A prototype of a quasi-monochromatic system for mammography applications.

Improvement in image contrast and dose reduction, in mammographic x-ray imaging, can be achieved using narrow energy band x-ray beams in the 16-24 keV range. As part of an Italian Government funded project, a quasi-monochromatic system for mammography applications has been developed. The system is based on a tunable narrow energy band x-ray source operating in the 16-24 keV energy range. The bremsstrahlung beam is monochromatized via Bragg diffraction by a highly oriented pyrolytic graphite mosaic crystal (HOPG). The scanning system provides a large field (18 x 24 cm2) of quasi-monochromatic x-rays with energy resolution ranging from 10% at 18 keV to 17.2% at 24 keV. The system has been characterized in terms of fluence rate and energy resolution. An x-ray tube developed ad hoc allows us to acquire images in a reasonable time to minimize the motion blur. A qualitative analysis has been performed in order to know if the prototype system performances are far from a clinical application, by evaluating the spatial resolution, the field uniformity and the image quality as a function of the quasi-monochromatic beam energy. Dose evaluation has been performed as a function of the energy and compared to a conventional system for mammography. The quasi-monochromatic prototype system can produce comparable image quality at half the dose.

Comparative in-vitro activity of levofloxacin against isolates of bacteria from adult patients with community-acquired lower respiratory tract infections.

This study was conducted to evaluate the activity of levofloxacin in comparison with a range of antibacterial agents against recent isolates obtained consecutively from patients with community-acquired pneumonia (CAP) or acute exacerbation of chronic bronchitis (AECB) during the period 1995 to 1996. Susceptibility testing was carried out by either microdilution or the Etest, and interpreted according to NCCLS breakpoints. The activity of levofloxacin was compared with that of amoxycillin, amoxycillin-clavulanate, cefuroxime, cefixime, erythromycin, roxithromycin, clarithromycin, azithromycin, ofloxacin and ciprofloxacin. Clinically significant numbers of bacteria were recovered from 31 CAP and 94 AECB specimens. The predominant bacterial species in the CAP specimens were Streptococcus pneumoniae (21 isolates) and Haemophilus influenzae (four isolates). The AECB isolates mainly consisted of S. pneumoniae (38%), Moraxella catarrhalis (26%), H. influenzae (19%) and Pseudomonas aeruginosa (10%). The overall percentage susceptible of the isolates for each antibiotic was: amoxycillin, 64%; amoxycillin-clavulanate, 89%; cefuroxime, 87%; cefixime, 78%; erythromycin, 85%; roxithromycin, 87%; clarithromycin, 87%; azithromycin, 85%; ofloxacin, 95%; ciprofloxacin, 95%; and levofloxacin, 97%. The activities of levofloxacin and the other agents were also compared against 40 S. pneumoniae isolates, of which 20 were penicillin-non-susceptible, recovered from CAP and AECB specimens during the period 1994 to 1996. These strains were all susceptible to levofloxacin, but only 50% were susceptible to ciprofloxacin and 80% to ofloxacin. Twenty M. catarrhalis, 20 H. influenzae and 20 methicillin-susceptible S. aureus isolates were also all susceptible to levofloxacin. Furthermore, 20 community-acquired P. aeruginosa isolates showed similar percentage susceptible rates to levofloxacin and ciprofloxacin. These in-vitro results suggest that levofloxacin may be useful in the treatment of community-acquired lower respiratory tract infections.

Prostate cancer induction in autoimmune rats and modulation of T cell apoptosis.

In this study we present an experimental model of prostate gland cancer induced by long term hormonal treatment with testosterone in combination with a chemical carcinogenic agent in male Wistar rats with autoimmune prostatitis (AIP). This system is particularly attractive in order to study the factors involved in the transition from a non-invasive to an invasive carcinoma, decisive in the risk of human cancer. At first, autoimmune prostatitis was induced by immunization in 3 months-old male Wistar rats with autologous accessory glands. Then, rats were treated with continuous intradermal implants of testosterone propionate (TP) and with single doses of the chemical carcinogen 7, 12 dimethylbenz (alpha) anthracene (DMBA) by intraperitoneal injection. Histopathological studies of the prostate gland revealed the presence of pre-malignant lesions, particularly the so-called prostatic intraepithelial neoplasm (PIN) in 50% of animals. Moreover, we observed the development of carcinomas in 50% of treated-animals, which could be histologically discriminated in adenocarcinomas, carcinoma of epidermal origin and undifferentiated carcinoma. In autoimmune rats which did not receive any other treatment, exposure to autoantigens gave rise to an atypical hyperplasia of the prostatic gland which could be attributed to the hyperactive state of the gland. Control groups constituted by autoimmune rats treated with TP or DMBA, and normal rats which were exposed to TP and/or DMBA evidenced the presence of PINs at different degrees, but did not develop carcinomas. Moreover, serum acid phosphatase significantly increased as treatment was accomplished, reaching its maximum levels in animals with carcinoma, in which DNA content, determined by image cytometry, showed to be aneuploid. Finally, we provided biochemical and cytofluorometrical evidence of the induction of apoptosis of spleen T cells in carcinoma-bearing hosts, and to a lesser extent in animals with PIN, but not in autoimmune or normal controls, which could represent an alternative molecular mechanism for explaining host immunosuppression triggered by tumors.