Cell reconstruction. Theoretical means of cell reconstruction

Over the past 15 years has been actively developing the reconstruction of cells, and the number of publications is growing like an avalanche. This is natural, since the reconstructed cells formed from the nucleus and cytoplasm of different origin can be used to solve a large number of important biological problems. At the moment, the problem of reconstruction of the cell enters a new phase in the emergence of a new effective physical method - elektrostimuliruemogo cell fusion.

 

Reconstruction of embryonic stem cells and the problem of developmental biology. Reconstruction embryonic substantially includes such important task developmental biology as mechanisms of genetic information. This direction is intended to address important issues such as the study of real totipotency of the genome of cells of different levels of differentiation, the ability of genomes to reprogramming, research approaches to obtaining paternal and maternal copies or cloning, the production of hybrid animals and interspecies chimeras by artificial fusion of genomes and the creation of reconstructed zygotes and early embryos. Reconstruction of embryonic stem cells allows us to look at the interaction between the nucleus and cytoplasm, and membrane receptor structures of the genome. A special place is occupied by the experiments on transplanting nuclei of tumor cells into enucleated oocyte. Reconstruction of embryonic stem cells opens up the possibility to study the role of heredity in the development of extranuclear.

 

Reconstruction of differentiated cells and the problems of cytology. Such methods of reconstruction is very important for elucidating the mechanisms of division, in particular the mechanisms of activation of chromatin in the reconstruction of cells from their predecessors, is in various stages of the mitotic cycle. These studies help to identify the mechanisms of the correlation of certain properties of the cells, such as the relationship between the increase in the ability of cells to metastasize, and malignant growth with reduced ability to form intercellular diffusion channels. Finally, it is important to study the mechanisms of cell aging.

 

Reconstruction of the cells and the problem of genetic information cryopreserved genomes of endangered species. With existing methods of cryopreservation and thawing of different cell structures (gametes, gonads, embryos) in 30-50% of cases of damaged cytoplasmic membrane. Cytoplasmic membrane may also be frustrated by peroxidation of membrane lipids. At the same time pointed out repeatedly that the chromosomes are much more resistant to the processes of freezing and thawing. In this regard, it is essential, of replacing the damaged cell membrane to the cell wall of the zygote from the other, but closely related species. In some cases it is very important to be able transplantation of individual chromosomes, such as the need to redefine gender. Similar problems arise when solving the problem of the role of maternal cytoplasm of developing organisms. It is interesting to develop instructional techniques to replace the cytoplasm as a whole and its individual elements. Of particular interest are the indicated task in connection with the implementation of the genetic information of cryopreserved genomes in interspecific nuclear transplantation. Also important task of getting interline and interspecific chimeras by replacing the single core in one of the cells at the stage of two blastomeres. Obtaining such chimeras can help overcome by interspecies embryo incompatibility of the recipient and the donor.

 

Reconstruction of the cell and biotechnology task. Primarily refers to such combination of the reconstructed parts of the cell when it will be possible to receive producer cells capable of active synthesis of these or other biological products. To solve the various problems of cell physiology is very important to obtain chimeras at the cellular level when the artificially created cells with this combination of properties, which do not occur naturally. For example, a combination of very large cell, which creates good conditions for physiological analysis, the synthesis of membrane receptors, ion channels, etc., which are characterized by the presence of a small cell, for physiological analysis difficult. Furthermore, the described features are reconstructed using cells, zygotes particular animal or plant cells cambial allows approach of cloning for agricultural animals.

 

31 Gametogenesis in animal. Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploidgametocytes into various gametes, or by mitotic division of haploid gametogenous cells. Animals produce gametes directly through meiosis in organs called gonads. Males and females of a species thatreproduces sexually have different forms of gametogenesis: spermatogenesis (male), oogenesis (female). Oogenesis is the creation of an ovum (egg cell). Oogenesis consists of several sub-processes: oocytogenesis, otidogenesis, and finally maturation to form an ovum (oogenesis proper). Oogonium —(Oocytogenesis)—> Primary Oocyte —(Meiosis I)—> First Polar Body (Discarded afterward) + Secondary oocyte —(Meiosis II)—> Second Polar Body (Discarded afterward) + Ovum. Oogenesis starts with the process of developing oogonia, which occurs via the transformation of primordial follicles into primary oocytes, a process called oocytogenesis. Oocytogenesis is complete either before or shortly after birth. When oocytogenesis is complete, no additional primary oocytes are created, in contrast to the male process of spermatogenesis, where gametocytes are continuously created. The succeeding phase of ootidogenesis occurs when the primary oocyte develops into an ootid. In late fetal life, all oocytes, still primary oocytes, have halted at this stage of development, called the dictyate. These cells then continue to develop, although only a few do so every menstrual cycle. Meiosis I of ootidogenesis begins during embryonic development, but halts in the diplotene stage of prophase I until puberty. As a result of meiosis I, the primary oocyte has now developed into the secondary oocyte and the first polar body. Immediately after meiosis I, the haploid secondary oocyte initiates meiosis II. However, this process is also halted at the metaphase II stage until fertilization, if such should ever occur. When meiosis II has completed, an ootid and another polar body have now been created. Folliculogenesis. Synchronously with ootidogenesis, the ovarian follicle surrounding the ootid has developed from a primordial follicle to a preovulatory one. Both polar bodies disintegrate at the end of Meiosis II, leaving only the ootid, which then eventually undergoes maturation into a mature ovum.. Spermatogenesis is the process by which male primordial germ cells called spermatogonia undergo meiosis, and produce a number of cells termed spermatozoa. The initial cells in this pathway are called primary spermatocytes. They gives rise to two cells, the secondary spermatocytes, and the two secondary spermatocytes by their subdivision produce four spermatozoa. In mammals it occurs in the male testes and epididymis in a stepwise fashion, and for humans takes approximately 64 days. It starts at puberty and usually continues uninterrupted until death. Spermatocytogenesis results in the formation of spermatocytes possessing half the normal complement of genetic material. In spermatocytogenesis, a diploid spermatogonium which resides in the basal compartment of seminiferous tubules, divides mitotically to produce two diploid intermediate cells called primary spermatocytes. Each primary spermatocyte then moves into the adluminal compartment of the seminiferous tubules and duplicates its DNA and subsequently undergoes meiosis I to produce two haploid secondary spermatocytes, which will later divide once more into haploid spermatids. This division implicates sources of genetic variation, such as random inclusion of either parental chromosomes, and chromosomal crossover, to increase the genetic variability of the gamete. Each cell division from a spermatogonium to a spermatid is incomplete; the cells remain connected to one another by bridges of cytoplasm to allow synchronous development. It should also be noted that not all spermatogonia divide to produce spermatocytes, otherwise the supply would run out. Spermatidogenesis is the creation of spermatids from secondary spermatocytes. Secondary spermatocytes produced earlier rapidly enter meiosis II and divide to produce haploid spermatids. During spermiogenesis, the spermatids begin to grow a tail, and develop a thickened mid-piece, where the microtubules gather and form an axoneme. Spermatid DNA also undergoes packaging, becoming highly condensed. The resultant tightly packed chromatin is transcriptionally inactive. One of the centrioles of the cell elongates to become the tail of the sperm.

32) Main objects of animal biotechnology:

Laboratory animals

ü Mouse

ü Drosophila

ü Chinese hamster

ü Sea urchin

ü Xenopus

ü Rat

ü Rabbit

Farm animals

ü cattle (cows, buffalo)

ü small ruminants (sheep and goats)

ü horses

ü pigs

ü poultry (chicken, turkey, duck, goose)

ü fish (salmon, carp, herring)

ü silkworm etc.

Improving human health depends on the understanding of inside biology (through genetics, biochemistry, physiology, immunology, anatomy etc) as well as outside (through environmental contacts with other living and non-living things/products).

For this purpose, many human diseases (e.g. genetic, acquired, metabolic or infectious) are modeled in animals to develop diagnostic assays, test therapies and

preclinical research on scientific basis. With advances in biotechnology, more and more assays and preclinical trials are conducted in the animal model systems to

understand the disease and functional biology because animal models mimic the human biology very closely. Popular lab animals include mice, rats, rabbits, fish and Drosophila. It is important to learn general biology and handling skills for these animals to use them inexperimental research.This is why the use of animals continue to be mandatory to meet the statutory requirements.

-Drosophila, usually the species Drosophila melanogaster - a kind of fruit fly, famous as the subject of genetics experiments by Thomas Hunt Morgan and others. Easily raised in lab, rapid generations, mutations easily induced, many observable mutations. Recently, Drosophila has been used for neuropharmacological research.

-Rat (Rattus norvegicus) - particularly useful as a toxicology model; also particularly useful as a neurological model and source of primary cell cultures, owing to the larger size of organs and suborganellar structures relative to the mouse.

-African clawed frog (Xenopus laevis) - eggs and embryos from these frogs are used in developmental biology, cell biology,biotech, toxicology, and neuroscience

-fish - has a nearly transparent body during early development, which provides unique visual access to the animal's internal anatomy. The fishs are used to study development, toxicology and toxicopathology,specific gene function and roles of signaling pathways.

-Mouse - the classic model vertebrate. Many inbred strains exist, as well as lines selected for particular traits, often of medical interest, e.g. body size, obesity, muscularity, voluntary wheel-running behavior.

-monkey - used for studies on infectious disease and cognition.

-Guinea pig - used by bacteriologists as a host for bacterial infections, hence a byword for "laboratory animal" even though less commonly used today.

-Chicken - used for developmental studies, as it is an amniote and excellent for micromanipulation (e.g. tissue grafting) and over-expression of gene products

-Cat - used in neurophysiological research

-Dog - an important respiratory and cardiovascular model, also contributed to the discovery of classical conditioning.