressure, relaxed amorphous ice undergoes a pronounced change of structure, ranging from the low-density amorphous ice at p=0, through a continuum of HDA states to the limiting very high-density amorphous ice (VHDA) regime above 10 kbar. The main part of the overall structural change takes place within the HDA megabasin, which includes a variety of structures with quite different local and medium-range order as well as network topology and spans a broad range of densities. The VHDA represents the limit to densification by adapting the hydrogen-bonded network topology, without creating interpenetrating networks. The connection between structure and metastability of various forms upon decompression and heating is studied and discussed. We also discuss the analogy with amorphous and crystalline silica. Finally, some conclusions concerning the relation between amorphous ice and supercooled water are drawn.

Polyamorphism of ice at low temperatures from constant-pressure simulations.

We report results of molecular dynamics simulations of amorphous ice in the pressure range 0-22.5 kbar. The high-density amorphous (HDA) ice prepared by compression of Ih ice at T=80 K is annealed to T=170 K at intermediate pressures in order to generate relaxed states. We confirm the existence of recently observed phenomena, the very high-density amorphous ice, and a continuum of HDA forms. We suggest that both phenomena have their origin in the evolution of the network topology of the annealed HDA phase with decreasing volume, resulting at low temperatures in the metastability of a range of densities.

Long-term and preventive effects of sublingual allergen-specific immunotherapy: a retrospective, multicentric study.

There is now an increasing body of evidence to support the practice of allergen-specific sublingual-swallow immunotherapy (SLIT) in the treatment of IgE-mediated respiratory allergies. Recent studies on traditional injection therapy have pointed out that this form of treatment is not only capable to decrease actual allergic symptoms, but may also have long-term clinical and preventive effects and may influence atopy natural history. In the year 2000, our group published a retrospective, multicenter study showing the efficacy and safety of SLIT in a survey of 302 patients. We now carried out a second study on the same patients, with the aim of investigating long-term and preventive effects of SLIT. Beside the well-known safety and efficacy of this treatment (80.8% of patients reported clinical benefits), SLIT proved also to elicit long term clinical effects: over a mean follow-up of 11.6 months after the end of treatment, 80.8% of patients still maintained the previously achieved benefits. During the follow-up period, only 1% of non-asthma patients reported an onset of respiratory symptoms, and only 9.6% of patients undergoing new skin tests showed new sensitizations. All the clinical benefits were strongly linked to the length of treatment: patients with long-lasting benefits were treated for a mean length of 29.1 months, while patients showing a return to pre-SLIT condition were treated for a mean 13.3 months. SLIT can obtain long-term and preventive effects so far attributed to injection immunotherapy.

Nanofriction behavior of cluster-assembled carbon films.

We have characterized the frictional properties of nanostructured carbon films grown by supersonic cluster beam deposition via an atomic force-friction force microscope (AFM-FFM). The experimental data are discussed on the basis of a modified Amonton's law for friction, stating a linear dependence of friction on load plus an adhesive offset accounting for a finite friction force in the limit of null total applied load. Molecular dynamics simulations of the interaction of the AFM tip with the nanostructured carbon confirm the validity of the friction model used for this system. Experimental results show that the friction coefficient is not influenced by the nanostructure of the films nor by the relative humidity. On the other hand the adhesion coefficient depends on these parameters.

Ab initio simulations of photoinduced interconversions of oxygen deficient centers in amorphous silica.

We have studied by ab initio molecular dynamics the interconversion between oxygen deficient centers (Si-Si bond, dicoordinated silicon =Si:, and E' centers) induced by UV irradiation in a-SiO2. By dynamical simulations in the excited state of a periodic model of a-SiO2 we have identified the reaction path and activation barrier for the Si-Si-->=Si: interconversion. A new competitive transformation of the excited, neutral Si-Si bond into two E' centers has been identified. Our results provide strong theoretical support to the viability of these processes, proposed experimentally on the basis of optical data only.

Safety and efficacy evaluation of sublingual allergen-specific immunotherapy a retrospective, multicenter study.

In recent years, several controlled studies have proved the efficacy and safety of sublingual specific immunotherapy, as a possible alternative to the classic subcutaneous route of administration. This alternative option has been officially confirmed by the recent WHO position paper "Allergen Immunotherapy: Therapeutic Vaccines for Allergic Diseases'". Since sublingual immunotherapy has now been widely used for years, we carried out an open, multicentric, retrospective study to investigate the efficacy and safety of this form of treatment in a large number of patients. To this end, we studied 302 subjects undergoing sublingual immunotherapy for at least three months with different allergen compositions. Notwithstanding the obvious limitations due to the study design, this survey has confirmed the high efficacy and safety of this form of treatment, as already reported in previous controlled studies. Sublingual immunotherapy appears to be a simple, well-tolerated and effective method of treatment of allergen-specific diseases.

Transurethral incision of prostate (TUIP) and retrograde ejaculation.

OBJECTIVE: Men of any age with bladder outlet obstruction and without measurable enlargement of the prostate constitute ideal candidates for TUIP. Effectiveness of any technique with respect to flow rate improvement is firmly established, indifferently whether unilateral or bilateral. But there is a wide variation in the reported incidence of retrograde ejaculation with unilateral and bilateral incision. MATERIAL AND METHODS: The retrospective analysis of our 45/57 available patients treated with this technique, between January 1993 and March 1995, does not show a major incidence of this complication for the bilateral incision, with an overall incidence of 6.6% (3/45 patients). CONCLUSIONS: Although ejaculation may be preserved, it cannot be guaranteed.

Bacillus Calmette-Guerin in the treatment of stage T1 grade 3 transitional cell carcinoma of the bladder: long-term results.

PURPOSE: We performed a retrospective long-term study to evaluate the results of immunotherapy in the treatment of high grade superficial bladder tumors. MATERIALS AND METHODS: Between 1981 and 1993, 593 patients with superficial transitional cell carcinoma of the bladder underwent transurethral resection. Of 64 patients with stage T1 grade 3 disease 50 received intravesical bacillus Calmette-Guerin after transurethral resection of all visible tumor. RESULTS: At a median followup of 42 months (range 12 to 112) 36 patients (72%) are disease-free and have not required further treatment. Superficial recurrence was noted in 8 patients (16%). Disease progressed in 6 patients (12%), including 5 with locally invasive and 1 with metastatic disease. Cystectomy was performed for progression in 4 patients and for recurrent stage T1 grade 3 disease in 1. There was 1 disease related death (2%). The overall survival rate is 94%. CONCLUSIONS: Intravesical bacillus Calmette-Guerin appears to be the most effective conservative treatment for patients with stage T1 grade 3 bladder cancer.

Value of autologous bone marrow transplantation in follicular lymphoma: a France Autogreffe retrospective study of 42 patients.

The value of high-dose chemotherapy with hematologic stem cell rescue has not been established in the treatment of low-grade non-Hodgkin's lymphoma. We report the results of a retrospective 'France Autogreffe' study of 42 patients grafted in first partial remission (n = 13) or chemosensitive relapse (n = 29) for follicular lymphoma before January 1990. The median age was 38 years (range 26-61 years). Preparative therapy was chemotherapy alone in 22 patients and total body irradiation (TBI)-containing regimens in 20 patients. Thirty-seven patients received hematopoietic marrow stem cells. Bone marrow purging was performed in 15 patients. Five patients received peripheral blood stem cells. Three patients died of bone marrow transplantation toxicity and two others died in complete remission 10 months after autologous bone marrow transplantation. With a median follow-up of 43 months, relapse-free survival is 60%, event-free survival 58% and overall survival 83%. To date no prognostic factors have been shown.

[Cardiotoxicity of anthracyclines]. / Cardiotoxicité des anthracyclines.

The only factor limiting the use of anthracyclines (very powerful antimitotic antibiotics) is their cardiotoxicity. The cardiac involvement is irreversible, dose-dependent and may be detected at an early stage by non-invasive (echocardiography, myocardial scintigraphy) or invasive investigations (endomyocardial biopsy). The mechanism of cardiac toxicity involves the oxidative metabolism of the cardiac myocyte and liberation of oxygen free radicals and is different from the antitumoral effect. Protocols of administration over 6 to 24 hours have enabled the use of higher total doses and the reduction of cardiotoxicity without affecting the therapeutic efficacy. The use of "antioxidants" such as ICRF 187 has given promising results in myocardial protection. The strategy of surveillance (screening) of cardiotoxicity, of the mode of administration of the anthracyclines, results from the essential coordination of the efforts of the chemotherapist, taking into account the pathology, the sensitivity of the tumor to anthracyclines therapy, enabling personalization of the prescription and the abandon of the concept of maximal dosage.

A study of 15 cases of primary mediastinal lymphoma of B-cell type.

Fifteen cases of pure supradiapragmatic lymphoma with initial prominent antero-superior mediastinal involvement displaying a B-cell pattern of reactivity were studied. These cases occurred in six men and nine women with a median age of 33 years at diagnosis (range, 23 to 75 years). Supradiapragmatic peripheral lymphadenopathies were present in three cases, and intrathoracic extension to the lung, pericardium, or pleura was possible. In five cases a thymic origin was obvious. All cases exhibited a B-cell pattern of differentiation, with a great variety of histopathologic aspects associated with a high frequency of fibrosis and/or necrosis. Hodgkin's disease was initially misdiagnosed in four cases. The evolution was purely local, with extrathoracic extension in five cases, at the ultimate phase of the disease. The prognosis appeared to be poor with only five patients still alive at a median survival time of 16 months. A complete chemoresistance and radio-resistance was observed in seven cases; only two complete remissions were achieved with aggressive chemotherapy. Prolonged remission could be achieved after surgical reduction of the mass. Primary B-cell mediastinal lymphoma appears to be a distinct clinical entity with local evolution and resistance to therapy. A new therapeutic regimen, which could include surgery in some cases, should be found for this disease.

Multicenter randomized study comparing cyclosporine-A alone and antithymocyte globulin with prednisone for treatment of severe aplastic anemia.

We report the results of a randomized multicenter study comparing the efficacy of antithymocyte globulin (ATG) with that of cyclosporin A (CsA) as first-line therapy for severe aplastic anemia (SAA). Patients were randomized to receive ATG and prednisone (PDN) or CsA; hematologic response and toxicity were compared. At 3-month evaluation, patients who had no or minimal response received the alternative therapy to assess the value of a sequential immunosuppressive therapy for treatment of severe aplastic anemia. One hundred nineteen patients were randomized; 25 were excluded, of whom 3 were misdiagnosed and 22 did not follow the cross-over protocol. Ninety-four patients were analyzed; 46 received CsA, and 48 received ATG-PDN. The actuarial survival was 66.7%, with a median follow-up time of 19 months. There was no significant difference in survival between the groups with, at 3 months, an actuarial survival of 88% in the CsA group and 75% in the ATG group (NS); at 12 months, it was 70% in the CsA group and 64% in the ATG group (NS). The percentage of complete and partial response was 11.6% and 16%, respectively, at 3 months, and 31.6% and 30%, respectively, at 12 months (NS). The main prognostic factor was the absolute neutrophil count (ANC) at entry: Patients with ANC less than 0.2 x 10(9)/L had a significantly lower survival as compared with patients with more than 0.2 x 10(9)/L ANC (P = .0001). At 12 months, 62 evaluable patients were alive, with a complete or partial response in 36 patients. Patients who had responded to the first treatment had a better recovery of bone marrow failure than those who had sequential immunosuppression. The main complication was infection, which was more often observed and more often lethal during ATG and PDN therapy. In this study, initial treatment of SAA with either CsA or ATG-PDN followed by cross-over therapy for nonresponders produced comparable response and survival rates.

A multicenter randomized study comparing cyclosporin-A alone and antithymocyte globulin with prednisone for treatment of severe aplastic anemia. The cooperative group on the treatment of aplastic anemia.

This article reports the results of a randomized multicentric study comparing the efficacy of antithymocyte globulin (ATG) with cyclosporin-A (CsA) as first line therapy for severe aplastic anemia (SAA). Patients were randomized to receive ATG and prednisone (PDN) or CsA; hematological response and toxicity were compared. At 3 months, patients who had no or minimal response received the alternative therapy in order to assess the value of a sequential immunosuppressive therapy for treatment of severe aplastic anemia. One hundred and sixteen patients were analysed, 60 received CsA and 56 received ATG/PDN. The actuarial survival was 55% with a median follow-up time of 19 months. There was no significant difference in survival between the two groups. The main prognostic factor was the absolute neutrophil count (ANC) at entry: patients with ANC less than 0.2 x 10(9)/L had a significantly lower survival when compared with patients with an ANC greater than 0.2 x 10(9)/L (P = 0.0001). At 3 months, 16% of patients had a complete or partial response and a cross-over treatment was given to 68 patients. At 12 months, 77 patients were alive, with a complete or partial response in 47 patients. Patients who had responded to the first treatment had a better recovery of bone marrow failure than those who had a sequential immunosuppression. The main complication was infection which was more often observed and was more often lethal during ATG and PDN. This study demonstrates that CsA is comparable to ATG for primary treatment of SAA, but it is less toxic with fewer infectious deaths.(ABSTRACT TRUNCATED AT 250 WORDS)

Doxorubicin and doxorubicinol plasma concentrations and excretion in parotid saliva.

The pharmacokinetics of doxorubicin (DOX) and doxorubicinol (DOXol) was studied in six patients with various advanced neoplastic diseases who received 28-72 mg/m2 DOX (nine courses). Plasma and parotid saliva were collected over a 48-h period, and DOX and DOXol were quantified by high-performance liquid chromatography with fluorescence detection. As reported previously, a wide range of plasma levels were found among our patients. It appears that in addition to being quickly cleared from the plasma, both DOX and DOXol are excreted in detectable amounts in parotid saliva, a route of elimination that has been given little attention, if any. Excretion in the saliva exposes the mucosa of the upper gastrointestinal tract to drug and may play a role in causing stomatitis in patients receiving DOX by the i.v. route. Since huge interindividual and pronounced intraindividual differences were found in S/P ratios that mostly were not systematically related to the plasma drug concentration, the concentration in parotid saliva was not useful in predicting the level of free DOX and DOXol in plasma. For the parent drug and its metabolite, the S/P ratios increased significantly with time during the 48-h period after dosing.

[Prevention of septicemia caused by gastrointestinal tract organisms in patients with granulopenia. Comparison of three gastrointestinal tract decontamination treatments]. / Prévention des septicémies d'origine digestive chez les granulopéniques: comparaison de trois traitements de décontamination digestive.

Three gastrointestinal tract decontamination regimens were tested in patients with granulopenia: vancomycin 250 mg, tobramycin 75 mg, and colistin 1 million international units (regimen A); vancomycin 125 mg, tobramycin 75 mg, and colistin 1 million IU (regimen B); and colistin 1 million IU (regimen C); nystatin was added to all three regimens. Effectiveness was evaluated by stool organism counts and blood cultures to detect bacterial translocation (passage of bacteria from the intestinal tract to the bloodstream). Regimen C proved insufficiently effective. Regimen A was found to be poorly tolerated by the digestive mucosa. Regimen B was the best treatment since the low dosage of vancomycin proved effective. Nystatin satisfactorily eliminated yeasts.