Time-resolved endogenous chlorophyll fluorescence sensitivity to pH: study on Chlorella sp. algae.

To better understand pH-dependence of endogenous fluorescence of algae, we employed spectroscopy and microscopy methods, including advanced time-resolved fluorescence imaging microscopy (FLIM), using green algae Chlorella sp. as a model system. Absorption spectra confirmed two peaks, at 400-420 nm and 670 nm. Emission was maximal at 680 nm, with smaller peaks between 520 and 540 nm. Acidification led to a gradual decrease in the red fluorescence intensity with the maximum at 680 nm when excited by 450 nm laser. FLIM measurements, performed using 475 nm picoseconds excitation, uncovered that this effect is accompanied by a shortening of the tau1 fluorescence lifetime. Under severe acidification, we also noted an increase in the green fluorescence with a maximum between 520-540 nm and a shift toward 690-700 nm of the red fluorescence, accompanied by prolongation of the tau2 fluorescence lifetime. Gathered data increase our knowledge on the responsiveness of algae to acidification and indicate that endogenous fluorescence derived from chlorophylls can potentially serve as a biosensing tool for monitoring pH change in its natural environment.

Increasing axial resolution of 3D data sets using deconvolution algorithms.

Deconvolution algorithms are tools for the restoration of data degraded by blur and noise. An incorporation of regularization functions into the iterative form of reconstruction algorithms can improve the restoration performance and characteristics (e.g. noise and artefact handling). In this study, algorithms based on Richardson-Lucy deconvolution algorithm are tested. The ability of these algorithms to improve axial resolution of three-dimensional data sets is evaluated on model synthetic data. Finally, unregularized Richardson-Lucy algorithm is selected for the evaluation and reconstruction of three-dimensional chromosomal data sets of Drosophila melanogaster. Problems concerning the reconstruction process are discussed and further improvements are proposed.

[Ablative treatment of rectosigmoidal precanceroses and early cancer]. / Ablatívna liecba rektosigmoideálnych prekanceróz a vcasných karcinómov.

Endoscopic mucosal resection and piece meal polypectomy are methods of choice in broad based unifocal rectosigmoideal lesions. Thermal ablative modalities are indicated for flat adenomas, lateral spreading tumors and as an adjunct therapeutic modality for incomplete polypectomy. Photodynamic therapy using ALA photosensitiser is effective in the treatment of multifocal lesions either alone or in a combination with thermal ablative techniques. At present "tailored suite" combination of these techniques for each patient according the character of the lesion is considered to be the most effective treatment for rectosigmoideal praecancerous lesions and early cancer.

In vivo fluorescence diagnostics and photodynamic therapy of gastrointestinal superficial polyps with aminolevulinic acid. A clinical and spectroscopic study.

In the present study initial results of clinical study related to the treatment of patients having different types of precancerous lesions in the area of esophagus, stomach and intestine by photodynamic therapy (PDT) based on aminolevulinic acid (ALA-PDT) are reported. The procedure was performed by laser fibre system with the light guides introduced through biopsy channel of an endoscope. In addition, in vivo fluorescent diagnostics and spectral analyses of biopsies were performed. Each patient had a positive response to therapy. In two cases there was a total response and in other five cases more than sixty percent of suspected area was removed. Additionally, sigilocellular carcinoma of stomach was revealed in one case. It appears from the results of this study, that the treatment of precancerous lesions with ALA-PDT could be successful treatment modality.

Spectral unmixing of flavin autofluorescence components in cardiac myocytes.

We applied linear unmixing approach to reveal individual components of intrinsic flavin fluorescence signal recorded in living cardiac cells by spectrally resolved confocal microscopy. Responses of whole-cell autofluorescence to modulators of cell metabolism and respiration were used as a tool of separation of its components; their spectral profiles, estimated by principal component analysis, correspond to free FAD and FAD bound to different enzymes of electron transport chain.

[Three-dimensional presentation of the electrocardiogram: new possibilities in comparative studies using cardiologic imaging methods]. / Trojrozmerná prezentácia elektrokardiogramu: nové moznosti pre komparatívne stúdie so zobrazovacími kardiologickými metódami.

The aim of the study was to demonstrate a biomathematical model for the topographic presentation of orthogonal electrocardiogram DECARTO, to present the possibilities for visualisation and processing of ECG in relation to others cardiological imaging methods. In DECARTO (Dipolar ElectroCARdioTOpography), the orthogonal ECG is used as an input signal, the signal is processed by the means of a biomathematical model and presented as areas of activated points on a spherical surface closely surrounding the heart, so-called decartograms. Decartograms can be visualised using the projection of the spherical image surface onto geometrically defined planar or 3D surfaces. The selection of the surface depends on the purpose of ECG imaging, on the evaluation of advantages and limitation of the particular possibilities, such as the degree of deformation, and their comparability with other imaging methods. Another possibility of 3D visualisation of decartograms is the utilisation of time as a 3rd dimension of the space. Additionally to analytically defined geometrical surfaces, it is possible to project decartograms onto a real surface of the heart, constructed from data of other image techniques. In this paper we present a superposition of decartogram and SPECT imaging, which combines graphic presentation of two diagnostic methods providing different but complementary information on the heart. The combination of comparable information allows to study the relationship between electrogenesis and perfusion of myocardium and its metabolism, to study diagnostic and prognostic importance of both agreements and disagreements of used methods. The fusion of information on the structure and function of the heart could potentially increase the diagnostic power of both methods.

[Changes in cell membrane fluidity evoked by removal of influenza virus receptors with neuraminidase]. / Zmeny vo fluidite bunkovej membrány vyvolané odstránením receptora vírusu chrípky neuraminidázou.

The effect of the removal of the influenza virus receptor (N-acetylneuraminic acid) from the erythrocyte membrane by neuraminidase (RDE = receptor destroying enzyme) on the biophysical properties of the cell membrane has been examined using a fluorescent polarization technique. Diphenylhexatriene (DPH) was used as a fluorescent probe for structural ordering in the core of the membrane. A statistically significant decrease in the steady state values of DPH anisotropy was observed in membranes treated with RDE as compared to control. The anisotropy decrease reflected a reduced ordering of the hydrocarbon region of the erythrocyte membrane as well as an increase of its fluidity. An increase of membrane fluidity evoked by the action of influenza virus neuraminidase may play a significant role in the process of influenza virus penetration into the susceptible cell by endocytosis.