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L Silvotti

Publications and source records attributed to L Silvotti.

16 recordsLinked to original sources
PubMed2003

How mammals detect pheromones.

One of the most intriguing discoveries in mammalian pheromone research is the report that a short exposure of women to volatile compounds from sweat can significantly alter their menstrual cycle. This work suggests that specific molecules are produced by women at different stages of the menstrual cycle and that this putative 'pheromonal' blend has effects on the timing of the cycle in women that were briefly exposed to it. What human pheromones are and how they work are not known, however a considerable progress has been made in understanding how other mammals are likely to detect pheromones with the discovery of pheromone receptors. Even though it is proved that pheromones affect human responses, it remains unlikely that similar receptors account for these effects.

Animals↗
PubMed2001

Co-expression of putative pheromone receptors in the sensory neurons of the vomeronasal organ.

Two large and divergent families of G-protein-coupled receptors (V1Rs and V2Rs) are expressed in subsets of neurons in the vomeronasal organ. These receptors are likely to mediate pheromone responses, but it appears that many V2R genes may encode expressed pseudogenes rather than functional proteins. Therefore we have raised antibodies to representative V2Rs and show labeling of vomeronasal neurons demonstrating that V2R genes encode expressed receptors. V2R immunoreactivity was detected at the sensory surface of the vomeronasal organ in dendritic terminals, indicating that these receptors are capable of directly interacting with pheromones and mediating physiological responses. Immunohistochemistry confirmed that three V2R receptors are expressed in small subsets of sensory neurons. However, surprisingly we found that a subfamily of V2R genes is broadly expressed in the Goalpha-layer of the vomeronasal organ and are coexpressed in the same cells as other V2Rs. This is in direct contrast to the main olfactory epithelium where sensory neurons express only a single receptor. Thus, our results suggest that different modes of the information processing may occur in the main and accessory olfactory systems.

Animals↗
PubMed1997

Immunotoxicological effects on piglets of feeding sows diets containing aflatoxins.

Three groups of four Large White sows were fed diets containing either 800 ppb purified aflatoxin B1 (group 1), 800 ppb purified aflatoxin G1 (group 2) or 400 ppb B1 and 400 ppb G1 (group 3) throughout gestation and lactation. A control group of four sows was fed a diet free of aflatoxins. Aflatoxins B1 and M1 were found in milk samples taken five and 25 days after parturition from the sows of group 1, aflatoxin G1 was present in the milk of the sows of group 2 and all three aflatoxins were present in samples from the sows of group 3. The concentration of aflatoxin in the milk was about 1000-fold lower than that in the feed, but increased over the 25 days after parturition. The piglet suckling on a central teat was selected from each sow, given sow milk until the fourth day of age, and was then free to eat prepared feed while suckling. At the 25th day of age the selected piglets were removed from the sow and sacrificed. Blood samples were collected from each piglet and cellular populations were separated for immunological measurements: an in vitro lymphocyte proliferation test, and tests to derive the phagocytic activity, phagocytic index and superoxide anion production of monocyte-derived macrophages were carried out along with studies on the motility, differential chemotaxis and chemotactic index of circulating granulocytes. The lymphoproliferative response to mitogens was reduced and monocyte-derived macrophages failed to efficiently produce superoxide anions after oxidative burst stimulation in vitro, while their ability to phagocytose red blood cells was not compromised. Granulocytic cells showed a reduction of chemotactic response in vitro to chemoattractant bacteria factor and casein.

Aflatoxins↗
PubMed1997

Modulation of host cell activation during feline immunodeficiency virus (FIV) infection.

The authors describe the mitogenic effect of feline immunodeficiency virus (FIV) infection (1) in vitro, on feline resting peripheral blood lymphocytes (PBL), and (2) in vivo, in experimentally infected cats. Infected PBL were more readily recruited than non-infected PBL, into the G1 phase of the cell cycle and showed increased expression of the specific cell-cycle markers p53 and p56. In-vivo lymphocyte activation following FIV infection was demonstrated by increased germinal centre activity in infected lymph nodes, together with a high expression of CD30, a B-cell activation marker. These results suggest that early events in FIV infection include modulation of host cell activation. Possible implications for pathogenesis are discussed.

Animals↗
PubMed1997

FIV induced encephalopathy: early brain lesions in the absence of viral replication in monocyte/macrophages. A pathogenetic model.

FIV induced encephalopathy represents a model for the study of the neuropathogenesis of AIDS. It has yet to be determined whether massive viral replication is a prerequisite for the development of early brain lesions. Using a drug delivery system developed by us, we have shown that early encephalic lesions appear in FIV infected subjects even when viral transport within the brain has been markedly reduced or blocked.

Acute Disease↗
PubMed1995

FIV infection of macrophages: in vitro and in vivo inhibition by dideoxycytidine 5'-triphosphate.

We have evaluated in vitro and in vivo whether it is possible to protect cat macrophages from feline immunodeficiency virus (FIV) infection by the administration of dideoxycytidine 5'-triphosphate (DDCTP). Since cell membranes are impermeable to phosphorylated drugs we have encapsulated DDCTP into autologous erythrocytes and modified erythrocyte membranes to target these drug-loaded cells to macrophages. DDCTP-loaded erythrocytes reduced FIV production by macrophages infected in vitro or obtained from naturally or experimentally infected cats. The same treatment protected the majority of peritoneal macrophages during a 7 month experimental FIV infection and reduced the percentage of circulating lymphocytes stained with an anti-p24 antibody. These results suggest that the administration of nucleoside analogues in phosphorylated form is feasible and their targeting to macrophages reduces FIV infection in vitro and in vivo.

Animals↗
PubMed1994

Feline immunodeficiency virus infection of macrophages: in vitro and in vivo inhibition by dideoxycytidine-5'-triphosphate-loaded erythrocytes.

Although HIV-1 and other mammalian lentiviruses infect macrophages, they are not cytopathic. Consequently, these infected long-lived cells serve as major virus reservoirs with a key role in the propagation of the virus throughout the body as well as in the pathogenesis of AIDS. Furthermore, well-differentiated macrophages possess low abilities to phosphorylate the most common reverse transcriptase inhibitors of the nucleoside analog family. In an attempt to overcome these problems we have evaluated in vitro and in vivo in a feline immunodeficiency animal model whether it is possible to protect macrophages from FIV infection by direct administration of dideoxycytidine-5'-triphosphate (ddCTP). Because the cell membranes are impermeable to phosphorylated drugs we have encapsulated ddCTP into autologous erythrocytes. The drug-loaded erythrocyte membranes were then modified to target these carrier cells to macrophages. ddCTP-loaded erythrocytes were able to reduce FIV production by macrophages infected in vitro or obtained from naturally or experimentally infected cats. Furthermore, the administration of ddCTP-loaded erythrocytes protected the majority of peritoneal macrophages during a 7-month experimental FIV infection and reduced the percentage of circulating lymphocytes stained by an anti-p24 antibody. These results suggest that the administration of nucleoside analogs in phosphorylate form is feasible and their targeting to macrophages reduces FIV infection both in vitro and in vivo.

Animals↗
PubMed1991

Differential adaptive response to hyperosmolarity of 3T3 and transformed SV3T3 cells.

Both 3T3 and simian virus 40-transformed 3T3 (SV3T3) cells were used to investigate differences in population kinetics, protein synthesis, monovalent ion levels, and amino acid accumulations between normal and transformed cells exposed to hyperosmolarity at 0.5 Osm. Under similar culture conditions, SV3T3 cells were found to be more sensitive in their proliferative response than normal cells to the hyperosmolar treatment. In the normal 3T3 cells, the increase in transport of amino acids was less sustained and was associated with higher levels of accumulated amino acids. The equilibrium distribution of intracellular monovalent cations and the rate of protein synthesis also returned faster to baseline values in the normal cells than in the transformed cells. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) analysis revealed the induction of a 69-kDa polypeptide in the 3T3 cells but not in the SV3T3 cells after exposure to hyperosmolarity. On electrofocusing and relative mass analysis, this polypeptide closely migrated with the 70-kDa heat shock protein (hsp) family, although it was unrelated immunologically to the inducible 72-kDa hsp.

Amino Acids↗
PubMed1989

Density-dependent regulation of amino acid transport in a Burkitt lymphoma cell line.

Rate of proliferation and amino acid transport were assessed in the Burkitt's lymphoma-derived Namalwa cells by measurements of growth rate and proline and serine uptake. Cell density of the cultures was varied by modifying the number of cells initially seeded and growing for different periods of time. Under these experimental conditions the growth rate was not correlated with cell density. In contrast, the activity of amino acid transport through Systems A and ASC, as assessed by the uptake of proline and serine, respectively, decreased as a function of cell density. This marked decrease of transport activity cannot be explained by large alterations of cell morphology since it was observed at a cell density range where minimal change of cell volume and surface area occurred. When a constant number of cells suspended in an identical volume of medium sedimented on different settling areas, a marked effect on amino acid transport activity occurred. These results indicate that cell to cell contacts may be involved in the density-dependent regulation of transport.

Amino Acids↗
PubMed1988

Enhancement of mitochondrial tyrosine kinase activity following viral transformation.

A tyrosine protein kinase activity has been detected in the mitochondrial fraction purified from normal and virus-transformed cultured cells. The addition of serum to cells whose growth was restricted by serum limitation induced a marked decrease of tyrosine kinase activity associated with the mitochondrial fraction. At all the culture conditions tested this enzyme activity always resulted several fold higher in the virus-transformed cells than in the normal parental cells.

Animals↗
PubMed1987

Hyperosmolarity-induced stress proteins in chick embryo fibroblasts.

The effects of a short exposure of chick embryo fibroblasts to a hyperosmolar medium on monovalent cation content, rate of protein synthesis, and polypeptide pattern expression were studied. The hyperosmolar shock gave an immediate and pronounced inhibition of the protein-synthesis rate temporally related to a marked alteration of the intracellular Na+ content. Following the return of the cells to an osmolar environment, the internal Na+ content quickly resumed its previous level, while the recovery of the protein-synthesis rate was more gradual. During the recovery period, there was enhanced expression of at least 12 proteins. The 4 major induced proteins exhibited apparent molecular weights of 96, 87, 70, and 48 kDa. A reduction in the synthesis of five protein bands including three large polypeptides of 220, 160, and 140 kDa was also observed. A comparison with the 3 major proteins induced by a 44 degrees C heat shock indicated an apparent similarity with only two of the hyperosmolarity-inducible polypeptides. Moreover, evidence has been also obtained of the close similarity between the 96 and 75 kDa glucose-regulated proteins and the 96 and 75 kDa proteins inducible by a hyperosmolar shock or by a continuous hyperosmolar treatment, respectively. The kinetics of the stress-proteins appearance indicated nonsimultaneous induction. The presence of actinomycin D during the exposure of the cells to the stress and the recovery period suggested that the expression of some hyperosmolarity-enhanced proteins is regulated at the transcriptional level.

Animals↗
PubMed1987

The effect of deazaadenosine analogues on the proliferation rate of cultured Vero cells.

Five adenosine analogues resistant to adenosine deaminase were analyzed for their effects on the proliferation on cultured Vero cells. Cells were exposed for 48 hr to various concentrations of 1-deazaadenosine (c1Ado), 3-deazaadenosine (c3Ado), 7-deazaadenosine (c7Ado), 1,3-dideazaadenosine (c1,3Ado) or 1,7-dideazaadenosine (c1,7Ado) and then counted with a hemocytometer. Results indicate that 1) whereas c7Ado produced a marked decrease in cell growth, c3Ado was toxic only at the highest concentration tested (30 microM), 2) c1Ado and c1,7Ado did not affect cell replication and 3) c1,3Ado produced a significant stimulation of cell proliferation. Further studies have suggested that none of the compounds tested is incorporated in the DNA.

Animals↗
PubMed1986

Association of tyrosine protein kinase activity with mitochondria in human fibroblasts.

A tyrosine protein kinase activity has been detected in the mitochondrial fraction purified from human fibroblasts. By enzymatic and sedimentation analysis this activity appeared to be localized in the mitochondrial outer membrane. Mitochondrial tyrosine phosphorylation was strictly dependent on the presence of Mn2+ ions. An inverse relationship between cell proliferation and mitochondrial protein phosphorylation on tyrosine residues has been found: a marked increase in the mitochondrial tyrosine kinase activity occurred when a significant reduction in the growth rate followed serum step-down. In mitochondria purified from resting cells, a protein band with apparent molecular weight of 50 kd appeared to be phosphorylated on tyrosine.

Electrophoresis, Polyacrylamide Gel↗
PubMed1986

Induction of stress proteins by hyperosmolarity in normal and transformed cells.

The synthesis of at least three proteins, with molecular weights of approximately 87, 70, and 53 kd, was enhanced following the exposure of chick embryo fibroblasts to hyperosmolar shock of 30 min at 0.6 osM. Two of these proteins, the 87 and 70 kd, comigrated on one-dimensional gel electrophoresis with the stress proteins induced by heat shock after 30 min at 44 degrees C. In 3T3 cells, the hyperosmolar shock enhanced the expression of two proteins of 88 and 52 kd, whereas the heat shock increased the synthesis of several new polypeptides including the 88 and 52 kd mw. In SV40-transformed 3T3 cells the synthesis of two proteins of 72 and 69 kd was enhanced by heat shock, but no change of the protein pattern was recorded after the hyperosmolar shock.

Animals↗