Biomedical subjects
Publications and source records attributed to I N Mikhaĭlov.
The character of the cell membrane component destruction of the human epidermis when kept in a humid camera at 4 degrees or 37 degrees C was studied electron microscopically and by a freezing-chopping method. Intermembranous proteins undergo considerable changes and are more labile than a lipid membranous component.
Ultrathin slices from the human abdominal skin and platinum-carbonic replicas, obtained by means of the freeze-fracture method have been studied electron microscopically. Transmembranous proteins are revealed on the membrane surface as membrane-bound particles with the diameter 5-7 nm. They mainly concentrate on the membrane protoplasmic surface. Certain difference is noted in distribution of tonofibrils in cytoplasm of the epidermal cells, when various methods for preparation of specimens to be investigated are used. Predominance of the freeze-fracture method comparing to the routine method of electron microscopy is discussed, since the specimens do not subjected to fixation, dehydration and resin saturation.
Chemically isolated preparations of acid and normal Mg2+, Ca2+-, and guanidine+ salts of cartilage proteoglycan aggregates were investigated by electron microscopy. Some differences between acid and normal salts depend on the amount, valency and distribution of basic ion as well as between carboxyl and sulphate groups.
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The skin of the negroid race albinos is studied light- and electron-microscopically. Morphological alterations, as compared to control, consist of the horny layer thickening, increase of the cellularity in the epidermis, appearance of numerous pronounced tonofibrillar-keratohyaline complexes in the granular cells and a well developed network of dense bundles of tonofibrils in the spinous layer. Melanocytes and Langerhans cells are similar by their structure and number to those in the control. The protein skeletons of melanosomes in keratinocytes and melanocytes are practically unchanged but they are completely deprived of melanine biopolymer. The dermal macrophages do not contain a melanin pigment. The morphological features of the albinos epidermis, particularly the horny layer thickening, increase of the cellularity and the presence of pronounced tonofibrillar-keratohyaline complexes represent most likely a compensatory protective mechanism against ultraviolet radiation.
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The data on complex histochemical and electron histochemical investigation reflecting specificity of the reactions applied in histochemical practice to reveal melanin are represented. Various ultrastructural localization of the substance is demonstrated both with silver and iron use (this demonstrate nonspecificity of the reactions mentioned above to melanin). Ultrastructures possessing affinity to the metal ions involved are detected; possible mechanisms of interaction between silver and iron with different cellular elements are suggested.
Collagenous carcass of human derma is formed by interconnected fibrils, fibrillar fasciculi, fibers and their fasciculi. The latter form a three-dimentional network or spatial carcass (collagenous dermal pattern) subdivided into three main types (layer-forming, rhombic and complex-looped) and several mixed types of pattern. Every pattern has its own definite topographic-anatomical localization in the human body, depends on the functional loading experienced by every part of the body and is historically connected with the erect posture and labour activity.
Histological and histochemical methods and fluorescent and rastral electron microscopy were used for complex investigation of intercellular connective tissue components of the human skin derm (collagenous and elastin fibres, basic substance). The structure of collagenous fibres in different levels of their organization was studied. The structure of periods and differently directed combination of fibrils in the fibre were revealed by different methods. Five types of ruthenies--positive structures in the basic substance and fibres--were found. A supposition is made and substantiated that two interconnected and diverse mechanisms take part in sustaining the structure--function integrity of the collagenous fibre. One of them prevents from rapprochement of fibrils (different direction of fibres, amorphous substance) and the other connect them (adhesive properties of the amorphous substance).
Freezing at -35 degrees C and -70 degrees C of unfixed human epidermis brings about an electron microscopic increase of intercellular spaces, a destruction of cellular membranes, homogenization of tonofibrils, and a decrease in the volume of mitochondria with a partial destruction of their inner surface. Nuclear changes are characterized by disruption of nuclear membranes and by massive passage of nucleoproteids into the cytoplasm. Destruction and fragmentation of cytolemma and nuclear membranes is accompanied by formation of myelin-like figures. Freezing at -70 degrees C leads to greater changes in the structure of the epidermis cells, and is accompanied by the appearance of vacuoles of different sizes and shape in the horny scales and in the cytoplasm of some epidermal cells. This is probably due to formation of ice crystals.
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