Investigation of membrane permeability of carp spermatozoa for water molecules

The fundamentals of a photometry method for determination of membrane permeability of some fish spermatozoa for water molecules are presented. Osmotic tolerance of carp spermatozoa membranes was studied using EPR-spectroscopy and photometric analysis methods. It was shown that carp spermatozoa look like the ideal osmometers in their reaction on media of different osmolarity. The value of membrane permeability of carp spermatozoa for water molecules was determined. Data obtained can be used in cryobiology for creating cryoprotective media and regimes of fish sperm cryopreservation.     

Plant Stress and Allelotoxicity of Soils

Doklady Biological Sciences - Stress exposures during vegetation are known to reduce the yield in crops, but the intensity and duration of stress is rather difficult to determine from the crop...     

Examination by fluorescence and EPR spectroscopy of the state of mitochondrial and lysosomal membranes upon freeze-thawing

The results of spectroscopic examination of mitochondria and lysosomes indicate that freeze-thawing leads to alterations of different character and extent in membrane structural organization which manifest as changes in the molecular packing of the organelle membrane lipid bilayer, lateral separation of lipids into individual domains, and impairment of membrane permeability. Supercooling of organelle suspensions without crystallization of external water has been found not to affect membrane barrier function markedly; however, such a decrease in the temperature results in a slight loosening of the membrane with an increase in the volume of subcellular structures. The crystallization of external water causes dehydration of organelles, which favors a decrease in their volume, increasing the viscosity of the liquid phase inside subcellular structures and packing the lipid bilayer. Changes in the permeability of mitochondrial and lysosomal membranes manifest during thawing after the formation of an external liquid phase and might be due to the sharp rehydration of these membranes through latent membrane defects formed upon freezing.     

Effect of freezing on cord blood serum proteins

The effect of freezing regimes and storage temperatures on protein conformation and the spectrum of cord blood serum was investigated. Changes in the parameters of EPR spectra of spin probes in cord blood serum after slow freezing and subsequent thawing were established, indicating protein conformational changes characterized by loosening. This fact was confirmed by an earlier, first stage of albumin heat denaturation, as indicated by calorimetric data. It was shown that slow cooling resulted in aggregation of serum protein in which serum albumin and immunoglobulins played an important role. It was concluded that, for retaining the properties of cord blood serum proteins, it is preferable to perform cooling at a rate not lower than 100°C/min and a storage temperature of ?80°C and lower.     

Antioxidant properties of proteins after freezing-thawing

Experimental data are presented which were obtained under comparative evaluation of influence of different freezing-thawing conditions on antioxidant properties of isolated proteins: human serum albumin, cytochrome c from the horse heart and glucose oxidase from Aspergillus niger. The observed protein antioxidant activity alterations are assumed to be a result of protein conformational changes. The character of freezing-thawing influence on the protein antioxidant activity depends on the molecular structure and cooling conditions.     

Effect of the permeability of lysosomal and mitochondrial membranes on the ability of their cryoextracts to inhibit the protein-synthesizing activity of cell-free systems

Changes in permeability of lysosomal and mitochondrial membranes were studied under different temperatures at which cryoextracts from organelles inhibit most distinctly the protein synthesizing activity of the cell-free system from the rat liver. It is found that mitochondria are more sensitive to the effect of low temperature effect than lysosomes. Overcooling of the mitochondria suspension to the temperature of the free water crystallization is shown to cause no release of the protein synthesis inhibitor. The inhibitor release from organelles occurs from the moment of crystallization and reaches its maximum at the eutectic temperatures of the freezing medium which is due to the injury effect of the complex of physicochemical factors on the membrane structures, occurring during the phase transition of the solvent.     

Protective effect of placenta extracts against nitrite-induced oxidative stress in human erythrocytes

Aqueous-saline human placenta extract (HPE) is known to possess antioxidant activity due to the high concentration of bioactive substances. This fact allows its application in clinical practice in order to treat oxidation-induced diseases. Extract antioxidant activity is mainly conditioned by proteins. Freezing of extracts has been shown to lead to their antioxidant activity increasing due to protein conformation changes.     

Study of erythrocyte dehydration using spin labels

Possibility of studying erythrocyte dehydration by ESR-spin probe is substantiated. Dehydration of erythrocytes in relation to osmolarity of sodium chloride solutions is investigated. The results are shown to agree with the data obtained by radioisotope method.