Endocrine Abstracts

For quite a long time, the brain has been considered as an insulin independent organ capable of utilizing glucose without participation of insulin. Today, insulin is thought to be not only a regulator of glucose transport and metabolism, but also as a modulator of some processes, including neuronal excitability, proliferation and differentiation of progenitor cells, synaptic plasticity, memory formation, secreting of neurotransmitters and apoptosis. The work was initiated to comparatively analyze the morphological changes in the hippocampus of rats with experimental diabetes mellitus.

Materials and Methods: We studied the brain material taken from 7 rats with a diabetes mellitus model on a high-calorie diet and from 7 controls on the standard diet. Morphological studies were performed on the hematoxylin and eosin histologically stained specimens. The slices of the brain tissues prepared from the paraffin blocks in compliance with the standard methods were examined.

Results and Discussion: The trans-synaptic degeneration providing transfer of the damage from the damaged neuron to the normal one via a synaptic contact is the common process for neurodegenerative diseases of the central nervous system. Apoptosis is thought to be the main mechanism of the neuronal death taking place in neurodegenerative diseases. The findings from examination of the histological specimens of tissues from rats with diabetes mellitus demonstrated pronounced atrophy of the nerve tissues as compared to those from the controls. Karyopycnosis of neurons could be seen in the cerebral cortex and in the hippocampus. In some places, neurofibrillary tangles could be seen in the cerebral cortex; there were perivascular edema, erythrostasis and a slight reduction in the neurons in the hippocampal region. In all regions under study, in rats with diabetes mellitus, the pronounced reduction of neurons as compared to the one in the controls could be seen. A reduction in the volume of the cytoplasm and nucleus, the membrane thickening and folding, moderate hyperchromatosis of the nucleus and the cytoplasm shrinking are the morphological signs evidencing the involvement of neurons in the apoptosis. Thus, the findings from the histomorphological studies demonstrated a reduction in the number of neurons and their karyopycnosis in the hippocampal region with the neurodegenerative damages, as well as changes in both composition of neurons and shape of the cell nuclei.