Biomedical subjects

K Radotić

Publications and source records attributed to K Radotić.

7 recordsLinked to original sources

PubMed2001

Fractal analysis of STM images of photochemical polymer of coniferyl alcohol.

Fractal analysis was applied to images of photochemical lignin polymer obtained using scanning tunneling microscope. We studied the polymer obtained in vitro by ionic mechanism through UV radiation--induced polymerization. The analysis showed the regularity of the lignin-like polymer at different levels of organization. At the 95% confidence level, there was no significant difference in the fractal dimension between images representing different organizational levels of photochemical lignin. That means that lignin produced in in vitro conditions by photochemical mechanism of synthesis, has a fractal structural organization. The obtained values of the fractal dimension are in good agreement with the theoretically predicted value for the polyaddition and polycondensation mechanism of polymerization, known as the bulk model.

Fractals↗

PubMed2000

Fractal analysis of STM images of lignin polymer obtained by in vitro synthesis.

Lignin, the structural polymer of the plant cell walls, is produced by free radical polymerization of phenolic alcohols, catalyzed by different peroxidases. The mechanism and the structural organization of lignin in the cell have not been completely understood. In this study we applied fractal analysis to images of lignin polymer obtained using scanning tunneling microscope. The analysis showed the regularity of the polymer at different levels of organization. According to the results obtained, at the 95% confidence level, there is no significant difference in the fractal dimension between images representing different organizational levels of lignin. In other words, lignin produced in in vitro conditions has fractal structural organization and, consequently the polymer can be expected to be regular in in vivo conditions. The value of the fractal dimension 1.929 +/- 0.021 is in good agreement with the theoretically predicted value for polyaddition and polycondensation mechanism of polymerization. The mechanism of in vivo lignin synthesis is discussed in terms of various experimental and theoretical evidences. In this paper, we could show that fractal analysis of the lignin polymer is a useful complementary approach to the experimental data collection in structural and phenomenological studies.

Cell Wall↗

PubMed1998

Spontaneous ultraweak bioluminescence in plants: origin, mechanisms and properties.

An analysis of theoretical knowledge and experimental results of ultraweak luminescence (UWL) is provided. The role of excited state of molecules and free radicals, formed in various biochemical reactions, in UWL is discussed. UWL of model reactions and in vivo systems are compared. The hypothesis of coherent electromagnetic field as a source of UWL is also discussed. Spectral, kinetic and temporal properties of UWL are summarised, as well as their connection with its origin and role in the organism. Attention is paid to recent progress in experimental methods of low-light detection. The possible use of UWL in environmental studies, selection and other applications is discussed.

Kinetics↗

PubMed1996

[Ultrastructural changes in transplantation glomerulopathy].

Twenty-eight biopsy specimens were obtained from patients 3-95 months after kidney transplantation and studied by light, electron and in some cases also by immunofluorescence microscopy. Electron microscopic studies showed that the most frequent glomerular lesion was widening of lamina rata interna which is accompanied with subendothelial accumulation of finely granular material, formation of new subendothelial basement membrane and deposition of microfibrils and fine filaments. The mesangial changes were mainly those of mesangiolysis and mesangial sclerosis with deposition of mesangial matrix and microfibrils, but little cellular proliferation. Fragmented red blood cells were seen in nearly half of the patients. Arterial intimal thickening and occasionally also thrombosis produced ischaemic changes in the kidney and in the glomeruli and contributed to the process of transplant rejection.

Graft Rejection↗

PubMed1996

[Electron microscopic analysis of eosinophilic renal cell carcinoma].

Renal cell carcinoma with cytoplasmic eosinophilic globules visualized on routine histologic preparations was analyzed. Eosinophilic globules in cytoplasm of the cells in renal cell carcinoma are very rate and till today we have not heard or found in the literature an attempt to analyze and describe them and that was the aim of our study. By electron microscopy, the globules most closely resembled non-membrane bound filamentous material that normally constitutes the cytoskeleton of normal and neoplastic renal epithelium.

Carcinoma, Renal Cell↗

PubMed1994

A study of lignin formation at the molecular level by scanning tunneling microscopy.

A scanning tunneling microscope (STM) was used to observe the temporal formation and organization of dehydrogenative polymer (DHP) synthesized from coniferyl alcohol. The images obtained elucidate this structure for the first time. The structure of DHP, as seen from STM images, shows long-range order. It appears that DHP consists of building units or modules assembled into larger assemblies called supermodules. Supermodules are interconnected into the overall lattice-like polymer structure with or without spherical regions. One module consists of about 20 monomers, while the supermodule contains about 500 monomers. Calculated molecular weights for modules and supermodules agree with DHP molecular weight distribution peaks. Samples prepared at two different pH values, 6.4 and 7.6, have the same characteristics. The results presented demonstrate that the process of lignification, even in in vitro conditions, is highly ordered, and as such contribute to our understanding of the structure of lignin, a significant constitutive and functional element of cell walls.

Hydrogen-Ion Concentration↗

PubMedDate not supplied

Effect of propagators and inhibitors on the ultraweak luminescence from maize roots.

This study has investigated the kinetics and mechanism of ultraweak luminescence in maize roots. Mannitol induced the second maximum and enhanced the main maximum of the relative intensity of luminescence from the roots. Hydroquinone and quinone enhanced the relative intensity of the luminescence. Catalase enhanced the maximum of the luminescence and changed the kinetics of the light emission. The effect of catalase on the kinetics was abolished by superoxide dismutase. Ascorbate in the presence of catalase on the kinetics was abolished by superoxide dismutase. Ascorbate in the presence of catalase reduced the luminescence maximum, but did not alter the kinetics. In the presence of catalase only, or in the combination with superoxide dismutase, or ascorbate, the luminescence intensity in the stationary phase was significantly lower compared to the control. The results support the participation of superoxide-radical, singlet oxygen, electron transfer and the role of peroxidase in the reactions generating ultraweak luminescence in the roots. Ascorbate, catalase and superoxide dismutase have a protective role in the luminescent reactions.

Ascorbic Acid↗