Holarctic Marmots as a factor of Biodiversity.
Rumiantsev V.Yu;, Nikol'skii A.A. & Brandler O.V. eds.,
3d Conference on Marmots (Cheboksary, Russia, 25-30 August 1997),
Moscow ABF 1997, 216p. : 204.
ULTRASTRUCTURAL ALTERNATIONS OF IMPULSE CONDUCTIVE (ATYPICAL) CARDIOMYOCYTES IN HIBERNIZING
S.M. Zavaleeva, R.Sh. Taiguzin
Orenburg State Agrarian University,
Hibernation is known to be of fundamental importanae for the survival of biological species, its annual cycles depend on the day Length and hormonal variations.
The present investigation was undertaken to determine the regular ultrastructural alterations of atypical cardiomyocytes in mamots before the start of hibernation period and during the first post-hibernation hours. Histological, electron-miaroscopic and morphometria methods were used to study the left ventriale myocard of the common marmot.
It was found that atypical cardiomyocytes had a great amount of sarcoplasm, an undeveloged myofibrillar apparatus and a redlike nucleus forming 58.27 mm of the area. The cariolemma is sometimes folded. The nuclei are comparatively high in euchromatin: 55.77 mm. The perinuclear area is 0.03 mm. The number of myofibrillae in the centre of the cells is scanty and they are mostly devoid of traverses. Peripherally the are located parallel to the long axes of the cells and have marked A, J and Z striations. They occupy 19.44 mm of the relative surface. Mitachondria are dispersed through the carcoplasm, their diameter varies widely.
They are characterized with compactly arranged crists and occupy 19.87 mm of the relative surface area.
There is a great amount of glycogen grains, lysosome-like formations, vacuoles and lyposomes in the atypical cardiomyocytes. The sarcolemma forms rather sparsed T-shaped tubes, the sarcoplasmic network is undeveloped.
In the first hours of post hibernation considerable alterations in the structure of atypical cardiomyocytes have been observed.
Nidus miofibrillae contractures are present in some of the cardiomyocytes, Z-lines fragmentation is evident. The relative band area of the myofibrillar apparatus is not changed. Small-sized mytochondria are often encountered.
A number of components with a light-coloured matrix and partly destroyed or circularly arranged christs are seen.
The suface oompactness of mitochondria is reduced (12.69 mm). The amount of heterochrom in the nuclei increases while the amount of achromatin is accordingly twice as that decreased. The nuclear membrane often forms invaginations.
The perinuclear band is narrowed (0.09 mm). The reduction of glycogen is observed, and it is of a cloddy polymorphic character in the concentration areas.
Thus the structure of atypical cardiomyocites is effected by the physiological state of the body.