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Biomedical subjects

S Donev

Publications and source records attributed to S Donev.

30 records · Page 2Linked to original sources
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Cartilage and bone formation in arterial wall. 1. Morphological and histochemical aspects.

Cartilaginous and/or osseous foci were observed in eight aortas from 20 rabbits immunized against heterologous aorta homogenates and sacrificed 11 to 24 months later. They were studied by means of histological and histochemical methods and compared with normal aortas, cartilage and bone. Some of the observed changes seemed to be true markers of these transformations. Chondroid metaplasia was characterized by 1) generalized increase in alcianophilic hyaluronidase sensitive substances. 2) Appearance of Dermatan and/or Keratan sulfates round some isolated cells. 3) Advent of G6 Pase and Alk. Phase activities in cells adjacent to osseous foci. Osteous metaplasia was characterized by 1) decrease, then disappearance of alcianophilic and PAS positive material, 2) increase in osteoblastic alkaline Pase-activities.

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PubMedDate not supplied

Cartilage and bone formation in arterial wall. 2. Ultrastructural patterns.

The ultrastructural aspects of cartilaginous and osseous foci developed in aorta of rabbits immunized against rat aorta homogenates was studied. Besides normal and modified smooth muscle cells, various types of transformed mediacytes were observed in and around these foci: some of them resembled connective and young mesenchymatous cells, others had the appearances of cartilaginous and osseous cells. The possible role of the modified (multipotential) smooth muscle cells in aortic chondro- and osteogenesis is considered in some cases. Following histogenetic pathway is suggested: s.m.c. leads to modified s.m.c. lead to young mesenchyme-like cells ("inducible osteogenic precursor cells") leads to "chondro-mediacytes", "osteomediacyte".

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PubMedDate not supplied

Ultrastructure of the neuro-insular complexes in the pancreas of sand rats (Psammomys obesus).

The ultrastructure of the nervous elements in Langerhans islets of Psammomys obesus has been studied. A great variety of neural structures present in the islets has been described: neuroganglion-, enterochromaffin- and satellite Schwann cells (neuro-insular complexes type I) and cholinergic, adrenergic and peptidergic nerve fibers (neuro-insular complexes type II) in direct contact with the endocrine cells. In the pericapillary space typical neuro-vasal endings of neurosecretory type have been described. The islets of Langerhans and some of the endocrine cells have a total or partial glial sheath. These findings support the thesis of the paraneuronal nature of the endocrine cells of the Langerhans islets.

Animals↗
PubMedDate not supplied

Immunohistochemical investigations of the endocrine pancreas in normoglycemic sand rats (Psammomys obesus).

A morphological analysis of the endocrine pancreas in the normoglycemic sand rat (Psammomys obesus) has been carried out and the immunoreactivity for insulin, glucagon, somatostatin and pancreatic polypeptide (PP) studied. The islets of both parts of the pancreas (pancreatic head and tail) investigated were of the 'mantle' type: centrally located B-cells and A-, D- and PP-cells at the periphery. In the 'glucagon islets' (tail of pancreas) predominated the A-cells, while the PP-cells were more abundant in the "PP-islets' (head of the pancreas).

Animals↗
PubMedDate not supplied

[Kinetics of triphosphoglyceric acid formation in Chlorella pyrenoidosa (in vivo) during alternation of light and darkness].

On the basis of specific features of carbon reduction cycle in photosynthesis (Kalvin cycle or reduction pentosophosphate cycle) and other processes, in which triphosphoryglyceric acid (3PGA) is an intermediate product, and taking into account the available data concerning the reaction of 3PGA pool of Ch. pyrenoidosa (in vivo) to light-dark disturbances approximate kinetic curves of the value of ribulosodiphosphate (RuDP)--carboxylating reaction product and of other 3PGA accumulations in the chloroplast strom aunder light-dark disturbances. Proceeding from the pecularities of these curves a hypothesis is advanced to the effect of some connection mechanisms of photosynthetic and glycolytic processes of 3PGA production.

Chlorella↗
PubMedDate not supplied

[Light activation of the enzyme ribulose diphosphate carboxylase].

Some activation mechanisms of RuDP-carboxylase under illumination are considered. It is assumed on the grounds of experimental data that under illumination thylacoid membranes pass from one phase (I) to another (II). Kinetics of this transition is taken as similar to that of surface phase transition of the first kind. It is assumed that the number of enzyme molecules passing from the inactive to active state is proportional to the area of thylacoid membranes in the II phase (as the time function). A change in the stroma determined by the kinetics of transition of thylocoid membranes in the transition process leads to a change of the mean time between two successive catalytic acts of the enzyme activated molecules. The obtained kinetic curve of RuDP-carboxylating reaction in the transition process under illumination coincides with the curve obtained in [1] by expanding the experimental curves of the values of labels 14C, 32P of 3PGA to constituents.

Carboxy-Lyases↗