EVIDENCE OF APOPTOSIS IN PARVOCELLULAR NUCLEI OF HYPOTHALAMUS IN DIABETES MELLITUS

Diabetes mellitus (DM) causes great socio-economic damage, which is determined by medical expenses and expenditure on social security to patients due to invalidity and loss of labour capacity. Researchers are studying the role of hypothalamic neuropeptides and their involvement in the regulation of pancreatic islet function. In view of the above, the aim of our study was to establish the features of morphofunctional changes in the arcuate nucleus (AN) and ventromedial nucleus (VN) of the hypothalamus in streptozotocin-induced diabetes mellitus (SIDM). Histological, immunohistochemical, electron-microscopic, biochemical and statistical research methods were used. Polymorphic changes were noted in AN and VN at early stages of development of SIDM (on the 14th day). In AN, the area of neurons and their nuclei became larger, the numerical density of dark functionally more active neurons increased, and dinuclear light neuroendocrine cells (NC) appeared. In light and dark NCs of AN, there was a significant increase in the bulk density of neurosecretory granules – by 2-4 times compared with the control, in VN – by 1.2-2 times. Such morphofunctional changes in parvocellular nuclei of the hypothalamus and the increase in the bulk density of neurosecretory granules in their NCs indicate boosted synthesis of neurohormones which directly affect the adenohypophysis and improving functional activity of NCs in AN and VN. On the 70th day of SIDM in AN and VN of the hypothalamus, there was a decrease in the numerical density of neurons due to light NC and increase in the numerical density of vacuolated, dark pycnomorphic and apoptotic neurons. The apoptotic index in the studied nuclei of the hypothalamus increased by 2-4 times compared with the control. The area of the profile field of NC increased and the area of nuclei decreased, which led to the reduced nuclear-cytoplasmic index and indicated a decrease in their functional activity and was confirmed by a decrease in the bulk density of neurosecretory granules in NC by 1.9-2.1 times in AN and by 2.7-4.7 times in VN. At the ultrastructural level, pronounced destructive processes such as vacuolar dystrophy, development of satelliteosis and neuronophagia were observed in light NCs. Thus, prolonged hyperglycemia in SIDM in parvocellular nuclei of the hypothalamus causes neuronal death to a lesser extent due to apoptosis, and to a greater extentdue due to hydropic dystrophy and colliquative necrosis, especially in the long term of the experiment (on the 70th day), and leads to the development of diabetic neuroendocrinopathy.

The influence of melatonin on stress-induced ultramicroscopic changes of the neurons of the supraoptic nuclei of the rat hypothalamus

The aim: to study the effect of melatonin on the ultrastructural state of the supraoptic nuclei of the hypothalamus of rats under immobilization stress.Materials and methods. The experiments were performed on non-linear male white rats weighing 200-220 g. The animals were divided into 3 study series, in each of which the biomaterial was collected at 2 p.m. and at 2 a.m. using electron microscopic method. Long immobilization stress was simulated by keeping rats in special plastic penal cages for 6 hours daily for 7 consecutive days. Melatonin (Sigma, USA, 99.5% purification degree) at a dose of 0.5 mg/kg, in 1.0 ml of solvent (0.9% ethanol solution on physiologic saline) was injected daily, intraperitoneally.Results. When the animals were kept under the standard light regime, the ultrastructural organization of the hypothalamic nuclei at 2 p.m. indicated their low functional activity in comparison with the studies carried out at 2 a.m. Prolonged exposure of rats to immobilization stress was reflected in a significant rearrangement of the ultrastructural organization of supraoptic nuclei of the hypothalamus. The established changes can be considered as a manifestation of neurosecretory activity suppression, a decrease in neurosecretase production by hypothalamic neurons. Melatonin injections against the background of immobilization stress resulted in relative normalization of ultrastructural state of neurons of supraoptic nuclei of the hypothalamus of animals. In particular, studies at 2 a.m. revealed light neurosecretory cells containing a large nucleus, it was pyknotically altered. Karyolema invaginations, euchromatin dominance in the nucleus were observed. Heterogeneous changes were observed on the part of mitochondria. Enlarged tubules of granular endoplasmic reticulum were seen. At the same time, a small number of ribosomes and few hormonal granules were noticeable in neuroplasm. The mentioned picture of neurosecretory cells reflects a relative improvement in their electron microscopic state, which is evidenced by the appearance of neurosecretory granules. However, the ultrastructure of other organelles of the studied neurons indicates a depleted state caused by prolonged immobilization.Conclusions. 1. In animals under standard photoperiod conditions, the structural organization of supraoptic neurons of the hypothalamic nuclei during the nighttime of the experiment reflects the intensity of intracellular synthesizing processes (at 2 a.m.). A decrease in the activity of the structures under study is noted during the daytime. 2. Under immobilization stress, the ultrastructural organization of the above neurons indicates a pronounced disturbance of reactive nature with the signs of decreased functional ability of the structures and the phenomena of edema and destruction during the period of observation. 3. Melatonin injections against the background of immobilization stress led to a relative improvement in the ultrastructural state of the animals’ hypothalamic nuclei neurons, which is evidenced by the appearance of neurosecretory granules. However, the ultrastructure of other organelles of the studied neurons indicated a depleted state caused by prolonged immobilization.