Zagoruyko G. E., Martsinovsky V. P., Kasyanchuk V. M., Filatova V. L., Panasyuk V. Yu.

BIOLOGY

Scentific article

After 15 days of postnatal development of rats, in cardiomyocytes (CMC) of the left ventricle there is a longitudinal splitting of myofibrils, which leads to an increase in their number in the contractile apparatus (CA). In newborn (n/b) rats, the number of myofibrils (MF) in the contractile apparatus of the cardiomyocytic (CMC) does not exceed 12-13 pieces. In the CMC of 45-day-old animals, this figure is 80 pieces. If we take the thrust of one CMC of newborn rats, for one conventional unit Fcmc (n/b) = 1conditional unit (c.u.). The thrust of one CMC of 45-dayold rats will be equal to Fcmc = (80 MF: 12 MF) ≈ 6.5 c.u. conditional unit. Thus, the total thrust of all CMC (Ncmc = 0.72 x 107 ) in the myocardium of newborn rats theoretically is ∑Fcmc = 0.72 x 107 c.u. The traction force of all CMC (Ncmc = 1.56 x 107 ) in the myocardium of 45 day-old rats will be: ∑Fcmc = 1.56 x 107 х 6.5 c.u ≈ 108 c.u In the time interval (n/b) – 45 days, there is a fluctuation of digital values of the cross-sectional area of the MF in the narrow range SØmf ϵ[0.65-1.05] μm2 . “Increase ↔ decrease” of the volume of sarcomeres in the MF occurs as result of fluctuations in the composition of each sarcomere of the number of structural elements – hundreds. In the center of the honeycomb is one thick, and around the perimeter of 12 thin filaments. Six thin filaments area ttached to the Z-disk on one side of the thick filament, the other six to the Z-disk on the other side of the thick filament. The area of one cell is 6,225 х 10-4 μm2 . During the period of postnatal maturation of the CMC (45 days), the number of cells in the sarcomere ranges from 1044 to 1690. Thus, in the time interval (n/r – 45) days of postnatal maturation of the CMC, the increase in the absolute volume of the contractile apparatus of the CMC occurs under the influence of the following intracellular mechanisms. 1. Increasing the length of myofibrils in 3.2 times from 25 μm to 81 μm. 2. Increasing the number of MF in the contractile apparatus of cardiomyocytes in ≈ 6.5 times from 12-13 pieces to 80 pieces. 3. Fluctuations in the cross-sectional area of myofibrils in the range [0,65-1,05] μm2 . 4. Neoplasms of honeycombs – structural and functional units in the sarcomere from 1044 to 1690 pieces. As a result of increasing the number of CMC in ≈ 2.17 times and the number of myofibrils in each CMC in ≈ 6.7 times there is an increase in the contractile force of myocardial traction in 14 times.

cardiogenesis, morphometry, contractile apparatus, cardiomyocyte.

1. Pavlyukova EN, Trubina EV, Karpov RS. Rotacziya, skruchivanie i povorot po osi levogo zheludochka u bolnykh ishemicheskoj i dilataczionnoj kardiomiopatiej. Ultrazvuk i funkczion. diagnostika. 2013;1:44-53. [in Russian].
2. Chernykh NYu, Groznova OS, Dovgan MI. Issledovanie kinetiki miokarda v klinicheskoj praktike: normativnye pokazateli deformaczii, rotaczii, skruchivaniya. Rossijskij vestnik perinatol. i pediatrii. 2016;4:32-6. [in Russian].
3. Goryelova NI. Kharakteristika gistogenetichnikh proczesiv u serczi lyudini na rannikh etapakh kardiogenezu. Morfologiya. 2007;1(1);58-62. [in Ukrainian].
4. Du A, Sanger JM, Sanger JW. Cardiac myofibrillogenesis inside intact embryonic hearts. Developmental Biology. 2008;318:236-46.
5. Marchenko DG, Tverdokhlib IV. Ontogenetichni mekhanizmi formuvannya skorotlivogo aparata kardiomioczitiv. Morfologiya. 2012;VІ(4):5- 11. [in Ukrainian].
6. Kozlov VA, Tverdokhleb IV, Shponka IS. Morfologiya razvivayushhegosya serdcza (struktura, ultrastruktura, metabolizm). DGMA; 1995. 220 s. [in Ukrainian].
7. Zagorujko GE, Zagorujko YuV. Morfometricheskij analiz prenatalnogo i postnatalnogo sozrevaniya kardiomioczitov krys. Visnik problem biologiyi i mediczini. 2017;2(136):290-3. [in Ukrainian].
8. Kozlov SV, Mayevsky AE, Mіshalov VD, Sulayeva ON. Ulʹtrastrukturnyy analiz budovy skorotlyvoho aparata sertsya shchuriv na etapakh ontohenetychnoho rozvytku. Morphologia. 2015;9(1):34-8. [in Ukrainian].
9.  Ivanova VV, Milto IV, Serebryakova ON. Serdcze krysy v prenatalnom i postnatalnom periode ontogeneza. Ontogenez. 2021;52(5):329-44. [in Russian].
10. Drew NK, Grosberg A. Methods of myofibrillogenesis modeling. Methods Mol. Biol. 2015;1299:75-91.
11. Yang H, Schmidt LP, Wang Z, Yang X, Shao Y, Borg TK, et al. Dynamic Myofibrillar Remodeling in Live Cardiomyocytes under Static Stretch. Sci Rep. 2016 Feb 10;6:20674. DOI: 10.1038/srep20674.
12. Yoldaş A, Özmen E, Aksoy G. The Anatomy of the Cardiac Veins in Storks (Ciconia ciconia). Journal Home-Page. 2013;19(4):687-92.
13. Tverdokhlib IV, Marchenko DG. Ultrastrukturni zmini skorotlivogo aparatu miokarda shlunochkiv shhuriv na etapakh prenatalnogo ontogenezu v normi ta pislya diyi alkogolyu. Svit mediczini ta biologiyi. 2019;3(69):225-31. [in Ukrainian].
14. Prishlyak AM, Gnatyuk MS. Informaczijnij analiz osoblivostej strukturnoyi perebudovi shlunochkiv serczya pid vplivom khloridu kadmiyu. Tavricheskij mediko-biologicheskij vestnik 2013;16.1(1):202-5. [in Ukrainian].
15. Morozova KN. Elektronnaya mikroskopiya v citologicheskih issledovaniyah: metodicheskoe posobie. Novosibirsk: NNIGU; 2013. 85 s. [in Russian].
16. Zagorujko GE, Zagorujko YuV, Shmulich AV. Kinetika proczessov rosta linejnykh razmerov i chislennosti kardiomioczitov v miokarde kompleksa (LZh+MZhP) do i posle rozhdeniya krys. Visnik problem biologiyi i mediczini. 2018;4(1):36-9. [in Ukrainian].
17. Samsonova AV, Samsonov GA. Sot- strukturnaya edinicza sarkomera. Trudy kafedry biomekhaniki universiteta imeni P. F. Lesgafta. 2016;10:16-21. [in Russian].
18. Samsonov GA, Samsonova AV. Vliyanie uvelicheniya ploshhadi poperechnogo secheniya sarkomera na sootnoshenie tonkikh i tolstykh filamentov. Trudy kafedry biomekhaniki universiteta imeni P. F. Lesgafta. 2016;10:22-7. [in Russian].

«Bulletin of problems biology and medicine» Issue 1 (163), 2022 year, 86-92 pages, index UDK 612.172: 611.127-018

10.29254/2077-4214-2022-1-163-86-92