Study of the mechanism of initiation of enzymatic NADPH-dependent lipid peroxidation in membranes of the endoplasmic reticulum

The localization and mechanism of generation of active oxygen species in the enzymatic NADPH-dependent lipid peroxidation system in liver microsomes were studied. Using the spin-trapping method, the key role of active oxygen species in the initiation of NADPH-dependent enzymatic lipid peroxidation was confirmed. It was shown that active oxygen species are generated via consecutive one-electron reduction of the oxygen molecule by NADPH-cytochrome P-450 reductase.     

Morphological characteristics of cultured fresh and thawed pericardium cells

The need for selection of the optimal material for the manufacturing of cardio-patches can be resolved by the use of cryostored autologous pericardial tissue. This short communication is a concise fragment of a large-scale research and demonstrates only the efficiency of cell culturing before and after pericardial preservation in the low temperature conditions.     

Elastase-like enzymes in human neutrophils localized by ultrastructural cytochemistry

The thiol ester N-t-Boc-L-alanine-p-nitrothiophenyl ester (Boc-Ala-SNp) was synthesized and applied as an ultrastructural cytochemical substrate for intracellular elastase-like enzymes. Mature human neutrophils incubated with Boc-Ala-SNp and gold ions generate an electron-dense reaction product, gold p-nitrothiophenolate, which is found in the nuclear membrane, Golgi complex, endoplasmic reticulum, mitochondria, and granules of these cells. Enzyme activity against Boc- Ala-SNp is also observed in developing monkey bone marrow neutrophils and in other blood cells. The intracellular neutrophil enzyme activity is elastase-like because it is characterized by a slightly alkaline pH optimum and is inactivated by exposure of the cells to general and specific active site inhibitors of neutrophil elastase. This substrate appears to have important potential for use in ultrastructural studies of intracellular elastase-like enzymes.     

Microbial transformation of steroids

A systematic study of transformation reactions of Actinomycetes with respect to the progesterone molecule was undertaken. The results obtained, i.e. the types of transformation reactions in different actinomycete species, were evaluated from the point of view of taxonomy. The actinomycetes tested were divided according to the transformation types into three groups: (1) a group of species transforming progesterone in the 16α-position; (2) a group of species transforming progesterone in the β-position; (3) a group of species in which no capacity to transform progesterone into another steroid derivative was established. From the point of view of Actinomycete classification the transformation reactions on the steroid molecule fulfil all the requirements of taxonomic features of Actinomycetes. They appear to be specific properties, independent of strictly cultivation conditions and common to all the strains of individual actinomycete species tested.     

Protection of the monoamine oxidase in brain synaptosomes by fat- and water-soluble antioxidants during lipid peroxidation

The protective effects of alpha-tocopherol, carnosine and their mixtures on monoamine oxidase activity, accumulation of lipid peroxidation products, lipid fatty acid composition, hydrophobicity and microviscosity of synaptic membranes during lipid peroxidation were studied. It was shown that the protective efficiency is more higher when the mixture of water and liposoluble antioxidants was used.     

Mechanism of stabilization of synaptosomes with alpha-tocopherol during exposure to phospholipase A2

Changes in potential-dependent fluorescence were studied, using fluorescent probe di-S-C3-(5), in synaptosome suspensions exposed to phospholipase A2, alpha-tocopherol and its derivatives. Phospholipase A2 increased potential-dependent fluorescence, i.e. depolarization of synaptosome membranes. The damaging phospholipase A2 effect was prevented and/or abolished by alpha-tocopherol added to synaptosome suspensions before and after phospholipase A2. Alpha-tocopherol derivatives (2,2,5,7,8-pentamethyl-6-hydroxychromane and alpha-tocopheryl-acetate as well as 4-methyl-2,6-di-tert-butylphenol) failed to exert a protective effect on synaptosome membranes modified by phospholipase A2. It is suggested that alpha-tocopherol effect is determined by its interaction with fatty acids, with 6-hydroxy groups of chromanol nucleus and phytol chain being essential for the complex formation.     

A physiological analogy of the niche for projecting the potential distribution of plants

Aim  To develop a physiologically based model of the plant niche for use in species distribution modelling. Location  Europe. Methods  We link the Thornley transport resistance (TTR) model with functions which describe how the TTR’s model parameters are influenced by abiotic environmental factors. The TTR model considers how carbon and nutrient uptake, and the allocation of these assimilates, influence growth. We use indirect statistical methods to estimate the model parameters from a high resolution data set on tree distribution for 22 European tree species. Results  We infer, from distribution data and abiotic forcing data, the physiological niche dimensions of 22 European tree species. We found that the model fits were reasonable (AUC: 0.79–0.964). The projected distributions were characterized by a false positive rate of 0.19 and a false negative rate 0.12. The fitted models are used to generate projections of the environmental factors that limit the range boundaries of the study species. Main conclusions  We show that physiological models can be used to derive physiological niche dimensions from species distribution data. Future work should focus on including prior information on physiological rates into the parameter estimation process. Application of the TTR model to species distribution modelling suggests new avenues for establishing explicit links between distribution and physiology, and for generating hypotheses about how ecophysiological processes influence the distribution of plants.