MONITORAGGIO DELLA CORROSIONE MICROBIOLOGICA INDOTTA SU ACCIAI INOSSIDABILI IN AMBIENTI CONTAMINATI DA BATTERI MANGANESE OSSIDANTI

Il manganese è un elemento necessario per la vita dei microrganismi. Molti enzimi hanno una specifica necessità di tale elemento sfruttandone, per esempio, la capacità redox. Da osservazioni effettuate su componenti di impianti industriali che operano in ambienti contaminati da batteri manganese ossidanti, è emersa la presenza in superficie di un biofilm di caratteristiche viscose e di colore scuro. Le analisi eseguite sui biofilm hanno evidenziato che tali depositi sono costituiti da ossidi e idrossidi di Mn. Una parte significante delle colonie batteriche identificate hanno mostrato la capacità di produrre MnO2 (1-2). La presenza di batteri manganese-ossidanti produce negli acciai inossidabili un tipico innalzamento del potenziale di corrosione. Questo spostamento verso valori più nobili, rende più aggressive le condizioni di corrosione a causa dell’avvicinamento del potenziale al potenziale di pitting dell’acciaio. Nel presente lavoro è stata monitorata la corrosione microbiologica di alcuni acciai inossidabili. I test sono stati condotti su acciai austenitici e austenoferritici, in campo e in acqua di fiume sintetica contaminata da batteri manganese ossidanti, utilizzando tecniche microbiologiche ed elettrochimich

Physical activity as a determinant of bone conservation in the radial diaphysis in rheumatoid arthritis.

OBJECTIVES--To determine if increasing physical activity is protective of diaphysial (cortical) bone mass METHODS--Fifteen patients attending two rheumatology clinics who had developed seropositive or classical rheumatoid arthritis up to 26 months previously were studied prospectively for two to three years. Rates of loss (or gain) in bone mass in the radial diaphysis and the trabecular bone of the distal radius were measured by quantitative computed tomography, and in the spine by dual photon absorptiometry. Physical activity was assessed by the Framingham physical activity index. Disease activity was followed at three-monthly clinic visits at which the haemoglobin, erythrocyte sedimentation rate, and platelet count were measured. The urinary hydroxyproline to creatinine ratio and plasma osteocalcin were measured at the beginning and end of the observation period. RESULTS--Eleven patients required treatment with disease modifying drugs but none was given corticosteroids. Those whose physical activity did not improve lost radial diaphysial bone at about 4% annually. There was, however, a statistically significant inverse relation, accounting for 48.5% of the variance, between bone loss at this site and improvement in physical activity as assessed by the Framingham index. The other two sites showed much weaker associations. Adjusting for indices of disease activity hardly affected the first relation. Three biochemical indices related to bone turnover showed weak tendencies to decrease with increasing physical activity. CONCLUSIONS--Peripheral cortical bone, distant from inflamed joints, is conserved more successfully in patients who achieve higher levels of physical rehabilitation. This may have implications for avoiding long bone fractures later in the disease

Bone turnover in early rheumatoid arthritis. 2. Longitudinal bone density studies.

Serial measurements of bone mineral in 17 ambulant female patients with rheumatoid arthritis (RA) of recent onset and 19 age matched female controls were made in the radius by computed tomography and in the vertebrae by dual photon absorptiometry. Loss of trabecular bone from the distal radius was more rapid in RA (p = 0.0014), but there was no difference in the rate of loss of bone mineral from the radial midshaft or lumbar spine compared with the controls. This study is consistent with the hypothesis that the predominant form of bone loss early in the disease is the vicinity of affected joints

Calcium absorption in rheumatoid arthritis.

Calcium absorption, assessed by a double isotope method, was found to be impaired in postmenopausal women with rheumatoid arthritis of recent onset (mean 14.2 months) compared with controls. Circulating levels of 1,25-dihydroxyvitamin D (calcitriol) were higher than in controls, suggesting a primary malabsorption of calcium in these patients. The reduction in calcium absorption correlated with several measures of disease activity, suggesting that the disease process was responsible for the intestinal defect, but an effect from non-steroidal anti-inflammatory agents cannot be excluded. A primary reduction in calcium absorption may increase the risk of osteoporosis in women with rheumatoid arthritis