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Biomedical subjects

D Ricci

Publications and source records attributed to D Ricci.

At least 73 records · Page 4Linked to original sources
PubMed1992

Cardiovascular responses of sinoaortic-denervated rats to intracerebroventricular injection of alpha 1- and alpha 2-adrenoceptor agonists.

The aim of the present work was to analyse the cardiovascular responses induced by i.c.v. administration of the alpha 1- and alpha 2-adrenoceptor agonists, phenylephrine and clonidine, respectively, in conscious normal and sinoaortic-denervated rats. Sinoaortic denervation involves changes in central and peripheral catecholaminergic pathways. Clonidine (1-10 micrograms) produced a dose-dependent rise in blood pressure and a bradycardiac response in sham-operated animals, whereas in sinoaortic-denervated rats it provoked a brief rise in blood pressure followed by a marked fall as well as bradycardia. The responses involved mostly activation of central alpha 2-adrenoceptors, but the blood pressure responses induced by clonidine in sinoaortic-denervated rats may also have involved alpha 1-adrenoceptors. The bradycardia induced by the alpha 2-agonist in both groups of rats involved preferentially central alpha 2-adrenoceptors but also partially stimulated alpha 1-adrenoceptors. Phenylephrine, at a dose of 10-60 micrograms, induced a rise in blood pressure and a bradycardiac response while 90 micrograms produced a biphasic pressure response (early transient rise followed by a fall) as well as bradycardia in both sham-operated and sinoaortic-denervated animals. Phenylephrine activated alpha 1-adrenoceptors in every case, but the fall in blood pressure and the bradycardia also involved alpha 2-adrenoceptors. The responses were significantly higher in the sinoaortic-denervated rats than in the sham-operated. Our findings suggest that arterial baroreceptor reflexes can modify the effects of alpha-agonists initiated in the central nervous system. Sinoaortic denervation preparations enable one to unmask the depressor response to clonidine and also demonstrate the true magnitude of the phenylephrine response.

Adrenergic alpha-Agonists↗
PubMed1990

Nuclear inositol lipids in Friend erythroleukemia cells. Changes related to differentiation induced by hexamethylenebisacetamide.

Subcellular distribution of inositol lipids has been studied in Friend Erythroleukemia Cells following induction to erythroid differentiation with hexamethylenebisacetamide, after labelling with [3H]myo-inositol. In situ autoradiography indicated that inositol-derived molecules were present also in the nuclear compartment of uninduced and induced cells. Fractionation studies showed that the nuclear polyphosphoinositides were deeply changed after short induction times, while the whole cell inositol lipids resulted only slightly modified by the inducer. The nuclear recovery of phosphatidylinositol 4,5-bisphosphate was largely increased after 2 hrs of induction, suggesting that inositol lipid metabolism is involved in the early differentiation events occurring at the nuclear level.

Acetamides↗
PubMed1990

[Dilated cardiomyopathy secondary to idiopathic hypoparathyroidism in adults. Description of a case].

The authors report the clinical history of a 56-year-old man with cardiomyopathy due to undiagnosed hypocalcemia. Heart dilation and hypokinesia were assessed by echocardiography. Cardiac failure was refractory to digitalis preparations and to diuretics. The restoration of serum calcium to normal levels obtained with adequate therapy dramatically improved the motion of ventricular walls and decreased the size of the left ventricle. The pathogenetic mechanisms of hypocalcemic cardiomyopathy are discussed and the importance of considering the possibility of hypocalcemia when dealing with the differential diagnosis of cardiomyopathies is underlined. In the presence of hypocalcemic cardiomyopathy, the correction of calcium deficiency with calcitriol is the treatment of choice.

Cardiomyopathy, Dilated↗
PubMed1989

Cross-correlation-based evaluations of the impulse transmission in a nerve: simulation and experimental studies.

Bidirectional impulse transmission can be evaluated by cross-correlation analysis when two recording points are simultaneously available on a nerve. This method was tested here on digitized experimental recordings--from the cerebro-buccal connective of Aplysia--and on computer-simulated recordings with predetermined signal and noise content. The data were processed as such, or after being subjected to one of two preliminary treatments aiming at improving the sensitivity and discrimination power of the method. In the first treatment--Positive Value Saving, PVS--digitized values that were larger than the mean level were left unmodified, while the others were replaced by the mean value itself; in the second treatment--Positive Peak Saving, PPS--the values left unmodified were those which were larger than the mean level and represented a relative maximum. PVS tended to eliminate the negative deflections of the extracellular spikes; PPS tended to transform each spike into a single value equal to the spike amplitude. The cross-correlation histograms obtained yielded a clear separation of the impulses travelling in one and the opposite direction of propagation, and provided their subdivision and quantitative estimation according to propagation velocity. In the conditions adopted, spikes comparable in size to the noise range could be revealed. PVS improved sensitivity and discrimination power; PPS provided a very sharp discrimination between impulses with similar propagation velocity, at the expense of a loss of sensitivity.

Animals↗
PubMed1987

Argyrophil cells in the rat duodenum after gastrectomy.

Two different techniques of reconstruction after total gastrectomy were performed in rats: Roux-en-Y (RY) and jejunal interposition (JI). Sham-operated rats were used as controls. Sixteen weeks after surgery the animals were sacrificed. The distribution of the enteroendocrine cells in the duodenal and proximal jejunal mucosa was examined using the Grimelius silver nitrate stain. The frequency of the Grimelius-positive cells was estimated as number of cells per square millimeter of gut surface and as number of cells per transverse section of intestine. Intestinal villi height was also measured in the same duodenojejunal tracts. After gastrectomy, the JI rats showed a better weight gain than RY rats (p less than 0.05). A significant difference in the distribution of intestinal argyrophil cells was seen. The bypassed duodenojejunal tracts in RY rats showed a marked reduction of the Grimelius-positive cells in comparison with JI rats and controls (p less than 0.01). A reduction in the number of argyrophil cells in the proximal duodenum was also noticed in the JI rats in comparison with controls (p less than 0.01). A decrease in the villi height resulted in all the gastrectomized rats (p less than 0.01), but a significant decrease was also noticed in RY rats in comparison with JI (p less than 0.01). Our experimental observations suggested that the exclusion of the duodenum from intestinal transit after gastrectomy caused atrophy of the gut mucosa and a marked reduction in the number of argyrophil enteroendocrine cells in the bypassed tracts.

Anastomosis, Roux-en-Y↗
PubMed1985

Preparation and allotransplantation of isolated hepatocytes in partially hepatectomized rats.

Three different dissociation techniques of rat liver were compared and yield, viability and morphology of the obtained cells were evaluated. The isolation methods used in this study were: 1. Enzymatic by immersion; 2. Mechanical; 3. Enzymatic by perfusion. The first method supplied 3.91 +/- 1.67 X 10(6) cells/g tissue (X +/- Standard Deviation) and a viability of 52.8 +/- 24.3%. The second method supplied 25.9 +/- 5.68 X 10(6) cells/g tissue and a viability of 62.3 +/- 18.6%. The third method supplied 50.5 +/- 26.6 X 10(6) cells/g tissue and a viability of 87 +/- 5.6%. The hepatocytes obtained according to the three methods were then transplanted into the spleen of allogeneic rats after partial hepatectomy. Allotransplantation of hepatocytes in partially hepatectomized rats proved to inhibit remaining liver regeneration in comparison to partially hepatectomized control rats using mechanically isolated hepatocytes (p less than 0.05), while the allotransplantation of hepatocytes obtained by the two enzymatic methods did not modify significantly liver regeneration.

Animals↗
PubMed1983

Inhibiting action of fusicoccin on the ethylene production of Pisum sativum.

The ability of several auxins to induce C2H4 production was examined. There is an ability scale among the various products in which IAA is the more efficient compound while 2,4-D seems to be the less efficient one. As well as other general phenomena, e.g. enlargement or weight increase, even in this case a biphasic action seems to exist, with an activation at the lower concentrations and an inhibition at the higher ones. The dose corresponding to the critical point, in which one can observe the inversion of the response, seems to be common to all the substances and to be 1 X 10(-4)M. Subsequently we verified the FC influence on the C2H4 production in the presence of the optimal dose of different auxins. The inhibiting action exerted by the toxine is a function of the concentration and does not depend on the inducing substance. The FC determines a drastic reduction in C2H4 production, nearly 60%, for the entire range of the concentrations studied. The described data give evidence of a strong FC interference on ethilene production of etiolated pea internodes.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1983

[Imidazopyrimidines with cytokinin activity].

Some imidazopyrimidines structurally analogous to the corresponding natural kinetics (adenine, benzyladenine, kinetic) were prepared and tested for cytokinin-like activity. Among the compounds tested for ability to retard degradation of the photosynthetic system, the 7-chloroderivatives (II-III) showed activity comparable with that of natural kinetic and confirm the chlorine function as a potentiator of biological activity.

Chlorophyll↗
PubMed1982

[Intestinal mechanisms of compensation and morphologic and functional adaptation after resection of bypass].

The intestine's ability to adapt following extensive resection is well known, and includes augmentation in calibre and the thickness of the wall, increased villus height, changes in motility, and qualitative and quantitative alterations in the flora. Positive identification of the mechanisms through which this morphological and functional adaptation takes place still forms the subject of research. An account is given of the latest views concerning the way in which compensation of the intestine takes place after resection and by-pass surgery.

Adaptation, Physiological↗