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The AFP-synthesizing cells were identified by ultrastructural localization of the antigen in regenerating liver of adult mice after CCl4 poisoning. An indirect immunoperoxidase method with rabbit anti-mouse AFP and peroxidase conjugates of anti-rabbit IgG or their Fab' was used. Good preservation of AFP and tissue structure, and sufficient permeability for the conjugates were obtained after 20' prefixation of small liver specimens in 8% formaldehyde -0.05% glutaraldehyde followed by 16 h fixation in 8% formaldehyde. The intracellular localization of AFP observed in the light microscope in most cases corresponded to its synthesis and secretion. It was found in two cell types, both concentrated mainly in the perinecrotic zones and constituting only a small part of the whole cell population. Most of the AFP-producing cells were normal differentiated hepatocytes without any structural signs of damage. A few smaller cells with active AFP synthesis were present in some animals. By their ultrastructure they resembled the oval cells found during chemical hepatocarcinogenesis in rats.

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The genes for bacterial phytases from Citrobacter freundii and Yersinia intermedia were expressed for the first time in a thermotolarant yeast Ogataea polymorpha. A comparative analysis of the properties of recombinant phytases produced by Ogataea polymorpha and Pichia pastoris yeasts was carried out. It was shown that the stability, pH and temperature profiles of the enzyme activities are the same regardless of the host strain. It was proved that O. polymorpha yeast can be used to create producers of feed enzymes and to develop a technology for their cultivation at temperatures above 37 °C. The prospects of using the O. polymorpha yeast for these purposes were evaluated. Ogataea (Hansenula) polymorpha, Pichia pastoris, methylotrophic yeast, thermal tolerance, producer, recombinant phytase The work was financially supported by the Ministry of Science and Higher Education of RF (Project Unique Identifier RFMEFI57917X0145) using the Multipurpose Scientific Installation of All-Russian National Collection of Industrial Microorganisms National Bioresource Center, NRC «Kurchatov Institute»-GosNIIgenetika.