| In order to study the correlation of different developmental stages of yak myocardial tissue characteristics with the hypoxic environment, we selected different developmental stages(pregnancy 4 months old, born 1 day of age, 1 month, 3 months, 6 months old) at the same altitude gradient, Datong yak as the object of study, using transmission electron microscopy(TEM) for qualitative and quantitative analysis of myocardial mitochondria stereo morphological index of different yak development stages; using molecular biology techniques to detect myocardial mitochondrial marker enzyme: cytochrome C oxidase(COX), succinate dehydrogenase(SDH) and hypoxia inducible factor(HIF-1 alpha) mRNA in real time fluorescent quantitative analysis; myocardial tissue in vascular endothelial growth factor(VEGF, veg) and micro vascular density(MVD) were detected.by using immunohistochemical methodThe results are as follows:(1) Myocardial mitochondrial morphology results: myocardial mitochondria in cells uniform neat rows, mostly circular or ovoid; outer and inner membranes are complete, membrane clearance, crest and matrix structure can be clearly seen, due to the delivery and the external environment of stress in the myocardial cell of born one day yak, cells became swollen and decrease in the number. In myocardial mitochondria of Datong yak, average cross-sectional area, average volume and numerical density on area, volume density showed an upward trend with age increased, and the difference is significant(P < 0.05) born at 1 day of age due to external environment strong stimulation indices change obviously. Mitochondrial average cross-sectional area(AX/μm2), average volume V/μm3 were greater than other age and number density(Na/μm2) were lower than those of other age, volume density(V/μm3) in addition to greater than 1 month of age were less than several other age segment(2) The expression of COX-II and mRNA COX-I in cardiac muscle showedmRNA COX-II expression and COX-I were relatively stable; at birth 1 days of age, II, mRNA COX-I were the highest, and the difference was significant(P < 0.05).(3) The expression of SDH 4 subunit transcripts in the birth of 1 days of age, the expression of SDH 4 subunit is the highest.(4) The expression of HIF-1 alpha mRNA increased steadily with the increase of developmental stage, and the difference was significant between different age groups(P< 0.05). HIF-1 alpha mRNAboth in the age of 1 day old yak and 6 months old yak).was significantly higher than other age groups and the difference was extremely significant(P < 0.01).(5) The VEGF and MVD in the myocardium of Datong yak were distributed at different developmental stages, and the percentage of VEGF and MVD in the myocardium of Datong yak increased with the increase of age, and the difference was significant(P < 0.05). Compared with other age groups, the ratio of VEGF and MVD was the lowest in the number of myocardial fibers in 1 day of birth.In summary, under high altitude hypoxia environment long-dwelling animals Datongyak,s myocardial mitochondrial number and the morphology and mitochondrial marker enzymes(SDH, Cox) expression, myocardial tissue) HIF-1α mRNA expression, myocardium MVD and VEGF protein percentage showed stable upward trend with the developmental stages of growth, which may be associated with the Datong yak mechanism to adapt to the chronic hypoxia environment. Due to the stress stimulus delivery, each parameter was born 1 day age compared with other age groups all had obvious changes, mitochondrial structure got a temporary damage 1 day birth age yaks under acute hypoxia stress, increase the HIF–1α expression quantity of myocardial tissue and strengthen control mitochondrial enzyme iconic COX, and SDH to rapidly increase oxygen supply of the tissue cells. HIF–1α rapidly accumulating inside the nucleus, which induced VEGF and MVD factor expression to decrease damage to cells by adjusting oxygen partial pressure, so it played a protective role by supplying oxygen and energy to myocardial tissue. |
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