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Biomedical subjects

P A Rossi

Publications and source records attributed to P A Rossi.

8 recordsLinked to original sources
PubMed1997

Membrane potential changes visualized in complete growth media through confocal laser scanning microscopy of bis-oxonol-loaded cells.

Confocal laser scanning microscopy (CLSM) was employed to visualize and measure membrane potential changes in several types of cultured adherent cells, such as human fibroblasts, mouse mammary tumor C127 cells, and human saphenous vein endothelial cells, preloaded with the anionic dye bis-1, 3,-diethylthiobarbituratetrimethineoxonol (bis-oxonol). The fluorescence of cell-associated bis-oxonol was detected in a single confocal plane. An original flow-chamber apparatus was employed to replace the extracellular medium, avoiding alterations of the plane selected for observation. In all the cell types and the experimental situations tested the intracellular distribution of the dye was typical; perinuclear zones accumulated the dye which, conversely, was excluded by the nucleus. Fluorescence was calibrated versus the membrane potential by varying the extracellular concentration of sodium in the presence of gramicidin. With this approach membrane potential was measured (i) in cultured human fibroblasts incubated under anisotonic conditions, (ii) in heterogeneous cell populations which respond unevenly to potential perturbing conditions, and (iii) in human macrovascular endothelial cells maintained in high-serum, complete growth medium. The results obtained indicate that CLSM can be successfully employed to measure changes of membrane potential in single, bis-oxonol-loaded adherent cells under experimental conditions which severely hinder conventional spectrofluorimetric approaches.

Animals↗
PubMed1994

Response of human fibroblasts to hypertonic stress. Cell shrinkage is counteracted by an enhanced active transport of neutral amino acids.

Regulatory volume increase (RVI) has been studied in cultured human fibroblasts (CHF) incubated in a complete hypertonic growth medium (400 mosmol/kg). After the initial cell shrinkage induced by hypertonic treatment, cells recover their volume almost completely within 3 h. This RVI response is associated with a marked increase of the cell content of free amino acids. The cell content of potassium increases only slightly. Chromatographic analysis of the intracellular amino acid pool shows that the RVI-associated increase in cell amino acids is mainly a result of changes in the L-glutamine content. The intracellular accumulation of the analog 2-methylaminoisobutyric acid, a specific substrate of transport system A, is increased in CHF undergoing RVI. Hypertonic treatment causes an immediate and sustained cell hyperpolarization, as demonstrated by changes in the trans-membrane distribution ratio of L-arginine and in the fluorescence of the potential-sensitive dye bis-1,3-diethylthiobarbiturate-trimethineoxonol. Because of cell hyperpolarization, at the end of RVI the trans-membrane gradient of the sodium electrochemical potential is higher than that of the control. The increase in the extracellular potassium concentration ([K+]out = 40 mM) abolishes the hyperpolarization induced by hypertonic treatment and delays volume recovery. Cycloheximide suppresses RVI at a high but not at physiologic [K+]out. It is proposed that CHF counteract hypertonic shrinkage through an enhanced accumulation of substrates of transport system A sustained, initially, by an increase in the energy available for transport and, subsequently, also by the synthesis of new site A carriers.

Adolescent↗
PubMed1994

Regulatory volume decrease of cultured human fibroblasts involves changes in intracellular amino-acid pool.

Regulatory volume decrease (RVD) has been studied in cultured human fibroblasts incubated in a complete growth medium at low osmolality (215 mosmolal). After the initial swelling induced by hypotonic treatment, cells recover their volume almost completely within about 60 min. This RVD is associated with comparable losses of cell potassium and amino acids. After an initial increase, cell content of sodium is kept at values close to control. Chromatographic analysis of intracellular amino-acid pool has shown that RVD-associated decrease in cell amino acids is due for the most part to changes in the intracellular concentration of L-glutamine. RVD-exerting cells undergo a rapid and marked depolarization that is maintained after cell volume recovery. This change in membrane potential has been detected with measurements of both the transmembrane distribution ratios of L-arginine and of fluorescence of potential-sensitive dye bis-oxonol. Due to depolarization, the trans-membrane gradient of sodium electrochemical potential is lowered. It is proposed that cell depolarization concurs to keep the intracellular concentration of amino acids low by inhibiting sodium-coupled uptake through system A.

Adolescent↗
PubMed1990

Phorbol esters stimulate the transport of anionic amino acids in cultured human fibroblasts.

The effect of phorbol esters on the transport of amino acids has been evaluated in cultured human fibroblasts. The activity of the Na(+)-dependent system XAG- for anionic amino acids is selectively and markedly stimulated by phorbol esters. The effect is maximal within 15 min; it is attributable to an increase in transport maximum (Vmax) and not prevented by inhibitors of protein synthesis. The half-maximal stimulation is observed at concentrations of phorbol 12,13-dibutyrate lower than 100 nM. Prolonged incubations in the presence of 1 microM phorbol 12,13-dibutyrate lower the binding of the ligand to its receptor with a loss of the stimulatory effect on transport. The results presented indicate that the stimulation of amino acid transport through system XAG- by phorbol esters requires the activation of protein kinase C.

Amino Acids↗
PubMed1990

The transport of L-glutamine into cultured human fibroblasts.

The transport of L-glutamine has been studied in diploid human fibroblasts in culture. Mathematical discrimination by nonlinear regression, competition analysis, and conditions varying the relative contribution of the various mediations have been used to characterize the systems engaged in the inward transport of this amino acid. The adopted criteria showed that L-glutamine enters the fibroblast by the Na(+)-dependent systems ASC and A and by a Na(+)-independent route identified as system L. The relative contribution of these agencies to the total saturable uptake of glutamine varied with the concentration of the amino acid and with the nutritional state of the cell. At amino acid concentrations approaching those encountered in human plasma: (1) system ASC represented the primary mediation for entry of L-glutamine in human fibroblasts; (2) the contribution of system A was lower, though significant, in unstarved repressed cells and became predominant in starved derepressed cells; (3) the Na(+)-dependent system L accounted for less than one-fifth of glutamine uptake in either nutritional condition. The changes in the relative contribution of the various systems to the uptake of glutamine as a function of its concentration may have implications in pathophysiology under conditions associated with enhanced glutamine concentrations in the extracellular fluids.

Amino Acids↗
PubMed1982

Carcinoid heart disease: a clinical pathologic, and therapeutic update.

The carcinoid syndrome is a rare clinical entity, the unique manifestations of which continue to excite the interest of physicians. Despite a common origin from neural crest tissue, the tumors are partially differentiated, as evidence by the different secretory products of foregut, midgut, and hindgut carcinoids. They also differ in their ability to metastasize, thus presenting an even more varied clinical picture. The prognosis of patients with carcinoid syndrome varies with the origin of the tumor and extent of metastases. The management of patients with carcinoid syndrome is difficult. Despite an understanding of the neurohormones that carcinoid tumors secrete, their various antagonists and inhibitors have been only partially successful in providing symptomatic relief. Carcinoid heart disease represents the most intriguing aspect of this syndrome. Although valvular dysfunction most often coexists with flushing and diarrhea, the findings of tricuspid regurgitation or stenosis occasionally provide the first clue to the presence of the disease. Despite intensive research, the definite etiology of these valvular lesions has not been established. A small group of patients has been managed by valve replacement. While surgical treatment has been successful in improving hemodynamics in most of these patients, it is expected to prolong life only in those without extensive liver metastases. In patients with extensive metastatic disease, one must carefully consider whether the risks and trauma of cardiac surgery for palliation are justified.

Anesthesia↗