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Biomedical subjects

R Pawlicki

Publications and source records attributed to R Pawlicki.

15 recordsLinked to original sources
PubMed1992

Disturbances of mineral metabolism in teeth of rats receiving corticosteroids for 3 generations.

Distribution of calcium and phosphorus was investigated with quantitative and qualitative methods in teeth of rats chronically treated with low doses of corticosteroids for 3 generations. In animals from 2nd and 3rd generation, scanning electron microscopy revealed focal lesions in enamel and dentin. The disturbances of the mineral metabolism in teeth of corticosteroid-treated rats were also reflected by abnormal calcium and phosphorus content in enamel and dentin, as assessed by X-ray microanalysis.

Adrenal Cortex Hormones↗
PubMed1991

X-ray microanalysis of fossil dinosaur bone: age differences in lead, iron, and magnesium content.

Bones of dinosaurs, Gallimimus bullatus, belonging to selected age groups, were studied using an X-ray microanalyser. The content of lead, iron, and magnesium, as well as the distribution of those elements in the investigated bone areas were determined. The results showed, that bones of old animals contained the highest level of lead and iron, whereas in young dinosaurs the respective values were lowest. The obtained data were compared with the results of X-ray microanalysis of the contemporary bone.

Aging↗
PubMed1978

Morphological differentiation of the fossil dinosaur bone cells. Light, transmission electron-, and scanning electron-microscopic studies.

The investigation was carried out on the fossil dinosaur bone from before 80 million years. Samples for examination were prepared with specially elaborated methods. Thus the isolated osteocytes of the dinosaur bone, which had previously undergone natural fossilizing processes, were obtained. This permitted their morphological assessment. On the basis of the images obtained in the light, transmission electron, and scanning electron microscopes, two types of osteocytes were distinguished. Type I was characterized by an elongated shape, its length exceeding the width several times; the mean dimensions of this osteocyte amounted to 28.8/7.03 micron. Type II was shorter, its mean dimensions being equal to 20.28/6.88 micron. Moreover, two types of osteocytes processes were differentiated: the first was represented by thick processes, so-called 'axial processes', whose diameter ranged from 0.5 to 1.5 micron, and which, as a rule, departed from the pole of the cell. They ran farther from the mother cell body to more distant osteocytes. The other type consisted of thin processes departing from various points of the cell body in no particular arrangement but always extrapolarly. They branched off in a close vicinity of the mother osteocyte. Their diameter ranged between 0.076 and 0.35 micron.

Animals↗
PubMed1978

Methods of preparation of fossil bone samples for light and transmission electron microscopy.

The methods described make possible the preparation of fossil samples for light nad transmission electron microscopy. To obtain good images with ground sections of bone, both the grinding process and classical bone staining techniques were modified, the latter by staining already made ground sections. Ground sections of suitable thickness were etched with a 4:1 mixture of 5% HNO3 and 2% OsO4 at a lowered temperature, thereby obtaining isolated osteocytes with a complete network of processes. Using the same method with thicker ground sections, the contents of vascular canals were isolated. The contents retained spatial relations permitting complete reconstruction of the vascular system of the bone in question. The isolated osteocytes, the vascular canal contents, and the isolated remnants of the intercellular organic part of this bone, subsequently embedded in Epon 812 and in methacrylate, made possible sections suitable for detailed analysis of the image of the surfaces of these elements. Polished surfaces of the fossil bone were replicated by the so-called clearing replicas technique adapted to fossil bone. The latter facilitated analysis of the ultrastructure of the surfaces of the vascular canals, isolated osteocytes and their processes, and analysis of the immediate proximity of these elements, since the technique preserves the mutual spatial relations intact.

Animals↗
PubMed1977

Topochemical localization of lipids in dinosaur bone by means of Sudan B black.

A dinosaur bone was examined with the aim to demonstrate in it the presence of lipids and to determine their localization. Ground sections of the bone in question revealed the presence of substances yielding positive reactions on application of a histochemical method used for identification of lipids. Moreover, these substances were found to be localized in the vascular canal, precisely, in the perivascular space. Localization of lipids in a dinosaur bone appeared to be comparable with the distribution of these substances in human bone and in bone of contemporary animals.

Animals↗
PubMed1977

Histochemical reactions for mucopolysaccharides in the dinosaur bone. Studies on Epon- and methacrylate-embedded semithin sections as well as on isolated osteocytes and ground sections of bone.

The dinosaur bone was examined with the aim to detect in it the presence of mucopolysaccharides. The methacrylate- and Epon-embedded semithin sections of the studied bone were found to contain substances giving positive reaction on application of histochemical procedures used for identification of mucopolysaccharides (mucosubstances). These substances were also shown to be localized in the perivascular space, within the vascular canal, and around the osteocytes. The distribution of mucopolysaccharides in the dinosaur bone turned out to be comparable with their distribution in the bones of contemporary animals.

Animals↗
PubMed1976

Correlation between the structure of the wall of the bone lacuna and the localization of the osteocyte within this lacuna. Electron-microscopic studies.

A correlation between the structure of the wall of the bone lacuna and the localization of the osteocyte within this lacuna was the object of investigation under light and electron microscopes. On the basis of the structural divergences detected, the author distinguished zones A and B in the osteocyte situated in the lacuna. Zone B is characterized by a parallel, compact system of collagen fibrils which form a characteristic ridge in the lacunar wall, a continuous demarcating line bordering this wall, the osteocyte cytoplasm in this part lying far from the lacuna wall and surrounding the nucleus with a narrow band, and the pericellular space which is wide here and containing a large number of mucopolysaccharides. This picture may correspond to the area of temporary non-reactivity of the osteocyte. Zone A is characterized by a loosened and disordered system of collagen fibrils forming the lacunar wall. These fibrils being exposed in this place by nature, the demarcating line bordering the lacunar wall is broken in some places, the osteocyte cytoplasm is considerably concentrated around the nucleus and contains a large number of organelles. It also lies closer to the lacunar wall, which results in a decreased width of the pericellular space and a diminished mucopolysaccharide content in this part of the lacuna. Structural variations in the lacuna wall and its space (zones A and B) observed in the images obtained with a normal bone in the light and electron microscopes show their immediate dependence on the position of the osteocyte in the lacuna, which may be associated with the osteocyte activity. On the other hand, the occurrence of significant changes in a definite zone (zone A) of the lacuna only points to the oriented character of this activity.

Animals↗
PubMed1976

Preparation of fossil bone specimens for scanning electron microscopy.

A method is described for preparing fossil bone specimens for scanning electron microscopy. To obtain bone surfaces suitable for study, material was embedded in Epon 812 and selected faces exposed by grinding were subjected to controlled etching with a 4:1 mixture of 5% HNO3 and 1% OsO4. Surfaces thus prepared were further processed by the so-called clearing replicas technique. As a result of this procedure the bone surfaces revealed a network of anastomosing vascular canals the innter surface of whose walls could be examined in the scanning electron microscope. By etching extremely thin ground sections of bone stuck to plastic tape the contents of vascular canals as well as osteocytes can be isolated. This method ensures the good preservation of spatial relations between bone elements essential for studies of fossil bones, which are sometimes very brittle.

Animals↗
PubMed1975

Bone canaliculus endings in the area of the osteocyte lacuna. Electron-microscopic studies.

Light- and electron-microscopic studies were carried out on the bone canaliculi and their endings in the wall fo the osteocyte lacuna. Two types of canalicular endings were distinguished in the lacuna wall. Those of the first type, fairly numerous, are the endings of small diameter, which do not branch off in the immediate proximity of the lacuna. The other type, occurring in twos or threes, are large in diameter and branch off in the close vicinity of the lacuna, invariably possessing two or three processes which run up to the point of branching of the canaliculus. The images obtained made it possible to demonstrate that the collagen fibrils in both types of endings in the lacuna wall are, in principle, arranged in a similar manner. Nonethless, the type of end formation found where the fibrils run along the axis of the lacuna differs from that for the fibrils in a plexus.

Animals↗
PubMed1975

Studies of the fossil dinosaur bone in the scanning electron microscope.

A fossil dinosaur bone, 80 million years old, was subjected to investigation in the scanning microscope. The bone surfaces to be examined were prepared with appropritely modified methods used in the technique of replication in transmission electron microscopy. In the scanning microscope pictures of vascular canals were obtained. The walls of these canals were shown to be formed of collagen fibrils. Moreover, it was demonstrated that the internal surface of the canal wall is made up of bundles of collagen fibrils which run obliquely, corkscrewwise, and in the form of plexus to the long axis of tke canal; Besides, osteocytes of the dinosaur bone were isolated and pictures of their spatial structure together with characteristic points of departure of processes from the cell body were obtained.

Animals↗