ULTRASTRUCTURE OF HEPATIC CELLS IN RABBITS AFTER INJECTION OF MAGNETITE NANOPARTICLES

A.N. Belousov, V.P.Nevzorov

 

Abstract: In order to determine ultrastructural reconstructions in hepatic cells under effect of magnetite nanoparticles, an experiment was conducted on 45 rabbits. They received a single intravenous injection of a magnetite nanoparticles at a dosage of 75 mg/kg of body weight 24 hours before the investigation. Analysis of the state of submicroscopic architectonics of hepatic cells in rabbits after injection of magnetite reveals a significant activation of metabolic intracellular processes in these organs. Ultrastructural organization of the liver testifies about intensification of synthetic intracellular processes, it being structurally manifested by enlargement of cisterns in the rough endoplasmic reticulum, an increased number of ribosomes, a moderate hypertrophy of the laminar cytoplasmic Goldi's complex.

Keywords: magnetite nanoparticles; intravenous injection; ultrastructural; hepatic cells; significant activation; metabolic; intracellular processes.

 

In order to determine ultrastructural reconstructions in hepatic cells under effect of magnetite, anexperiment was conducted on 45 rabbits. They received a single intravenous injection of a magnetite nanoparticles (size is 6 - 12 nm; ζ - potential is - 19 mV; total activity sorption surface is 800 - 1200 m2/g), at a dosage of 75 mg/kg of body weight 24 hours before the investigation.

Organs of intact animals were used as controls. After completion of the experiment the animals were killed and the above organs were taken for electron microscopic examinations.

Pieces of hepatic tissue were put for preliminary fixation into a buffered (3-4%) solution of glutaraldehyde cooled down to +4°C for 2-4 hours. After the preliminary fixation the tissue was washed in several mixtures of the buffer at the same temperature, and for final fixation it was put into 1% buffered solution of osmium tetraoxide for 2-3 hours at the temperature of +4° C. After the end of fixation the pieces of the tissue were washed in the buffer solution, dehydrated in alcohols with rising concentrations and acetone, and then embedded into a mixture of epoxy resins (epon-araldite) following conventional techniques. After polimerization in a thermostat at 60°C, the obtained blocks were used for making ultrathin sections by YMTIT - 6 ultramicrotom. These ultrathin sections were contrasted by lead citrate and uranyl acetate.

The preparations were studied under EME - 100VR electron microscope with accelerating voltage of 75 kilovolts. Magnification was selected to be adequate for purposes of the investigation and ranged within 15.000-45.000 times. Necessary areas of sections were photographed on photographic plates which served for subsequent taking of microphotographs. Electron microscopic preparations made out of organs of intact rabbits served as controls.

 Results

Ultrastructural changes in hepatocyte organelles manifested pronounced signs of activation of reparative intracellular processes.

Hepatocyte nuclei held their rounded shape. Nuclear membranes had well-defined contours. Chromatin, in the form of small clods, was evenly distributed throughout the section.Condensation of chromatin on the nuclear membrane was observed only in single hepatocytes. Perinuclear space was not enlarged. Single ribosomes were found on the outer membrane of the nucleus.

Mitochondria were evenly distributed in all parts of the cytoplasm of the hepatic cells. Mitochondrial matrix had a moderate electron density and a fine grane structure. Shape of the mitochondria varied from rounded to stick-like. Many cristae were revealed; they had a pronounced typical orientation. The outer membrane remained integral, without any foci of destruction. In single cells, there were mitochondria having the shape of dumb-bells and with septa. The rough endoplasmic reticulum under went the most characteristic reconstructions. In the majority of hepatocytes, their rough endoplasmic reticulum was an extensive network of membranes with numerous ribosomes localized on their surfaces. Cisterns of the endoplasmic reticulum were slightly enlarged and their shape resembled flattened vesicles. The substance which filled them was electrontransparent.

The smooth endoplasmic reticulum was well developed, its vacuoles were mostly localized in basal parts of the cytoplasm. It should be noted that there were great numbers of free ribosomes and granules of glycogen which were evenly distributed through out the cytoplasm.

The laminated cytoplasmic Golgi's complex was moderately hypertrophic, its membrane part consisted ofparallel smooth membranes. Packs of these membranes were surrounded with agreat number of large and small vesicles. Single vesicles were filled with arough fibrous osmiophil substance. There was rather a great number of primary lysosomes in the area of localization of the laminar cytoplasmic Golgi's complex, autophagosomes and small inclusions of lipids being observed in singlecells. Bile capillaries were filled with prolonged crimped microvilli and were moderately dilated.

Sinus capillaries and Disse's spaces were dilated rather extensively. Disse's spaces were filled with numerous microvilli. Changes in the ultrastructure of Kupffer cells testified about their functional activity. Nuclei of Kupffer cells were of irregular shape with deep invaginations of the nuclear membrane. Nuclear matrix had significant electron density. Karyolemma had no destructive changes.

The cytoplasm of Kupffer cells revealed single and slightly swollen mitochondria which contained a small number of cristae and single cisterns of the rough endoplasmic reticulum. The cytoplasmic membrane did not undergo any changes and held its well-defined bilaminated structure. It should be noted that there was a great number of small electron-transparent micropinocytic vesicles.

 Discussion

Thus, analysis of the state of submicroscopic architectonics of hepatic cells in rabbits after injection of magnetite nanoparticles reveals a significant activation of metabolic intracellular processes in these organs.

Ultrastructural organization of the liver testifies about intensification of synthetic intracellular processes, it being structurally manifested by enlargement of cisterns in the rough endoplasmic reticulum, an increased number of ribosomes,a moderate hypertrophy of the laminar cytoplasmic Goldi's complex.

Activation of reparative intracellular processes is another aspect of these reconstructions. It is confirmed by a revealed hyperplasia of the rough endoplasmic reticulum, this hyperplasia testifying about intensive processes of self-renewal in submicroscopic structures. Presence of mitochondria having the shape of dumb-bells and with constrictions in the cytoplasm of hepatic cells enables a statement that a process of an intensive increase in the number of these organelles tares place.

Availability of a great number of mitochondria with unchanged structure and numerous cristae in the cytoplasm of hepatocytes indicates a high activity of redox processes and those of oxidative phosphorylation which satisfy energy needs of synthetic intracellular reactions taking place on the level of membranes and macromolecules.

Submicroscopic structure of endotheliocytes in sinus capillaries indicates activation of processes of transcellular transportation of substances and electrolytes by endocytosis, it being confirmed by presence of numerous micropinocytic vesicles in the cytoplasm of these cells.

 


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