Biomedical subjects

M Rizzotti

Publications and source records attributed to M Rizzotti.

29 records · Page 2Linked to original sources

PubMed1977

Experimental arthrosis from intra-articular vitamin A injection in the rabbit. Morphological and biochemical study: considerations on the pathogenesis of human arthrosis in relation to the experimental model.

The key to the pathogenesis of arthrosis lies in the mechanism responsible for the initial lesions. In this experimental work the possibility of producing arthrosic changes is demonstrated by activating lysosomal chondrocytic enzymes by the intra-articular injection of Vitamin A in rabbits. On the basis of the experimental results the authors discuss the possible role that activation of the lysosomal hydrolytic enzymes might play in producing primary and secondary arthrosis in humans. They advance the hypothesis that this mechanism may be the common final step in the degradation of the articular cartilage, whatever the aetiological factor.

Acid Phosphatase↗

PubMed1976

[Histochemical demonstration of uridine diphospho-glucoso-4'-epimerase activity].

In the byosinthesis of glycosaminoglycans, UDP-glucose is utilized by two enzymes: UDP-glucose dehydrogenase which produces UDP-glucuronic acid (chondroitin sulphate precursor), and UDP-glucose 4'-epimerase which produces UDP-galactose (keratan sulphate precursor). The mechanisms regulating these two reactions have particular interest mainly considering that many connective tissues can modify its glycosaminoglycan production with aging; it is well-known that cartilage of young animals synthesizes almost exclusively chondroitin sulphate while cartilage of old animals synthesizes both chrondroitin sulphate and keratan sulphate. The kinetic parameters of both enzymes utilizing UDP-glucose have been recently investigated and some mechanisms responsible for UDP-glucose utilization in glycosaminoglycan biosynthesis have been evidenced. Under histoenzymological viewpoint, we have confirmed the inhibiting effect of UDP-xilose on UDP-glucose dehydrogenase and the possible role of such nucleotide in aging processes of cartilage. In order to study this problem even by a histoenzymological approach, an original method for histochemical determination of UDP-glucose 4'-epimerase activity in connective tissue cells was developed. This method seem to be more sensitive than that described by other authors. In standard conditions the sections of the frozen tissue were incubated in Tris-HCL buffer, pH 8.8 (Tris concentration 0.025 M), containing 0.5 mM UDP-galactose, 2 mM NAD, 0.6mM NBT and an excess of UDP-glucose dehydrogenase (about 300 mU). Control experiments in the absence of UDP-galactose, UDP-glucose dehydrogenase and in the absence of both UDP-galactose an- UDP-glucose dehydrogenase were also carried out. Under our experimental conditions, UDP-glucose 4'-epimerase present in the cells epimerizes UDP-galactose (added in the incubation mixture) to UDP-glucose which can bo oxidized by the excess of UDP-glucose dehydrogenase to UDP-glucuronic acid with a consequent NADH formation. The NADH formed is able to reduce and precipitate NBT. As a control of experimental sistem, we have determined the increase in O.D. at 525 nm of a reaction solution that was incubated directly in the spectrophotometer cuvette, at 37 degrees C with UDP-galactose 0.2 mM, NAD 2 mM, NBT 0.6 mM, 200 mU of UDP-glucose, dehydrogenase, 400mU of UDP-glucose 4'-epimerase and Tris HCL buffer pH 8.8 to a final volume of 1 ml. Histoenzymological and biochemical results demonstrate that this method is specific for and sensitive to UDP-glucose 4'-epimerase activity.

Animals↗

PubMed1976

[Distribution of the enterochromaffin ("EC") cells and those of the "APUD" series in the gastrointestinal tract of ruminants].

The research was carried out on the vorestomachs, abomasum and on the various tracts of gut of adult Cattle, Sheep and Goat, because Ruminants, not previously studied with respect to this problem, have, as is well known, particular morpho-functional characteristics of the digestive system. The results can be synthetized as follows: 1) either "EC" (5-HT-producing) or "APUD" cells (peptide hormones-producing) are not demonstrable in the vorestomachs. 2) "EC" cells are present in the various areas of abomasum (particularly numerous in the fundus glands) and in the different tracts of the gut (predominantly in the duodenum and in the rectum). 3) In the "APUD" cells of the abomasum gastrin-producing "G" cells are certainly demonstrable. They are present only in the pyloric glands, where they prevail in the middle third. Only in the cattle, cells which have all the histochemical characteristics of "G" cells, but are quite morphologically different, are also present in the same area. An interesting peculiarity seems to be the reduced number of "APUD" cells, compared with that of Monogastrics: it was impossible, in fact, to demonstrate some cells ("A", "A-like","X", "D", "D1", "ECL") which are described by other Authors in the stomach of various Mammals. 4) In the small intestine, endocrine cells, probably heterogenous are present, resulting more numerous in the duodenum. 5) In the coecum, colon and rectum, cells comparable to enteroglucagon-producing "EG" cells, are present; they are particularly numerous in the rectum, where cells similar to "H" cells are also present.

Abomasum↗

PubMed1976

[Distribution of the enterochromaffin ("EC") cells and those of the "APUD" series in the gastrointestinal tract of the calf].

Based on morphological and histochemical data, the Authors describe the distribution of "EC" (5-HT-producing) and of the other endocrine cells of the "APUD" series (polypeptide hormone-producing) in the gastro intestinal tract of weaned and unweaned 3-4 month old calves. The results demonstrate that: -- no difference concerning the different diet can be correlated; -- no endocrine cell is present in the vorestomachs; -- the "EC" cells in the abomasum prevail in the fundus glands; they are demonstrable also in every tract of the intestine and are more numerous in the duodenum and in the rectum; -- within the "APUD" series four cellular types are demonstrable in the abomasum; two are in the cardias, one in the fundus and one in the pylorus glands; the last one probably corresponds to the gastrin-producing "G" cells. -- In the small intestine, particularly numerous in the duodenum, a probably heterogeneous family of endocrine cells is present, while in the coecum, in the colon and, above all, in the rectum, cells probably corresponding to "EG" cells are identifiable. These results are compared to those previously obtained in the adult Cattle: remarkable differences are demonstrable only within "APUD" cells of abomasum.

Abomasum↗

PubMed1975