Clumping factor A-mediated virulence during Staphylococcus aureus infection is retained despite fibrinogen depletion

Clumping factor A (ClfA), a fibrinogen-binding protein expressed on the Staphylococcus aureus cell surface, has previously been shown to act as a virulence factor in experimental septic arthritis. Although the interaction between ClfA and fibrinogen is assumed to be of importance for the virulence of S. aureus, this has not been demonstrated in any in vivo model of infection. Therefore, the objective of this study was to investigate the contribution of this interaction to ClfA-mediated virulence in murine S. aureus-induced arthritis. Ancrod, a serine protease with thrombin-like activity, was used to induce in vivo depletion of fibrinogen in mice. Ancrod treatment significantly aggravated septic arthritis following inoculation with a ClfA-expressing strain (Newman) compared to control treatment. Also, ancrod treatment tended to enhance the arthritis induced by a clfA mutant strain (DU5876), indicating that fibrinogen depletion exacerbates septic arthritis in a ClfA-independent manner. Most importantly, the ClfA-expressing strain was much more arthritogenic than the isogenic clfA mutant, following inoculation of fibrinogen-depleted mice. This finding indicates that the interaction between ClfA and free fibrinogen is not required for ClfA-mediated functions contributing to S. aureus virulence. It is conceivable that ClfA contributes to the virulence of S. aureus through interactions with other host ligands than fibrinogen.     

Diel phytoplankton periodicity in Mikołajskie lake,Poland, as determined by different methods in parallel

Photosynthetic rates as measured by the oxygen light and dark bottle method were highly correlated with estimates using the ¹⁴C technique. The high O₂/¹⁴C ratios found are explained by algal respiration and extracellular release which are included in photosynthetic measurements by the oxygen technique, while the ¹⁴C method yields values close to net photosynthesis. Separation of net- and nannoplankton using a 50 μm plankton net for filtration was not comparable to distinctions made by microscopic examination. Separation of both by filtration caused a significant decrease in the photosynthetic activity of nannoplankton in 24-hour incubations, but had no detectable effect after 4 hours of exposure. “Bottle effects” in 24-hour measurements of photosynthesis were similar using both methods. Asymmetric photosynthetic time-curves as well as vertical phytoplankton migrations were the main reasons for errors in estimates of daily photosynthetic rates from part-day incubations which were extrapolated to the entire day.     

Vibrational spectroscopy of hydroxy-heterobiaryls. IR-active modes of [2,2'-bipyridyl]-3,3'-diol.

All observed IR-active vibrational modes of [2,2'-bipyridyl]-3,3'-diol (BP(OH)2) and its two isotopomers, BP(OD)2 and BP(OH)2-d6 have been assigned on the basis of the comparison of experimental results with predictions obtained from DFT (B3LYP/6-31G(d,p)) calculations. The sensitivity of the vibrational transitions to the environment has been studied by comparing the spectra recorded in vapour, different solutions, KBr pellets, and cryogenic argon matrices. The results may be useful for the quantum control of excited state single or double proton transfer in BP(OH)2.     

The Content of Elements in Rainwater and Its Relation to the Frequency of Hospitalization for Chronic Lymphocytic Leukemia and Chronic Myeloid Leukemia in Opole Voivodship, Poland, During 2000–2002

Environmental factors play an essential role in the etiology of diseases of the hematopoietic system. Such factors include soil and water pollution and the presence of metals and toxic compounds in the air. Measuring the content of metallic elements in rainwater has become an accepted procedure for environmental pollution monitoring. In accordance with the above, it was decided to study relations between the content of selected elements in rainwater and hospitalization frequency due to chronic lymphocytic leukemia (CLL, C91 on ICD-10) and chronic myeloid leukemia (CML, C92 on ICD-10). It can be assumed that hospitalization frequency is a reliable indicator of exacerbations of these diseases. The annual average of hospitalizations due to a given disease during the years 2000–2002 was correlated with the annual average content of a given element in rainwater using the Spearman’s correlation indicator to describe the relationship between the element content and the disease that is possibly a consequence of the element’s presence in rainwater. In cases of CLL for all the subjected population and for men, no statistically significant correlations were found. For women, statistically significant correlations were found for chromium (r?=?0.66), lead (r?=?0.58), copper (r?=?0.58), and cadmium (r?=?0.51). For CML in all the studied population significant, negative correlations were found for magnesium (r?=??0.6) and zinc (r?=?-0.52). In men, significant negative correlations were seen for magnesium (r?=??0.69 and zinc (r?=??0.55). No significant correlations were found in women. These results indicate the need of taking into account the environmental and gender factors in research connected with these diseases, which can be probably of help in improvements of therapy efficiency.     

Polyploidy, alien species and invasiveness in Polish angiosperms

Chromosome numbers, mainly for Polish flora, were examined in order to investigate whether such features as chromosome numbers and polyploid frequencies are correlated with a plant’s origin (native vs. alien) and invasiveness. Polyploid frequencies were estimated using three methods: the 11 and 14 thresholds and the 3.5 x value. Comparisons of the 2n values were done on different levels: in all angiosperms and in dicots and monocots separately. Invasive and non-invasive plants were compared in the entire dataset and in alien species only. Significant differences in both chromosome numbers and polyploid frequencies between alien and native species were observed. In most cases, native plants had more chromosomes and were more abundant in polyploids than in alien species. Also, monocots had higher polyploid frequencies than dicots. Comparisons of invasive and non-invasive plants done for all of the data and only for alien species showed that invasive species generally had more chromosomes and polyploids were more frequent in them than in the latter group; however, these differences were not always statistically significant. Possible explanations for these observations are discussed.     

Thermal and resonance neutrons generated by various electron and X-ray therapeutic beams from medical linacs installed in polish oncological centers

BackgroundHigh-energy photon and electron therapeutic beams generated in medical linear accelerators can cause the electronuclear and photonuclear reactions in which neutrons with a broad energy spectrum are produced. A low-energy component of this neutron radiation induces simple capture reactions from which various radioisotopes originate and in which the radioactivity of a linac head and various objects in the treatment room appear.AimThe aim of this paper is to present the results of the thermal/resonance neutron fluence measurements during therapeutic beam emission and exemplary spectra of gamma radiation emitted by medical linac components activated in neutron reactions for four X-ray beams and for four electron beams generated by various manufacturers’ accelerators installed in typical concrete bunkers in Polish oncological centers.Materials and methodsThe measurements of neutron fluence were performed with the use of the induced activity method, whereas the spectra of gamma radiation from decays of the resulting radioisotopes were measured by means of a portable high-purity germanium detector set for field spectroscopy.ResultsThe fluence of thermal neutrons as well as resonance neutrons connected with the emission of a 20 MV X-ray beam is ～10⁶ neutrons/cm² per 1 Gy of a dose in water at a reference depth. It is about one order of magnitude greater than that for the 15 MV X-ray beams and about two orders of magnitude greater than for the 18–22 MeV electron beams regardless of the type of an accelerator.ConclusionThe thermal as well as resonance neutron fluence depends strongly on the type and the nominal potential of a therapeutic beam. It is greater for X-ray beams than for electrons. The accelerator accessories and other large objects should not be stored in a treatment room during high-energy therapeutic beam emission to avoid their activation caused by thermal and resonance neutrons. Half-lives of the radioisotopes originating from the simple capture reaction (n,γ) (from minutes to hours) are long enough to accumulate radioactivity of components of the accelerator head. The radiation emitted by induced radioisotopes causes the additional doses to staff operating the accelerators.     

Amplification of evoked potentials recorded from mouse hippocampal slices by very low repetition rate pulsed magnetic fields

The influence of low repetition rate pulsed magnetic fields (LRMF) on the evoked potential (population spike) recorded from mouse hippocampal slices was investigated. LRMF were applied according to two protocols. In protocol A, LRMF applied with a constant strength (15 mT) and frequency ranging from 0.03 to 0.5 Hz resulted in an amplification of the potential. Although the frequency of 0.16 Hz was the most effective, enhancing the population spike by over 280%, it also caused an increase in spontaneous activity, seizures, and cessation of neuronal activity in 50% of the slices. In protocol B, LRMF were applied with a variable intensity (9-15 mT) and in cycles of different duration ranging from 5 to 20 min. While an increase in the amplitude of the population spike was observed in all slices exposed to LRMF applied according to protocol B, the longest exposure was the most effective. Neither seizures nor an increase in the spontaneous activity were observed in this group of the slices. These results support and extend our previous data and characterize further the relation between the pattern of applied magnetic fields and their influence on the nervous system.     

Structure of apo- and monometalated forms of NDM-1--a highly potent carbapenem-hydrolyzing metallo-β-lactamase

The New Delhi Metallo-β-lactamase (NDM-1) gene makes multiple pathogenic microorganisms resistant to all known β-lactam antibiotics. The rapid emergence of NDM-1 has been linked to mobile plasmids that move between different strains resulting in world-wide dissemination. Biochemical studies revealed that NDM-1 is capable of efficiently hydrolyzing a wide range of β-lactams, including many carbapenems considered as "last resort" antibiotics. The crystal structures of metal-free apo- and monozinc forms of NDM-1 presented here revealed an enlarged and flexible active site of class B1 metallo-β-lactamase. This site is capable of accommodating many β-lactam substrates by having many of the catalytic residues on flexible loops, which explains the observed extended spectrum activity of this zinc dependent β-lactamase. Indeed, five loops contribute "keg" residues in the active site including side chains involved in metal binding. Loop 1 in particular, shows conformational flexibility, apparently related to the acceptance and positioning of substrates for cleavage by a zinc-activated water molecule.     

The crystal structure of superoxide dismutase from Plasmodium falciparum

Background  

Superoxide dismutases (SODs) are important enzymes in defence against oxidative stress. In Plasmodium falciparum, they may be expected to have special significance since part of the parasite life cycle is spent in red blood cells where the formation of reactive oxygen species is likely to be promoted by the products of haemoglobin breakdown. Thus, inhibitors of P. falciparum SODs have potential as anti-malarial compounds. As a step towards their development we have determined the crystal structure of the parasite's cytosolic iron superoxide dismutase.