A two-centre validation study of sterility test of corneal storage media with elimination of interfering antimicrobials in compliance with the European Pharmacopoeia.

The purpose of this study was to validate the sterility test of corneal culture and deswelling/transport media using a device for removal of antimicrobials before incubation in BACTEC™ automated system in two Italian Eye Banks. Corneal culture medium, TISSUE-C, and deswelling/transport medium, CARRY-C, were inoculated with 10-100 cfu of six European Pharmacopoeia (EP) reference strains and either treated with medical device RESEP for removal of antimicrobials (RESEP+ group) or left untreated (RESEP- group) before injection into the BACTEC Plus bottles. The same steps were repeated in the absence of inocula with tryptone soy broth samples as negative controls, and the inocula were also directly injected in the BACTEC™ bottles as growth controls. All the samples were incubated in BACTEC™ automated system for 7 days, and the time to detection of microbial growth was recorded automatically. At both the Eye Banks, in the RESEP+ groups, microbial growth was detected in 100% of samples. In the RESEP- group, the method sensitivity ranged from 66.7 ± 21.1 to 88.9 ± 6.4% for TISSUE-C samples while for CARRY-C samples the method sensitivity ranged from 94.5 ± 5.1 to 100%. The method specificity corresponded to 100% for all the groups at both Eye Banks. This two-centre validation study showed that the use of RESEP increased the sensitivity of sterility test using BACTEC™ automated system up to 100% and, consequently, allowed validation of the method for sterility testing of corneal storage and deswelling/transport media according to the EP requirements. The test could not be validated without the use of RESEP.

Monomer dynamics in single- and double-stranded DNA coils.

In our paper (Tothova et al., Czech. J. Phys. 55, 221 (2005)), the first observation of the kinetics of individual polymer monomers using the fluorescence correlation technique (R. Shusterman et al., Phys. Rev. Lett. 92, 048303 (2004)) has been interpreted within the bead-spring theory. Optimizing the joint Rouse-Zimm model to the experimental data, the phenomenological parameters for the statistical-mechanical description of the universal behavior of double- and single-stranded DNA and the dominant types of their dynamics have been determined. Recently, these data have been corrected (R. Shusterman et al., Phys. Rev. Lett. 98, 029901 (2007)). In the present work, the fits of the theory to the new data are given. The main conclusions of our preceding paper remain unchanged but some of the polymer parameters have changed. The new data allow a significantly better agreement with the theory than the previous ones. Our calculations confirm that dsDNA follows mainly the classical Zimm-type kinetics rather than the Rouse one as it was proposed by Shusterman et al. Single-stranded DNA also behaves predominantly as the Zimm polymer. To support these conclusions, we analyze the draining effects on the monomer dynamics and the applicability of simple "universal" laws, according to which the monomer mean square displacement scales with the time as t 1/2 and t 2/3 for the Rouse and Zimm polymers, respectively.

Long-time dynamics of Rouse-Zimm polymers in dilute solutions with hydrodynamic memory.

The dynamics of flexible polymers in dilute solutions is studied taking into account the hydrodynamic memory, as a consequence of fluid inertia. As distinct from the Rouse-Zimm (RZ) theory, the Boussinesq friction force acts on the monomers (beads) instead of the Stokes force, and the motion of the solvent is governed by the nonstationary Navier-Stokes equations. The obtained generalized RZ equation is solved approximately using the preaveraging of the Oseen tensor. It is shown that the time correlation functions describing the polymer motion essentially differ from those in the RZ model. The mean-square displacement (MSD) of the polymer coil is at short times approximately t(2) (instead of approximately t). At long times the MSD contains additional (to the Einstein term) contributions, the leading of which is approximately t. The relaxation of the internal normal modes of the polymer differs from the traditional exponential decay. It is displayed in the long-time tails of their correlation functions, the longest lived being approximately t(-3/2) in the Rouse limit and t(-5/2) in the Zimm case, when the hydrodynamic interaction is strong. It is discussed that the found peculiarities, in particular, an effectively slower diffusion of the polymer coil, should be observable in dynamic scattering experiments.

Hypocrellin and hypericin-induced phototoxicity of HL-60 cells: apoptosis or necrosis?

Hypericin and hypocrellin are potential antiviral and antineoplastic agents with multiple modes of light-induced biological activity connected with a production of singlet oxygen and/or excited-state proton transfer and consequent pH drop formation in the drugs environment. In present work light-induced cytotoxicity of hypericin and hypocrellin and mechansim of cell death (apoptosis or necrosis) on human leukemic cell line HL-60 was studied. As a mean for apoptosis detection we used poly (ADP-ribose) polymerase (PARP) as a sensitive marker of early stages of apoptosis. Our results show that exposition of HL-60 cells to hypericin (1 x 10(-5) mol x l(-1)) for 4 hours has no effect on PARP cleavage. However, after 24 and 48 hours of illumination there is evident that hypericin in this concentration cleaved PARP (116 kDa) into two fragments (85 and 25 kDa). Contrary to hypericin, hypocrellin in concentration 1 x 10(-5) mol x l(-1) after 4 hours of illumination cleaved PARP into two fragments typical for apoptosis. In lower concentration (1 x 10(-6) mol x l(-1)) hypocrellin possess also significant cytotoxic activity. Because we detected no fragmentation of PARP in all observed time periods we suggest that cytotoxic effect of hypocrellin in this concentration is due to induction of necrosis. Our results support the hypotesis that the hypericin and hypocrellin has similar mechanism of action and illumination increases cytotoxic effect of both agents.

Potentiation of hypericin and hypocrellin-induced phototoxicity by omeprazole.

Hypericin and hypocrellin are potential antiviral and antineoplastic agents with multiple modes of light-induced biological activity connected with a production of singlet oxygen and/or excited-state proton transfer and consequent pH drop formation in the drugs environment. In present work light-induced cytotoxicity of hypericin (1 x 10(-5) - 10(-9) mol) and hypocrellin (1 x 10(-5) - 10(-9) mol) and potentiating effect of omeprazole on human leukemic cell line HL-60 was studied. Under dark condition cultivation none cytotoxicity was observed. The only one exception was hypocrellin in concentration 1 x 10(-5) mol which displayed full cytotoxic effect. However, illumination increased cytotoxic effect of hypericin and hypocrellin, both. Omeprazole, an inhibitor of H+K+-ATPase, has been used for testing the hypothetical pH decreasing effect of hypericin and hypocrellin in their cytotoxic mechanism of action. The results of our experiments have shown that in HL-60 cell line the effect of hypericin and hypocrellin at 1 x 10(-6) mol (both) was significantly potentiated by omeprazole in concentrations 1 x 10(-6) - 10(-9) mol. Our results support the hypothesis that the excited-state proton transfer and the consequent acidification of hypericin and hypocrellin environment could play a role in the biological activity of both agents.

Secondary structure differences between normal and tumour DNA studied by UV-spectrophotometry.

Some differences between the structure of tumour and normal DNA were studied. An increase of the methylation degree of the tumour DNA was observed (by 42% as compared with normal DNA). Changes between normal and tumour DNA were found in the melting temperature (Tm), the melting interval (delta T) and the shape of the differential melting curves (DMC). In tumour DNA, two types of regions with changed thermostability were observed differing in length. The first type regions contain more than 20-30 pairs of nucleotides and manifest themselves on DNA DMCs as a low-temperature plateau. The other type, much shorter, cause a shift of DNA DMCs towards lower temperatures. The value obtained for the concentration of tumour DNA regions with changed thermostability per one pair of nucleotides is 4.4 x 10(-4). The in vivo influences of three alkylating preparations on the structure differences of both kinds of DNAs were studied. The preparations tested lowered the content of 5-mC in tumour DNA, altered the total concentration of DNA regions with changed thermostability, and effectively suppressed these regions containing 20-30 pairs of nucleotides. Also, a correlation was found between the effect of the preparations studied on tumour DNA and their ability to suppress the growth of Sarcoma 45.