Conformational changes of DNA in the presence of 12-s-12 gemini surfactants (s=2 and 10). Role of the spacer's length in the interaction surfactant-polynucleotide

A multifaceted study on the interaction of calf-thymus DNA with two different cationic gemini surfactants alkanediyl-α-ω-bis(dodecyldimethyl-amonium)bromide, 12-s-12,2Br(-) (with s=2, G2, and 10, G10) was carried out. The measurements were done at different molar ratios X=[surfactant]/[DNA]. Results show two different conformational changes in DNA: a first compaction of the polynucleotide corresponding to a partial conformational (not total) change of DNA from an extended coil state to a globular state that happens at the lower molar ratio X. A second change corresponds to a breaking of the partial condensation, that is, the transition from the compacted state to a new more extended conformation (for the higher X values) different to the initial extension. According to circular dichroism spectra and dynamic light scattering measurements, this new state of DNA seems to be similar to a ψ-phase. Measurements confirm that interactions involved in the compaction are different to those previously obtained for the analog surfactant CTAB. X values at which the conformational changes happen depend on the length of the spacer in the surfactant along with the charge of the polar heads.

Evaluation of the VITEK 2 system to test the susceptibility of Candida spp., Trichosporon asahii and Cryptococcus neoformans to amphotericin B, flucytosine, fluconazole and voriconazole: a comparison with the M27-A3 reference method

We compared the susceptibilities of 302 isolates (209 Candida spp., 89 Cryptococcus neoformans and four Trichosporon asahii) against amphotericin B (AMB), flucytosine (5FC), fluconazole (FLC) and voriconazole (VRC) obtained with an automated commercial system (VITEK 2, bioMérieux, Spain) and the Clinical and Laboratory Standards Institute (CLSI M27-A3) reference broth microdilution method (BMD). Reference BMD MIC endpoints were determined visually after 24-72 h of incubation, depending on the species, and VITEK 2 system MIC endpoints were determined spectrophotometrically by automated components of this equipment. For Candida spp. and T. asahii, the overall MIC agreement between of the results of the VITEK 2 system and the 24/48-h BMD was: 34/62% for AMB; 96.3% at 24/48-h for 5FC; 87.8/87.3% for FLC and 95.3/92% for VRC, respectively. The overall categorical agreement between both methods was: 98.5/97.6% for AMB at 24/48-h; 95.3% for 5FC at 24/48-h; 85.4/84.4% at 24/48-h for FLC; and 97.6/92.95% at 24/48-h for VRC. For C. neoformans, essential agreement was good for FLC (91%) and 5FC (84.2%) but not so good for AMB (69%). Excellent categorical agreement was obtained for all antifungal agents tested except for 5FC (69.7%). This new system could play an important role in the clinical laboratory, but more studies are necessary to verify its ability to identify resistant isolates.

[Hydroxyethyl starch to protect renal function in laparoscopic surgery]

OBJECTIVE

To evaluate the effect of prehydration with hydroxyethyl starch 130/0.4 (Voluven) compared to lactated Ringer solution in laparoscopic cholecystectomy.

PATIENTS AND METHODS

We performed a randomized single-blind clinical trial on patients classified as ASA 1 and 2. The exclusion criteria were hypertension, kidney failure, treatment with diuretics or other antihypertensive drugs, diabetes, and use of nonsteroidal anti-inflammatory drugs. Balanced general anesthesia with remifentanil and sevoflurane was used. The total volume of administered fluids (including prehydration) was 2 mL x kg(-1) x h(-1) fasting plus 5 mL x kg(-1) x h(-1) during surgery. Group 1 was prehydrated 30 minutes before surgery with 500 mL of lactated Ringer solution in group 1; in group 2 the same quantity of Voluven was used. Ringer solution was used in both groups to provide additional fluids. Blood pressure was kept within 20% above or below baseline values. Standard anesthetic monitoring was performed. Intraoperative diuresis and creatinine clearance were recorded. The groups were compared using the t test; a P value of 05 or less was considered significant.

RESULTS

Twenty-nine patients were enrolled in the study. Diuresis and creatinine clearance were significantly higher in the group that received prehydration with Voluven. The mean (SD) creatinine clearance rate was 176.44 (1433) mL x min(-1) in group 1 and 61.90 (6.6) mL x min(-1) in group 2 (P = .036). The mean volume of urine excreted was 1.71 (0.06) mL x kg(-1) x h(-1) in group 1 and 0.47 (0.02) mL x kg(-1) x h(-1) in group 2 (P = .017).

CONCLUSION

Prehydration with Voluven can be an effective measure for protecting renal function against the adverse effects of pneumoperitoneum in laparoscopic surgery.

Los aspectos epidemiológicos cambiantes de la candidemia y sus implicaciones clinicoterapéuticas

Candida species are a major cause of healthcare-related bloodstream and invasive infections. Studies assessing nosocomial bloodstream infections during the two last decades ranked Candida species as the fourth most common nosocomial bloodstream pathogen. The incidence of Candida species has risen steadily during this period due to the increase in the number and type of patients at risk for these yeasts. Infections caused by Candida are especially frequent and serious in onco-hematological patients. Over the past decade, the introduction of azole antifungals as prophylactic agents, together with other factors, has led to a shift in the species of Candida that cause infection. During the period under review (1996 to 2005) several studies have confirmed the impact of antifungal prophylaxis with azoles on the emergence of Candida species other than Candida albicans. The widespread use of fluconazole has contributed to a relative decrease in the prevalence of C. albicans, while species inherently less susceptible, such as Candida glabrata and Candida krusei, appear to be isolated with greater frequency. Moreover, laboratory studies to determine the antifungal susceptibilities and virulence of non-albicans Candida species have enabled the design of microbe-specific management strategies. More of these studies will be necessary as we enter an age in which multiple antifungal compounds (echinocandins, new azoles) will become available for clinical use in invasive candidiasis or candidemia. The present review aims to highlight the different trends in the incidence, distribution and behavior of Candida bloodstream infections in the distinct types of patients at risk.

Testing biomaterials by the in-situ evaluation of cell response

In this work, we describe a technique for the in-situ observation of cells adhered on opaque biomaterial surfaces. The visualisation of the morphology of cells adhered onto a surface allows to derive nuclear apoptotic signs or even the existence of organisation between groups of these cells. The technique is based on the use of an auto-immune reaction combined with a fluorescent agent that allows a direct inspection of the cell behaviour. The versatility of the technique is demonstrated by presenting several examples with different cultured cells (human chondrosarcome cells (CSRCs) and pluripotential mesenchymal stem cells (MSCs) from bone marrow) seeded over two different Ti-based surfaces (TiO(2) and TiN, respectively). These in-vitro observations are compared with the behaviour of the same cells on bare TiAlV alloy. From our results it is concluded that both TiO(2) and TiN surfaces show enhanced biological responses.