The size, shape, density and ring of the dwarf planet Haumea from a stellar occultation.

Haumea-one of the four known trans-Neptunian dwarf planets-is a very elongated and rapidly rotating body. In contrast to other dwarf planets, its size, shape, albedo and density are not well constrained. The Centaur Chariklo was the first body other than a giant planet known to have a ring system, and the Centaur Chiron was later found to possess something similar to Chariklo's rings. Here we report observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multi-chord stellar occultation). Secondary events observed around the main body of Haumea are consistent with the presence of a ring with an opacity of 0.5, width of 70 kilometres and radius of about 2,287 kilometres. The ring is coplanar with both Haumea's equator and the orbit of its satellite Hi'iaka. The radius of the ring places it close to the 3:1 mean-motion resonance with Haumea's spin period-that is, Haumea rotates three times on its axis in the time that a ring particle completes one revolution. The occultation by the main body provides an instantaneous elliptical projected shape with axes of about 1,704 kilometres and 1,138 kilometres. Combined with rotational light curves, the occultation constrains the three-dimensional orientation of Haumea and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium. Haumea's largest axis is at least 2,322 kilometres, larger than previously thought, implying an upper limit for its density of 1,885 kilograms per cubic metre and a geometric albedo of 0.51, both smaller than previous estimates. In addition, this estimate of the density of Haumea is closer to that of Pluto than are previous estimates, in line with expectations. No global nitrogen- or methane-dominated atmosphere was detected.

Inactivation of urease by 1,4-benzoquinone: chemistry at the protein surface.

The high activity of urease, a Ni(ii) enzyme, has several adverse effects on human health and agriculture, and its modulation needs the use of inhibitors. 1,4-Benzoquinone (BQ) irreversibly inactivates Sporosarcina pasteurii urease (SPU), with first order kinetics for both the inhibitor and the enzyme. This reaction is stoichiometrically quenched in the presence of sulphite. The 2.07 Å crystal structure of SPU bound to BQ shows the presence of a 1,4-hydroquinone moiety covalently bound to the thiol group of αCys322, a key residue found on the mobile flap regulating the substrate access to the active site. The 1.75 Å crystal structure obtained when sulphite is added to a solution of SPU previously incubated with BQ shows the presence of a 2,5-dihydroxy-benzenesulphonate moiety bound to the αCys322 thiol group. These data reveal how the active site cysteine reacts with a prototypical BQ moiety, found in a large number of natural substances potentially suitable to control the urease activity.

Predictive indexes of nocturnal desaturation in COPD patients not treated with long term oxygen therapy.

Nocturnal oxygen desaturation during the sleep is very frequent in patients affected by chronic obstructive pulmonary disease (COPD). Hypoventilation, rather than sleeping apnea, is commonly considered as the most relevant factor in the onset of nocturnal oxygen desaturation. On this topic, the Authors have carried on a study on the nocturnal hypoxemia in 70 hospitalized COPD patients with a mean FEV1% of 40 +/- 21 and a mean PaO2 of 67.7 +/- 6.1. Anthropometric features (sex, age, body mass index) and functional respiratory parameters (FEV1, FEV1/VC, PaO2, PaCO2, SaO2, pH) were considered. Moreover all the patients were monitorized with transcutaneous pulse oxymetry, while breathing environmental air, in nighttime. Mean oxyhemoglobinic nocturnal saturation (SaO2 noct.%), minimum registered value of nocturnal SaO2 (min SaO2 noct.%) and the minutes of nighttime SaO2 < or = 90% and < or = 85% (tSaO2 < or = 90% e < or = 85%) were considered. Fiftyfour patients (77.15%) were nocturnal desaturating (NOD), whereas 16 (22.85%) were not desaturating (nNOD). A statistically significant difference was found between the two groups as to the values of FEV1 (p < 0.05), PaCO2, pH, SaO2 noct.%, minimum SaO2 noct.% and tSaO2 < or = 90% and < or = 85% (p < 0.0001). A statistically significant correlation was found between tSaO2 < 90% and BMI (r = 0.44), PaCO2 (r = 0.48) and pH (r = -0.44), as well as between tSaO2 < 85% and PaCO2 (r = 0.57) and pH (r= -0.50), between SaO2 noct.% and BMI (r = -0.45), PaCO2 (r = -0,50), FEV1 (r = 0.44) and pH (r = 0.46) and finally between minimum SaO2 noct.% and PaCO2 (r = -0.47) was found. Eighty percent of the NOD patients had PaO2 < 75 mm Hg and PaCO2 > 44 mm Hg. All the patients with PaCO2 > 50 mm Hg were NOD. In conclusion, all COPD subjects with FEV1 < 49% and daytime PaO2 > 60 mm Hg, particularly when associated to elevated PaCO2 values and high BMI, should undergo a nocturnal pulse oxymetry in order to identify possible nocturnal desaturations. In these patients reduced FEV1, high BMI and/or elevated PaCO2 appear to be predictive indexes of nocturnal desaturation. A PaCO2 > 50 mm Hg is highly indicative for a nocturnal oxygen desaturation.

[Amiodarone pulmonary toxicity]. / Tossicità polmonare da amiodarone.

The Authors discuss a case of amiodarone pulmonary toxicity, with simultaneous alveolar and interstitial infiltrates, in a female patient 75 years old, who took the drug for 6 months at a low dosage (200 mg/daily for 5 days a week). It is outlined that the diagnosis can be achieved only by exclusion of other aetiologies, since clinical and diagnostic features are not pathognomonic for such disease. The withdrawal of the drug and the administration of the steroid therapy determined a fast improvement of the clinical and radiological appearance.

Drug-resistance of Mycobacterium tuberculosis in time.

Tuberculosis is heavily worldwide spreading in the last years. More and more signalations seem to indicate that the incidence of drug-resistant Mycobacteria is increasing in almost all industrialized countries. The authors have carried on a study on the percentage of drug-resistant strains of Mycobacterium Tuberculosis (MT) among isolates from patients affected by active pulmonary tuberculosis hospitalized through the years 1992-94. Out of 59 isolates of MT, 20.3% were drug-resistant: 25% of them to 2 drugs and 16.6% to 3 or more drugs. Resistance to single drug was so distributed: Streptomycin 11.8%, Isoniazid 6.7%, Rifampycin 3.4%, Ethambutol 6.7%, Ansamycin 3.4%, Pyrazinamide 5.0%, Ethionamide 1.7%. These results were confronted with analogous data on MT drug-resistance collected in the same hospital division in the years 1978-82 and 1985-87. The data analysis shows that actual incidence of drug resistant strains of MT is only slightly decreased but quite similar to that observed in 1978-82, except for Ethambutol, while there is a remarkable reduction vs. 1985-87; in that period, in fact, the highest incidence of drug resistance was recorded. The authors' conclusion is that only little differences were observed in the total amount of resistant strains of MT through 20 years; they also outline that resistance to Ansamycin, most recent out of all tested drugs, is quite similar to that observed for Rifampycin, that is chemically analogous.

Post-tuberculosis chronic empyema of the "forty years after".

The authors present 110 cases of patients hospitalized in the last 5 years, with long-term disabling sequelae of pulmonary tuberculosis. Twelve out of them (= 10.9%) suffered from post-tuberculous chronic empyema, with an average latency period of 44.83 years between the acute tuberculous illness and the clinical manifestation of the empyema. Nine of the patients had been treated with collapsotherapy, induced by artificial intrapleural pneumothorax, 1 with thoracoplasty, and 2 only with late and inadequate anti-mycobacterial chemotherapy. Eleven patients (91.6%) also had a cutaneous fistula (7 cases) and/or a bronchopleural fistula (4 cases). The authors show how the issue of tuberculous sequelae is a significant not only from the numerical standpoint, but also for the seriousness of the caused pathological conditions, often posing problems for differential diagnosis. Moreover, they stress how tuberculosis should never be neglected or considered last in the differential diagnosis of empyema and pyopneumothorax.